JP2002314604A - Method for communicating packet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a packet communicating method that performs multicasting of a packet in a wide area in time division radio relay. SOLUTION: An originating station sets the transmission source address of a packet with a multicast identifier for identifying that the packet is a multicast packet attached thereto in an address allocated uniquely to communication equipment and a relay station in advance, and also sets a destination address in a broadcast address to transmit it to a communication path, one relay station decided based on a relay function among relay stations that have received the packet confirms the multicast identifier of the packet, sets the transmission source address in the address preallocated uniquely to the communication equipment and the relay station, also sets a transmission destination address in the broadcast address to retransmit it to the communication path, and the communication equipment receives the packet in which the destination address is the broadcast address and the transmission source is a specific address.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a packet communication method, and more particularly, to a data link layer and a network layer, in which digitalized data is time-divided by a single wireless channel using a wireless signal as a transmission medium. And a method of performing multicast transmission while relay-transmitting the data.

[0002]

2. Description of the Related Art Conventionally, there has been proposed a technique of relaying a digitalized data packet using a wireless signal as a transmission medium in a time-division manner over a wireless channel (Japanese Patent Laid-Open No. 8-274777). Hereinafter, this will be briefly described.

FIG. 4 is a diagram showing a configuration in a conventional packet communication for relaying and transmitting a packet. In FIG. 4, circles indicate areas where radio waves of each communication device can reach.
The master machine A can directly communicate with the satellite machines B, C, and F, but cannot directly communicate with the satellite machines D, E, G, and H. However, if satellite machine C relays the packet,
The master machine A and the satellite machines D and E can communicate with each other.
Further, if the satellite machine E or D relays the packet, the master machine A and the satellite machine G can communicate.

FIG. 6 shows the structure of a packet in packet communication. The packet is composed of the destination, source,
It is composed of the fields of the starting station, the last station, and relay information (relay stations n to 1), and data added thereafter. Here, the transmission destination and the transmission source physically indicate a one-to-one communication relationship, and the address of the transmission destination of the packet is set in the transmission destination field. In the transmission source field, the address of the side transmitting the packet is set. The address of the sender of the information data is set in the first station field, and the address of the receiver of the information data is set in the last station field. The address of the relay station to be used is set in the relay information field (each field of the relay stations n to 1).

For example, referring to the flow chart of FIG. 5, when the master station A collects data from the satellite station G, the master station A has a source address A, a destination address C, and a starting station address A. Then, a packet in which a header having the final station address G and the relay station address EC is added to the data collection command is transmitted. Since the destination address of this packet is addressed to C, the satellite station C receives this packet (S141). Since the last station address G of the header of this packet is different from the own station address C (S142), the satellite station C has the next (one previous) address next to the destination address C (own station address) set in the relay information field. ) Is taken out as the destination address (S144), set in the packet header (S146), the source address is set as C (S145), and retransmitted (S147).

Since the destination address of this packet is addressed to E, the satellite station E receives this packet (S1).
41). Since the last station address G in the header of this packet is different from the own station address E, the packet station E (S14).
2) The next (previous) address G of the destination address E (own address) set in the relay information field
The (final station address) is extracted as the destination address (S144) and set in the packet header (S146).
The transmission source address is set to E (S145), and retransmission is performed (S147).

Since the destination address of this packet is addressed to G, the satellite station G receives this packet (S1).
41). Since the last station address G in the header of this packet matches the own station address (S14).
2) Analyze the data (S143). As a result of the data analysis, since the command is a data collection command, the satellite station G returns data to the master station A (S143). Next, the procedure for returning data will be described. The satellite station G extracts the address of the relay station from the relay information field of the received packet (S143). By rearranging the addresses of the extracted relay stations in reverse, it is possible to know the relay route for transmitting the packet from the last station to the master unit while traveling backward to the original relay station. In this example, the relay field is CE.

