JP4156477B2 - Communication terminal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication terminal which efficiently performs broadcasting. <P>SOLUTION: A controller 7 detects a direction from a transmission source on the basis of a position of the transmission source and the present position of the own terminal. Moreover, the controller 7 detects in which region the own terminal locates on the basis of setting information, and at the same time, determines transmission timing of the broadcast from preference order of the detected region and a time slot waiting time T. And, the controller 7 rewrites position information in received broadcast data so as to show the present position on the basis of the present position of the own terminal. The controller 7 instructs broadcast of the received broadcast data to a transceiver 4 in the determined transmission timing, and the transceiver 4 which receives the instruction, modulates the broadcast data, and transmits to terminals around through an antenna 2. <P>COPYRIGHT: (C)2005,JPO&amp;NCIPI

Description

  The present invention relates to a communication terminal that performs a broadcast in which a terminal that has received information from another terminal transmits the information to all surrounding terminals in a wireless network.

  A multi-hop method is used to expand the communication range of a base station by relaying information transmitted from the base station to another terminal when there is a terminal that cannot directly communicate with the base station in a wireless network such as a cellular phone network. Called. This multi-hop method is also used in an ad hoc network in which communication is performed between terminals without going through a base station. In the multi-hop technique, a technique called flooding has been used for notification of control information and broadcast data (data transmitted to all terminals) to terminals.

  Flooding means that the sending terminal transmits broadcast data to all other terminals (broadcast), and all other terminals that receive the broadcast data repeat the transfer of the broadcast data. This is a method of distributing data to all terminals. 8 to 10 are diagrams showing a conventional flooding technique. FIG. 8 shows a state in which the transmission source terminal 10a transmits broadcast data. In FIG. 8, the range in which the terminal 10a can transmit data is indicated by a circle, and the terminals 10b to 10f within the circle receive this data.

  FIG. 9 shows a state in which the terminals 10b to 10f receiving data from the transmission source terminal 10a relay the data. Here, the terminals 10b to 10f are defined to exist at a position one hop away from the terminal 10a. At this time, for example, a terminal located in the middle of a plurality of relay terminals such as the terminal 10g and the terminal 10h cannot transmit a transmitted packet because transmission power from the plurality of relay terminals arrives almost simultaneously ( Packet collision). FIG. 10 shows a state in which the terminals 10i to 10k existing at a 2-hop position from the transmission source terminal 10a relay data. A terminal that cannot receive a packet due to a packet collision cannot relay a packet, and therefore, more terminals cannot receive a packet that should be received.

Patent Document 1 describes a method for specifying a message transmission path depending on the position of a node when the position of the node can be changed in an ad hoc network.
JP 2002-368789 A

  When a terminal performs flooding in a conventional wireless network, as described above, if terminal contention or packet collision increases in some relay terminals, the terminal that should originally perform relaying does not perform relaying, and eventually the packet arrival rate There was a problem of incurring deterioration. In addition, since all terminals that receive data broadcast in the same manner, there are more transmitting terminals than necessary, traffic in the network increases, and power is consumed even to terminals that do not need to relay packets. There was a problem.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a communication terminal that efficiently performs broadcasting.

  The present invention has been made to solve the above problems, and the invention according to claim 1 is a communication terminal that receives information broadcast from a transmission source and broadcasts the information to other communication terminals. A storage means for storing in advance setting information including a form of an area set around the transmission source and a transmission timing in the area; a receiving means for receiving the information broadcast from the transmission source; Position detecting means for detecting a position; area detecting means for detecting the area based on the position of the transmission source indicated by the position information added to the information and the current position detected by the position detecting means; Determination to determine the transmission timing of the information based on the area detected by the area detection means and the setting information in the storage means And a rewriting means for rewriting the position information in the information based on the current position, and a broadcast means for broadcasting the information at the transmission timing determined by the determination means. It is a terminal.

  According to a second aspect of the present invention, in the communication terminal according to the first aspect, the information broadcast from the transmission source includes the setting information, and the determination unit detects the region detected by the region detection unit. The transmission timing of the information is determined based on the setting information in the information.

  According to a third aspect of the present invention, in the communication terminal according to the first or second aspect, the area indicated by the setting information is set based on a direction from the transmission source. .

  According to a fourth aspect of the present invention, in the communication terminal according to any one of the first to third aspects, the distance from the transmission source is calculated based on the position of the transmission source and the current position. And a delay time determining means for determining a delay time according to the distance calculated by the calculating means, wherein the timing determining means is based on the region, the setting information, and the delay time. The transmission timing of the information is determined.

