JP5808680B2 - Wireless communication system, base station and wireless terminal - Google Patents

Description

  The present invention relates to a radio communication system, a base station, and a radio terminal, and more particularly to an interference control technique for a base station having a plurality of antennas.

Generally, in a digital mobile communication system using OFDMA (Orthogonal Frequency Division Multiple Access), radio resources that are further divided by frequency and time within a certain frequency band called a frame and a unit of time are allocated. To communicate with multiple terminals. In IMT-Advanced (International Mobile Communications-Advanced), which is a fourth generation communication system using OFDMA, as shown in Non-Patent Documents 1 and 2, MIMO (Multiple-Input Multiple-Output) technology is used to improve throughput. And the improvement of frequency utilization efficiency is demanded. In the following, DL (Downlink) throughput, which is particularly important in data communication, is targeted.
In order to improve frequency utilization efficiency, it is necessary for adjacent base stations to share the same frequency. However, when adjacent base stations use the same frequency, interference occurs between the base stations, and CINR (Carrier to Interference plus Noise Ratio) deteriorates. In general, since high CINR is required for MIMO transmission, when interference between base stations occurs, MIMO transmission becomes difficult and throughput deteriorates. Therefore, it is important for IMT-Advanced to efficiently perform MIMO transmission while sharing a frequency. Inter-base station interference suppression technology is important when sharing frequencies. As shown in Non-Patent Document 1 and Non-Patent Document 3, as inter-base station interference suppression technology, data of the same terminal is divided or copied to different base stations, and a plurality of base stations cooperate with the terminal. Thus, there is shown a method for avoiding interference by making a base station signal causing interference not a interference but a desired signal to a terminal by performing communication. On the other hand, as a method of not dividing data into a plurality of base stations, the time and frequency resources used in the own base station, as shown in Patent Document 1, are controlled so as not to be used in adjacent base stations. A method for avoiding inter-station interference has been proposed.

JP 2011-41084 A

IEEE802.16, P802.16m-2011, May 2011 3GPP, TR 36.913 v10.0.0, Mar. 2011 3GPP, TR 36.819 v1.0.0, May 2011

The method of dividing data between base stations requires that data for one terminal needs to be divided or copied for a plurality of base stations, so that data synchronization becomes complicated, and ARQ (Automatic Repeat and reQuest), etc. Retransmission control becomes complicated. On the other hand, in a method in which data is not divided between base stations, the base station communicates with the terminal using all the MIMO streams, and therefore there is a possibility that the received MIMO stream cannot be processed when the processing capability of the terminal is low. Also, if many MIMO stream transmissions are performed from the same base station, the correlation between antennas becomes high and signal separation becomes difficult.
An object of the present invention is to provide a radio communication system, a base station, and a radio terminal that efficiently perform MIMO transmission while suppressing inter-base station interference without dividing data between base stations. Another object of the present invention is to suppress interference caused by a terminal and prevent deterioration of throughput in a wireless communication system having a base station that transmits a plurality of data streams simultaneously.

In order to solve at least one of the above-described problems, according to one aspect of the present invention, there is provided a wireless communication system including a wireless communication base station having a plurality of antennas, and an interference base for a terminal having strong inter-base station interference. Information is exchanged between base stations so that the streams do not overlap with each other, and the reference signal information of the stream used by the base station with dominant interference power for communication is notified to the terminal.
In one embodiment of the present invention, the base station system includes:
Simultaneous communication (MIMO) with the terminal with multiple antennas per sector,
Depending on the communication status of the terminal accommodated in one sector, send a restriction request that restricts the resources used by other sectors,
Pilot information for determining resources used by other sectors is notified to the terminal.
The communication status is a status in which predetermined interference is received from another sector.

According to the first solution of the present invention,
A wireless communication system comprising a plurality of base stations that transmit a plurality of data streams using a plurality of antennas, and a terminal that estimates a propagation path using a pilot signal for each data stream and demodulates data. And
The plurality of base stations are
A first base station communicating in a first data stream;
A second data station that communicates with the terminal in a second data stream that is different from the first data stream and that is subject to interference from the first base station;
The second base station is
A second data stream different from the first data stream used by the first base station is allocated to the terminal belonging to the second base station;
Transmitting data and a second pilot signal to the terminal using the allocated second data stream;
Transmitting pilot signal identification information for identifying a first pilot signal of a first data stream transmitted from the first base station to the terminal;
The terminal demodulates data received from the first base station and the second base station using a first pilot signal and a second pilot signal specified according to the pilot signal identification information, and receives second data A wireless communication system for extracting stream data is provided.

According to the second solution of the present invention,
In a wireless communication system comprising a plurality of base stations that transmit a plurality of data streams using a plurality of antennas, and a terminal that estimates a propagation path using a pilot signal for each data stream and demodulates data, A base station that communicates with the terminal that receives interference from the interfering station using a second data stream different from the first data stream used by the interfering station that is one of the plurality of base stations,
A use stream restriction unit that assigns a second data stream different from the first data stream used by the interfering station as a data stream used by the terminal belonging to the base station;
A communication processing unit for transmitting data and a second pilot signal to the terminal using the allocated second data stream;
The terminal identifies a first pilot signal of a first data stream transmitted from an interference station and estimates a propagation path using the first pilot signal from the interference station and the second pilot signal from the own base station. And a control unit that transmits pilot signal identification information of the first pilot signal to the terminal.

According to the third solution of the present invention,
In a radio communication system comprising a plurality of base stations that transmit a plurality of data streams using a plurality of antennas, and a radio terminal that estimates a propagation path using a pilot signal for each data stream and demodulates data The wireless terminal comprising:
Data and a second pilot signal are received from the second base station and transmitted from the first base station using a second data stream different from the first data stream used by the first base station. A radio communication unit that receives, from the second base station, pilot signal identification information for identifying a first pilot signal of a first data stream;
Data received from the first base station and the second base station is demodulated using the first pilot signal and the second pilot signal specified according to the pilot signal identification information, and the data of the second data stream is The wireless terminal including a baseband processing unit for extraction is provided.

  According to the present invention, it is possible to provide a radio communication system, a base station, and a radio terminal that efficiently perform MIMO transmission while suppressing inter-base station interference without dividing data between base stations. Also, according to the present invention, in a wireless communication system having a base station that transmits a plurality of data streams simultaneously, it is possible to suppress interference caused by a terminal and prevent throughput deterioration.

