WO2015170417A1 - 無線通信システム、基地局および端末 - Google Patents
無線通信システム、基地局および端末 Download PDFInfo
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- WO2015170417A1 WO2015170417A1 PCT/JP2014/062532 JP2014062532W WO2015170417A1 WO 2015170417 A1 WO2015170417 A1 WO 2015170417A1 JP 2014062532 W JP2014062532 W JP 2014062532W WO 2015170417 A1 WO2015170417 A1 WO 2015170417A1
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- 238000004891 communication Methods 0.000 title claims abstract description 159
- 230000005540 biological transmission Effects 0.000 claims abstract description 326
- 238000001514 detection method Methods 0.000 claims description 22
- 230000008054 signal transmission Effects 0.000 claims description 13
- 230000003139 buffering effect Effects 0.000 claims description 6
- 238000010586 diagram Methods 0.000 description 42
- 238000000034 method Methods 0.000 description 21
- 238000013507 mapping Methods 0.000 description 14
- 238000006243 chemical reaction Methods 0.000 description 10
- 238000013468 resource allocation Methods 0.000 description 5
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- 239000002699 waste material Substances 0.000 description 3
- 230000000694 effects Effects 0.000 description 2
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
- H04W16/14—Spectrum sharing arrangements between different networks
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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
-
- 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
- H04L5/0051—Allocation of pilot signals, i.e. of signals known to the receiver of dedicated pilots, i.e. pilots destined for a single user or terminal
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
- H04W72/04—Wireless resource allocation
- H04W72/044—Wireless resource allocation based on the type of the allocated resource
- H04W72/0446—Resources in time domain, e.g. slots or frames
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
- H04W72/04—Wireless resource allocation
- H04W72/044—Wireless resource allocation based on the type of the allocated resource
- H04W72/0453—Resources in frequency domain, e.g. a carrier in FDMA
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
- H04W72/50—Allocation or scheduling criteria for wireless resources
- H04W72/54—Allocation or scheduling criteria for wireless resources based on quality criteria
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W74/00—Wireless channel access
- H04W74/08—Non-scheduled access, e.g. ALOHA
- H04W74/0808—Non-scheduled access, e.g. ALOHA using carrier sensing, e.g. carrier sense multiple access [CSMA]
- H04W74/0816—Non-scheduled access, e.g. ALOHA using carrier sensing, e.g. carrier sense multiple access [CSMA] with collision avoidance
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/0006—Assessment of spectral gaps suitable for allocating digitally modulated signals, e.g. for carrier allocation in cognitive radio
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/02—Amplitude-modulated carrier systems, e.g. using on-off keying; Single sideband or vestigial sideband modulation
- H04L27/06—Demodulator circuits; Receiver circuits
- H04L27/066—Carrier recovery circuits
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
- H04L27/2657—Carrier synchronisation
- H04L27/266—Fine or fractional frequency offset determination and synchronisation
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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
- H04L5/0001—Arrangements for dividing the transmission path
- H04L5/0003—Two-dimensional division
- H04L5/0005—Time-frequency
- H04L5/0007—Time-frequency the frequencies being orthogonal, e.g. OFDM(A), DMT
- H04L5/001—Time-frequency the frequencies being orthogonal, e.g. OFDM(A), DMT the frequencies being arranged in component carriers
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W76/00—Connection management
- H04W76/10—Connection setup
Definitions
- the present invention relates to a wireless communication system, a base station, and a terminal.
- an object of the present invention is to provide a wireless communication system, a base station, and a terminal that can improve communication efficiency.
- a first band dedicated to the own system and a second band shared between the own system and another wireless communication system are provided.
- a wireless communication system that performs wireless communication using the base station
- a control signal for permitting data transmission in the second band from a terminal to the own station is provided.
- Transmitting to the terminal in the first band continuously transmitting the second band radio wave during the period until the data transmission, and the terminal transmits the data after a predetermined time from the transmission of the control signal by the base station
- a wireless communication system, a base station and a terminal that perform transmission are proposed.
- a wireless communication system that performs wireless communication using a dedicated first band of the own system and a shared second band of the own system and another wireless communication system.
- the base station detects a vacant carrier in the second band in the first unit period, the base station continuously transmits the radio wave in the second band during at least a part of the remaining period of the first unit period. Transmitting a control signal indicating that data transmission in the second band from the local station to the terminal is performed in the second band following the first unit period, and transmitting the control signal to the terminal in the first band.
- a wireless communication system, a base station, and a terminal that perform the data transmission and that receive data of the data transmission based on the control signal transmitted by the base station are proposed.
- a wireless communication system that performs wireless communication using a dedicated first band of the own system and a shared second band of the own system and another wireless communication system.
- the base station detects a vacant carrier of the second band in the first unit period, at least a part of the remaining period of the first unit period and the next unit period after the first unit period.
- a control signal indicating that the signal transmission is performed in the second band from the local station to the terminal in two unit periods, and the signal transmission is performed in the at least a part of the period and the second unit period.
- the at least Wireless communication system for receiving a signal of the signal transmission in the part of the period the second unit period, a base station and a terminal is proposed.
- a wireless communication system that performs wireless communication using a dedicated first band of the own system and a shared second band of the own system and another wireless communication system.
- the base station transmits a control signal permitting data transmission in the second band from the terminal to the own station to the terminal in the first band, and a predetermined time after the control signal is transmitted by the base station.
- a wireless communication system, a base station, and a terminal that detect the vacant carrier of the second band later and wait for the vacant carrier to be detected before performing the data transmission are proposed.
- FIG. 1 is a diagram of an example of a wireless communication system according to the first embodiment.
- FIG. 2 is a diagram of an example of the operation of the wireless communication system according to the first embodiment.
- FIG. 3 is a flowchart of an example of processing by the base station according to the first embodiment.
- FIG. 4 is a flowchart of an example of processing performed by the terminal according to the first embodiment.
- FIG. 5A is a diagram of an example of a base station according to the first embodiment.
- FIG. 5B is a diagram illustrating an example of a signal flow in the base station illustrated in FIG. 5A.
- FIG. 5C is a diagram illustrating an example of a hardware configuration of the eNB.
- FIG. 5D is a diagram illustrating an example of a signal flow in the hardware configuration illustrated in FIG.
- FIG. 6A is a diagram illustrating an example of a terminal according to the first embodiment.
- 6B is a diagram illustrating an example of a signal flow in the terminal illustrated in FIG. 6A.
- FIG. 7 is a diagram of an example of scheduling by the base station according to the second embodiment.
- FIG. 8 is a flowchart of an example of scheduling processing by the base station according to the second embodiment.
- FIG. 9 is a diagram of an example of the operation of the wireless communication system according to the third embodiment.
- FIG. 10 is a flowchart of an example of processing by the base station according to the third embodiment.
- FIG. 11 is a flowchart of an example of processing performed by the terminal according to the third embodiment.
- FIG. 12 is a diagram of an example of the operation of the wireless communication system according to the fourth embodiment.
- FIG. 13 is a flowchart of an example of processing by the base station according to the fourth embodiment.
- FIG. 14 is a diagram of an example of the operation of the wireless communication system according to the fifth embodiment.
- FIG. 15 is a diagram illustrating an example of downlink transmission.
- FIG. 16 is a diagram illustrating another example of downlink transmission.
- FIG. 17 is a diagram illustrating an example of uplink transmission.
- FIG. 18 is a diagram illustrating another example of uplink transmission.
- FIG. 19 is a flowchart illustrating an example of processing of a base station and a terminal in downlink data transmission.
- FIG. 20 is a diagram of an example of the operation of the wireless communication system according to the sixth embodiment.
- FIG. 20 is a diagram of an example of the operation of the wireless communication system according to the sixth embodiment.
- FIG. 21 is a flowchart illustrating an example of downlink data transmission processing.
- FIG. 22A is a diagram (part 1) illustrating an example of operation of the wireless communication system according to the seventh embodiment
- FIG. 22B is a diagram (part 2) illustrating an example of operation of the wireless communication system according to the seventh embodiment
- FIG. 22C is a diagram (part 3) illustrating an example of operation of the wireless communication system according to the seventh embodiment
- FIG. 23A is a diagram (part 1) illustrating another example of operation of the wireless communication system according to the seventh embodiment.
- FIG. 23B is a diagram (part 2) illustrating another example of operation of the wireless communication system according to the seventh embodiment.
- FIG. 23C is a diagram (third) illustrating another example of operation of the wireless communication system according to the seventh embodiment;
- FIG. 24 is a flowchart of an example of processing by the base station according to the seventh embodiment.
- FIG. 25 is a flowchart of an example of processing by the terminal according to the seventh embodiment.
- FIG. 1 is a diagram of an example of a wireless communication system according to the first embodiment.
- the wireless communication system 100 according to the first embodiment includes a base station 110 and a terminal 101.
- a cell 111 is a cell formed by the base station 110.
- the terminal 101 is located in the cell 111 and performs wireless communication with the base station 110.
- the base station 110 and the terminal 101 perform LTE (Long Term Evolution) wireless communication.
- the base station 110 is, for example, an LTE eNB (evolved Node B).
- the terminal 101 is, for example, an LTE UE (User Equipment: user terminal).
- the base station 110 and the terminal 101 perform wireless communication with each other using the dedicated first band of the own system and the second band shared by the own system and other wireless communication systems.
- the first band is, for example, LC (Licensed band Carrier: licensed band carrier: licensed band carrier).
- the second band is, for example, UC (Unlicensed band Carrier: unlicensed band carrier).
- the second band is a band used also in a wireless LAN (Local Area Network) system.
- the second band may be a band shared with, for example, another (other vendor's) LTE system different from the wireless communication system 100.
- the first band is used for PCC (Primary Component Carrier) and the second band is used for SCC (Secondary Component Carrier).
- PCC Primary Component Carrier
- SCC Secondary Component Carrier
- FIG. 2 is a diagram of an example of the operation of the wireless communication system according to the first embodiment.
- the horizontal axis indicates time (t) in subframe units.
- the base station 110 performs carrier sense 201 (CS: Carrier Sense) in the UC when assigning UL (Up Link) transmission of the terminal 101 in the UC.
- CS Carrier Sense
- UL Up Link
- the base station 110 makes an RTS signal 202 (Request To Send: transmission request) that is a request signal for requesting data transmission from the own station in order to make a resource reservation for each terminal under the base station 110. ) Is transmitted (notified) by LC.
- the base station 110 transmits the RTS signal 203 by UC in order to perform resource reservation for other LTE systems (for example, including networks with different operators).
- the RTS signals 202 and 203 are transmitted in the subframe t3.
- the base station 110 transmits UL grants 211 to 214 (UL grant) to the terminal 101 by LC in subframes t5 to t8.
- the UL grant 211 is a signal indicating that the UL transmission from the terminal 101 after 4 subframes from the transmission of the UL grant 211 is permitted.
- UL grants 212 to 214 are signals indicating that UL transmission from the terminal 101 is permitted 4 subframes after the transmission of the UL grants 212 to 214, respectively.
- the base station 110 assigns subframes t9 to t12 to UL transmission from the terminal 101.
- the base station 110 transmits UL grants 211 to 214 to the terminal 101 in subframes t5 to t8 four subframes before.
- the terminal 101 performs UL transmissions 221 to 224 in subframes t9 to t12 four subframes after receiving each of the UL grants 211 to 214.
- the base station 110 performs DL (Down Link) transmission from the base station 110 in subframes t4 to t8 between the subframe t3 and the subframes t9 to t12 that transmitted the RTS signal 203.
- DL assignments 231 to 235 are transmitted.
- the base station 110 performs DL transmissions 241 to 245 by UC in subframes t4 to t8. That is, the base station 110 assigns UL transmissions 221 to 224 continuously to the DL transmissions 241 to 245.
- the DL assignment is also referred to as, for example, a DL assignment or a DL grant.
- DL transmissions 241 to 245 are DL transmissions to at least one of the terminals connected to the base station 110.
- Each terminal connected to the base station 110 may be the terminal 101 or a terminal different from the terminal 101.
- the bands (for example, resource blocks) of the DL transmissions 241 to 245 can be, for example, the same band as that of the UL transmissions 221 to 224 or a band including the bands of the UL transmissions 221 to 224.
