WO2013161054A1

WO2013161054A1 - Wireless base station, wireless terminal, wireless communication system, and communication control method

Info

Publication number: WO2013161054A1
Application number: PCT/JP2012/061362
Authority: WO
Inventors: 耕太郎椎▲崎▼; 大介実川; 伊藤　章
Original assignee: 富士通株式会社
Priority date: 2012-04-27
Filing date: 2012-04-27
Publication date: 2013-10-31

Abstract

In a wireless base station (1), in instances in which a plurality of wireless resources employed for transmission of known signals, and which wireless resources are at least partially redundant, are allocated to a plurality of wireless terminals (3-1, 3-7), interference of the known signals is minimized by controlling the transmission power of the wireless terminal (3-7) in such a way that the known signal transmitted by the wireless terminal (3-7), which of the plurality of wireless terminals (3-1, 3-7) is one located within the wireless area (5-2) of another wireless base station (2-2) different from its home station (1), is received by the wireless base station (2-2), while excluding the home station.

Description

Wireless base station, wireless terminal, wireless communication system, and communication control method

The present invention relates to a radio base station, a radio terminal, a radio communication system, and a communication control method.

In recent years, the Long Term Evolution-Advanced (LTE-A) of the 3rd Generation Partnership Project (3GPP), a standardization organization for wireless communication standards, has been actively discussed about Coordinated Multi Point (CoMP) technology. Yes.
In Patent Document 1 below, whether or not UpLink Coordinated Multiple Point (ULCoMP) is applicable to a UE is determined based on the difference of each propagation loss between a plurality of base station apparatuses and User Equipment (UE, user apparatus). However, a technique for performing transmission power control is described.

JP 2011-9866 A

In Release 11 of LTE-A, discussions have been made on the introduction of CoMP scenario 4.
In CoMP scenario 4, remote radio heads (RRH, overhanging stations) 200-1 and 200-2 are arranged in a radio area 400 of eNodeB (eNB, radio base station) 100, as illustrated in FIG. A system configuration is assumed in which the eNB 100 and each of the RRHs 200-1 and 200-2 are connected by a high-speed interface such as an optical fiber.

In the example shown in FIG. 1, UEs 300-1 to 300-7 are located in the radio area 400 of the eNB 100, and UEs 300-3 and 300-4 are located in the radio area 500-1 of the RRH 200-1. . Furthermore, UEs 300-5 to 300-7 are located in the radio area 500-2 of the RRH 200-2.
Also, in CoMP scenario 4, by sharing the cell ID between the eNB 100 and each of the RRHs 200-1 and 200-2, load reduction of mobility control, sharing of cell-specific resources, and the like are achieved.

In CoMP, each of the UEs 300-1 to 300-7 transmits a Sounding Reference Symbol (SRS) as an example of a known signal for estimating the quality of an uplink radio channel to the eNB 100 and the RRHs 200-1 and 200-2.
In Release 10 of LTE-A, the uplink transmission power control when each UE 300-1 to 300-7 transmits the SRS is offset to the Transmission Power Control (TPC) of the Physical Uplink Shared Channel (PUSCH). It is specified to be performed according to the following control equation (1) having the added shape.

here,

Is a subframe,

Is the transmission power of SRS,

Is the maximum transmit power,

Is an offset value from the transmission power of PUSCH,

Is the number of PUSCH allocation resources,

Is the PUSCH received power target value,

Is the path loss coefficient,

Is a propagation loss (path loss) between the UE 300-1 to 300-7 and the serving base station,

Represents the power adjustment coefficient of PUSCH, respectively.
The above control equation (1) is intended to compensate for the path loss of the serving cell.
On the other hand, the following control expression (2) is proposed in 3GPP contribution “R1-113328” and the like.

here,

Represents the maximum path loss in eNB 100, RRH 200-1, 200-2 (also referred to as a CoMP set) that is a target of CoMP reception.
The above control equation (2) is intended to receive the SRS in the entire CoMP set, and has the advantage that the reception quality of UpLink (UL, uplink) can be obtained by more eNBs 100, RRHs 200-1, 200-2. There is.

By the way, the UEs 300-1 to 300-7 are allocated radio resources for transmitting SRS from the eNB 100, and transmit SRSs using the allocated radio resources. Specifically, for example, each UE 300-1 to 300-7 is assigned radio resources that can be identified by different base sequences, cyclic shifts (CS), and comb teeth, and applies frequency hopping to the assigned radio resources. SRS is transmitted.

Here, an example of the radio resource allocation is shown in FIG. In the example shown in FIG. 2, radio resources defined by a combination of frequency and time (timing) are allocated to each UE. In FIG. 2, radio resources # 1 to # 7 represent radio resources allocated to the UEs 300-1 to 300-7, respectively.
However, in CoMP scenario 4, since a common cell ID is used by eNB 100 and each RRH 200-1 and 200-2, there is one base sequence. In addition, since there are 8 types of CS and 2 types of comb teeth, the eNB 100 can only identify SRSs from 16 UEs.

Further, not only in CoMP scenario 4, but also in CoMP scenario 3, for example, when the number of UEs increases, even when considering the difference in SRS transmission timing, the case of transmitting SRS in the same band and the same timing Can happen enough.
In such a case, SRS interference may occur. For example, when a plurality of UEs transmit SRS using the same radio resource, or when a plurality of UEs transmit SRS using radio resources at least partially overlapping each other, an SRS collision occurs and interference occurs. May occur.

In particular, when performing SRS transmission power control using the above control equation (2), SRS interference occurs because transmission power control (TPC) is performed so that the SRS reaches all reception points in the CoMP set. The possibility of doing is even higher.
Accordingly, an object of the present invention is to suppress interference of known signals.
Note that the present invention is not limited to the above-described objects, and is an operation and effect derived from each configuration shown in the embodiment for carrying out the invention described below, and also exhibits an operation and effect that cannot be obtained by conventional techniques. It can be positioned as one of the purposes.

(1) As a first proposal, for example, when a plurality of radio resources used when transmitting a known signal are allocated to a plurality of radio terminals at least partially overlapping with each other. The other signal so that a known signal transmitted by a wireless terminal located in a wireless area of another wireless base station different from the own station among the plurality of wireless terminals is received by a wireless base station other than the own station. A processing unit that controls transmission power of a wireless terminal located in the wireless area of the wireless base station, and at least a known signal transmitted by a wireless terminal located in the wireless area of the own station among the plurality of wireless terminals It is possible to use a radio base station that includes a receiving unit.