It is a sequence diagram in a 1st Example. It is a figure which shows an example of the mobile radio | wireless communications system to which each Example is applied. It is a figure which shows an example of a structure of the base station to which each Example is applied. It is a figure which shows an example of base station arrangement | positioning of the mobile communication system with which each Example is applied. It is a figure which shows an example of the communication frame transmitted with a terminal and a base station based on each Example. It is a software block diagram of the base station according to each embodiment. It is a figure which shows an example of the hardware of a base station in a 1st Example, and a block configuration. It is a figure which shows an example of the software of a terminal in a 1st Example, and a block configuration. It is a figure which shows an example of the hardware of a terminal in a 1st Example, and a block configuration. FIG. 3 is a sequence diagram according to the first embodiment. It is a block block diagram of the stream restriction | limiting part based on 1st Example. It is a figure which shows the structure of the interference power table based on a 1st Example. It is a figure which shows the flowchart of the interference determination part based on 1st Example. It is a figure which shows the structure of the interference station table based on a 1st Example. It is a figure which shows the flowchart of the stream restriction | limiting part based on 1st Example. It is a figure which shows the structure of the own base station stream restriction | limiting table based on 1st Example. It is a figure which shows an example of the state of a stream restriction | limiting based on 1st Example. It is a figure which shows the flowchart of step 1502 based on a 1st Example. It is a figure which shows the flowchart of step 1504 based on 1st Example. It is a figure which shows an example of the interference station table based on a 1st Example. It is a figure which shows the structure of the interference station stream restriction | limiting table based on a 1st Example. It is a figure which shows the decoding process of MIMO based on 1st Example. It is a figure which shows an example of Pilot position based on a 1st Example. It is a figure which shows the Pilot information notified to a terminal based on a 1st Example. It is a figure which shows the sequence based on a 2nd Example. It is a figure which shows the structure of the terminal based on a 2nd Example. It is a figure which shows the block configuration of the stream restriction | limiting part based on 2nd Example. It is a figure which shows the sequence based on a 3rd Example. It is a figure which shows the concept of the relationship between a primary base station and a secondary base station based on a 3rd Example. It is a figure which shows the structure of the interference electric power table based on a 3rd Example. It is a figure which shows the structure of the interference station table based on a 3rd Example. It is a figure which shows the flowchart of the use stream restriction | limiting part based on 3rd Example. It is a figure which shows the block configuration of the use stream restriction | limiting part of the secondary base station based on a 3rd Example. It is an example which shows the structure of DAS based on a 4th Example.

Hereinafter, various embodiments of the present wireless communication system and wireless communication base stations and wireless terminals in the wireless communication system will be described in detail with reference to the drawings. Prior to that, an embodiment of a wireless communication system to which various examples are applied will be described.
The wireless communication systems of various embodiments are applied in a network configuration as shown in FIG. 2, for example. The wireless communication system includes a plurality of base stations 20 b 1, 20 b 2,... 20 b N and a plurality of terminals 20 m 1 that communicate wirelessly with the base stations in the cells 2 c 1, 2 c 2,. , 20 m 2, and so on. The base stations 20b1, 20b2,... 20bN are connected to an external communication network such as the Internet (NW) 203 via a router (or L3 switch) 201 and a gateway (GW) 202. Alternatively, as shown in FIG. 3, a three-sector configuration in which three base stations 301, 302, and 303 coexist may be employed. In the three-sector configuration, the sectors are connected by an internal interface 304, and are connected to other adjacent base stations by a backhaul 305 as in FIG. However, the network configuration according to each embodiment is not limited to this, and any network configuration may be used as long as the base station and the terminal can perform wireless access.
Further, FIG. 4 shows a planar arrangement of base stations in the base station configuration of FIG. When the cell radius is uniform among the base stations, for example, a generally performed hexagonal cell arrangement may be adopted. The base station arrangement in that case is shown in FIG. The cell of base station 402 is indicated at 401. Further, when the cell radii are not uniform among the base stations, the hexagonal cell arrangement is not used, but an irregular base station arrangement as shown in FIG. The planar arrangement of the base stations in the base station configuration of FIG. 3 is a configuration in which the cell 401 of FIG. 4 is divided into three-directional sectors for each cell. Each of the embodiments is provided in such a base station arrangement.

FIG. 5 shows an example of a frame configuration used in this wireless communication system. FIG. 5 shows an IEEE 802.16m frame configuration. A frequency bandwidth that can be used for communication is called a system bandwidth 504. The system bandwidth is divided into subchannels 501, divided into subframes 502 in the time direction, and the time and frequency domain divided by one subchannel and one subframe are set to PRU (Physical Resource Unit, physical resource unit, radio Resource unit) 503. Control information such as radio resource allocation information to the terminal and system configuration is transmitted using the control channel 507 of one or a plurality of subframes 502. Also, DL and UL (uplink) control messages can be transmitted using PRUs other than the control channel 507 of each subframe 502. Such a configuration is, for example, a frame configuration assumed when OFDMA (Orthogonal Frequency Division Multiple Access) of TDD (Time Division Duplex) is assumed, and FDD (Frequency Division) is also the same.

As a wireless communication system according to the first embodiment, a base station has a plurality of antennas, a terminal measures received interference power and reports to the base station, and the base station gives interference to the terminal. A description will be given of a configuration in which the use stream is restricted between base stations by determining (interference station) and the reference signal (Pilot) information of the interference station is notified to the terminal. Also, the terminal that is notified of the pilot information of the interfering station performs MIMO stream separation using the pilot information of the own base station and the pilot information of the interfering station.
The device configuration (functional block configuration) of the base station 20b according to the first embodiment will be described with reference to the block diagram of FIG.
The base station 20b includes a controller 610, an antenna 609 that transmits and receives radio waves between terminals, a transmission / reception switching switch 608, a line interface 601 that is connected to a connection line to the router 201, and a line interface 601. Upper layer processing unit 602 connected, transmission RF (Radio Frequency) unit 106 and reception RF unit 607 connected to switch 608, Downlink baseband processing unit 604, Uplink baseband processing unit 605, upper layer control A scheduling unit 603 connected between the unit 602 and the Downlink baseband processing unit 604, and a usage stream limiting unit 611 that limits the usage streams of terminals to be allocated to the scheduling unit 603. In this specification, the transmission RF unit 106, the reception RF unit 607, the Downlink baseband processing unit 604, and the Uplink baseband processing unit 605 may be collectively referred to as a communication processing unit.
In the functional block configuration of the present embodiment shown in FIG. 6, in DL, first, data transmitted from the line interface 601 is subjected to header processing for communication with the GW by the higher layer control unit 602. Next, the use stream restriction unit 611 uses the information notified from the adjacent base station input from the higher layer control unit 602 or the interference report value from the terminal from the Uplink baseband processing unit 605 to Limit the streams used. Details of the use stream restriction unit 611 will be described later with reference to FIG.
In scheduling section 603, service information from higher layer control section 602, signal from reception RF section 607, signal from Uplink baseband processing section 605, and usable stream information of each terminal from use stream restriction section 611 Is used to measure the reception quality of each slot, and DL and UL resource allocation is determined. However, the information used in the scheduling unit 603 is not limited to the above, and information from other processing units may be used.
Thereafter, the data is transferred to the Downlink baseband processing unit 604, where processing such as encoding and modulation is performed, and then RF processing is performed in the transmission RF unit 606. Then, the switch 608 is switched to the transmission side, and a radio signal is transmitted from the antenna 609. For example, MIMO technology is applied to the base station 20b. The above processing operates according to a control signal from the controller 610.
In the UL, first, the switch 608 is switched to the receiving side, and a radio signal is received by the antenna 609. Next, the received data is subjected to RF processing in the reception RF unit 607. Thereafter, the data is transferred to the Uplink baseband processing unit 605, decoded and demodulated, and then processed by the upper layer control unit 602, and the data is transmitted from the line interface 601. The above processing operates according to a control signal from the controller 110. Further, as will be described later, the interference power information reported from the terminal is input to the use stream restriction unit 611.

