JP5732267B2 - COMMUNICATION SYSTEM, BASE STATION, AND COMMUNICATION CONTROL METHOD - Google Patents

Description

  The present invention relates to a communication system capable of cooperatively transmitting data from a plurality of base stations to a communication terminal by wireless communication, and a base station and a communication control method that can be used in the communication system.

  Conventionally, in order to realize improvement in throughput, improvement in communication quality, effective use of communication bandwidth, etc. in a boundary area where radio communication areas (cells) of a plurality of base stations overlap, the communication from the plurality of base stations There is known a communication system in which data having the same content or different content data is transmitted to a terminal in a coordinated manner (see, for example, Patent Document 1). The coordinated transmission from the plurality of base stations may be performed using the same frequency or may be performed using different frequencies. As for the timing of coordinated transmission from a plurality of base stations, synchronous transmission may be performed at the same transmission time, and transmission may be performed at different transmission times. In a communication system that performs such coordinated transmission, in any combination of the frequency and the transmission timing, each of the two geographically separated points can be surely executed with the predetermined frequency and transmission timing. It is necessary to manage resources for cooperation (frequency and transmission timing) between a plurality of base stations located.

  In addition, as a communication system that performs the coordinated transmission, one of a plurality of base stations is caused to function as an anchor base station of the cooperation source, the base station of the cooperation source receives data from the core node device, and the data is transferred to another cooperation base station. There is known an anchor type that can coordinately transmit data from each base station to a communication terminal by distributing the data to the previous base station (see Non-Patent Document 1). This anchor method can reduce control signals used for control of cooperative transmission and speed up response control compared to a method of distributing data to be cooperatively transmitted from a core node device to each of a plurality of base stations and performing cooperative transmission from each base station. Become.

If a plurality of base stations as in the above conventional communication system attempts to cooperatively transmit the data to the communication terminal in concert with any of reasons, it may fail to coordinated transmission of data. For example, if the communication terminal cannot receive each of the data transmitted cooperatively from both of the plurality of base stations, as a result, the cooperative transmission of the data has failed. In addition, when the cooperation-destination base station receives data to which information indicating the transmission timing is added, if the time of the transmission timing has already passed, the cooperation-destination base station is not in time for the transmission timing of the coordinated transmission. Data cannot be transmitted cooperatively to the communication terminal. In addition, even when the cooperation-destination base station fails to receive data to be coordinated transmission, the base station cannot perform coordinated transmission of data to the communication terminal. As described above, when the cooperative transmission of data fails, it is conceivable to perform a retransmission process in which the data is cooperatively transmitted again to the communication terminal.

  As retransmission processing from a single base station in a conventional mobile communication system (for example, LTE: Long Term Evolution mobile communication system), the following processing is known. For example, in a base station having a communication layer structure including a radio link control layer (RLC layer) and a media access control layer (MAC layer), the radio link control layer is based on ARQ (Automatic Repeat-Request) received from a communication terminal. A retransmission process to be performed and a retransmission process to be performed based on HARQ (Hybrid Automatic Repeat Request) received from a communication terminal by a media access control layer are known. In LTE ARQ and HARQ, when data is transmitted for the first time, a retransmission queue is provided in a base station serving as a transmission source, data is stored in the retransmission queue, and then transmitted to a communication terminal. Then, it is confirmed whether or not the communication terminal has normally received, and ACK is returned to the base station when reception is normal, and NACK is returned to the base station when reception error occurs. When the ACK is received at the base station, the data stored in the retransmission queue is deleted because there is no need for retransmission. On the other hand, when a NACK is received, a reception error can be compensated by taking out the data from the retransmission queue and retransmitting the data.

  However, the conventional retransmission processing such as ARQ and HARQ assumes a single radio section between the base station and the communication terminal. Therefore, if the conventional retransmission processing such as ARQ or HARQ is applied as it is in the case of the above-described coordinated transmission, the base station of the cooperation source and the base station of the cooperation destination execute the retransmission processing independently of each other. There is a possibility that it will not be a re-transmission process of cooperative transmission of data linked with each other. For example, when the communication terminal fails to receive only the data cooperatively transmitted from the cooperation base station among the data cooperatively transmitted from each base station (time-out of ACK from the communication terminal or from the communication terminal In the case of receiving NACK), data is retransmitted only from the cooperating base station. Therefore, the data retransmitting process in which the cooperation source base station and the cooperation destination base station cooperate is not performed, and the loss of data that has failed in the cooperative transmission cannot be reliably compensated.

  The present invention has been made in view of the above problems, and its object is to reliably perform retransmission processing of cooperative transmission of data when the cooperative transmission of data from a plurality of base stations fails. A communication system, a base station, and a communication control method are provided.

A communication system according to the present invention is a communication system capable of cooperatively transmitting data from a plurality of base stations to a communication terminal by wireless communication, wherein any one of the plurality of base stations is transmitted from each base station. The base station of the cooperation source having a function of controlling the coordinated transmission of data, and the other base station of the plurality of base stations is the base station of the cooperation destination whose coordinated transmission of data is controlled by the base station of the cooperation source The base station of the cooperation source is a wireless communication unit that wirelessly communicates with a communication terminal via a plurality of communication processing layers, a communication unit between base stations that communicates with the base station of the cooperation destination, and the plurality of communication A storage unit that stores data to be coordinated transmission in at least one of the processing layers, and when the coordinated transmission of the data to be coordinated transmission fails, the data to be coordinated transmission stored in the storage unit is retransmitted As read And transmitting the read retransmission data and retransmission cooperative control information including at least transmission time information to the base station of the cooperation destination, and transmitting the retransmission data read from the storage unit to the communication terminal. A base station that is the cooperation destination, a wireless communication unit that wirelessly communicates with a communication terminal, an inter-base station communication unit that communicates with the base station of the cooperation source, and the base station of the cooperation source Receiving the retransmission data and the cooperative control information for retransmission from a station, and based on the cooperative control information for retransmission received from the cooperative base station, the retransmission data received from the cooperative base station And a control unit that controls to transmit to the communication terminal.
Another communication system according to the present invention is a communication system capable of cooperatively transmitting data from a plurality of base stations to a communication terminal by wireless communication, wherein any one of the plurality of base stations is connected to each base station. A base station of a cooperation source having a function of controlling the coordinated transmission of data from the other base station, and the other base station of the plurality of base stations A base station that is a base station of cooperation, a wireless communication unit that wirelessly communicates with a communication terminal via a plurality of communication processing layers, an inter-base station communication unit that communicates with the base station of the cooperation destination, and the plurality of base stations A storage unit that stores the data to be coordinated transmission in at least one of the communication processing layers, and when the coordinated transmission of the data to be coordinated transmission fails, the data to be coordinated transmission stored in the storage unit Read as resend data A control unit that transmits the retransmission control information for retransmission to the base station of the cooperation destination, and controls the retransmission data read from the storage unit to be transmitted to the communication terminal. The station cooperates with at least one of the plurality of communication processing layers, a wireless communication unit that wirelessly communicates with a communication terminal via a plurality of communication processing layers, an inter-base station communication unit that communicates with the base station of the cooperation source, and A storage unit that stores data to be transmitted; and the cooperative control information for retransmission received from the base station of the cooperation source, and the storage based on the cooperative control information for retransmission received from the base station of the cooperation source A control unit configured to read out the data to be coordinated transmission stored in a unit as retransmission data and control the transmission of the read retransmission data to the communication terminal.

