Transmitter, transmission method, receiver, and reception method

Abstract

The present disclosure relates to a transmitter, a transmission method, a receiver, and a reception method which make it possible to more appropriately select a frequency channel. Provided is a transmitter comprising a control unit which performs control for transmitting a signal by: causing a node set, which is a set of nodes including at least channel numbers and depth levels as elements, to be configured as a circular linked list; updating the depth levels for respective target nodes in the node set; selecting, as a determined node, a node reached by advancing, from a starting node in the node set, by the number of node movements in accordance with the corresponding depth level; and using the channel number of the determined node as a transmission channel number. For example, the present disclosure can be applied to wireless communication using frequency hopping.

Description

Transmitter, transmission method, receiver, and reception method

[0001] The present disclosure relates to a transmitter, a transmission method, a receiver, and a receiving method, and more particularly to a transmitter, a transmission method, a receiver, and a receiving method that enable more appropriate frequency channel selection.

[0002] Radio regulations such as radio wave laws and wireless technical standards in each country impose restrictions on the selection of usable frequency channels. In addition, in wireless communication systems, frequency hopping is sometimes used when wireless communication is performed between a transmitter and a receiver. Frequency hopping requires the use of frequency channels to be random in the short term and uniform in the long term.

[0003] For example, Patent Document 1 discloses a technology applicable to frequency hopping, in which frequency channels are divided into multiple groups, a group is selected according to the time, and a frequency channel is selected randomly within the group, thereby preventing the same channel from being selected if the group is different.

[0004] International Publication No. 2019 / 220944

[0005] In conventional technology, the restrictions imposed by wireless regulations were avoided by making the transmission interval longer than the restricted time. However, the longer transmission time interval reduced the number of transmissions, which limited the number of terminals to which data could be transmitted. Furthermore, when frequency hopping was used, a table recording the channel numbers to be hopped was prepared, and the channel numbers to be used for transmission were read out in order. However, the table size was limited, and it was necessary to prepare a table according to the channel usage conditions.

[0006] Therefore, there has been a demand for a technique for more appropriately selecting a frequency channel when frequency hopping is used.

[0007] The present disclosure has been made in consideration of such circumstances, and aims to enable more appropriate frequency channel selection.

[0008] A transmitter according to one aspect of the present disclosure is a transmitter in which a node set, which is a set of nodes whose elements include at least a channel number and a depth level, is configured as a circular list, the depth level is updated for each target node in the node set, and a control unit is provided which selects a node that is a number of node movements away from a starting node in the node set according to the depth level as a decision node, and controls the transmission of a signal using the channel number of the decision node as a transmission channel number.

[0009] A transmission method according to one aspect of the present disclosure is a transmission method including: a transmitter configured as a circular list of a node set, the node set being a set of nodes whose elements include at least a channel number and a depth level; updating the depth level for each target node in the node set; selecting a node that is a node that is a number of node movements away from a starting node in the node set according to the depth level as a decision node; and transmitting a signal using the channel number of the decision node as a transmission channel number.

[0010] In a transmitter and transmission method according to one aspect of the present disclosure, a node set, which is a set of nodes whose elements include at least a channel number and a depth level, is configured as a circular list, the depth level is updated for each target node in the node set, and a node that is a node movement number from the starting node in the node set according to the depth level is selected as a decision node, and the channel number of the decision node is used as a transmission channel number to transmit a signal.

[0011] A receiver according to one aspect of the present disclosure is a receiver in which a node set, which is a set of nodes whose elements include at least a channel number and a depth level, is configured as a circular list, the depth level is updated for each target node in the node set, and a control unit is provided which selects a node that is a number of node movements away from a starting node in the node set according to the depth level as a decision node, and controls the reception of signals using the channel number of the decision node as a receiving channel number.

[0012] A receiving method according to one aspect of the present disclosure is a receiving method including: a receiver receiving a node set, which is a set of nodes whose elements include at least a channel number and a depth level, configured as a circular list; updating the depth level for each target node in the node set; selecting a node that is a number of node movements away from a starting node in the node set according to the depth level as a decision node; and receiving a signal using the channel number of the decision node as a receiving channel number.

[0013] In a receiver and receiving method according to one aspect of the present disclosure, a node set, which is a set of nodes whose elements include at least a channel number and a depth level, is configured as a circular list, the depth level is updated for each target node in the node set, and a node that is a node movement number from the starting node in the node set according to the depth level is selected as a decision node, and the channel number of the decision node is used as a receiving channel number to receive a signal.

[0014] It should be noted that the transmitter and receiver according to one aspect of the present disclosure may be independent devices or may be internal blocks constituting a single device.

[0015] 9 is a diagram illustrating an example configuration of an embodiment of a wireless communication system to which the present disclosure is applied. FIG. 10 is a diagram illustrating a radio waveform in wireless communication performed in the wireless communication system of FIG. 1. FIG. 11 is a diagram illustrating the relationship between transmission groups and transmission slots. FIG. 12 is a diagram illustrating an example of a node set used in determining a transmission channel number. FIG. 13 is a diagram illustrating an example of a node structure. FIG. 14 is a diagram illustrating an example of a description when node variables are defined in a structure. FIG. 15 is a diagram illustrating the node set of FIG. 4 in the form of a table. FIG. 16 is a diagram illustrating an overview of a method for determining a transmission channel number according to the present disclosure. FIG. 17 is a block diagram illustrating an example of a configuration of the transmitter of FIG. 1. FIG. 18 is a block diagram illustrating an example of a functional configuration of the control unit of FIG. 19. FIG. 19 is a block diagram illustrating an example of a configuration of the receiver of FIG. 1. FIG. 19 is a flowchart illustrating the flow of transmission control processing. FIG. 19 is a flowchart illustrating details of hopping plan generation processing. FIG. 19 is a flowchart illustrating details of node movement processing. FIG. 19 is a flowchart illustrating details of node update processing. FIG. 19 is a flowchart illustrating details of origin selection processing. FIG. 19 is a diagram illustrating a first example of calculation of a maximum depth D. FIG. 19 is a diagram illustrating a second example of calculation of a maximum depth D. FIG. 19 is a diagram illustrating a third example of calculation of a maximum depth D. FIG. 19 is a diagram illustrating an example configuration of a random number generator. FIG. 19 is a diagram illustrating the flow of pseudo-random number generation. FIG. 19 is a diagram illustrating an example implementation of an LFSR. FIG. 19 is a diagram illustrating an example implementation of an LFSR. FIG. 19 is a diagram illustrating an example calculation of a maximum depth D in the first embodiment. FIG. 10 is a diagram showing an example of a transmission channel determined for each transmission time in the first embodiment. FIG. 11 is a diagram showing node behavior in the first embodiment. FIG. 12 is a diagram showing an example of calculation of maximum depth D in the second embodiment. FIG. 13 is a diagram showing an example of a transmission channel determined for each transmission time in the second embodiment. FIG. 14 is a diagram showing node behavior in the second embodiment. FIG. 15 is a flowchart explaining details of node movement processing in the first modified example. FIG. 16 is a diagram explaining a first method for reversing the node movement direction in the second modified example. FIG. 17 is a diagram explaining a second method for reversing the node movement direction in the second modified example. FIG. 18 is a diagram showing an example of a transmission channel determined for each transmission time in the second modified example. FIG. 19 is a diagram showing an example of a transmission channel determined for each transmission time in the third modified example. FIG. 19 is a diagram showing another example of the node structure. FIG. 20 is a diagram showing the relationship between node numbers and ch field values ​​in the fifth modified example.FIG. 10 is a diagram illustrating an example of application in the time direction in the first application example. FIG. 11 is a diagram illustrating an example of a case where the channel selection restriction is satisfied across transmission groups in the second application example. FIG. 12 is a diagram illustrating the relationship between channel numbers and generation order in the second application example. FIG. 13 is a flowchart illustrating details of node update processing in the second application example. FIG. 14 is a diagram illustrating an example of a case where the channel selection restriction is satisfied even if a preceding transmission is treated as optional in the third application example. FIG. 15 is a diagram illustrating the relationship between channel numbers and generation order in the third application example. FIG. 16 is a diagram illustrating an example configuration of a wireless communication system in the fourth application example. FIG. 17 is a block diagram illustrating an example configuration of computer hardware.

[0016] <System Configuration> FIG. 1 is a diagram showing an example configuration of an embodiment of a wireless communication system to which the present disclosure is applied.

[0017] The wireless communication system in Fig. 1 is a wireless communication system using, for example, LPWA (Low Power Wide Area) communication. LPWA communication is a wireless communication system that enables data transmission over a wide area with a radius of approximately several tens of kilometers while minimizing the power consumption of terminals. A receiver 12 serving as a receiving station (base station) receives data transmitted by a transmitter 11 located within the receiving area managed by the receiver 12. In Japan, for example, data transmission is performed by one-way communication using the 920 MHz band.

[0018] While the receiver 12 is a device that is fixedly installed at a predetermined location such as the roof of a building or a utility pole, the transmitter 11 is a device (end device) that is carried by a user or attached to a mobile object such as a car.

[0019] 1 is used when a transmitter 11 transmits data detected by a sensor to a receiver 12. Furthermore, for example, when the wireless communication system is used in a location management system that manages the location of the transmitter 11, the transmitter 11 and the receiver 12 are equipped with a positioning function that receives signals from a positioning satellite 13 and measures the location. The positioning satellite 13 is a positioning satellite of the GNSS (Global Navigation Satellite System).

