JP2014165611A - Radio communication system and communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress generation of degradation in a transmission characteristic caused by unsuitable coordination as well as degradation in a coordination effect, in a communication system by the coordination of a plurality of transmission stations or a plurality of reception stations.SOLUTION: The communication system, performing concurrent coordination transmission of signals by a plurality of transmission station devices using the same frequency for a plurality of reception station devices, includes a measurement section that measures a characteristic between the reception station device and the respective transmission station devices, and a control section that determines the transmission station device satisfying conditions on the basis of a measurement result by the measurement section and, when the number of the transmission station devices satisfying conditions is plural, controls the plurality of transmission devices to perform coordination transmission for the reception station devices.

Description

  The present invention relates to a technique in which a plurality of transmitting stations or a plurality of receiving stations perform communication in cooperation.

  With an increase in the number of wireless communication terminals and an increase in the capacity of content handled in the terminals, it is required to improve the transmission speed of wireless communication and improve communication quality. As a technique for solving the problem, a multi-station cooperative communication technique and system in which a plurality of transmitting stations and receiving stations perform communication in cooperation have been studied.

  As a cooperation method of multiple stations, for example, in downlink transmission, beam processing or baseband processing is performed by performing signal processing in cooperation with each base station from simple multi-station transmission diversity in which each base station transmits the same signal. Wide cooperation such as precoding has been studied (see Non-Patent Documents 1 and 2). What is important when these base station cooperations are performed is the time between the base stations, the synchronization accuracy such as the oscillation frequency, and the propagation path state between the base stations and the terminal stations. If a base station with low synchronization accuracy is included in the cooperating base stations, it is conceivable that not only the cooperation effect is degraded, but also the transmission characteristics are degraded in some cases. In addition, it is considered that transmission characteristics can be improved by performing base station cooperation adaptively according to the situation, such as excluding a base station whose propagation path state with a terminal station has deteriorated from the cooperation.

A. Dammann and S. Kaiser, “Standard conformable antenna diversity techniques for OFDM systems and its application to the DVB-T system,” in Proc. IEEE Globecom 2001, pp. 3100-3105. Yusuke Asai, Takeshi Onizawa, Takeo Ichikawa, Hayato Mizoguchi, "Application of cyclic shift delay in MIMO-OFDM multi-station transmission diversity", IEICE Society Conference, B-5-120, September 2007

  FIG. 19 is a block diagram showing an example of conventional multi-station cooperative transmission. Base stations 101, 102, and 103 are connected to the network 1000 by wire. The base stations 101, 102, and 103 perform wireless communication by cooperative diversity with respect to the terminal stations 201 and 202 that are terminal stations under the base station group. At this time, the base stations 101, 102, and 103 always perform cooperative transmission regardless of the state of the propagation path between each base station and the terminal station and the synchronization accuracy such as the time or frequency between the base stations.

  Thus, in the conventional multi-base station cooperative transmission, the propagation path state between the base stations 101, 102, 103 and the terminal stations 201, 202, the time and frequency synchronization accuracy in each base station 101, 102, 103, etc. Regardless, a certain range of base stations always cooperated to transmit. Therefore, for example, when the distance between the terminal stations 201 and 202 and the base stations 101, 102, and 103 is widened and the received power at the terminal station is reduced, or when the synchronization accuracy is increased in the linked base stations 101, 102, and 103. Even in the case where a low base station is included, even if the effect of the cooperative transmission of the base stations 101, 102, 103 is deteriorated, the transmission is continued, and the transmission power of the entire system is increased, but the transmission characteristics are improved. There is a problem that the width becomes small or the transmission characteristics deteriorate.

  In view of the above circumstances, the present invention provides a technique for suppressing deterioration of the cooperation effect by suppressing deterioration of transmission characteristics due to incompatible cooperation in a system in which a plurality of transmitting stations or a plurality of receiving stations communicate in cooperation. It is an object.

  One aspect of the present invention is a communication system in which a plurality of transmitting station devices simultaneously transmit signals to a receiving station device using the same frequency, and the transmission station device is provided between the receiving station device and each transmitting station device. A measuring unit that measures characteristics and a transmitting station device that satisfies a condition based on a measurement result in the measuring unit are determined, and when there are a plurality of transmitting station devices that satisfy the condition, cooperative transmission to the receiving station device is performed. And a control unit that controls a plurality of the transmitting station devices to perform the wireless communication system.

  One aspect of the present invention is the above-described wireless communication system, wherein the measurement unit obtains at least one value of a reception intensity, a frequency offset, and a time offset between each receiving station apparatus and each transmitting station apparatus. Measure as a characteristic.

  One aspect of the present invention is the above wireless communication system, wherein the control unit controls the plurality of transmission station apparatuses to use different cyclic shift amounts when there are a plurality of transmission station apparatuses that satisfy the condition. To do.

  One aspect of the present invention is a communication system in which a plurality of receiving station apparatuses simultaneously receive signals from a transmitting station apparatus using the same frequency, and the characteristics between the transmitting station apparatus and each receiving station apparatus are Based on the measurement unit to be measured and the reception station device that satisfies the condition based on the measurement result in the measurement unit, and when there are a plurality of reception station devices that satisfy the condition, cooperative reception from the transmission station device is performed. And a control unit that controls a plurality of the receiving station devices.

  One aspect of the present invention is the above-described wireless communication system, wherein the measurement unit obtains at least one value of reception intensity, frequency offset, and time offset between each transmitting station apparatus and each receiving station apparatus. Measure as a characteristic.

  One aspect of the present invention is the above wireless communication system, in which the control unit receives a reception process based on maximum ratio combining in cooperation with the plurality of receiving station apparatuses when there are a plurality of receiving station apparatuses that satisfy the condition. Control to do.

  One aspect of the present invention is a communication method performed by a communication system in which a plurality of transmitting station apparatuses simultaneously transmit signals to a receiving station apparatus using the same frequency, and the receiving station apparatus and each transmitting station apparatus A measurement step for measuring the characteristics between the transmission station device and the transmission station device satisfying the condition based on the measurement result, and when there are a plurality of transmission station devices satisfying the condition, cooperative transmission to the reception station device is performed. And a control step of controlling a plurality of the transmitting station devices so as to be performed.

  One aspect of the present invention is a communication method performed by a communication system in which a plurality of receiving station apparatuses simultaneously receive signals from a transmitting station apparatus using the same frequency, and the transmission station apparatus and each receiving station apparatus A measuring step for measuring a characteristic between the receiving station apparatus and a receiving station apparatus satisfying the condition based on the measurement result, and when there are a plurality of receiving station apparatuses satisfying the condition, cooperative reception from the transmitting station apparatus is performed. And a control step for controlling a plurality of the receiving station devices.

  According to the present invention, in a method in which a plurality of transmitting stations or a plurality of receiving stations communicate in cooperation, it is possible to suppress deterioration in transmission characteristics due to incompatible cooperation and to suppress a decrease in cooperation effect.

It is a block diagram which shows the structural example of the radio | wireless communications system by 1st Embodiment. It is a schematic block diagram which shows the internal structure of the base station 1001 in 1st Embodiment. It is a schematic block diagram which shows the internal structure of the terminal station 2001 in 1st Embodiment. It is a frame sequence figure which shows an example of the communication procedure in 1st Embodiment. It is a flowchart which shows the example of a process sequence in which the terminal station 2001 of 1st Embodiment feeds back to each base station. It is a schematic block diagram which shows the internal structure of the base station 1101 in 2nd Embodiment. It is a schematic block diagram which shows the internal structure of the terminal station 2101 in 2nd Embodiment. It is a frame sequence figure showing a communication procedure in a 2nd embodiment. It is a flowchart which shows the example of a process sequence in which the base station 1101 of 2nd Embodiment performs base station cooperation transmission. It is a block diagram which shows the structural example of the radio | wireless communications system by 3rd Embodiment. It is a schematic block diagram which shows the internal structure of the base station 1201 in 3rd Embodiment. It is a schematic block diagram which shows the internal structure of the terminal station 2201 in 3rd Embodiment. It is a frame sequence figure showing an example of a communication procedure in a 3rd embodiment. It is a flowchart which shows the example of a process sequence in which the terminal station 2201 of 3rd Embodiment outputs a feedback signal. It is a schematic block diagram which shows the internal structure of the base station 1301 in 4th Embodiment. It is a schematic block diagram which shows the internal structure of the terminal station 2301 in 4th Embodiment. It is a frame sequence diagram which shows the communication procedure in 4th Embodiment. It is a flowchart which shows the example of a process sequence which the base station 1301 of 4th Embodiment performs a maximum ratio synthetic | combination reception process. It is a block diagram which shows an example of the multi-station cooperation transmission of a prior art.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
A. First Embodiment FIG. 1 is a block diagram showing a configuration example of a wireless communication system according to a first embodiment of the present invention. In FIG. 1, the wireless communication system according to the first embodiment includes three base stations 1001, 1002, and 1003 as transmitting station devices connected to a network 1000 by wire, and receiving station devices that wirelessly communicate with the transmitting station device. Two terminal stations 2001 and 2002 are provided. The base stations 1001, 1002, and 1003 perform data downlink transmission to the terminal stations 2001 and 2002 under the base station using the same frequency. That is, base stations 1001 to 1003 transmit data signals to terminal stations 2001 and 2002 under their common subordinates (in the cell).

  In the illustrated example, the configuration includes three base stations 1001, 1002, and 1003 and two terminal stations 2001 and 2002 connected to the network 1000. However, the configuration is not limited thereto, and a plurality of base stations and a plurality of terminals are used. It may consist of stations.

  For simplicity of explanation, the number of antenna elements of each of the base stations 1001 to 1003 is A (A ≧ 1, A is an integer), and the number of antenna elements of the terminal stations 2001 and 2002 is B (B ≧ 1). , B are integers). However, the present embodiment is applicable even when there are two or more base stations and one or more terminal stations, and the number of antenna elements of the base station and the number of antenna elements of the terminal station are different. Also good.

In the first embodiment, first, the base station 1001 wirelessly transmits a known signal frame (hereinafter referred to as “sounding frame”) to the terminal stations 2001 and 2002. The sounding frame is a signal for measuring an RSSI (received signal strength indication) value, a time offset value, and a frequency offset value between the base station and the terminal station group.
The terminal stations 2001 and 2002 measure the RSSI value, the time offset value, and the frequency offset value between the base station 1001 and the terminal station using the sounding frame received from the base station 1001. However, when the sounding frame cannot be received from the base station 1001, the terminal stations 2001 and 2002 hold values indicating that measurement is impossible as the RSSI value, the time offset value, and the frequency offset value with the base station 1001.

  Similar to the base station 1001, the base station 1002 wirelessly transmits a sounding frame to the terminal stations 2001 and 2002. The terminal stations 2001 and 2002 measure the RSSI value, the time offset value, and the frequency offset value between the base station 1002 and the terminal station using the sounding frame received from the base station 1002. However, when the sounding frame cannot be received from the base station 1002, the terminal stations 2001 and 2002 hold values indicating that measurement is impossible as the RSSI value, the time offset value, and the frequency offset value with the base station 1002.

  Similar to the base station 1001, the base station 1003 wirelessly transmits a sounding frame to the terminal stations 2001 and 2002. The terminal stations 2001 and 2002 measure the RSSI value, the time offset value, and the frequency offset value between the base station 1003 and the terminal station using the sounding frame received from the base station 1003. However, when the sounding frame cannot be received from the base station 1003, the terminal stations 2001 and 2002 hold values indicating that measurement is impossible as the RSSI value, the time offset value, and the frequency offset value with the base station 1003.

