JP2007019574A - Radio ad hoc communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce waste of energy of an entire network by improving efficiency of power, finding of flooding in an ad hoc network, and preventing useless data relay transmission and data discard. <P>SOLUTION: A radio node grasps positions of radio nodes near its own station, and continuously relays transmission data with directivity in the direction of a transmission destination node. The radio node also transmits ACK for the transmission data, for example, in non directivity, and gives priority of relay to a radio node having transmitted the ACK at first priority. If receiving the same transmission data, the radio node prevents an endless loop of relay by not relaying the received data. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a wireless communication network system including a plurality of wireless transmission / reception devices (hereinafter referred to as wireless nodes). More particularly, the present invention relates to a data relay method in an ad hoc network including a battery-powered wireless node.

  In a wireless communication network system, a plurality of wireless nodes within a communicable range transmit and receive data to and from each other. Each wireless node relays data from another wireless node to another wireless node at a certain time. In addition, each wireless node becomes a transmission source node at a certain time, and transmits data to the transmission destination node while utilizing other wireless nodes as relay nodes.

  As described above, the wireless node autonomously constructs a network having a flexible topology in accordance with the communication environment at each time, and forms a so-called ad hoc network as needed. In such an ad hoc net, when a wireless node wishes to transmit data, it searches for a nearby wireless node that is within the reach of its own radio wave and transmits the data. By repeating this relay operation, data is transmitted to the target wireless node. At this time, a data transmission delay occurs for each relay, and the power of the wireless node in charge of the relay is also consumed. For this reason, it is advantageous from the viewpoint of transmission delay and power consumption if the route to the target wireless node is selected so as to have the minimum number of relays. For this reason, various methods have been devised for obtaining the optimum relay route in an ad hoc network.

  For example, there is a method in which route control information is transmitted and received between wireless nodes over a wide area and an optimum route is selected from a plurality of acquired route information. The route control information includes inquiry information for searching for a route, route information for the inquiry, and the like. This method is called a flooding method because routing information is distributed throughout the ad hoc network like a flood to search for a route.

  Examples of conventional flooding methods include the methods described in Patent Document 1 and Patent Document 2. Patent Document 1 discloses a method in which wireless nodes are arranged so that service areas of the wireless nodes overlap, and relay transmission is performed one after another by broadcast transmission.

  FIG. 11 shows a communication state of the conventional wireless ad hoc communication method described in Patent Document 2.

  In the wireless network system shown in FIG. 11, data is transmitted from the transmission source node N1 to the transmission destination node N2 by ad hoc communication. Data is relayed and transmitted via relay nodes Na, Nb and the like. A concentric circle drawn around each wireless node is an electric field intensity distribution indicating a service area of each wireless node, and indicates that communication with other wireless nodes in the service area is possible.

The transmission source node N1 broadcasts a connection request message, which is a type of routing control information, in a state of unknown destination prior to data transmission. However, the address of the destination node as the final destination is described in the connection request message. Since the relay node Na and the relay node Nb exist in the service area of the transmission source node N1, the connection node receives the connection request message, and similarly broadcasts the connection request message while the destination is unknown, Relay transmission toward the next wireless node. By repeating these series of procedures, the connection request message finally reaches the target transmission destination node N2. Similarly for the return path, an ad hoc communication path is established by transmitting a connection response message, which is a kind of path control information, from the transmission destination node N2 to the transmission source node N1. At this time, which path is finally set as the communication path is determined based on the capability information of each wireless node collected at the time of transmission of the forward connection request message.
JP-A-8-97821 JP 2004-48478 A

  In the conventional configuration as described above, route determination in an ad hoc network is performed by route discovery by flooding route control information. For this reason, it is necessary to broadcast the route control information in all directions, and there is a problem that power efficiency and discovery efficiency are poor.

  Further, in order to determine the optimum path, it is necessary to detect the capability state of each wireless node and transmit the capability state information at the same time in the process of transmitting the route control information. Therefore, there is a problem that the processing procedure in each wireless node becomes complicated.

  Furthermore, since broadcast transmission is performed in all directions, relay transmission by broadcast propagates in the opposite direction to the destination node. The propagated route control information may be eventually discarded due to time out or data life expiration. That is, there is a problem that the electric power energy required for transmitting a lot of the routing information is wasted.

  An object of the present invention is to solve the conventional problems as described above, and to improve the power efficiency and path discovery efficiency of each wireless node in relaying data between wireless nodes. Another object of the present invention is to simplify the procedure for finding the optimum relay path. It is another object of the present invention to suppress wasteful data relay transmission and data discard and reduce energy waste of the entire network system.

In order to solve the above problems, the present invention 1 provides wireless communication performed by a wireless communication system that transmits transmission data from a transmission source node to a transmission destination node via another node (hereinafter referred to as a relay node) by wireless communication. Provide a method. The method includes the following steps.
A position storing step in which each node stores the direction of all or part of other nodes centered on its own station and the identifiers of the other nodes in association with each other;
A transmission step in which the transmission source node transmits transmission data including the identifier of the transmission destination node toward the transmission destination node stored in the position storage step;
The relay node that has received the transmission data specifies the direction of the transmission destination node stored in the location storing step based on the identifier of the transmission destination node included in the transmission data received, and A relay step for transmitting transmission data.

  Since all the wireless nodes including the transmission source node and the relay node recognize the direction of the transmission destination node viewed from the own station in advance, the transmission data is broadcasted in that direction. Since the transmission data to be transmitted includes a destination node identifier such as a destination address, the intermediate relay node specifies the direction of the destination node based on the destination identifier, and the direction of the destination node Send transmission data to broadcast. By repeating this, transmission data can be propagated to a target transmission destination node with low power.

