JP2006157528A - Mobile communication system, base station apparatus, mobile station apparatus, and method for controlling mobile communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mobile communication system in which the utilization efficiency of a base station apparatus is improved as the entire mobile communication system, the base station apparatus, a mobile station apparatus, and a method for controlling the mobile communication system. <P>SOLUTION: The mobile communication system 1 includes the plurality of base station apparatuses 3 and the plurality of mobile station apparatuses 2. The base station apparatus 3 judges whether or not each mobile station apparatus 2 that currently communicates with the base station apparatus 3 can perform handover itself, and selects a mobile station apparatus that is made to perform handover among mobile station apparatuses 2 judged to be able to perform handover as a result of the judgment, and the selected mobile station apparatus 2 performs handover. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a mobile communication system, a base station apparatus, a mobile station apparatus, and a control method for a mobile communication system.

  In mobile communication systems such as mobile phones and PHS, a plurality of base station devices are provided in a service providing area. Each base station apparatus communicates with a plurality of mobile station apparatuses existing in the respective cover areas. Also, the cover area of one base station apparatus is usually set so as to partially overlap with the cover areas of other base station apparatuses deployed in the geographical vicinity.

  Here, each base station apparatus has a predetermined number (allowable amount) of mobile station apparatuses that can communicate at the same time. For this reason, even when a communication start request is newly issued from another mobile station device while communicating with a plurality of mobile station devices corresponding to the permissible amount, the mobile station device that has made the start request Cannot start communication with. That is, a so-called call loss occurs.

  Therefore, various techniques for enabling the mobile station apparatus to communicate for a predetermined allowable amount have been proposed, and the technique described in Patent Document 1 is one of them.

In the technique described in Patent Document 1, in order to give as many mobile station apparatuses as possible communication opportunities, in the base station apparatus, all mobile station apparatuses in communication are in order of decreasing reception level of radio waves from the mobile station apparatuses. On the other hand, traffic is distributed by sending a handover instruction.
Japanese Patent No. 3153196

  However, in the above conventional method, a handover instruction is sent to all mobile station apparatuses in communication. In other words, in the conventional method, the base station apparatus that has performed the traffic distribution process is to hand over as many mobile station apparatuses as possible to other base station apparatuses. For this reason, there is a case where the above allowable amount may be exceeded in another base station apparatus that is the handover destination, and in such a case, a phenomenon of causing the mobile station apparatus to be handed over like a ping-pong occurs. .

  That is, with the above conventional method, the utilization efficiency of the base station apparatus cannot be increased as the entire mobile communication system.

  The present invention has been made to solve the above problems, and one of its purposes is a mobile communication system, a base station apparatus, and a mobile communication system capable of improving the utilization efficiency of the base station apparatus as a whole. It is an object to provide a mobile station apparatus and a mobile communication system control method.

  A mobile communication system according to the present invention for solving the above problems is a mobile communication system including a plurality of base station devices and a plurality of mobile station devices, wherein the base station device is communicating with the base station device. For each of the mobile station apparatuses, a handover possibility determining means for determining whether or not handover is possible, and a handover for selecting a mobile station apparatus to be handed over from among the mobile station apparatuses determined to be handoverable as a result of the determination Mobile station apparatus selection means, wherein the selected mobile station apparatus performs handover.

  By doing so, traffic can be distributed appropriately by selecting the mobile station apparatus to be handed over by the base station apparatus, and thus the utilization efficiency of the base station apparatus can be increased.

  Further, a base station apparatus according to the present invention is a base station apparatus used in a mobile communication system including a plurality of base station apparatuses and a plurality of mobile station apparatuses, and each of the mobiles communicating with the base station apparatus As a response to the inquiry by the handover availability inquiry means, handover availability information indicating whether handover is possible is received from the mobile station apparatus as a response to the inquiry from the station apparatus as to whether or not handover is possible. A handover availability information receiving means for receiving, a handover mobile station apparatus selection means for selecting a mobile station apparatus to be handed over from among the mobile station apparatuses indicated by the received handover availability information that handover is possible, and the selection Means for instructing a mobile station apparatus to perform handover , Characterized in that it comprises a.

