WO2011013504A1 - 無線基地局 - Google Patents
無線基地局 Download PDFInfo
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- WO2011013504A1 WO2011013504A1 PCT/JP2010/061752 JP2010061752W WO2011013504A1 WO 2011013504 A1 WO2011013504 A1 WO 2011013504A1 JP 2010061752 W JP2010061752 W JP 2010061752W WO 2011013504 A1 WO2011013504 A1 WO 2011013504A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/022—Site diversity; Macro-diversity
- H04B7/024—Co-operative use of antennas of several sites, e.g. in co-ordinated multipoint or co-operative multiple-input multiple-output [MIMO] systems
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/0001—Arrangements for dividing the transmission path
- H04L5/0014—Three-dimensional division
- H04L5/0023—Time-frequency-space
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
- H04W72/04—Wireless resource allocation
Definitions
- the present invention relates to a radio base station, and more particularly to a radio base station that performs radio communication using a plurality of antennas.
- MIMO Multiple Input Multiple Output
- Patent Document 1 Japanese Patent Laid-Open No. 2006-121703
- Typical types of MIMO used in communication systems between wireless terminals and wireless base stations are STC (Space-Time Coding) based and SM (Spatial Multiplex) based. There are things.
- one signal stream is arranged (that is, encoded) based on a certain rule regarding time and space (antenna), and the encoded signal bit stream is transmitted from a plurality of antennas.
- the STC-based downlink communication method is called DL MIMO MATRIX-A.
- WiMAX currently does not support STC-based uplink communication schemes.
- the SM base multiple signal streams are multiplexed and transmitted at the same frequency from multiple antennas.
- the SM-based downlink communication method is called DL MIMO MATRIX-B.
- the SM-based uplink communication method is called cooperative spatial multiplexing (Collaborative SM).
- any wireless terminal combination can be set as a wireless terminal that cooperatively multiplexes uplink signals to the wireless base station. Whether the reception performance is improved depends on the condition of the transmission path. At present, a method for appropriately setting a combination of wireless terminals for cooperative spatial multiplexing is not established depending on the state of the transmission path.
- the downlink communication method depending on the condition of the transmission path, it is better to use the space-time coding method (DL MIMO MATRIX-A) MIMO method for wireless terminal throughput characteristics, area characteristics, and frequency utilization efficiency.
- the throughput characteristics, area characteristics, and frequency utilization efficiency of a wireless terminal may be improved by using the spatial multiplexing (DL MIMO MATRIX-B) MIMO scheme.
- DL MIMO MATRIX-A space-time coding method
- DL MIMO MATRIX-B spatial multiplexing
- a first object of the present invention is to provide a radio base station capable of obtaining high reception performance in a radio base station by appropriately setting a combination of radio terminals that perform cooperative spatial multiplexing of uplink signals. Is to provide.
- the second object of the present invention is to appropriately switch the MIMO scheme of the downlink signal to the space-time coding scheme or the spatial multiplexing scheme, so that high throughput characteristics, area characteristics, and high frequency in the radio terminal are achieved. It is to provide a radio base station that can obtain utilization efficiency.
- the present invention is a radio base station that communicates with a plurality of radio terminals that transmit uplink signals, and based on a plurality of antennas and the throughput of uplink signals from the plurality of radio terminals, two or more radio terminals 2 or more for two or more wireless terminals set in the cooperative spatial multiplexing mode, and a mode setting unit for setting the cooperative spatial multiplexing mode to share the same uplink data burst region
- An area notification unit for notifying the uplink data burst area used in common between the wireless terminals, and a common from two or more wireless terminals set in the cooperative spatial multiplexing mode received by a plurality of antennas
- a receiving unit that separates an uplink signal spatially multiplexed in an uplink data burst region and extracts a signal from each wireless terminal;
- the mode setting unit creates a pair from a candidate selection unit that selects a candidate terminal that is a candidate to be set to the cooperative spatial multiplexing mode among a plurality of wireless terminals, and a pair of the selected candidate terminals.
- a throughput calculation unit that calculates the sum of the throughputs of uplink signals from all wireless terminals of the communication partner, and when the wireless terminal is set to the cooperative spatial multiplexing mode
- a terminal setting unit that specifies a pair with the maximum sum of the calculated throughputs and sets the wireless terminals of the specified pair to the cooperative spatial multiplexing mode.
- the mode setting unit creates a pair from a candidate selection unit that selects a candidate terminal that is a candidate to be set to the cooperative spatial multiplexing mode among a plurality of wireless terminals, and a pair of the selected candidate terminals.
- a power control unit that instructs to adjust the transmission power to both or either of the pair so that the difference in the reception power of the uplink signal of the wireless terminal is equal to or less than a predetermined value; Communication when a power difference measurement unit that measures a difference in received power of uplink signals of a pair of wireless terminals and a pair of wireless terminals whose received power difference is equal to or smaller than a predetermined value are set to the cooperative spatial multiplexing mode.
- a throughput calculation unit that calculates the sum of the uplink signal throughput from all the partner wireless terminals, and the calculated throughput sum when the cooperative spatial multiplexing mode is set Identify a large pair and a terminal setting unit to set the radio terminal of the identified pairs cooperative spatial multiplexing mode.
- a correlation coefficient calculation unit that calculates a spatial correlation coefficient of a known signal from a pair of wireless terminals is provided, and the throughput calculation unit spatially multiplexes uplink signals of the pair of wireless terminals based on the spatial correlation coefficient MCS (modulation scheme and coding rate) is specified, and the throughput of uplink signals from two wireless terminals in a pair is calculated based on the specified MCS.
- MCS modulation scheme and coding rate
- a candidate selecting unit that selects a candidate terminal to be set to the cooperative spatial multiplexing mode among a plurality of wireless terminals and a pair created from the selected candidate terminals are known from the paired wireless terminals.
- a correlation coefficient calculation unit that calculates a spatial correlation coefficient of a signal, and all communication partners in a case where two wireless terminals in a pair whose spatial correlation coefficient is less than the first threshold are set to the cooperative spatial multiplexing mode
- a throughput calculation unit that calculates the sum of the throughputs of uplink signals from the wireless terminals and a pair that maximizes the calculated sum of the throughputs when set to cooperative spatial multiplexing mode.
- a terminal setting unit that sets the wireless terminal to the cooperative spatial multiplexing mode.
- the throughput calculation unit is more than the MCS in the case where the MCS of the uplink signal from a pair of wireless terminals whose spatial correlation coefficient is greater than or equal to the second threshold and less than the first threshold is not set to the cooperative spatial multiplexing mode.
- the throughput of the uplink signal from the paired wireless terminal is calculated, and the MCS of the uplink signal from the paired wireless terminal whose spatial correlation coefficient is less than the second threshold is calculated in the cooperative space.
- the throughput of the uplink signal from the paired wireless terminal is calculated when the MCS is matched with the case where the multiplexing mode is not set.
- the radio base station further includes an MCS setting unit that sets the MCS of the uplink signal from the radio terminal set in the cooperative spatial multiplexing mode in the MCS used for throughput calculation, and the set MCS in the cooperative space.
- An MCS notification unit for notifying a wireless terminal in multiple mode.
- the radio base station further includes a communication quality measurement unit that measures the communication quality of the uplink signal from the radio terminal
- the MCS setting unit further includes a communication quality of the uplink signal from the radio terminal.
- the MCS of the uplink signal from the wireless terminal is set.
- the radio base station further includes a communication quality measurement unit for measuring communication quality of the uplink signal from the radio terminal, and an uplink signal from the radio terminal based on the communication quality of the uplink signal from the radio terminal.
- a communication quality measurement unit for measuring communication quality of the uplink signal from the radio terminal, and an uplink signal from the radio terminal based on the communication quality of the uplink signal from the radio terminal.
- the candidate selection unit specifies an MCS having the highest transmission data rate among MCSs of uplink signals of all wireless terminals of communication partners, and selects a candidate terminal from a plurality of wireless terminals having the specified MCS. select.
- the candidate selection unit selects, as a candidate terminal, a wireless terminal that is not currently set to the cooperative spatial multiplexing mode among all the wireless terminals that are communication partners.
- the throughput calculation unit further calculates a sum of throughputs of uplink signals from all wireless terminals of communication partners when the candidate terminal is not set to the cooperative spatial multiplexing mode, and the terminal setting unit For the paired wireless terminals that maximize the sum of the uplink signal throughput from all wireless terminals when set to type spatial multiplexing mode, the case when set to cooperative spatial multiplexing mode is not set.
- the cooperative spatial multiplexing mode is set only when the sum of the throughputs of uplink signals from all wireless terminals as communication partners is large.
- the present invention is a radio base station that transmits a downlink signal to a radio terminal through a plurality of antennas, the plurality of antennas, a quality management unit that acquires or calculates communication quality of the downlink signal at the radio terminal, A correlation calculation unit that calculates a spatial correlation coefficient of known signals from a plurality of antennas of a wireless terminal, and a downlink signal from a space-time coding method to a space multiplexing method or from a space multiplexing method to a space-time coding method.
- the radio base station further includes a burst allocation unit that determines an arrangement of user data in a data burst region of a downlink frame transmitted from the radio base station, and the burst allocation unit is configured to perform MIMO of the downlink signal by the switching unit.
- the wireless terminal whose downlink signal MIMO method is the spatial multiplexing method is transmitted from a plurality of antennas of the wireless terminal. Based on the spatial correlation coefficient of the known signal, the arrangement of user data in the data burst area is determined.
- conditions for switching the MIMO scheme of the downlink signal from the space-time coding scheme to the spatial multiplexing scheme are separately determined for each radio terminal.
- the radio base station further sets a mode of a radio communication mode from a normal mode to a trial mode at a predetermined timing, and, in the trial mode, changes the MIMO scheme of the downlink signal from a space-time coding scheme to a spatial mode.
- Change the communication quality condition when switching to the multiplexing scheme and switch the downlink signal MIMO scheme from the space-time coding scheme to the spatial multiplexing scheme based on the changed communication quality condition, to the spatial multiplexing scheme
- a trial control unit that determines whether or not the switching is successful based on whether or not the spatial multiplexing system is maintained for a certain period of time after switching, the trial control unit uses in the normal mode based on the determination result Set communication quality conditions.
- the mode setting unit sets the wireless communication mode from the normal mode to the verification mode at a predetermined timing
- the MIMO mode of the downlink signal set in the normal mode in the verification mode is a space-time coding method.
- the downlink MIMO method is switched from the space-time coding method to the spatial multiplexing method, and after switching to the spatial multiplexing method, the spatial multiplexing method is changed for a certain period of time.
- a verification control unit that determines whether or not the switching is successful based on whether the switching is successful, and the verification control unit causes the mode setting unit to shift to the trial mode based on the determination result.
- the present invention is a radio base station that transmits a downlink signal to a radio terminal through a plurality of antennas, the plurality of antennas, a quality management unit that acquires or calculates communication quality of the downlink signal at the radio terminal, A switching unit that switches the setting of the MIMO scheme of the downlink signal from the space-time coding scheme to the space multiplexing scheme or from the space multiplexing scheme to the space-time coding scheme, and when the set MIMO scheme is a space-time coding scheme And a transmitter that space-time-encodes one data stream and outputs the data stream to a plurality of antennas, and when the set MIMO scheme is a spatial multiplexing scheme, a plurality of data streams are spatially multiplexed and output to a plurality of antennas.
- the switching unit uses the same MIMO scheme for wireless terminals other than the first type wireless terminal that transmits known signals from a plurality of antennas.
- CS modulation scheme and coding rate
- the radio base station further sets a mode of a radio communication mode from a normal mode to a trial mode at a predetermined timing, and, in the trial mode, changes the MIMO scheme of the downlink signal from a space-time coding scheme to a spatial mode.
- Change the communication quality condition when switching to the multiplexing scheme and switch the downlink signal MIMO scheme from the space-time coding scheme to the spatial multiplexing scheme based on the changed communication quality condition, to the spatial multiplexing scheme
- a trial control unit that determines whether or not the switching is successful based on whether or not the spatial multiplexing system is maintained for a certain period of time after switching, the trial control unit uses in the normal mode based on the determination result Set communication quality conditions.
