JP5648861B2 - Packet transmission method and packet transmission apparatus - Google Patents

Description

  The present invention relates to a packet transmission method and a packet transmission apparatus that perform layer 3 diversity reception in, for example, a satellite satellite communication system.

  For public wireless LAN services for railways, use of satellite communication capable of broadband communication is being studied. However, there are many problems in satellite communication, such as high throughput in communication, interpolation reproduction technology for missing packets, and countermeasures against signal wave interruption. In particular, in satellite communication for railroads, there are many obstacles such as tunnels, mountains, buildings, etc. on the route, and signal wave interruption is likely to occur. Currently, as a countermeasure for blocking signal waves in mobile satellite communications, a method combining layer 3 diversity technology and a gap filler method has been proposed.

  Layer 3 diversity technology is a technology that supports small obstacles such as buildings. For example, IP packets demodulated by receivers connected to antennas installed in the first and last vehicles of a train are not duplicated. Select to suppress degradation of communication quality. That is, it is possible to determine the identifier uniquely determined by the source address of the IP header and the source host, output the packet received first among the packets received by a plurality of antennas, and discard the duplicate packet. Enables reception without packet duplication and loss. As described above, since the layer 3 diversity technique processes a packet with information included in the IP header, it can also be applied to signal reception between networks having different lower layers.

  The gap filler method is a technique for a long-distance obstacle such as a tunnel, and retransmits a satellite communication signal received at a receivable location such as outside the tunnel to the train by a wireless method (for example, WiFi) different from the satellite communication. By relaying, reception within the tunnel is enabled.

  FIG. 3 shows a configuration example of a conventional satellite communication system. This satellite communication system is a combination of layer 3 diversity technology and a gap filler system.

  In FIG. 3, a signal transmitted from a satellite base station 41 connected to the Internet is received by a satellite communication receiver 31 mounted on a vehicle 30 via a communication satellite and a satellite link 42, and a gap filler. The signal is received by the gap filler receiver 32 mounted on the vehicle 30 via the relay device 43. Here, the gap filler relay device 43 includes a satellite reception antenna that receives a satellite signal, a device that performs retransmission relay using a wireless method (for example, WiFi) different from satellite communication, and a transmission antenna.

  The train 30 includes a satellite communication receiver 31 and a gap filler receiver 32, and each receiver is connected to one layer 3 diversity device (hereinafter referred to as “L3-DIV”) 33. Here, a satellite communication receiver 31 is installed in each of the leading vehicle and the last vehicle of the train 30, and a gap filler receiver 32 is installed in the leading vehicle so that reception signals (IP packets) from a total of three routes are received. The structure input into L3-DIV33 is shown.

  However, FIG. 3 shows that the leading vehicle enters the tunnel and the satellite communication receiver 31 of the leading vehicle receives the satellite signal relayed by the gap filler receiver 32 instead of receiving the satellite signal. The state where the IP packet from the route is input to the L3-DIV 33 is shown. Outside the tunnel, a total of two routes of IP packets are input to the L3-DIV 33 from the two satellite communication receivers 31. For example, near the entrance of the tunnel, the two satellite communication receivers 31 and the gap filler are used. There are cases where IP packets of a total of three routes are input to the L3-DIV 33 from the receiver 32.

  The L3-DIV 33 performs layer 3 diversity processing on IP packets input from a plurality of routes, and distributes the previously received IP packets to a plurality of base stations (AP) 34 provided for each vehicle, for example. The IP packet transmitted from each base station 34 is received by the wireless terminal 35 in the vehicle.

  In L3-DIV33, since selection processing is performed using the source address and identifier of the IP header, there is no packet duplication or packet loss when switching the signal path between the satellite system and the gap filler system, and seamless reception is possible. Become. Further, the wireless terminal 35 in the vehicle does not receive duplicate packets, and the Internet connection service can be used without changing settings or protocols.

