JP2008053889A - Handover method, base station, terminal station, program recording medium and integrated circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a matter that communication is interrupted when the data stored in the receiving buffer 308 of a terminal station are drained during handover processing of the terminal station for switching the base station. <P>SOLUTION: Immediately before handover, a source base station transmits a data frame stored therein preferentially to a terminal station and increases the volume of data stored in the receiving buffer of the terminal station immediately before handover thus avoiding interruption of communication during handover processing. Preferential transmission is implemented by increasing the communication band to the terminal station and it is implemented even when an empty band does not exist by borrowing a part of the communication band from other terminal station. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a handover method for switching a base station to which a terminal station is connected in a wireless LAN (Local Area Network), and avoids communication interruption during the communication unavailable time of the terminal station caused by the base station switching process. Or a method for shortening the same.

  In a wireless LAN represented by IEEE 802.11, IAPP (Inter-Access Point Protocol) is defined as a handover method in which a station (hereinafter referred to as a terminal station) switches an access point (hereinafter referred to as a base station). . In IAPP, after a terminal station is handed over, a continuation data frame buffered by the source base station is wire-transferred to the destination base station, thereby realizing continuation of communication after the terminal station is handed over.

  FIG. 11 shows a case where the terminal station 301 is connected by the movement of the terminal station 301 in the network composed of the source base station 302, the destination base station 303, the relay device 403 connected to the external network, and the terminal station 301. FIG. 3 is a diagram showing a handover for switching a base station being switched from the base station 302 to the base station 303;

  FIG. 12 is a diagram showing a flow of handover processing using IAPP in the network of FIG.

  When the terminal station 301 is communicating with the base station 302, the terminal station 301 performs scanning in order to confirm whether it can be connected to another base station. In the IEEE 802.11 wireless LAN, there are active scanning and passive scanning as scanning methods. Among these, in the active scan, the terminal station transmits a probe request, and the base station returns a probe response (501 in FIG. 12).

  When the terminal station 301 determines the destination base station 303 by active scanning, the terminal station 301 transmits Deauthentication (deauthentication) and Dissociation (connection release) to the base station 302, and performs a disconnection process (502 in FIG. 12).

  Subsequently, the terminal station 301 transmits Authentication (authentication) and Reassociation (reconnection) to the movement-destination base station 303, and performs reconnection processing (503 and 504 in FIG. 12).

  The base station 303 requests a data frame addressed to the terminal station 301 buffered in the base station 302 by IAPP (505 in FIG. 12). The base station 302 transfers these data frames to the base station 303, and the destination base station 303 resumes communication with the terminal station 301.

  However, in the conventional method, since the terminal station 301 completes the reconnection process with the destination base station 303, the base station 303 requests transfer of the buffered data frame to the base station 302 using IAPP. The communication cannot be resumed immediately after the reconnection is completed, and the communication unavailable time of the terminal station becomes long.

  Here, the communication unavailable time means that the terminal station 301 performs disconnection processing with the source base station 303, performs reconnection processing with the destination base station, and the destination base station receives a continuation data frame from the source base station. It is time until communication with the terminal station is resumed. The communication disabled time is a time during which the terminal station 301 cannot transmit / receive data frames to / from both the source base station 302 and the destination base station 303.

  If there is no accumulated data frame in the reception buffer of the terminal station during this communication disabled time, communication interruption occurs.

  As a technique for solving this problem, for example, as disclosed in Patent Document 1, there is a method of advancing the start time of the transfer of the data frame buffered in the source base station 302.

  FIG. 13 is a diagram showing a flow of handover processing using the method disclosed in Patent Document 1. The network shown in FIG. 13 includes a source base station 306, a destination base station 307, a relay device 403 connected to an external network, and a terminal station 305, as in FIG.

  The process until the terminal station 305 determines the destination base station 307 by scanning (501 in FIG. 13) is the same as the conventional one.

  When the source base station 306 receives a Reassociation in which the destination MAC address does not match its own MAC address and the source base station MAC address matches its own MAC address, the buffered data frame To the destination base station 307.

  As a result, when the terminal station 305 completes reconnection with the base station 307, the continuous data frame buffered in the base station 306 has arrived, and immediate communication restart is possible.

That is, it becomes possible to shorten the communication unavailable time of the terminal station 305 generated by the handover.
JP 2005-323034 A

  The method of Patent Document 1 shortens the communication disabled time generated by the base station switching process by shortening the IAPP procedure. However, in the method of Patent Document 1, as long as the base station switching process is performed, the communication unavailable time does not disappear. When video streaming transmission or VoIP (Voice over Internet Protocol) transmission is performed, if the number of data frames stored in the reception buffer of the terminal station disappears within this communication unavailable time, communication interruption occurs.

  FIG. 14 shows a situation in which the number of data frames stored in the reception buffer of the terminal station disappears during communication unavailable time during the base station switching process, and communication interruption occurs.

  FIG. 14A shows a state immediately before the handover. The terminal station 305 is communicating with the base station 306. The number of data frames stored in the reception buffer 308 of the terminal station 305 is smaller than the number of data frames stored in the data frame addressed to the terminal station 305 in the transmission buffer 309 of the base station 306.

  FIG. 14B shows the reconnection process, and FIG. 14C shows immediately after the communication is resumed. When the terminal station 305 starts reconnection processing with the base station 307 and enters the communication unavailable time zone, the number of stored data frames in the reception buffer 308 of the terminal station 305 disappears, and communication interruption occurs.

  An object of the present invention is to solve the above-described conventional problems, and an object of the present invention is to avoid communication interruption by performing control in consideration of the number of data frames stored in a reception buffer of a terminal station before handover.

  In order to solve the above-mentioned problem, a handover method according to claim 1 of the present invention is a wireless communication system comprising a terminal station and a base station, and the terminal station moves from the source base station to the destination base by the movement of the terminal station. A handover method for switching a base station to a station, wherein the source base station performs priority transmission to the terminal station immediately before the start of handover of the terminal station, and the terminal station immediately before the handover of the terminal station starts And preferential transmission to the source base station.

  The handover method of claim 2 of the present invention is the handover method of claim 1, wherein the terminal station determines whether or not priority transmission is necessary, and the terminal station has its own reception buffer information, Determining from the transmission buffer information a request data amount to be received by priority transmission from the source base station and a transmission data amount to be transmitted by priority transmission to the source base station, and notifying them to the source base station And when the terminal station monitors the reception buffer and receives the requested data amount, a step of starting handover, and the terminal station notifies the identification information of the destination base station to the source base station And a step of transferring the continuation data after the requested data amount preferentially transmitted by the movement source base station to the movement destination base station by wire.

  The handover method according to claim 3 of the present invention is the handover method according to claim 1, wherein the terminal station notifies the source base station of a request for priority transmission with reception buffer information and transmission buffer information added thereto, A terminal station notifying the source base station of identification information of the destination base station, a step of determining whether or not the source base station requires priority transmission, and the source base station A station distinguishing a data amount to be preferentially transmitted to the terminal station and a data amount to be wire-transferred to the movement-destination base station by a threshold in its transmission buffer; and the movement-source base station A step of transferring the continuation data after the data preferentially transmitted to the base station by wire, the step of the source base station notifying the end of the preferential transmission to the terminal station, and the terminal station When notified of the termination, further comprising the step of initiating a handover.

