JP2006270914A - Sensor terminal, and control method of sensor terminal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform package data transmission to a neighboring sensor terminal, while reducing power consumption, in a sensor network constituted of a plurality of sensor terminals. <P>SOLUTION: By adopting a packet configuration in which identifiers are enumerated, a packet in which intensive processing was performed is transmitted and received. As a result, packets which must be originally transmitted separately can be bundled into one, so that power consumption of the sensor network system as a whole can be reduced. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sensor terminal and a sensor terminal control method, and more particularly to a sensor terminal and a sensor terminal control method for configuring a sensor network.

(General sensor network)
In order to realize a ubiquitous society where users can enjoy optimal services in various environments without any particular awareness, sensor networks composed of minute sensor terminals are being studied. These sensor terminals are installed in various places in the environment, and acquire various information such as user preferences and states, and environmental information. In addition, it is expected to be widely used in environments where it has been difficult to observe such as disaster sites and complex pipelines.

In the sensor network, a sensor terminal that collects information is referred to as “Sink”, and a sensor terminal that transmits information is referred to as “Source”. As control signals for wireless communication between sensor terminals, a transmission request signal is called an RTS (Request To Send) signal, a reception preparation completion signal is called a CTS (Clear To Send) signal, and an acknowledgment is called an ACK (Acknowledgment) signal.
An identifier different from the IP address and MAC address used in the IP network has been proposed for the identifier in the communication of the sensor terminal. With respect to identifiers (hereinafter referred to as end identifiers) of end-ends corresponding to IP addresses (that is, transmission terminals and reception terminals), attributes have been proposed to reduce the address setting load (see Non-Patent Document 1). Further, since the MAC address is redundant with 48 bits, a method of using a smaller bit length as an identifier between neighbors (hereinafter referred to as a neighbor identifier) has been proposed (see Non-Patent Document 2).

  When communication is actually performed using these identifiers in an existing sensor network, the address length and the like change, but a frame configuration close to the existing IP / MAC as shown in FIG. 16 is taken. The sensor packet shown in the figure includes a “recipient proximity identifier” and “sender proximity identifier” for 1-hop identification, and a “recipient end identifier” for end-end identification. And “sender end identifier” are added to the data. The sensor packet is transferred to the target sensor terminal while the neighborhood identifier is rewritten for each hop.

Here, the state of transmission of the sensor packet is shown in FIG. In the figure, two sensor terminals are indicated by solid circles. The number in each solid line circle is a neighborhood identifier of the sensor terminal.
In the figure, when data is sent from sensor A (Sensor A) to sensor B (Sensor B), sensor A receives the receiver proximity identifier “2” and the sender proximity identifier “1” for 1-hop identification, The sensor packet P11 is created by adding the sender end identifier “B” and the sender end identifier “A” to the data “DATA”.

When this sensor packet P11 is transmitted from the sensor A, the sensor C (Sensor C) adjacent to the sensor A receives it, and rewrites the receiver proximity identifier to “3” and the sender proximity identifier to “2”. A sensor packet P22 is created. When this sensor packet P22 is transmitted from the sensor C, the sensor D (Sensor D) adjacent to the sensor C receives it, and rewrites the receiver proximity identifier to “4” and the sender proximity identifier to “3”. A sensor packet P33 is created. When this sensor packet P33 is transmitted from the sensor D, the sensor B close to the sensor D receives it.
As described above, the sensor packet is transmitted with the neighborhood identifier rewritten for each hop.

(Wireless technology suitable for sensor networks)
As wireless technology suitable for sensor networks, various proposals have been made in consideration of power saving. SMAC achieves various power savings such as synchronization between neighboring sensors, Active / Sleep scheduling, communication only during Active, and completion of data transmission with one RTS signal / CTS signal. (Refer nonpatent literature 3).
The TMAC further shortens the active time by transmitting data in bursts, and if communication competes during active, explicitly specifying the communicable time to extend the sleep time and ensure communication reliability. (See Non-Patent Document 4).

William Adjie-Winoto, Elliot Schwartz, Hari Balakrishnan, Jeremy Lilley, The design and implementation of an intentional naming system, Proc. 17th ACM SOSP, Kiawah Island, SC, Dec. 1999. Jeremy Elson and Deborah Estrin, Random, Ephemeral Transaction Identifiers in Dynamic Sensor Networks, Proceedings of the Twenty First International Conference on Distributed Computing Systems (ICDCS-21), Phoenix, Arizona, April 2001. Wei Ye and John Heidemann and Deborah Estrin, “An Energy Efficient MAC Protocol for Wireless Sensor Networks,” In Proceedings 21st International Annual Joint Conference of the IEEE Computer and Communications Societies, 2002. Tijs van Dam, Koen Langendoen, “An adaptive energy-efficient MAC protocol for wireless sensor networks,” In Proceedings of the 1st international conference on Embedded networked sensor systems, 2003.

In the wireless communication control system according to the conventional sensor network, the communication frame and the control signal are based on 802.11 used for the wireless LAN of the IP network. For this reason, when there are a plurality of reception sensor terminals with respect to the transmission sensor terminal, there are the following problems.
That is, in the wireless communication control method according to the above-described prior art, when there are a plurality of communication partner sensors within the wireless communication range, control signals such as RTS signal / CTS signal / ACK signal and data are exchanged for each communication partner. . Therefore, even if the RTS signal and data are transmitted to the sensors once by the sender (the data is transmitted wirelessly, there is no mechanism to receive the data even though it has reached each sensor. Since the communication is performed for each sensor, a plurality of redundant RTS signal / data communication has occurred. This will be described with reference to FIGS.

In FIG. 18, seven sensor terminals are indicated by solid circles. The number in each solid line circle is a neighborhood identifier of the sensor terminal. In the figure, a circle indicated by a broken line is a range in which wireless transmission can be performed directly from Source A. In this state, consider a case where a sensor packet is transmitted from Source A to Sink B and Sink C.
In this case, the Source A includes the sensor packet P12 in which the receiver neighborhood identifier “1”, the sender proximity identifier “0”, the receiver end identifier “B”, and the sender end identifier “A” are added to the data “DATA”. Create When the sensor packet P12 is transmitted from the Source A, the sensor terminal D having the receiver neighborhood identifier “1” receives it.