  According to a second aspect of the present invention, in the first aspect, in the transmission step, the transmission source node includes the transmission destination node identifier, an identifier of the own station as a preceding node identifier, a transmission source node identifier, and the transmission source node There is provided a wireless communication method for transmitting transmission data including an identification code having a data identifier assigned to the transmission data. In the relay step of this method, the relay node rewrites the previous-stage node identifier in the identification code included in the received transmission data with the identifier of the own station and transmits it.

  In the configuration of the present invention, since the transmission destination node identifier is included in the transmission data, when the transmission destination node receives the transmission data, it can be detected that the transmission data is addressed to the own station.

  Since the transmission data always includes the preceding node identifier, the identification code has a unique value for each relay. Therefore, it is possible to avoid duplication with other transmission data having different relay nodes. Here, the upstream node is a node on the upstream side when viewed from the node that has received the transmission data. In the transmission data transmitted from the transmission source node, the identifier of the transmission source node itself is described as the identifier of the preceding node.

  In addition, if the transmission data includes the identifier of the transmission source node, the transmission destination node can transmit the final reception notification to the transmission source node.

  Furthermore, a plurality of transmission data from the same transmission source to the same transmission destination individually have a unique identification code by the data identifier given by the transmission source node. Therefore, it is possible to avoid duplication of transmission data in one node.

Invention 3 provides the wireless communication method according to Invention 2, further comprising the following steps.
A reception notification step in which the first relay node among the relay nodes that has received the transmission data transmits the reception notification of the transmission data toward a range wider than the transmission range of the transmission data;
A first relay stop step in which a second relay node other than the first relay node stops the execution of the relay step in response to receiving the reception notification from the first relay node.

  The relay node transmits data normal reception notification and abnormal reception notification in a direction of 360 degrees, for example. Thus, by relaxing the directivity of the transmission of the reception notification as compared with the transmission data, priority can be claimed to other relay nodes that have received the same transmission data. This is because the other relay nodes Nb, Nc... That have received the reception notification from the relay node Na stop relaying transmission data.

  A fourth aspect of the present invention provides the wireless communication method according to the third aspect, wherein, in the reception notification step, the first relay node transmits a reception notification including an identification code in the transmission data received by the local station. In the first relay stop step of this method, the second relay node compares the identification code in the transmission data received by the local station with the identification code in the reception notification received by the local station in the past, The execution of the relay step is stopped based on the comparison result.

  When the relay node that has received the transmission data (Na, N2) including the preceding node identifier Na and the transmission destination node identifier N2 receives a reception notification including the same identifier (Na, N2), the transmission data (Na, N2) Stop relaying. This is because other relay nodes relay transmission data. Therefore, congestion of the same transmission data by a plurality of relay nodes can be prevented. Even if transmission data relayed in the past is received again from a different route, it is possible to prevent relaying again. Therefore, even if the relay node fails to receive a reception response and the route branches in the middle of the relay and the same transmission data is relayed again, duplicate relay can be prevented. As a result, useless data relay can be suppressed.

A fifth aspect of the present invention provides the wireless communication method according to the second aspect, further including the following steps.
Whether any node that has received the transmission data is transmission data addressed to the own station based on the destination node identifier included in the identification code in the received transmission data and the identifier of the own station Judgment step to judge,
A second relay stop step in which the node stops executing the relay step when it is determined in the determination step that the transmission data is addressed to the own station;

  When it is detected that the transmission destination node that has received the transmission data is transmission data addressed to the own station, it is possible to reduce propagation of useless transmission data by interrupting further relaying.

A sixth aspect of the present invention provides the wireless communication method according to the second aspect, further including the following steps.
Whether any node that has received the transmission data is transmission data addressed to the own station based on the destination node identifier included in the identification code in the received transmission data and the identifier of the own station Judgment step to judge,
-If it is determined that the transmission data is addressed to the local station in the determination step, transmission is performed by rewriting the previous node identifier included in the identification code in the received transmission data with the identifier of the local station and transmitting a reception notification including the rewritten identification code. First response step,
A response relaying step in which an arbitrary node that has received the reception notification compares the preceding node identifier and the transmission destination node identifier in the identification code and, if they match, transmits a reception notification including the received identification code.

  When the transmission destination node identifier matches the preceding node identifier in the reception notification identification code transmitted by the transmission destination node, the relay node recognizes that the reception notification is from the transmission destination node. This reception notification reaches the transmission source node without rewriting the identification code. Therefore, the transmission source node can manage the success / failure of transmission for each data identifier.

  A seventh aspect of the present invention provides the wireless communication method according to the sixth aspect, wherein in the transmission destination response step and the response relay step, the reception notification is transmitted with directivity toward the transmission source node.

  By transmitting the reception notification relayed from the transmission destination node to the transmission source node with directivity in the direction of the transmission source node, the transmission of the reception notification from the transmission destination node is suppressed, The power of the entire system can be omitted.

  The present invention 8 provides the wireless communication method according to the first invention, wherein, in the transmission step, the transmission source node transmits transmission data including a relay upper limit number of times. In this method, in the relay step, the relay node transmits transmission data including a relay upper limit count that is one less than the relay upper limit count in the received transmission data. Further, in this method, an arbitrary node that has received the transmission data determines whether to further relay the received transmission data based on the relay upper limit number of times in the received transmission data, and according to the determination result It further includes a third relay stop step for stopping execution of the relay step.

  The source node can set a limit on the number of relays. For example, each wireless node monitors a relay history number that is subtracted every time it is relayed. If the relay history number of the received transmission data is “0”, further relaying is stopped. As a result, even if the reception response is missed in the relay process and the relay transmission is branched into a plurality of paths, it is possible to prevent the endless repeating of the relay by the limit of the number of relays. Further, even when the directional transmission cannot sufficiently perform depending on the radio wave condition, it is possible to prevent the relay from extending in the direction where the destination node does not exist and repeating the relay indefinitely. In that case, retransmission processing is performed due to timeout of the transmission source node.

