JP5369594B2 - Wireless communication system, handover storage device, control method, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless communication system avoiding a handover failure even when quality of a handover source is rapidly deteriorated. <P>SOLUTION: On the basis of position information of a mobile terminal 103 and information of a specific area, a handover storage device 108 determines whether or not the mobile terminal 103 gets proximate to the specific area. When determining that the mobile terminal 103 is proximate to the specific area, the handover storage device 108 transmits to the mobile terminal 103 a message indicating that a handover should be made when quality information of a handover destination cell 102 becomes equal to or higher than a threshold. Upon receipt from the mobile terminal 103 of a report indicating that the quality information of the handover destination cell 102 becomes equal to or higher than the threshold, a base station control device 107 transmits a message instructing execution of the handover. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a radio communication system, a handover storage device, a handover control method, and a program, and more particularly to a radio communication system, a handover storage device, a handover control method, and a program for controlling handover of a mobile terminal.

  In handover in a wireless communication (mobile communication) system, handover is executed in response to an event reported from a mobile terminal. The mobile terminal receives in advance the event to be generated and its report condition from the base station controller by Measurement Control. The mobile terminal that has received Measurement Control monitors the reception quality of the neighboring cell based on the condition. When the mobile terminal detects the event, it reports to the base station control device using Measurement Report. The base station controller that has received the Measurement Report makes a determination based on the acceptance control, and if permitted, transmits an Active Set Update to the mobile terminal. The mobile terminal that has received the Active Set Update transmits Active Set Update Complete to complete the handover. The specification of handover is described in Non-Patent Document 1 and the like.

  As a technique related to handover control, there is a technique described in Patent Document 1. In Patent Document 1, position information of a specific area where handover failures frequently occur is registered in advance in the specific area storage unit. In addition, specific handover data that enables an optimal handover to a mobile station in a specific area is stored in advance in the specific handover data storage means. The position identifying means refers to the specific area storage means and determines whether or not the mobile station is located in the specific area. When it is determined that the mobile station is located in a specific area, the handover data rewriting means rewrites the handover data from normal handover data to specific handover data held by the specific handover data storage means. In Patent Document 1, in a specific area, by performing handover with specific rewritten handover data, even when normal handover data is changed, optimal handover is smoothly executed without affecting others. You can do that.

3GPP TS25.331 V7.0.0 Japanese Patent Laid-Open No. 10-215474

  The reporting condition of each event notified from the mobile terminal to the base station is defined by the difference between the RF quality (RF: Radio Frequency) of the handover source cell and the RF quality of the handover destination cell. In this case, when the handover is performed, in a situation where the RF quality of the handover source cell rapidly deteriorates, even when the handover destination cell has sufficient RF quality to connect, the mobile station is the handover source cell, There was a case where the handover failed because the Active Set Update transmitted from the base station controller could not be received.

  In Patent Document 1, in a specific area where handover failures frequently occur, handover is performed using specific handover data different from normal handover data. The “specific handover data” referred to in Patent Document 1 is an RF quality difference threshold value that is different from the threshold value difference between the RF quality of the handover source cell and the RF quality of the handover destination cell that are normally used. It seems to be pointing. In this case, in a situation where the RF quality deteriorates sharply, the connection with the handover destination cell is suddenly cut off. Therefore, even if special handover data is used so that the handover does not fail, the handover failure can be avoided. It was difficult.

  An object of the present invention is to provide a wireless communication system, a handover storage device, a handover control method, and a program that can avoid a handover failure even when the quality of a handover source is rapidly deteriorated.

To achieve the above object, the wireless communication system of the present invention collects handover execution status information including location information of a mobile terminal at the time of handover execution and quality information of a handover destination cell from the mobile terminal, and the collected handover Refer to the handover execution status database, the handover execution status registration unit that registers the execution status information, information indicating success or failure of handover, and identification information of the handover source cell and the handover destination cell in the handover execution status database. A handover failure rate calculation unit for calculating a handover failure rate for an area obtained by dividing a base station service area into a plurality of areas, and a handover failure rate calculated by the handover failure rate calculation unit being equal to or greater than a predetermined threshold value Determine the area as a specific area and A specific area determination unit to be registered in the specific area storage unit for holding information of the area, based on the information stored in the specific area storage unit and the position information of the mobile terminal, the mobile terminal before Symbol specific area A terminal location determination unit that determines whether or not the mobile terminal is close, and when it is determined that the mobile terminal is close to the specific area, the quality information of the handover destination cell in the specific area When a handover execution condition designating unit that transmits a first message for handover when receiving the above and a report from the mobile terminal that the quality information of the handover destination cell is equal to or greater than a threshold value And a handover execution instructing unit that transmits a second message instructing execution of the handover.

