JP5103233B2 - Base station control apparatus and base station control method - Google Patents

Description

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

In a wireless communication system that expands a wireless communication area by cell or sector, wireless terminals that are located between cells or between sectors can have high communication throughput due to interference from multiple base stations or multiple sectors and high user throughput. Can not.
Conventionally, MIMO (Multi Input Multi Output) is known as a technique for solving such a problem. MIMO is a technique for increasing user throughput by transmitting separate data signals at the same frequency from a plurality of transmitting antennas, and receiving and restoring them by a plurality of receiving antennas. In the conventional MIMO wireless communication system described in Patent Document 1, simultaneous communication is performed by MIMO between a plurality of base stations and one wireless terminal (hereinafter referred to as cooperation between multiple base stations). When a plurality of base stations are linked, the user throughput of wireless terminals between cells or between sectors can be improved.
JP 2007-134844 A

However, in the conventional MIMO wireless communication system described in Patent Document 1 described above, when a plurality of base stations are linked, a lot of radio resources are consumed. For this reason, there is a problem that when the amount of traffic increases, a congestion state occurs at an early stage, and the user throughput in the wireless communication system decreases.
The present invention has been made in view of such circumstances, and the object thereof is the downlink direction (the direction from the base station to the wireless terminal) by cooperation of the plurality of base stations between the plurality of base stations and one wireless terminal. It is an object of the present invention to provide a radio base station control device and a radio base station control method capable of preventing a congestion state at an early stage when the amount of traffic increases in a radio communication system that performs simultaneous communication.

The present invention has been made to solve the above-described problem, and one aspect of the present invention is a wireless communication that performs simultaneous downlink communication between a plurality of base stations and one wireless terminal by cooperation of the plurality of base stations. in the base station controller in the system, based on whether or not a limit on the plurality of base stations cooperate with the base station cooperation determination unit determines, on the determination of the base station cooperation determination unit based on the traffic volume at the base station, the base And a base station controller that controls the station.

  Moreover, one aspect of the present invention is characterized in that, in the base station control device, the base station cooperation determination unit determines that the base station cooperation is stopped when the traffic amount exceeds a predetermined threshold.

  Further, according to one aspect of the present invention, in the base station control device, the base station cooperation determination unit determines to stop the multiple base station cooperation only when the utilization rate of the multiple base station cooperation exceeds a predetermined threshold. It is characterized by doing.

  Further, according to one aspect of the present invention, in the base station control device, the base station cooperation determination unit sets an upper limit number of wireless terminals that perform base station cooperation when the traffic amount exceeds a predetermined threshold. Features.

  Further, according to one aspect of the present invention, in the base station control device, the base station cooperation determination unit sets a maximum number of base stations that perform base station cooperation when a traffic amount exceeds a predetermined threshold. Features.

  Further, one aspect of the present invention is characterized in that, in the base station control device, the base station cooperation determination unit releases the restriction on the cooperation of a plurality of base stations when the traffic amount falls below a predetermined threshold.

One embodiment of the present invention is a base station control method in a wireless communication system that performs simultaneous downlink communication between a plurality of base stations and a single wireless terminal in cooperation with the plurality of base stations, and the amount of traffic in the base station Base station control, comprising: determining whether or not to provide restrictions on cooperation between a plurality of base stations based on the base station; and controlling the base station based on the determination of the base station cooperation determination unit Is the method.

  Further, one aspect of the present invention is characterized in that, in the base station control method, the base station cooperation is stopped when the traffic amount exceeds a predetermined threshold.

  One embodiment of the present invention is characterized in that, in the above-described base station control method, the multiple base station cooperation is stopped only when the utilization rate of the multiple base station cooperation exceeds a predetermined threshold.

  Further, one aspect of the present invention is characterized in that, in the above-described base station control method, an upper limit number of wireless terminals that perform cooperation with a plurality of base stations is set when the traffic volume exceeds a predetermined threshold.

One aspect of the present invention is characterized in that, in the above-described base station control method, the maximum number of base stations that perform cooperation with a plurality of base stations is set when the traffic volume exceeds a predetermined threshold.

  Further, one aspect of the present invention is characterized in that, in the base station control method described above, the restriction on cooperation between a plurality of base stations is released when the traffic volume falls below a predetermined threshold.

