Wireless communication system and wireless communication method

Abstract

To make it possible to relay data from a terminal without causing large delay even when the terminal and a relay are asynchronous with each other and to save power of the relay and the terminal by the relay and the terminal suspending their operation even if reporting from the terminal to the relay is not performed at fixed intervals.SOLUTION: A radio communication system comprises: a terminal that repeatedly acquires predetermined data and operates while performing changeover between a first mode and a second mode with power consumption lower than that in the first mode; and a relay that operates while performing changeover between a third mode and a fourth mode with power consumption lower than that in the third mode. The relay transmits a polling signal to the terminal in the third mode within a specific time and, after transmitting the polling signal, transits to the fourth mode within the specific time, and to the third mode before the specific time elapses. The terminal operates in the first mode when having the predetermined data and transits into the second mode after transmitting the predetermined data to the relay.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] Aspects of the present disclosure relate to a wireless communication system and a wireless communication method.

Background Art

[0002] When constructing a wireless network such as LPWA (Low Power Wide Area), the communication area can be expanded by relaying. As an example, consider a terminal equipped with a sensor reporting sensing data acquired by the sensor to a base station at regular intervals. In this example, the terminal may report the sensing data to a repeater, and the repeater may report the sensing data to the base station.

[0003] Regarding power consumption here, since the sensor and the terminal only perform sensing and reporting at regular intervals, the terminal can suspend its operation during time periods when reporting is not performed, and thus its power consumption can be reduced. However, as shown in FIG. 1A, since the repeater does not know when a report from the terminal will arrive, it cannot suspend its operation. Therefore, the repeater cannot significantly reduce its power consumption.

[0004] On the other hand, as shown in FIG. 1B, if both the terminal and the repeater are time-synchronized with a device that manages a reference timing such as a base station so that the operation suspension timings of the terminal and the repeater are aligned, the repeater can also suspend its operation. Techniques that utilize such time synchronization are described in, for example, Patent Document 1 and Patent Document 2. In the above example, since the terminal reports sensing data at regular intervals, the repeater can suspend its operation by utilizing time synchronization.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, when the terminal and the repeater are asynchronous, it is still difficult for the repeater to pause its operation.

[0007] Non-limiting embodiments of the present disclosure enable relaying data from a terminal without significant delay even when the terminal and the repeater are asynchronous, and contribute to providing a wireless communication system and a wireless communication method capable of reducing power consumption of the repeater and the terminal by pausing the operations of the repeater and the terminal.

Means for Solving the Problems

[0008] A wireless communication system according to an embodiment of the present disclosure includes a data generation device, a terminal that repeatedly acquires predetermined data from the data generation device and operates while switching between a first mode and a second mode having lower power consumption than the first mode, and a repeater that is communicable with the terminal and operates while switching between a third mode and a fourth mode having lower power consumption than the third mode. The repeater transmits a polling signal to the terminal in the third mode within a specific time, transitions from the third mode to the fourth mode after transmitting the polling signal and within the specific time, and transitions from the fourth mode to the third mode before the specific time elapses. The terminal operates in the first mode while having the predetermined data, and transitions from the first mode to the second mode after transmitting the predetermined data to the repeater in response to the polling signal.

[0009] A wireless communication method according to another embodiment of the present disclosure includes a data generation device, repeatedly acquires predetermined data from the data generation device, and operates while switching between a first mode and a second mode with lower power consumption than the first mode. A terminal, and a relay that can communicate with the terminal and operates while switching between a third mode and a fourth mode with lower power consumption than the third mode. A wireless communication method in a wireless communication system, wherein the relay transmits a polling signal to the terminal in the third mode within a specific time, and after the relay transmits the polling signal and within the specific time, the relay transitions from the third mode to the fourth mode, and the relay transitions from the fourth mode to the third mode before the specific time elapses. The terminal operates in the first mode while having the predetermined data, and after the terminal transmits the predetermined data to the relay in response to the polling signal, the terminal transitions from the first mode to the second mode.

[0010] These general or specific aspects may be implemented in a system, apparatus, method, integrated circuit, computer program, or recording medium, or may be implemented in any combination of a system, apparatus, method, integrated circuit, computer program, and recording medium.

Advantages of the Invention

[0011] According to an embodiment of the present disclosure, even if the terminal and the relay are asynchronous, data from the terminal can be relayed without significant delay, and power saving of the relay can be achieved by pausing the operation of the relay.

[0012] Further advantages and effects in an embodiment of the present disclosure will be apparent from the specification and drawings. Such advantages and / or effects are provided by some embodiments and the features described in the specification and drawings, respectively, but not necessarily all are provided in order to obtain one or more of the same features.

Brief Description of the Drawings

[0013]

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Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present disclosure will be described in detail with appropriate reference to the drawings. However, a more detailed description than necessary may be omitted. For example, a detailed description of well-known matters and a redundant description of substantially the same configuration may be omitted. This is to avoid making the following description unnecessarily redundant and to facilitate understanding by those skilled in the art.

[0015] Note that the accompanying drawings and the following description are provided for those skilled in the art to fully understand the present disclosure, and it is not intended to limit the subject matter described in the claims thereby.

[0016] [Overview of an Aspect of the Present Disclosure] First, with reference to FIG. 2, an overview of an aspect of the present disclosure will be described. FIG. 2 is a timing diagram for explaining an overview of an example of data communication between a terminal and a relay. FIG. 2 shows examples of data reporting between terminal 1 and the relay and data reporting between terminal 2 and the relay. In the example shown in FIG. 2, the interval between the dotted lines represents 1 second. Also, in the example shown in FIG. 2, sensing by terminal 1 and terminal 2 (more specifically, sensor 1 (not shown) and sensor 2 (not shown) respectively provided in and mounted or connected to terminal 1 and terminal 2) is performed at the timing of the rising edge of the timing diagram. Further, in the example shown in FIG. 2, data collection by the relay is performed at the timing of the rising edge of the timing diagram. The High period and the Low period of the timing diagram represent the steady state mode and the operation pause mode, which will be described later, respectively.

[0017] The sensor 1 mounted on or connected to the terminal 1 measures (senses) the temperature of the object, etc. at regular intervals (for example, every 7 seconds in FIG. 2), and transmits the sensing data to the terminal 1 together with the date and time when the sensing data was acquired. The terminal 1 associates the sensing data received from the sensor 1 with the date and time when the sensing data was acquired, and stores it in an internal memory (or other storage device). In the following, the sensing data and the date and time when the sensing data was acquired are treated as a set, and the date and time when the sensing data was acquired is not mentioned.

[0018] Similarly, the sensor 2 mounted on or connected to the terminal 2 measures (senses) the temperature of another object, etc. at regular intervals (for example, every 11 seconds in FIG. 1), and transmits the sensing data to the terminal 2. The terminal 2 stores the sensing data received from the sensor 2 in an internal memory (or other storage device).

[0019] The repeater transmits a signal for checking whether the terminal 1 has sensing data to the terminal 1 at regular intervals (for example, every 5 seconds in FIG. 2) in this example. Similarly, the repeater transmits a signal for checking whether the terminal 2 has sensing data to the terminal 2 at regular intervals. In the following, the above-mentioned signal for checking whether a certain communication device has given data such as sensing data is referred to as a "polling signal". The polling signal may be transmitted at regular intervals, at regular intervals, or at irregular intervals.

[0020] When the repeater transmits the first polling signal shown in FIG. 2 to the terminal 1, the terminal 1 transmits the sensing data stored in the internal memory to the repeater for relaying with a delay of 3 seconds, and deletes the sensing data. Similarly, when the repeater transmits the first polling signal to the terminal 2, the terminal 2 transmits the sensing data stored in the internal memory to the repeater for relaying with a delay of 4 seconds, and deletes the sensing data.

[0021] After transmitting the sensing data, Terminal 1 transitions (switches) from the steady state mode, which is the normal operation mode, to the operation suspension mode, which consumes less power than the steady state mode. The operation suspension mode continues until the sensing timing (next sensing timing) at which Sensor 1 next senses temperature or the like. Similarly, after transmitting the sensing data, Terminal 2 transitions from the steady state mode to the operation suspension mode. The operation suspension mode continues until the next sensing timing. Thereafter, Terminal 1 and Terminal 2 each transition from the operation suspension mode to the steady state mode at the next sensing timing. In this specification, the time interval between the exact timing at which the sensor performs sensing and the exact timing at which the sensor next performs sensing is referred to as the sensing interval.

[0022] On the other hand, after transmitting the first polling signal and within a predetermined period for receiving sensing data from Terminal 1 and Terminal 2, the repeater receives the sensing data from both Terminal 1 and Terminal 2, and thus relays (transmits) both of these sensing data to a base station (not shown). After transmitting the sensing data to the base station, the repeater transitions from the steady state mode, which is the communication operation mode, to the operation suspension mode, which consumes less power than the steady state mode. The operation suspension mode continues until the next timing at which the repeater transmits a polling signal. In this specification, the time interval between the exact timing at which the repeater transmits a polling signal and the exact timing at which the repeater next transmits a polling signal is referred to as the polling interval.

[0023] When the repeater transmits the second polling signal to Terminal 1 after a polling interval of 5 seconds has elapsed since the repeater transmitted the first polling signal, Terminal 1 transmits the sensing data stored in the internal memory to the repeater for relaying with a delay of 1 second. Similarly, when the repeater transmits the second polling signal to Terminal 2, Terminal 2 does not report to the repeater because it is in the operation suspension mode (has no sensing data).

[0024] After transmitting the sensing data, Terminal 1 transitions to the operation suspension mode. The operation suspension mode continues until the next sensing timing. Thereafter, Terminal 1 and Terminal 2 each transition from the operation suspension mode to the normal mode at the next sensing timing.

[0025] After the repeater transmits the second polling signal and within a predetermined period for receiving sensing data from Terminal 1 and Terminal 2, since the repeater receives sensing data only from Terminal 1, the repeater relays (transmits) only this sensing data to the base station. After transmitting the sensing data to the base station, the repeater transitions to the operation suspension mode. The operation suspension mode continues until the next timing when the repeater transmits a polling signal.

[0026] When the repeater transmits the third polling signal to Terminal 1 after the polling interval has elapsed since the repeater transmitted the second polling signal, Terminal 1, being in the operation suspension mode (having no sensing data), does not report to the repeater. Similarly, when the repeater transmits the third polling signal to Terminal 2, Terminal 2 transmits the sensing data stored in the internal memory to the repeater for relaying with a delay of 3 seconds.

[0027] Terminal 1 remains in the operation suspension mode until the next sensing timing. After transmitting the sensing data, Terminal 2 transitions to the operation suspension mode. The operation suspension mode continues until the next sensing timing. Terminal 1 and Terminal 2 each transition from the operation suspension mode to the normal mode at the next sensing timing.

[0028] After the repeater transmits the third polling signal and within a predetermined period for receiving sensing data from Terminal 1 and Terminal 2, since the repeater receives sensing data only from Terminal 2, the repeater relays (transmits) only this sensing data to the base station. After transmitting the sensing data to the base station, the repeater transitions to the operation suspension mode. The operation suspension mode continues until the next timing when the repeater transmits a polling signal.

[0029] After that, even when the repeater transmits the fourth and fifth polling signals shown in FIG. 2, the same process is repeated.

[0030] To briefly summarize the above process, in this example, the repeater transitions to the operation pause mode at (almost) regular intervals. When transitioning from the operation pause mode to the steady state mode, the repeater checks with the terminal whether the terminal has sensing data. If the terminal has sensing data, the repeater requests the terminal to transmit the sensing data and relays the sensing data to, for example, the base station. The terminal remains in the steady state mode until it transmits the sensing data to the repeater (as long as it has the sensing data). When the terminal transmits the sensing data to the repeater, it transitions to the operation pause mode. The operation pause mode continues until the next sensing timing. In the above process, there is a delay from when the terminal acquires the sensing data until the repeater acquires the sensing data from the terminal. However, when sensing something that does not change rapidly, such as air temperature or the temperature of an object, a certain degree of delay can be tolerated. If the polling interval of the repeater is X seconds, the delay can be suppressed to a maximum of X seconds.

[0031] As described above, the repeater operates while switching between the steady state mode and the operation suspension mode. When the repeater transmits a polling signal in the steady state mode within a specific time (polling interval), at least after transmitting the polling signal and within the specific time, it transitions from the steady state mode to the operation suspension mode and transitions from the operation suspension mode to the steady state mode before the elapse of the specific time. That is, the operation suspension mode continues until the next timing when the repeater transmits a polling signal. The terminal operates while switching between the steady state mode and the operation suspension mode, operates in the steady state mode while having sensing data, and transitions from the steady state mode to the operation suspension mode after transmitting the sensing data to the repeater in response to the polling signal. Note that the operation suspension mode continues until the next sensing timing. As a result, even if the terminal and the repeater are asynchronous, the sensing data from the terminal can be relayed without significant delay, and power consumption of the repeater and the terminal can be reduced by suspending the operation of the repeater and the terminal. Also, as a result, even if the reporting from the terminal to the repeater is not at regular intervals, power consumption of the repeater and the terminal can be reduced by suspending the operation of the repeater and the terminal. In the above, as an example of the data reported by the terminal to the repeater, the sensing data acquired by the sensor provided in the terminal has been described, but such data is not limited to the sensing data, and the device (data generation device) that generates such data is also not limited to the sensor. Further examples of such data and data generation devices will be described in Embodiment 1 below.

[0032] [Embodiment 1] Next, with reference to FIGS. 3 to 15D, the configuration and operation of the wireless communication system 2 according to Embodiment 1 of the present disclosure will be described.

[0033] [Wireless Communication System] FIG. 3 is a diagram showing an example of the configuration of the wireless communication system 2 according to Embodiment 1. As shown in the figure, the wireless communication system 2 includes a base station, one or more repeaters, and one or more terminals. In the following, the base station, the repeater, and the terminal may be collectively referred to as a "communication device", and in various drawings, the repeater may be denoted as a relay. The arrowed lines shown in FIG. 3 represent the connections between communication devices. In FIG. 3, there are six repeaters A-1 to A-6 and three terminals B-1 to B-3, but the number of repeaters and the number of terminals are not limited to six and three, respectively.

[0034] In Embodiment 1, it is mainly assumed the uplink data transmission, which is the wireless transmission of (sensed) data acquired by a sensor or the like from a terminal equipped or connected with a sensor or the like as a data generation device to a repeater. Then, the repeater that has received data from the terminal relays (transmits) the received data to the base station either via one or more other repeaters or directly.

[0035] <Basic Configuration of Communication Devices including Terminals, Repeaters, and Base Stations> FIG. 4 is a block diagram showing an example of the basic configuration of a communication device 30 including a terminal, a repeater, and a base station in the wireless communication system 2 according to Embodiment 1.

[0036] As a basic configuration, the communication device 30 includes a control device 31, a storage device 32, a radio unit 33, and an antenna 34. Needless to say, the communication device 30 also includes other well-known components such as an encoder and a decoder.

[0037] The control device 31 is composed of a controller, a processor, etc. The control device 31 processes data and controls the components and operations of the communication device 30 in general by executing program instructions stored in the storage device 32, for example.

[0038] The storage device 32 includes a volatile memory, a non-volatile memory, a cache memory, a hard disk, etc. The storage device 32 temporarily or permanently stores data necessary for the operation of the communication device 30, program instructions for controlling the overall operation of the communication device 30, data received, transmitted, generated, etc. during the operation of the communication device 30, and data necessary for these processes.

[0039] The radio 33 is composed of well-known receivers, transmitters, transceivers, etc. The radio 33 generates a radio frequency signal by modulating the baseband signal to be transmitted for transmission via the antenna 34. Also, the radio 33 extracts the baseband signal by demodulating the radio frequency signal received via the antenna 34.