Also, the Source A includes a sensor packet P21 in which the receiver neighborhood identifier “4”, the sender proximity identifier “0”, the receiver end identifier “C”, and the sender end identifier “A” are added to the data “DATA”. create. When the sensor packet P21 is transmitted from the Source A, the sensor terminal E having the receiver neighborhood identifier “4” receives it.
Thus, separate sensor packets are transmitted toward SinkB and SinkC. When separate sensor packets are transmitted in this way, a plurality of transmission / reception processes are performed as shown in FIG. That is, after the RTS signal and the CTS signal are exchanged between the source A and the sensor terminal D, the sensor packet P12 which is DATA is transmitted, and finally the ACK signal is returned. The RTS signal, CTS signal, and ACK signal in FIG. 6A are a Type field 61, which is an identification field for distinguishing data and control signals, as shown in FIG. It is configured to include a ReceiverList field 63 that represents the identifier of the proximity sensor to be received, and a SenderInfo field 64 for the proximity identifier of the transmission proximity sensor and the end identifier of the transmission source.

Further, after the RTS signal and the CTS signal are exchanged between the source A and the sensor terminal E, the sensor packet P21 which is DATA is transmitted, and the ACK signal is finally returned.
Thus, when separate sensor packets are transmitted and a plurality of transmission / reception processes are performed, power consumption increases. In order to solve this, it is conceivable to use broadcast to deliver data to a plurality of neighboring sensors in one communication. In this case, since the broadcast address is specified and the destination is not specified by the sensor terminal on the transmitting side, whether or not the received data is transferred to the next sensor is autonomously determined by the neighboring sensor that has received the data.

  For example, as shown in FIG. 20, with respect to the sensor packet P5 including the broadcast address “ALL” from Source A, all of a plurality of surrounding sensor terminals D, E, F, and G relay it. Become. In this case, if only the sensor terminals D and E among the surrounding sensors relay the sensor packet P5, the data can be delivered to all the sinks. However, in this case, the sensor terminal F and the sensor terminal G cannot easily determine that they do not have to relay. If unnecessary relay processing is performed, the power consumption of each sensor terminal is greatly affected. If necessary relay processing is not performed, data cannot be delivered to all sinks.

In addition, since the transmission partner is not specified in the broadcast described above, it is not known at what timing the CTS signal for the RTS signal and the ACK signal for the data are transmitted, and the number of signals. For this reason, an RTS signal / CTS signal collision may occur, and the collision cannot be avoided. Therefore, the above broadcast is not suitable for stable data communication.
An object of the present invention is to provide a sensor terminal and a sensor terminal control method capable of realizing collective data transmission to a plurality of neighboring sensor terminals while solving the above problems.

  When transmitting the same data to N destination terminals as transmission destinations, the sensor terminal according to claim 1 of the present invention and the identifiers of the destination terminal and M (N, M is a packet creation means (for example, a data packet (for example, data packet P in FIG. 1)) that is a packet including at least one identifier pair consisting of identifiers of natural numbers and at least one of which is 2 or more. 5 and 6 corresponds to the transmission data packet creation unit 15). If the sending terminal explicitly creates a data packet that specifies the sink to be relayed for each receiving sensor, and sends this data packet, when sending the same data to multiple neighboring sensors, perform multiple communications Since the communication can be completed only once, the number of times of wireless communication can be reduced, and power saving of communication between sensor terminals can be realized.

  A sensor terminal according to a second aspect of the present invention is the sensor terminal according to the first aspect, wherein the packet creating means creates the data packet in response to a request from the outside. When there is a request from the outside, if the same data is transmitted to multiple neighboring sensors, it is possible to perform one communication without performing multiple communication, so the number of wireless communication can be reduced, and the sensor Power saving of communication between terminals can be realized.

  The sensor terminal according to claim 3 of the present invention further comprises a routing table (for example, corresponding to the routing table 14 in FIG. 5 and FIG. 6) including the identifiers of the target terminal and the neighboring terminal. And the packet creation means creates the data packet with reference to the routing table. By referring to the routing table, it is possible to create a data packet in which the sending terminal explicitly specifies a sink to be relayed for each reception sensor.

  The sensor terminal according to claim 4 of the present invention includes identifiers of N destination terminals that are transmission destinations and M identifiers (N and M are natural numbers and at least one is 2 or more) of neighboring terminals that are close to the own terminal. A sensor terminal that receives a packet having at least one set of identifiers consisting of identifiers, and receives based on the set of identifiers included in the packet to determine whether the terminal is a reception target of the packet When the packet analyzing means (for example, corresponding to the received packet analyzing unit 12 in FIG. 5 and FIG. 6) and the received packet analyzing means determine that the own terminal is the reception target of the packet, the target terminal And a means for rewriting the identifier to transfer the packet toward (for example, corresponding to the transmission data packet creation unit 15 in FIGS. 5 and 6). Since it is determined whether the packet is a reception target based on the set of identifiers, if it is not the reception target, it is not necessary to perform subsequent processing, and power consumption can be reduced.

  The sensor terminal according to claim 5 of the present invention is the sensor terminal according to claim 4, wherein the received packet analyzing means determines that the own terminal is a reception target of the packet, and the packet includes a plurality of identifiers of neighboring terminals. In this case, the information processing apparatus further includes a means (for example, corresponding to the transmission timing control unit 163 in FIG. 6) for returning an acknowledgment packet at a timing according to the order of inclusion. By returning the acknowledgment packet at such timing, collision between the acknowledgment packets can be avoided.

  A sensor terminal according to claim 6 of the present invention comprises a packet creation means (for example, corresponding to the transmission timing control unit 162 in FIG. 6) for creating a data transmission request packet having a plurality of identifiers of neighboring terminals close to the own terminal. And means for transmitting the data transmission request packet created by the packet creating means (for example, corresponding to the transmission timing control unit 163 in FIG. 6). By creating such data transmission request packets, data requests can be aggregated, so that the number of times of wireless communication can be reduced, and power saving of communication between sensor terminals can be realized.

  A sensor terminal according to claim 7 of the present invention is a sensor terminal that receives a data transmission request packet (for example, corresponding to the RTS signal R in FIG. 2) having a plurality of identifiers of neighboring terminals close to the own terminal, It includes a means (for example, corresponding to the transmission timing control unit 163 in FIG. 6) for returning a reception preparation completion packet at a timing according to the order included in the data transmission request packet. By returning reception preparation completion packets at such timings, collision between reception preparation completion packets can be avoided.