A base station according to the present invention is a cooperating base station having a function of controlling cooperative transmission of data from the plurality of base stations in a communication system capable of cooperatively transmitting data from the plurality of base stations to a communication terminal by wireless communication A wireless communication unit that wirelessly communicates with a communication terminal via a plurality of communication processing layers, an inter-base station communication unit that communicates with a cooperation destination base station, and at least one of the plurality of communication processing layers. A storage unit that stores data to be transmitted, and when cooperative transmission of the data to be coordinated transmission fails, the data to be coordinated transmission stored in the storage unit is read as retransmission data, and the read retransmission data And retransmission cooperative control information including at least transmission time information to the cooperation destination base station, and the retransmission data read from the storage unit to the communication terminal A control unit for controlled so and is characterized in that it comprises.
Another base station according to the present invention is a cooperative source having a function of controlling cooperative transmission of data from the plurality of base stations in a communication system capable of cooperative transmission of data from the plurality of base stations to the communication terminal by wireless communication. A base station, a wireless communication unit that wirelessly communicates with a communication terminal via a plurality of communication processing layers, an inter-base station communication unit that communicates with a cooperation-destination base station, and at least one of the plurality of communication processing layers When the cooperative transmission of the cooperative transmission target data fails, the data of the cooperative transmission target stored in the storage unit is read as retransmission data when the cooperative transmission target data is stored in the storage unit. A control unit configured to transmit the cooperative control information to the base station of the cooperation destination, and to control transmission of the retransmission data read from the storage unit to the communication terminal.
Still another base station according to the present invention is a coordinated base station in which coordinated transmission of data is controlled by a coordinating base station in a communication system capable of coordinately transmitting data from a plurality of base stations to a communication terminal by wireless communication. A wireless communication unit that wirelessly communicates with a communication terminal via a plurality of communication processing layers, an inter-base station communication unit that communicates with the base station of cooperation, and at least one of the plurality of communication processing layers A storage unit that stores data to be coordinated transmission, and cooperative control information for retransmission including at least transmission time information from the cooperation source base station, and the retransmission cooperation received from the cooperation source base station Based on control information, the control unit that reads the data to be coordinated transmission stored in the storage unit as retransmission data, and controls to transmit the read retransmission data to the communication terminal; It is characterized in further comprising.

In the communication control method according to the present invention, any one of a plurality of base stations cooperates to control the coordinated transmission of data from each base station, and the other cooperation destination base station The coordinated transmission of data is controlled by the base station of the plurality of base stations by wireless communication to transmit data from the plurality of base stations to the communication terminal in a coordinated manner. Storing the data to be cooperatively transmitted in at least one of the plurality of communication processing layers when transmitting the data to be cooperatively transmitted to the communication terminal via the communication processing layer of When the station fails in cooperative transmission of the data to be coordinated transmission, the stored data to be coordinated transmission is read as retransmission data, and the read retransmission data and at least the transmission time Transmitting the cooperative control information for retransmission including the information to the base station of the cooperation destination, transmitting the retransmission data read from the storage unit to the communication terminal, and the base station of the cooperation destination Receiving the retransmission data and the cooperative control information for retransmission from the original base station, and the base station of the cooperation destination based on the cooperative control information for retransmission received from the base station of the cooperation source, And transmitting the retransmission data received from the cooperating base station to the communication terminal.
In another communication control method according to the present invention, any one of a plurality of base stations controls a coordinated transmission of data from each base station, and the other base of the plurality of base stations cooperates. Is a communication control method when data is cooperatively transmitted from the plurality of base stations to the communication terminal by wireless communication by controlling the coordinated transmission of data by the base station of the cooperation source, A step of storing the data to be cooperatively transmitted in at least one of the plurality of communication processing layers when the base station of the cooperation source transmits the data to be cooperatively transmitted to the communication terminal via the plurality of communication processing layers; And when the coordinated base station fails to coordinately transmit the data to be coordinated transmission, the data to be coordinated transmission stored in the storage unit is read as retransmission data, and the coordinated control information for retransmission The Transmitting the retransmitted data read from the storage unit to the communication terminal and transmitting the retransmitted data to the communication terminal, and the cooperation destination base station transmits the cooperation data to the communication terminal via a plurality of communication processing layers. Storing the data to be coordinated transmission in at least one of the plurality of communication processing layers when transmitting the data to be transmitted; and the base station that is the cooperation destination transmits the retransmission from the base station of the cooperation source And receiving the cooperative transmission target data, based on the retransmission cooperative control information received from the cooperation source base station by the cooperation-destination base station. Reading as retransmission data, and transmitting the read retransmission data to the communication terminal.

In the present invention, the plurality of communication processing layers include a radio link control layer and a media access control layer, and the data to be coordinated transmission is stored in at least one of the radio link control layer and the media access control layer. Also good.
Further, in the present invention, the cooperative control information for retransmission transmitted from the cooperation source base station to the cooperation destination base station includes information on frequency resources newly determined for cooperative transmission of the retransmission data. May be included.

In the present invention, coordinated transmission (including retransmission) from the plurality of base stations may be performed using the same frequency or using different frequencies.
In the present invention, the coordinated transmissions (including retransmissions) from the plurality of base stations may be performed at the same transmission time or at different transmission timings. Also good.
In the present invention, the data transmitted in cooperation from the plurality of base stations may be data having the same contents or data having contents different from each other.
In the present invention, the resource for cooperation may include transmission power used for cooperative transmission when transmission power can be set at a plurality of levels, and is used for cooperative transmission when multiple types of antennas can be used. An antenna may be included.
In the present invention, the cooperation-destination base station may be one base station or two or more base stations. That is, the plurality of base stations that cooperatively transmit data in cooperation with each other may be a combination of one cooperation source base station and one cooperation destination base station, or one cooperation source base station and It may be a combination with two or more cooperation-destination base stations.

