WO2015151207A1 - Radio communication system, radio communication method, radio station and control station - Google Patents

Abstract

A radio communication system (100) includes: a second radio station (130) that can communicate with a plurality of first radio stations (120a, 120b); and a control station (110) that controls the first radio stations (120a, 120b). The plurality of first radio stations (120a, 120b) cooperate to transmit, to the second radio station (130), data addressed thereto during a particular time period in which radio transmissions are performed by use of a lower electric power than during the other time periods. The second radio station (130) receives the data addressed thereto and transmitted via the cooperative communication performed by the plurality of first radio stations (120a, 120b).

Description

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

The present invention relates to a wireless communication system, a wireless communication method, a wireless station, and a control station.

Conventionally, in mobile communication in which a mobile station communicates via a base station, ICIC (Inter Cell Interference Coordination) that controls interference between a plurality of macro base stations is known. Further, FeICIC (Further enhanced ICIC) that controls interference between a macro base station and a small base station is known.

In addition, in 11G (3rd Generation: 3rd generation mobile communication system), Release 11 that further expands LTE (Long Term Evolution) -Advanced is being studied (for example, see Non-Patent Documents 1 to 10 below). In Release 11, for example, CoMP (Coordinated Multiple-Point transmission and reception: multipoint coordinated communication) is being studied in which a plurality of base stations perform communication in cooperation to improve cell edge performance.

Also, cooperative HARQ in which a plurality of base stations perform HARQ (Hybrid Automatic Repeat Request) in a coordinated manner is known (see, for example, Patent Document 1 below).

International Publication No. 2010/049970

However, in the above-described prior art, when many cells are installed, the edge area of the cell increases, so that a period for suppressing the transmission power of some cells is set to reduce interference. For this reason, the throughput in wireless communication may decrease.

In one aspect, an object of the present invention is to provide a wireless communication system, a wireless communication method, a wireless station, and a control station that can improve throughput.

In order to solve the above-described problems and achieve the object, according to one aspect of the present invention, a second radio station capable of communicating with a plurality of first radio stations, and a control station that controls the first radio station And the control station notifies the second radio station of radio resources for cooperative communication in which the plurality of first radio stations cooperate with each other to communicate with the second radio station, and so on. The cooperation in which the plurality of first wireless stations cooperate to use the wireless resource and transmit data addressed to the second wireless station to the second wireless station in a specific period in which wireless transmission is performed with lower power than the period of A wireless communication system, a wireless communication method, a wireless station, and a control station are proposed in which communication is performed and the second wireless station receives data addressed to itself transmitted by the cooperative communication on the wireless resource.

According to one aspect of the present invention, there is an effect that throughput can be improved.

FIG. 1 is a diagram of an example of a wireless communication system according to the first embodiment. FIG. 2A is a diagram illustrating an example of a communication system according to the second embodiment. FIG. 2B is a diagram illustrating an application example of the communication system according to the second embodiment. FIG. 3A is a sequence diagram illustrating an operation example 1 of the communication system. FIG. 3B is a sequence diagram illustrating an operation example 2 of the communication system. FIG. 3C is a sequence diagram illustrating an operation example 3 of the communication system. FIG. 4A is a flowchart illustrating an example of processing by the macro base station. FIG. 4B is a flowchart illustrating an example of processing by the small base station. FIG. 5 is a flowchart showing an example of processing by the mobile station. FIG. 6 is a diagram illustrating an example of each base station. FIG. 7 is a diagram illustrating an example of a mobile station. FIG. 8 is a diagram illustrating an example of a hardware configuration of the base station. FIG. 9 is a diagram illustrating an example of a hardware configuration of the mobile station. FIG. 10 is a diagram illustrating an example of the operation of each small base station according to each reception result of the response signal. FIG. 11 is a diagram illustrating an example of retransmission by an upper layer.

Hereinafter, embodiments of a wireless communication system, a wireless communication method, a wireless station, and a control station according to the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a diagram of an example of a wireless communication system according to the first embodiment. As illustrated in FIG. 1, the radio communication system 100 according to the first embodiment includes a control station 110, first radio stations 120a and 120b, and a second radio station 130. The second radio station 130 is a radio station capable of radio communication with the first radio stations 120a and 120b.

The control station 110 is a control station that controls the first radio stations 120a and 120b. The control station 110 is connected to the first radio stations 120a and 120b, for example, by wire. Further, the control station 110 may be able to communicate with the first radio stations 120a and 120b by radio.

<Control station>
The control station 110 includes a control unit 111 and a communication unit 112. The control unit 111 controls cooperative communication in which the first wireless stations 120a and 120b communicate with the second wireless station 130 in cooperation. For example, the communication unit 112 performs wireless communication with the second wireless station 130. In addition, the communication unit 112 notifies the second radio station 130 of radio resources for cooperative communication in which the first radio stations 120a and 120b cooperate to communicate with the second radio station 130. Radio resources include, for example, frequency resources. Further, the radio resource may include a time resource. Further, the communication unit 112 may notify the first radio stations 120a and 120b of radio resources for cooperative communication in which the first radio stations 120a and 120b cooperate to communicate with the second radio station 130.

<First radio station>
The first radio station 120a includes a control unit 121a and a communication unit 122a. The control unit 121a controls cooperative communication in which the first wireless stations 120a and 120b communicate with the second wireless station 130 in cooperation. The communication unit 122a is addressed to the second radio station 130 in cooperation with a first radio station (for example, the first radio station 120b) different from the own station (for example, the first radio station 120a) of the first radio stations 120a and 120b. The cooperative communication for transmitting the data to the second radio station 130 is performed. The cooperative communication by the communication unit 122a is controlled by the control unit 121a.

In addition, the communication unit 122a performs cooperative communication in a specific period in which wireless transmission is performed with lower power than other periods. Note that “lower power” includes a case where transmission on a certain radio channel is not performed at all. For example, the communication unit 122a performs wireless transmission with a first transmission power in a certain first period to other wireless stations including the second wireless station 130, and a second period (specific period) different from the first period. , Wireless transmission is performed with a second transmission power lower than the first transmission power. For example, the communication unit 122a transmits data addressed to the second radio station 130 to the second radio station 130 by cooperative communication with another first radio station in the second period.

The first wireless station 120b includes a control unit 121b and a communication unit 122b. The control unit 121b and the communication unit 122b are the same as the control unit 121a and the communication unit 122a of the first radio station 120a, respectively. That is, the control unit 121a of the first radio station 120a and the control unit 121b of the first radio station 120b perform cooperative communication in which communication with the second radio station 130 is performed in cooperation.

<Second radio station>
The second radio station 130 includes a control unit 131 and a communication unit 132. The control unit 131 controls communication between the first radio stations 120a and 120b and the second radio station 130 through cooperative communication in which the first radio stations 120a and 120b cooperate. The communication unit 132 receives data addressed to the local station, which is transmitted in cooperation by the first wireless stations 120a and 120b.