The sensor terminal according to claim 8 of the present invention is the sensor terminal according to any one of claims 1 to 3, wherein the packet creation means is a substitute represented by an identifier set with a smaller amount of information than the identifier set. Create a data packet in which the identifier is associated, and then create a data packet with a substitute identifier instead of a set of identifiers,
When a data packet is transmitted a plurality of times for the same identifier set, the data packet including the identifier set and the substitute identifier is transmitted first, and the subsequent data packet transmission does not include the identifier set but includes the substitute identifier. It is characterized by transmitting a data packet. According to such a configuration, it is possible to reduce the overhead of the packet header during the second and subsequent packet transmissions, thereby realizing communication power saving.

  When a sensor terminal according to claim 9 of the present invention receives for the first time a data packet including a set of identifiers and a substitute identifier obtained by substituting the set of identifiers with a smaller amount of information in claim 4 or 5, Storage means for storing the correspondence between the set of identifiers and the substitute identifier, and the identifier set and substitute identifier stored in the storage means when a data packet not including the identifier set and including the substitute identifier is received. Therefore, it is further characterized by further comprising determination means for determining whether the own terminal is a reception target of the packet. According to such a configuration, when a packet including a substitute identifier is received, subsequent reception processing and transfer processing can be performed based on the correspondence between the set of identifiers and the substitute identifier.

  In the sensor terminal control method according to claim 10 of the present invention, when the same data is transmitted to N destination terminals which are transmission destinations, the identifier of the target terminal and M pieces of neighboring terminals adjacent to the own terminal. (N and M are natural numbers, at least one of which is 2 or more) and a transmitting step of transmitting a data packet, which is a packet including at least one identifier pair, from the transmitting terminal, and receiving the data packet In the receiving terminal, based on a set of identifiers included in the data packet, a determination step of determining whether the terminal is a reception target of the packet, and the reception terminal receives the packet by the determination step And an identifier rewriting step for rewriting the identifier in order to transfer the packet to the target terminal. To. By controlling the center terminal in this way, when the same data is transmitted to a plurality of neighboring sensors, it is possible to perform one communication without performing a plurality of communications, so that the number of wireless communications can be reduced. Power saving of communication between terminals can be realized.

  According to the present invention, when the same data is transmitted to a plurality of neighboring sensors, it is possible to complete one communication without performing a plurality of communications, and the receiving sensor autonomously performs subsequent processing as in broadcasting. Rather than deciding the processing, the transmission side terminal can explicitly specify the sink to be relayed for each reception sensor, thereby suppressing data non-delivery and generation of redundant data signals. Thereby, the frequency | count of wireless communication can be reduced and there exists an effect which can implement | achieve the power saving of communication between sensor terminals. Since power consumption can be reduced by reducing power consumption, there is an effect that the size of the entire sensor terminal can be further reduced.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings referred to in the following description, the same parts as those in the other drawings are denoted by the same reference numerals.
(Example of wireless packet structure)
FIG. 1 is a diagram illustrating an example of a packet structure in a case where a sensor terminal on a transmission side transmits the same data to a plurality of neighboring sensors collectively in the sensor network system using the sensor terminal of the present embodiment.

In the figure, the packet P has a structure in which a Type field 61, an NbrNum field 62, a ReceiverList field 63, and a SenderInfo field 64 are added to data 65.
The Type field 61 is an identification field for distinguishing data / control signals.
The NbrNum field 62 is a field that represents the number of multiple neighboring sensors to be transmitted. In this example, since it transmits to the nearby receiver 1 and receiver 2, the value of the NbrNum field is “2”. When there is a single transmission destination, the value of this field is “1”. However, when the transmission destination is singular, the NbrNum field 62 may not be provided.

  The ReceiverList field 63 is a field indicating a reception list. This field includes (1) a neighbor identifier of a neighboring sensor to be received, (2) the number of sinks that the neighboring sensor should be a destination of, “SinkNum”, and (3) a sink number that the neighboring sensor should be a destination of A set of end identifiers is listed by the number corresponding to the value of the NbrNum field. In this example, a set 63a of “receiver 1 proximity identifier”, “SinkNum”, “sink 1 end identifier”, “sink 2 end identifier”, “receiver 2 proximity identifier”, “SinkNum”, “sink 3 end” A set of identifiers 63b. The former set 63a is a content in which the receiver 1 in the vicinity transmits a packet with the sink 1 and the sink 2 as target terminals, and the value of “SinkNum” is “2”. The latter set 63b is a content in which the neighboring receiver 2 transmits a packet whose sink 3 is the target terminal, and the value of “SinkNum” is “1”.

The SenderInfo field 64 is a field for the proximity identifier of the transmission proximity sensor and the end identifier of the transmission source.
The above is the basic structure of the wireless packet P when transmitting data in the sensor terminal of the present invention. A field provided as a standard in a wireless standard such as 802.11 such as “Duration” is added as necessary.

(Packet transmission / reception)
In the case of data transmission, the transmission sensor transmits the wireless packet P. The neighboring sensor terminal that has received this packet P detects the end identifier of the destination sink corresponding to the neighboring identifier of the own terminal when the neighboring identifier of the own terminal is included in the ReceiverList field 63, and On the other hand, data transfer is continued.
On the other hand, a sensor terminal whose neighbor identifier of the own terminal is not included in the ReceiverList field 63 does not perform transfer or the like as in normal 802.11 and waits until communication is completed.

(Example structure of radio control signal)
Further, in the case of performing wireless control by exchanging RTS signal / CTS signal / ACK signal, both the CTS signal and ACK signal are the same as the structure shown in FIG. On the other hand, the RTS signal is different from the structure shown in FIG. That is, as shown in FIG. 2, an NbrNum field 62 is added to the RTS signal R, and this field includes a value representing the number of neighboring sensors to be transmitted. In the ReceiverList field 63 of the RTS signal R, the identifiers of the reception-target neighboring sensors are listed by the number corresponding to the value of the NbrNum field 62. For example, when the value of the NbrNum field 62 is “2”, “neighbor 1 neighbor identifier” and “neighbor 4 neighbor identifier” are listed.
The above is the basic structure of the RTS signal exchanged between the center terminals of this embodiment. A field provided as a standard in a wireless standard such as 802.11, such as Duration, is added as necessary.