  According to a fifth aspect of the present invention, in the communication terminal according to any one of the first to third aspects, the distance from the transmission source is calculated based on the position of the transmission source and the current position. The broadcast means further stops broadcasting the information when the distance calculated by the calculation means is equal to or less than a specific value.

  The invention according to claim 6 is the communication terminal according to any one of claims 1 to 3, wherein the reception power detection means for detecting the reception power of the information received by the reception means; Delay time determining means for determining a delay time according to the received power detected by the received power detecting means, wherein the timing determining means is based on the region, the setting information, and the delay time. The information transmission timing is determined.

  The invention according to claim 7 further comprises reception power detection means for detecting the reception power of the information received by the reception means in the communication terminal according to any one of claims 1 to 3. The broadcast unit stops broadcasting the information when the reception power detected by the reception power detection unit is greater than or equal to a specific value.

  The invention according to claim 8 is the communication terminal according to any one of claims 1 to 7, wherein the information includes identification information unique to data, and a plurality of pieces of information are received by the receiving means. When the received identification information in the plurality of pieces of information is the same, the broadcast means stops broadcasting the plurality of pieces of information.

  According to a ninth aspect of the present invention, in the communication terminal according to any one of the first to eighth aspects, the information includes identification information unique to data, and a plurality of pieces of information are received by the receiving unit. When the identification information in the plurality of pieces of information received is the same, the information processing apparatus further includes a determination unit that determines whether or not the transmission source position indicated by the information is included in the region detected by the region detection unit. The broadcast unit stops broadcasting the information when the determination unit determines that the position of the transmission source indicated by the information is included in the region detected by the region detection unit. .

  According to a tenth aspect of the present invention, in the communication terminal according to any one of the first to ninth aspects, the transmission timing in the setting information is assigned to be different between adjacent areas. It is characterized by that.

According to the present invention, the region is divided in the direction centering on the transmission source, different transmission timings are assigned to each region, and the communication terminal broadcasts at different transmission timings for each region. As a result, an effect that broadcasting can be performed efficiently is obtained.
In addition, since communication terminals that received multiple identical packets stopped broadcasting the packets, the number of relay terminals increased, traffic in the network increased, and the power consumption of communication terminals that did not need to be relayed increased. The effect that it can suppress is also acquired.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration of a communication terminal according to an embodiment of the present invention. This communication terminal has a configuration corresponding to a GPS (Global Positioning System) receiver, and can detect a current position based on position information received from a GPS satellite.

  In FIG. 1, reference numeral 1 denotes a GPS antenna which receives position information from a GPS satellite and transmits it to the position detector 3. The antenna 2 receives broadcast data from other relay terminals or base stations and outputs it to the transmission / reception unit 4, and transmits broadcast data output from the transmission / reception unit 4 to other terminals. The position detection unit 3 detects the current position based on the position information acquired via the GPS antenna 1. The transmission / reception unit 4 modulates the transmission data and outputs it to the antenna 2, and demodulates the reception data received by the antenna 2.

  Reference numeral 5 denotes a storage unit that stores in advance setting information for performing flooding. This setting information includes information regarding the division type and the number of divisions, priority of each region, time slot waiting time T, and the like. The area division form indicates that the area is divided into a plurality of areas based on the direction from the transmission source. The priority of each area indicates the timing at which a terminal in the area broadcasts, which is set for each area. A reception level determination unit 6 determines the reception level of the signal received by the antenna 2. Reference numeral 7 denotes a control unit that controls the above-described units.

  Next, the first flooding method will be described. FIG. 2 is an example in which the area is divided every 90 degrees with the terminal serving as the broadcast transmission source as the center. The central terminal that is the source of broadcast data may be a base station. The circle centered on this terminal indicates the reach of transmission power transmitted by the terminal. Broadcast data broadcast from the terminal of the transmission source to all the surrounding terminals is received by the terminals existing in the areas A to D.

  Broadcast data transmitted by each terminal includes location information of the transmission source and a sequence number for identifying the data. The setting information in the storage unit 5 includes that the area is divided into four around the transmission source, that each area is identified as area A to area D by the direction seen from the transmission source, and each It is stipulated that the priority order of the areas is the order of area A, area B, area C, and area D. The setting information described above can also be included in the broadcast data. Moreover, the time slot waiting time T may be included in the broadcast data, and the time slot waiting time T in the setting information of each terminal may be changed by the time slot waiting time T in the broadcast data.

