WO2015151207A1 - Radio communication system, radio communication method, radio station and control station - Google Patents
Radio communication system, radio communication method, radio station and control station Download PDFInfo
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- WO2015151207A1 WO2015151207A1 PCT/JP2014/059579 JP2014059579W WO2015151207A1 WO 2015151207 A1 WO2015151207 A1 WO 2015151207A1 JP 2014059579 W JP2014059579 W JP 2014059579W WO 2015151207 A1 WO2015151207 A1 WO 2015151207A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
- H04W52/04—TPC
- H04W52/06—TPC algorithms
- H04W52/14—Separate analysis of uplink or downlink
- H04W52/143—Downlink power control
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
- H04W52/04—TPC
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
- H04W52/04—TPC
- H04W52/38—TPC being performed in particular situations
- H04W52/40—TPC being performed in particular situations during macro-diversity or soft handoff
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
- H04W72/04—Wireless resource allocation
- H04W72/044—Wireless resource allocation based on the type of the allocated resource
- H04W72/0473—Wireless resource allocation based on the type of the allocated resource the resource being transmission power
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W92/00—Interfaces specially adapted for wireless communication networks
- H04W92/16—Interfaces between hierarchically similar devices
- H04W92/20—Interfaces between hierarchically similar devices between access points
Definitions
- the present invention relates to a wireless communication system, a wireless communication method, a wireless station, and a control station.
- ICIC Inter Cell Interference Coordination
- FeICIC Frether enhanced ICIC
- Release 11 that further expands LTE (Long Term Evolution) -Advanced is being studied (for example, see Non-Patent Documents 1 to 10 below).
- CoMP Coordinatd Multiple-Point transmission and reception: multipoint coordinated communication
- a plurality of base stations perform communication in cooperation to improve cell edge performance.
- an object of the present invention is to provide a wireless communication system, a wireless communication method, a wireless station, and a control station that can improve throughput.
- a second radio station capable of communicating with a plurality of first radio stations, and a control station that controls the first radio station And the control station notifies the second radio station of radio resources for cooperative communication in which the plurality of first radio stations cooperate with each other to communicate with the second radio station, and so on.
- a wireless communication method, a wireless station, and a control station are proposed in which communication is performed and the second wireless station receives data addressed to itself transmitted by the cooperative communication on the wireless resource.
- FIG. 1 is a diagram of an example of a wireless communication system according to the first embodiment.
- FIG. 2A is a diagram illustrating an example of a communication system according to the second embodiment.
- FIG. 2B is a diagram illustrating an application example of the communication system according to the second embodiment.
- FIG. 3A is a sequence diagram illustrating an operation example 1 of the communication system.
- FIG. 3B is a sequence diagram illustrating an operation example 2 of the communication system.
- FIG. 3C is a sequence diagram illustrating an operation example 3 of the communication system.
- FIG. 4A is a flowchart illustrating an example of processing by the macro base station.
- FIG. 4B is a flowchart illustrating an example of processing by the small base station.
- FIG. 5 is a flowchart showing an example of processing by the mobile station.
- FIG. 6 is a diagram illustrating an example of each base station.
- FIG. 7 is a diagram illustrating an example of a mobile station.
- FIG. 8 is a diagram illustrating an example of a hardware configuration of the base station.
- FIG. 9 is a diagram illustrating an example of a hardware configuration of the mobile station.
- FIG. 10 is a diagram illustrating an example of the operation of each small base station according to each reception result of the response signal.
- FIG. 11 is a diagram illustrating an example of retransmission by an upper layer.
- FIG. 1 is a diagram of an example of a wireless communication system according to the first embodiment.
- the radio communication system 100 includes a control station 110, first radio stations 120a and 120b, and a second radio station 130.
- the second radio station 130 is a radio station capable of radio communication with the first radio stations 120a and 120b.
- the control station 110 is a control station that controls the first radio stations 120a and 120b.
- the control station 110 is connected to the first radio stations 120a and 120b, for example, by wire. Further, the control station 110 may be able to communicate with the first radio stations 120a and 120b by radio.
- the control station 110 includes a control unit 111 and a communication unit 112.
- the control unit 111 controls cooperative communication in which the first wireless stations 120a and 120b communicate with the second wireless station 130 in cooperation.
- the communication unit 112 performs wireless communication with the second wireless station 130.
- the communication unit 112 notifies the second radio station 130 of radio resources for cooperative communication in which the first radio stations 120a and 120b cooperate to communicate with the second radio station 130.
- Radio resources include, for example, frequency resources.
- the radio resource may include a time resource.
- the communication unit 112 may notify the first radio stations 120a and 120b of radio resources for cooperative communication in which the first radio stations 120a and 120b cooperate to communicate with the second radio station 130.
- the first radio station 120a includes a control unit 121a and a communication unit 122a.
- the control unit 121a controls cooperative communication in which the first wireless stations 120a and 120b communicate with the second wireless station 130 in cooperation.
- the communication unit 122a is addressed to the second radio station 130 in cooperation with a first radio station (for example, the first radio station 120b) different from the own station (for example, the first radio station 120a) of the first radio stations 120a and 120b.
- the cooperative communication for transmitting the data to the second radio station 130 is performed.
- the cooperative communication by the communication unit 122a is controlled by the control unit 121a.
- the communication unit 122a performs cooperative communication in a specific period in which wireless transmission is performed with lower power than other periods.
- “lower power” includes a case where transmission on a certain radio channel is not performed at all.
- the communication unit 122a performs wireless transmission with a first transmission power in a certain first period to other wireless stations including the second wireless station 130, and a second period (specific period) different from the first period.
- Wireless transmission is performed with a second transmission power lower than the first transmission power.
- the communication unit 122a transmits data addressed to the second radio station 130 to the second radio station 130 by cooperative communication with another first radio station in the second period.
- the first wireless station 120b includes a control unit 121b and a communication unit 122b.
- the control unit 121b and the communication unit 122b are the same as the control unit 121a and the communication unit 122a of the first radio station 120a, respectively. That is, the control unit 121a of the first radio station 120a and the control unit 121b of the first radio station 120b perform cooperative communication in which communication with the second radio station 130 is performed in cooperation.
- the second radio station 130 includes a control unit 131 and a communication unit 132.
- the control unit 131 controls communication between the first radio stations 120a and 120b and the second radio station 130 through cooperative communication in which the first radio stations 120a and 120b cooperate.
- the communication unit 132 receives data addressed to the local station, which is transmitted in cooperation by the first wireless stations 120a and 120b.
- the first wireless stations 120a and 120b perform coordinated transmission in a specific period in which low power transmission is performed, thereby improving the reception characteristics of the second wireless station 130 in the specific period. be able to. For this reason, even if many specific periods are set in the wireless communication system 100, the throughput can be improved.
- each radio station 110 can be a base station that forms a cell capable of wireless communication.
- each of the first radio stations 120 a and 120 b can be a base station located in the cell of the control station 110.
- the second radio station 130 can be a mobile station, for example.
- the second wireless station 130 may be capable of wireless communication with the control station 110 in addition to the first wireless stations 120a and 120b. Further, wireless communication may be possible simultaneously with the control station 110 and the first wireless station 120a or 120b.
- Examples of base stations corresponding to the control station 110 include macro base stations.
- examples of base stations corresponding to the first radio stations 120a and 120b include small base stations.
- the application destination of each base station is not limited to these.
- base stations corresponding to the first radio stations 120a and 120b receive various interferences from larger cells such as femto base stations and pico base stations. A base station that forms the victim cell can be applied.
- the communication unit 122a of the first wireless station 120a transmits data addressed to the second wireless station 130 without notifying the second wireless station 130 of the wireless resources of the cooperative communication in the cooperative communication with the first wireless station 120b. Also good. Similarly, the communication unit 122b of the first wireless station 120b transmits data addressed to the second wireless station 130 without notifying the second wireless station 130 of the wireless resources of the cooperative communication in the cooperative communication with the first wireless station 120a. You may send it.
- the communication unit 132 of the second radio station 130 receives the data addressed to the second radio station 130 transmitted in cooperation by the first radio stations 120a and 120b on the radio resource notified from the control station 110. can do. Thereby, the communication amount between the 1st radio stations 120a and 120b and the 2nd radio station 130 can be reduced.
- the communication unit 112 of the control station 110 may notify the second radio station 130 of radio resources for cooperative communication by the first radio stations 120a and 120b by radio signals. Thereby, for example, compared with the notification via the wired network between the control station 110 and the radio stations 120a and 120b, the radio resource of the cooperative communication can be notified to the second radio station 130 in a short time. For this reason, the determination result of the radio resource of the cooperative communication by the control station 110 can be reflected quickly, and the communication quality can be improved.
- ⁇ Resend> The retransmission when the second wireless station 130 cannot normally receive the data addressed to the second wireless station 130 in the cooperative communication by the first wireless stations 120a and 120b will be described. In this case, retransmission of data addressed to the second wireless station 130 is performed by one of the first wireless stations 120a and 120b, and the other first of the first wireless stations 120a and 120b. The radio station may not be performed.
- the communication unit 112 of the control station 110 notifies the second radio station 130 of the radio resources for cooperative communication by the first radio stations 120a and 120b, and then only changes the radio resources for the coordinated communication.
- the radio resource may be notified to the second radio station 130.
- the communication unit 132 of the second radio station 130 can receive data addressed to the own station on the radio resource notified last from the control station 110. Thereby, for example, the communication amount between the control station 110 and the second radio station 130 can be reduced as compared with the case where the radio resource is repeatedly notified regardless of whether or not the radio resource is changed.
- the specific period during which radio transmission is performed with lower power than other periods in the first radio stations 120a and 120b is, for example, an ABS (Almost Blank Subframe) set in common with the first radio stations 120a and 120b.
- ABS Almost Blank Subframe
- the time unit of the specific period is not limited to a subframe, and can be various time units (for example, a radio frame or a slot).
- CoMP can be used for cooperative communication in which the first wireless stations 120a and 120b communicate with the second wireless station 130 in cooperation.
- cooperative communication is not limited to CoMP, and various types of cooperative communication can be used.
- the wireless communication system 100 includes the first wireless stations 120a and 120b as the first wireless stations.
- the wireless communication system 100 includes three or more first wireless stations, and the three or more first wireless stations include The wireless communication with the second wireless station 130 may be performed in cooperation.
- FIG. 2A is a diagram illustrating an example of a communication system according to the second embodiment.
- the communication system 200 according to the second embodiment includes a macro base station 210, small base stations 221, 222, and a mobile station 230.
- the communication system 200 is a wireless communication system to which LTE or LTE-Advanced is applied.
- the control station 110 shown in FIG. 1 can be realized by the macro base station 210, for example.
- the first radio stations 120a and 120b shown in FIG. 1 can be realized by small base stations 221 and 222, for example.
- the second radio station 130 shown in FIG. 1 can be realized by the mobile station 230, for example.
- the macro cell 210a is a wireless communication range (cell) of the macro base station 210.
- the small cell 221a is a wireless communication range (cell) of the small base station 221.
- the small cell 222 a is a wireless communication range (cell) of the small base station 222.
- the small base stations 221 and 222 are located in the macro cell 210a.
- the mobile station 230 is a UE (User Equipment: user terminal) capable of wireless communication with a base station.
- the mobile station 230 is located in an overlapping portion of the small cells 221a and 222a, and can perform wireless communication with the small base stations 221 and 222. Further, since the mobile station 230 is also located in the macro cell 210a, wireless communication is possible with the macro base station 210.
- FeICIC for controlling interference between the macro base station 210 and the small base stations 221 and 222 is performed.
- an ABS that is a subframe required to perform low power transmission is set.
- an ABS ABS between the macro cell and the small cell to which the macro base station 210 performs low power transmission is set.
- an ABS ABS between small cells in which the small base stations 221 and 222 perform low power transmission is set.
- the small cells 221a and 222a can execute CoMP that performs radio communication with the mobile station 230 in cooperation with each other (Inter-eNB CoMP).
- CoMP by the small cells 221a and 222a is controlled by the macro base station 210, for example.
- the macro base station 210 transmits the same user data destined for the mobile station 230 to the small cells 221a and 222a.
- the macro base station 210 transmits a control signal indicating a subframe (including ABS) for performing CoMP transmission and a transmission scheme (for example, an encoding scheme and a modulation scheme) to the small cells 221a and 222a.
- a control signal indicating a subframe including ABS
- a transmission scheme for example, an encoding scheme and a modulation scheme
- the small cells 221a and 222a wirelessly transmit the same user data received from the macro base station 210 to the mobile station 230 simultaneously based on the control signal received from the macro base station 210.
- the mobile station 230 performs diversity reception for receiving the same user data wirelessly transmitted simultaneously from the small cells 221a and 222a. Thereby, even in a situation where a large number of ABSs are set, it is possible to improve the reception characteristics (for example, the received signal level) in the mobile station 230 (for example, 3 [dB]) and improve the data rate.
- the reception characteristics for example, the received signal level
- Xn interfaces 201 and 202 for example, an X2 interface
- a wired communication interface or a wireless communication interface different from the Xn interfaces 201 and 202 may be used for transmitting user data from the macro base station 210 to the small cells 221a and 222a.
- Wireless communication can be used for transmission of control signals from the macro base station 210 to the small cells 221a and 222a.
- the control signal can be transmitted with a small delay, the determination result of the radio resource and transmission method of the cooperative communication by the macro base station 210 can be reflected quickly, and the communication quality can be improved.
- FIG. 2B is a diagram illustrating an application example of the communication system according to the second embodiment.
- the communication system 200 shown in FIG. 2A can be applied to the communication system 200 shown in FIG. 2B, for example.
- the communication system 200 shown in FIG. 2B includes macro base stations 210 and 240 and small base stations 221, 222, 251 and 252.
- the macro cell 240a is a wireless communication range (cell) of the macro base station 240.
- the small cell 251a is a wireless communication range (cell) of the small base station 251.
- the small cell 252a is a wireless communication range (cell) of the small base station 252.
- the small base stations 251 and 252 are located in the macro cell 240a.
- FeICIC for controlling interference between the macro base station 240 and the small base stations 251 and 252 is performed.
- ICIC for controlling interference between the macro base station 210 and the macro base station 240 is performed.
- FIG. 3A is a sequence diagram illustrating an operation example 1 of the communication system.
- the same parts as those shown in FIG. 2A are denoted by the same reference numerals and description thereof is omitted.
- the horizontal axis indicates the passage of time.
- a partition 301 indicates a wireless frame partition.
- One radio frame includes 10 subframes.
- the macro base station 210 performs pre-configuration 302 (Configuration) with the small base stations 221 and 222.
- the macro base station 210 instructs the start (Activation) or the stop (Deactivation) of CoMP transmission by the small base stations 221 and 222 (Inter-eNB CoMP (Act / Deact)).
- the macro base station 210 instructs the small base stations 221 and 222 to start CoMP transmission.
- the macro base station 210 notifies the ABS position set in the macro base station 210 (FeICIC: ABS (Macro)). Further, in the pre-setting 302, for example, the macro base station 210 notifies the ABS position of the MBSFN (Multicast / Broadcast Single Frequency Network: MBMS single frequency network) set in the small base stations 221 and 222 (ABS_MBSFN (Small)). )).
- the ABS is, for example, ABS 351 or 352 described later.
- the macro base station 210 starts transmission of downlink user data 311 and 312 addressed to the mobile station 230 to the small base stations 221 and 222 (Data (via Xn)).
- the user data 311 and 312 are downlink data destined for the mobile station 230 and are the same data.
- User data 311 and 312 can be transmitted by, for example, the Xn interface (for example, the Xn interfaces 201 and 202 shown in FIG. 2A) between the macro base station 210 and the small base stations 221 and 222.
- the user data 311 and 312 can be transmitted by, for example, a PDCP (Packet Data Convergence Protocol) packet.
- PDCP Packet Data Convergence Protocol
- the feedbacks 321 and 322 are periodic feedback from the mobile station 230 to the macro base station 210, and are feedback of the measurement results of the wireless communication quality of the small base stations 221 and 222 in the mobile station 230.
- the macro base station 210 uses the results of the feedbacks 321 and 322 for controlling cooperative communication by the small base stations 221 and 222.
- the feedbacks 331 and 332 are periodic feedback from the mobile station 230 to the small base stations 221 and 222, and are feedback of measurement results of the wireless communication quality of the small cells 221a and 222a in the mobile station 230.
- the small cells 221a and 222a use the results of the feedbacks 331 and 332 for retransmission control.
- the feedbacks 321, 322, 331, and 332 include, for example, CQI (Channel Quality Indicator: channel quality index), PMI (Precoding Matrix Indicator: precoding matrix index), RI (Rank Indicator: rank index), and the like.
- CQI Channel Quality Indicator: channel quality index
- PMI Precoding Matrix Indicator: precoding matrix index
- RI Rank Indicator: rank index
- the feedback 321, 322, 331, 332 is not limited to these, and various types of wireless communication quality information can be used.
- ABSs 341 and 342 are subframes in which the macro base station 210 performs low power transmission.
- the timings (positions) of the ABSs 341 and 342 are determined by, for example, the macro base station 210, and are notified to the small base stations 221 and 222 by the preset 302.
- ABSs 351 to 354 are subframes in which both small base stations 221 and 222 perform low power transmission.
- ABSs 351 and 353 are MBSFNs.
- the ABSs 351 and 353 are designated from the macro base station 210 in the preset 302.
- the ABSs 351 and 353 which are MBSFNs include a control area 303 (Control Region) and a data area 304 (Data Region).
- the ABSs 351 and 353 may include a protection period (Guard Period) between the control area 303 and the data area 304.
- ABSs 352 and 354 are ABSs determined by the small base stations 221 and 222 based on the positions of the ABSs 351 and 353 designated from the macro base station 210. For example, the small base stations 221 and 222 determine the positions of the ABSs 352 and 354 so as not to overlap the ABSs 351 and 353.
- the ABSs 352 and 354 may be ABSs determined by the macro base station 210 and notified to the small base stations 221 and 222 by the control signals 361 and 362, for example.
- the ABSs 352 and 354 may be notified from the macro base station 210 to the mobile station 230 by, for example, control signals 371 and 372.
- Control signals 361 and 362 are control signals from the macro base station 210 to the small base stations 221 and 222. Control signals 361 and 362 are transmitted in control area 303 of ABSs 351 and 353, which are, for example, MBSFN.
- control signals 361 and 362 are signals indicating a data transmission method (modulation method and coding method) and radio resources from the small base stations 221 and 222 to the mobile station 230.
- the control signals 361 and 362 include RBA (Resource Block Assignment: resource block allocation) and MCS (Modulation and Coding Scheme: modulation / coding scheme).
- control signal 361 is a control signal indicating a data transmission method and radio resources determined by the macro base station 210 based on the feedback 321.
- the control signal 362 is a control signal indicating a data transmission scheme and radio resources determined by the macro base station 210 based on the feedback 322.
- the radio resource includes at least one of a frequency resource and a time resource, for example.
- the control signals 361 and 362 can be transmitted by radio, for example. Thereby, the control signals 361 and 362 can be transmitted to the small base stations 221 and 222 with a small delay. Therefore, it is possible to shorten the time until the feedbacks 321 and 322 from the mobile station 230 are reflected in the control of the small base stations 221 and 222. For this reason, wireless communication between the small base stations 221 and 222 and the mobile station 230 according to the wireless communication quality of the mobile station 230 in the small cells 221a and 222b becomes possible.
- Control signals 371 and 372 are control signals from the macro base station 210 to the mobile station 230.
- the control signals 371 and 372 are control signals having the same contents as the control signals 361 and 362, for example.
- the control signals 371 and 372 are transmitted in the control area 303 of the ABS 351 and 353 simultaneously with the control signals 361 and 362.
- the control signals 371 and 372 can be transmitted by radio, for example.
- User data 381 and 382 are user data transmitted from the small base stations 221 and 222 to the mobile station 230 by CoMP.
- User data 381 and 382 are, for example, user data 311 and 312.
- User data 381 and 382 may be PDSCH (Physical Downlink Shared Channel: physical downlink shared channel), for example.
- the user data 381 and 382 are transmitted by JT (Joint Transmission: joint transmission) that transmits the same user data 381 and 382 simultaneously.
- the small base stations 221 and 222 simultaneously transmit user data 381 by CoMP in the ABS 352 based on the control signal 361 received from the macro base station 210 in the ABS 351.
- the small base stations 221 and 222 simultaneously transmit user data 382 by CoMP in the ABS 354 based on the control signal 362 received from the macro base station 210 in the ABS 353.
- the mobile station 230 receives user data 381 simultaneously transmitted from the small base stations 221 and 222 in the ABS 352 based on the control signal 371 received from the macro base station 210.
