JP5935077B2 - Multi-hop communication system and multi-hop communication method - Google Patents

Description

  The present invention relates to a multi-hop communication system and a multi-hop communication method.

  Conventionally, when communication between communication terminals existing on a communication network cannot be performed directly between communication terminals to transmit information, communication is performed by using another communication terminal for relaying communication. Multi-hop communication is known that enables this. Such multi-hop communication is used particularly in a wireless network which is one of communication networks. Furthermore, multi-hop communication is also used in a PLC network, which is a communication network constructed using a technology of power line carrier communication (hereinafter abbreviated as “PLC” (Power Line Communication)).

  In such a communication network, a communication terminal having a relationship in which signals transmitted to each other cannot be directly received is referred to as a hidden terminal. If each of the communication terminals in the hidden terminal relationship transmits a packet, packet collision is likely to occur, and there are adverse effects such as frequent retransmissions and an increase in transmission delay. Therefore, the communication terminal, such as RTS / CTS (Request To Send / Clear To Send) defined in IEEE802.11, secures the communication channel for a certain period of time and then transmits the packet, thereby causing frequent retransmissions. There is a method for suppressing an increase in transmission delay.

  However, the method using RTS / CTS is not suitable because there is an overhead due to an increase in RTS packets and CTS packets, and therefore, when the packet length of data to be transmitted is short, the communication efficiency is greatly reduced.

  Also, in the method using RTS / CTS, a communication terminal that does not need to prohibit transmission is also prohibited from transmitting, so that spatial channel utilization efficiency is poor. For example, other transmitting terminals that are slightly away from a certain transmitting terminal can transmit packets at the same time without causing interference between the transmitting terminals. However, in the method using RTS / CTS, transmission is excessively suppressed. .

  Furthermore, in the method using RTS / CTS, even if the CTS packet is not normally returned due to the collision of the RTS packet or the like, the peripheral communication terminal suppresses transmission, so that the transmission efficiency of the entire network is lowered.

  In particular, in a control system using multi-hop wireless communication (for example, remote meter reading using a smart meter), since the packet length of data to be transmitted and received is relatively short, there is a hidden terminal avoidance method that does not use RTS / CTS. is necessary.

  Therefore, as in Patent Document 1, a configuration has been proposed in which RTS / CTS is used and a random delay is provided so that each communication terminal refrains from transferring a packet to the next hop along the communication route of multihop communication. .

JP 2009-105892 A

  However, in Patent Document 1 described above, each communication terminal on the communication route that actually transfers the packet by multi-hop communication has a random delay spontaneously, and the operation of the communication terminals around this communication route is as follows. Not considered.

  Therefore, each communication terminal on the communication route may suppress packet transmission more than necessary even though there is no risk of packet collision with the hidden terminal, and the spatial channel utilization efficiency is poor, and the network The transmission efficiency will decrease.

  The present invention has been made in view of the above-described reasons, and an object of the present invention is to reduce packet collisions caused by hidden terminals without using RTS / CTS, and to improve the transmission efficiency of the network. To provide a hop communication system and a multi-hop communication method.

The multihop communication system of the present invention is a multihop communication system in which a plurality of communication terminals establish a communication route and perform multihop communication. The first communication terminal transmits a first data packet to the first data packet. Whether the first data packet is transmitted from the second communication terminal to the third communication terminal, is transmitted to the second communication terminal of the next hop that is the transmission destination of the packet. First relay presence / absence information indicating whether or not, and first relay time information for determining a first transfer required time required for the second communication terminal to transfer the first data packet, The fourth communication terminal that is not the transmission destination of the first data packet by the first communication terminal receives the first data packet, based on the first relay presence / absence information, De Data packet is transferred from the second communication terminal, based on the first relay time information, the second terminal transmits a second data packet until the first transfer required time elapses. If the transmission destination of the second data packet is the first communication terminal in a period during which the transmission of the second data packet is suppressed , the fourth communication terminal The transmission of the second data packet is permitted .
The multi-hop communication system of the present invention is a multi-hop communication system in which a plurality of communication terminals establish a communication route to perform multi-hop communication, and each of the plurality of communication terminals can directly communicate with its own terminal. Information for identifying an adjacent terminal that is a terminal is stored, and the first communication terminal transmits the first data packet to the second communication terminal of the next hop that is the transmission destination of the first data packet. The first data packet includes first relay presence / absence information indicating whether the first data packet is transferred from the second communication terminal to the third communication terminal, and the second data packet. First relay time information for determining a first transfer required time required for processing for transferring the first data packet by the communication terminal, and a transmission destination of the first data packet by the first communication terminal When the fourth communication terminal receives the first data packet, the fourth communication terminal determines that the first data packet is transferred from the second communication terminal based on the first relay presence / absence information. Then, based on the first relay time information, the transmission of the second data packet from the own terminal is suppressed until the first transfer required time elapses, and the first data packet is Information for identifying the third communication terminal, and the fourth communication terminal that has received the first data packet suppresses the transmission of the second data packet in the period when the third data packet is being transmitted. The communication terminal is not the adjacent terminal of the fourth communication terminal, and the fifth communication terminal of the next hop to which the second data packet is transmitted is different from the second and third communication terminals The fifth communication terminal And permits the transmission of the second data packet to the destination.
The multi-hop communication system of the present invention is a multi-hop communication system in which a plurality of communication terminals establish a communication route to perform multi-hop communication, and each of the plurality of communication terminals can directly communicate with its own terminal. Storing information for identifying an adjacent terminal that is a terminal and information for identifying a 2-hop terminal that is the communication terminal with which each of the adjacent terminals can directly communicate, and the first communication terminal, The first data packet is transmitted to the second communication terminal of the next hop that is the transmission destination of the first data packet, and the first data packet is transmitted from the second communication terminal to the second communication terminal. First relay presence / absence information indicating whether or not to be transferred from the terminal to the third communication terminal, and a first transfer required time required for the second communication terminal to transfer the first data packet 4th communication terminal which is the transmission destination of the 1st data packet by the 1st communication terminal including the 1st relay time information to define, when receiving the 1st data packet, If it is determined that the first data packet is transferred from the second communication terminal based on the relay presence / absence information, the first transfer required time has elapsed based on the first relay time information. Until then, the transmission of the second data packet from the own terminal is suppressed, and the fourth communication terminal that has received the first data packet is in a period of suppressing the transmission of the second data packet, The third communication terminal is not the neighboring terminal of the fourth communication terminal, and the fifth communication terminal of the next hop that is the transmission destination of the second data packet is the second or third communication. Unlike the terminal, and When direct communication between the second communication terminal and the fifth communication terminal is impossible, permission to transmit the second data packet with the fifth communication terminal as a transmission destination is permitted. Features.

  In the present invention, it is preferable that the first relay time information indicates the first required transfer time.

  In this invention, it is preferable that the first relay time information is information used for calculating the first transfer time.

In the present invention, after the second communication terminal receives the first data packet, the second communication terminal returns a confirmation packet to the first communication terminal, and the confirmation packet triggers the confirmation packet. Second relay presence / absence information indicating whether or not the first data packet is transferred from the second communication terminal to the third communication terminal; and the second communication terminal transmits the first data packet Second relay time information for determining a second transfer required time required for the process of transferring the message , and each of the plurality of communication terminals is based on the second relay presence / absence information when receiving the confirmation packet. And determining that the first data packet is transferred from the second communication terminal, based on the second relay time information, until the second transfer required time elapses. Sending Preferably be suppressed.

In the present invention, after the second communication terminal receives the first data packet, the second communication terminal returns a confirmation packet to the first communication terminal, and the confirmation packet triggers the confirmation packet. The first data packet includes second relay presence / absence information indicating whether or not the second communication terminal is transferred to the third communication terminal , and each of the plurality of communication terminals includes the confirmation packet If it is determined that the first data packet is transferred from the second communication terminal based on the second relay presence / absence information, the transmission of the data packet is preferably suppressed for a certain period of time. .

  In the present invention, after the fourth communication terminal receives the first data packet from the first communication terminal, the second communication terminal returns the confirmation packet returned to the first communication terminal. When received, it is preferable to execute transmission suppression of the second data packet based on the first relay presence / absence information and not execute transmission suppression of the second data packet based on the second relay presence / absence information. .

In the present invention, each of the plurality of communication terminals includes communication quality indicating communication quality between the own terminal and each of the adjacent terminals and communication quality between each of the adjacent terminals and each of the two-hop terminals. Information is stored, and the fourth communication terminal can communicate directly with the fourth communication terminal even when the second communication terminal and the fifth communication terminal can directly communicate with each other. If the communication quality between the second communication terminal and the fifth communication terminal is better than the communication quality between the second communication terminal and the fifth communication terminal by a certain level or more, the fifth communication terminal It is preferable to permit transmission of the second data packet.

In the present invention, each of the plurality of communication terminals transmits the data packet after a predetermined transmission waiting time elapses when transmission of the data packet is permitted, and the fourth communication terminal When transmission of the second data packet is permitted during a period in which transmission of the second data packet is suppressed, it is preferable to shorten the transmission waiting time.

In the present invention, each of the plurality of communication terminals stores information for identifying a 2-hop terminal which is the communication terminal with which each of the adjacent terminals can directly communicate, and transmission of the data packet is permitted. The fourth communication terminal that has transmitted the data packet after a predetermined transmission waiting time has elapsed and received the first data packet has suppressed transmission of the second data packet. The third communication terminal is not the neighboring terminal of the fourth communication terminal, and the fifth communication terminal of the next hop to which the second data packet is transmitted is the second, third, When the transmission of the second data packet with the fifth communication terminal as the transmission destination is permitted, the second communication terminal and the fifth communication terminal communicate directly. Is bad The transmission waiting time is set to the first transmission waiting time, and if direct communication is possible between the second communication terminal and the fifth communication terminal, the transmission waiting time is set to It is preferable to set the second transmission waiting time shorter than the first transmission waiting time.

In the present invention, each of the plurality of communication terminals includes information for identifying a two-hop terminal that is the communication terminal with which each of the adjacent terminals can directly communicate, and the own terminal and each of the adjacent terminals. And communication quality information indicating communication quality between each of the adjacent terminals and each of the two-hop terminals, and when transmission of the data packet is permitted, a predetermined transmission waiting time is After the elapse of time, the fourth communication terminal that has transmitted the data packet and received the first data packet has the third communication terminal in a period during which transmission of the second data packet is suppressed. The fifth communication terminal of the next hop that is not the adjacent terminal of the fourth communication terminal and is the transmission destination of the second data packet is different from the second and third communication terminals, and If transmission of the second data packet with the communication terminal as the transmission destination is permitted, if direct communication between the second communication terminal and the fifth communication terminal is impossible, the transmission wait The time is set to the first transmission waiting time, direct communication is possible between the second communication terminal and the fifth communication terminal, and the fourth communication terminal and the fifth communication terminal If the communication quality between the second communication terminal and the fifth communication terminal is not better than a certain level, the transmission wait time is set to the first transmission wait time. , Direct communication is possible between the second communication terminal and the fifth communication terminal, and the communication quality between the fourth communication terminal and the fifth communication terminal is the second communication terminal. If the communication quality between the communication terminal and the fifth communication terminal is better than a certain level, the transmission It is preferred that the Chi time is set to the shorter than the first transmission waiting time the second transmission latency.