  Also by doing this, traffic can be suitably distributed by selecting a mobile station apparatus to be handed over by the base station apparatus, so that utilization efficiency of the base station apparatus can be improved.

  In the base station apparatus, the traffic determining means for determining whether or not the traffic of the base station apparatus is a predetermined amount or more, and the traffic of the base station apparatus is a predetermined amount or more by the traffic determining means. If it is determined, an inquiry may be made by the handover availability inquiry means. In this way, the handover process can be performed according to the traffic volume.

  In the base station apparatus, mobile station apparatus identification information storage means for storing mobile station apparatus identification information indicating each of at least one mobile station apparatus instructed to perform handover by the handover instruction means over a predetermined time; Base station apparatus identification information acquisition means for acquiring base station apparatus identification information indicating a base station apparatus in communication with the mobile station apparatus indicated by the mobile station apparatus identification information stored by the mobile station apparatus identification information storage means, A handover impossible notification means for causing the base station apparatus indicated by the base station apparatus identification information acquired by the base station apparatus identification information acquisition means to determine that the mobile station apparatus cannot be handed over to the base station apparatus; May be further included. In this way, since the mobile station apparatus once handed over does not return to the base station apparatus within a predetermined time, it is possible to prevent a situation where the handover is repeated.

  In the base station apparatus, the handover impossibility notification means is acquired by the base station apparatus identification information acquisition means when the traffic determination means determines that the traffic of the base station apparatus is a predetermined amount or more. The base station apparatus indicated by the base station apparatus identification information to be performed may determine that the mobile station apparatus cannot be handed over to the base station apparatus. In this way, the mobile station apparatus once handed over does not return to the base station apparatus while the traffic is high, so that the traffic of the base station apparatus can be stabilized.

  The base station apparatus further includes reception intensity information acquisition means for acquiring reception intensity information indicating a reception intensity of a signal received by the mobile station apparatus capable of handover from the base station apparatus capable of handover, The handover mobile station apparatus selection means may select a mobile station apparatus to be handed over based on the reception intensity indicated by the acquired reception intensity information. In this way, it is possible to increase the possibility that the handed over mobile station apparatus can continue communication.

  Further, in the base station apparatus, communication duration information acquisition means for acquiring communication duration information indicating a time during which the mobile station apparatus capable of handover is continuing communication using the base station apparatus, In addition, the handover mobile station apparatus selection means may select a mobile station apparatus to be handed over based on a time indicated by the acquired communication duration information. In this way, it is possible to fairly distribute the time during which each mobile station apparatus can continue communication.

  The base station apparatus further includes traffic information acquisition means for the mobile station apparatus capable of handover to acquire traffic information indicating traffic of the base station apparatus capable of handover, and the handover mobile station apparatus selection means includes The mobile station apparatus to be handed over may be selected according to the traffic indicated by the traffic information acquired by the traffic information acquisition means. Even in this case, the possibility that the handed over mobile station apparatus can continue communication can be increased.

  A mobile station apparatus according to an aspect of the present invention is a mobile station apparatus used in a mobile communication system including a plurality of base station apparatuses and a plurality of mobile station apparatuses, from the base station apparatus in communication Detecting means for detecting a base station apparatus that can be handed over when receiving an inquiry as to whether or not handover is possible, and a base station that is in communication when a base station apparatus that can be handed over is detected by the detecting means Handover availability information transmitting means for transmitting handover availability information indicating that handover is possible to the apparatus.

  Further, in the mobile station apparatus, a base station apparatus identification information acquisition unit that acquires base station apparatus identification information indicating the base station apparatus that can be handed over, and a reception intensity of a signal transmitted from the base station apparatus that can be handed over Reception strength information acquisition means for acquiring the received reception strength information, wherein the handover availability information transmission means includes the acquired base station apparatus identification information and the acquired reception strength information, The handover availability information may be transmitted.