[0020] In the wireless communication system of Figure 1, frequency hopping is used when wireless communication is performed between the transmitter 11 and the receiver 12. The wireless communication has the following characteristics: First, transmission is performed at equal intervals in transmission slot units, and the length of the transmission slot matches the transmission interval. Second, one transmission group is composed of multiple transmissions. Third, the frequency channels to be used for multiple transmissions within a transmission group are determined before the start of transmission of the transmission group. In the present disclosure, this is generated as a hopping plan, which will be described in detail later.

[0021] Hereinafter, in frequency hopping, one of the available frequency channels is selected and transmission is performed on that frequency channel. In the following description, frequency hopping is simply referred to as "hopping" and frequency channel as "channel." A hopping plan determines channel numbers in the order of transmission within a transmission group, and is determined before the first transmission within the transmission group. A channel number is a simple representation of a transmission channel, assigned a number in one-to-one correspondence to the transmission channel. A transmission channel is a frequency range used for transmission, with a specified center frequency and frequency boundaries.

[0022] Fig. 2 is a diagram showing a radio waveform in wireless communication performed in the wireless communication system of Fig. 1. In Fig. 2, the horizontal axis is time and the vertical axis is frequency, and the radio signal (signal) transmitted on the channel with channel number N is indicated by diagonal lines 101. The channel with channel number N has a channel center frequency of f N It is said that.

[0023] The transmitter 11 uses BSPK (Binary Phase Shift Keying) modulation for primary modulation and chirp modulation for secondary modulation as modulation methods. For example, the chip rate of BSPK modulation is approximately 6 kHz. Linear frequency chirp modulation is used for chirp modulation. The radio signal shown in FIG. 2 is a transmission signal after chirp modulation, with an occupied bandwidth of approximately 160 kHz and a maximum signal duration of 0.4 seconds.

[0024] In FIG. 2, the channels with channel numbers N-1 and N+1 before and after the channel with channel number N are shown, and the channel center frequencies are fN-1 , f N+1 In Figure 2, the channel boundaries are indicated by dashed lines and the channel center frequencies are indicated by dashed lines, with the channel width being 200 kHz and the channel spacing being 200 kHz. As shown in Figure 2, the channel number increases as the frequency increases. In the following explanation, we will assume that the total number of channels is 10. The total number of channels is the maximum number of channels that can be used as defined by radio regulations.

[0025] 3 is a diagram showing the relationship between transmission groups and transmission slots. In this figure, the horizontal axis represents time and the vertical axis represents frequency, and the radio signals (signals) transmitted on the transmission channels (CH0 to CH9) are indicated by diagonal lines 111.

[0026] A transmission channel (CH) is a frequency domain used for transmission, with a specified center frequency and frequency boundaries. A transmission group is a group consisting of a predetermined number of transmissions. After a transmission in a transmission group is completed, no transmission is performed for a certain period of time. A transmission slot is a fixed time interval during which one transmission is performed. A transmission group consists of multiple transmission slots.

[0027] 3, transmission group 1 and transmission group 2 each consist of four transmission slots, and after transmission by transmission group 1 is completed and a certain period of time has passed in which no transmission is performed, transmission by transmission group 2 begins. Specifically, transmission by transmission group 1 involves sequential transmission of signals using transmission channels CH0, CH6, CH2, and CH4 for each transmission slot. Then, after a certain period of time has passed, transmission by transmission group 2 involves sequential transmission using transmission channels CH5, CH1, CH9, and CH7 for each transmission slot.

[0028] <Outline of the Present Disclosure> An outline of a method for determining a transmission channel number according to the present disclosure will be described with reference to FIGS.

[0029] FIG. 4 is a diagram showing an example of a node set used in determining a transmission channel number. A node set is a set of nodes, and is composed of the same number of nodes as the total number of channels. The node set is composed of a circular list (channel list). A node contains as elements the channel number (CH) used for transmission, the depth level, and an index to the next node. For example, the depth level is specified by the value of "depth" that holds the depth. The index is composed of a pointer.

[0030] 4, the total number of channels is assumed to be 10, so the node set is made up of 10 nodes. Also, since the node set is made up of a circular list, each node is connected in a circular shape.

[0031] Fig. 5 is a diagram showing an example of the structure of the node in Fig. 4. As shown in Fig. 5, the node has a ch field, a depth field, and a next field. The ch field contains the channel number (CH) used for transmission. The depth field contains the depth value. The next field contains the index (next) to the next node. Fig. 6 shows an example of how the variables ch, depth, and next are defined in a structure.

[0032] The node set shown in Figure 4 can be represented by the table shown in Figure 7. Figure 7 shows the values ​​of ch, depth, and next for each of the 10 nodes corresponding to the total number of channels. Note that the values ​​of ch and next are set values, and the value of depth is the initial value. In other words, the value of depth is changed by the update process.

[0033] In node[0] to [9], the ch value is set to 0, 1, 2, 3, 4, 5, 6, 7, 8, or 9, corresponding to the channel number (CH), for each node. The depth value is set to an initial value of 0 for all nodes. The next value is set to 1, 2, 3, 4, 5, 6, 7, 8, 9, or 0, corresponding to the index to the next node, for each node.

[0034] Here, a node set is a set of nodes and is composed of a circular list, but for simplicity's sake, we will assume that each node is a raft. That is, as shown in Figure 4, each node connected in a circular pattern in the node set is a raft. The first and last of the 10 rafts are connected. A channel number is written on each raft. Also, assume that a person moves on the raft, and that the person moves forward the number of times indicated by the number rolled on a roulette wheel (equivalent to the random number described below). Also, assume that when a person on a raft jumps, the raft sinks, and that the raft will resurface over time.

[0035] For example, as shown in Figure 8, the value of "depth" indicates the depth to which the raft sinks. When "depth" = 0, the raft is on the water surface (wave front). As the value of "depth" increases, such as 1, 2, and 3, the raft sinks deeper. In Figure 8, of the ten rafts, the starting raft is the ninth raft from the left (CH8), and the second raft from the left (CH1) is submerged. In this case, when the roulette results in a move count of 5, the person on the starting raft (CH8) moves along the circular rafts according to the move count of 5. Here, the person moves along the five rafts, but because raft (CH1) is submerged, they skip raft (CH1) and move to the fifth raft from the left (CH4) and jump. When the person jumps on raft (CH4), raft (CH4) sinks to its deepest position (depth = 3). In addition, transmission is made on the channel number (CH4) written on the raft from which the jump was made.

[0036] Next, when the roulette rolls the number of moves to 2, the person on the starting raft (CH5) moves to the eighth raft from the left (CH7) in accordance with the number of moves of 2 and jumps. Here too, when a person jumps on the raft (CH7), the raft (CH7) sinks to its deepest position (depth = 3) and transmits on the channel number (CH7) of the raft that was jumped from. The sinking raft gradually rises over time, and when it rises to the surface, it becomes eligible for movement or jumping again.

[0037] In this manner, in the present disclosure, a node set, which is a set of nodes whose elements include a channel number (CH), a depth level (depth), and an index to the next node (next), is configured as a circular list, the depth level (depth) is updated for each target node in the node set, and a node that is located a number of node movements from the starting node in the node set according to the depth level (depth) is selected as the decision node, and the channel number of the decision node is used as the transmission channel number to transmit a signal.

[0038] Here, the origin node is the node selected as the origin of movement when determining the transmission channel. The node movement count is the number of nodes that move from the origin node on the candidate node set. The candidate node set is a subset of the node set with depth=0. The decision node is the node selected as a result of movement from the origin node. The channel number of the decision node is used to transmit the signal. In other words, applying the example of Figure 8, the candidate node set is multiple rafts on the water surface, and the decision node is the raft that a person jumps from after moving on a raft on the water surface.

[0039] <Device Configuration> Fig. 9 is a block diagram showing an example configuration of the transmitter 11 in Fig. 1. As shown in Fig. 9, the transmitter 11 includes a transmission data generation unit 21, a control unit 22, an LPWA communication unit 23, and a GNSS reception unit 24.

[0040] The transmission data generation unit 21 generates transmission data to be transmitted to the receiver 12 and supplies the data to the control unit 22. The transmission data generation unit 21 can acquire data detected by a sensor provided in the transmitter 11 and generate the transmission data. For example, the transmission data is generated from detected data such as images, sounds, temperature, humidity, acceleration, angular velocity, and illuminance. The transmission data generation unit 21 may also generate transmission data including position information supplied from the GNSS reception unit 24.

[0041] The control unit 22 is composed of a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), etc. The control unit 22 executes a predetermined program using the CPU and controls the overall operation of the transmitter 11. The control unit 22 performs necessary processing on the transmission data supplied from the transmission data generation unit 21 and supplies the data to the LPWA communication unit 23. The control unit 22 also supplies transmission parameters that specify the transmission channel, transmission timing, etc. to the LPWA communication unit 23 and controls the transmission of data.

[0042] The LPWA communication unit 23 generates a transmission signal by performing various processes such as BPSK modulation and chirp modulation on the transmission data supplied from the control unit 22. The LPWA communication unit 23 transmits the transmission signal using the transmission parameters supplied from the control unit 22. The transmission parameters specify the transmission timing of each signal, the transmission channel of each signal, etc.

[0043] The GNSS receiver 24 performs positioning by receiving GNSS signals from the positioning satellites 13, and outputs position information of the transmitter 11 to the transmission data generator 21. The GNSS receiver 24 can also generate time information based on the GNSS signals and supply it to the controller 22. This establishes time synchronization with the receiver 12 based on the GNSS signals received by the GNSS receiver 24.

[0044] Fig. 10 is a block diagram showing an example of the functional configuration of the control unit 22 in Fig. 9. As shown in Fig. 10, the control unit 22 is composed of an initial setting unit 31, a hopping plan generation unit 32, a communication control unit 33, and a storage unit 34. The control unit 22 also appropriately implements functional units that perform necessary processing on transmission data, etc. At least some of these functional units are implemented by the CPU of the control unit 22 executing a predetermined program.