The multihop communication method of the present invention is a multihop communication method in which each of a plurality of communication terminals establish a communication route with each other and perform multihop communication. The first communication terminal transmits a first data packet to the first data packet. The first data packet is transmitted from the second communication terminal to the third communication terminal. The first data packet is transmitted to the second communication terminal of the next hop that is the transmission destination of the first data packet. First relay presence / absence information indicating whether or not to be transmitted, and first relay time information for determining a first transfer required time required for the second communication terminal to transfer the first data packet. And the fourth communication terminal that is not the transmission destination of the first data packet by the first communication terminal receives the first data packet based on the first relay presence / absence information. First If it is determined that the data packet is transferred from the second communication terminal, the second terminal transmits the second data packet from the own terminal until the first transfer required time elapses based on the first relay time information. If the transmission destination of the second data packet is the first communication terminal in a period in which the transmission is suppressed and the fourth communication terminal suppresses transmission of the second data packet, The transmission of the second data packet is permitted .
The multi-hop communication method of the present invention is a multi-hop communication method in which each of a plurality of communication terminals constructs a communication route with each other and performs multi-hop communication. Each of the plurality of communication terminals can directly communicate with its own terminal. The information for identifying the adjacent terminal which is the communication terminal is stored, and the first communication terminal transmits the first data packet to the second communication of the next hop which is the transmission destination of the first data packet. Transmitting to the terminal, the first data packet includes first relay presence / absence information indicating whether or not the first data packet is transferred from the second communication terminal to the third communication terminal; First relay time information for determining a first transfer required time required for a process in which the second communication terminal transfers the first data packet, and the first communication terminal transmits the first data packet. Sending When the first data packet is received from the second communication terminal based on the first relay presence / absence information when the fourth communication terminal that is not the first receives the first data packet If it is determined, based on the first relay time information, the transmission of the second data packet from the own terminal is suppressed until the first transfer required time elapses, and the first data packet is The fourth communication terminal, which includes information for identifying a third communication terminal and receives the first data packet, suppresses transmission of the second data packet in the third data terminal. The communication terminal is not the adjacent terminal of the fourth communication terminal, and the fifth communication terminal of the next hop to which the second data packet is transmitted is different from the second and third communication terminals. If the fifth communication And permits the transmission of the second data packet to end the destination.
The multi-hop communication method of the present invention is a multi-hop communication method in which each of a plurality of communication terminals constructs a communication route with each other and performs multi-hop communication. Each of the plurality of communication terminals can directly communicate with its own terminal. Information for identifying adjacent terminals that are the communication terminals, and information for identifying the two-hop terminals that are the communication terminals with which each of the adjacent terminals can directly communicate, and store the first communication The terminal transmits the first data packet to the second communication terminal of the next hop that is the transmission destination of the first data packet, and the first data packet is transmitted from the first data packet. First relay presence / absence information indicating whether or not to be transferred from the second communication terminal to the third communication terminal, and a first transfer required for the second communication terminal to transfer the first data packet Required First communication time information that defines the interval, and a fourth communication terminal that is not a transmission destination of the first data packet by the first communication terminal receives the first data packet, If it is determined that the first data packet is transferred from the second communication terminal based on the first relay presence / absence information, the first transfer required time is determined based on the first relay time information. Until the time elapses, the transmission of the second data packet from the own terminal is suppressed, and the fourth communication terminal that has received the first data packet suppresses the transmission of the second data packet. The third communication terminal is not the neighboring terminal of the fourth communication terminal, and the fifth communication terminal of the next hop to which the second data packet is transmitted is the second, third, Unlike other communication terminals, When the direct communication between the second communication terminal and the fifth communication terminal is impossible, the transmission of the second data packet having the fifth communication terminal as a transmission destination is permitted. It is characterized by.

  As described above, in the present invention, when the second communication terminal transfers the data packet received from the first communication terminal, the adjacent terminal of the first communication terminal transmits the data packet from the own terminal. Is prohibited. In this case, the first to third communication terminals on the communication route that actually transfer the packet do not suppress transmission. On the other hand, the fourth communication terminal existing outside this communication route considers the operation of the surroundings (first to third communication terminals) and suppresses transmissions to be performed (or will be performed in the future). Yes. That is, the first to third communication terminals on the communication route that actually transfer the packet do not suppress transmission. Therefore, according to the present invention, there is an effect that packet collision by a hidden terminal can be suppressed and network transmission efficiency can be improved without using RTS / CTS.

1 is a configuration diagram illustrating a wireless network configured by a multi-hop communication system according to Embodiment 1. FIG. It is the schematic which shows a wireless network same as the above. It is a block diagram which shows the structure of a communication terminal same as the above. It is a table figure which shows the structure of an adjacent terminal management table same as the above. (A) (b) It is a table figure which shows the structure of a communication route table same as the above. It is a figure which shows the flame | frame of a packet same as the above. It is a block diagram which shows a wireless network same as the above. It is a sequence diagram which shows operation | movement same as the above. It is a figure which shows another frame of a packet same as the above. It is a block diagram which shows the radio | wireless network which the multihop communication system of Embodiment 3 comprises. It is a block diagram which shows the radio | wireless network which the multihop communication system of Embodiment 4 comprises. It is a sequence diagram which shows operation | movement same as the above. FIG. 10 is a configuration diagram illustrating a wireless network configured by a multi-hop communication system according to a fifth embodiment. It is a figure which shows the adjacent terminal address table same as the above. It is a block diagram explaining the effect of a wireless network same as the above. It is a block diagram which shows the radio | wireless network which the multihop communication system of Embodiment 6 comprises. It is a figure which shows the 2 hop terminal address table same as the above. It is a block diagram explaining the effect of a wireless network same as the above. FIG. 10 is a configuration diagram illustrating a wireless network configured by a multi-hop communication system according to a seventh embodiment. It is a figure which shows the adjacent terminal information table same as the above. It is a figure which shows a 2 hop terminal information table same as the above. FIG. 10 is a configuration diagram illustrating a wireless network configured by a multi-hop communication system according to an eighth embodiment. It is a sequence diagram which shows operation | movement same as the above.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 2 is a schematic diagram of a wireless network configured by the multi-hop communication system of the present embodiment. This wireless network is used in a dwelling unit group composed of a plurality of dwelling units X. Within the dwelling unit group, a parent communication terminal 1 is installed for each predetermined range (for example, every radius of 500 m). The communication terminal 2 as a child is installed. Hereinafter, the parent communication terminal 1 is referred to as a parent terminal 1 and the child communication terminal 2 is referred to as a child terminal 2. Furthermore, when individually identifying the child terminals 2, the child terminals 2-1, 2-2, 2-3,. . . Is used.

  The child terminal 2 has a function of wirelessly transmitting predetermined information about each dwelling unit X to one parent terminal 1. The parent terminal 1 has a function of acquiring predetermined information related to each dwelling unit X wirelessly from the plurality of child terminals 2 and transmitting the acquired predetermined information to an upper management device (not shown) using an optical fiber line or the like. For example, a remote meter reading system can be configured by the master terminal 1 acquiring meter reading information such as power usage, gas usage, and water usage in each dwelling unit X from the child terminal 2. Moreover, the remote monitoring system which monitors the state of the apparatus in each dwelling unit X, when the parent terminal 1 transmits / receives the preset predetermined information between the child terminals 2, The state of the apparatus in each dwelling unit X It is also possible to configure a remote control system or the like that controls

  In this wireless network, the parent terminal 1 and the child terminal 2 transmit and receive wireless signals to each other by multi-hop communication. That is, in this wireless network, communication is performed directly or indirectly between the parent terminal 1 and each child terminal 2, and the child terminal 2 that cannot directly communicate with the parent terminal 1 is connected to another child terminal within a communicable distance. 2 communicates with the parent terminal 1 by sequentially relaying communication packets.

  FIG. 3 is a block diagram of the communication terminal A. In the present embodiment, the same communication terminal A is used for the parent terminal 1 and the child terminal 2. For example, the communication terminal A is set to “parent” using setting means such as a jumper switch or a changeover switch. It functions as the parent terminal 1 and functions as the child terminal 2 by being set to “child”. Further, hereinafter, when the parent terminal 1 and the child terminal 2 are not distinguished, they are referred to as communication terminals A.

  The communication terminal A includes a storage unit 10, a control unit 20, and a wireless communication interface unit 30.

  The storage unit 10 includes a nonvolatile memory such as a ROM, a rewritable nonvolatile memory such as an EEPROM, and a volatile memory such as a RAM. And the memory | storage part 10 is provided with the table memory | storage part 101 which memorize | stores the link information etc. regarding the communication route and the communicable adjacent terminal (parent terminal 1 or child terminal 2 which can communicate directly). Further, the storage unit 10 stores each program such as a control program for operating the communication terminal A, information necessary for executing each program, and the like.

  In this embodiment, a unique terminal ID is assigned to each of the parent terminal 1 and the child terminal 2, and the terminal ID assigned to the own terminal is also stored in the storage unit 10 of each communication terminal A. In the present embodiment, the terminal ID “M1” is assigned to the parent terminal 1 in advance. Also, the child terminals 2-1, 2-2, 2-3,. . . . If a communication route for multi-hop communication is established with the parent terminal 1, the terminal IDs “T1”, “T2”, “T3”. . . Is assigned.

  In addition, each communication terminal A is assigned a device ID such as a MAC address or serial number (manufacturing number) in advance, and the storage unit 10 of each communication terminal A stores this device ID in advance. . The communication packet transmitted and received by the communication terminal A is subjected to communication control by adding this device ID.

  The table storage unit 101 of the parent terminal 1 and the child terminal 2 stores the adjacent terminal management table TB1 shown in FIG. 5 is stored in the table storage unit 101 of the parent terminal 1, and the communication route table TB22 shown in FIG. 5B is stored in the table storage unit 101 of the child terminal 2. Is stored.

  As illustrated in FIG. 4, the adjacent terminal management table TB1 includes information (adjacent terminal information) regarding a communication terminal A (adjacent terminal) that can directly communicate with the communication terminal A without being relayed by another communication terminal A. ) Is stored in a table format. Specifically, the adjacent terminal management table TB1 includes fields of adjacent terminal ID, terminal type, reception link communication quality, transmission link communication quality, and link communication quality.

  In the adjacent terminal management table TB1, the adjacent terminal ID is a terminal ID assigned to a communication terminal A that can directly communicate with the own terminal (hereinafter referred to as the adjacent terminal A). The terminal type indicates the type of the adjacent terminal A (parent terminal 1 “parent” or child terminal 2 “child”). The reception link communication quality indicates the communication quality of the communication link from the adjacent terminal A to the own terminal. The transmission link communication quality indicates the communication quality of the communication link from the own terminal to the adjacent terminal A. The link communication quality indicates the communication quality in the communication link between the adjacent terminal A and the own terminal.

  For example, the communication quality value SQ is used as the link communication quality in the communication link between the two communication terminals A-A capable of direct communication. The communication quality value SQ is represented by an integer value such as 10 steps or 20 steps that becomes smaller as the received signal strength between the two communication terminals A-A capable of direct communication becomes larger. That is, as the communication quality value SQ is smaller, the communication packet is less attenuated and the communication state is better.