  The mobile communication system control method according to the present invention is a mobile communication system control method for controlling a mobile communication system including a plurality of base station devices and a plurality of mobile station devices, wherein the base station In the apparatus, a handover feasibility judgment step for judging whether or not handover is possible for each of the mobile station apparatuses in communication with the base station apparatus, and in the base station apparatus, as a result of the judgment, it is judged that handover is possible. A handover mobile station apparatus selection step of selecting a mobile station apparatus to be handed over from among the mobile station apparatuses to be handed over, wherein the selected mobile station apparatus performs handover.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a configuration diagram of a mobile communication system 1 according to an embodiment of the present invention. As shown in FIG. 1, the mobile communication system 1 includes a plurality of mobile station devices 2, a plurality of base station devices 3, and a communication network 4.

  The mobile station device 2 and the base station device 3 transmit and receive radio signals to and from each other. This radio signal is a radio signal transmitted / received to perform mobile communication such as a mobile phone or PHS, and a user data signal for transmitting / receiving user data, which is a communication content such as voice or data, And control signals for performing communication control such as communication termination and position registration.

  Base station apparatus 3 is fixedly installed at a certain point. Then, the mobile station apparatus 2 selects a base station apparatus 3 that can communicate, and transmits and receives radio signals to and from the selected base station apparatus 3. To be communicable means that wireless signals to be transmitted can reach each other. The process of selecting the base station device 3 with which the mobile station device 2 can communicate and transmitting and receiving radio signals to and from the selected base station device 3 is performed by communication between the mobile station device 2 and the base station device 3. You can do it inside. In this case, communication with the base station apparatus 3 that was communicating first is disconnected. In this way, the mobile station apparatus 2 can continue communication while changing the base station apparatus 3 to be a communication partner. Such a process is called a handover process.

  The handover process will be described in more detail. FIG. 2 is an explanatory diagram for explaining a communication image between the base station apparatus 3 and the mobile station apparatus 2 in the mobile communication system 1. Each base station apparatus 3 has an area 5 that can communicate with the mobile station apparatus 2. This area 5 often overlaps with the area 5 of the base station device 3 located in the vicinity. For example, in the figure, area 5-1 and area 5-2, area 5-1 and area 5-3, and area 5-1 and area 5-4 overlap each other. The mobile station device 2 located in the overlapping area can communicate with a plurality of base station devices 3. In such a case, the mobile station apparatus 2 selects the base station apparatus 3 that performs communication according to a predetermined standard, and transmits and receives radio signals to and from the selected base station apparatus 3. For example, the mobile station device 2-1 can communicate with both the base station device 3-1 and the base station device 3-3. In such a case, the mobile station apparatus 2-1 selects the base station apparatus 3 that performs communication according to the reception strength of the control signal transmitted from each base station apparatus 3, for example.

  Normally, the mobile station device 2 itself selects the communication partner base station device 3 (mobile station side handover processing). On the other hand, in the present embodiment, handover is requested from the base station apparatus 3 to the mobile station apparatus 2 according to the circumstances on the base station apparatus side (base station side handover process).

  In the present embodiment, when base station side handover processing is performed in the base station apparatus 3, a handover instruction is selectively transmitted to a part of the mobile station apparatuses 2 capable of handover. Yes. Hereinafter, the operation of base station apparatus 3 according to the present embodiment will be described.

  FIG. 3 is a configuration diagram of the base station apparatus 3 according to the present embodiment. As shown in the figure, the base station apparatus 3 includes a control unit 31, a storage unit 32, a network interface unit 33, and a wireless communication unit 34.

  The control unit 31 controls each unit of the base station device 3 and executes communication signal processing and handover-related processing. Specifically, processing related to this handover will be described here. The control unit 31 inquires of each mobile station device 2 in communication whether or not handover is possible (handover availability inquiry processing). Then, the mobile station apparatus 2 to be actually handed over is selected from the mobile station apparatuses 2 (selection candidate mobile station apparatuses) that have made a response that handover is possible (handover mobile station apparatus selection process). Then, a handover instruction is sent to the selected mobile station apparatus 2 (handover instruction process).

  In the present embodiment, the start control of the handover that is normally performed in the mobile station apparatus 2 is performed under the initiative of the base station apparatus 3. Here, since the handover start control is performed in accordance with the traffic state, the control unit 31 executes a process for monitoring whether or not there is excessive traffic (traffic excessive detection process). When it is determined that it is, the process related to the handover is started. Here, excessive traffic refers to a state in which the number of mobile station apparatuses 2 communicating with the base station apparatus 3 has reached an allowable amount (or a value determined by a threshold) of the base station apparatus 3. Specifically, whether or not the traffic is excessive depending on whether or not the number of communication slots (each communication path in the multiplexed communication) used for communication with the mobile station apparatus 2 has reached a predetermined threshold. Deciding.