(Transmission and reception of radio control signals)
A sensor terminal (hereinafter referred to as a receiving sensor terminal) that has received the RTS signal shown in FIG. 2 includes the CTS signal of the source neighbor identifier when the neighbor identifier of the terminal is included in the ReceiverList field. Reply. The reply of the CTS signal is performed at different times so that the CTS signals between the plurality of receiving sensor terminals do not collide. Specifically, each receiving sensor terminal transmits a CTS signal based on the timing obtained by accumulating a fixed time in the order of the identifiers listed in the ReceiverList field. By doing so, the transmission timing of the CTS signal becomes different at each reception sensor terminal, and the collision of the CTS signal can be avoided. In general, since the data transmission speed of the sensor terminal is several tens of Kbps, the integration time is set in consideration of this.

  The transmission sensor that has received all the CTS signals transmits a data packet with the packet structure shown in FIG. As a result, when the same data is transmitted to a plurality of neighboring sensors, the packet is not transmitted a plurality of times (see FIG. 18), but only one communication can be performed as shown in FIG. That is, as shown in the figure, Source A has a receiver neighborhood identifier “1”, a receiver end identifier “B”, a receiver neighborhood identifier “4”, a receiver end identifier “C”, and a sender proximity. A sensor packet P is created by adding the identifier “0” and the sender end identifier “A” to the data “DATA”. When this sensor packet P is transmitted from the Source A, the sensor terminal D whose receiver neighborhood identifier is “1” and the sensor terminal E whose receiver neighborhood identifier is “4” respectively receive it. In this way, a plurality of packets can be aggregated into one. In FIG. 3, for simplicity, the Type, NbrNum, and SinkNum fields are not displayed.

The sensor terminals D and E that have received the data packet normally return an ACK signal to the source Source A. The transmission of the ACK signal is also performed based on the timing obtained by accumulating a certain period of time in the order of the identifiers included in the ReceiverList field in order to avoid a collision as in the transmission of the CTS signal.
As a result of the aggregation of the RTS signals and the aggregation of the data packets and avoiding the collision between the CTS signal and the ACK signal, as shown in FIG. 4, the aggregation is performed from the source A to the sensor terminals D and E. After the RTS signal is transmitted, the CTS signal is returned at a different timing. Thereafter, an aggregated sensor packet that is DATA is transmitted, and an ACK signal is returned at a different timing.

As described above, according to the sensor terminal of this embodiment, the receiving sensor does not autonomously determine the subsequent processing as in the case of broadcasting (see FIG. 20), but the sender explicitly receives the receiving sensor. By designating a sink to be relayed every time, it is possible to suppress data non-delivery and generation of redundant data signals.
In addition, when performing radio control using the RTS signal / CTS signal / ACK signal, the RTS signal can be aggregated into one packet, and the time difference based on the list order based on the CTS signal / ACK signal returned from a plurality of sensors. Therefore, collision avoidance can be realized and both power saving communication and reliable communication can be achieved.

(Configuration example 1 of sensor terminal)
FIG. 5 is a block diagram illustrating a configuration example of a sensor terminal that performs wireless communication of data according to the present embodiment, and is a block diagram illustrating a configuration example when wireless control of an RTS signal or the like is not performed during data transmission. It is. In the figure, the sensor terminal of this example includes an input / output interface 11, a received packet analysis unit 12, a database 13, a routing table 14, and a transmission data packet creation unit 15.
In such a configuration, when the input / output interface 11 receives a packet from another sensor terminal, the input / output interface 11 transfers the packet to the received packet analysis unit 12. Further, when the packet is transferred from the transmission data packet creation unit 15, the input / output interface 11 transmits the packet to another sensor terminal.

  The received packet analyzing unit 12 determines whether or not the own terminal is a reception target of the packet by analyzing whether the neighbor identifier of the own terminal and the end identifier of the own terminal are included in the ReceiverList field. For example, if the higher-order bits of these identifiers are included in the ReceiverList field, it can be determined that the own terminal is the reception target of the packet. As a result of this determination, if they are included in the ReceiverList field, data accommodation in the database 13 and packet header structure notification to the transmission data packet creation unit 15 are performed. Note that, as a result of the above determination, the received packet analysis unit 12 updates the routing table 14 as necessary even when the neighborhood identifier and end identifier of the terminal itself are not included.

  As will be described later, the routing table 14 includes identifiers of neighboring sensor terminals in its items. When the received packet analysis unit 12 determines that the own terminal is the reception target of the packet, the corresponding item in the routing table 14 is selected. In a state where a plurality of items are selected in the routing table 14, if the same identifier is included in these items, they can be aggregated, and are aggregated into one instead of creating separate packets. Packet is created.

When the data packet is transferred or autonomously transmitted, the transmission data packet creation unit 15 receives a neighbor identifier, which is an identifier for a terminal in the vicinity of the own terminal, an end identifier of the own terminal, data in the database 13, and reception Necessary information is collected from the packet analysis unit 12 and the packet described with reference to FIG. 1 is created. The created packet is output to the input / output interface 11.
If an environmental information acquisition unit that acquires information around the sensor terminal, such as the temperature, humidity, temperature, position, time, movement, and electric field strength of the object, is added to the sensor terminal, requests and data packets from the outside Even if it is not received, a data packet can be transmitted autonomously.

(Configuration example 2 of sensor terminal)
FIG. 6 is a block diagram illustrating another configuration example of the sensor terminal that performs wireless communication of data according to the present embodiment, and is a block diagram illustrating a configuration example when performing wireless control of an RTS signal or the like during data transmission. FIG. In the figure, the sensor terminal of this example has a configuration in which a wireless control unit 16 is added to the configuration of FIG. The radio control unit 16 controls a radio control buffer 161 that stores data packets, a radio control packet creation unit 162 that creates the RTS signal described with reference to FIG. 2, and transmission timings for the CTS signal and the ACK signal. And a transmission timing control unit 163.

In such a configuration, the transmission data packet creation unit 15 transfers the created transmission packet to the radio control buffer 161. The radio control buffer 161 stores the data packet and notifies the radio control packet creation unit 162 of an RTS signal transmission request.
The radio control packet creation unit 162 that has received the RTS signal transmission request creates the RTS signal described above with reference to the header of the transmission data packet, and outputs the RTS signal to the transmission timing control unit 163. The transmission timing control unit 163 transfers the RTS signal to the input / output interface 11. The input / output interface 11 transmits an RTS signal to other sensor terminals.

