WO2014162357A1 - 無線通信方法、無線通信システム、無線局および無線端末 - Google Patents
無線通信方法、無線通信システム、無線局および無線端末 Download PDFInfo
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- WO2014162357A1 WO2014162357A1 PCT/JP2013/002351 JP2013002351W WO2014162357A1 WO 2014162357 A1 WO2014162357 A1 WO 2014162357A1 JP 2013002351 W JP2013002351 W JP 2013002351W WO 2014162357 A1 WO2014162357 A1 WO 2014162357A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/003—Arrangements for allocating sub-channels of the transmission path
- H04L5/0048—Allocation of pilot signals, i.e. of signals known to the receiver
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
- H04W72/20—Control channels or signalling for resource management
- H04W72/23—Control channels or signalling for resource management in the downlink direction of a wireless link, i.e. towards a terminal
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/022—Site diversity; Macro-diversity
- H04B7/024—Co-operative use of antennas of several sites, e.g. in co-ordinated multipoint or co-operative multiple-input multiple-output [MIMO] systems
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/003—Arrangements for allocating sub-channels of the transmission path
- H04L5/0032—Distributed allocation, i.e. involving a plurality of allocating devices, each making partial allocation
- H04L5/0035—Resource allocation in a cooperative multipoint environment
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/003—Arrangements for allocating sub-channels of the transmission path
- H04L5/0044—Arrangements for allocating sub-channels of the transmission path allocation of payload
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/003—Arrangements for allocating sub-channels of the transmission path
- H04L5/0058—Allocation criteria
- H04L5/0073—Allocation arrangements that take into account other cell interferences
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/003—Arrangements for allocating sub-channels of the transmission path
- H04L5/0078—Timing of allocation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/0091—Signaling for the administration of the divided path
- H04L5/0094—Indication of how sub-channels of the path are allocated
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/022—Site diversity; Macro-diversity
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/003—Arrangements for allocating sub-channels of the transmission path
- H04L5/0053—Allocation of signaling, i.e. of overhead other than pilot signals
Definitions
- the present invention relates to a wireless communication method, a wireless communication system, a wireless station, and a wireless terminal.
- next-generation wireless communication technologies have been discussed in order to further increase the speed and capacity of wireless communication in wireless communication systems such as mobile phone systems.
- 3GPP 3rd Generation Partnership Project
- LTE Long Term Evolution
- LTE-A LTE-Advanced
- CoMP Coordinated MultiPoint
- the communication can be executed in various communication modes.
- a plurality of geographically distant communication points perform communication in order to reduce inter-cell interference and improve received signal strength.
- Each communication point corresponds to, for example, a base station, a communication unit, an antenna, or a cell formed by these.
- transmission or reception between multiple points is adjusted.
- downlink CoMP communication a method of dynamically selecting a communication point used for signal transmission among a plurality of communication points and a method of combining and transmitting signals from a plurality of communication points to a wireless terminal are being studied. Yes.
- various communication modes between cells can be used in order to reduce inter-cell interference and improve received signal strength in consideration of control delay and increased signaling. It is necessary to adjust appropriately.
- the communication mode of each communication point can be variously changed for each wireless terminal depending on the cell arrangement and the communication status. For example, there may be many communication points capable of CoMP communication, and the number and combination of communication points actually used for signal transmission in CoMP communication vary. Further, for example, various communication modes such as single antenna transmission and MIMO communication are assumed besides CoMP communication. In such a situation, a reference signal for receiving a signal needs to be transmitted so as to correspond to the communication mode that can be variously changed. At this time, if the radio resource for transmitting the reference signal is not efficiently allocated, there is a risk that improvement in communication performance may be hindered.
- the disclosed technology has been made in view of the above, and an object thereof is to provide a wireless communication method, a wireless communication system, a wireless station, and a wireless terminal capable of efficiently allocating wireless resources and improving communication performance. .
- a wireless communication method disclosed in the present application includes a plurality of pieces of configuration information indicating wireless resources prepared for transmission of wireless terminal-specific reference signals from wireless stations. Obtained at the terminal, and transmits a signal designating a use mode related to use of the radio resource indicated by each of the plurality of configuration information from the radio station to the radio terminal, and receives the signal at the radio terminal.
- the communication with the radio station is performed using the reference signal specific to the radio terminal transmitted from the radio station using the radio resource allocated according to the use mode.
- the wireless communication method disclosed in the present case it is possible to efficiently allocate wireless resources and improve communication performance.
- FIG. 1 is a diagram illustrating a configuration of a wireless communication system according to the first embodiment.
- FIG. 2 is a functional block diagram showing the configuration of the radio station according to the first embodiment.
- FIG. 3 is a block diagram illustrating a functional configuration of the wireless terminal according to the first embodiment.
- FIG. 4 is a diagram illustrating a hardware configuration of the radio station according to the first embodiment.
- FIG. 5 is a diagram illustrating a hardware configuration of the wireless terminal according to the first embodiment.
- FIG. 6 is a sequence diagram for explaining the operation of the wireless communication system according to the first embodiment.
- FIG. 7 is a functional block diagram showing the configuration of the radio station according to the second embodiment.
- 8A and 8B are diagrams for explaining configuration information indicating radio resources prepared for transmission of reference signals for individual radio terminals.
- FIG. 1 is a diagram illustrating a configuration of a wireless communication system according to the first embodiment.
- FIG. 2 is a functional block diagram showing the configuration of the radio station according to the first embodiment.
- FIG. 9 is a table showing an example of setting of the configuration information and the use mode of the reference signal for each wireless terminal.
- FIG. 10 is a block diagram illustrating a functional configuration of the wireless terminal according to the second embodiment.
- FIG. 11 is a sequence diagram for explaining the operation of the wireless communication system according to the second embodiment.
- 12A and 12B are tables showing an example of setting of configuration information and use modes of reference signals for individual wireless terminals.
- FIG. 13 is a diagram illustrating a configuration of a wireless communication system according to the third embodiment.
- FIG. 14 is a table showing an example of setting of configuration information and use modes of reference signals for individual wireless terminals.
- FIG. 15 is a sequence diagram for explaining the operation of the wireless communication system according to the third embodiment.
- FIG. 16 is a diagram illustrating a configuration of a wireless communication system according to the fourth embodiment.
- FIG. 17 is a diagram illustrating a configuration of a wireless communication system according to the fifth embodiment.
- FIG. 1 shows a configuration of a wireless communication system 1 according to the first embodiment.
- the wireless communication system 1 includes wireless stations 10A to 10B and wireless terminals 20A to 20B.
- Each of the radio stations 10A to 10B has an antenna and corresponds to a communication point.
- the radio station 10A forms a cell C10A
- the radio station 10B forms a cell C10B.
- the wireless stations 10A to 10B communicate with each other through a wired connection or a wireless connection.
- the radio stations 10A to 10B can perform single antenna communication and MIMO communication with the radio terminals 20A to 20B. Further, the radio stations 10A to 10B can perform CoMP communication with the radio terminals 20A to 20B. For example, in downlink CoMP communication with the radio terminal 20A, from one or more communication points selected as a set to be used in downlink CoMP communication among the radio stations 10A to B, the same time and frequency are transmitted to the radio terminal 20A. The combined transmission is performed to transmit data using the wireless resources.
- data from the radio terminal 20A is transmitted at one or more communication points selected as a set to be used for uplink CoMP communication among the radio stations 10A to 10B.
- Each reception is performed, and the combined reception is performed in which the received signals are combined between the communication points.
- the radio stations 10A to 10B are each connected to the network device 3 via a wired connection or a wireless connection, and the network device 3 is connected to the network 2 via a wired connection or a wireless connection.
- the radio stations 10A to 10B are provided so as to be able to transmit and receive data and control information via the network device 3 and the network 2.
- FIG. 2 is a block diagram showing a functional configuration of the radio station 10A.
- the radio station 10A includes a reception unit 11, a transmission unit 12, and a control unit 13. Each of these components is connected so that signals and data can be input and output in one direction or in both directions.
- the functional configuration and hardware configuration of the radio station 10B are the same as the functional configuration and hardware configuration of the radio station 10A.
- the radio station 10A is connected to the radio terminal 20A (a radio station connected to the radio terminal 20A, also referred to as a connected cell), and the radio station 10B is connected to the radio terminal 20B (a radio station (wireless). It is also referred to as a connected radio station or connected cell of terminal 20B).
- the receiving unit 11 receives data signals and control signals via an antenna (physical antenna). For example, the reception unit 11 receives an uplink signal transmitted on an uplink data channel or a control channel.
- An example of the uplink data channel is an individual data channel.
- examples of the uplink control channel include a random access channel and a dedicated control channel.
- signals to be received for example, signals for establishing connections from the radio terminals 20A to 20B, signals indicating communication levels at the radio terminals 20A to 20B, reference signals used for channel estimation and demodulation (pilot signals) Also called).
- the transmission unit 12 transmits a data signal and a control signal via an antenna (physical antenna).
- the antenna may be common for transmission and reception or may be separate.
- the transmission unit 12 transmits, for example, a downlink signal transmitted on a downlink data channel or control channel.
- Examples of the downlink data channel include a common data channel and a dedicated data channel.
- examples of the downlink control channel include a synchronization channel, a broadcast channel, a common control channel, and an individual control channel.
- a signal to be transmitted for example, a signal for informing system information, a control signal transmitted to the connected wireless terminal 20A on the dedicated control channel, or a control transmitted to the connected wireless terminal 20A on the dedicated data channel
- Signals and data signals transmitted on the dedicated data channel to the connected radio terminal 20A can be mentioned.
- the signal to be transmitted includes, for example, a paging signal for calling the wireless terminal 20A when a call arrives at the wireless terminal 20A, a signal indicating a communication level at the wireless stations 10A to 10B, A response signal to a signal for establishing a connection from B and a control signal for controlling uplink transmission power from the radio terminals 20A to 20B can be mentioned.
- the signal to be transmitted indicates, for example, a radio terminal-specific reference signal (also referred to as an individual pilot signal) used for channel estimation or demodulation, or a radio resource prepared for transmission of a radio terminal-specific reference signal. It includes a plurality of pieces of configuration information and a signal designating a use mode related to use of the radio resource indicated by each of the plurality of pieces of configuration information.
- the control unit 13 transmits / receives data and control information to / from the network device 3 and other wireless stations 10B via a wired connection or a wireless connection.
- the control unit 13 inputs received data and control information from the reception unit 11. Further, the control unit 13 outputs data to be transmitted and control information to the transmission unit 12.
- the control unit 13 transmits and receives data and control information via a wired network via a communication interface.
- the control unit 13 performs management such as access management with the radio terminals 20A to 20B and allocation of radio resources to the radio terminals 20A to 20B.
- the radio station 10A has a plurality of antenna ports, and the control unit 13 assigns antenna ports to be used for communication with the radio terminals 20A to 20B.
- the antenna port is a processing port and may not correspond to the physical antenna.
- the control unit 13 executes a process of notifying the wireless terminal 20A of a plurality of pieces of configuration information indicating wireless resources prepared for transmission of a reference signal for each wireless terminal. For example, the control unit 13 may notify the wireless terminal 20A of a plurality of pieces of configuration information itself, or notify the wireless terminal 20A of information specifying a plurality of pieces of configuration information from information stored in advance in the wireless terminal 20A. May be.
- Each of the plurality of pieces of configuration information includes, for example, the arrangement of resource elements (also referred to as time-frequency resources) used for transmission of reference signals for individual radio terminals, and antenna port information used for transmission of reference signals for individual radio terminals. And the spatial multiplexing number (also called rank or number of layers) of transmission signals.
- the prepared radio resources are different from each other with a plurality of pieces of configuration information.
- the prepared radio resources are arranged to be orthogonal to each other.
- the resource element is, for example, a minimum time-frequency unit (symbol-subcarrier) in transmission, and a resource block is formed by a group of resource elements (symbol and subcarrier). The resource block is used as a time frequency resource allocation unit.
- a plurality of pieces of configuration information are used in common by the radio station 10A and other radio stations around the own station.
- Other wireless stations around the own station include another wireless station 10B capable of CoMP communication.
- a plurality of pieces of configuration information may be stored in advance in each of the radio stations 10A to 10B, or may be acquired from the network device 3 by the radio stations 10A to 10B. Notification from one wireless station to the other wireless station may be made via wired communication or wireless communication.
- control unit 13 executes a process of transmitting a signal designating each use mode of the plurality of pieces of configuration information when transmitting data.
- the signal specifying the use mode has a relatively small amount of information than the configuration information itself.
- the control unit 13 determines the use mode according to the communication status at the time of data transmission.
- As the use mode for example, a mode indicating that the prepared radio resource is used for transmitting a reference signal for each radio terminal, or a mode indicating that a radio resource prepared for transmitting the reference signal for each radio terminal is not used. And a mode indicating that a radio resource prepared for transmitting a reference signal for each radio terminal is used for data transmission.
- the use mode is, for example, a mode in which a radio terminal-specific reference signal is transmitted with a predetermined transmission power using a prepared radio resource, and a mode in which the radio terminal-specific reference signal is set to 0 (no transmission). And a mode for allocating radio resources prepared for reference signals specific to the radio terminals to data signals.
- the control unit 13 individually designates the use mode for the plurality of wireless terminals. Then, the control unit 13 communicates with the radio terminals 20A to 20B using a reference signal for each radio terminal that is transmitted using radio resources allocated according to the use mode.
- the control unit 13 determines whether the radio station 10A transmits data to the radio terminals 20A to 20B by CoMP communication with the other radio station 10B, the number of radio terminals that the radio station 10A is connected to, and the radio station 10A.
- the use mode of each of the plurality of pieces of configuration information is determined according to at least one of the communication mode to be transmitted and the communication mode to transmit data from the other radio station 10B. Examples of the communication mode include single antenna communication, MIMO communication, and CoMP communication.
- the MIMO communication includes, for example, MU (Multi-User) -MIMO communication and SU (Single-User) -MIMO communication.
- the CoMP communication includes, for example, DPS (Dynamic Point Selection) -COMP communication and JT (Joint transmission) -CoMP communication described later.
- control unit 13 acquires the communication status of other wireless stations in the vicinity of the own station at the time of data transmission.
- Other radio stations include a radio station 20B capable of CoMP communication.
- control unit 13 determines a communication mode for transmitting data at the time of data transmission, and determines each use mode of the plurality of pieces of configuration information.
- the control unit 13 acquires the communication level between the radio stations 10A to 10B and the radio terminal 20A.
- the communication level is measured from, for example, an uplink reference signal or a downlink reference signal.
