JP5250840B2 - Base station control apparatus and base station cooperative communication control method - Google Patents

Description

  The present invention relates to a base station control device and a base station cooperative communication control method.

  In recent years, in the mobile phone service in Japan, the third generation called IMT-2000 (International Mobile Telecommunications 2000) represented by W-CDMA (Wideband Code Division Multiple Access) and CDMA2000 (Code Division Multiple Access 2000). Mobile communication systems are becoming popular. Further, as the IMT-2000 advanced system and the IMT-2000 next-generation system, a standard for a fourth generation mobile communication system called IMT-Advanced is being formulated.

  IMT-Advanced aims to achieve a transmission rate of 1 Gbps when moving at low speed and a transmission rate of 100 Mbps when moving at high speed. In order to realize such high-speed communication, it is necessary to use a communication method using a wide frequency band. As one of such communication methods, orthogonal frequency division multiple access (Orthogonal Frequency Division) Multiple Access (OFDMA) system is known. The OFDMA scheme is a scheme in which a wide frequency band is divided into orthogonal narrow bands called subcarriers, and information is transmitted on each subcarrier. According to this OFDMA method, frequency characteristics generated in a radio apparatus are corrected for each subcarrier, or frequency multiplex transmission and frequency division multiple access are adaptively performed with respect to time variations of frequency characteristics generated in a transmission path. Therefore, it is attracting attention as one of the leading transmission methods for realizing broadband communication.

  In addition, the multiple input multiple output (MIMO) technique using a plurality of antennas receives signals individually transmitted from a plurality of antennas on the transmission side by the plurality of antennas on the reception side, and receives the received signals. As a technique for improving frequency utilization efficiency by separating spatial signals from the signal.

  In the cellular mobile communication system, a plurality of base stations are arranged, and a continuous communication service area is constructed by the communication area (cell) of each base station. When applying a communication method using, a guideline for allocating the entire frequency band to each cell is conceivable due to the limitation of the usable frequency region. In this case, for a mobile station located in the vicinity of the base station, the desired signal from the communication base station can be received at a high level, and the radio signal from the adjacent base station is lowered due to distance attenuation. The user throughput can be expected to increase as an effect of broadband communication. However, for mobile stations located at cell boundaries, not only the level of the desired signal decreases due to distance attenuation, but also the radio signal of the adjacent base station becomes an interference signal at the same level as the communication signal, greatly degrading the communication quality. There is a problem that the effect of broadband communication cannot be obtained sufficiently. This problem becomes conspicuous especially in the downlink (line from the base station to the mobile station) because the transmission power of the base station is larger than that of the mobile station.

  For example, Patent Documents 1, 2, and 3 disclose countermeasures against the problem. FIG. 16 is a schematic configuration diagram of the conventional cellular mobile communication system. In FIG. 16, the conventional cellular mobile communication system concentrates a plurality of base stations 101 each providing a cell 103, a mobile station (user terminal) 102 that wirelessly communicates with the base station 101, and a plurality of base stations 101. A base station controller 107 for controlling. Each base station 101 is connected to the core network 105 via the backbone network 104. Each of the backbone network 104 and the core network 105 includes a router 106. The base station controller 107 is provided in the backbone network 104 and is connected to each base station 101 by wire. The base station controller 107 controls the plurality of base stations 101 so that the plurality of base stations 101 cooperate with each other and perform communication using the MIMO technology or the like with respect to the user terminals 102 on the cell boundary.

JP 2007-134844 A JP 2007-043332 A International Publication No. 2006/016485 Pamphlet

H. Zhang, H. Dai, “Cochannel Interference Mitigation and Cooperative Processing in Downlink Multicell Multiuser”, EURASIP Journal on Wireless Communications and Networking 2004, 2, pp.222-235

  However, the conventional cellular mobile communication system described above has a problem that the processing load on the base station controller increases as the number of base stations controlled by the base station controller increases. For this reason, it is conceivable to control a certain number of base stations by a plurality of base station controllers, but in this case, it is not possible to perform coordinated communication between base stations connected to different base station controllers. Also, if a non-control target base station or a relay station is provided for only some base stations in the cellular mobile communication system, the non-control target base station cannot perform communication in cooperation between the base stations. Therefore, a difference occurs in the communication service depending on the cell where the mobile station is located.

  The cellular mobile communication system that performs broadband communication such as IMT-Advanced is assumed to use a microcell having a cell range smaller than that of a conventional macrocell, and thus the number of base stations increases. Cannot be neglected.

  In the cellular mobile communication system, a handover technique for switching the connection to a different base station is used in order to obtain a stable communication state while maintaining the connection state of the user terminal. Handover includes hard handoff and soft handoff. In the hard handoff, communication is instantaneously interrupted, and transmission that is coordinated between base stations is not performed. In soft handoff, simultaneous transmission is performed from a plurality of base stations at the time of handover, but cooperation between base stations according to the state of wireless communication is not performed.