  When the transmission source terminal broadcasts broadcast data, the broadcast data is received by terminals existing in the areas A to D. In each terminal, broadcast data received by the antenna 2 is demodulated by the transmission / reception unit 4 and output to the control unit 7. The control unit 7 refers to the position information included in the broadcast data, detects the position of the terminal that is the data transmission source, and reads the setting information from the storage unit 5 for reference. The position detection unit 3 detects the current position based on the position information via the GPS antenna 1 and outputs the current position to the control unit 7. When the broadcast data includes setting information, the control unit 7 refers to the setting information in the broadcast data.

  The control unit 7 detects a direction based on the source terminal based on the position of the source terminal and the current position of the terminal, and the local terminal is located in any of the areas A to D based on the setting information. The broadcast transmission timing is determined from the priority of the detected area and the time slot waiting time T. Based on the current position of the terminal itself, the position information in the broadcast data is rewritten to indicate the current position. At the determined transmission timing, the control unit 7 instructs the transmission / reception unit 4 to broadcast the received broadcast data, and the transmission / reception unit 4 that has received the instruction modulates the broadcast data and directs it to surrounding terminals via the antenna 2. To send.

  In FIG. 2, assuming that the setting information is set so that flooding is performed in the order of area A, area B, area C, and area D, a terminal existing in area A first starts relaying (flooding). Then, when the time slot waiting time T has elapsed from this point, the terminal in the region B starts relaying. Furthermore, when the time slot waiting time T has elapsed from that point, the terminal in the area C starts relaying, and the terminal in the area D starts relaying in the same manner. Note that here, the delay time due to the difference in distance from the terminal of the transmission source to each terminal is ignored, and terminals in the same region perform broadcasting in the same time slot. The same applies to other examples described below. Assuming assumptions.

  3 to 5 show the flooding state of each terminal by the method described above. As shown in FIG. 3, the broadcast data broadcasted by the terminal 10a is received by the terminals 10b to 10f existing in the circle of FIG. Each terminal detects the direction from the terminal 10a, and determines the broadcast timing based on the setting information. FIG. 4 shows how the terminals 10b to 10f perform broadcasting. Since the terminals 10b to 10f broadcast in order at the transmission timings determined in each area, the packet collision is avoided in the terminals 10g and 10h in which packet collision has occurred in the conventional method shown in FIGS. Is done. FIG. 5 shows a state in which the terminals 10g to 10k existing at positions 2 hops from the terminal 10a perform broadcasting. Since packet collision is avoided, it can be seen that broadcast data is transmitted from all terminals existing at a 2-hop position from the terminal 10a.

  Note that the form and number of divisions of the areas and the broadcast priority set in each area are not limited to the above-described forms. For example, in FIG. 2, the transmission timings of the terminals in region A and region C may be the same, and the transmission timings of the terminals in region B and region D may be the same. In this case, for example, the terminals in the area A and the area C perform broadcasting, and then the terminals in the area B and the area D perform broadcasting. Further, when the number of divided areas is larger, the same transmission timing may be assigned to areas positioned so as to face each other by 180 degrees, or the same transmission timing may be assigned to areas that are not adjacent to each other.

  In addition, when the time slot waiting time T is very small, packet collision may occur. On the other hand, when the time slot waiting time T is very large, it takes time to transmit broadcast data far away. Although the waiting time T is preferably within a certain range, the packet collision can be sufficiently reduced only by making the timeslot waiting time T several times the packet time length.

  Next, the second flooding method will be described. The form of area division is as shown in FIG. 2, but each terminal further sets a delay time Tdelay_i in addition to the time slot waiting time T. For example, in each terminal that has received broadcast data broadcast by the transmission source, the control unit 7 calculates the distance from the transmission source terminal based on the current position of the transmission source terminal and its own terminal, and is inversely proportional to this distance. Thus, the delay time Tdelay_i is set. Alternatively, the reception level determination unit 6 detects the reception level of the broadcast data received by the transmission / reception unit 4 and outputs it to the control unit 7, and the control unit 7 sets the delay time Tdelay_i based on this reception level. Alternatively, the control unit 7 sets the delay time Tdelay_i based on both the distance and the reception level. Since the position information includes an error depending on the environment at the time of reception, the setting accuracy of the delay time can be improved by combining with the detection of the reception level.

  In FIG. 2, assuming that flooding is performed in the order of area A, area B, area C, and area D, each terminal in area A first receives broadcast data from the transmission source terminal. Relaying is started when the delay time Tdelay_i set in the terminal has elapsed. Subsequently, each terminal existing in the area B relays when the time slot waiting time T elapses from the time when the broadcast data is received, and when the delay time Tdelay_i set for each terminal in the area B elapses. To start. Thereafter, similarly, each terminal in region C and region D starts relaying.