  According to the ninth aspect of the present invention, in the first aspect, when the reception notification for the transmission data transmitted in the transmission step or the relay step is not within a predetermined time, each node transmits the transmission data until the reception notification for the transmission data is obtained. Provided is a wireless communication method further including an output adjustment step for gradually increasing an output.

  Even when there is no other wireless node in the service area of the local station, transmission data can be relayed and transmitted to the next station by increasing the transmission power and expanding the service area. Moreover, since the transmission power is gradually increased and the presence / absence of the reception notification is confirmed each time, transmission can be performed with the minimum necessary power, and the transmission power can be optimally set.

  If there is a reception notification, the amplified transmission output may be returned to normal. Optimal transmission power can be adjusted for each transmission. If the reception notification indicates abnormal reception, the transmission power may be increased immediately without performing timeout processing, and the transmission data may be retransmitted.

The present invention 10 provides a wireless node included in a wireless communication system that transmits transmission data from a transmission source node to a transmission destination node via another node (hereinafter referred to as a relay node) by wireless communication. This wireless node has the following means.
A position storage means for storing all or a part of other nodes when the local station is at the center and the identifiers of the other nodes in association with each other;
A transmission means for transmitting transmission data including an identifier of the transmission destination node toward the transmission destination node stored in the position storage means;
-When the transmission data is received, based on the identifier of the transmission destination node included in the transmission data received, the direction of the transmission destination node stored in the position storage means is specified, and the transmission data in that direction Relay means for transmitting.

  The wireless communication system including the wireless node executes the method of the first aspect and exhibits the above-described effects.

  According to the present invention, all wireless nodes including a transmission source node and a relay node perform broadcast transmission with increasing directivity toward a transmission destination node viewed from the own station. As a result, transmission data can be transmitted to a target transmission destination node with less power and a shorter communication path.

<First Embodiment>
Embodiments of the present invention will be described below with reference to the drawings.

(1) Outline of the Invention (1-1) Radio Communication System FIG. 1 is a configuration diagram of a radio communication system according to the first embodiment of the present invention. The wireless communication system 100 includes a plurality of wireless nodes N. In the following, for ease of explanation, data is transmitted by relaying other wireless nodes Na, Nb (hereinafter referred to as relay nodes) from the data transmission source node N1 to the transmission destination node N2. Take as an example. A communication path for data relay is formed as needed in an ad hoc network.

  In this system, transmission data transmitted from the transmission source node N1 is received / relayed by the relay node Na, received / relayed by the relay node Nb, and this is repeated to reach the final destination transmission destination node N2. This completes the transmission of the transmission data in the forward path. Similarly, on the return path, a normal response signal or an abnormal response signal (hereinafter sometimes collectively referred to as reception notification) from the transmission destination node N2 is relayed to the transmission source node N1 via the relay node. Thereby, one communication session is completed.

  Each wireless node has an antenna provided in multiple directions, transmits radio waves in multiple directions, and receives radio waves from multiple directions. In this embodiment, each wireless node has an antenna provided in the four directions of east, west, south, and north centering on its own station.

(1-2) Operation FIGS. 2 a to 2 f are explanatory diagrams illustrating the operation of the wireless communication system 100. First, as shown in FIG. 2a, the transmission source node N1 transmits transmission data having an ID code α (hereinafter simply referred to as transmission data α) in the direction of the transmission destination node N2. The direction of the destination node N2 has been learned by the position learning function described later. The ID code is an identifier that identifies transmission data in the entire wireless system. Details of the ID code will be described later. The transmission data α is received by a plurality of relay nodes Na and Np.

  In FIG. 2b, of the relay nodes Na and Np that have received the transmission data α, the relay node Na transmits a reception notification earlier than the relay node Np, for example, in all directions. In the figure, the normal response “ACK” is shown as the reception notification. This reception notification includes the same ID code α as the transmission data α (hereinafter referred to as reception notification α). By transmitting the reception notification over a wide range, the reception notification is transmitted to more relay nodes around the relay node Na. As a result, the relay node Na that has transmitted the reception notification promptly obtains the priority to relay the transmission data α to the other relay node Np that has received the same transmission data α. When the other relay node Np receives the reception notification from the relay node Na, the other relay node Np stops relaying the transmission data α. By this procedure, congestion of relay processing of transmission data α is prevented.

  As shown in FIG. 2c, the relay node Na transmits the transmission data in the direction of the transmission destination node N2. At this time, the ID code of the transmission data is rewritten from α to β. The transmission data β is simultaneously received by the relay nodes Nb, Nh, Nj.

  As shown in FIG. 2d, it is assumed that the relay node Nb first transmits the reception notification β among the relay nodes that have received the transmission data β. Then, the transmission data is further relayed by the relay node Nb, and the other relay nodes Nh and Nj stop relaying.

  FIG. 2e shows that the transmission data reaches the transmission destination node N2 from the relay node Ng by repeating the relay described above.

  In FIG. 2f, the transmission destination node N2 that has received the transmission data addressed to itself transmits a normal response signal (ACK in the figure) or an abnormal response signal (eg, NACK) in the direction of the transmission source node N1. The response signals are sequentially relayed and reach the transmission source node N1.

