JP7830396B2 - Wireless communication device and method - Google Patents

Description

Embodiments of the present invention relate to wireless communication devices and methods.

In recent years, it has become known that networks (hereinafter referred to as sensor networks) are constructed using multiple wireless communication devices and aggregation devices equipped with sensors.

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

However, when multiple wireless communication devices are installed in an environment where it is difficult to supply power, these devices must be powered by batteries or other sources, thus requiring power-saving features for these devices.

Japanese Patent Publication No. 2016-54349 Japanese Patent Publication No. 2011-029990

Therefore, the problem that this invention aims to solve is to provide a wireless communication device and method that can achieve power saving.

According to one embodiment, a wireless communication device is provided that constitutes a network with multiple other nodes and operates to receive data transmitted from other nodes in a first slot among multiple 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 occurs after 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 the slot for receiving data transmitted from other nodes in the second cycle following the first cycle.

A diagram showing an example of the network configuration of a communication system according to the first embodiment. A schematic diagram showing a communication system in the form of a network topology. A diagram illustrating an example of an environment in which a communication system is applied. A diagram illustrating the overview of slot communication performed in a communication system. A diagram illustrating how the communication range of a wireless communication device changes depending on its location. A diagram showing an example of the hardware configuration of a wireless communication device. A block diagram showing an example of the functional configuration of a wireless communication device. A flowchart illustrating an example of the processing procedure for a wireless communication device. A diagram illustrating a specific example of the operation of a wireless communication device. A diagram illustrating a specific example of the operation of a wireless communication device. A diagram illustrating a specific example of the operation of a wireless communication device. A block diagram showing an example of the functional configuration of a wireless communication device according to the second embodiment. A flowchart illustrating an example of the processing procedure for a wireless communication device. A diagram illustrating the process of changing the third slot. A diagram showing an example of the location of a wireless communication device. A diagram showing another example of the location of a wireless communication device. A block diagram showing an example of the functional configuration of a wireless communication device according to the third embodiment. A flowchart illustrating an example of the processing procedure for a wireless communication device. A diagram showing that a wireless communication device is in motion.

The embodiments will be described below with reference to the drawings.
(First Embodiment)
First, the first embodiment will be described. Figure 1 shows an example of the network configuration of the communication system in this embodiment.

The communication system 1 shown in Figure 1 comprises an aggregation device 10 having a wireless communication function (hereinafter referred to as the wireless communication function) and a plurality of wireless communication devices 20. In this embodiment, wireless communication is performed between the aggregation device 10 and the plurality of wireless communication devices 20, for example, using a time-division multiplexing scheme.

Furthermore, in the communication system 1 shown in Figure 1, the aggregation device 10 and the multiple wireless communication devices 20 constitute a multi-hop network in which the multiple wireless communication devices 20 are wirelessly connected to the aggregation device 10 in a tree structure. With this multi-hop network, the multiple wireless communication devices 20 constituting the multi-hop network transfer data in a bucket-brigade fashion, enabling long-distance communication to the aggregation device 10 that extends beyond the individual communication ranges of the multiple wireless communication devices 20.

Furthermore, the aggregation device 10 and the multiple wireless communication devices 20 that constitute the multi-hop network described above are referred to as nodes in the multi-hop network.

Figure 2 is a schematic diagram showing the communication system 1 shown in Figure 1 in network topology form. In Figure 2, "Root" represents the aggregation device 10 (root node), and "A" to "P" represent each of the multiple wireless communication devices 20.

Furthermore, the arrows shown in Figure 2 indicate the data transmission path. The source of the arrow represents the data source node (child node), and the tip of the arrow represents the data destination node (parent node).

Specifically, for example, the parent node of a wireless communication device 20 represented by "G" (hereinafter referred to as node G) is node E (represented by "E" as wireless communication device 20), which has one fewer hop from the root node than node G. On the other hand, the child nodes of node G are node I (represented by "I" as wireless communication device 20) and node L (represented by "L" as wireless communication device 20), which have one more hop from the root node than node G.

Note that while Figure 2 shows a network topology where node G is placed between nodes L and E, a network topology where nodes L and E are directly connected (communicate) is also possible.

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.

In Figures 1 and 2, a communication system 1 is assumed to include, for example, 16 wireless communication devices 20. However, in this embodiment, the number of wireless communication devices 20 can be two or more.