- the mobile station 230 receives user data 382 transmitted simultaneously from the small base stations 221 and 222 in the ABS 354 based on the control signal 372 received from the macro base station 210.
- Response signals 391 and 392 are response signals from the mobile station 230 to the small base stations 221 and 222 for the user data 381 and 382, respectively.
- Each of the response signals 391 and 392 is, for example, ACK (positive signal) indicating that user data has been normally received or NACK (negative signal) indicating that user data has not been normally received.
- the retransmission by the small base stations 221 and 222 based on the response signals 391 and 392 is, for example, retransmission by HARQ.
- retransmission by the small base stations 221 and 222 based on the response signals 391 and 392 is not limited to HARQ, and retransmission in various layers (for example, ARQ in RLC layer) can be applied.
- the small base stations 221 and 222 may transmit the data addressed to the mobile station 230 without notifying the mobile station 230 of the radio resources of the cooperative communication in the cooperative communication of the user data 381 and 382. Also in this case, the mobile station 230 can receive the data addressed to the mobile station 230 transmitted by the small base stations 221 and 222 in cooperation on the radio resource notified from the macro base station 210. Thereby, the communication amount between the small base stations 221 and 222 and the mobile station 230 can be reduced.
- the ABSs 352 and 354 are determined by the macro base station 210 and are notified to the small base stations 221 and 222 by, for example, control signals 361 and 362.
- the ABSs 352 and 354 are also notified to the mobile station 230 by control signals 371 and 372, for example.
- the radio resources indicated by the control signals 361, 362, 371, and 372 include a frequency resource and a time resource (ABS 352 and 354).
- FIG. 3B is a sequence diagram showing an operation example 2 of the communication system.
- the same parts as those shown in FIG. 3A are denoted by the same reference numerals and description thereof is omitted.
- the macro base station 210 does not change the data transmission method or radio resource for cooperative communication notified to the mobile station 230 by the control signal 371
- the macro base station 210 does not need to transmit the control signal 372 as shown in FIG. 3B. Good.
- the mobile station 230 receives user data 382 by cooperative communication in the ABS 354 based on the control signal 371 received last.
- SPS Semi-persistent-Scheduling
- the macro base station 210 notifies the mobile station 230 of the radio resources for cooperative communication by the small base stations 221 and 222 and then changes the radio resources for the cooperative communication only when the radio resources for the cooperative communication are changed. May be notified to the mobile station 230.
- the mobile station 230 can receive data addressed to itself on the radio resource last notified from the control station 110. Thereby, for example, the communication amount between the macro base station 210 and the mobile station 230 can be reduced as compared with a case where the radio resource is repeatedly notified regardless of whether or not the radio resource is changed.
- the ABSs 352 and 354 are determined by the macro base station 210 and notified to the small base stations 221 and 222 by, for example, the control signal 361.
- the ABSs 352 and 354 are also notified to the mobile station 230 by a control signal 371, for example.
- the radio resources indicated by the control signals 361 and 371 include frequency resources and time resources (ABS 352 and 354).
- FIG. 3C is a sequence diagram showing an operation example 3 of the communication system.
- the small base stations 221 and 222 may transmit the user data 381 together with a control signal indicating a data transmission method and radio resources for transmitting the user data 381.
- a control signal indicating a data transmission method and radio resources for transmitting the user data 381.
- PDCCH Physical Downlink Control Channel: physical downlink control channel
- the small base stations 221 and 222 transmit PDSCH together with PDCCH in transmitting user data 381 (PDCCH + PDSCH (JT)).
- PDCCH + PDSCH (JT) user data 381
- only one of the small base stations 221 and 222 may transmit the PDCCH.
- the mobile station 230 receives the PDSCH transmitted from the small base stations 221 and 222 based on the PDCCH transmitted together with the PDSCH.
- the macro base station 210 may not transmit the control signals 371 and 372 illustrated in FIG. 3A, for example.
- the ABSs 352 and 354 are determined by the small base stations 221 and 222 and are notified to the mobile station 230 by PDCCH, for example.
- the radio resource indicated by the control signals 361 and 362 includes a frequency resource.
- various methods can be used as the determination method and notification method of the ABSs 351 and 352 that perform cooperative communication.
- FIG. 4A is a flowchart illustrating an example of processing by the macro base station.
- the macro base station 210 executes the steps shown in FIG. 4A.
- the macro base station 210 determines whether or not to execute CoMP transmission (step S401), and waits until it is determined to execute CoMP transmission (step S401: No loop).
- the determination of whether or not to execute CoMP transmission can be made based on, for example, a report of communication quality from the mobile station 230, a request for CoMP transmission from the mobile station 230, or the like.
- step S401 If it is determined in step S401 that CoMP transmission is to be executed (step S401: Yes), the macro base station 210 performs CoMP communication settings (step S402).
- the communication setting performed in step S402 is, for example, the advance setting 302 shown in FIGS. 3A to 3C.
- the macro base station 210 transmits user data to the small base stations 221 and 222 (step S403).
- the user data transmitted in step S403 is, for example, the user data 311 and 312 shown in FIGS. 3A to 3C.
- the macro base station 210 receives feedback from the mobile station 230 (step S404).
- the feedback received in step S404 is, for example, the feedbacks 321 and 322 shown in FIGS. 3A to 3C.
- the macro base station 210 transmits a control signal to the small base stations 221 and 222 (step S405).
- the control signals transmitted in step S405 are, for example, control signals 361 and 362.
- the macro base station 210 determines whether or not to perform CoMP resetting (step S406).
- the determination of whether or not to perform CoMP resetting can be made based on, for example, a report of communication quality from the mobile station 230, a request for CoMP transmission from the mobile station 230, or the like. In this case, for example, the feedback in step S404 can be used for reporting the communication quality from the mobile station 230. If it is determined that resetting is to be executed (step S406: Yes), the macro base station 210 returns to step S402.
- step S406 when it is determined not to perform resetting (step S406: No), the macro base station 210 determines whether or not to end the CoMP transmission (step S407).
- the determination as to whether or not to end CoMP transmission can be made based on, for example, a report of communication quality from the mobile station 230, a request for CoMP transmission from the mobile station 230, or the like. In this case, for example, the feedback in step S404 can be used for reporting the communication quality from the mobile station 230. If it is determined that the CoMP transmission is not terminated (step S407: No), the macro base station 210 returns to step S403.
- step S407 If it is determined in step S407 that CoMP transmission is to be terminated (step S407: Yes), the macro base station 210 cancels the communication setting performed in step S402 (step S408), and the series of processes is terminated.
- the macro base station 210 may also transmit a control signal to be transmitted to the small base stations 221 and 222 to the mobile station 230. Further, in step S405, the macro base station 210 determines whether or not to change the CoMP transmission radio resource from the previous time. If it is determined not to change, the macro base station 210 sends a control signal to the small base stations 221 and 222 and the mobile station 230. You may make it not transmit. As a result, the amount of communication can be reduced.
- FIG. 4B is a flowchart illustrating an example of processing by the small base station. Although the processing by the small base station 221 will be described, the processing by the small base station 222 is the same as the processing by the small base station 221.
- the small base station 221 executes, for example, each step shown in FIG. 4B.
- the small base station 221 determines whether or not to execute CoMP transmission (step S411), and waits until it is determined to execute CoMP transmission (step S411: No loop).
- the determination as to whether or not to perform CoMP transmission can be made based on an instruction from the macro base station 210, for example.
- step S411 If it is determined in step S411 that CoMP transmission is to be executed (step S411: Yes), the small base station 221 performs CoMP communication settings (step S412).
- the communication setting performed in step S412 is, for example, the pre-setting 302 shown in FIGS. 3A to 3C.
- the small base station 221 receives user data from the macro base station 210 (step S413).
- the user data received in step S413 is, for example, user data 311 and 312 shown in FIGS. 3A to 3C.
- the small base station 221 receives the feedback from the mobile station 230 (step S414).
- the feedback received in step S414 is, for example, the feedbacks 321 and 322 shown in FIGS. 3A to 3C.
- control signals to be CoMP transmitted in step S415 are control signals 361 and 362, for example.
- the small base station 221 determines whether or not to perform CoMP reconfiguration (step S416).
- the determination as to whether or not to perform CoMP reconfiguration can be made based on an instruction from the macro base station 210, for example.
- the small base station 221 returns to step S412.
- step S416 when it is determined not to perform resetting (step S416: No), the small base station 221 determines whether or not to end the CoMP transmission (step S417). The determination of whether or not to end the CoMP transmission can be performed based on an instruction from the macro base station 210, for example. When it is determined that the CoMP transmission is not terminated (step S417: No), the small base station 221 returns to step S413.
- step S417 If it is determined in step S417 that CoMP transmission is to be terminated (step S417: Yes), the small base station 221 cancels the communication setting performed in step S412 (step S418), and the series of processes is terminated.
- the small base station 221 may receive a response signal from the mobile station 230 with respect to the CoMP transmission in step S415, and may retransmit the user data based on the received response signal.
- the retransmission of user data can be performed based on the feedback from the mobile station 230 received in step S414, for example.
- FIG. 5 is a flowchart showing an example of processing by the mobile station.
- the mobile station 230 executes the steps shown in FIG. First, the mobile station 230 performs communication settings (step S501).
- the communication setting performed in step S501 is the pre-setting 302 shown in FIGS. 3A to 3C, for example.
- the mobile station 230 determines whether or not to execute CoMP reception (step S502). The determination as to whether or not to perform CoMP reception can be made based on an instruction from the macro base station 210 or the small base stations 221 and 222, for example. If it is determined that CoMP reception is to be performed (step S502: Yes), the mobile station 230 transmits feedback to the macro base station 210 and the small base stations 221 and 222 (step S503).
- the feedback transmitted in step S503 is, for example, the feedbacks 321, 322, 331, and 332 shown in FIGS. 3A to 3C.
- step S504 the mobile station 230 receives the control channel (step S504).
- the control channel received in step S504 is, for example, the control signals 371 and 372 shown in FIGS. 3A and 3B.
- the control channel received by step S504 may be PDCCH accompanying the user data 381 and 382 shown in FIG. 3C.
- the mobile station 230 receives diversity data of user data transmitted by the small base stations 221 and 222 by CoMP (step S505).
- the user data that is diversity-received in step S505 is, for example, user data 381 and 382 shown in FIGS. 3A to 3C.
- the mobile station 230 transmits a response signal (ACK or NACK) to the reception in step S505 to the main small base station among the small base stations 221 and 222 (step S506).
- the main small base station of the small base stations 221 and 222 is notified to the mobile station 230 by the macro base station 210 or the small base stations 221 and 222, for example.
- the response signal transmitted in step S506 is, for example, the response signals 391 and 392 shown in FIGS. 3A to 3C.
- the mobile station 230 determines whether or not to end communication (step S507).
- the determination as to whether or not to end the communication can be made based on, for example, a user operation of the small base station 221 or an instruction from a communication application in the small base station 221. If it is determined not to end the communication (step S507: No), the mobile station 230 returns to step S503. Alternatively, the mobile station 230 may return to step S502 and determine again whether to perform CoMP transmission. When it is determined that the communication is to be ended (step S507: Yes), the mobile station 230 ends a series of processes.
- the mobile station 230 transmits feedback to the serving base station (step S508).
- the serving base station is, for example, a serving base station (primary cell) to which the mobile station 230 among the macro base station 210 and the small base stations 221 and 222 is connected.
- the mobile station 230 receives a control channel from the serving base station (step S509).
- the mobile station 230 receives user data from the serving base station based on the control channel received in step S509 (step S510).
- the mobile station 230 transmits a response signal (ACK or NACK) to the reception at step S510 to the serving base station (step S511).
- ACK or NACK response signal
- the mobile station 230 determines whether or not to end communication (step S512). The determination as to whether or not to end the communication can be made based on, for example, a user operation of the small base station 221 or an instruction from a communication application in the small base station 221. If it is determined that the communication is not terminated (step S512: No), the mobile station 230 returns to step S508. Alternatively, the mobile station 230 may return to step S502 and determine again whether to perform CoMP transmission. When it is determined that the communication is to be ended (step S512: Yes), the mobile station 230 ends a series of processes.
- FIG. 6 is a diagram illustrating an example of each base station.
- Each of macro base station 210 and small base stations 221 and 222 can be realized by base station 600 shown in FIG. 6, for example.
- the base station 600 includes, for example, a wireless communication unit 610, a control unit 620, a storage unit 630, and a communication unit 640.
- the wireless communication unit 610 includes a wireless transmission unit 611 and a wireless reception unit 612. Each of these components is connected so that signals and data can be input and output in one direction or in both directions.
- the wireless transmission unit 611 transmits user data and control signals by wireless communication via an antenna.
- the wireless signal transmitted by the wireless transmission unit 611 can include arbitrary user data, control information, and the like (encoded or modulated).
- the wireless reception unit 612 receives user data and control signals by wireless communication via an antenna.
- the radio signal received by the radio reception unit 612 can include arbitrary user data, a control signal, and the like (encoded or modulated).
- the antenna may be common for transmission and reception.
- the control unit 620 outputs user data and control signals to be transmitted to other wireless stations to the wireless transmission unit 611. In addition, the control unit 620 acquires user data and control signals received by the wireless reception unit 612. The control unit 620 inputs and outputs user data, control information, programs, and the like with a storage unit 630 described later. In addition, the control unit 620 inputs and outputs user data and control signals that are transmitted to and received from other communication devices and the like with the communication unit 640 described later. In addition to these, the control unit 620 performs various controls in the base station 600.
- the storage unit 630 stores various information such as user data, control information, and programs.
- the communication unit 640 transmits / receives user data and control signals to / from other communication devices, for example, by wired signals.
- the control unit 111 of the control station 110 illustrated in FIG. 1 can be realized by the control unit 620, for example.
- the communication unit 112 of the control station 110 illustrated in FIG. 1 can be realized by the wireless communication unit 610 or the communication unit 640, for example.
- the control units 121a and 121b of the first radio stations 120a and 120b illustrated in FIG. 1 can be realized by the control unit 620, for example.
- the communication units 122a and 122b of the first radio stations 120a and 120b illustrated in FIG. 1 can be realized by the radio communication unit 610 and the communication unit 640, for example.
- FIG. 7 is a diagram illustrating an example of a mobile station.
- the mobile station 230 can be realized by, for example, the mobile station 700 shown in FIG.
- the mobile station 700 includes a wireless communication unit 710, a control unit 720, and a storage unit 730.
- the wireless communication unit 710 includes a wireless transmission unit 711 and a wireless reception unit 712. Each of these components is connected so that signals and data can be input and output in one direction or in both directions.
- the wireless transmission unit 711 transmits user data and control signals by wireless communication via an antenna.
- the wireless signal transmitted by the wireless transmission unit 711 can include arbitrary user data, control information, and the like (encoded or modulated).
- the wireless reception unit 712 receives user data and control signals by wireless communication via an antenna.
- the radio signal received by the radio reception unit 712 can include arbitrary user data, a control signal, and the like (encoded or modulated).
- the antenna may be common for transmission and reception.
- the control unit 720 outputs user data and control signals to be transmitted to other radio stations to the radio transmission unit 711. In addition, the control unit 720 acquires user data and control signals received by the wireless reception unit 712. The control unit 720 inputs and outputs user data, control information, programs, and the like with the storage unit 730 described later. In addition, the control unit 720 performs input / output of user data and control signals transmitted / received to / from other communication devices and the like with a communication unit described later. In addition to these, the control unit 720 performs various controls in the mobile station 700.
- the storage unit 730 stores various information such as user data, control information, and programs.
- the control unit 131 of the second radio station 130 illustrated in FIG. 1 can be realized by the control unit 720, for example.
- the communication unit 132 of the second wireless station 130 illustrated in FIG. 1 can be realized by the wireless communication unit 710, for example.
- FIG. 8 is a diagram illustrating an example of a hardware configuration of the base station.
- the base station 600 shown in FIG. 6 can be realized by, for example, the base station 800 shown in FIG.
- Base station 800 includes antenna 811, RF circuit 812, processor 813, memory 814, and network IF 815. These components are connected so that various signals and data can be input / output via a bus, for example.
- the antenna 811 includes a transmission antenna that transmits a radio signal and a reception antenna that receives a radio signal.
- the antenna 811 may be a shared antenna that transmits and receives radio signals.
- the RF circuit 812 performs RF (Radio Frequency: high frequency) processing on a signal received by the antenna 811 and a signal transmitted by the antenna 811.
- the RF processing includes, for example, frequency conversion between the baseband band and the RF band.
- the processor 813 is, for example, a CPU (Central Processing Unit) or a DSP (Digital Signal Processor).
- the processor 813 may be realized by a digital electronic circuit such as an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or an LSI (Large Scale Integration).
- ASIC Application Specific Integrated Circuit
- FPGA Field Programmable Gate Array
- LSI Large Scale Integration
- the memory 814 can be realized by a random access memory (RAM) such as SDRAM (Synchronous Dynamic Random Access Memory), a ROM (Read Only Memory), a flash memory, or the like.
- RAM random access memory
- SDRAM Serial Dynamic Random Access Memory
- ROM Read Only Memory
- flash memory or the like.
- the memory 814 stores user data, control information, programs, and the like, for example.
- the network IF 815 is a communication interface that performs communication with a network by, for example, a wired connection.
- the network IF 815 may include, for example, Xn interfaces 201 and 202 (for example, see FIG. 2A) for performing wired communication between base stations.
- the control unit 620 illustrated in FIG. 6 can be realized by, for example, the processor 813 and the memory 814.
- the storage unit 630 illustrated in FIG. 6 can be realized by the memory 814, for example.
- the communication unit 640 shown in FIG. 6 can be realized by a network IF 815, for example.
- FIG. 9 is a diagram illustrating an example of a hardware configuration of the mobile station.
- the mobile station 700 can be realized by, for example, the mobile station 900 shown in FIG.
- the mobile station 900 includes, for example, an antenna 911, an RF circuit 912, a processor 913, and a memory 914. These components are connected so that various signals and data can be input / output via a bus, for example.
- the antenna 911 includes a transmission antenna that transmits a radio signal and a reception antenna that receives a radio signal.
- the antenna 911 may be a shared antenna that transmits and receives radio signals.
- the RF circuit 912 performs RF processing on a signal received by the antenna 911 and a signal transmitted by the antenna 911.
- the RF processing includes, for example, frequency conversion between the baseband band and the RF band.
- the processor 913 is, for example, a CPU or a DSP.
- the processor 913 may be realized by a digital electronic circuit such as an ASIC, FPGA, LSI, or the like.
- the memory 914 can be realized by, for example, a RAM such as SDRAM, a ROM, a flash memory, or the like.
- the memory 914 stores user data, control information, programs, and the like, for example.
- the control unit 720 illustrated in FIG. 7 can be realized by, for example, the processor 913, the memory 914, and the like.
- the storage unit 730 illustrated in FIG. 7 can be realized by the memory 914, for example.
- the small base stations 221 and 222 can improve the reception characteristics of the mobile station 230 in the ABS by performing coordinated transmission in the ABS. For this reason, even if many specific periods are set in the communication system 200, the throughput can be improved.
- Embodiment 3 In Embodiment 3, retransmission by small base stations 221 and 222 will be described.
- the small base stations 221 and 222 may perform retransmission only when one of the small base stations 221 and 222 performs retransmission when an error occurs in CoMP transmission in the ABS.
- a case will be described where, when an error occurs in CoMP transmission in the ABS, retransmission is performed by the small base station 221 and the small base station 222 does not perform retransmission.
- FIG. 10 is a diagram illustrating an example of the operation of each small base station according to each reception result of the response signal.
- a table 1000 in FIG. 10 shows cases 1001 to 1004 related to retransmission of CoMP transmission in the ABS.
- “Small 1” in the table 1000 indicates the small base station 221, and “Small 2” indicates the small base station 222.
- Cases 1001 and 1002 indicate cases where user data is normally received by the mobile station 230 and the mobile station 230 transmits ACK as a response signal.
- Cases 1003 and 1004 indicate a case where user data is not normally received by the mobile station 230 and the mobile station 230 transmits NACK as a response signal.
- Case 1001 shows a case where the small base station 221 has received ACK from the mobile station 230 normally, but the small base station 222 has received ACK from the mobile station 230 by mistake as NACK. In this case, the small base station 221 receives the ACK and discards the corresponding data. In addition, the small base station 222 discards the corresponding data because it has received NACK but does not retransmit it.
- Case 1002 shows a case where the small base station 221 receives the ACK from the mobile station 230 by mistake as a NACK, but the small base station 222 receives the ACK from the mobile station 230 normally.
- the small base station 221 since the small base station 221 receives the NACK, the small base station 221 HARQ retransmits the corresponding data. Since the user data by this HARQ retransmission has already been normally received by the mobile station 230, for example, the mobile station 230 discards it. For this reason, this retransmission may be wasted. Further, since the small base station 222 receives the ACK, the small base station 222 discards the corresponding data.