- the communication level may be reported from the radio terminal 20A, the communication level between the radio station 10A and the radio terminal 20A is measured by the radio station 10A, and the communication level between the radio station 10B and the radio station 20B is measured. May be measured by the radio station 10B and notified to the radio station 10A.
- control unit 13 transmits a signal requesting CoMP communication to another radio station 10B capable of CoMP communication with the radio terminal 20A (hereinafter also referred to as a coordinated radio station or a coordinated cell), and the other radio station 10B.
- the response signal is received from and preparation for CoMP communication is performed.
- the control unit 13 then transmits one or more radio stations (hereinafter referred to as selected radio stations) that transmit signals to the radio terminal 20A from the plurality of radio stations 10A to 10B capable of CoMP communication according to the communication level and other communication conditions. Select).
- One or more radio stations selected from a plurality of radio stations are one radio station selected by the DPS operation (DPS-CoMP communication) or two or more radio stations selected by the JT operation (JT-CoMP communication). It is.
- DPS is a method of dynamically selecting a communication point to be used for transmission among a plurality of communication points.
- JT is a method for combining (synthesizing) signals transmitted from a plurality of communication points.
- the control unit 13 selects a candidate radio station from other radio stations capable of CoMP communication at a predetermined timing, and performs data transmission of the radio station actually used from the candidate radio stations.
- the radio station may be selected in a plurality of stages.
- the control unit 13 exchanges control information between the radio station 10A and the radio station 10B, and sets parameters used in CoMP communication. At this time, reference signals and control information for individual radio terminals may be exchanged between the radio stations 10A to 10B and the radio terminal 20A. Thereby, it is determined to perform CoMP communication with the radio terminal 20A.
- the control unit 13 When CoMP communication is not performed for the radio terminal 20A, the control unit 13 performs single antenna communication, MU-MIMO communication, or SU-MIMO depending on the communication level and other communication conditions. Decide whether to communicate. In this way, the control unit 13 determines the communication mode for transmitting data.
- control part 13 determines each use mode of several structure information, transmits the signal which shows use mode to 20 A of radio
- control unit 13 performs communication modes and a plurality of pieces of configuration information in the same manner as the processing for the wireless terminal 20A.
- the use mode is determined, a signal indicating the use mode is transmitted, and communication is performed according to the use mode.
- the radio station 10A operates as a cooperative radio station of the radio station 10B, which is a radio station connected to the radio terminal 20B.
- the control unit 13 receives a signal requesting CoMP communication from the radio station 10B, transmits a response signal, and prepares for CoMP communication. Then, when the radio station 10A is selected as the selected radio station by the radio station 10B, the control unit 13 exchanges control information between the radio station 10A and the radio station 10B, and parameters used in CoMP communication. Set. At this time, reference signals and control information for individual radio terminals may be exchanged between the radio stations 10A to 10B and the radio terminal 20B. Thereby, it is determined to perform CoMP communication with the radio terminal 20B. And the control part 13 determines each use mode of several structure information, transmits the signal which shows use mode to the radio
- FIG. 3 is a functional block diagram showing the configuration of the wireless terminal 20A.
- the radio terminal 20 ⁇ / b> A includes a reception unit 21, a transmission unit 22, and a control unit 23. Each of these components is connected so that signals and data can be input and output in one direction or in both directions.
- the functional configuration and hardware configuration of the wireless terminal 20B are the same as the functional configuration and hardware configuration of the wireless terminal 20A.
- the receiving unit 21 receives data signals and control signals transmitted from the radio stations 10A to 10B via the antenna.
- Examples of the received signal include a signal for informing system information, a control signal transmitted from the connection radio station 10A on the dedicated control channel, and a control signal transmitted from the connection radio station 10A on the dedicated data channel.
- the received signals include, for example, a paging signal for calling the radio terminal 20A, a response signal to a signal for establishing a connection from the radio terminal 20A, a signal indicating the communication level at the radio stations 10A to B, And a control signal for controlling uplink transmission power.
- the received signal includes, for example, a reference signal for each wireless terminal used for channel estimation and demodulation, a plurality of pieces of configuration information indicating a radio resource prepared for transmission of a reference signal for each wireless terminal, and a plurality of configurations. Contains a signal that specifies the respective mode of use of the information.
- the transmission unit 22 transmits a data signal and a control signal via an antenna (physical antenna).
- the antenna may be common for transmission and reception or may be separate.
- the transmission unit 22 transmits, for example, an uplink signal transmitted on an uplink data channel or a control channel. Examples of the signal to be transmitted include a signal for establishing a connection, a signal indicating a communication level at the wireless terminal 20, and a reference signal used for channel estimation and demodulation.
- the control unit 23 inputs the received data and control information from the reception unit 21. In addition, data to be transmitted and control information are output to the transmission unit 22. Further, the control unit 23 controls the transmission power of the transmission signal.
- control unit 23 detects a cell-specific reference signal received from the radio stations 10A and 10B and a reference signal specific to each radio terminal, and acquires a communication level.
- the communication level includes, for example, reception power and reception quality.
- control unit 23 sets a plurality of pieces of configuration information indicating radio resources prepared for transmission of reference signals for individual radio terminals.
- the control unit 23 receives a signal indicating each use mode of the plurality of configuration information from the radio station 10A during downlink data transmission, and communicates with the radio station 10A according to each use mode of the plurality of configuration information. Communicate.
- the control unit 23 receives signals indicating the use modes of the plurality of pieces of configuration information from the radio stations 10A to 10B, Communication with the radio stations 10A to 10B is performed in accordance with each use mode of the plurality of pieces of configuration information.
- FIG. 4 is a diagram illustrating a hardware configuration of the radio station 10A.
- the radio station 10A includes, as hardware components, an RF (Radio Frequency) circuit 32 including an antenna 31, a CPU (Central Processing Unit) 33, a DSP (Digital Signal Processor) 34, and the like. , A memory 35 and a network IF (Interface) 36.
- the CPU is connected via a network IF 36 such as a switch so that various signals and data can be input and output.
- the memory 35 includes at least one of RAM (Random Access Memory) such as SDRAM (Synchronous Dynamic Random Access Memory), ROM (Read Only Memory), and flash memory, and stores programs, control information, and data.
- the transmission unit 12 and the reception unit 11 are realized by the RF circuit 32 or the antenna 31 and the RF circuit 32, for example.
- the control unit 13 is realized by, for example, an integrated circuit such as the CPU 33 or an integrated circuit such as the DSP 34.
- FIG. 5 is a diagram illustrating a hardware configuration of the wireless terminal 20A.
- the radio terminal 20 ⁇ / b> A includes, as hardware components, for example, an RF circuit 42 including an antenna 41, a CPU 43, and a memory 44.
- the radio terminal 20 ⁇ / b> A may include a display device such as an LCD (Liquid Crystal Display) connected to the CPU 43.
- the memory 44 includes at least one of RAM such as SDRAM, ROM, and flash memory, for example, and stores programs, control information, and data.
- the transmission unit 22 and the reception unit 21 are realized by the RF circuit 42 or the antenna 41 and the RF circuit 42, for example.
- the control unit 23 is realized by an integrated circuit such as the CPU 43, for example.
- FIG. 6 is a sequence diagram for explaining a downlink transmission operation of the wireless communication system 1.
- the wireless stations 10A to 10B have communication modes such as single antenna communication, SU-MIMO communication, MU-MIMO communication, and CoMP communication (JT-CoMP communication or DSP).
- -CoMP communication is provided.
- the radio station 10A is a connection radio station of the radio terminal 20A, and performs CoMP communication processing for the radio terminal 20A with the radio station 10B (cooperative radio station) in an aggregated manner.
- the radio station 10B is a connection radio station of the radio terminal 20B, and performs CoMP communication processing for the radio terminal 20B with the radio station 10A (cooperative radio station) in an integrated manner.
- the communication mode of each communication point is dynamically selected at a relatively short period, for example, every data transmission. And it is assumed that the communication mode of each communication point can change variously for every radio
- a reference signal (a reference signal used for demodulating a signal) specific to a wireless terminal for receiving a signal so as to correspond to a communication mode that can be variously changed.
- the radio resource for transmitting the reference signal for each radio terminal is not appropriately allocated, the communication performance may be prevented from improving. For example, if a radio resource for transmitting a reference signal for each radio terminal is allocated in advance so as to cover various patterns of communication modes that can be varied, a large number of radio resources are allocated for transmission of the reference signal for each radio terminal. Wireless resources are required. For this reason, the throughput of data transmission is reduced, and there is a risk of hindering improvement in communication performance.
- the radio resource allocated to the transmission of the reference signal for each wireless terminal is insufficient depending on the communication mode and the wireless resources for transmitting the reference signal for each wireless terminal overlap between communication points, interference between communication points may occur. There is a risk of hindering reduction and improvement of received signal strength. In particular, when cells having a relatively small scale are arranged at a relatively high density, the influence of interference increases, so that there is a high possibility that improvement in communication performance is hindered.
- a downlink transmission operation is performed as follows.
- the radio station 10A provides the radio terminal 20A with a plurality of pieces of configuration information (configuration information 1 and 2 of reference signals for individual radio terminals) indicating radio resources prepared for transmission of reference signals for individual radio terminals. ) Is notified (S1). The notification of the configuration information 1 and 2 of the reference signal for each wireless terminal by the wireless station 10A is notified when the connection with the wireless terminal 20A is established, for example. Similarly, the radio station 10B notifies the radio terminal 20B of a plurality of pieces of configuration information (configuration information 1 and 2 of reference signals for individual radio terminals) indicating radio resources prepared for transmission of reference signals for the individual radio terminals. (S2).
- the notification of the configuration information 1 and 2 of the reference signal for each wireless terminal by the wireless station 10B is notified when the connection with the wireless terminal 20B is established, for example.
- the configuration information 1 and 2 are used in common by the radio stations 10A to 10B.
- Each of the configuration information 1 and 2 includes resource element arrangement, antenna port information, and the number of layers.
- the radio resources prepared by the configuration information 1 and 2 are set to be different from each other.
- the radio stations 10A to 10B may re-report the configuration information 1 and 2 to the radio terminals 20A to 20B at a predetermined control timing.
- the wireless stations 10A to 10B may update the configuration information 1 and 2 and notify the wireless terminals 20A to 20B at a predetermined control timing.
- the radio station 10A determines a communication mode for transmitting data to the radio terminal 20A (S3).
- the radio station 10B determines a communication mode for transmitting data to the radio terminal 20B (S4).
- the radio station 10A and the radio station 10B exchange control information with each other to acquire a communication status.
- the communication mode is determined every time data is transmitted, for example.
- the determination of the communication mode is executed at an interval relatively shorter than the connection establishment.
- the radio station 10A determines to perform SU-MIMO communication as a communication mode with respect to the radio terminal 20A.
- the radio station 10B determines to perform SU-MIMO communication as a communication mode with respect to the radio terminal 20B.
- the radio station 10A determines whether the radio terminal 20A has a communication level between the radio station 10A and the radio terminal 20A and a communication level between the radio station 10B and the radio terminal 20A. It decides not to perform CoMP communication.
- the communication level between the radio station 10A and the radio terminal 20A is such that the radio terminal 20A receives a cell-specific reference signal transmitted from the radio station 10A, and transmits a measurement result from the radio terminal 20A to the radio station 10A. You can get it.
- the reference signal transmitted from the radio terminal 20A may be received by the radio station 10A and measured by the radio station 10A. Then, since the radio station 10A does not communicate with radio terminals other than the radio terminal 20A, it determines to perform SU-MIMO communication as a communication mode for the radio terminal 20A.
- the radio station 10B performs CoMP communication with the radio terminal 20B according to the communication level between the radio station 10A and the radio terminal 20B and the communication level between the radio station 10B and the radio terminal 20B. Decide not to do it.
- the communication level between the radio station 10B and the radio terminal 20A is such that the radio terminal 20A receives a cell-specific reference signal transmitted from the radio station 10B, and transmits a measurement result from the radio terminal 20A to the radio station 10A. You can get it.
- the reference signal transmitted from the radio terminal 20A may be received by the radio station 10B, and the measurement result may be transmitted from the radio station 10B to the radio station 10A for notification. Then, since the radio station 10B does not communicate with radio terminals other than the radio terminal 20B, the radio station 10B determines to perform SU-MIMO communication as a communication mode for the radio terminal 20B.
- the radio station 10A determines the use mode of the configuration information 1 and 2 based on the determined communication mode and other communication conditions. Further, the radio station 10B determines the use mode of the configuration information 1 and 2 based on the determined communication mode and other communication conditions.
- a mode for example, a mode (NZP, Non-zero power) in which a reference signal specific to a radio terminal is transmitted with a predetermined transmission power using a prepared radio resource, and a transmission power of a reference signal specific to a radio terminal is set to zero. It is possible to set a mode (ZP, Zero power) and a mode (OVR, Over ray) in which a radio resource prepared for a reference signal for each radio terminal is assigned to a data signal.
- ZP Zero power
- OVR Over ray
- the radio station 10A performs SU-MIMO communication to the radio terminal 20A under its control, and the radio station 10B performs SU-MIMO communication to the radio terminal 20B under its control.
- the usage mode of configuration information 1 is “NZP”
- the usage mode of configuration information 2 is “ZP”.
- the radio station 10B performs SU-MIMO communication with the radio terminal 20B under its control
- the radio station 10A performs SU-MIMO communication with the radio terminal 20A under control
- the radio station 10A From the usage modes of the configuration information 1 and 2 for the wireless terminal 20A, the usage mode of the configuration information 1 for the wireless terminal 20B is “ZP” and the usage mode of the configuration information 2 is “NZP”.
- the radio station 10A uses the radio resource used for the radio terminal individual reference signal transmitted to the radio terminal 20A and the radio station 10B uses the radio terminal individual reference signal transmitted to the radio terminal 20B.
- the use modes of the configuration information 1 and 2 are determined so that the radio resources are different. Thereby, when transmitting a reference signal for each wireless terminal, interference between communication points is reduced, channel estimation accuracy for receiving data is improved, and communication performance is improved.
- the radio station 10A transmits a signal indicating each use mode of the configuration information 1 and 2 to the radio terminal 20A (S5).
- the radio station 10B transmits a signal indicating each use mode of the configuration information 1 and 2 to the radio terminal 20B (S6).
- the radio station 10A transmits data to the radio terminal 20A (S7).
- the radio station 10A transmits a reference signal specific to the radio terminal for data reception using the resource element and antenna port prepared in the configuration information 1 according to the use mode transmitted in S5. And send the data.
- the wireless terminal 10A acquires a reference signal specific to the wireless terminal for receiving data from the use mode transmitted in S5, and uses the acquired reference signal specific to the wireless terminal to determine the SU-MIMO determined in S3. Receives data transmitted by communication.