According to one aspect of the present invention, when a cooperation-source base station fails in coordinated transmission of data for some reason, the cooperation stored in at least one of a plurality of communication processing layers in the cooperation-source base station The data to be transmitted is read as retransmission data, and the retransmission data and the cooperative control information for retransmission including at least the information on the transmission time are transmitted to the cooperation destination base station. Then, the cooperating base station transmits the read retransmission data to the communication terminal at a predetermined transmission time. on the other hand. The cooperation-destination base station receives the cooperation control information from the cooperation-source base station, and transmits the received retransmission data to the communication terminal at a predetermined transmission time based on the cooperation control information. Thus, even when the cooperative transmission of the data to be cooperatively transmitted fails, the base station of the cooperation source and the base station of the cooperation destination cooperate to reliably transmit the failed data to be cooperatively transmitted to the communication terminal. Can do.
Further, according to another aspect of the present invention, when the coordinated base station fails to perform coordinated transmission of data for some reason, it is stored in at least one of a plurality of communication processing layers in the coordinated base station. The cooperative transmission target data is read as retransmission data, and the cooperative control information for retransmission including at least transmission time information is transmitted to the cooperation-destination base station. Then, the cooperating base station transmits the read retransmission data to the communication terminal at a predetermined transmission time. on the other hand. The cooperation-destination base station receives the cooperation control information from the cooperation-source base station, and is stored in at least one of the plurality of communication processing layers in the cooperation-destination base station based on the cooperation control information. The cooperative transmission target data is read as retransmission data. Then, the cooperation-destination base station transmits the read retransmission data to the communication terminal at a predetermined transmission time. Thus, even when the cooperative transmission of the data to be cooperatively transmitted fails, the base station of the cooperation source and the base station of the cooperation destination cooperate to reliably transmit the failed data to be cooperatively transmitted to the communication terminal. Can do.

Explanatory drawing which shows an example of a structure of the communication system which concerns on one Embodiment of this invention. (A), (b) and (c) are explanatory drawings which show an example of the communication before a cooperative transmission start in the same communication system, during a cooperative transmission, and after the completion of a cooperative transmission, respectively. The functional block diagram which paid its attention to the communication layer structure of the base station in the cooperative communication in the communication system. The functional block diagram of the structural example which paid its attention to the communication layer structure of the base station which can be resent. The sequence diagram of the example of control of the retransmission processing. The functional block diagram of the other structural example which paid its attention to the communication layer structure of the base station which can be resent. The sequence diagram of the example of control of the retransmission processing by the base station. The functional block diagram of the further another structural example which paid its attention to the communication layer structure of the base station which can be resent. The sequence diagram of the example of control of the retransmission processing by the base station. The functional block diagram of the further another structural example which paid its attention to the communication layer structure of the base station which can be resent. The sequence diagram of the example of control of the retransmission processing by the base station. The functional block diagram of the further another structural example which paid its attention to the communication layer structure of the base station which can be resent. The sequence diagram of the example of control of the retransmission processing by the base station.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an explanatory diagram showing an example of a configuration of a communication system according to an embodiment of the present invention. The communication system 10 according to the present embodiment includes a first base station 110 and a second base station 120 as a plurality of radio base station apparatuses. These base stations 110 and 120 can communicate with each other via a wired or wireless communication line, and by cooperating with each other, the wireless communication areas of the base stations 110 and 120 exist in overlapping boundary areas. Data to be cooperatively transmitted can be cooperatively transmitted to a communication terminal (hereinafter referred to as “terminal”) 200. Through this coordinated transmission, it is possible to improve throughput during communication by the terminal 200, improve communication quality, and effectively use a communication band.

  In addition, although this embodiment demonstrates the case where there are two several base stations which can transmit data in cooperation with each other, the said several base stations may be three or more. Further, in this embodiment, a case will be described where a plurality of pieces of data cooperatively transmitted from a plurality of base stations are received by one terminal, but there are a plurality of terminals that receive the plurality of pieces of cooperatively transmitted data. May be. Further, in the present embodiment, a case where data is coordinated and transmitted at a predetermined transmission time with the same frequency from a plurality of base stations will be described. They may be different from each other, and the transmission times for cooperative transmission from each base station may be different from each other.

  In FIG. 1, among the plurality of base stations 110 and 120, one first base station 110 is a cooperating base station having a function of controlling the coordinated transmission of data from each base station. The other second base station 120 is a cooperation-destination base station whose data transmission is controlled by the cooperation-source base station 110. These base stations 110 and 120 are referred to as “NodeB” in the specifications of 3GPP (Third Generation Partnership Project), and are further referred to as “eNodeB (evolved Node B) as an evolved NodeB in the specifications of LTE (Long Term Evolution). ) ". In addition, the base station of the cooperation source is sometimes called an anchor base station or a master base station, and the base station of the cooperation destination is sometimes called a slave base station.

  The communication system 10 may include a core node device (hereinafter referred to as “core node”) 130 that distributes data to be cooperatively transmitted to a plurality of base stations 110 and 120. The core node 130 can communicate with an external network via the data communication network 141. The core node 130 and the plurality of base stations 110 and 120 are connected via a data communication network 140 such as a packet network. The communication system 10 may include a data communication network 140. In addition, the communication system 10 may include a terminal 200 that can receive a plurality of pieces of data transmitted cooperatively from a plurality of base stations 110 and 120. The terminal 200 may be called a user equipment (UE: User Equipment) because it is used by a user of a communication service, and may be called a mobile station because it is mobile, and Sometimes called.

  The terminal 200 may be a mobile communication terminal such as a mobile phone, and the network constructed by the base stations 110 and 120 and the data communication network 140 may be a cellular network of a mobile communication network. The data communication network 141 may be a core network of a mobile communication network. The wireless communication areas of the base stations 110 and 120 may be any one of various cells such as a macro cell, a micro cell, a femto cell, and a pico cell having different sizes.

  Any one of the plurality of base stations 110 and 120 capable of wireless communication with the terminal 200 has a function of controlling a cooperative communication operation of cooperatively transmitting data from the plurality of base stations 110 and 120. Station. Other base stations other than the cooperating base station are cooperating base stations as coordinated base stations that are controlled so as to perform cooperative operation by the cooperating base station. For example, the base station 110 that is the cooperation source is selected from among a plurality of base stations that can communicate with the terminal 200, that has the highest received electric field strength and the highest wireless communication quality in the wireless communication with the terminal 200. The base station 110 that is the source of cooperation is selected based on wireless communication quality information such as received electric field strength received from the terminal 200 or the like, and the base station that can communicate with the terminal 200 is autonomously and dynamically switched. It may be changed.