- Case 1003 shows a case where the small base station 221 has normally received the NACK from the mobile station 230, but the small base station 222 has received the NACK from the mobile station 230 by mistake as an ACK. In this case, since the small base station 221 receives the NACK, the small base station 221 HARQ retransmits the corresponding data. Further, since the small base station 222 receives the ACK, the small base station 222 discards the corresponding data.
- Case 1004 shows a case where the small base station 221 received the NACK from the mobile station 230 by mistake as an ACK, but the small base station 222 received the NACK from the mobile station 230 normally.
- the small base station 221 receives the ACK and discards the corresponding data.
- recovery is performed by retransmission by an upper layer, for example.
- the upper layer is, for example, an RLC (Radio Link Control: radio link control) layer.
- the retransmission by the higher layer will be described later (see, for example, FIG. 11).
- the small base station 222 discards the corresponding data because it has received NACK but does not retransmit it.
- the small base stations 221 and 222 perform CoMP transmission in the initial transmission of user data in the ABS, while the small base station 221 performs retransmission of the user data transmitted by CoMP, and the small base station 222 performs retransmission. Absent. This retransmission can be performed at any individual timing, not limited to ABS. For example, when receiving a NACK from the mobile station 230 for CoMP transmission, the small base station 221 retransmits user data to the mobile station 230 at a timing determined by the small base station 221.
- CoMP transmission is performed by the small base stations 221 and 222 also for retransmission, it is necessary to perform processing such as exchanging control signals in order to determine the retransmission timing in the small base stations 221 and 222. This leads to an increase in quantity.
- the mobile station 230 receives the retransmission data at the timing of each of the small base stations 221 and 222, so that an increase in communication amount and retransmission control are performed. Leads to an increase in the amount of processing.
- CoMP transmission is performed by the small base stations 221 and 222 for the initial transmission, and only the small base station 221 performs the retransmission related to CoMP transmission. The amount can be reduced.
- the small base station 222 may immediately discard user data transmitted by CoMP transmission.
- the small base station that performs retransmission among the small base stations 221 and 222 can be determined by an arbitrary method. it can.
- the macro base station 210 may determine a small base station that performs retransmission among the small base stations 221 and 222 and notify the small base stations 221 and 222 of the small base stations.
- the small base stations 221 and 222 may determine a small base station that performs retransmission among the small base stations 221 and 222 by the small base stations 221 and 222 communicating with each other.
- the small base station to be retransmitted among the small base stations 221 and 222 may be notified from the macro base station 210 to the mobile station 230, or from at least one of the small base stations 221 and 222 to the mobile station 230. You may be notified.
- FIG. 11 is a diagram illustrating an example of retransmission by an upper layer.
- the same parts as those shown in FIG. 3A are denoted by the same reference numerals, and the description thereof is omitted.
- the small base stations 221 and 222 and the mobile station 230 perform wireless communication by processing of each layer of PDCP, RLC, MAC (Media Access Control), and PHY (physical layer), respectively. .
- packet # 1 is transmitted from the macro base station 210 to the small base stations 221 and 222, and the small base stations 221 and 222 perform CoMP transmission of the packet # 1 to the mobile station 230 in the ABS.
- the mobile station 230 cannot normally receive the packet # 1 and transmits a NACK in the HARQ 1101.
- the small base station 222 has normally received a NACK from the mobile station 230, but the small base station 221 has erroneously received a NACK from the mobile station 230 as an ACK.
- packet # 1 is not retransmitted even if NACK is received.
- the small base station 221 since the small base station 221 has received the ACK, it does not retransmit the packet # 1.
- the mobile station 230 since the mobile station 230 does not retransmit the packet # 1 even though the NACK is transmitted, the mobile station 230 sends an unreceived report 1102 of the packet # 1 to the small base station 221 by the RLC layer processing. Do. In the RLC layer, POLL / STATUS type retransmission processing is performed on the transmission / reception side, and the transmission / reception state can be synchronized by exchanging these pieces of information.
- the unreceived report 1102 can be performed by, for example, RLC STATUS REPORT.
- the small base station 221 performs retransmission 1103 of the packet # 1 by processing of the RLC layer. Thereby, the mobile station 230 can receive packet # 1. Also for packet # 2 and subsequent packets after packet # 1, the small base stations 221 and 222 perform CoMP transmission to the mobile station 230 at the ABS in the initial transmission, and only the small base station 221 performs retransmission.
- CoMP transmission is performed by the small base stations 221 and 222 for the first transmission, and only the small base station 221 performs the retransmission related to CoMP transmission. Can be reduced.
- the wireless communication method, the wireless station, and the control station throughput can be improved.
- 100 wireless communication system 110 control station 111, 121a, 121b, 131, 620, 720 control unit 112, 122a, 122b, 132, 640 communication unit 120a, 120b first wireless station 130 second wireless station 200 communication system 201, 202 Xn Interface 210, 240 Macro base station 210a, 240a Macro cell 221, 222, 251, 252 Small base station 221a, 222a, 222b, 251a, 252a Small cell 230, 700, 900 Mobile station 301 Delimiter 302 Pre-setting 303 Control area 304 Data area 311, 312, 381, 382 User data 321, 322, 331, 332 Feedback 341, 342, 351 to 354 ABS 361, 362, 371, 372 Control signal 391, 392 Response signal 600, 800 Base station 610, 710 Wireless communication unit 611, 711 Wireless transmission unit 612, 712 Wireless reception unit 630, 730 Storage unit 811, 911 Antenna 812, 912 RF Circuit 813, 913 Processor 814
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Abstract
A radio communication system (100) includes: a second radio station (130) that can communicate with a plurality of first radio stations (120a, 120b); and a control station (110) that controls the first radio stations (120a, 120b). The plurality of first radio stations (120a, 120b) cooperate to transmit, to the second radio station (130), data addressed thereto during a particular time period in which radio transmissions are performed by use of a lower electric power than during the other time periods. The second radio station (130) receives the data addressed thereto and transmitted via the cooperative communication performed by the plurality of first radio stations (120a, 120b).
Description
本発明は、無線通信システム、無線通信方法、無線局および制御局に関する。
The present invention relates to a wireless communication system, a wireless communication method, a wireless station, and a control station.
従来、移動局が基地局を介して通信を行う移動体通信において、複数のマクロ基地局の間の干渉を制御するICIC(Inter Cell Interference Coordination:セル間干渉制御)が知られている。また、マクロ基地局とスモール基地局との間の干渉を制御するFeICIC(Further enhanced ICIC)が知られている。
Conventionally, in mobile communication in which a mobile station communicates via a base station, ICIC (Inter Cell Interference Coordination) that controls interference between a plurality of macro base stations is known. Further, FeICIC (Further enhanced ICIC) that controls interference between a macro base station and a small base station is known.
また、3G(3rd Generation:第3世代移動通信システム)において、LTE(Long Term Evolution)-Advancedをさらに拡張したRelease11が検討されている(たとえば、下記非特許文献1~10参照。)。Release11においては、たとえば複数の基地局が協調して通信を行うことによりセル端のパフォーマンスを上げるCoMP(Coordinated Multiple-Point transmission and reception:多地点協調通信)が検討されている。
In addition, in 11G (3rd Generation: 3rd generation mobile communication system), Release 11 that further expands LTE (Long Term Evolution) -Advanced is being studied (for example, see Non-Patent Documents 1 to 10 below). In Release 11, for example, CoMP (Coordinated Multiple-Point transmission and reception: multipoint coordinated communication) is being studied in which a plurality of base stations perform communication in cooperation to improve cell edge performance.
また、複数の基地局が協調してHARQ(Hybrid Automatic Repeat Request:ハイブリッド自動再送要求)を行う協調的HARQが知られている(たとえば、下記特許文献1参照。)。
Also, cooperative HARQ in which a plurality of base stations perform HARQ (Hybrid Automatic Repeat Request) in a coordinated manner is known (see, for example, Patent Document 1 below).
しかしながら、上述した従来技術においては、多くのセルが設置されると、セルのエッジ領域が増えるため、干渉を低減するために一部のセルの送信電力を抑える期間が多く設定される。このため、無線通信におけるスループットが低下する場合がある。
However, in the above-described prior art, when many cells are installed, the edge area of the cell increases, so that a period for suppressing the transmission power of some cells is set to reduce interference. For this reason, the throughput in wireless communication may decrease.
1つの側面では、本発明は、スループットの向上を図ることができる無線通信システム、無線通信方法、無線局および制御局を提供することを目的とする。
In one aspect, an object of the present invention is to provide a wireless communication system, a wireless communication method, a wireless station, and a control station that can improve throughput.
上述した課題を解決し、目的を達成するため、本発明の一側面によれば、複数の第1無線局との通信が可能な第2無線局と、前記第1無線局を制御する制御局と、を含む無線通信システムにおいて、前記制御局が、前記複数の第1無線局が協調して前記第2無線局と通信を行う協調通信の無線リソースを前記第2無線局に通知し、他の期間より低い電力によって無線送信を行う特定期間において、前記複数の第1無線局が協調して前記無線リソースを使用し前記第2無線局宛のデータを前記第2無線局に送信する前記協調通信を行い、前記第2無線局が、前記無線リソース上で前記協調通信によって送信された自局宛のデータを受信する無線通信システム、無線通信方法、無線局および制御局が提案される。
In order to solve the above-described problems and achieve the object, according to one aspect of the present invention, a second radio station capable of communicating with a plurality of first radio stations, and a control station that controls the first radio station And the control station notifies the second radio station of radio resources for cooperative communication in which the plurality of first radio stations cooperate with each other to communicate with the second radio station, and so on. The cooperation in which the plurality of first wireless stations cooperate to use the wireless resource and transmit data addressed to the second wireless station to the second wireless station in a specific period in which wireless transmission is performed with lower power than the period of A wireless communication system, a wireless communication method, a wireless station, and a control station are proposed in which communication is performed and the second wireless station receives data addressed to itself transmitted by the cooperative communication on the wireless resource.
本発明の一側面によれば、スループットの向上を図ることができるという効果を奏する。
According to one aspect of the present invention, there is an effect that throughput can be improved.
以下に図面を参照して、本発明にかかる無線通信システム、無線通信方法、無線局および制御局の実施の形態を詳細に説明する。
Hereinafter, embodiments of a wireless communication system, a wireless communication method, a wireless station, and a control station according to the present invention will be described in detail with reference to the drawings.
(実施の形態1)
図1は、実施の形態1にかかる無線通信システムの一例を示す図である。図1に示すように、実施の形態1にかかる無線通信システム100は、制御局110と、第1無線局120a,120bと、第2無線局130と、を含む。第2無線局130は、第1無線局120a,120bとの無線通信が可能な無線局である。 (Embodiment 1)
FIG. 1 is a diagram of an example of a wireless communication system according to the first embodiment. As illustrated in FIG. 1, theradio communication system 100 according to the first embodiment includes a control station 110, first radio stations 120a and 120b, and a second radio station 130. The second radio station 130 is a radio station capable of radio communication with the first radio stations 120a and 120b.
図1は、実施の形態1にかかる無線通信システムの一例を示す図である。図1に示すように、実施の形態1にかかる無線通信システム100は、制御局110と、第1無線局120a,120bと、第2無線局130と、を含む。第2無線局130は、第1無線局120a,120bとの無線通信が可能な無線局である。 (Embodiment 1)
FIG. 1 is a diagram of an example of a wireless communication system according to the first embodiment. As illustrated in FIG. 1, the
制御局110は、第1無線局120a,120bを制御する制御局である。制御局110は、たとえば有線によって第1無線局120a,120bと接続されている。また、制御局110は、無線によって第1無線局120a,120bと通信可能であってもよい。
The control station 110 is a control station that controls the first radio stations 120a and 120b. The control station 110 is connected to the first radio stations 120a and 120b, for example, by wire. Further, the control station 110 may be able to communicate with the first radio stations 120a and 120b by radio.
<制御局>
制御局110は、制御部111と、通信部112と、を備える。制御部111は、第1無線局120a,120bが協調して第2無線局130と通信を行う協調通信を制御する。通信部112は、たとえば、第2無線局130との間で無線通信を行う。また、通信部112は、第1無線局120a,120bが協調して第2無線局130と通信を行う協調通信の無線リソースを第2無線局130に通知する。無線リソースには、たとえば周波数リソースが含まれる。また、無線リソースには時間リソースが含まれてもよい。また、通信部112は、第1無線局120a,120bが協調して第2無線局130と通信を行う協調通信の無線リソースを第1無線局120a,120bに通知してもよい。 <Control station>
Thecontrol station 110 includes a control unit 111 and a communication unit 112. The control unit 111 controls cooperative communication in which the first wireless stations 120a and 120b communicate with the second wireless station 130 in cooperation. For example, the communication unit 112 performs wireless communication with the second wireless station 130. In addition, the communication unit 112 notifies the second radio station 130 of radio resources for cooperative communication in which the first radio stations 120a and 120b cooperate to communicate with the second radio station 130. Radio resources include, for example, frequency resources. Further, the radio resource may include a time resource. Further, the communication unit 112 may notify the first radio stations 120a and 120b of radio resources for cooperative communication in which the first radio stations 120a and 120b cooperate to communicate with the second radio station 130.
制御局110は、制御部111と、通信部112と、を備える。制御部111は、第1無線局120a,120bが協調して第2無線局130と通信を行う協調通信を制御する。通信部112は、たとえば、第2無線局130との間で無線通信を行う。また、通信部112は、第1無線局120a,120bが協調して第2無線局130と通信を行う協調通信の無線リソースを第2無線局130に通知する。無線リソースには、たとえば周波数リソースが含まれる。また、無線リソースには時間リソースが含まれてもよい。また、通信部112は、第1無線局120a,120bが協調して第2無線局130と通信を行う協調通信の無線リソースを第1無線局120a,120bに通知してもよい。 <Control station>
The
<第1無線局>
第1無線局120aは、制御部121aと、通信部122aと、を備える。制御部121aは、第1無線局120a,120bが協調して第2無線局130と通信を行う協調通信を制御する。通信部122aは、第1無線局120a,120bのうちの自局(たとえば第1無線局120a)と異なる第1無線局(たとえば第1無線局120b)と協調して、第2無線局130宛のデータを第2無線局130に送信する協調通信を行う。通信部122aによる協調通信は、制御部121aによって制御される。 <First radio station>
Thefirst radio station 120a includes a control unit 121a and a communication unit 122a. The control unit 121a controls cooperative communication in which the first wireless stations 120a and 120b communicate with the second wireless station 130 in cooperation. The communication unit 122a is addressed to the second radio station 130 in cooperation with a first radio station (for example, the first radio station 120b) different from the own station (for example, the first radio station 120a) of the first radio stations 120a and 120b. The cooperative communication for transmitting the data to the second radio station 130 is performed. The cooperative communication by the communication unit 122a is controlled by the control unit 121a.
第1無線局120aは、制御部121aと、通信部122aと、を備える。制御部121aは、第1無線局120a,120bが協調して第2無線局130と通信を行う協調通信を制御する。通信部122aは、第1無線局120a,120bのうちの自局(たとえば第1無線局120a)と異なる第1無線局(たとえば第1無線局120b)と協調して、第2無線局130宛のデータを第2無線局130に送信する協調通信を行う。通信部122aによる協調通信は、制御部121aによって制御される。 <First radio station>
The
また、通信部122aは、他の期間より低い電力によって無線送信を行う特定期間において協調通信を行う。なお、「より低い電力」とは、ある無線チャネル上の送信を一切行わない場合も含む。たとえば、通信部122aは、第2無線局130を含む他の無線局に対して、ある第1期間においては第1送信電力で無線送信を行い、第1期間と異なる第2期間(特定期間)においては第1送信電力より低い第2送信電力で無線送信を行う。そして、たとえば、通信部122aは、第2期間においては他の第1無線局との協調通信によって第2無線局130宛のデータを第2無線局130に送信する。
In addition, the communication unit 122a performs cooperative communication in a specific period in which wireless transmission is performed with lower power than other periods. Note that “lower power” includes a case where transmission on a certain radio channel is not performed at all. For example, the communication unit 122a performs wireless transmission with a first transmission power in a certain first period to other wireless stations including the second wireless station 130, and a second period (specific period) different from the first period. , Wireless transmission is performed with a second transmission power lower than the first transmission power. For example, the communication unit 122a transmits data addressed to the second radio station 130 to the second radio station 130 by cooperative communication with another first radio station in the second period.
第1無線局120bは、制御部121bと、通信部122bと、を備える。制御部121bおよび通信部122bは、それぞれ第1無線局120aの制御部121aおよび通信部122aと同様である。すなわち、第1無線局120aの制御部121aと、第1無線局120bの制御部121bと、が協調して第2無線局130と通信を行う協調通信を行う。
The first wireless station 120b includes a control unit 121b and a communication unit 122b. The control unit 121b and the communication unit 122b are the same as the control unit 121a and the communication unit 122a of the first radio station 120a, respectively. That is, the control unit 121a of the first radio station 120a and the control unit 121b of the first radio station 120b perform cooperative communication in which communication with the second radio station 130 is performed in cooperation.
<第2無線局>
第2無線局130は、制御部131と、通信部132と、を備える。制御部131は、第1無線局120a,120bが協調する協調通信による、第1無線局120a,120bと第2無線局130との通信を制御する。通信部132は、第1無線局120a,120bが協調して送信した自局宛のデータを受信する。 <Second radio station>
Thesecond radio station 130 includes a control unit 131 and a communication unit 132. The control unit 131 controls communication between the first radio stations 120a and 120b and the second radio station 130 through cooperative communication in which the first radio stations 120a and 120b cooperate. The communication unit 132 receives data addressed to the local station, which is transmitted in cooperation by the first wireless stations 120a and 120b.
第2無線局130は、制御部131と、通信部132と、を備える。制御部131は、第1無線局120a,120bが協調する協調通信による、第1無線局120a,120bと第2無線局130との通信を制御する。通信部132は、第1無線局120a,120bが協調して送信した自局宛のデータを受信する。 <Second radio station>
The
このように、実施の形態1によれば、第1無線局120a,120bが、低電力送信となる特定期間において協調送信を行うことで、特定期間における第2無線局130の受信特性を向上させることができる。このため、無線通信システム100において特定期間が多数設定されても、スループットの向上を図ることができる。
As described above, according to Embodiment 1, the first wireless stations 120a and 120b perform coordinated transmission in a specific period in which low power transmission is performed, thereby improving the reception characteristics of the second wireless station 130 in the specific period. be able to. For this reason, even if many specific periods are set in the wireless communication system 100, the throughput can be improved.
<各無線局の具体例>
たとえば、制御局110は、無線通信が可能なセルを形成する基地局とすることができる。この場合に、第1無線局120a,120bのそれぞれは、制御局110のセル内に位置する基地局とすることができる。また、第2無線局130は、たとえば移動局とすることができる。この場合に、第2無線局130は、第1無線局120a,120bに加えて制御局110とも無線通信が可能であってもよい。さらに、制御局110および第1無線局120aまたは120bと同時に無線通信が可能であってもよい。 <Specific examples of each radio station>
For example, thecontrol station 110 can be a base station that forms a cell capable of wireless communication. In this case, each of the first radio stations 120 a and 120 b can be a base station located in the cell of the control station 110. The second radio station 130 can be a mobile station, for example. In this case, the second wireless station 130 may be capable of wireless communication with the control station 110 in addition to the first wireless stations 120a and 120b. Further, wireless communication may be possible simultaneously with the control station 110 and the first wireless station 120a or 120b.
たとえば、制御局110は、無線通信が可能なセルを形成する基地局とすることができる。この場合に、第1無線局120a,120bのそれぞれは、制御局110のセル内に位置する基地局とすることができる。また、第2無線局130は、たとえば移動局とすることができる。この場合に、第2無線局130は、第1無線局120a,120bに加えて制御局110とも無線通信が可能であってもよい。さらに、制御局110および第1無線局120aまたは120bと同時に無線通信が可能であってもよい。 <Specific examples of each radio station>
For example, the
制御局110に相当する基地局としては、たとえばマクロ基地局を挙げることができる。また、第1無線局120a,120bに相当する基地局には、たとえばスモール基地局を挙げることができる。ただし、各基地局の適用先はこれらに限らず、たとえば第1無線局120a,120bに相当する基地局には、フェムト基地局やピコ基地局など、より大規模なセルからの干渉を受ける各種のビクティムセルを形成する基地局などを適用することができる。
Examples of base stations corresponding to the control station 110 include macro base stations. In addition, examples of base stations corresponding to the first radio stations 120a and 120b include small base stations. However, the application destination of each base station is not limited to these. For example, base stations corresponding to the first radio stations 120a and 120b receive various interferences from larger cells such as femto base stations and pico base stations. A base station that forms the victim cell can be applied.
