JP4357321B2 - Packet transmission apparatus and program - Google Patents

Description

  The present invention relates to a route control technique, and more particularly to a route control method in a wireless network and a packet transmission apparatus that can use the method.

  Recently, wireless communication technology has been widely spread, and the weight of wireless communication services is rapidly increasing with respect to communication services realized by wired networks such as the Internet and LAN. Needless to say, mobile phones are used not only for calls but also for packet communications such as e-mail and content download. In addition, wireless LANs are spreading in offices, and users using wireless LANs are increasing in homes. In urban areas, wireless hotspots have been established, and an environment in which a mobile terminal such as a laptop computer or PDA (Personal Data Assistant) can be connected to the Internet is being prepared in the city.

  Wireless networks include an infrastructure type that assumes the presence of a wireless access point and an ad hoc type that does not assume the existence of a wireless access point. In a wireless ad hoc network, terminals equipped with a wireless communication function are interconnected as necessary to form a network.

As the use of the network spreads, the user's consciousness about the communication quality of the network increases, and the user becomes very sensitive to the deterioration of the communication quality. In particular, a wireless network has a high error rate, and quality control is an important issue. Patent Document 1 discloses a technique for suppressing a communication quality difference due to a difference in the number of hops in a wireless multi-hop network.
JP 2003-273788 A

  In a wireless ad hoc network, data communication is performed in a form of multi-hop transmission over a wireless link, so that as the number of hops increases, the available transmission band tends to decrease and the error rate tends to increase. Also, in wireless ad hoc networks, as the number of nodes that send and receive data increases and traffic increases, the available bandwidth of each data flow decreases, end-to-end throughput performance decreases, and packet delays decrease. It occurs.

  In addition, in a wireless ad hoc network, the network topology is fixed because the terminal is moved, disconnected from the network, becomes stand-alone, or a new terminal joins the network. It changes dynamically. For this reason, even if a communication path is once established for data transmission / reception, if a link on the way becomes unavailable, it becomes necessary to search for and establish a new path during the communication.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a route control method capable of searching for a new route as appropriate according to the traffic state of the network, and a packet transmission apparatus capable of using the method. Is in the provision of.

  One embodiment of the present invention relates to a packet transmission apparatus. The apparatus includes: a determination unit that determines necessity of searching for a new route based on information on a traffic state notified from a node on an already established communication route in a wireless network; and a search for a new route by the determination unit. When it is determined that a new route is required, a route search request unit that transmits a route search request message to a node on the wireless network and a response message from the node to the route search request message is selected. A route selection unit. The determination unit specifies a link to be excluded on the communication route based on the information on the traffic status, and the route selection unit discards a response message including the link to be excluded in the route. Good.

  The “packet transmission apparatus” may be either a terminal functioning as a communication node of a wireless network or a wireless access point. The communication node includes a transmission source node, a relay node, and a destination node in data transmission / reception.

  Another aspect of the present invention also relates to a packet transmission apparatus. This device determines the necessity of searching for a new route based on information on the traffic status notified from a node on an already established communication route in the wireless network, and determines a link to be excluded on the communication route. And a route search request unit that transmits a route search request message specifying a link to be excluded to a node on a wireless network when the determination unit determines that a search for a new route is necessary. And a route selection unit that selects a new route based on a response message from the node in response to the route search request.

  Still another embodiment of the present invention also relates to a packet transmission apparatus. This apparatus refers to a route search request transfer unit that broadcasts a route search request message received from a node on a wireless network to another node, and designation information of a link to be excluded included in the route search request message. A determination unit that determines whether to limit the broadcast of the route search request message, wherein the determination unit determines whether the route search request message is included in the link to be excluded specified in the route search request message. If received, the route search request transfer unit restricts broadcast of the route search request message. This configuration is mainly used in a relay node in a wireless network.

  Still another embodiment of the present invention also relates to a packet transmission apparatus. This device determines the necessity of searching for a new route based on information on the traffic status notified from a node on an already established communication route in the wireless network, and determines a link to be excluded on the communication route. And a route table change request for transmitting a route table change message specifying a link to be excluded to a node on a wireless network when the determination unit determines that a search for a new route is necessary. Part.

  Still another embodiment of the present invention relates to a route control method. This method is based on the information on the traffic situation notified from the node on the already established communication path in the wireless network. A new route is selected by executing a route search procedure between

  The route search procedure is an on-demand route setting procedure in which a transmission source node on the wireless network is a main body and a new route is determined based on a response to a search request for a new route when data is transmitted. There may be. The route search procedure may be a table-driven route setting procedure in which a relay node on the wireless network is a main body and a route table in the relay node is changed.

