Wireless communication device and method

Abstract

To provide a wireless communication device and method capable of achieving power saving.SOLUTION: According to an embodiment, a wireless communication device is provided that forms a network with a plurality of other nodes and operates to receive data in a first slot of a plurality of slots in a first period. The wireless communication device includes first determination means, second determination means, and setting means. The first determination means determines whether data has been received in the first slot. The second determination means, when it is determined that data has not been received in the first slot, determines whether data has been received in a second slot that follows the first slot in the first period. When it is determined that data has been received in the second slot, the setting means sets the second slot as a slot for receiving data in a second period following the first period.SELECTED DRAWING: Figure 7

Description

Technical Field

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[0001] Embodiments of the present invention relate to a wireless communication device and method.

Background Art

[0002] In recent years, it has been known to configure a network (hereinafter referred to as a sensor network) by a plurality of wireless communication devices and an aggregation device equipped with sensors.

[0003] In such a sensor network, for example, data measured by sensors mounted on a plurality of wireless communication devices (hereinafter referred to as sensor data) is collected by an aggregation device directly from the wireless communication device or via another wireless communication device. The sensor data collected by the aggregation device can be used, for example, to monitor the state of an object (the object on which the wireless communication device is installed) for which the sensor data was measured.

[0004] However, when a plurality of wireless communication devices are installed in an environment where it is difficult to supply power, since the wireless communication devices need to be driven by power supplied from a battery or the like, power saving of the wireless communication devices is required.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] Therefore, the problem to be solved by the present invention is to provide a wireless communication device and method capable of achieving power saving.

Means for Solving the Problems

[0007] According to one embodiment, a wireless communication device is provided that constitutes a network with a plurality of other nodes and operates to receive data transmitted from other nodes in a first slot of a plurality of slots in a first cycle. The wireless communication device comprises a first determination means, a second determination means, and a setting means. The first determination means determines whether data has been received in the first slot. If the second determination means determines that data has not been received in the first slot, it determines whether data transmitted from other nodes has been received in a second slot that is later than the first slot in the first cycle. If the setting means determines that data has been received in the second slot, it sets the second slot as a slot for receiving data transmitted from other nodes in the second cycle following the first cycle. [Brief explanation of the drawing]

[0008] [Figure 1] A diagram showing an example of the network configuration of a communication system according to the first embodiment. [Figure 2] A schematic diagram showing a communication system in the form of a network topology. [Figure 3] A diagram illustrating an example of an environment in which a communication system is applied. [Figure 4] A diagram illustrating the overview of slot communication performed in a communication system. [Figure 5] A diagram illustrating how the communication range of a wireless communication device changes depending on its location. [Figure 6] A diagram showing an example of the hardware configuration of a wireless communication device. [Figure 7] A block diagram showing an example of the functional configuration of a wireless communication device. [Figure 8] A flowchart illustrating an example of the processing procedure for a wireless communication device. [Figure 9] A diagram illustrating a specific example of the operation of a wireless communication device. [Figure 10] A diagram for explaining a specific operation example of a wireless communication device. [Figure 11] A diagram for explaining a specific operation example of a wireless communication device. [Figure 12] A block diagram showing an example of the functional configuration of a wireless communication device according to the second embodiment. [Figure 13] A flowchart showing an example of the processing procedure of a wireless communication device. [Figure 14] A diagram for explaining the third slot change process. [Figure 15] A diagram showing an example of the position of a wireless communication device. [Figure 16] A diagram showing another example of the position of a wireless communication device. [Figure 17] A block diagram showing an example of the functional configuration of a wireless communication device according to the third embodiment. [Figure 18] A flowchart showing an example of the processing procedure of a wireless communication device. I [Figure 19] A diagram showing that the wireless communication device is in motion.

Embodiments for Carrying Out the Invention

[0009] Hereinafter, each embodiment will be described with reference to the drawings. (First Embodiment) First, the first embodiment will be described. FIG. 1 shows an example of the network configuration of the communication system in this embodiment.

[0010] The communication system 1 shown in FIG. 1 includes an aggregation device 10 having a function of performing wireless communication (hereinafter referred to as a wireless communication function) and a plurality of wireless communication devices 20. Between the aggregation device 10 and the plurality of wireless communication devices 20 in this embodiment, for example, wireless communication based on the time division multiplexing method is performed.

[0011] In the communication system 1 shown in FIG. 1, the aggregation device 10 and the plurality of wireless communication devices 20 form a multi-hop network in which the plurality of wireless communication devices 20 are wirelessly connected to the aggregation device 10 in a tree structure. According to the multi-hop network, by the plurality of wireless communication devices 20 constituting the multi-hop network transferring data in a bucket relay format, long-distance communication to the aggregation device 10 beyond the communication range of each of the plurality of wireless communication devices 20 can be realized.

[0012] The aggregation device 10 and the plurality of wireless communication devices 20 constituting the above-described multi-hop network are referred to as nodes in the multi-hop network.

[0013] FIG. 2 is a schematic diagram showing the communication system 1 shown in FIG. 1 in the form of a network topology. The "root" shown in FIG. 2 represents the aggregation device 10 (root node), and "A" to "P" each represent one of the plurality of wireless communication devices 20.

[0014] Also, the arrows shown in FIG. 2 indicate the data transmission paths. The origin of the arrow represents the node (child node) that is the data transmission source, and the tip of the arrow represents the node (parent node) that is the data transmission destination.

[0015] Specifically, for example, the parent node of the wireless communication device 20 represented by "G" (hereinafter referred to as node G) is node E (the wireless communication device 20 represented by "E") whose hop count from the root node is 1 less than that of node G. On the other hand, the child nodes of node G are node I (the wireless communication device 20 represented by "I") and node L (the wireless communication device 20 represented by "L") whose hop count from the root node is 1 greater than that of node G.

[0016] In FIG. 2, for example, a network topology in which node G is arranged between nodes L and E is shown, but a network topology in which nodes L and E are directly connected (communicate) may also be used.

[0017] Furthermore, while Figure 2 assumes that each wireless communication device 20 transmits data to the aggregation device 10 (root node), it is also possible for the aggregation device 10 to transmit data to each wireless communication device 20.

[0018] In Figures 1 and 2, a communication system 1 is assumed to have, for example, 16 wireless communication devices 20, but in this embodiment, the number of wireless communication devices 20 can be 2 or more.

[0019] Furthermore, the network topology and communication method of the communication system 1 in this embodiment described herein are merely examples, and other network topologies and communication methods may be employed. Specifically, although a tree-type network topology is shown in Figure 2, the communication system 1 may employ network topologies such as star, ring, or mesh. Also, while the communication system 1 is assumed to use communication based on, for example, time-division multiplexing, as described above, communication based on other communication methods may also be used.

[0020] In this embodiment of the communication system 1, the multiple wireless communication devices 20 are equipped with sensors, and these sensors measure sensor data relating to the object on which the sensor (wireless communication device 20) is installed. For example, sensor data measured by sensors mounted on the multiple wireless communication devices 20 are collected by the aggregation device 10, either directly from the wireless communication device 20 or via another wireless communication device 20. The sensor data collected in this way by the aggregation device 10 is used to monitor the state of the object (e.g., a structure or the natural environment) on which the sensor data was measured.