[0040] The antenna 34 transmits the radio frequency signal generated by the radio 33 as radio waves, for example, toward the communication device of the transmission destination. Also, the antenna 34 receives the radio frequency signal transmitted from another communication device (antenna) as radio waves.

[0041] <Operation of the terminal> The communication device 30 as a terminal (hereinafter referred to as the terminal) includes sensors as built-in components or external components as a data generation device, and is connected to such sensors by wire or wirelessly. Such sensors can measure (sense) the temperature, humidity of the surrounding environment, the heartbeat, respiration, temperature, movement, etc. of the subject / object. Note that the terminal may include a microphone, a camera, buttons, a keypad, switches, etc. as a data generation device instead of or in addition to the sensors, and may be connected to such a microphone, camera, buttons, keypad, switches, etc.

[0042] The terminal acquires sensing data such as the temperature acquired by the sensor from the sensor at regular intervals, irregular intervals, or non-regular intervals, and stores the sensing data in the storage device 32 of the terminal. This sensing interval is, for example, predetermined and stored in the sensor and the storage device 32 of the terminal. The sensing interval may be changed as needed by an operator of the terminal or the like and stored in the sensor and the storage device 32 of the terminal. Then, when the terminal wirelessly receives a polling signal from the communication device 30 as a repeater (hereinafter referred to as the repeater), the terminal wirelessly transmits the sensing data stored in the storage device 32 of the terminal to the repeater that transmitted the polling signal. After the terminal transmits the sensing data to the repeater, the terminal deletes the sensing data from the storage device 32 of the terminal. Depending on the situation, there may be cases where a plurality of sensing data are left in the storage device 32 of the terminal. In this case, when the terminal receives a polling signal from the repeater, the terminal may transmit all of the plurality of sensing data to the repeater, or may transmit only the latest sensing data among the plurality of sensing data to the repeater, or may transmit a predetermined number of sensing data in the order of newness among the plurality of sensing data to the repeater. In any case, after transmitting the sensing data, the terminal deletes all of the plurality of sensing data from the storage device 32 of the terminal. Note that instead of deleting the sensing data, the terminal may be configured to attach a transmitted flag to the transmitted sensing data. In this case, when the terminal receives a polling signal from the repeater, the terminal transmits the sensing data without the transmitted flag attached to the repeater, attaches the transmitted flag to this sensing data, and deletes the sensing data with the transmitted flag attached every time a predetermined period elapses. Note that when the terminal includes a microphone, a camera, a button, a keypad, a switch, or the like as a data generation device, such a data generation device acquires data other than the sensing data, for example, reports regularly generated in a call, button press, voice input, image input, life and death monitoring, etc., and the terminal can acquire such data from the data generation device.

[0043] After the terminal transmits the sensing data to the repeater, it transitions from the stationary mode, in which it can execute all functions of listening, which continues to wait to receive data addressed to the terminal during the transmission, reception, and idle periods when no data is being transmitted or received, to a sleep mode that consumes less power than the stationary mode. This transition is achieved by restricting the execution of some functions of transmission, reception, and listening, such as putting the device to sleep (cutting off the power supply to the radio 33 and other circuits (turning off the power of the radio 33 and other circuits)), and slowing down the operating clock of the radio 33 and other circuits. The sleep mode continues until the timing at which the sensor connected to the terminal next senses temperature or the like (the next sensing timing). Thereafter, the terminal transitions from the sleep mode to the stationary mode at the next sensing timing in order to acquire sensing data from the sensor connected to the terminal.

[0044] In this specification, the next sensing timing does not mean the exact timing at which the sensor performs sensing, but rather a point in time that is a predetermined time (for example, 1 second) earlier than the exact timing at which the sensor performs sensing. As the predetermined time, any time that can achieve power saving of the terminal can be set.

[0045] While the terminal has sensing data, it does not transition to the sleep mode and remains in the stationary mode, waiting for a polling signal from the repeater.

[0046] The terminal repeats operations such as acquisition of sensing data, reception of polling signals, transmission / deletion of sensing data, transition to the sleep mode, and transition to the stationary mode.

[0047] The terminal may also store (i.e., grasp) in the storage device 32 of the terminal the network topology of the wireless communication system 2, which represents the connection relationship and hierarchy among the terminal, the repeater, and the base station in the wireless communication system 2, or may not store (i.e., not grasp) it.

[0048] <Operation of the Repeater> The repeater wirelessly transmits a polling signal at regular intervals, irregular intervals, or constant intervals to another communication device (e.g., a terminal or another repeater) to check whether (or if) the other communication device has (stores) data to be transmitted to the repeater. After transmitting the polling signal, the repeater waits for data from the other communication device for a predetermined period (e.g., 3 seconds) for receiving data from the other communication device.

[0049] If the repeater receives data (e.g., sensing data) from another communication device within the predetermined period, the repeater wirelessly relays (transmits) the received data to yet another communication device (e.g., communication device 30 as a base station (hereinafter referred to as the base station) or another repeater). After transmitting the data to yet another communication device, the repeater continues to wait to be able to receive data addressed to the repeater during transmission, reception, and the idle period when no data is being transmitted or received within the polling interval, and transitions from the steady state mode, in which all functions of listening can be executed, to the operation suspension mode with lower power consumption than the steady state mode. This transition is realized by restricting the execution of some functions of transmission, reception, and listening, such as putting the device to sleep (cutting off the power supply to the wireless device 33 and other circuits (turning off the power to the wireless device 33 and other circuits)) and slowing down the operating clock of the wireless device 33 and other circuits. The operation suspension mode continues until the next timing when the repeater transmits the polling signal. At the next timing when the repeater transmits the polling signal, the repeater transitions from the operation suspension mode to the steady state mode and transmits the polling signal again.

[0050] On the other hand, even when the repeater does not receive data from another communication device within a predetermined period after transmitting a polling signal, the repeater may transition from the steady state mode to the operation suspension mode within the polling interval after the elapse of the predetermined period. The operation suspension mode continues until the next timing at which the repeater transmits a polling signal. The repeater transitions from the operation suspension mode to the steady state mode at the next timing of transmitting a polling signal and transmits the polling signal again. Note that when data is not received from another communication device, the transition to the operation suspension mode may not be executed, and the repeater may remain in the steady state mode. This is because power saving of the repeater can be achieved even by simply transitioning to the operation suspension mode after receiving data from another communication device.

[0051] When another communication device that has received a polling signal at a polling interval has sensing data, the repeater stores the sensing data received from the other communication device in the storage device 32 of the repeater. The polling interval is, for example, predetermined and stored in the storage device 32 of the repeater. The polling interval may be changed as necessary by an operator of the repeater or the like and stored in the storage device 32 of the repeater. Then, when the repeater wirelessly receives a polling signal from yet another communication device, the repeater wirelessly transmits the sensing data stored in the storage device 32 of the repeater to yet another communication device that has transmitted the polling signal. After the repeater transmits the sensing data to yet another communication device, the repeater deletes the sensing data from the storage device 32 of the repeater. Depending on the situation, there may be a case where a plurality of sensing data are left in the storage device 32 of the repeater. In this case, when the repeater receives a polling signal from yet another communication device, the repeater may transmit all of the plurality of sensing data to yet another communication device, or may transmit only the latest sensing data among the plurality of sensing data to yet another communication device, or may transmit a predetermined number of sensing data in the order of newness among the plurality of sensing data to yet another communication device. In any case, after transmitting the sensing data, the repeater deletes all of the plurality of sensing data from the storage device 32 of the terminal. Note that instead of deleting the sensing data, the repeater may be configured to attach a transmitted flag to the transmitted sensing data. In this case, when the repeater receives a polling signal from yet another communication device, the repeater transmits the sensing data without the transmitted flag attached to yet another communication device, attaches the transmitted flag to this sensing data, and deletes the sensing data with the transmitted flag attached every time a predetermined period has elapsed.

[0052] While having the sensing data, the repeater does not transition to the operation suspension mode and remains in the normal mode, waiting for a polling signal from another repeater or the base station.

[0053] Also, in this specification, the next timing for transmitting a polling signal does not refer to the exact timing at which the repeater transmits the polling signal, but rather refers to a point in time that is a predetermined time (e.g., 1 second) earlier than the exact timing at which the repeater transmits the polling signal. As the predetermined time, any time that can achieve power saving of the repeater can be set.

[0054] The repeater may transmit a polling signal to a plurality of communication devices simultaneously (e.g., by broadcast) or sequentially (e.g., almost simultaneously). In this case, there are the following three options.

[0055] As a first option, if the repeater receives data from all of the plurality of communication devices within a predetermined period, the repeater relays (transmits) the received data to another communication device. Then, after transmitting all of the received data, the repeater transitions to the operation suspension mode. The operation suspension mode continues until the next timing at which the repeater transmits a polling signal.

[0056] As a second option, if the repeater receives data from some of the plurality of communication devices, but not all, within a predetermined period, the repeater relays (transmits) only the received data to another communication device. Then, after transmitting only the received data, the repeater transitions to the operation suspension mode. The operation suspension mode continues until the next timing at which the repeater transmits a polling signal. Note that when data is received from some of the plurality of communication devices, but not all, the transition to the operation suspension mode may not be executed, and the repeater may remain in the steady state mode. This is because power saving of the repeater can be achieved even if the repeater only transitions to the operation suspension mode after receiving data from all of the plurality of communication devices.

[0057] As a third option, if the repeater does not receive data from all of the plurality of communication devices within a predetermined period, the repeater transitions to an operation suspension mode after the elapse of the predetermined period. The operation suspension mode continues until the next timing at which the repeater transmits a polling signal. Note that when data is not received from all of the plurality of communication devices, the transition to the operation suspension mode may not be executed, and the repeater may remain in the steady state mode. This is because even if the repeater only transitions to the operation suspension mode after receiving data from all of the plurality of communication devices, power consumption of the repeater can be reduced.

[0058] The repeater may or may not store (i.e., grasp) in the storage device 32 of the repeater, the network topology of the wireless communication system 2, which represents the connection relationship and hierarchy among the terminal, the repeater, and the base station in the wireless communication system 2.

[0059] <Operation of the base station> When the base station receives data from the repeater, depending on the purpose, the base station transmits the data to the target terminal via one or more repeaters (specifically, refer to Embodiment 2 of the present disclosure below), or transmits the data to the cloud for processing and analysis of so-called big data.

[0060] The base station may or may not store (i.e., grasp) in the storage device 32 of the base station, the network topology of the wireless communication system 2, which represents the connection relationship and hierarchy among the terminal, the repeater, and the base station in the wireless communication system 2.

[0061] <First example of data communication between the terminal and the repeater> Next, with reference to FIG. 5, a first example of data communication between the terminal and the repeater in the wireless communication system 2 will be described. FIG. 5 is a sequence diagram for explaining a first example of data communication between the terminal and the repeater in the wireless communication system 2 according to Embodiment 1 of the present disclosure.

[0062] The repeater A shown in FIG. 5 may be, for example, the repeater A-6 shown in FIG. 3, and the terminal B shown in FIG. 5 may be, for example, the terminal B-1 shown in FIG. 3.

[0063] In step S401, the sensor connected to the terminal B acquires sensing data such as temperature and transmits it to the terminal B. That is, the terminal B acquires the sensing data from the sensor.

[0064] In step S402, the repeater A transmits a polling signal to the terminal B.

[0065] Since the terminal B has the sensing data, in step S403, the terminal B transmits the sensing data to the repeater A, and the repeater A receives the sensing data from the terminal B within a predetermined period after transmitting the polling signal.

[0066] After the terminal B transmits the sensing data to the repeater A, in step S404, it transitions from the normal mode to the operation pause mode. The operation pause mode continues until the next sensing timing.

[0067] After the repeater A receives the sensing data from the terminal B, in step S405, it relays the sensing data to another repeater (for example, the repeater A-4 in FIG. 3) or a base station, which is its upper communication device, as appropriate, and transitions from the normal mode to the operation pause mode. The operation pause mode continues until the next timing when the repeater A transmits a polling signal. Therefore, the repeater A transitions from the normal mode to the operation pause mode at least within the polling interval after transmitting the polling signal to the terminal B.

[0068] At the next timing when the repeater A transmits a polling signal, it transitions to the normal mode, and in step S406, it transmits a polling signal to the terminal B again while the terminal B is in the operation pause mode. Therefore, the terminal B does not respond to the polling signal and does not transmit the sensing data to the repeater A.

[0069] If the repeater A does not receive sensing data from the terminal B within a predetermined period after transmitting the polling signal, in step S407, the repeater A transitions to the operation suspension mode after the elapse of the predetermined period. Therefore, even when the repeater A does not receive sensing data from the terminal B, it transitions from the steady state mode to the operation suspension mode. The operation suspension mode continues until the next timing when the repeater A transmits the polling signal. Note that the transition in step S407 may not be executed, and the repeater A may remain in the steady state mode.

[0070] The terminal B transitions to the steady state mode at the next sensing timing. In step S408, the sensor acquires sensing data such as temperature and transmits it to the terminal B. That is, the terminal B acquires sensing data from the sensor.

[0071] While the terminal B has sensing data, it does not transition to the operation suspension mode and waits for a polling signal from the repeater A in step S409.

[0072] The repeater A transitions to the steady state mode at the next timing when it transmits the polling signal and re-transmits the polling signal to the terminal B in step S410.

[0073] Since the terminal B has sensing data, in step S411, the terminal B transmits the sensing data to the repeater A, and the repeater A receives the sensing data from the terminal B within a predetermined period after transmitting the polling signal.

[0074] After the terminal B transmits the sensing data to the repeater A, it transitions to the operation suspension mode in step S412. The operation suspension mode continues until the next sensing timing.

[0075] After receiving the sensing data from terminal B, in step S413, repeater A relays the sensing data to another repeater or base station as appropriate and transitions to the operation suspension mode. The operation suspension mode continues until the next timing when repeater A transmits a polling signal.

[0076] Thereafter, the same processing is repeated. For example, at the next sensing timing, terminal B transitions to the steady state mode, and in step S414, the sensor acquires sensing data such as temperature and transmits it to terminal B. That is, terminal B acquires the sensing data from the sensor.

[0077] In the first example, if there is a communication error when repeater A transmits a polling signal to terminal B, repeater A may recognize that terminal B does not have sensing data and operate accordingly, and terminal B may recognize that repeater A is not transmitting a polling signal to terminal B and operate accordingly.

[0078] In the first example, if there is a communication error when terminal B transmits the sensing data to repeater A, repeater A may recognize that terminal B does not have sensing data and operate accordingly, and terminal B may operate as if it has transmitted the sensing data to repeater A. Therefore, in this case, one piece of sensing data is missing, but wireless communication system 2 may allow for a small amount of data loss and continue operating.

[0079] In the first example, there may be a case where a plurality of sensing data are left in the storage device 32 of the terminal. In this case, as described above, when the terminal receives a polling signal from the repeater, the terminal may transmit all the plurality of sensing data to the repeater, or may transmit only the latest sensing data among the plurality of sensing data to the repeater, or may transmit a predetermined number of sensing data in the order of newness among the plurality of sensing data to the repeater.

[0080] <Second example of data communication between the terminal and the repeater> Next, with reference to FIG. 6, a second example of data communication between a terminal and a repeater in the wireless communication system 2 will be described. FIG. 6 is a sequence diagram for explaining a second example of data communication between a terminal and a repeater in the wireless communication system 2 according to Embodiment 1 of the present disclosure.

[0081] The repeater A shown in FIG. 6 may be, for example, the repeater A-6 shown in FIG. 3. The terminal B-1 shown in FIG. 6 may be, for example, the terminal B-1 shown in FIG. 3. The terminal B-X (X is an integer of 2 or more) shown in FIG. 6 may be, for example, the terminal B-2 shown in FIG. 3 or a terminal not shown in FIG. 3. Here, each of the terminals B-1 to B-X can operate in the same manner as the terminal described in the example shown in FIG. 5 described above, and the repeater A can operate in the same manner as the repeater described in the example shown in FIG. 5 described above.