  Thereafter, the terminal stations 2001 and 2002 wirelessly transmit feedback signals to the base stations 1001 to 1003, respectively. The feedback signal includes the acquired RSSI values between the base stations 1001 to 1003, the time offset values of the base stations 1001 to 1003, and the frequency offset values of the base stations 1001 to 1003.

  The base stations 1001 to 1003 use the RSSI value, the time offset value, and the frequency offset value fed back from the terminal stations 2001 and 2002 to determine whether or not the base station performs base station cooperative transmission to each terminal station. And the parameters of the own base station at the time of cooperative transmission are set.

  In the first embodiment, if the RSSI value is acquired from the terminal stations 2001 and 2002 as the parameters of the own base station set by the base stations 1001, 1002 and 1003, the transmission power of the own base station is calculated based on the RSSI value. If the time offset value is acquired from the terminal stations 2001 and 2002, the transmission timing of the base station is determined based on the time offset value. For example, if the RSSI value of the sounding frame received by the terminal stations 2001 and 2002 is sufficiently large and the required SNR (signal-to-noise power ratio) is considered to be sufficiently satisfied, the base station Reduce the transmission power. Also, if there is a time offset value for the time of the base station whose own base station time is 2001, 2002, or the base station with the largest RSSI value, the transmission timing is adjusted so as to reduce the time offset value. .

  In addition, here, if each base station 1001 to 1003 has acquired a time offset value or a frequency offset value from the terminal stations 2001 and 2002, each base station 1001 to 1003 may adjust the time or frequency, respectively. Is possible.

  The base stations 1001 to 1003 determine whether or not the base station performs base station cooperative transmission with respect to the terminal stations 2001 and 2002, and sets parameters of the base station at the time of transmission. When two or more base stations transmit to the stations 2001 and 2002, cooperative transmission is performed, and when one base station transmits, base station single transmission is performed.

  When the base stations 1001 to 1003 transmit in cooperation, the base stations 1001 to 1003 perform space-time coding such as polarization diversity, STBC (space time block code), delay diversity, cyclic shift diversity, and the like. It can be used as a technique that does not use information. Further, when base station cooperation signal processing such as beam forming and precoding is performed, channel information, calibration processing, and the like are required in each of the base stations 1001 to 1003.

<Modification>
If the terminal stations 2001 and 2002 cannot receive sounding frames from the base stations 1001 to 1003, the terminal stations 2001 and 2002 are configured not to measure the RSSI value, the time offset value, and the frequency offset value with the base station that has not received the sounding frame. May be.
The feedback signals transmitted by the terminal stations 2001 and 2002 may include values obtained by encoding the RSSI value, the time offset value, and the frequency offset value. The feedback signal transmitted by the terminal stations 2001 and 2002 may include a determination value derived using the RSSI value, the time offset value, and the frequency offset value.
The determination value is a value indicating whether each of the base stations 1001 to 1003 performs cooperative transmission. There are the following methods for the terminal stations 2001 and 2002 to select a base station that performs cooperative transmission. Method of selecting a base station RSSI value becomes the threshold value _{P th} or more. A method of selecting a base station whose time offset value with respect to the terminal station is equal to or less than a threshold value t _th . A method of selecting a base station whose time offset value is equal to or less than a threshold value t _th with respect to the base station having the maximum RSSI value. A method of selecting a base station whose frequency offset value with respect to the terminal station is equal to or less than a threshold f _th . A method of selecting a base station having a frequency offset value that is equal to or less than a threshold f _{th based on} the base station having the largest RSSI value. Further, the determination value may be derived by other methods. Further, the threshold _values P _th , t _th , and f _th may be determined for each terminal station in advance based on the required power of the terminal station or the like, or may be adaptively set according to the communication state and the state of the propagation path. Also good.

A-1. Mathematical Expression of First Embodiment Hereinafter, as an example, base stations 1001 to 1003 transmit sounding frames to terminal stations 2001 and 2002, and the base station performs cooperative transmission to terminal stations 2001 and 2002, respectively. Based on the result of receiving the determination value of whether or not to perform as feedback from the terminal stations 2001 and 2002, cyclic shift diversity (CSD) linked to the terminal station group by the three base stations 1001 to 1003, respectively. ) Consider the case of transmission.

When i (i = 1, 2, 3) represents an index corresponding to the base stations 1001, 1002, and 1003, and j (j = 1, 2) represents an index corresponding to the terminal stations 2001 and 2002, respectively, the terminal station j The received signal vector y _{j, i} received from the base station i can be expressed as Equation (1).

Where t is a time index, p is a delay wave index, N _max is the maximum number of delay paths, H _{j, i} (t, p) is a B × A channel matrix from the base station i to the terminal station j, δ _{j and i} are cyclic shift amounts of transmission signals from the base station i to the terminal station j, and x _{j and i} (tp−δ _{j, i} ) are A × 1 transmission signal vectors from the base station i to the terminal station j. , N _j represents the B × 1 noise vector at terminal station j.

When the base station 1001 to 1003 to transmit a sounding frame, for each destination terminal station by the amount of cyclic shift 0, to transmit in separate timing, the terminal station _{2001, y 1,1, y 1,2, y} 1 _{, 3} are received independently, and the terminal station 2002 receives y ₂ , ₁ , y ₂ , ₂ , y ₂ , ₃ independently.

Further, when the base stations 1001 to 1003 perform CSD transmission, x _{j and i} are generated with different cyclic shift amounts for each destination terminal station, and the base stations 1001 to 1003 simultaneously transmit at different timings for each destination terminal station. To do. In the terminal stations 2001 and 2002, the signal components transmitted to the terminal station are synthesized and received. The received signal at each of the terminal stations 2001 and 2002 can be expressed as Equation (2).

The terminal stations 2001 and 2002 obtain transmission data by multiplying the received signals received by the A × B reception weight matrix W _j (t), respectively. Hereinafter, calculation of the reception weight matrix in each of the terminal stations 2001 and 2002 will be described. In the first embodiment, the transmission signals _{xj, i} are subjected to OFDM (orthogonal frequency division multiplexing) modulation, but may be single carrier modulation in addition to OFDM modulation. Further, it is assumed that the maximum delay amount δ of the delayed wave does not exceed the OFDM GI (guard interval), and this operation is performed for each OFDM subcarrier.

The terminal stations 2001 and 2002 that have received the CSD signals transmitted from the base stations 1001, 1002, and 1003 perform OFDM demodulation. Since all of the delayed wave signal components that do not exceed GI can be regarded as normal signal components, the received signal y _j ′ (t) after OFDM demodulation can be expressed as Equation (3).

However, H ′ _{j, i} (t) is a B × A matrix of the sum of delayed wave components of H _{j, i} (t, p), and x ′ _{j, i} (t) is x _{j, i} (t− p−δ _{j, i} ), the B × 1 matrix of the sum of the delayed wave components, _n ′ is the noise component vector included in the B × 1 OFDM demodulated signal, and H _j ′ (t) is H ′ _{j, i} The B × A matrix of the sum of the signal components received from each base station 1001, 1002, 1003 of (t), x _j ′ (t) is the base station 1001, 1002, x ′ _{j, i} (t) 100 represents a B × 1 vector of the sum of signal components received from 1003.

When H _j ′ (t) is estimated using a known signal component such as a pilot signal included in the reception signal, a reception weight matrix W _j (t) of ZF (zero-forcing) standard is generated as an example of the reception weight. , Expressed as Equation (4).

However, [·] ^H represents a Hermitian transpose matrix and [·] ⁻¹ represents an inverse matrix. By multiplying the reception weight matrix W _j (t) by the reception signal y _j ′ (t), a B × 1 desired signal vector x _j ′ (t) is obtained. In addition to the ZF criterion, the reception weight matrix may be a linear separation criterion such as maximum non-synthesis (MRC), mean square error minimization (MMSE), or nonlinear separation such as maximum likelihood detection (MLD) or sphere decoding. Norms and the like may be used.

A-2. Base Station Configuration in First Embodiment FIG. 2 is a schematic block diagram showing the internal configuration of the base station 1001 in the first embodiment. Hereinafter, a configuration when a determination value is included in the feedback signal will be described. Note that the same configuration can be used for the base stations 1002 and 1003 in the first embodiment, and therefore only the base station 1001 will be described here.

  As shown in FIG. 2, the base station 1001 includes a control signal generation unit 3001, a transmission signal generation unit 3002, radio units 3003-1 to 3003-A, antenna elements 3004-1 to 3004-A, and received signals. A demodulation unit 3005 and a transmission determination unit 3006 are provided. The control signal generation unit 3001 generates a sounding frame and a control signal for performing wireless communication, and outputs the control signal to the transmission signal generation unit 3002. The transmission signal generation unit 3002 receives a signal received from the network 1000, the control signal generation unit 3001, or the transmission determination unit 3006, generates a transmission signal in baseband, and outputs the transmission signal to the radio units 3003-1 to 3003-A. To do. Here, as a generation method of the transmission signal, for example, a method as shown in Reference Document 1 below can be used.

(Reference 1) “IEEE Standard for Information technology- Telecommunications and information exchange between systems Local and metropolitan area networks-Specific requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications,” IEEE Std 802.11TM -2012, March 2012.

  The radio unit 3003-i (i is an integer of 1 or more and A or less) converts the baseband signal for each antenna element output from the transmission signal generation unit 3002 into a radio signal and transmits the radio signal from the antenna element 3004-i. Radio section 3003-i converts a radio signal received by antenna element 3004-i into a baseband signal, and outputs the baseband signal to reception signal demodulation section 3005.

  Reception signal demodulation section 3005 demodulates the baseband signal input from radio sections 3003-1 to 3003-A, and outputs the data signal to transmission determination section 3006 and network 1000. The transmission determination unit 3006 receives a determination value as to whether or not the terminal station 2001 or the own base station transmitted from the terminal station 2002, which is input from the received signal demodulation unit 3005, performs cooperative transmission for each destination terminal station. The base station 1001 determines whether or not to perform CSD transmission and the cyclic shift amount of the CSD transmission, and outputs the result to the transmission signal generation unit 3002. The transmission signal generation unit 3002 performs CSD transmission using the transmission determination result output from the transmission determination unit 3006 and the cyclic shift amount.

A-3. Terminal Station Configuration in the First Embodiment FIG. 3 is a schematic block diagram showing the internal configuration of the terminal station 2001 in the first embodiment. Hereinafter, a configuration when a determination value is included in the feedback signal will be described. Since the same configuration can be used for the terminal station 2002 in the first embodiment, only the terminal station 2001 will be described here.

  As illustrated in FIG. 2, the terminal station 2001 includes antenna elements 4001-1 to 4001-B, radio units 4002-1 to 4002-B, a transmission signal generation unit 4003, a control signal generation unit 4004, and a reception signal. A demodulation unit 4005, a reception sensitivity measurement unit 4006, a time offset measurement unit 4007, a frequency offset measurement unit 4008, and a feedback signal generation unit 4009 are provided.

  The antenna elements 4001-1 to 4001-B, the radio units 4002-1 to 4002-B, the control signal generation unit 4004, and the reception signal demodulation unit 4005 are antenna elements 3004-1 to 3004-A shown in FIG. Radio units 3003-1 to 3003-A, control signal generation unit 3001, and reception signal demodulation unit 3005 have the same functions.

