JP5964698B2 - Wireless communication system - Google Patents

Description

  The present invention relates to a wireless communication system that performs multiple input multiple output (MIMO) communication between a terminal and a plurality of base stations that are candidates for wireless connection of the terminal.

  In a wireless communication system in which a certain area is covered by a plurality of base stations, user throughput may be reduced due to radio wave interference from adjacent base stations at the boundary of the coverage area of each base station.

  As a technique for preventing a decrease in user throughput, a base station cooperation MIMO communication technique is known. In base station cooperation MIMO communication, a radio wave received by a terminal from an adjacent base station is utilized not as an interference wave but as a desired wave. However, in this base station cooperation MIMO communication, since the radio band of the adjacent base station is also used, there is a possibility that the user throughput is lowered in the entire radio communication system.

  For such a problem, a predetermined control server determines whether or not the base station cooperation MIMO communication is necessary based on the CINR (Carrier to Interference plus Noise Ratio), the user throughput, and the position of the wireless terminal in the terminals under the base station. There is a wireless communication system to judge (see Patent Document 1 and Patent Document 2).

  In the wireless communication system of Patent Document 1, the distribution of the received radio wave level of each terminal, that is, the number of terminals within the coverage area of the base station and the coverage area of other base stations, and the coverage area of the base station and other base stations. Whether or not the base station cooperative MIMO communication is necessary is determined based on the ratio of the number of terminals in the coverage area of the station.

  In the wireless communication system of Patent Document 2, the necessity of base station cooperation MIMO communication is determined for each terminal based on the amount of wireless bandwidth required by each terminal.

JP 2009-2119010 A JP 2010-233087 A

  When base station-linked MIMO communication is performed in the wireless communication systems of Patent Literatures 1 and 2, it is possible to improve the throughput of the terminals located at the boundary of the cover area. However, the bandwidth resource utilization efficiency of the entire system may be lower than the case where base station cooperation MIMO communication is not performed.

  In addition, when base station-linked MIMO communication is not performed in the wireless communication systems of Patent Documents 1 and 2, it is impossible to improve the throughput of a terminal located at the cover area boundary. Furthermore, the bandwidth resource utilization efficiency of the entire system may be lower than when base station-linked MIMO communication is performed.

  Furthermore, in the wireless communication systems of Patent Documents 1 and 2, since the necessity of base station cooperation MIMO communication is not determined for each flow, the use efficiency of band resources may be reduced when viewed from the whole wireless communication system.

  Furthermore, since the desired throughput of the flows of Patent Documents 1 and 2 is not taken into consideration, there are cases where the allocated bandwidth resources are excessive regardless of whether or not the base station cooperation MIMO communication is performed. Thus, the bandwidth resource utilization efficiency may be worse than when the desired flow throughput is taken into account.

  The present invention has been made in consideration of the above-described problems, and an object of the present invention is to provide a wireless communication system capable of preventing a reduction in use efficiency of band resources in the entire wireless communication system.

  A wireless communication system according to the present invention includes a terminal that receives a plurality of flows, a plurality of base stations that are candidates for wireless connection of the terminal, and a control server, wherein the control server receives the terminal For each flow, when the throughput information of the flow is received, the throughput indicated by the received throughput information of the flow is compared with the transmission capability due to the free capacity of the band resource for each base station, and the throughput of the flow is When the transmission capability is larger than the transmission capability, base station cooperation MIMO (Multiple Input Multiple Output) communication by each base station is selected, and when the throughput of the flow is smaller than the transmission capability, distribution is performed only from a single base station. It is characterized by being.

  In the wireless communication system, the base station cooperative MIMO communication or distribution from only a single base station is performed according to a change in the required data rate of the flow.