  Yet another aspect of the present invention relates to a routing program executed on a node in a wireless network. The program includes a step of identifying a radio link to be excluded from a path based on information on a traffic state notified from a node on an already established communication path in the radio network, and a node located downstream in the radio network And a route search procedure to select a new route that does not include the radio link to be excluded.

  It should be noted that any combination of the above-described constituent elements and a conversion of the expression of the present invention between a method, an apparatus, a system, a recording medium, a computer program, etc. are also effective as an aspect of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, according to the traffic condition of a network, it can communicate by selecting the path | route with stable communication quality.

Embodiment 1
FIG. 1 shows an overall configuration of a wireless ad hoc network according to the first embodiment. A case of source routing type on-demand routing will be described. A wireless ad hoc network is a network configured by autonomously interconnecting a plurality of terminals having a wireless communication function, and data communication can be performed by multi-hop transmission of a wireless link between these terminals. For wireless communication, wireless LAN technology such as IEEE 802.11 is used.

  It is assumed that content such as multimedia data is transmitted from the transmission source terminal 200 to the destination terminal 100a. The transmission source terminal 200 first transmits data to the destination terminal 100a via the two transfer terminals 100c and 100b, and the first communication path 10 using the two transfer terminals 100c and 100b as a relay node is transmitted. Has been established.

  While the transmission source terminal 200 performs data transfer with the destination terminal 100a using the first communication path 10, the downstream terminals of the destination terminal 100a and the two transfer terminals 100b and 100c are respectively on the communication path. Traffic conditions such as throughput, packet loss rate, and delay in the radio link are periodically measured, and a traffic status message including the measurement results of the traffic of each radio link is periodically notified to the transmission source terminal 200.

  The destination terminal 100a measures the traffic status of the radio link with the transfer terminal 100b located upstream in the first communication path 10, and includes the measurement result in the traffic status message and transmits it to the source terminal 200 ( Reference numeral 18). Further, the transfer terminal 100b measures the traffic status of the radio link with the transfer terminal 100c located upstream in the first communication path 10, and includes the measurement result in the traffic status message and transmits it to the transmission source terminal 200. (Reference numeral 16). Further, the transfer terminal 100c measures the traffic situation of the radio link with the transmission source terminal 200 located upstream in the first communication path 10, and includes the measurement result in the traffic situation message to the transmission source terminal 200. Transmit (symbol 14).

  The transmission source terminal 200 receives the traffic status message from the downstream node, and grasps the traffic status of each radio link of the first communication path 10. The transmission source terminal 200 activates a procedure for searching for a new route when it is determined that the communication quality of any one of the radio links is poor and the current communication route cannot guarantee sufficient quality at the destination terminal 100a. Thereby, a new route is selected between the transmission source terminal 200 and the destination terminal 100a. Here, a second communication path 12 is newly established with another two transfer terminals 100d and 100b as relay nodes, and the source terminal 200 transmits data to the destination terminal 100a via these transfer terminals 100d and 100b. Continue sending.

  Hereinafter, the destination terminal 100a and the transfer terminals 100b to 100d are collectively referred to as the non-transmission source terminal 100.

  FIG. 2 is a configuration diagram of the transmission source terminal 200. The route request generation unit 204 is an example of a route search request unit. In this embodiment, the route request generation unit 204 generates a route request that is a route search request message specifying a destination node according to an on-demand type routing protocol. The route reply selecting unit 206 and the route holding unit 207 are an example of a route selecting unit, and select a route reply that is a response message to the route request.

  The on-demand routing protocol is a routing protocol that is triggered by a transmission source, and a route is searched only when the transmission source requests it. When a route from the transmission source to the destination becomes necessary at the time of data transmission, the route search process is started mainly by the transmission source, and the route search process is terminated when an appropriate route is found. Examples of on-demand routing protocols include DSR (Dynamic Source Routing) and AODV (Ad Hoc On-Demand Distance Vector) protocols. DSR is a source routing type routing protocol, and route information is stored in a route reply. AODV is a non-source routing type routing protocol, and route information is not included in the route reply.

  The packet receiving unit 201 receives a packet from the wireless link. When the received packet is a traffic status message from the non-transmission source terminal 100, the packet receiving unit 201 gives the traffic status message to the new path necessity determination unit 203. When the received packet is a route reply from the non-transmission source terminal 100, the packet receiving unit 201 gives the route reply to the route reply selecting unit 206.

