JP6440079B2 - Radio base station using distributed antenna and distributed antenna control method - Google Patents

Description

  The present invention relates to a radio base station and a distributed antenna control method using a distributed antenna having a plurality of base station antennas arranged in a distributed manner and performing multiuser MIMO transmission on a same radio channel to a plurality of terminal stations. .

  As a high-speed wireless access system using the 5 GHz band, there is an IEEE 802.11a standard. This system uses an Orthogonal Frequency Division Multiplexing (OFDM) modulation scheme, which is a technique for stabilizing characteristics in a multipath fading environment, and realizes a maximum throughput of 54 Mbit / s.

  Furthermore, in the IEEE802.11n standard, MIMO (Multiple input multiple output) technology that performs space division multiplexing on the same radio channel using a plurality of antennas, and two 20 MHz frequency channels that have been used individually so far are simultaneously used. Aiming to realize high-speed communication by using channel bonding technology that uses 40MHz frequency channel, the maximum transmission speed is 600Mbit / s.

  Furthermore, in the IEEE 802.11ac standard, a channel bonding technique that uses four 20 MHz frequency channels at the same time and uses it as an 80 MHz frequency channel, or a multi-user MIMO technique on the same radio channel, for multiple radio stations. In addition, a spatial division multiple access (SDMA) transmission technology that performs simultaneous transmission is adopted, and wireless communication that is faster and more efficient than the IEEE 802.11n standard is realized.

FIG. 9 shows an overview of a multi-user MIMO transmission system.
In FIG. 9, the radio base station 30 uses the same radio channel for terminal stations 40-1 to 40- by beam forming for directing signals transmitted from a plurality of base station antennas to the terminal stations 40-1 to 40-n, respectively. Simultaneous communication with n. H ₁ and H _n are propagation channel information between each base station antenna of the radio base station 30 and the terminal station 40-1 and the terminal station 40-n, and transmission weight and reception calculated from the propagation channel information. By using the weight, the radio base station 30 can simultaneously communicate with the terminal stations 40-1 to 40-n.

FIG. 10 shows an operation example of the multiuser MIMO transmission system. Here, an example is shown in which the radio base station 30 performs multi-user MIMO transmission with two terminal stations 40-1 and 40-2.
In FIG. 10, when data to be transmitted to the terminal stations 40-1 and 40-2 occurs, the radio base station 30 performs CSMA / CA (Carrier Sense Multiple Access / Collision Avoidance). Under control, carrier sense (CS) is performed at random time intervals, and it is determined whether an idle state where the communication frequency band is not used or a busy state where the communication frequency band is used. When the radio base station 30 detects that it is in an idle state, it transmits a null data packet announcement (NDPA: Null Data Packet Announcement) that informs the transmission of a null data packet, and is composed of null data for estimating propagation channel information. A null data packet (NDP) is transmitted.

  The terminal stations 40-1 and 40-2 receive the NDP transmitted from the radio base station 30 and calculate propagation channel information. The terminal station 40-1 transmits a beam for notifying the base station of the calculated propagation channel information. A forming report (BR) is transmitted. When the terminal station 40-2 receives a beamforming report poll (BRP: Beamforming Report Poll) requesting propagation channel information transmitted from the radio base station 30, the terminal station 40-2 notifies the radio base station 30 of the calculated propagation channel information. Send.

  The radio base station 30 calculates the transmission weight using the propagation channel information notified by the BR from the terminal stations 40-1 and 40-2, and transmits the transmission signals (Data1, Data2) to the terminal stations 40-1 and 40-2. Generate and send. Note that the transmission signal is converted into a frame suitable for wireless communication, for example. When frame aggregation is applied, the transmission signal is a data unit in which a predetermined number of frames are connected.