[0021] The sensors mounted on the multiple wireless communication devices 20 include, for example, acceleration sensors, temperature sensors, moisture sensors, water level sensors, and humidity sensors. If the sensors mounted on the multiple wireless communication devices 20 are acceleration sensors, the sensor data (acceleration data) measured by the acceleration sensors can be used to monitor, for example, the shaking of elevators or dams during an earthquake. If the sensors mounted on the multiple wireless communication devices 20 are temperature sensors, the sensor data (temperature data) measured by the temperature sensors can be used to monitor the abnormal operation of equipment that is overheating. Furthermore, if the sensors mounted on the multiple wireless communication devices 20 are moisture sensors, the sensor data (moisture content data) measured by the moisture sensors can be used to monitor the occurrence of landslides (presence or absence of sediment-related disasters) in forests, etc., according to the moisture content of the soil. Also, if the sensors mounted on the multiple wireless communication devices 20 are water level sensors, the sensor data (water level data) measured by the water level sensors can be used to monitor the occurrence of floods (presence or absence of flood damage) according to the water level of rivers, etc. Furthermore, if the sensors mounted on multiple wireless communication devices 20 are humidity sensors, it becomes possible to efficiently cultivate plants by utilizing the sensor data (humidity data) measured by these humidity sensors and combining it with temperature data, etc.

[0022] Incidentally, as mentioned above, when sensor data is used to monitor the condition of structures or the natural environment, the wireless communication device 20 equipped with the sensor that measures the sensor data may be installed in an environment where it is difficult to supply power from, for example, a commercial power source. In this case, the wireless communication device 20 needs to be driven by power supplied from, for example, a battery, and a mechanism for driving the wireless communication device 20 with low power consumption is useful.

[0023] Therefore, the wireless communication device 20 can achieve power saving by performing communication using time-division slots (hereinafter referred to as slot communication), sending and receiving data only when necessary, and sleeping at other times.

[0024] In this embodiment, at least one of the multiple wireless communication devices 20 may be a wireless communication device that operates solely as a relay node, for example, to relay sensor data measured by a sensor mounted on another wireless communication device 20 from that other wireless communication device 20 to another wireless communication device 20 or aggregation device 10.

[0025] Hereinafter, with reference to Figure 3, an example of an environment to which the communication system 1 in this embodiment is applied will be described.

[0026] Figure 3 shows an example where the communication system 1 in this embodiment is applied to an elevator system. As shown in Figure 3, an elevator 101 (cab) connected to one end of a main rope and a counterweight 102 connected to the other end of the main rope are arranged in the hoistway 100. The elevator 101 can be raised and lowered by driving a hoisting machine (not shown) around which the main rope is wound.

[0027] In the example shown in Figure 3, it is assumed that the aggregation device 10 and two wireless communication devices 20-1 and 20-2 are installed within the elevator shaft 100 described above. Specifically, the aggregation device 10 is installed near the upper floors of the building where the elevator 101 is installed, wireless communication device 20-1 is installed near the middle floors of the building, and wireless communication device 20-2 is installed near the lower floors of the building.

[0028] Furthermore, a wireless communication device 20-3 is installed on the elevator 101, which moves within the hoistway 100 (operates up and down within the hoistway 100). In this case, the wireless communication device 20-3 is equipped with an acceleration sensor for measuring acceleration data to monitor the shaking of the elevator 101. In Figure 3, the wireless communication device 20-3 is installed on the elevator 101, but as mentioned above, from the perspective of monitoring the shaking of the elevator 101, the wireless communication device (acceleration sensor) may also be installed on the counterweight 102, which operates up and down in conjunction with the elevator 101.

[0029] In the example shown in Figure 3, wireless communication devices 20-1 and 20-2 are wireless communication devices that operate solely as relay nodes for relaying, for example, sensor data. In this case, wireless communication devices 20-1 and 20-2 do not need to be equipped with sensors.

[0030] In Figure 3, wireless communication devices 20-1 and 20-2 are shown as wireless communication devices 20 that operate as relay nodes, but the number of relay nodes may be changed depending on the size of the building, etc., in which the elevator 101 is installed. Furthermore, in the example shown in Figure 3, for example, wired communication may be performed between the aggregation device 10 and wireless communication device 20-1, and wired communication may be performed between wireless communication device 20-1 and wireless communication device 20-2.

[0031] Referring to Figure 4, an overview of the slot communication performed in the communication system 1 applied to the elevator system as shown in Figure 3 will be described. Note that, as described above, the wireless communication device 20-3 is powered by electricity supplied from a battery or rechargeable battery (i.e., power saving is required), but the aggregation device 10 and wireless communication devices 20-1 and 20-2 are powered by electricity supplied from, for example, a commercial power supply, and are not subject to power saving in this embodiment.

[0032] As shown in Figure 4, in slot communication, multiple slots SL1 to SL10 are provided in a predetermined period (hereinafter referred to as the communication period) that repeats every second, for example, and the aggregation device 10 and wireless communication devices 20-1 to 20-3 operate to send and receive data (perform transmission and reception processing) in predetermined slots. Each of the multiple slots SL1 to SL10 is assigned to one of several time periods into which the communication period is divided.

[0033] Specifically, the aggregation device 10 operates to transmit data in slot SL6 (the time period assigned to it) in the communication cycle, and to receive data in the other slots SL1 to SL5 and SL7 to SL10 (the time periods assigned to them). In the following description, the slots to which the aggregation device 10 transmits data (slots to which time periods are assigned that allow the transmission of such data) will be referred to as the aggregation device 10's transmission slots, and the slots to which the aggregation device 10 receives data (slots to which time periods are assigned that allow the reception of such data) will be referred to as the aggregation device 10's reception slots.

[0034] Furthermore, the wireless communication device 20-1 operates to transmit data in slot SL7 during the communication cycle and to receive data in the other slots SL1 to SL6 and SL8 to SL10. In the following description, the slot from which the wireless communication device 20-1 transmits data will be referred to as the transmitting slot of the wireless communication device 20-1, and the slot from which the wireless communication device 20-1 receives data will be referred to as the receiving slot of the wireless communication device 20-1.

[0035] Furthermore, the wireless communication device 20-2 operates to transmit data in slot SL8 during the communication cycle and to receive data in the other slots SL1 to SL7, SL9, and SL10. In the following description, the slot from which the wireless communication device 20-2 transmits data will be referred to as the transmitting slot of the wireless communication device 20-2, and the slot from which the wireless communication device 20-2 receives data will be referred to as the receiving slot of the wireless communication device 20-2.

[0036] Meanwhile, the wireless communication device 20-3 operates by transmitting data in slot SL2 during the communication cycle, receiving data in slot SL6, and sleeping in the other slots SL1, SL3-SL5, and SL7-SL10. In the following description, the slot from which the wireless communication device 20-3 transmits data will be referred to as the transmitting slot of the wireless communication device 20-3, and the slot from which the wireless communication device 20-3 receives data will be referred to as the receiving slot of the wireless communication device 20-3. Multiple wireless communication devices that operate with low power consumption similar to the wireless communication device 20-3 may exist. Furthermore, any slot between SL1 and SL5 may be used as the transmitting slot. However, each wireless communication device shall use its own unique slot as the transmitting slot.