  A handover method according to claim 4 of the present invention is a handover method in which a terminal station switches a base station from a source base station to a destination base station by movement of the terminal station in a wireless communication system including a terminal station and a base station. Then, immediately after the terminal station is handed over to the destination base station, the destination base station performs priority transmission to the terminal station, and immediately after the terminal station is handed over to the destination base station, The terminal station performing priority transmission to the movement-destination base station.

  The handover method according to claim 5 of the present invention is the handover method according to claim 4, wherein the terminal station notifies the destination base station of its reception buffer information and transmission buffer information immediately after the handover, and the destination The base station further determining the necessity of priority transmission from the reception buffer information and transmission buffer information of the terminal station.

  The handover method according to claim 6 of the present invention is the handover method according to claim 5, wherein the step of determining the necessity of the priority transmission is performed when the accumulated amount of the reception buffer of the terminal station is equal to or less than a threshold value. Judgment that priority transmission from the destination base station to the terminal station is necessary, and priority transmission from the terminal station to the destination base station is necessary when the accumulated amount of the transmission buffer of the terminal station exceeds a certain threshold It is judged that it is.

  The handover method according to claim 7 of the present invention is the handover method according to any one of claims 1 to 6, wherein the priority transmission increases an allocated radio band of the terminal station. .

  The handover method according to claim 8 of the present invention is the handover method according to any one of claims 1 to 6, wherein the priority transmission reduces an IFS transmission signal interval value of the IEEE802.11 standard. It is characterized by.

  A handover method according to a ninth aspect of the present invention is the handover method according to the first to sixth aspects, wherein the priority transmission uses a part of a radio band of a terminal station other than immediately before the start of handover as a terminal station immediately before the handover. It is characterized in that it is allocated and increased in the radio band.

  The handover method according to claim 10 of the present invention is the handover method according to claim 9, wherein the terminal station used in the source base station after the terminal station has completed handover in the priority transmission. The source base station assigns it by returning it to other terminal stations other than immediately before the start of handover.

  A handover method according to an eleventh aspect of the present invention is the handover method according to the ninth aspect, wherein in the priority transmission, a part of the radio band of the other terminal station other than immediately before the start of handover is redundant for retransmission of the other terminal station. It is characterized by the communication band secured in the above.

  The handover method according to claim 12 of the present invention is the handover method according to claim 9, wherein the other terminal having the best propagation environment in the selection method of the other terminal station other than immediately before the start of handover, which is a plurality of the priority transmissions. It is characterized by selecting.

  The handover method according to claim 13 of the present invention is the handover method according to claim 9, wherein, in the priority transmission, a plurality of other terminal station selection methods other than immediately before the start of handover exist, and the most delayed transmission application in use. The other terminal having a large allowable value is selected.

  The handover method according to claim 14 of the present invention is the handover method according to claim 9, wherein the number of retransmissions is set to a maximum in the selection method of the other terminal station other than immediately before the start of handover, in which there are a plurality of priority transmissions. The other terminal is selected.

  A base station according to claim 15 of the present invention is a base station of a wireless communication system comprising a mobile terminal station and a plurality of base stations of a source base station and a destination base station, wherein the source base station A priority transmission determination unit for determining whether or not there is a need for priority transmission immediately before the start of handover of the terminal station; and the source base station prioritizes the terminal station immediately before the start of handover of the terminal station. A priority transmission control unit for transmitting or preferentially transmitting the terminal station to the source base station immediately before starting handover.

  The base station according to claim 16 of the present invention is the base station according to claim 15, wherein the continuation data after preferential transmission in the source base station based on the identification information of the destination base station notified from the terminal station. Is further provided with a prior transfer control unit that performs wired transfer in advance to the destination base station.

  The base station according to claim 17 of the present invention is the base station according to claim 16, in the source base station, based on transmission buffer information and reception buffer information notified from the terminal station, in its own transmission buffer, The apparatus further includes a threshold value determination unit that distinguishes between a threshold value and a data amount to be preferentially transmitted to the terminal station and a data amount to be wired to the destination base station.

  A base station according to claim 18 of the present invention is a base station of a radio communication system comprising a mobile terminal station and a plurality of base stations of a source base station and a destination base station, wherein the destination base station A priority transmission determination unit that determines whether or not there is a need for priority transmission immediately after handover of the terminal station, and the destination base station has priority over the terminal station immediately after handover of the terminal station A priority transmission control unit for transmitting or preferentially transmitting to the destination base station immediately after handover of the terminal station.

  The base station according to claim 19 of the present invention is the base station according to claim 18, wherein the priority transmission determination unit of the destination base station is configured to perform the movement when the accumulated amount of the reception buffer of the terminal station is less than or equal to a threshold value. Judgment that priority transmission from the destination base station to the terminal station is necessary, and priority transmission from the terminal station to the destination base station is necessary when the accumulated amount of the transmission buffer of the terminal station exceeds a certain threshold It is judged that it is.

  A base station according to a twentieth aspect of the present invention is the base station according to any one of the fifteenth to nineteenth aspects, wherein the preferential transmission increases an allocated radio band of the terminal station. To do.

  A base station according to a twenty-first aspect of the present invention is characterized in that, in the base station according to the fifteenth to nineteenth aspects, the preferential transmission reduces an IFS transmission signal interval value of the IEEE802.11 standard.

  A base station according to a twenty-second aspect of the present invention is the base station according to any one of the fifteenth to nineteenth aspects, wherein the priority transmission is a part of a radio band of a terminal station other than just before the start of handover. Is allocated to the radio band of the terminal station immediately before the handover and is increased.

  A base station according to a twenty-third aspect of the present invention is the base station according to the twenty-second aspect, wherein in the priority transmission, a radio band used by the source base station after the terminal station has completed handover in the priority transmission. The source base station assigns it by returning it to other terminal stations other than immediately before the start of handover.

  A base station according to a twenty-fourth aspect of the present invention is the base station according to the twenty-second aspect, wherein in the priority transmission, a part of the radio band of the other terminal station other than immediately before the start of handover is extra for retransmission of the other terminal station. It is characterized by the communication band secured in the above.

  The base station according to claim 25 of the present invention is the base station according to claim 22, wherein the other terminal having the best propagation environment is selected in the base station according to claim 22 in the selection method of the other terminal station other than immediately before the start of handover that exists in plural. It is characterized by selecting.

  A base station according to a twenty-sixth aspect of the present invention is the base station according to the twenty-second aspect, wherein, in the selection method of the other terminal station other than immediately before the start of handover, there are a plurality of delays in a transmission application in use. The other terminal having a large allowable value is selected.

  The base station according to claim 27 of the present invention is the base station according to claim 22, wherein, in the priority transmission, in the selection method of the other terminal station other than immediately before the start of handover, a plurality of retransmission count setting values are maximum. The other terminal is selected.