(2) Configuration of Radio Node FIG. 3 is a block diagram of the radio node in the first embodiment of the present invention. The wireless node includes the following configuration requirements.
(A) CPU 101: Controls each part of the wireless node and performs transmission / reception data processing. Details of the function of the CPU 101 will be described later.
(B) ROM 102: Stores a data processing program and a transmission / reception processing program. (C) RAM 103: Functions as a work memory of the CPU 101.
(D) Timer 104: Counts time.
(E) Battery 105: The power supply P1 is supplied to each unit including the CPU of the wireless node. The power supply P1 is an output of the battery 105, and is a line that constantly supplies power. The power source P1 is supplied to the receiving unit 110, the switching control unit 108, the switching unit 113, the incoming call detection unit 114, and the diversity antenna 109, and always supplies power to these parts that are necessary for radio wave reception. The wireless node N uses these parts to maintain a minimum reception state and receives signals from other wireless nodes. This state is called a sleep mode.
(F) Modulating unit 106: Modulates transmission data.
(G) Transmitter 107: High-frequency converts the IF signal.
(H) Switching control unit 108: Switches the connection of the diversity antenna 109 between the transmitting unit 107 and the receiving unit 110.
(I) Diversity antenna 109: Transmits and receives radio waves. In this example, the diversity antenna 109 is provided in four directions. With this configuration, the antenna directivity can be given to each of the four directions in the east, west, south, and north relationship with the wireless node N as the center. By using this configuration, it is possible to transmit radio waves aiming at the direction of the destination node.
(J) Receiving unit 110: Extracts the IF signal from the high frequency received signal.
(K) Demodulator 111: Regenerates received data by demodulating the IF signal.
(L) Switching unit 113: Switches the directivity of the diversity antenna. (M) Incoming call detection unit 114: Monitors the level of the IF signal S5 output from the receiving unit 110, and from other wireless nodes N using the same frequency band. Is detected and an incoming signal S10 is output.
(N) Power distribution unit 115: a power switch that switches and controls the output of the battery 105. The power supply P2 is output. The power source P2 is supplied to a portion other than the portion to which power is supplied by the power source P1. When there is an incoming call, the gate of the power distribution unit 115 is opened by the incoming signal S10 from the incoming call detection unit 114, and power is also supplied to the line of the power supply P2. This action drives all the wireless nodes. This state is called a full operation mode.

  The wireless node N having the above configuration operates as follows in the transmission mode and the reception mode. Further, in the transmission mode and the reception mode, the CPU 101 realizes functions to be described later.

(Transmission mode)
In the transmission mode, the CPU 101 executes a necessary program from a group of programs stored in the ROM 102 while using the RAM 103 as a work memory, and creates transmission data S1. The transmission data S1 is modulated into an IF signal S2 by the modulation unit 106, and the IF signal S2 is subjected to high-frequency conversion and power amplification by the transmission unit 107 into a high-frequency transmission signal S3. At this time, a channel number is designated to the transmission unit 107 by the channel selection signal S7 controlled by the CPU 101, and high-frequency conversion is performed at the frequency of the designated channel. Since different transmission numbers are used for different channel numbers, interference with other wireless network systems is avoided. The high-frequency transmission signal S3 is sent to the diversity antenna 109 by the switching control unit 108 and transmitted as a radio wave. The switching control unit 108 is set to the transmission mode by the transmission / reception switching signal S8. Further, the directivity of the transmission radio wave is designated by the antenna switching signal S9 designated by the CPU 101, and the switching unit 113 controls the diversity antenna 109 with the designated directivity.

(Reception mode)
On the other hand, in the reception mode, radio waves of other stations including other wireless nodes are received by the diversity antenna 109 and become a high frequency reception signal S4. The high frequency reception signal S4 is input to the reception unit 110 by the switching control unit 108 set to the reception mode by the RF switching signal S8. The receiving unit 110 tunes at the frequency of the channel specified by the channel selection signal S7 controlled by the CPU 101, and extracts the IF signal S5. The IF signal S5 is demodulated by the demodulator 111 to reproduce the received data S6, which is input to the CPU 101.

(CPU function)
In the transmission mode and the reception mode, the CPU 101 operates as follows. The CPU 101 selects a program stored in the ROM 102 as necessary. For example, a program for performing transmission data format processing, reception data analysis processing, and the like, and a wireless node system operation application program are stored in the ROM 102 as data processing programs. A transmission / reception processing program including communication procedures necessary for data transmission / reception, a processing program, and control of a high-frequency block from the modulation unit 106 to the demodulation unit 111 is stored in the ROM 102. The communication processing timing and other timings necessary for the CPU processing are calculated by the CPU 101 as necessary from the time measurement result obtained by performing the constant time processing by the timer 104, and the necessary timing is acquired.

  In communication, the CPU 101 adds an error correction code to the transmission data S1 by software processing, while performing error correction processing on the reception data S6. By this process, when the transmission line is in a radio wave state having a code error rate within the correction capability, error-free transmission / reception is performed. Thereby, the reliability of communication can be improved.

  Further, when no communication continues for a predetermined time or more, a sleep mode transition signal S11 is output from the CPU 101 to the power distribution unit 115. The power distribution unit 115 shuts off the power source P2 by the input of the sleep mode transition signal S11 and causes the wireless node N to transition to the sleep mode. In the sleep mode, if the switching control unit 108 is set to the reception state and the reception antenna is set to the omnidirectional state by the switching unit 113, incoming calls from all directions can be awaited. The wireless node N turns on the power of each part of the wireless node only during the relay operation for relaying transmission data and reception notifications from other nodes, and enters the sleep mode in the low power consumption state when the relay operation ends and a specified time elapses. enter. Thereby, the power consumption of the wireless node can be suppressed and the life of the battery 105 can be extended.

(3) Data Format Next, the data format of transmission data and reception notification transmitted by the wireless node N will be described.

(3-1) Transmission Data Format FIG. 4A is an example of a transmission data format for the wireless node to transmit transmission data. In the transmission data format, one packet has fields of (i) header code, (ii) ID code, (iii) relay history number, (iv) error correction code, and (v) data payload. Each field will be described below.

(I) Header code The header code further includes the following fields.

    (1) Preamble: Information for the PLL in the demodulator 111 of the receiving radio node to pull in the recovered clock.

    (2) Synchronization pattern: The motivation pattern indicates the head of byte alignment in serial bit data transmitted following the preamble. The synchronization pattern uses a unique word that does not normally appear in the received stream, such as a violation code, to reduce the probability of being misdetected by being emulated by other data words in the received stream. It is preferable to improve the detection accuracy.