  The reception sensitivity measuring unit 4006 receives signals transmitted from the base station 1001, the base station 1002, or the base station 1003 from the reception signals output from the radio units 4002-1 to 4002-B and received by the terminal station. Measure sensitivity. The reception sensitivity measurement unit 4006 measures the reception intensity (RSSI value) as the reception sensitivity and stores it together with the ID of the base station that transmitted the sounding frame (identification data, here, reference numerals 1001 to 1003 for convenience). As a measurement method of the RSSI value, it can be measured using a beacon as in a conventional wireless LAN, or can be measured using a known signal such as a sounding frame. Further, as the reception sensitivity, a reception CNR (carrier-to-noise power ratio) or reception SNR may be measured instead of the RSSI value. Further, any combination of these RSSI, reception CNR, and reception SNR may be used. Reception sensitivity measurement section 4006 outputs the measured RSSI value and base station ID to feedback signal generation section 4009.

  The time offset measurement unit 4007 measures the time lag (offset) between the base stations 1001 to 1003 and the terminal station from the reception signals output from the radio units 4002-1 to 4002-B, and transmits a sounding frame. Save with base station ID. As a method for measuring the time offset, for example, the input time at the leading portion of the reception signal can be used. Further, as a reference for measuring the time offset, an external time or a clock signal may be used without using the time of the terminal station. Time offset measuring section 4007 outputs the measured time offset value and base station ID to feedback signal generating section 4009.

  The frequency offset measurement unit 4008 measures the offset of the oscillation frequency between the base station 1001, the base station 1002, or the base station 1003 and the terminal station from the reception signals output from the radio units 4002-1 to 4002-B. The sounding frame is stored together with the ID of the base station that transmitted the sounding frame. As a method for measuring the offset of the oscillation frequency, it can be measured using a beacon as in a conventional wireless LAN, or can be measured using a known signal such as a sounding frame. Further, as a reference for measuring the frequency offset, the true value of the oscillation frequency may be used without using the oscillation frequency of the terminal station. Frequency offset measurement section 4008 outputs the measured frequency offset value and base station ID to feedback signal generation section 4009.

  The feedback signal generation unit 4009 includes the RSSI value of the sounding frame transmitted from the base stations 1001 to 1003 to the terminal station, the time offset value of each base station and the terminal station, and the frequency offset value of each base station and the terminal station. And the base station ID, each base station obtains a determination value as to whether or not to transmit to its own terminal station, and outputs it to the transmission signal generator 4003 as a feedback signal together with the base station ID.

  Transmission signal generation section 4003 receives the signal received from control signal generation section 4004 and the feedback signal received from feedback signal generation section 4009 as input, and generates a transmission signal in baseband. The transmission signal generation unit 4003 transmits a feedback frame to the base stations 1001, 1002, and 1003 via the radio units 4002-1 to 4002-B and the antenna elements 4001-1 to 4001-B.

A-4. Communication Procedure in First Embodiment FIG. 4 is a frame sequence diagram illustrating an example of a communication procedure in the first embodiment. Hereinafter, the communication procedure in 1st Embodiment is demonstrated with reference to FIGS.

  First, the control signal generation unit 3001 of the base station 1001 generates a sounding frame, and the transmission signal generation unit 3002 converts the generated sounding frame into a baseband signal. Radio sections 3003-1 to 3003-A convert the sounding frame of the baseband signal generated by transmission signal generation section 3002 into a radio signal. The antenna elements 3004-1 to 3004-A transmit the sounding frame 501 to the terminal stations 2001 and 2002 at the timing of time t1.

  The terminal stations 2001 and 2002 receive the sounding frame 501 through the antenna elements 4001-1 to 4001-B. Radio units 4002-1 to 4002-B convert sounding frames 501 received by antenna elements 4001-1 to 4001-B into baseband signals, and receive signal demodulation unit 4005, reception sensitivity measurement unit 4006, and time offset measurement unit. 4007 and the frequency offset measurement unit 4008.

  In the terminal stations 2001 and 2002, when receiving the sounding frame 501, the reception sensitivity measuring unit 4006 measures the RSSI value from the sounding frame 501 of the baseband signal, and uses the measured RSSI value together with the ID of the base station 1001 as a feedback signal. The data is output to the generation unit 4009.

  When receiving the sounding frame 501, the time offset measuring unit 4007 measures the time offset value from the sounding frame 501 of the baseband signal, and the measured time offset value together with the ID of the base station 1001 is used as a feedback signal generating unit 4009. Output to.

  In addition, when receiving the sounding frame 501, the frequency offset measuring unit 4008 measures a frequency offset value from the sounding frame 501 of the baseband signal, and the measured frequency offset value together with the ID of the base station 1001 as a feedback signal generating unit 4009. Output to.

  Next, the base station 1002 performs the same processing as when the base station 1001 transmits the sounding frame 501 and transmits the sounding frame 502 to the terminal stations 2001 and 2002 at the timing of time t2. The terminal stations 2001 and 2002 that have received the sounding frame 502 perform the same processing as when the sounding frame 501 is received. Accordingly, the terminal stations 2001 and 2002 measure the RSSI value, the time offset value, and the frequency offset value with the base station 1002 using the sounding frame 502, and the feedback signal generation unit 4009 together with the ID of the base station 1002 Output to.

  Next, the base station 1003 performs the same processing as when the base station 1001 transmits the sounding frame 501, and transmits the sounding frame 503 to the terminal stations 2001 and 2002 at the timing of time t3. The terminal stations 2001 and 2002 that have received the sounding frame 503 perform the same processing as when the sounding frame 501 and the sounding frame 502 are received. Accordingly, the terminal stations 2001 and 2002 measure the RSSI value, the time offset value, and the frequency offset value with the base station 1003 using the sounding frame 503, and the feedback signal generation unit 4009 together with the ID of the base station 1003. Output to.

  The feedback signal generator 4009 of the terminal stations 2001 and 2002 uses the RSSI value, time offset value, frequency offset value, and ID of each base station of the sounding frame received from the base stations 1001 to 1003, so that each base station itself. A determination value for determining whether to perform cooperative transmission to the terminal station is obtained. In each of the terminal stations 2001 and 2002, each transmission signal generation unit 4003 feeds back a determination value as to whether or not each base station performs cooperative transmission to the terminal station to the base stations 1001 to 1003. A signal feedback frame 504 or a feedback frame 505 is generated. Next, each of the radio units 4002-1 to 4002-B converts the baseband signal feedback frame 504 or the feedback frame 505 generated by the transmission signal generation unit 4003 into a radio signal.

  The terminal station 2001 transmits the feedback frame 504 to the base stations 1001, 1002, and 1003 at the timing of time t4 by the antenna elements 4001-1 to 4001-B. On the other hand, the terminal station 2002 transmits the feedback frame 505 to the base stations 1001 to 1003 at the timing of time t5 by the antenna elements 4001-1 to 4001-B.

  In this way, the determination value as to whether or not each base station performs cooperative transmission with respect to the terminal station 2001, obtained by the terminal station 2001, is fed back to the base stations 1001 to 1003 as the feedback frame 504 at the time t4. Is done. Further, the determination value as to whether or not each base station performs cooperative transmission to the terminal station 2001, which is obtained by the terminal station 2002, is fed back to the base stations 1001 to 1003 as a feedback frame 505 at the timing of time t5.

  Base stations 1001 to 1003 receive feedback frames 504 and 505 by antenna elements 3004-1 to 3004-A, respectively. Radio units 3003-1 to 3003-B convert feedback frames 504 and 505 received by antenna elements 3004-1 to 3004-B into baseband signals and output the received signals to received signal demodulation unit 3005. The received signal demodulation section 3005 of the base stations 1001 to 1003 demodulates the feedback frames 504 and 505 of the baseband signal, and each base station performs cooperative transmission to each terminal station calculated by the terminal stations 2001 and 2002. Is determined, and is output to the transmission determination unit 3006.

In the base stations 1001 to 1003, the transmission determination unit 3006 determines that the base station determines the terminal from the determination value of whether or not each base station performs cooperative transmission to each terminal station, fed back from the terminal stations 2001 and 2002. It is determined whether or not cooperative transmission is performed for the station 2001 and the terminal station 2002, and the cyclic shift amounts δ _{1,1 to} δ ₃ , ₂ for the respective terminal stations are calculated from the predetermined table. And output to the transmission signal generator 3002.

  Transmission signal generation section 3002 of base stations 1001 to 1003 generates a data transmission signal according to Equation (1) using the cyclic shift amount input from transmission determination section 3006 for transmission data input from network 1000. . Data transmission signals generated by transmission signal generation section 3002 are transmitted via radio sections 3003-1 to 3003-A and antenna elements 3004-1 to 3004-A.

  A data frame 506-1 is transmitted from the base station 1001 to the terminal station 2001 as a data frame 506-1, and a data frame 507-1 is transmitted from the base station 1001 to the terminal station 2002 as a data frame 507-1 at a time t7. Is done. Similarly, a data frame 506-2 is transmitted from the base station 1002 to the terminal station 2001 as a data frame 506-2, and a data frame 507-2 is transmitted from the base station 1002 to the terminal station 2002 at a time t7. Sent at timing. Further, data is transmitted from the base station 1003 to the terminal station 2001 as the data frame 506-3 at the timing of time t6, and from the base station 1003 to the terminal station 2002 is transmitted as the data frame 507-3 to the timing of time t7. Sent by

  In the above description, the base stations 1001 to 1003 transmit the sounding frames 501 to 503 and then the terminal stations 2001 and 2002 transmit the feedback frames 504 and 505. However, the frame sequence is not necessarily required. . For example, the base station 1001 transmits a sounding frame 501 to the terminal stations 2001 and 2002, and immediately thereafter, the base station 1001 estimates the sounding frame 501 using the sounding frame 501. A determination value as to whether or not to perform cooperative transmission is fed back to the base station 1001. Thereafter, the base station 1002 transmits a sounding frame 502 and receives a feedback frame from each terminal station in the same manner as the base station 1001, and then the base station 1003 transmits the sounding frame in the same manner as the base station 1001 and the base station 1003. 503 may be transmitted and a feedback frame may be received from each terminal station. Even in this case, the same exchange as the frame sequence shown in FIG. 4 can be realized.

  Further, the terminal stations 2001 and 2002 do not determine whether or not each base station performs cooperative transmission to the terminal station in the feedback signal generation unit 4009, and the measured RSSI value, time offset value, and frequency At least one or more of the offset values can be output to the transmission signal generation unit 4003 as a feedback signal. When the base stations 1001 to 1003 receive at least one feedback from the terminal stations 2001 and 2002 among the RSSI value, the time offset value, and the frequency offset value measured with each base station at each terminal station. Based on the acquired information, the base station can determine whether or not to perform coordinated transmission to each terminal station, and can set parameters for coordinated transmission such as a cyclic shift amount.

A-5. Example of Signal Processing Procedure FIG. 5 is a flowchart illustrating an example of a processing procedure in which the terminal station 2001 according to the first embodiment feeds back to each base station. Hereinafter, an example of a processing procedure when a determination value is included in the feedback signal will be described. The terminal station 2002 performs the same process.

  In the terminal station 2001, the radio units 4002-1 to 4002-B convert known signals such as beacons and sounding frames received from the base stations 1001 to 1003 into baseband signals by the antenna elements 4001-1 to 4001-B. The received signal demodulation section 4005, reception sensitivity measurement section 4006, time offset measurement section 4007, and frequency offset measurement section 4008 are output.

  The reception sensitivity measurement unit 4006 measures the RSSI value between the base stations 1001 to 1003 using the baseband known signals output from the radio units 4002-1 to 4002-B, and the base station ID (1001). -103) and output to the feedback signal generator 4009 (step S10-1). Note that, as described above, SNR or CNR may be measured instead of the RSSI value.

  The time offset measurement unit 4007 measures the time offset value between the base stations 1001 to 1003 and the terminal station using the baseband known signals output from the radio units 4002-1 to 4002-B, and It is output to the feedback signal generation unit 4009 together with the station ID (step S10-2).

