Communication control apparatus

Abstract

This communication control apparatus comprises: a plurality of directional antennas having mutually different coverages; a distribution unit for distributing the transmission power of a signal to the plurality of directional antennas in respective designated proportions; and a control unit for controlling the distribution unit such that the transmission power is only distributed to the directional antenna having the coverage within which a communication target terminal is present.

Description

communication control device

[0001] The present invention relates to a communication control device.

[0002] There is an Internet of Things (IoT) system that includes a slave device equipped with a sensor or the like and a master device that connects to a higher-level network as a wireless access point for the slave devices. Conventionally, the master device of an IoT system (hereinafter referred to as an "IoT master device") generally uses an omnidirectional antenna to transmit and receive signals to and from each of a plurality of slave devices (hereinafter referred to as "terminals") (see, for example, Non-Patent Document 1). The IoT master device can change the coverage area by changing its transmission power.

[0003] BA Homssi et al., "IoT Network Design Using Open-Source LoRa Coverage Emulator," IEEE Access, VOLUME 9, pp.53636-53646, April 2021.

[0004] When an IoT master device is powered by, for example, a battery or minute optical power supply, there is a limit to the amount of power that can be used. Therefore, power saving is required for such IoT master devices. However, in the case of IoT master devices that use omnidirectional antennas, the coverage becomes narrower as the transmission power is reduced. Therefore, in the past, when power saving was attempted by reducing the transmission power, there was a problem that some terminals had difficulty communicating with the IoT master device.

[0005] In view of the above circumstances, an object of the present invention is to provide a communication control device that can further reduce power consumption while suppressing the occurrence of terminals that have difficulty communicating with the device itself.

[0006] One aspect of the present invention is a communication control device comprising: a plurality of directional antennas having different coverage areas; a distribution unit that distributes the transmission power of a signal to the plurality of directional antennas at a specified ratio; and a control unit that controls the distribution unit so that the transmission power is distributed only to the directional antennas whose coverage areas include a terminal to be communicated with.

[0007] According to the present invention, it is possible to provide a communication control device that can further reduce power consumption while suppressing the occurrence of terminals that have difficulty communicating with the device itself.

[0008] 1 is an overall configuration diagram of a wireless communication system 1 according to an embodiment of the present invention. FIG. 1 is a conceptual diagram of power saving control by an IoT master 10 according to an embodiment of the present invention. FIG. 2 is a diagram showing power saving by a conventional wireless communication system 1a. FIG. 3 is a diagram showing an overview of the flow of operations during initial setup of an IoT master 10 according to an embodiment of the present invention. FIG. 4 is a flowchart showing the operations of phase 1 during initial setup of an IoT master 10 according to an embodiment of the present invention. FIG. 5 is a flowchart showing the operations of phase 2 during initial setup of an IoT master 10 according to an embodiment of the present invention. FIG. 6 is a diagram showing an example of information set 1 edited by an IoT master 10 according to an embodiment of the present invention. FIG. 7 is a diagram showing an example of information set 2 edited by an IoT master 10 according to an embodiment of the present invention. FIG. 8 is a flowchart showing another configuration example of the operations of phase 2 during initial setup of an IoT master 10 according to an embodiment of the present invention. FIG. 9 is a block diagram showing the functional configuration of an IoT master 10 according to an embodiment of the present invention. FIG. 10 is a flowchart showing the operations during operation of an IoT master 10a according to a modified embodiment of the present invention. FIG. 11 is a flowchart showing the operations during operation of an IoT master in the prior art.

[0009] A communication control device according to an embodiment of the present invention will be described in detail below with reference to the drawings.

[0010] FIG. 1 is a diagram showing the overall configuration of a wireless communication system 1 according to one embodiment of the present invention. The wireless communication system 1 according to this embodiment is an IoT system. However, the present invention can also be applied to wireless communication systems other than IoT systems. As shown in FIG. 1, the wireless communication system 1 includes an IoT master device 10 and a plurality of terminals 20. The IoT master device 10 is an example of a communication control device according to the present invention.

[0011] The IoT master device 10 is a communication device that is connected to a higher-level network (not shown) and functions as a wireless access point for multiple terminals 20. The IoT master device 10 is communicatively connected to each of the terminals 20 wirelessly. The IoT master device 10 is communicatively connected to the higher-level network by wire, wirelessly, or a combination thereof.

[0012] The terminal 20 is an IoT device equipped with, for example, a sensor. The terminal 20 may be a terminal device other than an IoT device. The terminal 20 transmits information to the IoT master 10. In this embodiment, the information transmitted from the terminal 20 to the IoT master 10 is, for example, measurement data obtained by measurement using a sensor. However, the information transmitted from the terminal 20 to the IoT master 10 is not limited to measurement data, and may be any information.

[0013] The IoT master device 10 receives the measurement data transmitted from the terminal 20. The IoT master device 10 transfers the received measurement data to a higher-level device (not shown) via a higher-level network.