The handover storage device of the present invention collects handover execution status information including location information of the mobile terminal at the time of handover execution and quality information of the handover destination cell from the mobile terminal, and the collected handover execution status information and the success of the handover Or, a handover execution status registration unit that registers information indicating failure and identification information of the handover source cell and the handover destination cell in the handover execution status database, and a plurality of service areas of the base station by referring to the handover execution status database A handover failure rate calculation unit for calculating a handover failure rate for the area divided into the areas, and an area where the handover failure rate calculated by the handover failure rate calculation unit is equal to or greater than a predetermined threshold is determined as a specific area, Holds information about the specific area A specific area determination unit to be registered in the specific area storage unit, based on the information stored in the specific area storage unit and the position information of the mobile terminal, whether the mobile terminal is close to the previous SL specific area When it is determined that the mobile terminal is close to the specific area, and when the quality information of the handover destination cell in the specific area exceeds a threshold, And a handover execution condition designating unit that transmits a first message for handover.

In the handover control method of the present invention, a computer collects handover execution status information including location information of a mobile terminal at the time of handover execution and quality information of a handover destination cell from the mobile terminal, and the collected handover execution status information; An implementation status registration step of registering information indicating success or failure of handover and identification information of the handover source cell and the handover destination cell in the handover implementation status database, and the computer refers to the handover implementation status database, and A handover failure rate calculation step for calculating a handover failure rate for an area obtained by dividing the service area into a plurality of areas, and a handover failure rate calculated by the computer in the handover failure rate calculation step is greater than or equal to a predetermined threshold value area Determined as the specific area, based a specific area determination step of registering the specific area storage unit for holding information of the specific area, to the computer, information stored in the specific area storage unit and the position information of the mobile terminal Te, a position determination step of determining whether the mobile terminal is close to the previous SL specific area, the computer, when the mobile terminal by said position determining step determines that proximate to said specific area, the mobile A message transmission step of transmitting to the terminal a message for handover when the quality information of the handover destination cell in the specific area exceeds a threshold value.

The program of the present invention collects handover execution status information including location information of a mobile terminal at the time of handover execution and quality information of a handover destination cell from a mobile terminal to a computer, A handover execution status registration process for registering information indicating success or failure and identification information of the handover source cell and the handover destination cell in the handover execution status database, and referring to the handover execution status database, the service area of the base station A handover failure rate calculation process for calculating a handover failure rate for an area divided into a plurality of areas, and an area where the handover failure rate calculated in the handover failure rate calculation process is equal to or greater than a predetermined threshold is determined as a specific area. And the specific area A specific area determination process of registering the specific area storage unit for holding information, based on the information stored in the specific area storage unit and the position information of the mobile terminal, the mobile terminal is close to the previous SL specific area A position determination process for determining whether or not the mobile terminal is close to the specific area in the position determination process, the quality information of the handover destination cell in the specific area is stored in the mobile terminal. And a message transmission process for transmitting a message for handover when the value exceeds the value.

  The wireless communication system, the handover storage device, the handover control method, and the program of the present invention can avoid a handover failure even when the quality of the handover source is rapidly deteriorated.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a wireless communication system according to an embodiment of the present invention. The radio communication system includes radio base stations 104 and 105, a base station control device 107, and a handover storage device 108. The mobile terminal 103 exists in the handover source cell 101 and is connected to the radio base station 104. The mobile terminal 103 moves across the handover area 109 that is a cell boundary and moves to the handover destination cell 102. The mobile terminal 103 performs handover from the handover source cell 101 to the handover destination cell 102 under the radio base station 105 in the handover area 109.

  When the mobile terminal 103 performs handover from the handover source cell 101 to the handover destination cell 102, the mobile terminal 103 transmits handover execution status information regarding the handover to the base station control apparatus 107. The handover execution status information includes a location where the handover is executed, a time, and RF quality information. The RF quality information includes RF quality information of the handover source cell and RF quality information of the handover destination cell (RF quality information of the cell having the second highest RF quality). For the RF quality information, DL (Down Link) RSCP (Received Signal Code Power) or Ec / No which is the ratio of the RSCP of the most powerful station and the total received power can be used. As the location information, the location information generated by the mobile terminal 103 based on the signal from the GPS satellite 106 can be used.

