JP6125107B2 - Packet transfer apparatus, radio communication system, and packet transfer method - Google Patents

Description

  The present invention relates to a packet transfer apparatus, a wireless communication system, and a packet transfer method for transferring a packet received from a terminal that transmits data to one or more of a plurality of paths.

  In recent wireless communication systems, it is required that signals having various communication characteristics can be transmitted simultaneously. For example, with the recent rapid increase in communication traffic, there is a growing demand for increased throughput even in high-speed mobile communication environments such as cars, trains, and airplanes, and large-capacity transmission of application data is required. On the other hand, control information such as an acknowledgment signal needs to be transmitted with high reliability. This is because an error in transmission of control information causes unnecessary retransmission, that is, unnecessary data transmission, and increases non-communication time due to instantaneous transmission interruption, resulting in a decrease in throughput. Thus, the required transmission quality differs depending on whether the transmission data is application data or data including control information, and it is necessary to be able to provide them on the same system.

  For example, Patent Document 1 discloses an invention in which a packet is divided into a header part and a payload part, a header part having high importance is transferred through a transfer path with high required quality, and the payload part is transferred through a transfer path with low required quality. Have been described.

JP 2005-65335 A

  In the wireless communication method described in Patent Literature 1, for example, when wirelessly transmitting a header portion that requires high reliability and a payload portion that does not need to be highly reliable in an RTP (Real-time Transport Protocol) packet, Is divided into separate packet segments, the header portion is transmitted through a channel with a high required quality, and the payload portion is transmitted through a channel with a low required quality, thereby increasing the transmission quality of the header portion.

  However, the transmission of the conventional header part and payload part is performed within a single system. For example, when signals transmitted from a plurality of base station apparatuses are simultaneously received by a mobile terminal performing handover, etc. There is a problem that the communication quality deteriorates due to interference of the other signal. That is, in such a situation, even if the required quality of the channel is high, the radio quality is degraded, and there is a problem that the reliability required when transmitting highly important information such as control information cannot be maintained. there were.

  Further, in the case of TCP (Transmission Control Protocol), the header part includes ACK (Acknowledgement) and functions as an acknowledgment response and retransmission control information, so that the influence of throughput degradation due to a decrease in radio quality becomes larger. was there.

  The present invention has been made in view of the above, and an object of the present invention is to obtain a packet transfer apparatus capable of realizing highly reliable transmission of retransmission control information.

  In order to solve the above-described problems and achieve the object, the present invention includes a first radio access system and a second radio access system, and the first radio access system is more than the second radio access system. In the wireless communication system in which large-capacity data transmission is possible and the second wireless access system has better communication quality than the first wireless access system, the second wireless access system receives a packet generated by a communication terminal and receives the packet A packet transfer apparatus for transferring to at least one of the first radio access system and the second radio access system, wherein when the packet received from the communication terminal does not include a payload, the received packet is transferred to the first radio access system. And the same packet as the received packet. Generate and transmit to the second radio access system or transfer the received packet to the second radio access system, and if the received packet includes a payload, the received packet is The packet is transferred to the first radio access system, and a packet in which a payload is deleted from the received packet is generated and transmitted to the second radio access system.

  According to the present invention, there is an effect that highly reliable transmission of retransmission control information can be realized.

The figure which shows an example of the radio | wireless communications system to which the packet transfer apparatus concerning this invention is applied. The figure which shows an example of the database which a positional infomation management server has The figure which shows the structural example of a positional infomation update notification The figure which shows an example of the database which a packet transmission apparatus has Diagram showing an example of data packet structure The figure which shows the format of IP header and TCP header The figure which shows an example of the sequence of the data flow at the time of data transmission from a data system terminal to a vehicle-mounted terminal The flowchart which shows an example of the operation | movement which the packet transfer apparatus of Embodiment 1 specifies a packet transfer destination The figure which shows the structural example of the IP packet which the packet transfer apparatus encapsulated The flowchart which shows an example of the packet transfer procedure by a packet transfer apparatus The flowchart which shows an example of the operation | movement which the packet transfer apparatus of Embodiment 2 specifies a packet transfer destination The figure which shows the structural example of the flame | frame transmitted / received in the radio | wireless communications system of Embodiment 3. The figure which shows an example of the protocol stack inside a millimeter wave base station The figure which shows the structural example of resending control information The figure which shows an example of the sequence which transmits retransmission control information in the radio | wireless communications system of Embodiment 3. The figure which shows an example of the protocol stack inside an LCX base station The figure which shows an example of the protocol stack inside an LCX mobile station Diagram showing an example of protocol stack inside millimeter wave mobile station The figure which shows an example of the processing circuit which implement | achieves a packet transfer apparatus

  Hereinafter, a packet transfer device, a wireless communication system, and a packet transfer method according to embodiments of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram showing an example of a radio communication system to which a packet transfer apparatus according to the present invention is applied, and is a communication system using a plurality of different radio access schemes. Specifically, an example of a train radio system in which a millimeter wave system is added to an LCX (Leaky CoaXial cable) system and these different radio access methods are coordinated is shown. The LCX system is already applied to some train radio systems. In the LCX system, LCX (leakage coaxial cable) is laid along the track. Therefore, the LCX system has a feature that it can communicate at a position always close to the train, and there is almost no distance attenuation due to radio propagation, and high-quality communication is possible. However, it is difficult to realize large capacity transmission in the LCX system. On the other hand, the millimeter wave system can provide a large-capacity transmission service by using a broadband frequency in the millimeter wave band. On the other hand, an antenna of a millimeter wave system has a strong directivity and a characteristic that propagation attenuation increases as the distance from the transceiver increases. Therefore, when a communication terminal equipped with a transmitter / receiver performs communication in the millimeter wave band while moving, when a communication quality deteriorates, a communication terminal is appropriately switched. The millimeter wave system is a first radio access system, and the LCX system is a second radio access system.

  Hereinafter, the radio communication system shown in FIG. 1 will be described. The wireless communication system can be divided into a ground-side system configured by various devices installed on the ground side and an on-vehicle side system configured by various devices mounted on a train that is a moving body. Therefore, the explanation will be divided into the ground side system and the vehicle upper side system.

  The ground system includes a location information management server 100 that manages train location information, a data system terminal 200 installed in a command station, etc., and an LCX base station and a millimeter wave base that will be described later with respect to packets received from the data system terminal 200 A packet transfer apparatus 300 for transferring a packet received from each of the plurality of base stations to the data system terminal 200, a packet transfer apparatus 300, and a plurality of bases And an IP (Internet Protocol) network 400 to which the stations are connected, an LCX base station 500 that is a base station of the LCX system, and millimeter wave base stations 600, 700, and 800 that are base stations of the millimeter wave system. Has been. The LCX base station 500 is connected to an LCX cable 501 that is designed to leak a weak radio wave and functions as an antenna of the LCX base station 500. The LCX base station 500 exists in a cell 502 that is a cover area. Communicate with a communication terminal. An antenna 601 is connected to the millimeter wave base station 600, and the millimeter wave base station 600 communicates with a communication terminal existing in the cell 602. An antenna 701 is connected to the millimeter wave base station 700, and the millimeter wave base station 700 communicates with a communication terminal existing in the cell 702. An antenna 801 is connected to the millimeter wave base station 800, and the millimeter wave base station 800 communicates with a communication terminal existing in the cell 802. In the wireless communication system of the present embodiment, it is assumed that one LCX base station 500 covers an area wider than the area covered by three millimeter wave base stations 600, 700, and 800. That is, cells 602, 702 and 802 and cell 502 overlap, but it is desirable that the cell boundaries of the millimeter wave base station and the LCX base station do not overlap each other. Further, the cell 602 and the cell 702 partially overlap, and the cell 702 and the cell 802 partially overlap. Therefore, the communication terminals existing in the cells 602, 702, or 802 can communicate with one or two millimeter wave base stations and can communicate with the LCX base station 500. In FIG. 1, only one LCX base station 500 is provided as the base station of the LCX system, but generally there are a plurality of LCX base stations. Even when there are multiple LCX base stations, the area covered by one LCX base station is wider than the area covered by one millimeter-wave base station, and is covered by multiple millimeter-wave base stations. Assume that one LCX base station covers the area to be operated.