  Further, in the handover mobile station apparatus selection process, it is assumed that selection is performed in order from the longest communication time with the base station apparatus 3 among the selection candidate mobile station apparatuses. Therefore, the control unit 31 performs a process of measuring the elapsed time since the communication with each mobile station device 2 is started (communication duration measuring process).

  The storage unit 32 functions as a work memory of the control unit 31 and stores various data related to communication processing of the base station device 3. Specifically, for example, mobile station apparatus identification information indicating the mobile station apparatus 2 that has been communicating so far for a predetermined time after the communication is completed is stored. Further, the communication duration time measured by the control unit 31 is stored in association with mobile station apparatus identification information indicating each mobile station apparatus 2 in communication. The mobile station apparatus identification information is identification information used for uniquely identifying the mobile station apparatus 2 included in the mobile communication system 1.

  The network interface unit 33 is connected to the communication network 4. And it functions as an interface of communication performed between the communication network 4 and the control unit 31. More specifically, a signal output from the control unit 31 is transmitted to the communication network 4. In addition, a signal transmitted from the communication network 4 to the base station device 3 is received and output to the control unit 31. The communication network 4 is configured to be communicable with all the base station devices 3 included in the mobile communication system 1, and the base station devices 3 can communicate with each other via the communication network 4.

  The radio communication unit 34 includes an antenna, and transmits and receives radio signals to and from the mobile station device 2. More specifically, each process such as a modulation process, a frequency conversion process, and an amplification process is performed on the signal output from the control unit 31 and is transmitted to the mobile station apparatus 2 via the antenna. In addition, it receives a radio signal from the mobile station apparatus 2 arriving at the antenna, performs each process such as an amplification process, a frequency conversion process, and a demodulation process, and outputs it to the control unit 31.

  FIG. 4 is a configuration diagram of mobile station apparatus 2 according to the present embodiment. As shown in the figure, the mobile station apparatus 2 includes a control unit 21, a storage unit 22, and a wireless communication unit 23.

  The control unit 21 controls each unit of the mobile station apparatus 2 and also performs processing of communication signals related to communication performed by the mobile station apparatus 2. In addition, when a signal for inquiring whether handover is possible transmitted by the base station apparatus 3 in the handover process according to the present embodiment is received, a detection process for detecting the base station apparatus 3 that can be handed over is performed, so that the handover itself A handover feasibility judgment process for judging whether or not it is possible is performed. Further, in response to the inquiry from the base station apparatus 3, handover enable / disable information including information on whether or not handover is possible is included in a signal to be transmitted to the base station apparatus 3 and is transmitted to the radio communication unit 23. The handover availability information transmission process to be output is also performed.

  The storage unit 22 functions as a work memory of the control unit 21 and stores various data related to communication processing of the mobile station device 2.

  The wireless communication unit 23 includes an antenna and transmits and receives radio signals to and from the base station device 3. More specifically, each process such as a modulation process, a frequency conversion process, and an amplification process is performed on the signal output from the control unit 21 and is transmitted to the base station apparatus 3 via the antenna. In addition, a radio signal from the base station apparatus 3 arriving at the antenna is received, and each process such as an amplification process, a frequency conversion process, and a demodulation process is performed and output to the control unit 21.

  In the base station apparatus 3 and the mobile station apparatus 2 having the above configuration, the present embodiment for increasing the utilization efficiency of the base station apparatus 3 by selectively handing over only the mobile station apparatus 2 that needs to be handed over A handover process according to the embodiment will be described with reference to a sequence diagram of the handover process.