    (3) Command field: When the type of transmission data and the content of the transmission data are control signals on the communication protocol, the control command type and the like are stored.

    (4) Data length: This indicates the length of the data combining the variable length data and the code accompanying the variable length data.

    (5) Error check code: Information for checking a code error in the header code. The frame header stores important data in terms of protocol such as commands and data length in the data reception processing of the wireless node. For this reason, in order to prevent malfunction due to transmission path code error, it is preferable to provide an error check code independently to improve reliability.

(Ii) ID code The ID code further includes the following fields. In this example, a network address is used as the identifier of the wireless node.

    (1) Relay address (corresponding to the preceding node identifier): The address of the wireless node that receives and transfers the transmission data, that is, the address of the wireless node that relays the transmission data. The relay address of the transmission data is rewritten to the own station address by the wireless node for each relay. Accordingly, since the ID code changes every relay, each ID code does not overlap with other ID codes that may exist with a time delay on the ad hoc network.

    (2) Destination address: Address of the destination wireless node N2. That is, the destination address of the transmission data.

    (3) Source address: Address of the source wireless node N1. That is, the transmission source address of transmission data.

    (4) Data number (corresponding to a data identifier): Information for identifying transmission data by a transmission source node. The transmission data is specified by combining the data number and the transmission source address. That is, all transmission data on the ad hoc network can be identified by a combination of a transmission source address and a data number.

(Iii) Relay history number In this embodiment, the relay history number is decremented each time transmission data is relayed. The initial value is set by the transmission source wireless node N1. Each wireless node N monitors the relay history number, and when the relay history number becomes “0” or less, it stops relaying more transmission data. As a result, the transmission source wireless node can set a limit on the number of relays, and it is possible to prevent the communication amount of the entire wireless network system from excessively increasing due to the relay of transmission data.

(Iv) Error correction code The error correction code is calculated for the ID code and the relay history number. By performing error correction and erasure correction, it is possible to improve the reliability of transmission of ID codes and relay history numbers that are important in ad hoc communication procedures. As the error correction code, a code exhibiting good error detection and correction performance for a random error of the code, such as a Reed-Solomon code, can be used.

(V) Data Payload The data payload is a data storage area that is open to the user. The user data is preferably subjected to an interleaving process. By doing so, even if a burst error occurs in the data code during transmission, if the interleaving is canceled on the receiving side, the burst error is dispersed into random errors. Note that the error correction code corresponding to the user data may be stored in the data payload together with the user data.

(3-2) Control Signal Format FIG. 4B is an example of a control signal format for transmitting a reception notification. The control signal format includes a header code, an ID code, a relay history number, and an error correction code. That is, the control signal format has a configuration in which the data payload and the error correction code are removed from the transmission data format. Control command types on the communication protocol, such as ACK, NACK, ENQ, etc., are stored in the command field. The wireless node N that has received the packet having the control signal format can determine the control command type by referring to the command field in the header code.

(4) Transition of ID Code FIG. 5 is an explanatory diagram showing the transition of the ID code in transmission data and reception notification. As shown in FIG. 4, the transmission data and the reception notification include an ID code. Now, the transition of the ID code when transmission data is relayed from the transmission source node N1 to the transmission destination node N2 via the relay node Na.

  In response to transmission data of the ID code α transmitted from the wireless node N1, that is, transmission data α, a reception notification of the ID code α, that is, a reception notification α is returned from the wireless node Na. Next, the wireless node Na rewrites the ID code α to β and transmits transmission data β. In this way, the transmission data propagates through the relay node while rewriting the ID code, and finally reaches transmission destination node N2 as transmission data γ.

  The transmission destination node N2 rewrites the ID code γ of the received transmission data with the ID code ε, and transmits a reception notification ε to the transmission source node N1. In the ID code ε, the relay address matches the transmission destination address. Therefore, the relay node N that has received the reception notification ε relays the reception notification ε as it is without rewriting the ID code ε. As a result, the reception notification ε from the transmission destination node N2 reaches the transmission source node N1 as it is. Therefore, the transmission source node N1 can determine whether or not the transmission destination node N2 has received normally. If the reception notification is a normal response signal, for example, “ACK”, the communication source node N1 completes the communication session. Conversely, when the destination node N1 receives an abnormal response signal, for example, “NACK”, the data number is updated and the transmission data is retransmitted.

  As described above, since the ID code includes the address of the transmission destination node N2, the transmission destination node N2 can discriminate transmission data addressed to itself and interrupt further relaying. Further, the transmission destination node N2 can transmit a reception notification to the transmission source node N1 toward the transmission source node using the transmission source address in the ID code. Further, since the relay code is included in the ID code of the transmission data, the ID code has a unique value for each relay, and at the same time, duplication with other ID codes existing on the wireless communication system can be avoided. Further, since the ID code includes a data number uniquely assigned by the transmission source node N1, it is possible to avoid duplication of a plurality of transmission data from the same transmission source in the relay process.

(5) Location Learning Function FIG. 6 is an explanatory diagram showing a location learning function executed by the CPU 101 of the wireless node N. FIG. 7 is an explanatory diagram illustrating the wireless node location learning process. In the position learning function, each wireless node N recognizes at which position the wireless node is located when viewed from its own station. For ease of explanation, a case where the transmission source node N1 learns the positions of surrounding wireless nodes is taken as an example.

  In FIG. 6A, there are nodes around the local station N1. The node N1 transmits inquiry signals in the four directions where the antenna is provided, that is, the “N direction”, the “S direction”, the “W direction”, and the “E direction”, centering on the own station.

  FIG. 6B is an explanatory diagram in which the wireless node that has received the inquiry signal transmits a response signal.

  FIG. 6C is a conceptual explanatory diagram of the position table 103a generated by position learning. The position table 103a is temporarily stored in the RAM 103. In the position table 103a, the address of the wireless node and its direction are stored in association with each other.

