WO2007141879A1

WO2007141879A1 - Node device

Info

Publication number: WO2007141879A1
Application number: PCT/JP2006/311650
Authority: WO
Inventors: Yasuo Koide; Hiroshi Ishida; Takeshi Kanazawa
Original assignee: Panasonic Corporation
Priority date: 2006-06-09
Filing date: 2006-06-09
Publication date: 2007-12-13

Abstract

Provided is a node device capable of improving communication reliability by reducing the packet loss even when a handover of a terminal under its control has failed. An access point control device (100) as a node device transfers data, upon decision of a handover, to a node device of the handover destination, stops the communication data transfer when the handover has failed, and transmits the communication data to the terminal of the destination. The access point control device (100) includes: a handover control unit (140) which stops transfer of the communication data when the handover has failed and controls buffering of the communication data; and a transmission order control management unit (150) which transmits the transferred communication data which has been returned from the node device of the handover destination, to the terminal of the destination and then transmits the buffered communication data to the terminal of the destination.

Description

Specification

Node equipment

Technical field

TECHNICAL FIELD [0001] The present invention relates to a node device, and more particularly, to a node device related to handover control of a terminal under its control.

Background art

In mobile communication, a mobile station changes the base station to be connected as it moves. This is called a nondo bar. When performing a handover, it is necessary to switch the radio link from the source base station to the destination base station and to switch the network path.

[0003] During handover, there is a non-communication time during which a mobile station cannot transmit and receive packets. As a high-speed handover method for reducing this no-communication time, a communication system has been proposed in which a method of transferring packets from a source base station to a destination base station before switching a radio link is applied. (For example, Non-Patent Document 1). According to this non-patent document, when handover to a new access router (NAR) that is a handover destination access point control device fails, PAR ( Figure 1 shows the sequence for returning to the Previous Access Router. In this figure, MN is a mobile station, and PAP (Previous Access Point) force under MN power PAR tries to make a node to NAP (New Access Point) under NAR. Failed to establish a wireless link and performs switchback processing.

[0004] Specifically, when the terminal (MN) finds a nearby access point (AP) in step 1001, it transmits an RtSolPr (Router Solicitation Proxy) message to the access point control device. This message includes the AP identifier.

[0005] In step 1002, the transmission source PAR transmits a Pr RtAdv (Proxy Router Advertisement) message to the terminal in response to the RtSolPr message. When the PAR has information about the AP included in the RtSolPr message, the PrRtAdv message includes the AP information and AR Link Layer address, IP address, prefix information, etc. as a set. When the terminal receives this message, it will be used after handover N CoA (New Care-of Address) can be generated.

[0006] In step 1003, the terminal sends an FBU (Fast Binding Update) message to the PAR. This message includes PCoA (Previous Care-of Address) and NCoA, and PAR performs binding (association) between PCoA and NCoA.

[0007] PAR retrieves the NAR's IP address from NCoA,

KHandover Initiate) message. This message includes the terminal's PCoA, Link Layer address, and NCoA. When this message is received, NAR registers NCoA and can receive packets addressed to NCoA.

[0008] If the U flag of the HI message is ON, in step 1005, the NAR

Buffers packets addressed to NCoA that are forwarded (transferred) from R.

[0009] In step ST1006, the NAR transmits HAck (Handover Initiate Ack) to the PAR as a response to the HI message.

[0010] Upon receiving HAck, in step 1007, PAR transmits FBack to the terminal as a response to the FBU message.

[0011] In step 1008, the terminal switches the radio link to the NAP (node over), but here it fails, so the switch back to PAP is performed.

[0012] In step 1009, the terminal transmits an FBU message with Lifetime = 0 set to PAR. PAR then releases the binding (association) between PCoA and NCoA.

[0013] In step 1010, the PAR sends FBack to the terminal as a response to the FBU message.

Non-Patent Document 1: IETF RFC4068 (Fast Handovers for Mobile IPv6)

Disclosure of the invention

Problems to be solved by the invention

[0014] However, in the conventional communication system, at the time of handover, since the buffering is not performed in the node device that is the handover source, the packet that has been transferred to the node device that is the handover destination is discarded at the time of switching back, and packet loss occurs. There is a problem that the reliability of communication deteriorates. [0015] An object of the present invention is to provide a node device that reduces packet loss and improves communication reliability even when handover of a subordinate terminal fails.