Next, an example of the device configuration (hardware configuration) of the base station 20b of the first embodiment will be described using the block configuration diagram shown in FIG.
The function block transmission RF unit 606, reception RF unit 607, switch 608, antenna 609, and use stream restriction unit 612 of the functional block shown in FIG. 6 are provided in the transceiver 703 that transmits and receives wireless signals, and the line interface 601 is an I / F 704. And is connected to the network 705. Other functional blocks are program modules executed by the processor 701, and these program modules are stored in the memory 702. As described later, the use stream restriction unit 611 refers to various tables formed on the data memory 706 to determine the transmission power of each antenna in each frequency band.
The processing performed by the controller 610 in FIG. 6 corresponds to a program module executed by the processor 701.
FIG. 8 is a block configuration diagram illustrating an example of a device configuration of the terminal 20m according to the present embodiment.
The terminal 20m includes a controller 810, an antenna 809 that transmits and receives radio waves between the base station, a transmission / reception switching switch 808 connected to the antenna 809, and an upper layer processing unit 802 connected to the user interface 801. The transmission RF unit 806 and the reception RF unit 807 connected to the switch 808, the Uplink baseband processing unit 804 connected between the upper layer processing unit 802 and the transmission RF unit 806, the upper layer processing unit 802, and the reception RF A downlink baseband processing unit 805 connected to the unit 807. Further, a reception quality measurement unit 813 connected between the upper layer processing unit 802 and the reception RF unit 807 is provided.
In the UL, first, data transmitted from the user interface 905 is processed by the upper layer control unit 802. Next, the data is transferred to the Uplink baseband processing unit 804, and after processing such as encoding and modulation, RF processing is performed in the transmission RF unit 806. Then, the switch 808 is switched to the transmission side, and a radio signal is transmitted from the antenna 809. The above processing operates according to a control signal from the controller 810.
In DL, first, the switch 808 is switched to the receiving side, and a radio signal is received by the antenna 809. Next, RF processing is performed in the reception RF unit 807. Thereafter, the data moves to the Downlink baseband processing unit 805, and after processing such as decoding and demodulation, the data is processed by the higher layer control unit 802 and output to the user interface 801. The downlink baseband processing unit 805 performs reception signal processing using pilot information notified from the base station, as will be described later. Also, the reception quality measurement unit 813 measures the reception quality and transmits it to the higher layer control unit 802. The above processing operates according to a control signal from the controller 810. The controller 810 has a function of transmitting frame configuration information transmitted in DL to each processing unit. Here, the user interface is not limited to this, and an interface with another device is also conceivable.

FIG. 9 shows an example of the hardware configuration of the terminal 20m. The transmission RF unit 806, the reception RF unit 807, the switch 808, and the antenna 809 of the terminal in FIG. 8 are provided in the transceiver 803 that transmits and receives radio signals, and the interface 801 is provided in the I / F 904 and is connected to the user interface 905. ing. The other functional blocks are program modules executed by the processor 901. These program modules are stored in the memory 902 and operate according to data from the user interface 905. Processing performed by the controller 810 corresponds to a program module executed by the processor 901.
In the first embodiment, the terminal 20m shown in FIGS. 8 and 9 measures the interference power, and the base station 20b shown in FIGS. 6 and 7 performs stream restriction based on the interference power information measured by the terminal, DL transmission is performed. A sequence diagram of the first embodiment is shown in FIG.
First, the base station 20b (second base station) transmits an interference measurement instruction to a terminal belonging to the base station in order to identify an interference station (first base station) (step 101). Here, the base station that instructs the measurement of interference may simultaneously designate a plurality of base stations as measurement targets. For example, a base station that is set in advance as a base station adjacent to a base station that issues a measurement instruction may be targeted.

The terminal that has received the interference measurement instruction (step 101) measures the interference power from the base station to be measured by the reception quality measurement unit 813 according to the instruction. For example, as the interference power, either or both of the received power of the measurement target base station and CINR may be measured. In addition to these, appropriate reception quality from the measurement target base station may be used.
The terminal that performed the interference measurement reports the measurement result to the base station in step 103. For example, it reports to the transmission source of the interference measurement instruction.
In step 104, the base station that has received the report determines a base station that gives dominant interference to the terminal as an interference station from the interference power of each base station that is the measurement target of interference measured by the terminal. A stream whose use is restricted is determined for the interfering station. Also, a stream that can be used by the base station is determined. Details will be described later.
After determining the stream that restricts the use of the interference station, the base station notifies the interference station of the stream restriction information indicating the judgment result of the stream to be restricted using Backhaul (stream restriction instruction) in Step 105. . The stream restriction instruction may be notified at other appropriate timing.
From the stream restriction information, each base station performs scheduling under stream restriction conditions in step 106.
After scheduling, in step 107, the base station notifies the terminal of pilot information (pilot signal identification information) of the base station that is an interfering station together with data allocation information of the base station. The pilot information of the interference station is known in advance by the base station.
In step 108, the terminal that has received the allocation information and the pilot information of the interfering station performs stream separation using the pilot information of the base station and the pilot information of the interfering station in decoding of the data addressed to the self terminal. Retrieve data addressed to the terminal. In the above description, one terminal has been described, but the same processing can be performed for a plurality of terminals belonging to the base station.

Also, as shown in FIG. 10, after notifying the stream determination result in step 105, it is determined whether the notified interfering station complies with the restriction information, and the determination result is notified to the transmission source base station. Also good. For example, when the restriction information is notified, another control interruption process may occur, and the restriction information may not be applied on the receiving side of the notice information. If you do not accept, reply as unacceptable. The base station that has been returned as unacceptable does not reflect the stream determination result at the timing in the scheduler.
Note that step 104 described above corresponds to the processing in the use stream restriction unit 611 in FIG. 6, and step 106 corresponds to the processing in the scheduling unit 603. Other steps may be performed by the controller 610, for example.
A block diagram of the use stream restriction unit 611 is shown in FIG. The use stream restriction unit 611 includes an interference power table (interference information table) 1101 that stores interference power information reported from the terminal, an interference station determination unit 1102 that determines an interference station from the interference power, and a use that determines a use stream. The stream determination unit 1103, the own base station stream restriction table 1104 that holds the notified stream restriction information, the interference station stream restriction table 1105 that stores a stream that restricts the interference station, and can be used by the own base station A usable stream table 1106 for storing various streams. The use stream restriction unit 611 stores the interference power information reported from the terminal in the interference power table 1101, and the interference station determination unit 1102 determines the dominant interference station for each terminal. After the interference station determination, the use stream determination unit 1103 stores, from the interference station stream restriction information stored in the own base station stream restriction table 1104 notified from Backhaul, radio resources corresponding to the streams that can be used by each terminal, The radio resource corresponding to the stream to be restricted with respect to the interference station is determined, the former is reflected in the usable stream table 1106, and the latter is reflected in the interference station stream restriction table 1105. The available stream table 1106 is used in the scheduling unit 603 at the subsequent stage. The information of the interference station stream restriction table 1105 is transmitted to the interference station through Backhaul.