  When the noise level and interference level at the place where the communication packet is received are different, the bidirectional communication quality in the communication link is different from each other. Composed. The received link communication quality is a received signal strength when the own terminal A receives a communication packet from another communication terminal A in a link between two communication terminals A-A capable of direct communication. As for the transmission link communication quality, in the link between two communication terminals A-A capable of direct communication, the own terminal A transmits a communication packet to the other communication terminal A, and the other communication terminal A receives the communication packet. Is the received signal strength.

  Also in the adjacent terminal management table TB1, fields of reception link communication quality and transmission link communication quality in the communication terminal A are provided. Then, from the viewpoint of guaranteeing communication reliability (reliability) when communication is performed between the communication terminals A and A, one of the reception link communication quality and the transmission link communication quality having the worse communication state (link communication). The higher quality value) is adopted as the link communication quality between the two communication terminals A-A.

  The route communication quality, which will be described later, which is an evaluation of the communication quality of the communication route between the parent terminal 1 and the child terminal 2, is the link of each communication link constituting the communication route between the parent terminal 1 and the child terminal 2. The sum of communication quality is adopted.

  The communication quality value SQ described above is associated with the received signal strength. However, instead of the received signal strength, the communication quality value SQ is associated with other elements such as an SN ratio, an EVM (Error Vector Magnitude), a bit error rate, and a packet error rate. May be calculated.

  Next, a communication route between the parent terminal 1 and the child terminal 2 is formed by one or more communication links. Then, the communication route table TB21 (see FIG. 5A) held by the parent terminal 1 includes information (communication route information) regarding the communication route between the parent terminal 1 and the child terminals 2 subordinate to the parent terminal 1. Stored in table format. Specifically, the communication route table TB21 is provided with terminal ID, route communication quality, hop count, and hop destination fields.

  In the communication route table TB21 held by the parent terminal 1, the terminal ID is a terminal ID assigned to the subordinate child terminal 2 in which the communication route is constructed. The route communication quality indicates the communication quality in the communication route to the child terminal 2 registered in the terminal ID field. The number of hops indicates the number of hops in the communication route to the child terminal 2 registered in the terminal ID field. The hop destination indicates the communication terminal A of the transmission destination at each hop in the communication route to the child terminal 2 registered in the terminal ID field.

  Next, the communication route table TB22 (see FIG. 5B) held by the child terminal 2 includes information (communication route information) regarding the communication route between the child terminal 2 and the parent terminal 1 that can communicate with the child terminal 2. , Stored in table format. Specifically, the communication route table TB22 includes fields for terminal ID, route communication quality, hop count, and hop destination.

  In the communication route table TB22 held by the child terminal 2, the terminal ID is a terminal ID assigned to the parent terminal 1 that can communicate with the child terminal 2. The route communication quality indicates the communication quality in the communication route to the parent terminal 1 registered in the terminal ID field. The number of hops indicates the number of hops in the communication route to the parent terminal 1 registered in the terminal ID field. The hop destination indicates the destination communication terminal A at each hop in the communication route to the parent terminal 1 registered in the terminal ID field.

  In the communication route tables TB21 and TB22, the number of hops is the number of communication terminals A in the communication route from the own terminal to the communication destination terminal. For example, in the case of a communication route in which the child terminal 2-4 communicates with the parent terminal 1 via the child terminal 2-3 and the child terminal 2-1, the number of hops is “3”. As the hop destination, the terminal IDs of the communication terminals A that are routed from the own terminal to the communication destination terminal are registered in order of passage, and finally, the terminal IDs of the communication terminals A registered in the terminal ID field are registered.

  The wireless communication interface unit 30 is a communication interface circuit for performing communication with another communication terminal A using a wireless signal.

  The control unit 20 is a device that controls the operation of the entire communication terminal A by controlling each unit of the communication terminal A, and includes, for example, a microprocessor and its peripheral circuits.

  When there is predetermined information addressed to the parent terminal 1, the child terminal 2 transmits a data packet including the predetermined information along a communication route established with the parent terminal 1. Then, the child terminal 2 that has received the data packet from the other child terminal 2 transfers the data packet to the child terminal 2 or the parent terminal 1 of the next hop along this communication route.

  A system that performs multi-hop communication along a communication route using the adjacent terminal management table TB1, the communication route tables TB21, TB22, and the like is well known in the art and will not be described in detail.

  The data packet transmitted by the communication terminal A has the format of the MAC frame FL1 shown in FIG. The MAC frame FL1 is composed of eight fields F1 to F8 and is used as a transmission / reception unit in the layer 2 MAC layer protocol.

  F1 is a frame control and stores information such as packet type.

  F2 is a duration and stores information such as a time (NAV) reserved for data packet transmission.

  F3 is a transmission destination address (Receiver Address), in which address information of the communication terminal A of the next hop that receives this data packet is stored. That is, on the communication route, the address information of the next hop communication terminal A that is the transmission destination (relay destination) of the data packet is stored.

  F4 is a transmission source address (Transmitter Address) in which address information of the communication terminal A that transmits this data packet is stored. That is, address information of the communication terminal A that is a transmission source (relay source) of the data packet is stored on the communication route.

  F5 is a destination address (Destination Address), in which the address information of the communication terminal A that is the destination to which this data packet finally arrives is stored.

  F6 is a source address (Source Address), in which address information of the communication terminal A that is the source that transmitted the data packet first is stored.

  That is, the source address F6 is the address information of the communication terminal A that first started transmission of the data packet, and the destination address F5 is the address information of the communication terminal A that finally receives the data packet. The destination address F5 and the source address F6 are determined by the communication terminal A that is the first source, and the communication that is the final destination from the communication terminal A that is the first source on the communication route of the multi-hop communication. It does not change until reaching terminal A.

  On the other hand, the transmission destination address F3 and the transmission source address F4 are rewritten at each communication terminal A on the communication route of multihop communication. Here, in communication between the parent terminal 1 and the child terminal 2, the communication terminal A that transfers the data packet received from the previous hop communication terminal A to the next hop communication terminal A is referred to as a relay terminal. Then, the relay terminal A changes the source address F4 of the received data packet to its own address information, and sets the destination address F3 of the received data packet to the address information of the next hop communication terminal A on the communication route. change. The relay terminal A transmits the data packet in which the transmission destination address F3 and the transmission source address F4 are rewritten as described above to the communication terminal A of the next hop.

  For example, a MAC address is set in each of the addresses F3 to F6.

  Next, F7 is a MAC payload (Mac Payload) in which various data are stored.

  F8 is a frame check sequence (Frame Check Sequence), which is added to check for errors in the received frame.

  The MAC frame FL1 described above is used in the layer 2 MAC layer protocol, but the MAC payload F7 stores an upper frame FL2 including information used in the layer 3 network layer protocol. As shown in FIG. 6, the upper frame FL2 includes four fields F21 to F24.

  In F21, the number of hops of the communication route from the communication terminal A (source) that first started transmission of the data packet to the communication terminal A (destination) that finally receives the data packet is set.

  In F22, the terminal ID of the communication terminal A (source) that first started transmission of the data packet is set.

  F23 is a destination communication terminal at each hop in a communication route from communication terminal A (source) that first started transmission of a data packet to communication terminal A (destination) that finally receives the data packet. A's terminal ID is set.

  F24 stores various data.

  The communication terminal A performs communication control with reference to the frame control F1, the duration F2, the transmission destination address F3, the transmission source address F4, the destination address F5, and the frame check F8 of the received data packet in the MAC layer protocol of layer 2. I do. For example, if the communication terminal A is a relay terminal, the communication terminal A transmits a data packet in which the transmission destination address F3 and the transmission source address F4 are rewritten as described above to the communication terminal A of the next hop. Further, if the communication terminal A is the destination communication terminal A, the communication terminal A acquires data stored in the MAC payload F7 and executes data processing.

  Here, the MAC payload F7 is a field referred to in the layer 3 network layer protocol, and is not referred to in the layer 2 MAC layer protocol.

  Note that multi-hop communication using the MAC frame FL1 and the upper frame FL2 is well known in the art and will not be described in detail.

  In addition, although the source routing method for enumerating the addresses of the hops in the communication route is used for the header (F21 to F23) of the upper frame FL2, here, it is not necessarily limited to this.

  For example, a hop-by-hop scheme in which each communication terminal A determines a next-hop transfer destination may be used. In this case, the source routing information of F21 to F23 is not necessary. As an example, when the child terminal 2 has the communication route table TB22 shown in FIG. 5B, each child terminal 2 has communication route information addressed to the parent terminal 1. In this case, if the destination of the packet is the parent terminal 1, the child terminal 2 can determine the next-hop communication terminal A without the source routing information of F21 to F23. Further, when the destination of the packet is the child terminal 2, if the child terminal 2 has communication route information destined for the other child terminal 2 (conventionally known), the child terminal 2 Even when a destination packet is received, the next hop relay destination can be determined.

  Next, a method for suppressing packet collision by a hidden terminal, which is the gist of the present invention, will be described.

  First, as shown in FIG. 1, a data packet (first data) in the order of communication terminal A1 (first communication terminal) → communication terminal A2 (second communication terminal) → communication terminal A3 (third communication terminal). An example is multi-hop communication in which a packet is transmitted. In FIG. 1, each range in which packets transmitted by the communication terminals A1, A2, and A3 reach is defined as communication ranges H1, H2, and H3. The communication terminal A1 may be either the source terminal that first transmitted the data packet or the relay terminal that transfers the data packet.

  The communication terminal A1 transmits the data packet to the next-hop communication terminal A2 that is the transmission destination.

  This data packet includes first relay presence / absence information and first relay time information. The first relay presence / absence information indicates whether or not this data packet is transferred from the communication terminal A2 to the next-hop communication terminal A (in this case, the communication terminal A3). The first relay time information indicates the first transfer required time required for the process in which the communication terminal A2 transfers the data packet to the next hop. The first transfer required time is set to at least the time from when the communication terminal A2 receives the data packet until the transfer processing is completed. Specifically, the first transfer required time is set to be equal to or longer than the time from when the communication terminal A2 receives the data packet until the data packet is transmitted to the communication terminal A3 and the confirmation packet is received from the communication terminal A3. The

  In the MAC frame FL1 constituting the data packet, the first relay presence / absence information is set depending on whether or not the transmission destination address F3 and the destination address F5 match. If the destination address F3 and the destination address F5 do not match, it is determined that this data packet is further transferred to the next hop. If the transmission destination address F3 and the destination address F5 match, it is determined that this data packet is not further transferred to the next hop. Thus, when the MAC frame FL1 is used for the data packet, the first relay presence / absence information can be included without changing the structure of the existing MAC frame.

  In the MAC frame FL1 constituting the data packet, the first relay time information is set to duration F2. As this first relay time information, a value of the first required transfer time determined in advance by simulation, actual measurement, or the like is set.

  Here, a communication terminal (adjacent terminal) existing in the communication range H1 of the communication terminal A1 is A4. This communication terminal A4 (fourth communication terminal) does not constitute a communication route for data packets transmitted by the communication terminal A1, and is not a data packet transmission destination by the communication terminal A1. Then, when the communication terminal A4 receives a data packet from the communication terminal A1 that does not have its own terminal as the transmission destination (with the communication terminal A2 as the transmission destination), the data packet is transmitted based on the first relay presence / absence information. It is determined whether or not the communication terminal A2 transfers to the next hop. If the communication terminal A4 determines that the data packet is further transferred, the data packet (second data packet) is transmitted from the own terminal until the first required transfer time elapses based on the first relay time information. Prohibit sending. Note that a period during which the transmission of the data packet is prohibited until the first required transfer time elapses is referred to as a transmission suppression period T1.