(2) As a second proposal, for example, among a plurality of radio resources used when transmitting a known signal, radio resources at least partially overlapping each other are allocated to a plurality of radio terminals including the own station. A processing unit that determines transmission power of the local station so that a known signal transmitted by the local station is received by some of the plurality of radio base stations, and the processing unit determines It is possible to use a wireless terminal including a transmission unit that transmits the known signal using the transmitted power.

(3) Furthermore, as a third proposal, for example, radio resources that are at least partially overlapping among a plurality of radio resources used when transmitting a known signal are allocated to a plurality of radio terminals. In this case, a known signal transmitted by a wireless terminal located in a wireless area of another wireless base station different from the own station among the plurality of wireless terminals is received by a wireless base station other than the own station. A radio base station that controls transmission power of a radio terminal located in the radio area of the other radio base station, and a transmission power that is located in the radio area of the other radio base station and controlled by the radio base station It is possible to use a wireless communication system that includes a wireless terminal that transmits the known signal using a wireless communication device.

(4) Further, as a fourth plan, for example, in a radio base station, radio resources at least partially overlapping each other among a plurality of radio resources used when transmitting a known signal to a plurality of radio terminals Among the plurality of wireless terminals, a known signal transmitted by a wireless terminal located in a wireless area of another wireless base station different from the own station is transmitted by a wireless base station other than the own station. The transmission power of a radio terminal located in the radio area of the other radio base station is controlled to be received, and the controlled transmission power is controlled in a radio terminal located in the radio area of the other radio base station. A communication control method can be used in which the known signal is transmitted using the.

It becomes possible to suppress interference of known signals.

It is a figure which shows an example of the system configuration assumed by the scenario 4 of CoMP. It is a figure which shows an example of allocation of the radio | wireless resource for SRS transmission. It is a figure which shows an example of a structure of the radio | wireless communications system which concerns on one Embodiment. It is a figure which shows an example of the communication control method which concerns on one Embodiment. It is a figure which shows an example of a structure of eNB and RRH shown in FIG. It is a figure which shows an example of operation | movement of eNB and RRH shown in FIG. It is a figure which shows an example of operation | movement of eNB and RRH shown in FIG. It is a figure which shows an example of operation | movement of eNB and RRH shown in FIG. (A) And (B) is a figure which shows an example of the transmission format of an instruction | indication signal. It is a figure which shows an example of a structure of UE shown in FIG. It is a figure which shows an example of operation | movement of UE shown in FIG. It is a figure which shows an example of the communication control method which concerns on a 1st modification. It is a figure which shows an example of operation | movement of eNB and RRH which concern on a 1st modification. It is a figure which shows an example of operation | movement of eNB and RRH which concern on a 1st modification. (A) And (B) is a figure which shows an example of the transmission format of a notification signal. It is a figure which shows an example of operation | movement of UE which concerns on a 1st modification. It is a figure which shows an example of the hardware constitutions of eNB and RRH. It is a figure which shows an example of the hardware constitutions of UE.

Embodiments of the present invention will be described below with reference to the drawings. However, the embodiment described below is merely an example, and there is no intention to exclude various modifications and technical applications that are not explicitly described in the embodiment described below. That is, it goes without saying that the embodiments described below can be implemented in various modifications by combining them without departing from the scope of the present invention.
[1] One Embodiment (1.1) Example of Configuration of Radio Communication System According to One Embodiment FIG. 3 is a diagram illustrating an example of the configuration of a radio communication system according to one embodiment.

The radio communication system 6 shown in FIG. 3 illustratively includes an eNB 1 that is an example of a radio base station, extended stations (RRH) 2-1 and 2-2, and a plurality of user apparatuses (UE) 3-1 to 3-7. In the following description, when RRHs 2-1 and 2-2 are not distinguished, they are simply expressed as RRH2, and when UEs 3-1 to 3-7 are not distinguished, they are simply expressed as UE3. Further, the numbers of RRH2 and UE3 are not limited to the numbers illustrated in FIG.

The eNB 1 provides a radio area 4 such as a cell or a sector, and can perform radio communication with the UEs 3-1 to 3-7 located in the radio area 4.
Further, the RRH 2-1 provides a radio area 5-1, and can perform radio communication with the UEs 3-3 and 3-4 located in the radio area 5-1. Similarly, the RRH 2-2 provides a radio area 5-2 and can perform radio communication with UEs 3-5 to 3-7 located in the radio area 5-2.

The eNB 1 and the RRHs 2-1 and 2-2 are connected by a high-speed interface such as an optical fiber and can communicate with each other. Note that the interface between the eNB 1 and the RRHs 2-1 and 2-2 is not limited to an optical fiber, and for example, an X2 interface or a wireless backhaul may be used.
In the wireless communication system 6 illustrated in FIG. 3, CoMP technology can be used.

For example, if attention is paid to the uplink (UL), the eNB 1 directly receives a signal transmitted from the UE 3 to the local station 1 and transmits a signal transmitted from the UE 3 to the other station 2 via a high-speed interface such as an optical fiber. By uploading and synthesizing the received signals, data upload can be accelerated. Similarly, the RRH 2 directly receives a signal transmitted from the UE 3 to the own station 2 and receives a signal transmitted from the UE 3 to the other station 1 via a high-speed interface such as an optical fiber, and combines the received signals. By doing so, uploading of data can be speeded up.

If attention is paid to DownLink (DL, downlink), the UE 3 receives a signal transmitted from the eNB 1 to the local station 3 and receives a signal transmitted from the RRH 2 to the local station 3. By combining, data download can be accelerated.
In CoMP, each UE 3 is pre-assigned from eNB 1 or RRH 2 radio resources for transmitting a known reference signal (SRS) for estimating the quality of an uplink radio channel, and uses the assigned radio resources for SRS. Send. Note that this SRS is not a target of the synthesis process in CoMP.

Here, if the number of UEs 3 is larger than the number of radio resources for SRS transmission, the same radio resource may be allocated to different UEs 3 in duplicate.
For example, when the same radio resource is allocated to UE 3-1 and UE 3-7, and UE 3-7 performs transmission power control according to the following control equation (2), UE 3-1 The UE 3-7 transmits the SRS to the eNB 1 and the RRH 2-2 using the same radio resource while transmitting the SRS to the eNB 1 using the resource.

In such a case, the eNB 1 may collide with the SRS transmitted from the UE 3-1 and the SRS transmitted from the UE 3-7, and there is a possibility that SRS interference occurs. When SRS interference occurs, the eNB 1 cannot appropriately estimate the uplink channel quality and may not be able to perform efficient CoMP.
Therefore, in this example, as illustrated in FIG. 4, first, the eNB 1 or the RRH 2 assigns radio resources for SRS transmission to each UE 3, and the same radio resource is duplicated in different UE 3. Detect whether it was assigned or not.