[0082] In step S501, the sensor-1 connected to the terminal B-1 acquires sensing data such as temperature and transmits it to the terminal B-1. That is, the terminal B-1 acquires the sensing data from the sensor-1.

[0083] In step S502, the sensor-X connected to the terminal B-X acquires sensing data such as temperature and transmits it to the terminal B-X. That is, the terminal B-X acquires the sensing data from the sensor-X.

[0084] In step S503, the repeater A transmits a polling signal to the terminal B-1. In step S503', the repeater A transmits a polling signal to the terminal B-X. These polling signals may be transmitted to a plurality of terminals simultaneously (for example, by broadcast) or sequentially (for example, almost simultaneously). When the repeater A transmits the polling signals sequentially, if the polling signals to the terminals B-1 to B-X are transmitted within a shorter period, the repeater A can pause its operation for a longer time.

[0085] Since terminal B-1 has sensing data, in step S504, terminal B-1 transmits the sensing data to repeater A, and repeater A receives the sensing data from terminal B-1 within a predetermined period after transmitting the polling signal.

[0086] After terminal B-1 transmits the sensing data to repeater A, in step S505, terminal B-1 transitions to the operation suspension mode. The operation suspension mode continues until the next sensing timing.

[0087] Since terminal B-X has sensing data, in step S506, terminal B-X transmits the sensing data to repeater A, and repeater A receives the sensing data from terminal B-X within a predetermined period after transmitting the polling signal.

[0088] After terminal B-X transmits the sensing data to repeater A, in step S507, terminal B-X transitions to the operation suspension mode. The operation suspension mode continues until the next sensing timing.

[0089] After repeater A receives the sensing data from terminal B-1 and terminal B-X, in step S508, repeater A relays the sensing data to another repeater (for example, repeater A-4 in FIG. 2) or a base station, which is its upper-level communication device, as appropriate, and transitions to the operation suspension mode. The operation suspension mode continues until the next timing when repeater A transmits the polling signal.

[0090] Terminal B-X transitions to the normal mode at the next sensing timing, and in step S509, sensor-X acquires sensing data such as temperature and transmits it to terminal B-X. That is, terminal B-X acquires the sensing data from sensor-X.

[0091] Relay A transitions to the steady state mode at the next timing of transmitting the polling signal, and in step S510, while terminal B-1 is in the operation suspension mode, it transmits the polling signal to terminal B-1 again. Therefore, terminal B-1 does not respond to the polling signal, and Relay A does not receive sensing data from terminal B-1 within a predetermined period after transmitting the polling signal. In step S510’, Relay A transmits the polling signal to terminal B-X. These polling signals may be transmitted to a plurality of terminals simultaneously (e.g., by broadcast) or sequentially (or almost simultaneously).

[0092] Since terminal B-X has sensing data, in step S511, terminal B-X transmits the sensing data to Relay A, and Relay A receives the sensing data from terminal B-X within a predetermined period after transmitting the polling signal.

[0093] After terminal B-X transmits the sensing data to Relay A, in step S512, it transitions to the operation suspension mode. The operation suspension mode continues until the next sensing timing.

[0094] Relay A has not received sensing data from terminal B-1 but has received sensing data from terminal B-X. Then, in step S513, it relays the sensing data to another relay or base station as appropriate and transitions to the operation suspension mode. The operation suspension mode continues until the next timing when Relay A transmits the polling signal.

[0095] Terminal B-1 transitions to the steady state mode at the next sensing timing, and in step S514, sensor-1 acquires sensing data such as temperature and transmits it to terminal B-1. That is, terminal B-1 acquires sensing data from sensor-1.

[0096] While terminal B-1 has sensing data, it does not transition to the operation suspension mode and waits for the polling signal from Relay A in step S515.

[0097] Terminal B-X transitions to the steady state mode at the following sensing timing. In step S516, sensor-X acquires sensing data such as temperature and transmits it to terminal B-X. That is, terminal B-X acquires sensing data from sensor-X.

[0098] Relay A transitions to the steady state mode at the timing of transmitting the polling signal. In step S517, Relay A transmits the polling signal to terminal B-1 again. In step S517’, Relay A transmits the polling signal to terminal B-X again. These polling signals may be sent to multiple terminals simultaneously (e.g., by broadcast) or sequentially (or almost simultaneously).

[0099] Since terminal B-1 has sensing data, in step S518, terminal B-1 transmits the sensing data to Relay A, and Relay A receives the sensing data from terminal B-1 within a predetermined period after transmitting the polling signal.

[0100] After terminal B-1 transmits the sensing data to Relay A, the next sensing timing arrives. Therefore, without terminal B-1 transitioning to the operation suspension mode, in step S519, sensor-1 acquires sensing data such as temperature and transmits it to terminal B-1. That is, terminal B-1 acquires sensing data from sensor-1. And while terminal B-1 has sensing data, it does not transition to the operation suspension mode and waits for the polling signal from Relay A.

[0101] Since terminal B-X has sensing data, in step S520, terminal B-X transmits the sensing data to Relay A, and Relay A receives the sensing data from terminal B-X within a predetermined period after transmitting the polling signal.

[0102] After transmitting the sensing data to the repeater A, the terminal B-X transitions to the operation suspension mode in step S521. The operation suspension mode continues until the next sensing timing.

[0103] After receiving the sensing data from the terminal B-1 and the terminal B-X, the repeater A relays the sensing data to another repeater or base station as appropriate in step S522 and transitions to the operation suspension mode. The operation suspension mode continues until the next timing when the repeater A transmits a polling signal.

[0104] Thereafter, the same process is repeated.

[0105] In the second example, when two or more terminals among the plurality of terminals B-1 to B-X transmit sensing data to the repeater A in response to the polling signal from the repeater A, there is a possibility that these signals will collide. To avoid such collisions, CDMA (Code Division Multiple Access), FDMA (Frequency Division Multiple Access), TDMA (Time Division Multiple Access), etc. may be used.

[0106] <The Third Example of Data Communication between the Terminal and the Repeater> Next, with reference to FIG. 7, a third example of data communication between the terminal and the repeater in the wireless communication system 2 will be described. FIG. 7 is a sequence diagram for explaining a third example of data communication between the terminal and the repeater in the wireless communication system 2 according to Embodiment 1 of the present disclosure. In the third example, in response to the transmission of data from the terminal B, the repeater A returns an ACK signal indicating that the data has reached the repeater A from the terminal B, and the terminal B does not retransmit the data if it does not receive the ACK signal.

[0107] The repeater A shown in FIG. 7 may be, for example, the repeater A-6 shown in FIG. 3, and the terminal B shown in FIG. 7 may be, for example, the terminal B-1 shown in FIG. 3. Here, the terminal B can operate in the same manner as the terminal described in the examples shown in FIGS. 5 and 6 described above, and the repeater A can operate in the same manner as the repeater described in the examples shown in FIGS. 5 and 6 described above.

[0108] In step S601, the sensor connected to the terminal B acquires sensing data such as temperature and transmits it to the terminal B. That is, the terminal B acquires the sensing data from the sensor.

[0109] In step S602, the repeater A transmits a polling signal to the terminal B.

[0110] Since the terminal B has the sensing data, in step S603, the terminal B transmits the sensing data to the repeater A, and the repeater A receives the sensing data from the terminal B within a predetermined period after transmitting the polling signal.

[0111] After receiving the sensing data from the terminal B, in step S604, the repeater A returns an ACK signal to the terminal B and relays the sensing data to another repeater (for example, the repeater A-4 in FIG. 3) or a base station, which is its upper communication device, as appropriate. Next, in step S605, the repeater A transitions to the operation suspension mode. The operation suspension mode continues until the next timing when the repeater A transmits a polling signal.

[0112] If the terminal B receives the ACK signal transmitted by the repeater A in step S604 within a predetermined period (for example, 3 seconds) after transmitting the sensing data, after receiving the ACK signal, in step S606, the terminal B transitions to the operation suspension mode. The operation suspension mode continues until the next sensing timing.

[0113] Terminal B transitions to the steady state mode at the following sensing timing. In step S607, the sensor acquires sensing data such as temperature and transmits it to terminal B. That is, terminal B acquires sensing data from the sensor.

[0114] Relay A transitions to the steady state mode at the timing of transmitting the polling signal. In step S608, relay A transmits the polling signal to terminal B again.

[0115] Since terminal B has the sensing data, in step S609, terminal B transmits the sensing data to relay A, and relay A receives the sensing data from terminal B within a predetermined period after transmitting the polling signal.

[0116] After receiving the sensing data from terminal B, in step S610, relay A returns an ACK signal to terminal B and relays the sensing data to another relay or base station, which is its upper communication device, as appropriate. Then, in step S611, relay A transitions to the operation suspension mode. The operation suspension mode continues until the next timing when relay A transmits the polling signal. Here, assume that a communication error occurred in step S610 and the ACK signal did not reach terminal B.

[0117] If terminal B cannot receive the ACK signal transmitted by relay A in step S610 within a predetermined period after transmitting the sensing data (due to a communication error), it does not transition to the operation suspension mode and remains in the steady state mode. If there is a communication error when relay A transmits the ACK signal to terminal B, relay A may operate recognizing that terminal B has received the ACK signal, and terminal B may operate recognizing that relay A has not transmitted the ACK signal to terminal B.

[0118] In step S612, the sensor acquires sensing data such as temperature and transmits it to terminal B. That is, terminal B acquires sensing data from the sensor.

[0119] Relay A transitions to the steady state mode at the next timing of transmitting the polling signal, and in step S613, transmits the polling signal to terminal B again.

[0120] Since terminal B has sensing data, in step S614, terminal B transmits the sensing data to relay A. Here, assuming that a communication error occurred in step S614 and the sensing data did not reach relay A.

[0121] If relay A does not receive the sensing data from terminal B within a predetermined period after transmitting the polling signal (due to a communication error), after the elapse of the predetermined period, in step S615, it transitions to the operation suspension mode. The operation suspension mode continues until the next timing when relay A transmits the polling signal. Note that the transition in step S615 may not be executed, and relay A may remain in the steady state mode. Since relay A does not receive the sensing data from terminal B within a predetermined period after transmitting the polling signal, it does not return an ACK signal to terminal B. In this case, relay A operates recognizing that terminal B does not have sensing data, and terminal B operates as if it has transmitted the sensing data to relay A. Therefore, in this case, one piece of sensing data is missing, but the wireless communication system 2 may continue to operate allowing for a slight data loss.

[0122] Thereafter, the same processing is repeated.

[0123] <Fourth Example of Data Communication between Terminal and Relay> Next, with reference to FIG. 8, a fourth example of data communication between a terminal and a repeater in the wireless communication system 2 will be described. FIG. 8 is a sequence diagram for explaining a fourth example of data communication between a terminal and a repeater in the wireless communication system 2 according to Embodiment 1 of the present disclosure. In the fourth example, in response to the transmission of data from terminal B, repeater A returns an ACK signal indicating that the data has reached repeater A from terminal B, and retransmits the data if terminal B does not receive the ACK signal.

[0124] The repeater A shown in FIG. 8 may be, for example, the repeater A-6 shown in FIG. 3, and the terminal B shown in FIG. 8 may be, for example, the terminal B-1 shown in FIG. 3. Here, the terminal B can operate in the same manner as the terminal described in the examples shown in FIGS. 5 to 7 above, and the repeater A can operate in the same manner as the repeater described in the examples shown in FIGS. 5 to 7 above.

[0125] In step S701, the sensor connected to terminal B acquires sensing data such as temperature and transmits it to terminal B. That is, terminal B acquires sensing data from the sensor.

[0126] In step S702, repeater A transmits a polling signal to terminal B.

[0127] Since terminal B has the sensing data, in step S703, terminal B transmits the sensing data to repeater A, and repeater A receives the sensing data from terminal B.

[0128] After receiving the sensing data from terminal B, in step S704, repeater A returns an ACK signal to terminal B and relays the sensing data to another repeater (for example, repeater A-4 in FIG. 3) or a base station, which is its upper communication device, as appropriate. Next, in step S705, repeater A transitions to the operation suspension mode. The operation suspension mode continues until the next timing when repeater A transmits a polling signal.

[0129] If the terminal B receives the ACK signal transmitted by the repeater A in step S704 within a predetermined period after transmitting the sensing data, after receiving the ACK signal, in step S706, it transitions to the operation suspension mode. The operation suspension mode continues until the next sensing timing.

[0130] At the next sensing timing, the terminal B transitions to the normal mode. In step S707, the sensor acquires sensing data such as temperature and transmits it to the terminal B. That is, the terminal B acquires the sensing data from the sensor.

[0131] At the timing of transmitting the polling signal next, the repeater A transitions to the normal mode. In step S708, the repeater A transmits the polling signal to the terminal B again.

[0132] Since the terminal B has the sensing data, in step S709, the terminal B transmits the sensing data to the repeater A, and the repeater A receives the sensing data from the terminal B.

[0133] After receiving the sensing data from the terminal B, in step S710, the repeater A returns an ACK signal to the terminal B and relays the sensing data to another repeater or base station which is its upper communication device as appropriate. Then, in step S711, the repeater A transitions to the operation suspension mode. The operation suspension mode continues until the next timing when the repeater A transmits the polling signal. Here, assume that a communication error occurred in step S710 and the ACK signal did not reach the terminal B.

[0134] If the terminal B cannot receive the ACK signal transmitted by the repeater A in step S710 within a predetermined period after transmitting the sensing data (due to a communication error), in step S712, it retransmits the sensing data to the repeater A. Here, since the repeater A is in the operation suspension mode, it does not receive the sensing data and thus does not return an ACK signal to the terminal B.

[0135] Therefore, since the terminal B does not receive the ACK signal within a predetermined period after retransmitting the sensing data, in step S713, the terminal B repeatedly retransmits the sensing data to the repeater A.

[0136] The retransmission of the sensing data by the terminal B may be repeated indefinitely until the ACK signal from the repeater A reaches the terminal B, or may be repeated until a predetermined upper limit number of retransmissions is reached.

[0137] In step S714, the sensor acquires sensing data such as temperature and transmits it to the terminal B. That is, the terminal B acquires the sensing data from the sensor.

[0138] The repeater A transitions to the steady state mode at the next timing of transmitting the polling signal, and in step S715, retransmits the polling signal to the terminal B.

[0139] Since the terminal B has the sensing data, in step S716, the terminal B transmits the sensing data to the repeater A. Here, assuming that a communication error occurred in step S716 and the sensing data did not reach the repeater A.

[0140] If the repeater A does not receive the sensing data from the terminal B (due to a communication error), it does not transition to the operation pause mode and remains in the steady state mode, waiting until the next polling signal is transmitted. In this case, the repeater A may transition to the operation pause mode.

[0141] Since the repeater A does not receive the sensing data, it does not return an ACK signal to the terminal B.

[0142] Therefore, since the terminal B does not receive the ACK signal within a predetermined period after retransmitting the sensing data, in step S717, the terminal B retransmits the sensing data to the repeater A.

[0143] While waiting until the next polling signal is transmitted, the repeater A can receive the retransmitted sensing data in step S718.

[0144] After receiving the sensing data from the terminal B, the repeater A returns an ACK signal to the terminal B in step S719, and relays the sensing data to another repeater or base station, which is its upper communication device, as appropriate. Next, in step S720, the repeater A transitions to the operation suspension mode. The operation suspension mode continues until the next timing when the repeater A transmits a polling signal.

[0145] If the terminal B receives the ACK signal transmitted by the repeater A in step S720 within a predetermined period after retransmitting the sensing data, the terminal B transitions to the operation suspension mode after receiving the ACK signal. The operation suspension mode continues until the next sensing timing.

[0146] Thereafter, the same processing is repeated.