  FIG. 7 is an explanatory diagram showing an example of the flow of the position learning process. For example, the node N1 transmits an inquiry signal “ENQ” in the direction “E” (# 1). The node N1 receives the response signal ACK from the nodes Na and Nb that have received “ENQ” among the wireless nodes existing on the “E” side as viewed from the node N1 (# 2, # 3). At this time, the addresses of the wireless nodes Na and Nb that transmitted “ACK” are embedded in “ACK” corresponding to “ENQ”. The node N1 extracts the address embedded in “ACK” and registers it in the position table in association with “E direction” (# 4). Similarly, the wireless node N1 learns the presence of other wireless nodes in the W direction, N direction, and S direction, and registers them in the position table (# 5). Note that “ENQ” is relayed between wireless nodes. However, if the upper limit of the number of relays is set to a small number such as 1 to 2 to detect neighboring wireless nodes, more accurate location learning is possible. .

  As described above, after the wireless nodes learn the positions of the wireless nodes in the vicinity of the own station, each wireless node exchanges the position tables to construct a position table that covers the entire wireless communication system 100. Can do. Using this position table, the wireless node N can determine in which direction the radio wave should be transmitted based on the address of the destination node.

(6) Process Flow Next, the process flow performed by the wireless node N will be described with reference to the drawings. The wireless node roughly performs transmission processing and reception processing. The wireless node basically executes reception processing as a main routine, and performs transmission processing when called by the reception processing.

(6-1) Reception Processing FIG. 8 is a flowchart illustrating an example of the flow of reception processing performed by the wireless node. This process is started when the wireless node is activated.

  Steps S1 and S2: The wireless node N waits for reception of transmission data from other wireless nodes, and when receiving transmission data, proceeds to step S3. If a reception notification is received, the process proceeds to step S2, and a response relay processing subroutine described later is executed.

  Steps S3 to S6: The wireless node N detects an error in the received transmission data (S3). If an error is detected, the wireless node N switches the directivity direction of the diversity antenna 109 to non-directional by the switching unit 113 (S4). Further, the node N checks the presence / absence of a carrier in the wireless communication path (S5). That is, the communication bandwidth is checked. If a carrier is detected, it waits until it is not detected (S5), and transmits a retransmission request, for example, “NACK” (S6). Then, it returns to step S1 and waits for the arrival of transmission data.

  Step S7: If no error is detected in the transmission data, the wireless node N determines whether or not the ID code of the received transmission data matches the ID code of the normal response received in the past. If they match, it indicates that relaying has already been performed by another relay node. Therefore, the transmission data is discarded, the relay is terminated, and the process returns to step S1 to wait for transmission data. That is, useless transmission data relay can be suppressed. If the ID code of the received transmission data does not match the past normal response ID code, the process proceeds to step S8.

  Step S8: The node N refers to the relay history number of the received transmission data. If the relay history number is less than or equal to zero, the wireless node N determines that the transmission data has reached the relay limit, discards the transmission data, and aborts the relay. Then, it returns to step S1 and waits for transmission data.

  If the relay history number is greater than zero, the wireless node N determines that the transmission data can still be relayed, and proceeds to step S9.

  Step S9: The wireless node N checks for the presence of a carrier in the wireless communication path. That is, the communication bandwidth is checked. If a carrier is detected, it waits until it is not detected, and proceeds to step S10.

  Step S10: The wireless node N refers to the transmission destination address included in the ID code of the transmission data, and determines whether the transmission data is addressed to the own station. When the transmission destination address in the ID code matches the own station address, the process proceeds to step S11. If not, the process proceeds to step S14 described later.

  Steps S11 to S13: Since the transmission data is data addressed to the own station, the wireless node N processes the transmission data (S11). Thereafter, the switching unit 113 switches the directivity direction of the diversity antenna 109 to the direction of the transmission source node N1 (S12), rewrites the relay address of the ID code with the local address, and transmits a normal response signal (S13).

  Steps S14 to S16: If the relay address in the transmission data does not match the own station address, the transmission data is addressed to another node. Therefore, the wireless node N switches the diversity antenna 109 to non-directional (S14), and transmits a normal response “ACK” having the same ID code as the transmission data (S15). Thereafter, the transmission process is called (S16). This is to relay transmission data.

  Through the above processing, any of the wireless nodes N that have received the transmission data transmits a reception notification having the same ID code as the transmission data with a reduced directivity. As a result, the wireless node can claim priority for relaying the transmission data to other wireless nodes that have received the same transmission data. As a result, other wireless nodes that have received the reception notification stop relaying the transmission data. Therefore, congestion of the same transmission data by a plurality of relay nodes can be prevented. Further, for example, even if the relay node fails to receive a reception response and the route is branched in the middle of the relay and the transmission data with the same ID code is relayed again, the same transmission data can be prevented from being relayed again.

(6-2) Response Relay Processing Subroutine FIG. 9 is a flowchart showing an example of the processing flow of the response relay processing subroutine. The following process is started when the process proceeds to step S2 in the reception process.

  Step S21: The wireless node N determines whether or not a reception notification, that is, a normal response or an abnormal response has been received. If none has been received, the process returns to step S1 of the reception process and waits for the next transmission data or reception notification. If any one is received, the process proceeds to step S22.

  Step S22: The wireless node N refers to the ID code in the reception notification and determines whether or not the relay address matches the transmission destination address. That is, the wireless node N determines whether it is a reception notification from the transmission destination node N2 or a reception notification from another relay node. This is because the reception notification from the transmission destination node N2 needs to be relayed to another relay node.

  Step S23: The wireless node N switches the directivity direction of the diversity antenna 109 to the direction of the transmission source node N1 by the switching unit 113 (S23). This is to prevent useless propagation of the received signal from the transmission destination node N2 and to reach the transmission source node N1 through the shortest possible communication path.