[0045] The initial setting unit 31 creates nodes in the same number as the total number of channels and sets initial values. For example, it sets the channel number in the ch field of the node and sets the connecting node in the next field. It also calculates the total number of nodes and the maximum depth.

[0046] The hopping plan generation unit 32 generates a hopping plan. When generating a hopping plan, it updates the value of the depth field for each target node in the node set within the destination group, selects a node that is a node movement count from the origin node in the node set according to the depth value as a determination node, and registers the channel number of the determination node as a transmission channel number. As a result, the channel numbers to be used for transmission within the destination group are determined in transmission order, and a hopping plan is generated.

[0047] The hopping plan generation unit 32 supplies the generated hopping plan to the communication control unit 33. Alternatively, the hopping plan generation unit 32 may record the hopping plan in the storage unit 34, and the communication control unit 33 may appropriately read out the hopping plan recorded in the storage unit 34. The communication control unit 33 controls transmission of a transmission signal by the LPWA communication unit 23 by supplying transmission parameters to the LPWA communication unit 23 based on the hopping plan.

[0048] Fig. 11 is a block diagram showing an example of the configuration of the receiver 12 in Fig. 1. As shown in Fig. 11, the receiver 12 is made up of an LPWA communication unit 51, a GNSS receiving unit 52, a control unit 53, and a transmission data processing unit 54.

[0049] The LPWA communication unit 51 receives transmission signals transmitted from the transmitter 11 in accordance with transmission parameters supplied from the control unit 53. The transmission parameters specify the reception timing and reception channel for each signal. The LPWA communication unit 51 performs various processes on the received signals, such as dechirp (demodulation of chirp signals) and BPSK demodulation, to generate transmission data. The LPWA communication unit 51 supplies the transmission data to the control unit 53.

[0050] The GNSS receiver 52 can generate time information based on the GNSS signals received from the positioning satellites 13 and supply the time information to the controller 53. This allows time synchronization to be established with the transmitter 11 based on the GNSS signals received by the GNSS receiver 52.

[0051] The control unit 53 is composed of a CPU, ROM, RAM, etc. The control unit 53 executes a predetermined program using the CPU and controls the overall operation of the receiver 12. The control unit 53 supplies transmission parameters specifying reception timing and reception channels to the LPWA communication unit 51 and controls data reception. The control unit 53 also performs necessary processing on the transmission data supplied from the LPWA communication unit 51 and supplies the data to the transmission data processing unit 54.

[0052] The transmission data processing unit 54 performs predetermined processing on the transmission data supplied from the control unit 53. Alternatively, the transmission data processing unit 54 may transmit the transmission data to a server via a network such as the Internet.

[0053] In the receiver 12, the control unit 53 may be configured in the same manner as the control unit 22 shown in Fig. 10. That is, the control unit 53 may be configured with an initial setting unit 31, a hopping plan generation unit 32, a communication control unit 33, and a storage unit 34.

[0054] In the control unit 53, when generating a hopping plan, the hopping plan generation unit 32 updates the value of the depth field for each target node in the node set, selects a node that is a node movement count from the origin node in the node set according to the depth value as a determination node, and registers the channel number of the determination node as a reception channel number. Then, the communication control unit 33 controls reception of a transmission signal by the LPWA communication unit 51 by supplying transmission parameters to the LPWA communication unit 51 based on the hopping plan. The reception channel is a channel that attempts reception when the channel of the incoming radio wave is known.

[0055] <Transmission Flow> FIG. 12 is a flowchart illustrating the flow of a transmission control process executed by the control unit 22 of FIG.

[0056] When the transmission control process is executed, transmission restrictions such as the total number of channels, the occupied time limit, and the same channel use restriction period imposed by the radio regulations of each country are acquired, and the transmission control process is executed in accordance with the transmission restrictions.

[0057] First, the initial setting unit 31 performs initial setting (S1). In this initial setting, the same number of nodes as the total number of channels are created, and a node set, which is a set of nodes, is configured as a circular list. Here, the total number of nodes is set to E0, the channel number is set in the ch field of each node, and the successor node is set in the next field. In addition, the maximum depth D is calculated. The method for calculating the maximum depth D will be described later.

[0058] Once the initial settings are complete, the hopping plan generation unit 32 performs a hopping plan generation process (S2). In the hopping plan generation process, the channel numbers to be used for transmission within the target transmission group are determined in transmission order, and a hopping plan is generated. The hopping plan generation process will be described in detail later.

[0059] When the hopping plan generation process is completed, the communication control unit 33 performs the processes of steps S3 to S6 based on the hopping plan. That is, it is determined whether it is time to transmit (S3), and if it is not time to transmit, it waits until the time to transmit. Then, when the time to transmit arrives, a signal is transmitted using a transmission channel included in the hopping plan (S4).

[0060] It is also determined whether the target group has been completed (S5), and steps S3 to S5 are repeated until the target group is completed, with multiple transmissions within the target group. If the target group is completed, the process waits for a transmission pause time (S6), and preparations are made for the next target group. After waiting, the process returns to step S2, and steps S2 to S6 are repeated for the next target group.

[0061] Fig. 13 is a flowchart illustrating in detail the hopping plan generation process in step S2 of Fig. 12. As described above, the hopping plan generation process is performed within the target destination group.

[0062] In the hopping plan generation process, initialization is first performed (S21). In this initialization, 0 is assigned to the depth field of each node in the node set, and the starting node is set to 0. Once the initialization is complete, node movement processing is performed (S22).

[0063] Figure 14 is a flowchart explaining the details of the node movement process. In Figure 14, right arrows represent conditions and results, with "condition" → "result." Left arrows represent assignments, for example, var ← 0 means that 0 is assigned to the variable var. The meanings of these arrows are the same in other figures described later.

[0064] In the node movement process, a random number P is generated (S31), and the number of nodes with depth = 0 is counted to determine the effective node number E i is calculated (S32). i is the number of effective nodes and the number of effective channels. The random number P is generated by a random number generator, the details of which will be described later. Next, mod(P, E i ) and calculate the node movement number R i mod(P, E i ) is P to E i This is a function that calculates the remainder when divided by . i A decision node is selected by moving through the node list (S34). Here, the circular list shown in FIG.

[0065] 13, when the node movement process is completed, the transmission channel is registered (S23). In the transmission channel registration, the channel number of the determined node is registered as the transmission channel number in the storage unit 34. It is then determined whether or not the transmission channel is the last in the target transmission group (S24). If it is determined that the transmission channel is not the last, a node update process is performed (S25).

[0066] Fig. 15 is a flowchart explaining the details of the node update process. In the node update process, the depth value is decremented by 1 for nodes excluding those with depth = 0, and the value 0 is maintained for those nodes with depth = 0 (S41). Furthermore, the depth value of the decision node is set to the maximum depth D (S42). Returning to Fig. 13, when the node update process is completed, the starting point selection process is performed (S26).

[0067] 16 is a flowchart illustrating the details of the start point selection process. In the start point selection process, the process moves to the node next to the decision node (S51), and it is determined whether or not depth = 0 for the next node (S52). If it is determined that depth = 0 is not true, the process returns to step S51, and the determination of whether or not depth = 0 is true for the next node is repeated (S51, S52). If it is determined that depth = 0 is true, that node is designated as the start point node (S53). In other words, the first node with depth = 0 found after the decision node is designated as the start point node.

[0068] 13, when the starting point selection process is completed, the process returns to step S22, and steps S22 and S23 are performed. Then, the loop process of S25, S26, and S22 to S24 is repeated until it is determined that the selected channel is the last transmission channel in the target transmission group. When it is determined in step S24 that the selected channel is the last transmission channel in the target transmission group, the hopping plan is finalized. Here, a decision node is selected for each loop process, and the channel number of the decision node is registered as the transmission channel number, so the registered channel number is included in the hopping plan in the order of transmission within the target transmission group.

[0069] As described above, in the hopping plan generation process, the depth value is updated for each target node in the node set, and a node that is located a number of node movements away from the starting node in the node set according to the depth value is selected as the decision node, and a hopping plan including the channel number of the decision node is generated.

[0070] Specifically, in node movement processing, the depth level of a node is specified by the depth value, and among the node sets, candidate node sets with a depth value of 0 are candidates for selection as decision nodes. On the other hand, among the node sets, nodes with a depth value other than 0 are nodes that cannot be selected as decision nodes. In addition, the number of node movements is determined by a random number, and a reproducible pseudo-random number can be used as the random number. For example, the number of node movements can be the remainder when the random number is divided by the number of candidate node sets that are candidates for selection as decision nodes (number of valid nodes).

[0071] In the node update process, the depth value of a node selected as a decision node is updated to a value other than 0, making it an unselectable node. Furthermore, the depth level of a node is updated, for example, by a node update process based on the passage of time, and an unselectable node is included in the candidate node set again when the depth value becomes 0. In the origin selection process, a node excluding the immediately preceding decision node is selected as the origin node, and that node is included in the candidate node set that is a candidate for selection as a decision node. For example, of the origin nodes, the origin node used for the first transmission within a transmission group can be set to a predetermined node, and the origin node used for the second and subsequent transmissions within the transmission group can be set to a node located near the immediately preceding decision node.

[0072] <Calculation method of maximum depth D> A method of calculating the maximum depth D set in the initial setting (S1) of Fig. 12 will be described. When the same channel is permitted to be used for up to R [seconds] for W [seconds], the maximum depth D is given by the following formula for a transmission interval of T [seconds].