  FIG. 5 is a sequence diagram of a handover process performed by the base station device 3 and the mobile station device 2. First, as an initial state, as shown in FIG. 2, it is assumed that the base station apparatus 3-1 is in communication with the mobile station apparatus 2-1, the mobile station apparatus 2-2, and the mobile station apparatus 2-3 (S100). , S102, S104). In this state, when the base station device 3-1 detects an excessive traffic state (S106), the base station device 3-1 makes an inquiry as to whether or not the mobile station device 2 in communication is in a state where handover is possible. Is transmitted as a control signal to each mobile station apparatus 2 in communication (S108, S110, S112). Each mobile station device 2 in communication that has received the handover destination detection request determines whether or not it can perform handover (S114, S116, S118). Specifically, by receiving a control signal transmitted from another base station apparatus 3 and determining whether the reception intensity of this control signal is equal to or higher than a predetermined value, the other base station apparatus 3 capable of communication can Judge whether there is. If it is determined that there is another base station apparatus 3, handover availability information (with handover destination) indicating that handover is possible is transmitted to the base station apparatus 3-1 (S120, S122). ). In this case, if it is not determined that there is another base station apparatus 3 capable of communication, handover availability information (no handover destination) indicating that handover is not possible is transmitted to the base station apparatus 3-1. It does not have to be transmitted. Further, the mobile station apparatus 2 includes base station apparatus identification information indicating a base station apparatus that can be handed over and reception intensity information indicating a reception intensity of a control signal transmitted from the base station apparatus, in the handover availability information. Send.

  The base station device 3-1 performs handover mobile station device selection processing for selecting the mobile station device 2 to be handed over from the mobile station devices 2 that have transmitted the handover availability information indicating that handover is possible (S124). Details of the handover mobile station apparatus selection process will be described later. Then, a handover instruction is sent to the selected mobile station apparatus 2-1 by transmitting a handover activation request (S126). The mobile station device 2-1 that has received the handover activation request performs handover to the base station device 3-3 that has been detected as the communicable base station device 3 (S128, S130). The handover process in S128 and S130 is performed by transmitting a communication start request signal indicating that the mobile station apparatus 2-1 requests the base station apparatus 3-3 to start communication.

  By handing over the mobile station apparatus 2 selected by the base station apparatus 3 in this way, the excessive traffic state is eliminated, and the mobile station apparatus 2-4 can newly perform communication (S132, S134).

  Hereinafter, the handover mobile station apparatus selection process will be described in detail.

  As described above, the handover availability information transmitted from the mobile station apparatus 2 to the base station apparatus 3 includes the base station apparatus identification information indicating the base station apparatus that can be handed over, and the control transmitted from the base station apparatus. Reception strength information indicating the reception strength of the signal. Further, the storage unit 32 of the base station device 3 stores the communication continuation time (communication continuation time information) of the communication from the start to the end of communication with the mobile station device 2.

  The control unit 31 selects the mobile station apparatus 2 to be handed over based on these pieces of information. Each will be described below.

  First, a process for selecting the mobile station apparatus 2 to be handed over based on the base station apparatus identification information will be described. The base station apparatus 3 (here, the base station apparatus 3-1) is the base station apparatus 3 (here, the base station apparatus 3-3) indicated by the base station apparatus identification information included in the received handover availability information. In response to this, a traffic state confirmation signal is transmitted via the communication network 4. The control unit 31 of the base station device 3-3 that has received the traffic state confirmation signal performs a traffic confirmation process for acquiring traffic information indicating the traffic state of the own device. The traffic information here is information indicating the remaining communication capacity of the base station apparatus 3-3, for example, the ratio of the number of mobile station apparatuses 2 in communication to the number of simultaneously communicable. And the signal containing the traffic information acquired is returned with respect to the base station apparatus 3-1 which transmitted the traffic state confirmation signal. In this way, the base station apparatus 3-1 can confirm the traffic state of the base station apparatus 3-3.

  Then, each base station apparatus 3 indicated by the base station apparatus identification information included in the plurality of handover availability information transmitted from the plurality of mobile station apparatuses 2 is subjected to processing for confirming the traffic state. The traffic state of the base station device 3 is acquired. Then, based on the acquired traffic state, for example, the mobile station apparatus 2 that is determined to be able to be handed over is selected in order from the mobile station apparatus 2 that can communicate with the base station apparatus 3 having the largest communication capacity, and the handover is performed. In this way, it is possible to increase the possibility that communication can be continued even after the mobile station apparatus 2 is handed over.

