JP2019021956A - Communication device and program - Google Patents

Abstract

To provide a communication device and a program that can configure a multi-hop network in a LoRa network.SOLUTION: A communication device for performing multi-hop communication obtains information that is a transmission object, and transmits a transmission object signal representing the obtained information. At this time, it performs control to start transmitting the transmission object signal after delaying by a delay time determined by a predetermined method.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a communication device and a program.

  In recent years, LoRa (Long Range), which is one of low power consumption wide area network technologies, has attracted attention. However, at present, the LoRa network is configured with a single-hop star topology, and its application is limited. For this reason, it is desired to configure the LoRa network as a multi-hop network.

  Although different from LoRa, Non-Patent Document 1 discloses an example in which a multi-hop network is configured by performing simultaneous transmission (CT) using a proximity communication standard (IEEE802.15.4) called ZigBee. ing.

F. Ferrari, et al., “Efficient network flooding and time synchronization with Glossy,” in Proc. ACM / IEEE IPSN’11, pp.73-84, April 2011.

  However, it has been found that if simultaneous transmission is applied as it is in a LoRa network, a collision occurs between signals having the same content, which hinders transmission.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a communication apparatus and a program that can configure a multi-hop network in a LoRa network.

  One aspect of the present invention that solves the problems of the conventional example is a communication device that performs multi-hop communication, and includes an acquisition unit that acquires information to be transmitted, and a transmission target signal that represents the acquired information. Transmission means for transmitting, and transmission control means for controlling the transmission means to start transmission of the transmission target signal after being delayed by a delay time determined by a predetermined method.

  According to the communication device of the present invention, when performing communication based on the LoRa standard, a collision between signals can be suppressed and a multi-hop network can be configured.

1 is a block diagram illustrating a configuration of a communication device 1 according to an embodiment of the present invention and an example of a system including the communication device 1. FIG. It is a functional block diagram showing the example of the communication apparatus 1 which concerns on embodiment of this invention. It is a timing chart figure showing the example of the communication timing by the communication apparatus 1 which concerns on embodiment of this invention. It is a flowchart figure showing the operation example of the communication apparatus 1 which concerns on embodiment of this invention. It is a timing chart figure showing another example of communication timing by communication apparatus 1 concerning an embodiment of the invention.

  Embodiments of the present invention will be described with reference to the drawings. As illustrated in FIG. 1, the communication device 1 according to the embodiment of the present invention includes a control unit 11, a storage unit 12, and a communication unit 13, and is connected to other communication devices 1. In multi-hop communication, signals are transmitted and received. That is, in the example of FIG. 1, the communication device 1a operates as an initiator, and information acquired from the outside (for example, a personal computer PC (not shown)) is transferred to other communication devices 1b and 1c that can communicate from the communication device 1a. Send to. Further, the communication devices 1b and 1c respectively transmit information received from the communication device 1a to the other communication devices 1d, 1e, and so on. Send information.

  The control unit 11 of each communication device 1 (hereinafter collectively referred to as the communication device 1 when the communication devices 1a, 1b,... Are not distinguished from each other) is a program control device such as a CPU and is stored in the storage unit 12. It operates according to the program. In the present embodiment, the control unit 11 acquires information to be transmitted and outputs the acquired information to the communication unit 13 to generate a transmission target signal encoded by a predetermined method.

  Further, the control unit 11 controls the communication unit 13 to start transmission of the transmission target signal after delaying by the delay time determined by a predetermined method. Detailed operation of the control unit 11 will be described later.

  The storage unit 12 is a memory device such as an EEPROM, and holds a program executed by the control unit 11. This program may be provided by being stored in a computer-readable and non-transitory recording medium and stored in the storage unit 12. The storage unit 12 may include a RAM (Random Access Memory) that operates as a work memory of the control unit 11.