- the radio station 10B transmits data to the radio terminal 20B (S8).
- the radio station 10B transmits a reference signal specific to the radio terminal for data reception using radio resources prepared in the configuration information 2 according to the use mode transmitted in S5, and S3
- the data is transmitted to the radio terminal 20B by SU-MIMO communication according to the communication mode determined in (1).
- the radio terminal 20B specifies the radio resource to which the reference signal specific to the radio terminal is transmitted according to the use mode transmitted in S5, and receives the reference signal specific to the radio terminal.
- the radio stations 10A to 10B perform the same processing as S3 to S8 in S9 to S14 and S15 to S22.
- the radio station 10A determines a communication mode for transmitting data to the radio terminal 20A (S9). Similarly, the radio station 10A determines a communication mode for transmitting data to the radio terminal 20B (S10). At this time, the radio station 10A and the radio station 10B exchange control information with each other and acquire the communication status.
- the radio station 10A determines to perform CoMP communication as a communication mode for the radio terminal 20A.
- the radio station 10B determines to perform CoMP communication as a communication mode for the radio terminal 20A.
- the communication mode for the radio terminal 20B is not determined.
- the radio station 10A determines whether the radio terminal 20A has a communication level between the radio station 10A and the radio terminal 20A and a communication level between the radio station 10B and the radio terminal 20A. Whether or not to perform CoMP communication is determined, and a selected station that actually transmits a signal by CoMP communication to the radio terminal 20A is determined.
- the radio station 10A When the radio station 10B is selected as the selected radio station for performing CoMP communication, the radio station 10A transmits a signal requesting CoMP communication to the radio station 10B. When the CoMP communication can be executed in cooperation with the radio station 10A, the radio station 10B transmits a response signal indicating that it can be executed to the radio terminal 20A. The radio station 10A receives the response signal, prepares for CoMP communication with the radio terminal 20A, and determines CoMP communication as a communication mode for the radio terminal 20A.
- the radio station 10B transmits a response signal indicating that CoMP communication can be performed in cooperation with the radio station 10A to the radio terminal 20A, and prepares for CoMP communication for the radio terminal 20A. To determine CoMP communication as a communication mode for the radio terminal 20A.
- the radio station 10A determines the use mode of the configuration information 1 and 2 based on the determined communication mode and other communication conditions. Further, the radio station 10B determines the use mode of the configuration information 1 and 2 based on the determined communication mode and other communication conditions.
- the wireless station 10A performs CoMP communication with the wireless terminal 20A in cooperation with the wireless station 10B, and the wireless station 10A does not communicate with wireless terminals other than the wireless terminal 20A.
- the usage mode of the configuration information 1 is “NZP” and the usage mode of the configuration information 2 is “OVR”.
- the radio station 10B performs CoMP communication with the radio terminal 20A in cooperation with the radio station 10B, does not communicate with radio terminals other than the radio terminal 20A, From the usage modes of the configuration information 1 and 2 for the terminal 20A, the usage mode of the configuration information 1 for the wireless terminal 20B is “NZP” and the usage mode of the configuration information 2 is “OVR”.
- the radio stations 10A to 10B use radio signals used for individual reference signals transmitted to the radio terminal 20A.
- the use modes of the configuration information 1 and 2 are appropriately determined so that the resources are the same. Further, it is assumed that the communication performance of transmitting a reference signal for each radio terminal to the radio terminal 20A is improved by the CoMP communication between the radio station 10A and the radio station 10B to the radio terminal 20A. Therefore, the use modes of the configuration information 1 and 2 are appropriately determined so that radio resources that are not used for the reference signal for each radio terminal are used for data transmission.
- the radio station 10A transmits a signal indicating each use mode of the configuration information 1 and 2 to the radio terminal 20A (S11).
- the radio station 10B transmits a signal indicating each use mode of the configuration information 1 and 2 to the radio terminal 20A (S12).
- the radio stations 10A to 10B transmit data to the radio terminal 20A in a coordinated manner (S13, S14).
- the radio station 10A determines a communication mode for transmitting data to the radio terminal 20A (S15). Similarly, the radio station 10A determines a communication mode for transmitting data to the radio terminal 20B (S16). At this time, the radio station 10A and the radio station 10B exchange control information with each other and acquire the communication status.
- the radio station 10A determines to perform CoMP communication as a communication mode for the radio terminal 20A.
- the radio station 10B determines to perform CoMP communication as a communication mode for the radio terminal 20A, and determines to perform MU-MIMO communication as a communication mode for the radio terminal 20B.
- the radio station 10A determines whether the radio terminal 20A has a communication level between the radio station 10A and the radio terminal 20A and a communication level between the radio station 10B and the radio terminal 20A. Whether or not to perform CoMP communication is determined, and a selected station that actually transmits a signal by CoMP communication to the radio terminal 20A is determined.
- the radio station 10A When the radio station 10B is selected as the selected radio station for performing CoMP communication, the radio station 10A transmits a signal requesting CoMP communication to the radio station 10B. When the CoMP communication can be executed in cooperation with the radio station 10A, the radio station 10B transmits a response signal indicating that it can be executed to the radio terminal 20A. The radio station 10A receives the response signal, prepares for CoMP communication with the radio terminal 20A, and decides to perform CoMP communication as a communication mode for the radio terminal 20A.
- the wireless station 10B transmits a response signal indicating that CoMP communication can be performed in cooperation with the wireless station 10A to the wireless terminal 20A, prepares for CoMP communication with the wireless terminal 20A, and performs wireless communication. It is determined to perform CoMP communication as a communication mode for the terminal 20A.
- the radio station 10B performs CoMP communication with the radio terminal 20B according to the communication level between the radio station 10A and the radio terminal 20B and the communication level between the radio station 10B and the radio terminal 20B. Decide not to. Then, since the radio station 10B performs CoMP communication with the radio terminal 20A, the radio station 10B determines to perform MU-MIMO communication as a communication mode for the radio terminal 20B.
- the radio station 10A determines the use mode of the configuration information 1 and 2 based on the determined communication mode and other communication conditions. Further, the radio station 10B determines the use mode of the configuration information 1 and 2 based on the determined communication mode and other communication conditions.
- the radio station 10A performs CoMP communication with the radio terminal 20A in cooperation with the radio station 10B, does not communicate with radio terminals other than the radio terminal 20A, Since 10B communicates with wireless terminals other than the wireless terminal 20A, the usage mode of the configuration information 1 for the wireless terminal 20A is “NZP” and the usage mode of the configuration information 2 is “OVR”.
- the radio station 10B performs CoMP communication with the radio terminal 20A in cooperation with the radio station 10A, performs MU-MIMO communication with the radio terminal 20B, and performs radio communication with the radio station 10A.
- the usage mode of the configuration information 1 and 2 for the terminal 20A is “NZP”
- the usage mode of the configuration information 2 is “OVR”
- the usage mode of the configuration information 1 for the radio terminal 20B Is “OVR” and the usage mode of the configuration information 2 is “NZP”.
- the radio stations 10A to 10B use radio signals used for individual reference signals transmitted to the radio terminal 20A.
- the use modes of the configuration information 1 and 2 are appropriately determined so that the resources are the same.
- the wireless station 10A-B uses the wireless resource used for the wireless terminal specific reference signal transmitted by the CoMP communication to the wireless terminal 20A, and the wireless terminal specific reference signal transmitted by the wireless station 10B to the wireless terminal 20B.
- the use modes of the configuration information 1 and 2 are determined so that the radio resources to be used are different.
- the use modes of the configuration information 1 and 2 are determined so that radio resources that are not used for the reference signal for each radio terminal are used for data transmission.
- the radio station 10A transmits a signal indicating each use mode of the configuration information 1 and 2 to the radio terminal 20A (S17).
- the radio station 10B transmits a signal indicating each use mode of the configuration information 1 and 2 to the radio terminal 20A (S18), and transmits a signal indicating each use mode of the configuration information 1 and 2 to the radio terminal. It transmits to 20B (S19).
- the radio stations 10A to 10B transmit data to the radio terminal 20A in a coordinated manner (S20, S21). At the same time, the radio station 10B transmits data to the radio terminal 20B (S22).
- radio resources prepared for transmission of reference signals for individual radio terminals from the radio stations 10A to 10B to the radio terminals 20A to 20B are efficiently allocated. Communication performance can be improved.
- the wireless communication system 1 has two wireless stations, but the number of wireless stations is arbitrary. Also, a radio station capable of CoMP communication and a radio station not capable of CoMP communication may be mixed.
- the wireless communication system 1 has two wireless terminals, but the number of wireless terminals is arbitrary. Also, wireless terminals capable of CoMP communication and wireless terminals not capable of CoMP communication may be mixed.
- the wireless communication system 1 uses two pieces of configuration information 1 and 2 as a plurality of pieces of configuration information indicating radio resources prepared for transmission of reference signals for individual radio terminals.
- the number and contents are not limited to this.
- the wireless communication system according to the second embodiment includes 50A to 50B (also referred to as Cell # 1 and Cell # 2) shown in FIG. 7 described later, instead of the wireless stations 10A to 10B, and includes wireless terminals 20A to 20B. Instead of the wireless terminals 70A-B (also referred to as UE # 1 and UE # 2) shown in FIG.
- the overall configuration of the wireless communication system according to the second embodiment is the same as that of the wireless communication system 1 shown in FIG.
- each of the wireless stations 50A to 50B is connected to the network device 3 via a wired connection or a wireless connection, and the network device 3 is connected to the network 2 via a wired connection or a wireless connection.
- the radio stations 50A to 50B are provided so as to be able to transmit and receive data and control information via the network device 3 and the network 2.
- each of the radio stations 50A to 50B has an antenna and corresponds to a communication point.
- the radio stations 50A-B form cells Cell # 1 and Cell # 2.
- the radio stations 50A to 50B communicate with each other through a wired connection or a wireless connection.
- the radio stations 50A to 50B can perform single antenna communication and MIMO communication with the radio terminals 70A to 70B. Further, the radio stations 50A to 50B can perform CoMP communication with the radio terminals 70A to 70B.
- the radio station 50A is a connection radio station (connection cell) of the radio terminal 70A
- the radio station 50B is a connection radio station (connection cell) of the radio terminal 70B.
- the connected radio station 50A aggregates and performs CoMP communication processing with the radio terminal 70A by the radio stations 50A and 50B.
- the connecting radio station 50A selects a communication point (selected radio station) to be used for CoMP communication processing from the radio stations 50A to 50B.
- the radio station 50B corresponds to another radio station capable of performing CoMP communication with the radio terminal 70A (hereinafter also referred to as a coordinated radio station or a coordinated cell).
- the connected radio station 50B aggregates and performs CoMP communication processing with the radio terminal 70B by the radio stations 50A to 50B.
- the connecting radio station 50B selects a communication point (selected radio station) to be used for CoMP communication processing from the radio stations 50A to 50B.
- the radio station 50A corresponds to another radio station capable of performing CoMP communication with the radio terminal 70B (hereinafter also referred to as a coordinated radio station or a coordinated cell).
- FIG. 7 is a block diagram showing a functional configuration of the radio stations 50A to 50B of the radio communication system according to the second embodiment.
- the radio station 50A includes a receiving antenna 51A, a receiving RF unit 52A, an FFT (Fast Fourier Transform) unit 53A, a physical channel separating unit 54A, a signal demodulating unit 55A, and a channel estimating unit 56A.
- the unit 63A, the transmission RF unit 64A, and the transmission antenna 65A are included.
- the radio station 50B communicates with the reception antenna 51B, the reception RF unit 52B, the FFT unit 53B, the physical channel separation unit 54B, the signal demodulation unit 55B, the channel estimation unit 56B, and the reception level measurement unit 57B.
- a control unit 58B, an upper layer data processing unit 59B, a signal generation unit 60B, a reference signal generation unit 61B, a physical channel multiplexing unit 62B, an IFFT unit 63B, a transmission RF unit 64B, and a transmission antenna 65B Have.
- the reception antenna 51A receives a radio signal and outputs it to the reception RF unit 52A.
- the reception antenna 51A includes, for example, a plurality of antennas (physical antennas). Further, the reception antenna 51A may be configured to be shared with the transmission antenna 65A and switched between transmission and reception by a transmission / reception switching unit or the like.
- the reception antenna 51A receives, for example, an upstream signal (data signal or control signal) transmitted on an upstream data channel or control channel. Examples of the physical channel that receives the signal include PRACH (Physical Random Access Channel), PUSCH (Physical Uplink Shared Channel), and PUCCH (Physical Uplink Control Channel).
- PRACH Physical Random Access Channel
- PUSCH Physical Uplink Shared Channel
- PUCCH Physical Uplink Control Channel
- Examples of the received signal include a RACH (Random Access Channel) signal for establishing a connection from the wireless terminals 70A to 70B, a signal indicating the reception level at the wireless terminals 70A to 70B (for example, RSRP Report), a channel Reference signals for estimation and demodulation are listed.
- RACH Random Access Channel
- the reception RF unit 52A performs processing such as A / D (Analog-to-Digital) conversion on the received signal.
- the FFT unit 53A performs an FFT process on the digital signal.
- the physical channel separation unit 54A separates each channel signal from the FFT-processed signal.
- the physical channel separation unit 54A extracts an uplink reference signal included in the uplink signal.
- the uplink reference signal includes, for example, SRS (Sounding Reference Signal) used for channel estimation for each uplink frequency and DM-RS (DeModulation RS) for demodulation of the uplink signal.
- the signal demodulator 55A demodulates the signal of each separated channel based on control information notified or stored in advance or a reference signal for demodulation.
- the channel estimation unit 56B acquires a channel estimation value indicating a channel propagation state based on control information notified or stored in advance or a received reference signal.
- the demodulated signal is decoded based on the channel estimation value.
- the data signal and control signal acquired through the decoding process are output to the communication control unit 58A. Further, ACK (ACKnowledgement) / NACK (Negative ACKnowledgement) is output to the communication control unit 58A as a result of decoding the data signal.
- the reception level measurement unit 57A measures the reception level (uplink reception power and uplink reception quality) from the received reference signal. Examples of the reception level include SIR and SINR.
- the communication control unit 58A transmits and receives data and control information to and from the network device and other wireless stations via a wired connection or a wireless connection.
- the communication control unit 58A performs management of access to the wireless terminals 70A and 70B and control of transmission power for transmitting signals.
- the transmission power is controlled by, for example, open loop control that compensates for a propagation loss (path loss) between communication points, adaptive modulation control, and closed loop control using a TPC (Transmission Power Control) command.