[0037] According to the operation of the wireless communication device 20-3 described above, the wireless communication device 20-3 performs reception processing only at limited timings compared to the aggregation device 10 and wireless communication devices 20-1 and 20-2 (i.e., minimizes the reception range), thus enabling power saving.

[0038] In the example shown in Figure 4, the transmission slot of the wireless communication device 20-3 is slot SL2, so the wireless communication device 20-3 transmits data in slot SL2. The data transmitted from the wireless communication device 20-3 in slot SL2 is, for example, sensor data measured by sensors mounted on the wireless communication device 20-3 (for example, acceleration data measured by an acceleration sensor).

[0039] For example, if the aggregation device 10, whose slot SL2 is a receiving slot, is within the communication range of the wireless communication device 20-3, then, as described above, the data transmitted from the wireless communication device 20-3 in slot SL2 will be received by the aggregation device 10. Furthermore, since slot SL2 is also a receiving slot for wireless communication devices 20-1 and 20-2, if these wireless communication devices 20-1 and 20-2 are within the communication range of the wireless communication device 20-3, they can similarly receive data transmitted from the wireless communication device 20-3.

[0040] As described above, when the aggregation device 10 receives data transmitted from the wireless communication device 20-3 in slot SL2, the aggregation device 10 transmits data corresponding to the received data in slot SL6, which is the aggregation device 10's transmission slot. The data transmitted from the aggregation device 10 in slot SL6 is, for example, data including delivery confirmation information for sensor data transmitted from the wireless communication device 20-3. Since the receiving slot of the wireless communication device 20-3 is slot SL6, if the aggregation device 10 is within the communication range of the wireless communication device 20-3, the wireless communication device 20-3 can receive the data transmitted from the aggregation device 10 in slot SL6 and continue to operate appropriately.

[0041] Furthermore, the transmission slots and reception slots of the aggregation device 10 and wireless communication devices 20-1 to 20-3 described above (i.e., the timing at which the transmission process is executed and the timing at which the reception process is executed) are predetermined based on, for example, the arrangement of the aggregation device 10 and wireless communication devices 20-1 to 20-3.

[0042] Furthermore, the communication cycle may consist of multiple sub-cycles. In this case, for example, if the time periods assigned to slots SL1 to SL5 correspond to the first sub-cycle, and the time periods assigned to slots SL6 to SL10 correspond to the second sub-cycle, then it becomes possible to, for example, determine the transmission slot for wireless communication device 20-3 from slots SL1 to SL5, and determine the transmission slots for aggregation device 10 and relay nodes (wireless communication devices 20-1 and 20-2) from slots SL6 to SL10 (i.e., manage transmission slots for each sub-cycle).

[0043] Incidentally, assuming that the wireless communication device 20-3 is installed in the elevator 101 as shown in Figure 3 above, as shown in Figure 5, the position of the wireless communication device 20-3 (i.e., the distance from, for example, the aggregation device 10, etc.) changes as the elevator 101 moves up and down within the hoistway 100. Hereinafter, for example, if the wireless communication device 20-3 is in the position shown in Figure 5, the aggregation device 10 and wireless communication device 20-1 are not within the communication range of the wireless communication device 20-3, while wireless communication device 20-2 is within the communication range of the wireless communication device 20-3.

[0044] As described above, if the elevator 101 moves and, for example, the aggregation device 10 is outside the communication range of the wireless communication device 20-3, the data transmitted by the wireless communication device 20-3 in slot SL2 will not be directly received by the aggregation device 10. However, it will be received by wireless communication device 20-2, for example, if slot SL2 is a receiving slot and is within the communication range of wireless communication device 20-3, and will also be transmitted from wireless communication device 20-2 in slot SL8, which is the transmitting slot of wireless communication device 20-2. The data transmitted from wireless communication device 20-2 in this way will be received by wireless communication device 20-1, if slot SL8 is a receiving slot and is within the communication range of wireless communication device 20-2, and will also be transmitted from wireless communication device 20-1 in slot SL7 in the next communication cycle, which is the transmitting slot of wireless communication device 20-1. The data transmitted from wireless communication device 20-1 in this way will be received by the aggregation device 10, where slot SL7 is a receiving slot.

[0045] Thus, even when the aggregation device 10 is outside the communication range of the wireless communication device 20-3 due to the movement of the elevator 101, the data transmitted from the wireless communication device 20-3 is relayed by wireless communication devices 20-1 and 20-2 and collected by the aggregation device 10.

[0046] On the other hand, as described above, when the aggregation device 10 receives data from the wireless communication device 20-3, the aggregation device 10 transmits data corresponding to that data in slot SL6, which is the transmission slot of the aggregation device 10. However, as described above, if the elevator 101 moves and, for example, the aggregation device 10 is outside the communication range of the wireless communication device 20-3, the wireless communication device 20-3 cannot receive the data transmitted from the aggregation device 10 in slot SL6.

[0047] Although the data transmitted from the aggregation device 10 is relayed by wireless communication devices 20-1 and 20-2, even if the data is transmitted from wireless communication device 20-2 in slot SL8, which is the transmission slot of wireless communication device 20-2, wireless communication device 20-3 cannot receive the data because slot SL8 is not the receiving slot of wireless communication device 20-3.

[0048] If the data transmitted from the aggregation device 10 (for example, delivery confirmation information) is not received by the wireless communication device 20-3, the wireless communication device 20-3 may not be able to continue operating properly.

[0049] As described above, if the wireless communication device 20-3 does not receive the data transmitted from the aggregation device 10, it will not be able to receive the data from the aggregation device 10 unless it searches for other nodes within the communication range of the wireless communication device 20-3 (in this case, wireless communication device 20-2) and changes the receiving slot (setting) of the wireless communication device 20-3. However, if the search is performed to execute the receiving process in all slots, for example (i.e., the search takes a long time), it will hinder power saving in the wireless communication device 20-3.

[0050] Furthermore, it is conceivable to receive data in a predetermined number of slots (each transmission slot of multiple candidate data sources) so as to avoid the need for searching. However, if reception processing is always performed in multiple slots, it becomes difficult to achieve power saving in the wireless communication device 20-3.

[0051] Therefore, in this embodiment, we will describe a configuration that efficiently changes the settings of the receiving slot (i.e., changes the reception timing) to achieve power saving when the wireless communication device 20 installed on a mobile object (for example, an elevator 101) does not receive data transmitted from another node.

[0052] The wireless communication device 20 described below is intended to be, for example, the wireless communication device 20-3 described in Figure 3, but any one of the multiple wireless communication devices 20 shown in Figure 1 will suffice.

[0053] Figure 6 shows an example of the hardware configuration of the wireless communication device 20. As shown in Figure 6, the wireless communication device 20 includes a microcontroller 20a, a wireless communication module 20b, a sensor 20c, and the like.

[0054] The microcontroller 20a consists of a processor (CPU) and memory, etc., which control the operation of each component in the wireless communication device 20. The wireless communication module 20b is configured to send and receive data and includes, for example, an antenna. The sensor 20c is configured to measure sensor data as described above.