[0073] In the first case, when (n+1)T - W = 0, the maximum depth D is calculated from (n+1)T = W by the following equation (1).

[0074]

[0075] In equation (1), n ​​is the smallest integer that satisfies the equation, T is the transmission interval [seconds], and W is the same channel usage limit time [seconds].

[0076] In the second case, when 0 < (n + 1)T - W ≦ R, the maximum depth D is calculated by the following formula (2) since n ≦ (W+R) / T - 1.

[0077]

[0078] In equation (2), n is the smallest integer that satisfies the formula, T is the transmission interval [seconds], R is the transmission duration [seconds] (the time during which radio waves are continuously transmitted), and W is the same channel usage limit [seconds].FLOOR(x) is a function that rounds down x to the nearest integer, giving the smallest integer less than or equal to x.

[0079] In the third case, when (n + 1)T - W > R, since n ≥ (W+R) / T - 1, the maximum depth D is calculated by the following formula (3).

[0080]

[0081] In equation (3), n is the smallest integer that satisfies the formula, T is the transmission interval (seconds), R is the transmission duration (seconds), and W is the same channel usage limit time (seconds). CEIL(x) is a function that rounds up the decimal point of x, and obtains the largest integer greater than or equal to x.

[0082] 17 to 19 are diagrams showing examples of calculations of maximum depth D when W = 20 seconds and R = 0.4. In Fig. 17 to 19, the horizontal direction represents time, and the transmitted signal is indicated by diagonal lines. Patterned diagonal lines 121A and 121B represent transmission on the same channel, while black diagonal line 121C represents transmission on a channel different from that of diagonal lines 121A and 121B.

[0083] FIG. 17 shows an example of calculating the maximum depth D in the first case above, where transmissions are made at intervals of T (= 1.25) seconds. In this case, from the above equation (1), D = W / T - 1 = 20 / 1.25 - 1 = 15 is calculated. As shown in FIG. 17, when transmission is made at the timing indicated by diagonal line 121A, the maximum depth D (d = 15) is set at the end of transmission at diagonal line 122B. With each transmission on another channel, the value of depth (d) decreases by 1 from 15, and transmission becomes possible when d = 0.

[0084] FIG. 18 shows an example of calculating the maximum depth D in the second case above, where transmissions are made at intervals of T (= 1.55) seconds. In this case, from the above equation (2), D = FLOOR(W+R / T - 1) = FLOOR((20+0.4) / 1.55 ​​- 1) = 12 is calculated. As shown in FIG. 18, when transmission is made at the timing indicated by diagonal line 121A, the maximum depth D (d = 12) is set at the end of transmission at diagonal line 122B. With each transmission on another channel, the value of d decreases by 1 from 12, and transmission becomes possible when d = 0.

[0085] FIG. 19 shows an example of calculating the maximum depth D in the third case above, where transmissions are made at intervals of T (= 2.55) seconds. In this case, from the above equation (3), D = CEIL(W+R / T - 1) = CEIL((20+0.4) / 2.55 - 1) = 7 is calculated. As shown in FIG. 19, when transmission is made at the timing indicated by diagonal line 121A, the maximum depth D (d = 7) is set at the end of transmission at diagonal line 122B. With each transmission on another channel, the value of d decreases by 1 from 7, and transmission becomes possible when d = 0.

[0086] If the same channel is not permitted to be used for W [seconds], the maximum depth D for a transmission interval T [seconds] is given by the following formula:

[0087] In the fourth case, when nT - W = 0 (n: integer), the maximum depth D is calculated from nT = W using the following formula (4), where n, T, and W are the same as those in the above formula (1).

[0088]

[0089] In the fifth case, when 0 < nT - W ≦ R, the maximum depth D is calculated by the following formula (5) from n ≦ (W+R) / T, where n, T, R, W, and FLOOR(x) are the same as in formula (2).

[0090]

[0091] In the sixth case, when (n + 1)T - W > R, since n ≥ (W + R) / T - 1, the maximum depth D is calculated by the following formula (6), where n, T, R, W, and CEIL(x) are the same as those in formula (3).

[0092]

[0093] <Example of Random Number Generator> The random number generator used in random number generation (S31) of the node movement process in Fig. 14 will be described. Fig. 20 is a diagram showing an example of the configuration of a random number generator. Fig. 21 is a diagram showing the flow of random number generation by the random number generator. The circled numbers 1 to 5 in Fig. 21 correspond to the circled numbers in Fig. 20.

[0094] As shown in FIG. 20 , the random number generator has a 40-bit Linear Feedback Shift Register (LFSR) 1 and a 32-bit LFSR 2. A 40-bit device ID is input as an initial value to LFSR 1, and LFSR 1 is initialized (circled number 1). 32-bit time information (Time Word) is input to LFSR 2, and LFSR 2 is initialized. The device ID is a terminal-specific ID, such as the device ID of the transmitter 11. Using the device ID prevents different terminals from repeatedly generating the same random number. The time information is an integer time, such as UNIX time. For example, time information based on a GNSS signal can be used.

[0095] The polynomial of LFSR1 is x 40 + x 35 + x 30 + x 25 + x20 + x 14 + x 10 + x 4 + 1. In LFSR1, the output bits (40-bit IDPRN) are stored (circled number 4) by idle counting 170 times (for bits) (circled number 2) and shifting out 40 times (for bits) (circled number 3). The output bits can be stored in the shift register that stores the first output bit of LFSR1 in the most significant position. The polynomial of LFSR2 is x 32 + x 30 + x 17 + x 12 + x 3 + x 1 + 1. In LFSR2, the output bits (40-bit TWPRN) are stored by idle counting 186 times (for bits) and shifting out 40 times (for bits).

[0096] Then, the pseudorandom number P is generated by taking the bitwise exclusive OR (XOR) of the 40-bit IDPRN and the 40-bit TWPRN. i can be generated (circled number 5).

[0097] Figures 22 and 23 are diagrams showing implementation examples of LFSRs. In Figures 22 and 23, the circled numbers 1 to 3 correspond to the circled numbers in Figures 20 and 21. As shown in Figure 22, in LFSR1, a 40-bit device ID is set as the initial value, and a 40-bit IDPRN (ID40PRN) is obtained by idling 170 times and outputting 40 times. As shown in Figure 23, in LFSR2, a 32-bit time information (Time Word) is set as the initial value, and a 40-bit TWPRN (TW40PRN) is obtained by idling 186 times and outputting 40 times.

[0098] As shown in FIG. 22 , the 40-bit IDPRN (ID40PRN) has a most significant bit (msb) that is the first LFSR1 output in the output of the circled number 3, and a least significant bit (lsb) that is the last LFSR1 output in the output of the circled number 3. Also, as shown in FIG. 23 , the 40-bit TWPRN (TW40PRN) has a most significant bit that is the first LFSR2 output in the output of the circled number 3, and a least significant bit that is the last LFSR2 output in the output of the circled number 3. A pseudo-random number P is generated by taking an exclusive OR (XOR) on each bit of the 40-bit IDPRN (ID40PRN) and the 40-bit TWPRN (TW40PRN). By using time information and a transmitter-specific ID (device ID) to generate the random number, a pseudo-random number P that changes over time can be obtained for each transmitter.

[0099] In generating a hopping plan, a reproducible pseudo-random number is used as the random number that determines the node movement number, so the receiving side can also reproduce (predict) the channel used for transmission. Therefore, there is no need for the receiving side to perform a brute force search for channels with radio waves.

[0100] First Embodiment Hereinafter, an embodiment of the present disclosure will be described, and a case will be described in which the same channel is permitted to be used for W [seconds] up to R [seconds].

[0101] FIG. 24 shows an example of calculating the maximum depth D in the first case above, where W = 10 seconds, R = 0.4 seconds, and transmission is performed at intervals of T = 5 seconds. In this case, equation (1) calculates D = W / T - 1 = 10 / 5 - 1 = 1. As shown in FIG. 24, when transmission is performed at the timing indicated by diagonal line 121A, the maximum depth D (d = 1) is set at the end of transmission at diagonal line 122B. Transmission on another channel indicated by diagonal line 121C decreases the value of d by 1, and transmission becomes possible when d = 0.

[0102] Fig. 25 shows an example of a transmission channel determined for each transmission time. In Fig. 25, W = 10 seconds, T = 5 seconds, and R = 0.4 seconds, and the maximum depth is D = 1, so the previous channel is not used.

[0103] In Fig. 25, the horizontal axis represents the transmission time and the vertical axis represents the transmission channel number, and the diagram shows how the transmission channel is determined for transmission times 0 to 7T when the transmission channel number is N = 10. Also, at the top of the diagram, E i , R i indicates the transmission channel determined by E i is the number of effective nodes, R i is the number of node movements. Since the transmission channel number is set to N=10, E0=10. The number of node movements is determined by the node movement processing in FIG.

[0104] In Figure 25, a circle corresponding to the transmission channel number is shown for each transmission time, and when the number inside the circle is 0, it indicates the starting point, and when the number inside the circle is n (1 to 9), it indicates movement number n. The thick circle indicates the selected transmission channel. Also, d indicates the depth level, and in this example, since the maximum depth is D = 1, it indicates that d = 1 is skipped. The positive direction is the direction of movement that increases the channel number of the node, and since each node is connected in a circular pattern, it returns to CH0 after CH9.

