wireless communication system

Abstract

To smooth power consumption between nodes and achieve low-latency operation.SOLUTION: In a wireless communication system in a network in which data frames between two or more nodes 3 arranged with a CS 2 as a root are transmitted and received based on time division multiple access (TDMA), each node 3 is assigned an active period in which the data frames can be transmitted and received and a sleep period in which operation is suspended, in consecutive intermittent standby cycles, and the node 3 is assigned the active period and the sleep period that are different from each other on a time-series basis.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] This relates to a wireless communication system in a network in which data frames are transmitted and received between two or more nodes located around a collection control station based on time division multiple access (TDMA). [Background technology]

[0002] In recent years, wireless networks have been using communication devices conforming to the IEEE802.15.4g standard, which are small, inexpensive, and capable of power-saving wireless communication (see, for example, Non-Patent Document 1). Networks conforming to the IEEE802.15.4g standard employ various topologies, each consisting of a collection control station (CS) and one or more nodes.

[0003] Among these, the IEEE802.15.4 standard proposes a power-saving superframe structure as shown in Fig. 8. In this superframe structure, a superframe is defined by a periodic beacon signal under Time Division Multiple Access (TDMA) control. The interval between these beacon signals (intermittent standby period) can be divided into an active period (AP) during which nodes wait for data frame signals to be transmitted or received, and a sleep period (SP) during which the power is turned off and no transmission, reception, or standby operations are performed. During the active period AP, each node can operate as a substantial communication period. Meanwhile, during the sleep period SP, each node can transition to a sleep state (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-167636 [Non-patent literature]

[0005] [Non-Patent Document 1] IEEE802.15.4g, “Part 15.4: Low-Rate Wireless Personal Area Networks (LR-WPANs), Amendment 3: Physical Layer (PHY) Specifications for Low-Data-Rate, Wireless, Smart Metering Utility Networks”, 2012 Summary of the Invention [Problem to be solved by the invention]

[0006] In the IEEE802.15.4 standard, each node operates independently and does not cooperate with other nodes. Especially when the nodes are close to each other, the network as a whole can receive and transmit data frames without any problems if any node is an AP during the active period. The other nodes then transition to a sleep state during that time, thereby reducing power consumption across the network.

[0007] However, if a particular node has an extremely high frequency of active periods (AP) while other nodes continue to have sleep periods (SP), this can lead to an imbalance in power consumption between the nodes. As a result, the node with the extremely high frequency of active periods (AP) consumes power faster, hindering efficient network operation. Furthermore, this extreme imbalance in power consumption between nodes can hinder the realization of low-latency operation, which reduces communication delays in sending and receiving data frames and in standby mode.

[0008] Therefore, it is necessary to achieve low-latency operation while smoothing out power consumption between nodes while satisfying the expected communication functions of the network as a whole, but until now, no technology has been proposed that can satisfy these conditions.

[0009] The present invention has been devised in consideration of the above-mentioned problems, and its purpose is to provide a wireless communication system that can smooth out power consumption between nodes and achieve low-latency operation while satisfying the communication functions expected in a wireless network conforming to the IEEE802.15.4 standard. [Means for solving the problem]

[0010] The inventors have resolved the above-mentioned problem by assigning active periods during which the data frames can be sent and received and sleep periods during which operation is suspended in successive intermittent standby periods, when transmitting and receiving data frames between two or more nodes arranged around a collection control station as the root, based on time division multiple access (TDMA), and further assigning active periods and sleep periods during which operation is suspended to each node that are different from each other in chronological order.