- TPC Transmission Power Control
- the upper layer data processing unit 59A performs a reordering process or the like of the decoded data signal, and acquires uplink user data. Further, the upper layer data processing unit 59A processes downlink user data acquired from a network device or another wireless station and control information to be transmitted to generate a transmission packet.
- the signal generator 60A encodes and modulates the transmission packet and outputs it to the physical channel multiplexer 62A.
- the signal generation unit 60A generates a control signal to be transmitted on the dedicated control channel and outputs the control signal to the physical channel multiplexing unit 62A.
- the reference signal generator 61A generates a downlink reference signal and outputs it to the physical channel multiplexer 62A.
- the downlink reference signal is a radio terminal used for downlink cell-specific CRS (Cell-specific Reference Signal), downlink CSI-RS (Channel State Information Reference Signal), downlink channel estimation and signal demodulation, for example. Includes an individual reference signal (DM-RS).
- the CRS is used for measurement of downlink communication quality and demodulation of downlink signals, and is set in association with cell identification information (cell ID).
- CSI-RS is used for measurement of downlink communication quality, and can be set for each communication point, for example.
- the physical channel multiplexing unit 62A allocates the encoded / modulated transmission packet, control signal, and reference signal to the radio resource of the physical channel according to the scheduling of the communication control unit 58A.
- the IFFT unit 63A performs IFFT processing on the multiplexed signal.
- the transmission RF unit 64A performs D / A conversion, distortion compensation processing, amplification processing, and the like on the signal after IFFT processing, and outputs the result to the transmission antenna 65A.
- the transmission antenna 65A transmits a radio signal input from the transmission RF unit 64A.
- the transmission antenna 65A includes, for example, a plurality of antennas (physical antennas).
- the transmission antenna 65A transmits, for example, a downlink signal (data signal or control signal) transmitted on a downlink data channel or control channel.
- Examples of physical channels that transmit signals include broadcast channels PBCH (Physical road Broadcast Channel), PMCH (Physical Multicast Channel), shared channel PDSCH (Physical Downlink Shared Channel), dedicated control channel PDCCH (Physical Downlink Control Channel), and the like.
- E-PDCCH Enhanced--Physical-Downlink-Control-Channel).
- a signal to be transmitted for example, when a call arrives at the wireless terminals 70A to 70B, a PCH (Paging Channel) signal for calling the wireless terminals 70A to 70B or a response signal (RAR, Random Access to the RACH signal) Response).
- a PCH Packet Control Channel
- RAR Random Access to the RACH signal
- examples of the signal to be transmitted include a signal indicating the reception level at the radio station 50A, and a control signal (for example, downlink transmission power information, a TPC command, etc.) for controlling the uplink transmission power.
- the signal to be transmitted is, for example, a reference signal for each wireless terminal used for channel estimation or demodulation, a plurality of configuration information indicating a radio resource prepared for transmission of a reference signal for each wireless terminal, or a plurality of configurations
- Each of the information includes a signal that specifies a use mode related to use of the radio resource indicated by the information.
- Examples of the control signal include L1 / L2 signaling transmitted over the dedicated control channel to the connected wireless terminal 70A, and RRC (Radio Resource Control) signaling transmitted over the shared channel to the connected wireless terminal 70A. It is done.
- the control signal includes, for example, system information that is stored in MIB (Master Information Block) or SIB (System Information Block) and transmitted on a broadcast channel or a shared channel designated by the broadcast channel.
- the communication control unit 58A performs scheduling such as allocation of radio resources to the radio terminals 70A-B.
- the radio station 50A has a plurality of antenna ports, and the communication control unit 58A assigns antenna ports to be used for communication with the radio terminals 70A-B.
- the antenna port is a processing port and may not correspond to the physical antenna.
- the communication control unit 58A executes a process of notifying the wireless terminal 70A of a plurality of pieces of configuration information each indicating a wireless resource prepared for the reference signal when establishing a connection with the wireless terminal 70A.
- the communication control unit 58A may notify the wireless terminal 70A of a plurality of pieces of configuration information itself, and information that specifies a plurality of pieces of configuration information from information stored in advance in the wireless terminal 70A. You may be notified.
- Each of the plurality of pieces of configuration information includes, for example, the arrangement of resource elements used for transmission of reference signals, information on antenna ports used for transmission of reference signals, and the number of layers of transmission signals.
- the prepared radio resources are different from each other with a plurality of pieces of configuration information.
- the prepared radio resources are arranged so as to be orthogonal to each other, for example.
- FIGS. 8A and 8B show examples of multiple pieces of configuration information.
- the wireless terminal 70A uses, for example, two pieces of configuration information (hereinafter also referred to as configuration, conf.) 1 and 2.
- 8A shows an example of the arrangement of resource elements and antenna ports of configuration information 1
- FIG. 8B shows an example of the arrangement of resource elements of configuration information 2.
- the left-right direction indicates time and the up-down direction indicates frequency.
- the hatched resource elements indicate DM-RS resources to which reference signals (DM-RSs) specific to wireless terminals are allocated.
- DM-RSs with up to 8 antenna ports are orthogonally multiplexed on the DM-RS resource.
- DM-RSs of four antenna ports ⁇ Port 9, 10, 12, 14 ⁇ are orthogonally multiplexed on DM-RS resources.
- DM-RSs of 4 antenna ports ⁇ Port 7, 8, 11, 13 ⁇ are orthogonally multiplexed on DM-RS resources.
- the configuration information 1 and 2 is used in common by the radio station 50A and other radio stations around the own station.
- Other wireless stations around the own station include another wireless station 50B capable of CoMP communication.
- the plurality of pieces of configuration information may be stored in advance in each of the radio stations 50A to 50B, acquired by the radio stations 50A to 50B from the network device, or from one of the radio stations 50A to 50B.
- the other wireless station may be notified via wired communication or wireless communication.
- the communication control unit 58A executes a process of transmitting a signal designating each use mode of the configuration information 1 and 2 at the time of data transmission.
- the communication control unit 58A determines the use mode of each of the configuration information 1 and 2 according to the communication status at the time of data transmission.
- a use mode for example, a mode (NZP) in which a radio terminal-specific reference signal is transmitted with a predetermined transmission power using a prepared radio resource, a mode (ZP) in which the radio terminal-specific reference signal is set to have a transmission power of 0, And a mode (OVR) in which a radio resource prepared for a reference signal for each radio terminal is allocated to a data signal can be set.
- the communication control unit 58A individually designates the use mode for the plurality of wireless terminals. Then, the communication control unit 58A performs communication with the wireless terminals 70A to 70B in accordance with each use mode of the plurality of pieces of configuration information.
- the communication control unit 58A determines whether or not the radio station 50A transmits data to the radio terminals 70A to 70B by CoMP communication with the other radio stations 50B, the number of radio terminals that the radio station 50A is connected to, and the radio station 50A.
- the use mode of each of the plurality of pieces of configuration information is determined in accordance with at least one of the communication mode for transmitting and the communication mode for transmitting data from the other radio station 50B.
- the communication mode includes, for example, at least one of single antenna communication, MIMO communication, and CoMP communication.
- the communication control unit 58A acquires the communication status of other wireless stations around its own station when transmitting data.
- Other radio stations include a radio station 50B capable of CoMP communication.
- the communication control unit 58A determines a communication mode for transmitting data, and determines each use mode of the plurality of pieces of configuration information.
- the communication control unit 58A acquires the communication level between the radio stations 50A and 50A and the radio terminal 70A.
- the communication level is measured from, for example, an uplink reference signal or a downlink reference signal.
- the communication level may be reported from the wireless terminal 70A, for example, and the communication level between the wireless station 50A and the wireless terminal 70A is measured by the wireless station 50A, and the communication level between the wireless station 50B and the wireless terminal 70B is measured. May be measured by the radio station 50B and notified to the radio station 50A.
- the communication control unit 58A transmits a signal requesting CoMP communication to the communication control unit 58B of another radio station 50B capable of CoMP communication with the radio terminal 70A, and a response signal is transmitted from the communication control unit 58B of the radio station 50B. To prepare for CoMP communication.
- the communication control unit 58A selects a selected wireless station that transmits a signal to the wireless terminal 70A from the plurality of wireless stations 50A to 50B capable of CoMP communication according to the communication level and other communication conditions.
- the selected radio station is one radio station selected by the DPS operation or two or more radio stations selected by the JT operation.
- the communication control unit 58A selects a candidate radio station from other radio stations capable of CoMP communication at a predetermined timing, and selects a radio station actually used from the candidate radio stations for data transmission.
- a radio station may be selected in a plurality of stages, such as when selecting.
- the communication control unit 58A exchanges control information between the radio station 50A and the radio station 50B, and sets parameters used in CoMP communication.
- the communication control unit 58A performs processing for exchanging information on communication points used for communication with the radio terminal 70A with the communication control unit of the cooperative radio station / selected radio station.
- reference signals and control information for individual wireless terminals may be exchanged between the wireless stations 50A-B and the wireless terminal 70A. Thereby, it is determined to perform CoMP communication with the wireless terminal 70A.
- the communication control unit 58A When CoMP communication is not performed for the wireless terminal 70A, the communication control unit 58A performs single antenna communication, MU-MIMO communication, or SU- depending on the communication level and other communication conditions. Decide whether to perform MIMO communication. In this way, the control unit 13 determines the communication mode for transmitting data.
- the communication control unit 58A determines each usage mode of the configuration information 1 and 2, transmits a signal indicating the usage mode to the wireless terminal 70A, and performs communication with the wireless terminal 70A according to the usage mode. If there is another wireless terminal connected, the communication control unit 58A, like the processing for the wireless terminal 70A, transmits the data to the other wireless terminal, and uses the communication mode and the configuration information use mode. Is transmitted, a signal indicating the use mode is transmitted, and communication is performed according to the use mode.
- the radio station 50A operates as a cooperative radio station of the radio station 50B that is a connection radio station of the radio terminal 70B.
- the communication control unit 58A receives a signal requesting CoMP communication from the communication control unit 58B of the radio station 50B, transmits a response signal to the communication control unit 58B of the radio station 50B, and prepares for CoMP communication. .
- the communication control unit 58A exchanges control information with the communication control unit 58B, and parameters used in CoMP communication (for example, , CoMP communication gain parameters) are set.
- parameters used in CoMP communication for example, , CoMP communication gain parameters
- reference signals and control information for individual radio terminals may be exchanged between the radio stations 50A to 50B and the radio terminal 70B. Thereby, it is determined to perform CoMP communication with the wireless terminal 70B.
- the communication control unit 58A determines the use mode of each of the configuration information 1 and 2, transmits a signal indicating the use mode to the wireless terminal 70B, and performs communication with the wireless terminal 70B according to the use mode.
- FIG. 9 shows an example of setting of the configuration information and the use mode of the reference signal for each wireless terminal for the wireless terminal.
- the upper part of the table in FIG. 9 shows a case where the communication mode from Cell # 1 to UE # 1 and the communication mode from Cell # 2 to UE # 2 are SU-MIMO communication or MU-MIMO communication.
- the middle part of the table of FIG. 9 shows a case where the communication mode from Cell # 1 to UE # 1 and the communication mode from Cell # 2 to UE # 2 are JT-CoMP communication.
- the lower part of the table of FIG. 9 shows the communication mode from Cell # 1 to UE # 1, the communication mode from Cell # 2 to UE # 2, and JT-CoMP communication, and the communication mode from Cell # 2 to UE # 2. Shows the case of MU-MIMO communication.
- FIG. 10 is a block diagram showing a functional configuration of the wireless terminal 70A of the second embodiment.
- the radio terminal 70A includes a reception antenna 71, a reception RF unit 72, an FFT unit 73, a physical channel separation unit 74, a signal demodulation unit 75, a channel estimation unit 76, and a reception level measurement.
- the functional configuration and hardware configuration of the wireless terminal 70B are the same as the functional configuration and hardware configuration of the wireless terminal 70A.
- the reception antenna 71 receives a radio signal and outputs it to the reception RF unit 72.
- the reception antenna 71 includes, for example, a plurality of antennas (physical antennas).
- the reception antenna 71 may be configured to be shared with the transmission antenna 85 and switched between transmission and reception by a transmission / reception switching unit or the like.
- the reception antenna 71 receives, for example, an uplink signal (data signal or control signal) transmitted on an uplink data channel or control channel. Examples of the received signal include a PCH signal for calling the wireless terminal 70A when a call arrives at the wireless terminal 70A, and a response signal to the RACH signal from the wireless terminal 70A.
- examples of the received signal include a signal indicating the reception level at the radio station 50A and a control signal for controlling uplink transmission power (for example, downlink transmission power information, a TPC command, etc.).
- the received signal includes, for example, a reference signal for each wireless terminal used for channel estimation and demodulation, a plurality of pieces of configuration information indicating wireless resources prepared for transmission of a reference signal for each wireless terminal, It includes a signal designating each use mode of the configuration information.
- Examples of the control signal include L1 / L2 signaling transmitted on the dedicated control channel from the connection radio station 50A and RRC signaling transmitted on the shared channel from the connection radio station 50A.
- the control signal includes, for example, system information stored in MIB or SIB and transmitted on a broadcast channel or a shared channel designated by the broadcast channel.
- the reception RF unit 72 performs processing such as A / D conversion on the received signal.
- the FFT unit 73 performs FFT processing on the digital signal.
- the physical channel separation unit 74 separates each channel signal from the FFT-processed signal. For example, the physical channel separation unit 74 obtains a subcarrier signal from a received OFDM (Orthogonal Frequency Division Multiplexing) signal.
- the signal demodulator 75 demodulates the signal of each separated channel based on control information notified or stored in advance or a reference signal specific to each radio terminal for demodulation.
- the channel estimation unit 76 acquires a channel estimation value indicating a channel propagation state based on control information notified or stored in advance or the received reference signal for each wireless terminal.
- the demodulated signal is decoded based on the channel estimation value.
- the user data and control information acquired through the decryption process are output to the communication control unit 78. Further, ACK / NACK is output to the communication control unit 78 as a decoding result of the data signal.
- the reception level measurement unit 77 measures the reception level (downlink reception power and downlink reception quality) from the received cell-specific reference signal. Examples of the reception level include SIR and SINR.
- the communication control unit 78 controls access to the radio stations 50A and 50B and transmission power for transmitting signals.
- the transmission power is controlled by, for example, open loop control that compensates for a propagation loss (path loss) between communication points, adaptive modulation control, and closed loop control using a TPC (Transmission Power Control) command.
- open loop control that compensates for a propagation loss (path loss) between communication points
- adaptive modulation control and closed loop control using a TPC (Transmission Power Control) command.