  The present invention has been made in consideration of such circumstances, and its purpose is to expand the range in which base station cooperative communication is possible in which a plurality of base stations cooperate to communicate with a mobile station, and to perform wireless communication. Another object of the present invention is to provide a base station control device and a base station cooperative communication control method capable of performing base station cooperative communication according to the situation.

  In order to solve the above problems, a base station control apparatus according to the present invention includes a plurality of base stations and a base station in a cellular mobile communication system in which a continuous communication service area is constructed by the communication area of each base station. A base station control apparatus provided for each station, wherein each base station control apparatus is configured to be able to communicate with each other via a communication network, and a plurality of base stations communicate with a mobile station in cooperation with each other. The control of the base station cooperative communication is performed by the base station control devices of the base stations involved in the base station cooperative communication in cooperation, and the communication area includes a cooperation area that is a target of the base station cooperative communication, The base station control device is divided into a non-cooperation area that is not a target of station cooperation communication, the base station control device includes an area selection unit that selects a cooperation area or a non-cooperation area, and a single site in the non-cooperation area. A single-site connection target selection means for selecting a mobile station to be connected, a multi-site connection target selection means for selecting a mobile station to perform a multi-site connection in the cooperation area, and a wireless communication status in the area selected by the area selection means. Based on the evaluation, the base station cooperation communication adjustment means for adjusting the base station cooperation communication between the base station control devices of the base station related to the base station cooperation communication, the base station cooperation communication adjustment means, When the area selection unit selects a non-cooperation area and receives a cooperative communication request from the base station controller of another base station, the evaluation value of the single site connection capacity in the non-cooperation area selected by the area selection unit and And base station cooperative communication in the cooperative area based on the evaluation value of the multi-site connection capacity in the cooperative area related to the received cooperative communication request It determines whether performed, characterized in that.

  In the base station control device according to the present invention, the base station cooperation communication adjustment means, when the area selection means selects a cooperation area, a base station of another base station related to the cooperation area selected by the area selection means The evaluation value of the multi-site connection capacity in the cooperation area is transmitted to the control device, and a response indicating whether or not to perform base station cooperation communication in the cooperation area is received.

  In the base station control device according to the present invention, when the area selection unit selects a cooperation area, the base station cooperation communication adjustment unit receives a cooperation communication request from a base station control device of another base station. When the cooperation area related to the received cooperation communication request matches the cooperation area selected by the area selecting means, the multi-site connection capacity in the cooperation area is set to perform base station cooperation communication in the cooperation area. Is sent to the base station controller of the cooperative communication request source. On the other hand, if the cooperative area related to the received cooperative communication request does not match the cooperative area selected by the area selecting means, the area The evaluation value of the multi-site connection capacity in the cooperation area selected by the selection means is transmitted to the base station controller of the cooperation communication request source, and the area selection means selects Receiving the base station cooperation whether to communicate responses in cooperation area, characterized in that.

  In the base station control apparatus according to the present invention, the area selection unit records a selection rate for each area, and selects the area based on the selection rate.

  In the base station control apparatus according to the present invention, the area selecting means selects the area having the lowest selection rate.

  In the base station control apparatus according to the present invention, the area selection means calculates an average value of the selection rate for each area, and selects the area having the maximum ratio of the average value to the latest selection rate. It is characterized by that.

  In the base station control apparatus according to the present invention, the area selecting means selects only the area where the mobile station is located.

A base station cooperation communication control method according to the present invention is a cellular mobile communication system in which a plurality of base stations are arranged and a continuous communication service area is constructed by the communication area of each base station. Each base station cooperation unit is configured to be able to communicate with each other via a communication network, and control of base station cooperation communication in which a plurality of base stations communicate with a mobile station in cooperation with each other. A base station cooperation communication control method performed in cooperation between base station cooperation units of base stations related to station cooperation communication, wherein the communication area includes a cooperation area that is a target of base station cooperation communication, and a base station cooperation communication The base station cooperation unit selects a cooperation area or a non-cooperation area, and the base station cooperation unit performs wireless communication in the selected area. Based on the evaluation of the situation, between the base stations cooperating unit of the base station according to the base station cooperative communication, a step of adjusting the base station cooperative communication, the base station cooperation unit, according to the result of the adjustment, uncoordinated area Selecting a mobile station that performs single-site connection in the network, or selecting a mobile station that performs multi-site connection in a cooperation area, and the base station cooperation unit selects a non-cooperation area, When a cooperative communication request is received from the base station cooperation unit of another base station, the evaluation value of the single site connection capacity in the selected non-cooperation area and the multi-site connection capacity in the cooperation area related to the received cooperation communication request Based on the evaluation value, it is determined whether to perform base station cooperative communication in the cooperative area.

  According to the present invention, it is possible to expand a range in which base station cooperative communication is possible in which a plurality of base stations cooperate to communicate with a mobile station, and to perform base station cooperative communication according to wireless communication conditions. An effect is obtained.