[0014] In addition, if the terminal 20 is a device equipped with various controllers (not shown), the host device may transmit a control signal generated in accordance with the received measurement data to the IoT master device. The control signal is, for example, a signal including data indicating the control amount of the controller, calculated by the host device based on measurement data obtained by measurements using a sensor in the terminal 20. The IoT master device 10 receives the control signal transmitted from the host device via the host network and transfers the control signal to the terminal 20. The terminal 20 controls the operation of the controller in accordance with the control amount indicated by the received control signal.

[0015] The IoT master device 10 in this embodiment is equipped with a plurality of directional antennas (not shown). As an example, Fig. 1 shows the IoT master device 10 equipped with ten directional antennas. Therefore, in Fig. 1, the coverage of each of the ten directional antennas is shown as coverages C1 to C10.

[0016] 1, the multiple directional antennas are installed so that the receiving directions radiate from the center of the IoT master device 10. The IoT master device 10 can communicate with any terminal 20 located within at least one of coverage areas C1 to C10.

[0017] An outline of the power saving control by the IoT master device 10 will be described below.

[0018] 2 is a conceptual diagram of power saving control by the IoT master device 10 according to an embodiment of the present invention. The IoT master device 10 according to this embodiment can individually control the transmission power of multiple directional antennas. The higher the transmission power, the wider (longer) the coverage. Therefore, the coverage of a directional antenna whose transmission power is changed by the IoT master device 10 changes.

[0019] The IoT master device 10 in this embodiment is configured to use only directional antennas whose coverage includes the terminal 20. That is, for directional antennas whose coverage does not include the terminal 20, the IoT master device 10 sets the transmission power to 0 and puts the antennas into a dormant state. This reduces the total amount of transmission power used by multiple directional antennas.

[0020] 2, for example, the only coverages in which terminals 20 exist are coverages C2, C4, and C10. Two, one, and two terminals 20 exist in coverages C2, C4, and C10, respectively. Therefore, the IoT master device 10 sets the transmission power of the seven directional antennas that cover coverages C1, C3, and C5 to C9 to 0. This reduces the total amount of transmission power used by the multiple directional antennas.

[0021] Furthermore, the IoT master device 10 in this embodiment is configured to set a minimum necessary transmission power for each directional antenna. The minimum necessary transmission power here refers to the minimum transmission power that enables the terminal 20 to receive a transmission signal transmitted from the IoT master device 10. More specifically, the IoT master device 10 acquires a received signal strength indicator (RSSI) value from each terminal 20 present within its coverage area. The IoT master device 10 sets an appropriate (minimum necessary) transmission power for each coverage area according to the acquired RSSI value.

[0022] 2, for example, in coverage areas C2 and C10, terminals 20 are present even in locations far away from the IoT master device 10 (around the position where the coverage distance is longest). On the other hand, in coverage area C4, terminals 20 are present only in locations relatively close to the IoT master device 10. In reality, the presence of obstructions and the like also affects the RSSI value, but basically, the closer the terminal 20 is to the IoT master device 10, the larger the RSSI value.

[0023] If the RSSI value is larger for terminals 20 located closer to the IoT master device 10, the minimum RSSI value for terminals 20 located within the same coverage area will be larger for coverage C4 than for coverages C2 and C10. In other words, the minimum transmission power of the directional antenna required for the IoT master device 10 to communicate with all terminals 20 will be smaller for the directional antenna with coverage C4 than for the directional antenna with coverages C2 and C10.

[0024] That is, the directional antenna with coverage C4 can communicate with all terminals 20 within its coverage area with relatively low transmission power. The IoT master device 10 controls the transmission power of the directional antenna for each coverage area to the minimum required transmission power. This reduces the total amount of transmission power used by multiple directional antennas.

[0025] FIG. 3 is a diagram showing power saving achieved by a conventional wireless communication system 1a for comparison. Unlike the IoT master device 10 of the present embodiment, the conventional IoT master device 10a is equipped with an omnidirectional antenna, such as a dipole antenna. Therefore, as shown in FIG. 3, the coverage shape is a circle centered on the position of the IoT master device 10a. In the conventional IoT master device 10a, if the transmission power of the omnidirectional antenna is reduced for the purpose of power saving, the size of the circular coverage becomes even smaller.

[0026] For example, in Fig. 3, coverage Ca is the coverage before the transmission power is reduced, and coverage Cb is the coverage after the transmission power is reduced. As the coverage becomes smaller, for example, as shown in Fig. 3, there are cases where terminals 20 fall outside the coverage (in Fig. 3, the two terminals 20 from the top fall outside the coverage). In this case, it becomes difficult for terminals 20 that fall outside the coverage to communicate with the IoT master device 10a and the higher-level device.

[0027] In contrast, the IoT master device 10 according to one embodiment of the present invention does not attempt to save power by simply reducing transmission power and narrowing coverage, but is configured to save power by controlling so as not to cover areas where no terminals 20 are present, as shown in Fig. 2. Therefore, the IoT master device 10 according to one embodiment of the present invention can further reduce power consumption while suppressing the occurrence of terminals 20 that have difficulty communicating with the device itself.