Furthermore, the network topology and communication method of the communication system 1 described here are merely examples, and other network topologies and communication methods may be employed. Specifically, while Figure 2 shows a tree-type network topology, 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, other communication methods may be used.

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

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 accordance with the moisture content in the soil in forests, etc. Furthermore, 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) in accordance with the water level of rivers, etc. Furthermore, if the sensors mounted on multiple wireless communication devices 20 are humidity sensors, efficient plant cultivation becomes possible by utilizing the sensor data (humidity data) measured by these humidity sensors and combining it with temperature data, etc.

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 powered by power supplied from, for example, a battery, and a mechanism for powering the wireless communication device 20 with low power consumption is useful.

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

Furthermore, at least one of the multiple wireless communication devices 20 in this embodiment 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.

The following describes an example of an environment to which the communication system 1 in this embodiment is applied, with reference to Figure 3.

Figure 3 illustrates the case where the communication system 1 of 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 within 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.

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 located, 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.

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 sway 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 sway of the elevator 101, the wireless communication device (accelerometer) may also be installed on the counterweight 102, which operates up and down in conjunction with the elevator 101.

In the example shown in Figure 3, wireless communication devices 20-1 and 20-2 operate solely as relay nodes for relaying, for example, sensor data. In this case, wireless communication devices 20-1 and 20-2 do not necessarily need to have sensors mounted on them.

In Figure 3, wireless communication devices 20-1 and 20-2 are shown as wireless communication devices 20 operating as relay nodes. However, the number of relay nodes may be changed depending on the size of the building, etc., where the elevator 101 is installed. Furthermore, in the example shown in Figure 3, for example, wired communication may be used between the aggregation device 10 and wireless communication device 20-1, and wired communication may be used between wireless communication device 20-1 and wireless communication device 20-2.

Here, referring to Figure 4, we will now describe the outline of slot communication performed in the communication system 1 applied to the elevator system as shown in Figure 3. Note that, as described above, the wireless communication device 20-3 is powered by electricity supplied from a battery (i.e., power saving is necessary), 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.

As shown in Figure 4, in slot communication, multiple slots SL1 to SL10 are provided in a predetermined cycle (hereinafter referred to as the communication cycle) that repeats, for example, every second. 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 the predetermined slots. Each of the multiple slots SL1 to SL10 is assigned to one of several time periods into which the communication cycle is divided.

Specifically, the aggregation device 10 operates to transmit data in slot SL6 (the time period assigned to it) during 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 slot to which the aggregation device 10 transmits data (the slot to which the data can be transmitted) will be referred to as the aggregation device 10's transmission slot, and the slot to which the aggregation device 10 receives data (the slot to which the data can be received) will be referred to as the aggregation device 10's reception slot.

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.

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.

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 operating 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 be assigned a unique slot to use as its transmitting slot.

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.

In the example shown in Figure 4, the transmission slot of the wireless communication device 20-3 is slot SL2; therefore, 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 (e.g., acceleration data measured by an acceleration sensor).

For example, if the aggregation device 10, where 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.

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 includes, for example, data containing 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.

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

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 the 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).

Incidentally, assuming that the wireless communication device 20-3 is installed on 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., its distance from, for example, the aggregation device 10) changes as the elevator 101 moves up and down within the hoistway 100. Hereafter, 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.

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

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.

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, for example, and 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.

Furthermore, although the data transmitted from the aggregation device 10 is relayed by wireless communication devices 20-1 and 20-2, even if, for example, 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.

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.

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

Furthermore, while it might be conceivable to receive data in a predetermined number of slots (each transmission slot for multiple candidate data sources) to avoid the need for searching, performing reception processing in multiple slots at all times would make it difficult to achieve power saving in the wireless communication device 20-3.

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.

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

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.

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

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.

In this embodiment, some or all of the parts 21-23 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 combination of software and hardware.

The transmission/reception processing unit 21 executes a data transmission process (data transmission process) based on, for example, a pre-configured transmission slot of the wireless communication device 20. If the data transmitted in the transmission process executed by the transmission/reception processing unit 21 is the sensor data described above, this sensor data can be obtained from the sensor 20c shown in Figure 6. Note that the data transmitted in the transmission process executed by the transmission/reception processing unit 21 may be data other than sensor data.