  The new route necessity determination unit 203 grasps the communication quality of each wireless link of the current communication route based on the traffic status message, and determines the necessity of searching for a new route. For example, when the communication quality of any wireless link is degraded in the current communication path, it is determined that a search for a new path is necessary. When determining that a new route needs to be searched, the new route necessity determination unit 203 instructs the route request generation unit 204 to search for a route.

Illustrate some criteria for determining the need for a new route search.
(1) A threshold value is provided for each measurement item of throughput, packet loss rate, delay, and jitter, and the measurement value of each measurement item notified by the traffic status message is compared with each threshold value. When there is one measurement item that does not satisfy the requirement standard based on the threshold, it is determined that a new route is necessary.

  (2) The threshold of each measurement item of the traffic situation is determined in advance before the start of content transmission / reception according to the type of content transmitted by the transmission source terminal 200. For example, in the case of data content, since real-time characteristics are not required so much, the request criteria based on threshold values for delay and jitter are relaxed. On the other hand, in the case of multimedia contents such as video and audio, real-time characteristics are relatively required, and therefore, the required criteria based on threshold values for delay and jitter are set strictly. Regarding the throughput, even for the same type of content, various settings are made depending on the terminal environment based on the screen size, audio codec, and the like. The same applies to the packet loss rate.

  (3) Searching for a new route frequently increases overhead associated with routing, increases traffic due to route search, and deteriorates network performance. Therefore, a predetermined limit is set for the search frequency for new routes. For example, when the number of times of searching for a new route exceeds a predetermined number during a certain period, the new route necessity determining unit 203 stops searching for a new route or disconnects the communication route. This is notified to an upper layer such as an application layer.

  Further, when determining that a new route needs to be searched, the new route necessity determining unit 203 identifies a wireless link with poor communication quality as a wireless link to be excluded, and an identification number of an upstream terminal of the wireless link And the excluded terminal number designating the identification number of the downstream terminal is supplied to the route reply selecting unit 206. The terminal identification number is normally specified by an IP (Internet Protocol) address.

  The route request generation unit 204 receives a route search instruction from the new route necessity determination unit 203, generates a route request specifying the destination terminal 100 a, and gives the packet request to the packet transmission unit 202. The packet transmission unit 202 broadcasts the route request to the wireless link. This route request reaches the destination terminal 100a via the relay node, and a route reply is returned from the destination terminal 100a.

  The route reply selecting unit 206 selects a new route according to the rules of the routing protocol based on the route reply acquired from the packet receiving unit 201. Here, based on the excluded terminal number received from the new route necessity determining unit 203, the route reply selecting unit 206 discards the route reply including the wireless link having the excluded terminal number as both ends, and the wireless to be excluded. Adopt a route reply that does not include links. The route holding unit 207 extracts and stores route information included in the adopted route reply.

  FIG. 3 is a configuration diagram of the non-transmission source terminal 100. The route request generation unit 110 is an example of a route search request transfer unit. In the present embodiment, the route request generation unit 110 generates a route request specifying a destination node according to an on-demand type routing protocol, and further broadcasts it.

  The packet receiving unit 101 receives a packet from a wireless link. In addition to the content data transmitted from the transmission source terminal 200, the received packet includes a route request transmitted from the transmission source terminal 200 and a route reply transferred from the downstream terminal.

  When the packet received by the packet receiving unit 101 is content data from the transmission source terminal 200, the throughput measuring unit 103, the packet loss rate measuring unit 104, the delay measuring unit 105, and the jitter measuring unit 106 The reception status is observed, the throughput, the packet loss rate, the delay, and the jitter are measured, and the measurement data is given to the traffic status message generation unit 107. The traffic status message generation unit 107 generates a traffic status message including the measurement data and having the transmission source terminal 200 as the destination address, and gives the generated packet to the packet transmission unit 102. The packet transmission unit 102 transmits the traffic status message as a packet to the wireless link. The traffic status message is transmitted in multihop and reaches the destination transmission source terminal 200.

  FIG. 4 is a diagram for explaining a traffic status message. The traffic status message includes, as data indicating the traffic status, the identification number 30 of the terminal located upstream of the wireless link to be measured by the non-transmission source terminal 100, the period 32 during which the traffic status is measured, the throughput 34, the packet loss rate 36, delay 38, and jitter 40 are included. The transmission source terminal 200 that receives this traffic status message can identify the non-transmission source terminal 100 that transmitted this message by the transmission source IP address or the like of this message. That is, the identification number of the non-transmission source terminal 100 that transmits the message need not be included in the message.