[0028] Alternatively, the IoT master device 10 in one embodiment of the present invention can include in its coverage a terminal 20 that is located further away without increasing power consumption. In other words, the IoT master device 10 in one embodiment of the present invention can control so as not to cover an area where no terminal 20 is present, and the power consumption saved thereby can be used to extend the distance of coverage in the desired receiving direction.

[0029] [Operation of IoT Master Device] The operation of the IoT master device 10 related to power saving control will be described in detail below with specific examples. The operation of the IoT master device 10 related to power saving control can be divided into an operation during initial setup (operation A) and an operation during operation (operation B) performed after the initial setup.

[0030] The operation during initial setup (operation A) is an operation for the IoT master device 10 to grasp its surroundings (such as the presence of terminals 20) after the IoT master device 10 and all terminals 20 have been installed. On the other hand, the operation during operation (operation B) is an operation for the IoT master device 10 to communicate with multiple terminals 20 (here, as an example, an operation for the IoT master device 10 to transmit information to multiple terminals 20).

[0031] First, we will explain the operation (operation A) during initial setup of the IoT master device 10. Fig. 4 is a diagram showing an overview of the flow of operations during initial setup of the IoT master device 10 in one embodiment of the present invention. As shown in Fig. 4, the operation (operation A) during initial setup of the IoT master device 10 includes a phase 1 operation (step S001) that is performed first and a phase 2 operation (step S002) that is performed later.

[0032] In phase 1, communication with terminal 20 is performed using all directional antennas in turn. In phase 2, communication with terminal 20 is performed by reducing the number of directional antennas used and the transmission power. Below, an example of operation in phase 1 and phase 2 will be described in detail.

[0033] FIG. 5 is a flowchart showing the operation of phase 1 during initial setup of the IoT master device 10 in one embodiment of the present invention.

[0034] First, the IoT master device 10 sets the antenna number n, which identifies each of the multiple directional antennas, to an initial value of 1 (n←1) ​​(step S101). Next, the IoT master device 10 sets the transmission power P of its own directional antenna to an initial value of P0 (P←P0) (step S102).

[0035] Next, the IoT master device 10 initializes two parameters, m_n and I_rssi (step S103). Here, m_n is a parameter used to count the number of terminals 20 present in the coverage of the directional antenna with antenna number n. Furthermore, I_rssi is a parameter into which the RSSI value (or a numerical value related to RSSI) of the terminal 20 is assigned.

[0036] Next, the IoT master device 10 transmits radio waves from the directional antenna with antenna number n (step S104). Next, the IoT master device 10 waits for reception of radio waves transmitted from the terminal 20 to itself in response to the transmitted radio waves, the radio waves including RSSI information transmitted from the terminal 20 that is present in the coverage of the directional antenna with antenna number n (step S105).

[0037] When the IoT master device 10 receives radio waves including RSSI information transmitted from the terminal 20 (step S105, yes), the IoT master device 10 associates the antenna number n of the directional antenna that transmitted the radio waves, the RSSI information (I_rssi) transmitted from the terminal 20, and the terminal number that identifies the terminal 20 that transmitted the RSSI information, and stores them as information set 1 (step S106). The configuration of information set 1 will be described later with an example.

[0038] If t_max seconds have passed without receiving RSSI information transmitted from terminal 20, or if t_max seconds have passed since the last time RSSI information was received (step S107: yes), IoT master device 10 ends the standby state for receiving radio waves including RSSI information transmitted from terminal 20. In other words, when t_max seconds, which is the timeout period, have passed, IoT master device 10 ends the standby state for receiving radio waves including RSSI information.

[0039] Next, the IoT master device 10 stores the number m_n of terminals 20 that transmitted the RSSI information received by the directional antenna with antenna number n (step S108). Next, if the antenna number n is less than n_max (no in step S109), the IoT master device 10 adds 1 to n (n←n+1) (step S110) and returns to the operation of step S103. Here, n_max is the maximum number for antenna number n. That is, the IoT master device 10 performs the operations of steps S103 to S108 for all directional antennas.

[0040] If the antenna number n is equal to n_max (step S109, yes), that is, if the IoT master 10 has completed the operations of steps S103 to S108 for all directional antennas, the operation of phase 1 during the initial setup of the IoT master 10 shown in the flowchart of Figure 5 is completed.

[0041] Information set 1, which will be described later, is created by the above-described operation of phase 1 during the initial setup of IoT master device 10. As described above, information set 1 is data about all directional antennas of IoT master device 10, in which the antenna number n of the directional antenna that transmitted the radio wave, the RSSI information (I_rssi) transmitted from terminal 20, and the terminal number that identifies terminal 20 that transmitted the RSSI information are linked.

[0042] FIG. 6 is a flowchart showing the operation of phase 2 during initial setup of the IoT master device 10 in one embodiment of the present invention.