[0105] As shown in Figure 25, when transmission time is 0, R1 = 6, E1 = E0, and CH6 is selected as the transmission channel number. When transmission time is T, R2 = 7, E2 = E0 - 1, and CH4 is selected. When transmission time is 2T, R3 = 3, E3 = E0 - 1, and CH8 is selected. When transmission time is 3T, R4 = 2, E4 = E0 - 1, and CH1 is selected. When transmission time is 4T, R5 = 8, E5 = E0 - 1, and CH0 is selected. When transmission time is 5T, R6 = 4, E6 = E0 - 1, and CH5 is selected. When transmission time is 6T, R7 = 5, E7 = E0 - 1, and CH1 is selected. When transmission time is 7T, R8 = 0, E8 = E0 - 1, and CH2 is selected.

[0106] Here, in FIG. 25, since the immediately preceding channel is not used, for example, if CH6 is selected at transmission time 0, CH6 is skipped at transmission time T and is excluded from selection. Also, if CH4 is selected at transmission time T, CH4 is skipped at transmission time 2T. If CH8 is selected at transmission time 2T, CH8 is skipped at transmission time 3T. If CH1 is selected at transmission time 3T, CH1 is skipped at transmission time 4T. If CH0 is selected at transmission time 4T, CH0 is skipped at transmission time 5T. The same applies to CH5 selected at transmission time 5T, CH1 selected at transmission time 6T, and CH2 selected at transmission time 7T.

[0107] Figure 26 is a diagram showing the behavior of the nodes corresponding to Figure 25. In Figure 26, circular lists corresponding to each transmission time from 0 to 7T in Figure 25 are arranged vertically. In the circular list, each node has a ch field, a depth field, and a next field, and the ch field contains #0 to #9 corresponding to CH0 to CH9.

[0108] The processes are performed in numerical order on the left side of the diagram. First, when (R1, E1) = (6, E0), CH6 (#6) is selected as the channel number of the decision node (Process 1). In the topmost circular list corresponding to Process 1, the selected decision node (ch: #6) is surrounded by a bold frame. Next, the node update process is performed (Process 2), and after the update, the maximum depth D (d = 1) is set as the depth of the decision node (ch: #6) in the second circular list from the top.

[0109] Next, when (R2, E2) = (7, E0-1), the previous decision node (d = 1) is excluded from the candidates, and CH4 (#4) is selected as the decision node's channel number (Process 3). In the second circular list from the top corresponding to Process 3, the selected decision node (ch: #4) is surrounded by a bold frame. Next, the node update process is performed (Process 4), and in the third circular list from the top corresponding to the update, the depth of node (ch: #6) is decremented by 1 and set to 0, and the depth of decision node (ch: #4) is set to the maximum depth D (d = 1).

[0110] Next, when (R3, E3) = (3, E0-1), the previous decision node is excluded from the candidates, and CH8 (#8) is selected as the decision node's channel number (Process 5). In the third circular list from the top corresponding to Process 5, the selected decision node (ch: #8) is surrounded by a bold frame. Next, the node update process is performed (Process 6), and in the fourth circular list from the top corresponding to the update, the depth of node (ch: #4) is decremented by 1 and set to 0, and the depth of decision node (ch: #8) is set to the maximum depth D (d = 1).

[0111] Next, when (R4, E4) = (2, E0-1), the previous decision node is excluded from the candidates, and CH1 (#1) is selected as the decision node's channel number (Process 7). In the fourth circular list from the top corresponding to Process 7, the selected decision node (ch: #1) is surrounded by a bold frame. Next, the node update process is performed (Process 8), and in the fifth circular list from the top corresponding to the update, the depth of node (ch: #8) is decremented by 1 and set to 0, and the depth of decision node (ch: #1) is set to the maximum depth D (d = 1).

[0112] Next, when (R5, E5) = (8, E0-1), the previous decision node is excluded from the candidates, and CH0 (#0) is selected as the decision node's channel number (Process 9). In the fifth circular list from the top corresponding to Process 9, the selected decision node (ch: #0) is surrounded by a bold frame. Next, the node update process is performed (Process 10), and in the sixth circular list corresponding to the update, the depth of node (ch: #1) is decremented by 1 and set to 0, and the depth of decision node (ch: #0) is set to the maximum depth D (d = 1).

[0113] Next, when (R6, E6) = (4, E0-1), the previous decision node is excluded from the candidates, and CH5 (#5) is selected as the decision node's channel number (Process 11). In the sixth circular list corresponding to Process 11, the selected decision node (ch: #5) is surrounded by a bold frame. Next, a node update process is performed (Process 12), and in the seventh circular list corresponding to the update, the depth of node (ch: #0) is decremented by 1 and set to 0, and the depth of decision node (ch: #5) is set to the maximum depth D (d = 1).

[0114] Next, when (R7, E7) = (5, E0-1), the previous decision node is excluded from the candidates, and CH1 (#1) is selected as the decision node's channel number (Process 13). In the seventh circular list from the top corresponding to Process 13, the selected decision node (ch: #1) is surrounded by a bold frame. Next, a node update process is performed (Process 14), and in the corresponding bottom circular list after the update, the depth of node (ch: #5) is decremented by 1 and set to 0, and the depth of decision node (ch: #1) is set to the maximum depth D (d = 1).

[0115] When (R8, E8) = (0, E0-1), the previous decision node is excluded from the candidates, and CH2 (#2) is selected as the decision node's channel number (Process 15). In the bottom circular list corresponding to Process 15, the selected decision node (ch: #2) is surrounded by a bold frame.

[0116] As described above, when W = 10 seconds, R = 0.4 seconds, and T = 5 seconds, the maximum depth is D = 1, so the node behavior is that the previous decision node (d = 1) is not included in the candidate node set and becomes an unselectable node, so the previous channel is not used.

[0117] Second Embodiment Fig. 27 is a diagram showing an example of calculating the maximum depth D in the first case described above, where W = 20 seconds, R = 0.4 seconds, and transmission is performed at intervals of T = 5 seconds. In this case, from equation (1), D = W / T - 1 = 20 / 5 - 1 = 3 is calculated. As shown in Fig. 27, when transmission is performed at the timing indicated by diagonal line 121A, the maximum depth D (d = 3) is set at the end of transmission at diagonal line 122B. The value of d decreases by 1 as transmissions on other channels indicated by diagonal line 121C occur, and transmission becomes possible when d = 0.

[0118] Figure 28 shows an example of transmission channels determined for each transmission time. In Figure 28, W = 20 seconds, T = 5 seconds, and R = 0.4 seconds, and the maximum depth is D = 3, so the previous three channels are not used. In Figure 28, the axes and symbols are the same as in Figure 25.

[0119] As shown in Figure 28, when transmission time is 0, R1 = 6, E1 = E0, and CH6 is selected as the transmission channel number. When transmission time is T, R2 = 7, E2 = E0 - 1, and CH4 is selected. When transmission time is 2T, R3 = 3, E3 = E0 - 2, and CH9 is selected. When transmission time is 3T, R4 = 3, E4 = E0 - 3, and CH3 is selected. When transmission time is 4T, R5 = 4, E5 = E0 - 3, and CH0 is selected. When transmission time is 5T, R6 = 5, E6 = E0 - 3, and CH7 is selected. When transmission time is 6T, R7 = 2, E7 = E0 - 3, and CH1 is selected. When transmission time is 7T, R8 = 1, E8 = E0 - 3, and CH3 is selected.

[0120] In FIG. 28, the three immediately preceding channels are not used, so for example, if CH6 is selected at transmission time 0, CH6 is skipped from transmission times T to 3T and is not available for selection. Also, if CH4 is selected at transmission time T, CH4 is skipped from transmission times 2T to 4T. If CH9 is selected at transmission time 2T, CH9 is skipped from transmission times 3T to 5T. If CH3 is selected at transmission time 3T, CH3 is skipped from transmission times 4T to 6T. If CH0 is selected at transmission time 4T, CH0 is skipped from transmission times 5T to 7T. The same applies to CH7, which is selected at transmission time 5T, CH1, which is selected at transmission time 6T, and CH3, which is selected at transmission time 7T.

[0121] Fig. 29 is a diagram showing the behavior of the nodes corresponding to Fig. 28. In Fig. 29, the structure of each node in the circular list and the order of processing are the same as in Fig. 26.

[0122] First, when (R1, E1) = (6, E0), CH6 (#6) is selected as the channel number of the decision node (Process 1). In the topmost circular list corresponding to Process 1, the selected decision node (ch: #6) is surrounded by a bold frame. Next, the node update process is performed (Process 2), and after the update, the depth of the decision node (ch: #6) in the second corresponding circular list from the top is set to the maximum depth D (d = 3).

[0123] Next, when (R2, E2) = (7, E0-1), the previous decision node (d = 3) is excluded from the candidates, and CH4 (#4) is selected as the decision node's channel number (Process 3). In the second circular list from the top corresponding to Process 3, the selected decision node (ch: #4) is surrounded by a bold frame. Next, the node update process is performed (Process 4), and in the third circular list from the top corresponding to the update, the depth of node (ch: #6) is decremented by 1 and set to 2, and the depth of decision node (ch: #4) is set to the maximum depth D (d = 3).

[0124] Next, when (R3, E3) = (3, E0-2), the two previous decision nodes (d = 3, 2) are excluded from the candidates, and CH9 (#9) is selected as the decision node's channel number (Process 5). In the third circular list from the top corresponding to Process 5, the selected decision node (ch: #9) is surrounded by a bold frame. Next, the node update process is performed (Process 6), and in the fourth circular list corresponding to the update, the depth of node (ch: #6) is decremented by 1 and set to 1, the depth of node (ch: #4) is decremented by 1 and set to 2, and the depth of decision node (ch: #9) is set to the maximum depth D (d = 3).