- the mode setting unit sets the wireless communication mode from the normal mode to the verification mode at a predetermined timing
- the MIMO mode of the downlink signal set in the normal mode in the verification mode is a space-time coding method.
- the downlink MIMO method is switched from the space-time coding method to the spatial multiplexing method, and after switching to the spatial multiplexing method, the spatial multiplexing method is changed for a certain period of time.
- a verification control unit that determines whether or not the switching is successful based on whether the switching is successful, and the verification control unit causes the mode setting unit to shift to the trial mode based on the determination result.
- high reception performance can be obtained in a radio base station by appropriately setting a combination of radio terminals that spatially multiplex uplink signals to the radio base station.
- the present invention it is possible to obtain high throughput characteristics, area characteristics, and frequency utilization efficiency in a radio terminal by appropriately switching the MIMO scheme of the downlink signal to a space-time coding scheme or a space coding scheme. it can.
- FIG. 6 is a flowchart illustrating an operation procedure of the wireless communication system according to the second embodiment. It is a flowchart showing the detailed procedure of operation
- FIG. 32 is a flowchart showing a detailed procedure of the operation in step S608 of the flowchart of FIG. 31.
- FIG. 1 is a diagram showing a configuration of a wireless communication system according to an embodiment of the present invention.
- this radio communication system includes a radio base station 2 and n radio terminals 3a to 3n.
- radio terminals 3a to 3n In the first embodiment, between the radio base station 2 of FIG. 1 and the n radio terminals 3a to 3n, user data is transmitted in a communication scheme using cooperative spatial multiplexing or a communication scheme using a single antenna. An uplink signal is transmitted.
- a wireless terminal 3 when any one of the wireless terminals 3a to 3n is represented, it is referred to as a wireless terminal 3.
- FIG. 2 is a diagram showing the configuration of the radio base station according to the embodiment of the present invention.
- the radio base station 2 includes a first antenna 10, a second antenna 11, a first coupler / distributor 182, a second coupler / distributor 183, and a transmission unit. 13, a receiving unit 12, and a MAC (Media Access Control) layer processing unit 14.
- the first combiner / distributor 182 is configured by, for example, a circulator, and outputs a signal from the transmission unit 13 to the first antenna 10 and outputs a signal from the first antenna 10 to the reception unit 12.
- the second coupler / distributor 183 is configured by, for example, a circulator, and outputs a signal from the transmission unit 13 to the second antenna 11 and outputs a signal from the second antenna 11 to the reception unit 12.
- the transmission unit 13 includes a multi-antenna transmission signal processing unit 24, a subcarrier arrangement unit 23, an IFFT (Inverse First Fourier Transform) unit 22, a CP (Cyclic Prefix) addition unit 21, an RF (Radio Frequency) unit 20, Is provided.
- IFFT Inverse First Fourier Transform
- CP Cyclic Prefix
- RF Radio Frequency
- the subcarrier arrangement unit 23 arranges subcarriers based on, for example, PUSC (Partial Usage of Subchannels).
- the multi-antenna transmission signal processing unit 24 performs space-time coding on one data stream when the configured downlink signal MIMO scheme is STC-based, and when the configured downlink signal MIMO scheme is SM-based. , Spatial multiplexing of a plurality of data streams.
- the IFFT unit 22 converts the plurality of subcarrier signals (frequency domain signals) output from the multi-antenna transmission signal processing unit 24 into time domain signals (OFDMA (Orthogonal Frequency Division Multiple Access) symbols) by IFFT.
- OFDMA Orthogonal Frequency Division Multiple Access
- the CP adding unit 21 adds the same signal as the tail part of the OFDMA symbol to the beginning of the OFDMA symbol as a CP.
- the RF unit 20 includes an up-converter that up-converts to a radio frequency band, a power amplification circuit that amplifies the up-converted signal, and passes only the signal component in the desired band of the amplified signal to pass through the first antenna 10 and the first antenna 10.
- a band-pass filter that outputs to the second antenna 11.
- the reception unit 12 includes an RF unit 15, a CP removal unit 16, an FFT (First Fourier Transform) unit 17, a subcarrier arrangement unit 18, and a multi-antenna reception signal processing unit 19.
- RF unit 15 a CP removal unit 16
- FFT First Fourier Transform
- the RF unit 15 includes a band-pass filter that allows only a signal component in a desired band among signals output from the first antenna 10 and the second antenna 11 to pass, a low-noise amplifier circuit that amplifies the RF signal, and the RF signal that is down Includes down coater to convert.
- the CP removal unit 16 removes the CP from the signal output from the RF unit 15.
- the FFT unit 17 converts the time domain signal output from the CP removal unit 16 into a frequency domain signal by FFT and demodulates the signal into a plurality of subcarriers.
- the subcarrier arrangement unit 18 extracts each subcarrier output from the FFT unit 17 based on PUSC, for example.
- the multi-antenna received signal processing unit 19 separates the spatially multiplexed uplink signal from the wireless terminal 3 set in the cooperative spatial multiplexing mode into the uplink signal from each wireless terminal 3.
- the MAC layer processing unit 14 includes a user data transmission management unit 42, an encoding unit 43, a modulation unit 44, a demodulation unit 25, a decoding unit 26, a user data reception management unit 27, and a communication quality measurement unit 28. , An MCS (Modulation and Code Scheme) setting unit 29, a mode setting unit 30, and a terminal control unit 37.
- MCS Modulation and Code Scheme
- the user data transmission management unit 42 manages user data transmitted to the wireless terminal 3.
- the encoding unit 43 encodes the downlink signal to the wireless terminal 3.
- the modulation unit 44 modulates the encoded downlink signal.
- the communication quality measuring unit 28 measures the packet error rate of the uplink signal from the wireless terminal 3.
- the MCS setting unit 29 sets the MCS (modulation scheme and coding rate) of the uplink signal for each wireless terminal 3 based on the packet error rate of the uplink signal from the wireless terminal 3.
- FIG. 3 is a diagram illustrating an example of the MCS switching table.
- the MCS switching table includes the current MCS (modulation scheme and coding rate), the threshold UP_TH of the uplink signal packet error rate when MCS is increased by one stage, and the case where the MCS is decreased by one stage.
- the uplink signal packet error rate threshold DN_TH is included in the uplink signal packet error rate.
- the MCS is level 3 “16QAM 1/2” when the packet error rate of the uplink signal is 1 (%) or less.
- the MCS is changed to “QPSK 1/2” of level 2.
- the demodulation unit 25 demodulates the uplink signal from the wireless terminal 3 based on the MCS modulation scheme for each wireless terminal 3 set by the MCS setting unit 29.
- the decoding unit 26 decodes the demodulated uplink signal based on the MCS encoding rate for each wireless terminal 3 set by the MCS setting unit 29.
- the user data reception management unit 27 manages user data received from the wireless terminal 3.
- the mode setting unit 30 uses cooperative spatial multiplexing that uses two wireless terminals 3 sharing the same uplink data burst region based on the throughput of uplink signals from all the wireless terminals 3 of the communication counterpart. Set to mode (Collaborative Spatial Multiplexing).
- the radio base station 2 regards the uplink signals from the two radio terminals 3 set to the cooperative spatial multiplexing mode as signal from the two antennas of the one radio terminal 3 and performs signal processing.
- the mode setting unit 30 includes a candidate selection unit 31, a correlation coefficient calculation unit 33, a power difference measurement unit 34, a throughput calculation unit 32, a table creation unit 35, and a terminal setting unit 36.
- the candidate selection unit 31 specifies the MCS having the highest transmission data rate among the MCSs of the uplink signals of all the radio terminals 3 of the communication partner, and among the plurality of radio terminals 3 having the specified MCS of the uplink signal. To select a candidate terminal in the cooperative spatial multiplexing mode.
- the power difference measurement unit 34 measures the difference between the received powers of the uplink signals from the two wireless terminals 3 constituting the candidate terminal pair.
- the correlation coefficient calculation unit 33 receives a sounding signal transmitted on a plurality of subcarriers (for example, four consecutive subcarriers) in the sounding zone from the radio terminal 3 of one user A constituting a pair of candidate terminals.
- a response vector and a reception response vector of a sounding signal transmitted on a plurality of subcarriers in the sounding zone from the wireless terminal 3 of the other user B constituting the candidate terminal pair are calculated.
- N1 (t) h11 ⁇ S1 (t) + h12 ⁇ S2 (t) + N1 (t)
- X2 (t) h21 ⁇ S1 (t) + h22 ⁇ S2 (t) + N2 (t)
- N1 (t) is a noise component included in the reception signal X1 (t) received by the first antenna 10
- N2 (t) is a reception signal X2 (t) received by the second antenna 11. It is a noise component contained in.
- the correlation coefficient calculation unit 33 receives the reception response vector H1 of the sounding signals of a plurality of subcarriers in the sounding zone from the wireless terminal 3 of the user A and the wireless of the user B according to the following equations (3) and (4).
- a reception response vector H2 of a sounding signal of a plurality of subcarriers in the sounding zone from the terminal 3 is calculated.
- U1 (t) is the same signal as S1 (t) held on the radio base station 2 side
- U2 (t) is S2 (t) held on the radio base station 2 side. Is the same signal.
- U1 * (t) is a complex conjugate of U1 (t)
- U2 * (t) is a complex conjugate of U2 (t).
- E (X) represents an ensemble average (time average) of X.
- the correlation coefficient calculation unit 33 calculates the spatial phase between the sounding signals of the plurality of subcarriers in the sounding zone of the user A's wireless terminal 3 and the sounding signals of the plurality of subcarriers in the sounding zone of the wireless terminal 3 of the user B.
- the relation number C is calculated by the following equation (5).
- the correlation coefficient calculation unit 33 calculates an average spatial correlation coefficient M_SR obtained by averaging the calculated spatial correlation coefficient C for each subcarrier for all subcarriers included in the sounding zone. For example, when the number of all subcarriers is 1024, correlation coefficient calculating unit 33 obtains 256 spatial correlation coefficients C for each of the four consecutive subcarriers, and obtains 256 spatial correlation coefficients C. An average spatial correlation coefficient M_SR is calculated by averaging.
- the throughput calculation unit 32 refers to the transmission data rate table shown in FIG. 4 and specifies the data transmission rate per slot corresponding to the MCS of the uplink signal of the wireless terminal 3.
- the throughput calculation unit 32 calculates the throughput of the uplink signal from the wireless terminal 3 by multiplying the transmission data rate per slot by the number of slots in the data burst area allocated to the uplink signal of the wireless terminal 3. To do.
- FIG. 4 is a diagram illustrating an example of a transmission data rate table.
- the transmission data rate table defines the correspondence between MCS and the data rate per slot. For example, when MCS is “QPSK 1/2”, the data rate per slot is d1 (bit).
- FIG. 5 is a diagram for explaining an example of throughput when uplink signals from the radio terminals 3 of all users of communication partners are not cooperatively spatially multiplexed.
- the signal throughput sum B_SP is calculated by the following equation.
- FIG. 6 is a diagram for explaining an example of throughput when the uplink signal from the wireless terminal 3 of the user A and the uplink signal from the wireless terminal 3 of the user B are cooperatively spatially multiplexed.
- the data rate per slot of MCS of user A's wireless terminal 3 when the uplink signal is cooperatively spatially multiplexed is RAc
- the MCS of user B's wireless terminal 3 when the uplink signal is cooperatively spatially multiplexed When the data rate per slot of RBc is RBc, the sum A_SP of the throughput of uplink signals from all wireless terminals of the communication counterpart is calculated by the following equation.
- A_SP RAc ⁇ (SA + SB) + RBc ⁇ (SA + SB) + RC ⁇ SC + RD ⁇ SD + RE ⁇ SE + RF ⁇ SF + RG ⁇ SG + RH ⁇ SH + RI ⁇ SI + RJ ⁇ SJ (7)
- the table creation unit 35 can set the difference in the received power of the uplink signal from the two wireless terminals 3 of the pair of cooperative spatial multiplexing candidate to 0 dB (that is, power control is possible).