  The vehicle upper system is mounted on the train 1000 and is an in-vehicle terminal 1100 that is a communication terminal that transmits and receives data to and from the data system terminal 200 of the ground side system, and an LCX mobile station 1400 and a millimeter wave that will be described later on packets received from the in-vehicle terminal 1100. A packet transfer apparatus 1200 that transfers to one or both of the mobile stations 1500 and also transfers packets received from the LCX mobile station 1400 and the millimeter wave mobile station 1500 to the in-vehicle terminal 1100, a packet transfer apparatus 1200, the LCX mobile station 1400, and a milli A local area network (LAN) 1300 to which a wave mobile station 1500 is connected, an LCX mobile station 1400 that is a mobile station of the LCX system, and a millimeter wave mobile station 1500 that is a mobile station of the millimeter wave system are configured. ing. An antenna 1401 is connected to the LCX mobile station 1400, and an antenna 1501 is connected to the millimeter wave mobile station 1500.

  In the following description, the presence of a train in a cell of a base station is expressed as “present line”. For convenience of explanation, when explaining operations of various devices mounted on a train, the subject of the operation may be a train. For example, the “message transmitted by the in-vehicle device 1100” may be described as “message transmitted by the train 1000”.

  In the wireless communication system of the present embodiment, the position information management server 100 manages position information for each train and has a database shown in FIG. 2A shows train information, FIG. 2B shows LCX base station information, and FIG. 2C shows millimeter wave base station information. The train information associates the train IDs 101 to 103 that are identification information of each train with the network addresses (hereinafter referred to as in-vehicle network addresses) 104 to 106 of the network connecting the in-vehicle terminal 1100 and the packet transfer apparatus 1200. It is. The LCX base station information associates the LCX base station IDs 107 to 109, which are identification information of the LCX base station, with the IP addresses 110 to 112. The millimeter wave base station information associates millimeter wave base station IDs 113 to 115, which are identification information of the millimeter wave base station, with IP addresses 116 to 118. Here, the composition ID 101 “1000”, the LCX base station ID 107 “500”, and the millimeter wave base station IDs 113 to 115 “600” to “800” shown in FIG. It is made to correspond with the code | symbol attached | subjected to the station and the millimeter wave base station.

  Each time the train 1000 executes a handover that moves between cells, the train 1000 transmits a location information registration request message that notifies the location information management server 100 that the in-line base station has been changed. The location information registration request message includes information on the train ID of the train that transmitted the message and the base station ID to which the train is handed over. When the location information management server 100 receives the location information registration request message, the location information management server 100 searches the in-vehicle network address of the train handed over and the IP address of the handover destination base station from the database shown in FIG. The state shown in FIG. 1 is a state after the train 1000 is traveling in the direction indicated by the arrow and handed over from the millimeter wave base station 700 to the millimeter wave base station 600. When the train 1000 performs handover between millimeter wave base stations, the millimeter wave mobile station 1500 transmits a location registration request message. When the train 1000 is handed over from the millimeter wave base station 700 to the millimeter wave base station 600, the location registration request message transmitted by the millimeter wave mobile station 1500 is transmitted via the millimeter wave base station 700, the IP network 400, and the packet transfer apparatus 300. The position information management server 100 is reached. Note that the handover from the LCX base station (not shown) to the LCX base station 500 has already been completed, and the position information has also been updated. At this time, the composition ID notified as the position information registration request message is “1000”, and the millimeter wave base station ID is “600”.

  When the location information management server 100 receives the location information registration request message, the location information management server 100 recognizes that the train 1000 has been handed over to the millimeter wave base station 600, and the corresponding in-vehicle network address “192.168.1. .0 ”and the millimeter wave base station IP address“ 192.168.31.6 ”. When the search is completed, writing is performed in the corresponding areas of the position information update notification having the configuration shown in FIG. The position information update notification is a message in which the position information management server 100 notifies the packet transfer device 300 that the train position information has been updated. As shown in FIG. An area 121 for storing the ID, an area 122 for storing the in-vehicle network address, an area 123 for storing the IP address of the handover destination LCX base station, and an area 124 for storing the IP address of the handover destination millimeter wave base station Is done. In the example shown in FIG. 1, the train with the composition ID 1000, that is, the train 1000 is handed over to the cell 602, so “1000” is displayed in the composition ID area 121 of the location information update notification and “192.168.8.1. “0” is written in the handover destination millimeter-wave base station IP address area 124, respectively. Further, since no handover between LCX base stations has occurred, no value is written in the handover destination LCX base station IP address area 123, and the initial value remains “0”. In the control information area 120, control information indicating a position information update notification is written. The position information management server 100 writes the composition ID notified by the position information registration request message and the above-described in-vehicle network address and millimeter wave base station IP address obtained by searching the database of FIG. 2 as update information. After generating the information update notification, the generated position information update notification is transmitted to the packet transfer apparatus 300. As described above, the location information management server 100 always knows the location information of the train, and when the location information changes, the location information management server 100 notifies the packet transfer device 300 of the latest location information by transmitting a location information update notification. In addition, although the case where the handover between millimeter wave base stations occurred was described, the operation of the location information management server 100 when the handover between LCX base stations occurs is the same. When handover between LCX base stations occurs, the location information management server 100 searches the in-vehicle network address and the LCX base station IP address, generates a location information update notification in which the search result is written, and sends it to the packet transfer apparatus 300. Send.

  The packet transfer apparatus 300 has the database shown in FIG. 4. When the position information update notification is received, the packet transfer apparatus 300 updates the database based on the update information written in the received position information update notification. In the database that the packet transfer apparatus 300 has, the train IDs 301 to 303 of the trains, the in-vehicle network addresses 304 to 306, the IP addresses 307 to 309 of the LCX base stations that are on the line, and the IP addresses 310 to 300 of the millimeter wave base stations 312 are associated with each other. FIG. 4A shows an example of database information before receiving a location information update notification from the location information management server 100, and FIG. 4B shows an update process after receiving the location information update notification from the location information management server 100. It shows an example of the database information after performing. Here, since the handover between the millimeter wave base stations has occurred, the millimeter wave base station IP address information 310 corresponding to the composition ID 301 is rewritten based on the information on the location information update notification transmitted from the location information management server 100. Here, the LCX base station IP address 307 is not rewritten because the handover destination LCX base station 123 of the location information update notification has an initial value “0”. In this way, the packet transfer apparatus 300 grasps the train line status.

  The packet transfer apparatus 300 transfers the packet received from the data system terminal 200 to an appropriate base station (LCX base station, millimeter wave base station) according to the information in the database shown in FIG. 4, and receives the packet received from each base station. It is a device for transferring to the data system terminal 200 and also functions as a router. The packet transfer apparatus 300 is connected to the location information management server 100 and the data system terminal 200 via an optical cable, and communicates with each base station via an IP network.

  The packet transfer device 1200 mounted on the train 1000 has the same function as the packet transfer device 300 on the ground side, but differs from the packet transfer device 300 in that it is connected to the packet transfer device 1200 and a millimeter wave mobile station. There is one station each. When determining the packet transfer destination, the packet transfer apparatus 1200 uniquely determines the transfer destination millimeter-wave mobile station and the LCX mobile station. The in-vehicle terminal 1100 and the packet transfer device 1200 are an in-vehicle network connected by a LAN cable. The LAN 1300 and the in-vehicle network are not the same network. In FIG. 1, the train 1000 is located in the cells of the LCX base station 500 and the millimeter wave base station 600, the LCX mobile station 1400 communicates with the LCX base station 500 via the antenna 1401, and the LCX base station 500 connects the LCX cable 501. And communicates with the LCX mobile station 1400. Also, the millimeter wave mobile station 1500 communicates with the millimeter wave base station 600 via the antenna 1501, and the millimeter wave base station 600 communicates with the millimeter wave mobile station 1500 via the antenna 601.

  The data system terminal 200 and the in-vehicle terminal 1100 are termination devices. The data system terminal 200 and the in-vehicle terminal 1100 communicate with each other by TCP / IP. Hereinafter, the flow of data transmission / reception will be described with reference to an example in which data is transmitted from the data system terminal 200 to the in-vehicle terminal 1100. First, FIG. 5 shows a packet configuration of data transmitted by the data system terminal 200. As shown in FIG. 5A, the TCP / IP packet has a configuration in which the IP header 210 is added before the TCP header 220. However, the packet transmitted by the data terminal 200 of this embodiment is shown in FIG. It is assumed that the configuration shown in b), that is, a configuration in which application data 230 is further added after the TCP header 220.