  According to the wireless communication system of the present invention, the wireless communication system includes: a terminal that receives a plurality of flows; a plurality of base stations that are candidates for wireless connection of the terminal; and a control server, wherein the control server receives the terminal For each flow, when the throughput information of the flow is received, the throughput indicated by the received throughput information of the flow is compared with the transmission capability due to the free capacity of the band resource for each base station, and the throughput of the flow is When base station cooperation MIMO communication by each base station is selected when the transmission capacity is larger than the transmission capacity, and when the throughput of the flow is smaller than the transmission capacity, it is delivered only from a single base station Therefore, it is possible to improve the use efficiency of band resources in the entire wireless communication system.

It is explanatory drawing of the radio | wireless communications system which concerns on embodiment of this invention. FIG. 2A is an explanatory diagram of the configuration of the control server, and FIG. 2B is an explanatory diagram of the configuration of the table recording unit. It is explanatory drawing of an adjacent base station table, a connection base station table, a propagation environment table, a base station cooperation pattern table, and a throughput table. 4A to 4C are explanatory diagrams of the flow table. It is explanatory drawing about the procedure of base station cooperation MIMO communication. It is explanatory drawing about the process sequence of a base station cooperation pattern. FIG. 7A is an explanatory diagram of conventional bandwidth resource utilization efficiency, and FIG. 7B is an explanatory diagram of bandwidth resource utilization efficiency of the wireless communication system according to the embodiment of the present invention. FIG. 8A is an explanatory diagram of the conventional band resource utilization efficiency, and FIG. 8B is an explanatory diagram of the band resource utilization efficiency of the wireless communication system according to the embodiment of the present invention.

  Embodiments of the present invention will be described below with reference to the drawings. 1 is an explanatory diagram of the wireless communication system 10 of the present invention, FIG. 2A is an explanatory diagram of the configuration of the control server 20, FIG. 2B is an explanatory diagram of the configuration of the table storage unit 28, and FIG. FIG. 4 is an explanatory diagram of an adjacent base station table 30, a connected base station table 32, a propagation environment table 34, a base station cooperation pattern table 36, and a throughput table 38, and FIGS. 4A to 4C are explanatory diagrams of the flow table 40. FIG. 5 is an explanatory diagram for the procedure of base station cooperation MIMO communication, and FIG. 6 is an explanatory diagram for the processing procedure of base station cooperation pattern.

  The wireless communication system 10 includes a terminal (MS) 12 such as a computer or a mobile phone having a communication function, base stations (BS) 14a and 14b to which the terminal 12 is wirelessly connected, a router 16, and a control server 20. Prepare. The base stations 14 a and 14 b are connected to the backbone network 18. The backbone network 18 is connected to the core network 22 via the router 16 and the router 21, and is connected to the Internet 23.

  The terminal 12 is located within the common cover area of the base stations 14a and 14b. The base stations 14a and 14b can perform MIMO communication with the terminal 12 through base station cooperation.

  The router 16 measures the throughput of a flow that is a flow of data including content stored as data such as video and music transmitted to the backbone network 18 via the Internet 23 and the core network 22, and also measures the flow. The control server 20 is notified of the achieved throughput. The router 16 identifies the flow with reference to the source IP address, the destination IP address, the port number, and the like.

  The control server 20 includes a table management unit 24, a control unit 26, and a table storage unit 28. The table management unit 24 manages each table in the table storage unit 28. The control unit 26 performs selection control regarding the base station cooperation pattern of the base station cooperation MIMO communication for each flow.

  The table storage unit 28 includes an adjacent base station table 30, a connected base station table 32, a propagation environment table 34, a base station cooperation pattern table 36, a throughput table 38, and a flow table 40.

  The adjacent base station table 30 is a table in which identifiers of adjacent base stations are set for each base station. The connected base station table 32 is a table in which identifiers of base stations to be wirelessly connected are set for each terminal. The propagation environment table 34 is a table in which propagation environment information (CINR) between a terminal and a base station that is wirelessly connected is set for each terminal. The base station cooperation pattern table 36 is a table in which a communication pattern for wireless connection for each terminal, specifically, a pattern for wireless connection with one base station or a pattern for base station cooperation MIMO communication with a plurality of base stations is set. It is. The throughput table 38 is a table in which the throughput for the pattern set in the base station cooperation pattern table 36 is set for each terminal. The flow table 40 is a table in which a desired throughput for each flow, a pattern set in the base station cooperation pattern table 36 that satisfies the desired throughput, and a state representing a flow distribution status are set.