As described above, according to Embodiment 1, the first wireless stations 120a and 120b perform coordinated transmission in a specific period in which low power transmission is performed, thereby improving the reception characteristics of the second wireless station 130 in the specific period. be able to. For this reason, even if many specific periods are set in the wireless communication system 100, the throughput can be improved.

<Specific examples of each radio station>
For example, the control station 110 can be a base station that forms a cell capable of wireless communication. In this case, each of the first radio stations 120 a and 120 b can be a base station located in the cell of the control station 110. The second radio station 130 can be a mobile station, for example. In this case, the second wireless station 130 may be capable of wireless communication with the control station 110 in addition to the first wireless stations 120a and 120b. Further, wireless communication may be possible simultaneously with the control station 110 and the first wireless station 120a or 120b.

Examples of base stations corresponding to the control station 110 include macro base stations. In addition, examples of base stations corresponding to the first radio stations 120a and 120b include small base stations. However, the application destination of each base station is not limited to these. For example, base stations corresponding to the first radio stations 120a and 120b receive various interferences from larger cells such as femto base stations and pico base stations. A base station that forms the victim cell can be applied.

<Non-notification of radio resources by the first radio station>
The communication unit 122a of the first wireless station 120a transmits data addressed to the second wireless station 130 without notifying the second wireless station 130 of the wireless resources of the cooperative communication in the cooperative communication with the first wireless station 120b. Also good. Similarly, the communication unit 122b of the first wireless station 120b transmits data addressed to the second wireless station 130 without notifying the second wireless station 130 of the wireless resources of the cooperative communication in the cooperative communication with the first wireless station 120a. You may send it.

Also in this case, the communication unit 132 of the second radio station 130 receives the data addressed to the second radio station 130 transmitted in cooperation by the first radio stations 120a and 120b on the radio resource notified from the control station 110. can do. Thereby, the communication amount between the 1st radio stations 120a and 120b and the 2nd radio station 130 can be reduced.

<Notification by radio signal of radio resource>
The communication unit 112 of the control station 110 may notify the second radio station 130 of radio resources for cooperative communication by the first radio stations 120a and 120b by radio signals. Thereby, for example, compared with the notification via the wired network between the control station 110 and the radio stations 120a and 120b, the radio resource of the cooperative communication can be notified to the second radio station 130 in a short time. For this reason, the determination result of the radio resource of the cooperative communication by the control station 110 can be reflected quickly, and the communication quality can be improved.

<Resend>
The retransmission when the second wireless station 130 cannot normally receive the data addressed to the second wireless station 130 in the cooperative communication by the first wireless stations 120a and 120b will be described. In this case, retransmission of data addressed to the second wireless station 130 is performed by one of the first wireless stations 120a and 120b, and the other first of the first wireless stations 120a and 120b. The radio station may not be performed.

That is, in the initial transmission to the second radio station 130, cooperative communication by the first radio stations 120a and 120b is performed, but for the retransmission of the second radio station 130, any one of the first radio stations 120a and 120b. Retransmission is performed only by one radio station. Thereby, since retransmission can be performed without performing cooperative control between the first radio stations 120a and 120b, the amount of retransmission control can be reduced.

<Reduction in the number of radio resource notifications>
The communication unit 112 of the control station 110 notifies the second radio station 130 of the radio resources for cooperative communication by the first radio stations 120a and 120b, and then only changes the radio resources for the coordinated communication. The radio resource may be notified to the second radio station 130. In this case, the communication unit 132 of the second radio station 130 can receive data addressed to the own station on the radio resource notified last from the control station 110. Thereby, for example, the communication amount between the control station 110 and the second radio station 130 can be reduced as compared with the case where the radio resource is repeatedly notified regardless of whether or not the radio resource is changed.

<Specific period>
The specific period during which radio transmission is performed with lower power than other periods in the first radio stations 120a and 120b is, for example, an ABS (Almost Blank Subframe) set in common with the first radio stations 120a and 120b. However, not only ABS but various periods can be applied to the specific period. In addition, the time unit of the specific period is not limited to a subframe, and can be various time units (for example, a radio frame or a slot).

<Collaborative communication>
For example, CoMP can be used for cooperative communication in which the first wireless stations 120a and 120b communicate with the second wireless station 130 in cooperation. However, cooperative communication is not limited to CoMP, and various types of cooperative communication can be used.

<Modification>
Although the case where the wireless communication system 100 includes the first wireless stations 120a and 120b as the first wireless stations has been described, the wireless communication system 100 includes three or more first wireless stations, and the three or more first wireless stations include The wireless communication with the second wireless station 130 may be performed in cooperation.

(Embodiment 2)
(Communication system according to Embodiment 2)
FIG. 2A is a diagram illustrating an example of a communication system according to the second embodiment. As illustrated in FIG. 2A, the communication system 200 according to the second embodiment includes a macro base station 210, small base stations 221, 222, and a mobile station 230. As an example, the communication system 200 is a wireless communication system to which LTE or LTE-Advanced is applied.

1 can be realized by the communication system 200, for example. The control station 110 shown in FIG. 1 can be realized by the macro base station 210, for example. The first radio stations 120a and 120b shown in FIG. 1 can be realized by small base stations 221 and 222, for example. The second radio station 130 shown in FIG. 1 can be realized by the mobile station 230, for example.

The macro cell 210a is a wireless communication range (cell) of the macro base station 210. The small cell 221a is a wireless communication range (cell) of the small base station 221. The small cell 222 a is a wireless communication range (cell) of the small base station 222. In the example shown in FIG. 2A, the small base stations 221 and 222 are located in the macro cell 210a.

The mobile station 230 is a UE (User Equipment: user terminal) capable of wireless communication with a base station. In the example shown in FIG. 2A, the mobile station 230 is located in an overlapping portion of the small cells 221a and 222a, and can perform wireless communication with the small base stations 221 and 222. Further, since the mobile station 230 is also located in the macro cell 210a, wireless communication is possible with the macro base station 210.

In the communication system 200, FeICIC for controlling interference between the macro base station 210 and the small base stations 221 and 222 is performed. For example, in the communication system 200, an ABS that is a subframe required to perform low power transmission is set.

For example, in order to reduce interference from the macro base station 210 to the radio communication of the small base stations 221 and 222, an ABS (ABS between the macro cell and the small cell) to which the macro base station 210 performs low power transmission is set.

Also, in order to reduce interference from the small base stations 221 and 222 to the radio communication of the macro base station 210, an ABS (ABS between small cells) in which the small base stations 221 and 222 perform low power transmission is set.

The small cells 221a and 222a can execute CoMP that performs radio communication with the mobile station 230 in cooperation with each other (Inter-eNB CoMP). CoMP by the small cells 221a and 222a is controlled by the macro base station 210, for example. For example, the macro base station 210 transmits the same user data destined for the mobile station 230 to the small cells 221a and 222a.