[0043] First, the IoT master 10 refers to information set 1 created by the operation of phase 1 described above. If the same terminal 20 can communicate with multiple directional antennas of the IoT master 10 in information set 1 (i.e., if a certain terminal 20 is included in the coverage of multiple directional antennas), the IoT master 10 leaves only the RSSI information for the directional antenna with the largest RSSI value and deletes the RSSI information for the other directional antennas (step S201). Figure 7 shows a specific example of the editing process of information set 1 performed by the operation of step S201.

[0044] 7 is a diagram showing an example of information set 1 edited by IoT master device 10 in one embodiment of the present invention. As shown in Fig. 7, information set 1 is tabular data in which the following items are associated with each other: "item number," "antenna number n," "RSSI information I_rssi (unit: mW) (obtained from terminal 20)," and "terminal number (of terminal that transmitted the RSSI information)."

[0045] The "item number" is an identification number of the record that is added in ascending order in the order in which the record is recorded. For example, the values ​​of the items "antenna number n," "RSSI information I_rssi (unit: mW)," and "terminal number" of the record with item number 1 are "1," "5," and "11," respectively. This indicates that the directional antenna with antenna number n of 1 received RSSI information transmitted from terminal 20 with terminal number 11, and the RSSI value included in the RSSI information was 5 [mW].

[0046] By the operation of the aforementioned step S201, if the same terminal 20 can communicate with multiple directional antennas of the IoT master 10 in information set 1, the IoT master 10 retains only the RSSI information for the directional antenna with the largest RSSI value and deletes the RSSI information for the other directional antennas.

[0047] 7, it can be seen that terminal 20 with terminal number 7 is capable of communicating with both the directional antenna with antenna number 1 and the directional antenna with antenna number 5. Therefore, IoT master device 10 references the RSSI information of both and identifies the one with the larger RSSI value. IoT master device 10 leaves record number 2, which has an RSSI value of 12, and deletes record number 23, which has an RSSI value of 2.

[0048] Returning to FIG. 6 for further explanation, the IoT master device 10 then sets the antenna number n, which identifies each of the multiple directional antennas, to an initial value of 1 (n←1) ​​(step S202). The IoT master device 10 then references information set 1 to determine whether one or more terminals 20 exist within the coverage of the directional antenna with antenna number n (step S203). That is, the IoT master device 10 determines whether or not a terminal 20 exists within the coverage based on whether or not a record for antenna number n exists in information set 1.

[0049] If no terminal 20 is present in the coverage of the directional antenna with antenna number n (i.e., if there is no record for antenna number n in information set 1) (step S203: no), the IoT master device 10 sets the value of the final transmission power P_n_final of the directional antenna with antenna number n to 0 and records it in information set 2 (step S204). Figure 8 shows a specific example of the editing process of information set 2 by the operation of step S201.

[0050] 8 is a diagram showing an example of information set 2 edited by IoT master device 10 in one embodiment of the present invention. As shown in Fig. 8, information set 2 is tabular data in which the items "item number," "antenna number n," and "final transmission power P_n_final (unit: mW)" are associated with each other.

[0051] The "item number" is an identification number of the record that is added in ascending order in the order in which the record is recorded. For example, the values ​​of the "antenna number n" and "final transmission power P_n_final (unit: mW)" items in the record with item number 1 are "1" and "0", respectively. This indicates that the final transmission power of the directional antenna whose antenna number n is 1 is set to 0 [mW]. Similarly, for example, the values ​​of the "antenna number n" and "final transmission power P_n_final (unit: mW)" items in the record with item number 2 are "2" and "20", respectively. This indicates that the final transmission power of the directional antenna whose antenna number n is 2 is set to 20 [mW]. The "final transmission power" here refers to the transmission power value that is finally determined for each directional antenna by power saving control.

[0052] 8 shows information set 2 in the case where no terminal 20 is present in the coverage of the directional antennas with antenna numbers 1 and 3. The IoT master device 10 records the value of the final transmission power P_n_final of the directional antennas with antenna numbers 1 and 3 as 0 in information set 2.

[0053] Returning to Figure 6 for further explanation, if one or more terminals 20 exist within the coverage of the directional antenna with antenna number n (i.e., if a record for antenna number n exists in information set 1) (step S203, yes), the IoT master device 10 refers to information set 1 and calculates the minimum value I_rssi_min of the RSSI information (I_rssi) obtained by the directional antenna with antenna number n (step S205). That is, the IoT master device 10 identifies the minimum value among the RSSI values ​​obtained from each of the terminals 20 present within the coverage.

[0054] Next, the IoT master device 10 determines whether the minimum RSSI value identified in step S205 is greater than the minimum receiving sensitivity of the terminal 20 (step S206). For example, the IoT master device 10 makes this determination based on whether the following formula (1) is satisfied:

[0055] I_rssi_min≧r_min+mar...(1)

[0056] Here, I_rssi_min is the minimum value of RSSI identified in step S205, r_min is the minimum receiving sensitivity of the terminal 20, and mar is a margin value.