  Next, base station cooperation MIMO communication in the wireless communication system 10 will be described with reference to FIGS.

  First, in the wireless communication system 10, the adjacent base station table 30 is set by the table management unit 24 as an initial setting (step S1). As shown in FIG. 1, the adjacent base station table 30 is set corresponding to the base station adjacent to the base station 14a being the base station 14b (FIG. 3). The table management unit 24 may set the adjacent base station table 30 based on the position information acquired by the GPS receiver, for example, with the identifier of the adjacent base station for each base station.

  Next, the terminal 12 transmits propagation environment information to the control server 20 via the base station 14a or the base station 14b (step S2).

  The table management unit 24 of the control server 20 that has received the propagation environment information sets the connection base station table 32, the propagation environment table 34, and the base station cooperation pattern table 36 based on the acquired propagation environment information (step). S3). The connection base station table 32 is set corresponding to the base stations from which the radio waves to be transmitted reach the terminal 12 being the base stations 14a and 14b (FIG. 3). Further, the propagation environment table 34 is set based on the propagation environment information between the terminal 12 and the base stations 14a and 14b (FIG. 3).

  The table management unit 24 sets the base station cooperation pattern table 36 based on the connected base station table 32. Since the base stations from which the radio waves to be transmitted reach the terminal 12 are the base stations 14a and 14, the base station cooperation pattern table 36 includes a single base station 14a, a single base station 14b, Three patterns of base station cooperation between the base stations 14a and 14b are set (FIG. 3).

  The table management unit 24 sets the throughput table 38 based on the propagation environment table 34 (step S4). The table management unit 24 calculates the throughput for each pattern based on the propagation environment information in the propagation environment table 34 and sets it in the throughput table 38. In the throughput table 38, the pattern 1 is set to 40 Mbps, the pattern 2 is set to 10 Mbps, and the pattern 3 is set to 50 Mbps. In pattern 3, the total throughput of patterns 1 and 2 is set as the base station cooperation.

  The table management unit 24 performs the processing from step S1 to step S4 every time the propagation environment information transmitted from the terminal 12 at predetermined time intervals is acquired, and updates each table.

  The router 16 notifies the control server 20 of the throughput information of the flow delivered to the terminal 12 and the identification information of the terminal 12 (step S5).

  Based on the flow throughput information notified from the router 16 and the identification information of the terminal 12, the table management unit 24 sets the desired throughput of the flow (step S6, FIG. 4A). In the flow table 40, the throughput of the flow F1 (another flow for which the base station cooperation pattern has already been determined) is 21 Mbps, and the throughput of the flow F2 (the flow for which the router 16 has notified the throughput information and the terminal 12 identification information) is 20 Mbps. Is set.

  The control unit 26 selects the base station cooperation pattern from the base station cooperation pattern table 36 for the flow F2 of the flow table 40, and sets the base station cooperation pattern of the flow F2 (step S7, FIG. 4B).

  This base station cooperation pattern is set based on the processing procedure shown in FIG. By comparing the transmission capacity based on the free capacity of the band resource with the base station cooperation pattern of the base station alone and the throughput required by the flow, the base station cooperation pattern whose transmission capacity is larger than the throughput required by the flow is searched ( Step S20).

  Here, the throughput of the base station cooperation pattern is assumed to be obtained by subtracting the bandwidth resource usage amount due to the flow that has already flowed from the throughput of the base station cooperation pattern set in the throughput table 38.

  When there is one base station cooperation pattern that satisfies the condition, the base station selects that pattern (YES in step S20). Further, when there are a plurality of base station cooperation patterns that satisfy the conditions, the base station cooperation pattern with the highest throughput is selected.