The interference power table 1101 is a table in which the interference power reported from the terminal is tabulated as shown in FIG. The base station ID column 1201 stores the ID of the measured base station. Here, the highest base station ID is the ID of the own base station. The received power column 1202 stores the measured received power of the base station. The CINR column 1203 stores the measured CINR of the base station. The received power p or CINR γ may be averaged by the following equation.
p (t) = αp (t−1) + (1−α) P (t)
γ (t) = αγ (t−1) + (1−α) Γ (t)
Here, p (t) is the average received power at time t, P (t) is the reported value of received power at time t, γ (t) is the average CINR at time t, and Γ (t) is the CINR at time t. The reported value, α, is a forgetting factor and satisfies 0 <= α <1. However, the interference power table 1101 is not limited to this as long as it stores the interference power of the base station. In addition, the averaging is not limited to this as long as the report values from the terminals are averaged.
The interference station determination unit 1102 refers to the interference power table 1101 and determines a base station that gives dominant interference to the terminal. A flowchart of the interference station determination unit 1102 is shown in FIG.
In step 1301, the interference station determination unit 1102 extracts interference power (received power and / or CINR, etc.) of base stations other than its own base station from the interference power table 1101.
In step 1302, the interference station determination unit 1102 calculates the difference between the received power of the own base station and the received power of the extracted base station, that is, the power difference between the signal of the own base station and the extracted signal of the base station. Further, the interference station determination unit 1102 may calculate the difference between the CINR of the own base station and the extracted CINR of the base station.

If the difference is equal to or smaller than a predetermined threshold value in step 1303, that is, if the power difference is small, the interference station determination unit 1102 determines that the terminal is near the boundary between the base station and the extracted base station. Migrate to On the other hand, when the difference exceeds the threshold value, the interference station determination unit 1102 determines that the terminal is located on the inner side (own base station side) from the boundary between the base station and the extracted base station, and determines that there is no interference state. Control goes to step 1305.
In step 1304, the interference station determination unit 1102 classifies the base station as an interference station candidate. For example, the identifier of the base station is stored.
In step 1305, the interference station determination unit 1102 returns to step 1301 if the determination of all base stations has not been completed. If all the base stations have been determined, the process proceeds to step 1306.
In step 1306, the interference station determination unit 1102 selects, for example, a base station having the maximum interference power from among the base stations classified as interference station candidates. In addition to the base station with the largest interference power, one of the base stations with the interference power larger than a predetermined threshold may be selected.
In step 1307, the interference station determination unit 1102 determines that the selected base station is an interference station, and ends the process. The above processing can be performed for a plurality of terminals belonging to the own base station.
The determined interference station is stored in the interference station table 1106 for each terminal. The interference station table 1106 is shown in FIG. The interference station table stores a terminal ID 1401 that is determined to be an interference station, an ID 1402 of the corresponding interference station, and interference power 1403 from the interference station.
If the interference station determination unit determines the correspondence between the terminal and the interference station, such as determining the base station having the strongest interference power as an interference station, the power difference between the own base station and the adjacent base station is equal to or less than the threshold, However, the present invention is not limited to this.
The used stream determination unit 1103 refers to the own base station stream restriction table 1104, controls so as not to use the radio resource instructed to restrict the stream, and uses it in the own base station for the terminal in which the interference station exists. A radio resource corresponding to the stream and a stream and radio resource to be restricted with respect to the interference station are determined. A flowchart of the stream restriction unit 1103 is shown in FIG.

In step 1501, the use stream determination unit 1103 extracts a stream number and a radio resource number that cannot be used by the own base station from the own base station stream restriction table 1104. The own base station stream restriction table 1104 is shown in FIG. The own base station stream restriction table 1104 holds, as a table, the correspondence between the restriction source notification base station ID 1601, the stream number 1602 instructed to be restricted, and the radio resource position 1603. In addition to the number, appropriate identification information may be used. The own base station stream restriction table 1104 is not limited to this as long as it is a table storing stream restriction information notified from other base stations. FIG. 17 shows an example of the stream restriction state when the restriction information as shown in FIG. 16 is notified. Here, the maximum number of streams is 4, and only the frequency direction is considered as a radio resource. For each stream, there is a radio resource 1701. Based on the notified stream number and the position of the radio resource, the stream number and the resource position that cannot be used by the own base station are as indicated by 1702. The number displayed in 1702 is the notification source base station ID.
In step 1502, the used stream determination unit 1103 determines the number of usable streams of the terminals existing in the interference station table 1106. A detailed flowchart of step 1502 is shown in FIG.
In step 1801, the used stream determination unit 1103 extracts the maximum number N of receivable streams of the terminal. The maximum number of receivable streams of the terminal is exchanged between the base station and the terminal when the terminal is connected.
In step 1802, the used stream determination unit 1103 extracts the maximum number M of streams that can be transmitted by the base station. The maximum number M of streams that can be transmitted can be obtained from, for example, the number of streams set in advance in the base station and the limited number of streams. If N> M / 2 in step 1803, the used stream determination unit 1103 sets the number of usable streams to M / 2, which is half the maximum number of streams that can be transmitted by the base station (step 1804). On the other hand, if N <= M / 2, the used stream determination unit 1103 sets the number of usable streams to N (step 1805).
Step 1502 is limited to this if the number of usable streams S is set to N or less and less than M based on the maximum number of streams N that can be received by the terminal and the maximum number M of streams that can be transmitted by the base station. is not.

In step 1503, the used stream determination unit 1103 determines the number of usable resources of the terminal existing in the interference station table 1106 from the number of usable streams determined in step 1502. Here, it is assumed that ceil (L / S) resources can be used per terminal for a preset number L of unit radio resources. Here, ceil (x) is a function that returns the smallest integer greater than or equal to x. The method for determining the number of usable resources is not limited to this as long as it is individually set for each terminal based on the number of usable streams. For example, when the decision value of the previous number of used resources is held and it is judged that more radio resources are needed from traffic, buffers, etc., the number of available resources is incremented and decremented in the opposite case But it ’s okay.
In step 1504, the used stream determination unit 1103 determines a stream position that can be actually used by the terminal from the obtained number of available streams and the number of available resources. In the determination of the stream position, the available stream and radio resource (PRU) are allocated with priority from the available stream with the radio resource at the same position as the unusable stream extracted in step 1501. Also, when there is restriction information from the interference station for the terminal existing in the interference station table 1106, a stream that is not restricted is preferentially assigned to the terminal by the radio resource restricted by the interference station. A flowchart of step 1504 is shown in FIG.

In step 1901, the used stream determination unit 1103 extracts the terminal ID from the interference station table 1106.
In step 1902, the use stream determination unit 1103 checks whether or not an interference station corresponding to the extracted terminal ID is included in the own base station stream restriction table 1104. If it is included, the process proceeds to step 1903. If it is not included, the process proceeds to step 1905.
In step 1903, the use stream determination unit 1103 extracts the radio resource number restricted by the interference station from the base station stream restriction table 1104.
In step 1904, the used stream determination unit 1103 sequentially assigns, as an available stream and an available radio resource, to the terminal, with respect to an unrestricted stream within the range of the extracted radio resource number. In the case of recognizing each other as an interfering station, it is possible to minimize radio resources to be restricted with respect to other base stations by using the same radio resource position in different streams.
In step 1905, the used stream determination unit 1103 checks whether or not all terminals have been searched. If not completed, the process returns to step 1901 to repeat the process for other terminals. If completed, the process proceeds to step 1906.
In step 1906, it is checked whether or not the number of radio resources (PRU) to be allocated remains for the terminals existing in the interference station table 1106. If it does not remain, the process ends. If it remains, the process proceeds to step 1907.
In step 1907, the number of remaining radio resources is extracted as radio resources that are not yet allocated as available resources but are restricted in the stream.
In step 1908, an available stream and an available radio resource are assigned to a terminal that needs to be assigned to a position where the stream is not restricted by the extracted radio resources in order.
In step 1909, it is checked whether or not the number of radio resources that need to be allocated remains for the terminals existing in the interference station table 1106. If it does not remain, the process ends. If it remains, the process proceeds to step 1910.