Furthermore, the transmission/reception processing unit 21 executes a data reception process (data reception processing) based on the pre-configured reception slot of the wireless communication device 20. While 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, it may also include, for example, control data transmitted from the aggregation device 10 (data for controlling the wireless communication device 20).

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

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).

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 is referred to as the target wireless communication device 20. Furthermore, "other nodes" in the following description include other wireless communication devices 20 other than the aggregation device 10 and the target wireless communication device 20.

First, the transmission/reception 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, for example, 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 include identification information indicating the target wireless communication device 20 as source information, and identification information for identifying the aggregation device 10 as destination information.

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.

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 its transmission slot. The data transmitted from the aggregation device 10 includes identification information to identify the aggregation device 10 as source information, and identification information to identify the target wireless communication device 20 as destination information. Furthermore, the data transmitted from the aggregation device 10 may also include slot information indicating the transmission slot to which the data is transmitted.

Here, the transmit/receive processing unit 21 included in the target wireless communication device 20 performs reception processing in the receive slot of the target wireless communication device 20 (step S2). In this case, for example, if the receive slot of the target wireless communication device 20 is the same as the transmit 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 receive slot of the target wireless communication device 20 is the same as the transmit 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.

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

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 and continues the reception process (step S4).

In this case, the target wireless communication device 20 (transmit/receive processing unit 21) operates to perform reception processing in subsequent slots 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).

Furthermore, for example, the slot setting unit 23 included in the target wireless communication device 20 manages the transmission slots (or slot information indicating them) of other nodes (the aggregation device 10 and other wireless communication devices 20). In this case, the slot in step S4 where the reception process is continuously executed (the slot following 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.

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

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).

Here, the determination 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 data was received) is within the communication range of the target wireless communication device 20.

Therefore, in the first slot change process, the slot where 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 where the data was received).

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). Note that 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 transmission slot of another node.

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 slots following the last slot in which the receiving process was performed.

On the other hand, if it is determined that the slot in 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).

Here, if it is determined in step S7 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 another node whose transmission slot is prior to the reception slot of the target wireless communication device 20 is within the communication range of the target wireless communication device 20.

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 the current receiving slot).

Furthermore, the slot M positions prior to the receiving slot of the target wireless communication device 20 may be one of multiple slots in the communication cycle, or it may be one of the transmission slots of another node, specifically the slot M positions prior to the receiving slot.

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 transmission/reception processing unit 21. The transmission/reception processing unit 21 then executes the receiving process for the next communication cycle of the target communication cycle based on this slot information (and the receiving slot indicated by it).

In steps S3 and S5 described above, if data with identification information for identifying the target wireless communication device 20 is received 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 (i.e., the data is not 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 without identification information for identifying the target wireless communication device 20 (i.e., data with identification information for identifying another wireless communication device 20) is received, the transmission/reception processing unit 21 transmits (transfers) the data in the transmission slot of the target wireless communication device 20.

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 without such delivery confirmation information is received, it may be determined in steps S3 and S5 that no data has been received.

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.

The following describes specific examples of the operation of the wireless communication device 20 according to this embodiment, with reference to Figures 9 to 11.

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; therefore, a detailed explanation of this is omitted here.

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

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.

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 cannot 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 its receiving slot to slot SL7 and continues the receiving process.

As described above, wireless communication device 20-3 cannot receive data transmitted from aggregation device 10 in slot SL6. However, 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.

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.

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, thereby enabling it to receive data transmitted from the wireless communication device 20-1.

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, where wireless communication device 20-3 does not receive data, as shown in the lower left of Figure 10, wireless communication device 20-3 extends its receiving slot to slot SL8 and continues the receiving process. Note that 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.

As described above, wireless communication device 20-3 cannot receive data transmitted from wireless communication device 20-1 in slot SL7. However, 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.

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.

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, thereby enabling it to receive data transmitted from the wireless communication device 20-2.

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 the aggregation device 10 in slot SL6. The data transmitted from the 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.

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, then the wireless communication device 20-3 cannot receive the data transmitted from the wireless communication device 20-2 in slot SL8.

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.

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, thereby enabling it to receive data transmitted from the wireless communication device 20-1.

In Figure 11, it was explained that slot SL7, which is one slot before slot SL8 (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), 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.

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 subsequent to 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.