  Next, a process for selecting the mobile station apparatus 2 to be handed over based on the reception strength information will be described. High reception intensity information usually means that the control signal received from the communicable base station apparatus 3 is received in the best electric field state. Therefore, the control unit 31 acquires the reception strength information of the signal received from the base station device 3 that can be handed over by the mobile station device 2 that can be handed over, and selects in order from the mobile station device 2 with the largest reception strength information. And hand over. This also increases the possibility that communication can be continued even after the mobile station apparatus 2 is handed over.

  Next, a process for selecting the mobile station apparatus 2 to be handed over based on the communication duration information will be described. As described above, the communication duration information is information indicating the time during which the mobile station device in communication with the base station device 3 continues communication. The control unit 31 acquires communication duration information indicating a time during which communication is continued using the base station device 3 in the mobile station device 2 that can be handed over, and the communication indicated by the communication duration information. A mobile station apparatus 2 with the longest duration is selected in order and handed over. By doing in this way, it becomes possible to distribute fairly the time which each mobile station apparatus 2 can continue communication.

  In the handover mobile station apparatus selection process, the mobile station apparatus 2 to be handed over is selected from the mobile station apparatuses 2 that can be handed over by the above processes.

  By the way, the mobile station device 2 handed over from the base station device 3 (here, the base station device 3-1) by the above-described processing is transferred to the base station device 3 (here, the base station device 3- 3) may be handed over in the same manner. Then, since the base station apparatus 3 that originally had the best communication state was the base station apparatus 3-1, the mobile station apparatus 2 that communicated with the base station apparatus 3-1, A handover process for returning to -1 is performed. This will result in repeated handovers. Therefore, in order to solve this problem, in the present embodiment, when a predetermined condition is satisfied, the mobile station device 2 is connected to the base station device 3-3 in communication with the mobile station device 2, and the base station device It is assumed that it is impossible to hand over to 3-1. Hereinafter, specific processing will be described with reference to a sequence diagram of the processing.

  FIG. 6 is a sequence diagram of processes performed in the base station apparatus 3 and the mobile station apparatus 2, and is a process performed following the process shown in the sequence diagram of FIG. First, when the base station apparatus 3-1 transmits a handover activation request which is the handover instruction (S126), the mobile station apparatus identification for identifying the mobile station apparatus 2-1 which has been handed over by transmitting the handover instruction. Information is stored in the storage unit 32 (S136). This mobile station apparatus identification information is stored only within a predetermined time, and is erased when the predetermined time elapses.

  When the base station apparatus 3-3 detects an excessive traffic state (S138), the base station apparatus 3-3 transmits a handover destination detection request to each mobile station apparatus 2 in communication (S140). The mobile station apparatus 2-1 that has received the handover destination detection request determines whether or not it can perform handover (S142). At this time, the mobile station apparatus 2-1 determines that the base station apparatus 3-1 can be handed over. Then, the mobile station apparatus 2-1 transmits handover availability information (with handover destination) indicating that handover is possible to the base station apparatus 3-1 (S144). The handover availability information at this time includes base station apparatus identification information indicating the base station apparatus 3-1, as base station apparatus identification information indicating a base station apparatus capable of handover.

  When the base station apparatus 3-3 that has received the handover availability information from the mobile station apparatus 2-1 selects the mobile station apparatus 2-1 in the handover mobile station apparatus selection process, the base included in the received handover availability information An acceptance / rejection inquiry signal is transmitted via the communication network 4 to the base station apparatus 3-1 which is the base station apparatus indicated by the station apparatus identification information (S146). An acceptability inquiry signal is for a certain base station apparatus 3 to inquire to another base station apparatus 3 whether or not the mobile station apparatus 2 in communication can be handed over to the other base station apparatus 3. Signal. The acceptability inquiry signal includes base station apparatus identification information indicating the base station apparatus 3 that has transmitted the acceptability inquiry signal.