  The communication unit 13 sends a signal to another communication device in accordance with an instruction input from the control unit 11. In the present embodiment, the communication unit 13 modulates transmission target information input from the control unit 11 by frequency shift keying having three or more signal points, that is, M-ary FSK (Frequency Shift Keying). Up-chirping is performed to obtain a transmission target signal defined by the LoRa network standard. This transmission target signal is a packet obtained by encoding and concatenating signals for a plurality of symbols. This packet may further include a preamble, a header, a footer, and the like. The communication unit 13 sends the transmission target signal in accordance with an instruction input from the control unit 11.

  In the present embodiment, as will be described later, the communication unit 13 receives an instruction indicating the transmission timing of the transmission target signal from the control unit 11 and transmits the transmission target signal at the transmission timing represented by the instruction. . An example of the operation of the communication unit 13 will be described later.

  The communication unit 13 may perform an operation of demodulating a transmission target signal received from another communication device 1 to obtain transmission target information and outputting the transmission target information to the control unit 11. Here, when chirp modulation is performed on the transmission side, the communication unit 13 performs down-chirp reception, further demodulates the transmission target signal to obtain transmission target information, and sends the transmission target information to the control unit 11. Output.

  In the present embodiment, the control unit 11 is functionally configured to include an information acquisition unit 21, a transmission control unit 22, and a transmission processing unit 23 as illustrated in FIG.

  In the communication device 1 that functions as an initiator, the information acquisition unit 21 acquires transmission target information to be transmitted from the outside (for example, a personal computer PC (not shown)) via the communication unit 13 or the like. The information acquisition unit 21 decodes a transmission target signal received from the other communication device 1 by the communication unit 13 in a communication device 1 (hereinafter referred to as a relay communication device 1) different from the initiator. To obtain the transmission target information to be transmitted.

  In the present embodiment, transmission target signals from a plurality of other communication devices 1 may arrive at the communication device 1 serving as a relay, but the information acquisition unit 21 has a maximum signal power. Are selectively received. As such a reception method, a widely known method can be adopted, and a detailed description thereof will be omitted here.

  The transmission control unit 22 determines the transmission timing of the transmission target signal. Specifically, in the communication device 1 serving as a relay, the transmission control unit 22 determines a delay time from a predetermined transmission timing as a timing for transmitting the transmission target signal generated by the communication unit 13.

  The transmission processing unit 23 outputs the transmission target signal to the communication unit 13 at the timing when the delay time determined by the transmission control unit 22 has elapsed from the expected transmission timing of the transmission target signal, and transmits the signal for one packet. Instruct.

[Operation]
The communication device 1 according to the present embodiment has the above configuration and operates as follows. As an example of the present embodiment, the transmission control unit 22 in the communication device 1 serving as a relay randomly sets a delay time from the original transmission start timing of the transmission target signal (packet) as a predetermined method for determining the delay time. decide. Here, the random delay time may be determined by a uniform random number having a value lower than a predetermined threshold value (maximum value Rmax of values that can be issued randomly).

  In this example, as illustrated in FIG. 3, transmission target information acquired from the personal computer PC by the communication device 1 a operating as an initiator is converted into M-ary FSK (Frequency), which is a modulation method defined by the LoRa network standard. The transmission target signal is generated by modulation by Shift Keying. The communication device 1a transmits the signal to be transmitted (chirp-modulated) wirelessly. FIG. 3 shows a state in which a signal (SS1a) for one packet is transmitted. In this embodiment, since the signal of each symbol is concatenated into a packet, if the symbol length is Ts, the packet length Tx for one packet is an integral multiple of the symbol length Ts. The signal for one packet in FIG. 3 has the packet length Tx. In general, Tx is usually 10 times or more of Ts. However, in FIG. 3, for the sake of illustration, the length of Tx is extremely small (for example, Tx = Ts). Yes.

  On the other hand, the communication devices 1b and 1c issue random values τ1 and τ2 representing delay times, respectively. Then, the communication devices 1b and 1c located in the range where the wireless signal from the communication device 1a arrives each receive a signal (SS1a) for one packet transmitted from the communication device 1a.

