WO2012018088A1 - 無線基地局および無線通信方法 - Google Patents
無線基地局および無線通信方法 Download PDFInfo
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- WO2012018088A1 WO2012018088A1 PCT/JP2011/067885 JP2011067885W WO2012018088A1 WO 2012018088 A1 WO2012018088 A1 WO 2012018088A1 JP 2011067885 W JP2011067885 W JP 2011067885W WO 2012018088 A1 WO2012018088 A1 WO 2012018088A1
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- WIPO (PCT)
- Prior art keywords
- resource
- wireless terminal
- user data
- base station
- transmission path
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
- H04W72/20—Control channels or signalling for resource management
- H04W72/23—Control channels or signalling for resource management in the downlink direction of a wireless link, i.e. towards a terminal
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
- H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
- H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
- H04L1/1829—Arrangements specially adapted for the receiver end
- H04L1/1854—Scheduling and prioritising arrangements
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
- H04L25/0212—Channel estimation of impulse response
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
- H04L25/0224—Channel estimation using sounding signals
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/003—Arrangements for allocating sub-channels of the transmission path
- H04L5/0048—Allocation of pilot signals, i.e. of signals known to the receiver
- 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
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
- H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
- H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
- H04B7/0617—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal for beam forming
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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
- H04W16/24—Cell structures
- H04W16/28—Cell structures using beam steering
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
- H04W88/08—Access point devices
Definitions
- the present invention relates to a radio base station and a radio communication method, and more particularly to a radio base station and a radio communication method for estimating a transmission path state based on a sounding signal.
- a wireless terminal transmits a reference signal to a wireless base station.
- the radio base station estimates the state of the transmission path based on the received reference signal, and forms the directivity of the antenna for downlink user data.
- the wireless terminal uses SPS (Sounding Reference Signal: Sounding Reference) as part of the UpPTS (uplink part) of the switching subframe or part of the uplink subframe (for example, the last symbol).
- SPS Sounding Reference Signal: Sounding Reference
- UpPTS uplink part of the switching subframe or part of the uplink subframe (for example, the last symbol).
- Signal is known (see, for example, JP 2010-28192 A (Patent Document 1)).
- the wireless base station in order to transmit SRS from a wireless terminal, the wireless base station must transmit a transmission command to the wireless terminal, and the wireless terminal must return a response to the transmission command. Further, in order to end the transmission of the SRS from the wireless terminal, the wireless base station must transmit an end command to the wireless terminal, and the wireless terminal must return a response thereto.
- the wireless base station After the transmission of the SRS is completed, when an error in the received downlink user data is detected in the wireless terminal and the wireless terminal requests retransmission, the wireless base station has not received the SRS. There is a possibility that the state of the transmission line cannot be estimated. In such a case, the wireless base station transmits an SRS transmission command to the wireless terminal, and the wireless terminal can send an SRS again from the wireless terminal by returning a response thereto. However, in this case, it may take a long time to retransmit the downlink user data.
- an object of the present invention is to provide a radio base station and a radio communication method capable of forming and retransmitting directivity of downlink user data when a retransmission request is generated in a radio terminal after completing the transmission of SRS Is to provide.
- the present invention determines at least a part of any downlink subframe as a first resource for transmitting downlink user data to a wireless terminal, and at least a part of an uplink part in a switching subframe Or a resource determination unit that determines a part of the uplink subframe as a second resource for the wireless terminal to periodically transmit the sounding reference signal, and a resource for notifying the wireless terminal of the determined second resource.
- a resource determination unit that determines a part of the uplink subframe as a second resource for the wireless terminal to periodically transmit the sounding reference signal, and a resource for notifying the wireless terminal of the determined second resource.
- the directivity of the downlink user data can be formed and retransmitted.
- FIG. 1 is a diagram illustrating a configuration of a wireless communication system according to an embodiment.
- this radio communication system is an LTE communication system in which a plurality of radio base stations A, B, and C are radio terminals in their own zones indicated by circles in the figure. Communicate with.
- the plurality of radio base stations A, B, and C receive uplink signals at the same timing and transmit downlink signals.
- FIG. 2 is a diagram illustrating the configuration of the radio base station according to the embodiment.
- the radio base station 1 includes a plurality of antennas 2 and 3, a transmission unit 4, a reception unit 5, a downlink user data management unit 6, an uplink user data management unit 10, and SRS management. Unit 13, resource determination unit 7, resource notification unit 8, transmission path state estimation unit 9, and network communication unit 11.
- the transmission unit 4 transmits control signals such as downlink user data, RRC (Radio Resource Control) connection reset message, and uplink user data allocation information to the wireless terminal through the plurality of antennas 2 and 3.
- the transmission unit 4 forms the directivity of the plurality of antennas 2 and 3 based on the state of the transmission path for each subcarrier estimated by the transmission path state estimation unit 9 and transmits downlink user data.
- the transmission unit 4 performs adaptive array transmission processing (weight control) on the downlink user data according to the state of the transmission path to form the directivity of the antennas 2 and 3.
- the beam forming that directs the beam (the part that strongly receives / transmits the signal) to the desired communication partner and the direction of the undesired signal source or the direction in which interference is not desired
- null steering that directs the null (the part that hardly receives / transmits the signal).
- the receiving unit 5 receives a control signal including uplink user data, an SRS, an RRC connection reconfiguration completion message, and the like from the wireless terminal through the plurality of antennas 2 and 3.
- the downlink user data management unit 6 holds downlink user data received from a control center (not shown) through the network communication unit 11.
- the uplink user data management unit 10 transmits the uplink user data received from the wireless terminal to a control center (not shown) through the network communication unit 11. Further, the uplink user data management unit 10 outputs DRS (Demodulation Reference Signal) included in the received uplink user data to the transmission path state estimation unit 9.
- DRS Demodulation Reference Signal
- the SRS management unit 13 outputs the SRS received from the wireless terminal to the transmission path state estimation unit 9.
- the resource determination unit 7 transmits the downlink user data to the wireless terminal at least in a part of any downlink subframe. 1 resource is determined.