- TPC Transmission Power Control
- the communication control unit 78 sets a plurality of pieces of configuration information (configuration information 1 and 2) indicating radio resources prepared for transmission of reference signals for individual radio terminals.
- configuration information 1 and 2 indicating radio resources prepared for transmission of reference signals for individual radio terminals.
- the communication control unit 78 receives a signal indicating each use mode of the configuration information 1 and 2 from the radio station 50A, and the radio station according to each use mode of the configuration information 1 and 2 Communicate with 50A.
- the communication control unit 78 receives a signal indicating the use mode from the radio stations 50A to 50B, and each of the plurality of pieces of configuration information. The communication with the radio stations 50A-B is performed according to the use mode.
- the upper layer data processing unit 79 performs a reordering process on the decoded data signal and acquires the downlink user data. Further, the upper layer data processing unit 79 processes uplink user data and control information to be transmitted, and generates a transmission packet.
- the signal generation unit 80 encodes and modulates the transmission packet, adjusts the amplitude based on the uplink transmission power information, and outputs it to the physical channel multiplexing unit 82.
- the reference signal generation unit 81 generates an uplink reference signal and outputs it to the physical channel multiplexing unit 82.
- the physical channel multiplexing unit 82 allocates the encoded and modulated transmission packet and reference signal to the physical channel radio resource.
- the IFFT unit 83 performs IFFT processing on the multiplexed signal.
- the transmission RF unit 84 performs D / A conversion, distortion compensation processing, amplification processing, and the like on the signal after IFFT processing, and outputs the result to the transmission antenna 85.
- the transmission antenna 85 transmits a radio signal input from the transmission RF unit 84.
- the transmission antenna 85 includes, for example, a plurality of antennas (physical antennas).
- the transmission antenna 85 transmits, for example, an uplink signal (data signal or control signal) transmitted on an uplink data channel or control channel.
- the transmitted signal includes, for example, a RACH signal for establishing a connection, a signal indicating a reception level at the wireless terminal 70, and a reference signal for channel estimation and demodulation.
- the hardware configuration of the radio stations 50A and 50B in the radio communication system according to the second embodiment is the same as the hardware configuration of the radio station 10A of FIG.
- the reception antennas 51A, B, the reception RF units 52A, B, the transmission RF units 64A, B, and the transmission antennas 65A, B of the radio stations 50A, B are realized by an antenna and an RF circuit, for example.
- the FFT units 53A, B, the physical channel separation units 54A, B, the signal demodulation units 55A, B, the channel estimation units 56A, B, and the reception level measurement units 57A, B of the radio stations 50A, B are communicated.
- the control units 58A, B, upper layer data processing units 59A, B, signal generation units 60A, B, reference signal generation units 61A, B, physical channel multiplexing units 62A, B, and IFFT units 63A, B For example, it is realized by an integrated circuit such as a DSP or an integrated circuit such as a CPU.
- the hardware configuration of the wireless terminal 70A in the wireless communication system according to the second embodiment is the same as the hardware configuration of the wireless terminal 20A of FIG.
- the reception antenna 71, the reception RF unit 72, the transmission RF unit 84, and the transmission antenna 85 of the wireless terminal 70 are realized by, for example, an antenna and an RF circuit.
- An FFT unit 73 An FFT unit 73, a physical channel separation unit 74, a signal demodulation unit 75, a channel estimation unit 76, a reception level measurement unit 77, a communication control unit 78, an upper layer data processing unit 79, and a signal of the wireless terminal 70
- the generation unit 80, the reference signal generation unit 81, the physical channel multiplexing unit 82, and the IFFT unit 83 are realized by an integrated circuit such as a CPU, for example.
- FIG. 11 is a sequence diagram for explaining a downlink transmission operation of the radio communication system according to the second embodiment.
- the radio station 50A notifies the radio terminal 70A of a plurality of pieces of configuration information (DM-RS configuration information 1 and 2) indicating radio resources prepared for transmission of reference signals specific to the radio terminals. (S31).
- the notification of the DM-RS configuration information 1 and 2 by the wireless station 50A is notified by RRC signaling when establishing a connection with the wireless terminal 70A, for example.
- the radio station 50B notifies the radio terminal 70B of a plurality of pieces of configuration information (DM-RS configuration information 1 and 2) indicating radio resources prepared for transmission of reference signals specific to the radio terminals (S32).
- the notification of the DM-RS configuration information 1 and 2 by the wireless station 50B is notified by RRC signaling when establishing a connection with the wireless terminal 70B, for example.
- the configuration information 1 and 2 are used in common by the radio stations 50A-B.
- Each of the configuration information 1 and 2 includes resource element arrangement, antenna port information, and the number of layers.
- the radio resources prepared by the configuration information 1 and 2 are set to be different from each other.
- the radio station 50A determines a communication mode for transmitting data to the radio terminals 70A and 70B (S33). Similarly, the radio station 50B determines a communication mode for transmitting data to the radio terminals 70A-B (S34). At this time, the radio station 50A and the radio station 50B exchange control information with each other and acquire the communication status.
- the communication mode is determined every time data is transmitted, for example. The determination of the communication mode is executed at an interval relatively shorter than the connection establishment.
- As the communication mode for example, JT-CoMP communication, SU-MIMO communication, and MU-MIMO communication can be selected.
- the radio station 50A determines to perform SU-MIMO communication as a communication mode for the radio terminal 70A.
- the radio station 50B determines to perform SU-MIMO communication as a communication mode for the radio terminal 70B.
- the radio station 50A determines whether or not the radio terminal 70A has a communication level between the radio station 50A and the radio terminal 70A and a communication level between the radio station 50B and the radio terminal 70A. It decides not to perform CoMP communication. And since the radio station 50A does not communicate with radio terminals other than the radio terminal 70A, it determines to perform SU-MIMO communication as a communication mode for the radio terminal 70A.
- the communication level between the radio station 50A and the radio terminal 70A is such that the cell-specific reference signal transmitted from the radio station 50A is received by the radio terminal 70A, and the measurement result is transmitted from the radio terminal 70A to the radio station 50A. You can get it.
- the reference signal transmitted from the wireless terminal 70A may be received by the wireless station 50A and measured by the wireless station 50A.
- the communication level between the radio station 50B and the radio terminal 70A can be acquired by receiving the reference signal transmitted from the radio station 50B by the radio terminal 70A and transmitting the measurement result from the radio terminal 70A to the radio station 50A.
- the cell-specific reference signal transmitted from the wireless terminal 70A may be received by the wireless station 50B, and the measurement result may be transmitted from the wireless station 50B to the wireless station 50A for notification.
- the radio station 50B performs CoMP communication with the radio terminal 70B according to the communication level between the radio station 50A and the radio terminal 70B and the communication level between the radio station 50B and the radio terminal 70B. Decide not to do it. Then, since the radio station 50B does not communicate with radio terminals other than the radio terminal 70B, it determines to perform SU-MIMO communication as a communication mode for the radio terminal 70B.
- the radio station 50A determines the use mode (DM-RS mode) of the configuration information 1 and 2 based on the determined communication mode and other communication conditions. Further, the radio station 50B determines the use mode of the configuration information 1 and 2 based on the determined communication mode and other communication status.
- DM-RS mode use mode of the configuration information 1 and 2
- a mode (NZP) in which a radio terminal-specific reference signal is transmitted with a predetermined transmission power using a prepared radio resource a mode (ZP) in which the radio terminal-specific reference signal is set to have a transmission power of 0,
- a mode (OVR) in which a radio resource prepared for a reference signal for each radio terminal is allocated to a data signal can be set.
- the radio station 50A performs SU-MIMO communication with the radio terminal 70A under its control, and the radio station 50B performs SU-MIMO communication with the radio terminal 70B under its control.
- the usage mode of the configuration information 1 is “NZP” and the usage mode of the configuration information 2 is “ZP”.
- the wireless station 50B performs SU-MIMO communication with the wireless terminal 70B under its control, and the wireless station 50A performs SU-MIMO communication with the wireless terminal 70A under the control of FIG.
- the usage mode of the configuration information 1 for the wireless terminal 70B is “ZP”
- the usage mode of the configuration information 2 is “NZP”.
- the radio resource used for the reference signal specific to the radio terminal transmitted from the radio station 50A to the radio terminal 70A and the radio resource used for the reference signal specific to the radio terminal transmitted from the radio station 50B to the radio terminal 70B are as follows.
- the use modes of the configuration information 1 and 2 are determined differently. Thereby, when transmitting a reference signal for each wireless terminal, interference between communication points is reduced, channel estimation accuracy for receiving data is improved, and communication performance is improved.
- the radio station 50A transmits a signal indicating each use mode of the configuration information 1 and 2 on the PDCCH to the radio terminal 70A (S35).
- 50 A of radio stations transmit the antenna port number and layer number which are actually used on PDCCH with the signal which shows each use mode of the structure information 1 and 2, for example.
- the signal indicating the use mode may be transmitted only when the use mode is changed.
- the signal indicating the use mode may include only the use mode for the configuration information whose use mode has been changed.
- the configuration information 1 and 2 may include information on the antenna port used and the number of layers together with a signal indicating the use mode, including the arrangement of resource elements.
- the radio station 50B transmits a signal indicating each use mode of the configuration information 1 and 2 to the radio terminal 70B on the PDCCH (S36).
- S36 PDCCH
- the radio station 50A transmits data on the PDSCH to the radio terminal 70A (S37).
- the radio station 50A transmits a reference signal for each radio terminal for data reception using the resource element and antenna port prepared in the configuration information 1 according to the use mode transmitted in S35. And send the data.
- the wireless terminal 70A acquires the reference signal specific to the wireless terminal for receiving data from the use mode transmitted in S35, and uses the acquired reference signal specific to the wireless terminal to determine the SU-MIMO determined in S33. Receives data transmitted by communication.
- the radio station 50B transmits data on the PDSCH to the radio terminal 70B (S38).
- the radio station 50B transmits a reference signal specific to the radio terminal for data reception using the radio resource prepared in the configuration information 2 according to the use mode transmitted in S36, and S34.
- Data is transmitted to the wireless terminal 70B by SU-MIMO communication according to the communication mode determined in (1).
- the wireless terminal 70B specifies a wireless resource to which a reference signal for each wireless terminal is transmitted according to the use mode transmitted in S36, and receives the reference signal for each wireless terminal.
- the radio stations 50A to 50B perform the same processing as S33 to S38 in S39 to S44 and S45 to S52.
- the radio station 50A determines a communication mode for transmitting data to the radio terminals 70A and 70B (S39). Similarly, the radio station 50B determines a communication mode for transmitting data to the radio terminals 70A-B (S40). At this time, the radio station 50A and the radio station 50B exchange control information with each other and acquire the communication status.
- the radio station 50A determines to perform CoMP communication as a communication mode for the radio terminal 70A.
- the radio station 50B determines to perform CoMP communication as a communication mode for the radio terminal 70A.
- the communication mode for the radio terminal 70B is not determined.
- the radio station 50A determines whether or not the radio terminal 70A has a communication level between the radio station 50A and the radio terminal 70A and a communication level between the radio station 50B and the radio terminal 70A. Whether or not to perform CoMP communication is determined as to a selected station that actually transmits a signal through CoMP communication with respect to the wireless terminal 70A.
- the radio station 50A When the radio station 50A selects the radio station 50B as the selected radio station for performing CoMP communication, the radio station 50A transmits a signal requesting CoMP communication to the radio station 50B.
- the radio station 50B transmits a response signal indicating that it can be executed, and prepares for CoMP communication with the radio terminal 70A.
- CoMP communication is determined as a communication mode for the wireless terminal 70A.
- the radio station 50A receives the response signal, prepares for CoMP communication with the radio terminal 70A, and determines CoMP communication as a communication mode for the radio terminal 70A.
- the radio station 50A determines the use mode of the configuration information 1 and 2 based on the determined communication mode and other communication conditions. Further, the radio station 50B determines the use mode of the configuration information 1 and 2 based on the determined communication mode and other communication status.
- the wireless station 50A performs JT-CoMP communication with the wireless terminal 70A in cooperation with the wireless station 50B, and the local station communicates with a wireless terminal other than the wireless terminal 70A. Since the wireless station 50B does not communicate with wireless terminals other than the wireless terminal 70A, as shown in the table of FIG. 9, the usage mode of the configuration information 1 is “NZP” and the usage mode of the configuration information 2 is “ OVR ".
- the wireless station 50B performs CoMP communication with the wireless terminal 70A in cooperation with the wireless station 50B, the wireless station 50A does not communicate with wireless terminals other than the wireless terminal 70A, Since the station does not communicate with wireless terminals other than the wireless terminal 70A, as shown in the table of FIG. 9, the usage mode of the configuration information 1 for the wireless terminal 70A is “NZP”, and the usage mode of the configuration information 2 is “OVR”. "
- the wireless stations 50A to 50B use the wireless terminal-specific reference signal transmitted to the wireless terminal 70A.
- the use modes of the configuration information 1 and 2 are appropriately determined so that the resources are the same. Further, it is assumed that the wireless station 50A and the wireless station 50B perform CoMP communication with the wireless terminal 70A, thereby improving the communication performance of transmitting a reference signal for each wireless terminal to the wireless terminal 70A. Therefore, the use modes of the configuration information 1 and 2 are appropriately determined so that radio resources that are not used for the reference signal for each radio terminal are used for data transmission.
- the radio station 50A transmits a signal indicating each use mode of the configuration information 1 and 2 to the radio terminal 70A on the PDCCH (S41).
- the radio station 50B transmits a signal indicating each use mode of the configuration information 1 and 2 to the radio terminal 70A on the PDCCH (S42).
- the radio stations 50A to 50B transmit data to the radio terminal 70A in a coordinated manner on the PDSCH (S43, S44).
- the radio station 50A determines a communication mode for transmitting data to the radio terminal 70A (S45). Similarly, the radio station 50A determines a communication mode for transmitting data to the radio terminal 70B (S46). At this time, the radio station 50A and the radio station 50B exchange control information with each other and acquire the communication status.
- the radio station 50A determines to perform CoMP communication as a communication mode for the radio terminal 70A.
- the radio station 50B determines to perform CoMP communication as a communication mode for the radio terminal 70A, and determines to perform MU-MIMO communication as a communication mode for the radio terminal 70B.
- the radio station 50A determines whether or not the radio terminal 70A has a communication level between the radio station 50A and the radio terminal 70A and a communication level between the radio station 50B and the radio terminal 70A. Whether or not to perform CoMP communication is determined as to a selected station that actually transmits a signal through CoMP communication with respect to the wireless terminal 70A.