  If there is no base station cooperation pattern that satisfies the condition for the base station cooperation pattern of the base station alone (NO in step S20), the transmission capability by the free capacity of the band resource by the base station cooperation pattern in which a plurality of base stations cooperate. Are compared with the throughput required by the flow, and a base station cooperation pattern in which a plurality of base stations having a transmission capability larger than the throughput required by the flow is searched among the base station cooperation patterns (step S22).

  When there is one base station cooperation pattern in which a plurality of base stations satisfying the condition cooperates, the relevant pattern is selected (step S22 YES step S23). When there are a plurality of base station cooperation patterns that satisfy the condition, a base station cooperation pattern in which a plurality of base stations having the largest transmission capability cooperate is selected.

  When the above-mentioned conditions are not satisfied (NO in step S22), among the base station cooperation patterns in which a plurality of base stations cooperate, the bandwidth resource due to the flow already flowing from the throughput of the base station cooperation pattern set in the throughput table 38 A base station cooperation pattern having the largest transmission capability shown excluding the usage amount is selected (step S23).

  When the base station cooperation pattern of flow F2 is selected, pattern 1 is set as the base station cooperation pattern and Active is set as the state for the flow F1 of the flow table 40. As a result, the throughput of pattern 1 is reduced by the throughput allocated to flow F1 to 19 Mbps.

  Further, since the throughput of the flow F2 is 20 Mbps, the throughput is larger than those of the patterns 1 and 2 (NO in step S20). The throughput of pattern 3 is larger than the throughput of flow F2. Therefore, pattern 3 is set as the base station cooperation pattern in the flow F2 (step S22 YES step S23 FIG. 4B).

  The control unit 26 transmits information on the distribution method for the terminal 12 of the flow F2 to the base stations 14a and 14b via the router 16 (step S8). That is, based on the update of the flow table 40, the control unit 26 continues to transmit the flow F1 with the pattern 1 to the base station 14a, that is, continues to transmit with the base station 14a alone, and the pattern 3 for the flow F2. Is transmitted, that is, information indicating that transmission is performed by the base station cooperative MIMO communication of the base stations 14a and 14b. In addition, the base station 14b is notified that the flow F2 is to be transmitted by the base station cooperation MIMO communication of the base stations 14a and 14b. Further, based on the instruction from the control unit 26, the table management unit 24 sets the status field of the flow F2 in the flow table 40 to Active, and notifies the router 16 that the distribution environment is ready (step S9, FIG. 4C).

  The router 16 that has received the message that the distribution environment is ready updates the routing table and transfers the flow F2 to the terminal 12 via the base stations 14a and 14b (step S10).

  When the throughput of the flow F1 is 2 Mbps and the throughput of the flow F2 is 7 Mbps, the table management unit 24 determines the desired throughput of the flow based on the flow throughput information notified from the router 16 and the identification information of the terminal 12. Is set (step S6). In the flow table 40, the throughput of the flow F1 (another flow whose base station cooperation pattern has already been determined) is 2 Mbps, and the throughput of the flow F2 (the flow for which the router 16 has notified the throughput information and the terminal 12 identification information) is 7 Mbps. Is set.

  The control unit 26 selects a base station cooperation pattern from the base station cooperation pattern table 36 for the flow F2 of the flow table 40, and sets the base station cooperation pattern of the flow (step S7).

  When the base station cooperation pattern of flow F2 is selected, pattern 1 is set as the base station cooperation pattern and Active is set as the state for the flow F1 of the flow table 40. As a result, the throughput of pattern 1 is reduced by the throughput allocated to the flow F1 to 38 Mbps. Here, since the throughput of flow F2 is 7 Mbps, pattern 1 (38 Mbps) and pattern 2 (10 Mbps) are listed as candidates. Therefore, pattern 1 which is the base station cooperation pattern with the highest throughput is set as the base station cooperation pattern of flow F2 (YES in step S20).

  The control unit 26 transmits information on the distribution method for the terminal 12 of the flow F2 to the base station 14a (step S8). That is, based on the update of the flow table 40, the control unit 26 continues to transmit the flow F1 to the base station 14a with the pattern 1, that is, continues to transmit the base station 14a alone, and the flow F2 to the flow F2 Is transmitted in the pattern 2, that is, the fact that the base station 14a is transmitted alone is transmitted.