- a coordinated spatial multiplexing pair table defining a value A_SP that is the sum of the throughputs of uplink signals from all wireless terminals 3 of the communication partner when the uplink signal is coordinated spatially multiplexed with respect to an increase in the sum of the throughputs Create
- FIG. 7 is a diagram illustrating an example of a cooperative spatial multiplexing pair table.
- a value A_SP obtained by adding up the throughputs of the uplink signals from all the radio terminals 3 of the communication partner is “ SP1 ".
- the terminal setting unit 36 identifies a pair having the maximum throughput sum A_SP among the pairs in the cooperative spatial multiplexing pair table, and sets the two wireless terminals 3 of the identified pair to the cooperative spatial multiplexing mode.
- the terminal control unit 37 includes an MCS notification unit 38, a burst region notification unit 41, a sounding transmission instruction unit 40, and a power control unit 39.
- the MCS notification unit 38 outputs a signal for notifying the wireless terminal 3 of the MCS of the uplink signal for each wireless terminal 3 set by the MCS setting unit 29.
- the sounding transmission instructing unit 40 outputs a signal to notify the created pair of wireless terminals 3 to transmit a sounding signal.
- the power control unit 39 transmits the uplink signal transmission power to one or both of the paired wireless terminals 3 so that the difference in the received power of the uplink signals from the paired wireless terminals 3 becomes a predetermined value (for example, 0 dB). A signal for notifying the control to be output is output.
- the burst region notifying unit 41 outputs a signal for notifying the allocated uplink data burst region to each wireless terminal 3 in a downlink frame. However, the burst region notifying unit 41 does not use the uplink data burst region (respectively used) between the paired wireless terminals 3 for the paired wireless terminals 3 set in the cooperative spatial multiplexing mode. A signal informing the region) is output in the downlink frame.
- FIG. 8 is a diagram showing the configuration of the wireless terminal according to the embodiment of the present invention.
- this wireless terminal 3 includes a coupler / distributor 283, a first antenna 50, a second antenna 51, a transmission unit 53, a reception unit 52, a MAC layer processing unit 54, Is provided.
- the subcarrier arrangement unit 63 arranges subcarriers based on PUSC, for example.
- IFFT unit 62 converts the plurality of subcarrier signals (frequency domain signals) output from subcarrier arrangement unit 63 into time domain signals (OFDMA symbols) by IFFT.
- the CP adding unit 61 adds the same signal as the tail part of the OFDMA symbol to the beginning of the OFDMA symbol as a CP.
- the RF unit 60 includes an up-converter that up-converts to a radio frequency band, a power amplification circuit that amplifies the up-converted signal, and passes only a signal component in a desired band out of the amplified signal and outputs it to the second antenna 51 Including a band pass filter.
- the RF unit 55 is a band-pass filter that passes only the signal component of the desired band among the signals output from the first antenna 50 and the second antenna 51, a low-noise amplifier circuit that amplifies the RF signal, and the RF signal that is down Includes down coater to convert.
- the CP removal unit 56 removes the CP from the signal output from the RF unit 55.
- the FFT unit 57 converts the time domain signal output from the CP removing unit 56 into a frequency domain signal by FFT and demodulates the signal into a plurality of subcarriers.
- the subcarrier arrangement unit 58 extracts each subcarrier output from the FFT unit 57 based on PUSC, for example.
- the multi-antenna received signal processing unit 59 performs space-time decoding on signals output from a plurality of antennas when the set downlink signal MIMO scheme is STC-based, extracts one data stream, and is set.
- the downlink signal MIMO scheme is SM-based, a plurality of data streams are extracted by separating signals output from a plurality of antennas.
- the user data transmission management unit 72 manages user data transmitted to the radio base station 2.
- the encoding unit 73 encodes the uplink signal to the radio base station 2 according to the MCS encoding rate set by the MCS setting unit 71.
- the demodulator 65 demodulates the downlink signal from the radio base station 2.
- the decoding unit 66 decodes the demodulated downlink signal.
- the user data reception management unit 67 manages user data received from the radio base station 2.
- the control unit 64 includes a burst area management unit 68, a power control unit 69, a sounding signal output unit 70, and an MCS setting unit 71.
- the burst area management unit 68 transmits an uplink data burst area from the radio base station 2 (however, when the cooperative spatial multiplexing mode is set, the uplink radio station commonly used with the partner radio terminal of the pair)
- the transmission unit 53 is controlled so as to allocate user data to the uplink data burst area that has been notified.
- the sounding signal output unit 70 outputs a sounding signal in accordance with an instruction from the radio base station 2.
- the MCS setting unit 71 controls the modulation scheme of the modulation unit 74 and the coding rate of the coding unit 73 in accordance with the MCS notification from the radio base station 2.
- MCS setting unit 29 sets user number i to 1 (step S101).
- the communication quality measuring unit 28 measures the packet error rate UL_PER (i) of the data of the wireless terminal 3 of the user i (user of the user number i) in the uplink frame (step S102).
- step S104 when the processes in steps S102 and S103 for all users have been completed (YES in step S104), the MCS setting unit 29 proceeds to step S106 and has not completed the processes for all users. In this case (NO in step S104), the user number i is incremented by 1 (step S105), and the process returns to step S102.
- the sounding transmission instruction unit 40 transmits a signal indicating an instruction to transmit sounding information to the wireless terminal 3 of the user i in the downlink frame (step S109).
- step S110 when the processes of steps S108 and S109 for all users are completed (YES in step S110), the candidate selection unit 31 proceeds to step S111 and the processes for all users are not completed. In this case (NO in step S110), the user number i is incremented by 1 (step S111), and the process returns to step S107.
- the terminal setting unit 36 uses the proportional fairness or the like to update the uplink of each wireless terminal 3.
- the data burst area is reassigned (step S113).
- the terminal setting unit 36 refers to the cooperative spatial multiplexing pair table and sets the pair with the highest throughput (referred to as the pair PX) to the cooperative spatial multiplexing mode (step S115).
- the burst area notifying unit 41 outputs a signal for notifying each wireless terminal 3 of the uplink data burst area allocated in step S113 in the downlink frame.
- the burst region notification unit 41 does not use the uplink data burst region (commonly used between the wireless terminals 3 of the pair PX) for the wireless terminals 3 of the pair PX set in the cooperative spatial multiplexing mode.
- a signal for notifying the area where the respective areas are merged) is output in the downlink frame (step S116).
- the burst region notifying unit 41 outputs a signal for notifying each wireless terminal 3 of the uplink data burst region allocated in step S118 in the downlink frame (step S119).
- the MCS notifying unit 38 transmits the wireless terminal 3 whose MCS has been changed in step S103 and the wireless terminal 3 temporarily set so that the MCS is lowered by one stage when cooperative spatial multiplexing is performed in later-described step S208.
- a signal notifying the changed MCS is output (step S120).
- the multi-antenna received signal processing unit 19 of the radio base station 2 performs spatial multiplexing in a common uplink data burst region transmitted from the two radio terminals 3 of the pair PX set in the cooperative spatial multiplexing mode.
- the separated uplink signal is separated, and the signal from each wireless terminal 3 is taken out.
- the demodulator 25 of the radio base station 2 demodulates user data based on the set MCS, and the decoding unit 26 of the radio base station 2 decodes user data based on the set MCS (step S122).
- FIG. 10 is a diagram showing details of step S114 in the flowchart of FIG. With reference to FIG. 10, the table creation unit 35 sets a pair (X, Y) from the candidate terminals in the cooperative spatial multiplexing mode (step S201).
- the power control unit 39 and the power difference measurement unit 34 set the difference between the received power of the uplink signal from the wireless terminal 3 of the user X and the received power of the uplink signal from the wireless terminal 3 of the user Y to 0 dB. Check if it can be set. Specifically, the power control unit 39 is based on the values measured so far of the received power of the uplink signal from the wireless terminal 3 of the user X and the received power of the uplink signal from the wireless terminal 3 of the user Y. Thus, a signal for notifying one or both of the radio terminal 3 of the user X and the radio terminal 3 of the user Y to adjust the transmission power of the uplink signal is output so that the difference in received power becomes 0 dB.
- the power control unit 69 of the wireless terminal 3 controls the transmission power of the uplink signal to be the instructed value.
- the power difference measurement unit 34 measures the difference between the received power of the uplink signal from the wireless terminal 3 of the user X and the received power of the uplink signal from the wireless terminal 3 of the user Y.
- the throughput calculation unit 32 sets the MCS temporarily set in step S206 or S208 for the users X and Y, the MCS set in step S103 for the other users of the communication partner, and the burst of each user allocated in step S113. Based on the size of the region (for X and Y, the size of the region obtained by merging the respective burst regions), all radios of the communication partner in the case of cooperative spatial multiplexing of the uplink signals of user X and user Y The sum A_SP of the throughput of the uplink signal from the terminal 3 is calculated (step S209).
- the table creating unit 35 performs the cooperative spatial multiplexing.
- the pair (X, Y) and the throughput sum A_SP are written in the table (step S211).
- step S212 when the processing of steps S201 to S211 is completed for all possible pairs (YES in step S212), the table creation unit 35 proceeds to step S213 and performs processing for all possible pairs. If not completed (NO in step S212), the process returns to step S201 to repeat the process for the unprocessed pair.
- the first combiner / distributor 182 is configured by, for example, a circulator, and outputs a signal from the transmission unit 13 to the first antenna 10 and outputs a signal from the first antenna 10 to the reception unit 12.
- the second coupler / distributor 183 is configured by, for example, a circulator, and outputs a signal from the transmission unit 13 to the second antenna 11 and outputs a signal from the second antenna 11 to the reception unit 12.
- the subcarrier arrangement unit 23 arranges subcarriers based on, for example, PUSC (Partial Usage of Subchannels).
- the multi-antenna transmission signal processing unit 24 performs space-time coding (for example, Aramuch coding) on one data stream, and when the set MIMO scheme is MATRIX-B In addition, a plurality of data streams are spatially multiplexed.
- space-time coding for example, Aramuch coding
- the CP adding unit 21 adds the same signal as the tail part of the OFDMA symbol to the beginning of the OFDMA symbol as a CP.
- the RF unit 15 includes a band-pass filter that allows only a signal component in a desired band among signals output from the first antenna 10 and the second antenna 11 to pass, a low-noise amplifier circuit that amplifies the RF signal, and the RF signal that is down Includes down coater to convert.
- the CP removal unit 16 removes the CP from the signal output from the RF unit 15.
- the FFT unit 17 converts the time domain signal output from the CP removal unit 16 into a frequency domain signal by FFT and demodulates the signal into a plurality of subcarriers.
- the subcarrier arrangement unit 18 extracts each subcarrier output from the FFT unit 17 based on PUSC, for example.
- the user data transmission management unit 42 manages user data transmitted to the wireless terminal 3.
- the encoding unit 43 encodes the encoded downlink signal according to the MCS encoding rate indicated by the switching unit 95.
- the modulation unit 44 modulates the downlink signal to the wireless terminal 3 in accordance with the MCS modulation method instructed from the switching unit 95.
- the user data reception management unit 27 manages user data received from the wireless terminal 3.
- the control unit 91 includes a communication quality management unit 92, a correlation coefficient calculation unit 93, a sounding instruction unit 94, a switching unit 95, a switching rule storage unit 96, and a switching notification unit 97.
- the communication quality management unit 92 receives a notification of the packet error rate of the downlink signal measured by each wireless terminal 3 from each wireless terminal 3, and stores the notified packet error rate.
- the correlation coefficient calculation unit 93 receives the reception response vector of the sounding signal transmitted from the first antenna 50 of each wireless terminal 3 using a plurality of subcarriers (for example, four consecutive subcarriers) in the sounding zone, and each wireless terminal.
- the reception response vector of the sounding signal transmitted from the second antenna 51 of the terminal 3 using a plurality of subcarriers in the sounding zone is calculated.
- Received signals X1 (t) of a plurality of subcarriers in the sounding zone received by the first antenna 10 of the radio base station 2 and a plurality of subs of the sounding zone received by the second antenna 11 of the radio base station 2 The carrier reception signal X2 (t) is transmitted from the sounding signal S1 (t) of a plurality of subcarriers in the sounding zone transmitted from the first antenna 50 of the wireless terminal 3 and from the second antenna 51 of the wireless terminal 3.