[0057] If the minimum RSSI value is greater than the minimum receiving sensitivity of the terminal 20 (step S206, yes), the IoT master device 10 sets the transmission power P of the directional antenna with antenna number n to be reduced (step S207). For example, the IoT master device 10 reduces the transmission power P according to the following equation (2).

[0058] P←P-(I_rssi_min-r_min-mar) ...(2)

[0059] That is, for example, the IoT base station 10 sets the new transmission power P to be the value obtained by reducing the current transmission power P by the difference value (a value to which a predetermined margin is added) obtained by subtracting the minimum receiving sensitivity of the terminal 20 from the minimum RSSI value.

[0060] Next, the IoT master device 10 transmits radio waves from the directional antenna with antenna number n at the reduced transmission power P (step S208). Next, the IoT master device 10 checks whether communication with all (i.e., m_n) terminals 20 present in the coverage of the directional antenna with antenna number n described in information set 1 has been successful (step S209).

[0061] If communication is successful with all (i.e., m_n) terminals 20 present in the coverage of the directional antenna with antenna number n (step S209, yes), the IoT master device 10 records the set transmission power P as the final transmission power (P_n_final) in information set 2 (step S211).

[0062] If there is a terminal 20 with which communication has not been successful among the m_n terminals 20 present in the coverage of the directional antenna with antenna number n (step S209, NO), the IoT master device 10 restores the transmission power P of the directional antenna with antenna number n to the transmission power P before the reduction process (step S210). That is, the IoT master device 10 restores the transmission power P to the value before the calculation of the above-mentioned equation (2). The IoT master device 10 then records this transmission power P in information set 2 as the final transmission power (P_n_final) (step S211).

[0063] Next, if the antenna number n is less than n_max (step S212, no), the IoT master device 10 adds 1 to n (n←n+1) (step S213), initializes the parameters of the transmission power P and the minimum RSSI value I_rssi_min (step S214), and returns to the operation of step S205. Here, n_max is the maximum number for the antenna number n. That is, the IoT master device 10 performs the operations of steps S205 to S211 for all directional antennas whose coverage includes terminals 20.

[0064] If the antenna number n is equal to n_max (step S212, yes), that is, if the IoT master 10 has set the final transmission power (P_n_final) for all directional antennas, the operation of phase 2 during the initial setup of the IoT master 10 shown in the flowchart of Figure 6 ends.

[0065] Note that the above step S210 is an operation of "returning the transmission power P of the directional antenna with antenna number n to the transmission power P before the reduction process," but instead of this, an operation such as step S210' shown in Figure 9 may be performed.

[0066] 9 is a flowchart showing another example of the operation of phase 2 during initial setup of the IoT master device 10 in one embodiment of the present invention. The operation of the IoT master device 10 shown in the flowchart of FIG. 9 differs from the operation of the IoT master device 10 shown in the flowchart of FIG. 6 only in that step S210 has been changed to step S210'. Therefore, the operations other than step S210' are given the same step numbers as in FIG. 6, and descriptions thereof will be omitted.

[0067] If there is a terminal 20 with which communication has not been successful among the m_n terminals 20 present in the coverage of the directional antenna with antenna number n (step S209, NO), the IoT master device 10 increases the transmission power P of the antenna with antenna number n by a predetermined fixed amount (step S201'). Then, the process returns to the determination operation of step S209. That is, the IoT master device 10 repeats the operation of step S210' in which the transmission power P is increased by a fixed amount until communication has been successful with all of the m_n terminals 20 present in the coverage of the directional antenna with antenna number n.

[0068] A specific example of the above operation will be described below, using numerical values. For example, assume that the transmission power P immediately before the operation of step S207 is 10 mW. Also, assume that the transmission power P after the operation of step S207 (i.e., after the transmission power P is reduced) is 3 mW. Also, assume that the fixed increase in transmission power P in step S210' is 1 mW.

[0069] In this case, after the transmission power P is reduced by 7 mW in the operation of step S207, the IoT master device 10 increases the transmission power P by 1 mW increments in the operation of step S210′ until communication is successful with all m_n terminals 20 present in the coverage of the directional antenna with antenna number n in the operation of step S209. With this configuration, even if the determination result in the determination operation of step S209 is no, it may be possible to ultimately reduce the transmission power P compared to, for example, returning the transmission power P to the value before the reduction process in the operation of step S210 of the flowchart shown in FIG.

[0070] Hereinafter, an operation (operation B) during operation performed after the initial setup of the IoT master device 10 will be described.

[0071] FIG. 10 is a flowchart showing the operation of the IoT master device 10 during operation in one embodiment of the present invention.

[0072] First, the IoT master device 10 calculates the sum P_sum of the transmission power of the plurality of directional antennas, for example, according to the following equation (3) (step S301).