- the radio station 50A When the radio station 50A selects the radio station 50B as the selected radio station for performing CoMP communication, the radio station 50A transmits a signal requesting CoMP communication to the radio station 50B. When the CoMP communication can be executed in cooperation with the radio station 50A, the radio station 50B transmits a response signal indicating that it can be executed to the radio terminal 70A. The radio station 50A receives the response signal, prepares for CoMP communication with the radio terminal 70A, and decides to perform CoMP communication as a communication mode for the radio terminal 70A.
- the wireless station 50B transmits a response signal indicating that CoMP communication can be performed in cooperation with the wireless station 50A to the wireless terminal 70A, prepares for CoMP communication with the wireless terminal 70A, and performs wireless communication. It is determined to perform CoMP communication as a communication mode for the terminal 70A. Further, the radio station 50B performs CoMP communication with the radio terminal 70B according to the communication level between the radio station 50A and the radio terminal 70B and the communication level between the radio station 50B and the radio terminal 70B. Decide not to. Then, since the radio station 50B performs CoMP communication with the radio terminal 70A, the radio station 50B determines to perform MU-MIMO communication as a communication mode for the radio terminal 70B.
- the radio station 50A determines the use mode of the configuration information 1 and 2 based on the determined communication mode and other communication conditions. Further, the radio station 50B determines the use mode of the configuration information 1 and 2 based on the determined communication mode and other communication status.
- the radio station 50A performs CoMP communication with the radio terminal 70A in cooperation with the radio station 50B, and the own station does not communicate with radio terminals other than the radio terminal 70A. Accordingly, as shown in the table of FIG. 9, the usage mode of the configuration information 1 for the wireless terminal 70A is “NZP” and the usage mode of the configuration information 2 is “OVR”.
- the radio station 50B performs CoMP communication with the radio terminal 70A in cooperation with the radio station 50A, and performs MU-MIMO communication with the radio terminal 70B.
- the usage mode of the configuration information 1 for the wireless terminal 70A is “NZP”
- the usage mode of the configuration information 2 is “OVR”
- the usage mode of the configuration information 1 for the wireless terminal 70B is “OVR”
- the configuration information 2 The mode of use is “NZP”.
- the wireless stations 50A to 50B use the wireless terminal-specific reference signal transmitted to the wireless terminal 70A.
- the use modes of the configuration information 1 and 2 are appropriately determined so that the resources are the same.
- the wireless station 50A-B uses the wireless resource used for the wireless terminal specific reference signal transmitted by the CoMP communication to the wireless terminal 70A and the wireless terminal specific reference signal transmitted by the wireless station 50B to the wireless terminal 70B.
- the use modes of the configuration information 1 and 2 are appropriately determined so that the radio resources to be used are different.
- the wireless station 50A and the wireless station 50B perform CoMP communication with the wireless terminal 70A, thereby improving the communication performance of transmitting a reference signal for each wireless terminal to the wireless terminal 70A. Therefore, the use modes of the configuration information 1 and 2 are appropriately determined so that radio resources that are not used for the reference signal for each radio terminal are used for data transmission.
- the radio station 50A transmits a signal indicating each use mode of the configuration information 1 and 2 to the radio terminal 70A on the PDCCH (S47).
- the radio station 50B transmits a signal indicating each use mode of the configuration information 1 and 2 to the radio terminal 70A on the PDCCH (S48), and transmits a signal indicating each use mode of the configuration information 1 and 2 Then, the data is transmitted on the PDCCH to the wireless terminal 70B (S49).
- the radio stations 50A to 50B transmit data on the PDSCH in cooperation with the radio terminal 70A (S50, S51). Further, the radio station 50B transmits data to the radio terminal 70B on the PDSCH (S52).
- the wireless resources prepared for transmission of the reference signals specific to the wireless terminals from the wireless stations 50A to 50B to the wireless terminals 70A and 70B can be efficiently allocated and communicated. Performance can be improved.
- the tables of FIGS. 12A and 12B may be used instead of the table of FIG.
- communication from Cell # 1 to UE # 2 is not performed as in the example of FIG.
- the communication mode from Cell # 1 to UE # 1 and the communication mode from Cell # 2 to UE # 2 are SU-MIMO communication or MU-MIMO communication, and Cell # 2
- the communication mode from Cell # 1 to UE # 1 and the communication mode from Cell # 2 to UE # 1 are JT-CoMP communication, and from Cell # 2 to UE # 2. The case where no communication is performed is shown.
- FIG. 13 shows a configuration of a wireless communication system 1A according to the third embodiment.
- the radio communication system 1A includes radio stations 50A to 50B (also referred to as Cell # 1 and Cell # 2) and radio terminals UE # 1 to UE # 4.
- the overall configuration of the radio communication system according to the third embodiment is the same as that of the radio communication system according to the first and second embodiments.
- each of the wireless stations 50A to 50B is connected to the network device 3 via a wired connection or a wireless connection
- the network device 3 is connected to the network 2 via a wired connection or a wireless connection.
- the radio stations 50A to 50B are provided so as to be able to transmit and receive data and control information via the network device 3 and the network 2.
- each of the radio stations 50A to 50B has an antenna and corresponds to a communication point.
- the radio stations 50A-B form cells Cell # 1 and Cell # 2.
- the radio stations 50A to 50B communicate with each other through a wired connection or a wireless connection. Further, the radio stations 50A to 50B can perform single antenna communication and MIMO communication with the UEs # 1 to # 4. Further, the radio stations 50A to 50B can perform CoMP communication with the UEs # 1 to # 4.
- the radio station 50A is a connected radio station (connected cell) of UE # 1 and UE # 2
- the radio station 50B is a connected radio station (connected cell) of UE # 3 and UE # 4.
- the connected radio station 50A aggregates and performs CoMP communication processing between the UEs # 1 and # 2 by the plurality of radio stations 50A to 50B.
- the connecting radio station 50A selects a communication point (selected radio station) to be used for CoMP communication processing from the radio stations 50A to 50B.
- the radio station 50B corresponds to another radio station capable of performing CoMP communication with the UE # 1 and UE # 2 (hereinafter also referred to as a cooperative radio station or a cooperative cell).
- the connected radio station 50B aggregates and performs CoMP communication processing between the UEs # 3 and UE4 by the radio stations 50A to 50B.
- the connecting radio station 50B selects a communication point (selected radio station) to be used for CoMP communication processing from the radio stations 50A to 50B.
- the radio station 50A corresponds to another radio station capable of performing CoMP communication with UE # 3 and UE # 4 (hereinafter also referred to as a cooperative radio station or a cooperative cell).
- the functional configuration and hardware configuration of the radio stations 50A to 50B according to the third embodiment are the same as those of the radio stations 50A to 50B of FIG. 7 of the second embodiment. Further, the functional configuration and hardware configuration of the radio terminals UE # 1 to UE # 4 according to the third embodiment are the same as those of the radio terminal 70A of FIG. 10 of the second embodiment.
- FIG. 14 is a table showing an example of setting for the wireless terminal of the configuration information and the use mode of the reference signal for each wireless terminal in the third embodiment.
- Cell # 1 performs MU-MIMO communication to UE # 1 and UE # 2 as a communication mode for transmitting a signal
- Cell # 2 transmits MU-MIMO to UE # 3 and UE # 4.
- the case where communication is performed is shown.
- the middle part of the table of FIG. 14 shows that Cell # 1 and Cell # 2 cooperate to perform JT-CoMP communication to UE # 2, and perform MU-MIMO communication from Cell # 2 to UE # 4. Indicates the case.
- Cell # 1 and Cell # 2 cooperate to perform JT-CoMP communication to UE # 3, and Cell # 1 to UE # 1 perform MU-MIMO communication. Indicates the case.
- FIG. 15 is a sequence diagram for explaining a downlink transmission operation of the wireless communication system 1A according to the third embodiment.
- the radio station 50A allows the UE # 1 and UE # 2 to receive a plurality of pieces of configuration information (DM-RS configuration information 1 and 2) indicating radio resources prepared for transmission of reference signals for individual radio terminals. ) Is notified (S61, 62).
- the notification of the DM-RS configuration information 1 and 2 by the radio station 50A is notified by RRC signaling, for example, when establishing a connection with UE # 1 and UE # 2.
- the radio station 50B notifies UE # 3 and UE # 4 of a plurality of pieces of configuration information (DM-RS configuration information 1 and 2) indicating radio resources prepared for transmission of reference signals specific to the radio terminals. (S63, 64).
- the notification of the DM-RS configuration information 1 and 2 by the wireless station 50B is notified by RRC signaling when establishing a connection with the wireless terminals 70B and 70D, for example.
- the configuration information 1 and 2 are used in common by the radio stations 50A-B.
- Each of the configuration information 1 and 2 includes resource element arrangement, antenna port information, and the number of layers.
- the radio resources prepared by the configuration information 1 and 2 are set to be different from each other.
- the radio station 50A determines a communication mode for transmitting data to the UE # 1 to UE # 4 (S65).
- the radio station 50B determines a communication mode for transmitting data to the UE # 1 to UE # 4 (S66).
- the radio station 50A and the radio station 50B exchange control information with each other and acquire the communication status.
- the communication mode is determined every time data is transmitted, for example.
- the determination of the communication mode is executed at an interval relatively shorter than the connection establishment.
- As the communication mode for example, JT-CoMP communication, SU-MIMO communication, and MU-MIMO communication can be selected.
- the radio station 50A determines to perform SU-MIMO communication as a communication mode for the UE # 2.
- the radio station 50B determines to perform SU-MIMO communication as a communication mode for the UE # 4.
- the radio station 50A when there is downlink data to UE # 2, the radio station 50A communicates between the radio station 50A and UE # 2 and the communication between the radio station 50B and UE # 2. According to the level, it is determined not to perform CoMP communication for UE # 2. In the case of S65, there is no downlink data to UE # 2 under the control of radio station 50A, and radio station 50A does not communicate with UE # 2. In addition, the radio station 50A does not perform CoMP communication with UE # 3 and UE # 4 under the control of the radio station 50B. Thus, since the radio station 50A does not communicate with radio terminals other than UE # 2, it determines to perform SU-MIMO communication as a communication mode for UE # 2.
- the communication level between the radio station 50A and the UE # 2 is obtained by receiving a cell-specific reference signal transmitted from the radio station 50A by the UE # 2, and transmitting a measurement result from the UE # 2 to the radio station 50A. You can get it.
- the reference signal transmitted from the wireless terminal 70A may be received by the wireless station 50A and measured by the wireless station 50A.
- the communication level between the radio station 50B and the UE # 2 is obtained by receiving a cell-specific reference signal transmitted from the radio station 50B by the UE # 2, and transmitting a measurement result from the UE # 2 to the radio station 50A. You can get it.
- the reference signal transmitted from the UE # 2 may be received by the radio station 50B, and the measurement result may be transmitted from the radio station 50B to the radio station 50A for notification.
- the radio station 50B sets the communication level between the radio station 50A and UE # 4 and the communication level between the radio station 50B and UE # 4. In response, it decides not to perform CoMP communication for UE # 4. In the case of S66, there is no downlink data to UE # 3 under control of radio station 50B, and radio station 50B does not communicate with UE # 3. Further, the radio station 50B does not perform CoMP communication with the UEs # 1 and UE # 2 under the control of the radio station 50A. Thus, since the radio station 50B does not communicate with radio terminals other than the UE # 4, the radio station 50B determines to perform SU-MIMO communication as a communication mode for the UE # 4.
- the radio station 50A determines the use mode (DM-RS mode) of the configuration information 1 and 2 for the UE # 2 based on the determined communication mode and other communication conditions. Also, the radio station 50B determines the use mode of the configuration information 1 and 2 for the UE # 4 based on the determined communication mode and other communication status.
- DM-RS mode DM-RS mode
- a mode (NZP) in which a radio terminal-specific reference signal is transmitted with a predetermined transmission power using a prepared radio resource a mode (ZP) in which the radio terminal-specific reference signal is set to have a transmission power of 0,
- a mode (OVR) in which a radio resource prepared for a reference signal for each radio terminal is allocated to a data signal can be set.
- the use mode of the configuration information 1 is set to “NZP”, as shown in the table of FIG.
- the use mode of the configuration information 2 is “ZP”.
- the use mode of the configuration information 1 for the UE # 4 is set to “ZP” as shown in the table of FIG.
- the usage mode of the configuration information 2 is “NZP”.
- the radio station 50A uses the radio resource used for the radio terminal specific reference signal transmitted to the UE # 2, and the radio station 50B uses the radio terminal specific reference signal transmitted to the UE # 4.
- the use modes of the configuration information 1 and 2 are determined so that the radio resources are different. As a result, when DM-RS is transmitted, interference between communication points is reduced, channel estimation accuracy for receiving data is improved, and communication performance is improved.
- the radio station 50A transmits a signal indicating each use mode (DM-RS mode) of the configuration information 1 and 2 to the UE # 2 on the PDCCH (S67).
- the radio station 50B transmits a signal (DM-RS mode) indicating each use mode of the configuration information 1 and 2 to the UE # 4 on the PDCCH (S68).
- This makes it possible to flexibly set radio resources to be used for reference signals for individual radio terminals transmitted from the radio stations 50A to 50A to the radio terminals 70A to B in accordance with the communication mode determination timing. In addition, this increases the signaling compared to the case where the configuration information indicating the radio resource prepared for the reference signal of each radio terminal is sequentially notified in accordance with the determination timing of the communication mode executed at a relatively short interval. Can be suppressed.
- the radio station 50A transmits data to the UE # 2 on the PDSCH (S69).
- the radio station 50A transmits the DM-RS using the resource element and the antenna port prepared in the configuration information 1 according to the use mode transmitted in S67, and the SU-MIMO determined in S65.
- Data is transmitted by communication.
- UE # 2 extracts the DM-RS from the received signal according to the use mode transmitted in S67, and uses the extracted DM-RS to transmit the data transmitted by the SU-MIMO communication determined in S65. Receive.
- the radio station 50B transmits data to the UE # 4 on the PDSCH (S70).
- the radio station 50B transmits a DM-RS using radio resources prepared in the configuration information 2 according to the use mode transmitted in S68, and performs data transmission by SU-MIMO communication determined in S66.
- UE # 4 extracts the DM-RS from the received signal according to the use mode transmitted in S68, and uses the extracted DM-RS to transmit the data transmitted by the SU-MIMO communication determined in S66.
- the radio stations 50A to 50B perform the same processing as S65 to S70 in S71 to S80 and S81 to S88.
- the radio station 50A determines a communication mode for transmitting data to the UE # 1 to UE # 4 (S71). Similarly, the radio station 50B determines a communication mode for transmitting data to the UE # 1 to UE # 4 (S72). At this time, the radio station 50A and the radio station 50B exchange control information with each other and acquire the communication status.