[0011] A wireless communication system according to a first aspect of the present invention is a wireless communication system in a network in which transmission and reception of data frames between two or more nodes arranged around a collection control station is performed based on time division multiple access (TDMA), wherein each of the nodes is assigned an active period in which the data frames can be transmitted and received and a sleep period in which the node does not operate during successive intermittent standby periods, and the nodes are assigned active periods and sleep periods that are different from each other in time series; When at least one node is assigned the sleep period, the other one or more nodes are assigned the active period for a time period corresponding to the sleep period. It is characterized by:

[0012] A wireless communication system according to a second aspect of the present invention is a wireless communication system in a network in which transmission and reception of data frames between two or more nodes arranged around a collection control station is performed based on time division multiple access (TDMA), wherein each of the nodes is assigned an active period in which the data frames can be transmitted and received and a sleep period in which the node does not operate, during successive intermittent standby periods, and the nodes are assigned active periods and sleep periods that are different from each other in time series; In the intermittent standby cycle, a total sleep period in which all nodes simultaneously suspend operation and an active period in which one or more nodes are active are allocated, and the proportion of the total sleep period in the intermittent standby cycle is set to be equal to or less than the proportion of the maximum allowable total sleep period set in advance. It is characterized by:

[0013] A third aspect of the present invention provides a wireless communication system according to the second aspect of the present invention, wherein the collection control station is configured to allocate the active period and the sleep period that are determined in advance. and others The method is characterized in that newly detected nodes are assigned to the one node or the other nodes according to the number or ratio of the one node that has been detected and the other nodes that have only been assigned the active period.

[0014] A wireless communication system according to a fourth aspect of the present invention is a wireless communication system in a network in which transmission and reception of data frames between two or more nodes arranged around a collection control station are performed based on time division multiple access (TDMA), wherein each of the nodes is assigned an active period in which the nodes can transmit and receive the data frames and a sleep period in which the nodes do not operate, during successive intermittent standby periods, and the active periods and the sleep periods that are chronologically different from each other are assigned to the nodes, When performing allocation for each intermittent standby cycle, if the ratio of the sleep period in one node is increased, the ratio of the sleep period in one or more other nodes is decreased, and if the ratio of the sleep period in one node is decreased, the ratio of the sleep period in one or more other nodes is increased. It is characterized by:

[0015] A fifth aspect of the present invention provides a wireless communication system according to the fourth aspect of the present invention, further comprising: 1 or more When there are a plurality of nodes, any one other node that decreases the proportion of the sleep period or increases the proportion of the sleep period is selected with equal probability. [Effects of the Invention]

[0017] According to the present invention having the above-described configuration, it is possible to achieve low-latency operation by smoothing out power consumption between nodes while satisfying the communication functions expected in a wireless network conforming to the IEEE802.15.4 standard. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a diagram showing an example in which a tree topology is adopted in a wireless communication system to which the present invention is applied. [Figure 2] FIG. 2 is a diagram showing an example in which a star topology is adopted in a wireless communication system to which the present invention is applied. [Figure 3] FIG. 3 is a diagram showing a superframe structure that is set for each node when transmitting and receiving a data frame. [Figure 4] FIG. 4 is a diagram showing an example of active periods and sleep periods assigned to each intermittent standby cycle in a node. [Figure 5] FIG. 5 is a diagram showing an example in which active periods AP and sleep periods SP are assigned to chronologically consecutive intermittent standby periods of a node. [Figure 6] FIG. 6 is a diagram for explaining another embodiment of a wireless communication system to which the present invention is applied. [Figure 7] FIG. 7 is a diagram showing an example in which a full sleep period is provided in a wireless communication system to which the present invention is applied. [Figure 8] FIG. 8 is a diagram for explaining the prior art. DETAILED DESCRIPTION OF THE INVENTION

[0019] A wireless communication system to which the present invention is applied will be described in detail below with reference to the drawings.

[0020] In Fig. 1, a wireless communication system 1 to which the present invention is applied includes wireless nodes 3-1, 3-2, 3-3, 3-4, 3-5, 3-6, and 3-7 with a collection control station (hereinafter referred to as CS) 2 as the root, and employs a so-called tree topology in which the nodes 3 are arranged in a tree shape. In this wireless communication system 1, lower nodes 3 perform upstream data communication with higher nodes 3 and CS2. Also, in the wireless communication system 1, higher nodes 3 and CS2 perform downstream data communication with lower nodes 3.

[0021] The CS2 is the highest-level master device, and collects data frames transmitted by upstream data communication from the nodes 3-1 to 3-7. The CS2 also serves as a central control unit for controlling the entire wireless communication system 1, and transmits control data frames to a specific node 3 via downstream data communication.