2A, 2 </ b> B, and 2 </ b> C are explanatory diagrams illustrating examples of communication before the start of coordinated transmission, during coordinated transmission, and after the completion of coordinated transmission in the communication system 10 according to the present embodiment, respectively.
Before the start of coordinated transmission shown in FIG. 2A, the terminal 200 is located in the cell 110a that is the radio management area of the first base station 110. When receiving data to be transmitted from the core node 130, the first base station 110 transmits a radio wave transmission signal generated for the data to the terminal 200 in the first cell. When receiving data from the first base station 110, the terminal 200 measures the radio wave reception strengths of the first base station 110 and the neighboring second base station 120, and uses the first base station 110 as field information. Report to station 110. Here, for example, if the difference between the reception strengths is within the threshold for starting cooperative transmission, the first base station 110 is in the boundary area A where both the cells 110a and 120a of the base stations 110 and 120 overlap. Terminal 200 is present, and a cooperation start instruction is issued. As a result, cooperative transmission from the first base station 110 and the second base station 120 to the terminal 200 is enabled. Here, the first base station 110 functions as a cooperation source base station, and the second base station 120 functions as a cooperation destination base station.

  During the coordinated transmission shown in FIG. 2 (b), the coordinated base station 110 distributes the data received from the core node 130 to the coordinated base station 120 for coordinated transmission. The data distributed to the cooperation-destination base station 120 is subjected to conversion processing such as encapsulation as necessary, and transferred to the cooperation-destination base station 120. For example, when data is distributed from the cooperation source base station 110 to the cooperation destination base station 120, a tunneling protocol such as GTPv2 (GPRS Tunneling Protocol Version 2) can be used. Further, when data is transferred to the cooperation destination base station 120, cooperation control information is added to the data. The cooperative control information includes, for example, MCS (Modulation and Coding Scheme) information such as a modulation scheme and a coding scheme of transmission signals, which are parameter information used for cooperative communication, radio wave reception quality information (for example, CQI: Channel Quality Indication), transmission Information such as frequency and transmission timing is included. And in each base station 110,120, the coordinate transmission of data is performed to the terminal 200 based on the said cooperation control information.

  At the end of the coordinated transmission shown in FIG. 2 (c), the base station 110 that is the source of coordination, for example, if the difference in radio wave reception intensity between the base stations 110 and 120 is greater than or equal to the threshold for termination of coordination, It determines that it came to be in the area of only the cell 120a of the cooperation destination base station 120, and issues a cooperation end instruction to the cooperation destination base station 120 and the terminal 200. Thereby, the cooperative communication by the base stations 110 and 120 ends, the first base station 110 finishes its role as a cooperation source, and the second base station 120 finishes its role as a cooperation destination. Thereafter, the first base station 110 stops distributing data to the terminal 200. The second base station 120 issues a path switching command to the core node 130 to change the data transmission path from the core node 130 to the second base station 120.

  FIG. 3 is a functional block diagram focusing on the communication layer structure of the base station 110 that is the cooperation source and the base station 120 that is the cooperation destination during the cooperative communication shown in FIG. Each of the base stations 110 and 120 includes an Internet protocol layer (IP layer) (not shown), a data convergence protocol layer (PDCP layer) 111 and 121, a radio link control layer (RLC layer) 112 and 122, a media access control layer (MAC). Layer) 113 and 123 and physical layers (PHY layers) 114 and 124, and has a multilayer communication layer structure. The PDCP layers 111 and 121 perform processing such as data compression, encryption arrangement expansion, and decryption. The RLC layers 112 and 122 perform processing such as data division, combination, order control, and retransmission (ARQ: Automatic Repeat-Request). The MAC layers 113 and 123 perform processing such as data transmission scheduling, multiplexing, and retransmission (HARQ: Hybrid Automatic Repeat Request). Accordingly, the RLC layer 112 and the MAC layer 113 include ARQ retransmission queues 112a and 122a and HARQ retransmission queues 113a and 123a, respectively. Note that retransmission (ARQ) processing in the RLC layers 112 and 122 is automatically executed at intervals of several hundreds ms (for example, intervals of 100 ms to 150 ms), and retransmission (HARQ) processing in the MAC layers 113 and 123 is relatively short several ms. Are automatically executed at intervals of 8 ms (for example, at intervals of 8 ms). The PHY layers 114 and 124 perform processing such as modulation, demodulation, and encoding of a high-frequency transmission / reception signal transmitted / received to / from the terminal 200. The PHY layers 114 and 124 function as a wireless communication unit that performs wireless communication with the terminal 200.

  The plurality of base stations 110 and 120 include inter-base station communication units 115 and 125 and schedulers 116 and 126, respectively. The inter-base station communication units 115 and 125 communicate with other base stations other than the base station via a wired or wireless communication line. In addition, the schedulers 116 and 126 constitute part of the control units 117 and 127 that control processing and operations in the base stations 110 and 120, respectively, and the RLC layers 112 and 122, the MAC layers 113 and 123, and the PHY layer described above. 114 and 124 are controlled to determine which resources (time and frequency) are used to transmit data.

  Further, the cooperation-destination base station 120 remotely controls cooperation resources (transmission frequency, transmission timing) and MCS of the data to be cooperatively transmitted based on the cooperation control signal transmitted from the cooperation-source base station 110. A resource control unit for coordination 128 is provided.

  In FIG. 3, the coordination resource control unit 128 receives the data to be coordinated transmission from the MAC layer 113 of the cooperation source base station 110 via the communication line, and sends it to the PHY layer 124 in the cooperation destination base station 120. Forward. Also, the coordination resource control unit 128 receives the coordination control information (transmission frequency information, transmission timing information, MCS information, reception quality information, etc.) from the scheduler 116 of the cooperating base station 110 via the communication line. To do. The coordination resource control unit 128 controls the transmission of data to be coordinated in the PHY layer 124 in the cooperation destination base station 120 based on the cooperation control information received from the cooperation source base station 110.

  Note that the function of the coordination resource control unit 128 may be incorporated into the control unit 127 in the cooperation destination base station 120 without providing the coordination resource control unit 128 independently.

  In FIG. 3, for convenience of explanation of the cooperative communication operation, the cooperation resource control unit 128 is provided only for the cooperation destination base station 120, but the cooperation source base station 110 in FIG. 3 is the cooperation destination base station. It may become. Therefore, the cooperation source base station 110 in FIG. 3 may also be configured to include the above-described cooperation resource control unit.