[0125] Next, when (R4, E4) = (3, E0-3), the three previous decision nodes (d = 3, 2, 1) are excluded from the candidates, and CH3 (#3) is selected as the decision node's channel number (Process 7). In the fourth circular list corresponding to Process 7, the selected decision node (ch: #3) is surrounded by a bold frame. Next, the node update process is performed (Process 8). In the fifth circular list corresponding to Process 7, the depth of node (ch: #6) is decremented by 1 and set to 0, the depth of node (ch: #4) is decremented by 1 and set to 1, the depth of node (ch: #9) is decremented by 1 and set to 2, and the depth of decision node (ch: #3) is set to the maximum depth D (d = 3).

[0126] Next, when (R5, E5) = (4, E0-3), the three previous decision nodes are excluded from the candidates, and CH0 (#0) is selected as the decision node's channel number (Process 9). In the fifth circular list from the top corresponding to Process 9, the selected decision node (ch: #0) is surrounded by a bold frame. Next, the node update process is performed (Process 10), and in the sixth circular list corresponding to the update, the depth of node (ch: #4) is decremented by 1 and set to 0, the depth of node (ch: #9) is decremented by 1 and set to 1, the depth of node (ch: #3) is decremented by 1 and set to 2, and the depth of decision node (ch: #0) is set to the maximum depth D (d = 3).

[0127] Next, when (R6, E6) = (5, E0-3), the three previous decision nodes are excluded from the candidates, and CH7 (#7) is selected as the decision node's channel number (Process 11). In the sixth circular list corresponding to Process 11, the selected decision node (ch: #7) is surrounded by a bold frame. Next, the node update process is performed (Process 12). In the seventh circular list corresponding to Process 11, the depth of node (ch: #9) is decremented by 1 and set to 0, the depth of node (ch: #3) is decremented by 1 and set to 1, the depth of node (ch: #0) is decremented by 1 and set to 2, and the depth of decision node (ch: #7) is set to the maximum depth D (d = 3).

[0128] Next, when (R7, E7) = (2, E0-3), the three previous decision nodes are excluded from the candidates, and CH1 (#1) is selected as the decision node's channel number (Process 13). In the seventh circular list corresponding to Process 13, the selected decision node (ch: #1) is surrounded by a bold frame. Next, a node update process is performed (Process 14). In the corresponding bottom circular list after the update, the depth of node (ch: #3) is decremented by 1 and set to 0, the depth of node (ch: #0) is decremented by 1 and set to 1, the depth of node (ch: #7) is decremented by 1 and set to 2, and the depth of decision node (ch: #1) is set to the maximum depth D (d = 3).

[0129] When (R8, E8) = (1, E0-3), the three previous decision nodes are excluded from the candidates, and CH3 (#3) is selected as the decision node channel number (Process 15). In the circular list at the bottom corresponding to Process 15, the selected decision node (ch: #3) is surrounded by a bold frame.

[0130] As described above, when W = 20 seconds, T = 5 seconds, and R = 0.4 seconds, the maximum depth is D = 3, and the behavior of the node is that the previous three decision nodes (d = 3, 2, 1) are not included in the candidate node set and become unselectable nodes, so the previous three channels are not used.

[0131] <Modifications> Modifications will be described below.

[0132] <<First Modification>> The random numbers generated in the node movement process (S22 in FIG. 13) may be generated all at once. Fig. 30 is a flowchart illustrating the details of the node movement process corresponding to step S22 in Fig. 13.

[0133] In the node movement process, a random number P is generated by a random number generator (S71), and the number of nodes with depth = 0 is counted to determine the effective node number E i The processing in steps S71 and S72 is the same as that in steps S31 and S32 in FIG. 14. Next, divmod(P, Ei ) to find Q and R. Q is P to E i R is the quotient of P divided by E i Here, the remainder R is divided by the node movement number R i As, R i By moving through the node list times, a decision node is obtained (S74).

[0134] Furthermore, the quotient Q is substituted into P (S75), and P is saved (S76). Then, when the process of step S73 is performed next time, the saved P is read (S77), and divmod(P, E i In this way, the random number P is generated by the random number generator only the first time, and from the second time onwards, divmod(P, E i ) is calculated, Q is assigned to P and stored, and divmod(P, E i ) can be used in the calculation.

[0135] <<Second Modification>> The movement direction of the node may be in the opposite direction. As a first method, the movement direction of the node can be reversed by moving the node in the negative direction (decreasing the channel number) instead of the positive direction (increasing the channel number).

[0136] FIG. 31 is a diagram showing an example in which the movement direction of a node is set to the negative direction using the first method. FIG. 31 shows the next field value corresponding to the node number, but for comparison, the next field value of FIG. 7 is also shown. That is, in the next field of FIG. 7, the movement direction of the node is set to the positive direction (positive side) by specifying a subsequent node number. On the other hand, as shown in the second column of FIG. 31, in the first method, the movement direction of the node can be set to the negative direction (negative side) by specifying the previous node number as the value of the next field.

[0137] As a second method, the node movement direction may remain forward, and the ch field values ​​of the nodes may be set in reverse order. FIG. 32 is a diagram showing an example of setting the ch field values ​​in reverse order using the second method. FIG. 32 shows ch field values ​​corresponding to node numbers, but for comparison, the ch field values ​​of FIG. 7 are also shown. That is, the ch field values ​​of FIG. 7 are set in forward order corresponding to the node numbers. On the other hand, as shown in the second column of FIG. 32, the second method sets the ch field values ​​in reverse order.

[0138] Figure 33 is a diagram showing an example of a transmission channel determined for each transmission time when the first method described above is used. That is, Figure 33 shows an example of determining a transmission channel when the node's movement direction is set to the negative direction, and the difference compared to Figure 28 is that the node's movement direction has changed from the positive direction to the negative direction. In Figure 33, W = 20 seconds, T = 5 seconds, and R = 0.4 seconds, and the maximum depth D = 3, so the previous three channels are not used.

[0139] In Figure 33, the movement direction of the node is set to the negative direction, so the node with the smallest channel number adjacent to the transmission channel is selected as the starting node. For example, when CH6 is selected as the transmission channel number at transmission time 0, the adjacent node CH5 is selected as the starting node. Note that in Figure 28, the movement direction of the node is set to the positive direction, so when CH6 is selected at transmission time 0, the adjacent node CH7 is selected as the starting node.

[0140] <<Third Modification>> The movement direction of the node is not limited to one direction, either the positive or negative direction, and may be switched regularly between the positive and negative directions.

[0141] Figure 34 shows an example of a transmission channel determined for each transmission time when the node's movement direction alternates between positive and negative directions. That is, compared to Figures 28 and 33, Figure 34 differs in that the node's movement direction alternates between positive and negative directions, rather than being unidirectional (either positive or negative). In Figure 34, W = 20 seconds, T = 5 seconds, and R = 0.4 seconds, resulting in a maximum depth of D = 3, meaning that the previous three channels are not used.

[0142] In Figure 34, to alternately switch the movement direction of the node, the node with a larger channel number adjacent to the transmission channel and the node with a smaller channel number adjacent to the transmission channel are alternately selected as the origin node. In Figure 34, transmission time 0 is the positive direction, transmission time T is the negative direction, transmission time 2T is the positive direction, transmission time 3T is the negative direction, transmission time 4T is the positive direction, transmission time 5T is the negative direction, transmission time 6T is the positive direction, and transmission time 7T is the negative direction.

[0143] For example, when CH6 is selected as the transmission channel number at transmission time 0, the node CH5 adjacent in the negative direction is selected as the starting node. Subsequently, when CH2 is selected as the transmission channel number at transmission time T, the node CH3 adjacent in the positive direction is selected as the starting node. Similarly, nodes with channel numbers adjacent in the negative and positive directions are selected alternately thereafter.

[0144] Here, it is possible to alternate the movement direction by switching the next field or ch field of the node as shown in Figures 31 and 32. Alternatively, a prev field that stores the previous node number may be added to switch the movement direction.

[0145] Fig. 35 is a diagram showing another example of the structure of a node. In Fig. 35, the node has a ch field, a depth field, and a next field, similar to the structure in Fig. 5, and further has a prev field that stores the previous node number added. By storing the previous node number in the prev field, it becomes possible to determine whether to switch to a positive direction or a negative direction.

[0146] <<Fourth Modification>> Various methods can be used to select the origin node. For example, in the above-described embodiment and modification, when determining the first transmission channel, the node having channel number 0 is set as the origin node (node ​​number 0). Here, the origin node used in the first transmission channel calculation does not necessarily have to be "node number 0" and may be determined according to a specific rule, such as fixing it to a specific node number, for example, using "node number 1."

[0147] When determining the transmission channel from the second time onward, in the first and second embodiments (movement in the positive direction) and in the positive movement of the third modified example, the node with the larger channel number adjacent to the decision node (transmission channel) was selected as the source node among the candidate nodes (depth=0). On the other hand, in the second modified example (movement in the negative direction) and in the negative movement of the third modified example, the node with the smaller channel number adjacent to the decision node (transmission channel) was selected as the source node. These directions are not limited to the direction of movement, and may be fixed to one of them. Also, instead of an adjacent node among the candidate nodes, a node next to the candidate node (a node located nearby) may be selected. Also, the selection may be made according to a specific rule, such as selecting and fixing a node two nodes away.

[0148] <<Fifth Modification>> The channel number field (the ch field of the node) may exclude specific channels. Here, when center frequencies are set at equal intervals, there may be devices with high transmission power, such as RFID, at those frequencies. In this case, it is expected that those frequencies will be excluded from use.

[0149] For example, in the EU Wide Harmonized band L (865 MHz to 868 MHz), if center frequencies are set every 200 kHz starting from 865.100 MHz, RFID capable of transmitting at 4 W is permitted at 865.700 MHz, 866.300 MHz, 866.900 MHz, and 867.500 MHz. LPWA transmission is limited to 25 mW. In this case, by defining channels with equally spaced center frequencies using the following equation (7) and then excluding the channel numbers you do not want to use, as shown in Figure 36, frequency hopping that excludes specific channels becomes possible without performing conditional processing.