  FIG. 2 shows configurations of the base station control device 107 and the handover storage device 108. The base station control apparatus 107 has a handover execution instruction unit 111. The handover storage device 108 includes a handover execution status registration unit 121, a handover execution status DB (database) 122, a handover failure rate calculation unit 123, a specific area determination unit 124, a specific area storage unit 125, a threshold value determination unit 126, a threshold. A value database 127, a terminal location determination unit 128, and a handover execution condition designation unit 129. The functions of each unit in the base station control device 107 and the handover storage device 108 can be realized by executing a predetermined program on the computer.

  The handover execution status registration unit 121 collects handover execution status information including the location information of the mobile terminal 103 at the time of handover execution and the quality information of the handover destination cell via the base station control apparatus 107. The base station control apparatus 107 adds information indicating success / failure of handover, information of the handover source cell, and the handover destination cell to the handover execution status information transmitted from the mobile terminal 103, and performs a handover execution status registration unit Pass to 121. The information indicating the failure includes information indicating the cause of the failure. Specifically, after the base station control apparatus 107 transmits Active Set Update to the mobile terminal 103, information indicating that the handover has failed without receiving Active Set Update Complete from the mobile terminal 103 is included.

  The handover execution status registration unit 121 collects handover execution status information from the mobile terminal 103 and stores the handover execution status information in the handover execution status database 122, that is, the handover execution location, time, quality information of the handover destination cell, Success / failure, handover source cell, and handover destination cell are registered. The handover failure rate calculation unit 123 refers to the handover execution status database 122 and calculates a handover failure rate for an area obtained by dividing the service area of the radio base station into a plurality of areas. More specifically, the handover failure rate calculation unit 123 obtains a rate (failure rate) in which the mobile terminal 103 fails to receive Active Set Update Complete and fails to perform handover after activation.

  The handover failure rate calculation unit 123 stores information for managing the location range of each area when the service area of the radio base station is divided into a plurality of areas. The handover failure rate calculation unit 123 determines an area where the mobile terminal 103 has started handover from the information and the handover execution location recorded in the handover execution status database 122. The handover failure rate calculation unit 123 refers to the handover execution status database 122 and fails for the handover activated in the same area because the mobile terminal 103 cannot receive Active Set Update Complete from the number of successful and failed handovers. The failure rate (percentage) of the completed handover is obtained.

  Based on the failure rate calculated by the handover failure rate calculation unit 123, the specific area determination unit 124 determines a specific area where the mobile terminal 103 cannot receive Active Set Update Complete and has a high probability of failing handover. The specific area determining unit 124 determines an area where the handover failure rate is higher than a predetermined threshold as a specific area where the handover is likely to fail. The specific area determination unit 124 registers information for identifying the determined specific area in the specific area storage unit 125.

  The threshold value determination unit 126 refers to the handover execution status database 122, and based on the handover execution status information in the specific area determined by the specific area determination unit 124, the quality information of the handover destination serving as the handover execution condition in the specific area Determine the threshold for. More specifically, the threshold value determination unit 126 statistically processes the quality information of the handover destination cell in the specific area, and determines which quality information is based on the statistical value of the quality information of the mobile terminal 103 connected to the handover destination cell. If so, it is determined whether connection to the handover destination cell is possible, and this is used as a threshold value.

  When there are a plurality of services provided by the wireless communication system, the threshold determination unit 126 determines the above-described threshold for each service. For example, for the voice call, the threshold value determination unit 126 determines to what extent the quality information is connectable to the voice call service from the statistical value of the quality information of the mobile terminal 103 connected by the voice call service. And the lower limit of the quality information that can be connected is set as a threshold value. For packet communication, based on the statistical value of quality information of the mobile terminal 103 connected by the packet communication service, the lower limit of the quality information that can be connected by the packet communication service is set as a threshold value.

  The threshold value determination unit 126 determines the threshold value for each of the specific areas determined by the specific area determination unit 124, that is, for each area stored in the specific area storage unit 125. The threshold value determination unit 126 registers the determined threshold value in the threshold value database 127 in association with information for identifying the specific area.