[0073] P_sum=P_1_final+P_2_final+...+P_(n_max)_final) ...(3)

[0074] Next, the IoT master device 10 sets the transmission power P to the sum value P_sum calculated in step S301 (P←P_sum) (step S302). Next, the IoT master device 10 distributes the transmission power P_sum to each directional antenna so that the transmission power of each directional antenna becomes the final transmission power (P_N_final) recorded in information set 2 generated in phase 2 of the initial setup (step S303).

[0075] Next, the IoT master device 10 simultaneously transmits the same signal from all directional antennas at the final transmission power (P_N_final) set for each (step S304). If communication with all terminals 20 is successful (step S305, yes), the IoT master device 10 waits for a pre-set time (step S307) and then returns to the operation of step S304 to transmit the next signal. Thereafter, the IoT master device 10 repeats the operations of steps S304 to S307.

[0076] If t_max2 (seconds) has elapsed (step S306: no) without successful communication with at least one terminal 20 (step S305: no), that is, if communication with all terminals 20 has not been successful even after a predetermined timeout period has elapsed, the IoT master device 10 waits for a pre-set period of time (step S307) and then returns to the operation of step S304 to transmit the next signal. Thereafter, the IoT master device 10 repeats the operations of steps S304 to S307.

[0077] [Functional Configuration of IoT Master Device] The functional configuration of the IoT master device 10 will be described below.

[0078] 11 is a block diagram showing the functional configuration of IoT master device 10 according to an embodiment of the present invention. As shown in FIG. 11, IoT master device 10 includes control unit 100, data storage unit 101, transmission signal generation unit 102, energy distribution unit 103, antennas 104-1 to 104-n_max, and reception signal processing unit 105.

[0079] The control unit 100 controls each functional unit of the IoT master device 10. The control unit 100 is configured to include a processor such as a CPU (central processing unit). For example, the control unit 100 controls the transmission signal generation unit 102 to generate a transmission signal to be transmitted to the terminal 20. Furthermore, for example, the control unit 100 controls the energy distribution unit 103 to distribute the total transmission power (P_sum) of the multiple directional antennas to each of the antennas 104-1 to 104-n_max in accordance with the determined final transmission power (P_N_final).

[0080] The data storage unit 101 stores the above-mentioned information set 1 and information set 2, etc. The data storage unit 101 is configured to include, for example, a semiconductor memory such as a random access memory (RAM) and an electrically erasable programmable read-only memory (EEPROM), a flash memory such as a solid state drive (SSD), a magnetic disk such as a hard disk drive (HDD), an optical disk, or any combination of these storage media. Note that the data storage unit 101 may also store various data other than the information set 1 and information set 2, and various programs such as a program for operating the IoT master device 10.

[0081] The transmission signal generation unit 102 generates a transmission signal to be transmitted to the terminal 20 and outputs the generated transmission signal to the energy distribution unit 103 .

[0082] The energy distribution unit 103 acquires the transmission signal output from the transmission signal generation unit 102. The energy distribution unit 103 outputs the acquired transmission signal to the antennas 104-1 to 104-n_max. The energy distribution unit 103 can also divide the input signal at any energy ratio and output it as multiple signals. The energy distribution unit 103 distributes the total transmission power (P_sum) of the multiple directional antennas to the antennas 104-1 to 104-n_max in accordance with the determined final transmission power (P_N_final).

[0083] Note that the energy distribution unit 103 simply divides the input transmission signals by energy, and therefore the energy is maintained at the input and output. That is, the total amount of the transmission signals input to the energy distribution unit 103 is the same as the total amount of the transmission signals output from the energy distribution unit 103.

[0084] The energy distribution unit 103 can also be realized using a commercially available product. For example, a product called a splitter, which is used to split a television antenna wire in an apartment building or the like, can also be used as the energy distribution unit 103.

[0085] The antennas 104-1 to 104-n_max are directional antennas. In the wireless communication system shown in FIGS. 1 and 2, n_max is 10. The antennas 104-1 to 104-n_max acquire the transmission signals output from the energy distribution unit 103 and transmit the transmission signals to the terminal 20. The antennas 104-1 to 104-n_max also receive signals including RSSI information transmitted from the terminal 20. The antennas 104-1 to 104-n_max each output the received signals to the received signal processing unit 105.

[0086] The received signal processing unit 105 acquires signals containing RSSI information received by the antennas 104-1 to 104-n_max, and outputs the RSSI information contained in the acquired signals to the control unit 100.

[0087] The control unit 100 acquires the RSSI information output from the received signal processing unit 105. The control unit 100 generates and updates information set 1 and information set 2 stored in the data storage unit 101 based on the acquired RSSI information.

[0088] As described above, the IoT master device 10 according to one embodiment of the present invention is configured to use only directional antennas whose coverage includes terminals 20. More specifically, for directional antennas whose coverage does not include terminals 20, the IoT master device 10 sets the transmission power to 0 and puts the antennas into a dormant state. This reduces the total amount of transmission power used by multiple directional antennas.