In step 1910, with respect to the number of remaining radio resources that need to be allocated, an available stream and an available radio resource are sequentially assigned to radio resources that are not yet assigned as assignable radio resources, and the process ends.
The processing of step 1504 preferentially assigns different streams to usable streams and usable radio resources for radio resources that are recognized as interfering stations, and then is not recognized as interfering stations. The stream is not limited to a limited radio resource as long as a different stream (a stream different from the restricted stream) is preferentially allocated to the usable stream and the usable radio resource.
In step 1505, in order to notify the radio resource allocated in step 1504 and the position of the stream as a combination of the limited radio resource and the limited stream position for limiting the interference station of the terminal, the interference station stream restriction table 1105 is notified. Write.
FIG. 20 shows an example of allocated radio resources and stream positions of terminals present in the interference station table 1106. For example, when the interference station of terminal # 2 is base station # 5, different streams of radio resources restricted by base station # 5 are allocated to terminal # 2. Further, the allocated radio resource and stream position are written in the interference station stream restriction table 1105 to notify the base station # 5 as a radio resource and stream position whose use is prohibited. The interference station stream restriction table 1105 is shown in FIG. The interference station ID column 2101 stores base station IDs (interference station IDs) that restrict radio resources and streams. The restricted stream number column 2102 stores a restricted stream number. The restricted radio resource number column 2103 stores radio resource positions to be restricted. However, the interference station stream restriction table 1105 is not limited to this as long as it stores a combination of the ID of the base station to be restricted, the restricted stream, and the position of the radio resource. Here, the restricted stream number and radio resource number correspond to the stream number and radio resource number assigned to the terminal by the own base station.

The used stream determination unit 1103 determines a combination of a stream and a radio resource that can be used for a terminal existing in the interference station table 1106 under the restriction of the own base station stream restriction table 1104. It is not limited.
Returning to the sequence diagram of FIG. 1, the base station performs data transmission in step 107 after scheduling in step 106. In data transmission, pilot signals of interference stations (known on the transmission and reception sides) used for decoding MIMO for terminals allocated to radio resources subject to stream restrictions from the interference stations together with resource allocation information during scheduling. Signal) Information is notified to the terminal. For example, when a terminal is assigned as shown in FIG. 20, since the terminal # 2 receives interference from the base station # 5, the base station sends the pilot information of the base station # 5, which is an interference station, to the terminal # 2. Notice.
FIG. 22 shows MIMO decoding processing in the Downlink baseband processing unit 805 of the terminal. First, the Downlink baseband processing unit 805 performs propagation path estimation 2202 on the received signal. In the propagation path estimation, the terminal recognizes which radio resource and which stream are allocated to its own terminal from the resource allocation information transmitted in step 107. Also, a pilot sequence used for propagation path estimation is acquired from the pilot information of the interfering station transmitted in step 107. Although the pilot sequence differs for each base station, the base station notifies the pilot information of the interfering station in step 107, so that the pilot sequence can be acquired in the terminal. The position of the pilot signal is determined from the relationship between the radio resource allocated to the terminal and the stream, and the propagation path is estimated using the position of the pilot signal and the acquired pilot sequence. Since the pilot signal is transmitted as an individual signal for each stream, the terminal can estimate the propagation path between each stream and each receiving antenna.
FIG. 23 shows an example of the pilot position. In the example of FIG. 23, the pilot of each stream has a different frequency and time, and the pilot positions of the other streams are set to Null, so that signals are not transmitted between the streams, thereby preventing the pilots from interfering with each other. By avoiding interference between pilots, the propagation path h is estimated from the pilot signal s and the received signal y as follows.

ここで、［ ］^＊は複素共役を表す。ただし、Ｐｉｌｏｔは図２３のように異なる周波数、時間で送信するものに限らず、送受信側で既知であればこれに限定するものではない。例えば、同じ周波数、時間で送信し、Ｃｏｄｅ多重されているものでも良い。Ｐｉｌｏｔの伝搬路推定後、データ信号部分の伝搬路推定を行う。データ信号の伝搬路推定では、Ｐｉｌｏｔ位置の伝搬路推定値から補間により求める。例えば、隣接Ｐｉｌｏｔ間の線形補間や、曲線による３次Ｓｐｌｉｎｅ補間がある。ただし、データの伝搬路推定では、Ｐｉｌｏｔの伝搬路推定値から、補間により求めるものであればこれに限定するものではない。送信ストリーム番号ｉと、受信アンテナｊの間の伝搬路推定値をｈｉｊとすると、伝搬路推定行列Ｈは以下で表される。

上記は４ストリーム送信、４アンテナ受信の場合を表す。また、受信信号は、送信信号をｘとすると以下で表される。

ここで、ｎは雑音である。等化２２０１では、Ｄｏｗｎｌｉｎｋベースバンド処理部８０５は、伝搬路推定行列Ｈと、受信信号ｙから、送信信号ｘを推定する。ＭＭＳＥ（ｍｉｎｉｍｕｍ ｍｅａｎ−ｓｑｕａｒｅｄ ｅｒｒｏｒ）の場合の、送信信号ｘの推定方法は以下で表される。

ただし、等化２２０１は、伝搬路推定行列と受信信号から、送信信号を推定するものであればこれに限定するものではない。例えば、ＢＬＡＳＴ（Ｂｅｌｌ−ｌａｂｏｒａｔｏｒｉｅｓ Ｌａｙｅｒｅｄ Ｓｐａｃｅ−Ｔｉｍｅ）やＭＬＤ（Ｍａｘｉｍｕｍ−Ｌｉｋｅｌｉｈｏｏｄ Ｄｅｔｅｃｔｉｏｎ）でも良い。

Here, [] ^* represents a complex conjugate. However, the Pilot is not limited to transmitting at different frequencies and times as shown in FIG. 23, and is not limited to this as long as it is known on the transmission / reception side. For example, it may be transmitted at the same frequency and time and code-multiplexed. After the pilot propagation path is estimated, the propagation path of the data signal portion is estimated. In the propagation estimation of the data signal, it is obtained by interpolation from the propagation path estimated value at the pilot position. For example, there are linear interpolation between adjacent pilots and cubic spline interpolation using curves. However, the data propagation path estimation is not limited to this as long as it is obtained by interpolation from the pilot propagation path estimated value. Assuming that the propagation path estimation value between the transmission stream number i and the receiving antenna j is hij, the propagation path estimation matrix H is expressed as follows.

The above represents the case of 4-stream transmission and 4-antenna reception. Further, the received signal is expressed as follows, where x is the transmission signal.

Here, n is noise. In equalization 2201, the Downlink baseband processing unit 805 estimates the transmission signal x from the propagation path estimation matrix H and the reception signal y. The estimation method of the transmission signal x in the case of MMSE (minimum mean-squared error) is expressed as follows.