  The terminal location determination unit 128 acquires location information from the mobile terminal 103 via the base station control device 107. The terminal position determination unit 128 compares the position information of the mobile terminal 103 with the specific area stored in the specific area storage unit 125 and determines whether the mobile terminal 103 is close to the specific area. When it is determined that the mobile terminal 103 is close to the specific area, the handover execution condition designating unit 129 determines that the quality information of the handover destination cell is not the threshold value of the quality information difference between the handover source and the handover destination. When this happens, a Measurement Control message (first message) for executing handover is transmitted to the mobile terminal 103.

  When it is determined that the mobile terminal 103 is close to the specific area, the handover execution condition specifying unit 129 searches the threshold value database 127 for a threshold value corresponding to the specific area where the mobile terminal 103 is close. The handover execution condition specifying unit 129 includes the searched threshold value in the Measurement Control message transmitted to the mobile terminal 103. That is, the handover execution condition specifying unit 129 specifies a threshold value corresponding to a specific area in which the mobile terminal 103 is close to the mobile terminal 103 as a handover execution condition.

  When receiving the Measurement Control message, the mobile terminal 103 determines whether or not the quality information of the handover destination cell is equal to or higher than the threshold value specified in the received message. When the state of the handover destination cell quality information equal to or higher than the specified threshold value continues for a predetermined time, the mobile terminal 103 transmits a measurement report message notifying the base station control apparatus 107 to that effect. When receiving the Measurement Report from the mobile terminal 103, the handover execution instructing unit 111 of the base station control apparatus 107 transmits an Active set Update message (second message) for instructing the mobile terminal 103 to execute the handover.

  When receiving the Active Set Update message, the mobile terminal 103 performs handover. After executing the handover, the mobile terminal 103 transmits Active Set Update Complete to the base station control apparatus 107. The handover execution instruction unit 111 receives the Active Set Update Complete transmitted from the mobile terminal 103, whereby the handover is completed.

  FIG. 3 shows the handover area 109 in an enlarged manner. The handover area 109 is divided into meshes 131, and the handover failure rate calculation unit 123 calculates the failure rate of handover that occurs without receiving Active Set Update Complete in the mesh-divided area. The specific area determination unit 124 determines a mesh whose handover failure rate is higher than the threshold as a specific area (handover failure area 132) that is likely to fail in handover due to rapid deterioration of RF quality, and stores it in the specific area storage unit 125. sign up.

Here, in the case where the base station controller 107 fails to receive Active Set Update Complete and fails in handover,
(1) After the mobile terminal 103 transmits the measurement report, the RF quality suddenly deteriorates and the mobile station 103 cannot receive the active set update transmitted by the base station control apparatus. The case where Update Complete cannot be received,
(2) After the mobile terminal 103 transmits the measurement report and the mobile terminal 103 receives the active set update transmitted by the base station controller, the RF quality suddenly deteriorates, and the mobile terminal 103 transmits the active set update. Case in which Complete cannot be received by the base station controller 107,
There are two possible ways. In any case, because the base station control device 107 cannot receive Active Set Update Complete from the mobile terminal 103 due to the rapid deterioration of RF quality, handover fails, and Active Set Update Complete cannot be received and handover is performed. The failing area is considered to be an area where the RF quality deteriorates rapidly and the handover fails.

  FIG. 4 shows a procedure for creating (updating) the handover execution status database 122. When the handover is executed, the mobile terminal 103 transmits the handover execution status information to the handover storage device 108 via the base station control device 107 (step A1). The mobile terminal 103 includes the location, time, and RF quality information where the handover is executed in the handover execution status information. When the handover fails, the mobile terminal 103 temporarily stores the location, time, and quality information, and transmits the stored information to the base station control apparatus 107 after reconnection.

  The base station control apparatus 107 adds information on the success / failure of the handover, the handover source cell, and the handover destination cell to the handover execution status information transmitted from the mobile terminal 103, and transfers the information to the handover storage apparatus 108 (step A2). When the handover execution status registration unit 121 of the handover storage device 108 receives the handover execution status information, it registers the received information in the handover execution status database 122 (step A3).

  FIG. 5 shows a procedure for determining a specific area. The handover failure rate calculation unit 123 refers to the handover execution status database 122 and calculates a handover failure rate for each area (step B1). The handover failure rate calculation unit 123 calculates a handover failure rate for each mesh-divided area shown in FIG. The handover failure rate calculation unit 123 calculates the active failure from the total number of handovers performed in the area and the number of handover failures that the base station controller 107 failed to receive Active Set Update Complete and failed to perform handover. Calculate the rate of failed handovers without receiving Set Update Complete.