When it detects that the same radio resource is assigned to different UEs 3 (duplication of SRS radio resources) (step S10), eNB1 or RRH2 detects at least one of UEs 3 to which the same radio resource is assigned. Then, switching of transmission power control is instructed (step S11).
The UE 3 instructed to switch the transmission power control performs, for example, transmission power control according to the following control equation (1) so that the SRS reaches only the serving cell (step S12), and the SRS is determined based on the determined transmission power. Is transmitted (step S13).

On the other hand, when eNB1 or RRH2 detects that the duplication of SRS radio resources has been resolved (step S14), among UE3s that have been assigned the same radio resource, to UE3 that has instructed step S11. Then, switching of transmission power control is instructed (step S15).
UE3 instructed to switch transmission power control performs transmission power control according to the following control equation (2), for example, so that the SRS reaches all reception points in the CoMP set (step S16). The SRS is transmitted with the determined transmission power (step S17).

According to this example, since different UEs 3 to which the same radio resource is allocated can prevent collision of SRS transmitted respectively, it is possible to suppress SRS interference.
(1.2) Example of Configuration of eNB1 and RRH2 FIG. 5 is a diagram illustrating an example of the configuration of eNB1. Since RRH2 has the same configuration as eNB1, description of the configuration example of RRH2 is omitted.

The eNB 1 illustrated in FIG. 5 exemplarily includes an antenna 11, a duplexer 12, a reception unit 13, a channel estimation unit 14, a control signal demodulation / decoding unit 15, a data signal demodulation / decoding unit 16, and a reception quality calculation. A unit 17 and a scheduler 18 are provided. In addition, eNB1 illustrated in FIG. 5 exemplarily includes a data signal generation unit 19, a control signal generation unit 20, a reference signal generation unit 21, a data signal encoding modulation unit 22, and a control signal encoding modulation unit 23. And an assigning unit 24 and a transmitting unit 25.

The antenna 11 functions as a reception antenna that receives a radio signal from the UE 3 and also functions as a transmission antenna that transmits a radio signal to the UE 3. That is, the antenna 11 of this example has a configuration in which the reception antenna and the transmission antenna are shared by the duplexer 12. Note that FIG. 5 merely shows an example of the configuration of the eNB 1. For example, when the duplexer 12 is not used, the eNB 1 may have a transmission antenna and a reception antenna individually.

The receiving unit 13 extracts a reference signal (SRS), a control signal, and a data signal from uplink radio signals such as PUSCH and Physical-Uplink-Control-Channel (PUCCH) transmitted from the UE 3 received by the antenna 11. The reference signal, control signal, and data signal extracted by the reception unit 13 are output to the channel estimation unit 14, the control signal demodulation / decoding unit 15, and the data signal demodulation / decoding unit 16, respectively.

That is, the receiving unit 13 functions as an example of a receiving unit that receives at least a known signal such as SRS transmitted by the wireless terminal 3 located in the wireless area of the local station 1 among the plurality of wireless terminals 3.
The channel estimation unit 14 calculates a channel estimation value using the reference signal extracted by the reception unit 13. The channel estimation value calculated by the channel estimation unit 14 is output to the control signal demodulation / decoding unit 15, the data signal demodulation / decoding unit 16, and the reception quality calculation unit 17, respectively.

The control signal demodulation / decoding unit 15 performs demodulation processing and decoding processing on the control signal extracted by the reception unit 13 using the channel estimation value calculated by the channel estimation unit 14. The control information obtained by the control signal demodulation / decoding unit 15 is output to the data signal demodulation / decoding unit 16 and the scheduler 18, respectively. Further, ACKnowledgement (ACK) indicating that the decoding result is normal or Negative ACKnowledgement (NACK) indicating that the decoding result is abnormal may be output to the scheduler 18.

The data signal demodulation / decoding unit 16 performs demodulation processing and decoding processing on the data signal extracted by the reception unit 13 using the channel estimation value calculated by the channel estimation unit 14. The data obtained by the data signal demodulation / decoding unit 16 is output to the scheduler 18. Further, ACK indicating that the decoding result is normal or NACK indicating that the decoding result is abnormal may be output to the scheduler 18.

The reception quality calculation unit 17 uses the channel estimation value calculated by the channel estimation unit 14 to calculate reception quality such as a signal-to-interference ratio (SIR). Information regarding the reception quality calculated by the reception quality calculation unit 17 is output to the scheduler 18.
The scheduler 18 sends a signal generation request to the data signal generation unit 19, the control signal generation unit 20, and the reference signal generation unit 21 based on each input information. Further, the scheduler 18 sends scheduling information indicating radio resource allocation for each signal to the allocation unit 24 based on each input information.

The data signal generator 19 generates a data signal based on the signal generation request from the scheduler 18.
The data signal encoding / modulating unit 22 performs encoding processing and modulation processing on the data signal generated by the data signal generating unit 19. The encoded and modulated data signal obtained by the data signal encoding / modulating unit 22 is output to the assigning unit 24.

The control signal generation unit 20 generates a control signal based on the signal generation request from the scheduler 18.
The control signal encoding / modulating unit 23 performs encoding processing and modulation processing on the control signal generated by the control signal generating unit 20. The encoded and modulated control signal obtained by the control signal encoding / modulating unit 23 is output to the allocating unit 24.

The reference signal generation unit 21 generates a reference signal based on the signal generation request from the scheduler 18.
The allocating unit 24 uses the scheduling information instructed by the scheduler 18 for the data signal from the data signal encoding and modulating unit 22, the control signal from the control signal encoding and modulating unit 23, and the reference signal from the reference signal generating unit 21. Wireless resources are allocated. Note that the radio resources include, for example, transmission / reception power, transmission / reception frequency (channel), transmission / reception timing, and the like as examples of communication resources used for transmission / reception of radio signals.

The transmission unit 25 transmits a data signal, a control signal, and a reference signal via the antenna 11 using the radio resource allocated by the allocation unit 24.
(1.3) Example of Operation of eNB1 and RRH2 Next, an example of the operation of eNB1 and RRH2 configured as described above will be described with reference to FIGS.

First, the scheduler 18 performs radio resource allocation control.
For example, as shown in FIG. 6, when the scheduler 18 starts radio resource allocation control (step S20), the scheduler 18 calculates the number of uplink radio resources that the UE 3 can use for transmission of SRS (step S21). Note that the number of uplink radio resources includes, for example, the number of resource blocks (RB, resource blocks) defined by the channel and transmission timing.