  Step S24: The wireless node N checks for the presence of a carrier in the wireless communication path. That is, the communication bandwidth is checked. If a carrier is detected, it waits until it is not detected, and proceeds to step S25.

  Step S25: The wireless node N transmits a reception notification having the same ID code as the received ID code in the reception notification. As a result, the normal response or the abnormal response transmitted by the transmission destination node N2 reaches the transmission source node N1 while storing the ID code.

  The transmission source node N1 that has received the reception notification recognizes the reception notification from the transmission destination node N2 by referring to the ID code. Accordingly, the transmission source node N1 manages the success and failure of transmission for each data number, and can retransmit transmission data as necessary.

(6-3) Transmission Processing FIG. 10 is a flowchart illustrating an example of the flow of transmission processing performed by the wireless node N. The following process is started when this process is called in step S16 of the reception process.

  Step S31: The wireless node N updates the ID code of the transmission data received in the reception process. Specifically, the wireless node N rewrites the relay address with its own address, and subtracts “1” from the relay history number.

  Steps S32 to S33: The wireless node N reads the transmission destination address from the ID code of the received transmission data (S32). Further, the wireless node N refers to the position table 103a based on the transmission destination address, and specifies the direction of the transmission destination node N2 as viewed from its own station (S33). That is, the wireless node N determines which of the N direction, the E direction, the S direction, and the W direction is the direction of the transmission destination node N2 viewed from its own station.

  Step S34: The wireless node N switches the transmission antenna of the diversity antenna 109 by the switching unit 113 according to the specified direction.

  Steps S35 to S36: The wireless node N checks the presence or absence of a carrier in the wireless communication path, and waits until it is not detected if a carrier is detected. If no carrier is detected, new transmission data with a new header code, an updated ID code, and other necessary fields added to the data payload included in the received transmission data is generated and transmitted in the specified direction.

  Steps S37 to S39: After transmitting the transmission data, the wireless node N waits for a reception notification from another relay node N (S37). When a normal response, for example, “ACK” is received, it is considered that the transmission data has been successfully relayed, and the ID code of “ACK” is stored in the RAM 103 (S38). Furthermore, if the transmission output is higher than the normal value, it is returned to the normal value (S39). Thereafter, this process is terminated, and the process returns to the reception process for the next relay sequence. If a normal response can be received, the transmission power that has been raised is returned to normal, and the optimum power is adjusted for each transmission. Therefore, useless power consumption can be suppressed.

  Steps S310 to S311: The wireless node N waits for a normal response for a predetermined time and, if timed out (S310), strengthens the transmission output (S311). Thereafter, the process returns to step S35, and the transmission data is retransmitted with the increased transmission output (S36). Since the transmission output is gradually increased until a normal response is obtained, even if there is no other wireless node in the service area of the local station, the service area can be gradually expanded and the transmission data can be relayed to the next node. it can. Since the transmission power is gradually increased and the reception notification is confirmed each time, transmission can be performed with the minimum necessary power, and the transmission power can be optimally set.

  In the above processing, when an abnormal response, for example, “NACK” is received, the transmission power may be immediately increased without performing the timeout processing, and the retransmission processing of the transmission data may be performed.

  Using the above processing, the wireless node N broadcasts transmission data with increased directivity toward the transmission destination node viewed from the local station. Since the transmission data to be transmitted is given an ID code including the transmission destination address, the intermediate relay node can analyze the transmission destination address. Therefore, each relay node N relays transmission data toward the transmission destination node N2. As a result, the transmission data can reach the target transmission destination node N2 through a short communication path while reducing the power consumption of the entire wireless communication system.

  Further, even if transmission data having an ID code relayed in the past is received again from a different route, it is possible to prevent relaying again. By limiting the number of times of relaying, it is possible to prevent infinite number of repeated relays. Further, even when the directional transmission cannot sufficiently perform depending on the radio wave condition, it is possible to prevent the relay from extending in the direction where the destination node does not exist and repeating the relay indefinitely.

<Other embodiments>
(A) In FIG. 3 of the first embodiment, the modulation unit 106 and the demodulation unit 111 are illustrated as individual hardware blocks. However, these can also be realized by software processing in the CPU 101. .

  (B) Moreover, it is good also as a structure which replaces with the structure which switches transmission / reception frequency using channel selection signal S7, and operates by a fixed frequency. For a single small-scale wireless network system application, the frequency synthesizer and the tuning mechanism built in the channel selection signal S7, the transmission unit 107, and the reception unit 110 can be simplified.

  (C) Furthermore, the direction of the diversity antenna is not necessarily limited to four directions in which the space is equally divided. The number of directivity directions and directivity characteristics of the diversity antenna 109 can be determined from the balance between the cost of the wireless node and the detection accuracy required in the system.

  (D) If the supply part of the power supply P1 is extended to the demodulator 111 and the incoming call detector 114 monitors the received data S6, which is the output of the demodulator 111, and controls the power supply, a more accurate incoming call determination becomes possible . However, since the demodulator 111 generally requires a large amount of operating power, it is only necessary to determine the incoming call detection accuracy based on the balance with the battery life requirement from the system.

  (E) The ID code may be a mechanical number unique to each wireless node, such as a MAC address, instead of the address of each wireless node, or may be a free name assigned to each wireless node. . When a free name is used, a wireless node or server that links the free name of the wireless node and the mechanical unique number of the wireless node may be provided in the wireless communication system.

  (F) In data transmission on an antenna transmission path, if data transmission is performed after further interleaving processing and error correction coding processing are performed as outer code processing, communication reliability is improved. At this time, in the outer code processing, it is desirable that the encoding process is provided in the input stage of the modulation unit 106 and the decoding process is provided in the output stage of the demodulation unit 111. Further, if an error correction code having a performance effective against continuous code errors such as a convolutional code or a turbo code is used, the reliability of communication is further improved.