  Next, the third flooding method will be described. FIG. 6 shows how the area is divided by the third method. The area is divided into eight areas, and among these, terminals in areas B, D, F and H (terminals within a certain distance from the transmission source terminal) relay received broadcast data. Not performed. Each terminal does not relay broadcast data when the distance from the transmission source terminal calculated from the position information of the transmission source terminal in the broadcast data and the position information acquired by the position detection unit 3 is a specific value or less. If the reception level of the broadcast data detected by the reception level determination unit 6 is equal to or higher than a specific value, it is determined not to relay the broadcast data.

  As a result, compared to the second method, the setting range of the delay time Tdelay_i in each terminal in the region A, the region C, the region E, and the region G can be reduced, and the time slot waiting time T can be reduced. . That is, the transmission delay time of broadcast data can be suppressed. In addition, the number of relay terminals can be limited.

  In the first to third flooding methods described above, the control unit 7 further monitors the sequence number in the broadcast data, and when broadcast data having the same sequence number is received, transmission of the broadcast data is performed thereafter. Cancel. Thereby, useless broadcast of the terminal can be avoided. Further, it may be determined whether the terminal broadcasts the broadcast data according to the area to which the transmission source belongs.

  For example, it is assumed that the areas are divided as shown in FIG. 2, the same transmission timing is assigned to areas A and C, and the same transmission timing is assigned to areas B and D. When a certain terminal receives broadcast data, the control unit 7 of the terminal refers to the sequence number in the broadcast data and determines whether or not it is the same as the sequence number of the broadcast data to be relayed.

  If the sequence numbers are the same, the control unit 7 further determines whether the position of the transmission source of the broadcast data received later is included in the area to which the own terminal belongs. When it is determined that the location of the transmission source is included in the area to which the terminal belongs, the control unit 7 instructs the transmission / reception unit 4 to cancel the broadcast, and the transmission / reception unit 4 cancels the broadcast of the broadcast data to be relayed from now on. To do.

  However, if a terminal receives broadcast data from a terminal in a different area from the terminal and the sequence number is the same as the sequence number of the broadcast data to be relayed, the broadcast data is broadcast. Do. In this way, for example, when the terminal exists only in the vicinity of the center in the area A, and broadcast data from the relay terminals in the area B and the area C reaches all the terminals in the area A, the area A It is possible to avoid the phenomenon that all the terminals in the broadcast stop broadcasting.

  Next, the fourth flooding method will be described. This is a technique for avoiding packet collisions by combining with conventional collision avoidance techniques such as CSMA / CA (Carrier Sense Multiple Access with Collision Avidance). In the present embodiment, this CSMA / CA will be described as an example. CAMA / CA is an access control method used for a wireless LAN, in which each terminal transmits a packet after confirming that the communication path is free for a certain time. The waiting time until each terminal transmits a packet is a predetermined time plus a random length of time.

  In FIG. 6, the reach of radio waves from a terminal that is a broadcast transmission source is represented by a circle. Let the radius of this circle be r, the terminal located at the left end of area A be terminal a, the terminal located at the right end of area A be terminal b, and the terminal located near the center of area A be terminal c. When the region is divided every 90 degrees as shown in FIG. 6, the distance between the left end and the right end of region A exceeds r, so that the radio wave from terminal a reaches terminal c but reaches terminal b. Will not reach.

  Terminals a, b, and c receive the broadcast data from the transmission source, and transmit this broadcast data when a further random time has elapsed from the transmission timing assigned to area A. If the transmission timing including random time is in the order of terminal a, terminal b, and terminal c, terminal a first transmits broadcast data. Assuming that the transmission delay time of broadcast data is sufficiently shorter than the random time, the terminal c can recognize that the terminal a has transmitted, but the terminal b cannot recognize that the terminal a has transmitted. . Then, the terminal b also transmits the broadcast data, and since the broadcast data reaches the terminal c from the terminals a and b, a packet collision occurs and the terminal c cannot recognize the broadcast data.

  On the other hand, when the region is divided every 60 degrees as shown in FIG. 7, the distance between the upper end and the lower end of region C is r, so that the radio wave from terminal a reaches terminal b and terminal c. If it demonstrates in the example similar to the example mentioned above, the terminal a will transmit broadcast data first. In this case, the terminal b and the terminal c can recognize that the terminal a has transmitted. Therefore, the terminal b recognizes that the terminal a has transmitted the broadcast data to be transmitted, and stops transmitting this broadcast data.