  A terminal station according to a twenty-eighth aspect of the present invention is a terminal station of a radio communication system including a movable terminal station and a plurality of base stations of a source base station and a destination base station, and monitors a transmission / reception buffer. And the terminal station notifies the source base station to add transmission buffer information and reception buffer information obtained by buffer monitoring and request priority transmission immediately before the start of handover. A prioritized transmission request unit.

  The terminal station according to claim 29 of the present invention is the terminal station according to claim 28, wherein the terminal station has received the amount of data requested by the priority transmission request unit from the source base station or the priority transmission request to the destination base station. The handover is started on the occasion that the transmission of the data amount requested by the unit is completed.

  A terminal station according to a thirty-third aspect of the present invention is a terminal station of a radio communication system including a movable terminal station and a plurality of base stations of a source base station and a destination base station, and monitors a transmission / reception buffer. And a buffer monitoring unit that performs the notification of requesting priority transmission to the destination base station by adding transmission buffer information and reception buffer information obtained by buffer monitoring immediately after handover. A prioritized transmission request unit.

  A terminal station according to a thirty-first aspect of the present invention is the terminal station according to any one of the twenty-eighth to thirty-third aspects, wherein the priority transmission requesting unit is a process for requesting a change in TXOP value compliant with IEEE802.11e. It is characterized by that.

  A program recording medium according to a thirty-second aspect of the present invention causes a computer to execute all or a part of the functions of the base station according to any one of the fifteenth to twenty-seventh aspects.

  A program recording medium according to a thirty-third aspect of the present invention is for causing a computer to execute all or part of the functions of the terminal station according to any one of the twenty-eighth to thirty-first aspects.

  An integrated circuit according to a thirty-fourth aspect of the present invention is obtained by integrating all or a part of the functions of the base station according to any one of the fifteenth to twenty-seventh aspects.

  An integrated circuit according to a thirty-fifth aspect of the present invention is obtained by integrating all or a part of the functions of the terminal station according to any one of the twenty-eighth to thirty-first aspects.

  According to the present invention, the source base station preferentially transmits data frames stored in the source base station to the terminal station immediately before the handover, and increases the number of stored data frames in the reception buffer of the terminal station. It is possible to prevent the number of data frames stored in the reception buffer of the terminal station from becoming empty within the communication unavailable time that occurs during the switching process to the destination base station, and avoid or shorten the communication interruption during the handover. .

  Further, in the present invention, the terminal station immediately before the handover preferentially transmits the data frame stored in the transmission buffer of the terminal station to the source base station, so that the reception buffer of the communication partner side can be transmitted within the communication unavailable time during the handover. It is possible to prevent the number of stored data frames from becoming empty, and to avoid or shorten communication interruption during handover.

  In the present invention, the destination base station preferentially transmits to the terminal station immediately after the handover of the terminal station, so that the number of data frames stored in the reception buffer of the terminal station immediately after the handover can be increased. Shortening is possible.

  In the present invention, the terminal station preferentially transmits to the destination base station immediately after the handover of the terminal station, so that it is possible to increase the number of stored data frames in the reception buffer on the communication partner side, and shorten communication interruption. It becomes possible.

  In the present invention, it is also possible to reduce the communication unavailable time that occurs during the base station switching process by transferring the continuation data frame in advance to the destination base station by wire transfer in the present invention. Can be avoided or shortened.

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

(Embodiment 1)
FIG. 1 is a functional block diagram showing an example of the configuration of the base station 1 according to Embodiment 1 of the present invention. The wireless transmission / reception unit 2 has a function of modulating / demodulating a data frame or other frame to / from a terminal station and transmitting / receiving the data frame. The wired transmission / reception unit 3 has a function of transmitting / receiving a data frame or other frame by wire. The priority transmission determination unit 4 has a function of determining whether or not to preferentially transmit a data frame addressed to a terminal station. The priority transmission control unit 5 has a function of executing priority transmission when the priority transmission determination unit 4 determines that priority transmission should be performed. The wireless band management unit 6 has a function of managing the setting state of the wireless communication band. The transmission / reception buffer 7 has a function of temporarily buffering data frames for transmission or reception from a wired transmission / reception unit or a wireless transmission / reception unit. The scan control unit 8 has a function of executing active scan and passive scan. The authentication / reconnection processing unit 9 has a function of performing an authentication (authentication) and a reassociation process. The disconnection processing unit 10 has a function of performing processing of deauthentication (deauthentication) and dissociation (disconnection).

  Here, the priority transmission of the priority transmission determination unit 4 or the priority transmission control unit 5 means that the base station 1 according to the first embodiment of the present invention gives priority to the terminal station immediately before the handover over other terminal stations. Alternatively, the data frame is transmitted with priority over the non-priority transmission.

  FIG. 2 is a diagram showing priority transmission performed by the base station 1 (A) that is the movement source of the present invention. In FIG. 2A, the number of data frames stored in the reception buffer 308 of the terminal station 301 before the handover is smaller than the number of data frames addressed to the terminal station 301 in the transmission buffer 309 of the source base station 1 (A). A state in which data frames are accumulated in the source base station 1 (A) is shown. The reason why the data frame addressed to the terminal station 301 is accumulated in the source base station 1 (A) is that it is accumulated due to the occurrence of a retransmission data frame due to a data frame error during transmission or the waiting time until the transmission opportunity addressed to the terminal station 301 There are data frames etc. The waiting time until the transmission opportunity means that the data frame addressed to the terminal station 301 is sent to the transmission / reception buffer 7 while the source base station 1 (A) is transmitting / receiving data frames to / from other terminal stations other than the terminal station 301. It is the time waiting temporarily after buffering. When a plurality of terminal stations are connected to the base station, a waiting time until this transmission opportunity always occurs.

  In the present invention, if a data frame addressed to the terminal station 301 is stored in the transmission buffer 309 of the source base station 1 (A) immediately before the handover, the data frame addressed to the terminal station 301 is preferentially transmitted to the terminal station 301, so The number of stored data frames in the reception buffer of the terminal station 301 is increased. A detailed method of priority transmission will be described later.

  FIG. 2B shows a state immediately after the priority transmission. FIG. 10 is a diagram immediately after preferential transmission of all data frames addressed to the terminal station 301 in the transmission buffer 309 of the source base station. It can be seen that many data frames are accumulated in the reception buffer 308 of the terminal station 301.

  FIG. 2C is a diagram in which the terminal station 301 subsequently performs disconnection processing with the source base station 1 (A) and performs authentication processing and reconnection processing with the destination base station 1 (B). At this time, the terminal station 301 is in a communication unavailable time zone, and data frames cannot be transmitted / received from either base station, and only the data frames in the reception buffer are reproduced.

  FIG. 2D is a diagram immediately after the reconnection process is completed, the communication is disabled, and the communication is resumed.

  In this way, the source base station 1 (A) prior to the handover preferentially transmits the data frames stored for the terminal station 301, so that the number of stored data frames in the reception buffer 308 of the terminal station 301 before the handover can be reduced. As a result, the number of data frames stored in the reception buffer during the reconnection process can be prevented from being depleted.