Means for solving the problem

[0016] The node device of the present invention transfers communication data to a handover destination node device with a handover decision, stops the transfer of the communication data with the failure of the handover, and the communication data A handover control means for stopping the transfer of the communication data due to the failure of the handover and controlling the buffering of the communication data, and the failure of the handover Transmission control means for transmitting the transferred communication data sent back to the destination terminal and then buffering and transmitting the communication data to the destination terminal. The structure which comprises these is taken.

[0017] Further, the node device of the present invention comprises a receiving means for receiving communication data transferred as a handover source node device in response to a handover decision, a buffer for buffering the communication data, And a control means for transmitting the buffered communication data to the handover source node apparatus in response to a handover failure.

The invention's effect

[0018] According to the present invention, it is possible to provide a node device that reduces packet loss and improves communication reliability in the system even when handover of a subordinate terminal fails.

Brief Description of Drawings

[0019] [Fig. 1] Sequence diagram for explaining movement at the time of handover in a conventional communication system

FIG. 2 is a block diagram showing a configuration of a handover source access point control apparatus according to Embodiment 1 of the present invention.

FIG. 3 is a block diagram showing a configuration of a handover destination access point control apparatus according to Embodiment 1.

FIG. 4 is a block diagram showing the configuration of the switchback control unit in FIG. FIG. 5 is a block diagram showing the configuration of the transmission order control management unit in FIG.

FIG. 6 is a block diagram showing the configuration of the switchback control unit in FIG.

FIG. 7 is a block diagram showing the configuration of the transmission order control management unit in FIG.

FIG. 8 is a sequence diagram for explaining movements in the communication system according to the first embodiment.

FIG. 9 is a sequence diagram for explaining movements in the communication system of the second embodiment. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that, in the embodiments, the same components are denoted by the same reference numerals, and the description thereof is omitted because it is redundant.

[0021] (Embodiment 1)

Fig. 2 shows a block diagram showing the configuration of the access point control device (PAR) that controls the access point (AP) that is the handover source, and Fig. 3 shows the control of the access point that is the handover destination. A block diagram showing the configuration of the access point controller (NAR) to be used is shown. The access point control apparatuses 100 and 200 shown in FIG. 2 and FIG. 3 have basically the same configuration. The operation differs depending on whether it is a handover source or a handover destination. . Fig. 2 shows the signal lines that are mainly necessary for a handover source, and Fig. 3 shows the signal lines that are mainly required for a handover destination.

As shown in FIG. 2, handover source access point control apparatus 100 includes radio transmission section 105, radio reception section 110, transmission / reception section 115, transmission / reception section 120, data processing section 125, and data processing. Unit 130, data processing unit 135, handover control unit 140, transmission order control management unit 150, and transfer processing unit 160.

[0023] Radio transmission section 105 transmits communication data from transmission order control management section 150 to the terminal. Radio receiving section 110 receives the signal transmitted from the terminal and sends it to data processing section 125.

The transmission / reception unit 115 includes an upper station reception interface 117 and an upper station transmission interface 119, and transmits and receives signals to and from the upper station. The transceiver 120 includes a handover destination node transmission interface 122, a handover destination node reception interface 124, And transmits and receives signals to and from the access point control device 200 that is the handover destination.

[0025] The data processing unit 125 receives a signal transmitted from the terminal via the wireless reception unit 110, and outputs the signal to the transmission / reception unit 115 or the handover control unit 140 according to the signal.

The data processing unit 130 outputs communication data from the upper station to the transfer processing unit 160 in accordance with the output destination instruction from the handover control unit 140. In addition, when the data processing unit 130 receives a notification that the handover has failed from the handover control unit 140, the data processing unit 130 stops outputting the communication data to the transfer processing unit 160 and outputs it to the transmission order control management unit 150. To do.