  As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to these embodiments, and includes design changes and the like without departing from the gist of the present invention. .

It is a block diagram which shows the structure of the communication terminal by one Embodiment of this invention. It is a figure which shows the area | region division by the 1st flooding method in the embodiment. It is a figure which shows the mode of the flooding of the terminal 10a by the 1st flooding method in the embodiment. It is a figure which shows the mode of the flooding of the terminals 10b-10f by the 1st flooding method in the embodiment. It is a figure which shows the mode of the flooding of the terminals 10g-10k by the 1st flooding method in the same embodiment. It is a figure which shows the area | region division by the 2nd flooding method in the embodiment. It is a figure which shows the area | region division by the 3rd flooding method in the embodiment. It is a figure which shows the mode of the flooding of the terminal 10a by the conventional flooding method. It is a figure which shows the mode of the flooding of the terminals 10b-10f by the conventional flooding method. It is a figure which shows the mode of the flooding of the terminals 10i-10k by the conventional flooding method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... GPS antenna, 2 ... Antenna, 3 ... Position detection part, 4 ... Transmission / reception part, 5 ... Memory | storage part, 6 ... Reception level determination part, 7 ... Control part

Claims (10)

In a communication terminal that receives information broadcast from a transmission source and broadcasts the information to other communication terminals,
Storage means for preliminarily storing setting information including a form of an area set according to a distance and a direction from the transmission source and transmission timing in the area;
Receiving means for receiving the information broadcast from the source;
Position detection means for detecting the current position;
Area detecting means for detecting the area based on the position of the transmission source indicated by the position information added to the information and the current position detected by the position detecting means;
Determining means for determining the transmission timing of the information based on the area detected by the area detecting means and the setting information in the storage means;
Rewriting means for rewriting the position information in the information based on the current position;
Broadcast means for broadcasting the information at the transmission timing determined by the determination means;
A communication terminal comprising: In a communication terminal that receives information broadcast from a transmission source and broadcasts the information to other communication terminals,
A receiving means for the include setting information including the transmission timing in accordance with the region of the distance and the area which is set in accordance with the direction from the source, receiving the information broadcast from the source,
Position detection means for detecting the current position;
Area detecting means for detecting the area based on the position of the transmission source indicated by the position information added to the information and the current position detected by the position detecting means;
Determining means for determining the transmission timing of the information based on the area detected by the area detecting means and the setting information in the information;
Rewriting means for rewriting the position information in the information based on the current position;
Broadcast means for broadcasting the information at the transmission timing determined by the determination means;
A communication terminal comprising:   The communication terminal according to claim 1 or 2, wherein the area indicated by the setting information is set based on a direction from the transmission source. Calculating means for calculating a distance from the transmission source based on the position of the transmission source and the current position;
Delay time determining means for determining a delay time according to the distance calculated by the calculating means;
The communication terminal according to any one of claims 1 to 3, wherein the timing determination unit determines a transmission timing of the information based on the area, the setting information, and the delay time. . Further comprising calculation means for calculating a distance from the transmission source based on the position of the transmission source and the current position;
4. The broadcast unit according to claim 1, wherein the broadcast unit stops broadcasting the information when the distance calculated by the calculation unit is equal to or less than a specific value. 5. Communication terminal. Received power detection means for detecting received power of the information received by the receiving means;
A delay time determining means for determining a delay time according to the received power detected by the received power detecting means;
The communication terminal according to any one of claims 1 to 3, wherein the timing determination unit determines a transmission timing of the information based on the area, the setting information, and the delay time. . Further comprising a received power detecting means for detecting a received power of the information received by the receiving means;
4. The broadcast device according to claim 1, wherein the broadcast unit stops broadcasting the information when the received power detected by the received power detection unit is a specific value or more. 5. The communication terminal described in 1. The information includes identification information unique to the data,
The plurality of pieces of information are received by the reception unit, and the broadcast unit stops broadcasting the plurality of pieces of information when the identification information in the plurality of pieces of information is the same. Item 8. The communication terminal according to any one of Item 7. The information includes identification information unique to the data,
Whether or not the transmission source position indicated by the information is included in the region detected by the region detection unit when a plurality of information is received by the reception unit and the identification information in the plurality of information is the same A determination means for determining;
The broadcast unit stops broadcasting the information when the determination unit determines that the position of the transmission source indicated by the information is included in the region detected by the region detection unit. The communication terminal according to any one of claims 1 to 7.   The communication terminal according to any one of claims 1 to 9, wherein the transmission timing in the setting information is assigned to be different between adjacent areas.

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