  FIG. 6 is a diagram showing the formats of the IP header 210 and the TCP header 220. FIG. 6A shows the format of the IP header 210. The IP header 210 includes a version area 21a, a header length area 21b, a service type area 21c, a packet length area 21d, an ID area 21e, a flag area 21f, a fragment / offset area 21g, a lifetime area 21h, a protocol number area 21i, and a header check. It includes a thumb area 21j, a source IP address area 21k, a destination IP address area 21l, and an option area 21m. Details of each of the illustrated areas will be described as appropriate in the following description. IP is a network layer protocol of the OSI (Open Systems Interconnection) reference model, and FIG. 6A shows the configuration of the IP header of version 4 (IPv4).

  FIG. 6B shows the format of the TCP header 220. The TCP header 220 includes a source port number area 22a, a destination port number area 22b, a sequence number area 22c, an acknowledgment (ACK) number area 22d, a data offset area 22e, an unused area, a reserved area 22f, and a control flag area. 22g, a window size area 22h, a checksum area 22i, an emergency pointer area 22j, and an option area 22k. If there is a remainder in the option area 22k, the remaining areas are all 0 (padding). TCP is a protocol that supports high-reliability communication at the transport layer of the OSI reference model. The TCP header includes retransmission control information such as ACK and sequence number, thereby supporting highly reliable communication. The TCP header and the TCP packet data area are stored in the data area of the IP packet following the IP header, and the application data is stored in the data area of the TCP packet, whereby the TCP / IP having the configuration shown in FIG. Packet. In the description of the present embodiment, it is assumed that the data terminal 200 transmits a TCP / IP packet of a total of 1040 bytes composed of a TCP header 20 bytes with application data 1000 bytes and an IPv4 header (no option) 20 bytes.

  Next, an operation in which the data terminal 200 transmits data to the in-vehicle terminal 1100 will be described. FIG. 7 is a diagram illustrating an example of a data flow sequence when data is transmitted from the data system terminal 200 to the in-vehicle terminal 1100.

  In data transmission from the data system terminal 200 to the in-vehicle terminal 1100, first, the data system terminal 200 generates a data packet having the configuration shown in FIG. 5B and transmits it to the packet transfer apparatus 300 (step S100). When the data terminal 200 generates a data packet, it writes the IP address of its own device in the source IP address area 21k of the IP header 210 and writes the IP address of the in-vehicle terminal 1100 in the destination IP address area 21l. Here, it is assumed that the IP address of the data terminal 200 is “192.168.10.1” and the IP address of the in-vehicle terminal 1100 is “192.168.1.1”. That is, the data terminal 200 generates and transmits a data packet in which these addresses are set as a source address and a destination address.

  The packet transfer apparatus 300 receives the data packet transmitted from the data terminal 200, reads the network address from the destination IP address set in the received data packet (the subnet mask is common), and has the configuration shown in FIG. By comparing with the existing line information registered in the database, the LCX base station or the millimeter wave base station where the train 1000 where the destination in-vehicle terminal 1100 exists is specified as the packet transfer destination. The transfer destination base station is specified according to the flowchart shown in FIG. Hereinafter, the operation when the packet transfer apparatus 300 receives a packet with application data and specifies a transfer destination base station will be described with reference to FIG.

  When receiving a packet from the data system terminal 200, the packet transfer apparatus 300 first checks the IP header (step S1). Specifically, all the information stored in the IP header having the configuration shown in FIG. 6A is temporarily stored, and the source information, the destination are selected from the temporarily stored information. Get information, upper layer protocol information and data size information. The source information is a value “C0A8A1” stored in the source IP address area 21k, and the destination information is a value “C0A811” stored in the destination IP address area 21l, which are “192.168.10. 1 "and a hexadecimal number representing" 192.168.1.1 ". Thereby, the packet transfer apparatus 300 determines that the data is data transmitted from the data system terminal 200 to the in-vehicle terminal 1100. The upper layer protocol information is a value “6” stored in the protocol number area 21i. Thereby, the packet transfer apparatus 300 determines that the upper layer protocol is TCP. The data size information is obtained from the value “5” stored in the header length area 21b and the value “104” stored in the packet length area 21d. The header length indicates the size of the IP header. Since there is no option for the header length, the minimum value is 20 bytes. However, since the header length is counted in units of 32 bits (4 bytes), the value of the header length area 21b is “5” in the case of 20 bytes. The packet length indicates the size of the entire packet including the IP header and is 1040 bytes. Since it is counted in units of 4 bytes as in the header length, 1040 ÷ 4 = 260, and “104” in hexadecimal notation is the value of the packet length area 21d. That is, by subtracting the value of the header length area from the value of the packet length area, data size information indicating the size of the TCP packet can be obtained.

  When the packet transfer apparatus 300 confirms that the upper layer protocol is TCP in step S1, the packet transfer apparatus 300 confirms the TCP header (step S2). Specifically, all the information stored in the TCP header having the configuration shown in FIG. 6B is temporarily stored, and the source information and the destination are selected from the temporarily stored information. Get information and data size information. The transmission source is a value stored in the transmission source port number area 22a, and the destination information is a value stored in the destination port number area 22b, both of which are “14”. This is a value representing the port number “20” of the FTP data in hexadecimal. The data size information is a value “5” stored in the data offset area 22e, which means a TCP header length of 20 bytes counted in units of 4 bytes.

  Next, the packet transfer apparatus 300 updates the connection information (step S3). Specifically, the values stored in the source IP address, destination IP address, and protocol number areas acquired in the IP header confirmation in step S1, and the source port number and destination acquired in the TCP header confirmation in step S2. Based on the port number, the connection of the received packet is specified. Further, the packet transfer apparatus 300 manages information on the IP header and TCP header (hereinafter referred to as header information) of data transmitted / received in each connection, and based on the information acquired in the above steps S1 and S2. When the connection is specified, the header information of the specified connection is rewritten and updated with the IP header value and the TCP header value temporarily held in steps S1 and S2. However, if the received packet is the first transmission packet after the connection is established, the values of the IP header and TCP header temporarily held in steps S1 and S2 are newly registered as the header information of the specified connection. To do.

  After updating the connection information, the packet transfer apparatus 300 confirms whether the received packet has a TCP payload (step S4). Specifically, the presence / absence of a TCP payload, which is application data, is determined based on the data size information of the IP header and the data size information of the TCP header acquired in steps S1 and S2. The value of the header length area of the IP header is “5” and the value of the packet length area is “104”. As described above, the value obtained by subtracting the header length area value from the packet length area value is the TCP packet size. Match. On the other hand, since the value “5” of the data offset area of the TCP header indicates the size of the TCP header, the presence or absence of the TCP payload can be determined by comparing the size of the TCP packet with the size of the TCP header. That is, the value obtained by subtracting the header length area value from the packet length area value of the IP header is compared with the data offset area value of the TCP header, and if they are equal, it is determined that the TCP packet is composed of only the header. If the value of the data offset area is small, it can be determined that the TCP packet is composed of a header part and a payload part. Specifically, the packet length area value “104” −the header length area value is “5” = “FF”> the data offset area value “5”, and the value of the data offset area is small. The packet is determined to be a payload part.

  When there is no TCP payload in the received packet (step S4: No), the packet transfer apparatus 300 sets the LCX system, that is, the LCX base station where the train 1000 is located as the packet transfer destination (step S6A). On the other hand, when the TCP payload is present in the received packet (step S4: Yes), the header portion of the received packet, that is, the IP header and the TCP header portion are duplicated, and the header portion having the configuration shown in FIG. A new packet consisting of only is created (step S5). At this time, the value of the header checksum area 21j of the IP header and the value of the checksum area 22i of the TCP header are updated. This is because the packet length has changed due to the absence of the payload. As described above, in step S5, a packet including only the header portion is newly created as a new packet from the packet with the payload portion which is the original packet received from the data terminal 200. That is, only the retransmission control information is copied. Then, the millimeter wave system and the LCX system, that is, the LCX base station and the millimeter wave base station where the train 1000 is located are set as packet transfer destinations (step S6B).

  Returning to the description of the operation shown in FIG. 7, when the packet transfer apparatus 300 determines the transfer destination base station by executing the procedure shown in FIG. 8, the packet to be transferred is tunneled and transferred to the base station (step) S101a, S101b).