  Reference is again made to FIG. When the packet received by the packet receiving unit 101 is a route reply transferred from a downstream terminal, the routing table routing information held in the routing table storage unit 113 is determined by the route reply according to the routing protocol. While being updated, the route reply is transferred to the upstream terminal via the packet transmission unit 102. The route reply is finally transferred from the downstream terminal to the upstream terminal in this way, and finally reaches the transmission source terminal 200.

  When the packet received by the packet receiving unit 101 is a route request transmitted from the transmission source terminal 200, the route request is given to the destination terminal determination unit 108. The destination terminal determination unit 108 checks the destination address included in the route request and determines whether or not the own node is the destination terminal. When the own node is the destination terminal, the route reply generation unit 111 is instructed to respond to the route request. When the own node is not the destination terminal, that is, when the own node is the transfer terminal, the route request generation unit 110 receives the route request. Instruct the generation of.

  The route request generation unit 110 receives a route request generation instruction from the destination terminal determination unit 108, generates a route request for broadcasting a route search request, and provides the packet transmission unit 102 with the route request. The packet transmission unit 102 transmits a route request to the radio link and broadcasts the route request.

  The route reply generation unit 111 receives a response instruction to the route request from the destination terminal determination unit 108, generates a route reply to be transmitted to the transmission source terminal 200, and provides the packet transmission unit 102 with the route reply. In addition, the route reply generation unit 111 updates the routing table route information held in the routing table storage unit 113 using the information in the route request in accordance with the rules of the routing protocol. The packet transmission unit 102 transmits the route reply generated by the route reply generation unit 111 to the wireless link. The route reply is transmitted in multihop and reaches the transmission source terminal 200.

  The configuration of the transmission source terminal 200 in FIG. 2 and the configuration of the non-transmission source terminal 100 in FIG. 3 can be realized by a CPU, memory, or other LSI of any computer in terms of hardware. Specifically, it is realized by a program having a path control function loaded in a memory, but here, functional blocks realized by their cooperation are illustrated. Therefore, those skilled in the art will understand that these functional blocks can be realized in various forms by hardware only, software only, or a combination thereof.

  A route control procedure by the transmission source terminal 200 and the non-transmission source terminal 100 configured as described above will be described with reference to the flowcharts of FIGS.

  FIG. 5 is a flowchart for explaining a new route search processing procedure by the transmission source terminal 200.

  The packet receiver 201 receives a traffic status message from the non-transmission source terminal 100 (S10). The new route necessity determination unit 203 determines whether or not a new route needs to be searched based on the received traffic status message (S12). When it is determined that the communication quality of the current communication path is stable and a new path is not necessary (N in S12), the process returns to step S10, and the current communication is performed according to the traffic status message transmitted from the non-transmission source terminal 100. Continue to monitor the communication quality of the route.

  When it is determined that the communication quality of the current communication path is unstable and a new path is necessary (Y in S12), the route request generation unit 204 generates a normal route request according to the rules of the routing protocol. (S14). The packet transmission unit 202 broadcasts the route request to terminals on the wireless network (S16). The broadcast route request reaches the destination terminal 100a via the relay node, and a route reply is transmitted from the destination terminal 100a toward the transmission source terminal 200.

  The packet receiver 201 receives a route reply from the non-transmission source terminal 100 (S18). The route reply selection unit 206 selects and discards the route reply to be adopted by discarding the route reply including the wireless link having the excluded terminal number as both ends as part of the route (S20). The route holding unit 207 stores the route information included in the route reply (S22). A new route is established by the adopted route reply, and communication is continued using the new route (S24).

  FIG. 6 is a flowchart for explaining the traffic status notification processing procedure by the non-transmission source terminal 100.

  The packet receiving unit 101 receives a data packet from the upstream terminal of the wireless link (S30). This data packet is content data sent from the transmission source terminal 200. The throughput measurement unit 103 measures the throughput of the data packet, the packet loss rate measurement unit 104 measures the loss rate of the data packet, the delay measurement unit 105 measures the delay of the data packet, and the jitter measurement unit 106 Data packet delay fluctuation, that is, jitter is measured (S32). The traffic status message generation unit 107 generates a traffic status message including these measurement data (S34). The packet transmitter 102 transmits a traffic status message to the transmission source terminal 200 (S36). The traffic status message is periodically transmitted so that the network is not loaded.