  The terminal station 40-1 receives the transmission signal (Data1) for its own station and transmits a block ACK (BACK: Block Acknowledgment) notifying that the signal has been correctly received. The terminal station 40-2 receives the transmission signal (Data2) for its own station, and transmits a BACK in response to a block ACK request (BACKR: Block Acknowledgment Request) requesting a BACK from the base station. Here, the radio base station 30 executes a predetermined process according to the reception of the BACK. For example, it is determined that the data is normally received on the receiving side by the reception of the BACK, and the process proceeds to the next data transmission / reception process. Further, when a timeout occurs without receiving the BACK, processing such as retransmission of the transmission target data is executed.

  Thus, in normal multi-user MIMO transmission, in order to perform beam forming at the radio base station 30, it is necessary to acquire propagation channel information from each of the terminal stations 40-1 and 40-2. In this example, propagation channel information is acquired from two terminal stations, but the operation of acquiring propagation channel information is repeated in the same manner for all terminal stations that are targets of multiuser MIMO transmission.

  In addition to the standardization technology shown above, a plurality of antennas possessed by a radio base station are distributed to reduce the distance between the base station antenna and the terminal antenna, resulting in an improvement in received power of each radio communication Investigation of antenna technology is in progress (Non-Patent Document 1). Here, an antenna configuration corresponding to SU-MIMO or NU-MIMO is shown by adaptively switching a plurality of base station antennas with a switch.

Roh, Wonil, and Arogyaswami Paulraj. "MIMO channel capacity for the distributed antenna." Vehicular Technology Conference, 2002. Proceedings. VTC 2002-Fall. 2002 IEEE 56th. Vol. 2. IEEE, 2002.

  In order for a radio base station to perform multi-user MIMO transmission, it is necessary for the radio base station to acquire propagation channel information from a plurality of terminal stations targeted for multi-user MIMO transmission and to perform beam forming using the information. is there. The radio transmission for notifying the propagation channel information is different from the data transmission desired by the terminal station, and thus becomes an overhead. As a result, a throughput is lowered due to a reduction in transmission efficiency of the terminal station.

  Therefore, when multi-user MIMO transmission is put into practical use, it is important to use multi-user MIMO transmission considering this overhead. Further, in the future system, it is expected that the number of antennas and the number of terminal stations in the radio base station and the terminal station will increase. An increase in the number of antennas and the number of terminal stations increases necessary propagation channel information, which leads to further increase in overhead.

  The present invention uses a distributed antenna that improves transmission efficiency by acquiring propagation channel information only from a terminal station that requires beamforming in a multi-user MIMO transmission system in which a distributed antenna is applied to a radio base station. An object is to provide a radio base station and a distributed antenna control method.

  A first aspect of the present invention is a distributed antenna control method for a radio base station having a plurality of base station antennas arranged in a distributed manner and performing multiuser MIMO transmission on a same radio channel to a plurality of terminal stations. A first step of measuring received power between the base station antenna and the antennas of the plurality of terminal stations, and for each terminal station, SIR is calculated from the received power of the plurality of base station antennas, and a beam is generated according to the SIR. A second step of selecting a terminal station that requires forming and a terminal station that does not require forming, a third step of acquiring propagation channel information from the terminal station that requires beam forming, and a propagation channel in the terminal station that does not require beam forming. The fourth step of supplementing the information with the specified value and the multi-channel using each propagation channel information of the terminal station that requires beam forming and the terminal station that does not need beam forming. A fifth step of calculating the transmission weight for the MIMO transmission, and a sixth step of generating and transmitting a signal for multiuser MIMO transmission to be transmitted to a plurality of terminal stations using the transmission weight for multiuser MIMO transmission; Have

  In the distributed antenna control method for a radio base station according to the first aspect of the present invention, in the second step, among the plurality of base station antennas, there is one base station antenna whose SIR exceeds a threshold, and the one base station antenna On the other hand, a terminal station whose SIR in another terminal station does not exceed the threshold is selected as a terminal station that does not require beamforming, and other terminal stations are selected as terminal stations that require beamforming.