  The specific area determining unit 124 determines a specific area where the handover is likely to fail based on the handover failure rate of each area calculated by the handover failure rate calculating unit 123 (step B2). The specific area determination unit 124 determines, as a specific area, an area in which the failure rate of handover that occurs without receiving Active Set Update Complete from a mesh-divided area (FIG. 3) is a predetermined threshold or more. The specific area determination unit 124 registers the determined specific area in the specific area storage unit 125 (step B3).

  FIG. 6 shows a procedure for determining a threshold value of quality information of a handover destination cell, which is a handover activation condition. The threshold value determination unit 126 refers to the specific area storage unit 125 to check a specific area where handover is likely to fail (step C1). The threshold determination unit 126 refers to the handover execution status database 122 and statistically processes the quality information of the handover destination cell for each specific area, and the measurement control message transmitted from the handover execution condition specifying unit 129 to the mobile terminal 103. The threshold value of the quality information of the handover destination cell specified by is determined (step C2). At this time, when there are a plurality of services that can be used by the mobile terminal 103, the threshold determination unit 126 determines a threshold corresponding to each service. The threshold value determination unit 126 registers the threshold value determined in step C2 in the threshold value database 127 in association with the specific area (step C3).

  In step C2, the threshold value determination unit 126 statistically processes the quality information of the handover destination cell for each specific area, and determines at least how much quality information is necessary to avoid a handover failure. Judge and determine the threshold. For example, with respect to the handover failure area 132 illustrated in FIG. 3, the threshold value determination unit 126 refers to the handover execution status database 122 and searches for data in which the handover execution location is within the handover failure area 132. The threshold value determination unit 126 statistically processes the quality information of the handover destination cell of the retrieved data, and determines in the handover failure area 132 how much quality information is present so that the handover will not fail. In the statistical processing, for example, the distribution of quality information is obtained for each of the handover failure / success in the handover failure area 132, and the lower limit value of the quality information that will succeed in the handover is obtained. The threshold value determination unit 126 determines the lower limit value thus obtained as a threshold value corresponding to the handover failure area 132.

  The handover storage device 108 receives the handover execution status from the mobile terminal 103 as needed, and updates the handover execution status database 122 according to the procedure shown in FIG. The handover storage device 108 periodically performs processing for determining a specific area (FIG. 5) and processing for determining a threshold value of a handover destination cell in the specific area (FIG. 6). Determine the value dynamically. By periodically determining the specific area and the threshold value, the area where the handover is likely to fail and the threshold value in the area are changed to the actual handover execution status according to the handover execution status of the mobile terminal 103. It can be updated together.

  FIG. 7 shows a procedure for performing the handover. The mobile terminal 103 periodically performs position calculation based on the signal from the GPS satellite 106 and transmits the position information to the handover storage device 108 (step D1). The terminal location determination unit 128 of the handover storage device 108 refers to the specific area storage unit 125 to determine whether or not the mobile terminal 103 is close to the specific area (step D2). If the terminal position determination unit 128 determines that the distance between the position of the mobile terminal 103 and the specific area is greater than a predetermined threshold value, the terminal position determination unit 128 waits for transmission of the next position information from the mobile terminal 103. To do.

  Note that the mobile terminal 103 exchanges messages with the base station control apparatus 107 and performs handover as usual, except for a position close to the specific area. That is, the mobile terminal 103 receives a Measurement Control message for reporting an event when the difference between the quality information of the handover source cell and the quality information of the handover destination cell exceeds a threshold from the base station controller 107, Sends a Measurement Report when the conditions are met. Thereafter, the mobile terminal 103 receives an Active Set Update message from the base station control apparatus 107, transmits Active Set Update Complete to the base station control apparatus 107, and completes the handover.

  The terminal position determination unit 128 determines that the mobile terminal 103 is close to the specific area when the distance between the position of the mobile terminal 103 and the specific area is closer than a predetermined threshold for a predetermined time. When determining that the mobile terminal 103 is close to the specific area, the terminal position determination unit 128 notifies the handover execution condition specifying unit 129 of the specific area where the mobile terminal 103 is close. For example, in FIG. 3, when the mobile terminal 103 is located in the handover activation area 133 adjacent to the handover failure area 132 that is a specific area, the terminal location determination unit 128 causes the mobile terminal 103 to approach the handover failure area 132. To the handover execution condition designating unit 129.