  Also, the frequency offset measurement unit 4008 measures the frequency offset value between the base stations 1001 to 1003 and the terminal station using the known baseband signals output from the radio units 4002-1 to 4002-B. It outputs to the feedback signal generation part 4009 with station ID (step S10-3).

  Next, in the terminal station 2001, it is determined whether or not information has been acquired from all the base stations 1001 to 1003 (step S11), and until the above is completed for all the base stations 1001 to 1003 that transmit the sounding frame, Measurement and output processing (steps S10-1 to S10-3) are repeated (NO in step S11).

  On the other hand, when measurement and output processing (steps S10-1 to S10-3) is completed for all base stations 1001 to 1003 that transmit sounding frames (YES in step S11), a feedback signal generator 4009 uses at least one piece of information among the RSSI value, the time offset value, and the frequency offset value input from the reception sensitivity measurement unit 4006, the time offset measurement unit 4007, and the frequency offset measurement unit 4008, The base stations 1001 to 1003 determine whether or not to perform cooperative transmission addressed to the terminal station.

  The feedback signal generation unit 4009 receives, as information (determination criteria) used for determining whether or not each base station performs cooperative transmission with respect to a predetermined own terminal station, an input RSSI value, time offset value, or It is determined which of the frequency offset values is used (step S12).

When using the RSSI value, the base station the RSSI value becomes the threshold value _{P th} or more is determined to perform the associated transmission addressed to its own terminal station (step S13-1). When using the time offset value, the base station having the time offset value equal to or less than the threshold value t _th is determined to perform cooperative transmission to the terminal station (step S13-2). When the frequency offset value is used, the base station having the frequency offset value equal to or smaller than the threshold f _th is determined to perform cooperative transmission addressed to the terminal station (step S13-3).

  Next, feedback signal generation section 4009 outputs the determination value determined in steps S13-1 to 13-3 to transmission signal generation section 4003 together with the ID of the base station. The transmission signal generation unit 4003 generates feedback frames to be transmitted to the base stations 1001 to 1003 using the input determination values, respectively, and performs radio units 4002-1 to 4002-B and antenna elements 4001-1 to 4001. It performs feedback transmission to the base stations 1001 to 1003 via -B (step S14).

  In the above description, the base stations 1001 to 1003 are connected to the network 1000. However, the base stations 1001 to 1003 are not necessarily connected to the network 1000, and each base station 1001 to 1003 has its own data. It is also applicable to a wireless communication system that generates a signal and transmits a signal to a subordinate terminal station group, or a wireless communication system that exchanges necessary data between base stations by wireless transmission.

B. Second Embodiment Next, a second embodiment of the present invention will be described. In the second embodiment, the difference from the first embodiment will be mainly described, and the description of the same parts as in the first embodiment will be omitted.

  The configuration of the wireless communication system according to the second embodiment is the same as that of the base stations 1001, 1002, and 1003 of the wireless communication system of the first embodiment shown in FIG. The terminal stations 2001 and 2002 of the wireless communication system according to the first embodiment shown in FIG. 1 are replaced with terminal stations 2101 and 2102 having a configuration shown in FIG.

  In the second embodiment, first, the terminal station 2101 wirelessly transmits a sounding frame for measuring the RSSI value, the time offset value, and the frequency offset value to the base stations 1101 to 1103. The base stations 1101 to 1103 measure the RSSI value, the time offset value, and the frequency offset value between the terminal station 2101 and its own base station using the sounding frame received from the terminal station 2101. However, if the base stations 1101 to 1103 cannot receive the sounding frame from the terminal station 2101, the base stations 1101 to 1103 hold information indicating that the RSSI value, the time offset value, and the frequency offset value with the terminal station 2101 cannot be measured. To do. The base stations 1101 to 1103 may be configured not to measure the RSSI value, the time offset value, and the frequency offset value with the terminal station 2101 when the sounding frame cannot be received from the terminal station 2101.

  Subsequently, as in the case of the terminal station 2101, the terminal station 2102 wirelessly transmits the sounding frame to the base stations 1101 to 1103. The base stations 1101 to 1103 measure the RSSI value, the time offset value, and the frequency offset value between the terminal station 2102 and the base station using the sounding frame received from the terminal station 2102. However, if the sounding frame cannot be received from the terminal station 2102, information indicating that the RSSI value, the time offset value, and the frequency offset value with the terminal station 2102 cannot be measured is retained or not measured. .

  Thereafter, the base stations 1101 to 1103 exchange RSSI values, time offset values, and frequency offset values between the base stations and the terminal stations 2101 and 2102 via the network 1000, respectively. Thereby, each base station 1101-1103 acquires the information of the RSSI value, time offset value, and frequency offset value between each base station and each terminal station, respectively.

  The base stations 1101 to 1103 use the acquired RSSI values, time offset values, and frequency offset value information to determine whether or not the base station performs coordinated transmission to each terminal station, In addition, parameters are set for coordinated transmission. When two or more base stations transmit to each terminal station, coordinated transmission is performed. When one base station transmits, each base station uses a single base station. Perform transmission.

B-1. Base Station Configuration in Second Embodiment FIG. 6 is a schematic block diagram showing the internal configuration of the base station 1101 in the second embodiment. In addition, since the same structure can be used for the base stations 1102 and 1103 in the second embodiment, only the base station 1101 will be described here.

  As shown in FIG. 6, the base station 1101 is different from the base station 1001 in the first embodiment shown in FIG. 2 in that a reception sensitivity measuring unit 3007, a time offset measuring unit 3008, and a frequency offset measuring unit 3009 are newly provided. And the transmission determination unit 3006 is connected to the reception sensitivity measurement unit 3007, the time offset measurement unit 3008, and the frequency offset measurement unit 3009 and is also connected to the network 1000.

  Sounding frames transmitted from the terminal stations 2101 and 2102 are converted into baseband signals via the antenna elements 3004-1 to 3004-A and the radio units 3003-1 to 3003-A of the base station 1101, and received signals The data is output to demodulation section 3005, reception sensitivity measurement section 3007, time offset measurement section 3008, and frequency offset measurement section 3009.

  Similar to the reception sensitivity measurement unit 4006 of the terminal station 2001 in the first embodiment shown in FIG. 3, the reception sensitivity measurement unit 3007 receives RSSI between the terminal stations 2101 and 2102 and its own base station from the input sounding frame. The value is measured and output to the transmission determination unit 3006 together with the terminal station ID (2101 or 2102).

  Similar to the time offset measurement unit 4007 of the terminal station 2001 in the first embodiment shown in FIG. 3, the time offset measurement unit 3008 calculates the time offset value between each terminal station and the base station from the input sounding frame. Measure and output to the transmission determination unit 3006 together with the terminal station ID.

  Similarly to the frequency offset measuring unit 4008 of the terminal station 2001 in the first embodiment shown in FIG. 3, the frequency offset measuring unit 3009 calculates the frequency offset value between each terminal station and its own base station from the input sounding frame. Measure and output to transmission determination section 3006 together with the terminal station ID.

  The transmission determination unit 3006 receives the RSSI value, the time offset value, the frequency offset value, and the ID of the terminal station between each terminal station and the own base station, and receives the ID of the own base station (1101, Or 1102 or 1103), and exchanges information of RSSI values, time offset values, frequency offset values, and terminal station IDs with other base stations via the network 1000.

  The transmission determination unit 3006 acquires the RSSI value, time offset value, frequency offset value, and terminal station ID information from other base stations, and combines the information with the information measured by the base station. 2102, whether or not to perform coordinated transmission and selection of parameters such as cyclic shift amount when coordinated transmission is performed are output to the transmission signal generation unit 3002. The determination of whether or not to perform coordinated transmission and the criteria for parameter selection are as described above.

  The transmission signal generation unit 3002 performs cooperative transmission using the determination value output from the transmission determination unit 3006 and the parameters.

B-2. Terminal Station Configuration in Second Embodiment FIG. 7 is a schematic block diagram showing the internal configuration of the terminal station 2101 in the second embodiment. Since the same configuration can be used for the terminal station 2102 in this embodiment, only the terminal station 2101 will be described here.

  As shown in FIG. 7, the terminal station 2101 is different from the terminal station 2001 of the first embodiment shown in FIG. 3 in that a reception sensitivity measuring unit 4006, a time offset measuring unit 4007, a frequency offset measuring unit 4008, and a feedback signal The point is that the generation unit 4009 is not provided.

  The control signal generation unit 4004 generates a sounding frame, a control signal for performing wireless communication, and the like, and outputs the generated signal to the transmission signal generation unit 4003. Transmission signal generation section 4003 receives a signal received from control signal generation section 3001 as an input, generates a transmission signal in baseband, and outputs the transmission signals to radio sections 4002-1 to 4002-B. The generation method of the transmission signal is the same as that of the base station 1001 in the first embodiment shown in FIG.

  Radio units 4002-1 to 4002-B convert baseband signals for each antenna element output from transmission signal generation unit 4003 into radio signals, and transmit the radio signals via antenna elements 4001-1 to 4001-B. Radio sections 4002-1 to 4002 -B convert radio signals received by antenna element antenna elements 4001-1 to 4001 -B into baseband signals and output them to received signal demodulation section 4005. Received signal demodulation section 4005 demodulates the baseband signal input from radio sections 4002-1 to 4002-B and outputs a data signal.

B-3. Communication Procedure in Second Embodiment FIG. 8 is a frame sequence diagram showing a communication procedure in the second embodiment. The difference from the first embodiment is that each terminal station transmits a sounding frame addressed to the base station group, and therefore no feedback frame is transmitted. Hereinafter, a communication procedure in the second embodiment will be described with reference to FIGS.

  First, in the terminal station 2101, the control signal generation unit 4004 generates a sounding frame, and the transmission signal generation unit 4003 converts the generated sounding frame into a baseband signal. Radio sections 4002-1 to 4002-B convert the sounding frame of the baseband signal generated by transmission signal generation section 4003 into a radio signal. The antenna elements 4001-1 to 4001-B wirelessly transmit the sounding frame 601 to the base stations 1101 to 1103 at the timing of time t1.

  Base stations 1101 to 1103 receive sounding frame 601 through antenna elements 3004-1 to 3004-A. Radio sections 3003-1 to 3003-A convert sounding frames 601 received by antenna elements 3004-1 to 3004-A into baseband signals, and receive signal demodulation section 3005, reception sensitivity measurement section 3007, and time offset measurement section. 3008 and the frequency offset measurement unit 3009.

  In the base stations 1101 to 1103, the reception sensitivity measurement unit 3007 measures the RSSI value between the base station and the terminal station 2101 from the sounding frame 601 of the baseband signal, and the measured base station and the terminal station 2101 Are output to the transmission determination unit 3006 together with the ID (2101) of the terminal station.

  The time offset measuring unit 3008 measures a time offset value between the base station and the terminal station 2101 from the sounding frame 601 of the baseband signal, and measures the time between the base station and the terminal station 2101 thus measured. The offset value is output to the transmission determination unit 3006 together with the terminal station ID (2101).

  Also, the frequency offset measurement unit 3009 measures the frequency offset value between the base station and the terminal station 2101 from the sounding frame 601 of the baseband signal, and the measured frequency between the base station and the terminal station 2101. The offset value is output to the transmission determination unit 3006 together with the terminal station ID (2101).

  Next, the terminal station 2102 performs the same processing as when the terminal station 2101 transmits the sounding frame 601 and wirelessly transmits the sounding frame 602 to the base stations 1101 to 1103 at the timing of time t2. The base stations 1101 to 1103 that have received the sounding frame 602 perform the same processing as when the sounding frame 601 is received. As a result, the base stations 1101 to 1103 measure the RSSI value, the time offset value, and the frequency offset value with the terminal station 2102 using the sounding frame 602, and the transmission determination unit 3006 together with the terminal station ID (2102). Output.