  That is, when the communication terminal A2 transfers the data packet received from the communication terminal A1, the adjacent terminal (communication terminal A4) of the communication terminal A1 prohibits transmission of the data packet from the own terminal. In this case, the communication terminals A1 to A3 on the communication route that actually transfer the packet do not suppress transmission. On the other hand, the communication terminal A4 outside this communication route suppresses transmission to be performed (or will be performed in the future) in consideration of the operation of the surroundings (communication terminals A1 to A3). That is, the communication terminals A1 to A3 on the communication route that actually transfer the packet do not suppress transmission. Therefore, without using RTS / CTS, the data packet transferred from the communication terminal A2 can be prevented from colliding with the data packet transmitted from the hidden terminal, and the transmission efficiency of the network can be improved.

  Further, after receiving from the communication terminal A1 a data packet whose destination is the communication terminal A2, the communication terminal A2 returns a confirmation packet (ACK packet) to the communication terminal A1, and sends the data packet to the next-hop communication terminal A3. Forward.

  The confirmation packet includes second relay presence / absence information and second relay time information. The second relay presence / absence information indicates whether or not the data packet that triggers the confirmation packet is transferred from the communication terminal A2 to the next-hop communication terminal A (in this case, the communication terminal A3). The second relay time information indicates a second transfer required time required for the process in which the communication terminal A2 transfers the data packet to the next hop. The second transfer required time is set to at least the time from when the communication terminal A2 returns the confirmation packet until the data packet transfer processing is completed. Specifically, the second transfer required time is set to be longer than the time from when the communication terminal A2 returns the confirmation packet to when the data packet is transmitted to the communication terminal A3 and when the confirmation packet is received from the communication terminal A3. The

  The second relay presence / absence information and the second relay time information in the confirmation packet are set by using each field of the MAC frame FL1, similarly to the first relay presence / absence information and the first relay time information in the data packet. The

  Then, the communication terminal A (including the communication terminal A1) that has received the confirmation packet from the communication terminal A2 receives the data packet that triggered the confirmation packet from the communication terminal A2 based on the second relay presence / absence information. Determine whether or not to forward to hop. If the communication terminal A that has received the confirmation packet determines that the data packet that triggered the confirmation packet is transferred from the communication terminal A2 to the next hop, the second transfer is performed based on the second relay time information. Until the required time elapses, transmission of data packets from the own terminal is prohibited. A period during which data packet transmission is prohibited until the second required transfer time elapses is referred to as a transmission suppression period T2.

  That is, when the communication terminal A2 transfers a data packet, adjacent terminals (including the communication terminal A1) of the communication terminal A2 prohibit transmission of the data packet from the own terminal. Therefore, without using RTS / CTS, the data packet transferred by the communication terminal A2 can be prevented from colliding with the data packet transmitted by the hidden terminal, and the transmission efficiency of the network can be improved.

  In this case, since the adjacent terminal of the communication terminal A2 can receive the confirmation packet transmitted by the communication terminal A2, there is no relationship between the communication terminal A2 and the hidden terminal, and the data packet transferred by the communication terminal A2 to the communication terminal A3 is a carrier. It can be detected. Therefore, although packet collision can be avoided by a CSMA / CA (Carrier Sense Multiple Access / Collision Avoidance) method, packet collision can be further suppressed by prohibiting packet transmission by the adjacent terminal of the communication terminal A2.

  When the communication terminal A receives a data packet whose destination is the local terminal from another communication terminal A during a period in which the transmission of the data packet from the local terminal is prohibited, the communication terminal A cancels the transmission prohibition and transmits the data packet. Allow packet transmission (forwarding).

  Next, as shown in FIG. 7, the data packet is subjected to multi-hop communication along the communication route of child terminal 2-4 → child terminal 2-3 → child terminal 2-2 → child terminal 2-1 → parent terminal 1. Shall be communicated by In FIG. 7, each range that packets transmitted by the parent terminal 1 and the child terminals 2-1, 2-2, 2-3 and 2-4 reach is communication ranges H 0, H 11, H 12, H 13 and H 14. . And the child terminal 2-5 (adjacent terminal of the child terminal 2-4) exists in the communication range H14 of the child terminal 2-4.

  FIG. 8 shows a sequence in which data packets are transmitted by multi-hop communication along a communication route from the child terminal 2-4 to the parent terminal 1.

  First, the child terminal 2-4 transmits a data packet (first data packet) having the parent terminal 1 as a destination and the child terminal 2-3 as a transmission destination (S1). After receiving the data packet from the child terminal 2-4, the child terminal 2-3 existing within the communication range H14 of the child terminal 2-4 returns a confirmation packet (ACK packet) to the child terminal 2-4 (S2). ). The child terminal 2-4 that has received the confirmation packet transmitted by the child terminal 2-3 prohibits transmission of the data packet (second data packet) during the transmission suppression period T2 from the reception timing of the confirmation packet.

  Then, the child terminal 2-3 transfers a data packet (first data packet) having the parent terminal 1 as a destination and the child terminal 2-2 as a transmission destination (S3). At this time, the child terminal 2-4 exists in the communication range H13 of the child terminal 2-3, and receives the data packet transmitted by the child terminal 2-3. The child terminal 2-4 that has received the data packet from the child terminal 2-3 resets the timing of the transmission suppression period T2, and newly receives the data packet (second data) from the reception timing of the data packet to the transmission suppression period T1. Packet) transmission is prohibited.

  After receiving the data packet from the child terminal 2-3, the child terminal 2-2 existing within the communication range H13 of the child terminal 2-3 returns a confirmation packet to the child terminal 2-3 (S4). The child terminal 2-3 that has received the confirmation packet transmitted by the child terminal 2-2 prohibits transmission of the data packet (second data packet) during the transmission suppression period T2 from the reception timing of the confirmation packet.

  Then, the child terminal 2-2 transfers a data packet (first data packet) having the parent terminal 1 as a destination and the child terminal 2-1 as a transmission destination (S5). At this time, the child terminal 2-3 exists in the communication range H12 of the child terminal 2-2, and receives the data packet transmitted by the child terminal 2-2. The child terminal 2-3 that has received the data packet from the child terminal 2-2 resets the timing of the transmission suppression period T2, and newly receives the data packet (second data) from the reception timing of the data packet to the transmission suppression period T1. Packet) transmission is prohibited.

  After receiving the data packet from the child terminal 2-2, the child terminal 2-1 existing within the communication range H12 of the child terminal 2-2 returns a confirmation packet to the child terminal 2-2 (S6). The child terminal 2-2 that has received the confirmation packet transmitted by the child terminal 2-1 prohibits transmission of the data packet (second data packet) during the transmission suppression period T2 from the reception timing of the confirmation packet.

  Then, the child terminal 2-1 transfers a data packet (first data packet) having the parent terminal 1 as a destination and the parent terminal 1 as a transmission destination (S7). At this time, the child terminal 2-2 exists within the communication range H11 of the child terminal 2-1, and receives the data packet transmitted by the child terminal 2-1. Since the data packet received from the child terminal 2-1 is not transferred from the parent terminal 1 to the next hop, the child terminal 2-2 continues the transmission inhibition period T2 without resetting the timing of the transmission inhibition period T2.

  After receiving the data packet from the child terminal 2-1, the parent terminal 1 existing in the communication range H11 of the child terminal 2-1 returns a confirmation packet to the child terminal 2-1 (S8). The child terminal 2-1 that has received the confirmation packet transmitted by the parent terminal 1 does not start counting the transmission suppression period T2 because the data packet that triggered the confirmation packet is not transferred from the parent terminal 1 to the next hop. . Accordingly, the child terminal 2-1 continues normal operation without prohibiting transmission of the data packet (second data packet).

  Thus, when the communication terminal A receives a data packet that does not have its own terminal as the transmission destination during the transmission suppression period T2, the communication terminal A determines whether or not this data packet is transferred to the next hop. Then, if the data packet is a packet to be further transferred, the communication terminal A resets the timing of the transmission suppression period T2, and performs priority processing after starting the timing of the transmission suppression period T1. Therefore, the communication terminal A can prohibit the transmission of data packets from its own terminal until the transfer process by the communication terminal A two hops ahead is completed.

  Further, the child terminal 2-5 exists within the communication range H14 of the child terminal 2-4, and the data packet (first data packet) having the child terminal 2-3 as the transmission destination is transmitted from the child terminal 2-4. ). When the child terminal 2-5 receives a data packet that does not have its own terminal as the transmission destination (with the child terminal 2-3 as the transmission destination), the child terminal 2-5 determines whether or not this data packet is transferred to the next hop. Then, if the data packet is a packet to be further transferred, the child terminal 2-5 prohibits the transmission of the data packet (second data packet) during the transmission suppression period T1 from the reception timing of the data packet.

  Therefore, when the child terminal 2-3 transfers the data packet, the child terminal 2-5, which is an adjacent terminal of the child terminal 2-4, prohibits transmission of the data packet from the own terminal. Therefore, it is possible to suppress the data packet transferred by the child terminal 2-3 from colliding with the data packet transmitted by the child terminal 2-5.

  The data packet transmitted by the communication terminal A may have the format of the MAC frame FL11 shown in FIG. The MAC frame FL11 is composed of six fields F11 to F16, and is used in the layer 2 MAC layer protocol.

  F11 is a frame control, and stores information such as the type of packet.

  F12 is a duration (Duration) in which information of a time (NAV) reserved for data packet transmission is stored.

  F13 is a transmission destination address (Destination Address), in which the address information of the communication terminal A of the next hop that receives this data packet is stored. That is, on the communication route, the address information of the next hop communication terminal A that is the transmission destination (relay destination) of the data packet is stored. The same address information as F3 of the MAC frame FL1 is stored in F13 of the MAC frame FL11.

  F14 is a transmission source address (Source Address), in which the address information of the communication terminal A that transmits this data packet is stored. That is, address information of the communication terminal A that is a transmission source (relay source) of the data packet is stored on the communication route. The same address information as F4 of the MAC frame FL1 is stored in F14 of the MAC frame FL11.

  F15 is a MAC payload (Mac Payload), in which various data are stored.

  F16 is a frame check sequence (Frame Check Sequence), which is added to check for errors in the received frame.

  For example, a MAC address is set in each address of F13 and F14.

  The MAC frame FL11 described above is used in the layer 2 MAC layer protocol, but the MAC payload F15 stores the upper frame FL2 used in the layer 3 network layer protocol.

  Note that multi-hop communication using the MAC frame FL11 and the upper frame FL2 is well known in the art and will not be described in detail.

  The data packet using the MAC frame FL11 also includes first relay presence / absence information and first relay time information.

  Specifically, the first relay presence / absence information is stored in a relay presence / absence flag B provided in the frame control F11. When the relay presence / absence flag B is “1”, it is determined that the data packet is further transferred to the next hop. When the relay presence / absence flag B is “0”, it is determined that the data packet is not further transferred to the next hop. The relay presence / absence flag B is reset when the data packet is transferred to the next hop in each relay terminal A.

  The first relay time information is set to duration F12.

(Embodiment 2)
The multi-hop communication system of the present embodiment has the same configuration as that of the first embodiment. In addition, the same code | symbol is attached | subjected to the structure similar to Embodiment 1, and description is abbreviate | omitted.