Nagase et al., "Improvement of Ku-band mobile satellite communication throughput by receiving layer 3 diversity", 2003 IEICE Society Conference

  In the satellite communication system illustrated in FIG. 3, the satellite communication receiver 31, the gap filler receiver 32, the L3-DIV 33, and the base station 34 mounted on the train 30 are referred to as “packet transmission device”.

  In a packet transmission device that combines layer 3 diversity technology and gap filler method, the same packet is input to L3-DIV from multiple paths with high probability, so a packet duplication determination process is required each time, and the amount of packets to be processed The load increases in proportion to In particular, when one L3-DIV is mounted on all vehicles as shown in FIG. 3, packets addressed to all users of the train are concentrated on one L3-DIV, and as the number of users increases, L3 -The processing load of DIV increases.

  Furthermore, the amount of packets processed by L3-DIV is also proportional to the number of receivers connected to L3-DIV. In the case of the configuration shown in FIG. 3, a total of three receivers, that is, two satellite communication receivers and one gap filler receiver are connected. The probability that three identical IP packets will be input to L3-DIV from these three receivers is small, but two identical IP packets are received from two satellite communication receivers while the train is traveling on a point without a shield. To enter more. Furthermore, when a receiver corresponding to another wireless system or the like is provided in order to widen the band, a larger number of the same IP packets are input. In this way, L3-DIV requires matching processing between the received list and the list that it has as many as the number of input IP packets. Therefore, if the number of receivers increases, the processing load on L3-DIV increases. Is inevitable.

  It is an object of the present invention to provide a packet transmission method and a packet transmission apparatus for distributing a load using a plurality of L3-DIVs and efficiently distributing IP packets to each L3-DIV.

The first invention is a layer 3 diversity in which a plurality of receivers receive and process broadcast signals transmitted through a plurality of routes, convert the signals into IP packets, and output the IP packets from the receivers. The device (L3-DIV) checks the source address and identifier for identifying whether each IP packet is the same, selects and outputs one of the same IP packets, and the IP output from the L3-DIV type a packet to a plurality of base stations, in the packet transmission method of the packet transmission device to be transmitted to the wireless terminal from each base station, the packet transmission device includes a plurality of L3-DIV, and the packet distributor, and an aggregation device The packet distribution device determines the number N of L3-DIVs that are operating or to be operated among the plurality of L3-DIVs, and inputs IP packets output from the plurality of receivers. The remainder obtained by dividing the identifier by N is calculated, and the remainder is associated with the L3-DIV that is in operation or activated, and distributed to L3-DIVs according to the identifiers of IP packets input from a plurality of receivers. The aggregation device performs processing for aggregating IP packets output from a plurality of L3-DIVs and transferring the packets to a plurality of base stations.

  In the packet transmission method of the first invention, L3-DIV periodically transmits a first specific signal indicating that it is operating to the packet distribution device, and the packet distribution device transmits the first specific signal. The L3-DIV is determined to be in operation.

  In the packet transmission method of the first invention, the L3-DIV transmits a second specific signal to the packet distribution device when the processing load exceeds a threshold, and the packet distribution device transmits the second specific signal. It is determined that L3-DIV is not in operation.

  In the packet transmission method of the first invention, the packet distribution device determines the number of IP packets input, determines an L3-DIV to be operated according to the input number, and operates a corresponding number of L3-DIVs.

  In the second aspect of the invention, whether or not a plurality of receivers that receive and process broadcast signals transmitted through a plurality of paths, respectively convert to IP packets, and IP packets input from the plurality of receivers are the same. A layer 3 diversity device (L3-DIV) that collates a source address and an identifier for identifying the same, selects and outputs one of the same IP packets, and wirelessly inputs an IP packet output from the L3-DIV In a packet transmission apparatus including a plurality of base stations that transmit to a terminal, a plurality of L3-DIVs are provided, and the number N of L3-DIVs that are operating or operated among a plurality of L3-DIVs is determined, and a plurality of receptions are performed. The IP packet output from the machine is input, the remainder obtained by dividing the identifier by N is calculated, and the remainder is associated with the L3-DIV that is in operation or in operation, and is input from a plurality of receivers. It includes a packet distributor for distributing the L3-DIV in accordance with the identifier of the IP packets, aggregating IP packet output from a plurality of L3-DIV, comprising a centralizing device for transferring a plurality of base stations.