  Whether the base station 1 (A) preferentially transmits all of the data frames stored in the transmission buffer 309 or a part thereof is preferentially transmitted. Therefore, this control will be described later in Embodiment 2 and Embodiment 3 of the present invention.

  FIG. 3 is a diagram showing a flow of handover processing in Embodiment 1 of the present invention, and is a diagram of a processing flow in which the terminal station 301 performs handover from the base station 1 (A) to the base station 1 (B). is there.

  The network configuration of FIG. 3 includes a source base station 1 (A), a destination base station 1 (B), a relay device 403 connected to an external network, and a terminal station 301 that performs handover.

  In FIG. 3, first, the terminal station 301 is communicating with the base station 1 (A). Here, when the base station 1 (A) recognizes a decrease in received electric field strength with the terminal station 301 as the terminal station 301 moves, the terminal station 301 is handed over to another base station by the priority transmission determination unit 4. It is determined that there is a high possibility, and it is determined that priority transmission is necessary in order to increase the accumulated data frame in the reception buffer of the terminal station 301 (101 in FIG. 3).

  The base station 1 (A) preferentially transmits the data frame stored in the base station 1 (A) to the terminal station 301 (102 in FIG. 3). In the base station 1 (A), the priority transmission control unit 5 controls the priority transmission and changes the setting of the radio band management 6.

  In the first embodiment of the present invention, when the terminal station 301 performs the active scan probe process (501 in FIG. 3) according to the 802.11 standard and determines the destination base station 1 (B), the source base station 1 (A), disconnection processing (502 in FIG. 3), destination base station and authentication processing (503 in FIG. 3), and reconnection processing (504 in FIG. 3) are performed.

  After that, the data frame buffered in the source base station 1 (A) is transferred to the destination base station 1 (B) by wire transmission using IAPP (505 and 506 in FIG. 3). Thereafter, the movement-destination base station 1 (B) resumes communication with the terminal station 301.

  Next, a method of preferential transmission to the terminal station 301 immediately before the handover of the source base station 1 (A) will be described.

  As a first method, the source base station 1 (A) increases the priority of the data frame addressed to the terminal station 301 immediately before the handover. This is a transmission signal value that can reduce the IFS (Inter-Frame Space) transmission interval value of DCF (Distributed Coordination Function) of the IEEE 802.11 standard or EDCA (Enhanced Distributed Channel Access) of the IEEE 802.11e standard.

  As a second method, the source base station 1 (A) increases the allocated bandwidth addressed to the terminal station 301 immediately before the handover. This is to increase the currently allocated TXOP (Transmission Opportunity) in the IEEE 802.11e draft HCCA (Hybrid Coordination Function Control Access), or to add a new TSID (Traffic Threat I). This can be realized by changing the scheduling at the source base station 1 (A).

  As a third method, the source base station 1 (A) realizes priority transmission even when there is no available communication band to be increased to the terminal station 301 immediately before the handover.

  FIG. 4 is a diagram for explaining the third priority transmission method. The terminal station 301 is handed over from the base station 1 (A) to the base station 1 (B). The terminal station 401 and the terminal station 402 are terminal stations that are communicating with the base station 1 (A) under the control of the base station 1 (A). It is assumed that the base station 1 (A) is communicating with the three terminal stations (301, 401, 402), uses the entire communication band, and has no free band.

  The base station 1 (A), when there is no free band for performing preferential transmission with respect to the terminal station 301 immediately before the handover, is a terminal station other than just before the handover (hereinafter referred to as another terminal station, in FIG. A part of the communication band used by the station 401 or the terminal station 402) is temporarily borrowed and assigned to the terminal station 301 to realize priority transmission.

  Usually, in communication band allocation, not only a band for transmitting a data frame, but also an extra band (hereinafter referred to as a retransmission retransmission band) for performing retransmission required when a frame error occurs is secured.

  In the present invention, the base station 1 (A) borrows this retransmission margin band of another terminal station and assigns it to the terminal station 301 immediately before the handover to realize the priority transmission.

  Which terminal station of a plurality of other terminal stations (terminal station 401 and terminal station 402 in FIG. 4) is selected as a retransmission margin band depends on a selection method in a propagation environment, a selection method in a transmission application, or a retransmission count setting value. There is a selection method.

  The selection method in the propagation environment is a method of borrowing the retransmission margin band of the terminal station having a good propagation environment with reference to the packet error rate and the value of the received electric field strength between the base station 1 (A) and the other terminal station. is there. If the propagation environment is good, retransmission is unlikely to occur, and it is considered that the influence of other terminal stations that have lent a retransmission margin band is small.

  The selection method in the transmission application is a method of determining from a terminal station having a large delay tolerance of the transmission application. For example, a terminal station that is transmitting video is given priority over a terminal station that is transmitting VoIP, and a terminal station that is transmitting data is selected with priority over a terminal station that is transmitting video. In real-time transmission with a small delay tolerance, it is considered that if retransmission margin bandwidth is lent and lost, immediate retransmission becomes impossible and communication is greatly affected.

  The selection method using the retransmission count setting value is a method of selecting a terminal station in which the maximum number of retransmissions is set large. This can be compensated by later retransmission if the maximum number of retransmissions is set to a large value even if the terminal station rents out a retransmission margin band and is lost.

  Further, a mechanism will be described in which the base station 1 (A) returns the borrowed retransmission bandwidth of another terminal station to the other terminal station after the handover of the terminal station 301.

  When the terminal station 301 performs handover and completes reconnection with the base station 1 (B), the band used by the terminal station 301 in the base station 1 (A) becomes an empty band. The base station 1 (A) can return the retransmission margin band of the other terminal station partially borrowed for the priority transmission of the terminal station 301 from this vacant band to the other terminal station.

  In the first embodiment, the transmission / reception buffer 7 is a transmission / reception buffer in a wireless communication section. However, the transmission / reception buffer 7 is not limited to this, and may be configured as an application buffer for reproducing VoIP, video transmission, and the like.

  In the first embodiment, the priority transmission is not limited to the Down Link from the base station 1 (A) to the terminal station 301, but immediately before the handover by the Up Link from the terminal station 301 to the base station 1 (A). The priority transmission may be performed. In this case, when the base station 1 (A) determines the possibility of handover of the terminal station 301 by the priority transmission determination unit 4, the priority transmission control unit 5 performs control to enable priority transmission using the Up Link, The priority transmission method is the same as that at the time of Down Link.

  In the first embodiment, the priority transmission is performed immediately before the handover. However, the transmission is not limited to this, and the priority transmission is performed on the Down Link from the destination base station 1 (B) to the terminal station 301 immediately after the handover. Alternatively, it may be preferentially transmitted via Up Link from the terminal station 301 to the destination base station 1 (B) immediately after the handover.

  In this case, immediately after the handover of the terminal station 301, the movement-destination base station 1 (B) controls the priority transmission of the Down Link or the Up Link in the priority transmission control unit 5.