- the bands of the DL transmissions 241 to 245 may be bands including a part of the bands of the UL transmissions 221 to 224.
- interruption to the UC in subframes t4 to t8 by a system other than LTE (for example, a wireless LAN system) that cannot receive the RTS signal 203 can be suppressed. For this reason, even if the terminal 101 does not perform carrier sense before the UL transmissions 221 to 224, interference with the UL transmissions 221 to 224 can be suppressed.
- LTE for example, a wireless LAN system
- the base station 110 may not transmit the RTS signal 203.
- the DL transmissions 241 to 245 can suppress, for example, interruption to the UC in the subframes t4 to t8 by another LTE network. Therefore, it is possible to suppress interference with the UL transmissions 221 to 224 even if the terminal 101 does not perform carrier sense before the UL transmissions 221 to 224.
- the base station 110 may perform DL transmission also in the subframe t3 and suppress interruption to the UC in the subframe t3.
- FIG. 3 is a flowchart of an example of processing by the base station according to the first embodiment.
- the base station 110 according to the first embodiment repeatedly executes, for example, each step shown in FIG. First, the base station 110 determines whether there is a UL transmission request or DL data (step S301).
- the UL transmission request is a request for UL transmission from the terminal 101.
- DL data is data to be transmitted from the base station 110 to the terminal 101.
- step S301 when there is no UL transmission request or DL data (step S301: No), the base station 110 returns to step S301. If it is determined that there is a UL transmission request or DL data (step S301: Yes), the base station 110 determines a bandwidth that needs to be reserved for the generated UL transmission request or DL data (step S302). The determination in step S302 is performed based on, for example, the size of UL data or DL data related to the UL transmission request.
- step S303 the base station 110 performs UC carrier sense and searches for available resources.
- step S304 the base station 110 determines whether there is a required resource available corresponding to the bandwidth determined in step S302 (step S304). If the required resources are not available (step S304: No), the base station 110 returns to step S303.
- step S304 when the required resource is available (step S304: Yes), the base station 110 broadcasts an RTS signal by LC (step S305). In addition, the base station 110 broadcasts an RTS signal through the UC (step S306).
- the base station 110 transmits DL data in a subframe following the RTS transmission in the UC in step S306 (step S307).
- the base station 110 transmits control information (UL grant) instructing transmission of UL data in a subframe following transmission of DL data in step S307 to the terminal 101 (step S308). ), A series of processing ends.
- FIG. 4 is a flowchart of an example of processing performed by the terminal according to the first embodiment.
- the terminal 101 according to the first embodiment executes, for example, each step shown in FIG. First, the terminal 101 determines whether or not it has received an RTS signal addressed to itself (step S401). When the RTS signal addressed to the own station has not been received (step S401: No), the terminal 101 determines whether an RTS signal addressed to another station has been received (step S402).
- step S402 when an RTS signal addressed to another station has not been received (step S402: No), the terminal 101 returns to step S401.
- step S402: Yes When an RTS signal addressed to another station is received (step S402: Yes), the terminal 101 sets a NAV (Network Allocation Vector: transmission prohibition period) in its own terminal based on the received RTS signal (step S403). The process returns to step S401.
- NAV Network Allocation Vector: transmission prohibition period
- step S401 when the RTS signal addressed to the own station is received (step S401: Yes), the terminal 101 receives the allocation information from the base station 110 through the LC (step S404).
- the allocation information includes, for example, UL grant and DL assignment.
- the terminal 101 receives DL data at the UC based on the allocation information received at step S404 (step S405). Also, the terminal 101 transmits UL data by UC based on the allocation information received in step S404 (step S406), and returns to step S401.
- FIG. 5A is a diagram of an example of a base station according to the first embodiment.
- FIG. 5B is a diagram illustrating an example of a signal flow in the base station illustrated in FIG. 5A.
- the base station 110 according to the first embodiment can be realized by the base station 110 shown in FIGS. 5A and 5B, for example.
- the base station 110 shown in FIGS. 5A and 5B includes antennas 501 and 502, a licensed band receiving unit 503, an unlicensed band receiving unit 508, a MAC / RLC processing unit 513, a radio resource control unit 514, and a carrier sense. Part 515.
- the base station 110 includes a MAC control unit 516, a packet generation unit 517, a MAC scheduling unit 518, a licensed band transmission unit 519, an unlicensed band transmission unit 525, and antennas 531 and 532.
- Each of the antennas 501 and 502 receives a signal wirelessly transmitted from another wireless communication device. Then, antennas 501 and 502 output the received signals to licensed band receiving unit 503 and unlicensed band receiving unit 508, respectively.
- the licensed band receiving unit 503 performs a licensed band reception process.
- the licensed band reception unit 503 includes a wireless processing unit 504, an FFT processing unit 505, a demodulation unit 506, and a decoding unit 507.
- the wireless processing unit 504 performs wireless processing on the signal output from the antenna 501.
- the wireless processing of the wireless processing unit 504 includes, for example, frequency conversion from a high frequency band to a baseband.
- the wireless processing unit 504 outputs the signal subjected to the wireless processing to the FFT processing unit 505.
- the FFT processing unit 505 performs FFT (Fast Fourier Transform) processing of the signal output from the wireless processing unit 504. As a result, the signal is converted from the time domain to the frequency domain.
- the FFT processing unit 505 outputs the signal subjected to the FFT processing to the demodulation unit 506.
- the demodulator 506 demodulates the signal output from the FFT processor 505.
- Demodulation section 506 outputs a signal obtained by demodulation to decoding section 507.
- the decoding unit 507 decodes the signal output from the demodulation unit 506. Then, the decoding unit 507 outputs the data obtained by the decoding to the MAC / RLC processing unit 513.
- the unlicensed band receiving unit 508 performs unlicensed band reception processing.
- the unlicensed band receiving unit 508 includes a wireless processing unit 509, an FFT processing unit 510, a demodulation unit 511, and a decoding unit 512.
- the wireless processing unit 509 performs wireless processing on the signal output from the antenna 502.
- the wireless processing of the wireless processing unit 509 includes, for example, frequency conversion from a high frequency band to a baseband.
- the wireless processing unit 509 outputs the signal subjected to the wireless processing to the FFT processing unit 510.
- the FFT processing unit 510 performs FFT processing on the signal output from the wireless processing unit 509. As a result, the signal is converted from the time domain to the frequency domain.
- the FFT processing unit 510 outputs the signal subjected to the FFT processing to the demodulation unit 511 and the carrier sense unit 515.
- the demodulator 511 demodulates the signal output from the FFT processor 510.
- Demodulation section 511 outputs a signal obtained by demodulation to decoding section 512.
- the decoding unit 512 decodes the signal output from the demodulation unit 511. Then, the decoding unit 512 outputs the data obtained by the decoding to the MAC / RLC processing unit 513.
- the MAC / RLC processing unit 513 performs each process of a MAC (Media Access Control) layer and an RLC (Radio Link Control: radio link control) layer based on the data output from the decoding unit 507.
- the MAC / RLC processing unit 513 outputs data obtained by processing of each layer.
- the signal output from the MAC / RLC processing unit 513 is input to, for example, a higher layer processing unit of the base station 110. Further, the MAC / RLC processing unit 513 outputs control information such as an RTS signal detection result included in the data obtained by the processing of each layer to the radio resource control unit 514.
- the radio resource control unit 514 performs radio resource control based on the control information output from the MAC / RLC processing unit 513. This radio resource control is processing of an RRC (Radio Resource Control) layer.
- the radio resource control unit 514 outputs control information based on radio resource control to the MAC control unit 516.
- RRC Radio Resource Control
- the carrier sense unit 515 performs carrier sense based on the unlicensed band signal output from the FFT processing unit 510. Then, carrier sense section 515 outputs carrier sense result information indicating the result of carrier sense to MAC control section 516.
- the MAC control unit 516 controls the MAC layer based on the control information output from the radio resource control unit 514 and the carrier sense result information output from the carrier sense unit 515. Then, the MAC control unit 516 outputs the individual control information and the RTS signal to the terminal 101 based on the control of the MAC layer to the multiplexing unit 522.
- the individual control information is, for example, PDCCH (Physical Downlink Control Channel: physical downlink control channel).
- the MAC control unit 516 outputs a DMRS (Data Demodulation Reference Signal) based on the control of the MAC layer, a dummy signal, an RTS signal, and the like to the multiplexing unit 528. Also, the MAC control unit 516 outputs control information based on the control of the MAC layer to the MAC scheduling unit 518.
- DMRS Data Demodulation Reference Signal
- the packet generation unit 517 generates a packet including user data output from the upper layer of the base station 110. Then, the packet generation unit 517 outputs the generated packet to the MAC scheduling unit 518.
- the MAC scheduling unit 518 performs scheduling of the MAC layer of the packet output from the packet generation unit 517 based on the control information output from the MAC control unit 516. Then, MAC scheduling section 518 outputs the packet to licensed band transmission section 519 and unlicensed band transmission section 525 based on the scheduling result.
- the licensed band transmission unit 519 performs a licensed band transmission process.
- licensed band transmission section 519 includes an encoding section 520, a modulation section 521, a multiplexing section 522, an IFFT processing section 523, and a wireless processing section 524.
- the encoding unit 520 encodes the packet output from the MAC scheduling unit 518. Then, encoding section 520 outputs the encoded packet to modulation section 521. Modulation section 521 performs modulation based on the packet output from encoding section 520. Modulation section 521 then outputs the signal obtained by the modulation to multiplexing section 522.
- the multiplexing unit 522 multiplexes the individual control information and RTS signal output from the MAC control unit 516 and the signal output from the modulation unit 521. Then, multiplexing section 522 outputs the signal obtained by multiplexing to IFFT processing section 523.
- the IFFT processing unit 523 performs an IFFT (Inverse Fast Fourier Transform) process on the signal output from the multiplexing unit 522. As a result, the signal is converted from the frequency domain to the time domain.
- the IFFT processing unit 523 outputs the signal subjected to the IFFT processing to the wireless processing unit 524.
- the wireless processing unit 524 performs wireless processing on the signal output from the IFFT processing unit 523.
- the wireless processing of the wireless processing unit 524 includes, for example, frequency conversion from a baseband band to a high frequency band.
- the wireless processing unit 524 outputs a signal subjected to wireless processing to the antenna 531.
- the unlicensed band transmission unit 525 performs unlicensed band transmission processing.
- the unlicensed band transmission unit 525 includes an encoding unit 526, a modulation unit 527, a multiplexing unit 528, an IFFT processing unit 529, and a wireless processing unit 530.
- the encoding unit 526 encodes the packet output from the MAC scheduling unit 518. Then, the encoding unit 526 outputs the encoded packet to the modulation unit 527.
- the modulation unit 527 performs modulation based on the packet output from the encoding unit 526. Modulation section 527 outputs the signal obtained by the modulation to multiplexing section 528.
- the multiplexing unit 528 multiplexes the individual control information and RTS signal output from the MAC control unit 516 and the signal output from the modulation unit 527. Then, multiplexing section 528 outputs the signal obtained by multiplexing to IFFT processing section 529.
- the IFFT processing unit 529 performs an IFFT process on the signal output from the multiplexing unit 528. As a result, the signal is converted from the frequency domain to the time domain. IFFT processing unit 529 outputs the signal subjected to IFFT processing to radio processing unit 530.
- the wireless processing unit 530 performs wireless processing on the signal output from the IFFT processing unit 529.
- the radio processing of the radio processing unit 530 includes, for example, frequency conversion from a baseband band to a high frequency band.
- the wireless processing unit 530 outputs a signal subjected to wireless processing to the antenna 532.
- the antenna 531 wirelessly transmits the signal output from the wireless processing unit 524 to another wireless communication device.
- the antenna 532 wirelessly transmits the signal output from the wireless processing unit 530 to another wireless communication device.
- FIG. 5C is a diagram illustrating an example of a hardware configuration of the eNB.
- FIG. 5D is a diagram illustrating an example of a signal flow in the hardware configuration illustrated in FIG. 5C.
- the base station 110 can be realized by the wireless communication device 550 shown in FIGS. 5C and 5D, for example.
