JP4543222B2 - Wireless device - Google Patents

Description

  The present invention relates to a radio apparatus, and more particularly to a radio apparatus constituting an ad hoc network that is autonomously and instantaneously constructed by a plurality of radio apparatuses.

  An ad hoc network is a network that is autonomously and instantaneously constructed by a plurality of wireless devices communicating with each other. In an ad hoc network, when two wireless devices that communicate with each other do not exist in the communication area, a wireless device located between the two wireless devices functions as a router and relays a data packet. Can be formed.

  Such an ad hoc network is about to be applied to various fields such as a wireless communication network in a stricken area and streaming in ITS (Intelligent Transport Systems) inter-vehicle communication (Non-Patent Document 1).

  Dynamic routing protocols that support multi-hop communication include table-driven protocols and on-demand protocols. The table-driven protocol periodically exchanges control information related to a route and constructs a route table in advance, and includes FSR (Fish-eye State Routing), OLSR (Optimized Link State Routing), and TBRPF (Topology). (Dissociation Based on Reverse-Path Forwarding) and the like are known.

  In addition, the on-demand protocol is a method for constructing a route to a destination for the first time when a data transmission request occurs, and includes DSR (Dynamic Source Routing) and AODV (Ad Hoc On-Demand Distance Vector Routing). Are known.

In a conventional ad hoc network, when data communication is performed from a transmission source to a transmission destination, a communication path is determined so that the number of hops from the transmission source to the transmission destination is as small as possible (Non-Patent Document 2).
Masahiro Watanabe “Wireless Ad Hoc Network”, Automobile Engineering Society Spring Meeting Humantronics Forum, pp 18-23, Yokohama, May 2003. Guangyu Pei, at al, “Fisheye state routing: a routing scheme for ad hoc wireless networks”, ICC2000. Commun., Volume 1, pp70-74, LA, June 2000.

  However, in the proactive routing protocol, each wireless device periodically updates the routing table. However, if the routing table update timing shifts between a plurality of wireless devices, locally incorrect network topology information is displayed. There is a problem that a wireless device appears, and that causes packet loss and delay.

  FIG. 12 is a conceptual diagram of packet throwing. When the wireless device 1 is transmitting data to the wireless device 4 via the wireless devices 2 and 3, even if the route between the wireless device 3 and the wireless device 4 is disconnected, routing is performed between the wireless devices 2 and 3. When the update timing of the table is different, the wireless device 2 tries to transmit data to the wireless device 4 using the route A, and the wireless device 3 knows that the route to the wireless device 4 is disconnected. Therefore, data is transmitted to the wireless device 2 in an attempt to transmit data to the wireless device 4 using the path B.

  As a result, so-called packet throwing occurs, in which packets collide between the wireless devices 2 and 3.

  FIG. 13 is a diagram showing experimental results of packet throwing. In FIG. 13, the vertical axis represents the number of hops, and the horizontal axis represents the number of packets. Note that the experimental result shown in FIG. 13 is a result of an experiment in a system that cannot count 9 hops or more, and therefore, in FIG. 13, 9 hops or more are displayed as 9 hops.

  Most packets arrive in 2 to 3 hops, but where 9 hops are displayed, packet throws occur.

  As described above, when a plurality of wireless devices existing in the wireless network update the routing table at different timings, there is a problem that packet throwing actually occurs and packet loss and delay occur.

  Accordingly, the present invention has been made to solve such a problem, and an object of the present invention is to provide a radio apparatus capable of preventing packet loss or delay based on packet throwing.

  According to the present invention, a wireless device is a wireless device that is autonomously established and constitutes a wireless network in which wireless communication is performed between a transmission source and a transmission destination, and includes a measurement unit, an adjustment unit, And table updating means. The measuring means measures a first time in the wireless device based on a time measuring device commonly used in the wireless network. The adjusting means adjusts the time measuring device so that the first time matches the second time when the first time is different from the second time based on the time measuring device in another wireless device. The table updating means updates the routing table in synchronization with the first time when the first time is substantially the same as the second time, and the first time is different from the second time in other wireless devices. At the same time, the routing table is updated in synchronization with the adjusted time from the timing device.