  FIG. 7 is a flowchart for explaining a processing procedure when the non-transmission source terminal 100 receives a route request.

  When the packet reception unit 101 receives the route request (S40), the destination terminal determination unit 108 checks whether the destination address specified in the route request matches the address of the own node, and the own node specifies the route request. It is determined whether or not the destination terminal has been set (S42).

  When the own node is the destination terminal (Y in S42), the route reply generation unit 111 generates a route reply for responding to this route request (S44). The packet transmission unit 102 transmits a route reply to the transmission source terminal 200 (S46).

  When the own node is not the destination terminal, that is, the own node is a transfer terminal that relays the route reply (N in S42), the route request generation unit 110 generates a route request to be transmitted to the downstream terminal (S48). The packet transmitter 102 broadcasts the generated route request (S50).

  According to the present embodiment, the transmission source terminal determines whether or not a search for a new route is necessary according to the traffic status of the radio link in the current communication route. A route request is broadcasted according to the routing protocol and a route reply is received from the destination terminal. Accordingly, the transmission source terminal can find a candidate for a new route, select a new route that does not include a wireless link with poor communication quality, and perform communication with stable communication quality.

Embodiment 2
In the first embodiment, when the transmission source terminal 200 determines that a search for a new route is necessary, a new route search procedure is performed by broadcasting a normal route request according to an on-demand routing protocol. Started. In this embodiment, the source terminal 200 starts a new route search procedure according to an on-demand type routing protocol as in the first embodiment, but broadcasts a route request specifying an excluded terminal number. Is different. A configuration and operation different from those of the first embodiment will be described.

  FIG. 8 is a configuration diagram of transmission source terminal 200 according to Embodiment 2. When the received packet is a traffic status message from the non-transmission source terminal 100, the packet reception unit 201 gives the new route necessity determination unit 203, and when the received packet is a route reply from the non-transmission source terminal 100, This is given to the holding unit 207.

  The new route necessity determination unit 203 grasps the communication quality of each wireless link of the current communication route based on the traffic status message, determines the necessity of searching for a new route, and determines the wireless link with poor communication quality. Is identified as a radio link to be excluded. If the new route necessity determination unit 203 determines that a search for a new route is necessary, the route request generation unit generates an excluded terminal number that specifies the identification number of the upstream terminal and the identification number of the downstream terminal of the radio link to be excluded. 204 to instruct route search to the route request generator 204.

  The route request generation unit 204 receives a route search instruction from the new route necessity determination unit 203, generates a route request including the excluded terminal number and destined for the destination terminal 100 a, and gives the packet request to the packet transmission unit 202. The packet transmitter 202 broadcasts the generated route request to the wireless link. This route request reaches the destination terminal 100a via the relay node, and a route reply is returned from the destination terminal 100a. Here, an excluded terminal number is specified in the route request, and no more route requests via the radio link to be excluded are broadcast, so it should be excluded from the route specified in the route reply to be returned. The wireless link will not be included.

  In the case of the source routing type routing protocol, the route holding unit 207 extracts and stores the route information included in the route reply acquired from the packet receiving unit 201.

  FIG. 9 is a configuration diagram of the non-transmission source terminal 100 according to the second embodiment. The difference from the non-transmission source terminal 100 of Embodiment 1 shown in FIG. 3 is that a route request broadcast determination unit 109 is provided after the destination terminal determination unit 108. Processing is different.

  The destination terminal determination unit 108 checks the destination address included in the route request received by the packet reception unit 101, determines whether or not the own node is the destination terminal, and if the own node is the destination terminal, generates a route reply. In response to the route request to the unit 111, when the own node is not the destination terminal, that is, when the own node is the transfer terminal, the route request broadcast determining unit 109 determines whether or not to broadcast the route request.

  The route request broadcast determining unit 109 determines whether or not to further broadcast the route request based on the excluded terminal number included in the route request. When the route request is received from the radio link to be excluded specified by the excluded terminal number, the route request broadcast determination unit 109 discards the route request and does not perform broadcast transmission of the route request. If the route request is not received from a radio link that should be excluded, the route request broadcast determination unit 109 instructs the route request generation unit 110 to generate a route request.

  When the route request generation unit 110 receives an instruction to generate a route request from the route request broadcast determination unit 109, the route request generation unit 110 further generates a route request including an excluded terminal number for broadcasting a route search request. 102 broadcasts the route request.