  For example, when a packet received from the data system terminal 200 has a TCP payload, that is, when an original packet and a new packet are transferred, tunneling with the millimeter wave base station 600 is performed for transferring the original packet, and for transferring a new packet. Tunnel with LCX base station 500. In order to indicate a destination to be tunneled, each TCP / IP packet shown in FIGS. 5A and 5B is encapsulated with an IP header to generate a packet shown in FIGS. 9A and 9B. . FIG. 9A shows the original packet encapsulated with the IP header 240, and FIG. 9B shows the new packet encapsulated with the IP header 240. In the original packet, as shown in FIG. 9A, the IP address “192.168.11.2” of the packet transfer apparatus 300 is set as the source IP address, and the millimeter-wave base station 600 is set as the destination IP address. The IP address “192.168.31.6” is encapsulated with the set IP header and transmitted (step S101b). In the new packet, as shown in FIG. 9B, the IP address “192.168.11.2” of the packet transfer apparatus 300 is set as the source IP address, and the IP address of the LCX base station 500 is set as the destination IP address. It is encapsulated with an IP header in which the address “192.168.21.5” is set and transmitted (step S101a).

  If the packet received from the data terminal 200 has no TCP payload, the IP address “192.168.11.2” of the packet transfer apparatus 300 is set to the source IP address of the received packet, and the destination IP address Is encapsulated with an IP header in which the IP address “192.168.21.5” of the LCX base station 500 is set and transmitted (step S101a). If the packet received from the data terminal 200 has no TCP payload, the transfer to the millimeter wave base station 600 in step S101b is not performed.

  The LCX base station 500 and the millimeter wave base station 600 that have received the packet forwarded by the packet forwarding device 300 decapsulate the IP header addressed to the device itself encapsulated for tunneling, and FIG. After returning to the packet having the configuration shown in b), the packet is transmitted to the mobile station. The LCX base station 500 transmits a packet toward the LCX mobile station 1400 (step S102a), and the millimeter wave base station 600 transmits a packet toward the millimeter wave mobile station 1500 (step S102b).

  As described above, when transmitting a packet composed of a header part and a payload part, the original packet is transmitted in the millimeter wave system, and a new packet composed only of the header part is generated and transmitted in the LCX system. Can be transmitted using a wireless access scheme that is more reliable than application data. In addition, since the header portion is transmitted using two radio access methods of the LCX system and the millimeter wave system, it is possible to obtain the spatial diversity effect of the retransmission control information. Since the LCX system transmits a packet consisting only of the header part, it is possible to prevent the LCX system band from being compressed more than necessary.

  In the train 1000, the LCX mobile station 1400 receives the packet transmitted in step S102a and transfers the packet to the packet transfer device 1200, and the millimeter-wave mobile station 1500 receives the packet transmitted in step S102b. The packet is transferred to the packet transfer device 1200 (steps S103a and S103b).

  When receiving a packet from one or both of the LCX mobile station 1400 and the millimeter wave mobile station 1500, the packet transfer apparatus 1200 transfers the packet to the in-vehicle terminal 1100 (step S104). In step S104, the packet transfer apparatus 1200 performs an operation according to the flow shown in FIG. 10 and transfers the packet. Hereinafter, an operation in which the packet transfer apparatus 1200 transfers a packet to the in-vehicle terminal 1100 will be described in detail.

  When receiving the packet from the LCX mobile station 1400 or the millimeter wave mobile station 1500, the packet transfer apparatus 1200 confirms the IP header (step S11). In this step S11, all the information stored in the IP header is temporarily held in the same manner as the packet transfer device 300 described above executes the step S1 shown in FIG. 8 and checks the IP header. In addition, transmission source information, destination information, higher layer protocol information, and data size information are acquired from the temporarily held information. Since the specific operation for acquiring each information is the same as that in step S1, the description thereof is omitted. The packet transfer apparatus 1200 that has confirmed the IP header determines that the received data is addressed to the in-vehicle terminal 1100 from the destination information, and determines that the upper layer protocol is TCP from the upper layer protocol information.

  Since the upper layer protocol is TCP, the packet transfer device 1200 next checks the TCP header (step S12). In this step S12, all the information stored in the TCP header is temporarily held in the same manner as in the operation in which the packet transfer apparatus 300 described above executes the step S2 shown in FIG. 8 to check the TCP header. In addition, transmission source information, destination information, and data size information are acquired from the temporarily held information. Since the specific operation for acquiring each information is the same as that in step S2, description thereof is omitted.

  Next, the packet transfer apparatus 1200 updates the connection information (step S13). In step S13, the source IP address, the destination IP address, and the protocol number acquired in step S11 are the same as the operation in which the packet transfer apparatus 300 described above executes step S3 shown in FIG. 8 to update the connection information. Based on the value stored in the area and the source port number and destination port number acquired in step S12, the connection of the received packet is specified. The packet transfer apparatus 1200 also manages header information of data transmitted / received in each connection as in the packet transfer apparatus 300. When the connection is specified based on the information acquired in steps S11 and S12, the specified connection The header information is rewritten and updated with the values of the IP header and the TCP header temporarily stored in steps S11 and S12. However, if the received packet is the first transmission packet after the connection is established, the IP header and TCP header values temporarily stored in steps S11 and S12 are newly registered as the header information of the specified connection. To do.

  When the update of the connection information is completed, the packet transfer apparatus 1200 establishes a communication path according to the destination IP address set in the IP header, and transfers the packet to the partner indicated by the destination IP address (step S14). Here, the packet is transferred to the in-vehicle terminal 1100.

  Steps S100 to S104 shown in FIG. 7 are a sequence when the data terminal 200 transmits data to the in-vehicle terminal 1100, that is, a downlink data flow sequence. In TCP communication, when a destination device receives a packet, it is necessary to return an acknowledgment packet to the transmission source device. Therefore, in the wireless communication system, the processes of steps S105 to S109 shown in FIG. 7 are further executed. Hereinafter, each of these steps will be described.

  When the in-vehicle terminal 1100 receives the TCP packet with the payload portion, it extracts the application data from the payload portion and passes it to the upper layer. At the same time, the in-vehicle terminal 1100 sends a confirmation response packet addressed to the data system terminal 200 for the confirmation response to the transmission source. Is generated. Hereinafter, this acknowledgment packet is referred to as an ACK packet. A payload can be added to the ACK packet, and if there is transmission data, the data may be sent together. However, here, for the sake of simplicity of explanation, a description will be given assuming that the header consists only of a header part. The value of the received packet is stored in the ACK number area 22d of the TCP header having the configuration shown in FIG. 6B. Specifically, the “sequence number of the received packet” and “the received application data The total value of “size” is stored. In this embodiment, since 1000 bytes of application data is assumed to be transmitted, for example, the sequence number of the packet transmitted from the data terminal 200 is “100”, and all of the transmitted packets are normally received. If so, the ACK number is 100 + 1000 = 1100. The flow control is also performed by storing a value indicating the receivable data size in the window size area 22h.

  The in-vehicle terminal 1100 converts the ACK packet generated only as described above and including only the header portion into a TCP / IP packet and transmits the packet to the packet transfer apparatus 1200 (step S105).

  When the packet transfer apparatus 1200 receives the TCP / IP packet from the in-vehicle apparatus 1100, the packet transfer apparatus 1200 analyzes the header and specifies the transfer destination of the packet. The operation of the packet transfer apparatus 1200 for specifying the packet transfer destination is the operation described above for specifying the transfer destination of the packet received from the data system terminal 200 by the packet transfer apparatus 300, specifically, as shown in FIG. This is the same as the operation according to the flowchart. Therefore, although a detailed description of the operation is omitted, the packet transfer apparatus 1200 determines that there is no TCP payload in the determination process of whether there is a TCP payload shown in step S4. That is, the value of the header length area 21b of the TCP / IP packet received from the in-vehicle device 1100 is “5”, the value of the data offset area 22e is “5”, the value of the packet length area 21d is “A”, and the packet length Since the area value “A” −the header length area value “5” = the data offset area value “5”, it is determined that there is no TCP payload. Then, the LCX system, that is, the LCX mobile station 1400 is set as a packet transfer destination.

  Note that if the TCP / IP packet received from the in-vehicle device 1100 is an ACK packet with a TCP payload portion, the packet transfer device 1200 executes steps S5 and S6B in FIG. That is, the header of the received ACK packet is duplicated to create a new ACK packet without a TCP payload, the transfer destination of the newly created ACK packet is the LCX mobile station 1400, the transfer destination of the ACK packet with the TCP payload portion is The millimeter wave mobile station 1500 is assumed.