<第1無線局による無線リソースの非通知>
第1無線局120aの通信部122aは、第1無線局120bとの協調通信において、協調通信の無線リソースを第2無線局130に通知せずに第2無線局130宛のデータを送信してもよい。同様に、第1無線局120bの通信部122bは、第1無線局120aとの協調通信において、協調通信の無線リソースを第2無線局130に通知せずに第2無線局130宛のデータを送信してもよい。 <Non-notification of radio resources by the first radio station>
Thecommunication unit 122a of the first wireless station 120a transmits data addressed to the second wireless station 130 without notifying the second wireless station 130 of the wireless resources of the cooperative communication in the cooperative communication with the first wireless station 120b. Also good. Similarly, the communication unit 122b of the first wireless station 120b transmits data addressed to the second wireless station 130 without notifying the second wireless station 130 of the wireless resources of the cooperative communication in the cooperative communication with the first wireless station 120a. You may send it.
第1無線局120aの通信部122aは、第1無線局120bとの協調通信において、協調通信の無線リソースを第2無線局130に通知せずに第2無線局130宛のデータを送信してもよい。同様に、第1無線局120bの通信部122bは、第1無線局120aとの協調通信において、協調通信の無線リソースを第2無線局130に通知せずに第2無線局130宛のデータを送信してもよい。 <Non-notification of radio resources by the first radio station>
The
この場合も、第2無線局130の通信部132は、第1無線局120a,120bが協調して送信する第2無線局130宛のデータを、制御局110から通知された無線リソース上で受信することができる。これにより、第1無線局120a,120bと第2無線局130との間の通信量を低減することができる。
Also in this case, the communication unit 132 of the second radio station 130 receives the data addressed to the second radio station 130 transmitted in cooperation by the first radio stations 120a and 120b on the radio resource notified from the control station 110. can do. Thereby, the communication amount between the 1st radio stations 120a and 120b and the 2nd radio station 130 can be reduced.
<無線リソースの無線信号による通知>
制御局110の通信部112は、第1無線局120a,120bによる協調通信の無線リソースを無線信号によって第2無線局130に通知してもよい。これにより、たとえば制御局110と無線局120a,120bとの間の有線ネットワークを介した通知に比べて、協調通信の無線リソースを第2無線局130に短時間で通知することができる。このため、制御局110による協調通信の無線リソースの決定結果を迅速に反映させ、通信品質の向上を図ることができる。 <Notification by radio signal of radio resource>
Thecommunication unit 112 of the control station 110 may notify the second radio station 130 of radio resources for cooperative communication by the first radio stations 120a and 120b by radio signals. Thereby, for example, compared with the notification via the wired network between the control station 110 and the radio stations 120a and 120b, the radio resource of the cooperative communication can be notified to the second radio station 130 in a short time. For this reason, the determination result of the radio resource of the cooperative communication by the control station 110 can be reflected quickly, and the communication quality can be improved.
制御局110の通信部112は、第1無線局120a,120bによる協調通信の無線リソースを無線信号によって第2無線局130に通知してもよい。これにより、たとえば制御局110と無線局120a,120bとの間の有線ネットワークを介した通知に比べて、協調通信の無線リソースを第2無線局130に短時間で通知することができる。このため、制御局110による協調通信の無線リソースの決定結果を迅速に反映させ、通信品質の向上を図ることができる。 <Notification by radio signal of radio resource>
The
<再送>
第1無線局120a,120bによる協調通信において第2無線局130が第2無線局130宛のデータを正常に受信できなかった場合の再送について説明する。この場合は、第2無線局130宛のデータの再送を、第1無線局120a,120bのうちのいずれかの第1無線局が行い、第1無線局120a,120bのうちの他の第1無線局は行わないようにしてもよい。 <Resend>
The retransmission when thesecond wireless station 130 cannot normally receive the data addressed to the second wireless station 130 in the cooperative communication by the first wireless stations 120a and 120b will be described. In this case, retransmission of data addressed to the second wireless station 130 is performed by one of the first wireless stations 120a and 120b, and the other first of the first wireless stations 120a and 120b. The radio station may not be performed.
第1無線局120a,120bによる協調通信において第2無線局130が第2無線局130宛のデータを正常に受信できなかった場合の再送について説明する。この場合は、第2無線局130宛のデータの再送を、第1無線局120a,120bのうちのいずれかの第1無線局が行い、第1無線局120a,120bのうちの他の第1無線局は行わないようにしてもよい。 <Resend>
The retransmission when the
すなわち、第2無線局130への初回送信においては第1無線局120a,120bによる協調通信を行うが、第2無線局130の再送については第1無線局120a,120bのうちのいずれかの第1無線局によってのみ再送を行う。これにより、第1無線局120a,120bの間の協調制御を行わなくても再送を行うことができるため、再送制御の処理量の低減を図ることができる。
That is, in the initial transmission to the second radio station 130, cooperative communication by the first radio stations 120a and 120b is performed, but for the retransmission of the second radio station 130, any one of the first radio stations 120a and 120b. Retransmission is performed only by one radio station. Thereby, since retransmission can be performed without performing cooperative control between the first radio stations 120a and 120b, the amount of retransmission control can be reduced.
<無線リソースの通知回数の低減>
制御局110の通信部112は、第1無線局120a,120bによる協調通信の無線リソースを第2無線局130に通知した後に、該協調通信の無線リソースを変更する場合にのみ、該協調通信の無線リソースを第2無線局130に通知するようにしてもよい。この場合は、第2無線局130の通信部132は、制御局110から最後に通知された無線リソース上で自局宛のデータを受信することができる。これにより、たとえば無線リソースの変更の有無に関わらず繰り返し無線リソースを通知する場合に比べて、制御局110と第2無線局130との間の通信量を低減することができる。 <Reduction in the number of radio resource notifications>
Thecommunication unit 112 of the control station 110 notifies the second radio station 130 of the radio resources for cooperative communication by the first radio stations 120a and 120b, and then only changes the radio resources for the coordinated communication. The radio resource may be notified to the second radio station 130. In this case, the communication unit 132 of the second radio station 130 can receive data addressed to the own station on the radio resource notified last from the control station 110. Thereby, for example, the communication amount between the control station 110 and the second radio station 130 can be reduced as compared with the case where the radio resource is repeatedly notified regardless of whether or not the radio resource is changed.
制御局110の通信部112は、第1無線局120a,120bによる協調通信の無線リソースを第2無線局130に通知した後に、該協調通信の無線リソースを変更する場合にのみ、該協調通信の無線リソースを第2無線局130に通知するようにしてもよい。この場合は、第2無線局130の通信部132は、制御局110から最後に通知された無線リソース上で自局宛のデータを受信することができる。これにより、たとえば無線リソースの変更の有無に関わらず繰り返し無線リソースを通知する場合に比べて、制御局110と第2無線局130との間の通信量を低減することができる。 <Reduction in the number of radio resource notifications>
The
<特定期間>
第1無線局120a,120bにおいて他の期間より低い電力によって無線送信を行う特定期間は、たとえば、第1無線局120a,120bに共通して設定されたABS(Almost Blank Subframe)である。ただし、特定期間には、ABSに限らず各種の期間を適用することができる。また、特定期間の時間単位もサブフレームに限らず各種の時間単位(たとえば無線フレームやスロット)とすることができる。 <Specific period>
The specific period during which radio transmission is performed with lower power than other periods in the first radio stations 120a and 120b is, for example, an ABS (Almost Blank Subframe) set in common with the first radio stations 120a and 120b. However, not only ABS but various periods can be applied to the specific period. In addition, the time unit of the specific period is not limited to a subframe, and can be various time units (for example, a radio frame or a slot).
第1無線局120a,120bにおいて他の期間より低い電力によって無線送信を行う特定期間は、たとえば、第1無線局120a,120bに共通して設定されたABS(Almost Blank Subframe)である。ただし、特定期間には、ABSに限らず各種の期間を適用することができる。また、特定期間の時間単位もサブフレームに限らず各種の時間単位(たとえば無線フレームやスロット)とすることができる。 <Specific period>
The specific period during which radio transmission is performed with lower power than other periods in the
<協調通信>
第1無線局120a,120bが協調して第2無線局130と通信を行う協調通信には、たとえばCoMPを用いることができる。ただし、協調通信には、CoMPに限らず各種方式の協調通信を用いることができる。 <Collaborative communication>
For example, CoMP can be used for cooperative communication in which the first wireless stations 120a and 120b communicate with the second wireless station 130 in cooperation. However, cooperative communication is not limited to CoMP, and various types of cooperative communication can be used.
第1無線局120a,120bが協調して第2無線局130と通信を行う協調通信には、たとえばCoMPを用いることができる。ただし、協調通信には、CoMPに限らず各種方式の協調通信を用いることができる。 <Collaborative communication>
For example, CoMP can be used for cooperative communication in which the
<変形例>
無線通信システム100が第1無線局として第1無線局120a,120bを含む場合について説明したが、無線通信システム100が3つ以上の第1無線局を含み、3つ以上の第1無線局が協調して第2無線局130との無線通信を行う構成としてもよい。 <Modification>
Although the case where thewireless communication system 100 includes the first wireless stations 120a and 120b as the first wireless stations has been described, the wireless communication system 100 includes three or more first wireless stations, and the three or more first wireless stations include The wireless communication with the second wireless station 130 may be performed in cooperation.
無線通信システム100が第1無線局として第1無線局120a,120bを含む場合について説明したが、無線通信システム100が3つ以上の第1無線局を含み、3つ以上の第1無線局が協調して第2無線局130との無線通信を行う構成としてもよい。 <Modification>
Although the case where the
(実施の形態2)
(実施の形態2にかかる通信システム)
図2Aは、実施の形態2にかかる通信システムの一例を示す図である。図2Aに示すように、実施の形態2にかかる通信システム200は、マクロ基地局210と、スモール基地局221,222と、移動局230と、を含む。通信システム200は、一例としては、LTEやLTE-Advancedを適用した無線通信システムである。 (Embodiment 2)
(Communication system according to Embodiment 2)
FIG. 2A is a diagram illustrating an example of a communication system according to the second embodiment. As illustrated in FIG. 2A, thecommunication system 200 according to the second embodiment includes a macro base station 210, small base stations 221, 222, and a mobile station 230. As an example, the communication system 200 is a wireless communication system to which LTE or LTE-Advanced is applied.
(実施の形態2にかかる通信システム)
図2Aは、実施の形態2にかかる通信システムの一例を示す図である。図2Aに示すように、実施の形態2にかかる通信システム200は、マクロ基地局210と、スモール基地局221,222と、移動局230と、を含む。通信システム200は、一例としては、LTEやLTE-Advancedを適用した無線通信システムである。 (Embodiment 2)
(Communication system according to Embodiment 2)
FIG. 2A is a diagram illustrating an example of a communication system according to the second embodiment. As illustrated in FIG. 2A, the
図1に示した無線通信システム100は、たとえば通信システム200によって実現することができる。図1に示した制御局110は、たとえばマクロ基地局210によって実現することができる。図1に示した第1無線局120a,120bは、たとえばスモール基地局221,222によって実現することができる。図1に示した第2無線局130は、たとえば移動局230によって実現することができる。
1 can be realized by the communication system 200, for example. The control station 110 shown in FIG. 1 can be realized by the macro base station 210, for example. The first radio stations 120a and 120b shown in FIG. 1 can be realized by small base stations 221 and 222, for example. The second radio station 130 shown in FIG. 1 can be realized by the mobile station 230, for example.
マクロセル210aは、マクロ基地局210の無線通信範囲(セル)である。スモールセル221aは、スモール基地局221の無線通信範囲(セル)である。スモールセル222aは、スモール基地局222の無線通信範囲(セル)である。図2Aに示す例では、スモール基地局221,222はマクロセル210aに位置している。
The macro cell 210a is a wireless communication range (cell) of the macro base station 210. The small cell 221a is a wireless communication range (cell) of the small base station 221. The small cell 222 a is a wireless communication range (cell) of the small base station 222. In the example shown in FIG. 2A, the small base stations 221 and 222 are located in the macro cell 210a.
移動局230は、基地局との間で無線通信が可能なUE(User Equipment:ユーザ端末)である。図2Aに示す例では、移動局230は、スモールセル221a,222aの重複部分に位置しており、スモール基地局221,222との間で無線通信が可能である。また、移動局230は、マクロセル210aにも位置しているため、マクロ基地局210との間でも無線通信が可能である。
The mobile station 230 is a UE (User Equipment: user terminal) capable of wireless communication with a base station. In the example shown in FIG. 2A, the mobile station 230 is located in an overlapping portion of the small cells 221a and 222a, and can perform wireless communication with the small base stations 221 and 222. Further, since the mobile station 230 is also located in the macro cell 210a, wireless communication is possible with the macro base station 210.
通信システム200では、マクロ基地局210とスモール基地局221,222との間の干渉を制御するFeICICが行われる。たとえば、通信システム200では、低電力送信を行うことが要求されるサブフレームであるABSが設定される。
In the communication system 200, FeICIC for controlling interference between the macro base station 210 and the small base stations 221 and 222 is performed. For example, in the communication system 200, an ABS that is a subframe required to perform low power transmission is set.
たとえば、スモール基地局221,222の無線通信に対するマクロ基地局210からの干渉を低減するために、マクロ基地局210が低電力送信を行うABS(マクロセル-スモールセル間のABS)が設定される。
For example, in order to reduce interference from the macro base station 210 to the radio communication of the small base stations 221 and 222, an ABS (ABS between the macro cell and the small cell) to which the macro base station 210 performs low power transmission is set.
また、マクロ基地局210の無線通信に対するスモール基地局221,222からの干渉を低減するために、スモール基地局221,222が低電力送信を行うABS(スモールセル間のABS)が設定される。
Also, in order to reduce interference from the small base stations 221 and 222 to the radio communication of the macro base station 210, an ABS (ABS between small cells) in which the small base stations 221 and 222 perform low power transmission is set.
スモールセル221a,222aは、互いに協調して移動局230との間で無線通信を行うCoMPを実行可能である(Inter-eNB CoMP)。スモールセル221a,222aによるCoMPは、たとえばマクロ基地局210によって制御される。たとえば、マクロ基地局210は、移動局230を宛先とする同一のユーザデータをスモールセル221a,222aへ送信する。
The small cells 221a and 222a can execute CoMP that performs radio communication with the mobile station 230 in cooperation with each other (Inter-eNB CoMP). CoMP by the small cells 221a and 222a is controlled by the macro base station 210, for example. For example, the macro base station 210 transmits the same user data destined for the mobile station 230 to the small cells 221a and 222a.
また、マクロ基地局210は、CoMP送信を行うサブフレーム(ABSも含む)や送信方式(たとえば符号化方式や変調方式)を示す制御信号をスモールセル221a,222aへ送信する。
Also, the macro base station 210 transmits a control signal indicating a subframe (including ABS) for performing CoMP transmission and a transmission scheme (for example, an encoding scheme and a modulation scheme) to the small cells 221a and 222a.
スモールセル221a,222aは、マクロ基地局210から受信した制御信号に基づいて、マクロ基地局210から受信した同一のユーザデータを同時に移動局230へ無線送信する。
The small cells 221a and 222a wirelessly transmit the same user data received from the macro base station 210 to the mobile station 230 simultaneously based on the control signal received from the macro base station 210.
移動局230は、スモールセル221a,222aから同時に無線送信された同一のユーザデータを受信するダイバーシティ受信を行う。これにより、ABSが多数設定される状況においても、移動局230における受信特性(たとえば受信信号レベル)を改善(たとえば3[dB])し、データレートを向上させることができる。
The mobile station 230 performs diversity reception for receiving the same user data wirelessly transmitted simultaneously from the small cells 221a and 222a. Thereby, even in a situation where a large number of ABSs are set, it is possible to improve the reception characteristics (for example, the received signal level) in the mobile station 230 (for example, 3 [dB]) and improve the data rate.
マクロ基地局210からスモールセル221a,222aへのユーザデータの送信には、たとえばマクロ基地局210とスモール基地局221,222との間のXnインタフェース201,202(たとえばX2インタフェース)を用いることができる。ただし、マクロ基地局210からスモールセル221a,222aへのユーザデータの送信に、Xnインタフェース201,202とは異なる有線通信インタフェースや無線通信インタフェースを用いることも可能である。
For transmitting user data from the macro base station 210 to the small cells 221a and 222a, for example, Xn interfaces 201 and 202 (for example, an X2 interface) between the macro base station 210 and the small base stations 221 and 222 can be used. . However, a wired communication interface or a wireless communication interface different from the Xn interfaces 201 and 202 may be used for transmitting user data from the macro base station 210 to the small cells 221a and 222a.
マクロ基地局210からスモールセル221a,222aへの制御信号の送信には、無線通信を用いることができる。これにより、少ない遅延により制御信号を送信することができるため、マクロ基地局210による協調通信の無線リソースや送信方式などの決定結果を迅速に反映させ、通信品質の向上を図ることができる。ただし、マクロ基地局210からスモールセル221a,222aへの制御信号の送信に、Xnインタフェース201,202や、Xnインタフェース201,202とは異なる有線通信インタフェースを用いることも可能である。
Wireless communication can be used for transmission of control signals from the macro base station 210 to the small cells 221a and 222a. Thereby, since the control signal can be transmitted with a small delay, the determination result of the radio resource and transmission method of the cooperative communication by the macro base station 210 can be reflected quickly, and the communication quality can be improved. However, it is also possible to use the Xn interfaces 201 and 202 or a wired communication interface different from the Xn interfaces 201 and 202 for transmitting control signals from the macro base station 210 to the small cells 221a and 222a.
図2Bは、実施の形態2にかかる通信システムの適用例を示す図である。図2Bにおいて、図2Aに示した部分と同様の部分については同一の符号を付して説明を省略する。図2Aに示した通信システム200は、たとえば図2Bに示す通信システム200に適用することができる。図2Bに示す通信システム200は、マクロ基地局210,240と、スモール基地局221,222,251,252と、を含む。
FIG. 2B is a diagram illustrating an application example of the communication system according to the second embodiment. In FIG. 2B, the same parts as those shown in FIG. The communication system 200 shown in FIG. 2A can be applied to the communication system 200 shown in FIG. 2B, for example. The communication system 200 shown in FIG. 2B includes macro base stations 210 and 240 and small base stations 221, 222, 251 and 252.
マクロセル240aは、マクロ基地局240の無線通信範囲(セル)である。スモールセル251aは、スモール基地局251の無線通信範囲(セル)である。スモールセル252aは、スモール基地局252の無線通信範囲(セル)である。図2Bに示す例では、スモール基地局251,252はマクロセル240aに位置している。
The macro cell 240a is a wireless communication range (cell) of the macro base station 240. The small cell 251a is a wireless communication range (cell) of the small base station 251. The small cell 252a is a wireless communication range (cell) of the small base station 252. In the example shown in FIG. 2B, the small base stations 251 and 252 are located in the macro cell 240a.
通信システム200では、マクロ基地局240とスモール基地局251,252との間の干渉を制御するFeICICが行われる。また、通信システム200では、マクロ基地局210とマクロ基地局240との間の干渉を制御するICICが行われる。
In the communication system 200, FeICIC for controlling interference between the macro base station 240 and the small base stations 251 and 252 is performed. In the communication system 200, ICIC for controlling interference between the macro base station 210 and the macro base station 240 is performed.
(通信システムの動作例)
図3Aは、通信システムの動作例1を示すシーケンス図である。図3Aにおいて、図2Aに示した部分と同様の部分については同一の符号を付して説明を省略する。また、図3Aにおいて、横軸は時間の経過を示している。区切り301は、無線フレームの区切りを示している。1個の無線フレームには10個のサブフレームが含まれている。 (Operation example of communication system)
FIG. 3A is a sequence diagram illustrating an operation example 1 of the communication system. In FIG. 3A, the same parts as those shown in FIG. 2A are denoted by the same reference numerals and description thereof is omitted. In FIG. 3A, the horizontal axis indicates the passage of time. Apartition 301 indicates a wireless frame partition. One radio frame includes 10 subframes.