  Next, in the base stations 1101 to 1103, the transmission determination unit 3006 receives the RSSI value between the own base station and the terminal stations 2101 and 2102 measured from the sounding frame received from the terminal stations 2101 and 2102, the time offset value, The base station ID is added to the frequency offset value and the ID information of each terminal station, and exchanged with each other via the network 1000. Thereafter, the transmission determination unit 3006 selects whether or not the base station performs cooperative transmission to each terminal station using at least one of the acquired RSSI value, time offset value, and frequency offset value. At the same time, parameters for cooperative transmission are determined. This selection processing method is the same as the processing in the feedback signal generation unit 4009 in the terminal stations 1101 and 1102 in the first embodiment.

  In base stations 1101 to 1103, transmission determination section 3006 outputs a determination value as to whether or not the base station performs coordinated transmission to each terminal station, and parameters for performing coordinated transmission to transmission signal generation section 3002. To do.

  Next, in base stations 1101 to 1103, transmission signal generation section 3002 uses the transmission data input from network 1000 and the information input from transmission determination section 3006 to generate a data transmission signal according to equation (1). The data frames 603-1 to 603-3 are transmitted to the terminal station 2101 via the radio units 3003-1 to 3003-A and the antenna elements 3004-1 to 3004-A at the timing of time t3. The data is transmitted to the terminal station 2102 as data frames 604-1 to 604-3 at the time t4.

  In the above description, the base stations 1101 to 1103 receive sounding frames from the terminal stations 2101 and 1022, and the RSSI value, time offset value, frequency offset value, and terminal station between the base station and each terminal station are determined. After acquiring the information of ID (2101, 2102) for all the terminal stations 2101 and 2102, the information is exchanged between the base stations via the network 1000, but the frame sequence is not necessarily required. . The base stations 1101 to 1103 receive the sounding frame from the terminal station 2101 and acquire the RSSI value, the time offset value, the frequency offset value, and the terminal station ID (2101) information between the base station and the terminal station 2101. At this time, without waiting for the reception of the sounding frame from the terminal station 2102, information exchange of the measured RSSI value, time offset value, frequency offset value, and terminal station ID is performed between the base stations via the network 1000. You can also

B-4. Signal Processing Procedure Example FIG. 9 is a flowchart illustrating a processing procedure example in which the base station 1101 of the second embodiment performs base station cooperative transmission. In the illustrated flowchart, after the base station 1101 receives sounding frames from the terminal station 2101 and the terminal station 2102 and exchanges information between the base stations via the network 1000, the RSSI value, the time offset value, and the frequency offset Using at least one of the values, the base station 1101 determines whether or not to perform coordinated transmission to each terminal station, sets parameters for coordinated transmission, and uses the result to determine the base station A processing procedure for performing cooperative transmission is shown. The base stations 1102 and 1103 perform similar processing.

  In base station 1101, radio sections 3003-1 to 3003-A convert known signals such as beacons and sounding frames received from terminal stations 2101 and 2102 by antenna elements 3004-1 to 3004-A into baseband signals. The received signal demodulation section 3005, the reception sensitivity measurement section 3007, the time offset measurement section 3008, and the frequency offset measurement section 3009.

  The reception sensitivity measurement unit 3007 measures the RSSI value between the base station and the terminal station 2101 and the terminal station 2102 using the baseband known signals output from the radio units 3003-1 to 3003-A. The terminal IDs (2101, 2102) are output to the transmission determination unit 3006 (step S20-1). Here, as described above, SNR or CNR may be measured instead of the RSSI value.

  Also, the time offset measuring unit 3008 uses the baseband known signals output from the radio units 3003-1 to 3003-A to calculate the time offset value between the terminal station 2101 and the terminal station 2102 and the own base station. Measure and output to the transmission determination unit 3006 together with the terminal station IDs (2101, 2102) (step S20-2).

  Also, the frequency offset measurement unit 3009 measures the frequency offset values of the terminal station 2101 and the terminal station 2102 and the own base station using the baseband known signals output from the radio units 3003-1 to 3003-A. The terminal IDs (2101, 2102) are output to the transmission determination unit 3006 (step S20-3).

  Next, the base station 1101 determines whether or not information has been acquired from all terminal stations (step S21), and performs the above measurement and output processing until the process is completed for all terminal stations that transmit sounding frames. (Steps S20-1 to S20-3) are repeated (NO in Step S21).

  In the base station 1101, the transmission determination unit 3006 receives the RSSI value between the own base station and the terminal station 2101 and the terminal station 2102, the time from the reception sensitivity measurement unit 3007, the time offset measurement unit 3008, and the frequency offset measurement unit 3009. The information input of the offset value, the frequency offset value, and the ID (2101, 2102) of the terminal station is received. The transmission determination unit 3006 acquires information on all terminal stations (YES in step S21), and then, via the network 1000, the RSSI value and time between the own base station and each terminal station acquired by the own base station. The base station ID is added to the offset value, frequency offset value, and ID information of each terminal station, and the information is exchanged with each other (step S22).

  The transmission determination unit 3006 acquires RSSI values, time offset values, frequency offset values, and ID information of each terminal station in all base stations, and the base station is addressed to each terminal station based on the information. It is determined whether or not to perform base station cooperative transmission, and parameters for performing cooperative transmission are set.

  The transmission determination unit 3006 determines at least one piece of information to be used as information (determination criterion) used for determination from the acquired RSSI value, time offset value, or frequency offset value (step S23).

When using the RSSI value, the base station the RSSI value becomes the threshold value _{P th} or more is determined to perform the associated transmission addressed to its own terminal station (step S24-1). When using the time offset value, the base station having the time offset value equal to or less than the threshold value t _th is determined to perform cooperative transmission to the terminal station (step S24-2). Further, when using the frequency offset value, the base station having the frequency offset value equal to or less than the threshold f _th is determined to perform cooperative transmission addressed to the own terminal station (step S24-3).

  Next, the transmission determination unit 3006 of the base station 1101 determines whether or not each base station performs cooperative transmission, and parameters for performing cooperative transmission, which are determined in steps S24-1 to 24-3. Is output to the transmission signal generation unit 3002 together with the ID of the base station (step S25). The transmission signal generation unit 3002 of the base station 1101 generates a baseband CSD transmission frame using the acquired transmission data, the output of the control signal generation unit 3001, and the output result of the transmission determination unit 3006 via the network 1000. It is generated, converted into a radio signal through the radio units 3003-1 to 3003-A, and CSD transmission is performed from the antenna elements 3004-1 to 3004-A.

  In the above description, the base stations 1101 to 1103 are connected to the network 1000. However, the base stations 1101 to 1103 are not necessarily connected to the network 1000. 2102 determines whether or not the own base station performs base station cooperative transmission based on the sounding frame received from 2102, sets parameters for cooperative transmission, and transmits signals to subordinate terminal stations. The present invention can also be applied to a communication system.

C. Third Embodiment Next, a third embodiment of the present invention will be described.
FIG. 10 is a block diagram illustrating a configuration example of a wireless communication system according to the third embodiment.
As shown in FIG. 10, the wireless communication system according to the third embodiment includes three base stations 1201, 1202, and 1203 as receiving station devices connected to a network 1000 by wire, and a transmitting station that performs wireless communication with the receiving station device. Two terminal stations 2201 and 2202 as devices are provided. The terminal stations 2201 and 2202 perform uplink transmission of data to the base stations 1201, 1202 and 1203 using the same frequency. That is, the base stations 1201 to 1203 receive data signals from the terminal stations 2201 and 2202 that are terminal stations under the common control (in the cell) of the base stations.

  In the illustrated example, for the sake of simplicity, the configuration includes three base stations 1201, 1202, 1203 and two terminal stations 2201, 2202 that are connected to the network 1000. Base stations and a plurality of terminal stations.

  In addition, for the sake of simplicity, as in the first and second embodiments, the number of antenna elements of each of the base stations 1201 to 1203 is A (A ≧ 1, A is an integer), terminal stations The number of antenna elements 2201 and 2202 is B (B ≧ 1, B is an integer). However, the present embodiment can be applied even when there are two or more base stations and one or more terminal stations, and the number of antenna elements of the base station and the number of antenna elements of the terminal station may be different.

  In the third embodiment, first, the base station 1201 transmits a sounding frame for measuring the RSSI value, the time offset value, and the frequency offset value between the base station and each terminal station to the terminal stations 2201 and 2202. Over the air. The terminal stations 2201 and 2202 measure the RSSI value, the time offset value, and the frequency offset value between the base station 1201 and the terminal station using the sounding frame received from the base station 1201. However, if a sounding frame cannot be received from the base station 1201, information indicating that the RSSI value, the time offset value, and the frequency offset value with the base station 1201 cannot be measured is retained or not measured. .

  Subsequently, similarly to the base station 1201, the base station 1202 wirelessly transmits the sounding frame to the terminal stations 2201 and 2202. The terminal stations 2201 and 2202 measure the RSSI value, the time offset value, and the frequency offset value between the base station 1202 and the terminal station using the sounding frame received from the base station 1202. However, when a sounding frame cannot be received from the base station 1202, information indicating that the RSSI value, the time offset value, and the frequency offset value with the base station 1202 cannot be measured is retained or not measured. .

  Subsequently, similarly, the base station 1203 wirelessly transmits the sounding frame to the terminal stations 2201 and 2202, and the terminal stations 2201 and 2202 use the sounding frame received from the base station 1203, and the base station 1203 and its own terminal station. RSSI value, time offset value, and frequency offset value are measured. However, if the sounding frame cannot be received from the base station 1203, information indicating that the RSSI value, the time offset value, and the frequency offset value with the base station 1203 cannot be measured is retained or not measured. .

  Thereafter, the terminal stations 2201 and 2202 wirelessly transmit data frames to the base stations 1201 to 1203, respectively. The data frame to be transmitted includes a desired data signal, an RSSI value between the base station 1201 and 1203 as a feedback signal, a time offset value of each base station 1201 to 1203, and a frequency of each base station 1201 to 1203. Each base station 1201-1203 calculated using an offset value or a value obtained by encoding the measured value using a codebook table or the like, or information thereof, with respect to a data frame from its own terminal station Each of them includes a determination value as to whether to perform cooperative reception.

As a calculation method when determining whether or not each base station 1201 to 1203 performs cooperative reception from a measured value, a method of selecting a base station whose RSSI value is equal to or greater than a threshold value P _th and a terminal station as a reference method time offset value to select a base station equal to or less than the threshold value t _th, techniques RSSI value to select a base station time offset relative to the base station of the maximum is equal to or less than the threshold t _th, the reference terminal station method frequency offset value to select a base station equal to or less than the threshold value f _th, such techniques RSSI value selects the base station that the frequency offset value based on the base station of the maximum is equal to or less than the threshold f _th is considered. Moreover, you may calculate combining several information and a threshold value from RSSI value, a time offset value, and a frequency offset value. In addition, threshold _values P _th , t _th , and f _th can be determined in advance for each terminal station based on the required power of the terminal station and the like, and can be adaptively set according to the communication status or the state of the propagation path. You can also.

  The base stations 1201 to 1203 receive and demodulate the data frames transmitted from the terminal stations 2201 and 2202, and the base station cooperates with each data frame using a feedback signal included in the data frame. Whether reception is to be performed and parameters of the base station at the time of cooperative reception are set, and reception processing is performed.

  As a parameter of the base station set by each of the base stations 1201 to 1203, a maximum ratio combining weight is set using the received SNR of the received data frame, a time offset value between the terminal stations 2201 and 2202, and a frequency Using the offset value, the reception timing of the base station can be determined, and the time and frequency can be adjusted. Each of the base stations 1201 to 1203 performs cooperative reception when signals received from the terminal stations 2201 and 2202 are received by two or more base stations, and performs single reception when only one base station receives. Do.