[0147] In the fourth example, if the ACK signal from the repeater A does not reach the terminal B and the terminal B acquires the next sensing data while retransmitting the sensing data one or more times, the terminal B may stop retransmitting the sensing data. In that case, the terminal B may delete the sensing data from the storage device 32.

[0148] In the fourth example, since the repeater A returns an ACK signal for the data transmission from the terminal B and the terminal B retransmits the data when it does not receive the ACK signal, the probability of data loss can be reduced.

[0149] <Fifth Example of Data Communication between Terminal and Repeater> Next, with reference to FIG. 9, a fifth example of data communication between a terminal and a repeater in the wireless communication system 2 will be described. FIG. 9 is a sequence diagram for explaining a fifth example of data communication between a terminal and a repeater in the wireless communication system 2 according to Embodiment 1 of the present disclosure.

[0150] The repeater A-1 shown in FIG. 9 may be, for example, the repeater A-4 shown in FIG. 3. The repeater A-2 shown in FIG. 9 may be, for example, the repeater A-6 shown in FIG. 3. The terminal B shown in FIG. 9 may be, for example, the terminal B-1 shown in FIG. 3. Here, the terminal B can operate in the same manner as the terminal described in the examples shown in FIGS. 5 to 8 above, and each of the repeaters A-1 and A-2 can operate in the same manner as the repeaters described in the examples shown in FIGS. 5 to 8 above.

[0151] In step S801, the sensor connected to the terminal B acquires sensing data such as temperature and transmits it to the terminal B. That is, the terminal B acquires sensing data from the sensor.

[0152] In step S802, the repeater A-2 transmits a polling signal to the terminal B-1.

[0153] Since the terminal B has sensing data, in step S803, the terminal B transmits the sensing data to the repeater A-2, and the repeater A-2 receives the sensing data from the terminal B within a predetermined period after transmitting the polling signal.

[0154] After transmitting the sensing data to the repeater A-2, the terminal B transitions to the operation pause mode in step S804. The operation pause mode continues until the next sensing timing.

[0155] After receiving the sensing data from the terminal B, the repeater A-2 does not transition to the operation pause mode and waits for a polling signal from the repeater A-1.

[0156] In step S805, the repeater A-1 transmits a polling signal to the repeater A-2.

[0157] Since repeater A-2 has the sensing data received from terminal B, in step S806, repeater A-2 transmits the sensing data to repeater A-1, and repeater A-1 receives the sensing data from repeater A-2 within a predetermined period after transmitting the polling signal.

[0158] After transmitting the sensing data to repeater A-1, in step S807, repeater A-2 transitions to the operation suspension mode. The operation suspension mode continues until the next timing when repeater A-2 transmits a polling signal.

[0159] After receiving the sensing data from repeater A-2, in step S808, repeater A-1 relays the sensing data to another repeater (for example, repeater A-2 in FIG. 3) or the base station as appropriate and transitions to the operation suspension mode. The operation suspension mode continues until the next timing when repeater A-1 transmits a polling signal.

[0160] At the next timing when repeater A-2 transmits a polling signal, it transitions to the steady state mode. In step S809, repeater A-2 transmits the polling signal to terminal B again. Similar to the above example, when terminal B is in the operation suspension mode, repeater A-2 does not receive the sensing data from terminal B. When terminal B has the sensing data, repeater A-2 may receive the sensing data from terminal B within a predetermined period after transmitting the polling signal, or may not receive it. In any case, similar to the above example, after the elapse of a predetermined period, in step S810, it is assumed that repeater A-2 has transitioned to the operation suspension mode.

[0161] At the next timing when repeater A-1 transmits a polling signal, it transitions to the steady state mode. In step S811, while repeater A-2 is in the operation suspension mode, it transmits the polling signal to repeater A-2 again. Therefore, repeater A-2 does not respond to the polling signal and does not transmit the sensing data to repeater A-1.

[0162] If Repeater A-1 does not receive sensing data from Repeater A-2 within a predetermined period after transmitting a polling signal, after the elapse of the predetermined period, in step S812, it transitions to the operation suspension mode. The operation suspension mode continues until the next timing when Repeater A-1 transmits a polling signal. Note that the transition in step S812 may not be executed, and Repeater A-1 may remain in the steady state mode.

[0163] Terminal B transitions to the steady state mode at the next sensing timing, and in step S813, the sensor acquires sensing data such as temperature and transmits it to Terminal B. That is, Terminal B acquires sensing data from the sensor.

[0164] While Terminal B has sensing data, it does not transition to the operation suspension mode and waits for a polling signal from Repeater A-2 in step S814.

[0165] Repeater A-2 transitions to the steady state mode at the next timing when it transmits a polling signal, and in step S815, it transmits the polling signal to Terminal B again.

[0166] Since Terminal B has sensing data, in step S816, Terminal B transmits the sensing data to Repeater A-2, and Repeater A-2 receives the sensing data from Terminal B within a predetermined period after transmitting the polling signal.

[0167] After Terminal B transmits the sensing data to Repeater A-2, it transitions to the operation suspension mode in step S817. The operation suspension mode continues until the next sensing timing.

[0168] After Repeater A-2 receives the sensing data from Terminal B, it does not transition to the operation suspension mode and waits for a polling signal from Repeater A-1.

[0169] Relay A-1 transitions to the steady state mode at the next timing when it transmits the polling signal, and in step S818, it transmits the polling signal to Relay A-2 again.

[0170] Since Relay A-2 has the sensing data received from Terminal B, in step S819, Relay A-2 transmits the sensing data to Relay A-1, and Relay A-1 receives the sensing data from Relay A-2 within a predetermined period after transmitting the polling signal.

[0171] After Relay A-2 transmits the sensing data to Relay A-1, in step S820, it transitions to the operation pause mode. The operation pause mode continues until the next timing when Relay A-2 transmits the polling signal.

[0172] After Relay A-1 receives the sensing data from Relay A-2, in step S821, it relays the sensing data to another relay or the base station as appropriate and transitions to the operation pause mode. The operation pause mode continues until the next timing when Relay A-1 transmits the polling signal.

[0173] Thereafter, the same processing is repeated. For example, Terminal B transitions to the steady state mode at the next sensing timing, and in step S822, the sensor acquires sensing data such as temperature and transmits it to Terminal B. That is, Terminal B acquires the sensing data from the sensor.

[0174] In the fifth example, there are two-stage relays, but there may also be three or more stages of relays. For example, if there is further Relay A-0 above Relay A-1 described above, Relay A-1 can operate with respect to Relay A-0 in the same manner as the operation of Relay A-2 with respect to Relay A-1. Also, in the fifth example, instead of Relay A-1, a base station may exist, and the base station may operate in the same manner as Relay A-1.

[0175] <Example of Route Selection for Data Communication between Terminal, Relay, and Base Station> Next, with reference to FIGS. 10A to 10D, an example of route selection for data communication between a terminal, a repeater, and a base station in the wireless communication system 2 will be described. FIGS. 10A to 10D are diagrams for explaining an example of route selection for data communication between a terminal, a repeater, and a base station in the wireless communication system 2 according to Embodiment 1 of the present disclosure. In the example shown in FIG. 10A, the interval between the dotted lines represents 1 second. Also, in the example shown in FIG. 10A, sensing by the terminal B (more specifically, the sensor provided in the terminal B) is performed at the timing of the rising edge of the timing diagram. Further, in the example shown in FIG. 10A, data collection by the repeaters A-1 and A-2 is performed at the timing of the rising edge of the timing diagram. The High period and the Low period of the timing diagram represent the steady state mode and the operation pause mode, respectively.

[0176] The repeater A-1 shown in FIGS. 10A to 10D may be, for example, the repeater A-3 shown in FIG. 3, the repeater A-2 shown in FIGS. 10A to 10D may be, for example, the terminal A-6 shown in FIG. 3, and the terminal B shown in FIGS. 10A to 10D may be, for example, the terminal B-1 shown in FIG. 3. Also, the repeater A-3 and the base station shown in FIG. 10C may be, for example, a repeater and a base station not shown in FIG. 3. Here, the terminal B can operate in the same manner as the terminal described in the examples shown in FIGS. 5 to 9 described above, and each of the repeaters A-1 and A-2 can operate in the same manner as the repeater described in the examples shown in FIGS. 5 to 9 described above.

[0177] As shown in FIG. 10A, the terminal B can be connected to both the repeaters A-1 and A-2.

[0178] Also, as shown in FIG. 10A, it is assumed that the sensing interval of the terminal B (the sensor connected thereto) is 7 seconds, the polling interval of the repeater A-1 is 11 seconds, and the polling interval of the repeater A-2 is 5 seconds.

[0179] In such a situation, the terminal B can select a relay device as the transmission destination for sending sensing data so that it does not fix the connection of the relay but relays through the path with the earliest possibility of relaying.

[0180] For example, for the first acquired sensing data shown in FIG. 10A, the terminal B can select the relay device A-2 with a small delay as the transmission destination of the sensing data. Also, for example, for the second acquired sensing data shown in FIG. 10A, the terminal B can select the relay device A-2 with a small delay as the transmission destination of the sensing data. Also, for example, for the third acquired sensing data shown in FIG. 10A, the terminal B can select the relay device A-2 with a small delay as the transmission destination of the sensing data. Also, for example, for the fourth acquired sensing data shown in FIG. 10A, the terminal B can select the relay device A-1 with a small delay as the transmission destination of the sensing data.

[0181] Here, the above path (relay device) selection is premised on the fact that both the relay device A-1 and the relay device A-2 have paths leading to the base station ultimately. That is, a relay device without an upper path does not send a polling signal to the terminal B. For example, in the cases shown in FIGS. 10B and 10C, the terminal B selects a relay device as the transmission destination for sending sensing data from the relay devices A-1 and A-2. On the other hand, in the case shown in FIG. 10D, since the relay device A-2 does not have a path to the base station, the relay device A-2 does not send a polling signal to the terminal B, and the terminal B inevitably selects the relay device A-1 as the relay device for sending sensing data.

[0182] In the examples shown in FIGS. 10A to 10D, although two relay devices can be connected to the terminal B, even when three or more relay devices can be connected to the terminal, it goes without saying that the terminal B can select the relay device with the smallest delay from the three or more relay devices in the same manner as above.

[0183] Also, even when a repeater can be connected to a plurality of other repeaters, it goes without saying that the repeater can select, in the same manner as a terminal, a repeater that transmits sensing data from a plurality of other repeaters.

[0184] With the above configuration, from the perspective of the terminal, by transmitting data to the repeater that can transmit data the fastest among the pollings from a plurality of repeaters, the time during which the terminal is in the operation suspension mode can be lengthened, and power saving of the terminal can be achieved.

[0185] Also, with the above configuration, from the perspective of the repeater, the polling interval of some of the plurality of repeaters may be lengthened, and risks such as battery depletion or radio errors of such repeaters can also be avoided.

[0186] <Further Example of Route Selection for Data Communication between Terminal, Repeater, and Base Station> Next, with reference to FIG. 11, a further example of route selection for data communication between a terminal, a repeater, and a base station in the wireless communication system 2 will be described. FIG. 11 is a diagram for explaining a further example of route selection for data communication between a terminal, a repeater, and a base station in the wireless communication system 2 according to Embodiment 1 of the present disclosure.

[0187] The terminal group, repeater group, and base station shown in FIG. 11 are each, for example, the same as the terminal group, repeater group, and base station shown in FIG. 3. Here, each of the terminal group shown in FIG. 11 can operate in the same manner as the terminal described in the examples shown in FIGS. 5 to 10D described above, and each of the repeater group shown in FIG. 11 can operate in the same manner as the repeater described in the examples shown in FIGS. 5 to 10D described above.

[0188] Each of the communication devices shown in FIG. 11 can be connected to other communication devices as indicated by the arrows in FIG. 11. Also, as shown in FIG. 11, a hierarchy is set for each of the communication devices. Each of the communication devices knows its own hierarchy, and it is assumed that the hierarchy number takes an integer of 0 or more. Here, the hierarchy number of the communication device represents the depth of the hierarchy from the base station whose hierarchy number is 0. Note that the hierarchy is set when installing a repeater, but it can be set from the beginning when performing station placement design, and when not performing station placement design, it is set by causing the communication device to first enter the initial mode. This will be described later with reference to FIGS. 13A to 13E.

[0189] In this example, when the repeater receives a response to the polling signal from a communication device in a lower layer (i.e., a communication device with a larger hierarchy number indicating which layer it is in), if there is a communication device in a higher layer (i.e., a communication device with a smaller hierarchy number), the repeater relays the signal to the communication device in the higher layer. Here, the repeater includes the hierarchy number of the repeater in the polling signal and transmits the polling signal to the communication device in the lower layer. Also, when the communication device that receives the polling signal determines that the hierarchy number included in the polling signal is smaller than the hierarchy number of the communication device itself, the communication device responds to the polling signal and transmits the sensing data to the repeater.

[0190] For example, when the repeater A-6 with a hierarchy number of 3 transmits a polling signal including the hierarchy number "3" to the terminal B-1 with a hierarchy number of 4, since the hierarchy number "3" included in the polling signal is smaller than the hierarchy number "4" of the terminal B-1, the terminal B-1 responds to the polling signal and transmits the sensing data to the repeater A-6. Then, when the repeater A-6 receives the sensing data from the terminal B-1 and the repeater A-4 with a hierarchy number of 2 transmits a polling signal including the hierarchy number "2" to the repeater A-6, since the hierarchy number "2" included in the polling signal is smaller than the hierarchy number "3" of the repeater A-6, the repeater A-6 responds to the polling signal and transmits the sensing data to the repeater A-4.

[0191] A communication device that has received a polling signal is not necessarily restricted to sending sensing data only to a communication device having a hierarchical number that is 1 less than the hierarchical number of the said communication device. Instead, it may send the sensing data to a communication device having a hierarchical number that is 2 or more less than the hierarchical number of the said communication device.

[0192] For example, terminal B-1 is under repeater A-6 with a hierarchical number of 3 and is also under repeater A-3 with a hierarchical number of 2. In such a situation, terminal B-1 receives a polling signal from both repeater A-6 and repeater A-3. In this case, even if the transmission of the polling signal and the sensing data via the route through repeater A-6 were originally planned, when terminal B-1 receives a polling signal from repeater A-3, it may send the sensing data to repeater A-3.

[0193] Similarly, repeater A-6 may relay the sensing data to repeater A-2 with a hierarchical number of 1 instead of repeater A-4 with a hierarchical number of 2.

[0194] Thus, there may be multiple relay routes. In this case, if the communication device grasps the network topology of wireless communication system 2, it may select the shortest route, for example, based on the number of hops to the base station which is the final destination of the sensing data.

[0195] By skipping hierarchies as described above, the route can be shortened, but the shortest route is not always the optimal route. This is because, for example, there are situations where the wireless communication quality of the shortest route is not good, or the route length is reversed at a higher hierarchy. Therefore, if the communication device is aware of such a situation, it may select a route other than the shortest route.

[0196] Also, if the communication device has received a polling signal from another communication device with a hierarchical number of X in the past, even if the communication device receives a polling signal from yet another communication device with a hierarchical number of X + 1, the communication device may not transmit sensing data to the yet another communication device and may wait for a polling signal from the another communication device. Then, if the communication device receives a polling signal from another communication device within a predetermined period after receiving a polling signal from yet another communication device, the communication device transmits sensing data to the another communication device; if the communication device does not receive a polling signal from another communication device within the predetermined period, the communication device may transmit sensing data to yet another communication device. For example, the communication device stores history data (including identification information and hierarchical numbers of other communication devices, etc.) regarding past communications with other communication devices in a storage device, and by selecting the destination communication device based on the history data, it becomes possible to transmit the sensing data via the shortest route in this way.

[0197] Alternatively, instead of selecting another communication device with the smallest (most) delay as the transmission destination, the communication device may select the destination communication device based on communication quality (such as radio wave conditions (strength)).