- the wireless communication device 550 includes, for example, a transmission / reception antenna 551, an amplifier 552, a multiplication unit 553, an analog / digital converter 554, a processor 555, and a memory 556.
- the wireless communication device 550 includes a digital-analog converter 557, a multiplication unit 558, an amplifier 559, and an oscillator 560.
- the wireless communication device 550 may include an interface that performs wired communication with an external communication device.
- the transmission / reception antenna 551 receives a signal wirelessly transmitted from the periphery of its own device, and outputs the received signal to the amplifier 552. Further, the transmission / reception antenna 551 wirelessly transmits the signal output from the amplifier 559 to the periphery of the own device.
- the amplifier 552 amplifies the signal output from the transmission / reception antenna 551. Then, the amplifier 552 outputs the amplified signal to the multiplier 553.
- the multiplier 553 multiplies the signal output from the amplifier 552 by the clock signal output from the oscillator 560, thereby performing frequency conversion from the high frequency band to the baseband band. Then, the multiplier 553 outputs the frequency-converted signal to the analog / digital converter 554.
- the analog / digital converter 554 (A / D) is an ADC (Analog / Digital Converter) that converts the signal output from the multiplier 553 from an analog signal to a digital signal.
- the analog-digital converter 554 outputs the signal converted into the digital signal to the processor 555.
- the processor 555 governs overall control of the wireless communication device 550.
- the processor 555 can be realized by, for example, a CPU (Central Processing Unit), a DSP (Digital Signal Processor), or the like.
- the processor 555 performs reception processing on the signal output from the analog-digital converter 554. Further, the processor 555 generates a signal to be transmitted by the own device, and performs a transmission process of outputting the generated signal to the digital / analog converter 557.
- the memory 556 includes, for example, a main memory and an auxiliary memory.
- the main memory is, for example, a RAM (Random Access Memory).
- the main memory is used as a work area for the processor 555.
- the auxiliary memory is a non-volatile memory such as a magnetic disk or a flash memory.
- Various programs for operating the processor 555 are stored in the auxiliary memory.
- the program stored in the auxiliary memory is loaded into the main memory and executed by the processor 555. Further, for example, various predetermined threshold values are stored in the auxiliary memory.
- the digital-analog converter 557 is a DAC (Digital / Analog Converter) that converts a signal output from the processor 555 from a digital signal to an analog signal.
- the digital-analog converter 557 outputs the signal converted into the analog signal to the multiplication unit 558.
- the multiplier 558 multiplies the signal output from the digital-analog converter 557 with the clock signal output from the oscillator 560, thereby performing frequency conversion from the baseband to the high-frequency band. Then, multiplication section 558 outputs the frequency-converted signal to amplifier 559.
- the amplifier 559 amplifies the signal output from the digital / analog converter 557. Then, the amplifier 559 outputs the amplified signal to the transmission / reception antenna 551.
- the oscillator 560 oscillates a clock signal (continuous wave AC signal) having a predetermined frequency. Then, the oscillator 560 outputs the oscillated clock signal to the multipliers 553 and 558.
- the antennas 501, 502, 531 and 532 shown in FIGS. 5A and 5B can be realized by, for example, the transmission / reception antenna 551.
- 5A and 5B includes, for example, an amplifier 552, a multiplier 553, an analog-digital converter 554, a digital-analog converter 557, a multiplier 558, an amplifier 559, and an oscillator 560.
- the other configurations shown in FIGS. 5A and 5B can be realized by the processor 555 and the memory 556, for example.
- FIG. 6A is a diagram illustrating an example of a terminal according to the first embodiment.
- 6B is a diagram illustrating an example of a signal flow in the terminal illustrated in FIG. 6A.
- the terminal 101 according to the first embodiment can be realized by, for example, the terminal 101 illustrated in FIGS. 6A and 6B.
- the terminal 101 includes a MAC processing unit 618, a packet generation unit 619, an encoding / modulation unit 620, a licensed band transmission unit 621, and an unlicensed band transmission unit 627.
- the antenna 601 receives a signal wirelessly transmitted from another wireless communication device. Antenna 601 then outputs the received signal to licensed band receiving section 602 and unlicensed band receiving section 608. Further, the antenna 601 wirelessly transmits each signal output from the licensed band transmission unit 621 and the unlicensed band transmission unit 627 to another wireless communication device.
- the licensed band receiving unit 602 performs licensed band reception processing.
- the licensed band receiving unit 602 includes a wireless processing unit 603, an FFT processing unit 604, an equalization processing unit 605, an IFFT processing unit 606, and a demodulation unit 607.
- the wireless processing unit 603 performs wireless processing on the signal output from the antenna 601.
- the radio processing of the radio processing unit 603 includes, for example, frequency conversion from a high frequency band to a base band.
- the wireless processing unit 603 outputs the signal subjected to the wireless processing to the FFT processing unit 604.
- the FFT processing unit 604 performs an FFT process on the signal output from the wireless processing unit 603. As a result, the signal is converted from the time domain to the frequency domain.
- the FFT processing unit 604 outputs the signal subjected to the FFT processing to the equalization processing unit 605.
- the equalization processing unit 605 performs equalization processing on the signal output from the FFT processing unit 604. Then, the equalization processing unit 605 outputs the signal subjected to the equalization process to the IFFT processing unit 606.
- the IFFT processing unit 606 performs an IFFT process on the signal output from the equalization processing unit 605. As a result, the signal is converted from the frequency domain to the time domain. IFFT processing unit 606 outputs the signal subjected to IFFT processing to demodulation unit 607. The demodulator 607 demodulates the signal output from the IFFT processor 606. Demodulation section 607 then outputs the signal obtained by demodulation to decoding section 614.
- the unlicensed band receiving unit 608 performs unlicensed band reception processing.
- the unlicensed band receiving unit 608 includes a wireless processing unit 609, an FFT processing unit 610, an equalization processing unit 611, an IFFT processing unit 612, and a demodulation unit 613.
- the wireless processing unit 609 performs wireless processing on the signal output from the antenna 601.
- the wireless processing of the wireless processing unit 609 includes, for example, frequency conversion from a high frequency band to a baseband band.
- the wireless processing unit 609 outputs the signal subjected to the wireless processing to the FFT processing unit 610 and the carrier sense unit 617.
- the FFT processing unit 610 performs an FFT process on the signal output from the wireless processing unit 609. As a result, the signal is converted from the time domain to the frequency domain.
- the FFT processing unit 610 outputs the signal subjected to the FFT processing to the equalization processing unit 611.
- the equalization processing unit 611 performs equalization processing on the signal output from the FFT processing unit 610. Then, the equalization processing unit 611 outputs the signal subjected to the equalization process to the IFFT processing unit 612.
- the IFFT processing unit 612 performs IFFT processing on the signal output from the equalization processing unit 611. As a result, the signal is converted from the frequency domain to the time domain.
- IFFT processing section 612 outputs the signal subjected to IFFT processing to demodulation section 613.
- the demodulator 613 demodulates the signal output from the IFFT processor 612. Then, demodulation section 613 outputs a signal obtained by demodulation to decoding section 614.
- the decoding unit 614 decodes the signals output from the licensed band receiving unit 602 and the unlicensed band receiving unit 608. Then, the decoding unit 614 outputs data obtained by decoding.
- the data output from the decoding unit 614 is input to, for example, the upper layer processing unit and the RTS signal detection unit 615 of the terminal 101.
- the data output from the decoding unit 614 includes, for example, user data.
- the RTS signal detection unit 615 detects an RTS signal transmitted from another wireless communication device included in the data output from the decoding unit 614. Then, the RTS signal detection unit 615 outputs detection information indicating the detection result of the RTS signal to the RRC processing unit 616.
- the RRC processing unit 616 performs RRC layer processing based on the RTS signal output from the RTS signal detection unit 615. Then, the RRC processing unit 616 outputs the processing result of the RRC layer to the MAC processing unit 618.
- the carrier sense unit 617 performs carrier sense based on the signal output from the wireless processing unit 609. Then, carrier sense section 617 outputs carrier sense result information indicating the result of carrier sense to MAC processing section 618.
- the MAC processing unit 618 performs MAC layer processing based on the processing result output from the RRC processing unit 616 and the carrier sense result information output from the carrier sense unit 617. Then, the MAC processing unit 618 outputs the DMRS, dummy signal, RTS signal, and the like to the terminal 101 based on the MAC layer processing to the multiplexing units 622 and 628.
- the MAC processing unit 618 outputs radio resource allocation information based on the MAC layer processing to the frequency mapping units 624 and 630. Also, the MAC processing unit 618 outputs radio resource allocation information based on the RRC layer processing of the RRC processing unit 616 to the encoding / modulation unit 620. Also, the MAC processing unit 618 confirms the availability of radio resources with which the terminal 101 communicates based on the carrier sense result information output from the carrier sense unit 617.
- the packet generation unit 619 generates a packet including user data output from the upper layer of the terminal 101. Then, the packet generation unit 619 outputs the generated packet to the encoding / modulation unit 620.
- the encoding / modulation unit 620 encodes and modulates the packet output from the packet generation unit 619. Then, the encoding / modulation unit 620 transmits the signal obtained by the encoding and modulation to the licensed band transmission unit 621 or the unlicensed band transmission unit 627 based on the radio resource allocation information output from the MAC processing unit 618. Output.
- the licensed band transmission unit 621 performs a licensed band transmission process.
- the licensed band transmission unit 621 includes a multiplexing unit 622, an FFT processing unit 623, a frequency mapping unit 624, an IFFT processing unit 625, and a radio processing unit 626.
- the multiplexing unit 622 multiplexes each signal output from the MAC processing unit 618 and the signal output from the encoding / modulation unit 620. Then, multiplexing section 622 outputs the signal obtained by multiplexing to FFT processing section 623.
- the FFT processing unit 623 performs FFT processing on the signal output from the multiplexing unit 622. As a result, the signal is converted from the time domain to the frequency domain.
- the FFT processing unit 623 outputs the signal subjected to the FFT processing to the frequency mapping unit 624.
- the frequency mapping unit 624 performs frequency mapping of the signal output from the FFT processing unit 623 based on the radio resource allocation information output from the MAC processing unit 618. Then, frequency mapping section 624 outputs the frequency mapped signal to IFFT processing section 625.
- the IFFT processing unit 625 performs IFFT processing on the signal output from the frequency mapping unit 624. As a result, the signal is converted from the frequency domain to the time domain.
- the IFFT processing unit 625 outputs the signal subjected to the IFFT processing to the wireless processing unit 626.
- the wireless processing unit 626 performs wireless processing on the signal output from the IFFT processing unit 625.
- the wireless processing of the wireless processing unit 626 includes, for example, frequency conversion from a baseband to a high frequency band.
- the wireless processing unit 626 outputs a signal subjected to wireless processing to the antenna 601.
- the unlicensed band transmission unit 627 performs unlicensed band transmission processing.
- the unlicensed band transmission unit 627 includes a multiplexing unit 628, an FFT processing unit 629, a frequency mapping unit 630, an IFFT processing unit 631, and a wireless processing unit 632.
- the multiplexing unit 628 multiplexes each signal output from the MAC processing unit 618 and the signal output from the encoding / modulation unit 620. Then, multiplexing section 628 outputs a signal obtained by multiplexing to FFT processing section 629.
- the FFT processing unit 629 performs an FFT process on the signal output from the multiplexing unit 628. As a result, the signal is converted from the time domain to the frequency domain.
- the FFT processing unit 629 outputs the signal subjected to the FFT processing to the frequency mapping unit 630.
- the frequency mapping unit 630 performs frequency mapping of the signal output from the FFT processing unit 629 based on the radio resource allocation information output from the MAC processing unit 618. Then, frequency mapping section 630 outputs the frequency mapped signal to IFFT processing section 631.
- the IFFT processing unit 631 performs IFFT processing on the signal output from the frequency mapping unit 630. As a result, the signal is converted from the frequency domain to the time domain.
- the IFFT processing unit 631 outputs the signal subjected to the IFFT processing to the wireless processing unit 632.
- the wireless processing unit 632 performs wireless processing on the signal output from the IFFT processing unit 631.
- the radio processing of the radio processing unit 632 includes, for example, frequency conversion from a baseband band to a high frequency band.