  In the first embodiment, the value of the first required transfer time is set in the first relay time information, and this first required transfer time (time length of the transmission suppression period T1) is simulated, measured, etc. It was decided beforehand by.

  However, the communication terminal A according to the present embodiment calculates the first transfer required time based on the first relay time information included in the received data packet. The first relay time information is the packet length of the data packet, and is set in any field of the data packet.

  If the destination of the received data packet (first data packet) is not its own terminal, the communication terminal A is a packet to which this data packet is further transferred, and a confirmation packet needs to be returned. The first transfer required time is calculated as in equation (1). SIFS (Short Interframe Space) is a frame transmission interval used when transmitting a confirmation packet. The ACK length is the packet length of the confirmation packet. AIFS (Arbitration IFS) is a frame transmission interval used when transmitting data packets. CWmin is the minimum value of the contention window, which is the waiting time before transmission. The packet length is the packet length of the data packet. The margin is a margin of the first transfer required time. The communication terminal A holds in advance each value of SIFS, ACK length, AIFS, CWmin, and margin. Furthermore, the communication terminal A refers to the first relay time information included in the received data packet, and acquires the packet length value.

First transfer required time = 2 × (SIFS + ACK length) + AIFS + CWmin + packet length + margin (1)
In addition, if the communication terminal A is not the transmission destination of the received data packet (first data packet), the data packet is further transferred, and a reply of the confirmation packet is unnecessary The first transfer time is calculated as shown in Equation (2).

First transfer required time = AIFS + CWmin + packet length + margin (2)
Further, the communication terminal A calculates the second required transfer time based on the second relay time information included in the received confirmation packet. This second relay time information is the packet length of the data packet that triggered the confirmation packet, and is set in any field of the confirmation packet.

  Then, the communication terminal A that has received the confirmation packet calculates the second required transfer time as shown in Expression (3) when the data packet that triggered the confirmation packet is transferred to the next hop.

Second transfer required time = SIFS + ACK length + AIFS + CWmin + packet length + margin (3)
Therefore, since the first transfer required time and the second transfer required time based on the actual packet length of the data packet can be used, the transmission efficiency is further improved without using a transfer required time longer than necessary. be able to.

  Further, in the present embodiment, it is not necessary to set a first transfer required time value (first relay time information) determined in advance by simulation, actual measurement, or the like in the header (duration) of the MAC frame. Therefore, the first relay time information can be included in the MAC frame without changing the structure of the existing MAC frame.

  The calculation of the first transfer time and the second transfer time may be performed in either the layer 2 MAC layer or the layer 3 network layer.

(Embodiment 3)
The multi-hop communication system of the present embodiment has the same configuration as that of the second embodiment. In addition, the same code | symbol is attached | subjected to the structure similar to Embodiment 2, and description is abbreviate | omitted.

  In the second embodiment, the confirmation packet includes second relay presence / absence information and second relay time information. However, in the present embodiment, the confirmation packet includes only the second relay presence / absence information and does not include the second relay time information.

  Then, the communication terminal A that has received the confirmation packet refers to the second relay presence / absence information and determines whether or not the data packet that has triggered the confirmation packet is transferred to the next hop. When the data packet that triggered the received confirmation packet is transferred to the next hop, the communication terminal A sets the transmission suppression period T2 by prohibiting the transmission of the data packet for a predetermined time.

  Thus, in this embodiment, since the second relay time information is not included in the confirmation packet, the existing MAC layer protocol can be used, and new development of the MAC layer protocol becomes unnecessary.

  In FIG. 10, the communication terminal A1 (first communication terminal) transmits a data packet (first data packet) having the communication terminal A2 (second communication terminal) as a transmission destination. The communication terminal A2 that has received the data packet returns a confirmation packet to the communication terminal A1, and transfers the data packet to the communication terminal A3 (third communication terminal). In FIG. 10, each range where packets transmitted by the communication terminals A1, A2, and A3 reach is defined as communication ranges H1, H2, and H3. The communication terminal A1 may be either the source terminal that first transmitted the data packet or the relay terminal that transfers the data packet.

  Then, the communication terminal A4 (fourth communication terminal) existing in the overlapping area between the communication range H1 of the communication terminal A1 and the communication range H2 of the communication terminal A2 transmits the data packet whose destination is the communication terminal A2 to the communication terminal A1. Receive from. Then, the communication terminal A4 also receives the confirmation packet returned from the communication terminal A2.

  In this case, the communication terminal A4 refers to the first relay presence / absence information and the first relay time information included in the data packet received from the communication terminal A1, and the transmission suppression is calculated based on the packet length of the data packet. A period T1 is set. However, even if the communication terminal A4 receives the confirmation packet returned by the communication terminal A2 during the transmission suppression period T1, it does not set the transmission suppression period T2 based on the second relay presence / absence information.

  That is, even if the communication terminal A receives the confirmation packet, the communication terminal A sets the transmission suppression period T2 only when the data packet that has triggered the confirmation packet is not received.

  On the other hand, the communication terminal A receives a data packet not destined for its own terminal, sets the transmission suppression period T1, and then receives a confirmation packet returned in response to this data packet. Do not set T2.

  This is because the transmission suppression period T2 of the present embodiment is a predetermined constant value, and if the data packet length is short, the transmission suppression period T2 may be longer than necessary. Therefore, the communication terminal A solves this problem by giving priority to the transmission suppression period T1 calculated based on the packet length of the data packet over the transmission suppression period T2.

(Embodiment 4)
The multi-hop communication system of this embodiment has the same configuration as that of any of Embodiments 1 to 3. In addition, the same code | symbol is attached | subjected to the structure similar to Embodiment 1 thru | or 3, and description is abbreviate | omitted.

  In the present embodiment, a case where the communication terminal A permits transmission of a data packet from its own terminal even during the transmission suppression period T1 will be described.

  In FIG. 11 and FIG. 12, the communication terminal A1 (first communication terminal) transmits a data packet (first data packet) destined for the communication terminal A2 (second communication terminal) (S11). The communication terminal A2 that has received the data packet returns a confirmation packet to the communication terminal A1 (S12), and transfers the data packet to the communication terminal A3 (third communication terminal) (S13). The communication terminal A3 that has received the data packet returns a confirmation packet to the communication terminal A2 (S14). In FIG. 11, each range in which packets transmitted by the communication terminals A1 and A2 reach is defined as communication ranges H1 and H2. The communication terminal A1 may be either the source terminal that first transmitted the data packet or the relay terminal that transfers the data packet.

  And communication terminal A4, A5 (4th communication terminal) exists in the communication range H1 of communication terminal A1. The communication terminals A4 and A5 receive the data packet destined for the communication terminal A2 from the communication terminal A1, and refer to the first relay presence / absence information and the first relay time information included in the data packet, A transmission suppression period T1 is set.

  That is, the communication terminals A4 and A5 set the transmission suppression period T1 by the data packet transmitted by the communication terminal A1. However, even if the communication terminals A4 and A5 are the data packet (second data packet) whose destination is the communication terminal A1 even during the transmission suppression period T1, the transmission of the data packet is permitted. The communication terminals A4 and A5 may be either a transmission source terminal that first transmits a data packet or a relay terminal that transfers the data packet.

  Even if the communication terminals A4 and A5 are the data packet whose transmission destination is the communication terminal A1 even in the transmission suppression period T1, the reason for permitting transmission of this data packet is as follows. First, it is clear that the next hop of the communication terminal A2 that relays the data packet from the communication terminal A1 is not the communication terminal A1 (if the next hop of the communication terminal A2 is the communication terminal A1, the communication route is Communication terminal A1 → communication terminal A2 → communication terminal A1). That is, the communication terminal A1 does not need to receive the data packet transferred by the communication terminal A2. The communication terminals A4 and A5 that have received the data packet transferred by the communication terminal A1 refer to the header information such as the transmission destination address and the transmission source address of the MAC frames FL1 and FL11 shown in FIGS. Judgment is possible. At this time, the communication terminals A4 and A5 do not need to refer to the header information of the upper layer such as the area F23 of the upper frame FL2 shown in FIGS.

  Therefore, the communication terminals A4 and A5 permit the transmission of the data packet if the transmission destination is the data packet whose communication destination is the communication terminal A1, even in the transmission suppression period T1. At this time, in the communication terminal A1, the data packet (first data packet) transferred from the communication terminal A2 to the communication terminal A3 and the data packet (second data packet) transmitted from the communication terminals A4 and A5 to the communication terminal A1. There is a risk of collision. However, if the signal strength of the second data packet is stronger than the signal strength of the first data packet, the communication terminal A1 can receive the second data packet.

  11 and 12, the communication terminal A4 transmits a data packet (second data packet) having the communication terminal A1 as a transmission destination during the transmission suppression period T1. Note that the communication terminal A4 cancels the transmission suppression period T1 when the transmission of the data packet having the communication terminal A1 as the transmission destination is permitted.

  Therefore, since the communication terminal A4 can transmit a data packet to the specific communication terminal A (communication terminal A1) even during the transmission suppression period T1, the spatial channel utilization efficiency is improved and the network transmission efficiency is improved. Is further improved.

  Further, the communication terminal A6 exists within the communication range H2 of the communication terminal A2. The communication terminal A6 receives the confirmation packet returned from the communication terminal A2 to the communication terminal A1, and refers to the second relay presence / absence information and the second relay time information included in the data packet to set the transmission suppression period T2. Set.

(Embodiment 5)
The multi-hop communication system of this embodiment has the same configuration as that of any of Embodiments 1 to 3. In addition, the same code | symbol is attached | subjected to the structure similar to Embodiment 1 thru | or 3, and description is abbreviate | omitted.

  In the present embodiment, a case where the communication terminal A permits transmission of a data packet from its own terminal even during the transmission suppression period T1 will be described.

  First, in FIG. 13, the communication terminal A1 (first communication terminal) transmits a data packet (first data packet) destined for the communication terminal A2 (second communication terminal) (S21). The communication terminal A2 that has received the data packet returns a confirmation packet to the communication terminal A1 (S22), and transfers the data packet to the communication terminal A3 (third communication terminal) (S23). The communication terminal A3 that has received the data packet returns a confirmation packet to the communication terminal A2 (S24). In FIG. 13, the ranges in which the packets transmitted by the communication terminals A1 and A2 reach are communication ranges H1 and H2. The communication terminal A1 may be either the source terminal that first transmitted the data packet or the relay terminal that transfers the data packet.

  And communication terminal A4, A5 exists in the communication range H1 of communication terminal A1. The communication terminals A4 and A5 receive the data packet destined for the communication terminal A2 from the communication terminal A1, and refer to the first relay presence / absence information and the first relay time information included in the data packet, A transmission suppression period T1 is set.

  In the present embodiment, the data packet includes not only the address information of the destination communication terminal A but also the address information of the destination communication terminal A to which the destination communication terminal A relays the data packet. That is, in FIG. 13, the data packet transmitted by the communication terminal A1 includes not only the address information of the destination communication terminal A2, but also the address information of the destination communication terminal A3 to which the communication terminal A2 relays the data packet. In this case, transfer destination address information (in this case, communication terminal A3) by the destination communication terminal A may be added to the header of the MAC frame FL1 shown in FIG. 6 or the MAC frame FL11 shown in FIG. Alternatively, the communication terminal A may recognize the transfer destination (in this case, the communication terminal A3) by the destination communication terminal A with reference to the area F23 (FIGS. 6 and 9) of the upper frame FL2.