  The base station apparatus 3-1 that has received the acceptance permission inquiry signal determines whether or not mobile station apparatus identification information indicating the mobile station apparatus 2-1 is stored (S148). That is, since the mobile station apparatus identification information is stored in the storage unit 32 only within a predetermined time, it is confirmed whether or not the mobile station apparatus identification information is not yet stored when the acceptance / rejection inquiry signal is received. If mobile station apparatus identification information indicating mobile station apparatus 2-1 is stored, an acceptability inquiry response signal indicating unacceptability is transmitted as a response to the acceptability inquiry signal (S150) (impossible handover) Notification processing). On the other hand, if the mobile station apparatus identification information indicating the mobile station apparatus 2-1 is not stored, an acceptability inquiry response signal indicating acceptance is transmitted as a response to the acceptability inquiry signal (S152). Note that the base station device 3-1 acquires the base station device identification information included in the acceptability inquiry signal, and receives an acceptability inquiry response signal to the base station device 3 indicated by the acquired base station device identification information. Is sending.

  The base station device 3-3 that has received the acceptance / rejection inquiry response signal does not select the mobile station device 2-1 when the received acceptance / rejection inquiry response signal indicates unacceptable ( S154, S162). On the other hand, when the received acceptance / rejection inquiry response signal indicates acceptance, a handover instruction is given to the mobile station apparatus 2-1 (S154, S156), and the mobile station apparatus 2-1 A handover process for performing handover to 3-1 is executed (S158, S160).

  In the above processing, handover to the base station device 3-1 is restricted for a predetermined time after the handover instruction is transmitted. However, when there is still a lot of traffic after a predetermined time, the mobile station apparatus 2-1 may be overloaded with traffic due to the handover to the base station apparatus 3-1. For this reason, in the process of S148, the traffic volume of the base station device 3-1 is further confirmed, and if the traffic volume is larger than a predetermined threshold, an acceptability inquiry response signal indicating unacceptable is transmitted, and the traffic volume is When the number is smaller than the predetermined threshold value, the process according to whether or not the data is stored in the storage unit 32 as described above may be performed. In this way, while the traffic is high, the mobile station apparatus 2 once handed over does not return to the base station apparatus 3-1, so that the traffic of the base station apparatus 3-1 can be stabilized.

  As described above, the traffic can be distributed by selecting the mobile station device to be handed over by the base station device, so that the utilization efficiency of the base station device can be improved. In addition, for a mobile station apparatus that has been once handed over, it does not return to the original base station apparatus within a predetermined time or until the traffic of the original base station apparatus drops, thus preventing repeated handovers. can do.

  In the above embodiment, the handover to the original base station apparatus is disabled until a predetermined time has elapsed after the handover instruction is transmitted to the selected mobile station apparatus 2 that can be handed over. When a repeat process is performed that allows returning to the original base station apparatus without performing a handover to another base station apparatus due to a communication failure or the like for a certain period of time after transmitting a handover instruction to the apparatus. May be configured such that handover to the original base station apparatus is disabled until a predetermined time elapses after this repeat processing times out.

1 is a configuration diagram of a mobile communication system according to an embodiment of the present invention. It is explanatory drawing of the handover process which concerns on embodiment of this invention. It is a block diagram of the base station apparatus which concerns on embodiment of this invention. It is a block diagram of the mobile station apparatus which concerns on embodiment of this invention. It is a sequence diagram of processing according to an embodiment of the present invention. It is a sequence diagram of processing according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mobile communication system, 2 Mobile station apparatus, 3 Base station apparatus, 4 Communication network, 5 Area, 21,31 Control part, 22, 32 Storage part, 23, 34 Wireless communication part, 33 Network interface part.

Claims (11)