  In addition, when a plurality of base stations receive in cooperation, a cooperative method such as diversity such as selective combining, threshold combining, maximum ratio combining, and equal gain combining can be used. In addition, when performing base station cooperation signal processing such as antenna array reception and spatial equalization over a plurality of base stations, it is necessary to exchange channel information between each base station, calibration processing, and the like.

C-1. Mathematical Expression of Third Embodiment Hereinafter, as an example, the base stations 1201 to 1203 transmit sounding frames to the terminal stations 2201 and 2202, and each base included in the data frame transmission signal from each of the terminal stations 2201 and 2202 Maximum ratio combining in which three base stations 1201 to 1203 cooperate with data frames from each of the terminal stations 2201 and 2202 based on a determination value as to whether or not each station performs cooperative reception on data frames. Consider the case of receiving.

  The sounding frame transmitted from each base station 1201 to 1203 to the terminal stations 2201 and 2202 and the data frame transmitted from each terminal station 2201 and 2202 to the base stations 1201 to 1203 are as shown in Equation (1). The signal is received as an independent signal for each transmitting station and each receiving station.

  When the three base stations 1201 to 1203 cooperatively receive the data transmission signal transmitted from the terminal station j by the maximum ratio combining, the received signal at the base station i is expressed as Equation (5).

Where t is a time index, p is a delay wave index, N _max is the maximum number of delay paths, H _{i, j} (t, p) is an A × B channel matrix from the terminal station j to the base station i, x _i, j (t-p) is B × 1 transmitted signal vector from the terminal station j to the base station i, the _{n i} represents an a × 1 noise vector at the base station i.

Each of the base stations 2201 to 2202 obtains desired data by multiplying each received signal by a B × A reception weight matrix W _{j, i} (t). Hereinafter, calculation of the reception weight matrix in the terminal stations 2201 and 2202 will be described. In this description, the transmission signal x _{j, i} is assumed to perform OFDM modulation, but may be single carrier modulation in addition to OFDM modulation. Further, the maximum delay amount δ of the delayed wave does not exceed the OFDM GI, and this operation is performed for each OFDM subcarrier.

The base stations 1201 to 1203 that have received the data frames transmitted from the terminal stations 2101 and 2102 perform OFDM demodulation. Since all the delayed wave signal components that do not exceed GI can be regarded as normal signal components, the received signal y _{i, j} ′ (t) after OFDM demodulation can be expressed as shown in Equation (6).

However, H ′ _{i, j} (t) is an A × B matrix of the sum of delayed wave components of H _{i, j} (t, p), and x ′ _{i, j} (t) is x _{i, j} (tp). An A × 1 matrix of the sum of the delayed wave components, n _i ′ represents a noise component vector included in the A × 1 OFDM demodulated signal.

H _j ′ (t) is estimated using a known signal component such as a pilot signal included in the received signal, and the received weight matrix W _{j, i} (t ) Is used to express as Equation (7).

Here, n ″ _i represents an A × 1 noise signal component vector included in the equalized signal. As a result, a signal vector x _{i, j} ′ (t) is obtained. In addition to the ZF criterion, a linear separation criterion such as MRC or MMSE, or a nonlinear separation criterion such as MLD or sphere decoding can be used as the reception weight matrix.

  Thereafter, in the maximum non-combination, the data signals received by the base stations 1201 to 1203 are combined using the SNR of the received signal as a weighting factor for each of the terminal stations 2101 and 2102 that have transmitted them. A desired signal obtained by synthesizing and receiving data signals transmitted from the terminal stations 2101 and 2102 is expressed as Equation (8).

Here, γ _{i, j} represents the received SNR of r _{i, j} (t). As a result, the base station 1201 to 1203 can receive data transmission signals received from the terminal stations 2101 and 2102 in cooperation with each other by maximum ratio combining.

C-2. Base Station Configuration in Third Embodiment FIG. 11 is a schematic block diagram showing the internal configuration of the base station 1201 in the third embodiment. Here, as an example, the base stations 1201 to 1203 transmit sounding frames addressed to the terminal stations 2201 and 2202, and the terminal stations 2201 and 2202 use the sounding frames so that each of the base stations 1201 to 1203 receives data from its own terminal station. Determining whether or not to perform cooperative reception for each frame is derived, and the information is added to transmit data frames to the respective base stations 1201 to 1203. The base stations 1201 to 1203 are the terminal stations 2201 and 2202. Suppose that the three base stations 1201, 1202, and 1203 perform maximum non-synthetic reception for data frames transmitted from the network. In addition, since the same structure can be used for the base stations 1202 and 1203 in the third embodiment, only the base station 1201 will be described here.

  As illustrated in FIG. 11, the base station 1201 includes a control signal generation unit 3001, a transmission signal generation unit 3002, radio units 3003-1 to 3003-A, antenna elements 3004-1 to 3004-A, and received signals. A demodulation unit 3005 and a reception processing unit 3010 are provided. The control signal generation unit 3001 generates a control signal for generating a sounding frame, and outputs the control signal to the transmission signal generation unit 3002. The transmission signal generation unit 3002 receives the signal from the control signal generation unit 3001 as input, generates a sounding frame in the baseband, and outputs it to the radio units 3003-1 to 3003-A.

  Radio section 3003-i (i is an integer not less than 1 and not more than A) converts the baseband signal of the sounding frame for each antenna element output from transmission signal generation section 3002 into a radio signal and transmits it from antenna element 3004-i. To do. Radio section 3003-i converts a radio signal received by antenna element 3004-i into a baseband signal, and outputs the baseband signal to reception signal demodulation section 3005. Reception signal demodulation section 3005 demodulates the baseband signal of the data frame input from radio sections 3003-1 to 3003-A, and outputs the demodulated baseband signal to reception processing section 3010. The reception processing unit 3010 acquires a determination value as to whether or not the base station cooperates with the base station and a data portion from the data frame signal input from the reception signal demodulation unit 3005, and Stations exchange the acquired information and combine the received data of each base station 1201-1203 with the maximum ratio to obtain a desired data signal.

C-3. Terminal Station Configuration in the Third Embodiment FIG. 12 is a schematic block diagram showing the internal configuration of the terminal station 2201 in the third embodiment. Since the same configuration can be used for the terminal station 2202 in the third embodiment, only the terminal station 2201 will be described here.

  As shown in FIG. 12, the configuration of the terminal station 2201 in the third embodiment is substantially the same as the configuration of the terminal station 2001 in the first embodiment shown in FIG. The terminal station 2201 is different from the terminal station 2001 in that the reception signal demodulator 3005 is not provided and data is added to the transmission signal generator 4003. In the third embodiment, in order to perform uplink data transmission from the terminal stations 2201 and 2202 to the base stations 1201 to 1203, the terminal stations 2201 and 2202 perform data transmission processing instead of data reception processing.

  The transmission signal generation unit 4003 of the terminal station 2201 generates a baseband data frame using the input data, the control signal input from the control signal generation unit 4004, and the feedback signal input from the feedback signal generation unit 4009. The data frames are transmitted to the base stations 1201 to 1203 via the radio units 4002-1 to 4002-B and the antenna elements 4001-1 to 4001-B.

C-4. Communication Procedure in Third Embodiment FIG. 13 is a frame sequence diagram illustrating an example of a communication procedure in the third embodiment. The communication procedure in the third embodiment will be described below with reference to FIGS.

  First, the control signal generation unit 3001 of the base station 1201 generates a sounding frame 701, and the transmission signal generation unit 3002 converts the generated sounding frame 701 into a baseband signal. Radio units 3003-1 to 3003-A convert sounding frame 701 of the baseband signal generated by transmission signal generation unit 3002 into a radio signal. The antenna elements 3004-1 to 3004-A transmit the sounding frame 701 to the terminal stations 2201 and 2202 at the timing of time t1.

  The terminal stations 2201 and 2202 receive the sounding frame 701 through the antenna elements 4001-1 to 4001-B. Radio units 4002-1 to 4002-B convert sounding frames 701 received by antenna elements 4001-1 to 4001-B into baseband signals, receive sensitivity measurement unit 4006, time offset measurement unit 4007, and frequency offset measurement. To the unit 4008.

  In the terminal stations 2201 and 2202, when receiving the sounding frame 701, the reception sensitivity measurement unit 4006 measures the RSSI value from the sounding frame 701 of the baseband signal, and uses the measured RSSI value together with the ID of the base station 1201 as a feedback signal. The data is output to the generation unit 4009.

  The time offset measurement unit 4007 measures a time offset value from the sounding frame 701 of the baseband signal, and outputs the time offset value to the feedback signal generation unit 4009 together with the ID of the base station 1201.

  Also, the frequency offset measurement unit 4008 measures a frequency offset value from the sounding frame 701 of the baseband signal, and outputs the measured frequency offset value to the feedback signal generation unit 4009 together with the ID of the base station 1201.

  Next, the base station 1202 performs the same processing as when the base station 1201 transmits the sounding frame 701, and transmits the sounding frame 702 to the terminal stations 2201 and 2202 at the timing of time t2. The terminal stations 2201 and 2202 that have received the sounding frame 702 perform the same processing as when the sounding frame 701 is received. Accordingly, the terminal stations 2201 and 2202 measure the RSSI value, the time offset value, and the frequency offset value with the base station 1202 using the sounding frame 702, and the feedback signal generation unit 4009 together with the ID of the base station 1202 Output to.

  Next, the base station 1203 performs the same processing as when the base station 1201 transmits the sounding frame 701, and transmits the sounding frame 703 to the terminal stations 2201 and 2202 at the timing of time t3. The terminal stations 2201 and 2202 that have received the sounding frame 703 perform the same processing as when the sounding frame 701 and the sounding frame 702 are received. Accordingly, the terminal station 2201 and the terminal station 2202 measure the RSSI value, the time offset value, and the frequency offset value with the base station 1203 using the sounding frame 703, and generate a feedback signal together with the ID of the base station 1203. Output to the unit 4009.

  The feedback signal generator 4009 of each of the terminal stations 2201 and 2202 uses the RSSI value, time offset value, frequency offset value, and ID of each base station of the sounding frame received from the base stations 1201 to 1203, so that each base station A determination value indicating whether or not to perform cooperative reception on a data frame transmitted from the terminal station is obtained and output to the transmission signal generation unit 4003.

  The transmission signal generator 4003 of the terminal stations 2201 and 2202 uses the input data, the input from the control signal generator 4004, and the input from the feedback signal generator 4009 as a baseband signal for the data frame 704 or the data frame 705. Generate. The radio units 4002-1 to 4002-B convert the data frame 704 or the data frame 705 of the baseband signal generated by the transmission signal generation unit 4003 into a radio signal.

  The terminal station 2201 transmits the data frame 704 to the base stations 1201 to 1203 at the time t4 by the antenna elements 4001-1 to 4001-B. Also, the terminal station 2202 transmits the data frame 705 to the base stations 1201 to 1203 at the time t5 by the antenna elements 4001-1 to 4001-B.

  Base stations 1201 to 1203 receive data frame 704 and data frame 705 by antenna elements 3004-1 to 3004-A. Radio sections 3003-1 to 3003-A convert data frames 704 and data frames 705 received by antenna elements 3004-1 to 3004-A into baseband signals and output the received signals to received signal demodulation section 3005. Reception signal demodulating section 3005 demodulates data frame 704 and data frame 705 of the baseband signal and outputs them to reception processing section 3010.