Next, the scheduler 18 calculates the number of UEs 3 to which uplink radio resources for SRS transmission are allocated (step S22).
Then, it is determined whether or not the number of UE3 is larger than the number of uplink radio resources (step S23). When it is determined that the number of UE3 is equal to or less than the number of uplink radio resources (No route of step S23), the scheduler 18 allocates different radio resources to each UE 3 (step S25), and ends the radio resource allocation control (step S26).

On the other hand, if it is determined that the number of UE3 is larger than the number of uplink radio resources (Yes route in step S23), the scheduler 18 will allocate the same radio resource to any of the plurality of UE3. The scheduler 18 in this example assigns the same radio resource to the UEs 3 having different radio areas in the same area (step S24), and ends the radio resource allocation control (step S26). Thereby, it is possible to prevent the SRS from the UE 3 to which the same radio resource is assigned in duplicate from colliding and interfering in the eNB 1 and the RRH 2 by the transmission power switching control of this example described later.

That is, the scheduler 18 locates radio resources at least partially overlapping among the plurality of radio resources in the radio areas of the radio terminal 3 and other radio base stations 2 located in the radio area of the own station 1. It can be assigned to the wireless terminal 3.
Next, the scheduler 18 performs transmission power switching control.
For example, as shown in FIG. 7, when the scheduler 18 starts transmission power switching control (step S30), the scheduler 18 determines whether or not the same radio resource is allocated to different UEs 3 (step S31). If there is no radio resource duplication (No route in step S31), the transmission power switching control is terminated (step S34).

On the other hand, when there is duplication of radio resources (Yes route in step S31), the scheduler 18 determines whether or not each UE 3 to which the same radio resource is assigned is an application target of CoMP (step S32). .
Here, when it is determined that at least one of the UEs 3 to which the same radio resource is allocated is not a CoMP application target (No route in Step S32), the scheduler 18 ends the transmission power switching control (Step S34). .

On the other hand, when it is determined that any of the UEs 3 to which the same radio resource is allocated is a CoMP application target (Yes route in step S32), the scheduler 18 Instructing UE 3 residing in a radio area provided by another station different from the radio area provided by

own stations

1 and 2 to switch transmission power control (TPC) (step S33), the transmission power switching control is terminated (step S34).

Further, the scheduler 18 performs the following transmission power re-switching control after performing the process of step S33.
For example, as shown in FIG. 8, when the scheduler 18 starts transmission power re-switching control (step S40), it is determined whether or not the situation where the same radio resource is allocated to different UEs 3 has been resolved. Determination is made (step S41).

If the overlapping state of the radio resources has been eliminated (Yes route in step S41), the scheduler 18 uses the radio provided by the

own stations

1 and 2 among the UEs 3 to which the same radio resource is allocated. A UE 3 located in a radio area provided by another station different from the area is instructed to switch transmission power control (TPC) (step S43), and the transmission power re-switching control is terminated (step S43). Step S44).

On the other hand, if the overlapping state of the radio resources has not been resolved (No route in step S41), the scheduler 18 determines whether or not at least one of the UEs 3 to which the same radio resource is allocated is not subject to CoMP application. Is determined (step S42).
Here, if it is determined that at least one of the UEs 3 to which the same radio resource is assigned is not subject to CoMP application (Yes route in step S42), the scheduler 18 has been assigned the same radio resource. In addition, among the UEs 3, the transmission power control (TPC) is switched for the UEs 3 located in the wireless areas provided by other stations different from the wireless areas provided by the

own stations

1 and 2. An instruction is given (step S43), and transmission power re-switching control is terminated (step S44).

On the other hand, when it is determined that each of the UEs 3 to which the same radio resource is allocated is a CoMP application target (No route in Step S42), the scheduler 18 ends the transmission power re-switching control (Step S44). ).
Here, a transmission power control (TPC) switching instruction and a transmission power control (TPC) switching instruction will be described in detail.

When the TPC switching instruction shown in step S33 and the TPC re-switching instruction shown in step S43 are performed, the scheduler 18 generates an instruction signal for instructing the control signal generation unit 20 to switch the TPC. Request that.
The instruction signal is configured as, for example, a flag that can take two values “1” and “0”. For example, in step S33, the scheduler 18 sets the instruction signal to “1” to cause the UE 3 to perform TPC according to the following control equation (1) from the following control equation (2).

That is, when the scheduler 18 allocates radio resources at least partially overlapping each other among the plurality of radio resources used when transmitting a known signal such as SRS to the plurality of radio terminals 3, Among the plurality of wireless terminals 3, a known signal transmitted by a wireless terminal 3 located in a wireless area of another wireless base station 2 different from the local station 1 is received by the wireless base station 2 except the local station 1. Thus, it functions as an example of a processing unit that controls the transmission power of the wireless terminal 3 located in the wireless area of the other wireless base station 2.

In step S43, the scheduler 18 sets the instruction signal to “0” to cause the UE 3 to perform TPC according to the following control equation (1) to the following control equation (2).

That is, the scheduler 18 transmits a radio terminal 3 located in a radio area of another radio base station 2 when different radio resources among a plurality of radio resources are allocated to a plurality of radio terminals. The transmission power of the radio terminal 3 located in the radio area of the other radio base station 2 can be controlled so that the known signal is received at least by the own station 1 and the other radio base station 2.

Note that the instruction signal may be stored and transmitted in downlink control information such as DCI (Downlink Control Information): A-CQI (Channel Quality Indicator) as shown in FIG. 9A, for example. Alternatively, for example, as shown in FIG. 9B, the instruction signal is added as a new field (srs-ConfigTPC) to a control signal in an upper layer such as SoundingRS-UL-Config of Radio 例えば resource control information elements. May be sent.

(1.4) Exemplary Configuration of UE3 FIG. 10 is a diagram illustrating an exemplary configuration of UE3.
The UE 3 shown in FIG. 10 exemplarily includes an antenna 31, a duplexer 32, a reception unit 33, a channel estimation unit 34, a control signal demodulation / decoding unit 35, a data signal demodulation / decoding unit 36, and a reception quality calculation. The unit 37 is provided. 10 exemplarily includes a data signal generation unit 38, a control signal generation unit 39, a reference signal generation unit 40, a data signal encoding modulation unit 41, and a control signal encoding modulation unit 42. And an allocating unit 43, a switching control unit 44, a transmission power determining unit 45, and a transmitting unit 46.

The antenna 31 functions as a reception antenna that receives radio signals from the eNB1 and RRH2, and also functions as a transmission antenna that transmits radio signals to the eNB1 and RRH2. That is, the antenna 31 of this example has a configuration in which the reception antenna and the transmission antenna are shared by the duplexer 32. Note that FIG. 10 merely shows an example of the configuration of the UE 3. For example, when the duplexer 32 is not used, the UE 3 may have a transmission antenna and a reception antenna individually.