- the received response vectors H1 ( [) of the sounding signals S2 (t) of the plurality of subcarriers in the transmitted sounding zone and the sounding signals of the plurality of subcarriers in the sounding zone from the first antenna 50 of the wireless terminal 3.
- N1 (t) is a noise component included in the received signal X1 (t) received by the first antenna 10 of the radio base station 2
- N2 (t) is a second antenna of the radio base station 2.
- 11 is a noise component included in the received signal X2 (t) received at 11.
- U1 (t) is the same signal as S1 (t) held on the radio base station 2 side
- U2 (t) is S2 (t) held on the radio base station 2 side. Is the same signal.
- U1 * (t) is a complex conjugate of U1 (t)
- U2 * (t) is a complex conjugate of U2 (t).
- E (X) represents an ensemble average (time average) of X.
- FIG. 12 is a diagram illustrating an example of a communication level table.
- the communication level “A1” indicates that the MIMO scheme is “MATRIX-A”, the MCS is “QPSK 1/2”, and the data rate is “1” (bit / symbol).
- MCS level down when changing to MCS with a high data rate, in this specification, it is described as “leveling up MCS”, and when changing to MCS with a low data rate, in this specification, , “MCS level down”.
- FIG. 13 is a diagram illustrating an example of a communication level switching rule in the first type wireless terminal.
- the communication level is determined based on the packet error rate PER of the downlink signal and the average spatial correlation coefficient SP of the sounding signals from the two antennas. Is switched. As described above, the average spatial correlation coefficient SP is used as the condition for switching the communication level.
- the first type wireless terminal can transmit the sounding signal from the two antennas. This is because, when the downlink signal from the radio base station 2 is spatially multiplexed by the spatial correlation coefficient, it can be determined whether or not the spatially multiplexed signal can be appropriately separated on the radio terminal side. .
- the communication level is increased to “B3”.
- the packet error rate PER of the downlink signal is “UPR1 (%)” or less
- the communication level is increased to “B3”.
- the packet error rate PER of the downlink signal is “5 (%)” or more and the average spatial correlation coefficient SP is “DSP” or less
- MATRIX-B If the packet error rate PER of the downlink signal is “5 (%)” or more and the average spatial correlation coefficient SP is greater than “DSP”, the MATRIX is changed. Level up to "A3".
- “1 (%)” can be set as “UPER1 (%)”.
- FIG. 14 is a diagram illustrating an example of a communication level switching rule in the second type wireless terminal.
- the communication level switching rule of the second type wireless terminal is based on the packet error rate threshold value UPER3 when MATRIX is increased and the packet error rate threshold value UPER2 when MCS is increased with the same MATRIX. Is set lower (that is, the communication quality is set better).
- the threshold UPER3 is made smaller than the threshold UPER2 because when the MATRIX is increased, it is not possible to predict how the throughput characteristic, the area characteristic, or the frequency use efficiency changes on the wireless terminal 3 side. This is because strict conditions are imposed on the communication quality when MATRIX is upgraded.
- the communication level is lowered by one step. If the packet error rate PER of the downlink signal is “UPER2 (%)” or less when the current communication level is “A6”, the level is increased to “A7” maintaining MATRIX-A. When the current communication level is “A7” and the packet error rate PER of the downlink signal is “UPER3 (%)” or less, the level is increased to “B4” for changing MATRIX.
- UPER2> UPER3 and the conditions of communication quality when MATRIX is changed are set strictly. For example, “1 (%)” can be set as “UPER2 (%)”, and “0.5 (%)” can be set as “UPER3 (%)”, for example.
- the switching notification unit 97 outputs a signal for notifying the wireless terminal of the MIMO scheme and MCS of the downlink signal after being switched by the switching unit 95.
- the wireless terminal 3 includes a first antenna 50, a second antenna 51, a transmission unit 53, a reception unit 52, and a MAC layer processing unit 78.
- the first coupler / distributor 282 is configured by, for example, a circulator, and outputs a signal from the transmission unit 53 to the first antenna 50 and outputs a signal from the first antenna 50 to the reception unit 52.
- the second coupler / distributor 283 is configured by, for example, a circulator, and outputs a signal from the transmission unit 53 to the second antenna 51 and outputs a signal from the second antenna 51 to the reception unit 52.
- the subcarrier arrangement unit 63 arranges subcarriers based on PUSC, for example.
- the IFFT unit 62 converts a plurality of subcarrier signals (frequency domain signals) output from the subcarrier arrangement unit 63 into time domain signals (OFDMA symbols) by IFFT.
- the CP adding unit 61 adds the same signal as the tail part of the OFDMA symbol to the beginning of the OFDMA symbol as a CP.
- the RF unit 60 includes an up-converter that up-converts to a radio frequency band, a power amplification circuit that amplifies the up-converted signal, and passes only the signal component in the desired band among the amplified signal, and the first antenna 50 and the first antenna 2 including a band-pass filter that outputs to the second antenna 51.
- the reception unit 52 includes an RF unit 55, a CP removal unit 56, an FFT unit 57, a subcarrier arrangement unit 58, and a multi-antenna reception signal processing unit 59.
- the CP removal unit 56 removes the CP from the signal output from the RF unit 55.
- the FFT unit 57 converts the time domain signal output from the CP removing unit 56 into a frequency domain signal by FFT and demodulates the signal into a plurality of subcarriers.
- the subcarrier arrangement unit 58 extracts each subcarrier output from the FFT unit 57 based on PUSC, for example.
- the multi-antenna reception signal processing unit 59 performs space-time decoding on the signals output from the two antennas 50 and 51 when the MIMO scheme of the downlink signal notified from the radio base station 2 is MATRIX-A, Two data streams are extracted, and when the MIMO scheme of the downlink signal notified from the radio base station 2 is MATRIX-B, the signals output from the two antennas 50 and 51 are separated, and a plurality of data streams are extracted. Extract.
- the MAC layer processing unit 78 includes a user data transmission management unit 72, an encoding unit 73, a modulation unit 74, a demodulation unit 65, a decoding unit 66, a user data reception management unit 67, and a control unit 8. .
- the user data transmission management unit 72 manages user data transmitted to the radio base station 2.
- the encoding unit 73 encodes an uplink signal to the radio base station 2.
- the decoding unit 66 demodulates and decodes the downlink signal according to the MCS encoding rate set by the MCS management unit 79.
- the user data reception management unit 67 manages user data received from the radio base station 2.
- the control unit 8 includes a communication quality measurement unit 75, an MCS management unit 79, a MIMO management unit 77, and a sounding output unit 76.
- the MCS management unit 79 controls the demodulation unit 65 and the decoding unit 66 based on the MCS notified from the radio base station 2.
- the MIMO management unit 77 controls the multi-antenna reception signal processing unit 59 based on the MIMO scheme notified from the radio base station 2.
- the sounding output unit 76 receives a sounding instruction from the radio base station 2 and generates a sounding signal included in the sounding zone of the uplink frame.
- the wireless terminal 3 in FIG. 15 is a first type wireless terminal
- the generated sounding signal is output from the first antenna 50 and the second antenna 51.
- the wireless terminal 3 in FIG. 15 is a wireless terminal that transmits a sounding signal from only one predetermined antenna among the second type wireless terminals
- the generated sounding signal is the first antenna 50 and the first antenna 50.
- the signal is output from only one of the two antennas 51 determined in advance.
- the wireless terminal 3 in FIG. 15 is a wireless terminal that does not transmit a sounding signal among the second type wireless terminals
- the sounding output unit 76 is not included.
- FIG. 16 is a flowchart illustrating an operation procedure for each frame of the wireless communication system according to the second embodiment.
- the switching unit 95 sets the user number i to 1 (step S802).
- the wireless terminal 3 with the user number i is a first type wireless terminal, that is, a wireless terminal capable of transmitting a sounding signal using two antennas, the switching unit 95 (YES in step S803). Then, the switching process of the first type wireless terminal is performed (step S804).
- step S806 when the user number i is not equal to the total number of users in communication (NO in step S806), the switching unit 95 increments the user number i by 1 and returns to step S803.
- the communication quality management unit 92 acquires the packet error rate PER of the downlink signal of the wireless terminal 3 of the user i included in the uplink frame (step S901).
- the correlation coefficient calculation unit 93 calculates the spatial correlation coefficient of the uplink signal from the two antennas of the radio terminal 3 of the user number i for each of the plurality of subcarriers in the sounding zone.
- the correlation coefficient calculation unit 93 calculates an average spatial correlation coefficient SP obtained by averaging the calculated spatial correlation coefficients for all subcarriers (step S902).
- the switching unit 95 is a case where the packet error rate PER is equal to or less than the threshold value UPER1 (%) (YES in step S903), and the current communication level is A2 to A7 (YES in step S904).
- the average spatial correlation coefficient SP is equal to or less than the threshold USP (YES in step S905), the current communication level is increased to any of B1 to B4 with MATRIX increase according to the communication level switching rule of FIG. (Step S906).
- the switching unit 95 determines that the current communication level is not A2 to A7 (NO in step S204), or the average spatial phase If the relationship number SP exceeds the threshold USP (YES in step S905), the current communication level is determined according to the communication level switching rule of FIG. 13 only when the current communication level is not A7 or B7 (NO in step S908). Is changed to a communication level in which MCS is increased by one stage while maintaining MATRIX (step S908).
- the switching unit 95 is a case where the packet error rate PER is 5.0 (%) or more (NO in step S903, YES in step S909), and the current communication level is B1 to B4 (in step S910). YES) If the average spatial correlation coefficient SP exceeds the threshold DSP (YES in step S905), the current communication level is set to any one of A2 to A7 accompanied by MATRIX down according to the communication level switching rule of FIG. The communication level is lowered (step S912).
- switching unit 95 determines that the current communication level is not B1 to B4 (NO in step S910). If the average spatial correlation coefficient SP is equal to or less than the threshold DSP (NO in step S911), only when the current communication level is not A1 or B1 (NO in step S913), the communication level switching rule of FIG. , While maintaining MATRIX, the communication level is changed to a communication level in which MCS is lowered by one stage (step S914).
- FIG. 18 is a flowchart showing a detailed procedure of the operation in step S805 of the flowchart of FIG.
- the communication quality management unit 92 acquires the packet error rate PER of the downlink signal of the wireless terminal 3 of the user i included in the uplink frame (step S301).
- the switching unit 95 determines that the current communication level is A7 (YES in step S302) and the packet error rate PER is 5.0 (%) or more (NO in step S303, YES in step S305).
- the communication level is changed to a communication level in which the MCS is lowered by one stage while maintaining MATRIX-A (step S306).
- the communication level is changed to a communication level obtained by increasing the MCS by one stage while maintaining MATRIX-B (step S309).
- the switching unit 95 determines that the current communication level is B4 (NO in step S302, YES in step S307) and the packet error rate PER is 5.0 (%) or more (NO in step S303).
- the communication level is lowered to A7 with MATRIX down according to the communication level switching rule of FIG. 14 (step S311).
- the switching unit 95 determines that the communication level in FIG. In accordance with the communication level switching rule, the communication level is changed to a communication level obtained by increasing the MCS by one stage while maintaining MATRIX (step S313).
- the switching unit 95 determines that the packet error rate PER is 5.0 (%) or more (NO in step S312 and NO in step S314). YES), according to the communication level switching rule of FIG. 14, the communication level is changed to a communication level in which the MCS is lowered by one stage while maintaining MATRIX (step S315).
- the packet error rate of the downlink signal and the spatial phase relationship between the sounding signals from the two antennas of the radio terminal is switched.
- the packet error rate threshold UPER3 when MATRIX is increased is set lower than the packet error rate threshold UPER2 of the downlink signal when MCS is increased with the same MATRIX. (In other words, set the one with better communication quality).
- MATRIX is improved according to a rule corresponding to the sounding signal transmission function of the wireless terminal, so that high throughput characteristics, area characteristics, and frequency utilization efficiency can be obtained in the wireless terminal.
- the values of the threshold values UPER1, USP, and DSP are the same for all the first type wireless terminals, and the values of the threshold values UPER2, UPER3 are the same for all the second type wireless terminals.