It is a schematic block diagram of the cellular mobile communication system which concerns on one Embodiment of this invention. The conceptual diagram of the communication structure of the cellular mobile communication system which concerns on the embodiment is shown. It is a block diagram which shows schematic structure of the base station 1 which concerns on the same embodiment. It is a conceptual diagram which shows the structural example of the communication area (cell) of the base station 1 which concerns on the same embodiment. It is an example of the relationship between base stations. It is a flowchart which shows the process sequence of the base station cooperation part 10 shown in FIG. It is a flowchart which shows the process sequence of the base station cooperation part 10 shown in FIG. It is a flowchart which shows the process sequence of the base station cooperation part 10 shown in FIG. It is an example of the relationship between base stations. It is an example of the relationship between base stations. It is an example of the relationship between base stations. It is an example of the relationship between base stations. It is an example of the relationship between base stations. It is an example of the relationship between base stations. It is an example of the relationship between base stations. It is a schematic block diagram of the conventional cellular mobile communication system.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a cellular mobile communication system according to an embodiment of the present invention. In FIG. 1, the cellular mobile communication system includes a plurality of base stations 1 each providing a cell and a mobile station (user terminal) 2 that communicates with the base station 1 by wireless connection. In FIG. 1, two base stations 1 (whose base station identifiers are A and B), a cell 3A provided by the base station 1 (A), and a cell 3B provided by the base station 1 (B) Illustrated. Each base station 1 has a base station cooperation unit 10. The base station cooperation unit 10 has a function for controlling base station cooperation communication.

  Each base station 1 is connected to the core network 5 via the backbone network 4. The backbone network 4 and the core network 5 each have a router 6. The base station cooperation unit 10 of each base station 1 communicates with each other via the backbone network 4. FIG. 2 shows a conceptual diagram of a communication configuration of the cellular mobile communication system according to the present embodiment. In FIG. 2, the real plane shows a communication configuration between the base station 1 and the user terminal 2. The cooperation plane is a communication configuration for controlling base station cooperation communication, and indicates a logical connection relationship in the backbone network 4. In the cooperation plane, the base station cooperation units 10 are connected to each other in a logically flat full mesh shape, and can transmit and receive data to and from any base station cooperation unit 10. The communication line in the backbone network 4 is wired and has a sufficient communication band as compared with the amount of data transmitted and received between the base station cooperation units 10. 2 is independent of an OSI (Open Systems Interconnection) reference model.

  In the cellular mobile communication system according to the present embodiment, the multiple access method between the base station 1 and the user terminal 2 is not limited. As the multiple access method, for example, an OFDMA method, a time division multiple access (TDMA) method, or the like can be used.

  In the cellular mobile communication system according to the present embodiment, the base station 1 and the user terminal 2 are provided with a plurality of antennas, and even when the base station 1 and the user terminal 2 communicate one-to-one, the plurality of base stations 1 cooperate. Even when communicating with the user terminal 2, transmission using MIMO technology (MIMO transmission) is performed. As a method of MIMO transmission (MIMO mode), for example, there are transmission diversity such as maximum ratio combining transmission diversity, space-time code, spatial multiplexing such as eigenbeam spatial multiplexing, and combinations thereof.

  FIG. 3 is a block diagram illustrating a schematic configuration of the base station 1 according to the present embodiment. In FIG. 3, the wireless unit 11 is wirelessly connected to the user terminal 2 and transmits / receives data such as user data and control messages. The user data / control message processing unit 12 transmits / receives data (user data) to / from the user terminal 2, to / from the base station cooperation unit 10 of another base station 1, and to / from the core network 5. , Control message). The wired unit 13 is wired to the backbone network 4 and transmits / receives data such as user data and control messages.

  The throughput calculation unit 14 calculates a throughput expected in wireless communication between the base station 1 and the user terminal 2. Information on the calculation target base station 1 and user terminal 2 is sent from the base station cooperation unit 10 to the throughput calculation unit 14. The throughput of the calculation result is sent from the throughput calculation unit 14 to the base station cooperation unit 10. The data holding unit 15 stores data of the base station cooperation unit 10. The data holding unit 15 writes and reads data from the base station cooperation unit 10.

  The base station cooperation unit 10 transmits and receives control messages to and from the user terminal 2 and with the base station cooperation unit 10 of another base station 1 via the user data / control message processing unit 12. . The base station cooperation unit 10 controls base station cooperation communication by exchanging the control message.