The receiving unit 33 extracts a reference signal, a control signal, and a data signal from downlink radio signals, such as Physical３１Downlink Shared Channel (PDSCH) and Physical Downlink Control Channel (PDCCH) transmitted from eNB1 and RRH2 received by the antenna 31. . The reference signal, control signal, and data signal extracted by the reception unit 33 are output to the channel estimation unit 34, the control signal demodulation / decoding unit 35, and the data signal demodulation / decoding unit 36, respectively.

The channel estimation unit 34 calculates a channel estimation value using the reference signal extracted by the reception unit 33. The channel estimation value calculated by the channel estimation unit 34 is output to the control signal demodulation / decoding unit 35, the data signal demodulation / decoding unit 36, and the reception quality calculation unit 37, respectively.
The control signal demodulation / decoding unit 35 uses the channel estimation value calculated by the channel estimation unit 34 to perform demodulation processing and decoding processing on the control signal extracted by the reception unit 33. The control information obtained by the control signal demodulation / decoding unit 35 is output to the data signal demodulation / decoding unit 36, the control signal generation unit 39, the allocation unit 43, and the switching control unit 44, respectively. Further, ACK indicating that the decoding result is normal or NACK indicating that the decoding result is abnormal may be output to the control signal generation unit 39.

The data signal demodulation / decoding unit 36 performs demodulation processing and decoding processing on the data signal extracted by the receiving unit 33 using the channel estimation value calculated by the channel estimation unit 34. The data obtained by the data signal demodulation / decoding unit 36 is output to the control signal generation unit 39. Further, ACK indicating that the decoding result is normal or NACK indicating that the decoding result is abnormal may be output to the control signal generation unit 39.

The reception quality calculation unit 37 calculates reception quality such as SIR using the channel estimation value calculated by the channel estimation unit 34. Information regarding the reception quality calculated by the reception quality calculation unit 37 is output to the control signal generation unit 39.
The data signal generation unit 38 generates a data signal.
The data signal encoding / modulating unit 41 performs encoding processing and modulation processing on the data signal generated by the data signal generating unit 38. The encoded and modulated data signal obtained by the data signal encoding / modulating unit 41 is output to the assigning unit 43.

The control signal generation unit 39 generates a control signal based on various information from the control signal demodulation / decoding unit 35, the data signal demodulation / decoding unit 36, and the reception quality calculation unit 37.
The control signal encoding / modulating unit 42 performs encoding processing and modulation processing on the control signal generated by the control signal generating unit 39. The encoded and modulated control signal obtained by the control signal encoding / modulating unit 42 is output to the allocating unit 43.

The reference signal generation unit 40 generates a reference signal.
The allocating unit 43 receives the data signal from the data signal encoding / modulating unit 41, the control signal from the control signal encoding / modulating unit 42, and the reference signal from the reference signal generating unit 40 from the control signal demodulation / decoding unit 35. Radio resources are allocated based on the control information. Note that the radio resources include, for example, transmission / reception frequencies (channels), transmission / reception timings, and the like as examples of communication resources used for transmission / reception of radio signals. For example, when the number of UE3 is larger than the number of radio resources that can be allocated in eNB1 and RRH2, UE3 allocates the same radio resource as other UE3 as the radio resource used for SRS transmission.

The switching control unit 44 switches transmission power control (TPC) in the UE 3 based on the control information input from the control signal demodulation / decoding unit 35. Specifically, for example, when the control information input from the control signal demodulation / decoding unit 35 includes the instruction signal set to “1” as the above-described instruction signal, the switching control unit 44 uses the following control expression (2 ) To transmit power control according to the following control equation (1). When the control information input from the control signal demodulation / decoding unit 35 includes the instruction signal set to “0” as the above-described instruction signal, the switching control unit 44 transmits transmission power according to the following control expression (1). Control is switched to transmission power control according to the following control equation (2).

The transmission power determination unit 45 determines the transmission power of the UE 3 according to the transmission power control method after switching by the switching control unit 44. More specifically, the transmission power determination unit 45 determines the transmission power for the SRS according to the transmission power control equation after switching by the switching control unit 44.
That is, the transmission power determination unit 45 is configured to respond to a plurality of wireless terminals 3 including the own station 3 with a plurality of wireless resources used when transmitting a known signal such as SRS, at least partially overlapping with each other. Processing for determining transmission power of own station 3 so that known signals transmitted by own station 3 are received by some radio base stations 2 (or 1) of a plurality of radio base stations when assigned It functions as an example of a unit.

The transmission unit 46 transmits a data signal, a control signal, and a reference signal via the antenna 31 using the radio resource allocated by the allocation unit 43 and the transmission power determined by the transmission power determination unit 45.
That is, the transmission unit 46 functions as an example of a transmission unit that transmits a known signal using the transmission power determined by the transmission power determination unit 45.

(1.5) Example of Operation of UE3 Next, an example of the operation of UE3 configured as described above will be described with reference to FIG.
As illustrated in FIG. 11, first, when the UE 3 starts the SRS transmission process (step S50), the UE 3 extracts the instruction signal described above from the control information received from the eNB 1 and the RRH 2 (step S51).

And UE3 switches the transmission power control method in the own station 3 according to the content of the extracted instruction | indication signal (step S52). Specifically, for example, when an instruction signal set to “1” is extracted, the UE 3 switches from transmission power control according to the following control equation (2) to transmission power control according to the following control equation (1). When the instruction signal set to “0” is extracted, the UE 3 switches from transmission power control according to the following control equation (1) to transmission power control according to the following control equation (2).

That is, when different radio resources among a plurality of radio resources are allocated to a plurality of radio terminals 3 including the own station 3, the UE 3 transmits at least a known radio signal transmitted by the own station 3 to the serving radio base. The transmission power of the local station 3 can be determined so as to be received by the station 2 (or 1) and the other radio base station 1 (or 2).
Next, UE3 determines the transmission power of SRS according to the transmission power control method (control formula) after switching in step S52 (step S53).

And UE3 transmits SRS with the transmission power determined by step S53 (step S54), and complete | finishes the transmission process of SRS (step S55).
As described above, according to this example, even when the radio resources for SRS transmission are insufficient, the influence of SRS collision due to the overlap of radio resources for SRS transmission can be reduced. It becomes possible to obtain a high-quality UL-CQI (UpLink-Channel Quality Indicator). As a result, the eNB 1 can appropriately perform CoMP control, so that it is possible to maintain the data communication efficiency by CoMP.