  When the transfer destination of the TCP / IP packet received from the in-vehicle device 1100 is determined, the packet transfer device 1200 transmits the packet to the determined transfer destination. Here, since there is no TCP payload in the received TCP / IP packet, that is, since an ACK packet without a TCP payload is received, an ACK packet is transmitted to the LCX mobile station 1400 (step S106). At this time, the packet transfer apparatus 1200 tunnels with the LCX mobile station 1400 for transferring the ACK packet. Specifically, the IP address “192.168.2.2” of the packet transfer apparatus 1200 is set as the source IP address, and the IP address “192.168.2.4” of the LCX mobile station 1400 is set as the destination IP address. An ACK packet is encapsulated with an IP header in which is set. Then, the ACK packet is transferred to the LCX mobile station 1400 using the tunneled communication path.

  If the TCP / IP packet received from the in-vehicle device 1100 is an ACK packet with a TCP payload portion, the packet transfer device 1200 transfers the ACK packet with a TCP payload portion, which is an original packet, to the millimeter wave mobile station 1500. Then, the newly generated ACK packet without the TCP payload is transferred to the LCX mobile station 1400.

  Upon receiving the ACK packet transferred by the packet transfer apparatus 1200, the LCX mobile station 1400 decapsulates the IP header addressed to itself that is encapsulated for tunneling, and sends the decapsulated ACK packet to the LCX base station 500. Transmit (step S107).

  When the packet transfer apparatus 1200 also executes a process of transferring an ACK packet with a TCP payload portion to the millimeter wave mobile station 1500, the millimeter wave mobile station 1500 decapsulates the received ACK packet with a TCP payload portion. , And transmit to the millimeter wave base station 600.

  As described above, in the packet transmission operation including only the header portion, the packet transfer apparatus 1200 transmits the received packet as it is in the LCX system. Further, in the packet transmission operation in which the payload portion exists, the packet transfer apparatus 1200 transmits the received packet as it is in the millimeter wave system, and copies the IP header and the TCP header, which are the header portion of the received packet, as a header. A new packet consisting of only a part is generated and transmitted by the LCX system. By transmitting a packet consisting only of the header portion by the LCX system, it is possible to realize highly reliable transmission of the retransmission control information included in the TCP header and to prevent the LCX system band from being compressed more than necessary.

  When receiving the packet from the LCX mobile station 1400, the LCX base station 500 transfers the received packet to the packet transfer apparatus 300 (step S108). When the millimeter wave base station 600 receives a packet from the millimeter wave mobile station 1400, the received packet is similarly transferred to the packet transfer apparatus 300.

  When receiving a packet from the LCX mobile station 1400, the packet transfer apparatus 300 transfers the packet to the data terminal 200 (step S109). In step S109, the packet transfer apparatus 300 is similar to step S104 in which the packet transfer apparatus 1200 mounted on the train 1000 receives a packet from the LCX mobile station 1400 or the millimeter wave mobile station 1500 and transfers the packet to the in-vehicle terminal 1100. The operation according to the flow shown in FIG. 10 is executed to transfer the packet. Since the operation of the packet transfer apparatus 300 for transferring the packet to the data terminal 200 is the same as the operation of the packet transfer apparatus 1200 for transferring the packet to the in-vehicle terminal 1100, the detailed description is omitted. At this time, if the received ACK packet is duplicated, the packet transfer apparatus 300 may discard the packet.

  Steps S105 to S109 shown in FIG. 7 are a sequence when the in-vehicle terminal 1100 transmits a packet to the data terminal 200, that is, a confirmation response transmission sequence.

  Thereafter, the data terminal 200 confirms the data delivery by referring to the value of the ACK number area 22d of the ACK packet received from the in-vehicle terminal 1100. If there is further transmission data, the value of the window size area 22h is referred to, and the packet is transmitted within a range not exceeding the size permitted by the window size.

  As described above, in the wireless communication system according to the present embodiment, when the packet transfer apparatuses 300 and 1200 receive a packet to be transmitted to the wireless section, the packet transfer apparatuses 300 and 1200 are suitable for transmission based on the presence / absence of the TCP payload of the received packet. The selected wireless access system is transferred to the base station or mobile station of the wireless access system. Specifically, if the received packet is a packet consisting only of the header part, the packet is transferred to the LCX system. If the received packet is a packet consisting of the header part and the payload part, the received original packet, which is a millimeter wave, is transferred. Along with the transfer to the system, a packet consisting only of the header part of the received packet is newly created and transferred to the LCX system. This makes it possible to transmit the retransmission control information with high reliability by using a highly reliable wireless access system that is different from the wireless access system that uses the header part including retransmission control information for transmitting application data. it can. In addition, since the transmission is performed by the highly reliable wireless access system only for the header portion, it is possible to prevent the band of the highly reliable wireless access system from being compressed more than necessary. Also, in a packet consisting only of a header part, an original packet that is a received packet may be transferred to the millimeter wave system, and a packet identical to the received packet may be newly created and transferred to the LCX system. .

  It is obvious that the network form in the present embodiment is not limited to that shown in FIG. 1 and can be constructed according to the system. Moreover, the form which combines the same kind of radio | wireless access system may be sufficient. The packet transfer apparatus is not limited to a configuration in which one packet transfer apparatus is installed in the system. For example, the area for constructing the system may be divided into a plurality of groups, and a packet transfer apparatus may be installed for each group. Also, the communication protocol is not limited to TCP, and any format may be used as long as retransmission control information is included in the header and application data is a payload. Obviously, the IP version is not limited to IPv4 but may be IPv6. The combination of wireless access systems is not limited to that shown in FIG.

Embodiment 2. FIG.
Next, a radio communication system according to the second embodiment will be described. The configuration of the wireless communication system is the same as that of the first embodiment. In the present embodiment, parts different from those of the first embodiment will be described.

  In the wireless communication system of the first embodiment, the packet transfer device on the transmission side selects a radio access system suitable for packet transmission, and transfers the packet to the selected radio access system. Specifically, the packet transfer device transfers to the LCX system if the packet received from the terminal device, which is the data system terminal 200 or the in-vehicle terminal 1100, consists only of the header part, and the original if it is a packet with a payload part. The packet was transferred to the millimeter wave system, and a new packet consisting only of the header portion of the original packet was generated and transferred to the LCX system. According to the radio communication system of the first embodiment, information in the header part can be transmitted with high reliability, and high-reliability transmission of retransmission control information included in the TCP header can be realized.

  On the other hand, in this embodiment, in addition to the above-described effects obtained in the wireless communication system of Embodiment 1, a wireless communication system capable of suppressing transmission of unnecessary retransmission control information will be described. Although details will be described later, the packet transfer apparatus according to the present embodiment updates whether or not the packet is an ACK packet and the ACK number in addition to checking whether or not the packet has a payload portion when specifying the packet transfer destination. Confirm whether it has been done or not and determine the transfer destination.

  As described in the first embodiment, the operation of the ground-side packet transfer apparatus 300 that receives and transfers a packet transmitted by the data terminal 200 and the vehicle-side packet transfer that receives and transfers the packet transmitted by the in-vehicle terminal 1100 The operation of apparatus 1200 is similar. Therefore, in this embodiment, an operation example of the packet transfer apparatus 300 will be described, and an operation description of the packet transfer apparatus 1200 will be omitted. The operation in which the packet transfer apparatus 300 and the packet transfer apparatus 1200 specify the packet transfer destination is as shown in FIG. The operation shown in FIG. 11 is obtained by replacing step S3 of the operation shown in FIG. 8 with step S3A and further adding steps S45 and S6C. The processing of each step other than these steps S3A, S45, and S6C is the same as the processing given the same step number in FIG.

  When the packet transfer apparatus 300 receives a packet from the data system terminal 200, in order to specify the transfer destination, the packet transfer apparatus 300 executes steps S1 and S2 in FIG. 11, and then executes step S3A to update the connection information. In the connection information update shown in step S3A, in addition to the connection information update operation shown in step S3 of FIG. 8, an update determination of the ACK number is further performed. That is, the packet transfer apparatus 300 is based on the values stored in the source IP address, destination IP address and protocol number area acquired in step S1, and the source port number and destination port number acquired in step S2. The connection of the received packet is specified, and the header information of the specified connection is rewritten and updated with the IP header value and the TCP header value temporarily held in steps S1 and S2. Further, it is determined whether or not the value of the ACK number area of the TCP header has been updated in updating the header information of the identified connection. Whether or not the ACK number is updated is determined by the difference between before and after updating the header information. If the difference is 0, it is determined that the ACK number has not been changed, and if it is not 0, it is determined that the ACK number has been updated. For example, ACK before updating the header information is set to “90”. At this time, if the ACK number after updating the header information is “90”, the difference is 90−90 = “0”, it is determined that the ACK number has not been updated, and the ACK number after updating the header information is “100”. For example, the difference is 100−90 = “10”, and it is determined that the ACK number has been updated. If it is determined that the ACK number has been updated, “ACK number update confirmation” is stored as internal information. For example, when the ACK number is updated, a flag indicating that is set.