  The reception processing unit 3010 of the base stations 1201 to 1203 determines from the data frames input from the reception signal demodulation unit 3005 whether or not the base station performs cooperative reception on each data frame, and the data portion. Are obtained, and exchange information is exchanged between the base stations via the network 1000, and a desired data signal is obtained by maximally non-synthesizing the received data of the base stations 1201-1203.

  In the above description, the terminal stations 2201 and 2202 transmit the data frames 704 and 705 after the base stations 1201 to 1203 transmit the sounding frames 701 to 703. However, the frame sequence is not necessarily required. For example, when a feedback signal transmitted from each of the terminal stations 2201 and 2202 is not included in the data frame but is transmitted as a feedback frame at another timing, the same exchange as the frame sequence shown in FIG. 13 can be realized.

  In addition, in the feedback signal generation unit 4009 of the terminal stations 2201 and 2202, measurement is performed without determining whether to perform cooperative reception on the data frames transmitted from the terminal stations by the base stations 1201 to 1203, respectively. At least one of the RSSI value, the time offset value, and the frequency offset value may be output to the transmission signal generation unit 4003 as a feedback signal. At this time, the base stations 1201 to 1203 determine whether or not the base station performs cooperative reception on the data frames 704 and 705 transmitted from the terminal stations 2201 and 2202 based on the acquired information. In addition, parameters for cooperative reception such as weighting coefficients are set.

C-5. Signal Processing Procedure Example FIG. 14 is a flowchart showing a processing procedure example in which the terminal station 2201 of the third embodiment outputs a feedback signal. In the illustrated flowchart, the terminal station 2201 receives sounding frames 701, 702, and 703 from the base stations 1201 to 1203 and uses at least one of measured RSSI values, time offset values, and frequency offset values. A processing procedure for deriving a determination value as to whether or not each base station performs cooperative reception on a data frame transmitted by a terminal station and outputting a feedback signal is shown. The terminal station 2202 performs similar processing.

  In the terminal station 2201, the radio units 4002-1 to 4002-B convert known signals such as beacons and sounding frames received from the base stations 1201 to 1203 into baseband signals by the antenna elements 4001-1 to 4001-B. And output to the reception sensitivity measuring unit 4006, the time offset measuring unit 4007, and the frequency offset measuring unit 4008.

  The reception sensitivity measurement unit 4006 measures the RSSI value with the base stations 1201 to 1203 using the baseband known signals output from the radio units 4002-1 to 4002-B, and the base station ID (1201). To 1203) and output to the feedback signal generator 4009 (step S30-1). Note that SNR and CNR may be measured instead of the RSSI value.

  The time offset measurement unit 4007 measures the time offset value between the base stations 1201 to 1203 and the terminal station using the baseband known signals output from the radio units 4002-1 to 4002-B, and It outputs to the feedback signal generation part 4009 with station ID (step S30-2).

  Further, the frequency offset measurement unit 4008 measures the frequency offset value between the base stations 1201 to 1203 and the terminal station using the known baseband signals output from the radio units 4002-1 to 4002-B, and It outputs to the feedback signal generation part 4009 with station ID (step S30-3).

  Next, in the terminal station 2201, it is determined whether or not information has been acquired from all the base stations 1201 to 1203 (step S31), and until the above is completed for all the base stations 1201 to 1203 that transmit the sounding frame, Measurement and output processing (steps S30-1 to S30-3) are repeated (NO in step S31).

  On the other hand, when the measurement and output processing (steps S10-1 to S10-3) is completed for all the base stations 1201 to 1203 that transmit sounding frames (YES in step S11),

  The feedback signal generation unit 4009 of the terminal station 2201 includes at least one of the RSSI value, the time offset value, and the frequency offset value input from the reception sensitivity measurement unit 4006, the time offset measurement unit 4007, and the frequency offset measurement unit 4008. Using the above information, each base station determines whether or not to perform cooperative reception on the data frame transmitted from its own terminal station.

  The feedback signal generation unit 4009 receives, as information (determination criteria) used for determining whether or not each base station performs cooperative transmission with respect to a predetermined own terminal station, an input RSSI value, time offset value, Alternatively, it is determined which of the frequency offset values is used (step S32).

When using the RSSI value, the base station the RSSI value becomes the threshold value _{P th} or more is determined to perform cooperative reception for the data frame to be transmitted from the own terminal station (step S33-1). When using the time offset value, the base station having the time offset value equal to or less than the threshold t _th determines to perform cooperative reception on the data frame transmitted from the terminal station (step S33-2). When the frequency offset value is used, the base station having the frequency offset value equal to or less than the threshold f _th determines to perform cooperative reception on the data frame transmitted from the terminal station (step S33-3).

  Then, the feedback signal generation unit 4009 of the terminal station 2201 outputs the determination value representing the determination result in Steps S33-1 to S3-3 as a feedback signal to the transmission signal generation unit 4003 together with the IDs of the base stations 1201 to 1203. (Step S34).

  In the above description, the base stations 1201 to 1203 are connected to the network 1000. However, the base stations 1201 to 1203 are not necessarily connected to the network 1000, and each base station 1201 to 1203 has its own data. It is also applicable to a wireless communication system that generates a signal and transmits a signal to a subordinate terminal station group, or a wireless communication system that exchanges necessary data between base stations by wireless transmission.

D. Fourth Embodiment Next, a fourth embodiment of the present invention will be described. In the fourth embodiment, the difference from the third embodiment will be mainly described, and the description of the same parts as those in the third embodiment will be omitted.

  The configuration of the wireless communication system according to the fourth embodiment is that base stations 1201, 1202, and 1203 of the wireless communication system according to the third embodiment shown in FIG. In this case, the terminal stations 2201 and 2202 are replaced with terminal stations 2301 and 2302 configured as shown in FIG.

  In the fourth embodiment, first, the terminal station 2301 sends a data frame including a sounding signal for measuring an RSSI value, a time offset value, and a frequency offset value and a data signal to the base stations 1301 to 1303. Wireless transmission. The base stations 1301 to 1303 measure the RSSI value, the time offset value, and the frequency offset value between the terminal station 2301 and the base station using the sounding signal included in the data frame received from the terminal station 2301. However, when a sounding frame cannot be received from the terminal station 2301, information indicating that the RSSI value, the time offset value, and the frequency offset value with the terminal station 2301 cannot be measured is retained or not measured. .

  Thereafter, the base stations 1301 to 1303 exchange the measured RSSI value, time offset value, frequency offset value, received SNR, and received data signal between the own base station and the terminal station 2101 via the network 1000. The base stations 1301 to 1303 use the acquired information to determine whether or not the base station performs coordinated reception for each data frame, and set parameters for coordinated reception. When two or more base stations each receive, coordinated reception is performed, and when one base station receives, reception by a single base station is performed. Each base station that has performed the reception operation performs maximum ratio combining using the received data signal and the received SNR to obtain desired data.

  For the data frame transmitted by the terminal station 2302, similar processing is performed in the transmitting terminal station 2302 and the receiving base stations 1301 to 1303, and desired data is obtained by maximum ratio combining.

D-1. Base Station Configuration in Fourth Embodiment FIG. 15 is a schematic block diagram showing the internal configuration of a base station 1301 in the fourth embodiment. In addition, since the same structure can be used for the base stations 1302 and 1303 in the fourth embodiment, only the base station 1301 will be described here.

  As shown in FIG. 15, the base station 1301 is different from the base station 1201 in the third embodiment shown in FIG. 11 in that the output from the radio units 3003-1 to 3003-A and the input to the reception processing unit 3010 As a point, a reception sensitivity measurement unit 3007, a time offset measurement unit 3008, and a frequency offset measurement unit 3009 are newly provided, and a control signal generation unit 3001 and a transmission signal generation unit 3002 are not provided.

  Data frames transmitted from the terminal stations 2301 and 2302 are converted into baseband signals via the antenna elements 3004-1 to 3004-A and the radio units 3003-1 to 3003-A of the base station 1301, and received signals The data is output to demodulation section 3005, reception sensitivity measurement section 3007, time offset measurement section 3008, and frequency offset measurement section 3009.

  Received signal demodulating section 3005 demodulates the input data frame to obtain a sounding signal portion and a data signal portion, and outputs them to reception processing section 3010. Similarly to the reception sensitivity measurement unit 4006 of the terminal station 2201 in the third embodiment shown in FIG. 12, the reception sensitivity measurement unit 3007 receives the terminal stations 2301 and 2302 and its own base station from the sounding signal portion of the input data frame. Is measured and output to the reception processing unit 3010 together with the ID (2301 or 2302) of the terminal station.

  Similar to the time offset measurement unit 4007 of the terminal station 2201 in the third embodiment shown in FIG. 12, the time offset measurement unit 3008 uses the sounding signal portion of the input data frame to determine the terminal stations 2301 and 2302 and its own base station. Is measured and output to the reception processing unit 3010 together with the ID of the terminal station.

  Similar to the frequency offset measurement unit 4008 of the terminal station 2201 in the third embodiment shown in FIG. 12, the frequency offset measurement unit 3009 uses the sounding signal portion of the input data frame to determine the terminal stations 2301 and 2302 and its own base station. Is measured and output to the reception processing unit 3010 together with the ID of the terminal station.

  The reception processing unit 3010 receives the sounding signal, the data signal, the measured RSSI value, the time offset value, and the frequency offset value, and automatically converts them into necessary information from the received SNR measured from the sounding frame. The base station ID (1301, 1302, or 1303) is added, and information is exchanged with other base stations via the network 1000. Also, the reception processing unit 3010 uses the acquired information to determine whether or not the own base station performs cooperative reception for each data frame, and sets parameters for the cooperative reception. When two or more base stations receive, cooperative reception is performed. When one base station receives, base station single reception is performed. Each of the base stations 1301 to 1303 that has performed the reception operation performs maximum ratio combining using the received data signal and the received SNR, and obtains desired data.

D-2. Terminal Station Configuration in the Fourth Embodiment FIG. 16 is a schematic block diagram showing the internal configuration of the terminal station 2301 in the fourth embodiment. Since the same configuration can be used for the terminal station 2302 in the fourth embodiment, only the terminal station 2301 will be described here.

  As shown in FIG. 16, the terminal station 2301 is different from the terminal station 2201 of the third embodiment shown in FIG. 12 in that a reception sensitivity measurement unit 4006, a time offset measurement unit 4007, a frequency offset measurement unit 4008, and a feedback signal The point is that the generation unit 4009 is not provided.

  The control signal generation unit 4004 generates a sounding signal and a control signal for performing wireless communication, and outputs the generated signal to the transmission signal generation unit 4003. Transmission signal generation section 4003 generates a data frame in baseband using input data and an input signal from control signal generation section 4004, and outputs the data frame to radio sections 4002-1 to 4002-B. Radio units 4002-1 to 4002-B convert the baseband signal of the data frame into a radio signal and transmit it from antenna elements 4001-1 to 4001-B.

D-3. Communication Procedure in Fourth Embodiment FIG. 17 is a frame sequence diagram showing a communication procedure in the fourth embodiment. Hereinafter, a communication procedure in the fourth embodiment will be described with reference to FIGS. 15 to 17.

  First, in the terminal station 2301, the control signal generation unit 4004 generates a data frame 801, and the transmission signal generation unit 4003 converts the data frame 801 into a baseband signal. Radio units 4001-1 to 4003-B convert data frame 801 of the baseband signal generated by transmission signal generation unit 4003 into a radio signal. Antenna elements 4001-1 to 4001-B transmit data frame 801 to base stations 1301 to 1303 at time t1.

  Base stations 1301 to 1303 receive data frame 801 through antenna elements 3004-1 to 3004-A. Radio sections 3003-1 to 4002-A convert data frames 801 received by antenna elements 3004-1 to 3004-A into baseband signals, receive signal demodulation section 3005, reception sensitivity measurement section 3007, and time offset measurement section. 3008 and the frequency offset measuring unit 3009.