  In the first embodiment, the priority transmission determination unit 4 of the source base station 1 (A) determines that there is a high possibility of handover to another base station due to a decrease in received electric field strength with the terminal station 301. However, the present invention is not limited to this, and parameters such as PER (Packet Error Rate) and BER (Bit Error Rate) for measuring other propagation environments, or information such as the moving speed, moving direction, and acceleration of the terminal station 301 Based on the above, the possibility of handover of the terminal station 301 may be determined.

  In the first embodiment, active scanning is used as scanning of the terminal station 301. However, the present invention is not limited to this, and other scanning methods such as passive scanning may be used.

  In the first embodiment, priority transmission between the base station 1 (A) and the terminal station 301 is performed before scanning. However, the present invention is not limited to this, and priority transmission is performed after scanning, or scanning. You may do this multiple times before and after scanning.

(Embodiment 2)
FIG. 5 is a functional block diagram showing an example of the configuration of the base station 21 according to Embodiment 2 of the present invention. The priority transmission determination unit 22 has a function of analyzing a priority transmission request from a terminal station. The advance transfer control unit 23 has a function in which the source base station performs data frame transfer in a wired manner ahead of the destination base station. In FIG. 5, the same components as those in FIG.

  FIG. 6 is a functional block diagram showing an example of the configuration of the terminal station 31 according to Embodiment 2 of the present invention. The priority transmission request unit 33 has a function of requesting priority transmission to the source base station. The buffer monitoring unit 34 has a function of monitoring increase / decrease in the transmission / reception buffer 7. The scan control unit 32 has a function of executing active scan and passive scan. The disconnection processing unit 35 has a function of performing processing of deauthentication (authentication cancellation) and dissociation (connection cancellation). The authentication / reconnection processing unit 36 has a function of performing authentication (authentication) and reassociation (reconnection) processing. In FIG. 6, the same components as those in FIGS. 1 and 5 are denoted by the same reference numerals, and description thereof is omitted.

  FIG. 7 is a diagram showing a flow of handover processing in Embodiment 2 of the present invention, and shows a flow in which the terminal station 31 performs handover from the base station 21 (A) to the base station 21 (B). It is.

  The network configuration of FIG. 7 includes a source base station 21 (A), a destination base station 21 (B), a relay device 403 connected to an external network, and a terminal station 31 that performs handover.

  In FIG. 7, the terminal station 31 is first communicating with the base station 21 (A). The terminal station 31 uses the scan processing unit 32 to perform active scan probe processing (501 in FIG. 7) to determine the destination base station 21 (B).

  Subsequently, the terminal station 31 uses the buffer monitoring unit 34 to check the number of data frames stored in the reception buffer in the transmission / reception buffer 7. Here, the terminal station 31 determines the number of data frames to be accumulated before the handover is started. The number of requested data frames is calculated by subtracting the current number of stored data frames from the number of data frames desired to be stored (111 in FIG. 7).

  When the number of requested data frames is a negative value (that is, when the current number of stored data frames is larger than the number of data frames desired to be stored before handover), it is determined that priority transmission is unnecessary. If the value is a positive value (that is, if the current number of stored data frames is smaller than the number of data frames desired to be stored before handover), it is determined that priority transmission of Down Link is necessary.

  The terminal station 31 also checks the number of data frames stored in the transmission buffer in the transmission / reception buffer 7 by using the buffer monitoring unit 34. If the stored data frame is also present in the transmission buffer, it is determined that the Up Link priority transmission is required from the base station 31 to the base station 21 (A).

  If the priority transmission request unit 33 determines that the priority transmission is necessary, the terminal station 31 uses the requested data frame number and the MAC address of the destination base station 21 (B) determined by scanning as a priority transmission request notification. And transmitted to the base station 21 (A) (112 in FIG. 7).

  When the base station 21 (A) receives the priority transmission request notification, the base station 21 (A) analyzes the priority transmission determination unit 22. The base station 21 (A) records the MAC address value of the destination base station 21 (B) included in the priority transmission request notification.

  Subsequently, the base station 21 (A) preferentially transmits the number of data frames requested by the terminal station 31 to the terminal station 31 using the Down Link (102 in FIG. 7). In addition, the terminal station 31 preferentially transmits to the base station 21 (A) by Up Link (102 in FIG. 7). Here, the priority transmission method is the same as that of the first embodiment, and the description thereof is omitted.

  After transmitting the priority transmission request notification, the terminal station 31 monitors the number of data frames stored in the reception buffer by the buffer monitoring unit 34 (113 in FIG. 7), receives the number of data frames requested by the Down Link, and uses the Up Link. Is terminated, handover is started, and disconnection processing is first performed with the base station 21 (A) (502 in FIG. 7).

  If the number of data frames requested by the terminal station 31 is not stored in the base station 21 (A), the base station 21 (A) cannot perform priority transmission of the requested number of data frames. In this case, the terminal station 31 provides an internal timer, and if the requested data frame does not arrive by priority transmission even after a certain time has elapsed, the terminal station 31 starts handover and first performs disconnection processing with the base station 21 (A) (see FIG. 7 of 502).

  When the base station 21 (A) performs the disconnection process with the terminal station 31, the preceding transfer control unit 23 uses the previously recorded MAC address value of the destination base station 21 (B) of the terminal station 31 as a basis. The continuation data frame addressed to the terminal station 31 is started in advance by wire (114 in FIG. 7).

  The terminal station 31 performs an authentication process (503 in FIG. 7) and a reconnection process (504 in FIG. 7) after the disconnection process. The terminal station 31 resumes communication immediately after the reconnection process with the base station 21 (B) is completed.

  This is because the continuous transfer of the data frame from the base station 21 (A) has reached the base station 21 (B), so that the communication can be resumed immediately. The communication disabled time 31 can also be shortened.

  In the second embodiment, the transmission / reception buffer 7 is a transmission / reception buffer in a wireless communication section. However, the transmission / reception buffer 7 is not limited to this, and may be configured as an application buffer for reproducing VoIP, video transmission, and the like.

  In the second embodiment, the start time of the preceding data frame transfer of the base station 21 (A) is set after the disconnection process. However, the present invention is not limited to this. Alternatively, the preceding data frame transfer may be started.

  In the second embodiment, the MAC address value of the destination base station 21 (B) is included in the priority transmission request notification. However, the present invention is not limited to this, and the control frame is moved to the disconnection process. The MAC address value of the destination base station 21 (B) is entered, or the terminal station 31 transmits a dedicated frame for notifying the MAC address value of the destination base station 21 (B) to the source base station 21 (A). May be. Further, not limited to the MAC address value, a BSSID (Basic Service Set IDentifier) that can identify the destination base station 21 (B) may be used.

  In the second embodiment, active scanning is used as scanning of the terminal station 31. However, the present invention is not limited to this, and other scanning methods such as passive scanning may be used.