[0089] Furthermore, the IoT master device 10 in this embodiment is configured to set the minimum required transmission power for each directional antenna. More specifically, the IoT master device 10 acquires an RSSI value from each terminal 20 present in its coverage area. The IoT master device 10 controls the transmission power of the directional antenna for each coverage area to an appropriate transmission power (for example, to match the minimum required transmission power) according to the acquired RSSI value. This reduces the total amount of transmission power used by multiple directional antennas.

[0090] (Modifications) Modifications of the above-described embodiment will now be described.

[0091] In the wireless communication system 1 of the above embodiment, as described with reference to Fig. 10, the IoT master device 10 is configured to perform broadcast-type transmission in which the same transmission signal is transmitted from multiple directional antennas at the same timing during operation (operation B) performed after initial setup. In contrast, in a modified example of the embodiment described below, the IoT master device (hereinafter referred to as "IoT master device 10a") is configured to perform individual communication-type transmission in which different information is transmitted from each directional antenna in sequence during operation (operation C) performed after initial setup.

[0092] [Operation of IoT Master Device] Hereinafter, an operation (operation C) during operation performed after the initial setting of the IoT master device 10a will be described.

[0093] FIG. 12 is a flowchart showing the operation of the IoT master device 10a during operation in a modified example of one embodiment of the present invention.

[0094] First, the IoT master 10a sets the antenna number n, which identifies each of the multiple directional antennas, to the initial value of 1 (n←1) ​​(step S401). Next, the IoT master 10a sets the transmission power P of the directional antenna with antenna number n to the final transmission power value determined at the time of initial installation (P←P_n_final) (step S402).

[0095] Next, the IoT master device 10a determines whether the set final transmission power (P_n_final) is 0 (step S403). If the set final transmission power (P_n_final) is 0 (step S403, yes), and if the antenna number n is less than n_max (step S407, no), the IoT master device 10a adds 1 to n (n←n+1) (step S408) and returns to the operation of step S402. Here, n_max is the maximum number for the antenna number n. That is, the IoT master device 10a performs the operations from step S402 onwards for all directional antennas.

[0096] If the set final transmission power (P_n_final) is not 0 (step S403: no), the IoT master device 10a transmits the transmission signal from the directional antenna with antenna number n (step S404).

[0097] If the IoT master device 10a has successfully communicated with all (i.e., m_n) terminals 20 present in the coverage of the directional antenna with antenna number n (step S405, yes), and if the antenna number n is less than n_max (step S407, no), it adds 1 to n (n←n+1) (step S408) and returns to the operation of step S402. That is, the IoT master device 10a performs the operations from step S402 onwards for all directional antennas.

[0098] If t_max3 (seconds) has elapsed (step S406, no) without successful communication with at least one terminal 20 (step S405, no), that is, if communication with at least one terminal 20 present in the coverage area has not been successful even after a predetermined timeout period has elapsed, and if antenna number n is less than n_max (step S407, no), the IoT master device 10a adds 1 to n (n←n+1) (step S408) and returns to the operation of step S402. That is, the IoT master device 10a performs the operations from step S402 onwards for all directional antennas.

[0099] If the antenna number n is equal to n_max (step S407, yes), the IoT master device 10a waits for a preset time (step S409) and then returns to the operation of step S401 to transmit the next signal. After that, the IoT master device 10a repeats the operations from step S401 onwards.

[0100] As described above, the IoT master device 10a in the modified example of the embodiment of the present invention has a configuration that uses only directional antennas whose coverage includes the terminal 20. More specifically, for directional antennas whose coverage does not include the terminal 20, the IoT master device 10a sets the transmission power to 0 and puts them into a dormant state. This reduces the total amount of transmission power used by multiple directional antennas.

[0101] Furthermore, the IoT master device 10a in this modification is configured to set the minimum necessary transmission power for each directional antenna. More specifically, the IoT master device 10a acquires an RSSI value from each terminal 20 present in its coverage area. The IoT master device 10a controls the transmission power of the directional antenna for each coverage area to an appropriate transmission power (for example, to match the minimum necessary transmission power) according to the acquired RSSI value. This reduces the total amount of transmission power used by multiple directional antennas.

[0102] For comparison, an example of the operation of an IoT master device in a conventional wireless communication system during operation will be described below.

[0103] 13 is a flowchart showing the operation of an IoT master device in operation according to the conventional technology. Note that the IoT master device in the conventional technology is assumed to be equipped with an omnidirectional antenna.

[0104] First, the IoT master sets the transmission power P of the omnidirectional antenna to the initial value P0 (P←P0) (step S501). Next, the IoT master transmits a transmission signal from the omnidirectional antenna with the transmission power of P0 (step S502).

[0105] Next, when the IoT master receives a signal from the terminal (step S503, yes), it stores the received signal in a storage area (step S504). If t_max (seconds) has elapsed since the transmission signal was sent in step S501 (step S505, yes), that is, if a predetermined timeout period has elapsed, the IoT master waits for a preset period of time (step S506) and then returns to the operation of step S502 to send the next signal. Thereafter, the IoT master repeats the operations of steps S502 to S506.