  In the packet transmission apparatus of the second invention, the L3-DIV periodically transmits a first specific signal indicating that it is in operation to the packet distribution apparatus, and the packet distribution apparatus transmits the first specific signal. The L3-DIV is determined to be in operation.

  In the packet transmission device of the second invention, the L3-DIV transmits a second specific signal to the packet distribution device when the processing load exceeds a threshold, and the packet distribution device transmits the second specific signal. It is determined that L3-DIV is not in operation.

  In the packet transmission device of the second invention, the packet distribution device determines the number of IP packets input, determines the L3-DIV to be operated according to the number of inputs, and operates the corresponding number of L3-DIVs.

  The present invention distributes IP packets input from a plurality of routes to a plurality of L3-DIVs corresponding to the identifiers in the packet distribution device, and distributes the IP packets with specific L3-DIVs for each identifier of the IP packet. Therefore, the load in each L3-DIV can be averaged.

  In addition, the L3-DIV to be operated or to be operated is determined, the L3-DIV whose processing load exceeds the threshold is excluded, and the distribution destination of the IP packet is determined according to the number N of the active L3-DIVs. Thus, packet distribution processing can be performed dynamically.

It is a block diagram which shows the Example of the packet transmission apparatus of this invention. 4 is a flowchart illustrating an example of a processing procedure of the packet distribution device 10. It is a figure which shows the structural example of the conventional satellite communication system.

  FIG. 1 shows an embodiment of a packet transmission apparatus of the present invention. Here, components common to the vehicle-mounted packet transmission apparatus in the conventional satellite communication system shown in FIG.

  In FIG. 1, two satellite communication receivers 31, a gap filler receiver 32, and a plurality of base stations (AP) 34 are the same as in the conventional configuration. In the present embodiment, four L3-DIVs 33-1 to 33-4 are provided, and packet distribution is performed between the four L3-DIVs and the two satellite communication receivers 31 and the gap filler receivers 32. In this configuration, the apparatus 10 is arranged, and the aggregation apparatus 20 is arranged between the four L3-DIVs and the plurality of base stations 34. The satellite communication receiver 31 and the gap filler receiver 32 may be provided one by one, or two receivers each may be provided, or another wireless receiver may be used as the packet distribution device 10. It is good also as a structure connected to.

  The feature of the present invention is that the packet distributor 10 distributes IP packets input from the two satellite communication receivers 31 and the gap filler receiver 32 to the L3-DIVs 33-1 to 33-4 according to a predetermined logic. The load on each L3-DIV is distributed. Each L3-DIV compares with the IP packet received in the past based on the source address and identifier of the input IP packet, outputs the first received IP packet, and discards the same IP packet However, this is the same as before. Non-overlapping IP packets output from each L3-DIV are transferred to the plurality of base stations 34 via the aggregation device 20 and transmitted from each base station 34 to the wireless terminal 35.

Hereinafter, functions of the packet distribution device 10 will be described.
(1) Identification method of L3-DIV of distribution destination The combination of the source address and the identifier included in the IP header of the IP packet is unique for each packet. L3-DIV determines whether or not the packets are the same by looking at the combination of the source address and the identifier. Since this identifier is a value uniquely determined by the transmission source host, there is no possibility of the same packet if this value is different. On the other hand, if the source address is different, there is also a packet with the same identifier. The packet distribution device 10 pays attention to this identifier, and determines the distribution destination L3-DIV according to the identifier.