[0008]

SUMMARY OF THE INVENTION The above-described conventional method uses a unicast communication for transmitting a packet from a specific master station to a specific satellite station or transmitting a packet from a specific satellite station to a specific master station. It is assumed.

Therefore, according to this method, it is impossible to perform broadcast-type communication in which image data of the satellite station G is simultaneously received and viewed by the satellite station H and the satellite station B. In order to realize this, the master station A collects image data from the satellite station G by the method described above, transmits the data to the satellite station H in the above-described procedure, and then transmits the same data to the satellite station B. Need to be sent in. The method of relaying a packet in a time-division manner using the same radio channel requires less radio frequency resources than the method of changing the radio channel for each relay section, and furthermore, one of the same channel in the relay apparatus is used. Since the wireless transmission / reception device can be relayed using time division, it is advantageous in terms of cost, space, and power consumption. However, there is a disadvantage that the communication time increases in proportion to the number of relay stages. In order to realize multipoint data reception, there is a further problem that a communication time is required for a total time of each time-division relay time.

On the other hand, if a wireless packet is relayed without performing the above-described route control, as shown in FIG. 7, for example, a packet transmitted by the satellite station C receives both the satellite station E and the satellite station D, so that these packets are retransmitted. The transmitted packet collides at the satellite station H and the satellite station G, and thus cannot be correctly received.

Therefore, an object of the present invention is to provide a multicast packet communication method capable of reducing the time required for communication and effectively utilizing radio resources without causing packet collision. is there.

[0012]

According to a first aspect of the present invention, a packet transmitted by a starting station is transmitted from a first to an M-th packet using a single communication path.
A packet communication method for multicast communication to a communication device, wherein the originating station sends a source address of a packet with a multicast identifier for identifying that the packet is a multicast packet to the communication device and the relay station in advance. Setting the address to a uniquely allocated address and setting the destination address to a broadcast address and transmitting the packet to a communication path; and selecting one of the first to Nth relay stations that have received the packet, the one being determined by the relay function. The relay station checks the multicast identifier of the packet, sets the source address to an address uniquely allocated to the communication device and the relay station in advance, sets the destination address to the broadcast address, and retransmits the packet to the communication path. Steps and the first to Mth communication devices determine that the destination address is De cast address a is and source address comprises receiving the packet is a specific address.

A second invention is an invention according to the first invention, wherein a relay station manages, as a relay function, a source address of a packet to be relayed and retransmitted as a relay source address. Determining a retransmission by comparing the relay source address with the source address of the received packet.

[0014] A third invention is an invention according to the first invention, wherein the relay station has a relay function of sequentially setting a relay route address in the packet, Determining a retransmission of the packet when the address of the relay station is set next to the source address of the packet received at the address of the set relay route.

[0015] A fourth invention is an invention according to the first to third inventions, wherein the first to Mth communication apparatuses are configured to transmit packets whose destination address is a broadcast address and whose source address is a specific address. The specific address in the step of receiving is selected according to the receiving situation.

A fifth invention is an invention according to the first to fourth inventions, wherein the first to Mth communication apparatuses are configured to transmit packets whose destination address is a broadcast address and whose source address is a specific address. The plurality of specific addresses in the step of receiving
Therefore, the M-th communication apparatus discards the second and subsequent packets when the same packet is correctly received in two or more packets.

A sixth invention is an invention according to the first invention to the fifth invention, wherein a single communication path is a wireless communication path.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A packet communication method according to an embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a diagram showing a configuration of a system using a packet communication method according to an embodiment of the present invention. FIG. 2 is a diagram showing an example of a frame configuration used in the packet communication method according to the embodiment of the present invention. FIG. 3 is a diagram showing a flow of the packet communication method according to the embodiment of the present invention.