  The communication devices 1b and 1c are determined in advance in common with each communication device 1 in advance from a reference transmission timing of a predetermined transmission target signal (for example, timing when reception of the transmission target signal is completed from the preceding communication device 1 or the timing). The timing at which the predetermined time Tp has elapsed, where the time Tp may be set to be equal to or greater than the maximum value Rmax of values that can be issued randomly, in the example of FIG. The transmission target signal corresponding to the received transmission target signal is transmitted (SS1b, SS1c) after being delayed by the time τ1, τ2 corresponding to the issued value. Hereinafter, the communication devices 1b and 1c also delay the transmission target signals (SS2, SS3,...) That are subsequently received from the timing of completion of reception by times τ1 and τ2, respectively, corresponding to the issued values. The transmission target signal corresponding to the received transmission target signal is transmitted.

  Furthermore, each of the communication devices 1d and 1e receives a signal having a strong signal strength among transmission target signals (SS1b or SS1c) for one packet transmitted by the communication device 1b or the communication device 1c. In the example of FIG. 3, the communication device 1d receives the transmission target signal of the communication device 1b, and the communication device 1e receives the transmission target signal of the communication device 1c. Here, it is assumed that the communication devices 1d and 1e issue random values τ3 and τ4 representing delay times, respectively.

  The communication devices 1d and 1e receive only the times τ3 and τ4 corresponding to the issued values from the predetermined reference transmission timing of the transmission target signal (here, the timing at which the reception of the transmission target signal is completed from the preceding communication device 1). After each delay, the transmission target signal corresponding to the received transmission target signal is transmitted (SS1d, SS1e). Therefore, in this example, the transmission target signals transmitted by the communication devices 1d and 1e are transmitted immediately at the timing when each communication device 1 completes reception of the transmission target signal from the preceding communication device 1. Compared to the case, the time τ1 + τ3 and the time τ2 + τ4 are delayed.

  Here, the maximum random value Rmax issued by the transmission control unit 22 may be a value corresponding to the symbol length Ts. In this case, the delay time is at most one symbol.

[Adjust delay time]
In the example described so far in the present embodiment, signals having the same contents transmitted through a plurality of routes may be distributed at significantly different times depending on values that are randomly issued. For example, in the above example, if τ1> τ2 and τ3> τ4, then τ1 + τ3 >> τ2 + τ4, and the delay of the signal transmitted through the path of the communication device 1a → the communication device 1b → the communication device 1d is It can be significantly greater than the delay of the signal transmitted on the path 1a → communication device 1c → communication device 1e.

  Therefore, in consideration of the case where it is not preferable that the delay difference between the paths becomes large, the communication device 1 of the present embodiment may operate as follows. That is, in communication device 1 (communication device 1 that serves as a relay) according to another example of the present embodiment, control unit 11 includes, for transmission target information, information on a random value that represents a delay time issued. . That is, in this example of the present embodiment, the communication device 1 serving as a relay includes information on a delay time related to transmission of the signal in a signal to be transmitted.

  In addition, the control unit 11 in this example determines whether or not the transmission target information obtained by demodulating the transmission target signal received from the preceding communication device 1 includes information related to the delay time. Then, using the information related to the delay time, the delay time when the self transmits the transmission target signal is determined. Specifically, as illustrated in FIG. 4, the control unit 11 (in the communication device 1 serving as a relay) in this example acquires transmission target information obtained by demodulating the transmission target signal received from the preceding communication device 1 (S11). ).

  The control unit 11 checks whether or not information indicating the delay time is included in the acquired transmission target information (S12). If not included (S12: No), the control unit 11 is determined in advance as in the above example. A random value lower than the threshold value (maximum value Rmax of values that can be issued randomly) is issued (S13), and the process proceeds to S17.

  In addition, when the control unit 11 determines that the acquired transmission target information includes information indicating the delay time (S12: Yes), the time T (actually determined as the time for transmitting the transmission target signal in advance) A time obtained by adding a predetermined guard time to a time Tx required to transmit a signal for one packet, where the guard time is at least a delay time T ′, which will be described later, for example, a random delay time. The time T ′ obtained by subtracting the delay time τp included in the information acquired in the process S11 is obtained (S14).