  The handover execution condition designating unit 129 searches the threshold value database 127 and acquires a threshold value corresponding to the specific area notified from the terminal position determining unit 128 (step D3). When there are a plurality of services, the handover execution condition specifying unit 129 receives information indicating which service the mobile terminal 103 is using from the base station control apparatus 107, and from the threshold database 127 to the service Get the corresponding threshold.

  The handover execution condition specifying unit 129 transmits a Measurement Control message to the mobile terminal 103 (step D4). In step D4, the handover execution condition specifying unit 129 transmits a measurement report to the base station control apparatus 107 when the quality information of the handover destination cell continues for a certain time or more and becomes equal to or greater than the threshold acquired in step D3. A Measurement Control message including an instruction to do so is transmitted to the mobile terminal 103.

  After receiving the Measurement Control message, the mobile terminal 103 reports an event occurrence to the base station controller 107 when the quality information of the handover destination cell is equal to or higher than the threshold value specified in the received Measurement Control message. Is transmitted (step D5). The subsequent procedure is the same as the normal handover. The handover execution instructing unit 111 of the base station control apparatus 107 transmits an Active Set Update message to the mobile terminal 103 that has transmitted the measurement report (step D6), and the mobile terminal 103 transmits Active Set Update Complete to the base station control apparatus 107. (Step D7) to complete the handover.

  In the present embodiment, the terminal location determination unit 128 determines whether or not the mobile terminal 103 is close to the specific area based on the location information of the mobile terminal 103 and the information stored in the specific area storage unit 125. to decide. When it is determined that the mobile terminal 103 is close to the specific area, the handover execution condition specifying unit 129 causes the mobile terminal 103 to perform a handover when the quality information of the handover destination cell exceeds a threshold value. Send. In the present embodiment, the mobile terminal 103 performs handover in the vicinity of the specific area when the quality information of the handover destination cell is equal to or higher than the threshold according to the message received from the handover execution condition specifying unit 129.

  In a normal handover, the handover is activated when the difference between the quality information of the handover source cell and the quality information of the handover destination cell exceeds a threshold value. In normal handover, as long as the quality information of the handover source cell is secured to some extent, it tries to stay in that cell as much as possible, and even when the quality information of the handover destination cell satisfies sufficient quality, Handover is not activated until is equal to or greater than the threshold. In this case, if the RF quality of the handover destination cell rapidly deteriorates, the mobile terminal 103 may not be able to connect to the handover source cell before the handover is completed, and the handover may fail.

  In the present embodiment, in the specific area, the handover is activated when the quality information of the handover destination cell becomes equal to or higher than a threshold value. Even when the quality information of the handover source cell is sufficiently high, the mobile terminal 103 performs handover to the handover destination cell at that stage when the quality information of the handover destination cell becomes high enough to connect. In an area where the RF quality of the handover source cell rapidly deteriorates, the RF quality of the handover destination cell may already satisfy the RF quality sufficient to continue the service currently used by the mobile terminal 103. . In this embodiment, in such a case, it is possible to perform handover to a handover destination cell that satisfies the RF quality at an early stage without waiting for the deterioration of the RF quality of the handover source cell. Therefore, it is possible to avoid a handover failure even in a situation where the RF quality deteriorates rapidly.

  In this embodiment, the handover execution status registration unit 121 is used to register the handover execution status information in the handover execution status database 122, and the handover failure rate calculation unit 123 is used to set the service area of the radio base station to a plurality of areas. The handover failure rate is calculated for the divided areas. The specific area determination unit 124 determines, as the specific area, an area in which the handover failure rate calculated by the handover failure rate calculation unit 123 is equal to or greater than a predetermined threshold. When such a configuration is adopted, the handover storage device 108 can dynamically set an area where the handover is likely to fail, as the specific area, based on the handover execution status.

  More preferably, the handover failure rate calculation unit 123 receives a report that the handover execution instruction unit 111 has received a report from the mobile terminal 103 that the quality information of the handover destination cell has exceeded a threshold value, that is, after the handover is started. Then, the failure rate of the handover that fails because the handover completion message cannot be received from the mobile terminal 103 is calculated. By doing in this way, the area where the handover is likely to fail due to the rapid deterioration of the RF quality can be set as the specific area. Also, in a specific area where handover is likely to fail, in the area where handover is likely to fail by giving a new handover opportunity to perform handover when the quality information of the handover destination cell exceeds a threshold value. Handover failure can be avoided.