  Further, the communication terminal A holds an adjacent terminal address table TB3 storing address information of adjacent terminals of the own terminal (see FIG. 14).

  Then, the communication terminal A4 (fourth communication terminal) during the transmission suppression period T1 is based on the data packet received from the communication terminal A1, and the data packet is transmitted along the route of the communication terminal A1 → the communication terminal A2 → the communication terminal A3. Recognize that it will be transferred. Furthermore, the communication terminal A4 during the transmission suppression period T1 recognizes the adjacent terminal with reference to the adjacent terminal address table TB3.

The communication terminal A4 during the transmission suppression period T1
(1) The communication terminal A3 is not an adjacent terminal.
(2) The next-hop communication terminal A5 (fifth communication terminal) that is the transmission destination of the data packet (second data packet) transmitted by the terminal itself is different from the communication terminals A2 and A3.
When the conditions (1) and (2) are all satisfied, the transmission of the data packet with the communication terminal A5 as the transmission destination is permitted. The communication terminal A4 permitted to transmit cancels the transmission suppression period T1 and transmits a data packet having the communication terminal A5 as a transmission destination (S25). The communication terminal A4 may be either a transmission source terminal that first transmits a data packet or a relay terminal that transfers the data packet.

  Accordingly, since the communication terminal A4 during the transmission suppression period T1 can transmit data packets to the communication terminals A other than the communication terminal A1, the spatial channel utilization efficiency is further improved, and the network transmission efficiency is further improved.

  If the communication terminal A4 during the transmission suppression period T1 does not satisfy the conditions (1) and (2) and there is a possibility of collision with a packet transmitted and received by the communication terminal A3, the communication terminal A4 continues the transmission suppression period T1. Therefore, communication reliability is also improved.

  For example, as shown in FIG. 15, it is assumed that the communication terminal A3 is an adjacent terminal of the communication terminal A4. In this case, when a data packet (second data packet) destined for the communication terminal A5 is transmitted from the communication terminal A4, the data packet (first data packet) transferred from the communication terminal A2 to the communication terminal A3 There may be a collision. In this case, the communication terminal A3 may not be able to receive the first data packet. In the present embodiment, the communication terminal A4 during the transmission suppression period T1 permits the transmission of the second data packet only when it can be determined that such a packet collision does not occur. It is possible to increase the use efficiency.

(Embodiment 6)
The multi-hop communication system of this embodiment has the same configuration as that of any of Embodiments 1 to 3. In addition, the same code | symbol is attached | subjected to the structure similar to Embodiment 1 thru | or 3, and description is abbreviate | omitted.

  In the present embodiment, a case where the communication terminal A permits transmission of a data packet from its own terminal even during the transmission suppression period T1 will be described.

  First, in FIG. 16, the communication terminal A1 (first communication terminal) transmits a data packet (first data packet) destined for the communication terminal A2 (second communication terminal) (S31). The communication terminal A2 that has received the data packet returns a confirmation packet to the communication terminal A1 (S32), and transfers the data packet to the communication terminal A3 (third communication terminal) (S33). The communication terminal A3 that has received the data packet returns a confirmation packet to the communication terminal A2 (S34). In FIG. 16, each range in which packets transmitted by communication terminals A1 and A2 reach is defined as communication ranges H1 and H2. The communication terminal A1 may be either the source terminal that first transmitted the data packet or the relay terminal that transfers the data packet.

  And communication terminal A4, A5 exists in the communication range H1 of communication terminal A1. The communication terminals A4 and A5 receive the data packet destined for the communication terminal A2 from the communication terminal A1, and refer to the first relay presence / absence information and the first relay time information included in the data packet, A transmission suppression period T1 is set.

  In the present embodiment, the data packet includes not only the address information of the destination communication terminal A but also the address information of the destination communication terminal A to which the destination communication terminal A relays the data packet. That is, in FIG. 16, the data packet transmitted by the communication terminal A1 includes not only the address information of the destination communication terminal A2, but also the address information of the destination communication terminal A3 to which the communication terminal A2 relays the data packet.

  Further, the communication terminal A holds an adjacent terminal address table TB3 storing address information of adjacent terminals of the own terminal (see FIG. 14). Furthermore, the communication terminal A also holds a 2-hop terminal address table TB4 that stores address information of a 2-hop terminal that is a communication terminal A with which each of the adjacent terminals of the terminal itself can directly communicate (see FIG. 17).

  The method of collecting the address information of the 2-hop terminal by the communication terminal A can be realized, for example, by storing each of the communication terminals A by storing the adjacent terminal address table TB3 in a routing protocol HELLO packet or the like. In this case, the communication terminal A can recognize the 2-hop terminal based on the adjacent terminal address table TB3 of each adjacent terminal. Note that the method for collecting the address information of the two-hop terminal is a well-known technique and will not be described in detail.

  Then, the communication terminal A4 (fourth communication terminal) during the transmission suppression period T1 is based on the data packet received from the communication terminal A1, and the data packet is transmitted along the route of the communication terminal A1 → the communication terminal A2 → the communication terminal A3. Recognize that it will be transferred. Furthermore, the communication terminal A4 during the transmission suppression period T1 refers to the adjacent terminal address table TB3, recognizes the adjacent terminal, and refers to the 2-hop terminal address table TB4 to recognize the 2-hop terminal.

The communication terminal A4 during the transmission suppression period T1
(1) The communication terminal A3 is not an adjacent terminal.
(2) The next-hop communication terminal A5 (fifth communication terminal) that is the transmission destination of the data packet (second data packet) transmitted by the terminal itself is different from the communication terminals A2 and A3.
(3) Direct communication is not possible between the communication terminal A2 and the communication terminal A5 (that is, the communication terminal A2 is not a two-hop terminal via the communication terminal A5 as viewed from the communication terminal A4).
When all the conditions (1) to (3) are satisfied, transmission of a data packet having the communication terminal A5 as a transmission destination is permitted. The communication terminal A4 permitted to transmit cancels the transmission suppression period T1 and transmits a data packet having the communication terminal A5 as a transmission destination (S35). The communication terminal A4 may be either a transmission source terminal that first transmits a data packet or a relay terminal that transfers the data packet.

  Accordingly, since the communication terminal A4 during the transmission suppression period T1 can transmit data packets to the communication terminals A other than the communication terminal A1, the spatial channel utilization efficiency is further improved, and the network transmission efficiency is further improved.

  Further, the communication terminal A4 during the transmission suppression period T1 does not satisfy the conditions (1) to (3), and if there is a possibility that the communication terminal A2 collides with a data packet transferred to the communication terminal A3, the transmission is performed. Since transmission suppression is performed by continuing the suppression period T1, communication reliability is also improved.

  For example, FIG. 18 shows a case where direct communication is possible between the communication terminal A2 and the communication terminal A5. The communication terminal A2 transfers the data packet received from the communication terminal A1 to the communication terminal A3, and the data packet transferred from the communication terminal A2 can be received not only by the communication terminal A3 but also the communication terminal A5 (S33). At this time, when a data packet destined for the communication terminal A5 is transmitted from the communication terminal A4 (S35), the data packet transferred from the communication terminal A2 collides with the data packet transmitted from the communication terminal A4. There is a fear. In this embodiment, such a packet collision can be avoided.

  Further, as in the fifth embodiment, the packet collision shown in FIG. 15 can be avoided.

(Embodiment 7)
The multi-hop communication system of the present embodiment has the same configuration as that of the sixth embodiment. In addition, the same code | symbol is attached | subjected to the structure similar to Embodiment 6, and description is abbreviate | omitted.

  In this embodiment, even if direct communication is possible between the communication terminal A2 and the communication terminal A5 in the sixth embodiment, the communication terminal A4 during the transmission suppression period T1 permits transmission of data packets from the own terminal. The case will be described.

  First, the communication terminal A holds an adjacent terminal information table TB5 that stores address information of adjacent terminals of the own terminal and communication quality information between the own terminal and each of the adjacent terminals (see FIG. 20). Further, the communication terminal A obtains the address information of the 2-hop terminal, which is the communication terminal A to which each of the adjacent terminals of the own terminal can directly communicate, and the communication quality information between each of the adjacent terminals and each of the 2-hop terminals. The stored 2-hop terminal information table TB6 is also held (see FIG. 21).

  In FIG. 19, it is assumed that direct communication is possible between the communication terminal A2 and the communication terminal A5 (that is, the communication terminal A2 becomes a two-hop terminal via the communication terminal A5 when viewed from the communication terminal A4). ).

  In this case, the communication terminal A4 during the transmission suppression period T1 recognizes the communication quality between the own terminal and the communication terminal A5 with reference to the adjacent terminal information table TB5. Further, the communication terminal A4 during the transmission suppression period T1 refers to the 2-hop terminal information table TB6 and recognizes the communication quality between the communication terminal A5 and the communication terminal A2. The communication terminal A4 during the transmission suppression period T1 communicates if the communication quality between the terminal itself and the communication terminal A5 is better than a certain level than the communication quality between the communication terminal A5 and the communication terminal A2. The transmission of the data packet destined for the terminal A5 is permitted. The communication terminal A4 permitted to transmit cancels the transmission suppression period T1 and transmits a data packet having the communication terminal A5 as a transmission destination (S35). That is, when there is a possibility that the packets on the two communication paths collide with each other, the communication terminal A4 determines that a communication path with a good communication quality is more likely to succeed.

  For example, the communication quality value SQ is used as the communication quality in FIGS. The communication quality value SQ is represented by an integer value such as 10 steps or 20 steps that becomes smaller as the received signal strength between the two communication terminals A-A capable of direct communication becomes larger. That is, as the communication quality value SQ is smaller, the communication packet is less attenuated and the communication state is better. In this case, if the communication quality value SQ between the communication terminal A4 and the communication terminal A5 is smaller than the communication quality value SQ between the communication terminal A5 and the communication terminal A2, the communication terminal A5 Permit transmission of data packets whose destination is.

  Thus, even if the communication terminal A4 during the transmission suppression period T1 can directly communicate between the communication terminals A2 and A5, the communication between the communication terminals A4 and A5 may be successful based on the communication quality. When it is determined that the data is high, the transmission of the data packet destined for the communication terminal A5 is permitted.

  Therefore, even if the communication terminal A4 during the transmission suppression period T1 can directly communicate between the communication terminals A2 and A5, the data packet can be transmitted to the communication terminal A5, and the spatial channel utilization efficiency is further improved.

  For example, when the communication terminal A5 is located closer to the communication terminal A2 than the communication terminal A4 (broken line in FIG. 19), the communication quality between the communication terminal A5 and the communication terminal A2 is the communication terminal A4 and the communication terminal A5. Communication quality between and will be better. In this case, the communication terminal A4 during the transmission suppression period T1 continues the transmission suppression period T1, and prohibits transmission of data packets whose destination is the communication terminal A5.

(Embodiment 8)
The multi-hop communication system of the present embodiment has the same configuration as that of the fifth embodiment. In addition, the same code | symbol is attached | subjected to the structure similar to Embodiment 5, and description is abbreviate | omitted.

  First, the communication terminal A performs the following operation when transmission of a data packet is permitted from its own terminal even during the transmission suppression period T1.