図3Aは、通信システムの動作例1を示すシーケンス図である。図3Aにおいて、図2Aに示した部分と同様の部分については同一の符号を付して説明を省略する。また、図3Aにおいて、横軸は時間の経過を示している。区切り301は、無線フレームの区切りを示している。1個の無線フレームには10個のサブフレームが含まれている。 (Operation example of communication system)
FIG. 3A is a sequence diagram illustrating an operation example 1 of the communication system. In FIG. 3A, the same parts as those shown in FIG. 2A are denoted by the same reference numerals and description thereof is omitted. In FIG. 3A, the horizontal axis indicates the passage of time. A
まず、マクロ基地局210が、スモール基地局221,222との間で事前設定302(Configuration)を行う。事前設定302において、マクロ基地局210は、たとえば、スモール基地局221,222によるCoMP送信の開始(Activation)または停止(Deactivation)を指示する(Inter-eNB CoMP(Act/Deact))。図3Aに示す例では、マクロ基地局210は、スモール基地局221,222によるCoMP送信の開始を指示したとする。
First, the macro base station 210 performs pre-configuration 302 (Configuration) with the small base stations 221 and 222. In the pre-setting 302, for example, the macro base station 210 instructs the start (Activation) or the stop (Deactivation) of CoMP transmission by the small base stations 221 and 222 (Inter-eNB CoMP (Act / Deact)). In the example illustrated in FIG. 3A, it is assumed that the macro base station 210 instructs the small base stations 221 and 222 to start CoMP transmission.
また、事前設定302において、マクロ基地局210は、たとえば、マクロ基地局210において設定するABSの位置を通知する(FeICIC:ABS(Macro))。また、事前設定302において、マクロ基地局210は、たとえば、スモール基地局221,222において設定するMBSFN(Multicast/Broadcast Single Frequency Network:MBMS単一周波数ネットワーク)のABSの位置を通知する(ABS_MBSFN(Small))。このABSは、たとえば後述のABS351,352である。
In advance setting 302, for example, the macro base station 210 notifies the ABS position set in the macro base station 210 (FeICIC: ABS (Macro)). Further, in the pre-setting 302, for example, the macro base station 210 notifies the ABS position of the MBSFN (Multicast / Broadcast Single Frequency Network: MBMS single frequency network) set in the small base stations 221 and 222 (ABS_MBSFN (Small)). )). The ABS is, for example, ABS 351 or 352 described later.
つぎに、マクロ基地局210が、移動局230を宛先とする下りのユーザデータ311,312のスモール基地局221,222への送信(Data(via Xn))を開始する。ユーザデータ311,312は、それぞれ移動局230を宛先とする下りデータであって、互いに同一のデータである。
Next, the macro base station 210 starts transmission of downlink user data 311 and 312 addressed to the mobile station 230 to the small base stations 221 and 222 (Data (via Xn)). The user data 311 and 312 are downlink data destined for the mobile station 230 and are the same data.
ユーザデータ311,312は、たとえばマクロ基地局210とスモール基地局221,222との間のXnインタフェース(たとえば図2Aに示したXnインタフェース201,202)によって送信することができる。また、ユーザデータ311,312は、たとえばPDCP(Packet Data Convergence Protocol)パケットによって送信することができる。
User data 311 and 312 can be transmitted by, for example, the Xn interface (for example, the Xn interfaces 201 and 202 shown in FIG. 2A) between the macro base station 210 and the small base stations 221 and 222. The user data 311 and 312 can be transmitted by, for example, a PDCP (Packet Data Convergence Protocol) packet.
フィードバック321,322は、移動局230からマクロ基地局210への周期的なフィードバックであって、移動局230におけるスモール基地局221,222の無線通信品質の測定結果のフィードバックである。マクロ基地局210は、フィードバック321,322の結果を、スモール基地局221,222による協調通信の制御に用いる。
The feedbacks 321 and 322 are periodic feedback from the mobile station 230 to the macro base station 210, and are feedback of the measurement results of the wireless communication quality of the small base stations 221 and 222 in the mobile station 230. The macro base station 210 uses the results of the feedbacks 321 and 322 for controlling cooperative communication by the small base stations 221 and 222.
フィードバック331,332は、移動局230からスモール基地局221,222への周期的なフィードバックであって、移動局230におけるスモールセル221a,222aの無線通信品質の測定結果のフィードバックである。スモールセル221a,222aは、フィードバック331,332の結果を再送制御に用いる。
The feedbacks 331 and 332 are periodic feedback from the mobile station 230 to the small base stations 221 and 222, and are feedback of measurement results of the wireless communication quality of the small cells 221a and 222a in the mobile station 230. The small cells 221a and 222a use the results of the feedbacks 331 and 332 for retransmission control.
図3Aに示す例では、フィードバック321,331が同時に行われ、フィードバック322,332が同時に行われている。フィードバック321,322,331,332には、たとえばCQI(Channel Quality Indicator:チャネル品質指標)、PMI(Precoding Matrix Indicator:プリコード化マトリクス指標)、RI(Rank Indicator:ランク指標)などが含まれる。ただし、フィードバック321,322,331,332には、これらに限らず各種の無線通信品質の情報を用いることができる。
In the example shown in FIG. 3A, feedback 321 and 331 are performed simultaneously, and feedback 322 and 332 are performed simultaneously. The feedbacks 321, 322, 331, and 332 include, for example, CQI (Channel Quality Indicator: channel quality index), PMI (Precoding Matrix Indicator: precoding matrix index), RI (Rank Indicator: rank index), and the like. However, the feedback 321, 322, 331, 332 is not limited to these, and various types of wireless communication quality information can be used.
ABS341,342は、マクロ基地局210が低電力送信を行うサブフレームである。ABS341,342のタイミング(位置)は、たとえばマクロ基地局210によって決定され、事前設定302によってスモール基地局221,222へ通知される。
ABSs 341 and 342 are subframes in which the macro base station 210 performs low power transmission. The timings (positions) of the ABSs 341 and 342 are determined by, for example, the macro base station 210, and are notified to the small base stations 221 and 222 by the preset 302.
ABS351~354は、スモール基地局221,222の両方が低電力送信を行うサブフレームである。ABS351,353はMBSFNである。たとえば、ABS351,353は、事前設定302においてマクロ基地局210から指定される。
ABSs 351 to 354 are subframes in which both small base stations 221 and 222 perform low power transmission. ABSs 351 and 353 are MBSFNs. For example, the ABSs 351 and 353 are designated from the macro base station 210 in the preset 302.
MBSFNであるABS351,353は、制御領域303(Control Region)およびデータ領域304(Data Region)を含む。また、ABS351,353は、制御領域303およびデータ領域304の間に保護区間(Guard Period)を含んでいてもよい。
The ABSs 351 and 353 which are MBSFNs include a control area 303 (Control Region) and a data area 304 (Data Region). In addition, the ABSs 351 and 353 may include a protection period (Guard Period) between the control area 303 and the data area 304.
ABS352,354は、マクロ基地局210から指定されたABS351,353の位置に基づいて、スモール基地局221,222が決定するABSである。たとえば、スモール基地局221,222は、ABS351,353と重ならないようにABS352,354の位置を決定する。
ABSs 352 and 354 are ABSs determined by the small base stations 221 and 222 based on the positions of the ABSs 351 and 353 designated from the macro base station 210. For example, the small base stations 221 and 222 determine the positions of the ABSs 352 and 354 so as not to overlap the ABSs 351 and 353.
または、ABS352,354は、マクロ基地局210によって決定され、たとえば制御信号361,362によってスモール基地局221,222へ通知されるABSであってもよい。この場合に、ABS352,354は、マクロ基地局210から移動局230へ、たとえば制御信号371,372によって通知されてもよい。
Alternatively, the ABSs 352 and 354 may be ABSs determined by the macro base station 210 and notified to the small base stations 221 and 222 by the control signals 361 and 362, for example. In this case, the ABSs 352 and 354 may be notified from the macro base station 210 to the mobile station 230 by, for example, control signals 371 and 372.
制御信号361,362は、マクロ基地局210からスモール基地局221,222への制御信号である。制御信号361,362は、たとえばMBSFNであるABS351,353の制御領域303において送信される。
Control signals 361 and 362 are control signals from the macro base station 210 to the small base stations 221 and 222. Control signals 361 and 362 are transmitted in control area 303 of ABSs 351 and 353, which are, for example, MBSFN.
また、制御信号361,362は、スモール基地局221,222から移動局230へのデータ送信の方式(変調方式や符号化方式)や無線リソースを示す信号である。たとえば、制御信号361,362には、RBA(Resource Block Assignment:リソースブロック割り当て)やMCS(Modulation and Coding Scheme:変調・符号化方式)が含まれる。
Further, the control signals 361 and 362 are signals indicating a data transmission method (modulation method and coding method) and radio resources from the small base stations 221 and 222 to the mobile station 230. For example, the control signals 361 and 362 include RBA (Resource Block Assignment: resource block allocation) and MCS (Modulation and Coding Scheme: modulation / coding scheme).
たとえば、制御信号361は、フィードバック321に基づいてマクロ基地局210によって決定されたデータ送信の方式や無線リソースを示す制御信号である。また、制御信号362は、フィードバック322に基づいてマクロ基地局210によって決定されたデータ送信の方式や無線リソースを示す制御信号である。無線リソースには、たとえば周波数リソースおよび時間リソースの少なくともいずれかが含まれる。
For example, the control signal 361 is a control signal indicating a data transmission method and radio resources determined by the macro base station 210 based on the feedback 321. The control signal 362 is a control signal indicating a data transmission scheme and radio resources determined by the macro base station 210 based on the feedback 322. The radio resource includes at least one of a frequency resource and a time resource, for example.
制御信号361,362は、たとえば無線によって送信することができる。これにより、制御信号361,362を少ない遅延でスモール基地局221,222へ送信することができる。したがって、移動局230からのフィードバック321,322を、スモール基地局221,222の制御に反映させるまでの時間を短縮することができる。このため、スモールセル221a,222bにおける移動局230の無線通信品質に応じたスモール基地局221,222と移動局230との間の無線通信が可能になる。
The control signals 361 and 362 can be transmitted by radio, for example. Thereby, the control signals 361 and 362 can be transmitted to the small base stations 221 and 222 with a small delay. Therefore, it is possible to shorten the time until the feedbacks 321 and 322 from the mobile station 230 are reflected in the control of the small base stations 221 and 222. For this reason, wireless communication between the small base stations 221 and 222 and the mobile station 230 according to the wireless communication quality of the mobile station 230 in the small cells 221a and 222b becomes possible.
制御信号371,372は、マクロ基地局210から移動局230への制御信号である。制御信号371,372は、たとえば、制御信号361,362と同内容の制御信号である。また、制御信号371,372は、制御信号361,362と同時にABS351,353の制御領域303において送信される。制御信号371,372についても、制御信号361,362と同様に、たとえば無線によって送信することができる。
Control signals 371 and 372 are control signals from the macro base station 210 to the mobile station 230. The control signals 371 and 372 are control signals having the same contents as the control signals 361 and 362, for example. The control signals 371 and 372 are transmitted in the control area 303 of the ABS 351 and 353 simultaneously with the control signals 361 and 362. Similarly to the control signals 361 and 362, the control signals 371 and 372 can be transmitted by radio, for example.
ユーザデータ381,382は、スモール基地局221,222がCoMPにより移動局230へ送信するユーザデータである。ユーザデータ381,382は、たとえばユーザデータ311,312である。ユーザデータ381,382は、たとえばPDSCH(Physical Downlink Shared Channel:物理下りリンク共有チャネル)とすることができる。また、ユーザデータ381,382は、同一のユーザデータ381,382を同時に送信するJT(Joint Transmission:ジョイントトランスミッション)によって送信される。
User data 381 and 382 are user data transmitted from the small base stations 221 and 222 to the mobile station 230 by CoMP. User data 381 and 382 are, for example, user data 311 and 312. User data 381 and 382 may be PDSCH (Physical Downlink Shared Channel: physical downlink shared channel), for example. The user data 381 and 382 are transmitted by JT (Joint Transmission: joint transmission) that transmits the same user data 381 and 382 simultaneously.
たとえば、スモール基地局221,222は、ABS351においてマクロ基地局210から受信した制御信号361に基づいて、ABS352においてユーザデータ381をCoMPにより同時に送信する。また、スモール基地局221,222は、ABS353においてマクロ基地局210から受信した制御信号362に基づいて、ABS354においてユーザデータ382をCoMPにより同時に送信する。
For example, the small base stations 221 and 222 simultaneously transmit user data 381 by CoMP in the ABS 352 based on the control signal 361 received from the macro base station 210 in the ABS 351. In addition, the small base stations 221 and 222 simultaneously transmit user data 382 by CoMP in the ABS 354 based on the control signal 362 received from the macro base station 210 in the ABS 353.
移動局230は、マクロ基地局210から受信した制御信号371に基づいて、ABS352においてスモール基地局221,222から同時に送信されたユーザデータ381を受信する。また、移動局230は、マクロ基地局210から受信した制御信号372に基づいて、ABS354においてスモール基地局221,222から同時に送信されたユーザデータ382を受信する。
The mobile station 230 receives user data 381 simultaneously transmitted from the small base stations 221 and 222 in the ABS 352 based on the control signal 371 received from the macro base station 210. The mobile station 230 receives user data 382 transmitted simultaneously from the small base stations 221 and 222 in the ABS 354 based on the control signal 372 received from the macro base station 210.
応答信号391,392(A/N)は、それぞれユーザデータ381,382に対する移動局230からスモール基地局221,222への応答信号である。応答信号391,392のそれぞれは、たとえば、ユーザデータを正常に受信できたことを示すACK(肯定信号)、またはユーザデータを正常に受信できなかったことを示すNACK(否定信号)である。
Response signals 391 and 392 (A / N) are response signals from the mobile station 230 to the small base stations 221 and 222 for the user data 381 and 382, respectively. Each of the response signals 391 and 392 is, for example, ACK (positive signal) indicating that user data has been normally received or NACK (negative signal) indicating that user data has not been normally received.
応答信号391,392に基づくスモール基地局221,222による再送は、たとえばHARQによる再送である。ただし、応答信号391,392に基づくスモール基地局221,222による再送には、HARQに限らず、各種のレイヤ(たとえば、RLCレイウアにおけるARQなど)における再送を適用することができる。
The retransmission by the small base stations 221 and 222 based on the response signals 391 and 392 is, for example, retransmission by HARQ. However, retransmission by the small base stations 221 and 222 based on the response signals 391 and 392 is not limited to HARQ, and retransmission in various layers (for example, ARQ in RLC layer) can be applied.
このように、スモール基地局221,222は、ユーザデータ381,382の協調通信において、協調通信の無線リソースを移動局230に通知せずに移動局230宛のデータを送信してもよい。この場合も、移動局230は、スモール基地局221,222が協調して送信する移動局230宛のデータを、マクロ基地局210から通知された無線リソース上で受信することができる。これにより、スモール基地局221,222と移動局230との間の通信量を低減することができる。
As described above, the small base stations 221 and 222 may transmit the data addressed to the mobile station 230 without notifying the mobile station 230 of the radio resources of the cooperative communication in the cooperative communication of the user data 381 and 382. Also in this case, the mobile station 230 can receive the data addressed to the mobile station 230 transmitted by the small base stations 221 and 222 in cooperation on the radio resource notified from the macro base station 210. Thereby, the communication amount between the small base stations 221 and 222 and the mobile station 230 can be reduced.
一例として、図3Aに示す例では、ABS352,354は、マクロ基地局210によって決定され、たとえば制御信号361,362によってスモール基地局221,222へ通知されるとする。この場合は、ABS352,354はたとえば制御信号371,372によって移動局230にも通知される。また、この場合は、制御信号361,362,371,372が示す無線リソースには周波数リソースおよび時間リソース(ABS352,354)が含まれる。
As an example, in the example illustrated in FIG. 3A, the ABSs 352 and 354 are determined by the macro base station 210 and are notified to the small base stations 221 and 222 by, for example, control signals 361 and 362. In this case, the ABSs 352 and 354 are also notified to the mobile station 230 by control signals 371 and 372, for example. In this case, the radio resources indicated by the control signals 361, 362, 371, and 372 include a frequency resource and a time resource (ABS 352 and 354).
図3Bは、通信システムの動作例2を示すシーケンス図である。図3Bにおいて、図3Aに示した部分と同様の部分については同一の符号を付して説明を省略する。マクロ基地局210は、制御信号371によって移動局230へ通知した協調通信のためのデータ送信の方式や無線リソースを変更しない場合は、図3Bに示すように、制御信号372を送信しなくてもよい。この場合は、移動局230は、ABS354における協調通信によるユーザデータ382を、最後に受信した制御信号371に基づいて受信する。なお、LTEにおいては、このような送信方式をSPS(Semi-persistent-Scheduling)と呼ぶ。
FIG. 3B is a sequence diagram showing an operation example 2 of the communication system. In FIG. 3B, the same parts as those shown in FIG. 3A are denoted by the same reference numerals and description thereof is omitted. When the macro base station 210 does not change the data transmission method or radio resource for cooperative communication notified to the mobile station 230 by the control signal 371, the macro base station 210 does not need to transmit the control signal 372 as shown in FIG. 3B. Good. In this case, the mobile station 230 receives user data 382 by cooperative communication in the ABS 354 based on the control signal 371 received last. In LTE, such a transmission method is called SPS (Semi-persistent-Scheduling).
このように、マクロ基地局210は、スモール基地局221,222による協調通信の無線リソースを移動局230に通知した後に、該協調通信の無線リソースを変更する場合にのみ、該協調通信の無線リソースを移動局230に通知するようにしてもよい。この場合は、移動局230は、制御局110から最後に通知された無線リソース上で自局宛のデータを受信することができる。これにより、たとえば無線リソースの変更の有無に関わらず繰り返し無線リソースを通知する場合に比べて、マクロ基地局210と移動局230との間の通信量を低減することができる。
As described above, the macro base station 210 notifies the mobile station 230 of the radio resources for cooperative communication by the small base stations 221 and 222 and then changes the radio resources for the cooperative communication only when the radio resources for the cooperative communication are changed. May be notified to the mobile station 230. In this case, the mobile station 230 can receive data addressed to itself on the radio resource last notified from the control station 110. Thereby, for example, the communication amount between the macro base station 210 and the mobile station 230 can be reduced as compared with a case where the radio resource is repeatedly notified regardless of whether or not the radio resource is changed.
一例として、図3Bに示す例では、ABS352,354は、マクロ基地局210によって決定され、たとえば制御信号361によってスモール基地局221,222へ通知されるとする。この場合は、ABS352,354はたとえば制御信号371によって移動局230にも通知される。また、この場合は、制御信号361,371が示す無線リソースには周波数リソースおよび時間リソース(ABS352,354)が含まれる。
As an example, in the example shown in FIG. 3B, it is assumed that the ABSs 352 and 354 are determined by the macro base station 210 and notified to the small base stations 221 and 222 by, for example, the control signal 361. In this case, the ABSs 352 and 354 are also notified to the mobile station 230 by a control signal 371, for example. In this case, the radio resources indicated by the control signals 361 and 371 include frequency resources and time resources (ABS 352 and 354).
図3Cは、通信システムの動作例3を示すシーケンス図である。図3Cにおいて、図3Aに示した部分と同様の部分については同一の符号を付して説明を省略する。スモール基地局221,222は、ユーザデータ381を、ユーザデータ381の送信のデータ送信の方式や無線リソースを示す制御信号とともに送信してもよい。この場合の制御信号には、たとえばPDCCH(Physical Downlink Control Channel:物理下りリンク制御チャネル)を用いることができる。
FIG. 3C is a sequence diagram showing an operation example 3 of the communication system. In FIG. 3C, the same parts as those shown in FIG. 3A are denoted by the same reference numerals and description thereof is omitted. The small base stations 221 and 222 may transmit the user data 381 together with a control signal indicating a data transmission method and radio resources for transmitting the user data 381. As the control signal in this case, for example, PDCCH (Physical Downlink Control Channel: physical downlink control channel) can be used.
たとえば、スモール基地局221,222は、ユーザデータ381の送信において、PDCCHとともにPDSCHを送信する(PDCCH+PDSCH(JT))。ただし、PDCCHを送信するのはスモール基地局221,222のうちのいずれかのみであってもよい。移動局230は、スモール基地局221,222から送信されたPDSCHを、PDSCHとともに送信されたPDCCHに基づいて受信する。この場合は、マクロ基地局210は、たとえば図3Aに示した制御信号371,372を送信しなくてもよい。
For example, the small base stations 221 and 222 transmit PDSCH together with PDCCH in transmitting user data 381 (PDCCH + PDSCH (JT)). However, only one of the small base stations 221 and 222 may transmit the PDCCH. The mobile station 230 receives the PDSCH transmitted from the small base stations 221 and 222 based on the PDCCH transmitted together with the PDSCH. In this case, the macro base station 210 may not transmit the control signals 371 and 372 illustrated in FIG. 3A, for example.