[0106] According to the above-described embodiment of the present invention and its modified example, the communication control device includes a plurality of directional antennas, a distribution unit, and a control unit. For example, the communication devices are the IoT master devices 10 and 10a in the embodiment, the directional antennas are the antennas 104-1 to 104-n_max in the embodiment, the distribution unit is the energy distribution unit 103 in the embodiment, and the control unit is the control unit 100 in the embodiment.

[0107] The multiple directional antennas have different coverages. For example, the different coverages are coverages C1 to C10 in the embodiment. The distributor distributes the transmission power of the signal to the multiple directional antennas at a specified ratio. For example, the signal is a transmission signal in the embodiment. The controller controls the distributor so that the transmission power is distributed only to the directional antennas whose coverage includes the terminal to be communicated with. For example, the terminal is terminal 20 in the embodiment.

[0108] In the communication control device, the control unit may allocate, to each directional antenna within the coverage area of ​​a terminal, a minimum amount of power required for the terminal within the coverage area to receive a signal. For example, the minimum amount of power is the minimum value (I_rssi_min) of the RSSI information (I_rssi) in the embodiment.

[0109] In the communication control device, the control unit may acquire, for each terminal, information indicating the received signal strength of the signal at the terminal, and determine the minimum required power for each directional antenna based on the received signal strength. For example, the information indicating the received signal strength of the signal at the terminal is RSSI information (I_rssi) in the embodiment.

[0110] In the above-described communication control device, the control unit may determine the minimum necessary transmission power based on a value obtained by subtracting the difference between the received signal strength and the minimum receiving sensitivity of the terminal from the transmission power. For example, the minimum receiving sensitivity of the terminal is the minimum receiving sensitivity (r_min) of the terminal 20 in the embodiment. The determined minimum necessary transmission power is the transmission power calculated by equation (2) in the embodiment.

[0111] In the above-described communication control device, when the same terminal is included in multiple coverage areas, the control unit may distribute the minimum necessary power based on the highest received signal strength value among the multiple coverage areas.

[0112] In the above-described communication control device, the control unit may manage the received signal strength for each combination of multiple directional antennas and multiple terminals in a list, and when the same terminal is included in multiple coverages, delete from the list all records other than the record containing the highest received signal strength value among the multiple coverages, and distribute the minimum necessary power based on the highest received signal strength value. For example, the list is information sets 1 and 2 in the embodiment.

[0113] The control unit provided in the communication control device of the present invention can also be realized by a computer and a program, and the program can be recorded on a recording medium or provided via a network.

[0114] Some or all of the configuration of the IoT master devices 10 and 10a in the above-described embodiments may be implemented by a computer. In this case, a program for implementing this function may be recorded on a computer-readable recording medium, and the program may be loaded into a computer system and executed. Note that the term "computer system" as used herein includes hardware such as an OS and peripheral devices. Furthermore, "computer-readable recording medium" refers to portable media such as floppy disks, optical magnetic disks, ROMs, and CD-ROMs, as well as storage devices such as hard disks built into computer systems. Furthermore, "computer-readable recording medium" may also include devices that dynamically store programs for a short period of time, such as communication lines used when transmitting programs via networks such as the Internet or telephone lines, or devices that store programs for a fixed period of time, such as volatile memory within the computer system that serves as the server or client. The program may be designed to implement some of the above-described functions, or may be capable of implementing the above-described functions in combination with programs already stored in the computer system, or may be implemented using a programmable logic device such as an FPGA (Field Programmable Gate Array).

[0115] Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and includes designs within the scope of the present invention that do not deviate from the gist of the present invention.

[0116] 1, 1a... wireless communication system, 10, 10a... IoT master device, 20... terminal, 100... control unit, 101... data storage unit, 102... transmission signal generation unit, 103... energy distribution unit, 104-1 to 104-n_max... antennas, 105... reception signal processing unit

Claims

1. A communication control device comprising: a plurality of directional antennas each having a different coverage; a distribution unit that distributes the transmission power of a signal to the plurality of directional antennas at a specified ratio; and a control unit that controls the distribution unit so that the transmission power is distributed only to the directional antennas whose coverage includes a terminal to be communicated with.

2. The communication control device according to claim 1, wherein the control unit distributes the minimum power necessary for the terminal present in the coverage area to receive the signal to each of the directional antennas in which the terminal is present in the coverage area.

3. The communication control device according to claim 2, wherein the control unit acquires information indicating the received signal strength of the signal at the terminal for each terminal, and determines the minimum required power for each directional antenna based on the value obtained by subtracting the difference between the received signal strength and the minimum receiving sensitivity of the terminal from the transmission power.

4. The communication control device according to claim 3, wherein when the same terminal is included in multiple coverage areas, the control unit distributes the minimum necessary power based on the highest received signal strength value among the multiple coverage areas.

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