Also, the macro base station 210 transmits a control signal indicating a subframe (including ABS) for performing CoMP transmission and a transmission scheme (for example, an encoding scheme and a modulation scheme) to the small cells 221a and 222a.

The small cells 221a and 222a wirelessly transmit the same user data received from the macro base station 210 to the mobile station 230 simultaneously based on the control signal received from the macro base station 210.

The mobile station 230 performs diversity reception for receiving the same user data wirelessly transmitted simultaneously from the small cells 221a and 222a. Thereby, even in a situation where a large number of ABSs are set, it is possible to improve the reception characteristics (for example, the received signal level) in the mobile station 230 (for example, 3 [dB]) and improve the data rate.

For transmitting user data from the macro base station 210 to the small cells 221a and 222a, for example, Xn interfaces 201 and 202 (for example, an X2 interface) between the macro base station 210 and the small base stations 221 and 222 can be used. . However, a wired communication interface or a wireless communication interface different from the Xn interfaces 201 and 202 may be used for transmitting user data from the macro base station 210 to the small cells 221a and 222a.

Wireless communication can be used for transmission of control signals from the macro base station 210 to the small cells 221a and 222a. Thereby, since the control signal can be transmitted with a small delay, the determination result of the radio resource and transmission method of the cooperative communication by the macro base station 210 can be reflected quickly, and the communication quality can be improved. However, it is also possible to use the Xn interfaces 201 and 202 or a wired communication interface different from the Xn interfaces 201 and 202 for transmitting control signals from the macro base station 210 to the small cells 221a and 222a.

FIG. 2B is a diagram illustrating an application example of the communication system according to the second embodiment. In FIG. 2B, the same parts as those shown in FIG. The communication system 200 shown in FIG. 2A can be applied to the communication system 200 shown in FIG. 2B, for example. The communication system 200 shown in FIG. 2B includes macro base stations 210 and 240 and small base stations 221, 222, 251 and 252.

The macro cell 240a is a wireless communication range (cell) of the macro base station 240. The small cell 251a is a wireless communication range (cell) of the small base station 251. The small cell 252a is a wireless communication range (cell) of the small base station 252. In the example shown in FIG. 2B, the small base stations 251 and 252 are located in the macro cell 240a.

In the communication system 200, FeICIC for controlling interference between the macro base station 240 and the small base stations 251 and 252 is performed. In the communication system 200, ICIC for controlling interference between the macro base station 210 and the macro base station 240 is performed.

(Operation example of communication system)
FIG. 3A is a sequence diagram illustrating an operation example 1 of the communication system. In FIG. 3A, the same parts as those shown in FIG. 2A are denoted by the same reference numerals and description thereof is omitted. In FIG. 3A, the horizontal axis indicates the passage of time. A partition 301 indicates a wireless frame partition. One radio frame includes 10 subframes.

First, the macro base station 210 performs pre-configuration 302 (Configuration) with the small base stations 221 and 222. In the pre-setting 302, for example, the macro base station 210 instructs the start (Activation) or the stop (Deactivation) of CoMP transmission by the small base stations 221 and 222 (Inter-eNB CoMP (Act / Deact)). In the example illustrated in FIG. 3A, it is assumed that the macro base station 210 instructs the small base stations 221 and 222 to start CoMP transmission.

In advance setting 302, for example, the macro base station 210 notifies the ABS position set in the macro base station 210 (FeICIC: ABS (Macro)). Further, in the pre-setting 302, for example, the macro base station 210 notifies the ABS position of the MBSFN (Multicast / Broadcast Single Frequency Network: MBMS single frequency network) set in the small base stations 221 and 222 (ABS_MBSFN (Small)). )). The ABS is, for example, ABS 351 or 352 described later.

Next, the macro base station 210 starts transmission of downlink user data 311 and 312 addressed to the mobile station 230 to the small base stations 221 and 222 (Data (via Xn)). The user data 311 and 312 are downlink data destined for the mobile station 230 and are the same data.

User data 311 and 312 can be transmitted by, for example, the Xn interface (for example, the Xn interfaces 201 and 202 shown in FIG. 2A) between the macro base station 210 and the small base stations 221 and 222. The user data 311 and 312 can be transmitted by, for example, a PDCP (Packet Data Convergence Protocol) packet.

The feedbacks 321 and 322 are periodic feedback from the mobile station 230 to the macro base station 210, and are feedback of the measurement results of the wireless communication quality of the small base stations 221 and 222 in the mobile station 230. The macro base station 210 uses the results of the feedbacks 321 and 322 for controlling cooperative communication by the small base stations 221 and 222.

The feedbacks 331 and 332 are periodic feedback from the mobile station 230 to the small base stations 221 and 222, and are feedback of measurement results of the wireless communication quality of the small cells 221a and 222a in the mobile station 230. The small cells 221a and 222a use the results of the feedbacks 331 and 332 for retransmission control.

In the example shown in FIG. 3A, feedback 321 and 331 are performed simultaneously, and feedback 322 and 332 are performed simultaneously. The feedbacks 321, 322, 331, and 332 include, for example, CQI (Channel Quality Indicator: channel quality index), PMI (Precoding Matrix Indicator: precoding matrix index), RI (Rank Indicator: rank index), and the like. However, the feedback 321, 322, 331, 332 is not limited to these, and various types of wireless communication quality information can be used.

ABSs 341 and 342 are subframes in which the macro base station 210 performs low power transmission. The timings (positions) of the ABSs 341 and 342 are determined by, for example, the macro base station 210, and are notified to the small base stations 221 and 222 by the preset 302.

ABSs 351 to 354 are subframes in which both small base stations 221 and 222 perform low power transmission. ABSs 351 and 353 are MBSFNs. For example, the ABSs 351 and 353 are designated from the macro base station 210 in the preset 302.

The ABSs 351 and 353 which are MBSFNs include a control area 303 (Control Region) and a data area 304 (Data Region). In addition, the ABSs 351 and 353 may include a protection period (Guard Period) between the control area 303 and the data area 304.

ABSs 352 and 354 are ABSs determined by the small base stations 221 and 222 based on the positions of the ABSs 351 and 353 designated from the macro base station 210. For example, the small base stations 221 and 222 determine the positions of the ABSs 352 and 354 so as not to overlap the ABSs 351 and 353.

Alternatively, the ABSs 352 and 354 may be ABSs determined by the macro base station 210 and notified to the small base stations 221 and 222 by the control signals 361 and 362, for example. In this case, the ABSs 352 and 354 may be notified from the macro base station 210 to the mobile station 230 by, for example, control signals 371 and 372.

Control signals 361 and 362 are control signals from the macro base station 210 to the small base stations 221 and 222. Control signals 361 and 362 are transmitted in control area 303 of ABSs 351 and 353, which are, for example, MBSFN.

Further, the control signals 361 and 362 are signals indicating a data transmission method (modulation method and coding method) and radio resources from the small base stations 221 and 222 to the mobile station 230. For example, the control signals 361 and 362 include RBA (Resource Block Assignment: resource block allocation) and MCS (Modulation and Coding Scheme: modulation / coding scheme).