  FIG. 4 is a conceptual diagram illustrating a configuration example of a communication area (cell) of the base station 1 according to the present embodiment. A cell provided by one base station 1 is divided into a cooperation area and a non-cooperation area. The cooperation area is an area that is a target of base station cooperation communication. The non-cooperation area is an area that is not a target of base station cooperation communication. In the example of FIG. 4, one cell is divided into one non-cooperation area (Area 0) and seven cooperation areas. In the cooperation area, identifiers (Area 1 to 9) are attached corresponding to the cells adjacent to the own cell. It is assumed that base station cooperation communication is performed between adjacent base stations 1 in adjacent cooperation areas (cooperation areas having the same identifier). For example, it is assumed that base station cooperation communication is performed in the adjacent cooperation area (Area 6) between the base station 1 (A) and the base station 1 (B). The reason why the cooperation area is divided into a plurality is that the base stations to be linked are different. In FIG. 4, the reason why the cooperation area is provided up to Area 9 is to construct the cooperation area without contradiction based on the cell arrangement of the cellular mobile communication system. Although FIG. 4 shows an example in cooperation between two base stations, the present invention is not limited to this, and a cooperation area can be set according to the operation policy of the cellular mobile communication system.

  Next, a base station cooperative communication control method according to this embodiment will be described.

  In the embodiment described here, the number of antennas of the base station 1 and the number of antennas of the user terminal 2 are both 2, but the present invention can be similarly applied even when the number of antennas is 3 or more. In this embodiment, the number of base stations 1 that perform base station cooperative communication is two. However, the present invention can be similarly applied even when there are three or more base stations 1 that perform base station cooperative communication. Further, the base station cooperative communication can be modified such as a combination of the base station cooperative communication performed by the two base stations 1 and the base station cooperative communication performed by the three base stations 1.

  “Single site connection” means one-to-one communication between one user terminal and one base station, and “multi-site connection” means one-to-many communication between one user terminal and a plurality of base stations. To do.

  Further, in this embodiment, as illustrated in FIG. 5, “slave base station” and “master base station” are defined. The slave base station refers to the base station 1 that transmits the cooperative communication request. The master base station refers to the base station 1 that receives the cooperative communication request. The cooperative communication request is a message in which the transmission source base station 1 (slave base station) requests base station cooperative communication from the destination base station 1 (master base station). The cooperative communication request includes a base station identifier of the transmission source base station 1 (slave base station), information indicating the wireless status of the user terminal 2 located in the cooperative area of the slave base station in the base station cooperative communication target, and the like. Including.

  The slave base station and the master base station are identified by the source and destination of the cooperative communication request, the source of the cooperative communication request is the slave base station, and the destination of the cooperative communication request is the master base station. In the example of FIG. 5, the base station 1 (A) that is the source of the cooperative communication request is a slave base station, and the base station 1 (B) that is the destination of the cooperative communication request is a master base station. Messages transmitted and received between the slave base station and the master base station, such as cooperative communication requests, are transmitted and received via the backbone network 4 between the base station cooperation units 10 of the respective base stations 1.

  Hereinafter, the base station cooperative communication control method according to the present embodiment will be described with reference to FIG. 6, FIG. 7, and FIG. 6, 7 and 8 are flowcharts showing the processing procedure of the base station cooperation unit 10 according to the present embodiment. 6, 7, and 8, messages transmitted and received between the base stations are transmitted and received between the base station cooperation units 10 of the respective base stations 1 via the backbone network 4.

  When the multiple access method is the TDMA method, the user terminal 2 to be transmitted in one transmission slot is determined by the processes of FIGS. 6, 7, and 8. On the other hand, when the multiple access scheme is the OFDMA scheme, while there are available radio resources at a certain scheduling timing, the processes shown in FIGS. Terminal 2 is determined. In the OFDMA scheme, one scheduling timing may be, for example, one PHY frame or a plurality of PHY frames.

  First, the base station cooperation unit 10 starts processing from step S1 of FIG.

  Step S1: A cooperation area or a non-cooperation area is selected in the cell of the own base station 1. As this area selection method, for example, a selection rate for each area is recorded, and area selection is performed based on the selection rate. Specifically, a method for selecting the area with the lowest selection rate or a method for calculating an average value of the selection rate for each area and selecting an area with the maximum ratio of the average value to the latest selection rate Etc. Further, only the area where the user terminal 2 is located may be selected.

  Step S2: It is determined whether the area selected in Step S1 is a non-cooperation area or a cooperation area. As a result, if the selected area is a non-cooperation area, the process proceeds to step S3. On the other hand, when the selected area is a cooperation area, it progresses to step S20 of FIG.

Step S3: A cooperative communication request is received from the adjacent base station 1.
Step S4: Determine whether or not a cooperative communication request has been received. As a result, if the cooperative communication request is not received, the process proceeds to step S5. On the other hand, when the cooperative communication request is received, the processing from step S8 to S10 is performed for each transmission source (slave base station) of the received cooperative communication request.

  Step S5: The single site connection capacity in the non-cooperation area selected in step S1 is calculated. FIG. 9 illustrates the relationship between the base stations 1 at this time. In FIG. 9, the own base station 1 (A) does not receive the coordinated communication request from the adjacent base station 1 (B), and the own base station (A) communicates with the adjacent base station 1 (B). The request has not been sent. The single site connection capacity represents the expected throughput when the base station 1 and the user terminal 2 make a single site connection. The theoretical formula disclosed in Non-Patent Document 1 can be used to calculate the single site connection capacity.