In addition, when an RTS signal is received from another sensor terminal, the received packet analysis unit 12 determines whether the neighbor identifier of the own terminal and the end identifier of the own terminal are included in the ReceiverList field. If they are included in the ReceiverList field, the RTS signal is transferred to the radio control packet creation unit 162.
Radio control packet creating section 162 creates a CTS signal destined for the sensor terminal that has transmitted the RTS signal, and outputs it to transmission timing control section 163. In order to avoid collision between CTS signals transmitted by a plurality of sensor terminals, the transmission timing control unit 163 generates a CTS signal based on a timing obtained by integrating a certain unit time in the order of identifiers included in the ReceiverList field. Output to the input / output interface 11.

In the sensor terminal on the transmission side, when the CTS signal is returned from all neighboring reception side sensor terminals, the data packet is taken out from the radio control buffer 161 and transmitted by the input / output interface 11.
When the data reception is completed, the radio control packet creation unit 162 of the nearby receiving sensor terminal creates an ACK signal destined for the transmitting sensor terminal of the RTS signal, and transmits the ACK signal to the transmission timing control unit 163.

The transmission timing control unit 163 inputs and outputs ACK signals based on the timing obtained by accumulating a certain unit time in the order of identifiers included in the ReceiverList field in order to avoid collision of ACK signals from a plurality of sensor terminals. Transmit to interface 11.
Note that the above RTS signal and CTS signal may not be exchanged. In this case, an ACK signal is returned when the data packet is normally received.

(Configuration example 3 of sensor terminal)
FIG. 21 is a block diagram illustrating another configuration example of the sensor terminal that performs wireless communication of data according to the present embodiment, and substitute identifiers are used when transmitting a plurality of packets to the same set of identifiers. It is a block diagram which shows the structure in the case of performing communication. When the sensor terminal in FIG. 5 receives the data packet including the substitute identifier for the first time in the configuration of FIG. 5 and the substitute identifier creating unit 17 that creates a substitute identifier represented by a smaller amount of information than the set of identifiers, A substitute identifier storage unit 18 for storing a correspondence between a set of identifiers and a substitute identifier is added. That is, when the received packet analysis unit 12 receives a packet including a set of identifiers and a substitute identifier, the received packet analysis unit 12 creates a correspondence table as shown in FIG. 22 and stores it in the substitute identifier storage unit 18.

  Referring to the figure, this correspondence table stores a set of substitute identifiers and identifiers corresponding to the substitute identifiers. When a packet including a substitute identifier is received without including a set of identifiers, the received packet analysis unit 12 refers to the correspondence table stored in the substitute identifier storage unit 18 and determines a set of identifiers corresponding to the substitute identifier. Ask. Then, the received packet analysis unit 12 performs processing according to the set of identifiers as described above.

  When the transmission data packet creation unit 15 creates a packet using the substitute identifier, the substitute identifier creation unit 17 creates a substitute identifier to create a transmission data packet. For example, as shown in FIG. 23, when a plurality of packets are transmitted to the same set of identifiers, a packet including the set of identifiers and a substitute identifier is created and transmitted during initial communication. Subsequent communication does not include the identifier pair, and performs communication by creating a packet including the substitute identifier.

For this substitute identifier, for example, a value obtained by applying an existing hash function (MD5 or the like) to the set of identifiers may be used. When the transmission sensor terminal sets the substitute identifier value, a continuous value may be set or a random value may be set.
By the way, as shown in FIG. 1 and FIG. 14, header information (NbrNum, SinkNum, RecvListLen, RecvListBit) other than the set of identifiers also exists in the packet. For this reason, if a substitute identifier is used for the contents including these pieces of information, the header length can be further reduced.
In addition, you may employ | adopt the structure which added the substitute identifier preparation part 17 and the substitute identifier memory | storage part 18 which were mentioned above to the structure of FIG. If comprised in this way, the sensor terminal which performs radio | wireless control and communicates by a substitute identifier is realizable.

(Aggregation operation example)
Although the above has described the aggregate transmission method to a plurality of neighboring sensors within the same wireless communication range, that is, the aggregation within the 1 hop communication range, here, the aggregation of the route itself from the Source to the Sink will be described.
When routes to a plurality of target sinks can be aggregated, it is desirable to aggregate the routes and transmit packets. The effect of route aggregation will be described with reference to FIG. In the case of FIG. 7A, since the same data is sent from Source A to Sink B and Sink H through different paths, the number of data transmission / reception increases and the power consumption increases. On the other hand, in the case of FIG. 7B, the data from Source A to Sink B and Sink H is sent through the same path, so the number of data transmission / reception is reduced and the power saving effect is high compared to the case of FIG.

An operation example of route aggregation in the sensor terminal for realizing the route aggregation will be further described with reference to FIG.
In the figure, first, a list of optimum proximity sensor groups is created based on the routing table (step S101). Next, it is determined whether there is an unsent destination in the list (step S102). Here, since there is an untransmitted destination in the list, a neighboring sensor that can aggregate the destinations most is selected (steps S102 → S103).
Then, the sensors that can be aggregated into the sensors are deleted from the list (step S104). Thereafter, the process returns to step S102, and the above operation is continued until there is no unsent destination in the list.

(Routing table)
An example of the routing table is shown in FIG. In the figure, “SrcAttr” indicating the attribute of the source, “SinkID” as the identifier of the sink, “LocalAdd” as the identifier of the neighboring sensor terminal, and “Value” as the cost value are shown.
In the same figure (a), the case where a data packet is transmitted with respect to several Sink A-E is demonstrated. In this case, first, the item having the smallest cost value “Value” to be transmitted to each of the sinks A to E is selected. If the cost values are the same, all of them are selected. In this example, an item with a thick line frame is selected.

  The item selected in FIG. 10A is shown in FIG. FIG. 4B shows an optimal neighborhood identifier list. In this optimum neighborhood identifier list, items having the same content of the identifier “LocalAdd” of the neighboring sensor terminals are selected. In this example, an item with a thick line frame is selected. If the contents of “LocalAdd” are the same, aggregation is possible. For this reason, the item including the same Sink ID as the item selected in FIG.