- the resource determination part 7 determines a part of UpPTS (uplink part) in a switching sub-frame as the 2nd resource which a radio
- the resource determination unit 7 receives a retransmission request signal in HARQ (Hybrid Automatic Repeat Request) from the wireless terminal, the resource determining unit 7 transmits at least part of any uplink subframe UL to the uplink including the DRS. It is determined as a third resource for transmitting user data.
- HARQ Hybrid Automatic Repeat Request
- the resource notification unit 8 transmits uplink user data allocation information representing the third resource determined by the resource determination unit 7 to the wireless terminal.
- the resource notification unit 8 transmits an RRC connection reconfiguration message representing the second resource determined by the resource determination unit 7 to the wireless terminal.
- the resource notification unit 8 receives an RRC connection reconfiguration completion message from the wireless terminal.
- the transmission path state estimation unit 9 estimates a transmission path state based on SRS or DRS.
- the transmission path state estimation unit 9 estimates the state of the transmission path with the wireless terminal based on the latest received SRS.
- the transmission path state estimation unit 9 determines the transmission path between the wireless terminal and the wireless terminal based on the DRS included in the uplink user data received from the wireless terminal. Estimate the state.
- the network communication unit 11 receives downlink user data from the control center through the network 12.
- the network communication unit 11 transmits uplink user data through the network 12 to the control center.
- FIG. 3 is a diagram illustrating the configuration of the wireless terminal according to the embodiment.
- the wireless terminal 51 includes a plurality of antennas 52, 53, a transmission unit 54, a reception unit 55, a user data management unit 57, and a sounding signal management unit 58.
- the receiving unit 55 receives control signals such as downlink user data and an RRC connection reconfiguration message through the plurality of antennas 52 and 53.
- the transmission unit 54 transmits control signals such as uplink user data and SRS, RRC connection reconfiguration completion message to the radio base station 1 through the plurality of antennas 52 and 53.
- the user data management unit 56 holds and manages downlink user data received from the radio base station 1 and uplink user data to be transmitted to the radio base station 1.
- the sounding signal management unit 58 When the sounding signal management unit 58 receives the RRC connection reconfiguration message, the sounding signal management unit 58 allocates radio resources for transmitting the SRS based on the RRC connection reconfiguration message. Thereafter, the sounding signal management unit 58 transmits an RRC connection reconfiguration completion message. The sounding signal management unit 58 transmits the SRS using the assigned radio resource.
- FIG. 4 is a diagram illustrating a configuration of a frame transmitted in the wireless communication system according to the embodiment.
- the configuration of this frame is a configuration when (Uplink-downlink configuration) in LTE is “1”.
- one frame is transmitted in a time of 10 ms.
- One frame is divided into half frames.
- Each half frame includes a downlink subframe DL, a switching subframe S, two consecutive uplink subframes UL, and a downlink subframe DL in time order.
- the switching subframe S is composed of DwPTS (Downlink Pilot Timeslot), GP (Guard Period: guard period), and UpPTS (Uplink Pilot Timeslot: also called uplink part).
- UpPTS is composed of two symbols.
- FIG. 5 is a diagram for explaining the processing timing of the first embodiment.
- the radio base station 1 determines a second resource for periodically transmitting SRS in the radio terminal 51 that is the transmission destination of downlink user data.
- the radio base station 1 transmits an RRC connection reset (representing transmission start) message representing the determined second resource (shown in (1)).
- the wireless terminal 51 transmits an RRC connection reconfiguration (indicating transmission start) completion message (shown in (2)). Thereby, the SRS transmission section is started.
- the wireless terminal 51 transmits the SRS through the notified second resource (shown in (3)).
- the radio base station 1 estimates the state of the transmission path with the radio terminal 51 based on the received SRS.
- the radio base station 1 determines at least a part of the downlink subframe as a first resource for transmitting downlink user data to the radio terminal.
- the radio base station 1 forms directivities of a plurality of antennas based on the estimated transmission path state, and the downlink user data is included in the first resource and the downlink user data is included in the first resource.
- the downlink user allocation information to be transmitted is transmitted (shown in (4)). This SRS transmission (3) by the wireless terminal 51 and the downlink user data transmission (4) based on the SRS by the wireless base station 1 are repeated.
- the radio base station 1 transmits an RRC connection resetting (representing transmission end) message (shown in (5)).
- the wireless terminal 51 transmits an RRC connection resetting (representing transmission end) completion message (shown in (6)). Thereby, the SRS transmission section ends.
- the wireless terminal 51 transmits a retransmission request signal when an error is detected in the received downlink user data (shown in (7)).
- the radio base station 1 determines a third resource for the radio terminal 51 to transmit uplink user data including DRS, and transmits uplink user data allocation information indicating the determined third resource (shown in (8)). .
- the wireless terminal 51 transmits the uplink user data including the DRS using the notified third resource (shown in (9)).
- the radio base station 1 estimates the state of the transmission path with the radio terminal 51 based on the received DRS.
- the radio base station 1 determines at least a part of the downlink subframe as a first resource for transmitting downlink user data to the radio terminal.
- the radio base station 1 forms the directivity of a plurality of antennas based on the estimated transmission path state, downlink user data requested to be retransmitted through the first resource, and downlink user data to the first resource. Is transmitted (shown in (10)). The processes (7) to (10) are repeated until no error is detected in the downlink user data received by the wireless terminal 51.
- FIG. 6 is a flowchart showing an operation procedure of the wireless communication system according to the first embodiment.
- the resource determination unit 7 of the radio base station 1 uses any resource in the UpPTS of the switching subframe S as a second resource for the radio terminal 51 to periodically transmit SRS. Determine (step S101).
- the resource notification unit 8 of the radio base station 1 transmits an RRC connection reconfiguration (representing transmission start) message representing the determined second resource (step S102).
- the sounding signal management unit 58 of the wireless terminal 51 receives an RRC connection resetting (representing transmission start) message (step S103).