  A route control procedure by the transmission source terminal 200 and the non-transmission source terminal 100 configured as described above will be described with reference to the flowcharts of FIGS.

  FIG. 10 is a flowchart for explaining a new route search processing procedure by the transmission source terminal 200. The processing of steps S10 and S12 is the same as the processing of the same sign in the first embodiment shown in FIG.

  When the new route necessity determination unit 203 determines that the communication quality of the current communication route is unstable and a new route is necessary (Y in S12), the route request generation unit 204 includes the excluded terminal number. A route request is generated (S15). The route request is created according to the rules of the routing protocol, and the excluded terminal number is stored in the optional data area of the route request.

  The processing of steps S16 and S18 is the same as the processing of the same sign in FIG. Here, the route request that reaches the downstream terminal of the wireless link via the wireless link to be excluded is discarded at the downstream terminal, and the route request is not broadcast after that. Therefore, there is no route reply that the packet reception unit 201 receives from the non-transmission source terminal 100 includes a wireless link to be excluded in the route. Therefore, unlike the first embodiment, the process of discarding the route reply including the wireless link having the excluded terminal number as both ends in the route is unnecessary. The processes in steps S22 and S24 are the same as the processes with the same symbols in FIG.

  FIG. 11 is a flowchart illustrating a processing procedure when the non-transmission source terminal 100 receives a route request.

  The processing of steps S40, S42, S44 and S46 is the same as the processing of the same sign in the first embodiment shown in FIG.

  When the destination terminal determination unit 108 determines that the own node is not the destination terminal based on the destination address specified in the route request, that is, the own node is a transfer terminal that relays the route reply (N in S42). The request broadcast determination unit 109 determines whether the route request is received from a radio link that should be excluded. In other words, the route request broadcast determination unit 109 receives the route request from the upstream terminal of the radio link to be excluded designated by the excluded terminal number, and the own node is downstream of the radio link to be excluded. It is determined whether it is a terminal (S47).

  If the route request broadcast determination unit 109 determines that the received route request has reached the terminal via a wireless link to be excluded (Y in S47), do not execute steps S48 and S50. , Discard the route request. Therefore, no further route requests are broadcast.

  When the route request broadcast determination unit 109 determines that the received route request has not reached the terminal via a wireless link to be excluded (N in S47), steps S48 and S50 are executed, and the route request is Further, broadcast transmission is performed.

  According to the present embodiment, the transmission source terminal determines whether or not a search for a new route is necessary according to the traffic status of the radio link in the current communication route. According to the routing protocol, a route request designating a radio link to be excluded with poor communication quality is broadcast and a route reply is received from the destination terminal. Since the route request via the radio link to be excluded is discarded at the transfer terminal, it is guaranteed that the route reply from the destination terminal does not include the radio link to be excluded in the route. As a result, the transmission source terminal can select a new route that does not include a wireless link with poor communication quality, and can perform communication with stable communication quality.

Embodiment 3
In Embodiments 1 and 2, when source terminal 200 determines that a new route search is necessary, it starts a new route search procedure according to an on-demand routing protocol. The embodiment is different in that a routing table update procedure is started according to a table-driven routing protocol.

  FIG. 12 is a configuration diagram of transmission source terminal 200 according to Embodiment 3. The routing table change message generation unit 205 is an example of a route table change request unit. In this embodiment, the routing table change message generation unit 205 generates a routing table change message as an optional function of a table-driven routing protocol.

  The table-driven routing protocol is a protocol that changes a routing table in a relay node mainly by the relay node. Each node has a routing table that stores route information, and propagates route update information throughout the network in response to changes in the network topology. Examples of table-driven routing protocols include protocols such as DSDV (Destination Sequenced Distance Vector) and WRP (Wireless Routing Protocol). In the present embodiment, a routing table change message is sent from the transmission source to the relay node using a table-driven routing protocol, thereby requesting the relay node to change the route.

  The traffic status message received from the non-transmission source terminal 100 by the packet receiving unit 201 is given to the new path necessity determination unit 203. Similar to Embodiments 1 and 2, the new route necessity determination unit 203 grasps the communication quality of each wireless link of the current communication route based on the traffic status message, and determines the necessity of searching for a new route. At the same time, a radio link with poor communication quality is identified as a radio link to be excluded. When it is determined that a new route search is necessary, the new route necessity determination unit 203 sets the upstream terminal identification number of the wireless link to be excluded and the excluded terminal number specifying the downstream terminal identification number to the routing table change message. The data is supplied to the generation unit 205, and the routing table change message generation unit 205 is instructed to change the routing table.