[0027] When it is determined that a terminal under the control of its own device is to be handed over, the handover control unit 140 transmits communication data (in this case, to the handover destination access point control device 200 along with this handover) Control is performed to transfer communication data from the upper station to the terminal. When the handover control unit 140 receives a notification that the determined handover has failed, the handover control unit 140 performs control to stop the transfer of communication data to the access point control device 200, and transmits the communication data to the destination. Controls transmission to the above terminals. In addition, when a notification is received from the terminal due to a handover failure, a switchback message is generated and transmitted to the access point control apparatus 200 via the transmission / reception unit 120. Further, the handover control unit 140 performs control for buffering communication data that is transmitted with higher local power from the time when the transfer of the communication data is stopped.

Specifically, the handover control unit 140 includes a handover control unit 170, a switchback control unit 180, and a QoS determination unit 190.

[0029] The handover control unit 170 outputs communication data from a higher-level station from the data processing unit 130 to the transfer processing unit 160 when it is determined that a terminal under its control is to be handed over. Communication data transfer control. Prior to the transfer of the communication data, the handover control unit 170 notifies the handover destination access point control device 200 of the handover via the transmission / reception unit 120, and the handover destination corresponding to this notification is sent. Response sent from access point controller 200 The signal is received and the transfer control is performed.

[0030] When the switchback control unit 180 receives a notification from the terminal via the radio reception unit 110 and the data processing unit 125 due to a handover failure, the switchback control unit 180 generates a switchback message and passes through the transmission / reception unit 120. Transmit to the handover destination access point control apparatus 200. Further, the switchback control unit 180 sends a command to change the output destination to the transmission order control management unit 150 to the data processing unit 130 along with the transmission of the switchback message, and sends it to the transmission order control management unit 150. In response, a buffering instruction is sent. Further, when the switchback control unit 180 receives the notification of the completion of the retransfer from the handover destination access point control device 200 via the data processing unit 135, the switchback control unit 180 receives the communication data in the transmission order control management unit 150. Control to stop buffering.

[0031] When processing according to QoS of communication data is performed, switch-back control unit 180 inquires QoS of communication data (or session) to QoS determination unit 190 and obtains it as a response. A buffering instruction is not sent to the transmission order control management unit 150 according to the traffic type. Specifically, when the traffic type is real-time traffic, there is no need to wait for communication data retransmitted by switchback, and therefore no buffering instruction is sent to the transmission order control management unit 150. On the other hand, when the traffic type is non-real time traffic, as described above, the switchback message is transmitted, the output destination change command, and the buffering instruction are output.

Specifically, as shown in FIG. 4, switchback control section 180 has an input signal determination section 182, a buffering instruction section 184, and a switchback message generation section 186.

[0033] The input signal determination unit 182 determines input signals from the data processing unit 125 and the data processing unit 135, and when the input signal is a notification signal transmitted from the terminal due to a handover failure. Then, a message generation command signal is sent to the switchback message generation unit 186. In this case, the input signal determination unit 182 sends an instruction to the data processing unit 130 to change the output destination to the transmission order control management unit 150, and the buffering instruction unit 184 receives a buffering instruction. A command signal to be transmitted to the transmission order control management unit 150 is output. Also, the input signal determination unit 182 receives a backup signal when the input signal is a notification signal for notifying completion of retransmission from the handover destination access point control apparatus 200. Generates a buffering stop instruction to the failing instruction unit 184 and transmits the transmission order control management unit

The command signal sent to 150 is output.

[0034] Switchback message generation section 186 generates a switchback message in accordance with the message generation command signal from input signal determination section 182 and transmits it to handover destination access point control apparatus 200 via transmission / reception section 120. .

The noffering instruction unit 184 sends a buffering instruction or a buffering stop instruction to the transmission order control management unit 150 in accordance with the command signal from the input signal determination unit 182. However, when processing according to QoS of communication data is performed as described above, no sending instruction is sent to the transmission order control management unit 150 according to the traffic type.

In response to the inquiry from the switchback control unit 180, the QoS determination unit 190 returns a traffic type corresponding to the communication data (or session).