  The hardware of the base stations 110 and 120 used in the communication system having the above configuration includes, for example, an antenna, a transmission amplifier, a reception amplifier, a radio signal processing unit, a baseband signal processing unit, a wired transmission path interface unit, and a computer device. Composed. Of these hardware configurations, the antenna, the transmission amplifier, and the reception amplifier correspond to the above-described wireless communication unit, and the wired transmission path interface unit corresponds to the above-described inter-base station communication unit. The computer device is constituted by, for example, a microcomputer, functions as the above-described control units 117 and 127 and the cooperation resource control unit 128, and controls each unit based on a predetermined control program incorporated in advance. In particular, the computer device controls a wireless signal processing unit and a baseband signal processing unit based on a predetermined control program, thereby, for example, a plurality of communication layer structures such as the PDCP layer, the RLC layer, the MAC layer, and the PHY layer described above. It processes data and signals sent and received via

  According to the communication system configured as described above, a plurality of base stations 110 and 120 cooperate with each other and receive data received via an asynchronous network such as the data communication network 140 with a predetermined frequency and transmission time (for example, the same frequency). And the radio communication resource at the same transmission time) can be cooperatively transmitted to the terminal 200.

  Hereinafter, data retransmission processing in a case where cooperative communication in which data is cooperatively transmitted from the plurality of base stations 110 and 120 to the terminal 200 in the communication system having the configuration illustrated in FIG.

  FIG. 4 is a diagram illustrating a first example of retransmission processing that can be performed in the coordinated communication using the configuration illustrated in FIG. 3. In the scheme shown in FIG. 4, the HARQ retransmission queue 113a provided in the MAC layer 113 of the cooperation source base station 110 performs the cooperation data retransmission processing.

  FIG. 5 is a sequence diagram illustrating a control example of data retransmission processing by the cooperation-source base station 110 and the cooperation-destination base station 120 in FIG. In FIG. 5, when the base station 110 of the cooperation source receives the data to be coordinated transmission from the core node 130 (step 1), the data to be coordinated transmission is stored in the HARQ retransmission queue 113a (step 2) and the cooperation is performed. Data to be transmitted is transmitted to the cooperation destination base station 120 (step 3). Thereafter, the base station 110, 120 transmits data to be cooperatively transmitted to the terminal 200 using predetermined cooperation resources (frequency and transmission time) set in advance (steps 4, 4 '). Here, if the terminal 200 fails to receive data cooperatively transmitted from the base stations 110 and 120 for some reason, a reception failure response (NACK) indicating the failure is transmitted to the transmission source base station 110 ( Step 5).

  When receiving the reception failure response (NACK) from the terminal 200 at the MAC layer 113 (step 5), the cooperating base station 110 determines the retransmission processing of the corresponding data by HARQ (step 6). Then, the cooperating base station 110 reads the data to be coordinated transmission stored in the HARQ retransmission queue 113a as retransmission data (step 7), and reads the read retransmission data and the cooperative control information for retransmission. It transmits to the base station 120 of cooperation destination (steps 8 and 9). The retransmission cooperative control information includes, for example, retransmission timing information, transmission frequency, information indicating that the data is retransmission processing, MCS information specifying a modulation scheme and a coding scheme, and the like.

  The cooperating base station 110 transmits the retransmission data read from the HARQ retransmission queue 113a to the terminal 200 (10). On the other hand, the cooperation-destination base station 120 transmits the retransmission data received from the cooperation-source base station 110 to the terminal 200 based on the cooperation control information for retransmission (10 '). As described above, the retransmission data is cooperatively transmitted from the base stations 110 and 120 to the terminal 200 (steps 10 and 10 '). When the terminal 200 succeeds in receiving the retransmission data cooperatively transmitted from the base stations 110 and 120, the terminal 200 transmits a reception success response (ACK) indicating the success to the base station 110 of the cooperation source (step 11).

FIG. 6 is a diagram illustrating a second example of retransmission processing that can be performed during cooperative communication using the configuration illustrated in FIG. 3. In the method shown in FIG. 6 , cooperation data retransmission processing is performed in the ARQ retransmission queue 112 a provided in the RLC layer 112 of the cooperation-source base station 110.

  FIG. 7 is a sequence diagram illustrating a control example of data retransmission processing by the cooperation-source base station 110 and the cooperation-destination base station 120 in FIG. Of the processing in FIG. 7, the description of the same parts as in FIG. 5 is omitted. In FIG. 7, when the base station 110 of the cooperation source receives the data to be cooperatively transmitted from the core node 130 (step 1), the data to be cooperatively transmitted is not the HARQ retransmission queue 113a but the ARQ retransmission of the RLC layer 112. Save in the queue 112a (step 2). When receiving the reception failure response (NACK) from the terminal 200 at the RLC layer 112 (step 5), the cooperating base station 110 determines retransmission processing of the corresponding data by ARQ (step 6), and the ARQ retransmission queue. The cooperative transmission target data stored in 123a is read as retransmission data (step 7). The cooperation-source base station 110 transmits the read retransmission data and the cooperation control information to the cooperation-destination base station 120 (steps 8 and 9). The retransmission cooperative control information includes, for example, retransmission timing information, transmission frequency, information indicating that the data is retransmission processing, MCS information specifying a modulation scheme and a coding scheme, and the like. When the retransmission transmission time comes, the cooperating base station 110 transmits the retransmission data read from the ARQ retransmission queue 112a to the terminal 200 (10). On the other hand, the cooperation-destination base station 120 transmits the retransmission data received from the cooperation-source base station 110 to the terminal 200 based on the information included in the cooperation control information for retransmission (10 '). As described above, the retransmission data is cooperatively transmitted from the base stations 110 and 120 to the terminal 200 (steps 10 and 10 ').

  FIG. 8 is a diagram illustrating a third example of retransmission processing that can be performed in the coordinated communication using the configuration illustrated in FIG. 3. In the scheme shown in FIG. 8, in the HARQ retransmission queue 113 a provided in the MAC layer 113 of the cooperation source base station 110 and the HARQ retransmission queue 123 a provided in the MAC layer 123 of the cooperation destination base station 120, Retransmission processing is performed.