Referring to FIG. 1, a system using a packet communication method according to an embodiment of the present invention includes a monitor station B, a master station A, relay stations C and E, and a camera station G.
This is an example of a system in which a monitor station receives image data of a camera station transmitted under the control of a master station. Referring to FIG. 1, master station A
Issues a command to perform multicast communication of image data to the camera station G via the relay stations C and E. This command is unicast-communicated according to the method described in the related art. The master station A transmits a packet in which a header having the source address A, the destination address C, the starting station address A, the last station address G, and the relay station address EC is attached to the data multicast transmission command.

Since the destination address of the packet is addressed to C, the relay station C receives the packet (S30).
1). In the relay station C, the last station address G of the header of this packet is the multicast address MC together with its own station address C.
(S142, S302), the next (previous) address E of the destination address C (own address) set in the relay information field is extracted as the destination address (S144), and the packet header (S146), and set the source address as C (S14).
5) Retransmit (S147).

Since the destination address of this packet is addressed to E, relay station E receives this packet (S30).
1). Since the last station address G of the header of this packet is different from the own station address E and the multicast address MC (S142, S302), the packet station E follows the destination address E (own station address) set in the relay information field. (The previous station address) is taken out as the destination address (S144).
The packet is set in the packet header (S146), the source address is set to E (S145), and the packet is retransmitted (S147).

Since the destination address of this packet is addressed to G, the first communication device G receives this packet (S
301). Since the last station address G in the header of this packet matches the own station address (S14).
2) Analyze the data (S143). As a result of the data analysis, since the command is a data multicast transmission command, the satellite station G multicasts data to the communication station (S143).

Next, the procedure of data multicast transmission will be described. The starting station G extracts the address of the relay station from the address of the starting station and the relay information field of the received packet (S143). By rearranging the addresses of the extracted relay stations in reverse, it is possible to know the relay route for transmitting the packet from the last station to the master unit while traveling backward to the original relay station. This is assigned to the relay stations 1 to n. In this example, CE
Becomes The address of the starting station that has been taken out is assigned to the relay station (n + 1) ahead of (before). In this example, A
It is. Therefore, in this example, the relay field is "AC
E ". The starting station address is the address G of the own station,
MC is set as the last station address. Then, a packet having its own address G as a source address, a broadcast address BC as a destination address, and a header attached to data to be multicast is transmitted.

The packet transmitted by the starting station G reaches the relay station E, the communication device D, and the communication device H in the wireless area. Here, the relay station G does not specify the source of the packet to be received. On the other hand, the communication device H specifies the transmission source of the received packet as G, and the communication device D specifies the transmission source of the received packet as E. Therefore, the relay station E receives this packet (S301). But,
Because the destination BC does not match the last station MC (S14
2) Check whether the last station is MC (S302). In this case, since the last station is the MC, the relay field is checked (S303). Since the own station is at the beginning of the relay field and the originating station is the transmission source, it determines to retransmit (S303). Then, the own station address E is set as the transmission source (S305), and BC is set as the transmission destination (S305).
306), retransmit the packet.

The relay station E recognizes the received packet as a packet addressed to itself, and processes the packet in its own device (S304). If the relay station E has no image monitor function, it does not perform any processing. The communication device H also receives this packet (S301). Similarly, since the destination BC does not match the last station MC (S142), it is checked whether the last station is MC (S302). In this case, since the last station is the MC, the relay field is checked (S303). Since the own station is not set in the relay field, the own station recognizes the packet as a packet addressed to the own station and processes the packet in the own station (S304). Since the communication device H has an image monitor function, it extracts image data from the received packet and processes it.
One communication device D does not receive the packet transmitted by the starting station G because the transmission source of the packet to be received is specified to E.

The packet retransmitted by the relay station E reaches the relay station C, the communication device D, and the communication device G in the wireless area. Here, the relay station C does not specify the source of the packet to be received. On the other hand, the communication device G does not specify the transmission source of the received packet, and the communication device D specifies the transmission source of the received packet as E. Therefore, the relay station C receives this packet (S301). However, because the destination BC does not match the last station MC (S14)
2) Check whether the last station is MC (S302). In this case, since the last station is the MC, the relay field is checked (S303). Since the own station is next to (before) the transmission source E in the relay field, it determines to retransmit (S303). Then, the own station address C is set as the transmission source (S305), BC is set as the transmission destination (S306), and the packet is retransmitted. The relay station C recognizes the received packet as a packet addressed to itself, and processes the packet in its own device (S304), but does not perform any processing if the relay station C has no image monitor function.

The communication device D similarly receives this packet (S301). Similarly, since the destination BC does not match the last station MC (S142), it is checked whether the last station is MC (S302). In this case, since the last station is the MC, the relay field is checked (S303). Since the own station is not set in the relay field, the own station recognizes the packet as a packet addressed to the own station and processes the packet in the own station (S304).
Since the communication device D has an image monitor function, it extracts image data from the received packet and processes it. The communication device G similarly receives this packet (S3).
01).

Similarly, since the destination BC does not match the last station MC (S142), it is checked whether the last station is MC (S302). In this case, since the last station is the MC, the relay field is checked (S303). Since the own station is not set in the relay field, the own station recognizes the packet as a packet addressed to the own station and processes the packet in the own station (S304). Since the communication device G does not have an image monitor function, it does not perform any processing.

The packet retransmitted by the relay station C reaches the communication devices A, D and B and the relay station E in the wireless area. Here, the communication device A does not specify the source of the packet to be received. On the other hand, the communication device D specifies the transmission source of the received packet as E, and the communication device B
Specifies that the source of the received packet is A. Therefore, the communication device A receives this packet (S30).
1). However, since the destination BC does not match the last station MC (S142), it is checked whether the last station is MC (S3).
02). In this case, since the last station is the MC, the relay field is checked (S303). Since the own station is in the relay field next to (before) the source C, it is a communication device, but makes a determination to retransmit (S30).
3). Then, the own station address C is set as the transmission source (S
305), BC is set as the transmission destination (S306), and the packet is retransmitted.

As described above, since the starting station A of the packet received at the starting station G of the multicast is set to the relay station n + 1 in the relay field, the communication apparatus A finally retransmits the packet. The communication area of the communication station A becomes a multicast area, and the communication apparatus B and the communication apparatus F can receive the multicast packet. The communication device A recognizes the received packet as a packet to the own station and processes the packet in its own device (S304). If the communication device A has an image monitor function, the control station can also monitor the image. It becomes possible. The communication devices B and D do not receive the packet of the relay station C. Since the relay station E does not have an image monitor function,
Do nothing.

As described above, according to the packet communication method according to the embodiment of the present invention, it is possible to broadcast each packet transmitted by a communication device or a relay station and simultaneously retransmit different relay stations by route control. Can prevent packet collision. Also, each communication device can receive a specific one of packets sequentially transmitted from the communication device and the plurality of relay stations.

Although the relay device in the packet communication system according to the embodiment of the present invention does not have a monitor function or a camera station function, the relay device having a monitor function or a camera station function and a communication device do not. The device may also serve as

Further, according to the packet communication method according to the embodiment of the present invention, information for routing is attached to the packet by the originating station, but each of the relay stations retransmits the information in advance according to the source of the packet. A determination table for determining whether to perform transmission may be set.

Further, according to the packet communication method according to the embodiment of the present invention, the transmission source of the packet received by the communication device is set in advance to a specific address, but this is not restrictive. Dynamically changing the specific address in case the radio propagation environment changes or the position of the relay station is changed greatly increases the degree of freedom of the present invention. It is possible to dynamically select a specific address by providing a sequence number to the packet and measuring the packet loss rate of the multicast packet to grasp the communication status.

Further, by setting a plurality of the specific addresses and detecting duplicate reception of the packets based on the sequence numbers of the packets, a plurality of packets of the same data can be received from different communication apparatuses or relay stations. By doing so, the reception probability is greatly increased.