For example, the control signal 361 is a control signal indicating a data transmission method and radio resources determined by the macro base station 210 based on the feedback 321. The control signal 362 is a control signal indicating a data transmission scheme and radio resources determined by the macro base station 210 based on the feedback 322. The radio resource includes at least one of a frequency resource and a time resource, for example.

The control signals 361 and 362 can be transmitted by radio, for example. Thereby, the control signals 361 and 362 can be transmitted to the small base stations 221 and 222 with a small delay. Therefore, it is possible to shorten the time until the feedbacks 321 and 322 from the mobile station 230 are reflected in the control of the small base stations 221 and 222. For this reason, wireless communication between the small base stations 221 and 222 and the mobile station 230 according to the wireless communication quality of the mobile station 230 in the small cells 221a and 222b becomes possible.

Control signals 371 and 372 are control signals from the macro base station 210 to the mobile station 230. The control signals 371 and 372 are control signals having the same contents as the control signals 361 and 362, for example. The control signals 371 and 372 are transmitted in the control area 303 of the ABS 351 and 353 simultaneously with the control signals 361 and 362. Similarly to the control signals 361 and 362, the control signals 371 and 372 can be transmitted by radio, for example.

User data 381 and 382 are user data transmitted from the small base stations 221 and 222 to the mobile station 230 by CoMP. User data 381 and 382 are, for example, user data 311 and 312. User data 381 and 382 may be PDSCH (Physical Downlink Shared Channel: physical downlink shared channel), for example. The user data 381 and 382 are transmitted by JT (Joint Transmission: joint transmission) that transmits the same user data 381 and 382 simultaneously.

For example, the small base stations 221 and 222 simultaneously transmit user data 381 by CoMP in the ABS 352 based on the control signal 361 received from the macro base station 210 in the ABS 351. In addition, the small base stations 221 and 222 simultaneously transmit user data 382 by CoMP in the ABS 354 based on the control signal 362 received from the macro base station 210 in the ABS 353.

The mobile station 230 receives user data 381 simultaneously transmitted from the small base stations 221 and 222 in the ABS 352 based on the control signal 371 received from the macro base station 210. The mobile station 230 receives user data 382 transmitted simultaneously from the small base stations 221 and 222 in the ABS 354 based on the control signal 372 received from the macro base station 210.

Response signals 391 and 392 (A / N) are response signals from the mobile station 230 to the small base stations 221 and 222 for the user data 381 and 382, respectively. Each of the response signals 391 and 392 is, for example, ACK (positive signal) indicating that user data has been normally received or NACK (negative signal) indicating that user data has not been normally received.

The retransmission by the small base stations 221 and 222 based on the response signals 391 and 392 is, for example, retransmission by HARQ. However, retransmission by the small base stations 221 and 222 based on the response signals 391 and 392 is not limited to HARQ, and retransmission in various layers (for example, ARQ in RLC layer) can be applied.

As described above, the small base stations 221 and 222 may transmit the data addressed to the mobile station 230 without notifying the mobile station 230 of the radio resources of the cooperative communication in the cooperative communication of the user data 381 and 382. Also in this case, the mobile station 230 can receive the data addressed to the mobile station 230 transmitted by the small base stations 221 and 222 in cooperation on the radio resource notified from the macro base station 210. Thereby, the communication amount between the small base stations 221 and 222 and the mobile station 230 can be reduced.

As an example, in the example illustrated in FIG. 3A, the ABSs 352 and 354 are determined by the macro base station 210 and are notified to the small base stations 221 and 222 by, for example, control signals 361 and 362. In this case, the ABSs 352 and 354 are also notified to the mobile station 230 by control signals 371 and 372, for example. In this case, the radio resources indicated by the control signals 361, 362, 371, and 372 include a frequency resource and a time resource (ABS 352 and 354).

FIG. 3B is a sequence diagram showing an operation example 2 of the communication system. In FIG. 3B, the same parts as those shown in FIG. 3A are denoted by the same reference numerals and description thereof is omitted. When the macro base station 210 does not change the data transmission method or radio resource for cooperative communication notified to the mobile station 230 by the control signal 371, the macro base station 210 does not need to transmit the control signal 372 as shown in FIG. 3B. Good. In this case, the mobile station 230 receives user data 382 by cooperative communication in the ABS 354 based on the control signal 371 received last. In LTE, such a transmission method is called SPS (Semi-persistent-Scheduling).

As described above, the macro base station 210 notifies the mobile station 230 of the radio resources for cooperative communication by the small base stations 221 and 222 and then changes the radio resources for the cooperative communication only when the radio resources for the cooperative communication are changed. May be notified to the mobile station 230. In this case, the mobile station 230 can receive data addressed to itself on the radio resource last notified from the control station 110. Thereby, for example, the communication amount between the macro base station 210 and the mobile station 230 can be reduced as compared with a case where the radio resource is repeatedly notified regardless of whether or not the radio resource is changed.

As an example, in the example shown in FIG. 3B, it is assumed that the ABSs 352 and 354 are determined by the macro base station 210 and notified to the small base stations 221 and 222 by, for example, the control signal 361. In this case, the ABSs 352 and 354 are also notified to the mobile station 230 by a control signal 371, for example. In this case, the radio resources indicated by the control signals 361 and 371 include frequency resources and time resources (ABS 352 and 354).

FIG. 3C is a sequence diagram showing an operation example 3 of the communication system. In FIG. 3C, the same parts as those shown in FIG. 3A are denoted by the same reference numerals and description thereof is omitted. The small base stations 221 and 222 may transmit the user data 381 together with a control signal indicating a data transmission method and radio resources for transmitting the user data 381. As the control signal in this case, for example, PDCCH (Physical Downlink Control Channel: physical downlink control channel) can be used.

For example, the small base stations 221 and 222 transmit PDSCH together with PDCCH in transmitting user data 381 (PDCCH + PDSCH (JT)). However, only one of the small base stations 221 and 222 may transmit the PDCCH. The mobile station 230 receives the PDSCH transmitted from the small base stations 221 and 222 based on the PDCCH transmitted together with the PDSCH. In this case, the macro base station 210 may not transmit the control signals 371 and 372 illustrated in FIG. 3A, for example.

As an example, in the example illustrated in FIG. 3C, it is assumed that the ABSs 352 and 354 are determined by the small base stations 221 and 222 and are notified to the mobile station 230 by PDCCH, for example. In this case, the radio resource indicated by the control signals 361 and 362 includes a frequency resource. As shown in FIGS. 3A to 3C, various methods can be used as the determination method and notification method of the ABSs 351 and 352 that perform cooperative communication.