- the sounding signal management unit 58 of the wireless terminal 51 transmits an RRC connection resetting (representing transmission start) completion message (step S104).
- the resource notification unit 8 of the radio base station 1 receives an RRC connection resetting (representing transmission start) completion message (step S105).
- the sounding signal management unit 58 of the wireless terminal 51 transmits the SRS using the notified second resource (step S106).
- the SRS management unit 13 of the radio base station 1 receives the SRS (step S107).
- the transmission path state estimation unit 9 of the wireless base station 1 estimates the state of the transmission path with the wireless terminal 51 based on the SRS received in step S107.
- the resource determination unit 7 of the radio base station 1 determines at least a part of any downlink subframe DL as a first resource for transmitting downlink user data to the radio terminal 51.
- the transmission unit 4 of the radio base station 1 forms the directivity of the plurality of antennas 2 and 3 based on the estimated transmission path state, and transmits the downlink user data and the first resource through the first resource.
- Downlink user allocation information indicating that downlink user data is included is transmitted (step S108).
- the receiving unit 55 of the wireless terminal 51 receives downlink user data through the plurality of antennas 52 and 53 (step S109).
- step S110 the resource notification unit 8 of the radio base station 1 transmits an RRC connection reconfiguration (representing transmission end) message (step S110).
- the sounding signal management unit 58 of the wireless terminal 51 receives an RRC connection resetting (representing transmission end) message (step S111).
- the sounding signal management unit 58 of the wireless terminal 51 transmits an RRC connection resetting (representing transmission end) completion message (step S112).
- the resource notification unit 8 of the radio base station 1 receives an RRC connection resetting (representing transmission end) completion message (step S113).
- the user data management unit 57 of the wireless terminal 51 sends a retransmission request signal (NACK: Negative ACKnowledgments, negative response) based on HARQ. Transmit (step S115).
- NACK Negative ACKnowledgments, negative response
- the radio terminal 51 performs DRS at least a part of any uplink subframe UL. Is determined as a third resource for transmitting uplink user data including.
- the resource notification unit 8 of the radio base station 1 transmits uplink user data allocation information representing the determined third resource (step S117).
- the user data management unit 57 of the wireless terminal 51 receives the uplink user data allocation information representing the third resource (step S118).
- the user data management unit 57 of the wireless terminal 51 transmits the uplink user data including the DRS using the third resource notified in step S118 (step S119).
- the uplink user data management unit 10 of the radio base station 1 receives the uplink user data including the DRS (Step S120).
- the transmission path state estimation unit 9 of the wireless base station 1 estimates the state of the transmission path with the wireless terminal 51 based on the DRS received in step S120.
- the resource determination unit 7 of the radio base station 1 determines at least a part of any downlink subframe DL as a first resource for transmitting downlink user data to the radio terminal 51.
- the transmission unit 4 of the radio base station 1 forms the directivity of the plurality of antennas 2 and 3 based on the estimated transmission path state, and transmits the downlink user data requested to be retransmitted through the first resource, and Downlink user allocation information indicating that downlink user data is included in the first resource is transmitted (step S121).
- the receiving unit 55 of the wireless terminal 51 receives the downlink user data through the plurality of antennas 52 and 53, and returns to step S114 (step S122).
- the wireless base station uses the DRS included in the uplink user data.
- the state of the transmission path can be quickly estimated, and downlink user data having directivity can be quickly retransmitted.
- FIG. 7 is a diagram for explaining the processing timing of the modified example of the first embodiment.
- the process shown in FIG. 7 is different from that shown in FIG. 5 as follows.
- the radio base station 1 determines the first resource every time before transmitting downlink user data, but in FIG. 7, the radio base station 1 periodically transmits the same first user data to the downlink user data.
- the radio base station 1 first determines the first resource only once and notifies the radio terminal 51 of the first resource.
- the radio base station 1 uses a first resource for periodically transmitting downlink user data after a predetermined downlink subframe DL, and a radio terminal 51 to which the downlink user data is transmitted.
- the second resource for periodically transmitting the SRS is determined (shown in (1)).
- the radio base station 1 transmits downlink user data allocation information representing the determined first resource (shown in (2)).
- FIG. 8 is a diagram illustrating the configuration of the radio base station according to the second embodiment.
- the resource determination unit 27 transmits the downlink user data to the wireless terminal at least in a part of any downlink subframe. 1 resource is determined. Moreover, the resource determination part 27 determines a part of UpPTS (uplink part) in a switching sub-frame as the 2nd resource which a radio
- the transmission path state estimation unit 29 estimates a transmission path state based on SRS or DRS.
- the transmission path state estimation unit 29 estimates the state of the transmission path with the wireless terminal based on the latest received SRS.
- the transmission path state estimation unit 29 receives the retransmission request signal after the transmission of the SRS is stopped.
- the transmission path state estimation unit 29 based on the last received SRS,
- the transmission path between the wireless terminal and the wireless terminal is estimated based on the DRS included in the uplink user data received from the wireless terminal. Is estimated.
- FIG. 9 is a diagram for explaining the processing timing of the second embodiment.
- radio base station 21 determines a second resource for periodically transmitting SRS in radio terminal 51 that is a transmission destination of downlink user data.
- the radio base station 21 transmits an RRC connection reconfiguration (representing transmission start) message representing the determined second resource (shown in (1)).
- the wireless terminal 51 transmits an RRC connection reconfiguration (indicating transmission start) completion message (shown in (2)). Thereby, the SRS transmission section is started.
- the wireless terminal 51 transmits the SRS through the notified second resource (shown in (3)).
- the radio base station 21 estimates the state of the transmission path with the radio terminal 51 based on the received SRS.
- the radio base station 21 determines at least a part of the downlink subframe as a first resource for transmitting downlink user data to the radio terminal.
- the radio base station 21 forms directivities of a plurality of antennas based on the estimated transmission path state, and downlink user allocation indicating that downlink user data and downlink user data are included in the first resource Information is transmitted (shown in (4)).