However, the equalization 2201 is not limited to this as long as the transmission signal is estimated from the channel estimation matrix and the received signal. For example, BLAST (Bell-laboratories Layered Space-Time) or MLD (Maximum-Likelihood Detection) may be used.

In MIMO equalization, it is necessary to estimate a channel estimation matrix for all streams received by a terminal. For example, in the case of terminal # 2 in FIG. 20, streams # 1 and # 2 estimate the propagation path from base station # 5, and streams # 3 and # 4 estimate the propagation path from the own base station. In the propagation path estimation from the own base station, since the pilot signal transmission method is known in advance, propagation path estimation is possible. In the present embodiment, it is possible to estimate the propagation path from the base station # 5 by notifying the terminal of the pilot information of the base station # 5 that is an interference station. Thereby, propagation paths of all streams can be estimated, and streams can be separated by equalization. The terminal acquires data of streams # 1 and # 2 assigned to the terminal among the separated streams.
Pilot information notified to the terminal is shown in FIG. Here, it is assumed that the pilot signal has a different series depending on the base station ID and a frequency and a time position different depending on the stream number. In 2401, the base station ID is notified to the terminal in order to identify the pilot sequence. In 2402, the terminal is notified of the stream number in order to identify the pilot position. However, the pilot signal information of the interfering station notified to the terminal is not limited to the above as long as the terminal can recognize the pilot signal of the base station serving as the interfering station.
In addition, for a plurality of base stations that perform the operation of the present embodiment, there is a possibility that the stream restriction may not be performed correctly if the stream restriction unit operates simultaneously. Therefore, a plurality of base stations performing the operation of the present embodiment have a common control cycle T [frame], operate the use stream restriction signal based on the following formula, and set the operation timing Frame number t of the stream restriction unit. decide.
t = CellID mod T
Here, CellID represents the base station ID, and mod (x) represents the remainder of x. However, the above operation is not limited to this as long as the operation timing of the stream restriction unit is different between base stations. For example, it may be determined based on a random number. In addition, when the stream restriction instruction is received within a certain period after the stream restriction instruction is transmitted, scheduling may be performed with the previous stream restriction information, and the stream restriction instruction may be transmitted again after random backoff.
In this way, in the MIMO stream separation process of the terminal, the interference station is dynamically determined, the stream is restricted between the target interference station and the own base station, and the pilot information for the stream of the interference station is notified to the terminal. It becomes possible to separate the interference between base stations.

Next, a second embodiment will be described with reference to the drawings. In the second embodiment, as shown in FIG. 25, after the terminal measures interference, the terminal also determines the interference station and notifies the base station of the interference station determination result. The stream limiting operation is the same as in the first embodiment.
The operation will be described with reference to FIG. The interference measurement instruction 2501 and the interference measurement 2502 are the same as those in the first embodiment. In step 2509, the terminal determines an interfering station.
The configuration of the terminal is shown in FIG. The terminal determines an interference station in the interference station determination unit 2614 from the measurement result of the interference power. The operation of the interference station determination unit 2614 is the same as that of the interference station determination unit 1102 in FIG. Other configurations are the same as those of the first embodiment.
In step 2503, the terminal notifies the determined interference station information to the base station. In step 2503, the base station ID of the base station to be an interference station is notified. However, step 2503 is not limited to this as long as it can identify the interference station.
The configuration of the use stream restriction unit 611 of the base station is shown in FIG. This embodiment is the same as the first embodiment except that the interference station information is directly held in the interference station table and there is no interference station determination unit.
In the second embodiment, it is possible to reduce the amount of information reported from the terminal to the base station by determining the interference station at the terminal.

Subsequently, a third embodiment will be described with reference to the drawings. As shown in FIG. 28, the third embodiment aggregates interference measurement results in a specific base station, determines stream restrictions in the aggregated base stations, and reports the results to other base stations.
First, as shown in FIG. 29, a primary base station that is a base station that aggregates interference measurement results and a secondary base station that receives a stream restriction instruction and defines the secondary base station are defined for each base station. Identification information of subordinate secondary base stations is set in the primary base station, and identification information of higher-order primary base stations is set in the secondary base station.
The operation will be described with reference to FIG. The interference measurement instruction 2801, the interference measurement 2802, and the measurement result report 2803 are the same as those in the first embodiment. This is performed by the primary base station, the secondary base station, and the terminals belonging to each base station.
In step 2809, the secondary base station aggregates the interference measurement results reported from the terminal (first terminal) belonging to the base station to the primary base station. The primary base station performs stream restriction using the interference measurement results aggregated from the terminal (second terminal) belonging to the base station and the secondary base station, and notifies the result to the secondary base station in step 2805. . Thereafter, in order to simplify the control, the range in which the primary base station performs stream restriction is limited to subordinate secondary base stations. In that case, according to the interference measurement instruction 2801, interference measurement can be performed within the range of the primary base station and its subordinate secondary base stations. Note that the range of the stream restriction is not necessarily limited in this way.
The configurations of the primary base station and the secondary base station are the same as those in FIG. However, the configuration of the use stream restriction unit 611 is different between the primary base station and the secondary base station.
The configuration of the use stream restriction unit 611 of the primary base station is the same as that of FIG. However, the input interference power information includes information from the subordinate terminals and information of the terminals subordinate to the secondary base station. The interference power information is received, for example, under the control of the controller, and can be stored in the interference power table 1101. Information from the secondary base station is received via the line interface 601, for example. FIG. 30 shows the interference power table 1101 in this embodiment. The same as the first embodiment, except that a connected base station ID column 3004 indicating the connected base station ID is added to the report value of each interference power.

The interference station determination unit 1102 performs the same operation as in the first embodiment, and determines the interference station of the primary base station and the interference station of the secondary base station. The interference station table 1106 is shown in FIG. The same as in the first embodiment, except that the connected base station ID column 3104 indicating the connected base station ID is added to the information of each interference station.
The own base station stream restriction table 1104 stores the information when there is a stream restriction instruction from outside the range where the own base station performs stream restriction.
If the range for performing the stream restriction is not limited, it is not necessary to restrict the base station for performing interference measurement within the range as described above. As a result of the stream restriction, if the base station to be restricted is other than the secondary base station under its control The operation is the same as in the first embodiment.
A flowchart of the used stream determination unit 1103 is shown in FIG.
Steps 3201, 3202, and 3203 are the same as steps 1501, 1502, and 1503 of FIG.
In step 3204, in the interfering station table of FIG. 31, the base station ID whose current use stream is to be restricted is identified in the column of the connecting base station ID 3104, and the corresponding interfering station ID is acquired. Then, it is checked whether or not there is an entry (terminal) in which the interference station ID is stored in the connected base station ID 3104. If the entry (terminal) exists, the base station ID that is currently trying to limit the use stream is stored in the interference station ID 3102 among the entries (terminals) in which the interference station ID is stored in the connected base station ID. Check whether there is an entry (terminal). When the entry (terminal) exists, since there are terminals that the two base stations recognize as interfering stations, the two terminals are assigned to different streams at the same radio resource position. The subsequent processing is the same as that after step 1906 in the detailed flow (FIG. 19) of step 1504 of the first embodiment.
In Step 2805, the primary base station (for example, the controller) notifies the stream identification information assigned to the terminal belonging to the secondary base station and the use stream information including the radio resource identification information (stream restriction instruction). Accordingly, the secondary base station communicates with the terminal by limiting to the allocated stream and radio resource. The secondary base station may transmit the identification information of the pilot signal transmitted from the primary base station or another secondary base station to a terminal belonging to the own base station.