[0037] Transmission order control management section 150 performs communication data buffering and transmission control received from data processing section 130 and data processing section 135. In other words, when a buffering command signal is received from the handover control unit 140 due to a handover failure, communication data (in this case, communication from a higher station to a terminal) corresponding to the command signal (data processing unit 130 is changed). Communication data received via the Internet). In addition, the communication data (communication data received via the data processing unit 135) returned (re-transmitted) from the access point control device 200 that is the destination of the handover due to the handover failure is directed to the terminal. Transmit via 105 (transmit without buffering), and then transmit the communication data being buffered to the terminal.

Specifically, the transmission order control management unit 150 includes a buffering management function unit 152 and a transmission processing unit 154 as shown in FIG. When the noffering management function unit 152 receives a nofering command signal from the switchback control unit 180 of the handover control unit 140, the communication data (in this case, communication from the higher station to the terminal) corresponding to the command signal is transmitted ( The communication data received via the data processing unit 130 is buffered. The transmission processing unit 154 transmits communication data (reception received via the data processing unit 135) returned (re-transferred) from the handover destination access point control device 200 due to the handover failure. Communication data) is transmitted to the terminal via the wireless transmission unit 105 (transmitted without buffering), and then the buffered communication data is transmitted to the terminal.

The data processing unit 135 sends various signals received via the handover destination access point control device 200 power transmission / reception unit 120 to the handover control unit 140 or the transmission order control management unit 150. In particular, when the data processing unit 135 receives communication data retransmitted from the access point control device 200 that is the handover destination via the transmission / reception unit 120, the data processing unit 135 is added to transfer and retransmit the data. The header part is removed and output to the transmission order control management unit 150.

[0040] Transfer processing section 160 performs processing to transfer communication data received from data processing section 130 to access point control apparatus 200 at the handover destination.

Next, the access point control apparatus 200 will be described.

As shown in FIG. 3, the access point control apparatus 200 includes a wireless transmission unit 205, a wireless reception unit 210, a transmission / reception unit 215, a transmission / reception unit 220, a data processing unit 225, a data processing unit 230, The data processing unit 235, the handover control unit 240, the transmission order control management unit 250, and the transfer processing unit 260 are included.

[0043] Radio transmission section 205 transmits communication data from transmission order control management section 250 to the terminal. The wireless reception unit 210 receives a signal transmitted from the terminal and sends it to the data processing unit 225.

The transmission / reception unit 215 includes an upper station reception interface 217 and an upper station transmission interface 219, and transmits and receives signals to and from the upper station. The transmission / reception unit 220 includes a handover source node transmission interface 222 and a handover source reception interface 224, and transmits and receives signals to and from the handover source access point control device 100.

[0045] Data processing unit 225 receives a signal transmitted from the terminal via radio reception unit 210, and outputs the signal to transmission / reception unit 215 in accordance with the signal. The data processing unit 230 inputs communication data from the upper station and outputs it to the transmission order control management unit 250.

When the handover control unit 240 determines that a terminal under the handover source access point control device 100 is to be handed over, the communication data transferred from the handover source access point control device 100 Buffer Take control. Further, when the handover fails, control is performed to retransmit the buffered communication data in accordance with a switchback message transmitted from the handover source access point control device 100. Then, when the retransmission is completed, the handover control unit 240 generates a switchback completion message as a completed notification and transmits it to the handover source access point control apparatus 100.

Specifically, the handover control unit 240 includes a handover control unit 270, a switchback control unit 280, and a QoS determination unit 290.

[0048] The handover control unit 240 determines that a terminal under the handover source access point control device 100 is to be handed over, and the handover source access point control device 100 receives the transmission / reception unit 220 and data processing from the handover source access point control device 100. When the notification is received via the unit 235, a command signal for buffering the communication data transferred to the transmission order control management unit 250 is output, and a response signal to the received notification is controlled by the access point of the handover source. The data is transmitted to the apparatus 100 via the transmission / reception unit 220.

When the switchback control unit 280 receives a switchback message from the handover source access point control apparatus 100 via the transmission / reception unit 220 and the data processing unit 235, the switchback control unit 280 is buffered in the transmission order control management unit 250. Control to re-transfer the communication data. Also, when the switchback control unit 280 receives a notification to that effect from the transmission order control management unit 250 when the retransmission is completed, the switchback control unit 280 generates a retransmission completion message, and the access point control device that Send to 100.