- This SRS transmission (3) by the wireless terminal 51 and downlink user data transmission (4) based on the SRS by the wireless base station 21 are repeated.
- the radio base station 21 transmits an RRC connection resetting (representing transmission end) message (shown in (5)).
- the wireless terminal 51 transmits an RRC connection resetting (representing transmission end) completion message (shown in (6)). Thereby, the SRS transmission section ends.
- the wireless terminal 51 After the end of the SRS transmission section, the wireless terminal 51 transmits a retransmission request signal when an error is detected in the received downlink user data (shown in (7)).
- the wireless base station 21 transmits a transmission path to the wireless terminal 51 based on the last received SRS. Is estimated.
- the radio base station 21 determines at least a part of the downlink subframe as a first resource for transmitting downlink user data to the radio terminal.
- the radio base station 21 forms directivities of a plurality of antennas based on the estimated transmission path state, and the downlink user data is included in the first resource through the first resource. Is transmitted (shown in (8)).
- the radio base station 21 sets a third resource for transmitting uplink user data including DRS.
- the uplink user data allocation information representing the determined third resource is transmitted (shown in (9)).
- the wireless terminal 51 transmits uplink user data including DRS by using the notified third resource (shown in (10)).
- the wireless base station 21 estimates the state of the transmission path with the wireless terminal 51 based on the received DRS.
- the radio base station 21 determines at least a part of the downlink subframe as a first resource for transmitting downlink user data to the radio terminal 51.
- the radio base station 21 forms directivities of a plurality of antennas based on the estimated transmission path state, downlink user data requested to be retransmitted through the first resource, and downlink user data to the first resource.
- Downlink user allocation information indicating that is included (shown in (11)).
- the resource determination unit 27 of the radio base station 21 transmits a second resource in which the radio terminal 51 periodically transmits an SRS to any resource in the UpPTS of the switching subframe S. As a resource (step S101).
- the resource notification unit 8 of the radio base station 21 transmits an RRC connection reconfiguration (representing transmission start) message representing the determined second resource (step S102).
- the sounding signal management unit 58 of the wireless terminal 51 receives an RRC connection resetting (representing transmission start) message (step S103).
- the sounding signal management unit 58 of the wireless terminal 51 transmits an RRC connection resetting (representing transmission start) completion message (step S104).
- the resource notification unit 8 of the radio base station 21 receives an RRC connection reconfiguration (indicating transmission start) completion message (step S105).
- the sounding signal management unit 58 of the wireless terminal 51 transmits the SRS using the notified second resource (step S106).
- the SRS management unit 13 of the radio base station 21 receives the SRS (step S107).
- the transmission path state estimation unit 29 of the wireless base station 21 estimates the state of the transmission path with the wireless terminal 51 based on the SRS received in step S107.
- the resource determining unit 27 of the radio base station 21 determines at least a part of any downlink subframe DL as a first resource for transmitting downlink user data to the radio terminal 51.
- the transmission unit 4 of the radio base station 21 forms the directivity of the plurality of antennas 2 and 3 based on the estimated transmission path state, and transmits the downlink user data and the first resource through the first resource. Downlink user allocation information indicating that downlink user data is included is transmitted (step S108).
- the receiving unit 55 of the wireless terminal 51 receives downlink user data through the plurality of antennas 52 and 53 (step S109).
- step S110 the resource notification unit 8 of the radio base station 21 transmits an RRC connection resetting (representing transmission end) message.
- the sounding signal management unit 58 of the wireless terminal 51 receives an RRC connection resetting (representing transmission end) message (step S111).
- the sounding signal management unit 58 of the wireless terminal 51 transmits an RRC connection resetting (representing transmission end) completion message (step S112).
- the resource notification unit 8 of the radio base station 21 receives an RRC connection resetting (representing transmission end) completion message (step S113).
- the user data management unit 57 of the wireless terminal 51 sends a retransmission request signal (NACK: Negative ACKnowledgments, negative response) based on HARQ. Transmit (step S115).
- NACK Negative ACKnowledgments, negative response
- the transmission path state estimation unit 29 of the radio base station 21 determines that the total number of receptions of the retransmission request signal is less than the threshold TH (NO in step S220). ) Based on the last received SRS, the state of the transmission path with the wireless terminal 51 is estimated.
- the resource determining unit 27 of the radio base station 21 determines at least a part of any downlink subframe DL as a first resource for transmitting downlink user data to the radio terminal 51.
- the transmission unit 4 of the radio base station 21 forms the directivity of the plurality of antennas 2 and 3 based on the estimated transmission path state, and transmits the downlink user data requested for retransmission through the first resource, and Downlink user allocation information indicating that downlink user data is included in the first resource is transmitted (step S221).
- the resource determination unit 27 of the radio base station 21 receives the retransmission request signal (YES in step S116)
- the total number of times of reception of the retransmission request signal is equal to or greater than the threshold value TH (YES in step S220)
- At least a part of the uplink subframe UL is determined as a third resource for the wireless terminal 51 to transmit uplink user data including DRS.
- the resource notification unit 8 of the radio base station 21 transmits uplink user data allocation information representing the determined third resource (step S222).
- the user data management unit 57 of the wireless terminal 51 receives the uplink user data allocation information representing the third resource (step S223).
- the user data management unit 57 of the wireless terminal 51 transmits the uplink user data including the DRS using the third resource notified in step S223 (step S224).
- the uplink user data management unit 10 of the radio base station 21 receives uplink user data including DRS (step S225).
- the transmission path state estimation unit 29 of the wireless base station 21 estimates the state of the transmission path with the wireless terminal 51 based on the DRS received in step S225.
- the resource determining unit 27 of the radio base station 21 determines at least a part of any downlink subframe DL as a first resource for transmitting downlink user data to the radio terminal 51.
- the transmission unit 4 of the radio base station 21 forms the directivity of the plurality of antennas 2 and 3 based on the estimated transmission path state, the downlink user data requested for retransmission through the first resource, and the first
- the downlink user allocation information indicating that the downlink user data is included in the resource is transmitted (step S226).