[0055] Figure 7 is a block diagram showing an example of the functional configuration of the wireless communication device 20. As shown in Figure 7, the wireless communication device 20 includes a transmission / reception processing unit 21, a determination unit 22, and a slot setting unit 23.

[0056] In this embodiment, some or all of the parts 21 to 23 shown in Figure 7 may be implemented by having the microcontroller 20a (processor) shown in Figure 6 execute a predetermined program (i.e., software), by hardware such as an IC (Integrated Circuit), or by a configuration combining software and hardware.

[0057] The transmit / receive processing unit 21 executes a process to transmit data in a transmission slot (data transmission process) based on, for example, a transmission slot of the wireless communication device 20 that has been set in advance. If the data transmitted in the transmission process executed by the transmit / receive processing unit 21 is the sensor data described above, the sensor data can be obtained from the sensor 20c shown in Figure 6. The data transmitted in the transmission process executed by the transmit / receive processing unit 21 may be data other than sensor data.

[0058] Furthermore, the transmission / reception processing unit 21 executes a process to receive data in a pre-configured receiving slot of the wireless communication device 20 (data reception processing). The data received in the reception processing executed by the transmission / reception processing unit 21 is assumed to include the delivery confirmation information described above, but it may also be control data transmitted from the aggregation device 10 (data for controlling the wireless communication device 20), for example.

[0059] The determination unit 22 determines whether or not data has been received in the receiving slot of the wireless communication device 20.

[0060] If the determination unit 22 determines that no data has been received, the slot setting unit 23 changes the setting of the receiving slot of the wireless communication device 20 (i.e., controls the receiving slot).

[0061] The following describes an example of the processing procedure for the wireless communication device 20, referring to the flowchart in Figure 8. In the following description, the wireless communication device 20 that performs the processing shown in Figure 8 will be referred to as the target wireless communication device 20. In the following description, "other nodes" includes other wireless communication devices 20 other than the aggregation device 10 and the target wireless communication device 20.

[0062] First, the transmit / receive processing unit 21 included in the target wireless communication device 20 transmits data (e.g., sensor data) to the aggregation device 10 as the destination in the transmission slot of the target wireless communication device 20 during a predetermined communication cycle. The data transmitted in step S1 is assumed to have identification information indicating the target wireless communication device 20 as source information indicating the source, and identification information for identifying the aggregation device 10 as destination information indicating the destination.

[0063] If the aggregation device 10 is within the communication range of the target wireless communication device 20, the data transmitted in step S1 is received directly by the aggregation device 10. On the other hand, if the aggregation device 10 is not within the communication range of the target wireless communication device 20, the data transmitted in step S1 is received by the aggregation device 10 via another wireless communication device 20 other than the target wireless communication device 20.

[0064] When data from the target wireless communication device 20 is received by the aggregation device 10, the aggregation device 10 transmits data corresponding to that data (for example, data including delivery confirmation information for sensor data) in the transmission slot of the aggregation device 10. The data transmitted from the aggregation device 10 is provided with source information indicating the source, which is identification information to identify the aggregation device 10, and destination information indicating the destination, which is identification information to identify the target wireless communication device 20. In addition, the data transmitted from the aggregation device 10 may be further provided with slot information indicating the transmission slot to which the data is transmitted.

[0065] Here, the transmit / receive processing unit 21 included in the target wireless communication device 20 performs a reception process in the receiving slot of the target wireless communication device 20 (step S2). In this case, for example, if the receiving slot of the target wireless communication device 20 is the same as the transmitting slot of the aggregation device 10, and the aggregation device 10 is within the communication range of the target wireless communication device 20, the data transmitted from the aggregation device 10 can be received by executing the process in step S2. On the other hand, even if the receiving slot of the target wireless communication device 20 is the same as the transmitting slot of the aggregation device 10, if the aggregation device 10 is not within the communication range of the target wireless communication device 20, the data transmitted from the aggregation device 10 cannot be received even if the process in step S2 is executed. Here, we have described data transmitted from the aggregation device 10, but the same applies to data transmitted from other wireless communication devices 20 that relay data from the aggregation device 10, for example.

[0066] Once the process in step S2 is executed, the determination unit 22 determines whether or not data has been received (step S3).

[0067] If it is determined that no data has been received (NO in step S3), the transmission / reception processing unit 21 extends the range of the receiving slot of the target wireless communication device 20 described above and continues to execute the reception process (step S4).

[0068] In this case, the target wireless communication device 20 (transmit / receive processing unit 21) operates to perform reception processing in slots after the reception slot of the target wireless communication device 20 in the communication cycle in which reception processing was performed in step S2 (hereinafter referred to as the target communication cycle).

[0069] In addition, for example, the slot setting unit 23 included in the target wireless communication device 20 manages, for example, the transmission slots (slot information indicating them) of other nodes (aggregation device 10 and other wireless communication devices 20). In this case, the slot in which the reception process is continuously executed in step S4 (the slot after the reception slot of the target wireless communication device 20) may be the slot immediately following the reception slot in the target communication cycle, or it may be the transmission slot of the other node that is closest to the reception slot.

[0070] Next, the determination unit 22 determines whether or not data was received in the reception process performed in step S4 (step S5).

[0071] If it is determined that data has been received (YES in step S5), the slot setting unit 23 executes the first slot change process (step S6).

[0072] In this case, determining that data has been received in step S5 means that another node whose transmission slot is the same slot in step S4 where the reception process was performed (i.e., the slot in which the data was received) is within the communication range of the target wireless communication device 20.

[0073] Therefore, in the first slot change process, the slot in which the reception process was performed in step S4 is newly set as the receiving slot of the target wireless communication device 20 (that is, the receiving slot of the target wireless communication device 20 is changed to the slot in which data was received).

[0074] On the other hand, if it is determined that no data has been received (NO in step S5), the slot setting unit 23 determines whether the slot in which the reception process was performed in step S4 is the last slot in the target communication cycle (step S7). The last slot in the target communication cycle may be the last slot among multiple slots in that target communication cycle (the slot to which the last time period constituting the target communication cycle is assigned), or it may be the last slot among the transmission slots of other nodes.

[0075] If it is determined that the slot in which the receiving process was performed is not the last slot (NO in step S7), the process returns to step S4 and is repeated. In this case, the receiving process continues in the slot after the slot in which the last receiving process was performed.

[0076] On the other hand, if it is determined that the slot on which the reception process was performed is the last slot (YES in step S7), the slot setting unit 23 executes the second slot change process ((step S8).

[0077] In step S7, if it is determined that the slot in which the reception process was performed is the last slot (i.e., no data is received until the last slot), then it is highly likely that other nodes whose transmission slot is earlier than the reception slot of the target wireless communication device 20 are within the communication range of the target wireless communication device 20.

[0078] Therefore, in the second slot change process, the slot M positions prior to the current receiving slot of the target wireless communication device 20 is newly set as the receiving slot of the target wireless communication device 20 (that is, the receiving slot of the target wireless communication device 20 is changed to the slot M positions prior to that receiving slot).

[0079] The slot M positions prior to the receiving slot of the target wireless communication device 20 may be one of the multiple slots in the communication cycle that precedes the receiving slot, or it may be one of the transmitting slots of another node that precedes the receiving slot.