(Processing by macro base station)
FIG. 4A is a flowchart illustrating an example of processing by the macro base station. For example, the macro base station 210 executes the steps shown in FIG. 4A. First, the macro base station 210 determines whether or not to execute CoMP transmission (step S401), and waits until it is determined to execute CoMP transmission (step S401: No loop). The determination of whether or not to execute CoMP transmission can be made based on, for example, a report of communication quality from the mobile station 230, a request for CoMP transmission from the mobile station 230, or the like.

If it is determined in step S401 that CoMP transmission is to be executed (step S401: Yes), the macro base station 210 performs CoMP communication settings (step S402). The communication setting performed in step S402 is, for example, the advance setting 302 shown in FIGS. 3A to 3C.

Next, the macro base station 210 transmits user data to the small base stations 221 and 222 (step S403). The user data transmitted in step S403 is, for example, the user data 311 and 312 shown in FIGS. 3A to 3C.

Next, the macro base station 210 receives feedback from the mobile station 230 (step S404). The feedback received in step S404 is, for example, the feedbacks 321 and 322 shown in FIGS. 3A to 3C.

Next, the macro base station 210 transmits a control signal to the small base stations 221 and 222 (step S405). The control signals transmitted in step S405 are, for example, control signals 361 and 362.

Next, the macro base station 210 determines whether or not to perform CoMP resetting (step S406). The determination of whether or not to perform CoMP resetting can be made based on, for example, a report of communication quality from the mobile station 230, a request for CoMP transmission from the mobile station 230, or the like. In this case, for example, the feedback in step S404 can be used for reporting the communication quality from the mobile station 230. If it is determined that resetting is to be executed (step S406: Yes), the macro base station 210 returns to step S402.

In step S406, when it is determined not to perform resetting (step S406: No), the macro base station 210 determines whether or not to end the CoMP transmission (step S407). The determination as to whether or not to end CoMP transmission can be made based on, for example, a report of communication quality from the mobile station 230, a request for CoMP transmission from the mobile station 230, or the like. In this case, for example, the feedback in step S404 can be used for reporting the communication quality from the mobile station 230. If it is determined that the CoMP transmission is not terminated (step S407: No), the macro base station 210 returns to step S403.

If it is determined in step S407 that CoMP transmission is to be terminated (step S407: Yes), the macro base station 210 cancels the communication setting performed in step S402 (step S408), and the series of processes is terminated.

In step S405, the macro base station 210 may also transmit a control signal to be transmitted to the small base stations 221 and 222 to the mobile station 230. Further, in step S405, the macro base station 210 determines whether or not to change the CoMP transmission radio resource from the previous time. If it is determined not to change, the macro base station 210 sends a control signal to the small base stations 221 and 222 and the mobile station 230. You may make it not transmit. As a result, the amount of communication can be reduced.

(Processing by small base station)
FIG. 4B is a flowchart illustrating an example of processing by the small base station. Although the processing by the small base station 221 will be described, the processing by the small base station 222 is the same as the processing by the small base station 221. The small base station 221 executes, for example, each step shown in FIG. 4B. First, the small base station 221 determines whether or not to execute CoMP transmission (step S411), and waits until it is determined to execute CoMP transmission (step S411: No loop). The determination as to whether or not to perform CoMP transmission can be made based on an instruction from the macro base station 210, for example.

If it is determined in step S411 that CoMP transmission is to be executed (step S411: Yes), the small base station 221 performs CoMP communication settings (step S412). The communication setting performed in step S412 is, for example, the pre-setting 302 shown in FIGS. 3A to 3C.

Next, the small base station 221 receives user data from the macro base station 210 (step S413). The user data received in step S413 is, for example, user data 311 and 312 shown in FIGS. 3A to 3C.

Next, the small base station 221 receives the feedback from the mobile station 230 (step S414). The feedback received in step S414 is, for example, the feedbacks 321 and 322 shown in FIGS. 3A to 3C.

Next, the small base station 221 transmits CoMP user data to the mobile station 230 (step S415). Control signals to be CoMP transmitted in step S415 are control signals 361 and 362, for example.

Next, the small base station 221 determines whether or not to perform CoMP reconfiguration (step S416). The determination as to whether or not to perform CoMP reconfiguration can be made based on an instruction from the macro base station 210, for example. When it is determined that resetting is to be executed (step S416: Yes), the small base station 221 returns to step S412.

In step S416, when it is determined not to perform resetting (step S416: No), the small base station 221 determines whether or not to end the CoMP transmission (step S417). The determination of whether or not to end the CoMP transmission can be performed based on an instruction from the macro base station 210, for example. When it is determined that the CoMP transmission is not terminated (step S417: No), the small base station 221 returns to step S413.

If it is determined in step S417 that CoMP transmission is to be terminated (step S417: Yes), the small base station 221 cancels the communication setting performed in step S412 (step S418), and the series of processes is terminated.

For example, after step S415, the small base station 221 may receive a response signal from the mobile station 230 with respect to the CoMP transmission in step S415, and may retransmit the user data based on the received response signal. The retransmission of user data can be performed based on the feedback from the mobile station 230 received in step S414, for example.

(Processing by mobile station)
FIG. 5 is a flowchart showing an example of processing by the mobile station. For example, the mobile station 230 executes the steps shown in FIG. First, the mobile station 230 performs communication settings (step S501). The communication setting performed in step S501 is the pre-setting 302 shown in FIGS. 3A to 3C, for example.

Next, the mobile station 230 determines whether or not to execute CoMP reception (step S502). The determination as to whether or not to perform CoMP reception can be made based on an instruction from the macro base station 210 or the small base stations 221 and 222, for example. If it is determined that CoMP reception is to be performed (step S502: Yes), the mobile station 230 transmits feedback to the macro base station 210 and the small base stations 221 and 222 (step S503). The feedback transmitted in step S503 is, for example, the feedbacks 321, 322, 331, and 332 shown in FIGS. 3A to 3C.

Next, the mobile station 230 receives the control channel (step S504). The control channel received in step S504 is, for example, the control signals 371 and 372 shown in FIGS. 3A and 3B. Or the control channel received by step S504 may be PDCCH accompanying the user data 381 and 382 shown in FIG. 3C.

Next, based on the control channel received in step S504, the mobile station 230 receives diversity data of user data transmitted by the small base stations 221 and 222 by CoMP (step S505). The user data that is diversity-received in step S505 is, for example, user data 381 and 382 shown in FIGS. 3A to 3C.

Next, the mobile station 230 transmits a response signal (ACK or NACK) to the reception in step S505 to the main small base station among the small base stations 221 and 222 (step S506). The main small base station of the small base stations 221 and 222 is notified to the mobile station 230 by the macro base station 210 or the small base stations 221 and 222, for example. The response signal transmitted in step S506 is, for example, the response signals 391 and 392 shown in FIGS. 3A to 3C.

Next, the mobile station 230 determines whether or not to end communication (step S507). The determination as to whether or not to end the communication can be made based on, for example, a user operation of the small base station 221 or an instruction from a communication application in the small base station 221. If it is determined not to end the communication (step S507: No), the mobile station 230 returns to step S503. Alternatively, the mobile station 230 may return to step S502 and determine again whether to perform CoMP transmission. When it is determined that the communication is to be ended (step S507: Yes), the mobile station 230 ends a series of processes.