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

In this embodiment, with the configuration described above, even in environments 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) frequently change due to the device's movement, the power efficiency of the wireless communication device 20 can be improved by appropriately changing its receiving slot. In other words, according to this embodiment, even if the wireless communication device 20 moves, it can change its receiving slot to receive data transmitted in the transmitting slot of another node with which it can communicate, thereby minimizing the reception range and achieving power savings.

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 (the slot M positions before 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 wireless communication device 20 can reconfigure the receiving slot to one that can receive data in the next communication cycle, thereby improving the efficiency of the receiving process in the wireless communication device 20.

Regarding the M slots prior to the one mentioned above, if, for example, the 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 capable of communication with fewer reception processing steps. 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 other nodes capable of communication can be searched for more reliably in the next communication cycle, and the transmitting slot of that other node can be reconfigured as the receiving slot of the wireless communication device 20. In other words, the M (number) in "M slots prior to the one" in this embodiment may be determined based on the type or characteristics of the moving object (e.g., the object on which sensor data is measured) on which the wireless communication device 20 is installed.

Furthermore, in this embodiment, it was explained that data including delivery confirmation information for sensor data transmitted from the wireless communication device 20 is transmitted from the aggregation device 10, and that this data is 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).

Furthermore, in this embodiment, it is determined whether or not data has been received. 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.

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

Furthermore, the data may include information such as destination information (identification information for the destination) indicating the recipient of the data, and slot information (slot information) indicating the transmission slot to which the data was sent. The aforementioned determination process may also be performed using this destination information and slot information.

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

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

(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.

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 wireless communication device's receiving slot.

The configuration of the wireless communication device according to this embodiment will be described below. However, 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.

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.

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.

The location information acquisition unit 24 acquires location information indicating the position 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, using the position of the elevator car.

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.

The following describes an example of the processing procedure for 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.

First, steps S11 to S17, which correspond to steps S1 to S7 shown in Figure 8 above, are executed.

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

In the first embodiment described above, a second slot change process was performed to newly set the slot M positions prior to the current receiving slot of the target wireless communication device 20 as the receiving slot of the target wireless communication device 20 (i.e., changing the receiving slot of the target wireless communication device 20 to a slot M positions prior to the current 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 location of the target wireless communication device 20 as described above.

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

In this case, the location information acquisition unit 24 included in the wireless communication device 20-3 acquires location information (hereinafter referred to as "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.

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).

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.

In this case, as shown on the right side of Figure 14, the wireless communication device 20-3 operates to perform reception processing in slot SL6 during the third communication cycle following the second communication cycle, thereby enabling it to receive data transmitted from the aggregation device 10.

Here, the explanation assumes that the location of wireless communication device 20-3, indicated by the first location information, is near an upper floor of the building. However, as shown in Figure 16, if the location of wireless communication device 20-3 is near a middle floor 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 wireless communication device 20-1, as the reception slot of wireless communication device 20-3.

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 near the acquired position (i.e., the third slot on which the other node transmits data) is set as the receiving slot of the wireless communication device 20.

In this embodiment, compared to the configuration described in the first embodiment where the receiving slot is set to M slots prior to the receiving slot of the wireless communication device 20, this configuration sets the receiving slot to a slot that receives 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 considered possible to reduce the time during which unnecessary receiving processing is performed (i.e., avoid an increase in power consumption).

In this embodiment, although it was explained that the third slot change process is executed when it is determined that the slot in step S17 shown in Figure 13 is the last slot (i.e., no data is received in the last slot), the third slot change process may also be executed, for example, when it is determined that no data has been received in step S13. To explain this more specifically 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 receiving process in slot SL8, which is the transmitting slot of wireless communication device 20-2.

Furthermore, 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 data is not received in the newly configured receiving slot after the execution of the third slot change process, and if a slot (a transmission slot of another node) exists after that receiving slot, the processes from step S14 onwards may be executed.

Furthermore, although this embodiment describes acquiring location information indicating the position of the wireless communication device 20 using, for example, GPS functionality, this location information can be any information that can identify other nodes close to the wireless communication device 20.

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 position information. Alternatively, position information may be acquired using, for example, an RFID tag installed in the hoistway 100. Furthermore, position information may be acquired based on, for example, control information (such as information indicating the stopping floor) that controls the elevator 101, output from the elevator control device.

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 train's operation.

Furthermore, although this embodiment describes position information indicating the locations of other nodes (aggregation device 10, wireless communication devices 20-1 and 20-2) as being pre-stored within the wireless communication device 20-3, this position information may also be acquired (received) from an external device when the third slot change process is executed.