[0080] When the process in step S6 (first slot change process) or step S8 (second slot change process) described above is executed, slot information indicating the newly set receiving slot is output from the slot setting unit 23 to the transmit / receive processing unit 21, and the transmit / receive processing unit 21 executes the receiving process in the next communication cycle of the target communication cycle based on the said slot information (and the receiving slot indicated thereby).

[0081] In steps S3 and S5 described above, if data is received to which identification information for identifying the target wireless communication device 20 is attached as destination information, it is determined that the data has been received. In other words, even if data is received, if the data does not have identification information for identifying the target wireless communication device 20 attached to it (i.e., the data is not data that is intended for the target wireless communication device 20), it is determined in steps S3 and S5 that the data has not been received. If data is received that does not have identification information for identifying the target wireless communication device 20 attached to it (i.e., data that has identification information for identifying another wireless communication device 20 attached to it), the transmission / reception processing unit 21 transmits (transfers) the data in the transmission slot of the target wireless communication device 20.

[0082] Furthermore, assuming that the receiving slot of the target wireless communication device 20 is expected to receive data including delivery confirmation information for sensor data from the target wireless communication device 20, if data that does not include such delivery confirmation information is received, it may be determined in steps S3 and S5 that no data has been received.

[0083] Furthermore, if it is determined in step S3 that data has been received (YES in step S3), it is presumed that another node whose receiving slot is the transmitting slot of the target wireless communication device 20 is within the communication range of the target wireless communication device 20 (i.e., the receiving slot is set to receive data transmitted from another node within the communication range of the target wireless communication device 20). In this case, the process shown in Figure 8 is terminated without changing the receiving slot (setting) of the target wireless communication device 20.

[0084] Hereinafter, with reference to Figures 9 to 11, a specific example of the operation of the wireless communication device 20 according to this embodiment will be described.

[0085] First, let's assume that the aggregation device 10 and wireless communication devices 20-1 to 20-3 shown in Figure 3 are performing transmission and reception processing based on the transmission and reception slots shown on the left side of Figure 9. Note that the left side of Figure 9 is the same as Figure 4 except that the communication cycle shown in Figure 4 is labeled as the first communication cycle, so a detailed explanation of it will be omitted here.

[0086] Here, for example, in the first communication cycle, data (e.g., sensor data) is transmitted from the wireless communication device 20-3 (target wireless communication device) in slot SL2, and data corresponding to that data (data including delivery confirmation information) is transmitted from the aggregation device 10 in slot SL6.

[0087] In this case, if the aggregation device 10 is within the communication range of the wireless communication device 20-3 (i.e., if the elevator 101 is near an upper floor), the wireless communication device 20-3 can receive the data transmitted from the aggregation device 10 in slot SL6, which is the receiving slot of the wireless communication device 20-3.

[0088] On the other hand, if the elevator 101 on which the wireless communication device 20-3 is installed moves and the aggregation device 10 is no longer within the communication range of the wireless communication device 20-3, the wireless communication device 20-3 will not be able to receive data transmitted from the aggregation device 10 in slot SL6. In this case, when the wireless communication device 20-3 does not receive data, as shown in the center of Figure 9, the wireless communication device 20-3 extends the receiving slot to slot SL7 and continues the receiving process.

[0089] As mentioned above, wireless communication device 20-3 cannot receive data transmitted from aggregation device 10 in slot SL6, but wireless communication device 20-1 receives data transmitted from aggregation device 10 in slot SL6 and operates to transmit (transfer) that data in slot SL7.

[0090] According to this, if wireless communication device 20-1 is within the communication range of wireless communication device 20-3 (i.e., elevator 101 is near a middle floor), wireless communication device 20-3 can receive data transmitted from wireless communication device 20-1 in slot SL7. When wireless communication device 20-3 receives data in slot SL7 in this way, slot SL7 is newly set as a receiving slot for wireless communication device 20-3.

[0091] In this case, as shown on the right side of Figure 9, in the second communication cycle following the first communication cycle, the wireless communication device 20-3 operates to perform reception processing in slot SL7, and is therefore able to receive data transmitted from the wireless communication device 20-1.

[0092] In Figure 9, the case where elevator 101 is near a middle floor is explained. However, if elevator 101 is near a lower floor and wireless communication device 20-1 is not within the communication range of wireless communication device 20-3, then wireless communication device 20-3 cannot receive data transmitted from wireless communication device 20-1 in slot SL7. In this case, when wireless communication device 20-3 does not receive data, as shown on the lower left of Figure 10, wireless communication device 20-3 extends its receiving slot to slot SL8 and continues the receiving process. The upper left and right sides of Figure 10 are the same as the left and center of Figure 9, indicating that the receiving slot of wireless communication device 20-3 has been extended to slot SL7.

[0093] As described above, wireless communication device 20-3 cannot receive data transmitted from wireless communication device 20-1 in slot SL7, but wireless communication device 20-2 receives data transmitted from wireless communication device 20-1 in slot SL7 and operates to transmit (transfer) that data in slot SL8.

[0094] According to this, if the wireless communication device 20-2 is within the communication range of the wireless communication device 20-3 (i.e., the elevator 101 is near a lower floor), the wireless communication device 20-3 can receive data transmitted from the wireless communication device 20-2 in slot SL8. When the wireless communication device 20-3 receives data in slot SL8 in this way, slot SL8 is newly set as the receiving slot for the wireless communication device 20-3.

[0095] In this case, as shown on the lower right of Figure 10, in the second communication cycle following the first communication cycle, the wireless communication device 20-3 operates to perform reception processing in slot SL8, and is therefore able to receive data transmitted from the wireless communication device 20-2.

[0096] Here, as shown on the left side of Figure 11, after slot SL8 is set as the receiving slot of wireless communication device 20-3, data is transmitted from wireless communication device 20-3 in slot SL2 during the second communication cycle, and data corresponding to that data is transmitted from aggregation device 10 in slot SL6. The data transmitted from aggregation device 10 in slot SL6 is received by wireless communication device 20-1 and transmitted (transferred) from wireless communication device 20-1 in slot SL7. Similarly, the data transmitted from wireless communication device 20-1 in slot SL7 is received by wireless communication device 20-2 and transmitted (transferred) from wireless communication device 20-2 in slot SL8.

[0097] In the example shown on the left side of Figure 11, the wireless communication device 20-3 performs reception processing in slot SL8. However, if, for example, the wireless communication device 20-3 moves and the wireless communication device 20-2 is no longer within the communication range of the wireless communication device 20-3, the wireless communication device 20-3 cannot receive the data transmitted from the wireless communication device 20-2 in slot SL8.

[0098] Assuming that the aforementioned slot SL8 is the last transmission slot of another node in the second communication cycle, the M slots prior to slot SL8 (the receiving slot of the wireless communication device 20-3) is newly set as the receiving slot of the wireless communication device 20-3. Specifically, for example, the slot SL7 immediately preceding slot SL8 can be set as the receiving slot of the wireless communication device 20-3.