If it is determined in step S502 that CoMP reception is not performed (step S502: No), the mobile station 230 transmits feedback to the serving base station (step S508). The serving base station is, for example, a serving base station (primary cell) to which the mobile station 230 among the macro base station 210 and the small base stations 221 and 222 is connected.

Next, the mobile station 230 receives a control channel from the serving base station (step S509). Next, the mobile station 230 receives user data from the serving base station based on the control channel received in step S509 (step S510). Next, the mobile station 230 transmits a response signal (ACK or NACK) to the reception at step S510 to the serving base station (step S511).

Next, the mobile station 230 determines whether or not to end communication (step S512). The determination as to whether or not to end the communication can be made based on, for example, a user operation of the small base station 221 or an instruction from a communication application in the small base station 221. If it is determined that the communication is not terminated (step S512: No), the mobile station 230 returns to step S508. Alternatively, the mobile station 230 may return to step S502 and determine again whether to perform CoMP transmission. When it is determined that the communication is to be ended (step S512: Yes), the mobile station 230 ends a series of processes.

(Each base station)
FIG. 6 is a diagram illustrating an example of each base station. Each of macro base station 210 and small base stations 221 and 222 can be realized by base station 600 shown in FIG. 6, for example. As illustrated in FIG. 6, the base station 600 includes, for example, a wireless communication unit 610, a control unit 620, a storage unit 630, and a communication unit 640. The wireless communication unit 610 includes a wireless transmission unit 611 and a wireless reception unit 612. Each of these components is connected so that signals and data can be input and output in one direction or in both directions.

The wireless transmission unit 611 transmits user data and control signals by wireless communication via an antenna. The wireless signal transmitted by the wireless transmission unit 611 can include arbitrary user data, control information, and the like (encoded or modulated). The wireless reception unit 612 receives user data and control signals by wireless communication via an antenna. The radio signal received by the radio reception unit 612 can include arbitrary user data, a control signal, and the like (encoded or modulated). The antenna may be common for transmission and reception.

The control unit 620 outputs user data and control signals to be transmitted to other wireless stations to the wireless transmission unit 611. In addition, the control unit 620 acquires user data and control signals received by the wireless reception unit 612. The control unit 620 inputs and outputs user data, control information, programs, and the like with a storage unit 630 described later. In addition, the control unit 620 inputs and outputs user data and control signals that are transmitted to and received from other communication devices and the like with the communication unit 640 described later. In addition to these, the control unit 620 performs various controls in the base station 600.

The storage unit 630 stores various information such as user data, control information, and programs. The communication unit 640 transmits / receives user data and control signals to / from other communication devices, for example, by wired signals.

The control unit 111 of the control station 110 illustrated in FIG. 1 can be realized by the control unit 620, for example. The communication unit 112 of the control station 110 illustrated in FIG. 1 can be realized by the wireless communication unit 610 or the communication unit 640, for example. The control units 121a and 121b of the first radio stations 120a and 120b illustrated in FIG. 1 can be realized by the control unit 620, for example. The communication units 122a and 122b of the first radio stations 120a and 120b illustrated in FIG. 1 can be realized by the radio communication unit 610 and the communication unit 640, for example.

(Mobile station)
FIG. 7 is a diagram illustrating an example of a mobile station. The mobile station 230 can be realized by, for example, the mobile station 700 shown in FIG. The mobile station 700 includes a wireless communication unit 710, a control unit 720, and a storage unit 730. The wireless communication unit 710 includes a wireless transmission unit 711 and a wireless reception unit 712. Each of these components is connected so that signals and data can be input and output in one direction or in both directions.

The wireless transmission unit 711 transmits user data and control signals by wireless communication via an antenna. The wireless signal transmitted by the wireless transmission unit 711 can include arbitrary user data, control information, and the like (encoded or modulated). The wireless reception unit 712 receives user data and control signals by wireless communication via an antenna. The radio signal received by the radio reception unit 712 can include arbitrary user data, a control signal, and the like (encoded or modulated). The antenna may be common for transmission and reception.

The control unit 720 outputs user data and control signals to be transmitted to other radio stations to the radio transmission unit 711. In addition, the control unit 720 acquires user data and control signals received by the wireless reception unit 712. The control unit 720 inputs and outputs user data, control information, programs, and the like with the storage unit 730 described later. In addition, the control unit 720 performs input / output of user data and control signals transmitted / received to / from other communication devices and the like with a communication unit described later. In addition to these, the control unit 720 performs various controls in the mobile station 700.

The storage unit 730 stores various information such as user data, control information, and programs.

The control unit 131 of the second radio station 130 illustrated in FIG. 1 can be realized by the control unit 720, for example. The communication unit 132 of the second wireless station 130 illustrated in FIG. 1 can be realized by the wireless communication unit 710, for example.

(Base station hardware configuration)
FIG. 8 is a diagram illustrating an example of a hardware configuration of the base station. The base station 600 shown in FIG. 6 can be realized by, for example, the base station 800 shown in FIG. Base station 800 includes antenna 811, RF circuit 812, processor 813, memory 814, and network IF 815. These components are connected so that various signals and data can be input / output via a bus, for example.

The antenna 811 includes a transmission antenna that transmits a radio signal and a reception antenna that receives a radio signal. The antenna 811 may be a shared antenna that transmits and receives radio signals. The RF circuit 812 performs RF (Radio Frequency: high frequency) processing on a signal received by the antenna 811 and a signal transmitted by the antenna 811. The RF processing includes, for example, frequency conversion between the baseband band and the RF band.

The processor 813 is, for example, a CPU (Central Processing Unit) or a DSP (Digital Signal Processor). The processor 813 may be realized by a digital electronic circuit such as an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or an LSI (Large Scale Integration).

The memory 814 can be realized by a random access memory (RAM) such as SDRAM (Synchronous Dynamic Random Access Memory), a ROM (Read Only Memory), a flash memory, or the like. The memory 814 stores user data, control information, programs, and the like, for example.

The network IF 815 is a communication interface that performs communication with a network by, for example, a wired connection. The network IF 815 may include, for example, Xn interfaces 201 and 202 (for example, see FIG. 2A) for performing wired communication between base stations.

6 can be realized by the RF circuit 812, the antenna 811, the RF circuit 812, or the like, for example. The control unit 620 illustrated in FIG. 6 can be realized by, for example, the processor 813 and the memory 814. The storage unit 630 illustrated in FIG. 6 can be realized by the memory 814, for example. The communication unit 640 shown in FIG. 6 can be realized by a network IF 815, for example.

(Mobile station hardware configuration)
FIG. 9 is a diagram illustrating an example of a hardware configuration of the mobile station. The mobile station 700 can be realized by, for example, the mobile station 900 shown in FIG. The mobile station 900 includes, for example, an antenna 911, an RF circuit 912, a processor 913, and a memory 914. These components are connected so that various signals and data can be input / output via a bus, for example.