- the present invention is not limited to this.
- a separate threshold may be used for each wireless terminal or each type of wireless terminal.
- the type of wireless terminal can be set based on, for example, the number of antennas used at the time of reception, the number of antennas used at the time of transmission, the reception control method of the wireless terminal (whether or not it has an adaptive array reception function), and the like.
- the third embodiment relates to a radio base station that can appropriately set the values of the threshold values UPER1, UPER2, and UPER3 used in the second embodiment by learning.
- FIG. 19 is a diagram illustrating a configuration of a radio base station according to the third embodiment.
- the table storage unit 88 stores a switching history table and a switching success rate table.
- FIG. 20 is a diagram illustrating an example of a switching history table of the first type wireless terminal.
- the switching history table of the first type wireless terminal defines a user number, a frame number when switching is performed, a communication level before switching, and a communication level after switching. For example, for the wireless terminal with the user number “1”, the communication level is switched from “A3” to “A4” in the “11th” frame, and the communication level is changed from “A4” to “A4” in the “14th” frame. It is recorded that it has been switched to “A3”.
- FIG. 22 is a diagram illustrating an example of a switching success rate table of the first type wireless terminals.
- the up-switching success rate represents the rate at which the communication level is not lowered to the original communication level within a predetermined frame after the communication level is increased.
- the up-switching success rate is “97 (%)”. This value is calculated based on the switching history table of the first type wireless terminal whose user number is “1” in FIG.
- FIG. 23 is a diagram illustrating an example of a switching success rate table of the second type wireless terminals.
- the switching success rate table of the second type wireless terminal determines the user number, the up switching success rate corresponding to threshold value UPER2, and the up switching success rate corresponding to threshold value UPER3. For example, for a wireless terminal with the user number “6”, when the threshold value UPER2 is “0.8 (%)”, the success rate of up-switching without changing MATRIX is “97 (%)”, and the threshold value UPER3 is Under “0.3 (%)”, the success rate of up-switching accompanied by the change of MATRIX is “95 (%)”. This value is calculated based on the switching history table of the second type wireless terminal whose user number is “6” in FIG.
- the mode setting unit 81 sets the wireless communication mode from the normal mode to the trial mode or the verification mode at a predetermined timing, for example, at regular intervals. In the normal mode, the operations shown in the flowcharts of FIGS. 16 to 18 described in the second embodiment are executed.
- the verification control unit 87 changes the communication level in the same manner as in the second embodiment under the thresholds UPER1, UPER2, and UPER3 set in the normal mode.
- the verification control unit 87 determines whether or not the up switching has succeeded based on whether or not the communication level has decreased within a predetermined number of frames after the up switching.
- the verification control unit 87 causes the mode setting unit 81 to shift to the trial mode based on the determination result.
- FIG. 24 is a diagram illustrating an operation procedure in the trial mode of the wireless communication system according to the third embodiment.
- trial control unit 86 sets the number of trials n to 1 (step S401).
- the trial control unit 86 sets the threshold values UPER1, UPER2, and UPER3 to any one of five stages out of the predetermined N stages (step S402).
- the trial control unit 86 sets the frame number f to 1 (step S403).
- the trial control unit 86 causes the radio base station 2 to execute steps S801 to S807 of FIG. 16 (step S404).
- the trial control unit 86 sets the user number i to 1 (step S405).
- the trial control unit 86 records the switching history of the user i in the switching history table as shown in FIGS. 20 and 21 (step S406).
- step S407 when the user number i is not equal to the total number of users in communication (NO in step S407), the trial control unit 86 increments the user number i by 1 (step S408), and proceeds to step S406. Return.
- the trial control unit 86 determines that the user number i is equal to the total number of users in communication (YES in step S407), and if the frame number f is not equal to the predetermined value FN1 (in step S409). NO), the frame number f is incremented by 1 (step S410), and the process returns to step S404. If the frame number f is equal to the predetermined value FN1 (YES in step S409), the process proceeds to step S411.
- step S411 the trial control unit 86 sets the user number i to 1 (step S411).
- the trial control unit 86 refers to the switching history table of the user i, calculates the success rate of switching up the communication level for the threshold values UPER1, UPER2, and UPER3 set in step S402, as shown in FIG. Record in the successful switching success rate table. Specifically, when the wireless terminal 3 of the user i is the first type wireless terminal, the trial control unit 86 determines the number of times that the communication level has been up-switched and the predetermined number of frames after the up-switching. Based on the number of times the communication level has been reduced, the success rate of up-switching at the threshold UPER1 is calculated.
- the trial control unit 86 performs the number of times of switching up the communication level other than up from A7 to B4 and after the switching up. Based on the number of times the communication level is lowered within the predetermined number of frames, the success rate of up-switching at the threshold value UPER2 is calculated, and the number of times the communication level is up-switched from A7 to B4 and the predetermined frame after the up-switching Based on the number of times the communication level falls within the number, the success rate of up-switching at the threshold value UPER3 is calculated (step S412).
- step S413 when the user number i is not equal to the total number of users in communication (NO in step S413), the trial control unit 86 increments the user number i by 1 (step S414), and proceeds to step S412. Return.
- the trial control unit 86 determines that the user number i is equal to the total number of users in communication (YES in step S413), and if the number of trials n is not equal to the predetermined value N (in step S415). NO), the number of trials n is incremented by 1 (step S416), and the process returns to step S402. If the number of trials n is equal to the predetermined value N (YES in step S415), the process proceeds to step S417.
- step S417 the trial control unit 86 sets the user number i to 1 (step S417).
- the trial control unit 86 refers to the user i switching success rate table and identifies the threshold value UPER1 or the threshold value UPER2 and the threshold value UPER3 of the user i such that the up switching success rate is Y (%) or more. Specifically, when the wireless terminal 3 of the user i is the first type wireless terminal, the trial control unit 86 specifies the threshold value UPER1 of the user i that causes the success rate of up switching to be Y (%) or more. To do. When the wireless terminal 3 of the user i is the second type wireless terminal, the trial control unit 86 specifies the threshold value UPER2 of the user i such that the success rate of up-switching with MATRIX maintenance is Y (%) or more. Then, the threshold value UPER3 of the user i is specified such that the success rate of up-switching in the MATRIX change is Y (%) or more (step S418).
- step S419 when the user number i is not equal to the total number of users in communication (NO in step S419), the trial control unit 86 increments the user number i by 1 (step S420), and proceeds to step S418. If the user number i is equal to the total number of users in communication (YES in step S419), the process ends.
- FIG. 25 is a diagram illustrating an operation procedure in the verification mode of the wireless communication system according to the third embodiment.
- verification control unit 87 sets frame number f to 1 (step S501).
- the verification control unit 87 causes the radio base station 2 to execute steps S801 to S807 in FIG. 16 (step S502).
- the verification control unit 87 sets the user number i to 1 (step S503).
- the verification control unit 87 records the switching history of the user i in the history table as shown in FIGS. 20 and 21 (step S504).
- step S505 when the user number i is not equal to the total number of users in communication (NO in step S505), the verification control unit 87 increments the user number i by 1 (step S506), and proceeds to step S504. Return.
- the verification control unit 87 refers to the switching history table of the user i, and calculates the switching success rate SR of the communication level up for all users with respect to the currently set thresholds UPER1, UPER2, and UPER3 (step S1). S509).
- the verification control unit 87 causes the mode setting unit 81 to set the trial mode and causes the radio base station 2 to The trial mode process of 24 steps S401 to S420 is performed (step S511).
- the verification control unit 87 ends.
- FIG. 26 is a diagram illustrating a configuration of a radio base station according to the fourth embodiment.
- radio base station 82 further includes table storage unit 5, received power difference detection unit 4, burst, And an allocating unit 6.
- the table storage unit 5 stores a first allocation table, a second allocation table, and an inspection table.
- FIG. 27 is a diagram illustrating an example of the first allocation table.
- the first allocation table includes a user number of a first type wireless terminal whose downlink MIMO scheme has been upgraded from MATRIX-A to MATRIX-B, and the user number down to the wireless terminal.
- the packet error rate PER of the link signal is determined.
- FIG. 28 is a diagram illustrating an example of the second allocation table.
- the second allocation table defines user numbers that are not registered in the first allocation table.
- FIG. 29 is a diagram illustrating an example of an inspection table.
- the inspection table includes subcarrier numbers Y to (Y + y-1) and symbols, with subcarrier number (Y) and symbol number (X), user data of subcarrier number x and symbol number y.
- the average spatial correlation coefficient (SP) of the sounding signals from the two antennas 50 and 51 of the wireless terminal 3 and the average value (RP) of the received power difference when assigned to the numbers X to (X + x ⁇ 1) are determined. .
- the total number of symbols in the downlink burst area is XSIZE and the total number of subcarriers is YSIZE. It is assumed that the number of user data symbols of user number j is x (j) and the number of subcarriers is y (j).
- the symbol number at the head of the user data allocation position is X, and the head subcarrier number is Y.
- X For each subcarrier number Y, one value of X where user data can be arranged is searched. The value of X is searched in the range of 1 to X ⁇ x (j) +1.
- an average spatial correlation coefficient SP and an average value RP of received power differences are detected in order to determine whether the position is appropriate.
- FIG. 31 is a flowchart showing an operation procedure of burst area allocation of the radio base station according to the fourth embodiment.
- step S601 the processes of steps S801 to S807 of FIG. 16 are performed.
- the burst allocation unit 6 Among the wireless terminals the user number of the wireless terminal using MATRIX-B is registered in the first allocation table together with the packet error rate PER of the downlink signal (step S603).
- the burst allocation unit 6 sorts the users in the first allocation table in ascending order of the packet error rate PER (step S604).
- the burst allocation unit 6 registers other users in communication that have not been registered in the first allocation table in the second allocation table (step S605).
- the burst allocation unit 6 releases the burst area of the downlink frame currently allocated to each user (step S606).
- the burst allocation unit 6 selects the users in the first allocation table one by one in the sorted order (that is, the order in which the packet error rate is small).
- the user number of the selected user is set to j (step S607).
- step S609 when there is an unselected user among the users in the first allocation table (NO in step S609), the burst allocation unit 6 returns to step S607.
- the burst allocation unit 6 allocates the user burst area in the second allocation table using proportional fairness. (Step S610).
- the burst allocation unit 6 sets the symbol number X to 1 (step S702).
- the burst allocator 6 assigns the user number j to the area specified by the subcarrier numbers Y to Y + y (j) -1 and the symbol numbers X to X + x (j) -1 in the burst area of the downlink frame. If data can be allocated, that is, if the specified area is unallocated and exists (YES in step S703), the sounding instruction unit 94 is instructed to sound the wireless terminal 3 with the user number j. An instruction to transmit a signal is transmitted (step S706).
- burst allocating section 6 gives correlation coefficient calculating section 93 2 of wireless terminal 3 of user number j in each subcarrier in the region of subcarrier number Y to subcarrier number Y + y (j) ⁇ 1.
- the spatial correlation coefficient of the sounding signals from the two antennas 50 and 51 is calculated, and further, the average spatial correlation coefficient SP is calculated by averaging the spatial correlation coefficient for all subcarriers included in the region (step). S707).
- the burst allocating unit 6 sends the received power difference detecting unit 4 to the two radio terminals 3 of the user number j in each subcarrier in the subcarrier number Y to subcarrier number Y + y (j) ⁇ 1 region.
- a difference in reception power of sounding signals from the antennas 50 and 51 is detected, and an average value RP of reception power differences obtained by averaging the reception power differences for all subcarriers included in the region is calculated (step S708). ).
- step S703 the burst allocation unit 6 If X is equal to or less than the value obtained by subtracting the number of symbols x (j) of the user data of user number j from the number of symbols XSIZE in the burst region of the downlink frame (NO in step S704), the symbol number X is incremented by one. Then (step S705), the process returns to step S702.
- the burst allocation unit 6 If X is larger than the value obtained by subtracting the number of symbols x (j) of the user data of user number j from the number of symbols XSIZE in the burst area of the downlink frame (YES in step S704), the subcarrier number Y It is determined that the user data of user number j cannot be allocated, and the process proceeds to step S710.