  FIG. 9 is a sequence diagram illustrating a control example of data retransmission processing by the cooperation-source base station 110 and the cooperation-destination base station 120 in FIG. Description of the same processing as in FIG. 5 in the processing in FIG. 9 is omitted. In FIG. 9, when the cooperation-destination base station 120 receives the data to be coordinated transmission from the cooperation-source base station 110 (step 3), it stores the data to be coordinated transmission in the HARQ retransmission queue 123a (step 3). 4). That is, the data to be cooperatively transmitted is stored not only in the HARQ retransmission queue 113a of the base station 110 that is the cooperation source, but also in the HARQ retransmission queue 123a of the base station 120 that is the cooperation destination. When receiving the reception failure response (NACK) from the terminal 200 at the MAC layer 113 (step 6), the cooperating base station 110 determines the retransmission processing of the corresponding data by HARQ (step 7), and performs retransmission. Only the cooperation control information is transmitted to the cooperation destination base station 120 (step 8). That is, the cooperation source base station 110 does not transmit retransmission data to the cooperation destination base station 120. This retransmission cooperative control information includes retransmission timing information, transmission frequency, MCS information designating a modulation scheme and coding scheme, and the like, and an ID for identifying retransmission data. The cooperating base station 110 reads the data to be coordinated transmission stored in the HARQ retransmission queue 113a as retransmission data. On the other hand, based on the cooperative control information for retransmission received from the cooperation source base station 110, the cooperation-destination base station 120 reads out the data to be coordinated transmission stored in the HARQ retransmission queue 123a as retransmission data (step S1). 10). Then, the base station 110 of the cooperation source transmits the retransmission data read from the HARQ retransmission queue 113a to the terminal 200, and the base station 120 of the cooperation destination transmits the base data based on the information included in the cooperation control information for retransmission. The retransmission data read from the HARQ retransmission queue 123a in the station 120 is transmitted to the terminal 200 (step 10 ′).

  FIG. 10 is a diagram illustrating a fourth example of retransmission processing that can be performed in the coordinated communication using the configuration illustrated in FIG. 3. In the scheme shown in FIG. 10, in the ARQ retransmission queue 112a provided in the RLC layer 112 of the cooperation source base station 110 and the ARQ retransmission queue 122a provided in the RLC layer 122 of the cooperation destination base station 120, Retransmission processing is performed.

  FIG. 11 is a sequence diagram illustrating a control example of data retransmission processing by the cooperation-source base station 110 and the cooperation-destination base station 120 in FIG. Of the processing in FIG. 11, the description of the same portions as those in FIGS. 5 and 7 is omitted. In FIG. 11, when the cooperation destination base station 120 receives the data to be coordinated transmission from the cooperation source base station 110 (step 3), the data to be coordinated transmission is stored in the ARQ retransmission queue 122a (step 3). 4). That is, the data to be cooperatively transmitted is stored not only in the ARQ retransmission queue 112a of the base station 110 that is the cooperation source, but also in the ARQ retransmission queue 122a of the base station 120 that is the cooperation destination. When receiving the reception failure response (NACK) from the terminal 200 in the RLC layer 112 (step 6), the cooperating base station 110 determines the retransmission processing of the corresponding data by ARQ (step 7), and performs retransmission. Only the cooperation control information is transmitted to the cooperation destination base station 120 (step 8). That is, the cooperation source base station 110 does not transmit retransmission data to the cooperation destination base station 120. This retransmission cooperative control information includes retransmission timing information, transmission frequency, MCS information designating a modulation scheme and coding scheme, and the like, and an ID for identifying retransmission data. The cooperating source base station 110 reads the data to be coordinated transmission stored in the ARQ retransmission queue 112a as retransmission data. On the other hand, the cooperation-destination base station 120 reads out the data to be coordinated transmission stored in the ARQ retransmission queue 122a as retransmission data based on the cooperation control information for retransmission received from the cooperation-source base station 110 (step S1). 10). Then, the base station 110 of the cooperation source transmits the retransmission data read from the ARQ retransmission queue 112a to the terminal 200, and the base station 120 of the cooperation destination transmits the base data based on the information included in the cooperation control information for retransmission. The retransmission data read from the ARQ retransmission queue 122a in the station 120 is transmitted to the terminal 200 (steps 11 and 11 ′).

  FIG. 12 is a diagram illustrating a fifth example of retransmission processing that can be performed in the coordinated communication using the configuration illustrated in FIG. 3. In the scheme shown in FIG. 12, the ARQ retransmission queue 112a provided in the RLC layer 112 of the cooperation source base station 110, the HARQ retransmission queue 113a used in the MAC layer 113 of the cooperation source base station 110, and the cooperation destination base station In the HARQ retransmission queue 123a provided in the 120 MAC layers 123, the data for cooperation is retransmitted. As described above, the present configuration example can cope with both HARQ retransmission processing and ARQ retransmission processing.

  FIG. 13 is a sequence diagram illustrating a control example of data retransmission processing by the cooperation-source base station 110 and the cooperation-destination base station 120 in FIG. Of the processing in FIG. 13, the description of the same parts as those in FIGS. 5, 9, and 11 is omitted. In FIG. 13, when the cooperation base station 110 receives the data to be coordinated transmission from the core node 130 (step 1), the data to be coordinated transmission is sent not only to the ARQ retransmission queue 112a but also to the HARQ retransmission queue 113a. Save (step 2). On the other hand, when the cooperation destination base station 120 receives the data to be coordinated transmission from the cooperation source base station 110 (step 3), it stores the data to be coordinated transmission in the HARQ retransmission queue 123a (step 4). . That is, the data to be coordinated transmission is stored in three locations: the ARQ retransmission queue 112 a and the HARQ retransmission queue 113 a of the cooperation source base station 110 and the HARQ retransmission queue 123 a of the cooperation destination base station 120.

In this configuration example, when the base station 110 of the cooperation source receives a reception failure response (NACK) from the terminal 200 at the MAC layer 113 (step 6), the retransmission processing by HARQ of the corresponding data is determined (step 7) Only the retransmission cooperative control information is transmitted to the cooperation destination base station 120 (step 8). This retransmission cooperative control information includes retransmission timing information, transmission frequency, MCS information designating a modulation scheme and coding scheme, and the like, and an ID for identifying retransmission data. Also, the cooperation source base station 110 reads out the data to be coordinated transmission stored in the HARQ retransmission queue 113a as retransmission data. On the other hand, based on the cooperative control information for retransmission received from the cooperation source base station 110, the cooperation-destination base station 120 reads out the data to be coordinated transmission stored in the HARQ retransmission queue 123a as retransmission data (step S1). 10). Then, the base station 110 that is the cooperation source transmits the retransmission data read from the HARQ retransmission queue 113a to the terminal 200, and the base station 120 that is the cooperation destination transmits the retransmission data in the base station 120 based on the cooperation control information for retransmission. The retransmission data read from the HARQ retransmission queue 123a is transmitted to the terminal 200 (steps 11 and 11 ').
Also, in this configuration example, when the cooperating base station 110 receives the reception failure response (NACK) from the terminal 200 at the RLC layer 112 (step 6), the retransmission processing by the ARQ of the corresponding data is determined. (Step 7), the data targeted for cooperative transmission stored in the ARQ retransmission queue 112a is read out as retransmission data. Thereafter, retransmission is performed according to the procedure shown in FIGS.
Retransmission (ARQ) processing in the RLC layer is automatically executed at intervals of several hundreds ms (for example, intervals of 100 ms to 150 ms), and retransmission (HARQ) processing in the MAC layer is performed at relatively short intervals of several ms (for example, intervals of 8 ms). Automatically executed. That is, when an error occurs in coordinated transmission, retransmission based on HARQ with a short retransmission interval is performed first, and retransmission based on ARQ is performed when the error cannot be compensated even with HARQ. In the configuration example of FIG. 12 and the control example of FIG. 13, the data retransmission process is reliably performed in both cases where the HARQ retransmission fails and the ARQ retransmission fails for the data to be cooperatively transmitted. Can do.