[0150] Transmit channel center frequency (center freq) = 865.100 + ch field value × 0.200 [MHz] ... (7)

[0151] In Figure 36, node numbers are associated with ch field values, but the ch field values ​​exclude channel number 3 corresponding to 865.700 MHz, channel number 6 corresponding to 866.300 MHz, channel number 9 corresponding to 866.900 MHz, and channel number 12 corresponding to 867.500 MHz.

[0152] <<Sixth Modification>> In the above-described embodiment and modifications, the number of node movements is determined by the remainder obtained when a random value is divided by the size of the candidate node set. The remainder is used here to minimize the number of movements while ensuring that candidate nodes are selected evenly (probabilistically). Therefore, other methods may be used to determine the number of node movements as long as they can select candidate nodes evenly (probabilistically).

[0153] For example, a random number value itself may be used as the node movement number. Even if the random number value is larger than the number of candidate nodes, the candidate nodes can be selected statistically (probably) uniformly.

[0154] <Application Examples> Application examples will be described below.

[0155] <<First Application Example>> The present disclosure is a technology related to frequency hopping (frequency direction), but can also be applied to the time direction. FIG. 37 is a diagram illustrating an example in which the present disclosure is applied to the time direction. In FIG. 37, the horizontal direction represents time, and the diagram schematically illustrates how signals are transmitted in units of transmission slots. The transmitted signals are indicated by diagonal lines 111. Furthermore, the numbers 0 to 9 in the horizontal direction for each transmission slot indicate the transmission delay time numbers. Here, the transmission delay time numbers are numbers assigned to each fixed time interval within the transmission slot, and represent the transmission timing to be delayed.

[0156] As shown in Figure 37, when there are radio waves 211 of other systems that transmit at regular intervals, it is expected that there will be collisions with the radio waves 211 of other systems depending on the transmission channel. However, by shifting the transmission timing forward or backward, interference by the radio waves 211 of other systems can be avoided.

[0157] <<Second Application Example>> In the present disclosure, channel selection restrictions can be satisfied across transmission groups. For example, if there is a gap between a data signal and a setup signal, a hopping plan (hopping list) is generated that includes the setup signal. As a result, in non-transmission intervals, channel restrictions between the setup signal and the data signal can be satisfied by performing only node update processing.

[0158] Figure 38 is a diagram showing an example of satisfying channel selection restrictions across transmission groups. In Figure 38, the horizontal axis represents time and the vertical axis represents the transmission channel number, showing the use of channels CH0 to CH9. Figure 38 also illustrates a case where W = 20 seconds, T = 5 seconds, R = 0.4 seconds, and the maximum depth D = 3, and the previous three channels are not used. In Figure 38, the setup signal is indicated by diagonal lines 111S, and the data signal is indicated by diagonal lines 111D.

[0159] 38 , there is a non-transmission interval between the period in which transmission group 1 transmits a setup signal and the period in which transmission group 2 transmits a data signal. For example, the non-transmission interval is a setup processing time. At this time, a hopping plan is generated that includes the setup signal as well as the data signal.

[0160] Figure 39 is a diagram showing the relationship between channel numbers and generation order. In Figure 39, channel numbers 0 to 3 in generation order correspond to transmission group 1 in Figure 38, and channel numbers 4 to 7 in generation order correspond to transmission group 2 in Figure 38. The portions of the generation order marked with "-" correspond to the non-transmission intervals in Figure 38. In other words, in transmission group 1, CH7, CH1, CH3, and CH8 are selected in that order, and in transmission group 2, CH3, CH9, CH4, and CH6 are selected in that order.

[0161] As shown in Figure 38, in transmission for transmission group 1, first, CH7 is selected as the transmission channel, and a setup signal is transmitted using CH7. In this case, since the maximum depth D = 3, d = 3 is set for the node of CH7, and it is decremented by 1 each time it is updated. Next, a setup signal is transmitted using CH1, and d = 3 is set for the node of CH1. Next, setup signals are transmitted using CH3 and CH8, and then a non-transmission interval begins. The value of d continues to be updated even during the non-transmission interval. When the non-transmission interval ends, transmission for transmission group 2 begins. In transmission for transmission group 2, data signals are transmitted using CH3, CH9, CH4, and CH6 in that order.

[0162] Here, a description will be given of the node update process corresponding to the second application example. When the second application example is implemented, the node update process shown in the flowchart of Fig. 40 is performed as the process of step S25 in Fig. 13.

[0163] In the node update process of FIG. 40 , the depth value is decremented by 1 for all nodes except for those with depth = 0 (S91). Nodes with depth = 0 maintain depth = 0. The process of step S91 is the same as step S41 of FIG. 15 . Next, it is determined whether the next slot is a non-transmission slot (i.e., the non-transmission interval of FIG. 38 ). If it is determined that the next slot is a non-transmission slot, the process returns to step S91, and steps S91 and S92 are repeated. As a result, as shown in FIG. 38 , no signal is transmitted during the non-transmission interval, but the node update process is performed, and the depth value of the target node is decremented by 1 each time it is updated. On the other hand, if it is determined that the next slot is not a non-transmission slot, the depth value of the decision node is set to the maximum depth D (S93). The process of step S93 is the same as step S42 of FIG. 15 . For example, in the period of transmission group 2 after the non-transmission interval of FIG. 38 , the depth of the decision node (CH3) is set to d = 3.

[0164] <<Third Application Example>> For example, if a preceding transmission is treated as optional, there is a possibility that a signal will not be transmitted in that transmission. In the present disclosure, in order to handle optional treatment and the presence or absence of a preceding transmission, the hopping plan may be applied in reverse order. When the hopping plan is applied in the normal order, it is necessary to calculate the transmission channel number even if there is a possibility that a signal will not be transmitted. On the other hand, when the hopping plan is applied in the reverse order, if no transmission is to be performed, the corresponding information can be discarded. It is also possible to handle cases where the number of optional transmissions differs between transmission groups. It is also possible to handle total transmission time limits, for example, within 360 seconds per hour.

[0165] Figure 41 shows an example of a case where the channel selection restriction is satisfied even if the preceding transmission is treated as optional. In Figure 41, similar to Figure 38, the horizontal axis represents time and the vertical axis represents the transmission channel number, and shows an example where channels CH0 to CH9 are used but the previous three channels are not used.

[0166] In Fig. 41, after transmitting the setup signal indicated by the diagonal line 111S, a data signal indicated by the diagonal line 111D is transmitted, but among the setup signals, the setup signals in parentheses () are optional. At this time, the hopping plans are applied in reverse order.

[0167] Figure 42 shows the relationship between channel numbers and generation order. As shown in Figure 42, when the generation order of channel numbers is 6, 2, 9, 3, 0, 7, 1, and 3, the order is reversed. That is, as shown in Figure 41, after transmitting a setup signal using CH3, CH1, CH7, and CH0 in that order, a data signal is transmitted using CH3, CH9, CH2, and CH6 in that order. Here, the setup signal transmitted using CH3 and CH1 is an optional preceding transmission, but it satisfies the channel selection restriction.

[0168] <<Fourth Application Example>> It is assumed that the hopping plan (hopping pattern) is generated by the transmitter 11 and the receiver 12, but a server connected via a network may be provided and the processing may be performed on the server side. Fig. 43 is a diagram showing another configuration example of a wireless communication system to which the present disclosure is applied. Compared to the wireless communication system of Fig. 1, the wireless communication system of Fig. 43 additionally includes a management server 14 in addition to the transmitter 11, receiver 12, and positioning satellite 13.

[0169] 43 , the management server 14 is connected to the transmitter 11 and the receiver 12 via a network such as the Internet, and can exchange data with them. The management server 14 can transmit reception setting parameters to the receiver 12. The management server 14 can also receive and register identifiers such as a device ID transmitted from the transmitter 11. For example, the management server 14 generates a hopping pattern based on the registered identifier (e.g., using a random number based on the device ID), includes the hopping pattern in the reception setting parameters, and transmits the same to the receiver 12. The receiver 12 can receive signals transmitted from the transmitter 11 based on the reception setting parameters (hopping pattern) received from the management server 14. This reduces the computational load on the receiver 12, and increases the number of devices that can be accommodated.

[0170] The management server 14 may also collect and store reception data received by the receiver 12. By generating a hopping pattern in the management server 14, it becomes possible to associate the reception data with the received channel number, and to perform post-analysis of changes in the radio wave environment for each channel frequency. The reception data corresponds to the transmission data transmitted from the transmitter 11.

[0171] As described above, according to the present disclosure, when frequency hopping is used, it is possible to select a frequency channel more appropriately. In particular, frequency hopping that corresponds to channel selection restrictions is possible. For example, it is not necessary to widen the transmission interval to satisfy the usage restrictions per channel, and transmission can be performed at the maximum frequency (number of times). Furthermore, since channels other than those with usage restrictions are selected randomly using random numbers, uniform channel usage can be achieved.

[0172] According to the present disclosure, as explained in the second application example, it is also possible to deal with cases where there are non-transmission intervals (non-transmission slots). Here, the simplest alternative method is to calculate a hopping pattern so that transmission is also performed in the non-transmission intervals, and not actually transmit in the non-transmission intervals. In this case, the channel number that was to be used in the non-transmission interval cannot be used in subsequent transmissions for a certain period of time (channel use restriction), resulting in ineffective use of frequencies. According to the present disclosure, as explained in the third application example, hopping that corresponds to channel selection restriction is possible even if the preceding transmission is treated as optional.