[2] First Modification In the above example, eNB1 and RRH2 have determined whether TPC switching is necessary. However, as in this example, UE3 is notified of the presence or absence of radio resource duplication from eNB1 and RRH2. Based on the notification contents, it may be determined whether or not TPC switching is necessary.
For example, as shown in FIG. 12, first, eNB1 or RRH2 assigns radio resources for SRS transmission to each UE3, and whether or not the same radio resources are assigned to different UE3 in duplicate. Is detected.

When it detects that the same radio resource is assigned to different UE3 in duplicate (duplication of SRS radio resource) (step S60), eNB1 or RRH2 detects at least one of UE3 to which the same radio resource is assigned. Then, it is notified that the radio resources for SRS transmission are allocated redundantly (step S61).
The UE 3 that is notified that the radio resources for SRS transmission are allocated redundantly performs, for example, transmission power control according to the following control equation (1) so that the SRS reaches only the serving cell ( Step S62), SRS is transmitted with the determined transmission power (step S63).

On the other hand, when eNB1 or RRH2 detects that the overlapping of the radio resources for SRS has been eliminated (step S64), among UE3 assigned with the same radio resource, UE3 that has instructed step S61 described above Then, it is notified that the SRS radio resource duplication has been resolved (step S65).
UE3 that has been notified that the duplication of SRS radio resources has been resolved, for example, performs transmission power control according to the following control equation (2) so that the SRS reaches all reception points in the CoMP set. (Step S66), SRS is transmitted with the determined transmission power (Step S67).

(2.1) Example of Operation of eNB 1 and RRH 2 Next, an example of the operation of eNB 1 and RRH 2 will be described using FIG. 6 and FIGS. 13 to 15.
First, the scheduler 18 performs radio resource allocation control.
For example, as shown in FIG. 6, when the scheduler 18 starts radio resource allocation control (step S20), the scheduler 18 calculates the number of uplink radio resources that the UE 3 can use for transmission of SRS (step S21). Note that the number of uplink radio resources includes, for example, the number of resource blocks (RB) defined by the channel and transmission timing.

Next, the scheduler 18 performs notification processing regarding the presence or absence of radio resource duplication.
For example, as illustrated in FIG. 13, when the scheduler 18 starts notification processing about the presence or absence of radio resource duplication (step S <b> 70), the scheduler 18 determines whether or not the same radio resource is assigned to different UEs 3 in duplicate. If there is no radio resource duplication (No route in step S71), the notification process is terminated (step S74).

On the other hand, when there is duplication of radio resources (Yes route in step S71), the scheduler 18 determines whether or not each UE 3 to which the same radio resource is assigned is a CoMP application target (step S72). .
Here, when it is determined that at least one of the UEs 3 to which the same radio resource is allocated is not a CoMP application target (No route in Step S72), the scheduler 18 ends the notification process (Step S74).

On the other hand, when it is determined that any of the UEs 3 to which the same radio resource is allocated is a CoMP application target (Yes route in step S72), the scheduler 18 Radio resources for SRS transmission are allocated to UE3 located in a radio area provided by another station different from the radio area provided by

own stations

1 and 2 Then, it is notified that there is a possibility of interference of SRS (step S73), and the notification process is terminated (step S74).

Further, the scheduler 18 performs the following re-notification process after performing the process of step S73.
For example, as shown in FIG. 14, when the scheduler 18 starts the re-notification process (step S80), the scheduler 18 determines whether or not the situation in which the same radio resource is allocated to different UEs 3 has been resolved. (Step S81).

If the overlapping state of the radio resources has been eliminated (Yes route in step S81), the scheduler 18 is the radio provided by the

own stations

1 and 2 among the UEs 3 to which the same radio resource is allocated. Radio resources for SRS transmission are not allocated redundantly to UE3 located in a radio area provided by another station different from the area, and there is no possibility of SRS interference occurring This is notified (step S83), and the re-notification process is terminated (step S84).

On the other hand, if the overlapping state of the radio resources has not been resolved (No route in step S81), the scheduler 18 determines whether or not at least one of the UEs 3 to which the same radio resource is assigned is not subject to CoMP application. Is determined (step S82).
Here, when it is determined that at least one of the UEs 3 to which the same radio resource is allocated is not subject to CoMP application (Yes route in step S82), the scheduler 18 has been allocated the same radio resource. In addition, among the UEs 3, there is a possibility that SRS interference may occur for UEs 3 located in radio areas provided by other stations different from the radio areas provided by the

own stations

1 and 2. Notify (step S83), and the re-notification process ends (step S84).

On the other hand, when it is determined that each of the UEs 3 to which the same radio resource is allocated is a CoMP application target (No route in Step S82), the scheduler 18 ends the re-notification process (Step S84).
Here, the notification process and the re-notification process will be described in detail.
When performing the notification process shown in step S73 and the re-notification process shown in step S83, the scheduler 18 notifies the control signal generation unit 20 that radio resources are allocated in duplicate. Request to generate a signal.

The notification signal is configured as a flag that can take two values, for example, “1” and “0”. For example, in the above step S73, the scheduler 18 sets the notification signal to “1” to notify the UE 3 that the radio resource is allocated redundantly. In step S83, the scheduler 18 sets the instruction signal to “0” to notify the UE 3 that the radio resources are not allocated redundantly.

Note that the notification signal may be transmitted by being stored in downlink control information such as DCI: A-CQI as shown in FIG. 15 (A), for example. Alternatively, the notification signal is added as a new field (srs-ConfigTPC) to a control signal in an upper layer such as SoundingRS-UL-Config of RadioConfigresource control information elements, for example, as shown in FIG. May be sent.

(2.2) Example of Operation of UE3 Next, an example of the operation of UE3 will be described with reference to FIG.
As illustrated in FIG. 16, first, when the UE 3 starts the SRS transmission process (step S90), the UE 3 extracts the notification signal described above from the control information received from the eNB 1 and the RRH 2 (step S91).

And UE3 switches the transmission power control method in the own station 3 according to the content of the extracted notification signal (step S92). Specifically, for example, when a notification signal set to “1” is extracted, the UE 3 switches from transmission power control according to the following control equation (2) to transmission power control according to the following control equation (1). When the notification signal set to “0” is extracted, the UE 3 switches from transmission power control according to the following control equation (1) to transmission power control according to the following control equation (2).

Next, UE3 determines the transmission power of SRS according to the transmission power control method (control equation) after switching in step S92 (step S93).
And UE3 transmits SRS with the transmission power determined by step S93 (step S94), and complete | finishes the transmission process of SRS (step S95).
As described above, according to this example, the same effect as that of the above-described embodiment can be obtained.