  In the second embodiment, the priority transmission is performed immediately before the handover. However, the transmission is not limited to this, and the priority transmission is performed on the Down Link from the destination base station 21 (B) to the terminal station 31 immediately after the handover. Alternatively, it may be preferentially transmitted via Up Link from the terminal station 31 to the destination base station 21 (B) immediately after the handover. In this case, immediately after the handover, the terminal station 31 notifies the destination base station 21 (B) of the data frame information stored in the transmission / reception buffer 7 of the terminal station 31 at the priority transmission request unit 33, and the destination base station 21 ( The priority transmission determination unit 22 of B) determines the necessity of priority transmission of Down Link or Up Link, and performs priority transmission if necessary. If the number of data frames stored in the transmission buffer of the terminal station 31 exceeds a certain value, the priority transmission determination unit 22 of the movement-destination base station 21 (B) determines that the priority transmission of the Up Link is necessary. If the number of data frames stored in the receiving buffer is equal to or less than a predetermined value, it is determined that priority transmission of the Down Link is necessary.

  In the second embodiment, priority transmission between the base station 21 (A) and the terminal station 31 is performed after scanning. However, the present invention is not limited to this, and prioritized transmission is performed a plurality of times before and after scanning. You can go.

(Embodiment 3)
FIG. 8 is a functional block diagram showing an example of the configuration of the base station 41 according to Embodiment 3 of the present invention. The priority transmission determination unit 42 has a function of analyzing a priority transmission request from a terminal station. The threshold value determination unit 43 has a function of determining a threshold value by classifying a data frame transmitted to the terminal station by the transmission buffer 7 of the base station 41 and a data frame transferred to the destination base station. The advance transfer control unit 44 has a function in which the source base station performs data frame transfer by wire in advance to the destination base station. In FIG. 8, the same components as those in FIGS. 1 and 5 are denoted by the same reference numerals and description thereof is omitted.

  FIG. 9 is a functional block diagram showing an example of the configuration of the terminal station 51 according to Embodiment 3 of the present invention. The priority transmission request unit 52 has a function of requesting priority transmission to the source base station. The buffer monitoring unit 53 has a function of monitoring the number of accumulated data frames in the transmission / reception buffer. The handover trigger analysis unit 54 has a function of analyzing a handover instruction from the source base station. In FIG. 9, the same components as those in FIG.

  FIG. 10 is a diagram showing a flow of handover processing in Embodiment 3 of the present invention, and shows a flow in which the terminal station 51 performs handover from the base station 41 (A) to the base station 41 (B). It is.

  The network configuration of FIG. 10 includes a source base station 41 (A), a destination base station 41 (B), a relay device 403 connected to an external network, and a terminal station 51 that performs handover.

  In FIG. 10, the terminal station 51 is communicating with the base station 41 (A). The terminal station 51 uses the scan processing unit 32 to perform active scan probe processing (501 in FIG. 10) to determine the destination base station 41 (B).

  Subsequently, the terminal station 51 uses the buffer monitoring unit 53 to check the number of data frames stored in the reception buffer and the number of data frames stored in the transmission buffer from the transmission / reception buffer 7.

  The terminal station 51 uses the priority transmission request unit 52 to determine the number of stored data frames in the reception buffer and the maximum number of buffer memories, the number of stored data frames in the transmission buffer and the maximum number of buffer memories, and the base station 41 ( The MAC address value of B) is transmitted to the base station 41 (A) as a priority transmission request notification (121 in FIG. 10).

  When receiving the priority transmission request notification, the base station 41 (A) analyzes this by the priority transmission determination unit 42 and determines the necessity of priority transmission.

  First, the base station 41 (A) records the MAC address value of the movement-destination base station 41 (B) included in the priority transmission request notification.

  Next, the base station 41 (A) confirms the number of data frames addressed to the terminal station 51 stored in its own transmission buffer 7, and the threshold determination unit 43 uses the Down Link to preferentially transmit data to the terminal station 51. Determine the number of frames. The number of data frames preferentially transmitted to the terminal station 51 determined by the threshold determining unit 43 is the maximum value obtained by subtracting the memory amount of the data frame currently accumulated from the maximum buffer memory amount of the reception buffer of the terminal station 51. It becomes.

  That is, the number of data frames that do not cause the reception buffer to overflow in the terminal station 51 is the maximum number of data frames that the base station 41 (A) can preferentially transmit on the Down Link.

  Here, when the maximum number of data frames that can be preferentially transmitted is zero, that is, when the number of data frames stored in the reception buffer of the terminal station 51 is the maximum value that causes overflow of the reception buffer, the base station 41 (A) It is determined that priority transmission is unnecessary.

  Conversely, when the base station 41 (A) determines that priority transmission is necessary, it checks whether or not the number of data frames equal to or greater than the maximum number of data frames that can be preferentially transmitted is stored in the transmission buffer. In this case, the continuation data frame after the maximum number of data frames is determined to be transferred in advance to the destination base station 41 (B) by wire.

  That is, the threshold value determination unit 43 classifies the number of data frames that are preferentially transmitted to the terminal station 51 on the Down Link and the data frame that is transferred to the destination base station, and determines the threshold value (122 in FIG. 10). ).

  Subsequently, the base station 41 (A) starts the data frame transfer by using the preceding transfer control unit 44 prior to the movement-destination base station 41 (B) with a data frame that is equal to or greater than the threshold (123 in FIG. 10). ).

  At the same time, the base station 41 (A) preferentially transmits a data frame equal to or less than the threshold value to the terminal station 51 on the Down Link (102 in FIG. 10). The priority transmission method of the base station 41 (A) is the same as that in the first embodiment, and a description thereof will be omitted.

  The priority transmission determination unit 42 of the base station 41 (A) determines the necessity of priority transmission on the Up Link from the number of data frames stored in the transmission buffer of the terminal station 51 included in the priority transmission request notification. The base station 41 (A) determines that priority transmission is necessary when there is a stored data frame of a certain value or more in the transmission buffer of the terminal station 51, and the priority transmission control unit 5 performs priority transmission on the Up Link. The terminal station 51 performs priority transmission on the Up Link to the base station 41 (A). The band allocation method for the Up Link priority transmission is the same as the priority transmission method of the first embodiment, and a description thereof will be omitted.

  When the base station 41 (A) finishes the priority transmission of the data frame addressed to the terminal station 51 or less, the base station 41 (A) transmits a handover trigger indicating the end of the priority transmission to the terminal station 51 (124 in FIG. 10).

  When receiving the handover trigger, the terminal station 51 analyzes the handover trigger analysis unit 54, confirms the end of the priority transmission on the Up Link, and starts the handover. First, the terminal station 51 performs a disconnection process with the base station 41 (A) (502 in FIG. 10).

  After the disconnection process, the terminal station 51 performs an authentication process (503 in FIG. 10) and a reconnection process (504 in FIG. 10). The terminal station 51 resumes communication immediately after the reconnection process with the base station 41 (B) is completed.

  This is because the continuous transfer of the data frame from the base station 41 (A) has reached the base station 41 (B), so that the communication can be resumed immediately. The communication disabled time 51 can also be shortened.

  In the third embodiment, the transmission / reception buffer 7 is a transmission / reception buffer in a wireless communication section. However, the transmission / reception buffer 7 is not limited to this, and may be configured as an application buffer for reproducing VoIP, video transmission, and the like.

  In the third embodiment, the active scan is used as the scanning of the terminal station 51. However, the present invention is not limited to this, and another scanning method such as a passive scan may be used.