In a mobile communication system including a plurality of base station devices and a plurality of mobile station devices,
The base station device
For each of the mobile station devices in communication with the base station device, a handover availability determination means for determining whether handover is possible,
As a result of the determination, handover mobile station apparatus selection means for selecting a mobile station apparatus to be handed over from among mobile station apparatuses determined to be capable of handover;
Including
The selected mobile station apparatus performs handover,
A mobile communication system. A base station device used in a mobile communication system including a plurality of base station devices and a plurality of mobile station devices,
Handover availability inquiry means for inquiring whether or not handover is possible for each mobile station device in communication with the base station device;
As a response to the inquiry by the handover availability inquiry means, handover availability information receiving means for receiving from the mobile station apparatus handover availability information indicating whether or not handover is possible;
Handover mobile station apparatus selection means for selecting a mobile station apparatus to be handed over from among the mobile station apparatuses indicated by the received handover availability information that handover is possible;
Handover instruction means for instructing the selected mobile station apparatus to perform handover;
A base station apparatus comprising: The base station apparatus according to claim 2,
Traffic judgment means for judging whether the traffic of the base station apparatus is a predetermined amount or more;
When the traffic determination unit determines that the traffic of the base station apparatus is equal to or greater than a predetermined amount, an inquiry is made by the handover availability inquiry unit.
A base station apparatus. In the base station apparatus according to claim 2 or 3,
Mobile station apparatus identification information storage means for storing mobile station apparatus identification information indicating each of at least one mobile station apparatus instructed to perform handover by the handover instruction means over a predetermined time;
Base station apparatus identification information acquisition means for acquiring base station apparatus identification information indicating a base station apparatus in communication with the mobile station apparatus indicated by the mobile station apparatus identification information stored by the mobile station apparatus identification information storage means;
Handover notifying means for causing the base station apparatus indicated by the base station apparatus identification information acquired by the base station apparatus identification information acquiring means to determine that the mobile station apparatus cannot be handed over to the base station apparatus; ,
The base station apparatus further comprising: In the base station apparatus according to claim 4,
The handover impossibility notifying means uses the base station apparatus identification information acquired by the base station apparatus identification information acquiring means when the traffic determining means determines that the traffic of the base station apparatus is a predetermined amount or more. Causing the mobile station apparatus to determine that the mobile station apparatus cannot be handed over to the base station apparatus.
A base station apparatus. In the base station apparatus in any one of Claims 2 thru | or 5,
Reception strength information acquisition means for acquiring reception strength information indicating a reception strength of a signal received by the mobile station device capable of handover from the base station device capable of handover;
Further including
The handover mobile station apparatus selection means selects a mobile station apparatus to be handed over based on the reception intensity indicated by the acquired reception intensity information.
A base station apparatus. In the base station apparatus in any one of Claims 2 thru | or 6,
Communication duration information acquisition means for acquiring communication duration information indicating a time during which the mobile station apparatus capable of handover is continuing communication using the base station apparatus;
Further including
The handover mobile station apparatus selection means selects a mobile station apparatus to be handed over based on a time indicated by the acquired communication duration information.
A base station apparatus. In the base station apparatus in any one of Claim 2 thru | or 7,
Traffic information acquisition means for the mobile station apparatus capable of handover to acquire traffic information indicating traffic of the base station apparatus capable of handover;
Further including
The handover mobile station apparatus selection means selects a mobile station apparatus to be handed over according to the traffic indicated by the traffic information acquired by the traffic information acquisition means;
A base station apparatus. A mobile station device used in a mobile communication system including a plurality of base station devices and a plurality of mobile station devices,
A detection means for detecting a base station apparatus capable of handover when receiving an inquiry from the base station apparatus in communication whether handover is possible;
Handover availability information transmitting means for transmitting handover availability information indicating that handover is possible to the communicating base station apparatus when a base station apparatus capable of handover is detected by the detection means;
A mobile station apparatus comprising: In the mobile station apparatus of Claim 9,
Base station apparatus identification information acquisition means for acquiring base station apparatus identification information indicating the base station apparatus capable of handover;
Reception strength information acquisition means for acquiring reception strength information indicating the reception strength of a signal transmitted from the base station apparatus capable of handover;
Further including
The handover availability information transmitting means transmits the handover availability information including the acquired base station apparatus identification information and the acquired reception strength information.
A mobile station apparatus. A control method of a mobile communication system for controlling a mobile communication system including a plurality of base station devices and a plurality of mobile station devices,
In the base station apparatus, for each of the mobile station apparatuses in communication with the base station apparatus, a handover possibility determination step for determining whether or not handover is possible,
In the base station apparatus, as a result of the determination, a handover mobile station apparatus selection step of selecting a mobile station apparatus to be handed over from among the mobile station apparatuses determined to be handed over,
Including
The selected mobile station apparatus performs handover,
A control method for a mobile communication system.

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