- the receiving unit 55 of the wireless terminal 51 receives the downlink user data through the plurality of antennas 52 and 53, and returns to step S114 (step S227).
- the wireless base station when a retransmission request is generated in a wireless terminal after completing the transmission of SRS, the wireless base station received the last at the beginning. This is used because the SRS represents the state of the current transmission path to some extent. Thereafter, the radio base station uses the DRS included in the uplink user data different from the SRS because the last received SRS does not represent the current transmission path status. As a result, the state of the transmission path can be estimated quickly and accurately, and downlink user data having directivity can be retransmitted quickly and accurately.
- FIG. 12 is a diagram for explaining the processing timing of the modified example of the second embodiment.
- the process shown in FIG. 12 is different from FIG. 9 as follows.
- the radio base station 21 determines the first resource every time before transmitting downlink user data.
- the radio base station 21 periodically transmits the same downlink user data to the first user data.
- the radio base station 21 first determines the first resource only once and notifies the radio terminal 51 of the first resource.
- the radio base station 21 uses a first resource for periodically transmitting downlink user data after a predetermined downlink subframe DL, and a radio terminal 51 to which the downlink user data is transmitted.
- the second resource for periodically transmitting the SRS is determined (shown in (1)).
- the radio base station 21 transmits downlink user data allocation information representing the determined first resource (shown in (2)).
- FIG. 13 is a diagram illustrating a configuration of a radio base station according to the third embodiment.
- 13 differs from the configuration of the radio base station 1 in FIG. 2 in a resource determination unit 37, a transmission path state estimation unit 39, and a terminal speed identification unit 32.
- the terminal speed identification unit 32 calculates the reception response vector of the wireless terminal 51 in communication.
- the terminal speed identification unit 30 estimates the Doppler frequency FD of the wireless terminal 51 by calculating the correlation value of two or more reception response vectors that are temporally changed by the wireless terminal 51. Further, the terminal speed identification unit 30 calculates the moving speed of the wireless terminal 51 as a value proportional to the Doppler frequency. See, for example, Japanese Patent Laid-Open No. 2003-32167 for a more detailed calculation principle of the moving speed.
- the resource determination unit 37 transmits the downlink user data to the wireless terminal at least in a part of any downlink subframe. 1 resource is determined. Moreover, the resource determination part 37 determines a part of UpPTS (uplink part) in a switching sub-frame as the 2nd resource which a radio
- the resource determining unit 37 determines the third resource as follows.
- the resource determining unit 37 at least partially in any uplink subframe UL Is determined as a third resource for the wireless terminal to transmit uplink user data including DRS.
- the resource determination unit 37 receives a retransmission request signal from the wireless terminal, the moving speed of the wireless terminal 51 is less than a predetermined value R, and the cumulative number of received retransmission request signals is greater than or equal to the threshold value TH2.
- the threshold value TH1 is a value smaller than the threshold value TH2. This is because the reliability of the old SRS is low because the state of the transmission path changes when the moving speed of the wireless terminal is fast.
- the transmission path state estimation unit 39 estimates a transmission path state based on SRS or DRS.
- the transmission path state estimation unit 39 estimates the state of the transmission path with the wireless terminal based on the latest received SRS.
- the transmission path state estimation unit 39 determines the transmission path state as follows when the moving speed of the wireless terminal 51 is equal to or higher than the predetermined value R. presume.
- the transmission path state estimation unit 39 estimates the state of the transmission path with the wireless terminal 51 based on the last received SRS.
- the transmission path state estimation unit 39 determines the state of the transmission path with the wireless terminal 51 based on the DRS included in the uplink user data received from the wireless terminal 51. Is estimated.
- the transmission path state estimation unit 39 determines the transmission path state as follows when the moving speed of the wireless terminal 51 is less than the predetermined value R. presume.
- the transmission path state estimation unit 39 estimates the state of the transmission path with the wireless terminal 51 based on the last received SRS.
- the transmission path state estimation unit 39 determines the state of the transmission path with the wireless terminal 51 based on the DRS included in the uplink user data received from the wireless terminal 51. Is estimated.
- the resource determination unit 37 of the radio base station 31 transmits a second resource in which the radio terminal 51 periodically transmits an SRS in any resource in the UpPTS of the switching subframe S. As a resource (step S101).
- the resource notification unit 8 of the radio base station 31 transmits an RRC connection reconfiguration (representing transmission start) message representing the determined second resource (step S102).
- the sounding signal management unit 58 of the wireless terminal 51 receives an RRC connection resetting (representing transmission start) message (step S103).
- the sounding signal management unit 58 of the wireless terminal 51 transmits an RRC connection resetting (representing transmission start) completion message (step S104).
- the resource notification unit 8 of the radio base station 31 receives an RRC connection reconfiguration (representing transmission start) completion message (step S105).
- the sounding signal management unit 58 of the wireless terminal 51 transmits the SRS using the notified second resource (step S106).
- the SRS management unit 13 of the radio base station 31 receives the SRS (step S107).
- the transmission path state estimation unit 39 of the wireless base station 31 estimates the state of the transmission path with the wireless terminal 51 based on the SRS received in step S107.
- the resource determination unit 37 of the radio base station 31 determines at least a part of any downlink subframe DL as a first resource for transmitting downlink user data to the radio terminal 51.
- the transmission unit 4 of the radio base station 31 forms the directivity of the plurality of antennas 2 and 3 based on the estimated transmission path state, and transmits the downlink user data and the first resource through the first resource. Downlink user allocation information indicating that downlink user data is included is transmitted (step S108).
- the receiving unit 55 of the wireless terminal 51 receives downlink user data through the plurality of antennas 52 and 53 (step S109).
- step S110 the resource notification unit 8 of the radio base station 31 transmits an RRC connection reconfiguration (representing transmission end) message (step S110).
- the sounding signal management unit 58 of the wireless terminal 51 receives an RRC connection resetting (representing transmission end) message (step S111).