  The routing table change message generation unit 205 generates a routing table change message including the excluded terminal number. The routing table change message generation unit 205 sets the destination address of this routing table change message to the upstream terminal of the radio link to be excluded specified by the excluded terminal number. The packet transmission unit 202 transmits the generated routing table change message to the upstream terminal of the radio link to be excluded.

  FIG. 13 is a configuration diagram of the non-transmission source terminal 100 according to the third embodiment. Similar to the first and second embodiments, various data indicating the traffic status are measured based on the content data received by the packet receiving unit 101, a traffic status message is generated and transmitted to the transmission source terminal 200. It is.

  When the packet receiving unit 101 receives the routing table change message including the excluded terminal number from the transmission source terminal 200, the routing table changing unit 112 transfers the data to the downstream terminal of the radio link to be excluded specified by the excluded terminal number. To avoid this, a route for transferring data to another terminal is selected, and the route information in the routing table held in the routing table storage unit 113 is updated. As a result, a new route that does not pass through the radio link to be excluded is established between the transmission source terminal 200 and the destination terminal 100a.

  The routing table changing procedure by the transmission source terminal 200 and the non-transmission source terminal 100 configured as described above will be described with reference to the flowcharts of FIGS.

  FIG. 14 is a flowchart for explaining a routing table change processing procedure by the transmission source terminal 200. The processing of steps S10 and S12 is the same as the processing of the same sign in the first embodiment shown in FIG.

  When the new route necessity determination unit 203 determines that the communication quality of the current communication route is unstable and a new route is necessary (Y in S12), the routing table change message generation unit 205 determines the excluded terminal number. And a routing table change message destined for the upstream terminal of the radio link to be excluded is generated (S60). The packet transmitting unit 202 transmits the generated routing table change message to the upstream terminal of the radio link to be excluded (S62).

  FIG. 15 is a flowchart for explaining a routing table change processing procedure by the non-transmission source terminal 100.

  The packet receiving unit 101 receives the routing table change message from the transmission source terminal 200 (S70). The non-transmission source terminal 100 is an upstream terminal of a radio link that is determined to be excluded by the transmission source terminal 200. The routing table changing unit 112 refers to the excluded terminal number included in the routing table change message, and selects a terminal other than the downstream terminal of the link to be excluded as a new transfer destination of the received packet (S72).

  The routing table changing unit 112 updates the routing table held in the routing table storage unit 113 with the route information for transferring the received packet to the new transfer destination, and stores the new routing table (S74). As a result, the current route that has been transmitted to the downstream terminal of the wireless link from which the received packet should be excluded is once discarded, and a route for transmitting the received packet to the new transfer destination is newly between the source terminal 200 and the destination terminal 100a. Established in By changing the routing table, the radio link to be excluded is not used.

  According to the present embodiment, the transmission source terminal determines whether or not a new route search is necessary according to the traffic status of the radio link in the current communication route, and when a new route search is necessary, the table-driven type As an optional function of the routing protocol, a routing table change message specifying a radio link to be excluded with poor communication quality is transmitted to an upstream terminal of the radio link to be excluded. When the terminal that has received this routing table change message changes the routing table, a new route that does not include a radio link with poor communication quality is established, and communication can be performed with stable communication quality.

  The present invention has been described based on the embodiments. The embodiments are exemplifications, and it will be understood by those skilled in the art that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are within the scope of the present invention. .

  As such a modification, in the embodiment, the routing control technology of the present invention has been described by taking a wireless ad hoc network configured by connecting terminals wirelessly without including a wireless access point. Even in a wireless network including an access point, the route control technology of the present invention can be applied. In that case, the wireless access point corresponds to either the transmission source terminal or the non-transmission source terminal of the embodiment, has the same configuration, and searches for a new route. A part of the wireless network may include a wired network.

  In the embodiment, the on-demand type routing method and the table-driven type routing method have been described separately. However, the transmission source terminal 200 and the non-transmission source terminal 100 are not limited to the embodiment so that both routing methods can be supported. You may have each structure of 1-3.