[0198] Therefore, based on the network topology of the wireless communication system 2 stored in its storage device 32 by the communication device, the communication device may determine which polling signal among the polling signals received from a plurality of repeaters to respond to, and based on this determination, select the destination communication device.

[0199] With the above configuration, an optimal network topology can be constructed regardless of how the repeaters are installed.

[0200] <Example of data communication between a terminal, a repeater, and a base station based on a hierarchical structure> Next, with reference to FIGS. 12A and 12B, an example of data communication between a terminal, a repeater, and a base station based on the hierarchical structure of FIG. 11 will be described. FIGS. 12A and 12B are timing diagrams for explaining an example of data communication between a terminal, a repeater, and a base station based on the hierarchical structure of FIG. 11 according to Embodiment 1 of the present disclosure. FIGS. 12A and 12B show a first scenario and a second scenario in which data is relayed via different routes, respectively.

[0201] First, the first scenario will be described.

[0202] In step S1101, sensor-1 connected to terminal B-1 acquires sensing data such as temperature and transmits it to terminal B-1. That is, terminal B-1 acquires sensing data from sensor-1.

[0203] In step S1102, repeater A-6 transmits a polling signal to terminal B-1, including the hierarchy "3" of repeater A-6 in the polling signal.

[0204] Since terminal B-1 has sensing data and the hierarchy number "3" included in the polling signal is smaller than the hierarchy number "4" of terminal B-1, in step S1103, terminal B-1 transmits the sensing data to repeater A-6.

[0205] In step S1104, repeater A-3 transmits a polling signal to terminal B-1, including the hierarchy number "2" of repeater A-3 in the polling signal. However, as described above, terminal B-1 has already transmitted the sensing data to repeater A-6 in response to the polling signal transmitted by repeater A-6 in step S1102, so terminal B-1 does not transmit the sensing data to repeater A-3.

[0206] In step S1105, repeater A-4 transmits a polling signal to repeater A-6, including the hierarchy number "2" of repeater A-4 in the polling signal.

[0207] Since repeater A-6 has sensing data and the layer number "2" included in the polling signal is smaller than the layer number "3" of repeater A-6, in step S1106, repeater A-6 transmits the sensing data to repeater A-4.

[0208] In step S1107, repeater A-5 includes the layer number "2" of repeater A-5 in the polling signal and transmits the polling signal to repeater A-6. In step S1108, repeater A-2 includes the layer number "1" of repeater A-2 in the polling signal and transmits the polling signal to repeater A-6. However, as described above, since repeater A-6 has already transmitted the sensing data to repeater A-4 in response to the polling signal transmitted by repeater A-4 in step S1105, repeater A-6 does not transmit the sensing data to repeater A-5 and repeater A-2.

[0209] In step S1109, repeater A-2 includes the layer number "1" of repeater A-2 in the polling signal and transmits the polling signal to repeater A-4.

[0210] Since repeater A-4 has sensing data and the layer number "1" included in the polling signal is smaller than the layer number "2" of repeater A-4, in step S1110, repeater A-4 transmits the sensing data to repeater A-2.

[0211] In step S1111, the base station includes the layer number "0" of the base station in the polling signal and transmits the polling signal to repeater A-2. Alternatively, if it is predetermined that the polling signal from the base station does not include a layer number, the base station may transmit a polling signal without the layer number "0" to repeater A-2.

[0212] The repeater A-2 has sensing data, and since the layer number "0" included in the polling signal is smaller than the layer number "1" of the repeater A-2 (or because the repeater A-2 recognizes that the polling signal without a layer number is a polling signal from the base station), in step S1112, the repeater A-2 transmits the sensing data to the base station.

[0213] In this way, in the first scenario, the sensing data is reported from the terminal B-1 to the base station via the repeater A-6, the repeater A-4, and the repeater A-2 in sequence.

[0214] Next, the second scenario will be described.

[0215] In step S1151, the repeater A-6 transmits the polling signal to the terminal B-1 including the layer number "3" of the repeater A-6 in the polling signal. Here, it is assumed that the terminal B-1 is in the operation suspension mode. Therefore, the terminal B-1 does not respond to the polling signal from the repeater A-6.

[0216] The terminal B-1 transitions to the steady state mode, and in step S1152, the sensor-1 connected to the terminal B-1 acquires sensing data such as temperature and transmits it to the terminal B-1. That is, the terminal B-1 acquires the sensing data from the sensor-1.

[0217] In step S1153, the repeater A-3 transmits the polling signal to the terminal B-1 including the layer number "2" of the repeater A-3 in the polling signal.

[0218] Since the terminal B-1 has the sensing data and the layer number "2" included in the polling signal is smaller than the layer number "4" of the terminal B-1, in step S1154, the terminal B-1 transmits the sensing data to the repeater A-3.

[0219] In step S1155, the repeater A-1 transmits the polling signal to the repeater A-3, including the layer number "1" of the repeater A-1 in the polling signal.

[0220] Since the repeater A-3 has sensing data and the layer number "1" included in the polling signal is smaller than the layer number "2" of the repeater A-3, in step S1156, the repeater A-3 transmits the sensing data to the repeater A-1.

[0221] In step S1157, the base station transmits the polling signal to the repeater A-1, including the layer number "0" of the base station in the polling signal. Alternatively, if it is predetermined that the polling signal without a layer number is the polling signal from the base station, the base station may transmit the polling signal without the layer number "0" to the repeater A-1.

[0222] Since the repeater A-1 has sensing data and the layer number "0" included in the polling signal is smaller than the layer number "1" of the repeater A-1 (or since the repeater A-1 recognizes that the polling signal without a layer number is the polling signal from the base station), in step S1158, the repeater A-1 transmits the sensing data to the base station.

[0223] In step S1159, the repeater A-6 transmits the polling signal to the terminal B-1, including the layer number "3" of the repeater A-6 in the polling signal. However, as described above, since the terminal B-1 has already transmitted the sensing data to the repeater A-3 in response to the polling signal transmitted by the repeater A-3 in step S1153, the terminal B-1 does not transmit the sensing data to the repeater A-6.

[0224] In this way, in the second scenario, the sensing data is reported from the terminal B-1 to the base station via the repeaters A-3 and A-1 in sequence.

[0225] In the first scenario, terminal B-1 immediately transmits sensing data to the relay A-6 that received the polling signal earlier. However, after receiving the polling signal from relay A-6, terminal B-1 may wait for a predetermined period for polling signals from other communication devices. In this case, for example, if terminal B-1 receives a polling signal from relay A-3 within the predetermined period, since it received the polling signal from relay A-6 earlier, terminal B-1 may decide to respond to the polling signal transmitted by relay A-6. Also, when terminal B-1 waits for a predetermined period for polling signals from other communication devices after receiving the polling signal from relay A-6, since the route via relay A-3 is the shortest route, as described above, terminal B-1 may select relay A-3 instead of relay A-6. Further, in the first scenario, considering the radio wave conditions of relay A-6 and relay A-3, if the radio wave of relay A-3 is stronger, as described above, terminal B-1 may select relay A-3 instead of relay A-6. Note that the method of selecting the transmission destination of the sensing data also applies to relays in the same way.

[0226] <Example of setting the network hierarchy constituting the wireless communication system> Next, with reference to FIGS. 13A to 13E, an example of how the network hierarchy of the wireless communication system 2 as shown in FIGS. 11 and 12A and 12B is set will be described. FIGS. 13A to 13E are diagrams for explaining an example of setting the network hierarchy of the wireless communication system 2 according to Embodiment 1 of the present disclosure in time series. Note that in FIGS. 13A to 13E, the short-cycle polling mode and the steady mode described below may be abbreviated as "short-cycle" and "steady", respectively.

[0227] First, the base station enters the short-cycle polling mode, and all repeaters and terminals enter the initial mode. Generally, a communication device enters the initial mode when it is powered on. Here, the short-cycle polling mode means a mode in which a short-cycle polling signal is transmitted (broadcast is performed using the short-cycle polling signal), and the initial mode means a mode in which the device waits for the short-cycle polling signal. Also, the short-cycle polling signal is a signal broadcast to set the hierarchy of the network constituting the wireless communication system 2 and is a signal transmitted in a short cycle like a beacon signal. The base station performs broadcast using a short-cycle polling signal including the hierarchy number "0". Then, only the repeater or terminal that receives this short-cycle polling signal sets its own hierarchy number to "1", transitions to the short-cycle polling mode, and performs broadcast using a short-cycle polling signal including the hierarchy number "1". This is shown in FIGS. 13A and 13B.

[0228] When the base station receives a short-cycle polling signal or a response from a repeater or terminal and a certain time (e.g., 30 seconds) has elapsed after transmitting the short-cycle polling signal, after the elapse of the certain time, the base station transitions to the steady state mode. That is, there will always be at least one of the one or more repeaters and terminals under the base station in the steady state mode. This is shown in FIGS. 13B and 13C.

[0229] A repeater in the initial mode remains in the initial mode until it receives a short-cycle polling signal. Then, when the repeater in the initial mode receives a short-cycle polling signal, it sets the hierarchy number of the repeater to "the hierarchy number included in the short-cycle polling signal + 1", transitions to the short-cycle polling mode, and performs broadcast using a short-cycle polling signal including the hierarchy number of the repeater. This is shown in FIGS. 13B to 13D.

[0230] A terminal in the initial mode remains in the initial mode until it receives a short-period polling signal. When the terminal in the initial mode receives a short-period polling signal, it sets the layer number of the terminal to "the layer number included in the short-period polling signal + 1", returns a response indicating that it has received the short-period polling signal to the base station or repeater that sent the short-period polling signal, and transitions to the steady state mode. This is shown in FIGS. 13D and 13E.

[0231] When the repeater that has transitioned to the short-period polling mode has elapsed a certain time (for example, 30 seconds) after transmitting a short-period polling signal, regardless of whether it has received a short-period polling signal (including a layer number larger than the layer number of the repeater) or a response from a lower-layer repeater, it transitions to the steady state mode. That is, there is not necessarily at least one of one or more repeaters and terminals under the repeater in the steady state mode.

[0232] When the repeater and terminal remaining in the initial mode receive a polling signal from a base station or repeater in the steady state mode, they may set the layer numbers of the repeater and terminal to "the layer number included in the polling signal + 1" and transition to the steady state mode.

[0233] By repeating the above operations, finally, as shown in FIG. 13E, the layers of the communication device group are automatically set and formed.

[0234] <Example of a flow for setting the layers of a network constituting a wireless communication system> Next, with reference to FIG. 14, an example of a flow for setting the layers of the network constituting the wireless communication system 2 in FIGS. 13A to 13E will be described. FIG. 13 is a sequence diagram for explaining an example of a flow for setting the layers of the network constituting the wireless communication system 2 in FIGS. 13A to 13E according to Embodiment 1 of the present disclosure.

[0235] In addition, in FIG. 14, the initial mode, short-cycle polling mode, and steady state mode are abbreviated as "Initial", "Short-cycle", and "Steady state", respectively. Also, in FIG. 14, although the short-cycle polling signals may be described as being transmitted at approximately the same timing, actually, the short-cycle polling signals are transmitted simultaneously by broadcast.

[0236] First, as described above, the base station enters the short-cycle polling mode, and all repeaters and terminals enter the initial mode.

[0237] In step S1301, the base station performs a broadcast using a short-cycle polling signal including the hierarchy number "0".

[0238] Relay A-1 and Relay A-2 that have received the short-cycle polling signal from the base station each set the hierarchy numbers of Relay A-1 and Relay A-2 to "1 (= 0 + 1)" in steps S1302 and S1303 and transition to the short-cycle polling mode. Then, Relay A-1 and Relay A-2 each perform a broadcast using a short-cycle polling signal including the hierarchy number "1" in steps S1304 and S1305. Here, it is assumed that the short-cycle polling signal transmitted by Relay A-2 in step S1305 did not reach Relay A-6.

[0239] Relay A-3 that has received the short-cycle polling signal from Relay A-1 sets the hierarchy number of Relay A-3 to "2 (= 1 + 1)" in step S1306 and transitions to the short-cycle polling mode. Then, Relay A-3 performs a broadcast using a short-cycle polling signal including the hierarchy number "2" in step S1310. Here, it is assumed that the short-cycle polling signal transmitted by Relay A-3 in step S1310 did not reach Terminal B-1.

[0240] Relay A-4 and Relay A-5 that have received the short-period polling signal from Relay A-2 each set the hierarchical numbers of Relay A-4 and Relay A-5 to "2(=1 + 1)" in steps S1307 and S1308, and transition to the short-period polling mode. Next, Relay A-4 and Relay A-5 each perform a broadcast using the short-period polling signal including the hierarchical number "2" in steps S1311 and S1312.

[0241] When the base station receives the short-period polling signal transmitted by Relay A-1 in step S1304 and the short-period polling signal transmitted by Relay A-2 in step S1305, and a certain amount of time has elapsed since the short-period polling signal was transmitted in step S1301, after the elapse of the certain amount of time, in step S1309, the base station transitions to the steady state mode.

[0242] Terminal B-3 that has received the short-period polling signal from Relay A-5 sets the hierarchical number of Terminal B to "3(=2 + 1)" in step S1313, returns a response indicating that the short-period polling signal has been received to Relay A-5, and immediately transitions to the steady state mode.

[0243] Relay A-6 that has received the short-period polling signal from Relay A-4 earlier than the short-period polling signal from Relay A-5 sets the hierarchical number of Relay A-6 to "3(=2 + 1)" in response to the short-period polling signal from Relay A-4 in step S1316, and transitions to the short-period polling mode. Next, Relay A-6 performs a broadcast using the short-period polling signal including the hierarchical number "3" in step S1317.

[0244] When a certain period of time has elapsed after the repeater A-1 in the short-cycle polling mode transmits a short-cycle polling signal in step S1304, after the elapse of the certain period of time, in step S1314, it transitions to the steady state mode. Note that the repeater A-1 receives the short-cycle polling signal transmitted by the repeater A-3 in step S1310 before a certain period of time elapses after transmitting the short-cycle polling signal in step S1304.

[0245] When a certain period of time has elapsed after the repeater A-2 in the short-cycle polling mode transmits a short-cycle polling signal in step S1305, after the elapse of the certain period of time, in step S1315, it transitions to the steady state mode. Note that the repeater A-2 receives the short-cycle polling signal transmitted by the repeater A-4 in step S1311 and the short-cycle polling signal transmitted by the repeater A-5 in step S1312 before a certain period of time elapses after transmitting the short-cycle polling signal in step S1305.

[0246] The terminal B-1 that has received the short-cycle polling signal from the repeater A-6 sets the hierarchy number of the terminal B-1 to "4 (= 3 + 1)" in step S1318, returns a response indicating that it has received the short-cycle polling signal to the repeater A-6, and immediately transitions to the steady state mode.

[0247] The terminal B-2 that has received the short-cycle polling signal from the repeater A-6 sets the hierarchy number of the terminal B-2 to "4 (= 3 + 1)" in step S1319, returns a response indicating that it has received the short-cycle polling signal to the repeater A-6, and immediately transitions to the steady state mode.

[0248] When a certain period of time has elapsed after the repeater A-3 in the short-period polling mode transmits a short-period polling signal in step S1310, after the elapse of the certain period of time, in step S1320, it transitions to the steady state mode. Note that the repeater A-3 has not received a short-period polling signal or a response during the period from when it transmits the short-period polling signal in step S1310 until a certain period of time has elapsed, and there are no other repeaters or terminals under the control of the repeater A-3.

[0249] When a certain period of time has elapsed after the repeater A-4 in the short-period polling mode transmits a short-period polling signal in step S1311, after the elapse of the certain period of time, in step S1321, it transitions to the steady state mode. Note that the repeater A-4 has received the short-period polling signal transmitted by the repeater A-6 in step S1317 during the period from when it transmits the short-period polling signal in step S1311 until a certain period of time has elapsed.