  In the third embodiment, the MAC address value of the movement-destination base station 41 (B) is put in the priority transmission request notification. However, the present invention is not limited to this, and the terminal station 51 is moved to the movement-destination base station. A dedicated frame for notifying the MAC address value of 41 (B) may be transmitted to the source base station 41 (A). Further, not limited to the MAC address value, a BSSID (Basic Service Set IDentifier) that can specify the destination base station 41 (B) may be used.

  In the third embodiment, the priority transmission is performed immediately before the handover. However, the transmission is not limited to this, and the priority transmission is performed from the movement-destination base station 41 (B) to the terminal station 51 by the Down Link immediately after the handover. Alternatively, it may be preferentially transmitted via Up Link from the terminal station 51 to the destination base station 41 (B) immediately after the handover. In this case, immediately after the handover, the terminal station 51 notifies the destination base station 41 (B) of the data frame information stored in the transmission / reception buffer 7 of the terminal station 51 at the priority transmission request unit 33, and the destination base station 41 ( The priority transmission determination unit 42 of B) determines the necessity of priority transmission of Down Link or Up Link, and performs priority transmission if necessary. The priority transmission determination unit 42 of the movement-destination base station 41 (B) determines that Up Link priority transmission is necessary if the number of data frames accumulated in the transmission buffer of the terminal station 51 is a certain value or more, and the terminal station If the number of data frames stored in the 51 reception buffers is less than a certain value, it is determined that Down Link priority transmission is necessary.

  In the third embodiment, the method of determining the threshold value of the transmission buffer in the source base station 41 (A) is determined based on the number of data frames stored in the reception buffer of the terminal station 51. However, the present invention is not limited to this. For example, the threshold value may be determined by the movement source base station 41 (A) grasping the movement speed information of the terminal station equipped with GPS. In this case, since the movement speed of the GPS-equipped terminal station is faster than a certain value, the movement-source base station 41 (A) reduces the number of data frames that are preferentially transmitted by the Down Link to the GPS-equipped terminal station. It is conceivable to increase the number of data frames for preceding data frame wired transfer to (B).

  In the third embodiment, priority transmission between the base station 41 (A) and the terminal station 51 is performed after scanning. However, the present invention is not limited to this, and priority transmission is performed a plurality of times before and after scanning. You can go.

  Further, in the configuration from the first embodiment to the third embodiment, all or part of the functions may be recorded on a program recording medium and executed by a computer.

  The configuration from the first embodiment to the third embodiment may be realized by an LSI (Large Scale Integration) which is typically an integrated circuit. These may be individually made into one chip, or may be made into one chip so as to include all or part of the structure. An integrated circuit may be referred to as an IC, a system LSI, a super LSI, an ultra LSI, or the like depending on the degree of integration. Further, the method of the integrated circuit is not limited to the LSI, and may be realized using a dedicated circuit or a general-purpose processor. Further, a Field Programmable Gate Array (FPGA) or a reconfigurable processor that can reconfigure the connection and setting of circuit cells inside the LSI may be used. Further, if integrated circuit technology comes out to replace current semiconductor technology as a result of the advancement of semiconductor technology or a derivative other technology, it is naturally also possible to carry out function block integration using this technology. For example, biotechnological applications can be considered.

  The base station and terminal station according to the present invention can be used for video transmission, VoIP transmission, and data transmission in a public wireless network such as a hot spot, a temporary wireless network in an event venue, or a wireless network in a home. is there.

  In particular, use in a wireless LAN system represented by IEEE 802.11 is useful.

Functional block diagram showing the configuration of the base station in Embodiment 1 of the present invention The figure which shows the receiving buffer of the terminal station in the priority transmission in Embodiment 1 to Embodiment 3 of this invention The figure which shows the flow of the handover process in Embodiment 1 of this invention The figure which shows the terminal station and other terminal station in Embodiment 1 to Embodiment 3 of this invention Functional block diagram showing the configuration of the base station in Embodiment 2 of the present invention Functional block diagram showing the configuration of a terminal station in Embodiment 2 of the present invention The figure which shows the flow of the handover process in Embodiment 2 of this invention Functional block diagram showing the configuration of the base station in Embodiment 3 of the present invention Functional block diagram showing the configuration of a terminal station in Embodiment 3 of the present invention The figure which shows the flow of the hand-over process in Embodiment 3 of this invention. The figure which shows the hand-over which a terminal station switches a base station The figure which shows the flow of the hand-over process using IAPP The figure which shows the flow of the handover process in a prior example The figure which shows the receiving buffer of the terminal station when priority transmission is not performed

Explanation of symbols

1 base station (A: source base station, B: destination base station)
DESCRIPTION OF SYMBOLS 2 Wireless transmission / reception part 3 Wired transmission / reception part 4 Priority transmission determination part 5 Priority transmission control part 6 Wireless band management part 7 Transmission / reception buffer memory 8 Scan processing part 9 Authentication / reconnection processing part 10 Disconnection processing part 11 Control part 21 Base station (A : Source base station, B: destination base station)
DESCRIPTION OF SYMBOLS 22 Priority transmission determination part 23 Precedence transfer control part 24 Control part 31 Terminal station 32 Scan process part 33 Priority transmission request part 34 Buffer monitoring part 35 Disconnection process part 36 Authentication / reconnection process part 37 Control part 41 Base station (A: Movement Former base station, B: Destination base station)
DESCRIPTION OF SYMBOLS 42 Priority transmission determination part 43 Threshold determination part 44 Precedence transfer control part 45 Control part 51 Terminal station 52 Priority transmission request part 53 Buffer monitoring part 54 Handover trigger analysis part 55 Control part 301 Terminal station 302 Base station 303 Base station 305 Terminal station 306 Base station 307 Base station 308 Terminal station reception buffer 309 Base station transmission buffer 401 Terminal station 402 Terminal station 403 Relay device

Claims (35)