  In the distributed antenna control method for a radio base station according to the first aspect of the present invention, when performing the second step, a group is formed so that there are many terminal stations that do not require beamforming and do not acquire propagation channel information from a plurality of terminal stations. And a terminal station that requires beam forming and an unnecessary terminal station are selected for each group according to the SIR.

  According to a second aspect of the present invention, there is provided a radio base station having a plurality of base station antennas arranged in a distributed manner and using a distributed antenna that performs multi-user MIMO transmission on a same radio channel to a plurality of terminal stations. A received power measurement unit that measures received power between the base station antenna and the antennas of the plurality of terminal stations, and for each terminal station, calculates SIR from the received power of the plurality of base station antennas, and generates a beam according to the SIR. A terminal station selection unit that selects a terminal station that requires forming and a terminal station that does not need to perform, a propagation channel information acquisition control unit that acquires propagation channel information from a terminal station that requires beam forming, and a terminal station that does not require beam forming Propagation channel information complementing section that supplements propagation channel information with specified values, and each propagation channel information of terminal stations that need beamforming and unnecessary terminal stations Using the multi-user MIMO transmission transmission weight calculation unit for calculating the multi-user MIMO transmission transmission weight and the multi-user MIMO transmission transmission weight, a multi-user MIMO transmission signal to be transmitted to a plurality of terminal stations is generated. And a multi-user MIMO transmission signal generation unit for transmission.

  In the radio base station using the distributed antenna of the second invention, the terminal station selection unit includes one base station antenna whose SIR exceeds a threshold value among the plurality of base station antennas, and the one base station antenna On the other hand, a terminal station whose SIR in other terminal stations does not exceed the threshold is selected as a terminal station that does not require beamforming, and other terminal stations are selected as terminal stations that require beamforming.

  In the radio base station using the distributed antenna of the second invention, the terminal station selection unit generates groups so that there are many terminal stations that do not need beam forming and do not acquire propagation channel information from a plurality of terminal stations. The configuration includes a group generation unit, and selects a terminal station that requires beam forming and an unnecessary terminal station for each group according to SIR.

  The present invention applies a distributed antenna to a radio base station in a multi-user MIMO transmission system, assigns a specified value without acquiring propagation channel information from a terminal station that does not require beam forming, and requires a beam forming. The transmission efficiency can be improved by acquiring the propagation channel information only from the network.

It is a figure which shows the outline | summary of the multiuser MIMO transmission system to which this invention is applied. It is a figure which shows the structural example of the wireless base station 10 in Example 1 of this invention. It is a figure which shows the structural example of the terminal station 20 in Example 1 of this invention. It is a flowchart which shows the example of a process sequence of the radio base station 10 and the terminal station 20 in Example 1 of this invention. It is a figure which shows the example of selection of the necessity / unnecessity of the beam forming in Example 1 of this invention. It is a figure which shows the structural example of the wireless base station 10 in Example 2 of this invention. It is a flowchart which shows the example of a process sequence of the wireless base station 10 in Example 2 of this invention. It is a figure which shows the example of grouping in Example 2 of this invention. It is a figure which shows the outline | summary of a multiuser MIMO transmission system. It is a time chart which shows the operation example of a multiuser MIMO transmission system.

Example 1
FIG. 1 shows an overview of a multi-user MIMO transmission system to which the present invention is applied.
1, the configuration is the same as that of the conventional multiuser MIMO transmission system shown in FIG. 9 except that a plurality of base station antennas 11-1 to 11-m of the radio base station 10 are distributed.

  A feature of the present invention is that, when a plurality of base station antennas 11-1 to 11-m of the radio base station 10 are distributed, transmission channel information is acquired only from terminal stations that require beamforming, thereby improving transmission efficiency. It is in the place of realizing improvement. That is, depending on the positional relationship between the base station antennas 11-1 to 11-m and the terminal stations 20-1 to 20-n, there are terminal stations that can obtain sufficient propagation characteristics without necessarily performing beamforming. Sometimes, the propagation channel information of the terminal station is not acquired, but is supplemented with a specified value, and the propagation channel information is acquired only from the terminal station that requires beam forming.