- step S710 the burst allocation unit 6 determines that the subcarrier number Y is equal to or smaller than the value obtained by subtracting the user data subcarrier number y (j) of the user number j from the subcarrier number YSIZE in the burst area of the downlink frame. (NO in step S710), the subcarrier number Y is incremented by 1 (step S711), and the process returns to step S702.
- step S710 When the subcarrier number Y is larger than the value obtained by subtracting the user data subcarrier number y (j) of the user number j from the subcarrier number YSIZE in the burst area of the downlink frame (step S710). YES), the process proceeds to the next step S712.
- the burst allocation unit 6 determines that the user data of the user number j cannot be allocated.
- the user j is registered in the second allocation table (step S713).
- the burst allocation unit 6 refers to the inspection table and checks whether one has the smallest average spatial correlation coefficient SP. .
- the burst allocation unit 6 has the smallest average spatial correlation coefficient SP and the received power difference
- the subcarrier number Y and the symbol number X that minimize the average value RP are specified (step S716).
- the burst allocation unit 6 allocates user j's user data to an area specified by subcarrier numbers Y to Y + y (j) and symbol numbers X to X + x (j) in the burst area of the downlink frame (step S717). ).
- a MATRIX-B radio single terminal is provided.
- the arrangement of user data in the downlink burst region is determined based on the spatial correlation coefficient of the sounding signal for each subcarrier transmitted from the two antennas of the wireless terminal and, if necessary, the received power difference.
- the radio base station side can transmit a spatially multiplexed downlink signal at an optimal frequency (subcarrier), so that high throughput characteristics, area characteristics, and frequency utilization efficiency can be achieved in the radio terminal. Can be obtained.
- Cooperative spatial multiplexing mode In the first embodiment of the present invention, two wireless terminals are set as one set of the cooperative spatial multiplexing mode, but the present invention is not limited to this. Three or more wireless terminals may be set as one set of the cooperative spatial multiplexing mode.
- the uplink signal of user data is transmitted by a communication method using a single antenna, except for the communication method by cooperative spatial multiplexing.
- the user data uplink signal may be transmitted by an STC-based communication method in addition to or instead of the communication method using a single antenna.
- the throughput calculation unit sets the difference in the received power of uplink signals from two wireless terminals in a pair of cooperative spatial multiplexing candidate pairs to 0 dB.
- the throughput is calculated when setting is possible, but the throughput may be calculated when the difference in received power is equal to or less than a predetermined value.
- the uplink of all the wireless terminals that are not currently set in the cooperative spatial multiplexing mode and that are among the wireless terminals that are the communication partners is set as the candidate terminal in the cooperative spatial multiplexing mode, the present invention is not limited to this.
- a wireless terminal that is not currently set to the cooperative spatial multiplexing mode may be selected as a candidate terminal from among a plurality of wireless terminals that are communication partners.
- the wireless terminal transmits an uplink signal from only one antenna, but the present invention is not limited to this.
- the radio terminal may transmit uplink signals from a plurality of antennas using an STC-based MIMO scheme and perform cooperative spatial multiplexing with other radio terminals.
- the reception response vectors of the sounding signals from the two wireless terminals and the spatial correlation coefficient are obtained.
- the sounding signal is an example of a known signal.
- a reception response vector of another type of known signal and a spatial correlation coefficient may be obtained.
- the up-switching success rate of all users is calculated in the flowchart of FIG.
- the up-switching success rate is calculated for each terminal) or for each user (wireless terminal) type, and when the up-switching success rate is less than a predetermined value, the user or the user type is set to the trial mode. It may be migrated.
- the threshold UPER1 of the packet error rate when increasing the communication level is set at any communication level.
- a different threshold value UPER1 may be used for each communication level.
- the packet error rate threshold value UPER2 when the communication level excluding the increase from A7 to B4 is increased is any communication level.
- the present invention is not limited to this.
- a different threshold value UPER2 may be used for each communication level.
- the up-switching success rate may be calculated for each communication level.
- the threshold values UPER1 and UPER2 for each communication level may be set based on the up-switching success rate for each communication level.
- the communication level for which the threshold values UPER1 and UPER2 need to be reset may be specified in the trial mode based on the up-switching success rate for each communication level.
- the packet error of the downlink signal is used as the communication quality of the downlink signal.
- the packet error rate is transmitted in the uplink frame from the wireless terminal to the wireless base station, but is not limited to this.
- calculating the rate at which NACK (Negative ACKnowledgement) signals are transmitted from radio terminals during automatic repeat request (ARQ) or hybrid automatic repeat request (HARQ) processing The same index value as the packet error rate of the downlink signal can be calculated.
- the reception response vector of the sounding signal from the two antennas of the wireless terminal and the spatial correlation coefficient are obtained. It is an example. A reception response vector of another type of known signal and a spatial correlation coefficient may be obtained.
- the first type wireless terminal may be a wireless terminal that can transmit known signals such as sounding signals from three or more wireless terminals at the same time or at different times, not from two antennas.
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Abstract
Description
[第1の実施形態]
(無線通信システムの構成)
図1は、本発明の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、本発明の実施形態の無線基地局の構成を表わす図である。
FFT部17は、CP除去部16から出力される時間領域の信号をFFTによって、周波数領域の信号に変換して、複数のサブキャリアに復調する。
符号化部43は、無線端末3へのダウンリンク信号を符号化する。
通信品質測定部28は、無線端末3からのアップリンク信号のパケットエラーレートを計測する。
図3を参照して、MCS切換えテーブルは、現状のMCS(変調方式および符号化率)と、MCSを1段階アップする場合のアップリンク信号のパケットエラーレートの閾値UP_TH、および1段階ダウンする場合のアップリンク信号のパケットエラーレートの閾値DN_THとの対応を定める。
モード設定部30は、通信相手のすべての無線端末3からのアップリンク信号のスループットに基づいて、2個の無線端末3を同一のアップリンクのデータバースト領域を共有して使用する協調型空間多重モード(Collaborative Spatial Multiplexing)に設定する。無線基地局2は、協調型空間多重モードに設定された2つの無線端末3からのアップリンク信号を、1つの無線端末3の2つのアンテナからの信号とみなして信号処理する。