(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.

This embodiment differs from the first and second embodiments described above in that it considers whether the wireless communication device (or the mobile device on which it is installed) is in motion when changing the settings of the wireless communication device's receiving slot.

The configuration of the wireless communication device according to this embodiment will be described below. However, 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.

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 identical to those in Figures 7 and 12, and their detailed descriptions are omitted.

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.

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 the acceleration sensor mounted on the wireless communication device 20.

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.

The following describes an example of the processing procedure for 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.

First, steps S21 to S27, which correspond to steps S1 to S7 shown in Figure 8 above, are executed.

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 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 the wireless communication device 20 is moving based on the detection result from the movement detection unit 25 (step S28).

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). Since the second slot change process is as described in the first embodiment above, a detailed explanation is omitted here.

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, making it 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. Therefore, 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 for the wireless communication device 20. In other words, in the second slot change process in this embodiment, because there is a high possibility that other nodes with good communication quality (i.e., other nodes near the wireless communication device 20) will change, 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.

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). Since the third slot change process is as described in the second embodiment above, a detailed explanation is omitted here.

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. Furthermore, even if it is not determined that no data has been received in the last slot, the system may determine whether or not the wireless communication device 20 is in motion after step S23 or step S25 and perform the slot change process.

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).

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.

In this embodiment, with this configuration, if the wireless communication device 20 does not receive data, and the wireless communication device 20 is moving, the receiving slot is changed so that the receiving process is executed for all other nodes, as there is a high probability that other nodes capable of properly receiving data will change. If the wireless communication device 20 is not moving, the receiving slot is changed to receive data from other nearby nodes that are expected to have good communication quality. This allows the receiving slot to be changed according to the status of the wireless communication device 20 (and the mobile device on which it is installed), even if the receiving slot becomes unusable due to the wireless communication device 20 moving (i.e., a connection interruption occurs), thereby avoiding an increase in power consumption.

In this embodiment, it was 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 acquired using GPS functionality, or on sensor data measured by other sensors mounted on the wireless communication device 20.

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 moving, based on information indicating the operating status (movement status) of the elevator 101 obtained from the elevator control device.

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.

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

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 implemented in various 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 within the scope and spirit of the invention, as well as within the scope of the claims and its equivalents.

1…Communication system, 10…Aggregation device, 20, 20-1 to 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 (13)

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.
A wireless communication device comprising: setting means, which, when it is determined that data has been received in the second slot, sets the second slot as a slot for receiving data transmitted from other nodes in the second cycle following the first cycle. The wireless communication device according to claim 1, wherein the wireless communication device is installed on a moving body that moves such that the distance to other nodes changes. The wireless communication device according to claim 2, wherein the wireless communication device is powered by electricity supplied from a battery or rechargeable battery. 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 the third slot, which is earlier than the first slot, as the slot for receiving data transmitted from other nodes in the second cycle. If the setting means determines that no data has been received in the second slot during the second cycle, it sets the third slot, which precedes the second slot, as the slot for receiving data transmitted from other nodes 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 . If the setting means determines that no data has been received in the second slot during the second cycle, it sets the third slot, which precedes the second slot, as the slot for receiving data transmitted from other nodes 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 . 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 wireless communication device according to claim 2, wherein the setting means sets a third slot to which another node close to the acquired position transmits data, as a slot for receiving data transmitted from another node in the second cycle. 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, the system further comprises acquisition means for acquiring the location of the wireless communication device,
The setting means is,
The wireless communication device according to claim 2, wherein if it is determined that the wireless communication device is in motion, the first of the plurality of third slots is set as the slot for receiving data transmitted from other nodes in the second cycle, and if the location of the wireless communication device is acquired, the third slot to which another node close to the location of the wireless communication device transmits data is set as the slot for receiving data transmitted from other nodes in the second cycle. 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. The wireless communication device according to claim 1, wherein the data includes delivery confirmation information for data transmitted from the wireless communication device. 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 wireless communication device according to claim 1, wherein 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 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 wireless communication device according to claim 1, wherein the second determination means determines whether the data has been received based on the number of times the data has been received in the second slot in each of the plurality of first cycles. 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.
A method comprising the steps of: if it is determined that data has been received in the second slot, setting the second slot as a slot for receiving data transmitted from other nodes in the second cycle following the first cycle.