  Hereinafter, the router 16 transfers the flow to the terminal 12 via the base stations 14a and 14b.

  FIG. 7 is a diagram in which when a flow is distributed at time (time slot) T, a band resource is represented as time T on the horizontal axis and a subcarrier of the band resource on the vertical axis. FIG. 7B is an explanatory diagram of band resource utilization efficiency of the wireless communication system according to the embodiment of the present invention. Note that F is a subcarrier axis component of all band resources of the base station.

  In the conventional wireless communication system, based on the ratio of the number of terminals within the coverage area of the base station and outside the coverage area of the other base station, and the number of terminals within the coverage area of the base station and the coverage area of the other base station. The necessity of base station cooperation MIMO communication has been determined. Further, based on the amount of radio bandwidth required by each terminal, whether or not the base station cooperative MIMO communication is necessary is determined for each terminal. As a result, when the terminal receives a plurality of flows, a band resource corresponding to the total desired throughput of each flow is used in each linked base station (FIG. 7A).

  On the other hand, since the radio communication system 10 considers the base station cooperation pattern for each flow, as shown in FIG. 7B, for the flow F1, there is a base station cooperation pattern (pattern 1) of the base station alone. In the flow F2, a base station cooperation pattern (pattern 3) by a plurality of base stations is set.

  Here, the utilization efficiency of band resources between the conventional wireless communication system and the wireless communication system 10 is compared. The bandwidth resource utilization efficiency is compared using the following definition formula.

  Bandwidth resource utilization efficiency E = throughput S / bandwidth resource usage R

  As described above, the throughput of pattern 1 is 40 Mbps, the throughput of pattern 2 is 10 Mbps, the throughput of flow F1 is 21 Mbps, and the throughput of flow F2 is 20 Mbps.

  Both the conventional throughput SX and the throughput SY of the wireless communication system 10 are as follows.

  Throughput SX, SY = throughput of flow F1 + throughput of flow F2 = 42 (Mbps)

  First, the conventional bandwidth resource usage RX is obtained. With respect to the conventional band resource usage amount RX, if the bandwidth resource free capacity RXBa in the base station 14a, the bandwidth resource usage amount RXa1 of the flow F1, and the bandwidth resource usage amount RXa2 of the flow F2, the ratios are as follows: .

  RXBa: RXa1: RXa2 = (360/50) :( 840/50) :( 800/50) = 9: 21: 20

  Similarly, assuming that the available bandwidth RXBb of the band resource in the base station 14b, the band resource usage RXb1 of the flow F1, and the band resource usage RXb2 of the flow F2, the ratios are as follows.

  RXBb: RXb1: RXb2 = (360/50) :( 840/50) :( 800/50) = 9: 21: 20

  Accordingly, the conventional bandwidth resource usage RX is as follows.

  Bandwidth resource usage RX = [T × F × {(21/50) + (20/50)}] + [T × F × {(21/50) + (20/50)}] = (82/50 ) TF

  Next, a bandwidth resource usage amount RY of the wireless communication system 10 is obtained. Regarding the bandwidth resource usage RY, assuming that the bandwidth resource free capacity RYBa in the base station 14a, the bandwidth resource usage RYa1 of the flow F1, and the bandwidth resource usage RYa2 of the flow F2, the ratios are as follows.

  RYBa: RYa1: RYa2 = (150/50) :( 1050/50) :( 800/50) = 3: 21: 16

  Similarly, assuming that the free capacity RYBb of the band resource in the base station 14b, the use amount RYb1 of the band resource of the flow F1, and the use amount RYb2 of the band resource of the flow F2, the ratios are as follows.

  RYBb: RYb1: RYb2 = (300/50): 0: (200/50) = 6: 0: 4

  Accordingly, the bandwidth resource usage amount RY of the wireless communication system 10 is as follows.