- the radio station 50A determines to perform MU-MIMO communication as a communication mode for the UE # 1 and UE # 2.
- the radio station 50B determines to perform MU-MIMO communication as a communication mode for the UE # 3 and UE # 4.
- the radio station 50A when there is downlink data to UE # 1, the radio station 50A communicates between the radio station 50A and UE # 1, and the communication between the radio station 50B and UE # 1. According to the level, it is determined that CoMP communication is not performed for UE # 1. Further, when there is downlink data to UE # 2, radio station 50A responds to the communication level between radio station 50A and UE # 2, and the communication level between radio station 50B and UE # 2. Thus, it is determined not to perform CoMP communication with UE # 2. In the case of S71, the radio station 50A does not perform CoMP communication with UE # 3 and UE # 4 under the control of the radio station 50B as described later. Therefore, the radio station 50A determines to perform MU-MIMO communication as a communication mode for the UE # 1 and UE # 2.
- the radio station 50B sets the communication level between the radio station 50A and UE # 3 and the communication level between the radio station 50B and UE # 3. In response, it decides not to perform CoMP communication for UE # 3. Further, when there is downlink data to UE # 4, the radio station 50B responds to the communication level between the radio station 50A and UE # 4 and the communication level between the radio station 50B and UE # 4. Thus, it is determined not to perform CoMP communication with UE # 4. In the case of S72, the radio station 50B does not perform CoMP communication with the UE # 1 and UE # 2 under the control of the radio station 50A as described above. Therefore, the radio station 50B determines to perform MU-MIMO communication as a communication mode for UE # 3 and UE # 4.
- the radio station 50A determines the use mode (DM-RS mode) of the configuration information 1 and 2 for the UE # 1 and UE # 2 based on the determined communication mode and other communication conditions.
- the radio station 50B determines the use mode (DM-RS mode) of the configuration information 1 and 2 for the UE # 3 and UE # 4 based on the determined communication mode and other communication conditions.
- the use mode of the configuration information 1 is set as shown in the table of FIG. “NZP” and the usage mode of the configuration information 2 are “ZP”.
- the radio station 50B since the radio station 50B performs MU-MIMO communication with the subordinate UE # 3 and UE # 4, as shown in the table of FIG. 14, the configuration information for the UE # 3 and UE # 4 The usage mode 1 is “ZP”, and the usage mode of the configuration information 2 is “NZP”.
- the radio resource used for the reference signal for each radio terminal transmitted by the radio station 50A to the UE # 1 and UE # 2, and the radio transmitted by the radio station 50B to the UE # 3 and UE # 4 The use modes of the configuration information 1 and 2 are determined so that the radio resources used for the terminal-specific reference signal are different.
- DM-RS is transmitted, interference between communication points is reduced, channel estimation accuracy for receiving data is improved, and communication performance is improved.
- the radio station 50A transmits a signal indicating each use mode (DM-RS mode) of the configuration information 1 and 2 to the UE # 1 and UE # 2 on the PDCCH (S73 and 74).
- the radio station 50B transmits a signal indicating each use mode (DM-RS mode) of the configuration information 1 and 2 to the UE # 3 and UE # 4 on the PDCCH (S75 and 76).
- the radio station 50A transmits data to the UE # 1 and UE # 2 on the PDSCH (S77, 78).
- the radio station 50A transmits the DM-RS using the resource element and the antenna port prepared in the configuration information 1 according to the use mode transmitted in S73 and 74, and determines in S71.
- Data is transmitted by MU-MIMO communication.
- UE # 1 and UE # 2 extract DM-RS from the received signal according to the use mode transmitted in S73 and 74, and use the extracted DM-RS to determine the MU-MIMO communication determined in S71.
- the data transmitted by is received.
- the radio station 50B transmits data to the UE # 3 and UE # 4 on the PDSCH (S79, 80).
- the radio station 50B transmits the DM-RS using the radio resource prepared in the configuration information 2 according to the use mode transmitted in S75, 76, and the MU- determined in S72.
- Data is transmitted by MIMO communication.
- UE # 3 and UE # 4 extract the DM-RS from the received signal according to the use mode transmitted in S75 and 76, and use the extracted DM-RS to determine the MU-MIMO communication determined in S72.
- the data transmitted by is received.
- the radio station 50A determines a communication mode for transmitting data to the UE # 1 to UE # 4 (S81). Similarly, the radio station 50B determines a communication mode for transmitting data to UE # 1 to UE # 4 (S82). At this time, the radio station 50A and the radio station 50B exchange control information with each other and acquire the communication status.
- the radio station 50A determines to perform CoMP communication as a communication mode for the UE # 2. Further, in the example of S82, the radio station 50B determines to perform CoMP communication as a communication mode for UE # 2, and determines to perform MU-MIMO communication as a communication mode for UE # 4.
- the radio station 50A communicates between the radio station 50A and UE # 2 and the communication between the radio station 50B and UE # 2.
- the radio station 50A communicates between the radio station 50A and UE # 2 and the communication between the radio station 50B and UE # 2.
- whether or not to perform CoMP communication for UE # 2 is determined, and a selected station that actually transmits a signal through CoMP communication for UE # 2 is determined.
- the radio station 50A selects the radio stations 50A to 50B as the selected radio stations that perform CoMP communication with the UE # 2, the radio station 50A transmits a signal requesting CoMP communication to the radio station 50B.
- the radio station 50B transmits a response signal indicating that it can be executed, and prepares for CoMP communication with the UE # 2.
- the radio station 50A receives the response signal, prepares for CoMP communication with the UE # 2, and determines CoMP communication as a communication mode for the UE # 2.
- S81 there is no downlink data to UE # 1 subordinate to radio station 50A, and radio station 50A does not communicate with UE # 1. Further, as will be described later, the radio station 50A does not perform CoMP communication with the UEs # 3 and UE # 4 under the control of the radio station 50B.
- the radio station 50B sets the communication level between the radio station 50A and UE # 4 and the communication level between the radio station 50B and UE # 4. In response, it decides not to perform CoMP communication for UE # 4. In the case of S82, there is no downlink data to UE # 3 under the control of radio station 50B, and radio station 50B does not communicate with UE # 3. Further, the radio station 50B does not perform CoMP communication with the UE # 1 under the control of the radio station 50A. Further, as described above, the radio station 50B transmits a response signal indicating that CoMP communication can be performed in cooperation with the radio station 50A to the UE # 2, and prepares for CoMP communication with the UE # 2. To determine CoMP communication as a communication mode for UE # 2. Then, the radio station 50B determines to perform MU-MIMO communication as a communication mode for the UE # 4.
- the radio station 50A determines the use mode of the configuration information 1 and 2 for the UE # 2 based on the determined communication mode and other communication conditions. Also, the radio station 50B determines the use mode of the configuration information 1 and 2 for the UE # 2 and UE # 4 based on the determined communication mode and other communication status.
- the radio station 50A performs JT-CoMP communication with UE # 2 in cooperation with the radio station 50B, and the own station communicates with radio terminals other than UE # 2. Since the radio station 50B performs MU-MIMO communication with UE # 4, the usage mode of configuration information 1 is “ZP” and the usage mode of configuration information 2 is “NZP” as shown in the table of FIG. And In the example of S82, the radio station 50B performs JT-CoMP communication with the radio station 50A in cooperation with the UE # 2, and the radio station 50A does not communicate with radio terminals other than the UE # 2. Since the own station performs MU-MIMO communication with UE # 4, as shown in the table of FIG. 14, the usage mode of configuration information 1 for UE # 2 and UE # 4 is “NZP”, and the configuration information 2 is used. The mode is “ZP”.
- the radio stations 50A to 50B use radio signals used for individual reference signals transmitted to the UE # 2 by the radio terminals.
- the use modes of the configuration information 1 and 2 are appropriately determined so that the resources are the same.
- the radio station 50A and the radio station 50B perform CoMP communication with the UE # 2
- the communication performance of the reference signal transmission for each radio terminal to the UE # 2 is improved. Therefore, it is assumed that the communication performance can be maintained even if the radio resource used for transmitting the reference signal specific to the radio terminal for UE # 2 and the radio resource used for transmitting the reference signal specific to the radio terminal for UE # 4 are the same.
- the configuration information 1 that is not used can be assigned to the transmission of a reference signal for each wireless terminal at other wireless stations existing in the vicinity, and can be set so that the wireless resources are different between communication points.
- the configuration information 1 that is not used can be used for data transmission to improve the throughput.
- the radio station 50B sets the usage mode of the configuration information 1 for the UE # 2 to “NZP”, the usage mode of the configuration information 2 to “ZP”, and sets the usage mode of the configuration information 1 to the UE # 4.
- “ZP” and the usage mode of the configuration information 2 may be “NZP”, and the radio resource may be set to be different between the communication for UE # 2 and the communication for UE # 4.
- the radio station 50A transmits a signal indicating each use mode of the configuration information 1 and 2 for the UE # 2 to the UE # 2 on the PDCCH (S83).
- the radio station 50B transmits a signal indicating each use mode of the configuration information 1 and 2 for the UE # 2 to the UE # 2 on the PDCCH (S84), and the configuration information 1 and 2 for the UE # 4.
- a signal indicating each use mode is transmitted to UE # 4 on the PDCCH (S85).
- the radio stations 50A to 50B transmit data to UE # 2 on the PDSCH in a coordinated manner (S86, 87). Further, the radio station 50B transmits data to the UE # 4 on the PDSCH (S88).
- the wireless communication system it is possible to efficiently allocate the wireless resources prepared for the transmission of the reference signal for each wireless terminal from the wireless station and improve the communication performance.
- the wireless communication system 100 includes wireless stations 101, 102A to J and wireless terminals 103A to 103B.
- the wireless station 101 forms a PCell (Primary cell), and the wireless stations 102A to 102J form an SCell (Secondary cell).
- the SCell is a cell whose function may be more limited than that of the PCell.
- uplink control information (ACK / NACK, CQI, etc.) of layer 1 is transmitted only by uplink communication of PCell.
- the radio station 101 corresponds to a relatively large cell (Macro Cell), and the radio stations 102A to 102J correspond to relatively small cells (Small Cell).
- the radio communication system 100 is also referred to as a heterogeneous network in which radio stations having different cell ranges are mixed.
- PCell is a serving cell (connected cell) of PCC (PrimaryPrimcomponent carrier)
- SCell is a serving cell (connected cell) of SCC (Secondary component carrier).
- PCC is switched by handover, while SCC is added or deleted as necessary.
- the functional configuration and hardware configuration of the radio stations 101, 102A to J according to the fourth embodiment are the same as those of the radio stations 50A to 50B of FIG. 7 of the second embodiment. However, as described above, the functions of the wireless stations 102A to 102J are more limited than the functions of the wireless station 101.
- the functional configuration and hardware configuration of the wireless terminals 103A to 103B according to the fourth embodiment are the same as those of the wireless terminal 70A of FIG. 10 of the second embodiment.
- the radio station 101 sends a plurality of pieces of configuration information (DM-RS configuration information 1 and 2) indicating radio resources prepared for transmission of reference signals for individual radio terminals to the radio terminals 103A to 103B, for example, the radio terminals 103A to 103B.
- DM-RS configuration information 1 and 2 indicating radio resources prepared for transmission of reference signals for individual radio terminals
- the wireless station 101 exchanges control information with wireless stations around the wireless terminal 103A among the wireless stations 102A to 102J, and determines a communication mode for transmitting data to the wireless terminal 103A.
- the wireless station 101 exchanges control information with wireless stations around the wireless terminal 103B among the wireless stations 102A to 102J, and determines a communication mode for transmitting data to the wireless terminal 103B.
- the communication mode is determined every time data is transmitted, for example.
- the determination of the communication mode is executed at an interval relatively shorter than the connection establishment.
- the wireless station that actually transmits data to the wireless terminal 103A determines the configuration information 1, 2 for the wireless terminal 103A based on the determined communication mode and other communication conditions.
- Use mode (DM-RS mode) is determined.
- the wireless station that actually transmits data to the wireless terminal 103B determines the configuration information 1, 2 for the wireless terminal 103B based on the determined communication mode and other communication conditions.
- Use mode (DM-RS mode) is determined.
- the usage modes of the configuration information 1 and 2 are determined so that the resources are different.
- the use modes of the configuration information 1 and 2 are appropriately set so that the radio resources used for the DM-RS transmitted to a radio terminal by a plurality of radio stations performing CoMP communication are the same. It is determined.
- the wireless station that actually transmits data to the wireless terminal 103A transmits a signal indicating each use mode (DM-RS mode) of the configuration information 1, 2 to the wireless terminal 103A. It transmits to terminal 103A on PDCCH.
- the wireless station that actually transmits data to the wireless terminal 103B transmits a signal indicating each use mode (DM-RS mode) of the configuration information 1 and 2 to the wireless terminal 103B. Transmit to terminal 103B on PDCCH.
- the wireless station that actually transmits data to the wireless terminal 103A transmits the DM-RS according to the transmitted use mode, and transmits the data according to the determined communication mode. To do.
- the wireless terminal 103A extracts the DM-RS from the received signal in accordance with the transmitted use mode, and receives the data transmitted by the determined communication mode using the extracted DM-RS.
- the wireless station that actually transmits data to the wireless terminal 103B transmits a DM-RS according to the transmitted use mode, and transmits the data according to the determined communication mode. Send.
- the wireless terminal 103B extracts the DM-RS from the received signal according to the transmitted use mode, and receives the data transmitted by the determined communication mode using the extracted DM-RS.
- the determination of the communication mode, the determination of the use mode of the configuration information, the notification of the determined use mode, and the data transmission are repeated.
- the radio communication system it is possible to efficiently allocate radio resources prepared for transmission of reference signals for individual radio terminals from radio stations, thereby improving communication performance.
- the wireless communication system 110 includes wireless stations 111A to 111A and wireless terminals 112A to 112B.
- the radio stations 111A to 111J form a PCell (Primary cell).
- the functional configuration and hardware configuration of the radio stations 111A to 111J according to the fifth embodiment are the same as those of the radio stations 50A to 50B of FIG. 7 of the second embodiment.
- the functional configuration and hardware configuration of the wireless terminals 112A and 112B according to the fifth embodiment are the same as those of the wireless terminal 70A of FIG. 10 of the second embodiment.
- the connecting wireless station gives the wireless terminals 112A to 112B a plurality of pieces of configuration information (DM-RS configuration information 1 and 2) indicating radio resources prepared for transmission of reference signals for the individual wireless terminals. For example, when establishing a connection with the wireless terminals 112A to 112B, notification is made by RRC signaling.