[3] Example of Hardware Configuration FIG. 17 shows an example of the hardware configuration of eNB1 and RRH2.
As illustrated in FIG. 17, the eNB 1 and the RRH 2 include an antenna 11, a wireless IF (wireless interface) 51, a processor 52, a memory 53, a logic circuit 54, and a wired IF (wired interface) 55. .

The wireless IF 51 is an interface device for performing wireless communication with the UE 3. The processor 52 is a device that processes data, and includes, for example, a Central Processing Unit (CPU), a Digital Signal Processor (DSP), and the like. The memory 53 is a device that stores data, and includes, for example, Read Only Memory (ROM), Random Access Memory (RAM), and the like. The logic circuit 54 is an electronic circuit that performs a logical operation, and includes, for example, Large Scale Integration (LSI), Field Programmable Gate Array (FPGA), and the like. The wired IF 55 is an interface device for performing wired communication with another eNB 1 and another RRH 2.

The correspondence relationship between the configurations of eNB1 and RRH2 illustrated in FIG. 5 and the configurations of eNB1 and RRH2 illustrated in FIG. 17 is as follows, for example.
The wireless IF 51 corresponds to, for example, the duplexer 12, the reception unit 13, and the transmission unit 25. The processor 52, the memory 53, and the logic circuit 54 include, for example, a channel estimation unit 14, a control signal demodulation / decoding unit 15, a data signal demodulation / decoding unit 16, a reception quality calculation unit 17, a scheduler 18, a data signal generation unit 19, and a control signal generation. This corresponds to the unit 20, the reference signal generation unit 21, the data signal encoding / modulation unit 22, the control signal encoding / modulation unit 23, and the allocation unit 24.

FIG. 18 shows an example of the hardware configuration of UE3.
As illustrated in FIG. 18, the UE 3 includes an antenna 31, a wireless IF 61, a processor 62, a memory 63, a logic circuit 64, an input IF (input interface) 65, and an output IF (output interface) 66. Is provided.
The wireless IF 61 is an interface device for performing wireless communication with the eNB 1 and the RRH 2. The processor 62 is a device that processes data, and includes, for example, a CPU and a DSP. The memory 63 is a device that stores data, and includes, for example, a ROM, a RAM, and the like. The logic circuit 64 is an electronic circuit that performs a logical operation, and includes, for example, an LSI, an FPGA, or the like. The input IF 65 is a device that performs input, and includes, for example, an operation button, a microphone, and the like. The output IF 66 is a device that performs output, and includes, for example, a speaker and a display.

The correspondence relationship between each configuration of UE 3 illustrated in FIG. 10 and each configuration of UE 3 illustrated in FIG. 18 is, for example, as follows.
The wireless IF 61 corresponds to, for example, the duplexer 32, the reception unit 33, and the transmission unit 46. The processor 62, the memory 63, and the logic circuit 64 include, for example, a channel estimation unit 34, a control signal demodulation / decoding unit 35, a data signal demodulation / decoding unit 36, a reception quality calculation unit 37, a data signal generation unit 38, a control signal generation unit 39, This corresponds to the reference signal generation unit 40, the data signal encoding / modulating unit 41, the control signal encoding / modulating unit 42, the allocating unit 43, the switching control unit 44 and the transmission power determining unit 45.

[4] Others In addition, each structure and each function of eNB1, RRH2, and UE3 in embodiment and the modification which were mentioned above may be selected as needed, and may be used in combination suitably. In other words, the above-described configurations and functions may be selected or used in appropriate combination so that the functions of the present invention can be exhibited.

In the embodiment and the modification described above, when radio resources for SRS transmission are allocated in duplicate, the SRS transmitted by the UE 3 is received only by the serving radio base station 2 (or 1). Although the transmission power is controlled, for example, the transmission power of UE3 is set so that the SRS transmitted by UE3 is received by a plurality of radio base stations other than radio base station 1 (or 2) where interference of SRS may occur. You may control. Specifically, for example, the transmission power can be determined based on the distance between the UE 3 and each of the

radio base stations

1 and 2, the radio communication environment, and the like. The plurality of radio base stations excluding the radio base station 1 (or 2) in which SRS interference may occur include the serving radio base station 2 (or 1).

Furthermore, in the above-described embodiment and the modification, when radio resources for SRS transmission are allocated in duplicate, the transmission power control method of UE3 is switched as a plurality of SRSs can interfere. When SRS interference actually occurs, the transmission power control method of UE 3 may be switched. Specifically, for example, in eNB1 and RRH2, SRS interference is detected by comparing the received power of each SRS, and based on the detection result, an instruction signal is transmitted to UE3 or a notification signal is transmitted. Then, the transmission power control method of UE3 may be switched.

In the embodiment and the modification described above, the radio communication system 6 includes the eNB 1 as an example of the macro base station that covers a radio area of the order of several hundred meters to several km, and the extension station (RRH) 2. The wireless communication system 6 is, for example, a micro base station (Micro eNB) that covers a wireless area on the order of several hundred meters, or a pico base that covers a wireless area on the order of several tens of meters to about 200 meters. A station (Pico eNB), a home base station dedicated to a specific user (also referred to as a Home eNB or a femtocell base station), a relay station that relays a radio signal, and the like may be provided. At this time, the micro base station, the pico base station, and the home base station may have the same configuration and function as the eNB 1 or the RRH 2 described above.

Furthermore, in the above-described embodiment and modification, when the same radio resource is assigned to different UEs 3 in a duplicated manner, the transmission power control method of UE 3 is switched. May be switched to the UE 3 transmission power control method.

1 eNB
2-1, 2-2 RRH
3-1 to 3-7 UE
4 Radio Area 5-1 and 5-2 Radio Area 6 Wireless Communication System 11 Antenna 12 Duplexer 13 Receiver 14 Channel Estimator 15 Control Signal Demodulator / Decoder 16 Data Signal Demodulator / Decoder 17 Reception Quality Calculator 18 Scheduler 19 Data Signal Generation Unit 20 control signal generation unit 21 reference signal generation unit 22 data signal encoding modulation unit 23 control signal encoding modulation unit 24 allocation unit 25 transmission unit 31 antenna 32 duplexer 33 reception unit 34 channel estimation unit 35 control signal demodulation decoding unit 36 data Signal demodulation decoding unit 37 Reception quality calculation unit 38 Data signal generation unit 39 Control signal generation unit 40 Reference signal generation unit 41 Data signal encoding modulation unit 42 Control signal encoding modulation unit 43 Allocation unit 44 Switching control unit 45 Transmission power determination unit 46 Transmitter 51 Wireless IF
52 Processor 53 Memory 54 Logic Circuit 55 Wired IF
61 Wireless IF
62 processor 63 memory 64 logic circuit 65 input IF
66 Output IF
100 eNB
200-1, 200-2 RRH
300-1 to 300-7 UE
400 Wireless area 500-1,500-2 Wireless area