  Bandwidth resource usage RY = [T × F × {(21/40) + (16/40)}] + [T × F × {(0/10) + (4/10)}] = (53/40 ) TF

  When the ratio between the bandwidth resource utilization efficiency EX of the conventional wireless communication system and the bandwidth resource utilization efficiency EY of the wireless communication system 10 is calculated,

  EY / EX = 328/265 = 1.24

  Next, the transmission capability BE according to the free capacity of the band resource between the conventional wireless communication system and the wireless communication system 10 is compared. Here, the throughput in the area covered by the base station 14a and not subject to interference from the base station 14b is 60 Mbps, and the throughput in the area covered by the base station 14b and not subject to interference from the base station 14a. Is 50 Mbps.

  First, the transmission capability BEX by the free capacity of the band resource of the conventional wireless communication system is obtained. In FIG. 7A, the transmission capacity BEXa based on the free capacity when the free capacity RXBa of the base station 14a is used for single transmission of the base station 14a outside the cover area of the base station 14b is as follows.

  BEXa = 60 × {9 / (9 + 21 + 20)} = 54/5

  Similarly, when the free capacity RXBb of the base station 14b is used for independent transmission of the base station 14b outside the cover area of the base station 14a, the transmission capacity BEXb based on the free capacity is as follows.

  BEXb = 50 × {9 / (9 + 21 + 20)} = 45/5

  Therefore, the transmission capability BEX by the free capacity of the band resource in the conventional wireless communication system is as follows.

  BEX = BEXa + BEXb = 99/5

  Next, the transmission capability BEY based on the free capacity of the band resource of the wireless communication system 10 is obtained. In FIG. 7B, outside the coverage area of the base station 14b, the transmission capacity BEYa based on the free capacity when the free capacity RYBa of the base station 14a is used for single transmission of the base station 14a is as follows.

  BEYa = 60 × {3 / (3 + 21 + 16)} = 18/4

  Similarly, when the free capacity RYBb of the base station 14b is used for single transmission of the base station 14b outside the cover area of the base station 14a, the transmission capacity BEYb based on the free capacity is as follows.

  BEYb = 50 × {6 / (6 + 0 + 4)} = 30

  Therefore, the transmission capability BEY due to the free capacity of the band resource in the wireless communication system 10 is as follows.

  BEY = BEYa + BEYb = 138/4

  When calculating the ratio between the transmission capability BEX due to the free capacity of the bandwidth resource of the conventional wireless communication system and the transmission capability BEY due to the free capacity of the bandwidth resource of the wireless communication system 10,

  BEY / BEX = 115/66 = 1.74

  8 is an explanatory diagram of band resource utilization efficiency when the throughputs of the flow F1 and the flow F2 are different from those of FIG. 7, and FIG. 8A is an explanatory diagram of conventional band resource utilization efficiency. FIG. 8B is an explanatory diagram of band resource utilization efficiency of the wireless communication system according to the embodiment of the present invention.

  In the conventional wireless communication system, as in the case shown in FIG. 7A, when the terminal receives a plurality of flows, the band resources corresponding to the total desired throughput of each flow are linked to each base station. (FIG. 8A).

  On the other hand, since the radio communication system 10 considers the base station cooperation pattern for each flow, as shown in FIG. 8B, for the flows F1 and F2, a base station cooperation pattern (pattern) for the base station alone is used. 1) is set.

  In the case of FIG. 8B, the throughput of pattern 1 is 40 Mbps, the throughput of pattern 2 is 10 Mbps, the throughput of flow F1 is 2 Mbps, and the throughput of flow F2 is 7 Mbps.

  Assuming that the conventional bandwidth resource RXBa in the conventional base station 14a, the bandwidth resource usage amount RXa1 of the flow F1, and the bandwidth resource usage amount RXa2 of the flow F2, the ratios are as follows.

  RXBa: RXa1: RXa2 = (1640/50) :( 80/50) :( 280/50) = 41: 2: 7

  Similarly, assuming that the available bandwidth RXBb of the band resource in the base station 14b, the band resource usage RXb1 of the flow F1, and the band resource usage RXb2 of the flow F2, the ratios are as follows.