  The packet transmission sequence of the communication terminal A is transmitted after the transmission sequence starts (the packet transmission is permitted) and a predetermined transmission waiting time elapses. This transmission waiting time is a fixed waiting time (Inter Frame Space) or a random contention window, and is used to suppress packet collision in the CSMA / CA system.

  Then, the communication terminal A (normal communication terminal A) not in the transmission suppression period T1 transmits a packet after a relatively long normal transmission waiting time T11 (first transmission waiting time) has elapsed.

  On the other hand, when the transmission of the data packet is permitted, the communication terminal A during the transmission suppression period T1 transmits the packet after a relatively short transmission waiting time T12 (second transmission waiting time) has elapsed. This transmission waiting time T12 is set to a time shorter than the normal transmission waiting time T11.

  The operation of this embodiment will be described with reference to FIGS.

First, the communication terminal A4 during the transmission suppression period T1, as in the fifth embodiment,
(1) The communication terminal A3 is not an adjacent terminal.
(2) The next-hop communication terminal A5 (fifth communication terminal) that is the transmission destination of the data packet (second data packet) transmitted by the terminal itself is different from the communication terminals A2 and A3.
When the conditions (1) and (2) are all satisfied, the transmission of the data packet with the communication terminal A5 as the transmission destination is permitted. The communication terminal A4 permitted to transmit cancels the transmission suppression period T1 and transmits a data packet having the communication terminal A5 as a transmission destination (S25).

  At this time, the communication terminal A4 uses a transmission waiting time T12 that is shorter than usual when transmitting a data packet whose destination is the communication terminal A5. Therefore, the communication terminal A4 can transmit a data packet whose destination is the communication terminal A5 at a timing earlier than usual.

  On the other hand, the communication terminal A2 transfers the data packet received from the communication terminal A1 to the communication terminal A3 using the normal transmission waiting time T11. The data packet transferred from the communication terminal A2 can be received not only by the communication terminal A3 but also by the communication terminal A5.

  Therefore, in the communication terminal A5, a data packet (first data packet) transferred from the communication terminal A2 to the communication terminal A3 and a data packet (second data packet) transmitted from the communication terminal A4 to the communication terminal A5 are used. A collision occurs. However, if the signal strength of the second data packet is sufficiently high and the reception of the second data packet is started first, the communication terminal A5 can demodulate the second data packet without any problem. On the other hand, if the communication terminal A5 detects the first data packet first and starts receiving the second data packet with high signal strength, the bit error occurs frequently and the first data As a result, the packet cannot be normally received, and the second data packet cannot be received.

  However, since the transmission waiting time T12 of the communication terminal A4 is shorter than the transmission waiting time T11 of the communication terminal A2, the communication terminal A5 receives the data packet transmitted by the communication terminal A4 before the data packet transferred by the communication terminal A2. The possibility of receiving increases. That is, when the communication terminal A4 during the transmission suppression period T1 permits transmission of a data packet whose destination is the communication terminal A5, the probability of successful transmission of this data packet increases, and the spatial channel utilization efficiency increases. Will be improved.

  In the fourth and seventh embodiments as well, when the communication terminal A during the transmission suppression period T1 is permitted to transmit the data packet, the communication terminal A transmits the packet after the short transmission waiting time T12 elapses. An effect can be obtained.

(Embodiment 9)
In the multi-hop communication system of the present embodiment, the communication terminal A that sets a short transmission waiting time T12 is further limited from that of the eighth embodiment. This is because if a different transmission waiting time is set for each communication terminal A, communication of the communication terminal A with a short transmission waiting time is likely to succeed, which is undesirable from the viewpoint of fairness of the communication opportunity. The purpose is to secure. Note that the present embodiment will be described below with reference to FIG. 22 as in the eighth embodiment.

  In this embodiment, the data packet includes not only the address information of the destination communication terminal A but also the address information of the destination communication terminal A to which the destination communication terminal A relays the data packet (see Embodiment 6). ).

  Further, the communication terminal A holds an adjacent terminal address table TB3 storing address information of adjacent terminals of the own terminal (see FIG. 14). Furthermore, the communication terminal A also holds a 2-hop terminal address table TB4 that stores address information of a 2-hop terminal that is a communication terminal A with which each of the adjacent terminals of the terminal itself can directly communicate (see FIG. 17).

  Then, the communication terminal A4 (fourth communication terminal) during the transmission suppression period T1 is based on the data packet received from the communication terminal A1, and the data packet is transmitted along the route of the communication terminal A1 → the communication terminal A2 → the communication terminal A3. Recognize that it will be transferred. Furthermore, the communication terminal A4 during the transmission suppression period T1 refers to the adjacent terminal address table TB3, recognizes the adjacent terminal, and refers to the 2-hop terminal address table TB4 to recognize the 2-hop terminal.

The communication terminal A4 during the transmission suppression period T1
(1) The communication terminal A3 is not an adjacent terminal.
(2) The next-hop communication terminal A5 (fifth communication terminal) that is the transmission destination of the data packet (second data packet) transmitted by the terminal itself is different from the communication terminals A2 and A3.
When the conditions (1) and (2) are all satisfied, the transmission of the data packet with the communication terminal A5 as the transmission destination is permitted. The communication terminal A4 permitted to transmit cancels the transmission suppression period T1 and transmits a data packet having the communication terminal A5 as a transmission destination (S25).

  At this time, when transmitting a data packet destined for the communication terminal A5, the communication terminal A4 determines whether or not to use a transmission waiting time T12 that is shorter than usual, as follows.

  First, the communication terminal A4 determines whether or not direct communication is possible between the communication terminal A2 and the communication terminal A5 (that is, the communication terminal A2 has two hops through the communication terminal A5 as viewed from the communication terminal A4). Whether it is a terminal or not. And communication terminal A4 will set long transmission waiting time T11, if direct communication is impossible between communication terminal A2 and communication terminal A5. In addition, the communication terminal A4 sets a short transmission waiting time T12 if direct communication is possible between the communication terminal A2 and the communication terminal A5.

  In FIG. 22, when a data packet destined for the communication terminal A5 is transmitted from the communication terminal A4 (S25), the data packet transferred from the communication terminal A2 collides with the data packet transmitted from the communication terminal A4. There is a risk of doing. However, in this embodiment, if direct communication is not possible between the communication terminal A2 and the communication terminal A5, the communication terminal A4 sets the normal transmission waiting time T11, assuming that such packet collision does not occur. And maintain fairness in communication opportunities.

  On the other hand, if direct communication is possible between the communication terminal A2 and the communication terminal A5, the communication terminal A4 sets a short transmission waiting time T12 and assumes that there is a possibility that such packet collision may occur. Improve success probability.

(Embodiment 10)
In the multi-hop communication system of this embodiment, the communication terminal A that sets a short transmission waiting time T12 is further limited from that of the ninth embodiment. Note that the present embodiment will be described below with reference to FIG. 22 as in the ninth embodiment.

  In this embodiment, the data packet includes not only the address information of the destination communication terminal A but also the address information of the destination communication terminal A to which the destination communication terminal A relays the data packet (see Embodiment 6). ).

  Further, the communication terminal A holds an adjacent terminal information table TB5 that stores address information of adjacent terminals of the own terminal and communication quality information between the own terminal and each of the adjacent terminals (see FIG. 20). Further, the communication terminal A obtains the address information of the 2-hop terminal, which is the communication terminal A to which each of the adjacent terminals of the own terminal can directly communicate, and the communication quality information between each of the adjacent terminals and each of the 2-hop terminals. The stored 2-hop terminal information table TB6 is also held (see FIG. 21).

  Then, the communication terminal A4 (fourth communication terminal) during the transmission suppression period T1 is based on the data packet received from the communication terminal A1, and the data packet is transmitted along the route of the communication terminal A1 → the communication terminal A2 → the communication terminal A3. Recognize that it will be transferred. Further, the communication terminal A4 during the transmission suppression period T1 refers to the adjacent terminal information table TB5 to recognize the adjacent terminal, and refers to the 2-hop terminal information table TB6 to recognize the 2-hop terminal.

The communication terminal A4 during the transmission suppression period T1
(1) The communication terminal A3 is not an adjacent terminal.
(2) The next-hop communication terminal A5 (fifth communication terminal) that is the transmission destination of the data packet (second data packet) transmitted by the terminal itself is different from the communication terminals A2 and A3.
When the conditions (1) and (2) are all satisfied, the transmission of the data packet with the communication terminal A5 as the transmission destination is permitted. The communication terminal A4 permitted to transmit cancels the transmission suppression period T1 and transmits a data packet having the communication terminal A5 as a transmission destination (S25).

  At this time, when transmitting a data packet destined for the communication terminal A5, the communication terminal A4 determines whether or not to use a transmission waiting time T12 that is shorter than usual, as follows.

  First, the communication terminal A4 determines whether or not direct communication is possible between the communication terminal A2 and the communication terminal A5 (that is, the communication terminal A2 has two hops through the communication terminal A5 as viewed from the communication terminal A4). Whether it is a terminal or not. Then, if direct communication is not possible between the communication terminal A2 and the communication terminal A5, the communication terminal A4 sets a long transmission waiting time T11 to maintain the fairness of the communication opportunity.

  Moreover, if the communication terminal A4 can directly communicate between the communication terminal A2 and the communication terminal A5, the communication terminal A4 switches the transmission waiting times T11 and T12 based on the communication quality information.

  Specifically, the communication terminal A4 can directly communicate between the communication terminal A2 and the communication terminal A5, and the communication quality between the communication terminal A4 and the communication terminal A5 is the communication terminal A2 and the communication terminal A5. If the communication quality is not better than a certain level, a long transmission waiting time T11 is set to maintain the fairness of the communication opportunity.

  In addition, the communication terminal A4 can directly communicate between the communication terminal A2 and the communication terminal A5, and the communication quality between the communication terminal A4 and the communication terminal A5 is between the communication terminal A2 and the communication terminal A5. If the communication quality is better than a certain level, a short transmission waiting time T12 is set.

  That is, when there is a possibility that the packets on the two communication paths collide with each other, the communication terminal A4 determines that a communication path with a good communication quality is more likely to succeed. And even if communication terminal A4 in transmission suppression period T1 can communicate directly between communication terminal A2 and communication terminal A5, the communication quality between communication terminal A4 and communication terminal A5 is favorable. If it is determined, a short transmission waiting time T12 is set to further improve the communication success probability.

  In each of the above embodiments, the communication terminal A may constitute a PLC network that is a communication network constructed using the power line carrier communication technology, and in this case, the same effect as described above can be obtained.