[0173] Furthermore, according to the present disclosure, it is possible to realize channel selection that takes into account the same channel selection restriction and its usage time. For example, compared to a method in which a channel is used / selected only once, it is possible to reuse channels, thereby maximizing the degree of freedom in channel selection. Furthermore, compared to a method using a table, there is an advantage in that it is not necessary to create multiple different tables, share tables, or store them on the transmitting side (transmitter 11) or the receiving side (receiver 12).

[0174] In the present disclosure, the node movement process uses time information based on GNSS signals to vary the time and a random number combined with a unique ID (e.g., device ID), thereby realizing NONCE (Number Used Once). This enables all transmitting terminals (transmitters 11) to perform channel hopping to prevent continued collisions between channels used for transmission. Furthermore, by using the algorithm of the present disclosure on the transmitting side (transmitter 11) and the receiving side (receiver 12), the receiving side does not need to search all channels and can perform reception processing only on the transmitted channel, thereby reducing the processing load on the receiving side. The present disclosure is applicable to a system in which the identifier (e.g., device ID) of the transmitting terminal (transmitter 11) that emits the radio waves to be received is known. A method for recognizing identifiers such as device IDs may be provided separately from the system of the present disclosure.

[0175] <Computer Configuration> The above-described series of processes can be executed by hardware or software. When the series of processes is executed by software, a program constituting the software is installed in a computer. Figure 44 is a block diagram showing an example of the hardware configuration of a computer that executes the above-described series of processes by a program.

[0176] In the computer, a CPU 1001, a ROM 1002, and a RAM 1003 are interconnected by a bus 1004. An input / output interface 1005 is further connected to the bus 1004. An input unit 1006, an output unit 1007, a storage unit 1008, a communication unit 1009, and a drive 1010 are connected to the input / output interface 1005.

[0177] The input unit 1006 includes a keyboard, a mouse, a microphone, etc. The output unit 1007 includes a display, a speaker, etc. The storage unit 1008 includes a hard disk, a non-volatile memory, etc. The communication unit 1009 includes a network interface, etc. The drive 1010 drives a removable recording medium 1011 such as a semiconductor memory, a magnetic disk, an optical disk, or a magneto-optical disk.

[0178] In a computer configured as described above, the CPU 1001 loads a program recorded in the ROM 1002 or memory unit 1008 into the RAM 1003 via the input / output interface 1005 and the bus 1004 and executes it, thereby performing the above-mentioned series of processes.

[0179] The program executed by the computer (CPU 1001) can be provided by being recorded on a removable recording medium 1011 such as a package medium, for example. The program can also be provided via a wired or wireless transmission medium such as a local area network, the Internet, or digital satellite broadcasting.

[0180] In a computer, the program can be installed in the storage unit 1008 via the input / output interface 1005 by inserting the removable recording medium 1011 into the drive 1010. The program can also be received by the communication unit 1009 via a wired or wireless transmission medium and installed in the storage unit 1008. Alternatively, the program can be installed in advance in the ROM 1002 or the storage unit 1008.

[0181] In this specification, the processing performed by a computer according to a program does not necessarily have to be performed in chronological order according to the order described in the flowchart. In other words, the processing performed by a computer according to a program also includes processing executed in parallel or individually (for example, parallel processing or object-based processing). Furthermore, the program may be processed by a single computer (processor), or may be distributed across multiple computers.

[0182] It should be noted that the embodiments of the present disclosure are not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of the present disclosure. Furthermore, the effects described in this specification are merely examples and are not intended to be limiting, and other effects may also be obtained.

[0183] The present disclosure can also be configured as follows.

[0184] (1) A transmitter comprising: a node set, which is a set of nodes whose elements include at least a channel number and a depth level, configured as a circular list; a control unit that performs control to update the depth level for each target node in the node set, select a node that is located a node movement count from a starting node in the node set according to the depth level as a decision node, and transmit a signal using the channel number of the decision node as a transmission channel number. (2) The transmitter according to (1), in which the node further includes an index to the next node as an element. (3) The transmitter according to (1) or (2), in which, when the depth level is specified by a depth value, a candidate node set in the node set whose depth value is 0 becomes a candidate for selection as the decision node. (4) The transmitter according to any of (1) to (3), in which, when the depth level is specified by a depth value, a node in the node set whose depth value is other than 0 is a node that cannot be selected as the decision node, and the node selected as the decision node has its depth value updated to a value other than 0, making it a node that cannot be selected. (5) The transmitter according to (4), wherein the depth level is updated by an update process based on the passage of time, and the unselectable node is included in a set of candidate nodes that are candidates for selection as the decision node when the value of depth becomes 0. (6) The transmitter according to any of (1) to (5), wherein the node movement count is determined by a random number. (7) The transmitter according to (6), wherein the node movement count uses the remainder when the random number is divided by the number of candidate nodes in a set of candidate nodes that are candidates for selection as the decision node. (8) The transmitter according to (6) or (7), wherein the random number is a reproducible pseudo-random number. (9) The transmitter according to any of (1) to (8), wherein the source node is a node excluding the immediately preceding decision node and is included in a set of candidate nodes that are candidates for selection as the decision node. (10) The transmitter according to (9), wherein the source node used for the first transmission in a transmission group is a predetermined node.(11) The transmitter according to (9) or (10), wherein, of the source nodes, the source node used for second and subsequent transmissions within the transmission group is a node located near the immediately preceding determination node. (12) A transmission method including: a node set, which is a set of nodes including at least a channel number and a depth level as elements, configured as a circular list, updating the depth level for each target node in the node set, and selecting a node that is advanced from the source node in the node set by the number of node movements according to the depth level as a determination node, and transmitting a signal by using the channel number of the determination node as a transmission channel number. (13) A receiver including: a node set, which is a set of nodes including at least a channel number and a depth level as elements, configured as a circular list, updating the depth level for each target node in the node set, and selecting a node that is advanced from the source node in the node set by the number of node movements according to the depth level as a determination node, and receiving a signal by using the channel number of the determination node as a reception channel number. (14) A receiving method including: a receiver, in which a node set, which is a set of nodes including at least a channel number and a depth level as elements, is configured as a circular list; the receiver updates the depth level for each target node in the node set; and selects a node that is located from a starting node in the node set by the number of node movements according to the depth level as a decision node; and receives a signal using the channel number of the decision node as a receiving channel number.

[0185] DESCRIPTION OF SYMBOLS 11 Transmitter, 12 Receiver, 13 Positioning satellite, 14 Management server, 21 Transmission data generation unit, 22 Control unit, 23 LPWA communication unit, 24 GNSS receiving unit, 31 Initial setting unit, 32 Hopping plan generation unit, 33 Communication control unit, 34 Storage unit, 51 LPWA communication unit, 52 GNSS receiving unit, 53 Control unit, 54 Transmission data processing unit

Claims

1. A transmitter comprising: a node set, which is a set of nodes whose elements include at least a channel number and a depth level, configured as a circular list; a control unit that updates the depth level for each target node in the node set; selects a node that is located a number of node movements from a starting node in the node set according to the depth level as a decision node; and transmits a signal using the channel number of the decision node as a transmission channel number.

2. The transmitter of claim 1, wherein the node further includes an index to the next node as an element.

3. The transmitter according to claim 1, wherein, when the depth level is specified by a value of "depth", a candidate node set among the node sets having a depth value of 0 is a candidate to be selected as the decision node.

4. The transmitter of claim 1, wherein, when the depth level is specified by a depth value, any node in the node set having a depth value other than 0 is a node that cannot be selected as the decision node, and the node selected as the decision node has its depth value updated to a value other than 0, making it a node that cannot be selected.

5. The transmitter of claim 4, wherein the depth level is updated by an update process based on the passage of time, and the non-selectable node is included in a set of candidate nodes that become candidates for selection as the decision node when the depth value becomes 0.

6. The transmitter according to claim 1, wherein the node movement number is determined by a random number.

7. The transmitter according to claim 6, wherein the node movement number is a remainder obtained by dividing the random number by the number of candidate nodes in a set that are candidates for selection as the decision node.

8. The transmitter according to claim 6, wherein the random numbers are reproducible pseudo-random numbers.

9. The transmitter according to claim 1, wherein the origin node is a node excluding the immediately preceding decision node and is a node included in a set of candidate nodes that are candidates for selection as the decision node.

10. The transmitter according to claim 9, wherein the source node used for the first transmission within the transmission group is a predetermined node.

11. The transmitter according to claim 9, wherein the source node used for the second and subsequent transmissions within the transmission group is a node located in the vicinity of the immediately preceding decision node.

12. A transmission method comprising: a transmitter configured as a circular list of a node set, the node set being a set of nodes whose elements include at least a channel number and a depth level; updating the depth level for each target node in the node set; and selecting a node that is a node that is a number of node movements away from a starting node in the node set according to the depth level as a decision node; and transmitting a signal using the channel number of the decision node as a transmission channel number.

13. A receiver comprising a control unit that performs control such that a node set, which is a set of nodes whose elements include at least a channel number and a depth level, is configured as a circular list, the depth level is updated for each target node in the node set, a node that is located a number of node movements from a starting node in the node set according to the depth level is selected as a decision node, and the channel number of the decision node is used as a receiving channel number to receive a signal.

14. A receiving method comprising: a receiver configured as a circular list of a node set, the node set being a set of nodes whose elements include at least a channel number and a depth level; updating the depth level for each target node in the node set; and selecting a node that is a node that is a number of node movements away from a starting node in the node set according to the depth level as a decision node; and receiving a signal using the channel number of the decision node as a receiving channel number.

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