First, the packet distribution device 10 grasps the number N of L3-DIV operations, and assigns an ID of 0 to N-1 to the currently operating L3-DIV. Next, the ID of the L3-DIV that is the distribution destination of the IP packet is obtained by the following equation.
ID = identifier mod N (1)

  That is, the distribution destination L3-DIV is determined to be an ID corresponding to a remainder (0 to N-1) obtained by dividing the identifier included in the IP header of the IP packet by N. Therefore, IP packets having the same identifier input from a plurality of receivers are always distributed to specific L3-DIVs out of N L3-DIVs. Moreover, each IP packet is equally distributed to each L3-DIV according to the identifier.

(2) Method of calculating the number N of L3-DIV operations Each L3-DIV periodically notifies the packet distribution device 10 of a Hello frame including its MAC address. The packet distribution device 10 determines the number N of L3-DIV operations based on the received Hello frame, and determines the distribution destination L3-DIV ID according to the above equation. Furthermore, if the packet distribution apparatus 10 cannot receive the Hello frame from the L3-DIV within a certain period, the L3-DIV is excluded from the management target. Then, the distribution destination ID is reassigned in the remaining L3-DIV, and the dynamic packet distribution processing is continued.

(3) Load distribution method of L3-DIV at distribution destination In the above packet distribution processing, if the remainder obtained by dividing the identifier by N is biased to a specific value, the IP packet is biased to a specific L3-DIV. Become. Therefore, when the number of packets received within a certain time exceeds a certain number, the L3-DIV transmits a state notification frame that conveys a high load situation to the packet distribution device 10. The packet distribution device 10 that has received this status notification frame temporarily removes the L3-DIV from the management target and prevents further distribution of packets to the L3-DIV. Then, in the same manner as when the Hello frame is interrupted, the distribution destination ID is reassigned in the remaining L3-DIV, and the dynamic packet distribution processing is continued.

(4) Dynamic power control In the configuration shown in FIG. 1, a maximum of four L3-DIVs are operated. However, when all the L3-DIVs are always operated when the number of received packets is small, the power consumption Is wasted. Therefore, the packet distribution device 10 measures the number of packets per fixed time, and turns on only the optimal number of L3-DIVs according to the number of packets using the WoL (Wake ON LAN) function. Is provided.

FIG. 2 shows a processing procedure example of the packet distribution device 10.
In FIG. 2, the packet distribution device 10 determines that an L3-DIV that has received a Hello frame within a certain period and has not received a status notification frame is in operation (S1), and determines the number N of L3-DIV operations. Obtain (S2). Next, IDs 0 to N-1 are assigned to the operating L3-DIV (S3). Next, the remainder obtained by dividing the identifier of the IP packet by N is associated with the ID of the L3-DIV of the distribution destination according to the expression (1) (S4). Thereafter, the packet distribution device 10 distributes the IP packet to the L3-DIV to which the ID corresponding to the identifier of the IP packet is assigned.

In the expression (1), the IP packet identifier (for example, sequence number) information is used to determine the L3-DIV to which the IP pattern is distributed, but this is based on the IP packet arriving at the packet distributor 10. This is because the value of the identifier can be expected to have a certain degree of randomness in the order. Therefore, the IP packet source IP address, destination IP address, or payload information (a bit string of one or more bits excluding the IP header of the IP packet) may be used instead of the identifier of the expression (1). It is valid. Moreover, the combination is also possible, for example,
(a) Source IP address XOR Destination IP address
(b) Source IP address XOR Destination IP address XOR identifier
(c) Source IP address XOR Destination IP address XOR Payload may be used. Here, A XOR B indicates an exclusive OR in the bit unit of A and B. If the number of bits of A and B is different, the smaller number of bits is used.