  According to the present invention, since it is determined whether or not there is a restriction on cooperation between a plurality of base stations based on the traffic volume in the base station, and the base station is controlled based on the determination result, a plurality of base stations and one wireless terminal In a wireless communication system that performs simultaneous downlink communication through cooperation between a plurality of base stations, it is possible to prevent an early congestion state when the amount of traffic increases.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic diagram illustrating a configuration of a wireless communication system according to an embodiment of the present invention. In this figure, a plurality of base stations 2 are connected to a base station control device 1 by communication lines. The wireless terminal 3 performs wireless communication with the base station 2.

  In the following description, a configuration related to wireless communication in the downlink direction (direction from the base station 2 to the wireless terminal 3) according to the present invention will be described. The wireless terminal 3 located between the cells where the communicable ranges (cells) of the plurality of base stations 2 overlap each other communicates with only one of the base stations 2 when not cooperating with the plurality of base stations. On the other hand, when performing cooperation with a plurality of base stations, the wireless terminal 3 performs simultaneous communication with the plurality of base stations 2.

[First Embodiment]
FIG. 2 is a block diagram illustrating configurations of the base station 2 and the base station control device 1 in the present embodiment. The base station 2 includes a traffic monitoring unit 21 that monitors the traffic volume of the base station 2 and periodically transmits information on the traffic volume to the base station controller 1. The traffic volume represents the number of packets processed by the base station 2 and the number of wireless terminals 3. The base station control device 1 includes a traffic collection unit 11, a base station cooperation determination unit 12, and a base station control unit 13. The base station control device 1 of the present invention controls each base station 2 based on the traffic volume of each base station 2.

  The traffic collection unit 11 receives traffic amount information from each base station 2 controlled by the base station control device 1, and outputs the received traffic amount information to the base station cooperation determination unit 12. The base station cooperation determination unit 12 determines whether or not to limit the base station cooperation based on the input traffic volume information, and outputs the determination result to the base station control unit 13. The base station control unit 13 controls each base station 2 based on the determination result of the base station cooperation determination unit 12.

FIG. 3 is a flowchart showing a flow of determination processing of the base station cooperation determination unit 12 in the present embodiment. The processing shown in this figure starts when traffic volume information is received from each base station 2. The base station cooperation determination unit 12 performs the following process on all base stations 2 controlled by the base station control device 1. x and y are constants.
In step S1, the base station cooperation determination unit 12 determines whether or not the traffic amount of the base station 2 exceeds the threshold value x. If it exceeds the threshold value x, the process proceeds to the next step S2. On the other hand, if the threshold value x is not exceeded, the process proceeds to step S5.

  In next step S <b> 2, the base station cooperation determination unit 12 calculates a utilization rate of the base station 2 for cooperation with a plurality of base stations. The utilization rate of multiple base station cooperation represents the ratio of the amount of radio resources used in cooperation with multiple base stations in the total amount of radio resources. As the utilization rate of multiple base station cooperation, for example, the ratio of the number of packets communicating by multiple base station cooperation out of the total number of packets communicating can be used. The number of packets being communicated by cooperation with a plurality of base stations and the number of packets being communicated by the single base station 2 are acquired from the base station control unit 13.

  In the next step S3, the base station cooperation determination unit 12 determines whether or not the calculated usage rate exceeds a predetermined threshold y (for example, 80%). If the usage rate exceeds the threshold y, the process proceeds to the next step S4. On the other hand, if the usage rate does not exceed the threshold value y, the process is terminated. In the next step S4, the base station cooperation determination unit 12 determines to stop the cooperation of the plurality of base stations, outputs the determination result together with the ID for identifying the base station 2 to the base station control unit 13, and ends the process. . When the determination result is input, the base station control unit 12 controls the base station 2 specified by the ID to stop the multiple base station cooperation.

  On the other hand, in step S5, it is determined whether or not the base station 2 has stopped cooperation with a plurality of base stations. Information on whether or not the multiple base station cooperation is stopped is acquired from the base station control unit 12. When the multiple base station cooperation is stopped, the process proceeds to step S6. On the other hand, if the multiple base station cooperation is not stopped, the process is terminated. In the next step S6, it is determined that the cooperation between the plurality of base stations is started, the determination result is output to the base station control unit 13 together with the ID of the base station 2, and the process is terminated. When the determination result is input, the base station control unit 12 controls the base station 2 specified by the ID to start the multiple base station cooperation.