  RXBb: RXb1: RXb2 = (410/50) :( 20/50) :( 70/50) = 41: 2: 7

  Accordingly, the conventional bandwidth resource usage RX is as follows.

  Bandwidth resource usage RX = [T × F × {(2/50) + (7/50)}] + [T × F × {(2/50) + (7/50)}] = (18/50 ) TF

  Next, assuming that the free capacity RYBa of the band resource in the base station 14a in the radio communication system 10, the use amount RYa1 of the band resource of the flow F1, and the use amount RYa2 of the band resource of the flow F2, the ratios are as follows. .

  RYBa: RYa1: RYa2 = (31/40) :( 2/40) :( 7/40) = 31: 2: 7

  Similarly, assuming that the free capacity RYBb of the band resource in the base station 14b, the use amount RYb1 of the band resource of the flow F1, and the use amount RYb2 of the band resource of the flow F2, the ratios are as follows.

  RYBb: RYb1: RYb2 = (10/10): 0: 0 = 10: 0: 0

  Accordingly, the bandwidth resource usage amount RY of the wireless communication system 10 is as follows.

  Bandwidth resource usage RY = [T × F × {(2/40) + (7/40)}] + [T × F × {(0/10) + (0/10)}] = (9/40 ) TF

  When the ratio between the bandwidth resource utilization efficiency EX of the conventional wireless communication system and the bandwidth resource utilization efficiency EY of the wireless communication system 10 is calculated,

  EY / EX = 720/450 = 1.6

  Next, the transmission capability BE according to the free capacity of the band resource between the conventional wireless communication system and the wireless communication system 10 is compared. Here, the throughput in the area covered by the base station 14a and not subject to interference from the base station 14b is 60 Mbps, and the throughput in the area covered by the base station 14b and not subject to interference from the base station 14a. Is 50 Mbps.

  First, the transmission capability BEX by the free capacity of the band resource of the conventional wireless communication system is obtained. In FIG. 8A, the transmission capacity BEXa based on the free capacity when the free capacity RXBa of the base station 14a is used for independent transmission of the base station 14a outside the cover area of the base station 14b is as follows.

  BEXa = 60 × {41 / (41 + 2 + 7)} = 2460/50

  Similarly, when the free capacity RXBb of the base station 14b is used for independent transmission of the base station 14b outside the cover area of the base station 14a, the transmission capacity BEXb based on the free capacity is as follows.

  BEXb = 50 × {41 / (41 + 2 + 7)} = 2050/50

  Therefore, the transmission capability BEX by the free capacity of the band resource in the conventional wireless communication system is as follows.

  BEX = BEXa + BEXb = 451/5

  Next, the transmission capability BEY based on the free capacity of the band resource of the wireless communication system 10 is obtained. In FIG. 8B, outside the coverage area of the base station 14b, the transmission capacity BEYa based on the free capacity when the free capacity RYBa of the base station 14a is used for single transmission of the base station 14a is as follows.

  BEYa = 60 × {31 / (31 + 2 + 7)} = 93/2

  Similarly, when the free capacity RYBb of the base station 14b is used for single transmission of the base station 14b outside the cover area of the base station 14a, the transmission capacity BEYb based on the free capacity is as follows.

  BEYb = 50 × {10 / (10 + 0 + 0)} = 50

  Therefore, the transmission capability BEY due to the free capacity of the band resource in the wireless communication system 10 is as follows.

  BEY = BEYa + BEYb = 193/2

  When calculating the ratio between the transmission capability BEX due to the free capacity of the bandwidth resource of the conventional wireless communication system and the transmission capability BEY due to the free capacity of the bandwidth resource of the wireless communication system 10,

  BEY / BEX = 965/902 = 1.06

  In the conventional wireless communication system, it is determined whether to perform base station cooperation MIMO for each terminal. Therefore, when performing base station cooperation MIMO communication to a terminal, both flow F1 and flow F2 are distributed by base station cooperation MIMO communication, and each base station performs base station cooperation MIMO communication. Necessary bandwidth resources are required for both flows F1 and F2.