- the wireless processing unit 632 outputs a signal subjected to wireless processing to the antenna 601.
- the terminal 101 may be provided with an antenna for radio transmission and an antenna for radio reception.
- the terminal 101 can be realized by the wireless communication device 550 shown in FIGS. 5C and 5D, for example.
- the wireless communication device 550 may not include an interface for performing wired communication with an external communication device.
- the antenna 601 shown in FIGS. 6A and 6B can be realized by the transmission / reception antenna 551, for example.
- 6A and 6B includes, for example, an amplifier 552, a multiplier 553, an analog-digital converter 554, a digital-analog converter 557, a multiplier 558, an amplifier 559, and an oscillator 560. Can be realized.
- the other configurations shown in FIGS. 6A and 6B can be realized by the processor 555 and the memory 556, for example.
- the base station 110 transmits a control signal permitting UL transmission from the terminal 101 to the own station through the LC, until the terminal 101 transmits the UL signal.
- UC DL data radio waves
- FIG. 7 is a diagram of an example of scheduling by the base station according to the second embodiment.
- the horizontal direction indicates time (t) in units of subframes, and the depth direction indicates UC frequency (f).
- the base station 110 according to the second embodiment performs DL transmission prior to UL transmission, as in the first embodiment.
- the base station 110 allocates UL transmissions 711 to 714 of the terminal 101 to the time resource T2 for 4 subframes, for example.
- the base station 110 assigns the DL transmissions 721 to 724 of the base station 110 to the time resource T1 for four subframes immediately before the time resource T2.
- the base station 110 transmits the DL data so as to transmit 4 subframes even if the amount of DL data to be transmitted to the time resource T1 for 4 subframes is small.
- Scheduling to allocate This scheduling can be, for example, TTI (Transmission Time Interval) bundling or scheduling for each subframe.
- the base station 110 assigns DL transmissions 721 to 724 to the same band as the band (band F1) of the UL transmissions 711 to 714 for the time resource T1, so that the DL transmissions 721 to 724 are assigned.
- the transmission can be 4 subframes long.
- the bandwidth of the DL transmissions 721 to 724 may be a bandwidth including at least a part of the bandwidth of the UL transmissions 711 to 714 (band F1).
- FIG. 8 is a flowchart of an example of scheduling processing by the base station according to the second embodiment.
- the base station 110 according to the second embodiment executes, for example, each step shown in FIG. 8 as UL scheduling processing in the UC.
- the base station 110 determines the bandwidth B of required radio resources necessary for UL data transmission requested from the terminal (step S801).
- the base station 110 reads out data of size N that can be transmitted with a radio resource of B ⁇ 4 subframes from a DL data buffer that stores DL data (step S802).
- the reading in step S802 is performed using a required MCS (Modulation and Coding Scheme).
- the base station 110 performs the process of step S803 for each of the four subframes to be scheduled. That is, the base station 110 cuts out data for one subframe (size N / 4) from the data read out in step S802 and schedules it for radio resources of B ⁇ 1 subframe (step S803). In step S803, the base station 110 uses the LTE rate matching function to map the modulation data to the radio resources to be allocated without any gaps.
- the base station 110 performs the scheduling from the base station 110 that performed the scheduling so that the data length becomes the length of the period until the terminal 101 transmits the UL to the terminal 101.
- DL data radio waves
- the effects according to the first embodiment can be obtained, and even if the DL data from the base station 110 to the terminal 101 is small, the DL data is continuously transmitted during the period until the UL transmission by the terminal 101, and other systems. Can be prevented from being interrupted.
- FIG. 9 is a diagram of an example of the operation of the wireless communication system according to the third embodiment.
- base station 110 performs carrier sense 201 in subframes t3 and t4, and assigns subframes t9 to t13 to UL transmission from terminal 101.
- the base station 110 transmits UL grants 211 to 215 to the terminal 101 in subframes t5 to t9.
- the terminal 101 performs UL transmissions 221 to 225 in subframes t9 to t13 four subframes after receiving each of the UL grants 211 to 215.
- the base station 110 transmits RTS signals 901 to 904 having a length of 4 subframes in the subframes t5 to t8 by UC.
- the bands (for example, resource blocks) of the RTS signals 901 to 904 can be, for example, the same band as that of the UL transmissions 221 to 225 or a band including the bands of the UL transmissions 221 to 225.
- the band of the RTS signals 901 to 904 may be a band including a part of the band of the UL transmissions 221 to 225.
- interruptions in subframes t5 to t8 by a system other than LTE for example, a wireless LAN system
- LTE for example, a wireless LAN system
- the base station 110 may transmit the RTS signal 202 in the LC as shown in FIG. 2 before transmitting the UL grants 211 to 215.
- FIG. 10 is a flowchart of an example of processing by the base station according to the third embodiment.
- the base station 110 according to the third embodiment repeatedly executes each step shown in FIG. 10, for example.
- the base station 110 determines whether there is a UL transmission request (step S1001). When there is no UL transmission request (step S1001: No), the base station 110 returns to step S1001. When there is a UL transmission request (step S1001: Yes), the base station 110 determines a bandwidth that needs to be reserved for the generated UL transmission request (step S1002).
- step S1003 the base station 110 performs UC carrier sense and searches for available resources.
- step S1004 the base station 110 determines whether there is a required resource available corresponding to the bandwidth determined in step S1002 (step S1004). If the required resources are not available (step S1004: No), the base station 110 returns to step S1003.
- step S1004 when the required resource is available (step S1004: Yes), the base station 110 broadcasts an RTS signal by LC (step S1005).
- the base station 110 broadcasts an RTS signal having a length of 4 subframes in UC (step S1006).
- the base station 110 transmits control information (UL grant) instructing transmission of UL data in a subframe following the RTS transmission in step S1006 to the terminal 101 (step S1007), and ends a series of processes.
- UL grant control information
- FIG. 11 is a flowchart of an example of processing performed by the terminal according to the third embodiment.
- the terminal 101 according to the third embodiment executes, for example, each step shown in FIG. Steps S1101 to S1104 shown in FIG. 11 are the same as steps S401 to S404 shown in FIG. Following step S1104, the terminal 101 transmits UL data by UC based on the allocation information received in step S1104 (step S1105), and returns to step S1101.
- Embodiment 3 when base station 110 transmits a control signal permitting UL transmission from terminal 101 to its own station by LC, the period until UL transmission by terminal 101 is reached.
- UC RTS signals radio waves
- the RTS signal is a request signal for requesting data transmission.
- FIG. 12 is a diagram of an example of the operation of the wireless communication system according to the fourth embodiment.
- the base station 110 transmits an RTS signal 203 having a length of 1 subframe in UC at the subframe t5.
- base station 110 transmits DMRSs 1201 to 1203 having a length of 3 subframes in UC in subframes t6 to t8 following subframe t5.
- DMRS is a reference signal for demodulating a data signal in terminal 101.
- the band (for example, resource block) of DMRS 1201 to 1203 can be the same band (UL allocated band) as the band of UL transmission 221 to 225, for example. Thereby, the UL allocated bandwidth can be reserved.
- interruptions in subframes t5 to t8 by a system other than LTE for example, a wireless LAN system
- LTE for example, a wireless LAN system
- the base station 110 may transmit the RTS signal 202 in the LC as shown in FIG. 2 before transmitting the UL grants 211 to 215.
- FIG. 13 is a flowchart of an example of processing by the base station according to the fourth embodiment.
- the base station 110 according to the fourth embodiment repeatedly executes, for example, each step shown in FIG. Steps S1301 to S1305 shown in FIG. 13 are the same as steps S1001 to S1005 shown in FIG. After step S1305, the base station 110 broadcasts an RTS signal using the UC (step S1306).
- the base station 110 transmits DMRS of 3 subframe length by UC (step S1307). Further, the base station 110 transmits control information (UL grant) instructing transmission of UL data in a subframe following DMRS transmission in step S1307 to the terminal 101 (step S1308), and ends a series of processing.
- control information UL grant
- the terminal 101 according to the fourth embodiment executes, for example, each step illustrated in FIG.
- the base station 110 transmits a control signal permitting UL transmission from the terminal 101 to the own station through the LC, the period until the UL transmission by the terminal 101 is reached.
- UC DMRS radio waves
- the base station 110 transmits a control signal permitting UL transmission from the terminal 101 to the own station via the LC
- the base station 110 continuously transmits a UC dummy signal (radio wave) during the period until the terminal 101 performs UL transmission. May be sent out.
- a UC dummy signal radio wave
- the base station 110 transmits a control signal permitting UL transmission from the terminal 101 to the own station via LC
- the base station 110 continuously transmits UC radio noise (radio waves) during the period until the terminal 101 performs UL transmission. May be sent out. Also in this case, it is possible to suppress interruption in another system during a period until UL transmission by the terminal 101, and to suppress interference in UL transmission by the terminal 101. For this reason, communication efficiency can be improved.
- the detecting unit that detects the vacant UC (second band) carrier is, for example, the antenna 502, the unlicensed band receiving unit 508, and the carrier shown in FIGS. 5A and 5B. This can be realized by the sense unit 515. Also, the base station 110 transmits a UC grant (control signal) permitting UC data transmission from the terminal 101 to the terminal 101 to the terminal 101 by LC (first band) when a vacant UC carrier is detected.
- a transmission unit that continuously transmits UC radio waves during a period from transmission to data transmission is provided.
- This transmission unit can be realized by, for example, the MAC control unit 516, the MAC scheduling unit 518, the licensed band transmission unit 519, the unlicensed band transmission unit 525, and the antennas 531 and 532 illustrated in FIGS. 5A and 5B.
- a receiving unit that receives a UC grant from base station 110 is implemented by antenna 601, licensed band receiving unit 602, and decoding unit 614 shown in FIGS. 6A and 6B, for example. Can do.
- a transmission unit that performs data transmission a predetermined time after receiving the UL grant can be realized by the unlicensed band transmission unit 627 and the antenna 601 shown in FIGS. 6A and 6B, for example.
- FIG. 14 is a diagram of an example of the operation of the wireless communication system according to the fifth embodiment.
- the horizontal axis indicates time (t) in subframe units.
- Data channel transmission in the LTE system is performed in subframe units in synchronization with the subframe timing of the base station 110.
- the data channel in the LTE system is, for example, PDSCH (Physical Downlink Shared Channel) or PUSCH (Physical Uplink Shared Channel).
- the base station 110 transmits a signal such as DMRS or a dummy signal that is not required to be received by the counterpart terminal in this gap time, so that the channel is transmitted to other devices. Make a reservation.
- the UC is busy 1401 (Busy) from the subframe t1 to the middle of the subframe t2.
- the base station 110 is in the busy state 1401 in the middle of the subframe t2.
- DL transmission is assigned to subframe t3.
- the base station 110 transmits DL assignment 1402 to the terminal 101 in subframe t3, and performs DL transmission 1403 (Data). For this reason, a gap time 1404 between the busy state 1401 and the subframe t3 occurs.
- the base station 110 wirelessly transmits the DMRS 1407 when the DIFS time 1405 and the backoff time 1406 have elapsed since the busy state 1401 ends. Further, the base station 110 may transmit a dummy signal instead of the DMRS 1407.
- the dummy signal is, for example, a wireless signal that does not request reception from a specific wireless communication device. Further, the base station 110 may transmit radio noise instead of the DMRS 1407.
- FIG. 15 is a diagram illustrating an example of downlink transmission.
- the horizontal axis indicates time (t) in units of subframes.
- t time in units of subframes.
- the UC is shared between the radio communication system 100 and an LTE system different from the radio communication system 100. It is assumed that the LTE system different from the radio communication system 100 synchronizes subframes with the radio communication system 100.
- subband SB1 is busy 1511 by another LTE system in the subframe t1.
- subband SB2 is busy 1512 by other LTE systems in subframes t1 to t4.
- subband SB3 is busy 1513 by another LTE system in subframe t1.
- subband SB4 is busy 1514 by other LTE systems in subframes t1 and t2.
- base station 110 when DL data is generated in subframe t1, base station 110 performs a new interval between back-off times 1531 and 1533 after DIFS time 1521 elapses from the end of busy states 1511 and 1513 of subbands SB1 and SB3.