A1 communication terminal (first communication terminal)
A2 communication terminal (second communication terminal)
A3 communication terminal (third communication terminal)
A4 communication terminal (fourth communication terminal)

Claims (15)

In a multi-hop communication system in which multiple communication terminals construct a communication route and perform multi-hop communication,
The first communication terminal transmits the first data packet to the second communication terminal of the next hop to which the first data packet is transmitted,
The first data packet includes first relay presence / absence information indicating whether or not the first data packet is transferred from the second communication terminal to the third communication terminal, and the second communication terminal. Includes first relay time information for determining a first transfer time required for the process of transferring the first data packet,
When the fourth communication terminal that is not the transmission destination of the first data packet by the first communication terminal receives the first data packet, based on the first relay presence / absence information, If the second data packet is transferred from the second communication terminal, the second data packet is transmitted from the own terminal until the first transfer required time elapses based on the first relay time information. Submit to the suppression of,
If the transmission destination of the second data packet is the first communication terminal in a period during which the transmission of the second data packet is suppressed, the fourth communication terminal is the second data packet. A multi-hop communication system characterized by permitting transmission of . In a multi-hop communication system in which multiple communication terminals construct a communication route and perform multi-hop communication,
Each of the plurality of communication terminals stores information for identifying an adjacent terminal that is the communication terminal capable of direct communication with the own terminal,
The first communication terminal transmits the first data packet to the second communication terminal of the next hop to which the first data packet is transmitted,
The first data packet includes first relay presence / absence information indicating whether or not the first data packet is transferred from the second communication terminal to the third communication terminal, and the second communication terminal. Includes first relay time information for determining a first transfer time required for the process of transferring the first data packet,
When the fourth communication terminal that is not the transmission destination of the first data packet by the first communication terminal receives the first data packet, based on the first relay presence / absence information, If the second data packet is transferred from the second communication terminal, the second data packet is transmitted from the own terminal until the first transfer required time elapses based on the first relay time information. The transmission of
The first data packet includes information for identifying the third communication terminal,
The fourth communication terminal that has received the first data packet has the third communication terminal connected to the neighboring terminal of the fourth communication terminal in a period during which transmission of the second data packet is suppressed. If the fifth communication terminal of the next hop that is the transmission destination of the second data packet is different from the second and third communication terminals, the fifth communication terminal is the transmission destination. features and to luma Ruchihoppu communication system to permit the transmission of the second data packet. Each of the plurality of communication terminals stores information for identifying a two-hop terminal that is the communication terminal with which each of the adjacent terminals can directly communicate, and when transmission of the data packet is permitted, Send the data packet after the transmission waiting time of elapses,
The fourth communication terminal that has received the first data packet,
In a period during which transmission of the second data packet is suppressed, the third communication terminal is not the adjacent terminal of the fourth communication terminal, and is the next hop that is the transmission destination of the second data packet Different from the second and third communication terminals, the fifth communication terminal permits transmission of the second data packet with the fifth communication terminal as a transmission destination.
If direct communication is not possible between the second communication terminal and the fifth communication terminal, the transmission waiting time is set to the first transmission waiting time,
If direct communication is possible between the second communication terminal and the fifth communication terminal, the transmission waiting time is set to a second transmission waiting time shorter than the first transmission waiting time. The multi-hop communication system according to claim 2 . Each of the plurality of communication terminals includes information for identifying a 2-hop terminal that is the communication terminal with which each of the adjacent terminals can directly communicate, and communication quality between the own terminal and each of the adjacent terminals And communication quality information indicating communication quality between each of the adjacent terminals and each of the two-hop terminals, and when transmission of the data packet is permitted, after a predetermined transmission waiting time has elapsed, Send data packets,
The fourth communication terminal that has received the first data packet,
In a period during which transmission of the second data packet is suppressed, the third communication terminal is not the adjacent terminal of the fourth communication terminal, and is the next hop that is the transmission destination of the second data packet Different from the second and third communication terminals, the fifth communication terminal permits transmission of the second data packet with the fifth communication terminal as a transmission destination.
If direct communication is not possible between the second communication terminal and the fifth communication terminal, the transmission waiting time is set to the first transmission waiting time,
Direct communication is possible between the second communication terminal and the fifth communication terminal, and the communication quality between the fourth communication terminal and the fifth communication terminal is the second communication. If the communication quality between the terminal and the fifth communication terminal is not better than a certain level, the transmission waiting time is set to the first transmission waiting time,
Direct communication is possible between the second communication terminal and the fifth communication terminal, and the communication quality between the fourth communication terminal and the fifth communication terminal is the second communication. If the communication quality between the terminal and the fifth communication terminal is better than a certain level, the transmission waiting time is set to a second transmission waiting time shorter than the first transmission waiting time. The multi-hop communication system according to claim 2 . In a multi-hop communication system in which multiple communication terminals construct a communication route and perform multi-hop communication,
Each of the plurality of communication terminals includes information for identifying an adjacent terminal that is the communication terminal capable of direct communication with the own terminal, and two hops each of the adjacent terminals is the communication terminal capable of direct communication Information for identifying the terminal,
The first communication terminal transmits the first data packet to the second communication terminal of the next hop to which the first data packet is transmitted,
The first data packet includes first relay presence / absence information indicating whether or not the first data packet is transferred from the second communication terminal to the third communication terminal, and the second communication terminal. Includes first relay time information for determining a first transfer time required for the process of transferring the first data packet,
When the fourth communication terminal that is not the transmission destination of the first data packet by the first communication terminal receives the first data packet, based on the first relay presence / absence information, If the second data packet is transferred from the second communication terminal, the second data packet is transmitted from the own terminal until the first transfer required time elapses based on the first relay time information. The transmission of
The fourth communication terminal that has received the first data packet has the third communication terminal connected to the neighboring terminal of the fourth communication terminal in a period during which transmission of the second data packet is suppressed. And the fifth communication terminal of the next hop that is the transmission destination of the second data packet is different from the second and third communication terminals, and the second communication terminal and the fifth communication If it is impossible to directly communicate with the terminal, the fifth feature and to luma Ruchihoppu communication system to permit the transmission of said second data packets to the destination communication terminal. Each of the plurality of communication terminals stores communication quality information indicating communication quality between the own terminal and each of the adjacent terminals and communication quality between each of the adjacent terminals and each of the two-hop terminals. And
Even though the fourth communication terminal can directly communicate between the second communication terminal and the fifth communication terminal, the fourth communication terminal is between the fourth communication terminal and the fifth communication terminal. If the communication quality is better than the communication quality between the second communication terminal and the fifth communication terminal by a certain level or more, the second data packet having the fifth communication terminal as a transmission destination The multi-hop communication system according to claim 5, wherein transmission of the network is permitted . Each of the plurality of communication terminals transmits the data packet after a predetermined transmission waiting time elapses when transmission of the data packet is permitted,
The fourth communication terminal shortens the transmission waiting time when transmission of the second data packet is permitted during a period in which transmission of the second data packet is suppressed. The multi-hop communication system according to claim 1, 2 or 6 . The multi-hop communication system according to any one of claims 1 to 7 , wherein the first relay time information indicates the first required transfer time . The multihop communication system according to any one of claims 1 to 7 , wherein the first relay time information is information used to calculate the first transfer required time . The second communication terminal, after receiving the first data packet, returns a confirmation packet to the first communication terminal,
The confirmation packet includes second relay presence / absence information indicating whether or not the first data packet that triggered the confirmation packet is transferred from the second communication terminal to the third communication terminal. , Second relay time information defining a second transfer required time required for the process of transferring the first data packet by the second communication terminal,
When each of the plurality of communication terminals receives the confirmation packet and determines that the first data packet is transferred from the second communication terminal based on the second relay presence / absence information, The multi-hop according to any one of claims 1 to 9 , wherein transmission of a data packet is suppressed until the second required transfer time elapses based on the second relay time information. Communications system. The second communication terminal, after receiving the first data packet, returns a confirmation packet to the first communication terminal,
The confirmation packet includes second relay presence / absence information indicating whether or not the first data packet that triggered the confirmation packet is transferred from the second communication terminal to the third communication terminal. Including
When each of the plurality of communication terminals receives the confirmation packet and determines that the first data packet is transferred from the second communication terminal based on the second relay presence / absence information, The multi-hop communication system according to any one of claims 1 to 9 , wherein transmission of a data packet is suppressed for a certain period of time . When the fourth communication terminal receives the first data packet from the first communication terminal and then receives the confirmation packet returned from the second communication terminal to the first communication terminal, The transmission suppression of the second data packet based on the first relay presence / absence information is executed, and the transmission suppression of the second data packet based on the second relay presence / absence information is not executed. 11. The multi-hop communication system according to 11 . In a multi-hop communication method in which each of a plurality of communication terminals establish a communication route with each other and perform multi-hop communication,
The first communication terminal transmits the first data packet to the second communication terminal of the next hop to which the first data packet is transmitted,
The first data packet includes first relay presence / absence information indicating whether or not the first data packet is transferred from the second communication terminal to the third communication terminal, and the second communication terminal. Includes first relay time information for determining a first transfer time required for the process of transferring the first data packet,
When the fourth communication terminal that is not the transmission destination of the first data packet by the first communication terminal receives the first data packet, based on the first relay presence / absence information, If the second data packet is transferred from the second communication terminal, the second data packet is transmitted from the own terminal until the first transfer required time elapses based on the first relay time information. The transmission of
If the transmission destination of the second data packet is the first communication terminal in a period during which the transmission of the second data packet is suppressed, the fourth communication terminal is the second data packet. features and to luma Ruchihoppu communication method that allow the transmission. In a multi-hop communication method in which each of a plurality of communication terminals establish a communication route with each other and perform multi-hop communication,
Each of the plurality of communication terminals stores information for identifying an adjacent terminal that is the communication terminal capable of direct communication with the own terminal,
The first communication terminal transmits the first data packet to the second communication terminal of the next hop to which the first data packet is transmitted,
The first data packet includes first relay presence / absence information indicating whether or not the first data packet is transferred from the second communication terminal to the third communication terminal, and the second communication terminal. Includes first relay time information for determining a first transfer time required for the process of transferring the first data packet,
When the fourth communication terminal that is not the transmission destination of the first data packet by the first communication terminal receives the first data packet, based on the first relay presence / absence information, If the second data packet is transferred from the second communication terminal, the second data packet is transmitted from the own terminal until the first transfer required time elapses based on the first relay time information. Submit to the suppression of,
The first data packet includes information for identifying the third communication terminal,
The fourth communication terminal that has received the first data packet has the third communication terminal connected to the neighboring terminal of the fourth communication terminal in a period during which transmission of the second data packet is suppressed. If the fifth communication terminal of the next hop that is the transmission destination of the second data packet is different from the second and third communication terminals, the fifth communication terminal is the transmission destination. A multi-hop communication method characterized by permitting transmission of a second data packet . In a multi-hop communication method in which each of a plurality of communication terminals establish a communication route with each other and perform multi-hop communication,
Each of the plurality of communication terminals includes information for identifying an adjacent terminal that is the communication terminal capable of direct communication with the own terminal, and two hops each of the adjacent terminals is the communication terminal capable of direct communication Information for identifying the terminal,
The first communication terminal transmits the first data packet to the second communication terminal of the next hop to which the first data packet is transmitted,
The first data packet includes first relay presence / absence information indicating whether or not the first data packet is transferred from the second communication terminal to the third communication terminal, and the second communication terminal. Includes first relay time information for determining a first transfer time required for the process of transferring the first data packet,
When the fourth communication terminal that is not the transmission destination of the first data packet by the first communication terminal receives the first data packet, based on the first relay presence / absence information, If the second data packet is transferred from the second communication terminal, the second data packet is transmitted from the own terminal until the first transfer required time elapses based on the first relay time information. The transmission of
The fourth communication terminal that has received the first data packet has the third communication terminal connected to the neighboring terminal of the fourth communication terminal in a period during which transmission of the second data packet is suppressed. And the fifth communication terminal of the next hop that is the transmission destination of the second data packet is different from the second and third communication terminals, and the second communication terminal and the fifth communication When direct communication with the terminal is impossible, transmission of the second data packet with the fifth communication terminal as a transmission destination is permitted.
And a multi-hop communication method.

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