[0050] When processing according to QoS of communication data is performed, the switchback control unit 280 inquires QoS of communication data (or session) to the QoS determination unit 290 and obtains it as a response. Depending on the traffic type, control is performed to discard without performing re-transfer control. Specifically, when the traffic type is real-time traffic, there is no need to retransmit by switching back, so the transmission order control management unit 250 outputs a communication data discard command that is buffered. . On the other hand, when the traffic type is non-real-time traffic, as described above, the retransmission is controlled and a switchback completion message is transmitted.

Specifically, as shown in FIG. 6, switchback control unit 280 has an input signal determination unit 282, a buffering instruction unit 284, and a switchback completion message generation unit 286. When the input signal determination unit 282 receives the switchback message via the data processing unit 235, the input signal determination unit 282 notifies the buffering instruction unit 284 accordingly.

[0053] Upon receiving the notification from the input signal determination unit 282, the buffering instruction unit 284 outputs a retransfer command signal instructing the transmission order control management unit 250 to retransmit the buffered communication data. . Further, when receiving the notification that the retransfer has been completed from the transmission order control management unit 250, the noffering instruction unit 284 outputs a message generation command signal to the switchback completion message generation unit 286. However, when processing according to QoS of communication data is performed as described above, a discard order command for discarding communication data that is not a re-transfer command signal is sent according to the traffic type. Output to.

When the switchback completion message generation unit 286 receives the message generation command signal from the noffering instruction unit 284, the switchback completion message generation unit 286 generates a switchback completion message and passes the transmission / reception unit 220 to the handover source access point control device 100. Send to.

In response to the inquiry from the switchback control unit 280, the QoS determination unit 290 returns a traffic type corresponding to the communication data (or session).

Transmission order control management unit 250 performs buffering and transmission control of communication data received from data processing unit 230 and data processing unit 235. That is, when a buffering command signal is received from the handover controller 240, the communication data transferred from the handover source access point controller 100 is buffered. In addition, when a retransfer command signal is received from the hand-over control unit 240, the communication data being nominated is retransferred to the handover source access point control device 100 via the transfer processing unit 260. When the re-transfer is completed, the handover control unit 240 is notified accordingly. Also, when a discard command is received from the handover control unit 240, the communication data transferred from the handover source access point control device 100 and buffered is deleted.

Specifically, as shown in FIG. 7, transmission order control management section 250 has buffering management function section 252 and buffering management function section 254.

The buffering management function unit 252 receives the communication data from the data processing unit 230 via the buffering function management unit 254 when the own device relays communication between the upper station and the terminal. Send to the end.

[0059] When receiving the buffering command signal from the handover control unit 270 of the handover control unit 240, the noffering management function unit 254 receives the communication data transferred from the handover source access point control device 100. Is received via the data processing unit 235 and is processed. In addition, when receiving the re-transfer command signal from the switchback control unit 280 of the handover control unit 240, the noffering management function unit 254 performs the noferring and transmits the communication data to the handover source access point control device 100. The data is retransmitted via the transfer processing unit 260. Then, when the retransfer is completed, the buffering management function unit 254 notifies the switchback control unit 280 to that effect. Further, when the noffering management function unit 254 receives a discard command from the switchback control unit 280, the buffering management function unit 254 erases the communication data that is buffered.

The data processing unit 235 sends various signals received via the transmission / reception unit 220 to the handover control unit 240 or the transmission order control management unit 250 as well as the handover source access point control apparatus 100.

The transfer processing unit 260 performs a process of retransferring the communication data received from the transmission order control management unit 250 to the access point control device 100 that is the node source.

Next, operations in a communication system including the access point control device 100 and the access point control device 200 having the above-described configuration will be described with reference to FIG. This section describes the case where the IPv6 high-speed hand-over technology specified in RFC 4068 of IE TF (Internet Engineering Task Force) is applied. Steps 1001 to 1010 are the same as those shown in the background art.

In step 1001, when the terminal (MN) finds a nearby access point (NAP), it transmits an RtSolPr (Router Solicitation Proxy) message to the access point controller (PAR) 100. This message includes the AP identifier.