- DL data is allocated to subframe t3 of subbands SB1 and SB3. Note that DL data cannot be assigned to the subframe t2 of the subbands SB1 and SB3 because the busy states 1511 and 1513 remain until the end of the subframe t1 of the immediately preceding subbands SB1 and SB3.
- Base station 110 transmits DL assignment 1501 to terminal 101 in subframe t3, and performs DL transmission 1502 and 1503 in subbands SB1 and SB3. For this reason, in the subbands SB1 and SB3, the subframe t2 becomes a gap time.
- the base station 110 wirelessly transmits the DMRS 1541 in the subband SB1 when the DIFS time 1521 and the backoff time 1531 have elapsed from the end of the busy state 1511. Also, base station 110 wirelessly transmits DMRS 1543 in subband SB3 when DIFS time 1521 and backoff time 1533 have elapsed since the busy state 1513 ended.
- the base station 110 may transmit a dummy signal instead of the DMRSs 1541 and 1543.
- the dummy signal is a radio signal without a destination, for example.
- the base station 110 may transmit radio noise instead of the DMRSs 1541 and 1543.
- FIG. 16 is a diagram illustrating another example of downlink transmission. 16, the same parts as those shown in FIG. 15 are denoted by the same reference numerals, and the description thereof is omitted.
- the wireless LAN system is asynchronous with the wireless communication system 100.
- the subbands SB1 to SB4 are assumed to be busy 1610 by the wireless LAN system from the subframe t1 to the subframe t2.
- the base station 110 when DL data is generated in the subframe t1, the base station 110 is in the busy state 1610 until the middle of the subframe t2. Therefore, after the DIFS time 1521 elapses from the end of the busy state 1610, the backoff times 1531 and 1533 are further increased. If a new busy state is not detected during this period, DL data is assigned to subframe t3. In the example illustrated in FIG. 16, the base station 110 assigns DL data to the subframe t3 of the subbands SB1 and SB3.
- the base station 110 transmits the DL assignment 1501 to the terminal 101 in the subframe t3, and performs DL transmission 1502 and 1503 in the subbands SB1 and SB3. For this reason, a gap time 1550 between the busy state 1610 and the subframe t3 occurs in the subbands SB1 and SB3.
- the base station 110 wirelessly transmits DMRS 1541 in the subband SB1 when the DIFS time 1521 and the backoff time 1531 have elapsed since the busy state 1610 ended. Also, base station 110 wirelessly transmits DMRS 1543 in subband SB3 when DIFS time 1521 and backoff time 1533 have elapsed since the busy state 1610 ended.
- the base station 110 may transmit a dummy signal instead of the DMRSs 1541 and 1543.
- the dummy signal is a radio signal without a destination, for example.
- the base station 110 may transmit radio noise instead of the DMRSs 1541 and 1543.
- FIG. 17 is a diagram illustrating an example of uplink transmission.
- the horizontal axis indicates time (t) in units of subframes.
- t time in units of subframes.
- the LTE system different from the radio communication system 100 synchronizes subframes with the radio communication system 100.
- subband SB1 is busy 1711 by other LTE systems in subframes t3 to t6.
- subband SB2 is busy 1712 by another LTE system in subframe t3.
- subband SB3 is busy 1713 by another LTE system in subframe t3.
- subband SB4 is busy 1714 by other LTE systems in subframes t3 and t4.
- the base station 110 determines necessary radio resources (number of subbands). In this example, assuming that this is two subbands, if no new busy state is detected during the backoff time 1731 after the DIFS time 1721 has elapsed since the end of the busy states 1712 and 1713 of the subbands SB2 and SB3, , Subframe t5 in subbands SB2 and SB3 is allocated to UL transmission of terminal 101. In this case, the base station 110 transmits the UL grant 1701 to the terminal 101 via the LC in the subframe t1. Then, base station 110 receives UL data by UL transmission 1702 from terminal 101 in subframe t5. For this reason, the subframe t4 is a gap time.
- base station 110 wirelessly transmits DMRS 1741 in subbands SB2 and SB3 when DIFS time 1721 and backoff time 1731 have elapsed since the end of busy states 1712 and 1713.
- the base station 110 may transmit a dummy signal instead of the DMRS 1741.
- the dummy signal is a radio signal without a destination, for example.
- the base station 110 may transmit radio noise instead of the DMRS 1741.
- FIG. 18 is a diagram illustrating another example of uplink transmission. 18, parts that are the same as the parts shown in FIG. 17 are given the same reference numerals, and descriptions thereof will be omitted.
- a case where the UC is shared between the wireless communication system 100 and the wireless LAN system will be described.
- the wireless LAN system is asynchronous with the wireless communication system 100.
- subbands SB1 to SB4 are in a busy state 1810 by the wireless LAN system from near the end of the subframe t2 to the middle of the subframe t4.
- a gap time 1850 occurs from the middle of subframe t4 to subframe t5.
- the base station 110 wirelessly transmits DMRS 1741 in the subbands SB2 and SB3 when the DIFS time 1821 and the back-off time 1731 have elapsed since the end of the busy state 1810.
- the base station 110 may transmit a dummy signal instead of the DMRS 1741.
- the dummy signal is a radio signal without a destination, for example.
- the base station 110 may transmit radio noise instead of the DMRS 1741.
- FIG. 19 is a flowchart illustrating an example of processing of a base station and a terminal in downlink data transmission.
- the base station 110 and the terminal 101 according to the fifth embodiment execute, for example, each step illustrated in FIG. First, the base station 110 determines whether or not there is room for the DIFS time in the UC (step S1901). If there is no space for DIFS time (step S1901: NO), the base station 110 returns to step S1901.
- step S1901 if there is a vacancy for DIFS time (step S1901: Yes), the base station 110 determines whether there is a vacancy for T (backoff) in the UC (step S1902).
- T (backoff) is a back-off time required for the back-off process.
- step S1902: No the base station 110 updates T (backoff) (step S1903), and returns to step S1901.
- step S1902 if there is a free space for T (backoff) (step S1902: Yes), the base station 110 transmits the DMRS to the terminal 101 in the UC up to the next subframe boundary (top) in the current subframe (n). Transmit (step S1904).
- the base station 110 schedules DL user data for the next subframe (n + 1) (step S1905).
- the base station 110 performs transmission of DL user data in UC and transmission of allocation information (DL assignment) in LC in the next subframe (n + 1) based on the result of scheduling in step S1905. This is performed (step S1906).
- the terminal 101 receives the UC DL user data transmitted from the base station 110 in the next subframe (n + 1) based on the allocation information transmitted in step S1906 (step S1907).
- Embodiment 5 when base station 110 detects the vacant UC carrier in the first subframe (first unit period) in DL, the rest of the first subframe is detected. UC radio waves are continuously transmitted during at least a part of the gap period. Then, in the second subframe (second unit period) subsequent to the first subframe, the base station 110 transmits a control signal indicating that data transmission in the UC from the local station to the terminal 101 is performed by the terminal 101 using the LC. To the UC for data transmission. Thereby, it is possible to prevent other systems from wirelessly transmitting in the gap time, and to suppress collision between DL transmission and wireless transmission by other systems.
- the base station 110 transmits a control signal permitting UL transmission from the terminal 101 to the own station through the LC
- the UL transmission by the terminal 101 is performed.
- UC DL data radio waves
- the detection unit that detects the vacant UC (second band) carrier is, for example, the antenna 502, the unlicensed band reception unit 508, and the carrier sense unit illustrated in FIGS. 5A and 5B. 515 can be realized.
- the base station 110 performs at least a part of the remaining period of the first subframe.
- a transmission unit that continuously transmits UC radio waves is provided.
- the transmission unit transmits a UC grant (control signal) indicating that data transmission is performed in the UC from the local station to the terminal 101.
- Data is transmitted by transmitting to the terminal 101 in the LC (first band).
- This transmission unit can be realized by, for example, the MAC control unit 516, the MAC scheduling unit 518, the licensed band transmission unit 519, the unlicensed band transmission unit 525, and the antennas 531 and 532 illustrated in FIGS. 5A and 5B.
- the first receiving unit that receives the UC grant from the base station 110 is realized by the antenna 601, the licensed band receiving unit 602, and the decoding unit 614 shown in FIGS. 6A and 6B, for example. Can do.
- the terminal 101 includes a second receiving unit that receives data transmitted by the base station 110 based on the received UC grant. This second receiving unit can be realized by the antenna 601, the unlicensed band receiving unit 608 and the decoding unit 614 shown in FIGS. 6A and 6B, for example.
- FIG. 20 is a diagram of an example of the operation of the wireless communication system according to the sixth embodiment.
- the horizontal axis represents time (t) in units of subframes.
- the base station 110 according to the sixth embodiment transmits a signal such as a control signal or a data signal to the terminal 101 during the gap time described in the fifth embodiment.
- the UC is busy 2010 (Busy) by another wireless LAN system from the subframe t1 to the middle of the subframe t2.
- base station 110 assigns DL transmission to subframe t3 because UC is busy 2010 in the middle of subframe t2.
- the base station 110 transmits DL assignment 2001 to the terminal 101 in subframe t3, and performs DL transmission 2002 (Data). For this reason, a gap time 2020 occurs between the busy state 2010 and the subframe t3.
- the base station 110 wirelessly transmits DL data 2023 (User Data) when the DIFS time 2021 and the back-off time 2022 have elapsed since the busy state 2010 ended. Further, the base station 110 may transmit a control signal instead of the DL data 2023. This makes it possible to reserve a channel for another device.
- DL data 2023 User Data
- the base station 110 stores information (scheduling information and the like) for receiving (for example, demodulating) the DL data 2023 in the DL assignment 2001.
- the terminal 101 buffers the received signal for the latest one subframe, and transmits the DL transmitted from the base station 110 at the gap time 2020 based on downlink scheduling information notified by the DL DL assignment 2001. Data 2023 is received (reproduced).
- FIG. 21 is a flowchart illustrating an example of downlink data transmission processing.
- the base station 110 and the terminal 101 according to the sixth embodiment execute, for example, each step illustrated in FIG. Steps S2101 to S2103 shown in FIG. 21 are the same as steps S1901 to S1903 shown in FIG.
- step S2102 if there is a free space for T (backoff) (step S2102: Yes), the base station 110 schedules DL user data to the UC until the next subframe boundary (top) in the current subframe (n). (Step S2104). Next, the base station 110 transmits DL user data by UC based on the result of scheduling in step S2104 (step S2105).
- the base station 110 schedules DL user data for the next subframe (n + 1) (step S2106).
- the base station 110 performs transmission of DL user data in UC and transmission of allocation information (DL assignment) in LC in the next subframe (n + 1) based on the scheduling result in step S2106. This is performed (step S2107).
- the terminal 101 receives the UC DL user data transmitted from the base station 110 in steps S2105 and S2107 based on the allocation information transmitted in step S2107 (step S2108).
- the base station 110 detects at least a part of the remaining gap period of the first subframe in which the UC carrier is detected in the first subframe in DL. UC signal transmission to the terminal 101 is performed in the second subframe. Then, the base station 110 transmits a DL assignment (control signal) indicating that the signal transmission is performed in each of these periods in the second subframe.
- the terminal 101 buffers the received signal from the base station, so that the signal of the signal transmission of the base station 110 in each period described above based on the DL assignment transmitted from the base station 110 in the second subframe. Receive.
- the detecting unit that detects the vacant UC (second band) carrier is, for example, the antenna 502, the unlicensed band receiving unit 508, and the carrier sensing unit illustrated in FIGS. 5A and 5B. 515 can be realized.
- the base station 110 includes a transmission unit. This transmission unit, when a vacant UC carrier is detected in the first subframe (first unit period), at least a part of the remaining period of the first subframe and the next of the first subframe. In the second subframe (second unit period), signal transmission by UC to the terminal 101 is performed.
- the transmission unit transmits at least a part of the remaining period of the first subframe, the second subframe next to the first subframe, and a DL assignment (control signal) indicating that signal transmission is performed to the second. Transmit in subframe.
- This transmission unit can be realized by, for example, the MAC control unit 516, the MAC scheduling unit 518, the licensed band transmission unit 519, the unlicensed band transmission unit 525, and the antennas 531 and 532 illustrated in FIGS. 5A and 5B.