The antenna 911 includes a transmission antenna that transmits a radio signal and a reception antenna that receives a radio signal. The antenna 911 may be a shared antenna that transmits and receives radio signals. The RF circuit 912 performs RF processing on a signal received by the antenna 911 and a signal transmitted by the antenna 911. The RF processing includes, for example, frequency conversion between the baseband band and the RF band.

The processor 913 is, for example, a CPU or a DSP. The processor 913 may be realized by a digital electronic circuit such as an ASIC, FPGA, LSI, or the like.

The memory 914 can be realized by, for example, a RAM such as SDRAM, a ROM, a flash memory, or the like. The memory 914 stores user data, control information, programs, and the like, for example.

7 can be realized by the RF circuit 912 or the antenna 911 and the RF circuit 912, for example. The control unit 720 illustrated in FIG. 7 can be realized by, for example, the processor 913, the memory 914, and the like. The storage unit 730 illustrated in FIG. 7 can be realized by the memory 914, for example.

Thus, according to the second embodiment, the small base stations 221 and 222 can improve the reception characteristics of the mobile station 230 in the ABS by performing coordinated transmission in the ABS. For this reason, even if many specific periods are set in the communication system 200, the throughput can be improved.

(Embodiment 3)
In Embodiment 3, retransmission by small base stations 221 and 222 will be described. For example, the small base stations 221 and 222 may perform retransmission only when one of the small base stations 221 and 222 performs retransmission when an error occurs in CoMP transmission in the ABS. Here, a case will be described where, when an error occurs in CoMP transmission in the ABS, retransmission is performed by the small base station 221 and the small base station 222 does not perform retransmission.

(Operation of each small base station according to each reception result of response signal)
FIG. 10 is a diagram illustrating an example of the operation of each small base station according to each reception result of the response signal. A table 1000 in FIG. 10 shows cases 1001 to 1004 related to retransmission of CoMP transmission in the ABS. “Small 1” in the table 1000 indicates the small base station 221, and “Small 2” indicates the small base station 222.

Cases 1001 and 1002 indicate cases where user data is normally received by the mobile station 230 and the mobile station 230 transmits ACK as a response signal. Cases 1003 and 1004 indicate a case where user data is not normally received by the mobile station 230 and the mobile station 230 transmits NACK as a response signal.

Case 1001 shows a case where the small base station 221 has received ACK from the mobile station 230 normally, but the small base station 222 has received ACK from the mobile station 230 by mistake as NACK. In this case, the small base station 221 receives the ACK and discards the corresponding data. In addition, the small base station 222 discards the corresponding data because it has received NACK but does not retransmit it.

Case 1002 shows a case where the small base station 221 receives the ACK from the mobile station 230 by mistake as a NACK, but the small base station 222 receives the ACK from the mobile station 230 normally. In this case, since the small base station 221 receives the NACK, the small base station 221 HARQ retransmits the corresponding data. Since the user data by this HARQ retransmission has already been normally received by the mobile station 230, for example, the mobile station 230 discards it. For this reason, this retransmission may be wasted. Further, since the small base station 222 receives the ACK, the small base station 222 discards the corresponding data.

Case 1003 shows a case where the small base station 221 has normally received the NACK from the mobile station 230, but the small base station 222 has received the NACK from the mobile station 230 by mistake as an ACK. In this case, since the small base station 221 receives the NACK, the small base station 221 HARQ retransmits the corresponding data. Further, since the small base station 222 receives the ACK, the small base station 222 discards the corresponding data.

Case 1004 shows a case where the small base station 221 received the NACK from the mobile station 230 by mistake as an ACK, but the small base station 222 received the NACK from the mobile station 230 normally. In this case, the small base station 221 receives the ACK and discards the corresponding data. In this case, recovery is performed by retransmission by an upper layer, for example. The upper layer is, for example, an RLC (Radio Link Control: radio link control) layer. The retransmission by the higher layer will be described later (see, for example, FIG. 11). In addition, the small base station 222 discards the corresponding data because it has received NACK but does not retransmit it.

As described above, the small base stations 221 and 222 perform CoMP transmission in the initial transmission of user data in the ABS, while the small base station 221 performs retransmission of the user data transmitted by CoMP, and the small base station 222 performs retransmission. Absent. This retransmission can be performed at any individual timing, not limited to ABS. For example, when receiving a NACK from the mobile station 230 for CoMP transmission, the small base station 221 retransmits user data to the mobile station 230 at a timing determined by the small base station 221.

If CoMP transmission is performed by the small base stations 221 and 222 also for retransmission, it is necessary to perform processing such as exchanging control signals in order to determine the retransmission timing in the small base stations 221 and 222. This leads to an increase in quantity. In addition, when each of the small base stations 221 and 222 performs retransmission individually, the mobile station 230 receives the retransmission data at the timing of each of the small base stations 221 and 222, so that an increase in communication amount and retransmission control are performed. Leads to an increase in the amount of processing.

On the other hand, according to the third embodiment, CoMP transmission is performed by the small base stations 221 and 222 for the initial transmission, and only the small base station 221 performs the retransmission related to CoMP transmission. The amount can be reduced.

Note that even if the small base station 222 receives NACK, the small base station 222 does not perform retransmission, so the small base station 222 may immediately discard user data transmitted by CoMP transmission.

Here, the case where retransmission is performed by the small base station 221 and the small base station 222 does not perform retransmission has been described. However, the small base station that performs retransmission among the small base stations 221 and 222 can be determined by an arbitrary method. it can. For example, the macro base station 210 may determine a small base station that performs retransmission among the small base stations 221 and 222 and notify the small base stations 221 and 222 of the small base stations. Alternatively, the small base stations 221 and 222 may determine a small base station that performs retransmission among the small base stations 221 and 222 by the small base stations 221 and 222 communicating with each other. Further, the small base station to be retransmitted among the small base stations 221 and 222 may be notified from the macro base station 210 to the mobile station 230, or from at least one of the small base stations 221 and 222 to the mobile station 230. You may be notified.

(Retransmission by upper layer)
FIG. 11 is a diagram illustrating an example of retransmission by an upper layer. In FIG. 11, the same parts as those shown in FIG. 3A are denoted by the same reference numerals, and the description thereof is omitted. As illustrated in FIG. 11, the small base stations 221 and 222 and the mobile station 230 perform wireless communication by processing of each layer of PDCP, RLC, MAC (Media Access Control), and PHY (physical layer), respectively. .

First, it is assumed that packet # 1 is transmitted from the macro base station 210 to the small base stations 221 and 222, and the small base stations 221 and 222 perform CoMP transmission of the packet # 1 to the mobile station 230 in the ABS. On the other hand, it is assumed that the mobile station 230 cannot normally receive the packet # 1 and transmits a NACK in the HARQ 1101.

In contrast, it is assumed that the small base station 222 has normally received a NACK from the mobile station 230, but the small base station 221 has erroneously received a NACK from the mobile station 230 as an ACK. In this case, since the small base station 222 is a small base station that does not retransmit, packet # 1 is not retransmitted even if NACK is received. On the other hand, since the small base station 221 has received the ACK, it does not retransmit the packet # 1.

In this case, since the mobile station 230 does not retransmit the packet # 1 even though the NACK is transmitted, the mobile station 230 sends an unreceived report 1102 of the packet # 1 to the small base station 221 by the RLC layer processing. Do. In the RLC layer, POLL / STATUS type retransmission processing is performed on the transmission / reception side, and the transmission / reception state can be synchronized by exchanging these pieces of information. The unreceived report 1102 can be performed by, for example, RLC STATUS REPORT.

On the other hand, the small base station 221 performs retransmission 1103 of the packet # 1 by processing of the RLC layer. Thereby, the mobile station 230 can receive packet # 1. Also for packet # 2 and subsequent packets after packet # 1, the small base stations 221 and 222 perform CoMP transmission to the mobile station 230 at the ABS in the initial transmission, and only the small base station 221 performs retransmission.

As described above, according to the third embodiment, CoMP transmission is performed by the small base stations 221 and 222 for the first transmission, and only the small base station 221 performs the retransmission related to CoMP transmission. Can be reduced.

As described above, according to the wireless communication system, the wireless communication method, the wireless station, and the control station, throughput can be improved.

100 wireless communication system 110 control station 111, 121a, 121b, 131, 620, 720 control unit 112, 122a, 122b, 132, 640 communication unit 120a, 120b first wireless station 130 second wireless station 200 communication system 201, 202 Xn Interface 210, 240 Macro base station 210a, 240a Macro cell 221, 222, 251, 252 Small base station 221a, 222a, 222b, 251a, 252a Small cell 230, 700, 900 Mobile station 301 Delimiter 302 Pre-setting 303 Control area 304 Data area 311, 312, 381, 382 User data 321, 322, 331, 332 Feedback 341, 342, 351 to 354 ABS
361, 362, 371, 372 Control signal 391, 392 Response signal 600, 800 Base station 610, 710 Wireless communication unit 611, 711 Wireless transmission unit 612, 712 Wireless reception unit 630, 730 Storage unit 811, 911 Antenna 812, 912 RF Circuit 813, 913 Processor 814, 914 Memory 815 Network IF
1001 to 1004 Case 1101 HARQ
1102 Unreceived report 1103 Resend

Claims (11)

1. A wireless communication system including a second wireless station capable of communicating with a plurality of first wireless stations, and a control station that controls the first wireless station,
   The control station
   A controller that controls cooperative communication in which the plurality of first wireless stations perform communication with the second wireless station in cooperation with each other;
   Each of the plurality of first wireless stations is
   A control unit for controlling the cooperative communication;
   In a specific period in which radio transmission is performed with lower power than other periods, data addressed to the second radio station using radio resources in cooperation with a first radio station different from its own among the plurality of first radio stations And a communication unit that performs the cooperative communication to transmit to the second wireless station,
   The second radio station is
   A control unit for controlling communication with the plurality of first wireless stations by the cooperative communication;
   A communication unit for receiving data addressed to the own station transmitted by the cooperative communication on the radio resource,
   A wireless communication system.
2. The control station is a base station;
   Each of the plurality of first wireless stations is a base station located in a cell of the control station,
   The second radio station is a mobile station;
   The wireless communication system according to claim 1.
3. The control station includes a communication unit that notifies the second wireless station of the radio resources of the cooperative communication,
   Each of the communication units of the plurality of first wireless stations transmits data addressed to the second wireless station without notifying the second wireless station of the wireless resource in the cooperative communication,
   The communication unit of the second radio station receives data addressed to the own station transmitted by the cooperative communication on the radio resource notified from the control station.
   The wireless communication system according to claim 1, wherein the wireless communication system is a wireless communication system.
4. The communication unit of the control station notifies the second radio station of the cooperative communication radio resource only when changing the radio resource of the cooperative communication after notifying the radio resource of the cooperative communication to the second radio station. Notify
   The communication unit of the second radio station receives data addressed to itself on the radio resource last notified from the control station.
   The wireless communication system according to claim 3.
5. 5. The radio communication system according to claim 1, wherein the control station includes a communication unit that notifies the plurality of first radio stations of radio resources for the cooperative communication by radio signals. .
6. In the cooperative communication, when the second wireless station cannot normally receive the data addressed to the second wireless station, any one of the plurality of first wireless stations receives the second wireless station. 6. The radio according to claim 1, wherein the data addressed to the station is retransmitted, and the other first radio station of the plurality of first radio stations does not perform the retransmission. Communications system.
7. 7. The wireless communication system according to claim 1, wherein the specific period is an ABS (Almost Blank Subframe) set in common to the plurality of first wireless stations.
8. A wireless communication method in a wireless communication system, comprising: a second wireless station capable of communicating with a plurality of first wireless stations; and a control station that controls the first wireless station,
   The control station controls cooperative communication in which the plurality of first wireless stations communicate with the second wireless station in cooperation with each other,
   The cooperation in which the plurality of first wireless stations cooperate to use radio resources and transmit data addressed to the second wireless station to the second wireless station in a specific period in which wireless transmission is performed with lower power than other periods. Communicate
   The second radio station receives data addressed to the own station transmitted by the cooperative communication on the radio resource;
   A wireless communication method.
9. A radio station included in the plurality of first radio stations in a radio communication system including a second radio station capable of communicating with a plurality of first radio stations and a control station that controls the first radio station. And
   A control unit for controlling cooperative communication in which the plurality of first wireless stations cooperate to communicate with the second wireless station;
   In a specific period in which radio transmission is performed with lower power than other periods, data addressed to the second radio station is transmitted to the second radio station in cooperation with a first radio station different from the own station among the plurality of first radio stations. A communication unit that performs the cooperative communication to be transmitted to a station;
   A radio station comprising:
10. A second wireless station in a wireless communication system, comprising: a second wireless station capable of communicating with a plurality of first wireless stations; and a control station that controls the first wireless station;
    A control unit that controls communication with the plurality of first wireless stations by cooperative communication in which the plurality of first wireless stations cooperate to communicate with the second wireless station;
    A communication unit that receives data addressed to the second radio station transmitted in cooperation by the plurality of first radio stations in a specific period in which radio transmission is performed with lower power than other periods;
    A radio station comprising:
11. A control station in a wireless communication system comprising: a second wireless station capable of communicating with a plurality of first wireless stations; and a control station that controls the first wireless station,
    A control unit that controls cooperative communication in which the plurality of first wireless stations cooperate to communicate with the second wireless station in a specific period in which the plurality of first wireless stations perform wireless transmission with lower power than other periods. A control station comprising:

Images