Items that have not been consolidated or deleted in FIG. 6B are shown in FIG. In FIG. 5C, items having the same content of the identifier “LocalAdd” of the neighboring sensor terminals are selected. In this example, an item with a thick line frame is selected. If the contents of “LocalAdd” are the same, aggregation is possible. As described above, since aggregation and deletion are performed, the minimum number of packets are transmitted, so that the power consumption of the entire system can be reduced.
In addition, in the case of the push type transmission process in which the sensor terminal itself transmits the data packet even if there is no request, in the case of the pull type transmission process in which the data packet is transmitted from the sensor terminal in response to the request from the outside. As shown in FIG. 1, there is a high possibility that they can be aggregated, and an effect of reducing power consumption can be expected.

  Next, Embodiment 1 of the sensor network system using the sensor terminal of the present invention will be described with reference to FIG. In the figure, packet P is a data packet, and for simplicity, each field of Type, NbrNum, and SinkNum is not drawn. Also, Source A, Sink B, etc. represent end identifiers, and numbers such as 0, 1, 2, 3, etc. represent neighborhood identifiers.

In the figure, the most basic application example is shown. In this example, Source A transmits the same data packet to Sink B and Sink C.
First, by referring to the routing table, Source A determines that Sink B should be transmitted to neighboring sensor D (identifier “1”), and Sink C should be transmitted to neighboring sensor E (identifier “4”). Then, Source A creates a packet P in the ReceiverList field 63 in which the neighboring sensor identifier “1” is associated with the end identifier “B”, and the neighboring sensor identifier “4” is associated with the end identifier “C”. Note that the SenderInfo field 64 of the packet P is a neighbor sensor identifier “0” and an end identifier “A” of the source Source A.

By transmitting the created packet P, data can be transmitted to two neighboring sensors in one communication.
The neighboring sensor terminal D and sensor terminal E that have received the packet P refer to the header of the packet P, the sensor terminal D transfers the packet toward Sink B, and the sensor terminal E transfers the packet toward Sink C. . When the packet P is transmitted as described above, unlike the broadcast, the sensor terminal F of the neighboring sensor identifier “2” and the sensor terminal G of the neighboring sensor identifier “3” are not included in the destination. Since the determination can be made, unnecessary transfer or the like is not performed even if the packet P is received.

That is, unlike broadcasting, the number of data transmissions is reduced, which can contribute to power saving in wireless communication. In addition, by clearly indicating the transfer destination after receiving a packet for each neighboring sensor terminal, it is guaranteed that necessary and sufficient transfer is performed, and it is possible to prevent a non-delivery of a packet and an increase in power consumption due to redundant packet transmission.
In this embodiment, when the RTS signal / CTS signal / ACK signal is controlled, the control is performed in the sequence shown in FIG. In this case, the number of transmissions for the RTS signal and the data packet is reduced, which can contribute to power saving in wireless communication.

Next, Embodiment 2 of the sensor network system using the sensor terminal of the present invention will be described with reference to FIG. In the figure, packet P is a data packet, and for simplicity, each field of Type, NbrNum, and SinkNum is not drawn. Also, Source A, Sink B, etc. represent end identifiers, and numbers such as 0, 1, 2, 3, etc. represent neighborhood identifiers.
The figure shows an application example in the case where there are a plurality of end identifiers for a certain neighborhood identifier. In this example, Source A transmits the same data to Sink B, Sink H, and Sink C.

  First, by referring to the routing table, Source A determines that Sink B and Sink H should be transmitted to neighboring sensor D (identifier “1”) and Sink C to be transmitted to neighboring sensor E (identifier “4”). Then, Source A creates a packet P in the ReceiverList field 63 in which the neighboring sensor identifier “1” is associated with the end identifiers “B” and “H”, and the neighboring sensor identifier “4” is associated with the end identifier “C”. . Note that the SenderInfo field 64 of the packet P is a neighbor sensor identifier “0” and an end identifier “A” of the source Source A.

  By transmitting the created packet P, data can be transmitted to two neighboring sensors in one communication. The neighboring sensor terminal E that has received the packet P refers to the header of the packet P and transfers the packet toward SinkC. At this time, unlike the broadcast, the sensor terminal F having the neighboring sensor identifier “2” and the sensor terminal G having the neighboring sensor identifier “3” can determine that the own terminal is not included in the destination, and therefore receive the packet P. However, unnecessary transfers are not performed.

  On the other hand, the neighboring sensor terminal D that has received the packet P performs batch transmission to the plurality of sensor terminals because Sink B and Sink H are designated as transmission destinations. That is, the sensor terminal D rewrites the identifier and associates the neighboring sensor identifier “5” with the end identifier “B” and the neighboring sensor identifier “6” with the end identifier “h” in the ReceiverList field 63, respectively. Create packet P ′. Note that the SenderInfo field of the packet P ′ is the proximity sensor identifier “1” and the end identifier “A” of the source Source A. By transmitting the created packet P ′, data can be transmitted to two neighboring sensors in one communication.

When the packet P is transmitted as described above, unlike the broadcast, the sensor terminal F of the neighboring sensor identifier “2” and the sensor terminal G of the neighboring sensor identifier “3” are not included in the destination. Since the determination can be made, unnecessary transfer or the like is not performed even if the packet P is received.
As described above, in this embodiment, the number of transmissions is reduced in the Source A and the sensor terminal D, which can contribute to power saving in wireless communication.

In the case of Example 2 described above, the route from Source A to Sink B and Sink H is aggregated for only one hop. Aggregation of routes is not limited to one hop but may be aggregated for a plurality of hops.
For example, as shown in FIG. 12A, when packets are separately transmitted from Source A to Sink B ′ and Sink H ′ as in the conventional case, the packets may be transmitted through different paths. . On the other hand, if packets aggregated by aggregation of destination neighbor sensor identifiers using the routing table described above are transmitted, as shown in FIG. 12B, from Source A to Sink B ′ and Sink H ′. Thus, one aggregated packet is transmitted through one route until immediately before. Therefore, route aggregation is performed for a plurality of hops, and the number of transmissions is reduced as a whole of the sensor network, which can contribute to power saving in wireless communication.

  Next, Embodiment 4 of the sensor network system using the sensor terminal of the present invention will be described with reference to FIG. In the figure, the packet P is a data packet, and the fields of Type, NbrNum, and SinkNum are not drawn for simplicity. Source A and Sink G represent end identifiers, and numbers such as 0, 1, 2, and 3 represent neighborhood identifiers.