一例として、図3Cに示す例では、ABS352,354は、スモール基地局221,222によって決定され、たとえばPDCCHによって移動局230へ通知されるとする。この場合は、制御信号361,362が示す無線リソースには周波数リソースが含まれる。図3A~図3Cに示したように、協調通信を行うABS351,352の決定方法および通知方法には各種の方法を用いることができる。
As an example, in the example illustrated in FIG. 3C, it is assumed that the ABSs 352 and 354 are determined by the small base stations 221 and 222 and are notified to the mobile station 230 by PDCCH, for example. In this case, the radio resource indicated by the control signals 361 and 362 includes a frequency resource. As shown in FIGS. 3A to 3C, various methods can be used as the determination method and notification method of the ABSs 351 and 352 that perform cooperative communication.
(マクロ基地局による処理)
図4Aは、マクロ基地局による処理の一例を示すフローチャートである。マクロ基地局210は、たとえば図4Aに示す各ステップを実行する。まず、マクロ基地局210は、CoMP送信を実行するか否かを判断し(ステップS401)、CoMP送信を実行すると判断するまで待つ(ステップS401:Noのループ)。CoMP送信を実行するか否かの判断は、たとえば、移動局230からの通信品質の報告や、移動局230からのCoMP送信の要求などに基づいて行うことができる。 (Processing by macro base station)
FIG. 4A is a flowchart illustrating an example of processing by the macro base station. For example, themacro base station 210 executes the steps shown in FIG. 4A. First, the macro base station 210 determines whether or not to execute CoMP transmission (step S401), and waits until it is determined to execute CoMP transmission (step S401: No loop). The determination of whether or not to execute CoMP transmission can be made based on, for example, a report of communication quality from the mobile station 230, a request for CoMP transmission from the mobile station 230, or the like.
図4Aは、マクロ基地局による処理の一例を示すフローチャートである。マクロ基地局210は、たとえば図4Aに示す各ステップを実行する。まず、マクロ基地局210は、CoMP送信を実行するか否かを判断し(ステップS401)、CoMP送信を実行すると判断するまで待つ(ステップS401:Noのループ)。CoMP送信を実行するか否かの判断は、たとえば、移動局230からの通信品質の報告や、移動局230からのCoMP送信の要求などに基づいて行うことができる。 (Processing by macro base station)
FIG. 4A is a flowchart illustrating an example of processing by the macro base station. For example, the
ステップS401において、CoMP送信を実行すると判断すると(ステップS401:Yes)、マクロ基地局210は、CoMPの通信設定を行う(ステップS402)。ステップS402において行われる通信設定は、たとえば図3A~図3Cに示した事前設定302である。
If it is determined in step S401 that CoMP transmission is to be executed (step S401: Yes), the macro base station 210 performs CoMP communication settings (step S402). The communication setting performed in step S402 is, for example, the advance setting 302 shown in FIGS. 3A to 3C.
つぎに、マクロ基地局210は、スモール基地局221,222へユーザデータを送信する(ステップS403)。ステップS403において送信されるユーザデータは、たとえば図3A~図3Cに示したユーザデータ311,312である。
Next, the macro base station 210 transmits user data to the small base stations 221 and 222 (step S403). The user data transmitted in step S403 is, for example, the user data 311 and 312 shown in FIGS. 3A to 3C.
つぎに、マクロ基地局210は、移動局230からのフィードバックを受信する(ステップS404)。ステップS404において受信されるフィードバックは、たとえば図3A~図3Cに示したフィードバック321,322である。
Next, the macro base station 210 receives feedback from the mobile station 230 (step S404). The feedback received in step S404 is, for example, the feedbacks 321 and 322 shown in FIGS. 3A to 3C.
つぎに、マクロ基地局210は、スモール基地局221,222へ制御信号を送信する(ステップS405)。ステップS405において送信される制御信号は、たとえば制御信号361,362である。
Next, the macro base station 210 transmits a control signal to the small base stations 221 and 222 (step S405). The control signals transmitted in step S405 are, for example, control signals 361 and 362.
つぎに、マクロ基地局210は、CoMPの再設定を実行するか否かを判断する(ステップS406)。CoMPの再設定を実行するか否かの判断は、たとえば、移動局230からの通信品質の報告や、移動局230からのCoMP送信の要求などに基づいて行うことができる。この場合の移動局230からの通信品質の報告には、たとえばステップS404のフィードバックを用いることができる。再設定を実行すると判断した場合(ステップS406:Yes)は、マクロ基地局210は、ステップS402へ戻る。
Next, the macro base station 210 determines whether or not to perform CoMP resetting (step S406). The determination of whether or not to perform CoMP resetting can be made based on, for example, a report of communication quality from the mobile station 230, a request for CoMP transmission from the mobile station 230, or the like. In this case, for example, the feedback in step S404 can be used for reporting the communication quality from the mobile station 230. If it is determined that resetting is to be executed (step S406: Yes), the macro base station 210 returns to step S402.
ステップS406において、再設定を実行しないと判断した場合(ステップS406:No)は、マクロ基地局210は、CoMP送信を終了するか否かを判断する(ステップS407)。CoMP送信を終了するか否かの判断は、たとえば、移動局230からの通信品質の報告や、移動局230からのCoMP送信の要求などに基づいて行うことができる。この場合の移動局230からの通信品質の報告には、たとえばステップS404のフィードバックを用いることができる。CoMP送信を終了しないと判断した場合(ステップS407:No)は、マクロ基地局210は、ステップS403へ戻る。
In step S406, when it is determined not to perform resetting (step S406: No), the macro base station 210 determines whether or not to end the CoMP transmission (step S407). The determination as to whether or not to end CoMP transmission can be made based on, for example, a report of communication quality from the mobile station 230, a request for CoMP transmission from the mobile station 230, or the like. In this case, for example, the feedback in step S404 can be used for reporting the communication quality from the mobile station 230. If it is determined that the CoMP transmission is not terminated (step S407: No), the macro base station 210 returns to step S403.
ステップS407において、CoMP送信を終了すると判断した場合(ステップS407:Yes)は、マクロ基地局210は、ステップS402によって行った通信設定を解除し(ステップS408)、一連の処理を終了する。
If it is determined in step S407 that CoMP transmission is to be terminated (step S407: Yes), the macro base station 210 cancels the communication setting performed in step S402 (step S408), and the series of processes is terminated.
また、ステップS405において、マクロ基地局210は、スモール基地局221,222へ送信する制御信号を移動局230に対しても送信してもよい。また、ステップS405において、マクロ基地局210は、CoMP送信の無線リソースを前回から変更するか否かを判断し、変更しないと判断した場合はスモール基地局221,222や移動局230へ制御信号を送信しないようにしてもよい。これにより、通信量の低減を図ることができる。
In step S405, the macro base station 210 may also transmit a control signal to be transmitted to the small base stations 221 and 222 to the mobile station 230. Further, in step S405, the macro base station 210 determines whether or not to change the CoMP transmission radio resource from the previous time. If it is determined not to change, the macro base station 210 sends a control signal to the small base stations 221 and 222 and the mobile station 230. You may make it not transmit. As a result, the amount of communication can be reduced.
(スモール基地局による処理)
図4Bは、スモール基地局による処理の一例を示すフローチャートである。スモール基地局221による処理について説明するが、スモール基地局222の処理もスモール基地局221の処理と同様である。スモール基地局221は、たとえば図4Bに示す各ステップを実行する。まず、スモール基地局221は、CoMP送信を実行するか否かを判断し(ステップS411)、CoMP送信を実行すると判断するまで待つ(ステップS411:Noのループ)。CoMP送信を実行するか否かの判断は、たとえば、マクロ基地局210からの指示に基づいて行うことができる。 (Processing by small base station)
FIG. 4B is a flowchart illustrating an example of processing by the small base station. Although the processing by thesmall base station 221 will be described, the processing by the small base station 222 is the same as the processing by the small base station 221. The small base station 221 executes, for example, each step shown in FIG. 4B. First, the small base station 221 determines whether or not to execute CoMP transmission (step S411), and waits until it is determined to execute CoMP transmission (step S411: No loop). The determination as to whether or not to perform CoMP transmission can be made based on an instruction from the macro base station 210, for example.
図4Bは、スモール基地局による処理の一例を示すフローチャートである。スモール基地局221による処理について説明するが、スモール基地局222の処理もスモール基地局221の処理と同様である。スモール基地局221は、たとえば図4Bに示す各ステップを実行する。まず、スモール基地局221は、CoMP送信を実行するか否かを判断し(ステップS411)、CoMP送信を実行すると判断するまで待つ(ステップS411:Noのループ)。CoMP送信を実行するか否かの判断は、たとえば、マクロ基地局210からの指示に基づいて行うことができる。 (Processing by small base station)
FIG. 4B is a flowchart illustrating an example of processing by the small base station. Although the processing by the
ステップS411において、CoMP送信を実行すると判断すると(ステップS411:Yes)、スモール基地局221は、CoMPの通信設定を行う(ステップS412)。ステップS412において行われる通信設定は、たとえば図3A~図3Cに示した事前設定302である。
If it is determined in step S411 that CoMP transmission is to be executed (step S411: Yes), the small base station 221 performs CoMP communication settings (step S412). The communication setting performed in step S412 is, for example, the pre-setting 302 shown in FIGS. 3A to 3C.
つぎに、スモール基地局221は、マクロ基地局210からユーザデータを受信する(ステップS413)。ステップS413において受信されるユーザデータは、たとえば図3A~図3Cに示したユーザデータ311,312である。
Next, the small base station 221 receives user data from the macro base station 210 (step S413). The user data received in step S413 is, for example, user data 311 and 312 shown in FIGS. 3A to 3C.
つぎに、スモール基地局221は、移動局230からのフィードバックを受信する(ステップS414)。ステップS414において受信されるフィードバックは、たとえば図3A~図3Cに示したフィードバック321,322である。
Next, the small base station 221 receives the feedback from the mobile station 230 (step S414). The feedback received in step S414 is, for example, the feedbacks 321 and 322 shown in FIGS. 3A to 3C.
つぎに、スモール基地局221は、移動局230へユーザデータをCoMP送信する(ステップS415)。ステップS415においてCoMP送信される制御信号は、たとえば制御信号361,362である。
Next, the small base station 221 transmits CoMP user data to the mobile station 230 (step S415). Control signals to be CoMP transmitted in step S415 are control signals 361 and 362, for example.
つぎに、スモール基地局221は、CoMPの再設定を実行するか否かを判断する(ステップS416)。CoMPの再設定を実行するか否かの判断は、たとえば、マクロ基地局210からの指示に基づいて行うことができる。再設定を実行すると判断した場合(ステップS416:Yes)は、スモール基地局221は、ステップS412へ戻る。
Next, the small base station 221 determines whether or not to perform CoMP reconfiguration (step S416). The determination as to whether or not to perform CoMP reconfiguration can be made based on an instruction from the macro base station 210, for example. When it is determined that resetting is to be executed (step S416: Yes), the small base station 221 returns to step S412.
ステップS416において、再設定を実行しないと判断した場合(ステップS416:No)は、スモール基地局221は、CoMP送信を終了するか否かを判断する(ステップS417)。CoMP送信を終了するか否かの判断は、たとえば、マクロ基地局210からの指示に基づいて行うことができる。CoMP送信を終了しないと判断した場合(ステップS417:No)は、スモール基地局221は、ステップS413へ戻る。
In step S416, when it is determined not to perform resetting (step S416: No), the small base station 221 determines whether or not to end the CoMP transmission (step S417). The determination of whether or not to end the CoMP transmission can be performed based on an instruction from the macro base station 210, for example. When it is determined that the CoMP transmission is not terminated (step S417: No), the small base station 221 returns to step S413.
ステップS417において、CoMP送信を終了すると判断した場合(ステップS417:Yes)は、スモール基地局221は、ステップS412によって行った通信設定を解除し(ステップS418)、一連の処理を終了する。
If it is determined in step S417 that CoMP transmission is to be terminated (step S417: Yes), the small base station 221 cancels the communication setting performed in step S412 (step S418), and the series of processes is terminated.
また、たとえばステップS415の後に、スモール基地局221は、ステップS415のCoMP送信に対する移動局230からの応答信号を受信し、受信した応答信号に基づくユーザデータの再送を行ってもよい。ユーザデータの再送は、たとえばステップS414によって受信した移動局230からのフィードバックに基づいて行うことができる。
For example, after step S415, the small base station 221 may receive a response signal from the mobile station 230 with respect to the CoMP transmission in step S415, and may retransmit the user data based on the received response signal. The retransmission of user data can be performed based on the feedback from the mobile station 230 received in step S414, for example.
(移動局による処理)
図5は、移動局による処理の一例を示すフローチャートである。移動局230は、たとえば図5に示す各ステップを実行する。まず、移動局230は、通信設定を行う(ステップS501)。ステップS501において行われる通信設定は、たとえば図3A~図3Cに示した事前設定302である。 (Processing by mobile station)
FIG. 5 is a flowchart showing an example of processing by the mobile station. For example, themobile station 230 executes the steps shown in FIG. First, the mobile station 230 performs communication settings (step S501). The communication setting performed in step S501 is the pre-setting 302 shown in FIGS. 3A to 3C, for example.
図5は、移動局による処理の一例を示すフローチャートである。移動局230は、たとえば図5に示す各ステップを実行する。まず、移動局230は、通信設定を行う(ステップS501)。ステップS501において行われる通信設定は、たとえば図3A~図3Cに示した事前設定302である。 (Processing by mobile station)
FIG. 5 is a flowchart showing an example of processing by the mobile station. For example, the
つぎに、移動局230は、CoMP受信を実行するか否かを判断する(ステップS502)。CoMP受信を実行するか否かの判断は、たとえばマクロ基地局210またはスモール基地局221,222からの指示に基づいて行うことができる。CoMP受信を実行すると判断した場合(ステップS502:Yes)は、移動局230は、マクロ基地局210およびスモール基地局221,222へフィードバックを送信する(ステップS503)。ステップS503によって送信されるフィードバックは、たとえば図3A~図3Cに示したフィードバック321,322,331,332である。
Next, the mobile station 230 determines whether or not to execute CoMP reception (step S502). The determination as to whether or not to perform CoMP reception can be made based on an instruction from the macro base station 210 or the small base stations 221 and 222, for example. If it is determined that CoMP reception is to be performed (step S502: Yes), the mobile station 230 transmits feedback to the macro base station 210 and the small base stations 221 and 222 (step S503). The feedback transmitted in step S503 is, for example, the feedbacks 321, 322, 331, and 332 shown in FIGS. 3A to 3C.
つぎに、移動局230は、制御チャネルを受信する(ステップS504)。ステップS504によって受信される制御チャネルは、たとえば図3A,図3Bに示した制御信号371,372である。または、ステップS504によって受信される制御チャネルは、図3Cに示したユーザデータ381,382に付随するPDCCHであってもよい。
Next, the mobile station 230 receives the control channel (step S504). The control channel received in step S504 is, for example, the control signals 371 and 372 shown in FIGS. 3A and 3B. Or the control channel received by step S504 may be PDCCH accompanying the user data 381 and 382 shown in FIG. 3C.
つぎに、移動局230は、ステップS504によって受信した制御チャネルに基づいて、スモール基地局221,222がCoMP送信するユーザデータをダイバーシティ受信する(ステップS505)。ステップS505においてダイバーシティ受信されるユーザデータは、たとえば図3A~図3Cに示したユーザデータ381,382である。
Next, based on the control channel received in step S504, the mobile station 230 receives diversity data of user data transmitted by the small base stations 221 and 222 by CoMP (step S505). The user data that is diversity-received in step S505 is, for example, user data 381 and 382 shown in FIGS. 3A to 3C.
つぎに、移動局230は、スモール基地局221,222のうちの主たるスモール基地局へ、ステップS505の受信に対する応答信号(ACKまたはNACK)を送信する(ステップS506)。スモール基地局221,222のうちの主たるスモール基地局は、たとえば、マクロ基地局210またはスモール基地局221,222によって移動局230へ通知されている。ステップS506において送信される応答信号は、たとえば図3A~図3Cに示した応答信号391,392である。
Next, the mobile station 230 transmits a response signal (ACK or NACK) to the reception in step S505 to the main small base station among the small base stations 221 and 222 (step S506). The main small base station of the small base stations 221 and 222 is notified to the mobile station 230 by the macro base station 210 or the small base stations 221 and 222, for example. The response signal transmitted in step S506 is, for example, the response signals 391 and 392 shown in FIGS. 3A to 3C.
つぎに、移動局230は、通信を終了するか否かを判断する(ステップS507)。通信を終了するか否かの判断は、たとえば、スモール基地局221のユーザ操作や、スモール基地局221における通信アプリケーションからの指示に基づいて行うことができる。通信を終了しないと判断した場合(ステップS507:No)は、移動局230は、ステップS503へ戻る。または、移動局230は、ステップS502へ戻り、CoMP送信を実行するか否かを再度判断してもよい。通信を終了すると判断した場合(ステップS507:Yes)は、移動局230は、一連の処理を終了する。
Next, the mobile station 230 determines whether or not to end communication (step S507). The determination as to whether or not to end the communication can be made based on, for example, a user operation of the small base station 221 or an instruction from a communication application in the small base station 221. If it is determined not to end the communication (step S507: No), the mobile station 230 returns to step S503. Alternatively, the mobile station 230 may return to step S502 and determine again whether to perform CoMP transmission. When it is determined that the communication is to be ended (step S507: Yes), the mobile station 230 ends a series of processes.
ステップS502において、CoMP受信を実行しないと判断した場合(ステップS502:No)は、移動局230は、サービング基地局へフィードバックを送信する(ステップS508)。サービング基地局は、たとえば、マクロ基地局210、スモール基地局221,222のうちの移動局230が接続中のサービング基地局(プライマリセル)である。
If it is determined in step S502 that CoMP reception is not performed (step S502: No), the mobile station 230 transmits feedback to the serving base station (step S508). The serving base station is, for example, a serving base station (primary cell) to which the mobile station 230 among the macro base station 210 and the small base stations 221 and 222 is connected.
つぎに、移動局230は、サービング基地局からの制御チャネルを受信する(ステップS509)。つぎに、移動局230は、ステップS509によって受信した制御チャネルに基づいて、サービング基地局からのユーザデータを受信する(ステップS510)。つぎに、移動局230は、サービング基地局へ、ステップS510の受信に対する応答信号(ACKまたはNACK)を送信する(ステップS511)。
Next, the mobile station 230 receives a control channel from the serving base station (step S509). Next, the mobile station 230 receives user data from the serving base station based on the control channel received in step S509 (step S510). Next, the mobile station 230 transmits a response signal (ACK or NACK) to the reception at step S510 to the serving base station (step S511).
つぎに、移動局230は、通信を終了するか否かを判断する(ステップS512)。通信を終了するか否かの判断は、たとえば、スモール基地局221のユーザ操作や、スモール基地局221における通信アプリケーションからの指示に基づいて行うことができる。通信を終了しないと判断した場合(ステップS512:No)は、移動局230は、ステップS508へ戻る。または、移動局230は、ステップS502へ戻り、CoMP送信を実行するか否かを再度判断してもよい。通信を終了すると判断した場合(ステップS512:Yes)は、移動局230は、一連の処理を終了する。
Next, the mobile station 230 determines whether or not to end communication (step S512). The determination as to whether or not to end the communication can be made based on, for example, a user operation of the small base station 221 or an instruction from a communication application in the small base station 221. If it is determined that the communication is not terminated (step S512: No), the mobile station 230 returns to step S508. Alternatively, the mobile station 230 may return to step S502 and determine again whether to perform CoMP transmission. When it is determined that the communication is to be ended (step S512: Yes), the mobile station 230 ends a series of processes.
(各基地局)
図6は、各基地局の一例を示す図である。マクロ基地局210およびスモール基地局221,222のそれぞれは、たとえば図6に示す基地局600によって実現することができる。図6に示すように、基地局600は、たとえば、無線通信部610と、制御部620と、記憶部630と、通信部640と、を備える。無線通信部610は、無線送信部611と、無線受信部612と、を備える。これらの各構成は、一方向または双方向に、信号やデータの入出力が可能なように接続されている。 (Each base station)
FIG. 6 is a diagram illustrating an example of each base station. Each ofmacro base station 210 and small base stations 221 and 222 can be realized by base station 600 shown in FIG. 6, for example. As illustrated in FIG. 6, the base station 600 includes, for example, a wireless communication unit 610, a control unit 620, a storage unit 630, and a communication unit 640. The wireless communication unit 610 includes a wireless transmission unit 611 and a wireless reception unit 612. Each of these components is connected so that signals and data can be input and output in one direction or in both directions.