  As described above, according to the present embodiment, the base station control device 1 calculates the utilization rate of the cooperation between multiple base stations of the base station 2 whose traffic volume exceeds the threshold value. In addition, when the calculated utilization rate exceeds a predetermined threshold, the base station 2 stops cooperation with the plurality of base stations. As a result, when the traffic volume increases, the wireless communication system can be prevented from falling into a congestion state at an early stage.

[Second Embodiment]
Next explained is a base station control apparatus 1 according to the second embodiment of the invention. The base station control device 1 of the present embodiment sets the upper limit number of wireless terminals 3 that perform cooperation with a plurality of base stations in the base station 2 whose traffic volume exceeds a threshold value.

  FIG. 4 is a flowchart showing a flow of determination processing of the base station cooperation determination unit 12 in the present embodiment. The processing shown in this figure starts when traffic volume information transmitted from each base station 2 is received. The base station cooperation determination unit 12 performs the following process on all base stations 2 controlled by the base station control device 1. Here, α, β, γ, a, b, and c are constants. Further, α <β <γ. Further, a> b> c.

  In step S101, the base station cooperation determination unit 12 determines whether or not the traffic amount of the base station 2 exceeds the threshold value α. If the threshold value α is exceeded, the process proceeds to the next step S102. On the other hand, if the threshold value α is not exceeded, the process proceeds to step S107.

  In the next step S102, the base station cooperation determination unit 12 determines whether or not the traffic amount of the base station 2 exceeds the threshold value β. If it exceeds the threshold β, the process proceeds to the next step S104. On the other hand, if the threshold value β is not exceeded, the process proceeds to step S103. In step S103, the base station cooperation determination unit 12 determines that the upper limit number of wireless terminals 3 that perform base station cooperation in the base station 2 is set to a, and the determination result together with the ID of the base station 2 It outputs to the control part 13 and complete | finishes a process.

  In step S104, the base station cooperation determination unit 12 determines whether the traffic amount of the base station 2 exceeds the threshold γ. If it exceeds the threshold γ, the process proceeds to the next step S106. On the other hand, if the threshold value γ is not exceeded, the process proceeds to step S105. In step S105, the base station cooperation determination unit 12 determines that the base station 2 sets the upper limit number of wireless terminals 3 that perform cooperation with a plurality of base stations to b, and the determination result together with the ID of the base station 2 Output to the control unit 13.

  In step S105, the base station cooperation determination unit 12 determines that the upper limit number of the wireless terminals 3 that perform base station cooperation in the base station 2 is set to c, and the determination result together with the ID of the base station 2 It outputs to the control part 13 and complete | finishes a process.

  On the other hand, in step S107, it is determined whether or not the upper limit number of the wireless terminals 3 that perform the cooperation of the base station 2 with the plurality of base stations is set. Information on whether or not the upper limit number is set is acquired from the base station control unit 13. When the upper limit number is set, the process proceeds to step S108. On the other hand, if the upper limit number is not set, the process is terminated. In the next step S108, it is determined to cancel the setting of the upper limit number, and the determination result is output to the base station control unit 13 together with the ID of the base station 2, and the process is terminated. The base station control unit 13 controls the base station 2 specified by the input ID according to the determination result of the base station cooperation determination unit 12. Since other configurations are the same as those of the first embodiment, description thereof is omitted. In this embodiment, three threshold values and an upper limit number are provided. However, the present embodiment is not limited to this example, and one or more threshold values and an upper limit number may be provided.

  Thus, according to the present embodiment, the upper limit number of wireless terminals 3 that perform cooperation with a plurality of base stations is set in the base station 2 whose traffic volume exceeds the threshold. As a result, when the traffic volume increases, the wireless communication system can be prevented from falling into a congestion state at an early stage.