The subsequent processing is the same as in the first embodiment.
The configuration of the use stream restriction unit 611 of the secondary base station is shown in FIG. In the secondary base station, the use stream information notified from the primary base station is held in the usable stream table 3306 and transmitted to the scheduling unit. The usable stream table is the same as that in the first embodiment.
In the third embodiment, one base station centrally controls the stream restriction of a plurality of base stations, thereby enabling efficient stream restriction.
For example, one of the secondary base stations of this embodiment corresponds to the interference station (first base station) in the first and second embodiments, and the primary base station is the base station (second base station) in the first and second embodiments. Base station).

In the above embodiment, the base station and the interference station are described as different base stations. However, in the DAS (Distributed Antenna System) in which the RF unit or the baseband processing unit is spatially dispersed and the control unit is integrated. Applicable. The configuration of the DAS is shown in FIG.
In the configuration of the base station according to the first embodiment illustrated in FIG. 6, the Downlink baseband processing unit 604, the Uplink baseband processing unit 605, the transmission RF unit 606, the reception RF unit 607, the switch 608, and the antenna 609 include an RRH (Remote Radio). (Head) 3402 is spatially distributed. Further, higher-level control than the scheduling unit 603 of a plurality of base stations is integrated by the centralized control device 3401. Centralized control device 3401 and RRH 3402 are connected by an interface 3404, and scheduling information is exchanged in DL and signals after Baseband processing are exchanged in UL. Here, of a plurality of RRHs 3402, ranges (clusters) in which the same pilot signal is used are represented by 3403a, 3403b, and 3403c. Within the range of the cluster 3403a, a plurality of RRHs 3402 perform transmission using the same pilot signal. In the present embodiment, the base station ID of the third embodiment is the ID of the cluster 3403, and the primary base station is the centralized control device 3401. Further, the use stream restriction information of the centralized control device 3401 is transmitted by transmitting all information to the scheduler unit. The pilot information of the interference station notified to the terminal is notified from the cluster 3403 to the terminal in the same unit as each base station unit of the primary base station and the secondary base station of the third embodiment. Other than the above, the third embodiment is the same as the third embodiment.

In contrast to the first embodiment, for example, the interference station (first base station) corresponds to one of the RRHs, and the base station (second base station) corresponds to a combination of the centralized control device and one of the RRHs.
The wireless communication system of the present embodiment includes, for example, a plurality of communication processing units that transmit a plurality of data streams using a plurality of antennas,
A control device for controlling the plurality of communication processing units;
A terminal that estimates a propagation path using a pilot signal for each data stream and demodulates data, and the plurality of communication processing units include:
A first communication processing unit communicating with the first data stream;
A second data stream different from the first data stream, including a second communication processing unit that communicates with the terminal that receives interference from the first communication processing unit;
The controller is
The first terminal belonging to the first communication processing unit receives reception quality from the plurality of communication processing units measured by the first communication processing unit, and the second terminal belonging to the second communication processing unit Receiving the reception quality from the plurality of communication processing units measured by the second communication processing unit,
Based on the received reception quality, identify the first communication processing unit and the second communication processing unit that interfere with each other,
Assigning a first data stream to a first terminal belonging to the first communication processor, assigning a second data stream to a second terminal belonging to a second communication processor,
The first pilot signal identification information for identifying the first pilot signal of the first data stream transmitted from the first communication processing unit is transmitted to the second terminal, and transmitted from the second communication processing unit. Transmitting second pilot signal identification information for identifying a second pilot signal of the second data stream to the first terminal;
The second terminal uses the first pilot signal specified according to the first pilot signal identification information and the second pilot signal to receive data received from the first communication processing unit and the second communication processing unit. Demodulate and extract data of the second data stream;
The first terminal uses the second pilot signal specified according to the second pilot signal identification information and the first pilot signal to receive data received from the first communication processing unit and the second communication processing unit. Demodulate and extract data of the first data stream.

(Configuration example)
[Configuration example 1]
The radio communication system, for example, allocates individual radio resources in a frame to a terminal located in its own cell area, and transmits a plurality of data streams using the same radio resources using the radio resources and a plurality of antennas. A wireless communication system comprising a wireless base station device that transmits and receives data to and from the terminal,
The radio resource includes a pilot signal that is known for each of the plurality of data streams and is known on a transmitting and receiving side,
The base station notifies the terminal of pilot signal identification information for the terminal to identify a pilot signal of a data stream other than the data stream assigned to the terminal,
The terminal demodulates data using the pilot signal identification information and the pilot signal.
[Configuration example 2]
A wireless communication system according to Configuration Example 1,
One feature of the present invention is that the pilot signal identification information is information for the terminal to identify a pilot signal of an interfering station having a large interference received by the terminal that notifies the pilot signal identification signal.
[Configuration example 3]
A wireless communication system according to Configuration Example 2,
The terminal measures interference power from a plurality of base stations including the base station, and notifies the measurement result to the base station to which the terminal is connected,
One of the characteristics of the base station is that the interference station determines that the base station with high interference power notified from the terminal is a base station with high interference received by the terminal.

[Configuration Example 4]
A wireless communication system according to Configuration Example 2,
The terminal measures interference power from a plurality of base stations including the base station, determines the interference station from the measured interference power, and notifies the determined interference station to the base station. And
[Configuration Example 5]
A wireless communication system according to Configuration Example 2,
One feature of the present invention is that the base station notifies the interference station determined for the terminal of the radio resource allocated to the terminal and data stream information.
[Configuration Example 6]
A wireless communication system according to Configuration Example 2,
The terminal measures interference power from a plurality of base stations including the base station, and notifies the measurement result to the base station to which the terminal is connected,
The base station notifies the information notified from the terminal to a preset primary base station,
The primary base station determines that the interfering station has a high interference power notified from the terminal as a base station having a large interference received by the terminal, and notifies the determination result to a base station other than the primary base station. One of the characteristics is to do.
[Configuration Example 7]
A wireless communication system according to Configuration Example 2,
The terminal measures interference power from a plurality of base stations including the base station, determines the interference station from the measured interference power, notifies the determined interference station to the base station,
The base station notifies the information notified from the terminal to a preset primary base station,
The primary base station determines that the interfering station has a high interference power notified from the terminal as a base station having a large interference received by the terminal, and notifies the determination result to a base station other than the primary base station. One of the characteristics is to do.

[Configuration Example 8]
A wireless base station device,
One or more antennas or antenna groups communicating with the terminal,
Allocate individual radio resources within a frame to terminals located in the own cell area, and use the radio resources and a plurality of antennas to transmit / receive data to / from the terminal using the same radio resources. A communication control unit to control;
A radio resource and data stream to be allocated to the terminal; a use stream limiting unit that determines an interference station to be a base station apparatus that receives a large amount of interference received by the terminal; and determines a data stream that limits use of the interference station;
Have
[Configuration Example 9]
The radio base station apparatus according to Configuration Example 8,
One of the features is that the use stream restriction unit determines that a base station with a large interference power reported from the terminal connected to the base station apparatus is an interference station.
[Configuration Example 10]
The radio base station apparatus according to Configuration Example 8,
One of the features is that the use stream restriction unit determines that an interference station reported from the terminal connected to the base station apparatus is an interference station.
[Configuration Example 11]
The radio base station apparatus according to Configuration Example 8,
The use stream restriction unit determines the radio resource and data stream assigned to the terminal as a data stream for restricting use of the interference station determined for the terminal.