Step S6: The evaluation value PF ^(m) of the single site connection capacity is calculated by the equation (1).

However, m is an identifier of the user terminal 2 located in the non-cooperation area. R _m (t) is the single site connection capacity (calculated in step S5) related to the user terminal 2 (m). T _m (t) is an average value of the throughput related to the user terminal 2 (m). The average value of the throughput is calculated by the throughput calculator 14 for each user terminal 2. In addition, evaluation value PF ^(m) represented by said (1) Formula is an evaluation value which concerns on proportional fair (PF).
The user terminal 2 having the maximum single-site connection capacity evaluation value PF ^(m) is selected as the user terminal 2 that performs single-site connection in the non-cooperation area.

  Step S7: The base station 1 performs single site connection with the selected user terminal 2 in a non-cooperation area.

  The processing from step S8 to S10 is performed for each transmission source (slave base station) of the cooperative communication request received by the own base station 1.

  Step S8: The multi-site connection capacity in the cooperation area related to the cooperation communication request received by the own base station 1 is calculated. FIG. 10 and FIG. 11 illustrate the relationship between the base stations 1 at this time. In FIG. 10, the own base station 1 (A, master base station) has received the cooperative communication request from the adjacent base station 1 (B, slave base station). In FIG. 11, the own base station 1 (A, master base station) has received a cooperative communication request from a plurality of adjacent base stations 1 (B, C, slave base stations).

  In the calculation of the multisite connection capacity, the user terminal 2 of the master base station located in the cooperation area with the adjacent base station that is the transmission source (slave base station) of the cooperation communication request and the cooperation area of the slave base station. Multi-user MIMO (MU-MIMO) is assumed for user terminals 2 in the service area, and multi-site connection capacity is calculated for all combinations of the user terminals 2. The theoretical formula disclosed in Non-Patent Document 1 can be used to calculate the multi-site connection capacity.

  The multi-site connection capacity represents the expected throughput when the base station 1 and another base station 1 perform multi-site connection to the user terminal 2. However, in the case of multi-user MIMO, it represents the sum of the multi-site connection capacities for a plurality of user terminals 2 in a set.

Next, the evaluation value CPF _{(1) i, j} of the multi-site connection capacity is calculated by the equation (2).

However, i is the identifier of the user terminal located in the cooperation area of the master base station. j is an identifier of a user terminal located in the cooperation area of the slave base station. R _{c (1) i, j} (t) is the instantaneous value of the multi-site connection capacity of the user terminal 2 (i) in the set of user terminals 2 (i, j) at time t (calculated in step S8). is there. R _{ave (1) _i} (t) is a time average value of the multi-site connection capacity of the user terminal 2 (i) up to time t. The time average value of the multi-site connection capacity is calculated by the throughput calculation unit 14 for each user terminal 2. The evaluation value CPF _{(1) i, j} represented by the above equation (2) is an evaluation value related to “Cooperative Proportional Fair (Cooperative PF)”.

Step S9: A multi-site connection capacity calculation request is transmitted to the slave base station. This multi-site connection capacity calculation request represents the base station identifier of the own base station 1 (master base station) and the radio status of the user terminal 2 located in the cooperation area of the base station cooperation communication target of the master base station. Include information etc. As a result, the slave base station calculates the multi-site connection capacity in the same manner as in step S8, and further calculates the evaluation value CPF _{(2) i, j} of the multi-site connection capacity using the equation (3). The slave base station returns the calculation result to the master base station.

However, i is the identifier of the user terminal located in the cooperation area of the master base station. j is an identifier of a user terminal located in the cooperation area of the slave base station. R _{c (2) i, j} (t) is an instantaneous value of the multi-site connection capacity of the user terminal 2 (j) in the set of user terminals 2 (i, j) at time t. R _{ave (2) _j} (t) is the time average value of the multi-site connection capacity of the user terminal 2 (j) up to time t.

Step S10: A set of user terminals 2 (i, j) using the evaluation value CPF _{(1) i, j} calculated in step S8 and the evaluation value CPF _{(2) i, j} received from the slave base station in step S9. The sum of the evaluation values is calculated for each, and the maximum value Z of the sum of the evaluation values of the multi-site connection capacity is calculated. The maximum value Z of the sum of the evaluation values of the multi-site connection capacity is expressed by equation (4).

  Next, a set of user terminals 2 (i, j) that gives the maximum sum Z of the evaluation values of the multisite connection capacity is selected.

  Step S11: It is determined whether there are a plurality of slave base stations. If there are a plurality of slave base stations, the process proceeds to step S12. If there is one slave base station, the slave base station is selected, and the process proceeds to step S14.

Step S12: Select a slave base station having the maximum sum Z of evaluation values calculated in step S10.
Step S13: A cooperation rejection response is returned to the slave base station that has not been selected in step S12.