- a buffering unit that buffers a received signal from the base station 110 can be realized by the memory 556 shown in FIGS. 5C and 5D, for example. Also, the terminal 101 transmits a signal from the base station 110 in at least a part of the remaining period of the first subframe and the second subframe based on the DL assignment transmitted from the base station 110 in the second subframe.
- a receiving unit for receiving a transmission signal is provided. The receiving unit receives (reproduces) each signal using the buffered received signal. This receiving unit can be realized by the antenna 601, the unlicensed band receiving unit 608, and the decoding unit 614 shown in FIGS. 6A and 6B, for example.
- 22A to 22C are diagrams illustrating an example of the operation of the wireless communication system according to the seventh embodiment.
- the horizontal axis represents time (t) in units of subframes.
- base station 110 assigns subframes t7 to t10 to the UL transmission of terminal 101 in UC.
- the UL transmission of terminal 101 may be shifted after subframes t7 to t10.
- the base station 110 transmits UL grants 2211 to 2214 to the terminal 101 via LC in subframes t3 to t6 without performing carrier sense.
- the terminal 101 performs carrier sense 2220 in subframe t6.
- carrier sense 2220 in subframe t6.
- terminal 101 performs UL transmission 2231 to 2234 in subframes t7 to t10. This is the shortest case from transmission of UL grants 2211 to 2214 to UL transmission 2231 to 2234.
- terminal 101 continues carrier sense 2220 also in subframe t7.
- vacancy is confirmed in carrier sense 2220 of subframe t7.
- terminal 101 performs UL transmission 2231 to 2234 in subframes t8 to t11.
- the terminal 101 continues carrier sense 2220 after subframe t8.
- the UC vacancy is confirmed in the carrier sense 2220 of the subframe t10.
- the terminal 101 performs UL transmission 2231 to 2234 in subframes t11 to t14. This is the longest case from transmission of UL grants 2211 to 2214 to UL transmission 2231 to 2234.
- the maximum carrier sense time 2221 is the maximum time for which the carrier sense 2220 is continued, and is preset in the base station 110 and the terminal 101, for example. In the example shown in FIG. 22C, the maximum carrier sense time 2221 is 5 subframes.
- the terminal 101 When the duration of the carrier sense 2220 exceeds the maximum carrier sense time 2221, the terminal 101 gives up UL transmission. For example, if no UC vacancy is confirmed in the carrier sense 2220 of the subframe t10, the terminal 101 gives up the UL transmissions 2231 to 2234.
- UL transmission may be assigned to a terminal different from the terminal 101 in the subframes t11 and t12.
- a terminal different from the terminal 101 also has the same function as the terminal 101, and determines that there is no UC available based on carrier sense in the subframes t11 and t12, and shifts UL transmission later. Thereby, collision with UL transmission in subframes t11 and t12 by terminal 101 can be suppressed.
- the base station 110 speculatively transmits the UL grant without performing UC carrier sense.
- the terminal 101 waits until the UC is detected by carrier sense and performs UL transmission. In this case, for example, channel reservation by RTS may not be performed. Further, by setting carrier sense 2220 and providing a limit on the waiting time of terminal 101, it is possible to avoid an increase in delay due to each terminal waiting in a superimposed manner.
- the UL grant transmission interval and the maximum carrier sense time 2221 may be controlled in accordance with the UC channel congestion degree.
- the base station 110 shortens the UL grant transmission interval for the terminal 101 as the UC channel congestion degree increases. Thereby, even if UL transmission is abandoned, the UL grant can be transmitted again in a short time, and a reduction in throughput can be suppressed.
- the base station 110 and the terminal 101 lengthen the maximum carrier sense time 2221 as the UC channel congestion degree increases. As a result, the probability of giving up UL transmission can be reduced, and a decrease in throughput can be suppressed.
- Various information such as the frequency of occurrence of UL transmission requests to the base station 110, the number of terminals connected to the base station 110, the frequency of occurrence of standby or abandonment of UL transmission can be used for the channel congestion level, for example.
- FIG. 23A to 23C are diagrams illustrating another example of the operation of the wireless communication system according to the seventh embodiment.
- the horizontal axis indicates time (t) in subframe units.
- terminal 101 may control the transmission power of UL transmissions 2231 to 2234 according to the duration of carrier sense 2220. For example, terminal 101 increases the transmission power of UL transmissions 2231 to 2234 as the duration of carrier sense 2220 is longer.
- the terminal 101 may control the MCS level of the UL transmissions 2231 to 2234 according to the duration of the carrier sense 2220. For example, the terminal 101 increases the MCS level of the UL transmissions 2231 to 2234 as the duration of the carrier sense 2220 is longer. For example, the terminal 101 applies the MCS level, which is a modulation scheme with lower propagation characteristics, to the UL transmissions 2231 to 2234 as the duration of the carrier sense 2220 is shorter.
- a modulation scheme with low propagation characteristics is, for example, a multi-level modulation scheme and a modulation scheme with a high coding rate.
- the base station 110 and the terminal 101 share in advance the correspondence information between the duration of the carrier sense 2220 and the MCS level. Thereby, the base station 110 can receive UL data in response to the terminal 101 changing the MCS level according to the duration.
- the transmission power and MCS level of the UL transmissions 2231 to 2234 are controlled according to the duration of the carrier sense 2220. Thereby, for example, even if the channel state has changed since the base station 110 performed scheduling, it is possible to suppress a decrease in throughput.
- the transmission power and MCS level of UL transmissions 2231 to 2234 may be controlled according to the channel state detected by carrier sense 2220.
- the terminal 101 increases the transmission power of the UL transmissions 2231 to 2234 as the channel state detected by the carrier sense 2220 is worse.
- the channel state is, for example, the magnitude of interference power.
- the transmission power of the UL transmissions 2231 to 2234 is controlled according to the channel state detected by the carrier sense 2220. Thereby, a decrease in throughput can be suppressed. Further, the transmission power and MCS level of UL transmissions 2231 to 2234 may be controlled according to the combination of the duration of carrier sense 2220 and the channel state.
- FIG. 24 is a flowchart of an example of processing by the base station according to the seventh embodiment.
- the base station 110 according to the seventh embodiment executes the steps shown in FIG. 24, for example.
- the base station 110 determines whether or not there is a UL transmission request (step S2401). When there is no UL transmission request (step S2401: No), the base station 110 returns to step S2401.
- step S2401 if there is a UL transmission request (step S2401: Yes), the base station 110 determines the required radio resource and the number of continuous transmission subframes for each subframe (step S2402).
- the base station 110 transmits an UL grant based on the determination result in step S2402 to the terminal 101 by LC (step S2403).
- the base station 110 determines whether or not UL data has been received from the terminal 101 within a predetermined time CS (max) +4 subframes (step S2404).
- the predetermined time CS (max) is, for example, the maximum carrier sense time 2221 described above.
- step S2404 when the UL data is not received (step S2404: No), the base station 110 returns to step S2403.
- step S2404: Yes when the UL data is received (step S2404: Yes), the base station 110 returns to step S2401.
- FIG. 25 is a flowchart of an example of processing by the terminal according to the seventh embodiment.
- the terminal 101 according to the seventh embodiment executes, for example, each step shown in FIG. First, the terminal 101 determines whether or not it has received a UL grant addressed to itself (step S2501). When the UL grant addressed to the own station has not been received (step S2501: No), the process returns to step S2501.
- step S2501 when receiving the UL grant addressed to the own station (step S2501: Yes), the terminal 101 starts UC carrier sense after 3 subframes after receiving the UL grant (step S2502).
- the terminal 101 determines whether or not the allocated resource due to the UL grant received in step S2501 has been detected based on the carrier sense started in step S2502 (step S2503).
- the terminal 101 continues to be busy for a predetermined time CS (max) after starting carrier sense in step S2502. It is determined whether or not there is (step S2504).
- the predetermined time CS (max) is, for example, the maximum carrier sense time 2221 described above.
- step S2504 if the busy state is not continued for the predetermined time CS (max) (step S2504: No), the terminal 101 returns to step S2503. If the busy state continues for the predetermined time CS (max) (step S2504: Yes), the terminal 101 gives up transmission of UL data and returns to step S2501.
- step S2503 when the vacant resource allocated by the UL grant is detected (step S2503: Yes), the terminal 101 transmits UL data by UC (step S2505), and returns to step S2501.
- the base station 110 does not perform UC carrier sense. Then, terminal 101 detects UC carrier vacancy after a predetermined time (for example, after 3 subframes) after UL grant is transmitted, and waits until carrier vacancy is detected before performing UL transmission. .
- the terminal 101 stops the carrier sense of the UC if no vacant carrier is detected even after waiting for the maximum carrier sense time 2221 (predetermined period) after starting the carrier sense (detection). In this case, the terminal 101 does not perform UL transmission based on the received UL grant. As a result, it is possible to prevent the standby time from increasing and the throughput of the wireless communication system 100 from decreasing.
- the base station 110 sets the UL grant permitting data transmission in the UC from the terminal 101 to the own station via the LC. Send it again. Thereby, UL transmission can be redone when UL transmission is abandoned.
- the base station 110 may instruct the terminal 101 by the UL grant whether or not the terminal 101 needs carrier sense.
- the terminal 101 performs carrier sense based on an instruction from the UL grant.
- the base station 110 can control whether or not the terminal 101 performs carrier sense.
- the terminal 101 may control at least one of the transmission power, the modulation scheme, and the coding rate of UL transmission according to the standby time until the vacant carrier is detected. Also, the terminal 101 may control the transmission power of UL transmission according to the degree of UC congestion.
- the base station 110 transmits an UL grant (control signal) permitting data transmission in the UC (second band) from the terminal 101 to the terminal 101 to the terminal 101 in the LC (first band).
- a transmission unit is provided. This transmission unit can be implemented by, for example, the MAC control unit 516, the MAC scheduling unit 518, the licensed band transmission unit 519, and the antenna 531 illustrated in FIGS. 5A and 5B.
- the base station 110 detects the UC carrier vacancy after a predetermined time since the UL grant is transmitted, and waits until the carrier vacancy is detected before data transmission by the terminal 101 that performs data transmission. Is provided.
- This receiving unit can be realized by the antenna 502 and the unlicensed band receiving unit 508, for example.
- the receiving unit that receives the UC grant from the base station 110 can be realized by the antenna 601, the licensed band receiving unit 602, and the decoding unit 614 shown in FIGS. 6A and 6B, for example.
- the terminal 101 detects a UC carrier empty after three subframes (predetermined time) after the UL grant is received, and waits until the carrier empty is detected before transmitting a data transmission unit. Prepare.
- This transmission unit can be realized by, for example, the carrier sense unit 617, the unlicensed band transmission unit 627, and the antenna 601 shown in FIGS. 6A and 6B.
- the base station According to the wireless communication system, the base station, and the terminal, communication efficiency can be improved.
- a method of using an unlicensed band as an additional carrier in LTE using a licensed band has been studied.
- use of a licensed band carrier has been studied for transmission of control information.
- a coexistence method with a wireless LAN in an unlicensed band has been studied.
- the base station considers the processing time in the terminal, and notifies the terminal of scheduling information (UL grant) of the data by PCC before k subframes of UL data transmission.
- UL grant scheduling information
- the terminal Since the base station does not know whether or not the SCC is free after k subframes at the time of scheduling, the terminal performs carrier sense to determine whether the channel is free before actually transmitting data using the scheduled resource. Check. If the channel is not free at this time, there is a problem that scheduling is canceled and waste occurs. In contrast, for example, according to the above-described seventh embodiment, it is possible to prevent the scheduling from being wasted.
- the base station when the base station performs carrier sense, the base station reserves a channel for other terminals by transmitting a CTS (Clear To Send) packet by SCC after checking an empty channel by carrier sense. To do.
- CTS Car To Send
- SCC Serial To Send
- the base station since there is a time difference of k subframes from CTS packet transmission to data transmission, there is a problem that resources during this time are wasted or a channel is used by another system such as a wireless LAN.