X2(t)=h21×S1(t)+h22×S2(t)+N2(t) ・・・ (2)
ただし、N1(t)は、第1のアンテナ10で受信した受信信号X1(t)に含まれるノイズ成分であり、N2(t)は、第2のアンテナ11で受信した受信信号X2(t)に含まれるノイズ成分である。
H2=[h12,h22]T=[E[X1(t)U2*(t)], E[X2(t)U2*(t)]]T ・・・ (4)
ここで、U1(t)は、無線基地局2側で保持しているS1(t)と同一の信号であり、U2(t)は、無線基地局2側で保持しているS2(t)と同一の信号である。U1*(t)は、U1(t)の複素共役であり、U2*(t)は、U2(t)の複素共役である。E(X)は、Xのアンサンブル平均(時間平均)を表わす。
ここで、(X・Y)は、ベクトルXとベクトルYの内積を表わし、|X|は、ベクトルXの大きさを表わす。
図4を参照して、伝送データレートテーブルは、MCSと、1スロット当たりのデータレートとの対応を定める。たとえば、MCSが「QPSK 1/2」の場合の、1スロット当たりデータレートは、d1(bit)である。
図6は、ユーザAの無線端末3からのアップリンク信号とユーザBの無線端末3からのアップリンク信号が協調型空間多重された場合のスループットの例を説明するための図である。
テーブル作成部35は、協調型空間多重の候補ペアのうち、ペアの2つの無線端末3からのアップリンク信号の受信電力の差が0dBに設定可能(つまり、パワーコントロールが可能)であり、ペアの2つの無線端末3からのサウンディング信号の平均空間相関係数が所定の閾値未満であり、かつアップリンク信号が協調型空間多重した場合において通信相手のすべての無線端末3からのアップリング信号のスループットの和が増加するものについて、アップリンク信号が協調型空間多重した場合の、通信相手のすべての無線端末3からのアップリンク信号のスループットを合計した値A_SPを定めた協調型空間多重ペアテーブルを作成する。
図7を参照して、たとえば、ペア(A,B)のアップリンク信号が協調型空間多重した場合における、通信相手のすべての無線端末3からのアップリンク信号のスループットを合計した値A_SPは「SP1」となる。
図8は、本発明の実施形態の無線端末の構成を表わす図である。
送信部53は、サブキャリア配置部63と、IFFT部62と、CP付加部61と、RF部60とを備える。
IFFT部62は、サブキャリア配置部63から出力される複数のサブキャリア信号(周波数領域の信号)をIFFTによって、時間領域の信号(OFDMAシンボル)に変換する。
FFT部57は、CP除去部56から出力される時間領域の信号をFFTによって、周波数領域の信号に変換して、複数のサブキャリアに復調する。
符号化部73は、MCS設定部71で設定されたMCSの符号化レートに従って、無線基地局2へのアップリンク信号を符号化する。
復号部66は、復調されたダウンリンク信号を復号する。
制御部64は、バースト領域管理部68と、電力制御部69と、サウンディング信号出力部70と、MCS設定部71とを備える。
図9は、本発明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。この動作は、1個のOFDMAシンボルごとまたは一定数のOFDMAシンボルごとに行なわれる。
次に、候補選択部31は、ユーザiの無線端末3のMCSが通信相手のすべての無線端末3のアップリンク信号のMCSの中で最も伝送データレートの大きなものに対応し、かつユーザiの無線端末3が協調型空間多重モードに設定されていない場合には(ステップS107でYES)、ユーザiを協調型空間多重モードの候補端末に設定する(ステップS108)。
図10を参照して、テーブル作成部35は、協調型空間多重モードの候補端末からペア(X,Y)を設定する(ステップS201)。
以上のように、本発明の実施形態の無線通信システムによれば、無線基地局へのアップリンク信号を空間多重する無線端末の組合せをスループットに基づいて設定することによって、無線端末において高い受信性能を得ることができる。
第2~第4の実施形態では、図1の無線基地局2と、n個の無線端末3a~3nとの間は、時空間符号化方式(DL MIMO MATRIX-A)によるMIMO方式、または空間多重化方式(DL MIMO MATRIX-B)によるMIMO方式でユーザデータのダウンリンク信号が伝送される。
(無線基地局の構成)
図11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。
FFT部17は、CP除去部16から出力される時間領域の信号をFFTによって、周波数領域の信号に変換して、複数のサブキャリアに復調する。
符号化部43は、切替部95から指示されるMCSの符号化レートに従って、符号化されたダウンリンク信号を符号化する。
復号部26は、復調されたアップリンク信号を復号する。
制御部91は、通信品質管理部92と、相関係数算出部93と、サウンディング指示部94と、切替部95と、切替ルール記憶部96と、切替通知部97とを備える。
X2(t)=h21×S1(t)+h22×S2(t)+N2(t) ・・・ (9)
ただし、N1(t)は、無線基地局2の第1のアンテナ10で受信した受信信号X1(t)に含まれるノイズ成分であり、N2(t)は、無線基地局2の第2のアンテナ11で受信した受信信号X2(t)に含まれるノイズ成分である。
H2=[h12,h22]T=[E[X1(t)U2*(t)], E[X2(t)U2*(t)]]T ・・・ (11)
ここで、U1(t)は、無線基地局2側で保持しているS1(t)と同一の信号であり、U2(t)は、無線基地局2側で保持しているS2(t)と同一の信号である。U1*(t)は、U1(t)の複素共役であり、U2*(t)は、U2(t)の複素共役である。E(X)は、Xのアンサンブル平均(時間平均)を表わす。
ここで、(X・Y)は、ベクトルXとベクトルYの内積を表わし、|X|は、ベクトルXの大きさを表わす。
切替部95は、切替ルール記憶部96の通信レベル切替ルールにしたがって、無線端末3ごとに、ダウンリンク信号のMIMO方式とMCS(変調方式および符号化レート)とを切替える。
図12は、通信レベルテーブルの例を表わす図である。
図13は、第1タイプの無線端末における通信レベル切替ルールの一例を表わす図である。
図15は、第2の実施形態の無線端末の構成を表わす図である。
FFT部57は、CP除去部56から出力される時間領域の信号をFFTによって、周波数領域の信号に変換して、複数のサブキャリアに復調する。
符号化部73は、無線基地局2へのアップリンク信号を符号化する。
復調部65は、MCS管理部79で設定されるMCSの変調方式に従って、無線基地局2からのダウンリンク信号を復調する。
制御部8は、通信品質計測部75と、MCS管理部79と、MIMO管理部77と、サウンディング出力部76とを備える。
図16は、第2の実施形態における無線通信システムの1フレームごとの動作手順を表わすフローチャートである。
次に、切替部95は、ユーザ番号iの無線端末3が第1タイプの無線端末、すなわち2個のアンテナを用いたサウンディング信号の送信が可能な無線端末の場合には(ステップS803でYES)、第1タイプの無線端末の切替処理を行なう(ステップS804)。
図17は、図16のフローチャートのステップS804の動作の詳細な手順を表わすフローチャートである。
図18は、図16のフローチャートのステップS805の動作の詳細な手順を表わすフローチャートである。
以上のように、第2の実施形態の無線通信システムによれば、第1タイプの無線端末においては、ダウンリンク信号のパケットエラーレートと、無線端末の2つのアンテナからのサウンディング信号の空間相関係数に基づいて、ダウンリンク信号のMIMO方式を切替る。また、第2タイプの無線端末においては、MATRIXをアップさせるときのパケットエラーレートの閾値UPER3を、同一のMATRIXでMCSをアップさせるときのダウンリンク信号のパケットエラーレートの閾値UPER2よりも低く設定する(つまり、通信品質が良い方に設定する)。これによって、無線端末のサウンディング信号の送信機能に応じたルールによって、MATRIXをアップするようにしたので、無線端末において高いスループット特性やエリア特性、しいては周波数利用効率を得ることができる。
本発明の実施形態では、第1タイプのすべての無線端末について、閾値UPER1、USP、DSPの値は同一であり、第2タイプのすべての無線端末について、閾値UPER2、UPER3の値は同一であるとして説明したが、これに限定するものではない。無線端末ごと、あるいは無線端末の種類ごとに別個の閾値を用いることとしてもよい。無線端末の種類については、たとえば、受信時に用いるアンテナの数、送信時に用いるアンテナの数、無線端末の受信制御方式(アダプティブアレイ受信機能を有するか否か)などに基づいて設定できる。
第3の実施形態は、第2の実施形態で用いた閾値UPER1、UPER2、UPER3の値を学習によって適切に設定することのできる無線基地局に関する。
図19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。
(切替履歴テーブル)
図20は、第1タイプの無線端末の切替履歴テーブルの例を表わす図である。
図21を参照して、第2タイプの無線端末の切替履歴テーブルは、ユーザ番号と、切替えが行なわれたときのフレーム番号と、切替前の通信レベルと、切替え後の通信レベルとを定める。たとえば、ユーザ番号が「6」の無線端末については、第「15」フレームにおいて、通信レベルが「A3」から「A4」に切替わり、第「22」フレームにおいて、通信レベルが「A4」から「A3」に切替わったことが記録されている。
図22は、第1タイプの無線端末の切替え成功率テーブルの例を表わす図である。
図23を参照して、第2タイプの無線端末の切替え成功率テーブルは、ユーザ番号と、閾値UPER2に対応するアップ切替え成功率、閾値UPER3に対応するアップ切替え成功率を定める。たとえば、ユーザ番号が「6」の無線端末について、閾値UPER2が「0.8(%)」の下では、MATRIXの変更のないアップ切替え成功率が「97(%)」であり、閾値UPER3が「0.3(%)」の下では、MATRIXの変更を伴うアップ切替え成功率が「95(%)」である。この値は、図21のユーザ番号が「6」の第2タイプの無線端末の切替履歴テーブルに基づいて算出される。
図24は、第3の実施形態の無線通信システムのトライアルモードにおける動作手順を表わす図である。
次に、トライアル制御部86は、図20および図21に示すような切替履歴テーブルにユーザiの切替え履歴を記録する(ステップS406)。
図25は、第3の実施形態の無線通信システムの検証モードにおける動作手順を表わす図である。
次に、検証制御部87は、図20および図21に示すような履歴テーブルにユーザiの切替え履歴を記録する(ステップS504)。
以上のように、第3の実施形態の無線通信システムによれば、トライアルモードおよび検証モードによって、通信レベルをアップするときのパケットエラーレートの閾値を無線端末ごとに適切な値に調整することができる。
第4の実施形態は、ダウンリンクのMIMO方式がMATRIX-Bに変更される無線端末があった場合に、MATRIX-Bの無線端末のユーザデータのデータバースト領域を適切に変更することのできる無線基地局に関する。これは、MATRIX-BのMIMO方式では、どのデータバースト領域にユーザデータを割当てるかによって、無線端末のスループット特性やエリア特性、しいては周波数利用効率が変化するからである。一方、MATRIX-AのMIMO方式では、ユーザデータをどのデータバースト領域に割当てても、無線端末のスループット特性やエリア特性、しいては周波数利用効率は大きくは変化しない。
図26は、第4の実施形態の無線基地局の構成を表わす図である。
図27は、第1の割当テーブルの例を表わす図である。
図28を参照して、第2の割当テーブルは、第1割当テーブルに登録されていないユーザ番号を定める。
図29は、検査用テーブルの例を表わす図である。
図30は、ダウンリンクバースト領域内のユーザデータの割当位置を決定する過程を説明するための図である。
図31は、第4の実施形態の無線基地局のバースト領域の割当ての動作手順を表わすフローチャートである。
次に、バースト割当部6は、ダウンリンクフレームのバースト領域における、サブキャリア番号Y~Y+y(j)-1、シンボル番号X~X+x(j)-1で特定される領域にユーザ番号jのユーザデータが割当て可能な場合、つまり、この特定された領域が未割り当てで、かつ存在する場合には(ステップS703でYES)、サウンディング指示部94を指示して、ユーザ番号jの無線端末3へサウンディング信号を送信させる指示を送信させる(ステップS706)。
以上のように、第4の実施形態の無線通信システムによれば、ダウンリンクのMIMO方式がMATRIX-Bに変更される第1タイプの無線端末があった場合に、MATRIX-Bの無線単端末について、その無線端末の2つのアンテナから送信されるサブキャリアごとのサウンディング信号の空間相関係数と、必要に応じて受信電力差に基づいて、ダウンリンクバースト領域内のユーザデータの配置を決める。これによって、無線基地局側は、最適な周波数(サブキャリア)で、空間多重化されたダウンリンク信号を送信することができるので、無線端末において高いスループット特性やエリア特性、しいては周波数利用効率を得ることができる。
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。
本発明の第1の実施形態では、2個の無線端末を協調型空間多重モードの1セットとして設定したが、これに限定するものではない。3個以上の無線端末を協調型空間多重モードの1セットとして設定することとしてもよい。
本発明の第1の実施形態では、ユーザデータのアップリンク信号は、協調型空間多重による通信方式以外では、単一アンテナを用いた通信方式で伝送されるものとしたが、これに限定するものではない。ユーザデータのアップリンク信号は、単一アンテナを用いた通信方式に加えて、またはこれに代えてSTCベースによる通信方式で伝送されるものとしてもよい。
本発明の第1の実施形態では、スループット算出部は、協調型空間多重の候補ペアのうち、ペアの2つの無線端末からのアップリンク信号の受信電力の差が0dBに設定可能な場合に、スループットを算出したが、受信電力の差が所定値以下の場合に、スループットを算出することとしてもよい。
本発明の第1の実施形態では、通信相手のすべての無線端末の中から、現在協調型空間多重モードに設定されておらず、かつ通信相手のすべての無線端末のアップリンク信号のMCSの中で最も伝送データレートの大きなMCSを有する無線端末を協調型空間多重モードの候補端末に設定したが、これに限定するものではない。たとえば、通信相手のすべての複数の無線端末の中から、現在協調型空間多重モードに設定されていない無線端末を候補端末としてもよい。
本発明の第1の実施形態では、図10のステップS208において、平均空間相関係数M_SRが閾値TH2(TH1<TH2)未満の場合には、アップリンク信号を協調型空間多重する場合のユーザXの無線端末のMCSを協調型空間多重しない場合のユーザXの無線端末のMCSよりも1レベルだけダウンしたMCSに仮設定し、アップリンク信号を協調型空間多重する場合のユーザYの無線端末のMCSを協調型空間多重しない場合のユーザYの無線端末のMCSよりも1レベルだけダウンしたMCSに仮設定したが、これに限定するものではなく、ダウンさせるMCSのレベル数は2、3など所定数であってもよい。
本発明の第1の実施形態で説明した式(1)~(4)の受信応答ベクトルの算出方法、式(5)の空間相関係数の算出方法は、一例であって、他の方法で算出することととしてもよい。
本発明の第1の実施形態では、無線端末は、1つのアンテナからのみアップリンク信号を送信するものとしたが、これに限定するものではない。無線端末は、複数のアンテナからSTCベースなどのMIMO方式でアップリンク信号を送信するとともに、他の無線端末との間で協調型空間多重を行なえるものであってもよい。