[0099] In this case, as shown on the right side of Figure 11, in the third communication cycle following the second communication cycle, the wireless communication device 20-3 operates to perform reception processing in slot SL7, and is therefore able to receive data transmitted from the wireless communication device 20-1.

[0100] In Figure 11, it is explained that slot SL7, which is one slot before slot SL8, which is the receiving slot of the wireless communication device 20-3, is set as the receiving slot of the wireless communication device 20-3. However, for example, slot SL6, which is two slots before slot SL8 (the first transmission slot of the aggregation device 10, which is the transmission slot of the aggregation device 10, which is the transmission slot of another node), may be set as the receiving slot of the wireless communication device 20-3, or any other slot before slot SL8 may be set as the receiving slot of the wireless communication device 20-3.

[0101] As described above, in this embodiment, if it is determined that no data has been received in the first slot during the first communication cycle, it is determined whether data transmitted from another node (second data) has been received in the second slot, which is later than the first slot. If it is determined that data has been received in the second slot, the second slot is set as the receiving slot (the slot for receiving data transmitted from another node) of the wireless communication device 20 for the second communication cycle following the first communication cycle.

[0102] In this embodiment, it is assumed that the wireless communication device 20 is installed on a moving object (e.g., an elevator 101) that moves so that its distance from other nodes changes. Furthermore, it is assumed that the wireless communication device 20 is installed in an environment where it is difficult to obtain power from, for example, a commercial power source, and is powered by a battery or other power source.

[0103] In this embodiment, with the above configuration, even in an environment where the other nodes with which the wireless communication device 20 can communicate (i.e., other nodes within the communication range of the wireless communication device 20) change frequently due to the movement of the wireless communication device 20, the power saving of the wireless communication device 20 can be improved by appropriately changing the receiving slot of the wireless communication device 20. In other words, according to this embodiment, even if the wireless communication device 20 moves, the receiving slot can be changed to receive data transmitted in the transmitting slot of another node with which communication is possible, thereby minimizing the reception range and achieving power saving.

[0104] Furthermore, in this embodiment, if it is determined that no data is received in the second slot (the last slot among multiple slots in the communication cycle), the third slot preceding the first slot (the M slots preceding the receiving slot of the wireless communication device 20) is newly set as the receiving slot of the wireless communication device 20. In this embodiment, with this configuration, if no data is received in the last slot, the receiving slot of the wireless communication device 20 can be reset to a slot that can receive data in the next communication cycle, thereby improving the efficiency of the reception processing in the wireless communication device 20.

[0105] Regarding the M slots prior to the one described above, if, for example, the amount of movement of the wireless communication device 20 is expected to be small, setting the slot immediately preceding the receiving slot of the wireless communication device 20 as the receiving slot may allow for searching for other nodes that can communicate with a smaller number of reception processes. On the other hand, if, for example, the first slot among multiple slots is set as the receiving slot of the wireless communication device 20, it is considered that it is possible to more reliably search for other nodes that can communicate in the next communication cycle and reset the transmitting slot of that other node as the receiving slot of the wireless communication device 20. In other words, the M (number) in "M slots prior to the one described above" may be determined based on the type or characteristics of the moving object (for example, the object on which sensor data is measured) on which the wireless communication device 20 is installed.

[0106] Furthermore, in this embodiment, it has been described that data including delivery confirmation information for sensor data transmitted from the wireless communication device 20 is transmitted from the aggregation device 10 and received by the wireless communication device 20. However, this data may be other data (for example, control data instructed by the aggregation device 10 to the wireless communication device 20).

[0107] Furthermore, in this embodiment, it is determined whether or not data has been received, but this determination process may be performed based on whether or not the data contains delivery confirmation information. Specifically, for example, even if data has been received, if the data does not contain delivery confirmation information, it may be determined that the data has not been received.

[0108] Furthermore, the determination process may be performed based on the signal strength of the received data. Specifically, for example, even if data has been received, if the signal strength of the received data is less than a predetermined value, it may be determined that the data has not been received.

[0109] Furthermore, the data may include, for example, destination information (identification information of the destination) indicating the recipient of the data, and slot information (slot information) indicating the transmission slot to which the data was sent. In the determination process described above, this destination information and slot information may be used.

[0110] Furthermore, the determination process may be performed based, for example, on the number of times data is received in the receiving slot in each of multiple communication cycles (first cycle). Specifically, it may be determined that data has been received if data is received in the receiving slot across multiple communication cycles (i.e., data reception is successful multiple times), and it may be determined that data has not been received if the number of successful data receptions is less than a predetermined number.

[0111] In this embodiment, the elevator 101 was mainly described as an example of a mobile body on which the wireless communication device 20 is installed. However, the wireless communication device 20 may also be installed on other mobile bodies, such as trains.

[0112] (Second Embodiment) Next, a second embodiment will be described. In this embodiment, detailed explanations of parts that are the same as those described in the first embodiment will be omitted.

[0113] This embodiment differs from the first embodiment described above in that it utilizes the position of the wireless communication device (or the mobile device on which it is installed) when changing the settings of the receiving slot of the wireless communication device.

[0114] The configuration of the wireless communication device according to this embodiment will be described below, but since the hardware configuration of the wireless communication device 20 is the same as that of the first embodiment described above, a detailed explanation will be omitted here.

[0115] Figure 12 is a block diagram showing an example of the functional configuration of a wireless communication device according to this embodiment. In Figure 12, the same reference numerals are used for parts identical to those in Figure 7, and their detailed descriptions are omitted.

[0116] As shown in Figure 12, the wireless communication device 20 includes a location information acquisition unit 24. The location information acquisition unit 24 may be implemented by software, by hardware, or by a combination of software and hardware.

[0117] The location information acquisition unit 24 acquires location information indicating the location of the wireless communication device 20. This location information can be acquired, for example, using the GPS (Global Positioning System) function of the wireless communication device 20 (or the mobile device on which the wireless communication device is installed), or, in the case of an elevator, the location of the elevator car.

[0118] The location information acquired by the location information acquisition unit 24 is output to the slot setting unit 23, which uses it to change the settings of the receiving slot of the wireless communication device 20.

[0119] The following describes an example of the processing procedure of the wireless communication device 20, referring to the flowchart in Figure 13. In the following description, the wireless communication device 20 that performs the processing shown in Figure 13 will be referred to as the target wireless communication device 20.

[0120] First, the processes S11 to S17, which correspond to the processes S1 to S7 shown in Figure 8 above, are executed.

[0121] If it is determined that the slot on which the reception process was performed is the last slot (YES in step S17), the slot setting unit 23 performs the third slot change process (step S18).

[0122] In the first embodiment described above, a second slot change process was performed in which a slot M positions prior to the receiving slot of the target wireless communication device 20 is newly set as the receiving slot of the target wireless communication device 20 (that is, the receiving slot of the target wireless communication device 20 is changed to a slot M positions prior to the said receiving slot). However, in the third slot change process in this embodiment, the receiving slot of the target wireless communication device 20 is newly set using the position information indicating the position of the target wireless communication device 20 as described above.

[0123] The third slot change process will now be explained. First, let's assume that the aggregation device 10 and wireless communication devices 20-1 to 20-3 shown in Figure 3 operate as shown on the left side of Figure 14. Specifically, let's assume that the third slot change process is executed when, for example, no data is received in slot SL8 (the last slot), which is the receiving slot of wireless communication device 20-3 in the second communication cycle as described in the first embodiment above.