[0036]

According to the first aspect of the present invention, when the relay station recognizes that the packet is a multicast packet by the multicast identifier, the relay route can be determined from the transmission source address. Each packet can be broadcasted, and the collision of packets due to simultaneous retransmission by different relay stations by route control can be prevented. Also, each communication device can receive a specific one of packets sequentially transmitted from the communication device and the plurality of relay stations.

According to the second aspect, the relay station can determine the relay route from the source address based on the preset information, so that it is not necessary to have the information of the relay route in the packet and the redundancy of the packet can be determined. Can be reduced.

According to the third aspect, there is no need to set relay route information in the relay station, and the relay route can be set freely for each packet at the transmission source.

According to the fourth aspect, it is possible to receive a packet having the best reception condition among the packets broadcast by the communication device or the relay station on the relay route.

According to the fifth aspect, it is possible to receive packets from a plurality of devices even in a packet broadcasted by a communication device or a relay station on the relay route, and particularly stable even when the communication state fluctuates over time. Packet reception is possible.

According to the sixth invention, efficient wireless packet multicast communication with a wide communication area can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a system using a packet communication method according to an embodiment of the present invention.

FIG. 2 is a diagram showing a packet format of the packet communication method according to the embodiment of the present invention.

FIG. 3 is a diagram showing a flow according to the embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a system using a conventional packet communication method.

FIG. 5 is a diagram showing a flow of a conventional packet communication method.

FIG. 6 is a diagram showing a packet format of a conventional packet communication method.

FIG. 7 is a diagram showing a configuration of a system using a conventional packet communication method.

[Explanation of symbols]

 A first communication device, third relay station B fourth communication device C second relay station D third communication device E first relay station F fifth communication device G starting station H second communication apparatus

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5K030 GA02 GA08 HA08 JL01 LD05 LD06 5K033 CB13 CC01 DA17 DB18 5K067 AA22 AA25 BB21 CC14 DD17 EE06 EE10

Claims (6)

[Claims] 1. A packet communication method for performing multicast communication of a packet transmitted by a starting station to first to Mth communication devices using a single communication path, wherein the starting station determines that the packet is a multicast packet. The source address of a packet provided with a multicast identifier for identifying the communication channel is set to an address uniquely allocated to the communication device and the relay station in advance, and the destination address is set to a broadcast address. Transmitting one of the first to Nth relay stations receiving the packet, one relay station determined by a relay function confirms the multicast identifier of the packet, and relays the source address with the communication device in advance. Set the address uniquely assigned to the station and broadcast the destination address. Packet communication comprising the steps of: setting an address and retransmitting to the communication path; and the first to Mth communication apparatuses receiving a packet whose destination address is a broadcast address and whose source address is a specific address. Method. 2. As the relay function, the relay station manages a source address of a packet to be relayed and retransmitted as a relay source address, and compares the relay source address with a source address of a received packet. 2. The packet communication method according to claim 1, further comprising the step of determining retransmission. 3. The relay function, wherein the originating station sequentially sets an address of a relay route in a packet, and the relay station transmits a packet received at the address of the relay route set in the received packet. 2. The packet communication method according to claim 1, further comprising: determining a retransmission of the packet when an address of the relay station is set next to an original address. 4. The method according to claim 1, wherein the first to Mth communication apparatuses receive a packet whose destination address is a broadcast address and whose source address is a specific address, wherein the specific address is selected according to a reception situation. The packet communication method according to any one of claims 1 to 3, wherein the packet communication method is characterized in that: 5. The method according to claim 1, wherein the first to Mth communication apparatuses select a plurality of specific addresses in the step of receiving a packet whose destination address is a broadcast address and whose source address is a specific address.
The packet communication method according to any one of claims 1 to 4, wherein the second to Mth communication devices discard the second and subsequent packets when each of the two or more packets correctly receives the same packet. 6. The packet communication method according to claim 1, wherein the single communication path is a wireless communication path.