[Third Embodiment]
Next explained is a base station control apparatus 1 according to the third embodiment of the invention. The base station control device 1 of the present embodiment limits the maximum number of base stations 2 that perform cooperation with a plurality of base stations when the total traffic amount of all base stations 2 controlled by the base station control device 1 exceeds a threshold value. To do.

FIG. 5 is a flowchart showing the flow of processing of the base station cooperation determination unit 12 in the present embodiment. The processing shown in this figure starts when traffic volume information transmitted from each base station 2 is received. The base station cooperation determination unit 12 in this embodiment holds a restriction table in which the maximum number of base stations corresponding to the traffic volume is stored.
First, in step S201, the base station cooperation determination unit 12 calculates the total traffic amount of all base stations 2 controlled by the base station control apparatus 1. In the next step S202, the maximum number of base stations corresponding to the calculated total value is acquired from the restriction table. In the next step S203, the acquired maximum number of base stations is output to the base station control unit 13, and the process is terminated. The base station control unit 13 controls each base station 2 so that the maximum number of base stations 2 that cooperate with a plurality of base stations becomes the input maximum number of base stations. Since other configurations are the same as those of the first or second embodiment, the description thereof is omitted.

  Thus, according to this embodiment, when the total value of the traffic volume exceeds the threshold value, the maximum number of base stations 2 that perform cooperation with a plurality of base stations is limited. As a result, when the traffic volume increases, the wireless communication system can be prevented from falling into a congestion state at an early stage.

The embodiments of the present invention have been described in detail above with reference to the drawings. However, the specific configuration is not limited to the above-described one, and various design changes and the like can be made without departing from the scope of the present invention. Is possible.
For example, the traffic monitoring unit 21 in each base station 2 may be in the base station control device 1, and the traffic collection unit 11 may have the function of the traffic monitoring unit 21.
In the present embodiment, the base station control device 1 restricts cooperation between a plurality of base stations when the traffic amount becomes larger than the threshold value. However, when the state where the traffic amount becomes larger than the threshold value continues for a predetermined period or longer. The base station cooperation may be limited.
In the present embodiment, the base station control device 1 sets the threshold value for setting the restriction and the threshold value for releasing the restriction to the same value, but may use different values.

It is the schematic which shows the structure of the radio | wireless communications system of this invention. It is a block diagram which shows the structure of the base station and base station control apparatus in 1st Embodiment. It is a flowchart which shows the flow of the determination process of the base station cooperation determination part in this embodiment. It is a flowchart which shows the flow of the determination process of the base station cooperation determination part in 2nd Embodiment. It is a flowchart which shows the flow of the determination process of the base station cooperation determination part in 3rd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Base station control apparatus 2 ... Base station 3 ... Wireless terminal 11 ... Traffic collection part 12 ... Base station cooperation determination part 13 ... Base station control part 21 ... Traffic monitoring part

Claims (4)

In a base station control apparatus in a wireless communication system that performs simultaneous downlink communication by cooperation of a plurality of base stations between a plurality of base stations and one wireless terminal,
Based on the traffic volume at the base station, it is determined whether or not to limit the multi-base station cooperation so that the multi-base station cooperation is stopped when the traffic volume exceeds a predetermined threshold, in this case, Only when the utilization rate of multiple base station cooperation exceeds a predetermined threshold, a base station cooperation determination unit that determines to stop multiple base station cooperation,
Based on the determination of the base station cooperation determination unit, a base station control unit that controls the base station,
A base station control device comprising: The base station control device according to claim 1 , wherein the base station cooperation determination unit releases the restriction on the cooperation of the plurality of base stations when the traffic amount falls below a predetermined threshold. A base station control method in a wireless communication system for performing simultaneous downlink communication by cooperation of a plurality of base stations between a plurality of base stations and one wireless terminal,
Based on the traffic volume at the base station, it is determined whether or not to limit the multi-base station cooperation so that the multi-base station cooperation is stopped when the traffic volume exceeds a predetermined threshold, in this case, Only when the utilization rate of multiple base station cooperation exceeds a predetermined threshold, determining to stop multiple base station cooperation;
Controlling a base station based on the determination of the base station cooperation determination unit;
A base station control method comprising: The base station control method according to claim 3, wherein when the traffic volume falls below a predetermined threshold, the restriction on cooperation with a plurality of base stations is released.

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