図6は、各基地局の一例を示す図である。マクロ基地局210およびスモール基地局221,222のそれぞれは、たとえば図6に示す基地局600によって実現することができる。図6に示すように、基地局600は、たとえば、無線通信部610と、制御部620と、記憶部630と、通信部640と、を備える。無線通信部610は、無線送信部611と、無線受信部612と、を備える。これらの各構成は、一方向または双方向に、信号やデータの入出力が可能なように接続されている。 (Each base station)
FIG. 6 is a diagram illustrating an example of each base station. Each of
無線送信部611は、ユーザデータや制御信号を、アンテナを介して無線通信で送信する。無線送信部611が送信する無線信号には、任意のユーザデータや制御情報など(符号化や変調等がなされる)を含めることができる。無線受信部612は、ユーザデータや制御信号を、アンテナを介して無線通信で受信する。無線受信部612が受信する無線信号には、任意のユーザデータや制御信号など(符号化や変調等がなされる)を含めることができる。なお、アンテナは送信と受信で共通でもよい。
The wireless transmission unit 611 transmits user data and control signals by wireless communication via an antenna. The wireless signal transmitted by the wireless transmission unit 611 can include arbitrary user data, control information, and the like (encoded or modulated). The wireless reception unit 612 receives user data and control signals by wireless communication via an antenna. The radio signal received by the radio reception unit 612 can include arbitrary user data, a control signal, and the like (encoded or modulated). The antenna may be common for transmission and reception.
制御部620は、他の無線局へ送信するユーザデータや制御信号を無線送信部611に出力する。また、制御部620は、無線受信部612によって受信されたユーザデータや制御信号を取得する。制御部620は、後述する記憶部630との間でユーザデータ、制御情報、プログラムなどの入出力を行う。また、制御部620は、後述する通信部640との間で、他の通信装置などとの間で送受信するユーザデータや制御信号の入出力を行う。制御部620は、これら以外にも、基地局600における種々の制御を行う。
The control unit 620 outputs user data and control signals to be transmitted to other wireless stations to the wireless transmission unit 611. In addition, the control unit 620 acquires user data and control signals received by the wireless reception unit 612. The control unit 620 inputs and outputs user data, control information, programs, and the like with a storage unit 630 described later. In addition, the control unit 620 inputs and outputs user data and control signals that are transmitted to and received from other communication devices and the like with the communication unit 640 described later. In addition to these, the control unit 620 performs various controls in the base station 600.
記憶部630は、ユーザデータ、制御情報、プログラムなどの各種情報の記憶を行う。通信部640は、たとえば有線信号によって、他の通信装置との間でユーザデータや制御信号を送受信する。
The storage unit 630 stores various information such as user data, control information, and programs. The communication unit 640 transmits / receives user data and control signals to / from other communication devices, for example, by wired signals.
図1に示した制御局110の制御部111は、たとえば制御部620によって実現することができる。図1に示した制御局110の通信部112は、たとえば無線通信部610や通信部640によって実現することができる。図1に示した第1無線局120a,120bの制御部121a,121bは、たとえば制御部620によって実現することができる。図1に示した第1無線局120a,120bの通信部122a,122bは、たとえば無線通信部610や通信部640によって実現することができる。
The control unit 111 of the control station 110 illustrated in FIG. 1 can be realized by the control unit 620, for example. The communication unit 112 of the control station 110 illustrated in FIG. 1 can be realized by the wireless communication unit 610 or the communication unit 640, for example. The control units 121a and 121b of the first radio stations 120a and 120b illustrated in FIG. 1 can be realized by the control unit 620, for example. The communication units 122a and 122b of the first radio stations 120a and 120b illustrated in FIG. 1 can be realized by the radio communication unit 610 and the communication unit 640, for example.
(移動局)
図7は、移動局の一例を示す図である。移動局230は、たとえば図7に示す移動局700によって実現することができる。移動局700は、無線通信部710と、制御部720と、記憶部730と、を備える。無線通信部710は、無線送信部711と、無線受信部712と、を備える。これらの各構成は、一方向または双方向に、信号やデータの入出力が可能なように接続されている。 (Mobile station)
FIG. 7 is a diagram illustrating an example of a mobile station. Themobile station 230 can be realized by, for example, the mobile station 700 shown in FIG. The mobile station 700 includes a wireless communication unit 710, a control unit 720, and a storage unit 730. The wireless communication unit 710 includes a wireless transmission unit 711 and a wireless reception unit 712. Each of these components is connected so that signals and data can be input and output in one direction or in both directions.
図7は、移動局の一例を示す図である。移動局230は、たとえば図7に示す移動局700によって実現することができる。移動局700は、無線通信部710と、制御部720と、記憶部730と、を備える。無線通信部710は、無線送信部711と、無線受信部712と、を備える。これらの各構成は、一方向または双方向に、信号やデータの入出力が可能なように接続されている。 (Mobile station)
FIG. 7 is a diagram illustrating an example of a mobile station. The
無線送信部711は、ユーザデータや制御信号を、アンテナを介して無線通信で送信する。無線送信部711が送信する無線信号には、任意のユーザデータや制御情報など(符号化や変調等がなされる)を含めることができる。無線受信部712は、ユーザデータや制御信号を、アンテナを介して無線通信で受信する。無線受信部712が受信する無線信号には、任意のユーザデータや制御信号など(符号化や変調等がなされる)を含めることができる。なお、アンテナは送信と受信で共通でもよい。
The wireless transmission unit 711 transmits user data and control signals by wireless communication via an antenna. The wireless signal transmitted by the wireless transmission unit 711 can include arbitrary user data, control information, and the like (encoded or modulated). The wireless reception unit 712 receives user data and control signals by wireless communication via an antenna. The radio signal received by the radio reception unit 712 can include arbitrary user data, a control signal, and the like (encoded or modulated). The antenna may be common for transmission and reception.
制御部720は、他の無線局へ送信するユーザデータや制御信号を無線送信部711に出力する。また、制御部720は、無線受信部712によって受信されたユーザデータや制御信号を取得する。制御部720は、後述する記憶部730との間でユーザデータ、制御情報、プログラムなどの入出力を行う。また、制御部720は、後述する通信部との間で、他の通信装置などとの間で送受信するユーザデータや制御信号の入出力を行う。制御部720は、これら以外にも、移動局700における種々の制御を行う。
The control unit 720 outputs user data and control signals to be transmitted to other radio stations to the radio transmission unit 711. In addition, the control unit 720 acquires user data and control signals received by the wireless reception unit 712. The control unit 720 inputs and outputs user data, control information, programs, and the like with the storage unit 730 described later. In addition, the control unit 720 performs input / output of user data and control signals transmitted / received to / from other communication devices and the like with a communication unit described later. In addition to these, the control unit 720 performs various controls in the mobile station 700.
記憶部730は、ユーザデータ、制御情報、プログラムなどの各種情報の記憶を行う。
The storage unit 730 stores various information such as user data, control information, and programs.
図1に示した第2無線局130の制御部131は、たとえば制御部720によって実現することができる。図1に示した第2無線局130の通信部132は、たとえば無線通信部710によって実現することができる。
The control unit 131 of the second radio station 130 illustrated in FIG. 1 can be realized by the control unit 720, for example. The communication unit 132 of the second wireless station 130 illustrated in FIG. 1 can be realized by the wireless communication unit 710, for example.
(基地局のハードウェア構成)
図8は、基地局のハードウェア構成の一例を示す図である。図6に示した基地局600は、たとえば図8に示す基地局800によって実現することができる。基地局800は、アンテナ811と、RF回路812と、プロセッサ813と、メモリ814と、ネットワークIF815と、を備える。これら各構成要素は、たとえばバスを介して各種信号やデータの入出力が可能なように接続されている。 (Base station hardware configuration)
FIG. 8 is a diagram illustrating an example of a hardware configuration of the base station. Thebase station 600 shown in FIG. 6 can be realized by, for example, the base station 800 shown in FIG. Base station 800 includes antenna 811, RF circuit 812, processor 813, memory 814, and network IF 815. These components are connected so that various signals and data can be input / output via a bus, for example.
図8は、基地局のハードウェア構成の一例を示す図である。図6に示した基地局600は、たとえば図8に示す基地局800によって実現することができる。基地局800は、アンテナ811と、RF回路812と、プロセッサ813と、メモリ814と、ネットワークIF815と、を備える。これら各構成要素は、たとえばバスを介して各種信号やデータの入出力が可能なように接続されている。 (Base station hardware configuration)
FIG. 8 is a diagram illustrating an example of a hardware configuration of the base station. The
アンテナ811は、無線信号を送信する送信アンテナと、無線信号を受信する受信アンテナと、を含む。また、アンテナ811は、無線信号を送受信する共用アンテナであってもよい。RF回路812は、アンテナ811によって受信された信号や、アンテナ811によって送信される信号のRF(Radio Frequency:高周波)処理を行う。RF処理には、たとえばベースバンド帯とRF帯との周波数変換が含まれる。
The antenna 811 includes a transmission antenna that transmits a radio signal and a reception antenna that receives a radio signal. The antenna 811 may be a shared antenna that transmits and receives radio signals. The RF circuit 812 performs RF (Radio Frequency: high frequency) processing on a signal received by the antenna 811 and a signal transmitted by the antenna 811. The RF processing includes, for example, frequency conversion between the baseband band and the RF band.
プロセッサ813は、たとえばCPU(Central Processing Unit:中央処理装置)やDSP(Digital Signal Processor)などである。また、プロセッサ813は、ASIC(Application Specific Integrated Circuit)、FPGA(Field Programmable Gate Array)、LSI(Large Scale Integration:大規模集積回路)などのデジタル電子回路によって実現してもよい。
The processor 813 is, for example, a CPU (Central Processing Unit) or a DSP (Digital Signal Processor). The processor 813 may be realized by a digital electronic circuit such as an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or an LSI (Large Scale Integration).
メモリ814は、たとえばSDRAM(Synchronous Dynamic Random Access Memory)などのRAM(Random Access Memory:ランダムアクセスメモリ)、ROM(Read Only Memory)、フラッシュメモリなどによって実現することができる。メモリ814は、たとえばユーザデータ、制御情報、プログラムなどを格納する。
The memory 814 can be realized by a random access memory (RAM) such as SDRAM (Synchronous Dynamic Random Access Memory), a ROM (Read Only Memory), a flash memory, or the like. The memory 814 stores user data, control information, programs, and the like, for example.
ネットワークIF815は、たとえば有線によってネットワークとの間で通信を行う通信インタフェースである。ネットワークIF815は、たとえば基地局間で有線通信を行うためのXnインタフェース201,202(たとえば図2A参照)を含んでもよい。
The network IF 815 is a communication interface that performs communication with a network by, for example, a wired connection. The network IF 815 may include, for example, Xn interfaces 201 and 202 (for example, see FIG. 2A) for performing wired communication between base stations.
図6に示した無線通信部610は、たとえばRF回路812、あるいはアンテナ811およびRF回路812などによって実現することができる。図6に示した制御部620は、たとえばプロセッサ813およびメモリ814などによって実現することができる。図6に示した記憶部630は、たとえばメモリ814などによって実現することができる。図6に示した通信部640は、たとえばネットワークIF815などによって実現することができる。
6 can be realized by the RF circuit 812, the antenna 811, the RF circuit 812, or the like, for example. The control unit 620 illustrated in FIG. 6 can be realized by, for example, the processor 813 and the memory 814. The storage unit 630 illustrated in FIG. 6 can be realized by the memory 814, for example. The communication unit 640 shown in FIG. 6 can be realized by a network IF 815, for example.
(移動局のハードウェア構成)
図9は、移動局のハードウェア構成の一例を示す図である。移動局700は、たとえば図9に示す移動局900によって実現することができる。移動局900は、たとえば、アンテナ911と、RF回路912と、プロセッサ913と、メモリ914と、を備える。これら各構成要素は、たとえばバスを介して各種信号やデータの入出力が可能なように接続されている。 (Mobile station hardware configuration)
FIG. 9 is a diagram illustrating an example of a hardware configuration of the mobile station. Themobile station 700 can be realized by, for example, the mobile station 900 shown in FIG. The mobile station 900 includes, for example, an antenna 911, an RF circuit 912, a processor 913, and a memory 914. These components are connected so that various signals and data can be input / output via a bus, for example.
図9は、移動局のハードウェア構成の一例を示す図である。移動局700は、たとえば図9に示す移動局900によって実現することができる。移動局900は、たとえば、アンテナ911と、RF回路912と、プロセッサ913と、メモリ914と、を備える。これら各構成要素は、たとえばバスを介して各種信号やデータの入出力が可能なように接続されている。 (Mobile station hardware configuration)
FIG. 9 is a diagram illustrating an example of a hardware configuration of the mobile station. The
アンテナ911は、無線信号を送信する送信アンテナと、無線信号を受信する受信アンテナと、を含む。また、アンテナ911は、無線信号を送受信する共用アンテナであってもよい。RF回路912は、アンテナ911によって受信された信号や、アンテナ911によって送信される信号のRF処理を行う。RF処理には、たとえばベースバンド帯とRF帯との周波数変換が含まれる。
The antenna 911 includes a transmission antenna that transmits a radio signal and a reception antenna that receives a radio signal. The antenna 911 may be a shared antenna that transmits and receives radio signals. The RF circuit 912 performs RF processing on a signal received by the antenna 911 and a signal transmitted by the antenna 911. The RF processing includes, for example, frequency conversion between the baseband band and the RF band.
プロセッサ913は、たとえばCPUやDSPなどである。また、プロセッサ913は、ASIC、FPGA、LSIなどのデジタル電子回路によって実現してもよい。
The processor 913 is, for example, a CPU or a DSP. The processor 913 may be realized by a digital electronic circuit such as an ASIC, FPGA, LSI, or the like.
メモリ914は、たとえばSDRAMなどのRAM、ROM、フラッシュメモリなどによって実現することができる。メモリ914は、たとえばユーザデータ、制御情報、プログラムなどを格納する。
The memory 914 can be realized by, for example, a RAM such as SDRAM, a ROM, a flash memory, or the like. The memory 914 stores user data, control information, programs, and the like, for example.
図7に示した無線通信部710は、たとえばRF回路912、あるいはアンテナ911およびRF回路912などによって実現することができる。図7に示した制御部720は、たとえばプロセッサ913、メモリ914などによって実現することができる。図7に示した記憶部730は、たとえばメモリ914などによって実現することができる。
7 can be realized by the RF circuit 912 or the antenna 911 and the RF circuit 912, for example. The control unit 720 illustrated in FIG. 7 can be realized by, for example, the processor 913, the memory 914, and the like. The storage unit 730 illustrated in FIG. 7 can be realized by the memory 914, for example.
このように、実施の形態2によれば、スモール基地局221,222が、ABSにおいて協調送信を行うことで、ABSにおける移動局230の受信特性を向上させることができる。このため、通信システム200において特定期間が多数設定されても、スループットの向上を図ることができる。
Thus, according to the second embodiment, the small base stations 221 and 222 can improve the reception characteristics of the mobile station 230 in the ABS by performing coordinated transmission in the ABS. For this reason, even if many specific periods are set in the communication system 200, the throughput can be improved.
(実施の形態3)
実施の形態3においては、スモール基地局221,222による再送について説明する。たとえば、スモール基地局221,222は、ABSにおけるCoMP送信でエラーが発生した場合の再送については、スモール基地局221,222のうちの1つのスモール基地局でのみ行うようにしてもよい。ここでは、ABSにおけるCoMP送信でエラーが発生した場合に、スモール基地局221によって再送を行い、スモール基地局222は再送を行わない場合について説明する。 (Embodiment 3)
In Embodiment 3, retransmission by small base stations 221 and 222 will be described. For example, the small base stations 221 and 222 may perform retransmission only when one of the small base stations 221 and 222 performs retransmission when an error occurs in CoMP transmission in the ABS. Here, a case will be described where, when an error occurs in CoMP transmission in the ABS, retransmission is performed by the small base station 221 and the small base station 222 does not perform retransmission.
実施の形態3においては、スモール基地局221,222による再送について説明する。たとえば、スモール基地局221,222は、ABSにおけるCoMP送信でエラーが発生した場合の再送については、スモール基地局221,222のうちの1つのスモール基地局でのみ行うようにしてもよい。ここでは、ABSにおけるCoMP送信でエラーが発生した場合に、スモール基地局221によって再送を行い、スモール基地局222は再送を行わない場合について説明する。 (Embodiment 3)
In Embodiment 3, retransmission by
(応答信号の各受信結果に応じた各スモール基地局の動作)
図10は、応答信号の各受信結果に応じた各スモール基地局の動作の一例を示す図である。図10の表1000は、ABSにおけるCoMP送信の再送に関するケース1001~1004を示す。表1000の「スモール1」はスモール基地局221を示し、「スモール2」はスモール基地局222を示している。 (Operation of each small base station according to each reception result of response signal)
FIG. 10 is a diagram illustrating an example of the operation of each small base station according to each reception result of the response signal. A table 1000 in FIG. 10 showscases 1001 to 1004 related to retransmission of CoMP transmission in the ABS. “Small 1” in the table 1000 indicates the small base station 221, and “Small 2” indicates the small base station 222.
図10は、応答信号の各受信結果に応じた各スモール基地局の動作の一例を示す図である。図10の表1000は、ABSにおけるCoMP送信の再送に関するケース1001~1004を示す。表1000の「スモール1」はスモール基地局221を示し、「スモール2」はスモール基地局222を示している。 (Operation of each small base station according to each reception result of response signal)
FIG. 10 is a diagram illustrating an example of the operation of each small base station according to each reception result of the response signal. A table 1000 in FIG. 10 shows
ケース1001,1002は、移動局230においてユーザデータが正常に受信され、移動局230が応答信号としてACKを送信した場合を示す。ケース1003,1004は、移動局230においてユーザデータが正常に受信されず、移動局230が応答信号としてNACKを送信した場合を示す。
Cases 1001 and 1002 indicate cases where user data is normally received by the mobile station 230 and the mobile station 230 transmits ACK as a response signal. Cases 1003 and 1004 indicate a case where user data is not normally received by the mobile station 230 and the mobile station 230 transmits NACK as a response signal.
ケース1001は、スモール基地局221では移動局230からのACKが正常に受信されたが、スモール基地局222では移動局230からのACKが誤ってNACKとして受信された場合を示す。この場合は、スモール基地局221は、ACKを受信したため該当データを破棄する。また、スモール基地局222は、NACKを受信したが自局は再送を行わないため該当データを破棄する。
Case 1001 shows a case where the small base station 221 has received ACK from the mobile station 230 normally, but the small base station 222 has received ACK from the mobile station 230 by mistake as NACK. In this case, the small base station 221 receives the ACK and discards the corresponding data. In addition, the small base station 222 discards the corresponding data because it has received NACK but does not retransmit it.
ケース1002は、スモール基地局221では移動局230からのACKが誤ってNACKとして受信されたが、スモール基地局222では移動局230からのACKが正常に受信された場合を示す。この場合は、スモール基地局221は、NACKを受信したため該当データをHARQ再送する。このHARQ再送によるユーザデータは、すでに移動局230によって正常に受信されているため、たとえば移動局230において破棄される。このため、この再送は無駄になる場合がある。また、スモール基地局222は、ACKを受信したため該当データを破棄する。
Case 1002 shows a case where the small base station 221 receives the ACK from the mobile station 230 by mistake as a NACK, but the small base station 222 receives the ACK from the mobile station 230 normally. In this case, since the small base station 221 receives the NACK, the small base station 221 HARQ retransmits the corresponding data. Since the user data by this HARQ retransmission has already been normally received by the mobile station 230, for example, the mobile station 230 discards it. For this reason, this retransmission may be wasted. Further, since the small base station 222 receives the ACK, the small base station 222 discards the corresponding data.
ケース1003は、スモール基地局221では移動局230からのNACKが正常に受信されたが、スモール基地局222では移動局230からのNACKが誤ってACKとして受信された場合を示す。この場合は、スモール基地局221は、NACKを受信したため該当データをHARQ再送する。また、スモール基地局222は、ACKを受信したため該当データを破棄する。
Case 1003 shows a case where the small base station 221 has normally received the NACK from the mobile station 230, but the small base station 222 has received the NACK from the mobile station 230 by mistake as an ACK. In this case, since the small base station 221 receives the NACK, the small base station 221 HARQ retransmits the corresponding data. Further, since the small base station 222 receives the ACK, the small base station 222 discards the corresponding data.
ケース1004は、スモール基地局221では移動局230からのNACKが誤ってACKとして受信されたが、スモール基地局222では移動局230からのNACKが正常に受信された場合を示す。この場合は、スモール基地局221は、ACKを受信したため該当データを破棄する。この場合は、たとえば上位層による再送で回復が行われる。上位層はたとえばRLC(Radio Link Control:無線リンク制御)層である。上位層による再送については後述する(たとえば図11参照)。また、スモール基地局222は、NACKを受信したが自局は再送を行わないため該当データを破棄する。
Case 1004 shows a case where the small base station 221 received the NACK from the mobile station 230 by mistake as an ACK, but the small base station 222 received the NACK from the mobile station 230 normally. In this case, the small base station 221 receives the ACK and discards the corresponding data. In this case, recovery is performed by retransmission by an upper layer, for example. The upper layer is, for example, an RLC (Radio Link Control: radio link control) layer. The retransmission by the higher layer will be described later (see, for example, FIG. 11). In addition, the small base station 222 discards the corresponding data because it has received NACK but does not retransmit it.