[0022] Node 3 is a generic term for devices capable of transmitting and receiving data, including transmitting and relaying data, and is, for example, a communication device conforming to the IEEE802.15.4 standard. Node 3 may be embodied as a sensor that senses and wirelessly transmits predetermined data, or as a terminal device capable of wireless communication, such as a mobile phone, smartphone, tablet device, wearable device, or laptop personal computer (PC). Node 3 may also include a control system for a machine tool, such as an actuator. In such a case, it may be embodied as a device capable of, for example, controlling the stopping of a valve, controlling a robot, or controlling the stopping of gas. If node 3 is embodied as an actuator or the like including a control system, it will perform various control operations based on control data transmitted downstream from CS2 via other nodes 3.

[0023] 2 shows an example of a wireless communication system 1 to which the present invention is applied, which employs a star topology. The star topology includes one CS 2 and multiple nodes 3-1 to 3-5 that directly transmit and receive data frames to and from this CS 2. A master device-slave device relationship is established between the CS 2 and the nodes 3-1 to 3-5.

[0024] The wireless communication system 1 to which the present invention is applied may adopt either a tree topology or a star topology.

[0025] In a wireless communication system 1 to which the present invention is applied, a superframe structure set for each node 3 when transmitting and receiving data frames is shown in Figure 3. In this superframe structure, the superframe is defined by periodic beacon signals under Time Division Multiple Access (TDMA) control. The interval between these beacon signals is called an intermittent standby period. The superframe includes an active period (AP) during which nodes wait for data frames to be transmitted or received, and a sleep period (SP).

[0026] Incidentally, the intermittent standby period of a superframe is not necessarily limited to being determined by a beacon signal. In other words, it is not necessary for a beacon signal to be transmitted or received at the start or end of the intermittent standby period of a superframe. Multiple superframes may be included within the interval of a beacon signal. Furthermore, the intermittent standby period of each superframe may be set to, for example, the minimum interval between beacon signals. In such a case, superframes whose intermittent standby period is set to the minimum interval between beacon signals will be consecutive, regardless of the interval between beacon signals transmitted or received thereafter.

[0027] The length of the intermittent standby period of the superframe, and the start point (start time) and end point (end time) of the superframe can be freely changed. The intermittent standby period of the superframe can be adjusted by adjusting the interval of the beacon signal.

[0028] The active period AP starts at the start of the superframe and waits for a predetermined time in an intermittent standby cycle for data frames to be transmitted and received. During this active period AP, at least the information written in the header of the data frame is read. From the information in the header of the data frame read during the active period AP, it is possible to determine whether or not the entire data frame needs to be received.

[0029] As shown in Figure 3(a), the active period AP may be shorter than the length of the data frame being transmitted or received. The end point of the data frame is not necessarily limited to within the active period, but may extend beyond the active period AP. Because only the information contained in the header of the data frame needs to be read, the active period AP may be shortened to the extent that the header information can be read regardless of the data frame length. In other words, as long as the active period AP can listen for only the header portion of the data frame sent by each node, the active period AP can be shortened and the node can transition to a sleep state, regardless of the length of the data frame. Therefore, the IEEE 802.15.4 standard allows the sleep state to be extended longer than usual, thereby reducing power consumption. However, because the active period AP must reliably receive at least the header of the data frame being transmitted, it is required to remain in a standby state without transitioning to a sleep state.

[0030] The length of this active period AP can be freely set in each node 3. The active period AP may be 0 at its shortest. In other words, there may be no active period AP from the start to the end of one superframe, and it may be entirely composed of a sleep period SP. Furthermore, this active period AP can be extended at its longest from the start to the end of the superframe. In other words, one superframe may entirely be composed of an active period AP.

[0031] In a superframe, the sleep period SP extends from the end of the active period AP to the end of the superframe. As described above, the length of the active period AP is variable, and therefore the sleep period SP can also be varied according to the length of the active period AP. During the sleep period SP, node 3 enters a sleep state, i.e., the power is turned off and node 3 transitions to a period in which it does not transmit or receive data frames or wait for them. In a superframe, by providing not only the active period AP but also the sleep period SP in which node 3 transitions to this sleep state, it is possible to reduce the power consumption of node 3. Incidentally, the sleep period SP extends from the end of the active period AP to the end of the superframe.