  In the configuration examples and control examples of FIGS. 4 to 13 described above, the cooperative control information for retransmission transmitted from the cooperating base station 110 to the cooperating base station 120 during the data retransmitting process is the cooperating base station. Information on frequency resources for cooperation newly determined in 110 may be included. By using frequency resources with better wireless communication quality between the base stations 110 and 120 and the terminal 200 for data retransmission processing, the coordinated transmission of retransmission data can be completed more reliably.

As described above, according to the present embodiment, when the coordinated base station 110 fails to perform coordinated data transmission for some reason, it is stored in at least one of the RLC layer 112 or the MAC layer 113 in the coordinated base station 110. The coordinated transmission target data is read as retransmission data, and the retransmission data and retransmission cooperative control information including at least transmission time information are transmitted to the cooperation-destination base station 120. The cooperating base station 110 transmits the read retransmission data to the terminal 200 at a predetermined transmission time. on the other hand. The cooperation-destination base station 120 receives the cooperation control information from the cooperation-source base station 110, and transmits the received retransmission data to the terminal 200 at a predetermined transmission time based on the cooperation control information. Thus, even when the coordinated transmission target data fails, the cooperation-source base station 110 and the cooperation-destination base station 120 cooperate to reliably transmit the failed data to be coordinated to the terminal 200. can do.
Further, according to the present embodiment, when the coordinated base station 110 fails to perform coordinated data transmission due to some cause, the coordinated base station 110 stores in at least one of the RLC layer 112 or the MAC layer 113 in the coordinated base station 110. The coordinated transmission target data is read as retransmission data, and retransmission cooperative control information including at least transmission time information is transmitted to the cooperation-destination base station 120. The cooperating base station 110 transmits the read retransmission data to the terminal 200 at a predetermined transmission time. on the other hand. The cooperation-destination base station 120 receives the cooperation control information from the cooperation-source base station 110, and based on the cooperation control information, at least one of the RLC layer 122 or the MAC layer 123 in the cooperation-destination base station 120. Is read out as retransmission data. Then, the cooperation-destination base station 120 transmits the read retransmission data to the terminal 200 at a predetermined transmission time. Thus, even when the coordinated transmission target data fails, the cooperation-source base station 110 and the cooperation-destination base station 120 cooperate to reliably transmit the failed data to be coordinated to the terminal 200. can do.
Further, according to the present embodiment, the cooperative base station 110 newly determines the cooperative control information for retransmission transmitted from the cooperative base station 110 to the cooperative base station 120 during the data retransmission process. By including the information on the frequency resource for cooperation, the cooperative transmission of retransmission data can be completed more reliably.

  In the above-described embodiment, the case where the data cooperatively transmitted from the base stations 110 and 120 is the same data having the same content has been described. However, the present invention is similarly applied to the case of cooperatively transmitting data having different content. Can be applied to.

10 COMMUNICATION SYSTEM 110 Cooperation source base station (first base station)
120 Base station to cooperate with (second base station)
111, 121 Data convergence protocol layer (PDCP layer)
112, 122 Radio link control layer (RLC layer)
112a, 122a ARQ retransmission queue 113, 123 Media access control layer (MAC layer)
113a, 123a HARQ retransmission queues 114, 124 Physical layer (PHY layer)
115, 125 Inter-base station communication unit 116, 126 Scheduler 117, 127 Control unit 128 Resource control unit for cooperation 130 Core node 200 Terminal

JP 2009-171382 A

Gen Baoshan, Takao Okamani, Hideki Hayashi, “Basic Design and Implementation of Network Control System for Cooperative Transmission between Multiple Base Stations”, Proceedings of the 2010 IEICE Society Conference, page 119

Claims (8)