このように、スモール基地局221,222は、ABSにおけるユーザデータの初回送信ではCoMP送信を行う一方、CoMP送信したユーザデータの再送についてはスモール基地局221が行い、スモール基地局222は再送を行わない。この再送は、ABSに限らず任意の個別のタイミングで行うことができる。たとえば、スモール基地局221は、CoMP送信について移動局230からNACKを受信すると、スモール基地局221において決定したタイミングにおいてユーザデータの移動局230への再送を行う。
As described above, the small base stations 221 and 222 perform CoMP transmission in the initial transmission of user data in the ABS, while the small base station 221 performs retransmission of the user data transmitted by CoMP, and the small base station 222 performs retransmission. Absent. This retransmission can be performed at any individual timing, not limited to ABS. For example, when receiving a NACK from the mobile station 230 for CoMP transmission, the small base station 221 retransmits user data to the mobile station 230 at a timing determined by the small base station 221.
仮に、再送についてもスモール基地局221,222によるCoMP送信を行う場合は、スモール基地局221,222において再送のタイミングを決定するために制御信号を交換するなどの処理を要するため、再送制御の処理量の増加につながる。また、スモール基地局221,222のそれぞれが再送を個別に行う場合は、移動局230がスモール基地局221,222のそれぞれのタイミングで再送データを受信することになり、通信量の増加や再送制御の処理量の増加につながる。
If CoMP transmission is performed by the small base stations 221 and 222 also for retransmission, it is necessary to perform processing such as exchanging control signals in order to determine the retransmission timing in the small base stations 221 and 222. This leads to an increase in quantity. In addition, when each of the small base stations 221 and 222 performs retransmission individually, the mobile station 230 receives the retransmission data at the timing of each of the small base stations 221 and 222, so that an increase in communication amount and retransmission control are performed. Leads to an increase in the amount of processing.
これに対して、実施の形態3によれば、初回送信についてはスモール基地局221,222によるCoMP送信を行うとともに、CoMP送信に関する再送についてはスモール基地局221のみが行うことで、再送制御の処理量の低減を図ることができる。
On the other hand, according to the third embodiment, CoMP transmission is performed by the small base stations 221 and 222 for the initial transmission, and only the small base station 221 performs the retransmission related to CoMP transmission. The amount can be reduced.
なお、スモール基地局222はNACKを受信しても再送を行わないため、スモール基地局222は、CoMP送信によって送信したユーザデータを即時破棄するようにしてもよい。
Note that even if the small base station 222 receives NACK, the small base station 222 does not perform retransmission, so the small base station 222 may immediately discard user data transmitted by CoMP transmission.
ここではスモール基地局221によって再送を行い、スモール基地局222は再送を行わない場合について説明したが、スモール基地局221,222のうちの再送を行うスモール基地局は任意の方法で決定することができる。たとえば、スモール基地局221,222のうちの再送を行うスモール基地局をマクロ基地局210が決定してスモール基地局221,222へ通知してもよい。または、スモール基地局221,222のうちの再送を行うスモール基地局をスモール基地局221,222が互いに通信を行うことによって決定してもよい。また、スモール基地局221,222のうちの再送を行うスモール基地局を、マクロ基地局210から移動局230へ通知してもよいし、スモール基地局221,222の少なくともいずれかから移動局230へ通知してもよい。
Here, the case where retransmission is performed by the small base station 221 and the small base station 222 does not perform retransmission has been described. However, the small base station that performs retransmission among the small base stations 221 and 222 can be determined by an arbitrary method. it can. For example, the macro base station 210 may determine a small base station that performs retransmission among the small base stations 221 and 222 and notify the small base stations 221 and 222 of the small base stations. Alternatively, the small base stations 221 and 222 may determine a small base station that performs retransmission among the small base stations 221 and 222 by the small base stations 221 and 222 communicating with each other. Further, the small base station to be retransmitted among the small base stations 221 and 222 may be notified from the macro base station 210 to the mobile station 230, or from at least one of the small base stations 221 and 222 to the mobile station 230. You may be notified.
(上位層による再送)
図11は、上位層による再送の一例を示す図である。図11において、図3Aに示した部分と同様の部分については同一の符号を付して説明を省略する。図11に示すように、スモール基地局221,222および移動局230は、それぞれPDCP、RLC、MAC(Media Access Control:メディアアクセス制御)、PHY(物理層)の各レイヤの処理によって無線通信を行う。 (Retransmission by upper layer)
FIG. 11 is a diagram illustrating an example of retransmission by an upper layer. In FIG. 11, the same parts as those shown in FIG. 3A are denoted by the same reference numerals, and the description thereof is omitted. As illustrated in FIG. 11, the small base stations 221 and 222 and the mobile station 230 perform wireless communication by processing of each layer of PDCP, RLC, MAC (Media Access Control), and PHY (physical layer), respectively. .
図11は、上位層による再送の一例を示す図である。図11において、図3Aに示した部分と同様の部分については同一の符号を付して説明を省略する。図11に示すように、スモール基地局221,222および移動局230は、それぞれPDCP、RLC、MAC(Media Access Control:メディアアクセス制御)、PHY(物理層)の各レイヤの処理によって無線通信を行う。 (Retransmission by upper layer)
FIG. 11 is a diagram illustrating an example of retransmission by an upper layer. In FIG. 11, the same parts as those shown in FIG. 3A are denoted by the same reference numerals, and the description thereof is omitted. As illustrated in FIG. 11, the
まず、マクロ基地局210からスモール基地局221,222へパケット#1が送信され、スモール基地局221,222がABSにおいて移動局230へパケット#1をCoMP送信したとする。これに対して、移動局230は、パケット#1を正常に受信できず、HARQ1101においてNACKを送信したとする。
First, it is assumed that packet # 1 is transmitted from the macro base station 210 to the small base stations 221 and 222, and the small base stations 221 and 222 perform CoMP transmission of the packet # 1 to the mobile station 230 in the ABS. On the other hand, it is assumed that the mobile station 230 cannot normally receive the packet # 1 and transmits a NACK in the HARQ 1101.
これに対して、スモール基地局222は移動局230からのNACKを正常に受信したが、スモール基地局221は移動局230からのNACKを誤ってACKとして受信したとする。この場合に、スモール基地局222は再送を行わないスモール基地局であるため、NACKを受信してもパケット#1の再送を行わない。一方、スモール基地局221はACKを受信したためパケット#1の再送を行わない。
In contrast, it is assumed that the small base station 222 has normally received a NACK from the mobile station 230, but the small base station 221 has erroneously received a NACK from the mobile station 230 as an ACK. In this case, since the small base station 222 is a small base station that does not retransmit, packet # 1 is not retransmitted even if NACK is received. On the other hand, since the small base station 221 has received the ACK, it does not retransmit the packet # 1.
この場合に、移動局230は、NACKを送信したにも関わらずパケット#1の再送が行われないため、RLC層の処理によって、スモール基地局221に対してパケット#1の未受信報告1102を行う。RLC層では、送受信側でPOLL/STATUS型の再送処理が行われ、これらの情報を交換し合うことによって送受信状態の同期を取ることができる。未受信報告1102は、たとえばRLC STATUS REPORTによって行うことができる。
In this case, since the mobile station 230 does not retransmit the packet # 1 even though the NACK is transmitted, the mobile station 230 sends an unreceived report 1102 of the packet # 1 to the small base station 221 by the RLC layer processing. Do. In the RLC layer, POLL / STATUS type retransmission processing is performed on the transmission / reception side, and the transmission / reception state can be synchronized by exchanging these pieces of information. The unreceived report 1102 can be performed by, for example, RLC STATUS REPORT.
これに対して、スモール基地局221は、RLC層の処理によって、パケット#1の再送1103を行う。これにより、移動局230は、パケット#1を受信することができる。パケット#1の後のパケットであるパケット#2以降についても、初回送信においてはスモール基地局221,222がABSにおいて移動局230へCoMP送信し、再送はスモール基地局221のみが行う。
On the other hand, the small base station 221 performs retransmission 1103 of the packet # 1 by processing of the RLC layer. Thereby, the mobile station 230 can receive packet # 1. Also for packet # 2 and subsequent packets after packet # 1, the small base stations 221 and 222 perform CoMP transmission to the mobile station 230 at the ABS in the initial transmission, and only the small base station 221 performs retransmission.
このように、実施の形態3によれば、初回送信についてはスモール基地局221,222によるCoMP送信を行うとともに、CoMP送信に関する再送についてはスモール基地局221のみが行うことで、再送制御の処理量の低減を図ることができる。
As described above, according to the third embodiment, CoMP transmission is performed by the small base stations 221 and 222 for the first transmission, and only the small base station 221 performs the retransmission related to CoMP transmission. Can be reduced.
以上説明したように、無線通信システム、無線通信方法、無線局および制御局によれば、スループットの向上を図ることができる。
As described above, according to the wireless communication system, the wireless communication method, the wireless station, and the control station, throughput can be improved.
100 無線通信システム
110 制御局
111,121a,121b,131,620,720 制御部
112,122a,122b,132,640 通信部
120a,120b 第1無線局
130 第2無線局
200 通信システム
201,202 Xnインタフェース
210,240 マクロ基地局
210a,240a マクロセル
221,222,251,252 スモール基地局
221a,222a,222b,251a,252a スモールセル
230,700,900 移動局
301 区切り
302 事前設定
303 制御領域
304 データ領域
311,312,381,382 ユーザデータ
321,322,331,332 フィードバック
341,342,351~354 ABS
361,362,371,372 制御信号
391,392 応答信号
600,800 基地局
610,710 無線通信部
611,711 無線送信部
612,712 無線受信部
630,730 記憶部
811,911 アンテナ
812,912 RF回路
813,913 プロセッサ
814,914 メモリ
815 ネットワークIF
1001~1004 ケース
1101 HARQ
1102 未受信報告
1103 再送 100wireless communication system 110 control station 111, 121a, 121b, 131, 620, 720 control unit 112, 122a, 122b, 132, 640 communication unit 120a, 120b first wireless station 130 second wireless station 200 communication system 201, 202 Xn Interface 210, 240 Macro base station 210a, 240a Macro cell 221, 222, 251, 252 Small base station 221a, 222a, 222b, 251a, 252a Small cell 230, 700, 900 Mobile station 301 Delimiter 302 Pre-setting 303 Control area 304 Data area 311, 312, 381, 382 User data 321, 322, 331, 332 Feedback 341, 342, 351 to 354 ABS
361, 362, 371, 372 Control signal 391, 392 Response signal 600, 800 Base station 610, 710 Wireless communication unit 611, 711 Wireless transmission unit 612, 712 Wireless reception unit 630, 730 Storage unit 811, 911 Antenna 812, 912 RF Circuit 813, 913 Processor 814, 914 Memory 815 Network IF
1001 to 1004Case 1101 HARQ
1102Unreceived report 1103 Resend
110 制御局
111,121a,121b,131,620,720 制御部
112,122a,122b,132,640 通信部
120a,120b 第1無線局
130 第2無線局
200 通信システム
201,202 Xnインタフェース
210,240 マクロ基地局
210a,240a マクロセル
221,222,251,252 スモール基地局
221a,222a,222b,251a,252a スモールセル
230,700,900 移動局
301 区切り
302 事前設定
303 制御領域
304 データ領域
311,312,381,382 ユーザデータ
321,322,331,332 フィードバック
341,342,351~354 ABS
361,362,371,372 制御信号
391,392 応答信号
600,800 基地局
610,710 無線通信部
611,711 無線送信部
612,712 無線受信部
630,730 記憶部
811,911 アンテナ
812,912 RF回路
813,913 プロセッサ
814,914 メモリ
815 ネットワークIF
1001~1004 ケース
1101 HARQ
1102 未受信報告
1103 再送 100
361, 362, 371, 372
1001 to 1004
1102
Claims (11)
- 複数の第1無線局との通信が可能な第2無線局と、前記第1無線局を制御する制御局と、を含む無線通信システムであって、
前記制御局は、
前記複数の第1無線局が協調して前記第2無線局と通信を行う協調通信を制御する制御部を備え、
前記複数の第1無線局のそれぞれは、
前記協調通信を制御する制御部と、
他の期間より低い電力によって無線送信を行う特定期間において、前記複数の第1無線局のうちの自局と異なる第1無線局と協調して無線リソースを使用し前記第2無線局宛のデータを前記第2無線局に送信する前記協調通信を行う通信部と、を備え、
前記第2無線局は、
前記協調通信による前記複数の第1無線局との通信を制御する制御部と、
前記無線リソース上で前記協調通信によって送信された自局宛のデータを受信する通信部と、を備える、
ことを特徴とする無線通信システム。 A wireless communication system including a second wireless station capable of communicating with a plurality of first wireless stations, and a control station that controls the first wireless station,
The control station
A controller that controls cooperative communication in which the plurality of first wireless stations perform communication with the second wireless station in cooperation with each other;
Each of the plurality of first wireless stations is
A control unit for controlling the cooperative communication;
In a specific period in which radio transmission is performed with lower power than other periods, data addressed to the second radio station using radio resources in cooperation with a first radio station different from its own among the plurality of first radio stations And a communication unit that performs the cooperative communication to transmit to the second wireless station,
The second radio station is
A control unit for controlling communication with the plurality of first wireless stations by the cooperative communication;
A communication unit for receiving data addressed to the own station transmitted by the cooperative communication on the radio resource,
A wireless communication system. - 前記制御局は基地局であり、
前記複数の第1無線局のそれぞれは前記制御局のセル内に位置する基地局であり、
前記第2無線局は移動局である、
ことを特徴とする請求項1に記載の無線通信システム。 The control station is a base station;
Each of the plurality of first wireless stations is a base station located in a cell of the control station,
The second radio station is a mobile station;
The wireless communication system according to claim 1. - 前記制御局は、前記協調通信の無線リソースを前記第2無線局に通知する通信部を備え、
前記複数の第1無線局のそれぞれの前記通信部は、前記協調通信において、前記無線リソースを前記第2無線局に通知せずに前記第2無線局宛のデータを送信し、
前記第2無線局の前記通信部は、前記制御局から通知された前記無線リソース上で前記協調通信によって送信された自局宛のデータを受信する、
ことを特徴とする請求項1または2に記載の無線通信システム。 The control station includes a communication unit that notifies the second wireless station of the radio resources of the cooperative communication,
Each of the communication units of the plurality of first wireless stations transmits data addressed to the second wireless station without notifying the second wireless station of the wireless resource in the cooperative communication,
The communication unit of the second radio station receives data addressed to the own station transmitted by the cooperative communication on the radio resource notified from the control station.
The wireless communication system according to claim 1, wherein the wireless communication system is a wireless communication system. - 前記制御局の前記通信部は、前記協調通信の無線リソースを前記第2無線局に通知した後に、前記協調通信の無線リソースを変更する場合にのみ前記協調通信の無線リソースを前記第2無線局に通知し、
前記第2無線局の前記通信部は、前記制御局から最後に通知された無線リソース上で自局宛のデータを受信する、
ことを特徴とする請求項3に記載の無線通信システム。 The communication unit of the control station notifies the second radio station of the cooperative communication radio resource only when changing the radio resource of the cooperative communication after notifying the radio resource of the cooperative communication to the second radio station. Notify
The communication unit of the second radio station receives data addressed to itself on the radio resource last notified from the control station.
The wireless communication system according to claim 3. - 前記制御局は、前記協調通信の無線リソースを無線信号によって前記複数の第1無線局に通知する通信部を備えることを特徴とする請求項1~4のいずれか一つに記載の無線通信システム。 5. The radio communication system according to claim 1, wherein the control station includes a communication unit that notifies the plurality of first radio stations of radio resources for the cooperative communication by radio signals. .
- 前記協調通信において前記第2無線局が前記第2無線局宛のデータを正常に受信できなかった場合に、前記複数の第1無線局のうちのいずれかの第1無線局が前記第2無線局宛のデータの再送を行い、前記複数の第1無線局のうちの他の第1無線局は前記再送を行わないことを特徴とする請求項1~5のいずれか一つに記載の無線通信システム。 In the cooperative communication, when the second wireless station cannot normally receive the data addressed to the second wireless station, any one of the plurality of first wireless stations receives the second wireless station. 6. The radio according to claim 1, wherein the data addressed to the station is retransmitted, and the other first radio station of the plurality of first radio stations does not perform the retransmission. Communications system.
- 前記特定期間は、前記複数の第1無線局に共通して設定されたABS(Almost Blank Subframe)であることを特徴とする請求項1~6のいずれか一つに記載の無線通信システム。 7. The wireless communication system according to claim 1, wherein the specific period is an ABS (Almost Blank Subframe) set in common to the plurality of first wireless stations.
- 複数の第1無線局との通信が可能な第2無線局と、前記第1無線局を制御する制御局と、を含む無線通信システムにおける無線通信方法であって、
前記制御局が、前記複数の第1無線局が協調して前記第2無線局と通信を行う協調通信を制御し、
他の期間より低い電力によって無線送信を行う特定期間において、前記複数の第1無線局が協調して無線リソースを使用し前記第2無線局宛のデータを前記第2無線局に送信する前記協調通信を行い、
前記第2無線局が、前記無線リソース上で前記協調通信によって送信された自局宛のデータを受信する、
ことを特徴とする無線通信方法。 A wireless communication method in a wireless communication system, comprising: a second wireless station capable of communicating with a plurality of first wireless stations; and a control station that controls the first wireless station,
The control station controls cooperative communication in which the plurality of first wireless stations communicate with the second wireless station in cooperation with each other,
The cooperation in which the plurality of first wireless stations cooperate to use radio resources and transmit data addressed to the second wireless station to the second wireless station in a specific period in which wireless transmission is performed with lower power than other periods. Communicate
The second radio station receives data addressed to the own station transmitted by the cooperative communication on the radio resource;
A wireless communication method. - 複数の第1無線局との通信が可能な第2無線局と、前記第1無線局を制御する制御局と、を含む無線通信システムにおける前記複数の第1無線局に含まれる無線局であって、
前記複数の第1無線局が協調して前記第2無線局と通信を行う協調通信を制御する制御部と、
他の期間より低い電力によって無線送信を行う特定期間において、前記複数の第1無線局のうちの自局と異なる第1無線局と協調して前記第2無線局宛のデータを前記第2無線局に送信する前記協調通信を行う通信部と、
を備えることを特徴とする無線局。 A radio station included in the plurality of first radio stations in a radio communication system including a second radio station capable of communicating with a plurality of first radio stations and a control station that controls the first radio station. And
A control unit for controlling cooperative communication in which the plurality of first wireless stations cooperate to communicate with the second wireless station;
In a specific period in which radio transmission is performed with lower power than other periods, data addressed to the second radio station is transmitted to the second radio station in cooperation with a first radio station different from the own station among the plurality of first radio stations. A communication unit that performs the cooperative communication to be transmitted to a station;
A radio station comprising: - 複数の第1無線局との通信が可能な第2無線局と、前記第1無線局を制御する制御局と、を含む無線通信システムにおける前記第2無線局であって、
前記複数の第1無線局が協調して前記第2無線局と通信を行う協調通信による前記複数の第1無線局との通信を制御する制御部と、
他の期間より低い電力によって無線送信を行う特定期間において、前記複数の第1無線局が協調して送信した前記第2無線局宛のデータを受信する通信部と、
を備えることを特徴とする無線局。 A second wireless station in a wireless communication system, comprising: a second wireless station capable of communicating with a plurality of first wireless stations; and a control station that controls the first wireless station;
A control unit that controls communication with the plurality of first wireless stations by cooperative communication in which the plurality of first wireless stations cooperate to communicate with the second wireless station;
A communication unit that receives data addressed to the second radio station transmitted in cooperation by the plurality of first radio stations in a specific period in which radio transmission is performed with lower power than other periods;
A radio station comprising: - 複数の第1無線局との通信が可能な第2無線局と、前記第1無線局を制御する制御局と、を含む無線通信システムにおける前記制御局であって、
前記複数の第1無線局が他の期間より低い電力によって無線送信を行う特定期間において、前記複数の第1無線局が協調して前記第2無線局と通信を行う協調通信を制御する制御部を備えることを特徴とする制御局。 A control station in a wireless communication system comprising: a second wireless station capable of communicating with a plurality of first wireless stations; and a control station that controls the first wireless station,
A control unit that controls cooperative communication in which the plurality of first wireless stations cooperate to communicate with the second wireless station in a specific period in which the plurality of first wireless stations perform wireless transmission with lower power than other periods. A control station comprising:
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