[Configuration Example 12]
A wireless terminal device,
One or more antennas or antenna groups communicating with the base station;
A radio communication unit that transmits and receives data to and from the base station using the same radio resource for a plurality of data streams, using individual radio resources in a frame, and the plurality of antennas;
The wireless communication unit includes a baseband processing unit that demodulates the plurality of data streams using a pilot signal that is known for each of the plurality of data streams and is included in the wireless resource, on the transmission and reception side,
The baseband processing unit includes information for identifying a pilot signal of a base station to which the terminal is connected, and pilots of base stations other than the base station to which the terminal is connected, which is notified from the base station The information for identifying the signal is used to demodulate the plurality of data streams.
[Configuration Example 13]
A wireless terminal device according to Configuration Example 12,
The use stream restriction unit determines the radio resource and data stream assigned to the terminal as a data stream for restricting use of the interference station determined for the terminal.

  The present invention is applicable to a wireless communication system that performs communication using a plurality of antennas such as MIMO transmission.

20b1 to 20bN, 402, 404 Base station 20m1, 20m2 Terminals 2c1 to 2cN, 401, 403 Cell 301, 609 Antenna 302, 303, 304 Sector base station 611 Use stream restriction unit 603 Scheduling unit 813 Reception quality measurement unit 2614 Interference station determination Part 2614
3401 Central control unit 3402 RRH
3403 clusters

Claims (15)

A wireless communication system comprising a plurality of base stations that transmit a plurality of data streams using a plurality of antennas, and a terminal that estimates a propagation path using a pilot signal for each data stream and demodulates data. And
The plurality of base stations are
A first base station communicating in a first data stream comprising one or more data streams;
A second base station that communicates with the terminal that is interfered with by the first base station in a second data stream that includes one or more data streams different from the first data stream;
The second base station is
A second data stream different from the first data stream used by the first base station is allocated to the terminal belonging to the second base station;
Transmitting data and a second pilot signal to the terminal using the allocated second data stream;
Transmitting pilot signal identification information for identifying a first pilot signal of a first data stream transmitted from the first base station to the terminal;
The terminal demodulates data received from the first base station and the second base station using a first pilot signal and a second pilot signal specified according to the pilot signal identification information, and receives second data A wireless communication system for extracting stream data.   The second base station receives data stream restriction information including identification information of a first data stream used by the first base station from the first base station, and according to the data stream restriction information, The wireless communication system according to claim 1, wherein a different second data stream is assigned to the terminal. The data stream restriction information further includes identification information of radio resource units in the first data stream used by the first base station,
The second base station, according to the data stream restriction information, out of radio resource units in a second data stream different from the first data stream, a radio resource at a position corresponding to a radio resource unit used by the first base station The wireless communication system according to claim 2, wherein a unit is assigned to the terminal.   The second base station receives the reception quality from the plurality of base stations measured by the terminal from the terminal, and based on the reception quality, interferes the terminal communicating with the second base station. The radio communication system according to claim 1, wherein one base station is specified.   The radio communication system according to claim 4, wherein the reception quality includes at least one of reception power and CINR at a terminal.   The second base station selects one of the base stations other than the base station whose measured received power is maximum or one of the base stations whose received power is greater than a predetermined threshold. The radio | wireless communications system of Claim 4 specified as a base station.   The said 2nd base station receives the identification information of the 1st base station which the said terminal specified based on the reception quality from these base stations from this terminal, and specifies this 1st base station. Wireless communication system.   The radio communication system according to claim 1, wherein the second base station transmits data stream restriction information including identification information of a second data stream assigned to the terminal to the first base station. The terminal includes a first terminal belonging to a first base station and a second terminal belonging to a second base station,
The first base station receives the reception quality measured by the first terminal from the first terminal and transmits it to the second base station;
The second base station is
Receiving the reception quality measured by the second terminal from the second terminal;
Based on the reception quality received from the first base station and the second terminal, identify the first base station and the second base station that interfere with each other,
Assigning a first data stream to a first terminal belonging to the first base station, assigning a second data stream to a second terminal belonging to the second base station;
The wireless communication system according to claim 1, wherein identification information of the first data stream assigned to the first terminal is transmitted to the first base station.   The second base station allows each terminal so that the position of the radio resource unit in the first data stream assigned to the first terminal corresponds to the position of the radio resource unit in the second data stream assigned to the second terminal. The wireless communication system according to claim 9, wherein the data stream and the wireless resource unit are allocated to the wireless communication system. In a wireless communication system comprising a plurality of base stations that transmit a plurality of data streams using a plurality of antennas, and a terminal that estimates a propagation path using a pilot signal for each data stream and demodulates data, Using a second data stream including one or a plurality of data streams different from a first data stream including one or a plurality of data streams used by an interfering station that is one of the plurality of base stations. A base station communicating with the terminal receiving interference from the interfering station,
A use stream restriction unit that assigns a second data stream different from the first data stream used by the interfering station as a data stream used by the terminal belonging to the base station;
A communication processing unit for transmitting data and a second pilot signal to the terminal using the allocated second data stream;
The terminal identifies a first pilot signal of a first data stream transmitted from an interference station and estimates a propagation path using the first pilot signal from the interference station and the second pilot signal from the own base station. The base station comprising: a control unit that transmits pilot signal identification information of the first pilot signal to the terminal.   The use stream restriction unit receives data stream restriction information including identification information of a first data stream used by the interference station from the interference station, and second data different from the first data stream according to the data stream restriction information The base station according to claim 11, wherein a stream is allocated to the terminal. The data stream restriction information further includes identification information of radio resource units in the first data stream used by the interfering station,
The use stream restriction unit determines a radio resource unit at a position corresponding to a radio resource unit used by the interfering station among radio resource units in a second data stream different from the first data stream according to the data stream restriction information. The base station according to claim 12 assigned to the terminal. The control unit receives the reception quality measured by the first terminal belonging to the interference station from the interference station, and receives the reception quality measured by the second terminal belonging to the base station from the second terminal. And
The use stream restriction unit identifies an interference station that interferes with its own base station based on reception quality received from the interference station and the second terminal, and sends a first data stream to a first terminal belonging to the interference station. Assign a second data stream to a second terminal belonging to the base station,
The base station according to claim 11, wherein the control unit transmits identification information of the first data stream assigned to the first terminal to the interference station. In a radio communication system comprising a plurality of base stations that transmit a plurality of data streams using a plurality of antennas, and a radio terminal that estimates a propagation path using a pilot signal for each data stream and demodulates data The wireless terminal comprising:
Data and second pilots using a second data stream that includes one or more data streams different from the first data stream that includes one or more data streams used by the first base station A signal is received from the second base station, and pilot signal identification information for identifying a first pilot signal of a first data stream transmitted from the first base station is received from the second base station. A wireless communication unit;
Data received from the first base station and the second base station is demodulated using the first pilot signal and the second pilot signal specified according to the pilot signal identification information, and the data of the second data stream is The said radio | wireless terminal provided with the baseband process part to extract.

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