[0064] In step 1002, the access point control device (PAR) 100 of the transmission source transmits a PrRtAdv (Proxy Router Advertisement) message to the terminal in response to the RtSolPr message. If the PAR has information about the AP included in the RtSolPr message! /, The PrRtAdv message will include the AP information and the AR Link Label address, IP address, Fix information is included as a set. When the terminal receives this message, it can generate an NCoA (New Care-of Address) to be used after the handover.

In step 1003, the terminal transmits an FBU (Fast Binding Update) message to PAR 100. This message includes PCoA (Previous Care-of Address) and NCoA, and PAR100 performs binding (association) between PCoA and NCoA.

[0066] The PAR 100 searches the IP address of the access point control device (NAR) 200 of the destination AP from the NCoA, and transmits a HI (Handover Initiate) message to the NAR 200 in step 1004. This message includes the terminal's PCoA, Link Layer address, and NCoA. When this message is received, the NAR 200 registers NCoA and can receive packets addressed to NCoA.

[0067] When the U flag of the HI message is ON, in step 1005, in the NAR 200, the packet destined for the NCoA forwarded (transferred) from the PAR is controlled by the switchback control unit 280. Will buffer.

[0068] In step 1006, the NAR 200 transmits HAck (Handover Initiate Ack) to the PAR 100 as a response to the HI message.

[0069] When HAck is received, PAR100 transmits FBack as a response to the FBU message to the terminal in step 1007.

[0070] In step 1008, the terminal switches the radio link to the NAP (node over), but here, since it failed, the switch back to PAP is performed.

[0071] In step 1009, the terminal transmits an FBU message in which lifetime = 0 is set to PAR100. Then, PAR100 releases the binding (association) between PCoA and NCoA.

[0072] In step 1010, the PAR 100 transmits FBack as a response to the FBU message to the terminal.

[0073] In step 1011, when FPAR with lifetime = 0 is received from the terminal in PAR100, the transmission order control management unit 150 is transmitted to the terminal (from HA to the terminal) under the control of the handover control unit 140. (Destination address is PCoA packet). However, the QoS of the packet can be identified, and the retransmitted packet from the NAR200 If it is determined that the request delay time cannot be satisfied (that is, real-time packet, etc.), it is transmitted to the terminal without performing noffering.

[0074] In step 1012, the terminal transmits an FBU message to NAR 200 via PAR 100 in order to receive retransmission of the packet buffered in NAR 200.

[0075] In Step 1013, when the NAR 200 receives the FBU message, the transmission order control management unit 250 tunnels the buffering packet addressed to the NCoA with the header addressed to the PCoA by the control of the handover control unit 240, and sends it to the PAR100. Perform retransfer. However, if it is possible to identify the QoS of the packet and it is determined that the delay time does not satisfy the QoS, the packet is discarded without being retransmitted.

[0076] In step 1014, in PAR100, the data processing unit 135 determines the contents of the header, and if the destination address of the outer IP header is PCoA and the source address is NAR, FMIP Remove the tunneling header (this is the IP header that was added when the packet was transferred from the PAR to the NAR when attempting a handover) and the above IP header. In other words, packets retransmitted from the NAR 200 are encapsulated with double headers! / ヽ, so the headers are removed.

In Step 1015, the PAR 100 transmits the packet from which the header is removed from the data processing unit 235 to the terminal without buffering.

[0078] In step 1016, in the NAR 200, when all of the packets buffered in the transmission order control management unit 250 have been retransferred to the PAR 100, the handover control unit 240 sends FBack to the terminal via the PAR 100. To send. However, if it is discarded in step 1013 without retransmitting the packet, FBack is sent immediately after receiving the FBU.

[0079] In step 1017, in PAR 100, when data processing unit 135 confirms FBack reception, data processing unit 135 sends a notification signal to switch-back control unit 180, and switch-back control is performed according to the notification signal. The unit 180 sends the transmission command signal of the packet buffered in the transmission order control management unit 150 to the transmission order control management unit 150. Then, the transmission order control management unit 150 transmits all the packets that are being buffered to the terminal, and at the same time, releases the buffering and transmits the packet addressed to the terminal to which HA power is further transmitted. Send to the end.