  Preferably, the adjusting means adjusts the time measuring device so that the first time matches the second time when the first time is later than the second time.

  Preferably, the adjusting unit includes a receiving unit and a setting unit. The receiving unit receives a packet including the second time from another wireless device. When the receiving means receives the packet, the setting means extracts the second time from the received packet, compares the extracted second time with the first time, and the second time is the first time When it is different from the time, the second time is set in the timing device.

  Preferably, the first and second times consist of first and second time counter values, respectively.

  Preferably, the packet is a packet that includes information on a wireless device adjacent to the wireless device and is transmitted periodically.

  Preferably, the table update means updates the routing table in synchronization with the set time.

  In the wireless device according to the present invention, when the first time in the wireless device is different from the second time in the other wireless device, the time measuring device is adjusted so that the first time matches the second time, The routing table is updated in synchronization with the adjusted time. Then, by repeating the above adjustment in each wireless device, the time in each wireless device becomes substantially the same, and each wireless device existing in the wireless network updates the routing table at substantially the same timing.

  Therefore, according to the present invention, it is possible to prevent packet loss or delay based on packet throwing.

  Embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  FIG. 1 is a schematic diagram of a wireless network system using a wireless device according to an embodiment of the present invention. The wireless network system 100 includes wireless devices 31 to 43. The wireless devices 31 to 43 are arranged in a wireless communication space and autonomously configure a network. The antennas A51 to A63 are attached to the wireless devices 31 to 43, respectively.

  For example, in the wireless network system 100, when data is transmitted from the wireless device 31 to the wireless device 42, the wireless devices 32, 35, 36, 37, 38, 39, 40, and 41 relay data from the wireless device 31. To the wireless device 42.

  In this case, the wireless device 31 can perform wireless communication with the wireless device 42 via various routes. That is, the wireless device 31 can perform wireless communication with the wireless device 42 via the wireless devices 37 and 41, and perform wireless communication with the wireless device 42 via the wireless devices 32, 36, and 39. It is also possible to perform wireless communication with the wireless device 42 via the wireless devices 32, 35, 38, and 40.

  When wireless communication is performed via the wireless devices 37 and 41, the number of hops is the smallest “3”, and when wireless communication is performed via the wireless devices 32, 36, and 39, the number of hops is “4”. When wireless communication is performed via the devices 32, 35, 38, and 40, the number of hops is as many as “5”.

  Accordingly, when a route for performing wireless communication via the wireless devices 37 and 41 is selected, the number of hops becomes the smallest “3”.

  As described above, in the wireless network system 100, when wireless communication is performed between the wireless device 31 as the transmission source and the wireless device 42 as the transmission destination, the number of hops is minimized by referring to the routing table. The route from the wireless device 31 to the wireless device 42 is determined.

  However, if the wireless devices 31, 37, 41, and 42 update the routing table at different timings in the route of the wireless device 31 -the wireless device 37 -the wireless device 41 -the wireless device 42, packet throwing occurs, Packet loss and delay occur.

  Therefore, in the following, a method will be described in which the wireless devices 31 to 43 update the routing table almost synchronously in the wireless network system 100.

  The OLSR protocol is used as an example of a protocol for establishing a communication path between a transmission source and a transmission destination. The OLSR protocol is a table-driven routing protocol, and is a protocol for exchanging route information by using a Hello message and a TC (Topology Control) message to create a routing table.

  FIG. 2 is a schematic block diagram showing the configuration of the wireless device 31 shown in FIG. The wireless device 31 includes an antenna 11, an input unit 12, an output unit 13, a user application 14, and a communication control unit 15.

  The antenna 11 constitutes each of the antennas A51 to A63 shown in FIG. The antenna 11 receives data from other wireless devices via the wireless communication space, outputs the received data to the communication control unit 15, and transmits the data from the communication control unit 15 via the wireless communication space. Send to other wireless device.