- the sounding signal management unit 58 of the wireless terminal 51 transmits an RRC connection resetting (representing transmission end) completion message (step S112).
- the resource notification unit 8 of the radio base station 31 receives an RRC connection resetting (representing the end of transmission) completion message (step S113).
- the user data management unit 57 of the wireless terminal 51 sends a retransmission request signal (NACK: Negative ACKnowledgments, negative response) based on HARQ. Transmit (step S115).
- NACK Negative ACKnowledgments, negative response
- the movement speed of the radio terminal 51 calculated by the terminal speed identification unit 30 is the predetermined value R. This is the above (YES in step S320), and when the total number of retransmission request signals received is less than the threshold TH1 (NO in step S321), or the moving speed of the wireless terminal 51 is less than the predetermined value R ( If NO in step S320) and the cumulative number of retransmission request signals received is less than the threshold TH2 (NO in step S322), the state of the transmission path with the wireless terminal 51 is estimated based on the last received SRS. To do.
- the resource determination unit 37 of the radio base station 31 determines at least a part of any downlink subframe DL as a first resource for transmitting downlink user data to the radio terminal 51.
- the transmission unit 4 of the radio base station 31 forms the directivity of the plurality of antennas 2 and 3 based on the estimated transmission path state, and transmits the downlink user data requested for retransmission through the first resource, and Downlink user allocation information indicating that downlink user data is included in the first resource is transmitted (step S323).
- the moving speed of the radio terminal 51 is equal to or higher than the predetermined value R (YES in step S320), and When the total number of retransmission request signal receptions is greater than or equal to threshold TH1 (YES in step S321), or the moving speed of wireless terminal 51 is less than predetermined value R (NO in step S320), and retransmission request signal reception
- threshold TH1 YES in step S321
- the third resource for wireless terminal 51 to transmit uplink user data including DRS at least in part of any uplink subframe UL Determine as.
- the resource notification unit 8 of the radio base station 31 transmits uplink user data allocation information representing the determined third resource (step S324).
- the user data management unit 57 of the wireless terminal 51 receives the uplink user data allocation information representing the third resource (step S325).
- the user data management unit 57 of the wireless terminal 51 transmits the uplink user data including the DRS using the third resource notified in step S325 (step S326).
- the uplink user data management unit 10 of the radio base station 31 receives uplink user data including DRS (step S327).
- the transmission path state estimation unit 39 of the wireless base station 31 estimates the state of the transmission path with the wireless terminal 51 based on the DRS received in step S327.
- the resource determination unit 37 of the radio base station 31 determines at least a part of any downlink subframe DL as downlink user data to the radio terminal 51 as the first resource.
- the transmission unit 4 of the radio base station 31 forms the directivity of the plurality of antennas 2 and 3 based on the estimated transmission path state, and the downlink user data requested to be retransmitted through the first resource, and the first Downlink user allocation information indicating that downlink resource data is included in one resource is transmitted (step S328).
- the receiving unit 55 of the wireless terminal 51 receives the downlink user data through the plurality of antennas 52 and 53, and returns to step S114 (step S329).
- the wireless base station receives it first at the end. This is used because the SRS represents the status of the current transmission path to some extent. Thereafter, the radio base station uses DRS included in uplink user data different from SRS because the last received SRS does not represent the current transmission path status.
- the state of the transmission path can be estimated quickly and accurately, and downlink user data having directivity can be retransmitted quickly and accurately.
- the reliability of the last received SRS can be changed according to the moving speed of the wireless terminal by changing the period of using the last received SRS according to the moving speed of the wireless terminal. Can do.
- the radio base station determines the third resource for transmitting the uplink user data including the DSR by the radio terminal, and notifies the radio terminal of the third resource.
- the present invention is limited to this. It is not a thing. If the radio base station has already received the uplink user data from the radio terminal, the DRS included in the uplink user data can be used for the estimation of the transmission path state. There is no need to decide.
- the resource determination unit determines a part of the UpPTS (uplink part) in the switching subframe as the second resource for the wireless terminal to periodically transmit the SRS, but the present invention is not limited to this.
- the resource determination unit may determine all of the UpPTS (uplink part) in the switching subframe as the second resource for the wireless terminal to periodically transmit the SRS.
- the resource determination unit may determine a part (for example, the last symbol) in the switching subframe or the uplink subframe UL as the second resource for the wireless terminal to periodically transmit the SRS. .
- the resource for transmitting downlink user data is shown as using the same downlink subframe for each half frame, but this is an example.
- the first resource may be allocated to any of the plurality of downlink subframes DL and DwPTS of the switching subframe S.
- the uplink user data allocation information is transmitted in the first downlink subframe DL after switching from the uplink.
- the present invention is not limited to this. Any of the plurality of downlink subframes DL and DwPTS of the switching subframe S may be used to transmit the uplink user data allocation information.
- the uplink user data transmitted based on the uplink user data allocation information may use any of the plurality of uplink subframes UL.