- Wireless communication system 101
- Terminal 110 Base station 111 Cell 201, 2220 Carrier sense 202, 203, 901-904 RTS signal 211-215, 1701, 2112-1214 UL grant 221-225, 711-714, 1702, 2231-2234 UL Transmission 231 to 235, 1402, 1501, 2001 DL assignment 241 to 245, 721 to 724, 1403, 1502, 1503, 2002 DL transmission 501, 502, 531, 532, 601 Antenna 503, 602 Licensed band receiver 504, 509, 524, 530, 603, 609, 626, 632 Wireless processing unit 505, 510, 604, 610, 623, 629 FFT processing unit 506, 511, 607, 613 Demodulation unit 507, 512 614 Decoding unit 508,608 Unlicensed band reception unit 513 MAC / RLC processing unit 514 Radio resource control unit 515,617 Carrier sense unit 516 MAC control unit 517,619 Packet generation unit 518 MAC scheduling unit 519,
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Abstract
Description
(実施の形態1にかかる無線通信システム)
図1は、実施の形態1にかかる無線通信システムの一例を示す図である。図1に示すように、実施の形態1にかかる無線通信システム100は、基地局110と、端末101と、を含む。セル111は、基地局110が形成するセルである。端末101は、セル111に在圏しており、基地局110との間で無線通信を行う。
図2は、実施の形態1にかかる無線通信システムの動作の一例を示す図である。図2において、横軸はサブフレーム単位の時間(t)を示している。基地局110は、UCにおける端末101のUL(Up Link:上りリンク)送信の割り当てを行う際に、UCにおいてキャリアセンス201(CS:Carrier Sense)を行う。図2に示す例では、基地局110は、キャリアセンス201の結果、UCに空きリソースがあると判断したとする。
図3は、実施の形態1にかかる基地局による処理の一例を示すフローチャートである。実施の形態1にかかる基地局110は、たとえば図3に示す各ステップを繰り返し実行する。まず、基地局110は、UL送信要求またはDLデータが有るか否かを判断する(ステップS301)。UL送信要求は、端末101からのUL送信の要求である。DLデータは、基地局110から端末101へ送信すべきデータである。
図4は、実施の形態1にかかる端末による処理の一例を示すフローチャートである。実施の形態1にかかる端末101は、たとえば図4に示す各ステップを実行する。まず、端末101は、自局宛てRTS信号を受信したか否かを判断する(ステップS401)。自局宛てRTS信号を受信していない場合(ステップS401:No)は、端末101は、他局宛てのRTS信号を受信したか否かを判断する(ステップS402)。
図5Aは、実施の形態1にかかる基地局の一例を示す図である。図5Bは、図5Aに示した基地局における信号の流れの一例を示す図である。実施の形態1にかかる基地局110は、たとえば図5A,図5Bに示す基地局110により実現することができる。
図5Cは、eNBのハードウェア構成の一例を示す図である。図5Dは、図5Cに示したハードウェア構成における信号の流れの一例を示す図である。基地局110は、たとえば図5C,図5Dに示す無線通信装置550により実現することができる。
図6Aは、実施の形態1にかかる端末の一例を示す図である。図6Bは、図6Aに示した端末における信号の流れの一例を示す図である。実施の形態1にかかる端末101は、たとえば図6A,図6Bに示す端末101により実現することができる。
端末101は、たとえば図5C,図5Dに示した無線通信装置550により実現することができる。この場合に、無線通信装置550は、外部の通信装置との間で有線通信を行うインタフェースを備えていなくてもよい。
実施の形態2について、実施の形態1と異なる部分について説明する。
図7は、実施の形態2にかかる基地局によるスケジューリングの一例を示す図である。図7において、横方向はサブフレーム単位の時間(t)を示し、奥行方向はUCの周波数(f)を示す。実施の形態2にかかる基地局110は、実施の形態1と同様に、UL送信に先行してDL送信を行う。
図8は、実施の形態2にかかる基地局によるスケジューリング処理の一例を示すフローチャートである。実施の形態2にかかる基地局110は、UCにおけるULのスケジューリング処理として、たとえば図8に示す各ステップを実行する。
実施の形態3について、実施の形態1と異なる部分について説明する。
図9は、実施の形態3にかかる無線通信システムの動作の一例を示す図である。図9において、図2に示した部分と同様の部分については同一の符号を付して説明を省略する。図9に示す例では、基地局110は、サブフレームt3,t4においてキャリアセンス201を行い、サブフレームt9~t13を端末101からのUL送信に割り当てる。
図10は、実施の形態3にかかる基地局による処理の一例を示すフローチャートである。実施の形態3にかかる基地局110は、たとえば図10に示す各ステップを繰り返し実行する。まず、基地局110は、UL送信要求が有るか否かを判断する(ステップS1001)。UL送信要求が無い場合(ステップS1001:No)は、基地局110は、ステップS1001へ戻る。UL送信要求が有る場合(ステップS1001:Yes)は、基地局110は、発生したUL送信要求のために予約を要する帯域幅を決定する(ステップS1002)。
図11は、実施の形態3にかかる端末による処理の一例を示すフローチャートである。実施の形態3にかかる端末101は、たとえば図11に示す各ステップを実行する。図11に示すステップS1101~S1104は、図4に示したステップS401~S404と同様である。ステップS1104のつぎに、端末101は、ステップS1104によって受信した割り当て情報を基にUCでULデータを送信し(ステップS1105)、ステップS1101へ戻る。
実施の形態4について、実施の形態1と異なる部分について説明する。
図12は、実施の形態4にかかる無線通信システムの動作の一例を示す図である。図12において、図9に示した部分と同様の部分については同一の符号を付して説明を省略する。図12に示す例では、基地局110は、サブフレームt5においてUCで1サブフレーム長のRTS信号203を送信する。
図13は、実施の形態4にかかる基地局による処理の一例を示すフローチャートである。実施の形態4にかかる基地局110は、たとえば図13に示す各ステップを繰り返し実行する。図13に示すステップS1301~S1305は、図10に示したステップS1001~S1005と同様である。ステップS1305のつぎに、基地局110は、UCでRTS信号を報知する(ステップS1306)。
実施の形態4にかかる端末101は、たとえば図11に示した各ステップを実行する。
実施の形態5について、実施の形態1と異なる部分について説明する。
図14は、実施の形態5にかかる無線通信システムの動作の一例を示す図である。図14において、横軸はサブフレーム単位の時間(t)を示している。LTEシステムにおけるデータチャネルの送信は、基地局110のサブフレームタイミングに同期してサブフレーム単位で行われる。なお、LTEシステムにおけるデータチャネルは、たとえばPDSCH(Physical Downlink Shared Channel:物理下りリンク共有チャネル)やPUSCH(Physical Uplink Shared Channel:物理上りリンク共有チャネル)である。
図15は、下りリンク送信の一例を示す図である。図15において、横軸はサブフレーム単位の時間(t)を示している。図15に示す例では、UCのサブバンドSB1~SB4のうちのサブバンドSB1,SB3においてDL送信を行う場合について説明する。また、無線通信システム100と、無線通信システム100とは異なるLTEシステムと、でUCを共用するとする。無線通信システム100とは異なるLTEシステムは、無線通信システム100との間で互いにサブフレームを同期しているとする。
図17は、上りリンク送信の一例を示す図である。図17において、横軸はサブフレーム単位の時間(t)を示している。図17に示す例では、無線通信システム100と、無線通信システム100とは異なるLTEシステムと、でUCを共用する場合について説明する。無線通信システム100とは異なるLTEシステムは、無線通信システム100との間で互いにサブフレームを同期しているとする。
図19は、下りリンクデータ送信における基地局および端末の処理の一例を示すフローチャートである。実施の形態5にかかる基地局110および端末101は、たとえば図19に示す各ステップを実行する。まず、基地局110は、UCにDIFS時間分の空きが有るか否かを判断する(ステップS1901)。DIFS時間分の空きが無い場合(ステップS1901:No)は、基地局110は、ステップS1901へ戻る。
実施の形態6について、実施の形態1と異なる部分について説明する。
図20は、実施の形態6にかかる無線通信システムの動作の一例を示す図である。図20において、横軸はサブフレーム単位の時間(t)を示している。実施の形態6にかかる基地局110は、実施の形態5において説明した隙間時間において、端末101に制御信号やデータ信号などの信号を送信する。
図21は、下りリンクデータ送信の処理の一例を示すフローチャートである。実施の形態6にかかる基地局110および端末101は、たとえば図21に示す各ステップを実行する。図21に示すステップS2101~S2103は、図19に示したステップS1901~S1903と同様である。
実施の形態7について、実施の形態1と異なる部分について説明する。
図22A~図22Cは、実施の形態7にかかる無線通信システムの動作の一例を示す図である。図22A~図22Cにおいて、横軸はサブフレーム単位の時間(t)を示している。図22A~図22Cに示す例では、基地局110は、UCでの端末101のUL送信にサブフレームt7~t10を割り当てたとする。ただし、実施の形態7においては、端末101のUL送信がサブフレームt7~t10より後にずれる場合もある。基地局110は、キャリアセンスを行わずに、サブフレームt3~t6においてULグラント2211~2214をLCで端末101へ送信する。
図23A~図23Cに示すように、端末101は、キャリアセンス2220の継続時間に応じてUL送信2231~2234の送信電力を制御してもよい。たとえば、端末101は、キャリアセンス2220の継続時間が長いほどUL送信2231~2234の送信電力を高くする。
または、キャリアセンス2220によって検出したチャネル状態に応じてUL送信2231~2234の送信電力やMCSレベルを制御してもよい。たとえば、端末101は、キャリアセンス2220によって検出したチャネル状態が悪いほどUL送信2231~2234の送信電力を高くする。チャネル状態は、たとえば干渉電力の大きさである。
図24は、実施の形態7にかかる基地局による処理の一例を示すフローチャートである。実施の形態7にかかる基地局110は、たとえば図24に示す各ステップを実行する。まず、基地局110は、UL送信要求が有るか否かを判断する(ステップS2401)。UL送信要求が無い場合(ステップS2401:No)は、基地局110は、ステップS2401へ戻る。
図25は、実施の形態7にかかる端末による処理の一例を示すフローチャートである。実施の形態7にかかる端末101は、たとえば図25に示す各ステップを実行する。まず、端末101は、自局宛てULグラントを受信したか否かを判断する(ステップS2501)。自局宛てULグラントを受信していない場合(ステップS2501:No)は、ステップS2501へ戻る。
101 端末
110 基地局
111 セル
201,2220 キャリアセンス
202,203,901~904 RTS信号
211~215,1701,2211~2214 ULグラント
221~225,711~714,1702,2231~2234 UL送信
231~235,1402,1501,2001 DLアサイン
241~245,721~724,1403,1502,1503,2002 DL送信
501,502,531,532,601 アンテナ
503,602 ライセンスドバンド受信部
504,509,524,530,603,609,626,632 無線処理部
505,510,604,610,623,629 FFT処理部
506,511,607,613 復調部
507,512,614 復号部
508,608 アンライセンスドバンド受信部
513 MAC・RLC処理部
514 無線リソース制御部
515,617 キャリアセンス部
516 MAC制御部
517,619 パケット生成部
518 MACスケジューリング部
519,621 ライセンスドバンド送信部
520,526 符号化部
521,527 変調部
522,528,622,628 多重部
523,529,606,612,625,631 IFFT処理部
525,627 アンライセンスドバンド送信部
550 無線通信装置
551 送受信アンテナ
552,559 アンプ
553,558 乗算部
554 アナログデジタル変換器
555 プロセッサ
556 メモリ
557 デジタルアナログ変換器
560 発振器
605,611 等化処理部
615 RTS信号検出部
616 RRC処理部
618 MAC処理部
620 符号化・変調部
624,630 周波数マッピング部
1201~1203,1407,1541,1543,1741 DMRS