As described above, according to the present embodiment, as the handover is determined !, the communication data is transferred to the handover destination node apparatus (access point control apparatus 200), and the handover fails. The transfer of the communication data to the node device (access point control device 100) that stops the transfer of the communication data and transmits the communication data to the destination terminal is stopped when the handover fails, and the communication A handover control unit 140 that controls buffering of data, and the transferred communication data sent back from the handover destination node apparatus in response to the failure of the handover to the destination terminal, and then the buffering And a transmission order control management unit 150 for transmitting the communication data to the destination terminal.

[0081] By so doing, it is possible to prevent communication data loss even when handover of a subordinate terminal fails. As a result, communication reliability in the communication system can be improved.

In addition, when the communication data is data that requires real-time property, the handover control unit 140 performs control to transmit the communication data to the destination terminal without buffering.

[0083] In addition, a transmission / reception unit 220 that receives communication data that is transferred to the access point control device 200 as a node device when the handover is determined, and a transmission that buffers the communication data An order control management unit 250 and a handover control unit 240 that transmits the communication data to the hand-over source node device after buffering in response to the failure of the handover are provided.

In this way, loss of communication data can be prevented even when the handover of a terminal under the handover source node apparatus fails. As a result, communication reliability in the communication system can be improved.

In addition, when the communication data buffered in the transmission order control management unit 250 is data that requires real-time properties, the handover control unit 240 transmits the data to the handover source node device. Discard without.

[0086] Note that communication data is not transmitted to the terminal !, preventing the situation, that is, loss of communication data To do so, the handover source node device transfers the communication data to the handover destination node device in the same manner as described above, and the handover source node device also buffers the communication data. Therefore, if the handover fails, the node device power of the handover destination does not retransmit the transferred communication data. The node node power of the handover can also transmit the communication data buffered to the terminal. Conceivable. At this time, the transferred communication data is discarded in the handover destination node device.

However, in this case, it is necessary to secure a large storage capacity for buffering communication data in both the handover source node apparatus and the handover destination node apparatus. There is a problem that becomes. This is because the access points and base stations have been downsized in recent years!

[0088] On the other hand, with the present embodiment, it is not necessary to secure a large storage capacity in the node device due to the failure of handover, which is frequently occurring in the first place. A small and light weight can be realized. In addition, the cost of the node equipment can be reduced.

[0089] (Embodiment 2)

In the first embodiment, the description has been made on the assumption that the technology defined in the Internet Engineering Task Force (IETF) IPv6 fast handover (RFC4068) is applied. On the other hand, in Embodiment 2, a case will be described in which the present invention is applied to a 3GPP LTE (Long Term Evolution) RAN (Radio Access Network) network. The communication system in this embodiment has a terminal (UE), a base station (ENB), and an upper station (aGW). ENB has a function that combines the access point and the access point control device in the first embodiment in a sense that it directly communicates with the terminal and controls the handover of the terminal. Therefore, the base station (ENB) has the same configuration as that of the access point control apparatus 100 of Embodiment 1 (see FIG. 2) when it is a handover source, and when it is a handover destination. Has the same configuration as that of the access point control apparatus 200 of Embodiment 1 (see FIG. 3).

Next, FIG. 2, FIG. 3, and FIG. 9 show the operation of the communication system according to the present embodiment. The description will be given with reference. The handover source base station (ENB) is called Source ENB, and the handover destination base station (ENB) is called Target ENB.

[0091] The terminal measures the radio quality such as the radio strength of the ENB adjacent to the connected Source ENB. In step 2001, the terminal transmits a measurement report including the measurement result to the source ENB. The Source ENB makes a handover execution decision based on this report information and a database that maintains the radio quality as a condition for executing handover.

[0092] When it is decided to hand over to the Target ENB,

The ENB sends a Context Transfer message to the Target ENB. This message includes context information necessary for handover.

[0093] In Step 2003, the Target ENB sends an H and over (H.O) Preparation Request message to the aGW in order to secure the resources of the upper station (aGW).