FIG. 2 shows a configuration example of the radio base station 10 according to the first embodiment of the present invention.
In FIG. 2, a radio base station 10 includes base station antennas 11-1 to 11-m, transmission / reception units 12-1 to 12-m, a received power measurement unit 13, a terminal station selection unit 14, and a propagation channel information acquisition control unit 16. , A propagation channel information complementing unit 17, a multi-user MIMO transmission weight calculation unit 18, and a multi-user MIMO transmission signal generation unit 19. Here, a transmission system related to the present invention in the configuration of the radio base station 10 will be described.

  The base station antennas 11-1 to 11-m radiate signals input from the transmission / reception units 12-1 to 12-m as radio waves in the air. Alternatively, signals received from the air are output to the transmission / reception units 12-1 to 12-m.

  The transmission / reception units 12-1 to 12-m convert the multiuser MIMO transmission signal input from the multiuser MIMO transmission signal generation unit 19 into frequencies and transmission powers defined by the wireless system, and perform base station antennas 11 to 11 Output to 11-m. Also, the frequency of the signal received by the base station antennas 11-1 to 11-m is converted, converted into a format that can be processed in the radio base station, and output to the received power measuring unit 13.

  The received power measurement unit 13 measures and stores the received power for each terminal station at each base station antenna using the signals from the transmission / reception units 12-1 to 12-m, and further according to instructions from the terminal station selection unit 14 The received power information of the terminal station is output to the terminal station selection unit 14.

  The terminal station selection unit 14 acquires received power information of a terminal station that is a target of multi-user MIMO transmission from the received power storage unit 13, and determines a terminal station that needs beamforming and an unnecessary terminal station from the acquired received power information. select. Information on terminal stations that require beamforming is output to the propagation channel information acquisition control unit 16, and information on terminal stations that do not require beamforming is output to the propagation channel information complementing unit 17. A specific selection method will be described separately with reference to FIGS.

  The propagation channel information acquisition control unit 16 acquires the propagation channel information for the terminal station that needs beam forming by the procedure of NDPA, NDP, BR, BRP, BR,. Further, the acquired propagation channel information is output to the propagation channel information complementing unit 17.

  The propagation channel information complementing unit 17 receives the propagation channel information obtained from the terminal station that requires beamforming input from the propagation channel information control unit 16 and the terminal station that does not require beamforming input from the terminal station selection unit 15. The propagation channel information is complemented with a specified value and output to the multi-user MIMO transmission weight calculation unit 18.

  The multi-user MIMO transmission weight calculation unit 18 calculates a transmission weight from the propagation channel information of each wireless station input from the propagation channel information setting unit 17 according to a transmission weight calculation method used in general multi-user MIMO transmission. To the multi-user MIMO transmission signal generator 19.

  The multi-user MIMO transmission signal generator 19 generates a radio for multi-user MIMO transmission from the input signal for each terminal station that is the target of multi-user MIMO transmission and the transmission weight input from the multi-user MIMO transmission weight calculator 18. A signal is generated and output to the transmission / reception units 12-1 to 12-m.

FIG. 3 shows a configuration example of the terminal station 20 according to the first embodiment of the present invention.
3, the terminal station 20 includes a terminal station antenna 21, a transmission / reception unit 22, a propagation channel information measurement notification unit 23, and a multi-user MIMO transmission signal reception unit 24.