[0250] When a certain period of time has elapsed after the repeater A-5 in the short-period polling mode transmits a short-period polling signal in step S1312, after the elapse of the certain period of time, in step S1322, it transitions to the steady state mode. Note that the repeater A-5 has received the response transmitted by the terminal B-3 in step S1313 during the period from when it transmits the short-period polling signal in step S1312 until a certain period of time has elapsed.

[0251] When a certain period of time has elapsed after the repeater A-6 in the short-period polling mode transmits a short-period polling signal in step S1317, after the elapse of the certain period of time, in step S1323, it transitions to the steady state mode. Note that the repeater A-6 has received the response transmitted by the terminal B-1 in step S1318 and the response transmitted by the terminal B-2 in step S1319 respectively during the period from when it transmits the short-period polling signal in step S1317 until a certain period of time has elapsed.

[0252] In this way, through the hierarchical automatic setting process including the above steps, finally, as shown in FIG. 13E, the hierarchy of the communication device group is automatically set and formed.

[0253] <Example of Reconfiguration of the Hierarchy of the Network Constituting the Wireless Communication System> Next, an example of reconfiguring the hierarchy of the network constituting the wireless communication system 2 will be described.

[0254] As shown in FIG. 13E, the hierarchy of the network constituting the wireless communication system 2 may be reviewed and reconfigured, for example, by the above hierarchical automatic setting process, in response to a change in the configuration of the network constituting the wireless communication system 2. For example, such reconfiguration may be performed during a time period when the system does not need to operate temporarily, such as late at night, or when replacing the batteries of some of the repeaters and terminals, or newly adding a repeater or a terminal. Such a reconfiguration method includes, for example, the following first to third methods that can correspond to the above hierarchical automatic setting process.

[0255] (First Method) In the first method, all the base stations, repeaters, and terminals are manually reset (e.g., by an operator) to cause all the communication devices to enter the initial mode, and then, as described with reference to FIGS. 13A to 14, the hierarchy of the network constituting the wireless communication system 2 is set.

[0256] (Second Method) In the second method, first, the base station transmits a reset polling signal, and the repeater that receives the reset polling signal relays the reset polling signal to the repeaters or terminals in the lower layer according to the hierarchy. After the base station and the repeaters transmit the reset polling signal a certain number of times, they transition to the initial mode. The terminal transitions to the initial mode immediately upon receiving the reset polling. Then, as described with reference to FIGS. 13A to 14, the hierarchy of the network constituting the wireless communication system 2 is set.

[0257] (Third method) In the third method, only some of the repeaters and terminals are reset, for example, manually or by sending a reset polling signal specifying its ID. Then, the repeater or terminal in the reset initial mode transitions to the steady state mode by receiving the above-described normal polling signal for checking whether it has sensing data. Each of the repeaters and terminals has only one communication device directly above it in the network topology. However, each of the repeaters and terminals can receive the above-described normal polling signal from communication devices other than the directly above communication device in the network topology and can also transmit data. And each of the repeaters and terminals can switch which communication device it belongs to or can belong to multiple communication devices in response to receiving the normal polling signal from such a communication device.

[0258] (Example of the third method) Next, with reference to FIGS. 15A to 15D, an example of the third method described above will be described. FIGS. 15A to 15D are diagrams for explaining an example of the reset of the hierarchy of the network constituting the wireless communication system 2 according to Embodiment 1 of the present disclosure in time series.

[0259] FIG. 15A shows the hierarchical structure of the network constituting the same wireless communication system 2 as shown in FIG. 13E. Here, it is assumed that the repeater A-4 and the terminal B-1 are removed from the hierarchical structure as shown in FIG. 15B for battery replacement.

[0260] As shown in FIG. 15A, when the repeater A-6, which was under the repeater A-4, receives a polling signal from the repeater A-5 in the steady state mode, it comes under the repeater A-5 and transitions to the steady state mode. Then, as shown in FIG. 15C, it is assumed that the repeater A-5 is removed from the hierarchical structure for battery replacement, and further, the terminal B-1 is restarted. In this case, the restarted terminal B-1 is reset and enters the initial mode.

[0261] As shown in FIG. 15C, when the repeater A-6 receives a polling signal from the repeater A-4 in the steady state mode, it comes under the repeater A-4 again and transitions to the steady state mode. Since the restarted terminal B-1 in the initial mode receives a polling signal from the repeater A-3 in the steady state mode earlier than receiving a polling signal from the repeater A-6 in the steady state mode as shown in FIG. 15C, it comes under the repeater A-3, sets its own hierarchical number to 3, which is obtained by adding 1 to the hierarchical number 2 of the repeater A-3, and transitions to the steady state mode. On the other hand, since the upper-layer communication device of the terminal B-3 connected to the repeater A-5 is temporarily absent, the terminal B-3 becomes in a state where data transmission and reception are impossible. Then, it is assumed that the repeater A-5 is restarted as shown in FIG. 15D. In this case, the restarted repeater A-5 is reset and enters the initial mode.

[0262] As shown in FIG. 15D, when the reset repeater A-5 in the initial mode receives a polling signal from the repeater A-2 in the steady state mode, it comes under the repeater A-2 again and transitions to the steady state mode. As shown in FIG. 15D, when the terminal B-3 receives a polling signal from the repeater A-5 in the steady state mode, it comes under the repeater A-5 again and transitions to the steady state mode.

[0263] [Embodiment 2] Next, referring to FIGS. 16 to 20, Embodiment 2 of the present disclosure will be described. Embodiment 2 is different from Embodiment 1 in that it assumes data transmission not only in the upward direction but also in the downward direction.

[0264] <Wireless communication system> Since the wireless communication system according to Embodiment 2 has the same configuration as the wireless communication system 2 according to Embodiment 1, the description thereof is omitted here.

[0265] <Configuration and operation of communication devices including terminals, repeaters, and base stations> Since the communication device according to Embodiment 2 also has the same configuration and operation as the communication device according to Embodiment 1, most of the description thereof is omitted here, and only the parts different from Embodiment 1 will be described below.

[0266] As described above, in Embodiment 2, not only uplink data transmission but also downlink data transmission is assumed. Therefore, in the wireless communication system according to Embodiment 2, two-way data communication including not only data transmission from the terminal to the base station but also data transmission from the base station to the terminal may be performed. In such a case, the repeater or the terminal can perform both uplink (from the terminal to the base station) data communication and downlink (from the base station to the terminal) data communication.

[0267] The communication method as described above includes, for example, the following first method to fifth method.

[0268] (First method) The repeater or the terminal shares one radio for both uplink and downlink use. In this case, the repeater or the terminal is made capable of simultaneously performing uplink communication and downlink communication (alternatively, there may be separate uplink and downlink radios, but these radios may be tightly coupled to operate in the same manner as one radio). In this case, the repeater or the terminal can pause its operation only during time periods when it can pause operation in both uplink and downlink communication.

[0269] (Second method) The repeater or terminal shares one radio for both the upstream and downstream directions. In this case, the repeater or terminal conducts upstream communication and downstream communication at different times (alternatively, there may be separate upstream and downstream radios, but these radios can be tightly coupled to operate in the same manner as one radio). In this situation, the repeater or terminal can pause its operation during the operating time period of the downstream communication in upstream communication, and can pause its operation during the operating time period of the upstream communication in downstream communication.

[0270] (The third method) The repeater or terminal separately holds an upstream radio and a downstream radio, and these two radios are loosely coupled (their operations are independent of each other). In this case, the two radios can pause their operations at their respective required timings (i.e., regardless of the operation of the other radio).

[0271] (The fourth method) In the above second method or third method, the repeater or terminal uses the same channel (frequency, spreading code, etc.) in both the upstream and downstream directions. In this case, fewer channels are required, but since the repeater or terminal is basically asynchronous with other repeaters or terminals, there is a possibility that upstream and downstream will be mixed on one channel. Therefore, this fourth method is preferably applied to the exchange of less frequent information.

[0272] (The fifth method) In the above first method, second method, or third method, the repeater or terminal uses different channels (frequency, spreading code, etc.) in both the upstream and downstream directions. In this case, twice as many channels are required compared to the above fourth method, but upstream and downstream will not be mixed on one channel. Therefore, this fifth method is also applicable to the exchange of frequent information.

[0273] In the upward direction, there is only one base station as the final destination. However, in the downward direction, there can be multiple terminals as the final destinations. Therefore, in the above method, it is necessary to assign an ID to the terminal to specify the destination.

[0274] To enable the transmission of downlink data, the following is done.

[0275] The repeater that has received the "response" from the terminal responds to the polling signal received from the higher-level repeater or the base station, and reports to the higher-level repeater that it has received a response from the terminal, that is, that relaying to the terminal is possible, as described in the example shown in FIG. 14 above. Then, the repeater that has received such a report similarly reports to the higher-level communication device (eventually reporting to the base station), so that each repeater can recognize the transmission destination of the downlink data. When the repeater transmits downlink data, the repeater determines whether the route to be transmitted by that repeater or the terminal is the correct one when receiving a polling signal from the lower-level repeater or the terminal. And if the route to be transmitted by that repeater or the terminal is the correct one, the repeater responds to the polling signal from that repeater or the terminal and transmits downlink data to that repeater or the terminal; if not, the repeater does not respond to the polling signal from that repeater or the terminal. Such transmission of downlink data can be realized by the repeater responding to the polling signal from the higher-level repeater or the base station when in the steady state mode and transmitting information based on special data (downlink route determination data indicating which repeater can relay to which terminal).

[0276] <Example of data communication between terminal, repeater, and base station> FIG. 16 is a sequence diagram for explaining an example of data communication among a terminal, a repeater, and a base station in a wireless communication system according to Embodiment 2 of the present disclosure. FIG. 16 shows the continuation of the sequence in FIG. 14, that is, it shows data communication after all of the base station, the repeater, and the terminal have transitioned to the steady state mode. In FIG. 16, the connection relationship among the base station, the repeater, and the terminal is the same as that shown in FIG. 11, and the steady state mode is abbreviated as "steady".

[0277] First, after all of the base station, the repeater, and the terminal have transitioned to the steady state mode, since repeater A-5 has received a response from terminal B-3, it has downlink route determination data indicating that relaying to terminal B-3 is possible. Similarly, since repeater A-6 has received responses from terminal B-1 and terminal B-2, it has downlink route determination data indicating that relaying to terminal B-1 and terminal B-2 is possible. By having this downlink route determination data, when repeater A-5 receives a polling signal from terminal B-3, it transmits data destined for terminal B-3 to terminal B-3, but does not transmit downlink data destined for terminals other than terminal B-3. By having this downlink route determination data, when repeater A-6 receives a polling signal from terminal B-1, it transmits data destined for terminal B-1 to terminal B-1, and when it receives a polling signal from terminal B-2, it transmits data destined for terminal B-2 to terminal B-2, but does not transmit downlink data destined for terminals other than terminal B-1 and terminal B-2.

[0278] In steps S1501 and 1501' respectively, the base station transmits a polling signal to repeaters A-1 and A-2.

[0279] After receiving the polling signal from the base station, repeater A-2 transmits a polling signal to repeaters A-4, A-5, and A-6 in steps S1502, S1502', and S1502'' respectively.

[0280] In response to the polling signal received from Repeater A-2, Repeater A-5 reports to Repeater A-2 in step S1503 that relay to Terminal B-3 is possible.

[0281] In response to the polling signal received from Repeater A-2, Repeater A-6 reports to Repeater A-2 in step S1504 that relay to Terminal B-1 and Terminal B-2 is possible.

[0282] Therefore, by receiving the reports from Repeater A-5 and Repeater A-6, Repeater A-2 will have downlink route determination data indicating that relay to Terminal B-3 via Repeater A-5 is possible and that relay to Terminal B-1 and Terminal B-2 via Repeater A-6 is possible. Since Repeater A-2 has this downlink route determination data, when it receives a polling signal from Repeater A-5, it transmits data destined for Terminal B-3 to Repeater A-5 but does not transmit downlink data destined for terminals other than Terminal B-3. Also, since Repeater A-2 has this downlink route determination data, when it receives a polling signal from Repeater A-6, it transmits data destined for Terminal B-1 or Terminal B-2 to Repeater A-6 but does not transmit downlink data destined for terminals other than Terminal B-1 and Terminal B-2.

[0283] In steps S1505 and 1505', the base station re-transmits the polling signal to Repeater A-1 and Repeater A-2 respectively.

[0284] In response to the polling signal received from the base station, Repeater A-2 reports to the base station in step S1506 that relay to Terminal B-3 via Repeater A-5 is possible and that relay to Terminal B-1 and Terminal B-2 via Repeater A-6 is possible.

[0285] Therefore, by receiving the report from Repeater A-2, the base station will have downlink route determination data indicating that it is possible to relay to Terminal B-3 via Repeater A-2 and Repeater A-5, and that it is possible to relay to Terminals B-1 and B-2 via Repeater A-2 and Repeater A-6. When the base station has this downlink route determination data and receives a polling from Repeater A-2, it transmits downlink data destined for a specific terminal in the same way as above. On the other hand, at this point, Repeater A-1 does not have the downlink route determination data and has not sent a report to the base station indicating that it is possible to relay to a specific terminal. Therefore, even if the base station receives a polling signal from Repeater A-1, it does not transmit downlink data destined for a specific terminal to Repeater A-1.

[0286] <Example of Communication between Terminals> In the case of a call between terminals, data obtained via a microphone or the like may be communicated between the terminals via the base station. However, if these terminals are under the same repeater, such data may be communicated via the repeater without passing through the base station. Such communication is not limited to calls between terminals, and may be data communication for sharing sensing data obtained from sensors as described above between terminals. By performing such communication, it is possible to reduce the delay compared to communication via the base station, and also to reduce the use of the radio channel, and thus to reduce the total power consumption. Note that when performing such communication, it is necessary to assign an ID to each terminal.

[0287] Such a method of communicating via a repeater without passing through the base station includes, for example, the following first method and second method.

[0288] (First Method) The repeater is assumed to understand the network topology by means of the placement design or the automatic hierarchical setting shown in the above example. If the destination of the data arriving at this repeater is under the control of this repeater, the repeater does not transfer the data to the repeater or base station in the upper layer. Instead, the repeater transfers the data in the direction of the destination (if the destination is directly below this repeater, it is transferred to the terminal directly below, or if the destination is under the control of a repeater under the control of this repeater, it is transferred to the repeater under its control, etc.). That is, even if the repeater receives a polling signal from the repeater or base station in the upper layer, without disclosing the existence of the data to the repeater or base station in the upper layer, in response to the polling signal from the direction of the destination, the repeater transmits the data in the direction of the destination.

[0289] (The second method) If the repeater does not grasp the network topology and receives data from a lower-layer repeater or terminal, it responds to a polling signal from a higher-layer repeater or base station, transmits the data to the higher-layer repeater or base station, and stores the data in the cache. Also, the repeater responds to a polling signal from another higher-layer repeater or base station and transmits the data in the cache to the repeater or base station that is the source of the polling signal. And when the repeater receives a polling signal from a subordinate terminal, if the source of the polling signal is the terminal that is the destination of the data in the cache, the repeater transmits the data in the cache to that subordinate terminal and deletes the data in the cache. When the repeater receives a polling signal from a subordinate repeater rather than a subordinate terminal, if the subordinate repeater is not another subordinate repeater that originally had data and transmitted the data to the repeater, the repeater transmits the data to that subordinate repeater. In this case, the repeater deletes the data in the cache after a certain period of time has elapsed since the data was stored in the cache. Also, after the repeater transmits a polling signal to a higher-layer base station or repeater and receives data from the higher-layer base station or repeater, the repeater compares the received data with the data in the cache. If the repeater determines as a result of the comparison that these data are the same, the repeater deletes the received data. On the other hand, if the repeater determines as a result of the comparison that these data are not the same, the repeater stores the received data in the cache. When a certain period of time has elapsed after the repeater stores the received data in the cache without receiving a polling signal from a lower-layer repeater or terminal, the repeater deletes the data in the cache after the certain period of time has elapsed.