Abstract
Description
[第1の実施形態]
(無線通信システムの構成)
図1は、実施形態の無線通信システムの構成を表わす図である。
図2は、実施形態の無線基地局の構成を表わす図である。
リソース決定部7は、下りユーザデータ管理部6がネットワーク通信部11から下りユーザデータを受けると、いずれかのダウンリンクサブフレーム内の少なくとも一部を、無線端末への下りユーザデータを送信する第1のリソースとして決定する。また、リソース決定部7は、切替サブフレーム内のUpPTS(アップリンクパート)の一部を無線端末がSRSを周期的に送信する第2のリソースとして決定する。また、リソース決定部7は、無線端末からHARQ(Hybrid Automatic Repeat Request)における再送要求信号を受信したときに、いずれかのアップリンクサブフレームUL内の少なくとも一部を、無線端末がDRSを含む上りユーザデータを送信するための第3のリソースとして決定する。
図3は、実施形態の無線端末の構成を表わす図である。
図4は、実施形態の無線通信システムで伝送されるフレームの構成を表わす図である。
図5は、第1の実施形態の処理タイミングを説明するための図である。
図6は、第1の実施形態の無線通信システムの動作手順を表わすフローチャートである。
次に、無線基地局1の伝送路状態推定部9は、ステップS107で受信したSRSに基づいて、無線端末51との間の伝送路の状態を推定する。無線基地局1のリソース決定部7は、いずれかのダウンリンクサブフレームDL内の少なくとも一部を無線端末51への下りユーザデータを送信するための第1のリソースとして決定する。無線基地局1の送信部4は、推定した伝送路の状態に基づいて、複数のアンテナ2,3の指向性を形成して、第1のリソースを通じて、下りユーザデータ、およびこの第1のリソースに下りユーザデータが含まれることを表わす下りユーザ割当情報を送信する(ステップS108)。
次に、無線基地局1のリソース通知部8は、RRC接続再設定(送信終了を表わす)メッセージを送信する(ステップS110)。
(第1の実施形態の変形例の処理タイミング)
図7は、第1の実施形態の変形例の処理タイミングを説明するための図である。
図5では、無線基地局1は、下りユーザデータを送信する前ごとに、第1のリソースを決定したが、図7では、無線基地局1は、下りユーザデータを周期的に同一の第1のリソースを用いて送信することとし、無線基地局1は、最初に一度だけこの第1のリソースを決定して、無線端末51へ通知する。
[第2の実施形態]
図8は、第2の実施形態の無線基地局の構成を表わす図である。
図9は、第2の実施形態の処理タイミングを説明するための図である。
図10および図11は、第2の実施形態の無線通信システムの動作手順を表わすフローチャートである。
次に、無線基地局21のリソース通知部8は、RRC接続再設定(送信終了を表わす)メッセージを送信する(ステップS110)。
(第2の実施形態の変形例の処理タイミング)
図12は、第2の実施形態の変形例の処理タイミングを説明するための図である。
図9では、無線基地局21は、下りユーザデータを送信する前ごとに、第1のリソースを決定したが、図12では、無線基地局21は、下りユーザデータを周期的に同一の第1のリソースを用いて送信することとし、無線基地局21は、最初に一度だけこの第1のリソースを決定して、無線端末51へ通知する。
[第3の実施形態]
図13は、第3の実施形態の無線基地局の構成を表わす図である。
図14および図15は、第3の実施形態の無線通信システムの動作手順を表わすフローチャートである。
次に、無線基地局31のリソース通知部8は、RRC接続再設定(送信終了を表わす)メッセージを送信する(ステップS110)。
本発明は、上記の実施形態に限定されるものではなく、たとえば以下のような変形例も含む。
実施形態では、無線基地局が、無線端末がDSRを含む上りユーザデータを送信する第3のリソースを決定して、その無線端末に第3のリソースを通知することとしたが、これに限定するものではない。無線基地局が、すでにその無線端末から上りユーザデータを受信している場合には、その上りユーザデータに含まれるDRSを伝送路状態の推定に用いることができるので、新たに第3のリソースを決定する必要はない。
実施形態では、リソース決定部は、切替サブフレーム内のUpPTS(アップリンクパート)の一部を無線端末がSRSを周期的に送信する第2のリソースとして決定したが、これに限定するものではない。たとえば、リソース決定部は、切替サブフレーム内のUpPTS(アップリンクパート)の全部を無線端末がSRSを周期的に送信する第2のリソースとして決定することとしてもよい。また、リソース決定部は、切替サブフレーム内のまたはアップリンクサブフレームULの一部(たとえば、最後のシンボル)を無線端末がSRSを周期的に送信する第2のリソースとして決定することとしてもよい。
図5および図9では、下りユーザデータが送信されるリソースは、ハーフフレーム単位ごとに同じダウンリンクサブフレームが用いられるものとして示してあるが、これは一例である。図5および図9では、複数のダウンリンクサブフレームDLおよび切替サブフレームSのDwPTSのうちのいずれに第1のリソースを割り当てててもよい。
図5、7、9、12では、上りユーザデータ割当情報を、アップリンクから切替わった後の最初のダウンリンクサブフレームDLで送信することとしたが、これに限定するものではない。上りユーザデータ割当情報を送信するのに、複数のダウンリンクサブフレームDLおよび切替サブフレームSのDwPTSのうちのいずれを用いてもよい。
Claims (14)
- いずれかのダウンリンクサブフレーム内の少なくとも一部を、無線端末への下りユーザデータを送信するための第1のリソースとして決定し、切替サブフレーム内のアップリンクパートの少なくとも一部、またはアップリンクサブフレームの一部を、前記無線端末がサウンディングレファレンス信号を周期的に送信するための第2のリソースとして決定するリソース決定部と、
前記決定した第2のリソースを前記無線端末に通知するリソース通知部と、
前記サウンディングレファレンス信号の送信が停止された後、再送要求を受信したときには、前記無線端末から受信する上りユーザデータに含まれるレファレンス信号に基づいて、前記無線端末との間の伝送路の状態を推定する伝送路状態推定部と、
前記推定した伝送路の状態に基づいて複数のアンテナの指向性を形成して、前記第1のリソースを通じて前記下りユーザデータを送信する送信部とを備えた、無線基地局。 - 前記伝送路状態推定部は、前記サウンディングレファレンス信号の送信区間では、受信した最新のサウンディングレファレンス信号に基づいて、前記無線端末との間の伝送路の状態を推定する、請求項1記載の無線基地局。