  The control unit 11 further issues a random value that is lower than a predetermined threshold value (maximum value Rmax of values that can be issued randomly) (S15), the time τc ′ represented by the random value, and the processing The delay time τc = τc ′ + T ′ is obtained by adding the time T ′ obtained in S14 (S16).

  The control unit 11 generates transmission target information (S17). Here, when it is determined in the processing S12 that the information indicating the delay time is not included in the acquired transmission target information, the transmission target information is set to the value issued in the processing S13 in the transmission target information acquired in the processing S11. The information including the corresponding delay time information is generated as new transmission target information.

  When the control unit 11 determines in step S12 that the acquired information includes information indicating the delay time, the information related to the delay time among the transmission target information acquired in step S11 (the previous communication device) 1), information including the delay time obtained in step S16 is used as new transmission target information.

  The control unit 11 further determines a delay time corresponding to the value issued in the process S13 from the reference transmission timing of a predetermined symbol (for example, the timing when the transmission target signal is completely received from the preceding communication device 1), or the process The transmission target signal obtained by encoding the transmission target information generated in the process S17 is transmitted by the time delayed by the delay time obtained in S17 (S18).

  According to the example of the present embodiment, as illustrated in FIG. 5, the transmission target information acquired from the personal computer PC by the communication device 1a operating as the initiator is modulated by the LoRa network standard. A transmission target signal is generated by modulation using M-ary FSK (Frequency Shift Keying). The communication device 1a transmits the signal to be transmitted (chirp-modulated) wirelessly. FIG. 5 shows a state in which the transmission target signal (SS1a) is transmitted.

  On the other hand, each of the communication devices 1b and 1c located in the range where the wireless signal from the communication device 1a arrives receives the transmission target signal (SS1a) transmitted from the communication device 1a. Here, since the transmission target information represented by the transmission target signal transmitted by the communication device 1a does not include information related to the delay time, the communication devices 1b and 1c include the transmission target information corresponding to the received transmission target signal. , Transmission target signals (SS1b, SS1c: transmission targets including delay time signals) obtained by generating new transmission target information including information representing the respective delay times τ1, τ2, and encoding the new transmission target information Signal). Each of the communication devices 1b and 1c is delayed by a time τ1 and τ2 corresponding to the issued values from a predetermined reference transmission timing (here, the timing at which reception of the transmission target signal is completed from the preceding communication device 1a). After that, the generated transmission target signals (SS1b, SS1c) are transmitted.

  Hereinafter, the communication devices 1b and 1c also delay the transmission target signals (SS2, SS3,...) That are subsequently received from the timing of completion of reception by times τ1 and τ2, respectively, corresponding to the issued values. The transmission target signal corresponding to the received transmission target signal (each of which may include delay time information) is transmitted.

  Furthermore, each of the communication devices 1d and 1e receives a transmission target signal having a strong signal strength among the transmission target signals (SS1b or SS1c) transmitted by the communication device 1b or the communication device 1c. In the example of FIG. 5, it is assumed that the communication device 1d receives the transmission target signal of the communication device 1b, and the communication device 1e receives the transmission target signal of the communication device 1c.

  The transmission target information corresponding to the transmission target signal received by the communication device 1d includes information representing the delay time τ1 by the communication device 1b. Therefore, the communication device 1d issues a random value τ3 representing the delay time, and from the predetermined time Ts (a time equal to or greater than the time represented by the maximum value Rmax of values that can be issued as a random value), A delay time ((Ts−τ1) + τ3) obtained by adding the time τ3 represented by the issued random value to the time (Ts−τ1) obtained by subtracting the delay time τ1 represented by the information included in the received symbol. obtain.

  Similarly, the transmission target information corresponding to the transmission target signal received by the communication device 1e includes information representing the delay time τ2 by the communication device 1c. Therefore, the communication device 1e issues a random value τ4 representing the delay time, and subtracts the delay time τ2 represented by the information included in the received transmission target signal from the predetermined time Ts. A delay time ((Ts−τ2) + τ4) is obtained by adding the time τ4 represented by the issued random value to (Ts−τ2).