  If the packet transfer apparatus 300 determines that the received packet has a TCP payload (step S4: Yes), the packet transfer apparatus 300 checks whether or not the ACK number has been updated in the connection information update process of step S3A (step S45). If the “ACK number update confirmation” is stored, it is determined that the ACK number has been updated (step S45: Yes), and step S5 is executed. If it is determined that the ACK number has been updated, “ACK number update confirmation” is also deleted. On the other hand, if the “ACK number update confirmation” is not stored, it is determined that the ACK number has not been updated (step S45: No), and the millimeter wave system is set as the packet transfer destination (step S6C). In this case, the packet transfer apparatus 300 tunnels with the millimeter wave base station 600 and transfers an original received packet that is a packet with a payload portion. Specifically, the IP address “192.168.11.2” of the packet transfer apparatus 300 is set as the source IP address, and the IP address “192.168.31.6” of the millimeter wave base station 600 is set as the destination IP address. The received packet is encapsulated with the IP header set with "". When the ACK number is not updated in the connection information update process, it can be determined that an ACK having the same ACK number has already been transmitted.

  In the wireless communication system according to the present embodiment, when packet transfer apparatuses 300 and 1200 receive a packet including a header part and a payload part, the packet transfer apparatuses 300 and 1200 check whether or not the ACK number has been updated. If it is transferred to the base station or mobile station of the millimeter wave system and the ACK number has been updated, the received original packet is transferred to the base station or mobile station of the millimeter wave system and consists only of the header part of the received packet. A new packet is created and transferred to the base station or mobile station of the LCX system. Here, the condition for newly creating a packet consisting only of the header portion of the received packet is “when the ACK number is updated” in order to suppress unnecessary retransmission in TCP. In TCP, retransmission control is performed when ACK of the same value is received three times. That is, if the header is copied and transmitted without considering the update of the ACK number as in the packet transfer apparatus described in the first embodiment, the same ACK is always transmitted twice in one transmission. This increases the possibility of receiving ACKs three times and unnecessary retransmissions occur frequently. However, by duplicating and transmitting only the header of the first packet with the updated ACK number, it is possible to reduce the chance that the data transmission source terminal receives duplicate ACKs, and the data receiving terminal transmits retransmission control information. Can be sent reliably only when necessary. It is also possible to prevent the LCX system band from being compressed. Note that in the packet transfer apparatus described in the first embodiment, when a packet including only a header part is transmitted by duplicating the header without considering the update of the ACK number, whether the ACK number is updated or not is confirmed. Is transferred to the base station or mobile station of the LCX system if it is not updated, and if the ACK number is updated, the received original packet is transferred to the base station or mobile station of the millimeter wave system, and the received packet The same packet is newly created and transferred to the base station or mobile station of the LCX system.

Embodiment 3 FIG.
Next, a radio communication system according to the third embodiment will be described. The configuration of the wireless communication system is the same as in the first and second embodiments. In the present embodiment, parts different from the first and second embodiments will be described.

  In the wireless communication systems according to Embodiments 1 and 2, in the packet transfer device on the transmission side, the retransmission control information is increased by transferring the packet based on the presence / absence of the payload of the transmission packet in the transport layer and the presence / absence of the ACK number update. Realized reliable transmission. In contrast, in the radio communication system according to the present embodiment, highly reliable transmission of retransmission control information in the data link layer is realized.

  The transmitter of the millimeter wave system, that is, the transmitter included in each of the millimeter wave base stations 600, 700, and 800 and the millimeter wave mobile station 1500, frames the packets received from the packet transfer apparatuses 300 and 1200 in the data link layer. And send it. At the data link layer of the receiver of the millimeter wave system, that is, the receiver of each of the millimeter wave base stations 600, 700, and 800 and the millimeter wave mobile station 1500, the order of received frames is controlled to ensure data consistency. And then hand it over to the upper layer IP. At this time, a retransmission request is made by transmitting retransmission control information which is ACK or NACK (Negative Acknowledgment) to the frame transmission side. This function is called ARQ (Automatic Repeat reQuest), and the data link layer has an ARQ function, so that data errors can be repaired at an earlier stage than retransmission control in a transport layer such as TCP.

  FIG. 12 is a diagram illustrating a configuration example of a frame transmitted and received in the data link layer of the wireless communication system according to the present embodiment. The data link layer in the radio communication system according to the present embodiment is a unique protocol having functions such as order control, retransmission control, and flow control. This unique protocol is described as “ORI” in FIG.

  A frame transmitted and received in the data link layer of the wireless communication system according to the present embodiment is configured by an ORI header 610, application data 620 that is ARQ retransmission data or IP packet, and FCS (Frame Check Sequence) 630 that is an error detection bit. Has been. The ORI header 610 includes a transmission source ID area 611 for storing a transmission ID of 6 bytes, a destination ID area 612 for storing a transmission ID of 6 bytes, and the total frame length from the ORI header 610 to the FCS 630. A frame length area 613 for storing the 2-byte length frame information, a type area 614 for storing the 2-byte length type information indicating the type of the frame, and a 6-byte length sequence number information indicating the frame serial number. It consists of a sequence number area 615 for storing. The value stored in type field 614 indicates whether the frame is a frame including application data, an ACK frame, or a NACK. For example, if the value is “0”, it is application data, “1” is ACK, and “2” is NACK. The sequence number area 615 includes a mobile station ID area 615a for storing a 3-byte long mobile station ID, and a serial number area 615b for storing 3-byte long serial number information indicating a frame serial number. . The sequence number information stored in the sequence number area 615 is a value obtained by combining the mobile station ID stored in the mobile station ID area 615a and the serial number information stored in the serial number area 615b. This avoids duplication of sequence numbers between mobile stations. However, the value of the type information is “1”, that is, the value of the sequence number in the case of an ACK frame is the value of the sequence number of the last frame that has been received. In addition, the value of the type information is “2”, that is, the value of the sequence number in the case of the NACK frame is the value of the sequence number of the frame in which the error is detected. Note that a frame for transmitting ACK and a frame for transmitting NACK have a frame configuration including only the ORI header 610 and the FCS 630 that does not include the application data 620.

  FIG. 13 is a diagram illustrating an example of a protocol stack inside the millimeter wave base station 600. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. The same applies to millimeter wave base stations 700 and 800. The protocol stack in the millimeter wave base station 600 includes a physical layer Ethernet (registered trademark) 603, a data link layer MAC (Media Access Control) 604, a network layer IP 605, a data link layer ORI 606, and a physical conforming to millimeter wave communication. Layer 607 is included. Hereinafter, the physical layer 607 compliant with millimeter wave communication is referred to as a millimeter wave physical layer 607.

  For example, when the millimeter wave base station 600 receives data from the packet transfer apparatus 300 shown in FIG. 1 via the IP network 400, the received data is demodulated by the Ethernet 603 and then transferred to the MAC 604 in the protocol stack shown in FIG. MAC 604 removes the MAC header and passes it to IP 605. In IP605, the packet received from the MAC 604 is transferred to the ORI 606, and in the ORI 606, the packet received from the IP 605 is framed by adding an ORI header and transferred to the millimeter wave physical layer 607. In the millimeter wave physical layer 607, the frame received from the ORI 606 is modulated and transmitted from the antenna 601 to the millimeter wave mobile station 1500 shown in FIG.

  On the other hand, when the millimeter wave base station 600 receives data from the millimeter wave mobile station 1500 via the antenna 601, in the protocol stack shown in FIG. 13, the data is transferred to the ORI 606 after being demodulated by the millimeter wave physical layer 607. . In the ORI 606, the ORI header is removed and the packet is transferred to the IP 605. In IP605, the packet received from ORI 606 is transferred to MAC 604, and in MAC 604, a MAC header is added to the packet received from IP 605 to form a frame, and the packet is transferred to Ethernet 603. The Ethernet 603 modulates the frame received from the MAC 604 and transmits it to the packet transfer apparatus 300 shown in FIG. 1 via the IP network 400.