Step S14: The same processing as in steps S5 and S6 is performed on the non-cooperation area selected in step S1, and the evaluation value PF ^(m) of the single site connection capacity is calculated. Next, the maximum value Z of the total sum of the evaluation values of the multi-site connection capacity related to the slave base station selected in step S11 or step S12 is compared with the calculated evaluation value PF ^{(m) of} the single-site connection capacity. As a result, when the maximum value Z of the total sum of the evaluation values of the multisite connection capacity is larger than the evaluation value PF ^{(m) of the} single site connection capacity, the process proceeds to step S15. On the other hand, if the maximum value Z of the sum of the evaluation values of the multisite connection capacity is equal to or less than the evaluation value PF ^{(m) of the} single site connection capacity, the process proceeds to step S17.

Step S15: A response indicating that cooperation is possible is returned to the slave base station selected in step S11 or step S12. The response indicating that cooperation is possible includes information on the user terminal 2 that is a base station cooperative communication target (the user terminal 2 (i, j) selected in step S10 related to the slave base station selected in step S11 or step S12), and the like. include.
Step S16: The user terminal 2 (i, j) selected in step S10 related to the slave base station selected in step S11 or step S12 is selected as the user terminal 2 that performs multi-site connection in the cooperation area. As a result, the own base station 1 (master base station) and the slave base station perform multi-site connection to the user terminal 2 (i, j) in the cooperation area.

Step S17: A cooperation rejection is returned to the slave base station selected in step S11 or step S12. Then, the procedure proceeds to step S7, based on the evaluation value PF ^(m) of the single-site connection capacity calculated in step S14, the user terminal 2 evaluation value PF ^(m) is the maximum, single-site connection uncoordinated Area The user terminal 2 is selected. As a result, the base station 1 performs single site connection with the selected user terminal 2 in the non-cooperation area.

As a result of step S2, when the cooperation area is selected in step S1, the process proceeds to step S20 in FIG.
Step S20: A cooperative communication request is transmitted to the adjacent base station 1 which is a base station cooperative communication target in the selected cooperative area. Also, a cooperative communication request is received from the adjacent base station 1.

  Step S21: Confirm the number of received cooperative communication requests received in step S20. If the number of received cooperative communication requests is 0, the process proceeds to step S22. If the number of received cooperative communication requests is 1, the process proceeds to step S26. When the number of received cooperative communication requests is 2 or more, the process proceeds to step S40 in FIG.

Step S22: The multisite connection capacity in the cooperation area selected in step S1 is calculated. FIG. 5 illustrates the relationship between the base stations 1 at this time. In FIG. 5, the own base station 1 (A, slave base station) transmits a cooperative communication request to the adjacent base station 1 (B, master base station). Thereby, when the multisite connection capacity calculation request is received from the master base station, the multisite connection capacity in the cooperation area selected in step S1 is calculated. The calculation of the multisite connection capacity here is the same as that in the slave base station in step S9. First, the multisite connection capacity is calculated in the same manner as in step S8, and the multisite connection capacity evaluation values CPF _{(2) i, j} are set to (3 ₎ for all combinations of the user terminals 2 located in the cooperation area. ).
Step S23: The calculation result of step S22 is transmitted to the master base station.

Step S24: A response from the master base station is received and the response content is confirmed. If the response content is cooperation rejection, the process proceeds to step S5 in FIG. If the response content can be linked, the process proceeds to step S25 in FIG. The response indicating that cooperation is possible includes information on the user terminal 2 (i, j) that is a base station cooperative communication target.
Note that a timer for waiting for a response from the master base station may be provided, and if there is no response from the master base station before the time is up, it may be determined that the cooperation is rejected.

  Step S25: Based on the information included in the response indicating that cooperation is possible, the user terminal 2 (i, j) subject to base station cooperation communication is selected as the user terminal 2 that performs multi-site connection in the cooperation area. Thereby, the own base station 1 (slave base station) and the master base station perform multi-site connection to the user terminal 2 (i, j) in the cooperation area.

When the number of received cooperative communication requests received in step S20 is 1, the process proceeds to step S26.
Step S26: It is determined whether or not the cooperation area related to the received cooperation communication request matches the cooperation area selected by the own base station 1. As a result, if they match, the process proceeds to step S27. If they do not match, the process proceeds to step S30.

Step S27: The multisite connection capacity in the cooperation area selected in step S1 is calculated. FIG. 12 illustrates the relationship between the base stations 1 at this time. In FIG. 12, the own base station 1 (A, slave base station) transmits a cooperative communication request to the adjacent base station 1 (B, master base station), and the own base station 1 (A, master base station). Has received a cooperative communication request from the adjacent base station 1 (B, slave base station). That is, both base stations 1 (A, B) are master base stations and slave base stations. In this case, a master base station determination process is performed. As master base station determination processing, for example,
・ A base station with a small base station identifier is set as a master base station.
・ Determine the master base station using random numbers.
・ The master communication base station with the smaller number of received cooperative communication requests
and so on.