In a wireless communication system composed of a terminal station and a base station, a handover method in which a terminal station switches a base station from a source base station to a destination base station by movement of the terminal station,
The source base station performs priority transmission to the terminal station immediately before the start of handover of the terminal station;
A handover method in which the terminal station performs priority transmission to the source base station immediately before the start of handover of the terminal station. In the handover method,
The terminal determines whether priority transmission is required; and
The terminal station determines, from its own reception buffer information and transmission buffer information, a request data amount that is desired to be received by priority transmission from the source base station, and a transmission data amount that is desired to be transmitted by priority transmission to the source base station, Notifying them to the source base station;
When the terminal station monitors a reception buffer and receives the requested amount of data, starting a handover;
The terminal station notifying the source base station of identification information of the destination base station;
The handover method according to claim 1, further comprising a step in which the movement source base station transfers continuation data after the requested data amount preferentially transmitted to the movement destination base station by wire. In the handover method,
The terminal station notifies the source base station of the priority transmission request with the reception buffer information and the transmission buffer information added;
The terminal station notifying the source base station of identification information of the destination base station;
The source base station determining whether priority transmission is required; and
The source base station distinguishes in a transmission buffer its data amount to be preferentially transmitted to the terminal station and data amount to be wire-transferred to the destination base station by a threshold,
The source base station forwards the continuation data after the data preferentially transmitted to the destination base station by wire;
The source base station notifying the end of priority transmission to the terminal station;
The handover method according to claim 1, further comprising a step of starting handover when the terminal station is notified of the end of priority transmission. In a wireless communication system composed of a terminal station and a base station, a handover method in which a terminal station switches a base station from a source base station to a destination base station by movement of the terminal station,
Immediately after the terminal station is handed over to the destination base station, the destination base station performs priority transmission to the terminal station;
A method in which the terminal station performs priority transmission to the destination base station immediately after the terminal station has handed over to the destination base station. In the handover method,
Immediately after the handover, the terminal station notifies the destination base station of its reception buffer information and transmission buffer information;
The handover method according to claim 4, further comprising the step of the destination base station determining the necessity of priority transmission from the reception buffer information and transmission buffer information of the terminal station. The step of determining the necessity of the priority transmission determines that the priority transmission from the destination base station to the terminal station is necessary when the accumulation amount of the reception buffer of the terminal station is equal to or less than a threshold, 6. The handover method according to claim 5, wherein when the accumulated amount of the transmission buffer of the terminal station is greater than or equal to a threshold value, it is determined that priority transmission from the terminal station to the destination base station is necessary. The handover method according to claim 1, wherein the priority transmission is to increase an assigned radio band of the terminal station. 7. The handover method according to claim 1, wherein the preferential transmission is a method of reducing an IFS transmission signal interval value of the IEEE802.11 standard. 7. The priority transmission means that a part of a radio band of a terminal station other than immediately before the start of handover is allocated and increased in a radio band of the terminal station immediately before the handover. The handover method according to claim 1. In the priority transmission, after the terminal station has completed handover, the source base station returns the radio band used by the source base station to another terminal station other than just before the start of handover. 10. The handover method according to claim 9, wherein the handover method is assigned. 10. The preferential transmission, wherein a part of a radio band of another terminal station other than immediately before the start of handover is a communication band that is reserved for retransmission of the other terminal station. Handover method. The handover method according to claim 9, wherein, in the priority transmission, the other terminal station having the best propagation environment is selected in the selection method of the other terminal stations other than immediately before the start of handover, which is present in plural. 10. The selection method of the other terminal station other than immediately before the start of handover, in which there is a plurality of prioritized transmissions, wherein the other terminal having the largest delay tolerance is selected in a transmission application in use. Handover method. 10. The handover method according to claim 9, wherein, in the priority transmission, in the selection method of the other terminal stations other than immediately before the start of handover, the other terminal having the maximum retransmission count setting value is selected. A base station of a wireless communication system composed of a mobile terminal station and a plurality of base stations of a source base station and a destination base station,
A priority transmission determination unit that determines whether or not the source base station needs priority transmission immediately before handover of the terminal station;
A priority transmission control unit for preferentially transmitting the source base station to the terminal station immediately before the start of handover of the terminal station, or preferentially transmitting the terminal station to the source base station immediately before the start of handover; base station. The moving source base station further includes a preceding transfer control unit that wire-transfers continuation data after priority transmission to the moving destination base station in advance, based on the identification information of the moving destination base station notified from the terminal station. The base station according to claim 15. In the source base station, based on the transmission buffer information and reception buffer information notified from the terminal station, the amount of data to be preferentially transmitted to the terminal station in its own transmission buffer and wired transfer to the destination base station The base station according to claim 16, further comprising a threshold value determination unit that distinguishes the amount of data to be processed by a threshold value. A base station of a wireless communication system composed of a mobile terminal station and a plurality of base stations of a source base station and a destination base station,
A priority transmission determination unit that determines whether or not there is a need for priority transmission immediately after the destination base station has handed over the terminal station;
The destination base station includes a priority transmission control unit for preferentially transmitting to the terminal station immediately after handover of the terminal station, or preferentially transmitting to the destination base station immediately after handover of the terminal station base station. The priority transmission determination unit of the destination base station determines that priority transmission from the destination base station to the terminal station is necessary when the accumulated amount of the reception buffer of the terminal station is equal to or less than a threshold, 19. The base station according to claim 18, wherein when the accumulated amount of the transmission buffer of the terminal station is equal to or greater than a threshold value, it is determined that priority transmission from the terminal station to the destination base station is necessary. The base station according to any one of claims 15 to 19, wherein the priority transmission is to increase an allocated radio band of the terminal station. The base station according to any one of claims 15 to 19, wherein the priority transmission is a reduction in an IFS transmission signal interval value of the IEEE 802.11 standard. 20. The priority transmission means that a part of a radio band of a terminal station other than immediately before the start of handover is allocated and increased to a radio band of the terminal station just before the handover. The base station according to claim 1. In the priority transmission, after the terminal station completes the handover, the source base station returns the radio band used by the source base station to the other terminal station other than immediately before the start of the handover. 23. The base station according to claim 22, wherein the base station is assigned. 23. The preferential transmission, wherein a part of a radio band of another terminal station other than immediately before the start of handover is an extra communication band reserved for retransmission of the other terminal station. base station. 23. The base station according to claim 22, wherein, in the priority transmission, the other terminal station having the best propagation environment is selected in a selection method of the other terminal stations other than immediately before the start of handover, which is present in plural. 23. In the selection method of the other terminal station other than immediately before the start of handover, a plurality of the other terminals having the largest allowable delay value are selected in a transmission application in use in the priority transmission. Base station. 23. The base station according to claim 22, wherein, in the prioritized transmission, a plurality of other terminal stations other than immediately before the start of handover are selected, and the other terminal having the maximum retransmission count setting value is selected. A terminal station of a wireless communication system composed of a mobile terminal station and a plurality of base stations of a source base station and a destination base station,
A buffer monitor for monitoring the send / receive buffer;
A priority transmission requesting unit for notifying the source base station of transmission request information and reception buffer information added to the source base station immediately before the start of handover, and requesting priority transmission; A terminal station equipped. The terminal station starts handover when the reception of the data amount requested by the priority transmission request unit from the source base station is completed or the transmission of the data amount requested by the priority transmission request unit to the destination base station is completed. The terminal station according to claim 28. A terminal station of a wireless communication system composed of a mobile terminal station and a plurality of base stations of a source base station and a destination base station,
A buffer monitor for monitoring the send / receive buffer;
A priority transmission requesting unit for sending a notification requesting priority transmission by adding transmission buffer information and reception buffer information obtained by buffer monitoring to the destination base station immediately after handover is performed by the terminal station; A terminal station equipped. The terminal station according to any one of claims 28 to 30, wherein the priority transmission request unit is a change request process of a TXOP value compliant with IEEE 802.11e. A program recording medium for causing a computer to execute all or part of the functions of the base station according to any one of claims 15 to 27. 32. A program recording medium for causing a computer to execute all or part of the functions of the terminal station according to any one of claims 28 to 31. An integrated circuit in which all or some of the functions of the base station according to any one of claims 15 to 27 are integrated. 32. An integrated circuit in which all or some of the functions of the terminal station according to any one of claims 28 to 31 are integrated.

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