  On the other hand, in the wireless communication system 10, when the throughput information of the flow is received for each flow received by the terminal, the throughput indicated by the received throughput information of the flow and the free capacity of the band resource for each base station Compared with the transmission capability by. Based on the comparison result, the base station cooperation pattern is selected for the flows F1 and F2. For example, for the flow F1, the bandwidth resource required in each base station for performing base station cooperation MIMO communication is not used, and in each base station for performing base station cooperation MIMO communication only for the flow F2. It is possible to select to use the required bandwidth resources. In addition, for the flow F1 and the flow F2, it is possible to select that the base station 14a communicates alone. As described above, by selecting an appropriate base station cooperation pattern when the flow throughput information is received, the wireless communication system 10 can use the bandwidth resources more efficiently than the conventional wireless communication system. The transmission capability by capacity can be improved.

  The wireless communication system 10 includes a terminal 12 that receives a plurality of flows, base stations 14a and 14b that are candidates for wireless connection of the terminal 12, and a control server 20, and the control server 20 receives the terminal 12 For each flow, when the throughput information of the flow is received, the throughput indicated by the received throughput information of the flow is compared with the transmission capability based on the free capacity of the band resources of the base stations 14a and 14b. When the transmission capacity of each of the base stations 14a and 14b is larger than the transmission capacity of the base stations 14a and 14b, the base station cooperation MIMO communication by the base stations 14a and 14b is selected, and the throughput of the flow F2 is more than at least one of the transmission capabilities of each base station Is also distributed from only a single base station, the bandwidth resource in the entire wireless communication system It is possible to improve the scan utilization efficiency of.

  In addition, when the throughput of the flow F2 is larger than the transmission capability of the base stations 14a and 14b, the flow F2 is distributed by base station cooperation MIMO communication. Further, each flow is distributed only from the base station cooperative MIMO communication or a single base station according to a change in desired throughput. That is, it is possible to adaptively change the cooperation pattern in accordance with a change in desired throughput.

  It should be noted that the present invention is not limited to the above-described embodiment, and various configurations can be adopted without departing from the gist of the present invention.

  Further, the control unit 26 sets the base station cooperation pattern for each flow (step S7) so that the requested data rate is set when the flow is in the variable bit rate format and the requested data rate is changed or during the flow distribution. You may make it carry out when it changes. In such a case, if the requested data rate is changed during the flow distribution, it can be dealt with by starting the processing from the above-described step S5 using it as a trigger.

  Furthermore, an OpenFlow switch may be provided in the base stations 14a and 14b so that the base station cooperative MIMO communication is determined for each flow.

10. Wireless communication system 12 ... Terminal (MS)
14 ... Base station (BS)
16, 21 ... Router 18 ... Backbone network 20 ... Control server 22 ... Core network 23 ... Internet 24 ... Table management unit 26 ... Control unit 28 ... Table storage unit 30 ... Neighboring base station table 32 ... Connection base station table 34 ... Propagation environment Table 36 ... Base station cooperation pattern table 38 ... Throughput table 40 ... Flow table

Claims (2)

A terminal that receives multiple flows;
A plurality of base stations that are candidates for wireless connection of the terminal;
A control server;
With
When the control server receives throughput information of the flow for each flow received by the terminal, the control server transmits the throughput indicated by the received throughput information of the flow and the free capacity of the band resource for each base station. And compare
When the throughput of the flow is larger than the transmission capability, select base station cooperation MIMO (Multiple Input Multiple Output) communication by each base station,
A wireless communication system, wherein the flow is distributed from only a single base station when the throughput of the flow is smaller than the transmission capability. The wireless communication system according to claim 1, wherein
A wireless communication system, wherein the base station cooperative MIMO communication or distribution from only a single base station is performed in accordance with a change in the required data rate of the flow.

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