  In addition, since information related to the delay time is included in the information represented by the transmission target signals transmitted by the communication apparatuses 1b and 1c, the communication apparatuses 1d and 1e can determine the delay time from the transmission target information corresponding to the received transmission target signal. The transmission target information including the information representing the delay times τ3 and τ4 issued by each of them is generated and the transmission target signals (SS1d, SS1e: transmission target signals including the delay time signal) are encoded. Generate.

  Then, the communication devices 1d and 1e respectively receive the delay times ((Ts−τ1) + τ3), obtained by the above method from the timing when the transmission target signal is completely received from the preceding communication device 1b or the communication device 1c. After being delayed by ((Ts−τ2) + τ4), the generated transmission target signals are transmitted (SS1d, SS1e). Therefore, in this example, the transmission target signals transmitted by the communication devices 1d and 1e are transmitted immediately at the timing when each communication device 1 completes reception of the transmission target signal from the preceding communication device 1. Compared to the case, the time τ1 + (Ts−τ1) + τ3 = Ts + τ3 and the time τ2 + (Ts−τ2) + τ4 = Ts + τ4 are delayed.

  According to this example, the difference between the delay times of the transmission target signals transmitted by the communication devices 1d and 1e is at most | τ4−τ3 | (where | x | means the absolute value of x). Regardless of the delay time, it is determined by the delay time from the reference time Ts (if the packet transmission time is included, Tx + Ts becomes the reference time after receiving the signal from the previous stage). There is no big difference.

[Effect of the embodiment]
According to the present embodiment, when transmission target signals including transmission target information having the same contents are transmitted from a plurality of nodes, in general, transmission is performed with a delay time different from each other, thereby reducing the possibility of interference. Can be reduced. That is, when M-ary FSK is used as in communication based on the LoRa network standard in the example of the present embodiment, the energy distribution (1 symbol) of communication signals output from a plurality of communication devices 1 that transmit the same signal. The ratio of the signal strength of the communication signal power for a certain time (the signal strength of the signal while receiving a signal of a certain communication device 1 and the signal strength of a signal transmitted by another communication device 1) The ratio of the accumulated values of the communication device 1 and the communication device 1 is relatively large because the plurality of communication devices 1 are shifted by a delay time as compared to when signals are transmitted all at once (without a delay time), It becomes easy to selectively receive a signal from a specific communication device 1.

  Accordingly, even in communication based on the LoRa network standard, simultaneous transmission (CT) can be efficiently performed to configure a multi-hop network.

DESCRIPTION OF SYMBOLS 1 Communication apparatus, 11 Control part, 12 Storage part, 13 Communication part, 21 Information acquisition part, 22 Transmission control part, 23 Transmission processing part

Claims (6)

A communication device that performs multi-hop communication,
Obtaining means for obtaining information to be transmitted;
Transmitting means for transmitting a transmission target signal representing the acquired information;
Transmission control means for controlling the transmission means and starting transmission of the transmission target signal after being delayed by a delay time determined by a predetermined method;
Including a communication device. The communication device according to claim 1,
The transmission control means is a communication device that randomly determines the delay time as the predetermined method. The communication device according to claim 1,
The transmission unit is a communication device that transmits a delay time signal representing a delay time determined by the transmission control unit together with the acquired transmission target signal. The communication device according to claim 1 or 3,
The acquisition means acquires a delay time signal representing a delay time determined in the other communication device and a transmission target signal to be transmitted from another communication device,
The transmission control means transmits the transmission target signal to the transmission means after delaying by a delay time determined by the predetermined method from a reference time determined based on a delay time represented by the acquired delay time signal. Start
The transmission unit is a communication device that transmits a delay time signal representing a delay time determined by the transmission control unit together with the acquired transmission target signal. The communication device according to any one of claims 1 to 4,
The transmission means modulates the transmission target signal by frequency shift keying having three or more signal points and transmits the modulated signal. A communication device that performs multi-hop communication,
Obtaining means for obtaining information to be transmitted;
Transmitting means for transmitting a transmission target signal representing the acquired information;
Transmission control means for controlling the transmission means and starting transmission of the transmission target signal after being delayed by a delay time determined by a predetermined method;
Program to function as.

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