The terminal station antenna 21 radiates a signal input from the transmission / reception unit 22 as a radio wave in the air. Alternatively, a signal received from the air is output to the transmission / reception unit 22.
The transmission / reception unit 22 converts the frequency and transmission power defined by the radio system into the radio signal and outputs the radio signal to the terminal station antenna 21. Also, the frequency of the signal input from the terminal station antenna 21 is converted, converted into a format that can be processed in the terminal station, and output to the propagation channel information measurement notifying unit 23 or the signal receiving unit 24 for multiuser MIMO transmission.

The propagation channel information measurement notifying unit 23 measures the propagation channel information for each base station antenna by the procedure of NDPA, NDP, BR, BRP, BR,... Processing for notifying the radio base station 10 is performed.
The multi-user MIMO transmission signal reception unit 24 performs a reception process of the multi-user MIMO transmission signal input from the transmission / reception unit 21.

Hereinafter, the processing content of each unit will be described with reference to the processing procedure example of the radio base station 10 and the terminal station 20 shown in FIGS. 4 (a) and 4 (b).
First, the received power measuring unit 13 of the radio base station 10 measures received power (RSSI) for each of the base station antennas 11-1 to 11-m from radio signals transmitted from the terminal stations 20-1 to 20-n. (S01). Here, the terminal stations 20-1 to 20-n are targeted for multi-user MIMO transmission.

  FIG. 5A shows a measurement example of received power in the first embodiment. Next, the terminal station selection unit 14 of the radio base station 10 determines, from the reception power measurement result shown in FIG. 5 (a), a terminal station that requires beamforming, that is, a terminal station that acquires propagation channel information, and beamforming. Is selected, that is, a terminal station that does not acquire propagation channel information is selected (S02).

  Specifically, the received power measurement result shown in FIG. 5 (a) is converted into the ratio of signal power to interference power (SIR) shown in FIG. 5 (b). The SIR calculated here uses the RSSI of the terminal station 20-a and the base station antenna 11-b as a desired signal, and the total RSSI of the base station antennas other than the terminal station 20-a and the base station antenna 11-b is an interference signal. Is calculated as Or it is good also as a calculation result at the time of setting the electric energy set beforehand as an interference signal. Based on this SIR, a terminal station that does not require beamforming is selected based on the following two conditions.

  The first condition is to detect, for each terminal station, a terminal station in which only one SIR of each base station antenna exceeds the threshold value. The second condition is to detect a terminal station whose SIR in another terminal station does not exceed the threshold value in the base station antenna that exceeds the threshold value in the first condition. This terminal station is a terminal station that does not require beamforming, that is, a terminal station that does not acquire propagation channel information. For example, if the threshold is 30 dB, in the example of FIG. 5B, only the SIR at the base station antenna 11-m is 40 dB at the terminal station 20-1, and the SIR at the base station antenna 11-m at other terminal stations. Is 30 dB or less, the terminal station 20-1 is selected as a terminal station that does not require beamforming. On the other hand, the terminal station 20-2 and the terminal station 20-3 are both selected as terminal stations that do not satisfy the second condition and require beamforming because the SIR at the base station antenna 11-3 is 40 dB.

  Next, the propagation channel information acquisition control unit 16 performs the propagation channel according to the procedure of NDPA, NDP, BR, BRP, BR,. Information is acquired (S03). Next, the propagation channel information complementation unit 17 supplements the propagation channel information of the terminal station that does not require beamforming with the specified value for the propagation channel information obtained from the terminal station that requires beamforming obtained in S03. (S04). For example, the specified value of the propagation channel information of the terminal station 20-1 that does not require beam forming is “1” for the propagation channel information in the base station antenna 11-m whose SIR exceeds the threshold, and the other base station antenna 11-1 The propagation channel information of ˜11- (m−1) is set to “0”. That is, for the terminal station 20-1 that does not require beamforming, transmission is performed from only one base station antenna whose SIR exceeds the threshold.