  In the present embodiment, the threshold value determination unit 126 refers to the handover execution status database 122 and based on the quality information in the specific area, sets the quality information of the handover destination cell that is the start condition for the handover in the specific area. Determine the threshold. The handover execution condition designating unit 129 includes the threshold value determined by the threshold value determining unit 126 in the Measurement Control message transmitted to the mobile terminal 103. In this way, the threshold value of the quality information of the handover destination cell in the specific area that is the condition for starting the handover can be dynamically determined according to the actual handover implementation status. Appropriate settings are possible.

  In the above-described embodiment, the handover destination cell is a cell in which the received RF quality of the mobile terminal 103 is the next highest after the handover source cell, that is, a cell having the second highest RF quality. Is not limited to the second cell. If the mobile terminal 103 is a cell that can continue the service being used, the cell having the third highest reception RF quality may be set as the handover destination cell and handed over to that cell. For example, when the load of the cell with the second highest received RF quality of the mobile terminal 103 is high, the third cell or higher cell with the highest received RF quality that can continue the service is set as the handover destination cell. By selecting such a handover destination cell, an appropriate handover destination can be selected.

  In FIG. 3, the handover area 109 is divided into meshes, but the area division is not limited to mesh division. The shape of the area division may be a shape other than the mesh division shown in FIG. 3, for example, the area may be divided by other polygons. In the area division, it is not necessary to divide the service area of the radio base station equally, and the service area may be divided into a plurality of areas having different sizes and shapes. For example, it is possible to appropriately determine the handover failure area (specific area) by changing the division method in the area division according to the land use situation or the like.

  Although the present invention has been described based on the preferred embodiments, the radio communication system, the handover storage device, the handover control method, and the program of the present invention are not limited to the above embodiments, and What changed and changed variously from the structure of embodiment is also contained in the scope of the present invention.

1 is a block diagram showing a wireless communication system according to an embodiment of the present invention. The block diagram which shows the structure of a base station control apparatus and a handover memory | storage device. The block diagram which expands and shows a hand-over area. The sequence diagram which shows the procedure at the time of handover implementation status database registration. The flowchart which shows the procedure at the time of specific area determination. The flowchart which shows the procedure at the time of threshold value determination. The sequence diagram which shows the procedure at the time of a hand-over.

Explanation of symbols

101: Handover source cell 102: Handover destination cell 103: Mobile terminal 104, 105: Radio base station 106: GPS satellite 107: Base station controller 108: Handover storage device 109: Handover area 111: Handover execution instructing unit 121: Handover execution Status registration unit 122: Handover execution status database 123: Handover failure rate calculation unit 124: Specific area determination unit 125: Specific area storage unit 126: Threshold determination unit 127: Threshold database 128: Terminal location determination unit 129: Handover Implementation condition specifying unit 131: Mesh 132: Handover failure area 133: Handover activation area

Claims (8)