  The wireless communication method according to the present invention can be used for ad hoc communication processing by a battery-powered wireless node constituting a wireless communication system. Also, it can be applied to uses such as a sensor network system by wireless ad hoc communication.

The block diagram of the radio | wireless communications system in 1st Embodiment of this invention Explanatory drawing (1) which shows operation | movement of the radio | wireless communications system 100 Explanatory drawing which shows operation | movement of the radio | wireless communications system 100 (2). Explanatory drawing (3) which shows operation | movement of the radio | wireless communications system 100 Explanatory drawing which shows operation | movement of the radio | wireless communications system 100 (4). Explanatory drawing which shows operation | movement of the radio | wireless communications system 100 (5) Explanatory drawing which shows operation | movement of the radio | wireless communications system 100 (6) The block diagram of the radio | wireless node in 1st Embodiment (A) An explanatory diagram showing an example of a transmission data format for a wireless node to transmit transmission data. (B) An explanatory diagram showing an example of a control signal format for transmitting a reception notification. Explanatory drawing which shows transition of ID code in transmission data and reception notification (A) Explanatory diagram showing position learning function (1) (b) Explanatory diagram showing position learning function (2) (c) Conceptual explanatory diagram of a position table generated by position learning Explanatory drawing which shows an example of the flow of a position learning process The flowchart which shows an example of the flow of the reception process which a wireless node performs Flowchart showing an example of the processing flow of the response relay processing subroutine The flowchart which shows an example of the flow of the transmission process which a wireless node performs Explanatory drawing which shows the communication state of the conventional wireless ad hoc communication method

Explanation of symbols

100 wireless communication system 101 CPU
102 ROM
103 RAM
104 timer 105 battery 106 modulation unit 107 transmission unit 108 switching control unit 109 diversity antenna 110 reception unit 111 demodulation unit 113 switching unit 114 incoming detection unit 115 power distribution unit

Claims (10)

A wireless communication method performed by a wireless communication system that transmits transmission data from a transmission source node to a transmission destination node via another node (hereinafter referred to as a relay node) by wireless communication,
A position storing step in which each node stores the direction of all or part of other nodes when the own station is at the center and the identifiers of the other nodes in association with each other;
A transmission step in which the transmission source node transmits transmission data including an identifier of the transmission destination node toward the transmission destination node stored in the position storage step;
The relay node that has received the transmission data identifies the direction of the transmission destination node stored in the location storage step based on the identifier of the transmission destination node included in the received transmission data, and the transmission is performed in that direction. A relay step for transmitting data;
A wireless communication method including: In the transmission step, the transmission source node includes the transmission destination node identifier, an identifier of the local station as a preceding node identifier, a transmission source node identifier, and a data identifier that the transmission source node assigns to the transmission data; Transmitting transmission data including an identification code having
2. The wireless communication method according to claim 1, wherein, in the relay step, the relay node rewrites a previous-stage node identifier in an identification code included in the received transmission data with an identifier of the own station and transmits the same. . A reception notification step in which the first relay node among the relay nodes that has received the transmission data transmits the reception notification of the transmission data toward a range wider than the transmission range of the transmission data;
A first relay stop step in which a second relay node other than the first relay node stops the execution of the relay step in response to reception of the reception notification from the first relay node;
The wireless communication method according to claim 2, further comprising: In the reception notification step, the first relay node transmits a reception notification including an identification code in the transmission data received by the local station,
In the first relay stop step, the second relay node compares the identification code in the transmission data received by the local station with the identification code in the reception notification received by the local station in the past, Stop execution of the relay step based on:
The wireless communication method according to claim 3, wherein: Whether any node that has received the transmission data is transmission data addressed to the own station based on the destination node identifier included in the identification code in the received transmission data and the identifier of the own station A judgment step to judge;
If it is determined in the determination step that the transmission data is addressed to the own station, the node stops a second relay stop step for stopping the relay step;
The wireless communication method according to claim 2, further comprising: Whether any node that has received the transmission data is transmission data addressed to the own station based on the destination node identifier included in the identification code in the received transmission data and the identifier of the own station A judgment step to judge;
When it is determined that the transmission data is addressed to the local station in the determination step, the transmission destination that transmits the reception notification including the rewritten identification code by rewriting the previous node identifier included in the identification code in the received transmission data with the identifier of the local station A response step;
Any node that has received the reception notification compares the preceding node identifier and the transmission destination node identifier in the identification code, and if both match, a response relay step of transmitting the reception notification including the received identification code;
The wireless communication method according to claim 2, further comprising:   The wireless communication method according to claim 6, wherein in the transmission destination response step and the response relay step, the reception notification is transmitted with directivity toward the transmission source node. In the transmission step, the transmission source node transmits transmission data including the relay upper limit number of times,
In the relay step, the relay node transmits transmission data including a relay upper limit number that is one less than a relay upper limit number in the received transmission data;
An arbitrary node that has received the transmission data determines whether to further relay the received transmission data based on the relay upper limit count in the received transmission data, and executes the relay step according to the determination result. The wireless communication method according to claim 1, further comprising a third relay stop step of stopping.   Each node performs an output adjustment step for gradually increasing the transmission output of the transmission data until the reception notification for the transmission data is obtained when the reception notification for the transmission data transmitted in the transmission step or the relay step is not within a predetermined time. The wireless communication method according to claim 1, further comprising: A wireless node included in a wireless communication system that transmits transmission data from a transmission source node to a transmission destination node via another node by wireless communication,
A position storage means for storing all or a part of other nodes when the local station is at the center and an identifier of the other nodes in association with each other;
Transmission means for transmitting transmission data including an identifier of a transmission destination node toward the transmission destination node stored in the position storage means;
When the transmission data is received, based on the identifier of the transmission destination node included in the transmission data received, the direction of the transmission destination node stored in the position storage unit is specified, and the transmission data is set in that direction. A relay means for transmitting;
A wireless communication means including:

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