DESCRIPTION OF SYMBOLS 10 Packet distribution apparatus 20 Aggregation apparatus 31 Receiver for satellite communication 32 Receiver for gap filler 33 Layer 3 diversity apparatus (L3-DIV)
34 Base station (AP)
35 Wireless terminal 41 Satellite base station 42 Satellite link 43 Gap filler relay device

Claims (8)

A plurality of receivers receive and process signals broadcast on multiple paths, convert them into IP packets, and output them.
In a layer 3 diversity device that inputs the IP packets from the plurality of receivers, a source address and an identifier for identifying whether or not each IP packet is the same are collated, and one of the same IP packets is selected and output And
In the packet transmission method of the packet transmission apparatus, the IP packet output from the layer 3 diversity apparatus is input to a plurality of base stations and transmitted from each base station to the wireless terminal.
The packet transmission device includes a plurality of the layer 3 diversity apparatus, and a packet distributor, and an aggregation device,
The packet distribution device determines the number N of layer 3 diversity devices that are operating or to be operated among the plurality of layer 3 diversity devices, inputs IP packets output from the plurality of receivers, and sets the identifier to N Calculating the remainder divided by the number, making the remainder correspond to a layer 3 diversity device that is operating or to be operated, and performing a process of distributing to the layer 3 diversity device according to the identifier of the IP packet input from the plurality of receivers,
The aggregation apparatus performs a process of aggregating IP packets output from the plurality of layer 3 diversity apparatuses and transferring them to the plurality of base stations. The packet transmission method according to claim 1,
The layer 3 diversity device periodically transmits a first specific signal indicating that it is in operation to the packet distribution device,
The packet distribution apparatus determines that the layer 3 diversity apparatus that has transmitted the first specific signal is in operation. The packet transmission method according to claim 1,
The layer 3 diversity device transmits a second specific signal to the packet distribution device when a processing load exceeds a threshold,
The packet distribution apparatus determines that the layer 3 diversity apparatus that has transmitted the second specific signal is not in operation. The packet transmission method according to claim 1,
The packet distribution device determines the number of inputs of the IP packet, determines a layer 3 diversity device to be operated according to the number of inputs, and operates a corresponding number of layer 3 diversity devices. Method. A plurality of receivers for receiving and processing broadcast signals transmitted through a plurality of paths, respectively converting them into IP packets, and outputting them;
A layer 3 diversity device that collates source addresses and identifiers that identify whether or not the IP packets input from the plurality of receivers are the same, and selects and outputs one of the same IP packets;
A packet transmission apparatus comprising: a plurality of base stations that input IP packets output from the layer 3 diversity apparatus and transmit the IP packets to a wireless terminal;
A plurality of the layer 3 diversity devices,
Judging the number N of layer 3 diversity devices that are operating or to be operated among the plurality of layer 3 diversity devices, inputting IP packets output from the plurality of receivers, and calculating a remainder obtained by dividing the identifier by N And a packet distribution device that associates the surplus with a layer 3 diversity device that is in operation or operates, and distributes the layer 3 diversity device according to an identifier of an IP packet input from the plurality of receivers,
A packet transmission device comprising: an aggregation device that aggregates IP packets output from the plurality of layer 3 diversity devices and forwards the packets to the plurality of base stations. The packet transmission apparatus according to claim 5, wherein
The layer 3 diversity device periodically transmits a first specific signal indicating that it is in operation to the packet distribution device,
The packet distribution apparatus determines that the layer 3 diversity apparatus that has transmitted the first specific signal is in operation. The packet transmission apparatus according to claim 5, wherein
The layer 3 diversity device transmits a second specific signal to the packet distribution device when a processing load exceeds a threshold,
The packet distribution apparatus determines that the layer 3 diversity apparatus that has transmitted the second specific signal is not in operation. The packet transmission apparatus according to claim 5, wherein
The packet distribution device determines the number of inputs of the IP packet, determines a layer 3 diversity device to be operated according to the number of inputs, and operates a corresponding number of layer 3 diversity devices. apparatus.

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