  In base stations 1301 to 1303, reception sensitivity measurement section 3007 measures the RSSI value from data frame 801 of the baseband signal, and outputs the measured RSSI value to reception processing section 3010 together with the ID of terminal station 2301.

  The time offset measurement unit 3008 measures a time offset value from the data frame 801 of the baseband signal, and outputs the measured time offset value to the reception processing unit 3010 together with the ID of the terminal station 2301.

  Also, the frequency offset measurement unit 3009 measures the frequency offset value from the data frame 801 of the baseband signal, and outputs the measured frequency offset value to the reception processing unit 3010 together with the ID of the terminal station 2301.

  Next, in the base stations 1301 to 1303, the reception processing unit 3010 receives the sounding signal, the data signal, and the measured RSSI value, time offset value, and frequency offset value, and measures from the information and the sounding frame. The received SNR and the ID of the own base station (1301, 1302, or 1303) are added, and information is exchanged with other base stations via the network 1000. Also, the reception processing unit 3010 uses the acquired information to determine whether or not the own base station performs cooperative reception for each data frame, and sets parameters for the cooperative reception. When two or more base stations receive, cooperative reception is performed. When one base station receives, base station single reception is performed. Each of the base stations 1301 to 1303 that has performed the reception operation performs maximum ratio combining using the received data signal and the received SNR, and obtains desired data.

  The terminal station 2302 also performs the same processing as the terminal station 2301, and transmits the data frame 802 to the base stations 1031 to 1303 at the timing of time t2. The base stations 1301 to 1303 that have received the data frame 802 perform the same processing as when the data frame 801 is received, and obtain desired data by maximum ratio combining.

  In the above description, each terminal station collectively transmits the sounding signal and the data signal to the base stations 1301 to 1303 as data frames 801 and 802, but the frame sequence is not necessarily required. For example, when sending a sounding signal as a sounding frame at another timing, the same exchange as the frame sequence shown in FIG. 17 can be realized.

D-4. Signal Processing Procedure Example FIG. 18 is a flowchart illustrating a processing procedure example in which the base station 1301 according to the fourth embodiment performs the maximum ratio combining reception process. In the illustrated flowchart, the base station 1301 receives a data frame from the terminal station 2301, and uses at least one information from the RSSI value, the time offset value, and the frequency offset value measured from the included sounding signal, An example of a processing procedure for deriving a determination value as to whether or not to perform cooperative reception on a data frame received by the base station and performing a maximum ratio combining reception process is shown. Similar processing is performed for reception of the data frame 802 from the terminal station 2302 and reception of the data frame at the base stations 1302 and 1303.

  In base station 1301, radio sections 3003-1 to 3003-A convert data frame 801 received from terminal station 2301 by antenna elements 3004-1 to 3004-A into baseband signals, and receive signal demodulation section 3005 and receive Output to the sensitivity measurement unit 3007, the time offset measurement unit 3008, and the frequency offset measurement unit 3009.

  Received signal demodulating section 3005 measures the received SNR value from the baseband data frame output from radio sections 3003-1 to 3003-A and acquires the data signal portion, and receives the processing section along with the ID of terminal station 2301. It outputs to 3010 (step S40-1).

  Further, the reception sensitivity measurement unit 3007 measures the RSSI value with the terminal station 2301 using the known signal included in the baseband data frame output from the radio units 3003-1 to 3003-A, and the terminal The information is output to the reception processing unit 3010 together with the ID of the station 2301 (step S40-2). Note that SNR and CNR may be measured instead of the RSSI value.

  The time offset measurement unit 3008 measures a time offset value with the terminal station 2301 using a known signal included in the baseband data frame output from the radio units 3003-1 to 3003-A, and The information is output to the reception processing unit 3010 together with the ID of the station 2301 (step S40-3).

  Further, the frequency offset measurement unit 3009 measures the frequency offset value with the terminal station 2301 using the known signal included in the baseband data frame output from the radio units 3003-1 to 3003-A, and the terminal The information is output to the reception processing unit 3010 together with the ID of the station 2301 (step S40-4).

  Next, the reception processing unit 3010 of the base station 1301 is used to determine whether or not the base station performs cooperative reception on the data frame from the input RSSI value, time offset value, and frequency offset value. Information (determination criteria) is selected (step S41).

  When the RSSI value is used as a criterion for determining whether or not to perform cooperative reception, the reception processing unit 3010 exchanges RSSI values possessed by other base stations via the network 1000 (step S42-1). When the time offset value is used as a criterion for determining whether or not to perform cooperative reception, the reception processing unit 3010 exchanges the time offset value possessed by another base station via the network 1000 (step S42-2). When the frequency offset value is used as a criterion for determining whether to perform cooperative reception, the reception processing unit 3010 exchanges the frequency offset value possessed by another base station via the network 1000 (step S42-3).

Next, the reception processing unit 3010 determines whether to perform cooperative reception processing on the data frame received by the base station using the acquired information. If the criteria used RSSI value for the data frame to the RSSI value of the own base station is the threshold _{P th} or more is determined to perform cooperative reception (step S43-1). When the time offset value is used, it is determined to perform cooperative reception on the data frame whose time offset value is equal to or less than the threshold value t _th (step S43-2). When the frequency offset value is used, it is determined to perform cooperative reception on a data frame whose frequency offset value is equal to or less than the threshold f _th (step S43-3).

  The reception processing unit 3010 of the base station 1301 performs reception processing on the data portion of the received data frame and maximum ratio combined reception based on the determination value representing the determination result in Steps S43-1 to 43-3 and the reception SNR. Is weighted (step S44). Next, the reception processing unit 3010 obtains reception signal processing results in other base stations via the network 1000 and performs maximum ratio combining with the reception data processing results of the own base station to obtain desired data. (Step S45).

  In the above description, the base stations 1301 to 1303 are connected to the network 1000. However, the base stations 1301 to 1303 are not necessarily connected to the network 1000. The present invention is also applicable to a wireless communication system that exchanges necessary data.

  According to the first to fourth embodiments described above, in downlink transmission, a base station as a transmitting station transmits a sounding frame and receives feedback from a terminal station, or each terminal station transmits a sounding frame, By exchanging information via, the base station in each base station uses at least one of the RSSI value, the time offset value, and the frequency offset value between the terminal station and each base station. By determining whether or not to perform coordinated transmission and setting the parameters at that time, it is possible to effectively perform base station coordinated transmission. Thereby, the cooperation effect per base station can be heightened and it can lead to the characteristic improvement of the whole system. Therefore, a plurality of base stations can perform high-throughput communication by performing cooperative transmission at the same time and the same frequency.

  In uplink transmission, a sounding frame is received from a terminal station that is a transmitting station, or information obtained from each terminal station is received by a sounding frame transmitted from a base station, and information is exchanged via a network. Whether the base station in each base station performs cooperative reception using at least one of the RSSI value, the time offset value, and the frequency offset value between the terminal station and each base station. By determining whether or not and setting the parameters at that time, it is possible to effectively perform base station cooperative reception. Thereby, the cooperation effect per base station can be improved and it leads to the characteristic improvement of the whole system. Therefore, a plurality of base stations can perform communication with high system throughput by performing cooperative reception at the same time and the same frequency.

  Note that the base stations 1001, 1002, 1003, 1101, 1102, 1103, 1201, 1202, 1203, 1301, 1302, and 1303 and terminal stations 2001, 2002, 2101, 1022, 2201, 2202, 2301, 2302 in the above-described embodiment. Each functional unit may be realized by dedicated hardware (for example, wired logic), and a program for realizing each functional unit is recorded on a computer-readable recording medium and recorded on the recording medium. The program may be realized by reading the executed program into a computer system and executing it. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer system” includes a WWW system having a homepage providing environment (or display environment). The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Further, the “computer-readable recording medium” refers to a volatile memory (RAM) in a computer system that becomes a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In addition, those holding programs for a certain period of time are also included.

  The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, and what is called a difference file (difference program) may be sufficient.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes designs and the like that do not depart from the gist of the present invention.

1000 ... Network 1001 to 1003, 1101 to 1103, 1201 to 1203, 1301 to 1303 Base station 2001, 2002, 2101, 2102, 2201, 2202, 2301, 2302 Terminal station 3001 Control signal generation unit 3002 Transmission signal generation unit 3003-1 ˜3003-A Radio unit 3004-1 to 3004-A Antenna element 3005 Received signal demodulation unit 3006 Transmission determination unit 3007 Reception sensitivity measurement unit 3008 Time offset measurement unit 3009 Frequency offset measurement unit 3010 Reception processing unit 4001-1 to 4001-B Antenna element 4002-1 to 4002-B Radio unit 4003 Transmission signal generation unit 4004 Control signal generation unit 4005 Reception signal demodulation unit 4006 Reception sensitivity measurement unit 4007 Time offset measurement unit 4008 Frequency Number offset measurement unit 4009 Feedback signal generation unit

Claims (8)

A communication system in which a plurality of transmitting station apparatuses simultaneously transmit signals to the receiving station apparatus using the same frequency,
A measuring unit for measuring characteristics between the receiving station device and each transmitting station device;
Based on the measurement result in the measurement unit, the transmitting station apparatus that satisfies the condition is determined. When there are a plurality of transmitting station apparatuses that satisfy the condition, the plurality of transmitting stations are configured to perform cooperative transmission to the receiving station apparatus. A control unit for controlling the device;
A wireless communication system comprising:   The wireless communication system according to claim 1, wherein the measurement unit measures at least one value among reception strength, frequency offset, and time offset between the transmission station apparatuses in the reception station apparatus as the characteristic.   The wireless communication system according to claim 1, wherein the control unit controls the plurality of transmission station apparatuses to use different cyclic shift amounts when there are a plurality of transmission station apparatuses that satisfy the condition. A communication system in which a plurality of receiving station devices simultaneously receive signals from a transmitting station device using the same frequency,
A measuring unit for measuring characteristics between the transmitting station device and each receiving station device;
A plurality of receiving stations are determined so as to perform cooperative reception from the transmitting station apparatus when there are a plurality of receiving station apparatuses that satisfy the condition based on a measurement result in the measurement unit and satisfy the condition. A control unit for controlling the device;
A wireless communication system comprising:   The wireless communication system according to claim 4, wherein the measurement unit measures at least one value of reception intensity, frequency offset, or time offset between the receiving station devices in the transmitting station device as the characteristic.   The radio according to claim 4 or 5, wherein when there are a plurality of receiving station devices that satisfy the condition, the control unit controls the plurality of receiving station devices to perform reception processing by maximum ratio combining in cooperation. Communications system. A communication method performed by a communication system in which a plurality of transmitting station devices simultaneously transmit signals in cooperation with a receiving station device using the same frequency,
A measurement step of measuring characteristics between the receiving station device and each transmitting station device;
Based on the measurement result, a transmitting station apparatus that satisfies the condition is determined, and when there are a plurality of transmitting station apparatuses that satisfy the condition, the plurality of transmitting station apparatuses are controlled to perform cooperative transmission to the receiving station apparatus. Control steps;
A communication method comprising: A communication method performed by a communication system in which a plurality of receiving station devices simultaneously receive signals from a transmitting station device simultaneously using the same frequency,
A measuring step of measuring characteristics between the transmitting station device and each receiving station device;
Based on the measurement result, a receiving station apparatus that satisfies the condition is determined, and when there are a plurality of receiving station apparatuses that satisfy the condition, the plurality of receiving station apparatuses are controlled to perform cooperative reception from the transmitting station apparatus. Control steps;
A communication method comprising:

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