  The input unit 12 accepts a message and data destination input by the operator of the wireless device 1 and outputs the accepted message and destination to the user application 14. The output unit 13 displays a message according to control from the user application 14.

  The user application 14 generates data based on the message and destination from the input unit 12 and outputs the data to the communication control unit 15.

  The communication control unit 15 includes a plurality of modules that perform communication control in accordance with an ARPA (Advanced Research Projects Agency) Internet hierarchical structure. That is, the communication control unit 15 includes a radio interface module 16, a MAC (Media Access Control) module 17, a buffer 18, an LLC (Logical Link Control) module 19, an IP (Internet Protocol) module 20, and a routing table 21. A TCP module 22, a UDP module 23, a routing daemon 24, and a time counter 25.

  The wireless interface module 16 belongs to the physical layer, modulates / demodulates a transmission signal or a reception signal according to a predetermined rule, and transmits / receives a signal via the antenna 11. The wireless interface module 16 detects the received signal strength of the Hello packet received by the antenna 11 from another wireless device, and outputs the detected received signal strength to the routing daemon 24.

  The MAC module 17 belongs to the MAC layer, executes the MAC protocol, and executes various functions described below.

  That is, the MAC module 17 broadcasts the Hello packet received from the routing daemon 24 via the wireless interface module 16.

  The MAC module 17 performs retransmission control of data (packets).

  The buffer 18 belongs to the data link layer and temporarily stores packets.

  The LLC module 19 belongs to the data link layer and executes the LLC protocol to connect and release a link with an adjacent wireless device.

  The IP module 20 belongs to the Internet layer and generates an IP packet. The IP packet includes an IP header and an IP data portion for storing a packet of a higher protocol. Then, when receiving data from the TCP module 22, the IP module 20 stores the received data in the IP data portion and generates an IP packet.

  Then, the IP module 20 searches the routing table 21 according to the OLSR protocol, which is a table-driven routing protocol, and determines a route for transmitting the generated IP packet. Then, the IP module 20 transmits the IP packet to the LLC module 19 and transmits the IP packet to the transmission destination along the determined path.

  The routing table 21 belongs to the Internet layer and stores path information in association with each transmission destination, as will be described later.

  The TCP module 22 belongs to the transport layer and generates a TCP packet. The TCP packet is composed of a TCP header and a TCP data part for storing data of an upper protocol. Then, the TCP module 22 transmits the generated TCP packet to the IP module 20.

  The UDP module 23 belongs to the transport layer, broadcasts an Update packet created by the routing daemon 24, receives an Update packet broadcast from another wireless device, and outputs it to the routing daemon 24.

  The routing daemon 24 belongs to the process / application layer, monitors the execution state of other communication control modules, and processes requests from other communication control modules.

  Further, when the routing daemon 24 transmits the route information in the wireless network system 100 to another wireless device, the routing daemon 24 creates a Hello packet including various messages such as information about the adjacent wireless device, and the created Hello packet is transmitted to the MAC. Output to module 17.

Furthermore, the routing daemon 24 calculates the optimum route based on the route information of the Hello packet received from another wireless device, and dynamically creates the routing table 21 in the Internet layer.
Further, the routing daemon 24 obtains the time counter value Tcnt1 indicating the time at the wireless device 1 from the time counter 25, and detects the time counter value Tcnt2 included in the Hello packet received from another wireless device. Then, the routing daemon 24 compares the time counter value Tcnt1 with the time counter value Tcnt2, and when the time counter value Tcnt1 is smaller than the time counter value Tcnt2, the time counter value Tcnt2 is set in the time counter 25 as the time in the wireless device 1. To do. On the other hand, when the time counter value Tcnt1 is equal to or greater than the time counter value Tcnt2, the routing daemon 24 maintains the time counter value Tcnt1 of the time counter 25 as it is.

  Further, the routing daemon 24 updates the routing table 21 at a predetermined timing in synchronization with the time counter value Tcnt1 from the time counter 25.

  For example, the time counter 25 counts up every 10 msec and outputs the time in the wireless device 1 to the routing daemon 24.

  Note that each of the wireless devices 32 to 43 illustrated in FIG. 1 has the same configuration as the configuration of the wireless device 31 illustrated in FIG. 2.

  FIG. 3 is a configuration diagram of the IP header. The IP header includes a version, header length, service type, packet length, identification number, flag, fragment offset, lifetime, protocol, header checksum, source IP address, destination IP address, and options.

  FIG. 4 is a configuration diagram of the TCP header. The TCP header includes a transmission source port number, a transmission destination port number, a sequence number, an acknowledgment (ACK) number, a data offset, a reservation, a flag, a window size, a header checksum, and an argent pointer.

  The transmission source port number is a number that identifies an application that has output a TCP packet when a plurality of applications are operating on the transmission source wireless device. The transmission destination port number is a number that identifies an application that delivers a TCP packet when a plurality of applications are operating on the transmission destination wireless device.

  TCP communication is an end-to-end connection-oriented communication protocol. A TCP module 22 of a wireless device that requests a connection connection of TCP communication (hereinafter referred to as “TCP communication connection request device”) has a connection in which SYN (Synchronize Flag) is set in Code Bit in the TCP header when the connection is established. The first packet indicating the connection request is transmitted to the TCP module 22 of the terminal that accepts the connection connection of TCP communication (hereinafter referred to as “TCP communication connection accepting device”). In response to this, the TCP module 22 of the TCP communication connection accepting apparatus connects the second packet indicating the connection request acceptance and connection completion of the connection in which SYN and ACK (acknowledgement) are set in the Code Bit in the TCP header to the TCP communication connection. Transmit to the TCP module 22 of the requesting device. In response to this, the TCP module 22 of the TCP communication connection requesting device sends a third packet indicating the completion of connection of the connection in which the Code Bit in the TCP header is set to ACK (acknowledgment response) to the TCP of the TCP communication connection receiving device. Transmit to module 22.

  The connection disconnection request can be made from either the TCP communication requesting device or the TCP communication receiving device. A TCP module 22 of a wireless device that requests disconnection of TCP communication (hereinafter referred to as “TCP communication disconnection request device”) has a connection in which Code Bit in the TCP header is set to FIN (Finish Flag) when the connection is disconnected. The first packet indicating the disconnection request is transmitted to the wireless device that accepts the disconnection of the TCP communication (hereinafter referred to as “TCP communication disconnection accepting device”). In response to this, the TCP module 22 of the TCP communication disconnection accepting apparatus receives the second packet indicating acceptance of the disconnection request for the connection in which the Code Bit in the TCP header is set to ACK (acknowledgment response), and the Code Bit in the TCP header. A third packet indicating completion of disconnection of the connection set in FIN is transmitted to the TCP module 22 of the TCP communication disconnection requesting device. Further, in response to this, the TCP module 22 of the TCP communication disconnection requesting device sends a fourth packet indicating the completion of disconnection of the connection in which the Code Bit in the TCP header is set to ACK (acknowledgment response) to the TCP communication disconnection receiving device TCP. Transmit to module 22.

  FIG. 5 is a configuration diagram of a packet PKT in the OLSR protocol. The packet PKT includes a packet header PHD and message headers MHD1, MHD2,. Note that the packet PKT is transmitted and received using the port number 698 of the UDP module 23.

  The packet header PHD includes a packet length and a packet sequence number. The packet length consists of 16-bit data and represents the number of bytes of the packet. The packet sequence number consists of 16-bit data and is used to distinguish which packet is new. The packet sequence number is incremented by “1” every time a new packet is generated. Therefore, the larger the packet sequence number, the newer the packet PKT.

  Each of the message headers MHD1, MHD2,... Includes a message type, a valid time, a message size, a source address, a TTL, a hop count, a message sequence number, and a message.

  The message type is composed of 8-bit data and represents the type of message written in the message body, and 0 to 127 are reserved. The valid time consists of 8-bit data, and represents the time when this message must be managed after reception. The valid time is composed of a mantissa part and an exponent part.

  The message size consists of 16-bit data and represents the length of the message. The source address is made up of 32-bit data and represents the wireless device that generated the message. The TTL is composed of 8-bit data and specifies the maximum number of hops to which a message is transferred. The TTL is decremented by “1” when the message is transferred. If the TTL is “0” or “1”, the message is not transferred. The number of hops consists of 8-bit data and represents the number of hops from the message generation source. The number of hops is initially set to “0” and is incremented by “1” every time it is transferred. The message sequence number consists of 16-bit data and represents an identification number assigned to each message. The message sequence number is incremented by “1” every time a message is created. The message is a message to be transmitted.

  In the OLSR protocol, various messages are transmitted and received using the packet PKT having the configuration shown in FIG.

  FIG. 6 is another configuration diagram of the packet. The packet PKT_T is a packet that is transmitted and received between the wireless devices 31 to 43 when the time counter values in the wireless devices 31 to 43 are substantially synchronized.

  The packet PKT_T includes a header part HD, a time information part TIFO, and a data part DATA. The header part HD stores the address of the wireless device that has transmitted the packet PKT_T. The time information unit TIFO stores the time counter value counted by the time counter 25. The data part DATA stores routing table information.

  The packet PKT_T is periodically transmitted as an OLSR protocol Hello packet.

  FIG. 7 is a configuration diagram of the routing table 21 shown in FIG. The routing table 21 includes a transmission destination, a next wireless device, and the number of hops. The transmission destination, the next wireless device, and the number of hops are associated with each other. “Destination” represents the IP address of the destination wireless device. “Next wireless device” represents the IP address of the wireless device to be transmitted next when transmitting the packet PKT to the transmission destination. “Hop number” represents the number of hops to the destination. For example, in FIG. 1, when wireless communication is performed between the wireless device 31 and the wireless device 42 through the route of the wireless device 31 -the wireless device 32 -the wireless device 36 -the wireless device 39 -the wireless device 42, the wireless device 32 “3” is stored as the number of hops in the routing table 21.

  The creation of the routing table 21 according to the OLSR protocol will be described in detail. When creating the routing table 21, the wireless devices 31 to 43 transmit and receive a Hello message and a TC message.

  The Hello message is periodically transmitted for the purpose of distributing information included in each of the wireless devices 31 to 43. By receiving this Hello message, each of the wireless devices 31 to 43 can collect information on peripheral wireless devices, and recognizes what wireless devices exist in the vicinity of the wireless devices.

  In the OLSR protocol, each of the wireless devices 31 to 43 manages local link information. The Hello message is a message for constructing and transmitting the local link information. The local link information includes “link set”, “adjacent radio device set”, “two-hop adjacent radio device set and link set to those radio devices”, “MPR (Multipoint Relay) set”, and “MPR selector set”. including.

  A link set is a link to a set of wireless devices (adjacent wireless devices) through which radio waves directly reach, and each link is expressed by an effective time of a set of addresses between two wireless devices. The valid time is also used to indicate whether the link is unidirectional or bidirectional.

  The neighboring wireless device set is configured by the address of each neighboring wireless device, the retransmitting degree (Willingness) of the wireless device, and the like. The 2-hop adjacent wireless device set represents a set of wireless devices adjacent to the adjacent wireless device.

  The MPR set is a set of wireless devices selected as MPRs. Note that MPR means that when each packet PKT is transmitted to all the wireless devices 31 to 43 of the wireless network system 100, each wireless device 31 to 43 transmits and receives all the packets PKT by transmitting and receiving one packet PKT only once. The relay wireless device is selected so that it can be transmitted to the wireless devices 31-43.

  The MPR selector set represents a set of wireless devices that have selected themselves as MPRs.

  The process of establishing local link information is generally as follows. In the initial stage of the Hello message, each wireless device 31 to 43 transmits a Hello message containing its own address to an adjacent wireless device in order to notify its existence. All of the wireless devices 31 to 43 perform this operation, and each of the wireless devices 31 to 43 grasps what address the wireless device has around itself. In this way, a link set and an adjacent wireless device set are constructed.

  The constructed local link information is continuously sent again by a Hello message again. By repeating this, it is gradually clarified whether each link is bidirectional or what kind of wireless device exists ahead of the adjacent wireless device. Each of the wireless devices 31 to 43 stores the local link information that is gradually constructed in this way.

  Further, information regarding MPR is also periodically transmitted by a Hello message and notified to each of the wireless devices 31 to 43. Each of the wireless devices 31 to 43 selects several wireless devices from among neighboring wireless devices as a set of MPRs as wireless devices that request retransmission of the packet PKT transmitted by itself. Then, since the information regarding this MPR set is transmitted to the adjacent radio apparatus by the Hello message, the radio apparatus that has received this Hello message sets the set of radio apparatuses that it has selected as the MPR as the “MPR selector set”. to manage. By doing in this way, each radio | wireless apparatus 31-43 can recognize immediately which packet apparatus PKT received should be retransmitted.

  When a local link set is established in each of the wireless devices 31 to 43 by transmission / reception of the Hello message, a TC message for notifying the topology of the entire wireless network system 100 is transmitted to the wireless devices 31 to 43. This TC message is periodically transmitted by all wireless devices selected as MPRs. Since the TC message includes a link between each wireless device and the MPR selector set, all the wireless devices 31 to 43 of the wireless network system 100 know all the MPR sets and all the MPR selector sets. Based on all the MPR sets and all the MPR selector sets, the topology of the entire wireless network system 100 can be known. Each of the wireless devices 31 to 43 calculates the shortest path using the topology of the entire wireless network system 100 and creates a route table based on the calculated shortest path.

  In addition, each radio | wireless apparatus 31-43 exchanges a TC message frequently separately from a Hello message. MPR is also used for exchanging TC messages.

  The UDP module 23 of each of the wireless devices 31 to 43 transmits and receives the above-described Hello message and TC message, and the routing daemon 24 determines the topology of the entire wireless network system 100 based on the Hello message and TC message received by the UDP module 23. The shortest path is calculated based on the topology of the entire wireless network system 100, and the routing table 21 shown in FIG. 7 is dynamically created based on the calculated shortest path.

  The adjustment of the time counter value in each of the wireless devices 31 to 43 will be described in detail.

  The routing daemon 24 receives the Hello packet PKT_T received from another wireless device from the UDP module 23, and detects the time counter value Tcnt2 stored in the time information part TIFO of the received Hello packet PKT_T.

  Further, the routing daemon 24 obtains the time counter value Tcnt1 from the time counter 25. Then, the routing daemon 24 compares the time counter value Tcnt1 with the time counter value Tcnt2, and when the time counter value Tcnt1 is smaller than the time counter value Tcnt2, the time counter 25 uses the time counter value Tcnt2 as the time counter value in the wireless device. Set to.

  When the time counter value Tcnt2 is set in the time counter 25, the routing daemon 24 updates the routing table 21 in synchronization with the time counter value Tcnt1 received from the time counter 25 after the setting. As a result, the routing daemon 24 can update the routing table 21 in synchronization with a timing close to the update timing of the routing table 21 in another wireless device existing in the wireless network system 100. Then, by repeating the operation of adjusting the time counter value Tcnt1 to the time counter value Tcnt2, the time counter values of the wireless devices 31 to 43 existing in the wireless network system 100 become substantially constant, and each of the wireless devices 31 to 43 is set. The routing daemon 24 can update the routing table 21 at almost the same timing.

  On the other hand, when the time counter value Tcnt1 is equal to or greater than the time counter value Tcnt2, the routing daemon 24 maintains the time counter value of the time counter 25.

  FIG. 8 is a flowchart for explaining operations related to creation and update of the routing table 21.

  When a series of operations is started, in each of the wireless devices 31 to 43, the routing daemon 24 creates the routing table 21 by the above-described operation (step S1).

  Thereafter, the routing daemon 24 adjusts the time counter value Tcnt1 of the time counter 25 (step S2). Then, the routing daemon 24 updates the routing table 21 in synchronization with the adjusted time counter value Tcnt1 (step S3).

  As a result, a series of operations is completed.

  FIG. 9 is a flowchart for explaining the detailed operation of step S2 shown in FIG. After step S1 shown in FIG. 8, the routing daemon 24 receives the Hello packet PKT_T (step S21). Then, the routing daemon 24 reads the time counter value Tcnt2 stored in the time information part TIFO of the Hello packet PKT_T, and acquires the time counter value Tcnt1 from the time counter 25.

  Then, the routing daemon 24 determines whether or not its own time counter value is smaller by determining whether or not the time counter value Tcnt1 is smaller than the time counter value Tcnt2 (step S22).

  When the time counter value Tcnt1 is greater than or equal to the time counter value Tcnt2, the series of operations proceeds to step S3 shown in FIG. On the other hand, when the time counter value Tcnt1 is smaller than the time counter value Tcnt2, the routing daemon 24 sets the time counter value Tcnt1 to the time counter value Tcnt2 (step S23).

  That is, when the time counter value Tcnt1 is smaller than the time counter value Tcnt2, the routing daemon 24 adjusts the time counter value Tcnt1 to the time counter value Tcnt2 in another wireless device.

  Thereby, the time counter value of the wireless device having the time counter value Tcnt1 smaller than the time counter value Tcnt2 in the other wireless device can be matched with the time counter value Tcnt2 in the other wireless device. Then, each of the wireless devices 31 to 43 existing in the wireless network system 100 adjusts its own time counter value according to the flowchart shown in FIG. 9, so that the time counter value in the wireless devices 31 to 43 is substantially constant. Converges to a value.

  As a result, the wireless devices 31 to 43 can update the routing table 21 in synchronization with the time counter value that has converged almost uniformly, and can prevent packet throws and delays.

  When the time counter value Tcnt1 is smaller than the time counter value Tcnt2, setting the time counter value Tcnt1 to the time counter value Tcnt2 in step S23 means that the time at the wireless device is later than the time at the other wireless device. This corresponds to adjusting the time in the wireless device to the time in another wireless device.

  A description will be given of the results of experiments conducted on the occurrence of packet throwing when the time counter value is adjusted as described above.

  FIG. 10 is a plan view showing an experimental environment for throwing packets. A number such as “68” in FIG. 10 represents a wireless device, and a black circle represents an arrangement position of the wireless device. “EV” represents an elevator. The experiment was then conducted in an environment where many rooms, corridors, stairs, elevators and atriums were located.

  A plurality of wireless devices are arranged in many rooms or corridors to constitute an ad hoc network. In the experiment, a route from the wireless device 60 to the wireless device 67 is defined as a route 1, and a route from the wireless device 68 to the wireless device 62 is defined as a route 2.

  However, in FIG. 10, a solid line arrow or a dotted line arrow indicates a path through which radio waves radiated from the radio apparatus 60 propagate to the radio apparatus 67 via many radio apparatuses or radio waves radiated from the radio apparatus 68, respectively. This indicates that the path propagates to the radio apparatus 62 through many radio apparatuses, and the radio wave radiated from the radio apparatus 60 propagates linearly and propagates to the radio apparatus 67 or from the radio apparatus 68. It does not indicate that the radiated radio wave propagates linearly and propagates to the wireless device 62.

  FIG. 11 is a diagram showing experimental results. FIG. 11A shows the experimental results when the time counter value is not adjusted in the path 1, and FIG. 11B shows the case where the time counter value is not adjusted in the path 2. FIG. 11C shows the experimental result when the time counter value is adjusted in the path 1, and FIG. 11D shows the adjustment of the time counter value in the path 2. It is an experimental result at the time of performing.

  In each of (a) to (d) of FIG. 11, the vertical axis represents the number of throws and the packet error rate, and the horizontal axis represents the number of experiments.

  In the path 1, regardless of whether or not the time counter value is adjusted as described above, packet thrown-in hardly occurs and the packet error rate is almost zero (see (a) and (c) in FIG. 11). ). This is because the route 1 is a stable route.

  On the other hand, in the route 2, when the above-described time counter value is not adjusted, the number of packet throws is as high as about 70 to 200 times, and the packet error rate is as high as 10 to 20%. (See FIG. 11B).

  However, when the above-described time counter value is adjusted, the number of packet throws and the packet error rate are almost zero.

  Therefore, by adjusting the time counter value described above, each wireless device updates the routing table almost synchronously, can prevent packet throwing, and can reduce the packet error rate to substantially zero. Has been demonstrated.

  In the flowchart shown in FIG. 9, it has been described that the time counter value Tcnt2 is set as the time counter value of the time counter 25 when the time counter value Tcnt1 is smaller than the time counter value Tcnt2. The time counter value Tcnt1 may be set to the time counter value of the time counter 25 when the time counter value Tcnt1 is larger than the time counter value Tcnt2.

  Therefore, in the present invention, generally, when the time counter value Tcnt1 is different from the time counter Tcnt2, the time counter value Tcnt2 is set to the time counter value of the time counter 25.

  In the above description, the time counter 25 measures the time in each wireless device. However, the present invention is not limited to this, and the time in each wireless device may be measured by a device other than the time counter 25. .

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include meanings equivalent to the scope of claims for patent and all modifications within the scope.

  The present invention is applied to a wireless device capable of preventing packet loss or delay based on packet throwing.

1 is a schematic diagram of a wireless network system using a wireless device according to an embodiment of the present invention. It is a schematic block diagram which shows the structure of the radio | wireless apparatus shown in FIG. It is a block diagram of an IP header. It is a block diagram of a TCP header. It is a block diagram of a packet in the OLSR protocol. It is another block diagram of a packet. It is a block diagram of the routing table shown in FIG. It is a flowchart for demonstrating the operation | movement regarding creation and update of a routing table. It is a flowchart for demonstrating the detailed operation | movement of step S2 shown in FIG. It is a top view which shows the experiment environment of packet throwing. It is a figure which shows an experimental result. It is a conceptual diagram of packet throwing. It is a figure which shows the experimental result of packet throwing.

Explanation of symbols

  1 to 6, 31 to 43 wireless device, 11, A51 to A63 antenna, 12 input unit, 13 output unit, 14 user application, 15 communication control unit, 16 wireless interface module, 17 MAC module, 18 buffer, 19 LLC module, 20 IP module, 21, 21A routing table, 22 TCP module, 23 UDP module, 24 routing daemon, 25 time counter, 100 wireless network system.

Claims (6)

A wireless device that is autonomously established and constitutes a wireless network in which wireless communication is performed between a transmission source and a transmission destination,
Measuring means for measuring a first time in the wireless device based on a timing device commonly used in the wireless network;
An adjusting means for adjusting the timing device so that the first time matches the second time when the first time is different from the second time based on the timing device in another wireless device;
When the first time is substantially the same as the second time, the routing table is updated in synchronization with the first time, and the first time is different from the second time in another wireless device A wireless device comprising table update means for updating a routing table in synchronization with the adjusted time from the time measuring device.   The said adjustment means adjusts the said time measuring device so that the said 1st time may match the said 2nd time, when the said 1st time is late | slower than the said 2nd time. Wireless devices. The adjusting means includes
Receiving means for receiving a packet including the second time from the other wireless device;
When the receiving means receives the packet, it extracts the second time from the received packet, compares the extracted second time with the first time, and the second time is The wireless device according to claim 1, further comprising a setting unit that sets the second time in the time measuring device when different from the first time.   The radio apparatus according to claim 3, wherein the first and second times are respectively composed of first and second time counter values.   The wireless device according to claim 3, wherein the packet includes information related to a wireless device adjacent to the wireless device, and is a packet that is periodically transmitted.   The wireless device according to claim 1, wherein the table updating unit updates the routing table in synchronization with the set time.

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