- 前記リソース決定部は、前記再送要求を受信したときには、いずれかのアップリンクサブフレーム内の少なくとも一部を、前記無線端末が、前記レファレンス信号を含む上りユーザデータを送信するための第3のリソースとして決定し、
前記リソース通知部は、前記決定した第3のリソースを前記無線端末に通知する、請求項1記載の無線基地局。 - 前記無線基地局は、LTE(Long Term Evolution)方式の通信システムにおける無線基地局であり、
前記リソース決定部は、Uplink-downlink configurationが「1」のフレーム構成に従って、前記第1のリソース、前記第2のリソース、および前記第3のリソースを決定する、請求項3記載の無線基地局。 - 前記伝送路状態推定部は、前記サウンディングレファレンス信号の送信が停止された後、前記再送要求を受信した場合に、前記受信した再送要求の累計が第1の値未満のときには、最後に受信した前記サウンディングレファレンス信号に基づいて、前記無線端末との間の伝送路の状態を推定し、前記受信した再送要求の累計が前記第1の値以上のときには、前記無線端末から受信する上りユーザデータに含まれるレファレンス信号に基づいて、前記無線端末との間の伝送路の状態を推定する、請求項1記載の無線基地局。
- 前記無線端末の移動速度を管理する端末速度管理部をさらに備え、
前記伝送路状態推定部は、前記無線端末の速度が所定値以上の場合には、前記無線端末の速度が前記所定値未満の場合よりも、前記第1の値を小さくして、前記伝送路の状態を推定する、請求項5記載の無線基地局。 - 前記無線基地局は、LTE(Long Term Evolution)方式の通信システムにおける無線基地局であり、
前記アップリンクパートは、UpPTS(Uplink Pilot Timeslot)である、請求項1記載の無線基地局。 - いずれかのダウンリンクサブフレーム内の少なくとも一部を、無線端末への下りユーザデータを送信するための第1のリソースとして決定し、切替サブフレーム内のアップリンクパートの少なくとも一部、またはアップリンクサブフレームの一部を、前記無線端末がサウンディングレファレンス信号を周期的に送信するための第2のリソースとして決定するリソース決定部と、
前記決定した第2のリソースを前記無線端末に通知するリソース通知部と、
前記サウンディングレファレンス信号の送信区間では、受信した最新のサウンディングレファレンス信号に基づいて、前記無線端末との間の伝送路の状態を推定し、前記サウンディングレファレンス信号の送信が停止された後、再送要求を受信した場合に、前記受信した再送要求の累計が第1の値未満のときには、最後に受信した前記サウンディングレファレンス信号に基づいて、前記無線端末との間の伝送路の状態を推定し、前記受信した再送要求の累計が前記第1の値以上のときには、前記無線端末から受信する上りユーザデータに含まれるレファレンス信号に基づいて、前記無線端末との間の伝送路の状態を推定する伝送路状態推定部と、
前記推定した伝送路の状態に基づいて複数のアンテナの指向性を形成して、前記第1のリソースを通じて前記下りユーザデータを送信する送信部とを備えた、無線基地局。 - 前記リソース決定部は、前記再送要求を受信した場合に、前記受信した再送要求の累計が前記第1の値以上のときには、いずれかのアップリンクサブフレーム内の少なくとも一部を、前記無線端末が、前記レファレンス信号を含む上りユーザデータを送信するための第3のリソースとして決定し、
前記リソース通知部は、前記決定した第3のリソースを前記無線端末に通知する、請求項8記載の無線基地局。 - 前記無線基地局は、LTE(Long Term Evolution)方式の通信システムにおける無線基地局であり、
前記リソース決定部は、Uplink-downlink configurationが「1」のフレーム構成に従って、前記第1のリソース、前記第2のリソース、および前記第3のリソースを決定する、請求項9記載の無線基地局。 - 前記無線端末の移動速度を管理する端末速度管理部をさらに備え、
前記伝送路状態推定部は、前記無線端末の速度が所定値以上の場合には、前記無線端末の速度が前記所定値未満の場合よりも、前記第1の値を小さくして、前記伝送路の状態を推定する、請求項8記載の無線基地局。 - 前記無線基地局は、LTE(Long Term Evolution)方式の通信システムにおける無線基地局であり、
前記アップリンクパートは、UpPTS(Uplink Pilot Timeslot)である、請求項8に記載の無線基地局。 - いずれかのダウンリンクサブフレーム内の少なくとも一部を、無線端末への下りユーザデータを送信するための第1のリソースとして決定し、切替サブフレーム内のアップリンクパートの少なくとも一部、またはアップリンクサブフレームの一部を、前記無線端末がサウンディングレファレンス信号を周期的に送信するための第2のリソースとして決定するステップと、
前記決定した第2のリソースを前記無線端末に通知するステップと、
前記サウンディングレファレンス信号の送信が停止された後、再送要求を受信したときには、前記無線端末から受信する上りユーザデータに含まれるレファレンス信号に基づいて、前記無線端末との間の伝送路の状態を推定するステップと、
前記推定した伝送路の状態に基づいて複数のアンテナの指向性を形成して、前記第1のリソースを通じて前記下りユーザデータを送信するステップとを備えた、無線通信方法。 - いずれかのダウンリンクサブフレーム内の少なくとも一部を、無線端末への下りユーザデータを送信するための第1のリソースとして決定し、切替サブフレーム内のアップリンクパートの少なくとも一部、またはアップリンクサブフレームの一部を、前記無線端末がサウンディングレファレンス信号を周期的に送信するための第2のリソースとして決定するステップと、
前記決定した第2のリソースを前記無線端末に通知するステップと、
前記サウンディングレファレンス信号の送信区間では、受信した最新のサウンディングレファレンス信号に基づいて、前記無線端末との間の伝送路の状態を推定するステップと、
前記サウンディングレファレンス信号の送信が停止された後、再送要求を受信した場合に、前記受信した再送要求の累計が第1の値未満のときには、最後に受信した前記サウンディングレファレンス信号に基づいて、前記無線端末との間の伝送路の状態を推定するステップと、
前記サウンディングレファレンス信号の送信が停止された後、再送要求を受信した場合に、前記受信した再送要求の累計が前記第1の値以上のときには、前記無線端末から受信する上りユーザデータに含まれるレファレンス信号に基づいて、前記無線端末との間の伝送路の状態を推定するステップと、
前記推定した伝送路の状態に基づいて複数のアンテナの指向性を形成して、前記第1のリソースを通じて前記下りユーザデータを送信するステップとを備えた、無線通信方法。
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