This figure shows an application example in the case where there are a plurality of neighboring sensor terminals for a certain target sensor terminal. In this example, when Source A transmits a data packet to Sink G, a multiple route policy is adopted instead of the single route policy as in the first to third embodiments.
Wireless communication is unstable compared to wired communication, and the fluctuation in communication quality is particularly severe in low-power wireless communication such as sensor networks. Therefore, Source A may transmit data to Sink G using a plurality of routes.

  In the figure, Source A selects neighboring sensor terminal D (identifier “1”) and sensor terminal B (identifier “5”) from the routing table as a plurality of routes to Sink G, and transmits the same data packet. In the ReceiverList field 63 of this data packet, the neighboring sensor identifier “1” and the neighboring sensor identifier “5” are associated with the end identifier “G”. Note that the SenderInfo field 64 of the packet P is a neighbor sensor identifier “0” and an end identifier “A” of the source Source A.

  By transmitting this packet P, data can be transmitted to the two sensor terminals B and D by one communication. That is, the packet P is transmitted by the route reaching SinkG via the sensor terminals D and F and the route reaching SinkG via the sensor terminals B and E. With such data transfer, one packet can be transmitted through two routes. When there are many neighboring sensor terminals, there are many routes. It is not preferable from the viewpoint of power consumption to transmit packets separately for these multiple paths. Therefore, in this example, these many routes are aggregated into two routes, so that power consumption can be reduced.

  Furthermore, in this example, unlike the case where packets are transmitted separately for these two routes, the first one hop is only required to transmit one packet, so that the power consumption can be further reduced. In addition, a relay sensor located in the middle of a route may transmit a packet to a plurality of routes. In this case as well, it is only necessary to transmit a single aggregated packet, so that power consumption can be reduced and packet transmission with improved stability can be realized using a plurality of paths.

  By the way, when there are many neighboring sensor terminals to be received, the contents of the SenderInfo field 64 may become enormous. Therefore, in this case, the identifiers of all sensor terminals are not included in the SenderInfo field 64, but a threshold value or the like is provided, and the packet is transmitted in a smaller number of packets. For example, the maximum value (MTU: Maximum Transmission Unit) of packet data that can be transmitted in one transfer becomes a threshold value, and the packet data is transmitted separately so as to become packet data below this threshold value. Even in such a case, instead of transmitting a huge number of packets separately, only a few packets need to be transmitted, and a power saving effect due to a decrease in the number of transmissions can be expected.

(Modification)
Packets transmitted and received in the present invention are not limited to the structure shown in FIG. Another structural example of the packet will be described with reference to FIG. The packet P1 shown in the figure has a structure in which a Type field 61, an RcvListLen 62a, an RcvListBits 62b, a ReceiverList field 63, and a SenderInfo field 64 are added to the data 65. Unlike the structure shown in FIG. 1, RcvListLen 62a and RcvListBits 62b are provided instead of the NbrNum field 62, and “SinkNum” in the ReceiverList field 63 is deleted.

  The RcvListLen 62a in the packet P1 indicates the number of addresses in the ReceiverList field 63 that is a field indicating a reception list. In this example, the ReceiverList field 63 includes a set 63a ′ of “receiver 1 proximity identifier”, “sink 1 end identifier”, and “sink 2 end identifier”, “receiver 2 proximity identifier”, and “sink 3 end identifier”. The set 63b ′ includes five addresses. Therefore, the value of RcvListLen 62a is “5”.

The RcvListBits 62b in the packet P1 is a bit string that indicates whether each transmission destination address in the ReceiverList field 63 is a neighborhood identifier or an end identifier. When the neighborhood identifier is represented by “1” and the end identifier is represented by “0”, the value of RcvListBits 62b is “10010”.
Note that the above-described set 63a is such that the neighboring receiver 1 transmits a packet having the sink 1 and the sink 2 as target terminals. In addition, the above set 63b is a content in which the neighboring receiver 2 transmits a packet having the sink 3 as a target terminal.
If the packet structure as described above is adopted, the structure of the entire packet can be further simplified.

(When sending multiple data packets to the same set of identifiers)
The operation when a plurality of data packets are transmitted to the same set of identifiers will be described with reference to FIG. In the figure, when a plurality of data packets are transmitted to the same set of identifiers, the transmitted / received packet has a structure as shown in FIG. 23 instead of the structure as shown in FIGS. That is, a data packet including a set of identifiers and a substitute identifier corresponding to the set of identifiers is transmitted (step S201).

A neighboring sensor terminal that receives this data packet (hereinafter referred to as a neighboring receiving sensor terminal) stores the correspondence between the identifier set and the substitute identifier (steps S202a and S202b). The transmission sensor terminal that has transmitted the data packet transmits the data packet including the substitute identifier without including the identifier set in the subsequent transmission (step S203).
Since the proximity reception sensor terminal stores the identifier pair corresponding to the substitute identifier, that is, the above-described correspondence table, it is determined whether or not the own terminal should receive the substitute identifier alone, and subsequent transfer processing is performed ( Steps S204a and S204b). As described above, by substituting a set of identifiers with substitute identifiers, it is possible to reduce the byte length necessary for identifying neighboring reception sensor terminals, and to realize power-saving communication.

  The presence or absence of a substitute identifier can be determined from the value of the Type field. In other words, the receiving sensor refers to the Type field of the received packet, whether the packet is transmitted using a pair of identifiers, whether a pair of identifiers and a substitute identifier is included, or only a substitute identifier It is possible to determine whether or not the message is being transmitted. Further, instead of the Type field, an Option field for determining presence / absence of a substitute identifier may be newly provided and set using the Option field.

(Sensor terminal control method)
In the sensor terminal described above, the following control method is employed. That is, when the same data is transmitted to N destination terminals that are transmission destinations, the identifier of the target terminal and M pieces of neighboring terminals close to the own terminal (N and M are natural numbers and at least one is 2). A transmission step of transmitting a data packet, which is a packet including at least one identifier set consisting of identifiers of the above), from the transmission side terminal, and the reception side terminal receiving the data packet includes the data packet. A determination step of determining whether the terminal is a reception target of the packet based on a set of identifiers, and the target terminal when the determination of the self terminal is a reception target of the packet by the determination step And a control method including an identifier rewriting step for rewriting the identifier to transfer the packet toward the network.
By controlling the center terminal in this way, when the same data is transmitted to a plurality of neighboring sensors, it is possible to perform one communication without performing a plurality of communications, so that the number of wireless communications can be reduced. Power saving of communication between terminals can be realized.