1401,1511~1514,1610,1711~1714,1810,2010 ビジー状態
1404,1550,1850,2020 隙間時間
1405,1521,1721,1821,2021 DIFS時間
1406,1531,1533,1731,2022 バックオフ時間
2023 DLデータ
2221 最大キャリアセンス時間
Claims (30)
- 自システムの専用の第1帯域と、自システムと他の無線通信システムとの共用の第2帯域と、を用いて無線通信を行う無線通信システムであって、
前記第2帯域の搬送波の空きを検出した場合に、端末から自局への前記第2帯域でのデータ送信を許可する制御信号を前記第1帯域で前記端末へ送信し、前記データ送信までの期間に前記第2帯域の電波を連続して送出する基地局と、
前記基地局によって前記制御信号が送信されてから所定時間後に前記データ送信を行う端末と、
を含むことを特徴とする無線通信システム。 - 前記端末は、前記第2帯域の搬送波の空きの検出を行わずに前記データ送信を行うことを特徴とする請求項1に記載の無線通信システム。
- 前記第2帯域の電波は、データ長が前記期間の長さとなるようにスケジューリングを行った自局から端末へのデータ信号であることを特徴とする請求項1または2に記載の無線通信システム。
- 前記第2帯域の電波は、前記基地局からのデータ送信を要求する要求信号であることを特徴とする請求項1または2に記載の無線通信システム。
- 前記第2帯域の電波は、データ信号を復調するための復調参照信号であることを特徴とする請求項1または2に記載の無線通信システム。
- 前記第2帯域の電波は、ダミー信号であることを特徴とする請求項1または2に記載の無線通信システム。
- 前記第2帯域の電波は、無線ノイズであることを特徴とする請求項1または2に記載の無線通信システム。
- 自システムの専用の第1帯域と、自システムと他の無線通信システムとの共用の第2帯域と、を用いて無線通信を行う無線通信システムの基地局であって、
前記第2帯域の搬送波の空きを検出する検出部と、
前記検出部によって前記第2帯域の搬送波の空きが検出された場合に、端末から自局への前記第2帯域でのデータ送信を許可する制御信号を前記第1帯域で前記端末へ送信し、前記データ送信までの期間に前記第2帯域の電波を連続して送出する送信部と、
を備えることを特徴とする基地局。 - 自システムの専用の第1帯域と、自システムと他の無線通信システムとの共用の第2帯域と、を用いて無線通信を行う無線通信システムの端末であって、
前記第2帯域の搬送波の空きを検出した場合に、端末から自局への前記第2帯域でのデータ送信を許可する制御信号を前記第1帯域で前記端末へ送信し、前記データ送信までの期間に前記第2帯域の電波を連続して送出する基地局から前記制御信号を受信する受信部と、
前記受信部によって前記制御信号が受信されてから所定時間後に前記データ送信を行う送信部と、
を備えることを特徴とする端末。 - 自システムの専用の第1帯域と、自システムと他の無線通信システムとの共用の第2帯域と、を用いて無線通信を行う無線通信システムであって、
第1単位期間において前記第2帯域の搬送波の空きを検出した場合に、前記第1単位期間の残りの期間の少なくとも一部の期間に前記第2帯域の電波を連続して送出し、前記第1単位期間の次の第2単位期間において、自局から端末への前記第2帯域でのデータ送信を行うことを示す制御信号を前記第1帯域で前記端末へ送信して前記データ送信を行う基地局と、
前記基地局によって送信された前記制御信号に基づいて前記データ送信のデータを受信する端末と、
を含むことを特徴とする無線通信システム。 - 前記第2帯域の電波は、データ信号を復調するための復調参照信号であることを特徴とする請求項10に記載の無線通信システム。
- 前記第2帯域の電波は、ダミー信号であることを特徴とする請求項10に記載の無線通信システム。
- 前記第2帯域の電波は、無線ノイズであることを特徴とする請求項10に記載の無線通信システム。
- 自システムの専用の第1帯域と、自システムと他の無線通信システムとの共用の第2帯域と、を用いて無線通信を行う無線通信システムの基地局であって、
前記第2帯域の搬送波の空きを検出する検出部と、
前記検出部によって第1単位期間において前記第2帯域の搬送波の空きが検出された場合に、前記第1単位期間の残りの期間の少なくとも一部の期間に前記第2帯域の電波を連続して送出し、前記第1単位期間の次の第2単位期間において、自局から端末への前記第2帯域でのデータ送信を行うことを示す制御信号を前記第1帯域で前記端末へ送信して前記データ送信を行う送信部と、
を備えることを特徴とする基地局。 - 自システムの専用の第1帯域と、自システムと他の無線通信システムとの共用の第2帯域と、を用いて無線通信を行う無線通信システムの端末であって、
第1単位期間において前記第2帯域の搬送波の空きを検出した場合に、前記第1単位期間の残りの期間の少なくとも一部の期間に前記第2帯域の電波を連続して送出し、前記第1単位期間の次の第2単位期間において、自局から端末への前記第2帯域でのデータ送信を行うことを示す制御信号を前記第1帯域で前記端末へ送信して前記データ送信を行う基地局によって送信された前記制御信号を受信する第1受信部と、
前記第1受信部によって受信された前記制御信号に基づいて前記データ送信のデータを受信する第2受信部と、
を備えることを特徴とする端末。 - 自システムの専用の第1帯域と、自システムと他の無線通信システムとの共用の第2帯域と、を用いて無線通信を行う無線通信システムであって、
第1単位期間において前記第2帯域の搬送波の空きを検出した場合に、前記第1単位期間の残りの期間の少なくとも一部の期間と、前記第1単位期間の次の第2単位期間と、において自局から端末への前記第2帯域での信号送信を行うとともに、前記少なくとも一部の期間と前記第2単位期間とにおいて前記信号送信を行うことを示す制御信号を前記第2単位期間において送信する基地局と、
前記基地局からの受信信号をバッファリングすることにより、前記第2単位期間において前記基地局から送信された前記制御信号に基づいて、前記少なくとも一部の期間と前記第2単位期間とにおける前記信号送信の信号を受信する端末と、
を含むことを特徴とする無線通信システム。 - 自システムの専用の第1帯域と、自システムと他の無線通信システムとの共用の第2帯域と、を用いて無線通信を行う無線通信システムの基地局であって、
前記第2帯域の搬送波の空きを検出する検出部と、
前記検出部によって第1単位期間において前記第2帯域の搬送波の空きが検出された場合に、前記第1単位期間の残りの期間の少なくとも一部の期間と、前記第1単位期間の次の第2単位期間と、において自局から端末への前記第2帯域での信号送信を行うとともに、前記少なくとも一部の期間と前記第2単位期間とにおいて前記信号送信を行うことを示す制御信号を前記第2単位期間において送信する送信部と、
を備えることを特徴とする基地局。 - 自システムの専用の第1帯域と、自システムと他の無線通信システムとの共用の第2帯域と、を用いて無線通信を行う無線通信システムの端末であって、
第1単位期間において前記第2帯域の搬送波の空きを検出した場合に、前記第1単位期間の残りの期間の少なくとも一部の期間と、前記第1単位期間の次の第2単位期間と、において自局から端末への前記第2帯域での信号送信を行うとともに、前記少なくとも一部の期間と前記第2単位期間とにおいて前記信号送信を行うことを示す制御信号を前記第2単位期間において送信する基地局からの受信信号をバッファリングするバッファリング部と、
前記第2単位期間において前記基地局から送信された前記制御信号に基づいて、前記バッファリング部によってバッファリングされた受信信号を用いて、前記少なくとも一部の期間と前記第2単位期間とにおける前記信号送信の信号を受信する受信部と、
を備えることを特徴とする端末。 - 自システムの専用の第1帯域と、自システムと他の無線通信システムとの共用の第2帯域と、を用いて無線通信を行う無線通信システムであって、
端末から自局への前記第2帯域でのデータ送信を許可する制御信号を前記第1帯域で前記端末へ送信する基地局と、
前記基地局によって前記制御信号が送信されてから所定時間後に前記第2帯域の搬送波の空きの検出を行い、前記搬送波の空きが検出されるまで待機してから前記データ送信を行う端末と、
を含むことを特徴とする無線通信システム。 - 前記基地局は、前記第2帯域の搬送波の空きの検出を行わずに前記制御信号を送信することを特徴とする請求項19に記載の無線通信システム。
- 前記端末は、前記検出を開始してからの所定期間待機しても前記搬送波の空きが検出されない場合は、前記検出を停止し、前記制御信号に基づく前記データ送信を行わないことを特徴とする請求項19または20に記載の無線通信システム。
- 前記基地局は、前記所定期間が経過しても前記端末が前記データ送信を行わない場合は、前記制御信号を前記第1帯域で前記端末へ再度送信することを特徴とする請求項21に記載の無線通信システム。
- 前記基地局は、前記検出の要否を前記制御信号によって前記端末へ指示し、
前記端末は、前記制御信号による指示に基づいて前記検出を行う、
ことを特徴とする請求項19~22のいずれか一つに記載の無線通信システム。 - 前記基地局は、前記第2帯域の混雑度に応じて前記制御信号の送信間隔を制御することを特徴とする請求項19~23のいずれか一つに記載の無線通信システム。
- 前記端末は、前記第2帯域の混雑度に応じて前記所定期間の長さを制御することを特徴とする請求項21または22に記載の無線通信システム。
- 前記端末は、前記搬送波の空きが検出されるまでの待機時間に応じて前記データ送信の送信電力を制御することを特徴とする請求項19~25のいずれか一つに記載の無線通信システム。
- 前記端末は、前記搬送波の空きが検出されるまでの待機時間に応じて前記データ送信の変調方式および符号化率の少なくともいずれかを制御することを特徴とする請求項19~26のいずれか一つに記載の無線通信システム。
- 前記端末は、前記第2帯域の混雑度に応じて前記データ送信の送信電力を制御することを特徴とする請求項19~27のいずれか一つに記載の無線通信システム。
- 自システムの専用の第1帯域と、自システムと他の無線通信システムとの共用の第2帯域と、を用いて無線通信を行う無線通信システムの基地局であって、
端末から自局への前記第2帯域でのデータ送信を許可する制御信号を前記第1帯域で前記端末へ送信する送信部と、
前記送信部によって前記制御信号が送信されてから所定時間後に前記第2帯域の搬送波の空きの検出を行い、前記搬送波の空きが検出されるまで待機してから前記データ送信を行う端末から前記データ送信のデータを受信する受信部と、
を備えることを特徴とする基地局。 - 自システムの専用の第1帯域と、自システムと他の無線通信システムとの共用の第2帯域と、を用いて無線通信を行う無線通信システムの端末であって、
端末から自局への前記第2帯域でのデータ送信を許可する制御信号を前記第1帯域で前記端末へ送信する基地局から前記制御信号を受信する受信部と、
前記受信部によって前記制御信号が受信されてから所定時間後に前記第2帯域の搬送波の空きの検出を行い、前記搬送波の空きが検出されるまで待機してから前記データ送信を行う送信部と、
を備えることを特徴とする端末。
Priority Applications (8)
Application Number | Priority Date | Filing Date | Title |
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JP2016517792A JP6332442B2 (ja) | 2014-05-09 | 2014-05-09 | 無線通信システム、基地局および端末 |
PCT/JP2014/062532 WO2015170417A1 (ja) | 2014-05-09 | 2014-05-09 | 無線通信システム、基地局および端末 |
EP14891339.5A EP3142403A4 (en) | 2014-05-09 | 2014-05-09 | Wireless communication system, base station and terminal |
KR1020167030832A KR101838840B1 (ko) | 2014-05-09 | 2014-05-09 | 무선 통신 시스템, 기지국 및 단말기 |
CN201480078581.9A CN106465133A (zh) | 2014-05-09 | 2014-05-09 | 无线通信***、基站及终端 |
CN201911104303.7A CN110677229B (zh) | 2014-05-09 | 2014-05-09 | 无线通信***、基站及终端 |
US15/332,687 US10999828B2 (en) | 2014-05-09 | 2016-10-24 | Wireless communications system, base station, and terminal |
US16/233,874 US11206647B2 (en) | 2014-05-09 | 2018-12-27 | Wireless communications system, base station, and terminal |
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CN110677229A (zh) | 2020-01-10 |
US11206647B2 (en) | 2021-12-21 |
KR20160143738A (ko) | 2016-12-14 |
US10999828B2 (en) | 2021-05-04 |
JP6332442B2 (ja) | 2018-05-30 |
JPWO2015170417A1 (ja) | 2017-04-20 |
EP3142403A4 (en) | 2017-05-03 |
CN106465133A (zh) | 2017-02-22 |
KR101838840B1 (ko) | 2018-03-14 |
US20190132825A1 (en) | 2019-05-02 |
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