- DM-RS configuration information 1 and 2 indicating radio resources prepared for transmission of reference signals for the individual wireless terminals.
- the connecting wireless station exchanges control information with wireless stations around the wireless terminal 112A among the wireless stations 111A to 111J, and determines a communication mode for transmitting data to the wireless terminal 123A.
- the connecting radio station among the radio stations 111A to 111J exchanges control information with radio stations around the radio terminal 112B among the radio stations 112A to 112J, and determines a communication mode for transmitting data to the radio terminal 112B.
- the communication mode is determined every time data is transmitted, for example. The determination of the communication mode is executed at an interval relatively shorter than the connection establishment.
- the wireless station that actually transmits data to the wireless terminal 112A uses the configuration information 1 and 2 for the wireless terminal 112A based on the determined communication mode and other communication conditions. Determine the mode (DM-RS mode).
- the wireless station that actually transmits data to the wireless terminal 112B uses the configuration information 1 and 2 for the wireless terminal 112B based on the determined communication mode and other communication conditions. Determine the mode (DM-RS mode).
- the radio resource used for the DM-RS transmitted from the radio station to the radio terminal 112A and the radio resource used for the DM-RS transmitted from the radio station to the radio terminal 112B The usage modes of the configuration information 1 and 2 are determined so that the resources are different. As a result, when DM-RS is transmitted, interference between communication points is reduced, channel estimation accuracy for receiving data is improved, and communication performance is improved. Also, for example, in the case of JT-CoMP communication, the use modes of the configuration information 1 and 2 are appropriately set so that the radio resources used for the DM-RS transmitted to a radio terminal by a plurality of radio stations performing CoMP communication are the same. It is determined.
- the wireless station that actually transmits data to the wireless terminal 112A sends a signal indicating the use mode (DM-RS mode) of the configuration information 1 and 2 to the wireless terminal 112A.
- the wireless station that actually transmits data to the wireless terminal 112B sends a signal indicating each use mode (DM-RS mode) of the configuration information 1 and 2 to the wireless terminal 112B.
- the PDCCH On the PDCCH.
- the radio resources used for the DM-RS transmitted to the radio terminals 112A-B by the radio station that actually transmits data among the radio stations 111A-J can be flexibly set. It can be set. In addition, this suppresses an increase in signaling compared to the case of sequentially notifying the configuration information indicating the radio resources prepared for the DM-RS at the timing of determining the communication mode executed at a relatively short interval. be able to.
- the wireless station that actually transmits data to the wireless terminal 112A among the wireless stations 111A to 111J transmits the DM-RS according to the transmitted use mode, and transmits the data according to the determined communication mode.
- the wireless terminal 112A extracts the DM-RS from the received signal according to the transmitted use mode, and receives the data transmitted by the determined communication mode using the extracted DM-RS.
- the wireless station that actually transmits data to the wireless terminal 112B transmits the DM-RS according to the transmitted use mode, and transmits the data according to the determined communication mode. .
- the wireless terminal 112B extracts the DM-RS from the received signal according to the transmitted use mode, and receives the data transmitted in the determined communication mode using the extracted DM-RS.
- the determination of the communication mode, the determination of the use mode of the configuration information, the notification of the determined use mode, and the data transmission are repeated.
- the fifth embodiment in the wireless communication system, it is possible to efficiently allocate the wireless resources prepared for transmission of the reference signal for each wireless terminal from the wireless station and improve the communication performance.
- the wireless communication systems of the first to fifth embodiments can be realized as, for example, an LTE-A system. Note that the present invention can also be applied to a wireless communication system using a communication method other than LTE-A.
- the wireless terminal is also referred to as a mobile station or a user equipment (User (Equipment, UE).
- the present invention can be applied to mobile terminals such as mobile phones, smartphones, PDAs (Personal Digital Assistants) as wireless terminals.
- the first to fifth embodiments can be applied to various communication devices that perform communication with a radio station such as a mobile relay station.
- the radio station is also referred to as a base station, a radio base station, or an access point.
- the radio station can be applied to base stations of various scales such as a macro base station, a pico base station, and a femto base station.
- the first to fifth embodiments can be applied to various communication devices that perform communication with wireless terminals such as relay stations.
- the wireless communication system can be realized by using a wireless station as a base station.
- the radio station can be realized as an independent eNodeB (evolved Node B).
- the radio communication system may be realized by using some radio stations as base station control units and other radio stations as base station remote units.
- the control unit can be realized as, for example, a centralized eNodeB and the remote unit can be realized as, for example, an RRH (Remote Radio Head) included in the centralized eNodeB.
- the control unit is connected to the remote unit via a wired connection such as an optical cable.
- the control unit forms a cell, and each remote unit forms a cover area that overlaps the cell.
- the control unit and the remote unit may use common cell identification information.
- each component of the radio station and radio terminal is not limited to the mode of the first to fifth embodiments, and all or a part thereof can be used for various loads, usage conditions, etc. Accordingly, it may be configured to be functionally or physically distributed / integrated in an arbitrary unit.
- the memory may be connected via a network or a cable as an external device of a wireless station or a wireless terminal.
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Abstract
Description
図1は、第1実施形態に係る無線通信システム1の構成を示す。図1に示すように、無線通信システム1は、無線局10A~Bと、無線端末20A~Bとを有する。無線局10A~Bはそれぞれ、アンテナを有し、通信ポイントに相当する。無線局10AはセルC10Aを形成し、無線局10BはセルC10Bを形成している。
第2実施形態に係る無線通信システムは、無線局10A~Bの代わりに、後述の図7に示す50A~B(Cell#1,Cell#2とも記載する)を有し、無線端末20A~Bの代わりに、後述の図10に示す無線端末70A~B(UE#1,UE#2とも記載する)を有する。第2実施形態に係る無線通信システムの全体的構成は、図1に示す無線通信システム1と同様である。例えば、無線局50A~Bはそれぞれ、有線接続あるいは無線接続を介してネットワーク装置3と接続され、ネットワーク装置3は有線接続あるいは無線接続を介してネットワーク2に接続される。そして、無線局50A~Bは、ネットワーク装置3及びネットワーク2を介して、データや制御情報を送受信可能に設けられている。
次に、第3実施形態に係る無線通信システムについて、図13~図15を参照して説明する。図13は、第3実施形態に係る無線通信システム1Aの構成を示す。図13に示すように、無線通信システム1Aは、無線局50A~B(Cell#1,Cell#2とも記載する)と、無線端末UE#1~UE#4とを有する。第3実施形態に係る無線通信システムの全体的構成は、第1~2実施形態に係る無線通信システムと同様である。例えば、無線局50A~Bはそれぞれ、有線接続あるいは無線接続を介してネットワーク装置3と接続され、ネットワーク装置3は有線接続あるいは無線接続を介してネットワーク2に接続される。そして、無線局50A~Bは、ネットワーク装置3及びネットワーク2を介して、データや制御情報を送受信可能に設けられている。
次に、第4実施形態に係る無線通信システム100について、図16を参照して説明する。無線通信システム100は、無線局101,102A~Jと、無線端末103A~Bとを有する。第4実施形態において、無線局101はPCell(Primary cell)を形成し、無線局102A~JはSCell(Secondary cell)を形成する。SCellは、PCellよりも機能が制限される場合があるセルである。制限される機能としては例えば、レイヤ1のアップリンク制御情報(ACK/NACKやCQI等)をPCellの上り通信のみで送信することが挙げられる。無線局101は、比較的規模の大きいセル(Macro Cell)に相当し、無線局102A~Jは、比較的規模の小さいセル(Small Cell)に相当する。無線通信システム100は、セル範囲の異なる無線局が混在するヘテロジニアス(Heterogeneous)ネットワークとも称される。
次に、第5実施形態に係る無線通信システム110について、図17を参照して説明する。無線通信システム110は、無線局111A~Jと、無線端末112A~Bとを有する。第5実施形態において、無線局111A~JはPCell(Primary cell)を形成する。
2 ネットワーク
3 ネットワーク装置
10A~B,50A~B,101,102A~J,111A~J 無線局
20A~B,70A~B,UE#1~#4,103A~B,112A~B 無線端末
C10A~B,Cell#1~#2,PCell,SCell セル
11,21 受信部
12,22 送信部
13,23 制御部
31,41 アンテナ
32,42 RF回路
33,43 CPU
34 DSP
35,44 メモリ
36 ネットワークIF
51A,B 受信アンテナ
52A,B 受信RF部
53A,B FFT部
54A,B 物理チャネル分離部
55A,B 信号復調部
56A,B チャネル推定部
57A,B 受信レベル測定部
58A,B 通信制御部
59A,B 上位レイヤデータ処理部
60A,B 信号生成部
61A,B 参照信号生成部
62A,B 物理チャネル多重部
63A,B IFFT部
64A,B 送信RF部
65A,B 送信アンテナ
71 受信アンテナ
72 受信RF部
73 FFT部
74 物理チャネル分離部
75 信号復調部
76 チャネル推定部
77 受信レベル測定部
78 通信制御部
79 上位レイヤデータ処理部
80 信号生成部
81 参照信号生成部
82 物理チャネル多重部
83 IFFT部
84 送信RF部
85 送信アンテナ
Claims (15)
- 無線通信方法であって、
無線局からの無線端末個別の参照信号の送信に準備される無線リソースを示す複数の構成情報を、無線端末で取得し、
前記無線局から前記無線端末へ、前記複数の構成情報のそれぞれが示す前記無線リソースについての使用に関する使用モードを指定する信号を送信し、
前記無線端末で前記信号を受信して、前記使用モードに応じて割当てられる前記無線リソースで前記無線局から送信される前記無線端末個別の参照信号を用いて、前記無線局との通信を行う、
ことを特徴とする無線通信方法。 - 前記複数の構成情報で、準備される前記無線リソースは互いに異なる、
ことを特徴とする請求項1に記載の無線通信方法。 - 前記複数の構成情報で、準備される前記無線リソースは互いに直交するように配置される、
ことを特徴とする請求項1又は2に記載の無線通信方法。 - 前記無線局から前記無線端末へ、接続確立の際に前記複数の構成情報を通知する、
ことを特徴とする請求項1~3のいずれかに記載の無線通信方法。 - 前記無線局から前記無線端末へ、データ送信の際に前記使用モードを指定する信号を送信する、
ことを特徴とする請求項1~4のいずれかに記載の無線通信方法。 - 前記無線局で、通信状況に応じて前記複数の構成情報のそれぞれの使用モードを決定する、
ことを特徴とする請求項1~5のいずれかに記載の無線通信方法。 - 前記無線局で、データ送信の際に、CoMP(Coordinated MultiPoint)通信可能な他の無線局の通信状況を取得し、データを送信する通信態様を決定し、前記複数の構成情報のそれぞれの使用モードを決定する、
ことを特徴とする請求項1~6のいずれかに記載の無線通信方法。 - 前記無線局で、前記無線局が他の無線局とCoMP(Coordinated MultiPoint)通信により前記無線端末へデータを送信するか否か、前記無線局が接続中の無線端末の数、前記無線局と接続中の無線端末との間の通信レベル、前記他の無線局が接続中の無線端末の数、前記他の無線局と接続中の無線端末との間の通信レベル、前記無線局からデータを送信する通信態様、前記他の無線局からデータを送信する通信態様、の少なくともいずれかに応じて前記複数の構成情報のそれぞれの使用モードを決定する、
ことを特徴とする請求項1~7のいずれかに記載の無線通信方法。 - 前記通信態様は、MIMO(Multi Input Multi Output)通信およびCoMP通信の少なくともいずれかを含む
ことを特徴とする請求項7又は8に記載の無線通信方法。 - 前記無線端末は複数あり、
前記複数の構成情報は前記複数の無線端末で共通に設定され、
前記使用モードは前記複数の無線端末で個別に指定される、
ことを特徴とする請求項1~9のいずれかに記載の無線通信方法。 - 前記無線局と、前記無線局とCoMP(Coordinated MultiPoint)通信可能な他の無線局とで、前記複数の構成情報が共通に使用される、
ことを特徴とする請求項1~10のいずれかに記載の無線通信方法。 - 前記使用モードは、前記無線端末個別の参照信号に準備される無線リソースにて前記無線端末個別の参照信号を所定の送信電力で送信するモード、前記無線端末個別の参照信号の送信電力を0にするモード、および前記無線端末個別の参照信号に準備される無線リソースをデータ信号に割り当てるモードを含む、
ことを特徴とする請求項1~11のいずれかに記載の無線通信方法。 - 無線局と無線端末とを有する無線通信システムであって、
前記無線端末は、前記無線局からの無線端末個別の参照信号の送信に準備される無線リソースを示す複数の構成情報を取得し、
前記無線局は、前記複数の構成情報のそれぞれが示す前記無線リソースについての使用に関する使用モードを指定する信号を前記無線端末へ送信し、
前記無線端末は、前記使用モードに応じて割当てられる前記無線リソースで前記無線局から送信される前記無線端末個別の参照信号を用いて、前記無線局との通信を行う、
ことを特徴とする無線通信システム。 - 無線局であって、
無線端末で取得される、前記無線局からの無線端末個別の参照信号の送信に準備される無線リソースを示す複数の構成情報の、それぞれが示す前記無線リソースについての使用に関する使用モードを指定する信号を、前記無線端末へ送信する送信部と、
前記使用モードに応じて割当てる前記無線リソースで送信する前記無線端末個別の参照信号を用いて、前記無線端末との通信を行う制御部と、を有する
ことを特徴とする無線局。 - 無線端末であって、
前記無線局からの無線端末個別の参照信号の送信に準備される無線リソースを示す複数の構成情報を取得する制御部と、
前記複数の構成情報のそれぞれが示す前記無線リソースについての使用に関する使用モードを指定する信号を、前記無線局から受信する受信部と、を有し、
前記制御部は、前記使用モードに応じて割当てられる前記無線リソースで前記無線局から送信される前記無線端末個別の参照信号を用いて、前記無線局との通信を行う、
ことを特徴とする無線端末。
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PCT/JP2013/002351 WO2014162357A1 (ja) | 2013-04-04 | 2013-04-04 | 無線通信方法、無線通信システム、無線局および無線端末 |
JP2015509600A JPWO2014162357A1 (ja) | 2013-04-04 | 2013-04-04 | 無線通信方法、無線通信システム、無線局および無線端末 |
KR1020157027132A KR20150128772A (ko) | 2013-04-04 | 2013-04-04 | 무선 통신 방법, 무선 통신 시스템, 무선국 및 무선 단말기 |
CN201380075329.8A CN105122916A (zh) | 2013-04-04 | 2013-04-04 | 无线通信方法、无线通信***、无线站以及无线终端 |
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