JP4281264B2 - Broadcast communication method, broadcast communication terminal, and broadcast communication system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a communication protocol for efficiently performing broadcast communication in an ad hoc wireless network that performs route control using a distance vector type algorithm.
[0002]
[Prior art]
Conventionally, in an ad hoc wireless network including a “wireless communication network system” disclosed in, for example, Japanese Patent Laid-Open No. 2000-13376, broadcast communication is performed to transmit the same information packet to all terminals in the network. The following two methods are known as communication protocols for this purpose.
[0003]
The first method is a method in which all wireless terminals that have received a broadcast packet perform relay transmission to adjacent wireless terminals. That is, in the wireless network as shown in FIG. 8, when the wireless terminal A transmits a broadcast packet, the wireless terminals B, C, and D within the communication range 81 of the wireless terminal A receive this packet and are shown in FIG. As described above, the wireless terminals A, B, and C perform relay transmission to adjacent wireless terminals in the communication ranges 91, 92, and 93, respectively. However, a wireless terminal that has received a broadcast packet once and relayed it will not relay it even if it receives the same broadcast packet from an adjacent wireless terminal terminal again. In this way, the broadcast packet transmitted from the wireless terminal A is relay-transmitted to the adjacent wireless terminals in the communication range 101, 102, 103, 104, 105, 106, 107 as shown in FIG. Is transmitted to the wireless terminal in the network. This method is called a flatting method.
[0004]
The second method, in order to improve the above situation, the wireless terminal receiving the broadcast packet, determines the electric field intensity, if the electric field strength has received a certain level below packet only, relay transmission It is a method of performing. In Figure 11, the broadcast packet transmitted from the wireless terminal A (adjacent) is within communication range 111 of the wireless terminal A wireless terminal B, C, upon reaching D, each wireless terminal is the electric field strength reference level Determine if: As is shown in Fig 12, only the wireless terminal B and the radio terminal C was a reference level or less is within the communication range 121, 122 (adjacent) by relay transmission to the wireless terminal performs relay transmission . A wireless terminal that is above the reference level relays a wireless terminal that is distant from the sender because it is determined that the broadcast packet should have been received. By using this method, it is possible to perform broadcast communication in which the traffic on the wireless transmission path is suppressed to some extent.
[0005]
[Problems to be solved by the invention]
However, in broadcast communication by the conventional flatting method, which is the first method, all wireless terminals that have received a packet perform relay transmission processing, radio wave collision or the like is likely to occur between adjacent wireless terminals. Further, since the wireless terminal receives the broadcast packet from all the adjacent wireless terminals, a state in which the same packet is received a plurality of times occurs, which is inefficient.
The second conventional method is based on the premise that there is always a wireless terminal capable of receiving a broadcast packet at a reference level or lower with a certain degree of wireless terminal distribution density. That is, when the distribution of wireless terminals is sparse or depending on the criteria of the electric field strength level for whether or not to perform relay transmission, as shown in FIG. 13, wirelesss that are within (adjacent to) communication ranges 131, 132, and 133 Even if relay transmission is performed to a terminal, there is a possibility that a wireless terminal such as the wireless terminals I and K cannot receive a packet.
[0006]
As described above, when performing broadcast communication in an ad hoc wireless network, there is a problem of how to efficiently and surely transmit packets by suppressing traffic on the wireless transmission path.
[0007]
Here, in an ad hoc wireless network that performs route control using a distance vector type algorithm, including the “wireless communication network system” disclosed in Japanese Patent Application Laid-Open No. 2000-13376, which was previously filed and published by the applicant of the present invention, broadcast communication is performed. Describe the issues when trying to do.
[0008]
FIG. 14 is a diagram illustrating an example of an ad hoc network. In an ad hoc network, unlike an existing network (for example, the Internet) as shown in FIG. 15, a limited device such as a router does not manage routing, but all terminals connected to the network control routing. To perform communication.
[0009]
A distance vector type algorithm, which is a route control method, is widely used in LANs, and determines the position of a target terminal according to the distance and direction. Here, the distance is the number of terminals that have passed until reaching the target terminal, that is, the number of relays, and the direction is a terminal adjacent to the terminal.
[0010]
FIG. 16 is a diagram illustrating a routing algorithm of the routing network. The terminal (1) is the route information of other terminals in the network, as shown in the table of FIG. 16 (b), adjacent terminals (adjacent terminals (2) and (3)), and from the adjacent terminal to the target terminal. Owns the information table for the shortest number of relays. For example, when the terminal (1) wants to relay and transmit a packet to the terminal (9), the number of relays is eight from the adjacent terminal (2) to the terminal (9) from the route information table. From (3) to terminal (9), it can be seen that the number of relays is four, and if relay transmission is performed to terminal (3), it can be seen that packets can be communicated with a smaller number of relays. In this way, the route control type algorithm does not know the connection state of the entire network, and owns only the route information of the terminal that it is adjacent to, so it can be said that the processing is relatively simple.
[0011]
Then, the distance in the vector ad hoc wireless network, and to all the network of non-linear device, consider the case of performing broadcast communication. In a network that performs distance vector type route control, each wireless terminal manages only the number of relays until it reaches an adjacent wireless terminal and the target wireless terminal. There is no information to do.
[0012]
FIG. 17 is a diagram illustrating a case where broadcast communication is performed by the flatting method in a route control type ad hoc wireless network. In addition, the continuous line which connects between the terminals in a figure shows the radio | wireless transmission path which can communicate.
[0013]
First, the wireless terminal (1) transmits a broadcast packet (* 1). The wireless terminals (2), (3), (4), and (7) that have received this packet perform relay transmission to all the adjacent wireless terminals that can directly communicate with each other (* 2). Among these communications, communications between the wireless terminal (2) and the wireless terminal (3), between the wireless terminal (3) and the wireless terminal (4), and between the wireless terminal (4) and the wireless terminal (7) are relayed. When the timings to be transmitted are the same, they collide with each other and the communication success rate decreases. Even if these packets can be communicated with each other, the wireless terminal of the communication partner has already received the broadcast packet. Therefore, the wireless terminal does not need the packet and increases unnecessary traffic on the wireless transmission path. As a result, the communication efficiency becomes very poor.
[0014]
The present invention provides a protocol for efficiently performing communication by suppressing traffic on a wireless transmission path when performing broadcast communication in an ad hoc wireless network system that performs route control using a distance vector type algorithm. With the goal.
[0015]
[Means for Solving the Problems]
The present invention employs the following communication algorithm to solve the above problems.
[0016]
That is, in an ad hoc wireless network that performs route control with a distance vector type algorithm, in order to suppress an increase in packets and perform broadcast communication efficiently, each wireless terminal uses the following route information table owned by itself, Relay transmission is performed according to the above conditions.
[0017]
When selecting a wireless terminal as a destination, a determination is made based on the positional relationship between the transmission source wireless terminal that transmitted the broadcast packet first, the own wireless terminal, and the wireless terminal adjacent to the transmitting wireless terminal. Then, the number of relays from the transmission source wireless terminal to the own wireless terminal is compared with the number of relays from the transmission source wireless terminal to the adjacent wireless terminal, and it is assumed that the relay transmission has already been specified from other than itself. The estimated adjacent wireless terminals are not selected as wireless terminals for relay transmission in order to avoid duplicate communication of the same broadcast packet. This suppresses an increase in broadcast packets.
[0018]
Next, in order to avoid collision of radio waves transmitted between adjacent wireless terminals, when the wireless terminal transmits a broadcast packet, it controls each relay transmission timing. Specifically, the wireless terminal transmits by adding the timing information for relay transmission to the header portion of the broadcast packet, and the wireless terminal that has received this broadcast packet transmits the time for relay transmission from the header information of the received packet. And the packet is relayed and transmitted at that timing.
[0019]
Alternatively, as a method of avoiding collision of radio waves transmitted between adjacent wireless terminals, each wireless terminal determines a transmission timing at random. Specifically, when transmitting a broadcast packet, the above-mentioned relay transmission timing information is not added, and the wireless terminal receiving this broadcast packet adds the relay transmission timing information to the header information of the incoming packet. If not, it determines the relay transmission time by itself and transmits according to the timing.
[0020]
Thus, by limiting the non-linear device that relays transmission, it is possible to reduce wasteful broadcast communication, increase in packet can be suppressed. Also, by calculating the relay transmission timing based on the information in the broadcast packet received by the own wireless terminal, or by allowing each wireless terminal to randomly determine the transmission timing, other adjacent wireless terminals can Collisions with transmitted radio waves can be avoided and efficient wireless communication becomes possible.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing a data format of a broadcast packet according to the present invention.
[0022]
The broadcast packet includes a unique information part (FIG. 1A), a relay header part (FIG. 1B), and an information data part (FIG. 1C).
The unique information section stores information necessary for network operation such as operation parameters in addition to the terminal ID of the own wireless terminal.
[0023]
The relay header, a packet identification number, source terminal ID, the relay specified ID number, the relay specified ID (relay specified ID1, relay designated ID2, · · ·), transmission Daewon terminal ID, the final destination ID, packet Consists of survival time information.
[0024]
The packet identification number is a serial number unique to the packet. When the incoming wireless terminal processes the packet, it determines whether the broadcast packet is newly received or has already been received in the past. It is a number for.
[0025]
The transmission source terminal ID is the ID of the wireless terminal that actually transmitted the packet.
The number of relay designation IDs is the number of IDs of adjacent radio terminals to be relayed when the radio terminal wants to control the timing of relay transmission by itself. The relay designation ID stores the ID of the radio terminal to be relayed. The If there are a plurality of wireless terminals to be relayed, all of their IDs are stored. The wireless terminal that has received the broadcast packet refers to this area and calculates the relay transmission timing. If no relay matching ID is found in the relay designation ID, this packet is not relayed.
[0026]
In addition, when it is desired to randomly change the relay transmission timing of the wireless terminal, the number of relay designation IDs is set to zero. When the number of relay designation IDs is 0, the wireless terminal that has received the broadcast packet selects the adjacent wireless terminal to be relayed next, then randomly calculates the relay transmission time by itself, and at the obtained timing Send.
[0027]
The transmission source terminal ID stores the ID of the wireless terminal that first transmitted the broadcast packet. When the wireless terminal that has received this packet performs relay transmission processing on an adjacent wireless terminal, the wireless terminal is selected as a destination to be relayed by referring to this transmission source terminal ID.
[0028]
As the final destination terminal ID, in the case of a broadcast packet, an ID reserved for exclusive use is stored. This ID cannot be used for a normal terminal ID. When a packet arrives, it is determined whether the packet is a broadcast packet addressed to all wireless terminals, or a multicast packet or unicast packet designated by the partner wireless terminal. To do.
[0029]
The packet lifetime is the time that exists in the network since the broadcast packet was first transmitted. The wireless terminal updates this value every time it performs relay transmission processing, and discards it without relay transmission if it exceeds a predetermined value. By doing so, traffic on the network communication transmission path can be suppressed.
[0030]
Information data stores information data to be transmitted.
FIG. 2 is a diagram for explaining a relay method when broadcast communication is performed in a distance vector type ad hoc wireless network.
[0031]
Assume that the wireless terminal A transmits a broadcast packet to all wireless terminals in the network.
First, a first embodiment of the present invention will be described.
[0032]
When wireless terminal A first transmits a broadcast packet, the IDs of all adjacent wireless terminals (terminals B and C in this case) capable of direct communication are stored in the relay designation ID in the relay header, as shown in FIG. A relay header part is created and a packet is transmitted (* 1 in FIG. 2).
[0033]
Next, consider a case where the wireless terminal B receiving the broadcast packet relays this packet. When wireless terminal B receives a broadcast packet, it first checks the packet identification number stored in the relay header portion of the packet, and after confirming that it has not received a broadcast packet with the same packet identification number in the past Incoming this packet. Further, the relay designation ID is checked, and after confirming that the ID that matches the terminal ID of the own wireless terminal is stored, the process proceeds to the relay transmission process. Here, if the same packet has already been received, this packet is discarded without being received.
[0034]
Next, with reference to a route information table as shown in FIG. 4, a partner to be relayed next is selected from among wireless terminals adjacent to the own wireless terminal. FIG. 4 shows a route information table held by the wireless terminal B. The selection criterion is an adjacent wireless terminal located at a position farther than the distance from the transmitting wireless terminal of the broadcast packet to the own wireless terminal, or an adjacent wireless connection terminal located near or at the same position. Then, although the adjacent radio terminal the radio terminal to be next relay located far, the adjacent non-line terminals in the position or the same position near the already (estimated) and considered to have received the packet It is not a wireless terminal to be relayed next. Specifically, the number of relays (X) from the transmission source wireless terminal to the own wireless terminal of the broadcast packet is compared with the number of relays (Y) from the transmission source wireless terminal to the adjacent wireless terminal from the route information table. If Y−X> 0, the adjacent wireless terminal is assumed to be at a position farther from the transmitting wireless terminal than its own wireless terminal, and is the wireless terminal to be relayed next. If X ≦ 0, it is assumed that the adjacent wireless terminal is located near or at the same position as the own wireless terminal and is not a transmission partner.
[0035]
For example, the route information table as shown in FIG. 4 is route information owned by the wireless terminal B shown in FIG. 2, and the wireless terminal B refers to this route information table and transmits the broadcast packet source wireless terminal. And the number of relays from the transmitting wireless terminal to the adjacent wireless terminal is compared. Wireless terminals adjacent to the wireless terminal B are wireless terminals A, C, D, and E, and the number of relays (X) from the wireless terminal A to the wireless terminal B is 1 (the wireless terminal B is Because it is adjacent to wireless terminal A). Next, for the wireless terminals A, C, D, and E adjacent to the wireless terminal B, the number of relays (Y) with the wireless terminal A that is the source of transmission is 0 times from the wireless terminal A to the terminal wireless terminal A (see FIG. 4) * a), wireless terminal A to wireless terminal C once (* b in FIG. 4), wireless terminal A to wireless terminal D twice (* c in FIG. 4), wireless terminal A To terminal E is twice (* d in FIG. 4). From this result, the value of Y−X is −1 for the wireless terminal A, 0 for the wireless terminal C, 1 for the wireless terminal D, and 1 for the wireless terminal E. From this result, the wireless terminal A determines that the distance from the transmitting wireless terminal is smaller than the distance to its own wireless terminal, and the wireless terminal C determines that the distance from the transmitting wireless terminal is the same. Assuming that the same broadcast packet has already been received, it is not regarded as a relay transmission partner. The wireless terminal D and the wireless terminal E are assumed to be located at a position farther from the transmission source wireless terminal than the distance between the wireless terminal D and the wireless terminal, and are set as relay transmission partners. From these selection results, the information of the relay header portion of the broadcast packet to be relayed is as shown in FIG. The wireless terminal B creates and transmits a broadcast packet including the relay header portion (* 2 in FIG. 2).
[0036]
Further, for example, when considering the wireless terminal J, if the distance is calculated from the route information table (FIG. 6) owned by the wireless terminal J using the above formula, the value of Y−X is set to −1 by the wireless terminal E. As a result, the wireless terminal F results in −1 (see * e and * f in FIG. 6).
[0037]
Therefore, the wireless terminal J has no relay transmission destination wireless terminal. In such a case, only incoming processing of the received broadcast packet is performed. As described above, when the relay transmission destination is selected by itself, if none of the adjacent wireless terminals correspond, only the packet is received and relay transmission is not performed (* 3 in FIG. 2). .
[0038]
As described above, when relay transmission of a broadcast packet is performed, reference is made to the route information of adjacent wireless terminals, and wireless terminals that have already received the same broadcast packet are not designated as relay transmission destinations. Duplicate communication can be prevented and an increase in packets on the communication transmission path can be suppressed.
[0039]
Next, when relay transmission processing is actually performed, collision between radio waves transmitted from adjacent wireless terminals is avoided by changing the time from reception of a broadcast packet to relay transmission.
[0040]
When a broadcast packet is transmitted from the wireless terminal A, the wireless terminal C receives this packet and performs relay transmission processing in the same manner as the wireless terminal B, so that radio waves are transmitted between the wireless terminal B and the wireless terminal C. There is a possibility of collision. Therefore, the relay transmission time is calculated according to the timing corresponding to the position where the relay designation ID is stored in the relay header portion of the received broadcast packet.
[0041]
Specifically, the relay designation ID information of the relay header part (FIG. 1B) of the broadcast packet transmitted from the wireless terminal A, the wireless designation B as the relay designation ID1, and the ID of the wireless terminal C as the relay designation ID2. Is stored, the wireless terminal B and the wireless terminal C that have received this packet indicate the time until the wireless terminal B next relay-transmits the wireless terminal B by t (seconds) (t: a predetermined fixed time). And the wireless terminal C is assumed to be 2t (seconds) (FIG. 7). And the timing which actually selects a destination and performs relay transmission is delayed. By doing so, it is possible to avoid collision of radio waves when adjacent wireless terminals relay each other broadcast packets.
[0042]
Next, a second embodiment of the present invention will be described.
In the second embodiment, it is not the preceding radio terminal that determines whether or not to relay, but the radio terminal that has received the broadcast packet. Therefore, there is no relay designation ID in the relay header portion shown in the first embodiment, and the number of relay designation IDs is zero. The wireless terminal that has received this broadcast packet makes an incoming call determination similar to that in the first embodiment, and then repeats the transmission from the transmission source wireless terminal to its own wireless terminal, and the wireless terminal adjacent to the transmission source terminal. And the relay transmission is performed only when (the number of relays from the transmission source wireless terminal to the own wireless terminal) <(the number of relays from the transmission source wireless terminal to the adjacent wireless terminal). The principle is the same as in the first embodiment. In this case, if the time from reception to relay transmission is independently calculated from the clock information managed by the user and the transmission is made according to the timing, the relay transmission timing changes randomly in the entire network. Accordingly, not only the collision of radio waves between adjacent wireless terminals, but also the traffic when those wireless terminals perform relay transmission can be suppressed.
[0043]
As described above, the embodiment of the present invention has been described with reference to the drawings. However, the communication protocol to which the present invention is applied is limited to the above-described embodiment as long as the function is executed. Never done.
[0044]
In addition, a ROM or RAM memory, an external recording device, and a portable recording medium in which the program code of the software that realizes the communication protocol of the above-described embodiment is recorded are supplied to the wireless terminal. Needless to say, this can also be achieved by reading and executing the code.
[0045]
In this case, the program code itself read from the recording medium realizes the novel function of the present invention, and a portable recording medium or the like on which the program code is recorded constitutes the present invention.
[0046]
Examples of portable recording media for supplying the program code include a floppy disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a DVD-ROM, a DVD-RAM, a magnetic tape, and a nonvolatile memory. Various recording media recorded through a network connection device (in other words, a communication line) such as a card, a ROM card, electronic mail or personal computer communication can be used.
[0047]
In addition, the function of the above-described embodiment is realized by executing the program code read out on the memory by the computer, and the OS running on the computer based on the instruction of the program code is actually used. Some or all of the processing is performed, and the functions of the above-described embodiments are also realized by the processing.
[0048]
Furthermore, after the program code read from the portable recording medium is written to a memory provided in a function expansion board inserted in the computer or a function expansion unit connected to the computer, the program code is read based on the instruction of the program code. A function expansion board or a CPU provided in the function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments can be realized by the processing.
[0049]
That is, the present invention is not limited to the embodiments described above, and can take various configurations or shapes without departing from the gist of the present invention.
[0050]
【The invention's effect】
As described above, according to the present invention, when performing broadcast communication in an ad hoc wireless network that performs route control using a distance vector type algorithm, a wireless terminal selects a transmission destination and performs relay transmission, or By selecting whether or not the wireless terminal that relays and transmits in a similar manner selects whether or not to relay, unnecessary broadcast communication can be reduced.
[0051]
Further, by calculating the relay transmission timing based on the header information of the broadcast packet or by randomly changing each wireless terminal, it is possible to avoid collision of radio waves between adjacent wireless terminals.
[0052]
As a result, an increase in packets is suppressed and efficient communication is possible.
[Brief description of the drawings]
FIG. 1 is a diagram showing a data format of a broadcast packet in the present invention.
FIG. 2 is a diagram for explaining a relay method when broadcast communication is performed in a distance vector type ad hoc wireless network;
3 is a diagram showing a relay header part of a broadcast packet relayed and transmitted by the wireless terminal A shown in FIG.
4 is a diagram showing a route information table held by the wireless terminal B shown in FIG. 2. FIG.
5 is a diagram showing a relay header portion of a broadcast packet relay-transmitted by the wireless terminal B shown in FIG.
6 is a diagram showing a route information table that the wireless terminal J shown in FIG. 2 has. FIG.
FIG. 7 is a diagram for explaining avoiding a collision between radio waves transmitted from adjacent wireless terminals by changing a time from reception of a broadcast packet to relay transmission.
FIG. 8 is a diagram (part 1) for explaining a first conventional method as broadcast communication in which the same information packet is transmitted to all terminals in a network;
FIG. 9 is a diagram (No. 2) for explaining the first conventional method as broadcast communication in which the same information packet is transmitted to all terminals in the network;
FIG. 10 is a diagram (No. 3) for explaining the first conventional method as broadcast communication in which the same information packet is transmitted to all terminals in the network;
FIG. 11 is a diagram (No. 1) for describing a second conventional method as broadcast communication in which the same information packet is transmitted to all terminals in the network;
FIG. 12 is a diagram (No. 2) for explaining the second conventional method as broadcast communication in which the same information packet is transmitted to all terminals in the network;
FIG. 13 is a diagram (No. 3) for explaining the second conventional method as broadcast communication in which the same information packet is transmitted to all terminals in the network.
FIG. 14 is a diagram illustrating an example of an ad hoc network.
FIG. 15 is a diagram showing an existing network (for example, the Internet).
FIG. 16 is a diagram showing a route control algorithm of a route control type network.
FIG. 17 is a diagram illustrating a case where broadcast communication is performed by a flatting method in a route control type ad hoc wireless network.
[Explanation of symbols]
81, 91, 92, 93, 101, 102, 103, 104, 105, 106, 107, 111, 121, 122, 131, 132, 133 Communication range

Claims (5)

Consists of a plurality of wireless terminals that perform wireless data communication, any of the wireless terminals on a wireless communication network capable of communicating with all other wireless terminals directly or through one or more other wireless terminals, In a broadcast communication method executed by a wireless terminal,
Each wireless terminal that constitutes the wireless communication network uses each wireless terminal as its own wireless terminal when the wireless communication network is formed, and the number of relays until the wireless terminal adjacent to the own wireless terminal and the target wireless terminal are reached Each route information is managed as a route information table,
A wireless terminal that transmits a broadcast packet on the wireless communication network includes at least a packet identification number, a transmission source terminal ID, the number of relay designation IDs, a number of relay designation IDs corresponding to the number of relay designation IDs, and transmission in the broadcast packet format. A broadcast communication method having a relay header part having each storage area of a source terminal ID, and storing information of a wireless terminal to be relayed next in the relay designation ID area of the relay header part,
The distance between the transmission source terminal and the wireless terminal adjacent to the own wireless terminal is greater than the distance between the transmission source wireless terminal that first transmitted the broadcast packet and the own wireless terminal that received the broadcast packet. When a wireless terminal adjacent to the remote wireless terminal located at a distant position refers to the route information table, the wireless terminal transmits the relay specified ID number area of the relay header portion, the relay specified ID. A broadcast communication method characterized by storing information on wireless terminals adjacent to the own wireless terminal corresponding to each of a number of relay designation ID areas corresponding to the number, and relay-transmitting the broadcast packet . When the wireless terminal that has received the broadcast packet stores a number of 2 or more in the relay designation ID number area of the relay header part, the wireless terminal depends on the order of the relay designation ID area of the relay header part. The broadcast communication method according to claim 1 , wherein the relay transmission timing is varied . The wireless terminal that has received the broadcast packet randomly determines a timing for performing the relay transmission when 0 is stored in the relay designation ID number area of the relay header portion. The broadcast communication method according to 1.   A wireless terminal that performs broadcast communication by the broadcast communication method according to claim 1.   A computer-executable communication program including software program code for executing the broadcast communication method according to any one of claims 1 to 3.

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