A communication system capable of cooperatively transmitting data from a plurality of base stations to a communication terminal by wireless communication,
Any one of the plurality of base stations is a cooperating base station having a function of controlling coordinated transmission of data from each base station, and the other base stations of the plurality of base stations It is a base station of cooperation destination in which cooperative transmission of data is controlled by the base station of cooperation source,
The cooperating base station is
A wireless communication unit that wirelessly communicates with a communication terminal via a plurality of communication processing layers;
An inter-base station communication unit that communicates with the cooperating base station;
A storage unit for storing cooperative transmission target data in a media access control layer in the plurality of communication processing layers;
When coordinated transmission of the data to be coordinated transmission fails, the data to be coordinated transmission stored in the storage unit is read as retransmission data, and the read retransmission data and the transmission timing and frequency for the retransmission data are Including the coordination resource, the modulation scheme, and the coding scheme information for retransmission including the information of the coding scheme, to the base station of the coordination destination, and read from the storage unit based on the coordination control information for retransmission The retransmission data is controlled to be transmitted from the physical layer of the plurality of communication processing layers of the base station of the cooperation source to the communication terminal, and the base station of the cooperation destination is controlled based on the cooperation control information for retransmission. a control unit for remotely controlling the coordination destination base station to transmit the transmitted retransmission data from the cooperation-destination base station to the communication terminal, Provided,
The coordinated base station is
A wireless communication unit that wirelessly communicates with a communication terminal via a plurality of communication processing layers ;
An inter-base station communication unit that communicates with the cooperating base station;
A resource control unit for cooperation for the base station of the cooperation source to remotely control the base station of the cooperation destination,
The cooperative resource control unit receives the retransmission data and the cooperative control information for retransmission from the base station of the cooperative source, and transmits the retransmission data using a modulation scheme and a coding scheme included in the cooperative control information for retransmission. performs modulation and coding, to the communication terminal from the physical layer before Symbol plurality of communication processing layer of the base station of the cooperation destination by using the transmission timing and frequency of coordination for resources included in the cooperative control information for the retransmission communication system comprising a benzalkonium controls to transmit the retransmission data. A communication system capable of cooperatively transmitting data from a plurality of base stations to a communication terminal by wireless communication,
Any one of the plurality of base stations is a cooperating base station having a function of controlling coordinated transmission of data from each base station, and the other base stations of the plurality of base stations It is a base station of cooperation destination in which cooperative transmission of data is controlled by the base station of cooperation source,
The cooperating base station is
A wireless communication unit that wirelessly communicates with a communication terminal via a plurality of communication processing layers;
An inter-base station communication unit that communicates with the cooperating base station;
A storage unit for storing cooperative transmission target data in a media access control layer in the plurality of communication processing layers;
When cooperative transmission of the data to be coordinated transmission fails, the data to be coordinated transmission stored in the storage unit is read as retransmission data, and includes the transmission timing and frequency for the retransmission data to be coordinated transmission target Cooperative control information for retransmission including resource, modulation scheme, and coding scheme information is transmitted to the base station of the cooperation destination, and based on the cooperative control information for retransmission, the retransmission data read from the storage unit is transmitted to the cooperative base station. Control is performed to transmit from the physical layer in the plurality of communication processing layers of the original base station to the communication terminal, and based on the cooperative control information for retransmission, the retransmission data read from the base station of the cooperation destination A controller that remotely controls the cooperation-destination base station to transmit to the communication terminal from the cooperation-destination base station ,
The coordinated base station is
A wireless communication unit that wirelessly communicates with a communication terminal via a plurality of communication processing layers;
An inter-base station communication unit that communicates with the cooperating base station;
A storage unit for storing cooperative transmission target data in a media access control layer in the plurality of communication processing layers;
A resource control unit for cooperation for the base station of the cooperation source to remotely control the base station of the cooperation destination,
The cooperative resource control unit receives the cooperative control information for retransmission from the base station of the cooperative source, reads the data to be cooperatively transmitted stored in the storage unit as retransmission data , and Modulation and coding of the retransmission data is performed using the modulation scheme and coding scheme included in the cooperative control information, and using the transmission timing and frequency of the cooperative resource included in the cooperative control information for retransmission, the base station of the cooperation destination communication system comprising a benzalkonium controls to transmit the retransmission data to the communication terminal from the physical layer in the plurality of communication process layer. In 請 Motomeko 1 or 2 of the communication system,
Communication system, characterized in that prior Symbol frequency coordination for resources included in the cooperative control information for retransmission, the a frequency newly determined for coordinated transmission of the retransmission data. In a communication system capable of cooperatively transmitting data from a plurality of base stations to a communication terminal by wireless communication, a cooperation source base station having a function of controlling cooperative transmission of data from the plurality of base stations,
A wireless communication unit that wirelessly communicates with a communication terminal via a plurality of communication processing layers;
An inter-base station communication unit that communicates with a cooperating base station;
A storage unit for storing cooperative transmission target data in a media access control layer in the plurality of communication processing layers;
When it fails to cooperative transmission of data of the cooperative transmission target, reads data of the cooperative transmission subject the stored in the storage unit of the media access control layer as the retransmission data, and retransmission data thus read out, for retransmitted data Coordinating resources including transmission timing and frequency, cooperative control information for retransmission including modulation scheme and coding scheme information, is transmitted to the base station of the cooperation destination , based on the cooperative control information for retransmission, The retransmission data read from the storage unit is controlled to be transmitted from the physical layer in the plurality of communication processing layers to the communication terminal, and is transmitted to the cooperation destination base station based on the cooperative control information for retransmission. control unit for remotely controlling the coordination destination base station to transmit a retransmission data from the cooperation-destination base station to the communication terminal , The base station characterized in that it comprises a. In a communication system capable of cooperatively transmitting data from a plurality of base stations to a communication terminal by wireless communication, a cooperation source base station having a function of controlling cooperative transmission of data from the plurality of base stations,
A wireless communication unit that wirelessly communicates with a communication terminal via a plurality of communication processing layers;
An inter-base station communication unit that communicates with a cooperating base station;
A storage unit for storing cooperative transmission target data in a media access control layer in the plurality of communication processing layers;
When the coordinated transmission target data has failed in the coordinated transmission, the coordinated transmission target data stored in the storage unit of the media access control layer is read as retransmission data, and the transmission timing for the coordinated transmission target retransmission data; The cooperative control information for retransmission including information on the resources for cooperation including the frequency, modulation scheme and coding scheme is transmitted to the base station of the cooperation destination, and read from the storage unit based on the cooperative control information for retransmission The retransmission data is controlled to be transmitted from the physical layer in the plurality of communication processing layers to the communication terminal, and based on the retransmission cooperative control information, the retransmission data read from the cooperation-destination base station is and a control unit for remotely controlling the coordination destination base station to transmit from a previous base station to the communication terminal Base station and wherein the door. In a communication system capable of cooperatively transmitting data from a plurality of base stations to a communication terminal by wireless communication, a cooperative base station whose cooperative transmission of data is controlled by a cooperative base station,
A wireless communication unit that wirelessly communicates with a communication terminal via a plurality of communication processing layers;
An inter-base station communication unit that communicates with the cooperating base station;
A resource control unit for cooperation for the base station of the cooperation source to remotely control the base station of the cooperation destination,
The cooperative resource control unit receives retransmission data and the cooperative control information for retransmission from the base station of the cooperative source, and transmits the retransmission data using the modulation scheme and the coding scheme included in the cooperative control information for retransmission. Modulation and coding are performed, and control is performed such that the retransmission data is transmitted from the physical layer in the plurality of communication processing layers to the communication terminal using the transmission timing and frequency of the resource for cooperation included in the cooperation control information for retransmission. A base station characterized by: In a communication system capable of cooperatively transmitting data from a plurality of base stations to a communication terminal by wireless communication, a cooperative base station whose cooperative transmission of data is controlled by a cooperative base station,
A wireless communication unit that wirelessly communicates with a communication terminal via a plurality of communication processing layers;
An inter-base station communication unit that communicates with the cooperating base station;
A storage unit for storing cooperative transmission target data in a media access control layer in the plurality of communication processing layers;
A resource control unit for cooperation for the base station of the cooperation source to remotely control the base station of the cooperation destination,
The cooperative resource control unit receives the cooperative control information for retransmission from the base station of the cooperation source, reads the data to be coordinated transmission stored in the storage unit as retransmission data , In the plurality of communication processing layers, the retransmission data is modulated and coded by the modulation scheme and the coding scheme included in the cooperative control information, and the transmission timing and frequency of the cooperative resource included in the cooperative control information for retransmission are used. It said base station and benzalkonium controls to transmit the retransmission data to the communication terminal from the physical layer.   In the base station according to any one of claims 4 to 7,
  The base station characterized in that the frequency of the resource for cooperation included in the cooperative control information for retransmission is a newly determined frequency for cooperative transmission of the retransmission data.

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