  Also, ORI 606 transmits an ACK frame when data is normally received, and transmits an NACK frame from antenna 601 to millimeter wave mobile station 1500 when an error is detected in the received data. The ACK frame and NACK frame generated at this time are retransmission control information. The configuration of retransmission control information in this case is as shown in FIG. FIG. 14 is a diagram showing a specific example of values stored in each area of the ORI header 610 shown in FIG. As shown in FIG. 14, “258” representing the ID “600” of the millimeter wave base station 600 in hexadecimal is stored in the transmission source ID area 611, and the millimeter wave mobile station 1500 is in the destination ID area 612. “5DC” representing the ID “1500” in hexadecimal is stored. In the frame length area 613, “1A” indicating the total “26” bytes of the ORI header + FCS in hexadecimal is stored, and in the type area 614, “1” indicating an ACK frame is stored. The sequence number area 615 stores a hexadecimal number “5DC064”, which is expressed as a decimal number as “15000100”. This value is the “0100” -th transmitted by the millimeter-wave mobile station 1500 whose ID is “1500”. This indicates that data frames, that is, up to the 100th data frame can be received.

  In the radio communication system according to the present embodiment, retransmission control information that is an ACK frame or a NACK frame is not transmitted from the antenna 601 via the millimeter wave physical layer 607, but is once transmitted to the LCX system via the Ethernet 603 and the IP network 400. The detour is transmitted to the millimeter wave mobile station 1500.

  Therefore, in ORI 606, when generation of an ACK frame or NACK frame is completed as retransmission control information, it is passed to IP 605. At this time, it is passed using a dedicated interface to distinguish it from normal received data. When the IP 605 determines that the data received by reception from the dedicated interface is the ORI retransmission control information, the IP 605 adds an IP header to encapsulate the data, and passes it to the MAC 604. The source IP address of the added IP header is set to the IP address of the millimeter wave base station 600, and the destination IP address is set to the IP address of the LCX base station 500, thereby tunneling with the LCX base station 500. At this time, “140” is stored in the protocol number area. This value indicates that the data following the IP header is an ORI frame. Packets encapsulated by IP 605 are sequentially transmitted via MAC 604 and Ethernet 603.

  The sequence for transmitting retransmission control information in the wireless communication system according to the present embodiment is as shown in FIG.

  When the millimeter wave base station 600 generates retransmission control information by the ORI 606 shown in FIG. 13, the millimeter wave base station 600 transmits the IP packet with retransmission control information to the LCX base station 500 via the IP network 400 (step S200).

  When receiving the IP packet with retransmission control information transmitted from the millimeter wave base station 600 via the IP network 400, the LCX base station 500 transfers the received IP packet to the LCX mobile station 1400 (step S201). The operation in step S201 will be described in detail. FIG. 16 is a diagram illustrating an example of a protocol stack inside the LCX base station 500. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. The protocol stack inside the LCX base station 500 includes an Ethernet 503, a MAC 504, an IP 505, a data link layer 506 compliant with LCX communication, and a physical layer 507 compliant with LCX communication. Hereinafter, the data link layer 506 compliant with LCX communication is referred to as an LCX data link layer 506, and the physical layer 507 compliant with LCX communication is referred to as an LCX physical layer 507. A received packet from the millimeter wave base station 600 is transferred to the IP 505 through processing in the Ethernet 503 and the MAC 504. In IP505, the value stored in the protocol number area of the IP header is confirmed, and since the value is “140”, it is determined that the encapsulated data is ORI retransmission control information. Then, the IP 505 removes the IP header and returns to the state of the ORI frame shown in FIG. Thereafter, the IP 505 encapsulates the retransmission control information that has become the ORI frame again with the IP header. At this time, the IP address of the LCX base station 500, that is, the IP address of its own device is set as the source IP address of the IP header, and the IP address of the LCX mobile station 1400 is set as the destination IP address. Further, “140” is stored in the protocol number area. When the encapsulation is completed, the IP 505 passes the packet to the LCX data link layer 506, and the LCX data link layer 506 frames the received packet. Then, the LCX data link layer 506 passes the frame to the LCX physical layer 507, and the LCX physical layer 507 modulates the received frame and transmits it to the LCX mobile station 1400 via the LCX cable 501.

  When the LCX mobile station 1400 receives the IP packet with retransmission control information transmitted from the LCX base station 500 via the LCX cable 501, the antenna 1401 transfers the IP packet to the millimeter wave mobile station 1500 (step S202). Note that the transfer from the LCX mobile station 1400 to the millimeter wave mobile station 1500 is performed via the LAN 1300. The operation of step S202 will be described in detail. FIG. 17 is a diagram illustrating an example of a protocol stack inside the LCX mobile station 1400. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. The protocol stack inside the LCX mobile station 1400 includes Ethernets 1403 and 1404, IP 1405, an LCX data link layer 1406, and an LCX physical layer 1407. A received packet from the LCX base station 500 is transferred from the antenna 1401 to the LCX physical layer 1407, and is transferred to the IP 1405 through processing in the LCX physical layer 1407 and the LCX data link layer 1406. In IP 1405, since the value stored in the protocol number area of the IP header is “140”, it is determined that the encapsulated data is ORI retransmission control information. Then, the IP 1405 removes the IP header and returns to the ORI frame state. After that, the IP 1405 encapsulates the ORI frame again with the IP header. At this time, the IP address of the LCX mobile station 1400, that is, the IP address of its own device is set as the source IP address of the IP header, and the IP address of the millimeter wave mobile station 1500 is set as the destination IP address. Further, “140” is stored in the protocol number area. When the encapsulation is completed, the IP 1405 passes the packet to the Ethernet 1404, and the packet is transferred to the millimeter wave mobile station 1500 via the Ethernet 1404 and 1403 and further via the LAN 1300.

  The millimeter wave mobile station 1500 receives the frame transferred from the LCX mobile station 1400 via the LAN 1300. Thereafter, when there is data to be transmitted, the data is transmitted to the millimeter wave base station 600 (step S203). The operation when the millimeter wave mobile station 1500 receives a frame from the LCX mobile station 1400 will be described in detail. FIG. 18 is a diagram illustrating an example of a protocol stack inside the millimeter wave mobile station 1500. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. The protocol stack inside the millimeter wave mobile station 1500 includes Ethernet 1503 and 1504, IP 1505, ORI 1506, and millimeter wave physical layer 1507. In millimeter wave mobile station 1500, a frame received from LCX mobile station 1400 via LAN 1300 is passed to IP 1505 in the form of an IP packet via Ethernet 1503 and 1504. In IP 1505, since the value stored in the protocol number area of the IP header is “140”, it is determined that the encapsulated data is ORI retransmission control information. The IP 1505 removes the IP header and returns to the state of the ORI frame, and then passes it to the ORI 1506 using a dedicated interface. The ORI 1506 confirms the ORI header 610 of the ORI frame received from the dedicated interface, specifically, the transmission source ID 611 and the destination ID 612 of the ORI header 610 set with the values shown in FIG. It is confirmed that it is transmitted from the millimeter wave base station 600 to its own device. This completes the delivery confirmation of data frames up to the sequence number “15000100”. When the retransmission control information is NACK, the ORI frame having the sequence number indicated by the value stored in the sequence number area is retransmitted. In addition, even when the retransmission control information is ACK, it can be seen that when an ACK having a sequence number smaller than the maximum sequence number of a frame for which transmission has been completed is received, no frame has arrived. It is also possible to retransmit all transmission completion frames after the sequence number.

  In the present embodiment, the data transmission on the uplink, that is, the operation in the case where the in-vehicle terminal 1100 transmits data to the data system terminal 200 has been described. Similarly, in the data transmission on the downlink, the millimeter wave It is possible to send the retransmission control information of the data transmitted through the system by bypassing the LCX system.

  The first and second embodiments can be combined with the present embodiment, and when combined, the reliability can be further improved.

  As described above, in the radio communication system according to the present embodiment, the millimeter wave base stations 600, 700, and 800 transmit the retransmission control information of the data received from the millimeter wave mobile station 1500 via the LCX system. The mobile station 1500 transmits the retransmission control information of the data received from the millimeter wave base station 600, 700 or 800 via the LCX system. As a result, retransmission control information can be transmitted using the LCX system, which is a radio access system with higher reliability than the millimeter wave system, and retransmission control information can be transmitted with high reliability. The retransmission control information is not limited to being transmitted only via the LCX system, and may be transmitted by both the millimeter wave system and the LCX system.

  It is obvious that this embodiment can be realized without depending on a higher-level protocol. For example, it is also possible to support a protocol that does not have a retransmission control function such as UDP (User Datagram Protocol).

  The packet transfer apparatuses 300 and 1200 described in each embodiment are realized by, for example, the processing circuit illustrated in FIG. 19, specifically, the processing circuit including the processor 11, the memory 12, the communication device 13, and the network interface 14. Is done. Specifically, the processor 11 reads the program for operating as the packet transfer apparatus 300 or 1200 from the memory 12 and executes it, whereby the packet transfer apparatus 300 or 1200 is realized.