Collecting handover execution status information including the location information of the mobile terminal at the time of handover execution and the quality information of the handover destination cell from the mobile terminal, the collected handover execution status information, information indicating success or failure of handover, and handover A handover execution status registration unit for registering identification information of a source cell and a handover destination cell in a handover execution status database;
A handover failure rate calculation unit that calculates a handover failure rate for an area obtained by dividing the base station service area into a plurality of areas with reference to the handover execution status database;
A specific area determining unit that determines an area having a handover failure rate calculated by the handover failure rate calculating unit equal to or greater than a predetermined threshold as a specific area, and registers the specific area in a specific area storage unit that holds information on the specific area;
And wherein the location information of the mobile terminal based on the information stored in the specific area storage unit, determines the terminal position determination unit whether the mobile terminal is close to the previous SL specific area,
When it is determined that the mobile terminal is close to the specific area, a first message to the effect that the mobile terminal is to be handed over when quality information of a handover destination cell in the specific area exceeds a threshold value A handover execution condition designating section to transmit;
A wireless communication system comprising: a handover execution instructing unit that transmits a second message instructing execution of a handover when receiving a report from the mobile terminal that the quality information of the handover destination cell is equal to or greater than a threshold value . The handover failure rate calculation unit receives a handover completion message from the mobile terminal after the handover execution instructing unit receives a report from the mobile terminal that the quality information of the handover destination cell is equal to or higher than a threshold value. The wireless communication system according to claim 1 , wherein a failure rate of a failed handover that cannot be received is calculated. Referring to the handover execution status database, the quality information in the specific area determined by the specific area determination unit is statistically processed, the threshold value of the quality information specified by the first message is determined, and the threshold value database A threshold value determination unit to be registered in
The handover execution condition designating unit searches the threshold database for a threshold corresponding to the specific area that is determined to be close to the mobile terminal, and in the first message transmitted to the mobile terminal, The wireless communication system according to claim 1 or 2 , wherein the searched threshold value is included. Collecting handover execution status information including the location information of the mobile terminal at the time of handover execution and the quality information of the handover destination cell from the mobile terminal, the collected handover execution status information, information indicating success or failure of handover, and handover A handover execution status registration unit for registering identification information of a source cell and a handover destination cell in a handover execution status database;
A handover failure rate calculation unit that calculates a handover failure rate for an area obtained by dividing the base station service area into a plurality of areas with reference to the handover execution status database;
A specific area determining unit that determines an area having a handover failure rate calculated by the handover failure rate calculating unit equal to or greater than a predetermined threshold as a specific area, and registers the specific area in a specific area storage unit that holds information on the specific area;
And wherein the location information of the mobile terminal based on the information stored in the specific area storage unit, determines the terminal position determination unit whether the mobile terminal is close to the previous SL specific area,
When it is determined that the mobile terminal is close to the specific area, a first message to the effect that the mobile terminal is to be handed over when quality information of a handover destination cell in the specific area exceeds a threshold value A handover storage device comprising: a handover execution condition specifying unit for transmitting. The computer collects handover execution status information including location information of the mobile terminal at the time of handover execution and quality information of the handover destination cell from the mobile terminal, and the collected handover execution status information and information indicating success or failure of the handover And an implementation status registration step of registering identification information of the handover source cell and the handover destination cell in the handover implementation status database;
A handover failure rate calculating step in which a computer calculates a handover failure rate for an area obtained by dividing a service area of a base station into a plurality of areas with reference to the handover execution status database;
A specific area determining step in which the computer determines an area where the handover failure rate calculated in the handover failure rate calculating step is equal to or greater than a predetermined threshold as a specific area, and registers the specific area in a specific area storage unit that holds information on the specific area When,
Computer, on the basis of the positional information of the mobile terminal and said information stored in the specific area storage unit, a position determination step of determining whether the mobile terminal is close to the previous SL specific area,
When the computer determines in the position determination step that the mobile terminal is close to the specific area, the mobile terminal is caused to perform a handover when quality information of a handover destination cell in the specific area exceeds a threshold value. A message transmission step of transmitting a message to the effect. 6. The handover control method according to claim 5 , wherein, in the handover failure rate calculation step, after the handover is started, the computer calculates a failure rate of a failed handover because a handover completion message cannot be received from the mobile terminal. The computer refers to the handover execution status database, statistically processes quality information in the specific area determined in the specific area determination step, determines a threshold value of quality information specified by the message, Further comprising a threshold determination step for registering in the database;
In the message transmission step, the computer searches the threshold database for a threshold corresponding to the specific area determined to be close to the mobile terminal, and sends the search to a message to be transmitted to the mobile terminal. The handover control method according to claim 5 or 6 , wherein a threshold value is included. On the computer,
Collecting handover execution status information including the location information of the mobile terminal at the time of handover execution and the quality information of the handover destination cell from the mobile terminal, the collected handover execution status information, information indicating success or failure of handover, and handover A handover execution status registration process for registering identification information of a source cell and a handover destination cell in a handover execution status database;
A handover failure rate calculation process for calculating a handover failure rate for an area obtained by dividing the base station service area into a plurality of areas with reference to the handover execution status database;
A specific area determination process in which an area having a handover failure rate calculated in the handover failure rate calculation process is determined as a specific area and registered in a specific area storage unit that holds information on the specific area;
On the basis of the position information stored in said specific area storage unit information of the mobile terminal, the position determination process determines whether the mobile terminal is close to the previous SL specific area,
A message indicating that when the mobile terminal determines that the mobile terminal is close to the specific area in the location determination process, the mobile terminal is handed over when quality information of a handover destination cell in the specific area exceeds a threshold value A program that executes message transmission processing for transmitting messages.

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