  The terminal having the wireless communication function of the embodiment may be an in-vehicle terminal, and the route control technique of the present invention can be applied when a wireless ad hoc network is configured between vehicles traveling on a road. As an application example to ITS (Intelligent Transport Systems), in order to notify traffic information and the like from the vehicle ahead to the vehicle behind, it is possible to configure a wireless ad hoc network between in-vehicle terminals and use it for data communication. Since the communication status and the communication route between the in-vehicle terminals are frequently changed depending on the traveling state of the vehicle, it is possible to ensure stable communication quality by searching for a new route as appropriate by the route control technology of the present invention. it can.

1 is an overall configuration diagram of a wireless ad hoc network according to Embodiment 1. FIG. It is a block diagram of the transmission source terminal of FIG. It is a block diagram of the non-transmission source terminal of FIG. It is a figure explaining the traffic status message notified to a transmission source terminal from the non-transmission source terminal of FIG. It is a flowchart explaining the new route search processing procedure by the transmission source terminal of FIG. It is a flowchart explaining the traffic condition notification processing procedure by the non-transmission source terminal of FIG. It is a flowchart explaining the process sequence at the time of the route request reception by the non-transmission source terminal of FIG. 6 is a configuration diagram of a transmission source terminal according to Embodiment 2. FIG. 6 is a configuration diagram of a non-transmission source terminal according to Embodiment 2. FIG. It is a flowchart explaining the new route search processing procedure by the transmission source terminal of FIG. It is a flowchart explaining the process sequence at the time of the route request reception by the non-transmission source terminal of FIG. FIG. 9 is a configuration diagram of a transmission source terminal according to Embodiment 3. FIG. 10 is a configuration diagram of a non-transmission source terminal according to Embodiment 3. 13 is a flowchart illustrating a new route search processing procedure by the transmission source terminal of FIG. 12. It is a flowchart explaining the process sequence at the time of the route request reception by the non-transmission source terminal of FIG.

Explanation of symbols

  100a destination terminal, 100b to d transfer terminal, 100 non-transmission source terminal, 200 transmission source terminal, 101 packet reception unit, 102 packet transmission unit, 103 throughput measurement unit, 104 packet loss rate measurement unit, 105 delay measurement unit, 106 jitter Measurement unit 107 Traffic status message generation unit 108 Destination terminal determination unit 109 Route request broadcast determination unit 110 Route request generation unit 111 Route reply generation unit 112 Routing table change unit 113 Routing table storage unit 201 Receive packet , 202 packet transmission unit, 203 new route necessity determination unit, 204 route request generation unit, 205 routing table change message generation unit, 206 route Reply selection unit, 207 path holding unit.

Claims (6)

A determination unit that determines the necessity of searching for a new route based on information on a traffic state notified from a node on an already established communication route in a wireless network;
A route search request unit that transmits a route search request message to a node on the wireless network when the determination unit determines that a search for a new route is necessary;
Based on the response message from node for the route search request message, looking contains a path selection section for selecting a new route,
The determination unit identifies a link to be excluded on the communication path based on the information on the traffic status,
The packet transmission device , wherein the route selection unit discards a response message including the link to be excluded in the route . A determination unit that determines the necessity of searching for a new route based on information on a traffic state notified from a node on an already established communication route in a wireless network and identifies a link to be excluded on the communication route When,
A route search request unit that transmits a route search request message specifying a link to be excluded to a node on a wireless network when the determination unit determines that a search for a new route is necessary;
A packet transmission apparatus comprising: a route selection unit that selects a new route based on a response message from a node in response to the route search request. A route search request transfer unit that broadcasts a route search request message received from a node on the wireless network to another node;
A determination unit that determines whether to limit broadcasting of the route search request message with reference to designation information of a link to be excluded included in the route search request message;
The determination unit restricts broadcast of the route search request message by the route search request transfer unit when the route search request message is received from the link to be excluded specified in the route search request message. A packet transmission apparatus. A determination unit that determines the necessity of searching for a new route based on information on a traffic state notified from a node on an already established communication route in a wireless network and identifies a link to be excluded on the communication route When,
A route table change request unit that transmits a route table change message that specifies the link to be excluded to a node on a wireless network when the determination unit determines that a search for a new route is necessary. A characteristic packet transmission apparatus. 5. The determination unit according to claim 1 , wherein the determination unit determines the necessity of searching for the new route in consideration of a restriction defined with respect to a frequency of searching for the new route. Packet transmission equipment. A routing program executed on a node in a wireless network,
Identifying a radio link to be excluded from the path based on information on traffic status notified from a node on an already established communication path in the wireless network;
Executing a route search procedure with a node located downstream on a wireless network, and selecting a new route that does not include the wireless link to be excluded.

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