[0094] In Step 2004, the aGW responds to the Handover Preparation Request message, and transmits the Handover (H.O Preparation Acknowledge message) to the Target ENB.

[0095] In step 2005, the Target ENB replies to the Context Transfer message as a response to the Context Transfer Complete message Source ENB.

[0096] In Step 2006, when a Context Transfer Complete message is received, forwarding (transfer) of the downstream packet to the Source ENB force Target ENB is started. At this time, the source ENB does not copy or buffer the transfer packet.

[0097] In step 2007, the Source ENB transmits an RB Reconfiguration message to the terminal to notify the radio link switching.

[0098] In step 2008, the packet forwarded from Source ENB

Buffered with ENB.

[0099] In step 2009, the terminal receives the RB Reconfiguration message,

The power to try to establish a radio link with the ENB fails here.

[0100] In step 2010, the terminal performs RB Reco for Source ENB to perform switchback. Send nfiguration message (no-over failure).

[0101] In step 2011, the Source ENB transmits a RB Reconfiguration Complete message as a response to the RB Reconfiguration message (no-over failure), and establishes a radio link.

[0102] In step 2012, the Source ENB stops forwarding to the Target ENB.

[0103] In step 2013, the Source ENB processes the packet received from the aGW according to the context information. That is, if the packet is a real-time packet, the Source ENB transmits it to the terminal without performing the noferring. On the other hand, if the packet is a non-real-time packet, the Source ENB performs buffering.

[0104] In step 2014, the Source ENB sends an H.O failure Notify message that is a handover failure notification to the Target ENB.

[0105] In step 2015, the Target ENB processes the buffered packet according to the context information. In other words, if the buffering packet is a real-time packet, it is meaningless to retransmit to the Source ENB and is discarded. On the other hand, if it is a non-real-time buffer rig packet, re-transfer processing is performed to the Source ENB.

[0106] In step 2016, Target ENB § H.O Preparation Cancel message § Releases reservation resource to aGW.

[0107] In step 2017, the aGW sends an H.O Preparation Cancel Response message to Tar get ENB as a response to the H.O Preparation Cancel message.

[0108] In step 2018, the Source ENB controls the transmission order of the non-real-time packet received from the aGW and the retransmitted packet from the Target ENB. That is, the Source ENB transmits the retransmitted packet from the Target ENB to the terminal immediately without buffering, and then buffers the packet and transmits the packet from the aGW to the terminal.

[0109] In step 2019, when the transfer of all the buffering packets is completed, the Target ENB transmits a HO failure Notify Response message to the Source ENB. [0110] In step 2020, the Source ENB stops buffering non-real-time received packets from the aGW and transmits them to the terminal.

[0111] Thus, in this embodiment as well, as in Embodiment 1, communication data loss is prevented even when handover of a terminal under the handover source node device fails. be able to. As a result, communication reliability in the communication system can be improved. Furthermore, the node device can be reduced in size and weight and cost can be reduced.

Industrial applicability

[0112] The node device of the present invention is useful for reducing packet loss and improving communication reliability in the system even when handover of a subordinate terminal fails.

Claims

The scope of the claims

[1] When the handover is determined, the communication data is transferred to the node device to which the handover is performed, and when the handover fails, the transfer of the communication data is stopped and the communication data is transferred to the destination terminal. A node device for transmitting,

A handover control means for stopping the transfer of the communication data due to the failure of the handover and controlling the buffering of the communication data;

When the handover fails, the handover destination node device sends back the transferred communication data to the destination terminal, and then sends the buffered communication data to the destination terminal. Transmission control means;

A node device comprising:

2. The node device according to claim 1, wherein the handover control means performs control to transmit the communication data to the destination terminal without buffering according to the quality required for the communication data.

[3] A reception means for receiving the communication data to be transferred in response to the node device power of the node over source in accordance with the handover decision,

A buffer for buffering the communication data;

In response to the failure of the handover, the buffering and the control means for transmitting the communication data to the handover source node device,

A node device comprising:

[4] The node device according to claim 3, wherein the control means discards without transmitting to the handover source node device according to the quality required for the communication data buffered in the buffer.