[0124] In this case, the location information acquisition unit 24 included in the wireless communication device 20-3 acquires location information (hereinafter referred to as the first location information) indicating the location of the wireless communication device 20-3. Here, as shown in Figure 15, the location of the wireless communication device 20-3 indicated by the first location information is assumed to be near the upper floors of the building where the elevator 101 is installed.

[0125] Here, it is assumed that the wireless communication device 20-3 has internally stored location information (hereinafter referred to as "second location information") indicating the locations of other nodes (aggregation device 10, wireless communication devices 20-1 and 20-2).

[0126] In this case, the slot setting unit 23 identifies the aggregation device 10 as another node close to the location of the wireless communication device 20-3 based on the first and second position information. The slot setting unit 23 then newly sets slot SL6, which is the transmission slot of the aggregation device 10 identified in this way, as the reception slot of the wireless communication device 20-3.

[0127] In this case, as shown on the right side of Figure 14, in the third communication cycle following the second communication cycle, the wireless communication device 20-3 operates to perform reception processing in slot SL6, and is therefore able to receive data transmitted from the aggregation device 10.

[0128] Here, the explanation assumes that the location of the wireless communication device 20-3, indicated by the first location information, is near the upper floors of the building. However, as shown in Figure 16, if the location of the wireless communication device 20-3 is near the middle floors of the building, wireless communication device 20-1 is identified as another node close to that location. In this case, the slot setting unit 23 can receive data transmitted from wireless communication device 20-1 in the third communication cycle by newly setting slot SL7, which is the transmission slot of the wireless communication device 20-1 identified in this way, as the reception slot of the wireless communication device 20-3.

[0129] As described above, in this embodiment, if it is determined that data has not been received in the last slot (second slot) of the communication cycle, for example, the position of the wireless communication device 20 is acquired, and the transmission slot of another node close to the acquired position (i.e., the third slot to which the other node transmits data) is set as the receiving slot of the wireless communication device 20.

[0130] In this embodiment, compared to the configuration described in the first embodiment above, where the receiving slot is set to M slots earlier than the receiving slot of the wireless communication device 20, the receiving slot is set to receive data from another node closer to the location of the wireless communication device 20 in the next communication cycle (i.e., another node where communication quality is expected to be good). Therefore, even if the wireless communication device 20 (or the mobile device on which it is installed) moves, it is possible to reduce the time during which reception processing is performed unnecessarily (i.e., avoid an increase in power consumption).

[0131] In this embodiment, it has been explained that the third slot change process is executed when it is determined in step S17 shown in Figure 13 that the slot in which the reception process was performed is the last slot (i.e., no data is received in the last slot). However, the third slot change process may also be executed, for example, when it is determined in step S13 that no data has been received. To explain this in more detail using Figures 3 and 4, for example, if the receiving slot of wireless communication device 20-3 is slot SL6 and no data is received in slot SL6, and another node close to the location of wireless communication device 20-3 is wireless communication device 20-2, then wireless communication device 20-3 may perform the reception process in slot SL8, which is the transmitting slot of wireless communication device 20-2.

[0132] In a configuration where the third slot change process is executed if it is determined in step S13 that no data has been received, if no data is received in the newly set receiving slot after the execution of the third slot change process, and there is a slot (a transmitting slot of another node) that is after the receiving slot, the processes from step S14 onwards may be executed.

[0133] Furthermore, although this embodiment describes acquiring location information indicating the position of the wireless communication device 20 using, for example, a GPS function, any location information that can identify other nodes close to the wireless communication device 20 is acceptable.

[0134] Therefore, for example, if the wireless communication device 20 is installed in the elevator 101, information indicating the position (stopping floor) of the elevator 101, obtained from the elevator control device that controls the elevator 101, may be acquired as location information. Alternatively, location information may be acquired using, for example, an RFID tag installed in the hoistway 100. Furthermore, location information may be acquired based on, for example, control information (information indicating the stopping floor, etc.) that controls the elevator 101 output from the elevator control device.

[0135] Furthermore, if, for example, the wireless communication device 20 is installed on a train, location information (location information indicating the train's position) may be obtained from, for example, a train operation management system that manages the operation of the train.

[0136] Furthermore, although this embodiment has been described as assuming that location information indicating the locations of other nodes (aggregation device 10, wireless communication devices 20-1 and 20-2) is pre-stored inside the wireless communication device 20-3, this location information may also be acquired (received) from an external device when the third slot change process is executed.

[0137] (Third embodiment) Next, a third embodiment will be described. In this embodiment, detailed explanations of parts that are the same as those described in the first and second embodiments will be omitted.

[0138] This embodiment differs from the first and second embodiments described above in that it considers whether or not the wireless communication device (or the mobile device on which it is installed) is in motion when changing the settings of the receiving slot of the wireless communication device.

[0139] The configuration of the wireless communication device according to this embodiment will be described below, but since the hardware configuration of the wireless communication device 20 is the same as that of the first and second embodiments described above, a detailed explanation will be omitted here.

[0140] Figure 17 is a block diagram showing an example of the functional configuration of a wireless communication device according to this embodiment. In Figure 17, the same reference numerals are used for parts that are the same as those in Figures 7 and 12 described above, and their detailed explanations are omitted.

[0141] As shown in Figure 17, the wireless communication device 20 includes a movement detection unit 25. The movement detection unit 25 may be implemented by software, by hardware, or by a combination of software and hardware.

[0142] The movement detection unit 25 detects whether or not the wireless communication device 20 is moving. Whether or not the wireless communication device 20 is moving can be detected based on acceleration data measured by an acceleration sensor mounted on the wireless communication device 20.

[0143] The detection result from the movement detection unit 25 is output to the slot setting unit 23, which uses it to change the setting of the receiving slot of the wireless communication device 20.

[0144] The following describes an example of the processing procedure of the wireless communication device 20, referring to the flowchart in Figure 18. In the following description, the wireless communication device 20 that performs the processing shown in Figure 18 will be referred to as the target wireless communication device 20.

[0145] First, the processes S21 to S27, which correspond to the processes S1 to S7 shown in Figure 8 above, are executed.

[0146] If it is determined that the slot in which the reception process was performed is the last slot (YES in step S27), the movement detection unit 25 included in the wireless communication device 20 detects whether or not the wireless communication device 20 is moving, for example, based on acceleration data measured by an acceleration sensor mounted on the wireless communication device 20. The slot setting unit 23 determines whether or not the wireless communication device 20 is moving based on the detection result by the movement detection unit 25 (step S28).

[0147] If it is determined that the wireless communication device 20 is in motion (YES in step S28), the slot setting unit 23 executes the second slot change process (step S29). The second slot change process is as described in the first embodiment above, so a detailed explanation is omitted here.