本発明の第1の実施形態では、2つの無線端末からのサウンディング信号の受信応答ベクトル、および空間相関係数を求めたが、サウンディング信号は、既知信号の一例である。別の種類の既知信号の受信応答ベクトル、および空間相関係数を求めることとしてもよい。
本発明の第1の実施形態では、図6で説明したように、ユーザAの無線端末3からのアップリンク信号とユーザBの無線端末3からのアップリンク信号が協調型空間多重した場合には、ユーザAの無線端末3およびユーザBの無線端末3は、協調型空間多重しない場合にユーザAの無線端末3に割当てられたデータバースト領域151、および協調型空間多重しない場合にユーザBの無線端末3に割当てられたデータバースト領域152を用いてユーザデータを送信することとしたが、これに限定するものではない。
本発明の第3の実施形態では、図25のフローチャートにおいて、全ユーザ(通信中の全無線端末)のアップ切替え成功率を計算したが、ユーザ(無線端末)ごとに、またはユーザ(無線端末)の種別ごとに、アップ切替え成功率を計算し、アップ切替え成功率が所定値未満の場合に、そのユーザ、またはそのユーザの種別に対してトライアルモードに移行させることとしてもよい。
本発明の第2~第4の実施形態では、第1タイプの無線端末について、通信レベルをアップするときのパケットエラーレートの閾値UPER1は、どの通信レベルにおいても同一としたが、これに限定するものではない。通信レベルごとに異なる閾値UPER1を用いることとしてもよい。
本発明の第2~第4の実施形態では、ダウンリンク信号の通信品質として、ダウンリンク信号のパケットエラーを用いた。そして、このパケットエラーレートは、無線端末から無線基地局へアップリンクフレームにおいて伝送されることとしたが、これに限定するものではない。無線基地局側で、自動再送要求(Automatic Repeat Request: ARQ)やハイブリッド自動
再送要求(Hybrid Automatic Repeat Request: HARQ)処理時のNACK(Negative ACKnowledgement)信号が無線端末から伝送される割合を算出することによっても、ダウンリンク信号のパケットエラーレートと同様の指標値が算出できる。
本発明の第2~第4の実施形態では、無線端末の2つのアンテナからのサウンディング信号の受信応答ベクトル、および空間相関係数を求めたが、サウンディング信号は、既知信号の一例である。別の種類の既知信号の受信応答ベクトル、および空間相関係数を求めることとしてもよい。また、第1タイプの無線端末は、2個のアンテナからではなく、3個以上の無線端末からサウンディング信号などの既知信号を互いに同時または別時刻で送信できる無線端末であるとしてもよい。
Claims (20)
- アップリンク信号を送信する複数の無線端末と通信する無線基地局であって、
複数のアンテナと、
複数の無線端末からのアップリンク信号のスループットに基づいて、2個以上の無線端末を同一のアップリンクのデータバースト領域を共有して使用する協調型空間多重モードに設定するモード設定部と、
前記協調型空間多重モードに設定された2個以上の無線端末に対して、前記2個以上の無線端末間で共通して使用するアップリンクのデータバースト領域を通知する領域通知部と、
前記複数のアンテナで受信した、前記協調型空間多重モードに設定された2個以上の無線端末からの前記共通のアップリンクのデータバースト領域で空間多重化されたアップリンク信号を分離して、各無線端末からの信号を取り出す受信部とを備えた無線基地局。 - 前記モード設定部は、
複数の無線端末のうちの協調型空間多重モードに設定する候補となる候補端末を選択する候補選択部と、
前記選択された候補端末からペアを作成して、前記ペアの無線端末が協調型空間多重モードに設定された場合の、通信相手のすべての無線端末からのアップリンク信号のスループットの和を算出するスループット算出部と、
前記協調型空間多重モードに設定された場合の前記算出されたスループットの和が最大となるペアを特定し、前記特定したペアの無線端末を協調型空間多重モードに設定する端末設定部とを含む、請求の範囲1記載の無線基地局。 - 前記モード設定部は、
複数の無線端末のうちの協調型空間多重モードに設定する候補となる候補端末を選択する候補選択部と、
前記選択された候補端末からペアを作成して、前記ペアの無線端末のアップリンク信号の受信電力の差が所定値以下となるように、前記ペアの両方またはいずれかに送信電力を調整するように指示する電力制御部と、
前記送信電力の調整を指示した後における、前記ペアの無線端末のアップリンク信号の受信電力の差を計測する電力差計測部と、
前記受信電力の差が前記所定値以下のペアの無線端末が協調型空間多重モードに設定された場合における、通信相手のすべての無線端末からのアップリンク信号のスループットの和を算出するスループット算出部と、
前記協調型空間多重モードに設定された場合の前記算出されたスループットの和が最大となるペアを特定し、前記特定したペアの無線端末を協調型空間多重モードに設定する端末設定部とを含む、請求の範囲1記載の無線基地局。 - 前記ペアの無線端末からの既知信号の空間相関係数を算出する相関係数算出部を備え、
前記スループット算出部は、前記空間相関係数に基づいて前記ペアの無線端末のアップリンク信号を空間多重化させた場合のMCS(変調方式および符号化レート)を特定し、前記特定したMCSに基づいて、前記ペアの2つの無線端末からのアップリンク信号のスループットを算出する、請求の範囲3記載の無線基地局。 - 前記モード設定部は、
複数の無線端末のうちの協調型空間多重モードに設定する候補となる候補端末を選択する候補選択部と、
前記選択された候補端末からペアを作成して、前記ペアの無線端末からの既知信号の空間相関係数を算出する相関係数算出部と、
前記空間相関係数が第1の閾値未満のペアの2つの無線端末が協調型空間多重モードに設定された場合における、通信相手のすべての無線端末からのアップリンク信号のスループットの和を算出するスループット算出部と、
前記協調型空間多重モードに設定された場合の前記算出されたスループットの和が最大となるペアを特定し、前記特定したペアの無線端末を協調型空間多重モードに設定する端末設定部とを含む、請求の範囲1記載の無線基地局。 - 前記スループット算出部は、前記空間相関係数が第2の閾値以上、前記第1の閾値未満のペアの無線端末からのアップリンク信号のMCSを前記協調型空間多重モードに設定しない場合のMCSよりも所定レベル数減少させた場合における、前記ペアの無線端末からのアップリンク信号のスループットを算出し、前記空間相関係数が前記第2の閾値未満のペアの無線端末からのアップリンク信号のMCSを前記協調型空間多重モードに設定しない場合のMCSと一致させた場合における、前記ペアの無線端末からのアップリンク信号のスループットを算出する、請求の範囲5記載の無線基地局。
- 前記無線基地局は、さらに、
前記協調型空間多重モードに設定された無線端末からのアップリンク信号のMCSを前記スループット算出に用いたMCSに設定するMCS設定部と、
前記設定したMCSを前記協調型空間多重モードの無線端末に通知するMCS通知部とを含む、請求の範囲6記載の無線基地局。 - 前記無線基地局は、さらに、
前記無線端末からのアップリンク信号の通信品質を測定する通信品質測定部を備え、
前記MCS設定部は、さらに、前記無線端末からのアップリンク信号の通信品質に基づいて、前記無線端末からのアップリンク信号のMCSを設定する、請求の範囲7記載の無線基地局。 - 前記無線基地局は、さらに、
前記無線端末からのアップリンク信号の通信品質を測定する通信品質測定部と、
前記無線端末からのアップリンク信号の通信品質に基づいて、前記無線端末からのアップリンク信号のMCSを設定するMCS設定部を含む、請求の範囲6に記載の無線基地局。 - 前記候補選択部は、通信相手のすべての無線端末のアップリンク信号のMCSの中で最も伝送データレートの高いMCSを特定し、前記特定したMCSを有する複数の無線端末の中から前記候補端末を選択する、請求の範囲9記載の無線基地局。
- 前記候補選択部は、通信相手のすべての無線端末のうち、現在協調型空間多重モードに設定されていない無線端末を前記候補端末として選択する、請求の範囲5に記載の無線基地局。
- 前記スループット算出部は、さらに、前記候補端末を協調型空間多重モードに設定しない場合における、通信相手のすべての無線端末からのアップリンク信号のスループットの和を算出し、
前記端末設定部は、前記協調型空間多重モードに設定された場合における、すべての無線端末からのアップリンク信号のスループットの和が最大となるペアの無線端末について、協調型空間多重モードに設定した場合の方が設定しない場合よりも、通信相手のすべての無線端末からのアップリンク信号のスループットの和が大きい場合にのみ、協調型空間多重モードに設定する、請求の範囲5記載の無線基地局。 - 複数のアンテナを通じて、ダウンリンク信号を無線端末へ送信する無線基地局であって、
複数のアンテナと、
無線端末でのダウンリンク信号の通信品質を取得または算出する品質管理部と、
前記無線端末の複数のアンテナからの既知信号の空間相関係数を算出する相関算出部と、
時空間符号化方式から空間多重方式へ、または前記空間多重方式から前記時空間符号化方式へ、前記ダウンリンク信号のMIMO方式の設定を切替える切替部と、
前記設定されたMIMO方式が前記時空間符号化方式の場合に、1つのデータストリームを時空間符号化して前記複数のアンテナへ出力し、前記設定されたMIMO方式が前記空間多重方式の場合に、複数のデータストリームを空間多重化して前記複数のアンテナへ出力する送信部とを備え、
前記切替部は、複数のアンテナから既知信号を送信する第1タイプの無線端末については、前記通信品質および前記空間相関係数が所定の条件を満たすときに、前記ダウンリンク信号のMIMO方式を前記時空間符号化方式から前記空間多重方式へ切替える、無線基地局。 - 前記無線基地局は、さらに、
無線基地局から送信されるダウンリンクフレームのデータバースト領域におけるユーザデータの配置を決めるバースト割当部を備え、
前記バースト割当部は、前記切替部によって前記ダウンリンク信号のMIMO方式が前記空間多重方式に変更された無線端末がある場合に、前記第1タイプの無線端末のうち前記ダウンリンク信号のMIMO方式が前記空間多重方式である無線端末について、前記無線端末の複数のアンテナから送信される既知信号の空間相関係数に基づいて、前記データバースト領域内のユーザデータの配置を決める、請求の範囲13記載の無線基地局。 - 前記ダウンリンク信号のMIMO方式を前記時空間符号化方式から前記空間多重方式へ切替えるときの前記条件は、無線端末ごとに別個に定められている、請求の範囲13記載の無線基地局。
- 前記無線基地局は、さらに、
所定のタイミングで無線通信のモードを通常モードからトライアルモードに設定するモード設定部と、
前記トライアルモードにおいて、前記ダウンリンク信号のMIMO方式を前記時空間符号化方式から前記空間多重方式へ切替える際の前記通信品質の条件を変化させて、前記変化させた通信品質の条件に基づいて、前記ダウンリンク信号のMIMO方式を前記時空間符号化方式から前記空間多重方式へ切替えさせ、前記空間多重方式への切替え後に、一定期間前記空間多重方式を維持しているかに基づいて切替えが成功したか否かを判定するトライアル制御部とを備え、
前記トライアル制御部は、前記判定の結果に基づいて、前記通常モードで使用する前記通信品質の条件を設定する、請求の範囲13記載の無線基地局。 - 前記モード設定部は、所定のタイミングで、前記無線通信のモードを通常モードから検証モードに設定し、
前記検証モードにおいて、前記通常モードで設定されている前記ダウンリンク信号のMIMO方式を前記時空間符号化方式から前記空間多重方式へ切替える際の前記通信品質の条件に基づいて、前記ダウンリンク信号のMIMO方式を前記時空間符号化方式から前記空間多重方式へ切替えさせ、前記空間多重方式への切替え後に、一定期間前記空間多重方式を維持しているかに基づいて切替えが成功したか否かを判定する検証制御部とを備え、
前記検証制御部は、前記判定の結果に基づいて、前記モード設定部にトライアルモードに移行させる、請求の範囲16記載の無線基地局。 - 複数のアンテナを通じて、ダウンリンク信号を無線端末へ送信する無線基地局であって、
複数のアンテナと、
無線端末でのダウンリンク信号の通信品質を取得または算出する品質管理部と、
時空間符号化方式から空間多重方式へ、または前記空間多重方式から前記時空間符号化方式へ、前記ダウンリンク信号のMIMO方式の設定を切替える切替部と、
前記設定されたMIMO方式が前記時空間符号化方式の場合に、1つのデータストリームを時空間符号化して前記複数のアンテナへ出力し、前記設定されたMIMO方式が前記空間多重方式の場合に、複数のデータストリームを空間多重化して前記複数のアンテナへ出力する送信部とを備え、
前記切替部は、複数のアンテナから既知信号を送信する第1タイプの無線端末以外の無線端末については、同一のMIMO方式でMCS(変調方式および符号化レート)を1段階アップするときの通信品質についての条件よりも、より高い通信品質についての条件が満たされたときに、前記ダウンリンク信号のMIMO方式を前記時空間符号化方式から前記空間多重方式へ切替える、無線基地局。 - 前記無線基地局は、さらに、
所定のタイミングで無線通信のモードを通常モードからトライアルモードに設定するモード設定部と、
前記トライアルモードにおいて、前記ダウンリンク信号のMIMO方式を前記時空間符号化方式から前記空間多重方式へ切替える際の前記通信品質の条件を変化させて、前記変化させた通信品質の条件に基づいて、前記ダウンリンク信号のMIMO方式を前記時空間符号化方式から前記空間多重方式へ切替えさせ、前記空間多重方式への切替え後に、一定期間前記空間多重方式を維持しているかに基づいて切替えが成功したか否かを判定するトライアル制御部とを備え、
前記トライアル制御部は、前記判定の結果に基づいて、前記通常モードで使用する前記通信品質の条件を設定する、請求の範囲18記載の無線基地局。 - 前記モード設定部は、所定のタイミングで、前記無線通信のモードを通常モードから検証モードに設定し、
前記検証モードにおいて、前記通常モードで設定されている前記ダウンリンク信号のMIMO方式を前記時空間符号化方式から前記空間多重方式へ切替える際の前記通信品質の条件に基づいて、前記ダウンリンク信号のMIMO方式を前記時空間符号化方式から前記空間多重方式へ切替えさせ、前記空間多重方式への切替え後に、一定期間前記空間多重方式を維持しているかに基づいて切替えが成功したか否かを判定する検証制御部とを備え、
前記検証制御部は、前記判定の結果に基づいて、前記モード設定部にトライアルモードに移行させる、請求の範囲19記載の無線基地局。
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CN105406905B (zh) * | 2014-09-10 | 2019-11-29 | 南京中兴新软件有限责任公司 | 用户配对处理方法、装置及基站 |
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CN107666712B (zh) * | 2016-07-27 | 2020-04-24 | 中国移动通信有限公司研究院 | 一种上行传输方法及设备 |
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US11297509B2 (en) * | 2017-01-27 | 2022-04-05 | Nippon Telegraph And Telephone Corporation | Wireless communication system and wireless communication method |
CN113595686B (zh) * | 2021-07-28 | 2023-09-01 | 广州海格通信集团股份有限公司 | 一种短波通信数传方法及其系统 |
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