When the own base station 1 becomes the master base station, the process proceeds to step S8 in FIG. 6 (not shown). Here, it is assumed that the own base station 1 has become a slave base station. In this case, similarly to step S22, the multisite connection capacity in the cooperation area selected in step S1 is calculated, and the evaluation value of the multisite connection capacity for all combinations of the user terminals 2 located in the cooperation area. CPF _{(2) i, j} is calculated. Here, since the master / slave base station is determined by the master base station determination process, there is no need for a multisite connection capacity calculation request from the master base station.
Step S28: The calculation result of step S27 is transmitted to the master base station.
Step S29: When a response from the master base station is received, the process proceeds to step S25. This response includes information of the user terminal 2 (i, j) that is a base station cooperative communication target.

As a result of step S26, when the cooperation area related to the received cooperation communication request and the cooperation area selected by the own base station 1 do not match, the process proceeds to step S30.
Step S30: The multi-site connection capacity in the cooperation area selected in step S1 is calculated. FIG. 13 illustrates the relationship between the base stations 1 at this time. In FIG. 13, the own base station 1 (A, slave base station) is transmitting a cooperative communication request to the adjacent base station 1 (B, master base station), and the own base station 1 (A, master base station). Has received a cooperative communication request from an adjacent base station 1 (C, slave base station). That is, the own base station 1 (A) is a slave base station for the base station 1 (B, master base station) and a master base station for the base station 1 (C, slave base station). Thus, when the own base station 1 becomes a master base station and a slave base station, first, processing as a slave base station is performed. Thus, as in step S22, when a multisite connection capacity calculation request is received from the master base station, the multisite connection capacity in the cooperation area selected in step S1 is calculated, and further, the user terminals located in the cooperation area Multi-site connection capacity evaluation value CPF _{(2) i, j} is calculated for all combinations of ₂ .
Step S31: The calculation result of step S30 is transmitted to the master base station.

  Step S32: The response from the master base station is received and the response content is confirmed. If the response content is cooperation rejection, the process proceeds to step S8 in FIG. 6, and this time, processing as a master base station is performed. If the response content can be linked, the process proceeds to step S33. The response indicating that cooperation is possible includes information on the user terminal 2 (i, j) that is a base station cooperative communication target.

  Step S33: A cooperation rejection is returned to the slave base station (the base station 1 that has transmitted the cooperation communication request received by the own base station 1). Thereafter, the process proceeds to step S25, and the user terminal 2 (i, j) that is the base station cooperative communication target is selected as the user terminal 2 that performs multi-site connection in the cooperation area based on the information included in the response indicating that cooperation is possible. To do. Thereby, the own base station 1 (slave base station) and the master base station perform multi-site connection to the user terminal 2 (i, j) in the cooperation area.

If the number of cooperative communication requests received in step S20 is 2 or more, the process proceeds to step S40 in FIG.
Step S40: It is determined whether any of the cooperation areas related to the received cooperation communication request matches the cooperation area selected by the own base station 1. As a result, if there is a match, the process proceeds to step S41, and if there is no match, the process proceeds to step S30 in FIG.
Step S41: A cooperation rejection is returned to the base station 1 (slave base station) that is the transmission source of the cooperation communication request related to the cooperation area that is inconsistent with the cooperation area selected by the own base station 1. Thereafter, the process proceeds to step S27 in FIG. FIG. 14 illustrates the relationship between the base stations 1 at this time. In FIG. 14, the own base station 1 (A, slave base station) transmits a cooperative communication request to the adjacent base station 1 (B, master base station), and the own base station 1 (A, master base station). Has received a cooperative communication request from the adjacent base station 1 (B, slave base station). Further, the own base station 1 (A, master base station) has received the cooperative communication request from the adjacent base stations 1 (C, D, slave base stations). In this situation, priority is given to processing related to the base stations 1 (base stations 1 (A, B) in FIG. 14) that are mutually sending and receiving cooperative communication requests. Therefore, as the relationship between the base stations 1 shown in FIG.

  On the other hand, FIG. 15 illustrates the relationship between the base stations 1 when the cooperation area related to the cooperation communication request received by the own base station 1 does not match the cooperation area selected by the own base station 1. ing. In FIG. 15, its own base station 1 (A, slave base station) transmits a cooperative communication request to an adjacent base station 1 (B, master base station). Further, the own base station 1 (A, master base station) has received the cooperative communication request from the adjacent base stations 1 (C, D, slave base stations). In this situation, first, processing as a slave base station is performed. Therefore, the process proceeds to step S30.

  According to the present embodiment, it is possible to expand the range in which base station cooperative communication is possible in which a plurality of base stations cooperate to communicate with a mobile station, and to perform base station cooperative communication according to the state of wireless communication. The effect is obtained. As a result, it is possible to contribute to the improvement of the throughput of the user terminal at the cell boundary and to the improvement of the frequency utilization efficiency.

  As mentioned above, although embodiment of this invention was explained in full detail with reference to drawings, the specific structure is not restricted to this embodiment, The design change etc. of the range which does not deviate from the summary of this invention are included.