[0148] However, in this embodiment, when the second slot change process is executed, for example, as shown in Figure 19, the wireless communication device 20 (wireless communication device 20-3) is in motion, and it is difficult to identify other nodes (aggregation device 10, wireless communication devices 20-1 and 20-2) with which the wireless communication device 20 can communicate. For this reason, in the second slot change process executed in this embodiment, for example, the first slot among multiple slots (transmission slots of other nodes) is set as the receiving slot of the wireless communication device 20. In other words, in the second slot change process in this embodiment, there is a high possibility that other nodes with good communication quality (i.e., other nodes near the wireless communication device 20) will change, so the receiving slot is changed so that the receiving process starts from the node with the earliest data transmission timing within the communication cycle, so that the receiving process can be executed sequentially in the transmission slots of all other nodes.

[0149] On the other hand, if it is determined that the wireless communication device 20 is not in motion (NO in step S28), the slot setting unit 23 executes the third slot change process (step S30). The third slot change process is as described in the second embodiment above, so a detailed explanation is omitted here.

[0150] As described above, in this embodiment, for example, if it is determined that no data has been received in the last slot (second slot) of the communication cycle, it is determined whether or not the wireless communication device 20 is in motion. In addition, even if it is not determined that no data has been received in the last slot, it may be determined whether or not the wireless communication device 20 is in motion after step S23 or step S25 and the slot change process may be performed.

[0151] In this embodiment, if it is determined that the wireless communication device 20 is in motion, the first of the multiple slots is set as the receiving slot of the wireless communication device 20 (the slot that receives data transmitted from other nodes in the second cycle).

[0152] Furthermore, in this embodiment, if it is determined that the wireless communication device 20 is not moving, the location of the wireless communication device 20 is acquired, and the transmission slot of another node close to the location of the wireless communication device 20 (the third slot to which the other node transmits data) is set as the reception slot of the wireless communication device 20.

[0153] In this embodiment, with this configuration, if the wireless communication device 20 does not receive data, and the wireless communication device 20 is in motion, the receiving slot is changed so that the receiving process is performed on all other nodes, as there is a high possibility that other nodes capable of properly receiving data will change. If the wireless communication device 20 is not in motion, the receiving slot is changed to receive data from other nearby nodes that are expected to have good communication quality. As a result, even if the wireless communication device 20 is in motion and therefore unable to receive data in the receiving slot (i.e., a connection is lost), the receiving slot is changed according to the status of the wireless communication device 20 (and the mobile device on which it is installed), thus avoiding an increase in power consumption.

[0154] In this embodiment, it has been explained that whether or not the wireless communication device 20 is moving is detected based on acceleration data measured by an acceleration sensor mounted on the wireless communication device 20. However, whether or not the wireless communication device 20 is moving may also be detected based on changes in the position of the wireless communication device 20 indicated by location information obtained using the GPS function, or on sensor data measured by other sensors mounted on the wireless communication device 20.

[0155] Furthermore, if the wireless communication device 20 is installed on the elevator 101, the system may be configured to detect whether or not the wireless communication device 20 installed on the elevator 101 is in motion based on information indicating the operating status (movement status) of the elevator 101 obtained from the elevator control device.

[0156] Furthermore, if the wireless communication device 20 is installed on a train, the configuration may include detecting whether or not the wireless communication device 20 installed on the train is in motion based on information indicating the train's operating status (movement status) obtained from the train operation management system.

[0157] According to at least one embodiment described above, it is possible to provide a wireless communication device and method that can achieve power saving.

[0158] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Explanation of symbols]

[0159] 1...Communication system, 10...Aggregation device, 20, 20-1~20-3...Wireless communication device, 20a...Microcontroller, 20b...Wireless communication module, 20c...Sensor, 21...Transmission / reception processing unit, 22...Determination unit, 23...Slot setting unit, 24...Location information acquisition unit, 25...Movement detection unit, 100...Housing shaft, 101...Elevator, 102...Counterweight.

Claims

1. A wireless communication device that forms a network with multiple other nodes, and which operates to receive data transmitted from other nodes in the first slot of multiple slots in the first cycle, A first determination means for determining whether data has been received in the first slot, If it is determined that no data has been received in the first slot, a second determination means determines whether data transmitted from another node has been received in a second slot that is later than the first slot in the first cycle. If it is determined that data has been received in the second slot, the setting means sets the second slot as the slot for receiving data transmitted from other nodes in the second cycle following the first cycle. A wireless communication device equipped with the following features.

2. The wireless communication device according to claim 1, wherein the wireless communication device is installed on a mobile body that moves such that the distance from other nodes changes.

3. The wireless communication device according to claim 2, wherein the wireless communication device is driven by power supplied from a battery or rechargeable battery.

4. The wireless communication device according to claim 1, wherein if the setting means determines that no data has been received in the second slot, it sets a third slot prior to the first slot as a slot for receiving data transmitted from other nodes in the second cycle.

5. If the setting means determines that no data has been received in the second slot during the second cycle, it sets a third slot prior to the second slot as the slot for receiving data transmitted from another node during the third cycle following the second cycle. The third slot is the slot immediately preceding the second slot. The wireless communication device according to claim 1.

6. If the setting means determines that no data has been received in the second slot during the second cycle, it sets a third slot prior to the second slot as the slot for receiving data transmitted from another node during the third cycle following the second cycle. The third slot is the first of the plurality of slots. The wireless communication device according to claim 1.

7. If it is determined that no data has been received in the second slot, the system further comprises acquisition means for acquiring the position of the wireless communication device. The setting means sets a third slot, which receives data transmitted from other nodes in the second cycle, to be a slot where other nodes close to the acquired position transmit data. The wireless communication device according to claim 2.

8. If it is determined that no data has been received in the second slot, a third determination means determines whether the wireless communication device is in motion, If it is determined that the wireless communication device is not in motion, an acquisition means for acquiring the location of the wireless communication device is provided. It further comprises, The setting means is, If it is determined that the wireless communication device is in motion, the first of the multiple slots, the third slot, is set as the slot for receiving data transmitted from other nodes in the second cycle. When the location of the wireless communication device is acquired, a third slot is set as the slot to receive data transmitted from other nodes in the second cycle, where other nodes close to the location of the wireless communication device transmit data. The wireless communication device according to claim 2.

9. The wireless communication device according to any one of claims 4 to 8, wherein the second slot is the last slot among the plurality of slots.

10. The wireless communication device according to claim 1, wherein the data includes delivery confirmation information for data transmitted from the wireless communication device.

11. The first determination means determines whether the data has been received based on the received signal strength of the data received in the first slot. The second determination means determines whether the data has been received based on the received signal strength of the data received in the second slot. The wireless communication device according to claim 1.

12. The first determination means determines whether the data has been received based on the number of times the data has been received in the first slot in each of the plurality of first cycles. The second determination means determines whether the data has been received based on the number of times the data was received in the second slot in each of the plurality of first cycles. The wireless communication device according to claim 1.

13. A method performed by a wireless communication device that forms a network with multiple other nodes, and which operates to receive data transmitted from other nodes in the first slot of multiple slots in the first cycle, A step of determining whether data has been received in the first slot, If it is determined that no data has been received in the first slot, the step is to determine whether data transmitted from another node has been received in a second slot that is later than the first slot in the first cycle. If it is determined that data has been received in the second slot, the second slot is set as the slot for receiving data transmitted from other nodes in the second cycle following the first cycle. A method that provides for this.

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