(Summary)
A simulation result when a sensor network system is configured using the sensor terminal of the present invention will be described with reference to FIG. The figure assumes that pull-type communication is performed according to a request from a user in a sensor network system in which the number of sensor terminals is “100”, the number of sinks is “10”, and the number of sources is “1”. . In the same figure, the power consumption in the case of the prior art is assumed to be 100%, and when radio aggregation is performed, when route aggregation is performed, and when both radio and routes are aggregated, RTS signal transmission ( The power consumption of the data (shaded in the figure), data packet transmission (white in the figure), and total (hatched in the figure) are shown in percentage. As shown in the figure, it can be seen that when at least one of wireless aggregation and route aggregation is performed, power consumption can be reduced as compared with the case of the prior art.

  INDUSTRIAL APPLICABILITY The present invention can be used in a sensor network when the power consumption is reduced by reducing power consumption and the size of the entire sensor terminal is further reduced.

It is a figure which shows the structural example of the packet which the sensor terminal by this invention transmits / receives. It is a figure which shows the structural example of the communication request signal which the sensor terminal by this invention transmits / receives. It is a topology diagram which shows the example of the packet transmission of the sensor terminal by this invention. It is a sequence diagram which shows the example of the packet transmission of the sensor terminal by this invention. It is a block diagram which shows the structural example of the sensor terminal concerning embodiment of this invention. It is a block diagram which shows the other structural example of the sensor terminal concerning embodiment of this invention. It is a figure for demonstrating the effect of route aggregation. It is a flowchart which shows the route aggregation process at the time of employ | adopting the sensor terminal of this invention. It is a figure which shows the content of the aggregation process performed with reference to a routing table. It is a figure concerning Example 1 of the present invention. It is a figure concerning Example 2 of this invention. It is a figure concerning Example 3 of this invention. It is a figure concerning Example 4 of this invention. It is a figure which shows the other structural example of a data packet. It is a figure which shows the power consumption reduction effect at the time of employ | adopting the sensor terminal of this invention. It is a figure which shows the structural example of the packet which the conventional sensor terminal transmits / receives. It is a figure which shows the packet transfer example in the sensor network by the conventional sensor terminal. It is a topology diagram which shows transmission of the packet several times by the conventional sensor terminal. It is a sequence diagram which shows the multiple times transmission of the packet by the conventional sensor terminal. It is a figure which shows the subject at the time of utilizing a broadcast. It is a block diagram which shows the structural example of the sensor terminal which performs communication using the substitute identifier concerning embodiment of this invention. It is a figure which shows the example of the conversion table of a substitute identifier memorize | stored in the substitute identifier memory | storage part in FIG. It is a figure which shows the structural example of the packet using a substitute identifier concerning embodiment of this invention. It is a sequence diagram of the example of communication using a substitute identifier concerning embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Input / output interface 12 Reception packet analysis part 13 Database 14 Routing table 15 Transmission data packet creation part 16 Radio control part 17 Substitution identifier creation part 18 Substitution identifier storage part 61 Type field 62 NbrNum field field 63 ReceiverList field 64 SenderInfo field 161 Radio control Buffer 162 Radio control packet creation unit 163 Transmission timing control unit A to H Sensor terminal

Claims (10)

  When transmitting the same data to N destination terminals as transmission destinations, the identifier of the destination terminal and M of neighboring terminals close to the own terminal (N and M are natural numbers and at least one is 2 or more) A sensor terminal comprising: a packet creating means for creating a data packet that is a packet including at least one set of identifiers including identifiers.   The sensor terminal according to claim 1, wherein the packet creating unit creates the data packet in response to a request from the outside.   3. The sensor terminal according to claim 1, further comprising a routing table including identifiers of the target terminal and the neighboring terminal, wherein the packet creation unit creates the data packet with reference to the routing table.   It has at least one set of identifiers including identifiers of N destination terminals that are transmission destinations and M identifiers (N and M are natural numbers and at least one is 2 or more) of neighboring terminals that are close to the own terminal. A sensor terminal that receives a packet, and based on a set of identifiers included in the packet, a received packet analysis unit that determines whether the terminal is a reception target of the packet; and the received packet analysis unit A sensor terminal comprising: means for rewriting an identifier to transfer the packet to the target terminal when it is determined that the terminal is a reception target of the packet.   When the received packet analysis means determines that the own terminal is the reception target of the packet and the packet includes a plurality of identifiers of neighboring terminals, confirmation is made at a timing according to the included order. 5. The sensor terminal according to claim 4, further comprising means for returning a response packet.   A sensor terminal comprising: a packet creating means for creating a data transmission request packet having a plurality of identifiers of neighboring terminals close to the own terminal; and a means for transmitting the data transmission request packet created by the packet creating means .   A sensor terminal that receives a data transmission request packet having a plurality of identifiers of neighboring terminals adjacent to the own terminal, and that returns a reception preparation completion packet at a timing according to the order included in the data transmission request packet A sensor terminal comprising: The packet creation means creates a data packet in which a substitute identifier represented by a smaller amount of information than the set of identifiers is associated with a set of identifiers, and thereafter a data packet in which a substitute identifier is assigned instead of the set of identifiers Create
When a data packet is transmitted a plurality of times for the same identifier set, the data packet including the identifier set and the substitute identifier is transmitted first, and the subsequent data packet transmission does not include the identifier set but includes the substitute identifier. The sensor terminal according to any one of claims 1 to 3, wherein a data packet is transmitted.   Storage means for storing a correspondence between the identifier set and the substitute identifier when a data packet including the identifier set and a substitute identifier obtained by substituting the identifier set with a smaller amount of information is received for the first time; and the identifier When the data packet including the substitute identifier is received, the terminal determines whether the terminal is the reception target of the packet from the correspondence between the identifier set stored in the storage unit and the substitute identifier. 6. The sensor terminal according to claim 4, further comprising a determination unit.   When transmitting the same data to N destination terminals as transmission destinations, the identifier of the destination terminal and M of neighboring terminals close to the own terminal (N and M are natural numbers and at least one is 2 or more) A transmission step of transmitting a data packet, which is a packet including at least one set of identifiers consisting of identifiers from the transmission side terminal, and the reception side terminal that has received the data packet, A determination step of determining whether the terminal is a reception target of the packet based on a set of identifiers; and when the determination step determines that the terminal is a reception target of the packet, And an identifier rewriting step for rewriting the identifier to transfer the packet.

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