  Next, the multi-user MIMO transmission weight calculation unit 18 calculates a transmission weight for multi-user MIMO transmission from the propagation channel information acquired from the terminal station and the propagation channel information supplemented with the specified value (S05). Finally, the multi-user MIMO transmission signal generation unit 19 generates a multi-user MIMO transmission signal using the calculated transmission weight (S06).

  The terminal station 20 receives a radio signal (S11). In S11, when a signal for measuring propagation channel information is received, the propagation channel information measurement notification unit 23 measures the propagation channel information and notifies the measurement result to the radio base station (S12). When the multi-user MIMO transmission signal is received, the multi-user MIMO transmission signal receiving unit 24 performs reception processing of the multi-user MIMO transmission signal (S13).

(Example 2)
In the first embodiment, when the terminal stations 20-1 to 20-n illustrated in FIG. 5 are wireless stations to be subjected to multi-user MIMO transmission, the wireless station 20-2 and the terminal station 20-3 are connected to the base station antenna 11-. Although both SIRs in 3 are 40 dB and the first condition is satisfied, the second condition is not satisfied. Therefore, the propagation channel information is acquired as a terminal station that requires beam forming.

  In the second embodiment, in order to reduce the notification of the propagation channel information from the radio station that is the target of multi-user MIMO transmission and reduce the overhead, the terminal station that does not require beamforming from the acquired received power information, that is, the propagation channel information A combination including as many terminal stations as possible that do not perform acquisition is detected, and radio stations to be subjected to multi-user MIMO transmission are grouped.

FIG. 6 shows a configuration example of the radio base station 10 according to the second embodiment of the present invention.
In FIG. 6, the group generation unit 15 performs grouping of radio stations to be subjected to multi-user MIMO transmission on the basis of the above criteria, and selects terminal stations in units of groups as with the terminal station selection unit 14 of the first embodiment. Do. Other configurations are the same as those of the first embodiment.

FIG. 7 shows a processing procedure example of the radio base station 10 according to the second embodiment of the present invention.
In FIG. 7, S01 to S06 indicate the same processing as in the first embodiment. The reception power measurement unit 13 of the radio base station 10 calculates the reception power (RSSI) for each of the base station antennas 11-1 to 11-m from the radio signals transmitted from the terminal stations 20-1 to 20-n before grouping. Measure (S01). The group generation unit 15 of the radio base station 10 performs grouping from the SIR calculation result shown in FIG. 8A so as to include many terminal stations that do not require beam forming (S21). Similar to the terminal station selection unit 14, a terminal station that requires beam forming for each group, that is, a terminal station that acquires propagation channel information, and a terminal station that does not require beam forming, that is, a terminal that does not acquire propagation channel information A station is selected (S22). The subsequent steps are the same as those in S03 and after in the first embodiment.

FIG. 8 shows an example of grouping in the second embodiment of the present invention.
In FIG. 8, from the SIR calculation result, the terminal station 20-2 is set as the group 1 and the terminal station 20-3 is set as the group x. In the group x, the terminal station 20-3 and the terminal station 20-6 are terminal stations that do not require beam forming, and terminal stations that do not acquire propagation channel information.

  Only terminal stations that do not require beamforming may be selected and grouped. For example, in the example of FIG. 8, the terminal station 20-1, the terminal station 20-2 or 20-3, and the terminal station 20-6 are a group of terminal stations that satisfy the first condition and the second condition. In this group, even if the propagation channel information is not acquired from each terminal station, the propagation channel information at the base station antenna whose SIR exceeds the threshold is “1”, and the propagation channel information of the other base station antennas is “0”. By doing so, multi-user MIMO transmission is possible.