  When the processing circuit shown in FIG. 19 implements the packet transfer device 300, the communication device 13 is used when the packet transfer device 300 communicates with the location information management server 100 and with the data system terminal 200. The network interface 14 is used when the packet transfer apparatus 300 communicates with the LCX base station 500 and the millimeter wave base station 600, 700, or 800 via the IP network 400. When the processing circuit illustrated in FIG. 19 implements the packet transfer device 1200, the communication device 13 is used when the packet transfer device 1200 communicates with the in-vehicle terminal 1100. The network interface 14 is used when the packet transfer apparatus 1200 communicates with the LCX mobile station 1400 and the millimeter wave mobile station 1500 via the LAN 1300.

  The processor 11 is a CPU (Central Processing Unit, central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, processor, DSP), system LSI (Large Scale Integration), or the like. The memory 102 is a nonvolatile or volatile semiconductor such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), etc. Memory, magnetic disk, flexible disk, optical disk, compact disk, mini disk, DVD (Digital Versatile Disc), and the like.

  The configuration described in the above embodiment shows an example of the contents of the present invention, and can be combined with another known technique, and can be combined with other configurations without departing from the gist of the present invention. It is also possible to omit or change the part.

  100 location information management server, 101 to 103, 121 organization ID, 104 to 106, 122 in-vehicle network address, 107 to 109 LCX base station ID, 110 to 112, 116 to 118 IP address, 113 to 115 millimeter wave base station ID, 200 data system terminal, 300, 1200 packet transfer device, 400 IP network, 500 LCX base station, 501 LCX cable, 502, 602, 702, 802 cell, 503, 603, 1403, 1503 Ethernet, 504, 604 MAC, 505 605, 1405, 1505 IP, 600, 700, 800 mm-wave base station, 601, 701, 801, 1401, 1501 antenna, 606, 1506 OR, 607, 1507 mm-wave physical layer, 610 OR 611, sender ID area, 612 destination ID area, 613 frame length area, 614 type area, 615 sequence number area, 615a mobile station ID area, 615b serial number area, 620 application data, 630 FCS, 1000 train, 1100 Terminal, 1300 LAN, 1400 LCX mobile station, 1500 millimeter wave mobile station.

Claims (7)

A first radio access system and a second radio access system, wherein the first radio access system is capable of transmitting a larger amount of data than the second radio access system, and the second radio access system Is a packet transfer apparatus for transferring a packet to at least one of the first radio access system and the second radio access system in a radio communication system having better communication quality than the first radio access system. ,
When the packet does not include a payload, the packet is transferred to the first radio access system, and the same packet as the packet is generated and transmitted to the second radio access system, or the packet is Forwarding to the second radio access system, and if the packet contains a payload, forwarding the packet to the first radio access system and generating a packet with the payload removed from the packet Transmitting to the second radio access system;
A packet transfer apparatus. A first radio access system and a second radio access system, wherein the first radio access system is capable of transmitting a larger amount of data than the second radio access system, and the second radio access system Is a packet transfer apparatus for transferring a packet to at least one of the first radio access system and the second radio access system in a radio communication system having better communication quality than the first radio access system. ,
If the packet does not include a payload, if the ACK number included in the header of the packet is the same as the ACK number included in the header of the previously transferred packet, the packet is transferred to the second radio access system. If the ACK number included in the header of the packet is not the same as the ACK number included in the header of the previously transferred packet, the packet is transferred to the first radio access system and the packet When the packet includes the payload, the ACK number included in the packet header is included in the header of the previously transferred packet. If the received ACK number is the same, the packet is transferred to the first radio access system. If the ACK number included in the header of the packet is not the same as the ACK number included in the header of the previously transferred packet, the packet is transferred to the first radio access system and the payload is transferred from the packet. And generate a packet that is deleted and transmit it to the second radio access system.
A packet transfer apparatus. A first wireless access system;
A second wireless access system;
A packet transfer apparatus for transferring a packet to at least one of the first radio access system and the second radio access system;
With
The first radio access system can transmit a larger amount of data than the second radio access system, and the second radio access system has better communication quality than the first radio access system. ,
When the packet does not include a payload, the packet transfer apparatus transfers the packet to the first radio access system, generates the same packet as the packet, and transmits the packet to the second radio access system Or if the packet is transferred to the second radio access system and the packet contains a payload, the packet is transferred to the first radio access system and the payload is deleted from the packet. Generating the transmitted packet and transmitting it to the second radio access system,
A wireless communication system. A first wireless access system;
A second wireless access system;
A packet transfer apparatus for transferring a packet to at least one of the first radio access system and the second radio access system;
With
The first radio access system can transmit a larger amount of data than the second radio access system, and the second radio access system has better communication quality than the first radio access system. ,
If the packet does not include a payload, the packet transfer apparatus determines the packet if the ACK number included in the header of the packet is the same as the ACK number included in the header of the previously transferred packet. The packet is transferred to the second radio access system, and if the ACK number included in the header of the packet is not the same as the ACK number included in the header of the previously transferred packet, the packet is transferred to the first radio access system. And the same packet as the packet is generated and transmitted to the second radio access system. When the packet includes a payload, the ACK number included in the header of the packet is transferred last time If it is the same as the ACK number included in the header of the packet, the packet is If the ACK number included in the header of the packet is not the same as the ACK number included in the header of the previously transferred packet, the packet is transferred to the first radio access system. And generating a packet with a payload removed from the packet and transmitting the packet to the second radio access system.
A wireless communication system. A first radio access system for communication between a first base station and a first mobile station;
A second radio access system for communication between the second base station and the second mobile station;
An inter-base station communication network for direct communication between the first base station and the second base station;
A communication network between mobile stations for direct communication between the first mobile station and the second mobile station;
With
The first radio access system can transmit a larger amount of data than the second radio access system, and the second radio access system has better communication quality than the first radio access system. ,
When the first base station transfers the first packet that does not include a payload, the first base station transfers the first packet to the first mobile station via the first radio access system, and Generating the same packet as the first packet and transmitting it to the first mobile station via the inter-base station communication network, the second radio access system and the inter-mobile station communication network, or Transmitting the first packet to the first mobile station via the inter-base station communication network, the second radio access system, and the inter-mobile station communication network ;
When the first mobile station transfers a second packet that does not include a payload, the first mobile station transfers the second packet to the first base station via the first radio access system, and A packet identical to the second packet is generated and transmitted to the first base station via the mobile station communication network, the second radio access system and the base station communication network, or 2 packets are transmitted to the first base station via the mobile station communication network, the second radio access system and the base station communication network ,
A wireless communication system. A first radio access system and a second radio access system, wherein the first radio access system is capable of transmitting a larger amount of data than the second radio access system, and the second radio access system Is executed by a packet transfer apparatus for transferring a packet to at least one of the first radio access system and the second radio access system in a radio communication system having better communication quality than the first radio access system. A packet forwarding method,
Analyzing the packet to determine whether it contains a payload; and
When the packet does not include a payload, the packet is transferred to the first radio access system, and the same packet as the packet is generated and transmitted to the second radio access system, or the packet is Forwarding to the second radio access system, and if the packet contains a payload, forwarding the packet to the first radio access system and generating a packet with the payload removed from the packet Transferring to the second radio access system;
A packet transfer method comprising: A first radio access system and a second radio access system, wherein the first radio access system is capable of transmitting a larger amount of data than the second radio access system, and the second radio access system Is executed by a packet transfer apparatus for transferring a packet to at least one of the first radio access system and the second radio access system in a radio communication system having better communication quality than the first radio access system. A packet forwarding method,
Analyzing the packet to determine whether it contains a payload; and
If the packet does not include a payload, if the ACK number included in the header of the packet is the same as the ACK number included in the header of the previously transferred packet, the packet is transferred to the second radio access system. If the ACK number included in the header of the packet is not the same as the ACK number included in the header of the previously transferred packet, the packet is transferred to the first radio access system and the packet When the packet includes the payload, the ACK number included in the packet header is included in the header of the previously transferred packet. If the received ACK number is the same, the packet is transferred to the first radio access system. If the ACK number included in the header of the packet is not the same as the ACK number included in the header of the previously transferred packet, the packet is transferred to the first radio access system and the payload is transferred from the packet. A transfer step of generating a packet from which is deleted and transmitting it to the second radio access system;
A packet transfer method comprising:

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