[0290] FIG. 17 is a diagram for explaining an example of communication between terminals via a base station and via a repeater and an example of communication between terminals via a repeater without passing through a base station according to Embodiment 2 of the present disclosure.

[0291] In Example 1 shown in FIG. 17, the communication between terminal B-1 and terminal B-2 is carried out not only via repeater A-6 but also via a base station. In Example 2 shown in FIG. 17, the communication between terminal B-1 and terminal B-2 is carried out by being folded back by repeater A-6 without passing through a base station. In Example 3 shown in FIG. 17, the communication between terminal B-1 and terminal B-3 is carried out not only via repeater A-2 but also via a base station. In Example 4 shown in FIG. 17, the communication between terminal B-1 and terminal B-2 is carried out by being folded back by repeater A-2 without passing through a base station.

[0292] (Example of the first method) Next, with reference to FIG. 18, an example of the above-described first method in which a communication device grasps a network topology will be described. FIG. 18 is a sequence diagram for explaining a first example of data communication between terminals in a wireless communication system according to Embodiment 2 of the present disclosure.

[0293] First, it is assumed that terminal B-1 has data addressed to terminal B-2.

[0294] In step S1701, terminal B-1 receives a polling signal from repeater A-6.

[0295] Since terminal B-1 has data addressed to terminal B-2, in step S1702, terminal B-1 transmits the data addressed to terminal B-2 to repeater A-6.

[0296] In step S1703, repeater A-6 receives a polling signal from repeater A-2.

[0297] Here, since repeater A-6 grasps the network topology and recognizes that the data addressed to terminal B-2 should be folded back at repeater A-6, repeater A-6 does not respond to the polling signal from repeater A-2.

[0298] In step S1704, the repeater A-6 receives a polling signal from the terminal B-2.

[0299] Since the repeater A-6 has data addressed to the terminal B-2, in step S1705, the repeater A-6 transmits the data addressed to the terminal B-2 to the terminal B-2.

[0300] In this way, without going through the base station, the repeater A-6 folds back the data from the terminal B-1 addressed to the terminal B-2, and communication between the terminal B-1 and the terminal B-2 is carried out.

[0301] Furthermore, assume that the terminal B-1 has data addressed to the terminal B-3.

[0302] In step S1706, the terminal B-1 receives a polling signal from the repeater A-6.

[0303] Since the terminal B-1 has data addressed to the terminal B-3, in step S1707, the terminal B-1 transmits the data addressed to the terminal B-3 to the repeater A-6.

[0304] In step S1708, the repeater A-6 receives a polling signal from the terminal B-2.

[0305] Here, since the repeater A-6 only has data addressed to the terminal B-3, the repeater A-6 does not respond to the polling signal from the terminal B-2.

[0306] In step S1709, the repeater A-6 receives a polling signal from the repeater A-4.

[0307] Here, since the repeater A-6 grasps the network topology and knows that the terminal B-3 is ahead of the repeater A-4, in step S1710, the repeater A-6 transmits the data addressed to the terminal B-3 to the repeater A-4.

[0308] In step S1711, repeater A-4 receives a polling signal from repeater A-2.

[0309] Here, since repeater A-4 grasps the network topology and knows that terminal B-3 is beyond repeater A-2, in step S1712, repeater A-4 transmits the data destined for terminal B-3 to repeater A-2.

[0310] In step S1713, repeater A-2 receives a polling signal from the base station.

[0311] Here, since repeater A-2 grasps the network topology and recognizes that the data destined for terminal B-2 should be relayed back at repeater A-2, repeater A-2 does not respond to the polling signal from the base station.

[0312] In step S1714, repeater A-2 receives a polling signal from repeater A-4.

[0313] Here, since the data destined for terminal B-2 is the data arriving from repeater A-4, repeater A-2 does not respond to the polling signal from repeater A-4.

[0314] In step S1715, repeater A-2 receives a polling signal from repeater A-5.

[0315] Here, since repeater A-2 grasps the network topology and knows that terminal B-3 is beyond repeater A-5, in step S1716, repeater A-2 transmits the data destined for terminal B-3 to repeater A-5.

[0316] In step S1717, repeater A-5 receives a polling signal from terminal B-3.

[0317] Since the repeater A-5 has data addressed to the terminal B-3, in step S1718, the repeater A-5 transmits the data addressed to the terminal B-3 to the terminal B-3.

[0318] In this way, without going through the base station, the repeater A-2 folds back the data addressed to the terminal B-3 from the terminal B-1, and communication is carried out between the terminal B-1 and the terminal B-3.

[0319] (The first example of the second method) Next, with reference to FIG. 19, a first example of the above-described second method in which the communication device does not grasp the network topology will be described. FIG. 19 is a sequence diagram for explaining a second example of data communication between terminals in a wireless communication system according to Embodiment 2 of the present disclosure.

[0320] First, it is assumed that the terminal B-1 has data addressed to the terminal B-2.

[0321] In step S1801, the terminal B-1 receives a polling signal from the repeater A-6.

[0322] Since the terminal B-1 has data addressed to the terminal B-2, in step S1802, the terminal B-1 transmits the data addressed to the terminal B-2 to the repeater A-6.

[0323] In step S1803, the repeater A-6 receives a polling signal from the repeater A-4.

[0324] Here, the repeater A-6 does not grasp the network topology and recognizes that the terminal B-2 may be ahead of the repeater A-4. Therefore, in step S1804, the repeater A-6 transmits the data addressed to the terminal B-2 to the repeater A-4 and stores the data addressed to the terminal B-2 in the cache of the repeater A-6.

[0325] In step S1805, the repeater A-4 receives a polling signal from the repeater A-2.

[0326] Here, the repeater A-4 does not grasp the network topology and recognizes that the terminal B-2 may be beyond the repeater A-2. Therefore, in step S1806, the repeater A-4 transmits the data destined for the terminal B-2 to the repeater A-2 and stores the data destined for the terminal B-2 in the cache of the repeater A-4 and leaves it there.

[0327] In step S1807, the repeater A-6 receives a polling signal from the terminal B-2.

[0328] Since the repeater A-6 has the data destined for the terminal B-2 (in the cache), in step S1808, the repeater A-6 transmits the data destined for the terminal B-2 to the terminal B-2. Since the repeater A-6 has transmitted the data destined for the terminal B-2 to the final destination (the terminal B-2), in step S1809, the repeater A-6 deletes the data destined for the terminal B-2 from the cache (that is, clears the cache).

[0329] In this way, without going through the base station, the repeater A-6 folds back the data destined for the terminal B-2 from the terminal B-1, and thus the communication between the terminal B-1 and the terminal B-2 is carried out.

[0330] When the communication device does not grasp the network topology, the following further steps are executed.

[0331] In step S1810, the repeater A-2 receives a polling signal from the base station.

[0332] Here, the repeater A-2 does not grasp the network topology and recognizes that the terminal B-2 may be beyond the base station. Therefore, in step S1811, the repeater A-2 transmits the data destined for the terminal B-2 to the base station and stores the data destined for the terminal B-2 in the cache of the repeater A-2 and leaves it there.

[0333] In step S1812, repeater A-2 receives a polling signal from repeater A-4. Here, since the data destined for terminal B-2 is the data arriving from repeater A-4, repeater A-2 does not respond to the polling signal from repeater A-4.

[0334] In step S1813, the base station receives a polling signal from repeater A-1.

[0335] Here, the base station does not grasp the network topology and recognizes that terminal B-2 may be ahead of repeater A-1. Therefore, in step S1814, the base station transmits the data destined for terminal B-2 to repeater A-1 and stores the data destined for terminal B-2 in the cache of the base station.

[0336] In step S1815, repeater A-1 receives a polling signal from repeater A-3.

[0337] Here, repeater A-1 does not grasp the network topology and recognizes that terminal B-2 may be ahead of repeater A-3. Therefore, in step S1816, repeater A-1 transmits the data destined for terminal B-2 to repeater A-3 and stores the data destined for terminal B-2 in the cache of repeater A-1.

[0338] In step S1817, repeater A-2 receives a polling signal from repeater A-5.

[0339] Here, repeater A-2 does not grasp the network topology and recognizes that terminal B-2 may be ahead of repeater A-5. Therefore, in step S1818, repeater A-2 transmits the data destined for terminal B-2 to repeater A-5 and stores the data destined for terminal B-2 in the cache of repeater A-2.

[0340] In step S1819, repeater A-2 receives a polling signal from the base station.

[0341] Here, since repeater A-2 has already transmitted the data destined for terminal B-2 to the base station, repeater A-2 does not respond to the polling signal from the base station.

[0342] Since a certain period of time has elapsed after repeater A-4 stored the data destined for terminal B-2 in the cache, in step S1820, repeater A-4 deletes the data destined for terminal B-2 from the cache.

[0343] Since a certain period of time has elapsed after repeater A-2 stored the data destined for terminal B-2 in the cache, in step S1821, repeater A-2 deletes the data destined for terminal B-2 from the cache.

[0344] In step S1822, repeater A-5 receives a polling signal from repeater B-3.

[0345] Here, since repeater A-5 only has the data destined for terminal B-2, repeater A-5 does not respond to the polling signal from terminal B-3.

[0346] Since a certain period of time has elapsed after the base station stored the data destined for terminal B-2 in the cache, in step S1823, the base station deletes the data destined for terminal B-2 from the cache.

[0347] Since a certain period of time has elapsed after repeater A-1 stored the data destined for terminal B-2 in the cache, in step S1824, repeater A-1 deletes the data destined for terminal B-2 from the cache.

[0348] Since a certain period of time has elapsed after repeater A-3 stored the data destined for terminal B-2 in the cache, in step S1825, repeater A-3 deletes the data destined for terminal B-2 from the cache.

[0349] Since a certain amount of time has elapsed after the repeater A-5 stored the data addressed to the terminal B-2 in the cache, in step S1826, the repeater A-5 deletes the data addressed to the terminal B-2 from the cache.

[0350] (Second example of the second method) Next, with reference to FIG. 20, a second example of the second method in which the communication device does not grasp the network topology will be described. FIG. 20 is a sequence diagram for explaining a third example of data communication between terminals in a wireless communication system according to Embodiment 2 of the present disclosure.

[0351] First, it is assumed that the terminal B-1 has data addressed to the terminal B-3.

[0352] In step S1901, the terminal B-1 receives a polling signal from the repeater A-6.

[0353] Since the terminal B-1 has data addressed to the terminal B-3, in step S1902, the terminal B-1 transmits the data addressed to the terminal B-3 to the repeater A-6.

[0354] In step S1903, the repeater A-6 receives a polling signal from the repeater A-4.

[0355] Here, the repeater A-6 does not grasp the network topology and recognizes that the terminal B-3 may be ahead of the repeater A-4. Therefore, in step S1904, the repeater A-6 transmits the data addressed to the terminal B-3 to the repeater A-4 and stores the data addressed to the terminal B-3 in the cache of the repeater A-6 and leaves it there.

[0356] In step S1905, the repeater A-4 receives a polling signal from the repeater A-2.

[0357] Here, repeater A-4 does not grasp the network topology and recognizes that terminal B-3 may be beyond repeater A-2. Therefore, in step S1906, repeater A-4 transmits the data addressed to terminal B-3 to repeater A-2 and stores the data addressed to terminal B-3 in the cache of repeater A-4 for later reference.

[0358] In step S1907, repeater A-6 receives a polling signal from terminal B-2. Here, since repeater A-6 only has data addressed to terminal B-3, repeater A-6 does not respond to the polling signal from terminal B-2.

[0359] In step S1908, repeater A-2 receives a polling signal from the base station.

[0360] Here, repeater A-2 does not grasp the network topology and recognizes that terminal B-3 may be beyond the base station. Therefore, in step S1909, repeater A-2 transmits the data addressed to terminal B-3 to the base station and stores the data addressed to terminal B-3 in the cache of repeater A-2 for later reference.

[0361] In step S1910, repeater A-2 receives a polling signal from repeater A-4.

[0362] Here, since the data addressed to terminal B-3 is the data that arrived from repeater A-4, repeater A-2 does not respond to the polling signal from repeater A-4.

[0363] In step S1911, the base station receives a polling signal from repeater A-1.

[0364] Here, the base station does not grasp the network topology and recognizes that terminal B-3 may be ahead of repeater A-1. Therefore, in step S1912, the base station transmits the data destined for terminal B-3 to repeater A-1 and stores the data destined for terminal B-3 in the cache of the base station for later use.

[0365] In step S1913, repeater A-1 receives a polling signal from repeater A-3.

[0366] Here, repeater A-1 does not grasp the network topology and recognizes that terminal B-3 may be ahead of repeater A-3. Therefore, in step S1914, repeater A-1 transmits the data destined for terminal B-3 to repeater A-3 and stores the data destined for terminal B-3 in the cache of repeater A-1 for later use.

[0367] In step S1915, repeater A-2 receives a polling signal from repeater A-5.

[0368] Here, repeater A-2 does not grasp the network topology and recognizes that terminal B-3 may be ahead of repeater A-5. Therefore, in step S1916, repeater A-2 transmits the data destined for terminal B-3 to repeater A-5 and stores the data destined for terminal B-3 in the cache of repeater A-2 for later use.

[0369] In step S1917, repeater A-2 receives a polling signal from the base station.

[0370] Here, since repeater A-2 has already transmitted the data destined for terminal B-3 to the base station, repeater A-2 does not respond to the polling signal from the base station.

[0371] Since a certain period of time has elapsed after the repeater A-4 stored the data addressed to terminal B-3 in the cache, in step S1918, the repeater A-4 deletes the data addressed to terminal B-3 from the cache.

[0372] In step S1919, the repeater A-5 receives a polling signal from the terminal B-3.

[0373] Since the repeater A-5 has the data addressed to terminal B-3 (in the cache), in step S1920, the repeater A-5 transmits the data addressed to terminal B-3 to the terminal B-3. Since the repeater A-5 has transmitted the data addressed to terminal B-3 to the final destination (terminal B-3), in step S1921, the repeater A-5 deletes the data addressed to terminal B-3 from the cache.

[0374] In this way, without going through the base station (without using the data folded back at the base station), the repeater A-2 folds back the data addressed to terminal B-3 from the terminal B-1, and communication between the terminal B-1 and the terminal B-3 is carried out.

[0375] When the communication device does not grasp the network topology, the following further steps are executed.

[0376] Since a certain period of time has elapsed after the repeater A-2 stored the data addressed to terminal B-3 in the cache, in step S1922, the repeater A-2 deletes the data addressed to terminal B-3 from the cache.

[0377] Since a certain period of time has elapsed after the base station stored the data addressed to terminal B-3 in the cache, in step S1923, the base station deletes the data addressed to terminal B-3 from the cache.

[0378] Since a certain period of time has elapsed after the repeater A-1 stored the data addressed to terminal B-3 in the cache, in step S1924, the repeater A-1 deletes the data addressed to terminal B-3 from the cache.

[0379] Since a certain amount of time has elapsed after Repeater A-3 stored the data addressed to Terminal B-3 in the cache, in step S1925, Repeater A-3 deletes the data addressed to Terminal B-3 from the cache.

[0380] <Example of Polling Interval> Next, an example of the polling interval of the repeater will be described. The repeater may be, for example, the repeater described in the examples shown in FIGS. 5 to 20 described above.

[0381] Such a polling interval of the repeater includes, for example, the intervals of Example 1 to Example 8 below.

[0382] (Example 1) When the data transmitted from the terminal (that is, the data acquired by the data generation device such as a sensor) is periodic data (for example, reporting the temperature every minute), since the period is known, the polling interval may be set according to the period.