DESCRIPTION OF SYMBOLS 10 Radio base station 11-1 to 11-m Base station antenna 12-1 to 12-m Transmission / reception part 13 Reception power measurement part 14 Terminal station selection part 15 Group generation part 16 Propagation channel information acquisition control part 17 Propagation channel information complement part 18 Multiuser MIMO transmission weight calculation unit 19 Multiuser MIMO transmission signal generation unit 20-1 to 20-n Terminal station 21 Terminal station antenna 22 Transmission / reception unit 23 Propagation channel information measurement notification unit 24 Multiuser MIMO transmission signal reception unit

Claims (6)

In a distributed antenna control method of a radio base station having a plurality of base station antennas distributed and performing multi-user MIMO transmission on a same radio channel to a plurality of terminal stations,
A first step of measuring received power between the plurality of base station antennas and the plurality of terminal station antennas;
For each terminal station, a ratio of signal power to interference power (hereinafter referred to as SIR) is calculated from the received power of the plurality of base station antennas, and a terminal station that requires beamforming and an unnecessary terminal station according to the SIR. A second step of selecting
A third step of obtaining propagation channel information from a terminal station that requires beamforming;
A fourth step of supplementing propagation channel information in a terminal station that does not require beamforming with a specified value;
A fifth step of calculating a transmission weight for multi-user MIMO transmission using each propagation channel information of the terminal station that requires the beamforming and the terminal station that does not need beamforming;
And a sixth step of generating and transmitting a multi-user MIMO transmission signal to be transmitted to the plurality of terminal stations using the transmission weight for multi-user MIMO transmission. Control method. In the distributed antenna control method of the radio base station according to claim 1,
In the second step, among the plurality of base station antennas, there is one base station antenna whose SIR exceeds a threshold value, and the SIR in another terminal station is equal to the one base station antenna. A distributed antenna control method for a radio base station, wherein a terminal station that does not exceed a threshold is selected as a terminal station that does not require beamforming, and another terminal station is selected as a terminal station that requires beamforming. In the distributed antenna control method of the radio base station according to claim 1,
When performing the second step, groups are generated from the plurality of terminal stations so that there are many terminal stations that do not need the beamforming and do not acquire the propagation channel information, and for each group, the SIR A method of controlling a distributed antenna of a radio base station, comprising: selecting a terminal station that requires beamforming and an unnecessary terminal station according to In a radio base station using a distributed antenna having a plurality of base station antennas distributed and performing multi-user MIMO transmission on the same radio channel to a plurality of terminal stations,
A received power measuring unit that measures received power between the plurality of base station antennas and the antennas of the plurality of terminal stations;
For each terminal station, a ratio of signal power to interference power (hereinafter referred to as SIR) is calculated from the received power of the plurality of base station antennas, and a terminal station that requires beamforming and an unnecessary terminal station according to the SIR. A terminal station selection unit for selecting
A propagation channel information acquisition control unit for acquiring propagation channel information from a terminal station that requires beam forming;
A propagation channel information complementing unit that complements the propagation channel information in a terminal station that does not require beamforming with a specified value;
A transmission weight calculation unit for multiuser MIMO transmission that calculates a transmission weight for multiuser MIMO transmission using each propagation channel information of the terminal station that requires beam forming and an unnecessary terminal station;
A multi-user MIMO transmission signal generation unit that generates and transmits a multi-user MIMO transmission signal to be transmitted to the plurality of terminal stations using the multi-user MIMO transmission transmission weight; A radio base station using an antenna. In the radio base station using the distributed antenna according to claim 4,
The terminal station selection unit includes one base station antenna whose SIR exceeds a threshold among the plurality of base station antennas, and the SIR in another terminal station is the base station antenna with respect to the one base station antenna. It is configured to select a terminal station that does not exceed a threshold as a terminal station that does not require beamforming, and to select another terminal station as a terminal station that requires beamforming. Bureau. In the radio base station using the distributed antenna according to claim 4,
The terminal station selection unit includes a group generation unit that generates a group so that there are more terminal stations that do not need the beamforming and do not acquire the propagation channel information from the plurality of terminal stations, and for each group A radio base station using a distributed antenna, characterized in that a terminal station that requires beamforming and an unnecessary terminal station are selected according to the SIR.

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