DESCRIPTION OF SYMBOLS 1 ... Base station, 2 ... Mobile station (user terminal), 3, 3A, 3B ... Cell, 4 ... Backbone network, 5 ... Core network, 6 ... Router, 10 ... Base station cooperation part (base station control apparatus), 11 ... Wireless unit, 12 ... User data / control message processing unit, 13 ... Wired unit, 14 ... Throughput calculation unit, 15 ... Data holding unit

Claims (8)

In a cellular mobile communication system in which a plurality of base stations are arranged and a continuous communication service area is constructed by the communication area of each base station, a base station controller provided for each base station,
Each base station controller is configured to be able to communicate with each other via a communication network,
Control of base station cooperation communication in which a plurality of base stations cooperate to communicate with a mobile station is performed in cooperation between base station control devices of base stations related to the base station cooperation communication,
The communication area is divided into a cooperation area that is a target of base station cooperation communication and a non-cooperation area that is not a target of base station cooperation communication,
The base station controller is
An area selection means for selecting a linked area or a non-linked area;
Single site connection target selection means for selecting a mobile station that performs single site connection in a non-cooperation area,
Multi-site connection target selection means for selecting a mobile station that performs multi-site connection in the cooperation area;
Based on the evaluation of the wireless communication status in the area selected by the area selection means, base station cooperation communication adjustment means for adjusting base station cooperation communication between the base station control devices of the base station involved in base station cooperation communication, With
The base station cooperation communication adjusting means is
When the area selection unit selects a non-cooperation area, when a cooperative communication request is received from a base station controller of another base station,
Based on the evaluation value of the single site connection capacity in the non-cooperation area selected by the area selection means and the evaluation value of the multi-site connection capacity in the cooperation area related to the received cooperation communication request, the base station in the cooperation area Determine whether to perform cooperative communication,
A base station controller characterized by that. The base station cooperation communication adjusting means is
When the area selection means selects a cooperation area,
Whether to transmit the evaluation value of the multi-site connection capacity in the cooperation area to the base station controller of the other base station related to the cooperation area selected by the area selection means, and perform base station cooperation communication in the cooperation area Receive the response of the
The base station control device according to claim 1. The base station cooperation communication adjusting means is
When the area selection unit selects a cooperation area, when receiving a cooperation communication request from a base station controller of another base station,
When the cooperation area related to the received cooperation communication request matches the cooperation area selected by the area selection means, the multi-site connection capacity of the cooperation area is determined in order to perform base station cooperation communication in the cooperation area. Send the evaluation value to the base station controller of the cooperative communication request source,
On the other hand, when the cooperation area related to the received cooperation communication request and the cooperation area selected by the area selection unit do not match, the evaluation value of the multisite connection capacity in the cooperation area selected by the area selection unit is displayed. Transmitting to the base station controller of the communication request source, and receiving a response as to whether or not to perform base station cooperation communication in the cooperation area selected by the area selection means,
The base station control device according to claim 2.   The base station control apparatus according to any one of claims 1 to 3, wherein the area selection unit records a selection rate for each area and selects the area based on the selection rate.   5. The base station control apparatus according to claim 4, wherein the area selection unit selects the area with the lowest selection rate.   The said area selection means calculates the average value of the said selection rate for every said area, and selects the said area where the ratio of this average value with respect to the latest said selection rate is the largest. Base station controller.   The base station control apparatus according to claim 1, wherein the area selection unit selects only the area where the mobile station is located. In a cellular mobile communication system in which a plurality of base stations are arranged and a continuous communication service area is constructed by the communication area of each base station,
A base station cooperation unit is provided for each base station, and each base station cooperation unit is configured to be able to communicate with each other via a communication network.
This is a base station cooperation communication control method in which base station cooperation communication in which a plurality of base stations cooperate to communicate with a mobile station is controlled in cooperation between base station cooperation sections of the base stations involved in the base station cooperation communication. And
The communication area is divided into a cooperation area that is a target of base station cooperation communication and a non-cooperation area that is not a target of base station cooperation communication,
The base station cooperation unit selecting a cooperation area or a non-cooperation area; and
The base station cooperation unit adjusts the base station cooperation communication between the base station cooperation units of the base station involved in the base station cooperation communication based on the evaluation of the wireless communication status in the selected area;
The base station cooperation unit selects a mobile station that performs single-site connection in a non-cooperation area according to the result of the adjustment, or selects a mobile station that performs multi-site connection in a cooperation area, and
When the base station cooperation unit selects a non-cooperation area and receives a cooperative communication request from a base station cooperation unit of another base station, the evaluation value of the single site connection capacity in the selected non-cooperation area, Based on the evaluation value of the multi-site connection capacity in the cooperation area related to the received cooperation communication request, determine whether to perform base station cooperation communication in the cooperation area,
The base station cooperation communication control method characterized by the above-mentioned.

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