[0383] (Example 2) In the above Example 1, when there are a plurality of terminals connected to the repeater and the periods of each of the plurality of terminals (that is, the periods in which data is acquired by the data generation device such as a sensor) are different, the polling interval may be set to the shortest period among the sensing intervals (periods) of the plurality of terminals (data generation devices such as sensors). By setting in this way, the delay of the data with the shortest period can be suppressed. Note that the delay of the data with the longest period becomes the maximum delay. For example, as shown in FIG. 21A (in the example shown in FIG. 21A, the interval between the dotted lines represents 1 minute), when the sensing interval of Terminal 1 is 5 minutes and the sensing interval of Terminal 2 is 3 minutes, the polling interval of the repeater can be set to 3 minutes.

[0384] (Example 3) In the above Example 1, when there are a plurality of terminals connected to the repeater and the periods of each of the plurality of terminals are different, the polling interval may be set to the longest period among the sensing intervals (periods) of the plurality of terminals. By setting it in this way, the delay of data of any period will fall within the delay of data of the longest period (maximum delay). For example, as shown in FIG. 21B (in the example shown in FIG. 21B, the interval between dotted lines represents 1 minute), when the sensing interval of Terminal 1 is 5 minutes and the sensing interval of Terminal 2 is 3 minutes, the polling interval of the repeater can be set to 5 minutes.

[0385] (Example 4) In the above Example 1, when there are a plurality of terminals connected to the repeater and the periods of each of the plurality of terminals are different, the polling interval may be set to the least common multiple of the sensing intervals (periods) of the plurality of terminals. By setting it in this way, the maximum delay will be the least common multiple, so the repeater can enter the operation suspension mode for a longer time and its power consumption can be reduced. For example, as shown in FIG. 21C (in the example shown in FIG. 21C, the interval between dotted lines represents 1 minute), when the sensing interval of Terminal 1 is 5 minutes and the sensing interval of Terminal 2 is 3 minutes, the polling interval of the repeater can be set to 15 minutes. Here, as shown in FIG. 21C, five data from Terminal 1 and three data from Terminal 2 will be transmitted to the repeater simultaneously.

[0386] (Example 5) Even if data generation or data acquisition is irregular, when the next data generation or data acquisition can be predicted (for example, when it is roughly known when the bus comes and when the next bus will come), the polling interval may be set based on that prediction. In this Example 5, the above Example 1 or Example 2 is also applicable. In this Example 5, the concept of the least common multiple is not assumed, so Example 4 above is not applicable to this Example 5, but a similar effect can be obtained by determining the time to be 20 minutes later, etc.

[0387] (Example 6) In the above Example 5, when it is thought that although it is not possible to predict the next data generation or data acquisition, it is likely not to come for a while (such as in the case of a truck delivering goods to a convenience store where it is unknown when it will come, but it is assumed that once it comes, it will not come for a while), for example, as shown in FIG. 21D (in the example shown in FIG. 21D, the interval between the dotted lines represents 1 minute), initially, a long polling interval is set, and then, by setting the polling interval to gradually become shorter, the total time in the operation suspension mode can be lengthened.

[0388] (Example 7) In the case of having a conversation using the uplink and downlink, the conversation start time is unknown, but once the conversation starts, it is assumed that the interaction will continue for a while. In such a case, as described above, assume that the repeater has an independent uplink radio and a downlink radio. In this case, if there is uplink data, use it as a trigger to transition the downlink radio to the normal mode, and if there is downlink data, use it as a trigger to transition the uplink radio to the normal mode, and set the polling interval accordingly.

[0389] (Example 8) As described above, in the case of having a conversation using the uplink and downlink, the conversation start time is unknown, but once the conversation starts, it is assumed that the interaction will continue for a while. In such a case, as described above, assume that the repeater has an independent uplink radio and a downlink radio. In this case, while the conversation is continuing, keep both the uplink radio and the downlink radio in the normal mode, and if the conversation stops and a certain amount of time (for example, 5 seconds) has passed, set the polling interval so that both the uplink radio and the downlink radio transition to the operation suspension mode.

[0390] Regarding the intervals in Example 2 to Example 4, the polling interval of the repeater may be appropriately set according to the allowable data delay.

[0391] In the above embodiments, the notation "··· section" used for each component may be replaced with other notations such as "··· circuitry", "··· assembly", "··· device", "··· unit", or "··· module".

[0392] As described above, the embodiments have been explained with reference to the drawings, but the present disclosure is not limited to such examples. It is obvious that those skilled in the art can conceive various modification examples or correction examples within the scope described in the claims. Such modification examples or correction examples are also understood to belong to the technical scope of the present disclosure. Also, within the scope not departing from the gist of the present disclosure, the components in the embodiments may be arbitrarily combined.

[0393] The present disclosure can be realized by software, hardware, or software in cooperation with hardware. Each functional block used in the description of the above embodiments is realized as an LSI which is an integrated circuit, partially or entirely, and each process described in the above embodiments may be controlled, partially or entirely, by one LSI or a combination of LSIs. The LSI may be composed of individual chips, or may be composed of one chip so as to include part or all of the functional blocks. The LSI may have data input and output. Depending on the degree of integration, the LSI may also be referred to as an IC, a system LSI, a super LSI, or an ultra LSI.

[0394] The method of integrating into a circuit is not limited to LSI, and it may be realized by an application specific circuit, a general-purpose processor, or a dedicated processor. Also, after manufacturing the LSI, an FPGA (Field Programmable Gate Array) that can be programmed, or a reconfigurable processor that can reconfigure the connection and setting of circuit cells inside the LSI may be used. The present disclosure may be realized as digital processing or analog processing.

[0395] Furthermore, if a technology for integrating circuits that replaces LSI emerges due to advancements in semiconductor technology or other derived technologies, it is natural that the integration of functional blocks may be performed using such technology. The application of biotechnology or the like is a possible example.

[0396] The present disclosure can be implemented in any type of device, apparatus, system having a communication function (collectively referred to as a communication device). The communication device may include a wireless transceiver (transceiver) and a processing / control circuit. The wireless transceiver may include a receiving unit and a transmitting unit, or may include them as functions. The wireless transceiver (transmitting unit, receiving unit) may include an RF (Radio Frequency) module and one or more antennas. The RF module may include an amplifier, an RF modulator / demodulator, or the like. Non-limiting examples of the communication device include a telephone (mobile phone, smartphone, etc.), a tablet, a personal computer (PC) (laptop, desktop, notebook, etc.), a camera (digital still / video camera, etc.), a digital player (digital audio / video player, etc.), a wearable device (wearable camera, smartwatch, tracking device, etc.), a game console, a digital book reader, a telehealth / telemedicine (remote healthcare / medical prescription) device, a vehicle or mobile transportation means with a communication function (automobile, airplane, ship, etc.), and combinations of the above various devices.

[0397] The communication device is not limited to being portable or movable, and includes any type of device, apparatus, system that is not portable or is fixed, for example, a smart home device (home appliance, lighting device, smart meter or measuring device, control panel, etc.), a vending machine, and any "Thing" that can exist on the IoT (Internet of Things) network.

[0398] Communication includes data communication by a cellular system, a wireless LAN system, a communication satellite system, etc., as well as data communication by combinations thereof.

[0399] In addition, the communication device also includes devices such as a controller and a sensor that are connected or coupled to a communication device that executes the communication function described in the present disclosure. For example, a controller and a sensor that generate control signals and data signals used by the communication device that executes the communication function of the communication device are included.

[0400] In addition, the communication device includes infrastructure facilities, such as base stations, access points, and any other devices, devices, and systems, that communicate with or control the above-described various non-limiting devices.

Industrial Applicability

[0401] One embodiment of the present disclosure is useful for a wireless communication system that can operate with low power consumption.

Explanation of Signs

[0402] 2 Wireless communication system A, A-1 to A-6 Repeaters B, B-1 to B-3, B-X Terminals 30 Communication device 31 Control device 32 Storage device 33 Radio 34 Antenna

Claims

1. A terminal comprising a data generation device, repeatedly acquiring predetermined data from the data generation device, and operating while switching between a first mode and a second mode with lower power consumption than the first mode; A repeater capable of communicating with the terminal, and operating while switching between a third mode and a fourth mode with lower power consumption than the third mode; Comprising: The repeater: Within a specific time, in the third mode, transmit a first polling signal to the terminal; After transmitting the first polling signal and within the specific time, transition from the third mode to the fourth mode; Before the specific time elapses, transition from the fourth mode to the third mode; The terminal: While having the predetermined data, operate in the first mode; After transmitting the predetermined data to the repeater in response to the first polling signal, transition from the first mode to the second mode; Further comprising a communication device which is another repeater or a base station; The communication device transmits a second polling signal to the repeater; The repeater: In response to the second polling signal, transmit the predetermined data to the communication device; After transmitting the predetermined data and within the specific time, transition from the third mode to the fourth mode; A wireless communication system.

2. The terminal transitions from the second mode to the first mode before next acquiring the predetermined data from the data generation device. The wireless communication system according to Claim 1.

3. After transmitting an ACK signal indicating reception of the predetermined data to the terminal and within the specific time, the repeater transitions from the third mode to the fourth mode. The wireless communication system according to Claim 1.

4. There are a plurality of the terminals; The repeater: Within the specific time, in the third mode, transmit a third polling signal to a first terminal and a fourth polling signal to a second terminal; After transmitting the third polling signal and the fourth polling signal and within the specific time, transition from the third mode to the fourth mode; The wireless communication system according to Claim 1.

5. A terminal comprising a data generation device, repeatedly acquiring predetermined data from the data generation device, and operating while switching between a first mode and a second mode with lower power consumption than the first mode; A repeater that can communicate with the terminal and operates while switching between a third mode and a fourth mode with lower power consumption than the third mode, comprising: The repeater is Within a specific time, in the third mode, transmit a polling signal to the terminal, After transmitting the polling signal and within the specific time, transition from the third mode to the fourth mode, Before the specific time elapses, transition from the fourth mode to the third mode, The terminal is While having the predetermined data, operate in the first mode, After transmitting the predetermined data to the repeater in response to the polling signal, transition from the first mode to the second mode, There are multiple repeaters, The first repeater transmits a first polling signal to the terminal, The second repeater transmits a second polling signal to the terminal, The terminal transmits the predetermined data to either the first repeater or the second repeater that transmitted one of the polling signals in response to one of the first polling signal and the second polling signal, The repeater that receives the predetermined data transitions from the third mode to the fourth mode after receiving the predetermined data and within the specific time, A wireless communication system.

6. The terminal determines to respond to one of the first polling signal and the second polling signal based on the network topology of the wireless communication system stored in the terminal. The wireless communication system according to claim 5.

7. The terminal transmits the predetermined data to the repeater with the shortest route to the final destination of the data. The wireless communication system according to claim 6.

8. A wireless communication system, comprising a data generation device, a terminal that repeatedly acquires predetermined data from the data generation device and operates while switching between a first mode and a second mode with lower power consumption than the first mode, A repeater that can communicate with the terminal and operates while switching between a third mode and a fourth mode with lower power consumption than the third mode, comprising: The repeater is Within a specific time, in the third mode, transmit a polling signal to the terminal, After transmitting the polling signal and within the specific time, transition from the third mode to the fourth mode, Before the elapse of the specific time, transition from the fourth mode to the third mode, The terminal While having the predetermined data, operate in the first mode, After transmitting the predetermined data to the repeater in response to the polling signal, transition from the first mode to the second mode, Further include a base station, There are a plurality of the terminals, There are a plurality of the repeaters, The hierarchy of the network constituting the wireless communication system is The base station broadcasts a signal including a hierarchy number representing the depth of the hierarchy, The repeater that receives the signal broadcast by the base station sets its own hierarchy number based on the hierarchy number included in the signal and broadcasts a signal including the hierarchy number, The repeater that receives the signal broadcast by the repeater sets its own hierarchy number based on the hierarchy number included in the signal and broadcasts a signal including the hierarchy number, The terminal that receives the signal broadcast by the base station or the signal broadcast by the repeater sets its own hierarchy number based on the hierarchy number included in the signal and transmits a response to the base station or the repeater that broadcast the signal received by the terminal, Set by a hierarchy automatic setting process including this, Each terminal responds to a polling signal from a repeater or the base station in a higher hierarchy based on the set hierarchy, Wireless communication system.

9. The set hierarchy is reset by the hierarchy automatic setting process in response to a change in the configuration of the network constituting the wireless communication system, The wireless communication system according to claim 8.

10. The repeater or the base station that receives the response transmitted by the first terminal receives a report from the first terminal indicating that relaying to the first terminal is possible, Each repeater and the base station receive a report from another repeater in a lower hierarchy indicating that relaying to a specific terminal including the first terminal via the other repeater in the lower hierarchy is possible, The second terminal transmits data addressed to the first terminal to the repeater in a higher hierarchy in response to a polling signal from the repeater in the higher hierarchy, Each repeater capable of relaying to the first terminal responds to a polling signal from another repeater in the upper layer or the base station and transmits data addressed to the first terminal to another repeater in the upper layer or the base station. The base station responds to a polling signal from a repeater in the lower layer or the first terminal and transmits data addressed to the first terminal to the repeater in the lower layer or the first terminal. Each repeater capable of relaying to the first terminal that has received the data addressed to the first terminal responds to a polling signal from another repeater in the lower layer or the first terminal and transmits the data addressed to the first terminal to another repeater in the lower layer or the first terminal. As a result, the first terminal obtains the data addressed to the first terminal transmitted from the second terminal. The wireless communication system according to claim 8. **Claim 11** A terminal including a data generation device, repeatedly acquiring predetermined data from the data generation device, and operating while switching between a first mode and a second mode with lower power consumption than the first mode. A repeater capable of communicating with the terminal and operating while switching between a third mode and a fourth mode with lower power consumption than the third mode. Comprising: The repeater: Transmits a polling signal to the terminal in the third mode within a specific time. After transmitting the polling signal and within the specific time, transitions from the third mode to the fourth mode. Before the specific time elapses, transitions from the fourth mode to the third mode. The terminal: Operates in the first mode while having the predetermined data. After transmitting the predetermined data to the repeater in response to the polling signal, transitions from the first mode to the second mode. There are a plurality of the terminals. There are a plurality of the repeaters. The second terminal responds to a polling signal from a repeater in the upper layer and transmits data addressed to the first terminal to the repeater in the upper layer. Each repeater that has received the data addressed to the first terminal responds to a polling signal from another repeater in the upper layer and transmits the data addressed to the first terminal to another repeater in the upper layer, and responds to a polling signal from another repeater in the lower layer and transmits the data addressed to the first terminal to another repeater in the lower layer. The repeater in the upper layer of the first terminal responds to a polling signal from the first terminal and transmits the data addressed to the first terminal to the first terminal. As a result, the first terminal obtains the data addressed to the first terminal transmitted from the second terminal. Wireless communication system.

12. A wireless communication method in a wireless communication system including a terminal that includes a data generation device, repeatedly obtains predetermined data from the data generation device, and operates while switching between a first mode and a second mode with lower power consumption than the first mode, and a repeater that can communicate with the terminal and operates while switching between a third mode and a fourth mode with lower power consumption than the third mode, the method comprising: The repeater transmits a first polling signal to the terminal in the third mode within a specific time. After transmitting the first polling signal, the repeater transitions from the third mode to the fourth mode within the specific time. Before the specific time elapses, the repeater transitions from the fourth mode to the third mode. The terminal operates in the first mode while having the predetermined data. After the terminal transmits the predetermined data to the repeater in response to the first polling signal, the terminal transitions from the first mode to the second mode. Including: The wireless communication system further includes a communication device that is another repeater or a base station. The communication device transmits a second polling signal to the repeater. The repeater transmits the predetermined data to the communication device in response to the second polling signal. After transmitting the predetermined data, the repeater transitions from the third mode to the fourth mode within the specific time. Wireless communication method.

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