Claims

When a plurality of radio resources used when transmitting a known signal are assigned to a plurality of radio terminals at least partially overlapping with each other, Is located in the radio area of the other radio base station so that a known signal transmitted by a radio terminal located in the radio area of another different radio base station is received by the radio base station other than the local station. A processing unit for controlling the transmission power of the wireless terminal;
A receiving unit that receives at least a known signal transmitted by a wireless terminal located in the wireless area of the local station among the plurality of wireless terminals;
A radio base station characterized by that.
The processing unit is
When radio resources that at least partially overlap each other among the plurality of radio resources are allocated to a plurality of radio terminals, radios of other radio base stations different from the own station among the plurality of radio terminals Controlling the transmission power of a wireless terminal located in the wireless area of the other wireless base station so that a known signal transmitted by the wireless terminal located in the area is received only by the other wireless base station;
The radio base station according to claim 1, wherein:
The processing unit is
When different radio resources among the plurality of radio resources are allocated to a plurality of radio terminals, at least a known signal transmitted by a radio terminal located in a radio area of the other radio base station is at least Controlling the transmission power of a radio terminal located in the radio area of the other radio base station so as to be received by the station and the other radio base station;
The radio base station according to claim 1 or 2, wherein
The processing unit is
A radio resource at least partially overlapping among the plurality of radio resources is allocated to a radio terminal located in a radio area of the own station and a radio terminal located in a radio area of the other radio base station,
The radio base station according to any one of claims 1 to 3, characterized in that:
The processing unit is
An instruction signal for instructing switching of the transmission power, or a notification signal for notifying that radio resources at least partially overlapping each other among the plurality of radio resources are allocated to the plurality of radio terminals By controlling transmission power of the wireless terminal by transmitting to the wireless terminal located in the wireless area of another wireless base station,
The radio base station according to any one of claims 1 to 4, characterized in that:
The instruction signal or the notification signal is downlink control information transmitted to a radio terminal located in a radio area of the other radio base station, or a communication layer higher than a communication layer in which the known signal is processed And stored in a control signal transmitted to a wireless terminal located in a wireless area of the other wireless base station.
The radio base station according to claim 5, wherein:
A known resource transmitted by the own station when a plurality of wireless resources used when transmitting a known signal are assigned to a plurality of wireless terminals including at least one part of the wireless resource. A processing unit that determines the transmission power of the local station so that the signal is received by some of the plurality of wireless base stations;
A transmission unit that transmits the known signal using the transmission power determined by the processing unit;
A wireless terminal characterized by that.
The processing unit is
When radio resources at least partially overlapping each other among the plurality of radio resources are allocated to a plurality of radio terminals including the own station, a known signal transmitted by the own station is transmitted only by the serving radio base station. Determine the transmission power of your station so that it can be received.
The wireless terminal according to claim 7, wherein:
The processing unit is
When different radio resources among the plurality of radio resources are allocated to a plurality of radio terminals including the own station, at least the serving radio base station and another radio base Determine the transmission power of your station so that it is received by the station.
The wireless terminal according to claim 7, wherein the wireless terminal is a wireless terminal.
When a plurality of radio resources used when transmitting a known signal are assigned to a plurality of radio terminals at least partially overlapping with each other, Is located in the radio area of the other radio base station so that a known signal transmitted by a radio terminal located in the radio area of another different radio base station is received by the radio base station other than the local station. A radio base station that controls the transmission power of the radio terminal;
A wireless terminal located in a wireless area of the other wireless base station and transmitting the known signal using transmission power controlled by the wireless base station;
A wireless communication system.
The radio base station is
When radio resources that at least partially overlap each other among the plurality of radio resources are allocated to a plurality of radio terminals, radios of other radio base stations different from the own station among the plurality of radio terminals Controlling the transmission power of a wireless terminal located in the wireless area of the other wireless base station so that a known signal transmitted by the wireless terminal located in the area is received only by the other wireless base station;
The wireless communication system according to claim 10, wherein:
The radio base station is
When different radio resources among the plurality of radio resources are allocated to a plurality of radio terminals, at least a known signal transmitted by a radio terminal located in a radio area of the other radio base station is at least Controlling the transmission power of a radio terminal located in the radio area of the other radio base station so as to be received by the station and the other radio base station;
The wireless communication system according to claim 10 or 11, characterized by the above.
The radio base station is
A radio resource at least partially overlapping among the plurality of radio resources is allocated to a radio terminal located in a radio area of the own station and a radio terminal located in a radio area of the other radio base station,
The wireless communication system according to any one of claims 10 to 12, characterized in that:
Multipoint coordinated (CoMP: Coordinated Multi Point) communication is performed between the wireless base station and the wireless terminal.
The wireless communication system according to any one of claims 10 to 13, wherein the wireless communication system is characterized in that:
In the radio base station
When a plurality of radio resources used when transmitting a known signal are assigned to a plurality of radio terminals at least partially overlapping with each other, Is located in the radio area of the other radio base station so that a known signal transmitted by a radio terminal located in the radio area of another different radio base station is received by the radio base station other than the local station. Control the transmission power of the wireless terminal,
In a radio terminal located in a radio area of the other radio base station,
Transmitting the known signal using the controlled transmission power;
A communication control method.
In the radio base station,
When radio resources that at least partially overlap each other among the plurality of radio resources are allocated to a plurality of radio terminals, radios of other radio base stations different from the own station among the plurality of radio terminals Controlling the transmission power of a wireless terminal located in the wireless area of the other wireless base station so that a known signal transmitted by the wireless terminal located in the area is received only by the other wireless base station;
The communication control method according to claim 15, wherein:
In the radio base station,
When different radio resources among the plurality of radio resources are allocated to a plurality of radio terminals, at least a known signal transmitted by a radio terminal located in a radio area of the other radio base station is at least Controlling the transmission power of a radio terminal located in the radio area of the other radio base station so as to be received by the station and the other radio base station;
The communication control method according to claim 15 or 16, characterized by the above.
In the radio base station,
A radio resource at least partially overlapping among the plurality of radio resources is allocated to a radio terminal located in a radio area of the own station and a radio terminal located in a radio area of the other radio base station,
The communication control method according to any one of claims 15 to 17, characterized in that:
Multipoint coordinated (CoMP: Coordinated Multi Point) communication is performed between the wireless base station and the wireless terminal.
The communication control method according to any one of claims 15 to 18, characterized in that: