JP4692021B2 - Mobile communication method - Google Patents

Description

  The present invention relates to a communication method for providing a stable communication environment for a moving body that moves at high speed.

  As a technique for providing continuous IP communication even when a communication device (mobile host) that continues to move in an IP network changes a network such as a wireless area and the subnet to which it belongs is changed, IETF (Internet) The Mobile IP (RFC2002) system has been proposed by Engineering Task Force).

  The mobile IP system will be outlined with reference to FIG.

  The mobile IP system is an industry standard protocol that enables continuous IP communication without changing the IP address even when a terminal is moved between a plurality of wireless networks. Even when the wireless area is moved during the movement, the service using the IP communication is not interrupted in principle.

  In the mobile IP system, a foreign agent router (hereinafter referred to as FA) that has received a notification that it has entered a wireless area from a mobile router (hereinafter referred to as MR) mounted on a train or the like receives the information as a home agent router (hereinafter referred to as FA). (Hereinafter referred to as HA), and the HA generates a tunnel (IP tunnel) for carrying IP packets to the FA and the FA to the MR, so that the IP communication device (PC) on the moving vehicle (PC) , Server, etc.), each time a vehicle equipped with MR enters a different wireless area, this IP tunnel is newly created or has already been created. The IP tunnel is reused.

  Since the HA always advertises (advertises) the IP address of the network or host belonging to the MR using the routing protocol, the IP packet addressed to the network or host belonging to the MR first arrives at the HA. The HA transfers the IP packet to the MR via the FA using the IP tunnel described above. An IP packet released from the tunnel by MR is delivered to a target network or host such as a vehicle.

  An IP packet transmitted from a network or host belonging to the MR is delivered to the terrestrial IP network via the MR, and thereafter transferred to the target host by normal IP routing.

  The problem with the mobile IP method is that it is necessary to execute a predetermined procedure with the home agent every time the mobile host moves on the network, and therefore when the logical or physical distance is far from the home agent. The time required for switching the IP packet transfer destination (hereinafter referred to as handover) increases.

  Therefore, the mobile host cannot receive the IP frame until the necessary procedure is completed when moving on the network, and real-time communication continuity such as VoIP call continuity cannot be guaranteed. Occurs.

  According to the invention described in Patent Literature 1, in order to solve the above problem, a method for addressing the handover is disclosed by assigning a multicast address to a mobile host and using a multicast frame for data transmission. Multicast communication is to broadcast the same data to a specific number of hosts, and a multicast address is an address that can be used in common by a number of hosts. The fact that a large number of hosts can use a common address means that even if a movement involving a change in the subnet of a mobile host occurs, the multicast IP address can be used in common between subnets before and after the movement. The host can continuously receive data while moving.

  In addition, the above-mentioned handover problem is caused by the fact that the mobile host has already moved in the existing wireless area as the speed of the mobile host increases, and the wireless area before the movement has moved. There is a problem that the number of communication frames that arrives increases and the transit time of the wireless area is shortened, so that the above-described situation occurs remarkably.

  In order to avoid this problem, according to Non-Patent Document 1, the mobile host sets the destination address before moving and registers itself with the access router of the link immediately before moving, so that the moving host moves. Until the registration to the home agent, the access router before moving forwards the frame to the destination access router, thereby avoiding frame lost during handover. .

  In addition, although the above-mentioned method of Patent Document 1 can be used to reduce packet lost during handover of Mobile IP, it cannot be completely avoided. Therefore, Non-Patent Document 2 includes a plurality of interfaces. Thus, a system for realizing mobile IP in which frame dropping does not occur by constantly maintaining communication in two or more wireless areas is disclosed.

JP 2003-37626 A US Patent Publication No. 5,901,009 Fast Handovers for Mobile IP (draft-ietf-mobileIPfast-mIPv6-08.txt) “Design and Implementation of a Mechanism that Does Not Drop Frames in Mobile IPv6 Handover” Academic Publications Research Reports Vol. 2003, No. 67 ISSN 0919-6072

  However, the method using multicast disclosed in Patent Document 1 is effective for an application using multicast IP, but cannot be used for other applications.

  In particular, it is difficult to use TCP, which is an upper connection type protocol premised on the use of the IP protocol. For example, in an area where cells overlap, there is a possibility that two identical IP packets may be received. In such a case, if the second and subsequent frames are not discarded, a communication error has occurred in TCP. The service is stopped due to the blocking process.

  Next, there is disclosed means for notifying the relay host of the address of a valid mobile host in the cell and changing the registration information to perform transfer from the relay host. According to the above, until the registration information is changed, the IP packet is not delivered to the necessary cell, and as a result, the mobile host cannot receive the IP packet.

  Furthermore, according to the method disclosed in Non-Patent Document 1, a high speed handover is realized between the connection to the destination link and the registration of the movement. Since the connection to the destination link is still present, there is still a state where it is disconnected from the network, and the IP packet is lost.

  Normally, with regard to such lost IP packets, a higher level protocol such as TCP makes a retransmission request for an IP frame to avoid a communication stop, but in this case, the retransmission frame consumes resources such as network bandwidth. Occurs. TCP also implements an IP packet transfer algorithm called slow start. This is because when IP packet lost is detected, it is considered that congestion has occurred in the network, the communication speed is lowered to the minimum speed, and then gradually It is a communication algorithm that increases the communication speed. Even in the method of Non-Patent Document 1, since the lost IP packet occurs every time handover is performed, the communication speed decreases every time, and as a result, efficient communication cannot be performed in the mobile IP environment.

  Furthermore, according to the method disclosed in Non-Patent Document 2, it is possible to avoid IP packet lost by using a plurality of network interface cards. However, in order to implement this method, a plurality of interfaces are used. Since it is necessary, there is a problem that the cost becomes high. Also, in a communication environment, in order for a plurality of network interface cards to function effectively, it is necessary to use different network media or different radio frequencies between adjacent wireless areas, and the cost is also high. There is a problem of becoming.

  Non-Patent Document 2 discloses the continuity of communication by simultaneously maintaining wireless links of two different wireless areas, but presupposes that two or more wireless areas overlap. However, in an actual environment, there may be a dead zone between the wireless areas due to interference caused by interference between the wireless areas or radio wave conditions. In such an environment, the method of Non-Patent Document 2 is used. However, it is difficult for mobile IP to guarantee the continuity of IP communication.

  Further, in Patent Document 1 and Non-Patent Document 1 or 2, each wireless area is adjacent, but by adding another wireless area to a certain existing wireless area, A case where another wireless area is completely included in the wireless area cannot be handled.

  For example, in contrast to the first wireless communication means having a bandwidth of 2 Mbps and an effective range of 20 km, another second wireless having a bandwidth of 100 Mbps but having an effective range of less than 100 m. This is a case where a communication means is added.

  Furthermore, in the above example, in the case where the first wireless communication means and the second wireless communication means are different wireless communication means, it is necessary to manage from which route the communication frame is transferred. In addition, when successive frames are transferred via another communication means, it is difficult to control the arrival order of the frames.

  Further, in the above example, in the case where the first wireless communication means and the second wireless communication means are the same type of wireless communication means, in addition to the above problem, in a certain existing wireless area Even when the newly added other wireless area can be recognized on the mobile communication means side, there is a problem that a frame loss occurs in a period until it is recognized that the wireless area has left.

  In addition, there may be a problem even when a new wireless communication means is added for the purpose of supplementing the distant portion of the wireless area. This is because, for example, the effective range of the wireless communication means continues to fluctuate due to external factors such as temperature, humidity, fine weather, and rain, deterioration over time, and the speed of the mobile body using the wireless communication means. In such a case, the originally planned complementation may not serve the purpose, and a dead zone may occur between adjacent zones, or the inclusion relationship as described above may occur.

  In the present invention, as an aspect of the case where the wireless areas do not overlap, (1) when the wireless zone is actually physically separated, (2) due to the nature of the wireless communication system, when entering a new wireless area, A case in which a wireless link in an old wireless area is discarded and a new wireless link is constructed. (3) A case in which there is a place where the wireless areas are actually dead zones due to interference caused by interference between wireless areas or due to radio wave conditions. Shall be included.

  For convenience, a frame transferred from a mobile host to a host that communicates with the mobile host is called an “upstream frame”, and a frame transferred in the opposite direction is called a “downstream frame”. In addition, a base station base station for radio communication that constitutes a radio area is referred to as a “base station”. In the present invention, a communication frame acquired in a first wireless area transmitted / received from a moving host or a network moving with one or more hosts is transmitted in the moving direction of the host or network. Providing a means for transferring to an existing second wireless area, and transmitting the communication frame transferred to the second wireless area to the host or network when the host or network enters the second wireless area; A means for transferring the communication frame is provided.

  In the present invention, the communication frame transferred to the second wireless area is transferred to the host or network when the host or network enters the second wireless area. A means for rewriting the content of the communication frame as if the communication frame was transferred via the second wireless area, and further, the communication frame transferred to the second wireless area Means are provided for storing or discarding the communication frame when the host or network is not in the second wireless area.

  Further, in the present invention, the communication frame length is changed or expanded or the frame is divided into two or more to control the communication frame before putting the communication packet in the network range including the wireless network. To secure an area to which information is to be assigned, create a new frame to which the control information is assigned to the area, and before issuing a communication frame from a network range including the wireless network, Providing means for acquiring information, releasing an area to which information for controlling the communication frame is given, and changing the communication frame length to a state before the communication frame is put in a network range including the wireless network .

  Specifically, a serial number that is the order in which communication frames are sent out before putting a communication frame in the network range including the wireless network is assigned, and the serial number is assigned before the communication frame is output from the network range including the wireless network. Provides a means to dispose of information.

  Furthermore, in the present invention, when moving from the first wireless area to the second wireless area, the first serial number value acquired before discarding the serial number information in the first wireless area Loss when moving from the first wireless area to the second wireless area by comparing with the second serial number value obtained before discarding the serial number information in the second wireless area This is realized by identifying the communication frame, specifically, by transferring the communication frame that has reached the first wireless area to the second wireless area.

  Further, in the present invention, when moving from the first wireless area to the second wireless area, before the communication packet is put into the network range including the wireless network in the first wireless area, A network that provides means for taking over the assigned serial number as the serial number assigned to the communication packet before putting the communication frame in the network range including the wireless network in the second wireless area, and includes the wireless network Before placing a communication frame in the range, always keep a certain number of copies of the latest communication frame among the communication frames, receive the notification of the serial number of the specified lost communication frame, and Means for retransmitting a frame are provided.

  Further, in the present invention, information such as communication quality provided by the second wireless area when moving from the first wireless area to the second wireless area included in the first wireless area. In consideration of the above, a means for switching the communication means to the second wireless area is provided, or a means for continuing communication using both the first communication means and the second communication means is provided. Is.

  Furthermore, in the present invention, when a third wireless area is added to the first wireless area and the second wireless area, the position information of the first, second and third wireless base stations, or the mobile body Means for determining a wireless area to which a communication frame acquired in the first wireless area is transferred using the position information and the traveling direction.

  According to the present invention, it is possible to avoid both upstream and downstream lost frames during handover, and to eliminate frame arrival delay that occurs during handover. In particular, even when the mobile host is moving at high speed, it is possible to guarantee stable IP communication continuity.

  Furthermore, according to the present invention, it is possible to provide means for realizing continuous mobile IP communication using a single network interface card without using a plurality of network interface cards.

  In addition, according to the present invention, even in a communication environment that includes a wireless area in a wireless area, or when a wireless area is added step by step, the continuity of the stable IP communication is improved. It is possible to provide guaranteed mobile IP communication.

  Hereinafter, embodiments of the present invention will be described.

  In this embodiment, between a host connected to a network in a train (hereinafter referred to as an on-vehicle network) and a base station on the ground side, a subnetwork, a backbone network, and a host on the Internet, An embodiment of a communication method that provides stable IP continuous communication even when a train is moving at high speed will be described.

  First, before describing the present embodiment, an outline of the mobile IP scheme assumed by the present system will be described with reference to FIG.

  The mobile IP system is an industry standard protocol that enables continuous IP communication without changing an IP address even when a terminal is moved between a plurality of wireless networks.

  In the mobile IP system, a foreign agent router (hereinafter referred to as FA) that has received notification from the mobile router (hereinafter referred to as MR) that it has entered the wireless area receives the information as a home agent router (hereinafter referred to as HA). To the FA, and the FA generates a tunnel (IP tunnel) for carrying the IP packet to the MR, so that the IP communication equipment (PC, server, etc.) in the vehicle is generated. Whenever an MR enters a different radio area, this IP tunnel is newly created or reused.

  Since the HA always advertises (advertises) the IP address of the network or host belonging to the MR using the routing protocol, the IP packet addressed to the network or host belonging to the MR deployed in the moving train. (Downlink frame) first arrives at the HA. The HA transfers the IP packet to the MR via the FA using the IP tunnel described above. The IP packet released from the tunnel by MR is deployed on the target on-vehicle network and delivered to the host on the on-vehicle network.

  An IP packet transmitted from a network or host belonging to the MR is transferred to the ground-side IP network via the MR, and thereafter transferred to the target host by normal IP routing. .

  FIG. 2 shows an overall view of the system in the present embodiment.

  The train 3 includes an on-board network 30 to which a mobile router (hereinafter referred to as MR) 31, an on-board server 35, and a passenger personal computer (hereinafter simply referred to as passenger PC) 36 are connected. The on-vehicle network 30 may be any network such as a wired LAN or a wireless LAN. Further, the PC 36 may be fixedly provided on the on-vehicle network, or may be a passenger brought into the train.

  MR 31 includes a leakage radio wave from the vehicle upper frame control device (abbreviated as “AIR_T” in the figure) 32 and a digital leaky coaxial cable (digital leakage coaxial cable, hereinafter referred to as DLCX). Are connected in series to a vehicle-side transceiver (hereinafter referred to as “vehicle-side DLCX transceiver”, referred to as “DLCX_T” in the figure) 33 and a ground-side DLCX antenna 34. In addition, DLCX is to secure a radio sensitive band only in a small area (several tens of meters) around DLCX by providing a slight slit (clearance) in the shield of the coaxial cable to leak radio waves. It is also used for mobile phone / car telephone relay in the Tokyo Metropolitan Expressway tunnel and for business radio in the tunnel.

  The backbone network 10 is connected to a foreign agent router (hereinafter referred to as “FA”) 11, and further includes a ground side frame control device (abbreviated as “AIR_G” in the figure) 12, A side DLCX transceiver (abbreviated as “DLCX_G” in the drawing) 13 and DLCX 14 are connected in series. The ground side frame control devices 12 are VLAN-connected to another adjacent ground side frame control device via the VLAN switch 15 (abbreviated as “SW” in the drawing) and the regional network 20. Yes.

  Further, a home agent router (hereinafter referred to as “HA”) 19 is connected to the backbone network 10 and serves as a gateway between the business network 40 and the Internet 50. A business server 41 is connected to the business network 40, and an Internet server 51 is connected to the Internet 50. Note that the services provided by the business server 41 or the Internet server 51 include a Web service, a mail service, a network management server, and the like, and there is no particular limitation regarding the contents of the server service.

  FIG. 3 shows a hardware configuration of the vehicle upper side frame control device 32.

  Network interface card 322 for connecting to MR 31, network interface card 323 for connecting to vehicle upper DLCX transceiver 33, CPU 325, memory 324, hard disk controller 327 connected to hard disk 328, display, mouse, keyboard, RS232C, etc. An external interface group 329 for locally controlling the apparatus is connected by an internal communication line (hereinafter referred to as a bus) 321 such as a bus.

  FIG. 4 shows a hardware configuration of the ground frame controller 12.

  A network interface card 122 for connecting to the in-vehicle DLCX transceiver 33, a network interface card 123 for connecting to the FA 11, a network interface card 124 for connecting to an adjacent ground side frame control device via the regional network 20, or 125, a CPU 126, a memory 127, a hard disk controller 128 connected to the hard disk 129, a display, a mouse, a keyboard, or an external interface group 130 for locally controlling the apparatus via an interface such as RS232C is connected by a bus 121. ing.

  FIG. 5 shows a software configuration of the vehicle upper side frame control device 32.

  A network interface card control driver 324-2 for controlling the network interface cards 322 and 323, a communication management module 324-4 for performing communication with the MR 31 or the vehicle-side DLCX transceiver 33 in FIG. 2, and a transmission queue 324- 6, an input / output device control driver 324-8 for controlling input / output of data to / from the reception queue 324-4 and the hard disk 328 is stored.

  MTU control module 324-10 for controlling the MTU length of MR31 ("MTU" is an abbreviation of "Max Transfer Unit", which determines the frame size that can be transmitted at once), and assigns serial numbers to upstream frames. Or a serial number benefit / deletion module 324-12 for deleting a downstream frame serial number, a downstream frame lost detection / retransmission request module 324-14 for detecting a lost downstream frame and requesting retransmission of the lost frame, an upstream frame lost In this case, a retransmission processing module 324-26 that performs retransmission processing, a wireless zone movement detection module 324-16 that receives information indicating that movement of the wireless area has been detected from the vehicle upper DLCX transceiver 33, and the vehicle upper side via a network from a remote location Log in to the packet controller 32, A remote server module 324-18 that provides functions for performing various settings and maintenance, a driver group 324-22 of an external interface group 329 for locally accessing the apparatus, and a setting module 324-20 for performing various settings of the apparatus The upstream frame temporary storage module 324-24 for storing a certain number of the latest upstream frames is stored.

  FIG. 6 shows a software configuration of the ground side frame control device 12.

A communication management module 127-that performs communication with the network interface card control driver 127-2 for controlling the network interface cards 122, 123, 124, and 125, the ground side DLCX transceiver 13, the FA 11, or the regional network 20. 4, a transmission queue 127-6, a reception queue 127-4, and an input / output device control driver 127-8 for controlling input / output of data to / from the hard disk 129 are stored.
MTU control module 127-10 for controlling the MTU length of MR11, serial number benefit / deletion module 127-12 for assigning serial numbers to downlink IP packets or deleting serial numbers of upstream frames, detecting lost upstream frames The upstream frame lost detection / retransmission request module 127-14 that requests retransmission of the lost frame, the retransmission processing module 127-30 that performs retransmission processing when the downstream frame is lost, and the terrestrial DLCX transceiver 13 A wireless area movement detection module 127-16 that receives information indicating that movement has been detected, and a remote server module 127- that provides functions for performing various settings and maintenance by logging in to the ground side frame control device 12 from the remote via the network. 18. Access this device locally. Pass through this device in order to examine the contents of the driver group 127-22 of the external interface group 329, the setting module 127-20 for making various settings of the device, the mobile IP agent request message, the agent advertisement message, etc. Frame monitor module 127-24 for monitoring IP packets to be received, frame rewrite module 127-26 for obtaining the MAC or IP address of the monitored frame from the module, and rewriting the contents of the frame using the information, progress of train A packet forward module 127-32 for transferring a frame to the ground side frame control device 12 in the wireless area in the direction, and an upstream frame temporary storage module 324-24 for storing a certain number of the latest downstream frames are stored. It has been.

  Next, the operation of the vehicle upper side frame control device 32 will be described in order from the start.

  In the present embodiment, in order to facilitate understanding of the contents of the description, Ethernet (registered trademark) (including wide area Ethernet) is used as a physical network medium for communication, and the vehicle upper frame control device 32 or the ground Although the side frame control device 12 is also described as handling Ethernet, in the present invention, the use of Ethernet is not the essence of the invention, and any network medium capable of providing an IP network carrying IP packets can be used. Anything can be used.

  The vehicle upper side frame control device 32 activates the setting module 324-20 from an interface such as a display, a mouse, a keyboard, or an RS232C via an external interface group 329, so that the network interface card 322 or 323 is An IP address, a subnet mask, a default gateway, a broadcast address, or a setting to use an IP address dynamically provided by a DHCP function or the like is set. Since the network can be used after the IP address is set in this way, it can also be set remotely via the remote server module 324-18.

  Next, the setting module 324-20 is started up remotely or locally, and the MAC address of the MR 31 connected to the network interface card 322 and the MTU value of the frame Ethernet frame set for the MR 31 are input. . In the case of Ethernet, the maximum MTU value is 1500 (bytes), so a value smaller than 1500 bytes (for example, 1400 (bytes)) is set.

  In addition, the direction in which the train travels is also set. For example, 0 is set for a train heading toward Tokyo, and 1 is set for a train moving away from Tokyo.

  Further, the number of frames (for example, 300,000 frames) for always storing a certain number of the latest frames in the storage area is set so that retransmission processing can be performed when the upstream frame is lost. When the number exceeds a certain number, the old frame is discarded by overwriting the latest frame in the area where the old frame is recorded.

  The ground side frame control device 12 starts the setting module 127-20 from an interface such as a display, a mouse, a keyboard, or an RS232C via the external interface group 130, so that the network interface cards 122, 123, A setting is made to use an IP address dynamically provided by an IP address 124 or 125, a subnet mask, a default gateway, a broadcast address, a VLAN ID, or a DHCP function. Since the network can be used after the IP address is set in this way, it can also be set remotely via the remote server module 127-18.

  Next, the setting module 127-20 is activated from the remote or the local, and the MAC address of the FA 11 connected to the network interface card 123 and the MTU value of the frame Ethernet frame set for the FA 11 are input. . This MTU value is the same as the value set by the vehicle upper side frame control device 32.

  In addition, when the downlink frame is lost, the number of frames for always storing the latest number of frames (for example, 300,000 frames) in the storage area is set for each train so that retransmission processing can be performed. When it exceeds a certain number, the old frame is discarded by overwriting the latest frame in the area where the old frame is recorded.

  FIG. 7 shows a frame generated by the terrestrial frame control device 32, and the description of the CRC for MAC (4 octets) is omitted.

  The frame Ethernet frame that has arrived at the MR as an upstream frame from the on-vehicle network 30 is converted into an upstream message 1-1 with an MTU of 1400 bytes or less by changing the setting value of the MTU value described above. Arrives at the network interface card 322 of the device 32.

  The upstream message 1-1 is transferred to the serial number benefit / deletion module 324-12 in FIG. 5 and temporarily transferred onto the memory, and then the upstream ID is assigned after the 1400th byte in the memory. .

  The uplink ID is composed of a traveling direction flag, a train identification number, and an uplink frame sequence number. The traveling direction flag is loaded with the traveling direction of the train input via the setting module 324-20. For example, 0 is set if the train is toward Tokyo, and 1 is set if the train is away from Tokyo. In addition, any train identification number may be used as long as a unique value is given to all trains. In this embodiment, a MAC address (12 bytes) is used. This is because the MAC address is given a unique value when the Ethernet card is manufactured, and MAC address collision does not occur.

  Further, an integer value is used for the upstream frame sequence number. The serial number is reset to 0 at the start of train operation, increases by one each time one frame is transmitted, and is reset to 0 again when the maximum value is reached. By using a serial number with a sufficiently large number of digits, it is possible to dispense with measures for resetting. In the present embodiment, an integer value of 4 bytes (0-4294967295) is used as a serial number, and even if 50,000 frames are transferred per second, it can be used for about 23 hours.

  In the above example, only an uplink ID of 16 bytes in total is given, but in addition to this, control data related to the encryption is added to the encrypted IP data as shown in 1-3. By adding a secure header, HMAC, or the like, it is possible to encrypt the frame between the vehicle-side frame control device 32 and the ground-side frame control device 12.

  The frame information to which the uplink ID is assigned in this manner is transferred to a normal MTU Ethernet packet and sent as a frame Ethernet frame 1-2 from the network interface card 323 in FIG. 3 to the in-vehicle DLCX transceiver 33. Arriving at the ground frame controller 12 via the ground side DLCX antenna 34, the ground side DLCX 14, and the ground side DLCX transceiver 13.

  The downstream message is also transferred to the serial number benefit / deletion module 127-12 in FIG. 6 and temporarily transferred onto the memory, and thereafter, the downstream ID is assigned after the 1400th byte on the memory.

  As a method other than the method described above, as an upstream frame, MR 31 issues a request for changing the MTU to the passenger PC 36 (for example, a request to set the MTU to 1400), and AIR_T32 sends 100 bytes of control information. By assigning, it is possible to perform the same processing as described above. Note that the same processing is performed for downstream frames.

  The maximum MTU value of an Ethernet frame is 1500. By using the property that information of 1600 bytes or more can be added by performing processing such as modifying the network card driver, Also, by adding 100 bytes of control information to the Ethernet frame of maximum 1500 bytes sent from the passenger PC 36 via the MR 31 to the AIR_T32, sending it to the AIR_G12, and removing the control information in the AIR_G12, It is possible to carry out processing for the same purpose as described above. Note that the same processing is performed for downstream frames.

  Note that since the maximum MTU value of an Ethernet frame is 1500, frame division occurs for messages that exceed this value. However, the method described above uses AIR_T32 or AIR_G12, and the ID is assigned to the frame. The purpose of this is to avoid the occurrence of frame division due to the provision of.

  If frame division occurs in AIR_T32 or AIR_G12, the first half of the frame is transferred without being given control information, and frame processing including discarding a serial number cannot be performed in AIR_T32 or AIR_G12.

  However, by assigning an ID with AIR_T32 or AIR_G12, even if the frame is such that the MTU value exceeds 1500 (for example, 1600 bytes), the frame is finally reassembled with AIR_T32 or AIR_G12. If possible (ie if it can be assembled as a 1600 byte Ethernet frame), there is no problem. This is because, except between AIR_T32 and AIR_G12, the ID is removed and, as a result, the MTU value is 1500 bytes or less and transferred.

  FIG. 18 illustrates this method.

  The frame (a) is a frame having a total length of 1560 by giving an ID of 100 bytes to a frame having a total length of 1460 bytes. In normal processing, frame division occurs. Therefore, in AIR_T32 or AIR_G12, this frame (a) is intentionally divided into a frame (b) and a frame (c).

  That is, after dividing 1560 bytes into frames of the first half of 1480 bytes and the latter half of 80 bytes, the last 20 bytes of the first half frame describe the number for displaying its own frame and the number of the frame linked to this frame. . Similarly, the frame number of the second half is also described, but since there is no frame connected to this frame, NULL is described here.

  The frames (b) and (c) are reassembled with the received AIR_T32 or AIR_G12 to restore the original frame. As described above, it is possible to transfer a frame having a maximum MTU value or more in practice without being restricted by frame control based on the maximum MTU value.

  FIG. 8 is a serial number management table 127-50 used in common by the module group of the terrestrial frame control apparatus 12 shown in FIG.

  The direction entry describes whether the train is a train heading toward Tokyo or a train away from Tokyo. As a result, the ground side frame control device 12 can determine to which of the adjacent ground side frame control devices 12 the frame should be transferred.

  The train identification number entry indicates a train in which the terrestrial frame control device 12 is performing frame control management at that time, and the terrestrial frame control device 12 includes an upstream frame sequence number entry and a downstream frame sequence number entry, respectively. The latest serial number of the handled upstream and downstream frames is described.

  The serial number of the downlink ID is determined by the serial number benefit / deletion module 127-12 of the terrestrial frame control device 12 in conjunction with the progress of the train. To ensure consistency of serial numbers. The downlink ID management control method will be described later.

  When the wireless area movement detection module 127-16 detects the entry of a train to the wireless area and there is no entry with a train identification number that matches the train identification number, it is recognized that the train has started. Then, the entry is added and 0 is set to the downstream frame sequence number.

  The frame information to which the downlink ID is assigned in this manner is transferred to an ordinary MTU Ethernet packet, sent from the network interface card 122 of FIG. 4 to the ground side DLCX transceiver 13, and the DLCX 14, the ground side DLCX antenna 34, The vehicle arrives at the vehicle upper frame control device 32 via the vehicle upper DLCX transceiver 33.

  An outline of upstream frame processing is shown in FIG. 9 or FIG. In FIG. 9, description of DLCX-related devices and other networks is omitted. In addition, the indications “eth0” and “eth1” in the figure indicate Ethernet network interface cards in each device. It is assumed that the train is traveling in the right direction in the figure.

  As described above, the frame Ethernet frame transmitted from the MR 31 with the MTU value 1400 is given the serial number ID by the serial number benefit / deletion module 324-12, and then becomes the frame Ethernet frame with the MTU value 1500. After being copied to the temporary storage area (the temporary storage area may be created in either the memory 324 or the hard disk 328 shown in FIG. 3) by the frame temporary storage module 324-24, the wireless area is transmitted via the eth1 interface. 1 is transferred to the eth0 interface of the terrestrial frame control device 12-1 and directly from the eth3 interface via the VLAN of the regional network 20 to the terrestrial frame control device 12 of the wireless area 2 in the traveling direction of the train. -2.

  Here, the uplink ID of the sent frame Ethernet frame is checked by the uplink frame lost detection / retransmission request module 127-14 of the ground side frame controller 12-2, and the train recognition in the downlink sequence number management table 127-50 is checked. The latest serial number is recorded in the upstream frame serial number entry corresponding to the number. If there is no entry corresponding to the train identification number, a new entry is created. After the serial number recording is completed, the frame Ethernet frame is passed to the serial number benefit / deletion module 127-12, and the upstream ID is deleted, the CRC is recalculated, and the like, and then transmitted from the Ethernet interface card eth2. It is sent to the backbone network via the FA 11-2 (Step 1).

  Even when the train 3 enters a dead zone where communication between the wireless area 1 and the wireless area 2 cannot be performed, the upper frame control device 32 continues to send frames, and the frames during this time are lost (Step 2). .

  When the train 3 enters the wireless area 2, the upper DLCX transmitter / receiver 33 and the terrestrial DLCX transmitter / receiver 13-2 in the wireless area 2 recognize the presence of the train 3 and control the on-board frame control. It notifies to the apparatus 32 and the ground side frame control apparatus 12-2, and each wireless area movement detection module 324-16 and 127-16 confirms. At this point, the on-board frame control device 32 and the ground side frame control device 12-2 enter a standby state in response to the request for retransmission of the lost frame immediately across the wireless area (Step 3). ).

  After the train 3 enters the wireless area 2, the upstream frame lost detection / retransmission request module 127-14 receives the first frame transmitted from the on-board frame control device 32 to the ground frame control device 12-2. Then, the upstream frame serial number of the entry corresponding to the train identification number in the serial number management table 127-50 is confirmed. If this serial number is not a continuous value, a frame lost has occurred between the wireless zone 1 and the wireless area 2, and therefore the upstream frame lost detection / retransmission request module 127-14 has information on the serial number that seems to have been lost. Is sent to the retransmission processing module 324-26 of the on-board frame control device 32.

  Upon receipt of the request, the retransmission processing module 324-26 finds the frame corresponding to the request from the copy of the frame described in the temporary storage area by the upstream frame temporary storage module 324-24, and the ground side frame control device Transfer to 12-2. This packet is also transferred from the ground side frame control device 12-2 in the wireless area 2 to the ground side frame control device 12-3 in the wireless area 3 in the same manner as described above (Step 4).

  Even if an agent registration request is made after the processing of the mobile IP agent request message, agent advertisement message, etc. after or before the above processing, the above processing is not affected (Step. 5) The uplink frame is transferred to the ground frame controller 12-3 in the wireless area 3.

  Note that for trains that have passed through the wireless area, the entry in the serial number management table 127-50 is not necessary, so the wireless area movement detection module 127-16 can receive an uplink frame for a certain time (for example, 60 seconds). When there is no change in both the serial number entry and the downstream frame serial number entry, the train identification number entry is deleted.

  An outline of downstream frame processing is shown in FIG. In this figure, descriptions of DLCX-related devices and other networks are omitted. Note that the indications “eth0” and “eth1” in the figure indicate Ethernet network interface cards in each device. It is assumed that the train is traveling in the right direction in the figure.

  By exchanging the mobile IP agent request message and agent advertisement message between the MR 31 and the FA 11-1 in the wireless area 1, the MR 31 sends an agent registration request to the HA 19, and an agent registration response is returned as a response. Then, the frame monitor module 127-24 of the terrestrial frame control device 12-1 detects the content of the agent registration response and acquires the MAC address of the network interface card of the MR 31.

  Next, the terrestrial frame control device 12-1 in the wireless area 1 connects the terrestrial packet control device 12-1 to the downlink frame temporary storage module 127-34 of the terrestrial packet control device 12-2 in the wireless area 2. A request for creating a temporary storage area for recording a passing downstream frame (the temporary storage area may be created in either the memory 127 or the hard disk 129 shown in FIG. 4) is sent to the downstream frame temporary storage module 324-34. Against.

  The downstream frame temporary storage module 127-34 creates a temporary storage file using the MAC address of the network interface card of MR31. For example, if the MAC address of MR31 of the train is 00-50-56-C0-00-08, the file name may be “00-50-56-C0-00-08.buf” (Step .1).

  Thereafter, the downlink frame sent from the FA 11-1 is duplicated by the terrestrial frame control device 12-1 and sent to the terrestrial frame control device 12-2 immediately before being sent to the terrestrial DLCX transceiver 13-1. The file name of the MAC address is stored in a temporary storage area (Step. 2).

  When the train 3 enters the dead zone of the wireless area 1 and the wireless area 2, the above Step. 2 is performed, but the frame transmitted by the ground side DLCX transceiver 13-1 is not received (Step 2).

  When the train 3 enters the wireless area 2, each of the vehicle-side DLCX transceiver 33 and the ground-side DLCX transceiver 13-2 detects and notifies the wireless area movement detection modules 324-14 and 127-16. The movement detection module 127-16 instructs the downstream frame temporary storage module 127-32 to stop storing in the temporary storage area and transfer it to the terrestrial DLCX transceiver 13-2 as it is (transfer start). Instructions). This is because at this point of time, there is no room for frame loss when moving over the wireless area, and unnecessary overwriting by a newly arrived frame in the temporary storage area is avoided. Further, at this time, the serial number benefit / deletion module 127-12 performs Step. 5 or Step. 7 records the maximum value of the serial number of the transmitted downstream frame (Step. 4).

  Frames that MR 31 could not receive in wireless area 1 due to entry into the dead zone or registration processing delay are stored in ground side frame control device 12-2 in wireless area 2 and are ready for retransmission. Yes. The vehicle upper frame control device 32 receives the packet first sent to the wireless area 2 in response to the transfer start instruction, and checks its downlink serial number, whereby the lost frame can be specifically identified. The frame control device 32 makes a retransmission request for the lost frame to the terrestrial frame control device 12-2 (Step 6), and the terrestrial frame control device 12-2 performs a retransmission process of the frame (step 6). Step.7).

  Thereafter, Step. After the process of 8 or 9, the terrestrial frame control device 12-2 in the wireless area 2 makes a temporary storage area creation request to the terrestrial frame control device 12-3 in the wireless area 3 according to the procedure described above. At this point, the serial number benefit / deletion module 127-12 is set to Step. 5 or Step. 7, the maximum value of the serial number of the transmitted downstream frame is set as the initial value of the serial number managed by the serial number benefit / deletion module 127-12.

  However, there is no possibility that the frame is transferred from the wireless area 1 to the wireless area 2 after the agent registration. This is because a transfer delay or the like of the backbone network 10 or the regional network 20 may occur.

  Therefore, Step. For the frame transferred from the wireless area 1 to the wireless area 2 after the processing of 9, the frame rewrite module 127-26 causes the frame header portion to be transmitted from the FA 11-2 by the frame rewriting module 127-26. Perform rewriting of Specifically, the source MAC address is rewritten to that of FA 11-2 in wireless area 2, and the destination IP address is rewritten to the new IP address of MR 31 acquired by the agent registration response. Further, the serial number managed by the serial number benefit / deletion module 127-12 of the ground side frame control device 12-2 from the number assigned by the serial number benefit / deletion module 127-12 of the ground side frame control device 12-1 as the serial number of the downlink ID. (Step. 10).

  Regarding the downstream frame performed after the agent registration request, the above Step. This is the same as the processing after 2.

  In the present embodiment, an embodiment of the present invention when the VLAN switch 15 and the regional network 20 do not exist in the system configuration of FIG. 2 of the first embodiment will be described.

  FIG. 13 shows a schematic diagram of a system showing upstream frame processing in the present embodiment.

  In the first embodiment, the method for solving the mobile IP frame lost by forwarding the frame to the ground side frame transfer device in the wireless area in the moving direction of the train 3 has been described. However, in the actual system construction, It is expected that it is often difficult in terms of cost to prepare a new network for transferring the frame from the ground side frame control device 12-1 to another ground side frame control device 12-1. . Therefore, in the present embodiment, an example will be described in which the effect of the invention similar to that of the first embodiment can be received by using the backbone network 10 without using such a regional network.

  In the present embodiment, the frame forward module 127-34 shown in FIG. 6 has an IP tunneling function.

  First, the setting module 127-20 is started from remote or local, an appropriate IP address is assigned to each eth1 and eth3 of all the terrestrial frame control devices 12, and mutual communication is performed via the backbone network 20. IP communication is enabled.

  Next, the entire frame transmitted from eth3 of the ground side frame control device 12-1 is encapsulated as data carried by the IP frame, and this is transmitted to the IP address of eth1 of the ground side frame control device 12-2. Since the FA 11 also functions as a normal router, if the destination address is an IP address, it can be delivered to the network card of the target IP address. The encapsulated IP packet is received by the frame forward module 127-34 of the terrestrial frame control device 12-2 and developed as the original frame Ethernet frame. Thereafter, the same processing as in the first embodiment is performed. Is called.

  Although only the uplink frame has been described with reference to FIG. 13, it is possible to forward the frame to the front radio area by performing the same process as described above for the downlink frame.

  In the present embodiment, an embodiment of the present invention will be described in the case where a new same type or different type of wireless communication means is added to the system configuration of FIG.

  14 shows a wireless LAN base station (abbreviated as “SS_G” in the figure) 16 and a second ground side DLCX transceiver (abbreviated in the figure as “SS_G”). DLCX_GS ”) 17 and a wireless LAN adapter 37 are added.

  The radio area of SS_G16 or DLCX_GS17 is included in the radio area of DLCX_G13, and is set in advance so as not to cause interference between these radio areas.

  The upper DLCX transceiver 33 of the train 3 performs passive scan or active scan and continues to search for the ground DLCX transceiver. For the passive scan and active scan, “802.11 Wireless Networks The Defective Guide” Matte S. There is a detailed description in O'REILLY by Gast.

  The DLCX_GS 17 continues to transmit a beacon signal including information such as the currently available communication band and the total length of the wireless area provided by the DLCX_GS. When the DLCX_T 33 receives the beacon signal, the DLCX_GS 17 transfers this signal to the AIR_T 32.

  The AIR_T 32 determines whether to re-establish the communication connection with the DLCX_GS 17 by releasing the communication connection with the DLCX_G 13. If it is determined not to do so, the AIR_T 32 maintains the communication connection with the DLCX_G 13 as it is. If it is determined to do so, AIR_T32 sends a message to AIR_G12 to switch communication, interrupts the process of transferring the upstream frame to DLCX_T33, and uses the buffer to send the message sent from on-vehicle network 30. Keep storing.

  The AIR_G12 that has received the message for switching the communication also interrupts the process of transferring the downstream frame to the DLCX_G13, and continues to store the message transferred from the FA11 or the SW15 in the buffer.

  Next, the AIR_T32 commands the DLCX_T33 to release the connection with the DLCX_G13 and the connection establishment process with the DLCX_GS17. After receiving a signal from the DLCX_T33 that the establishment of the connection process is completed, the AIR_T32 stores the connection in the buffer. The sending of frames is resumed in order from the stored frames.

  Similarly, after receiving a signal indicating that the establishment of the connection process has been completed from the DLCX_GS 17, the AIR_G 12 resumes the transmission of frames in order from the frame stored in the buffer.

  Further, the upper DLCX transceiver 33 of the train 3 performs passive scan or active scan, and when it detects that it has left the radio area provided by the DLCX_GS17, it notifies the AIR_T32, and the AIR_T32 notifies the DLCX_GS33 of the connection of the DLCX_GS17. After issuing a command to release the DLCX_G13, the DLCX_G13 connection is reestablished, and the frame buffer storage and transmission processing is performed in accordance with the above. AIR_G12 also performs processing corresponding to this.

  However, at the stage where it is detected that the wireless network provided by the DLCX_GS 17 is disconnected, the communication is already disabled, and it is highly likely that the frame transmitted from the DLCX_GS 17 or the DLCX_T 32 is lost.

  Therefore, also in this embodiment, the lost frame is relieved by the method used in the first embodiment. That is, the number of frames (for example, 300,000 frames) for storing a certain number of the latest frames in the storage area is set so that retransmission processing can be performed when the upstream frame or downstream frame is lost. When the number exceeds a certain number, the old frame is discarded by overwriting the latest frame in the area where the old frame is recorded.

  In the first embodiment, the lost frame is retransmitted by performing the same process as the process performed when the train 3 enters the wireless area 2 even when the departure from the wireless area provided by the DLCX_GS 17 is detected. It can be realized.

  When DLCX_T33 can maintain two or more communication connections at the same time, it is possible to omit the process of releasing the communication connection with DLCX_G13 and perform the above process. In this case, the communication connection release process and the communication connection establishment process time can be shortened, and the amount of messages stored in the buffer is reduced, so that an effect of improving communication continuity can be expected.

  In addition, when DLCX_T33 maintains two or more communication connections at the same time, there is also a method of performing communication with DLCX_GS17 in parallel while maintaining the communication connection with DLCX_G13. In such a case, there is a possibility that the downstream frame arrives at AIR_T32 in the reverse order due to a difference in transfer rate depending on the communication band between DLCX_G13 and DLCX_GS17. In this case, a serial number benefit / deletion module 324-12 that deletes the serial number of the down frame of the upper frame control device 32 in FIG. 5 has a function of referring to the serial number and rearranging the frames in ascending order. After rearrangement, the data is sent to the on-vehicle network 30.

  In the case of an upstream frame, the function of rearranging the ascending order by referring to the serial number in the serial number benefit / deletion module 127-12 that deletes the serial number of the upstream frame of the ground side frame control device 12 of FIG. The frame order is rearranged and then sent to the FA 11 or SW 15.

  The upper DLCX transmitter / receiver 33 of the train 3 performs passive scan or active scan, and continues to search not only the ground side DLCX transmitter / receiver but also the wireless LAN base station. Since the DLCX and the wireless LAN have different wireless communication means in the first place, the DLCX and the wireless LAN are based on the above two methods using the DLCX except that processing such as connection release, establishment, and re-establishment is not necessary.

  When the DLCX_T 33 maintains two or more communication connections at the same time, the AIR_G 12 or the AIR_T 32 controls to transfer different types of frames for each communication connection. In AIR_G12 or AIR_T32, the port number of the received IP packet is checked, and a process of switching to a communication connection for transferring a frame is performed according to the port number.

  For example, when DLCX_G13, DLCX_GS17 and DLCX_T33 maintain communication connections, respectively, or when DLCX_G13 and DLCX_T33, SS_G16 and SS_T37 maintain communication connections, DLCX_GS17 and DLCX_T33 or SS_G16 and SS_T37 communication, respectively. In the connection, only a frame including a packet having a specific TCP or UDP port number is transferred.

  As a result, it is possible to perform processing such that a file transfer (FTP) packet is intermittently transferred, and a network management packet (such as SNMP) is always transferred.

  In this embodiment, the present invention is applicable not only to a vehicle such as a train that travels in only one direction as in the above embodiment, but also to a vehicle such as an automobile that has no restriction in the traveling direction, and is the same or different. Unlike the case of the third embodiment in which the wireless communication means is terminated at the ground side frame control device, when new wireless communication means are added step by step, the wireless areas are included and superimposed. Even when the system configuration is such that it is not possible to determine which state is discrete, or when the state fluctuates due to factors such as weather, the stability described in the first to third embodiments above. An embodiment for providing the communication environment will be described.

FIG. 15 shows the mode of the system of the present embodiment, but in order to clearly show the contents, the HA connected to the higher order of FA1, FA2, and FA3, and the wireless LAN base station connected to the lower order of AIR-G The description of the base station is omitted. Further, it is assumed that a system including a wireless LAN adapter, AIR_T, MR, and an on-vehicle network included in the vehicle 3 illustrated in FIG. 19 is configured inside the vehicle 4.
In this embodiment, a wireless LAN is used as the wireless communication means. However, this may be DLCX or other wireless communication means, and there is no problem even if they are mixed.

  The upper diagram of FIG. 15 shows a state where the wireless area 3 is newly added to the system by the FA 3, AIR_G 3 and the wireless LAN base station base station in the area between the wireless area 1 and the wireless area 2. When the direction of the vehicle 4 travels from the wireless area 1 to the wireless area 2, the frame forward from AIR_G1 to AIR_G2 is forwarded to the front wireless area from AIR_G1 to AIR_G3, and from AIR_G3 to AIR_G2. Change to perform frame transfer.

  However, in the lower diagram of FIG. 15, when the case where the wireless area 3 is rarely included in the wireless area 1 due to various conditions as described above occurs, the vehicle 4 has the wireless area 1 and the wireless area 3. After entering in order, it will enter the wireless area 1 again. In such a case, since it becomes impossible to forward to the front wireless area, there arises a problem that the mobile continuous communication realized by the first to third embodiments of the present invention cannot be performed. In order to solve this problem, it is necessary to forward from AIR_G3 to AIR_G1.

  FIG. 16 is a diagram illustrating a situation in which the wireless area 5 is added to the system including the wireless areas 1 to 4. First, when the AIR_G5 acquires the position information by inputting the manual operation via the GPS receiver 1301 or the console screen through the external interface group 130 of FIG. 4, a message including the position information of the AIR_G5 is transmitted using IP broadcast. And transmitted to each AIR_G via the FA 5, the backbone network 10, and each FA. Next, each AIR_G refers to the source IP address of the IP broadcast and returns its position information to AIR_G5. In this way, all AIR_Gs exchange their own location information to obtain the position and IP address of the other AIR_G, and the relationship between adjacent radio areas between each radio area is grasped by each AIR_G. Will be.

  FIG. 17 shows a diagram in which the information on the surrounding AIR_G included in AIR_G5 is mapped to the map information. Note that AIR_G5 does not necessarily require map information. In addition, the description “AIR-G5:“ 192.168.21.35 ”” 139.31.29.257/35.35.00.592 ”indicates the AIR_G identification name, IP address, latitude / Indicates mild information. AIR_G5 can grasp the adjacent wireless area from the position information of other AIR_G.

  In the first to third embodiments, the frame is forwarded to the wireless area in the traveling direction of the vehicle. In the present embodiment, the frame is forwarded to the adjacent wireless area.

  The frame forwarded to the wireless area in which the vehicle 4 has not entered is not used and is discarded after a predetermined time.

  By performing such a frame forward, the present invention can be applied to an object such as an automobile whose traveling direction is uncertain. Also, as shown in the lower diagram of FIG. Even if it is included in the situation, it is not necessary to consider that there is an inclusion relationship between at least non-adjacent zones, so the vehicle 4 enters after the wireless area 1 and the wireless area 3 in this order. Even when the wireless area 1 is entered again, the continuous communication method is maintained by forwarding the frame from the wireless area 3 to the wireless area 1.

  However, forwarding frames to all the adjacent AIR_Gs in this way uses the bandwidth of the backbone network 10 wastefully, and forces a large amount of resources to be consumed for storing frames in AIR_G. .

  Therefore, when the moving body travels in only one direction as in a train, it is sufficient to forward the frame to the AIR_G in the direction opposite to the traveling direction, and it is also a case like an automobile. However, the same applies to the case where the direction is one direction, such as an expressway. When the road is branched, it is sufficient to transfer only in the branching direction.

  Further, as indicated by a broken-line circle in FIG. 17, it is also possible to perform forward transfer only to AIR_G located at a certain distance from the position of its own AIR_G.

  The present invention can be used in all systems that provide a continuous communication environment for a mobile object.

It is a figure which shows the outline | summary of a mobile IP system. It is a figure which shows the whole system figure in a 1st Example. It is a figure which shows the hardware constitutions of the vehicle upper side frame control apparatus. It is a figure which shows the hardware constitutions of the ground side frame control apparatus. It is a figure which shows the software structure of the vehicle upper side frame control apparatus. FIG. 6 is a diagram showing a software configuration of the ground side frame control device 12. It is a figure which shows the flame | frame produced | generated by the ground side frame control apparatus. It is a figure which shows the serial number management table of the terrestrial frame control apparatus. It is a figure which shows the outline | summary of a process of an upstream frame. It is a sequence diagram which shows the outline | summary of a process of an upstream frame. It is a figure which shows the outline | summary of a process of a downstream frame. It is a sequence diagram which shows the outline | summary of a process of a downstream frame. It is a schematic diagram of a system showing processing of an upstream frame in the second embodiment. It is a figure which shows the system configuration | structure which includes several radio | wireless communication means in one FA domain. It is a figure which shows the image of implementation of a 4th Example. It is a figure which shows the aspect of the system of a 4th Example. It is a figure explaining the content of the various information of the other ground side frame control apparatus which a ground side frame control apparatus has. It is a figure for demonstrating the method which makes it possible to transfer the flame | frame beyond this value, without receiving restrictions by the frame control by the maximum MTU value.

Explanation of symbols

Business server 41, business network 40,
Internet server 51, Internet 50,
Home agent router 19, backbone network 10,
Regional network 20, foreign agent router 11,
VLAN switch 15, ground side frame control device 12,
Ground side DLCX transceiver 13, DLCX14,
Vehicle upper frame control device 34, vehicle upper DLCX transceiver 33,
On-vehicle frame control device 32, mobile router 31, on-vehicle server 35,
Passenger personal computer 36, on-vehicle network 30,
Network interface card 322,
Network interface card 323, CPU 325,
Memory 324, hard disk 328,
A hard disk controller 327, an external interface group 329,
Bus 321,
Network interface cards 122, 123, 124, 125,
External interface group 130, hard disk 129,
Hard disk controller 128, CPU 126, memory 127,
Bus 121, input / output device control driver 324-8,
Upstream frame temporary storage module 324-24,
External interface driver group 324-22,
Setting module 324-20,
Remote server module 324-18,
MTU control module 324-10,
Serial number benefit / deletion module 324-12,
Downlink frame loss detection / retransmission request module 324-14,
Wireless area movement detection module 324-16,
Retransmission processing module 324-26, transmission queue 324-6,
Reception queue 324-4, communication management module 324-4,
Network interface card control driver 324-2,
I / O device control driver 127-8,
Frame rewriting module 127-26,
Retransmission processing module 127-30,
Frame forward module 127-32,
Downstream frame temporary storage module 127-34,
Frame monitor module 127-24,
External interface driver group 127-22,
Setting module 127-20,
Remote server module 127-18,
MTU control module 127-10,
Serial number benefit / deletion module 127-12,
Uplink frame loss detection / retransmission request module 127-14,
Wireless area movement detection module 127-16,
Communication management module 127-4,
Network interface card control driver 127-2,
Transmission queue 127-6, upstream message 1-1,
Frame Ethernet frame 1-2, vehicle 4, GPS receiver 1301.

Claims (11)

A moving body in a case where a moving body having a moving body side frame control device moves from a first wireless area having a first ground side frame control device to a second wireless area having a second ground side frame control device. In the communication method of
A step of storing a fixed number of extended communication frames in which a communication number in that order is assigned to an upstream frame, and transmitting the extended communication frame to the first radio area;
Sending the extended communication frame to the second ground side frame control device each time the first ground side frame control device receives the extended communication frame from the mobile;
The second ground side frame control device receives the extended communication frame from the mobile side frame control device of the mobile unit that has reached the second radio area, extracts a communication number from the extended communication frame, Comparing the communication number with a communication number included in an extended communication frame received from the first ground frame controller;
As a result of the comparison, the communication number included in the extended communication frame received from the mobile-side frame control device and the communication number included in the extended communication frame received from the first ground-side frame control device are not continuous. The second ground frame controller requests the mobile frame controller of the mobile to retransmit the lost communication frame; and
A communication method for a mobile unit comprising : A moving body in a case where a moving body having a moving body side frame control device moves from a first wireless area having a first ground side frame control device to a second wireless area having a second ground side frame control device. In the communication method of
Each time the first terrestrial frame control device transmits an extended communication frame in which a communication number that is the order of the downlink frame is given to the mobile body, the extended communication frame is sent to the second terrestrial frame control device. Sending to
The second terrestrial frame control device stores a fixed number of extended communication frames received from the first terrestrial frame control device;
When the mobile body reaches the second radio area, the second ground side frame control device transmits an extended communication frame to the mobile body side frame control device of the mobile body, and the movement of the mobile body A body-side frame control device extracts a communication number included in the extended communication frame, and compares the communication number with a communication number included in the extended communication frame received from the first ground frame control device; ,
As a result of the comparison, the communication number included in the extended communication frame received from the second terrestrial frame control device and the communication number included in the extended communication frame received from the first terrestrial frame control device are consecutive. If not, the mobile requesting the second ground side frame controller to retransmit the lost extended communication frame;
A communication method for a mobile unit comprising : 2. The mobile communication according to claim 1, wherein the second ground side frame control device receives the extended communication frame, deletes the communication number of the extended communication frame, and transmits the frame to the backbone network. Method. 2. The mobile communication method according to claim 1, wherein the second ground side frame control device receives and holds the extended communication frame . 3. 3. The mobile communication method according to claim 2, wherein in the second radio area, the mobile-side frame control device receives and holds the extended communication frame . 4. The mobile that has identified the lost extended communication frame requests retransmission of the lost extended communication frame, and receives a copy of the extended communication frame transmitted from the first radio area toward the second radio area. The mobile communication method according to claim 2, wherein: 2. The mobile communication method according to claim 1, wherein the mobile gives a communication number to the extended communication frame so that the extended communication frame is not divided . The mobile communication method according to claim 2, wherein the second ground side control device assigns a communication number to the extended communication frame so that the extended communication frame is not divided . 2. The mobile communication method according to claim 1, wherein the mobile body divides an extended communication frame in which a communication number is assigned to an upstream frame before sending the extended communication frame toward the second radio area. 3. . 3. The mobile unit according to claim 2, wherein the second ground side control device divides an extended communication frame in which a communication number is assigned to a downlink frame before sending the extended communication frame toward the mobile unit. Communication method. The mobile communication method according to claim 1, wherein the second wireless area is a wireless area adjacent to the first wireless area .

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