[0032] 3(b), if the time period for transmitting and receiving a data frame in a superframe exceeds the active period AP and it is determined that transmitting and receiving a data frame is necessary, the active period AP may be extended until after the end of the data frame in actual communication. In actual communication, by controlling the time for transmitting and receiving a data frame and the active period AP to overlap in time series, the device is always in a standby state, but after transmitting and receiving a data frame is completed, there is no particular problem if the device transitions to the sleep period SP without delay.

[0033] In a wireless communication system 1 to which the present invention is applied, such active periods AP and sleep periods SP are set for each node 3. At this time, each node 3 is assigned an active period AP and a sleep period SP that are chronologically different from each other. Here, the chronologically different active periods AP and sleep periods SP may include time periods in which the active periods AP or sleep periods SP overlap chronologically between each node 3. In other words, it is sufficient if there is a difference at even a moment in the chronological patterns of the active periods AP and sleep periods SP between the nodes 3.

[0034] 4 shows an example of active periods AP and sleep periods SP assigned to each intermittent standby cycle in nodes 3-1 to 3-3 that directly communicate data frames with CS2. The vertical axis of the graph in FIG. 4, which changes over time for each of nodes 3-1 to 3-3, represents power consumption. That is, power consumption increases during active periods AP, and decreases during sleep periods SP. It can be seen that the active periods AP and sleep periods SP assigned to nodes 3-1 to 3-3 are different from each other over time when viewed over consecutive intermittent standby cycles, in other words, when viewed over a group of consecutive superframes rather than in units of a single superframe.

[0035] In this way, by allocating active periods AP and sleep periods SP that are different in time series to each other among a plurality of nodes 3, it is possible to prevent a situation in which the frequency of active periods AP is extremely high for a particular node 3 while other nodes 3 continue to experience sleep periods SP. As a result, it is possible to balance power consumption among a plurality of nodes 3, and to prevent a situation in which only a certain node 3 consumes power extremely quickly, causing a disruption to efficient operation of the network.

[0036] Note that when nodes 3-1 to 3-3 are close to one another, data frames can be transmitted and received as long as at least one node is in an active period AP, so as shown in Fig. 4, if at least one node 3 is in an active period in each of the intermittent standby periods T1 to T3, the other nodes 3 may shorten their active periods AP and extend their sleep periods SP, or may set all of the intermittent standby periods T1 to T3 as sleep periods SP. In other words, if at least one node 3 is assigned an active period AP and a sleep period SP, or if at least one node 3 is assigned a sleep period, the other nodes 3 will be assigned only active periods AP in all of the consecutive intermittent standby periods T1 to T3.

[0037] Hereinafter, a state in which only an active period AP is assigned in one intermittent standby cycle is referred to as a fully active state, and a state in which an active period AP and a sleep period SP are assigned in one intermittent standby cycle, or in which only a sleep period SP is assigned, is referred to as a mixed sleep state.

[0038] In the example of Figure 4, in intermittent standby cycle T1, node 3-2 is assigned only active periods AP throughout the entire intermittent standby cycle, and is therefore in the fully active state, while the remaining nodes 3-1 and 3-3 are assigned active periods AP and sleep periods SP, and are therefore in the sleep-mixed state. In intermittent standby cycle T2, node 3-1 is in the fully active state, and the remaining nodes 3-2 and 3-3 are in the sleep-mixed state. In intermittent standby cycle T3, node 3-3 is in the fully active state, and the remaining nodes 3-1 and 3-3 are in the sleep-mixed state.

[0039] This allows the network as a whole to reduce power consumption by increasing the proportion of node 3's sleep period SP, and also allows at least one node 3 to be in a fully active state in each intermittent standby cycle, making it possible to send and receive data frames and standby without any omissions, thereby reducing communication delays and realizing so-called low-latency operation.

[0040] In the present invention, in each such intermittent standby cycle, one node 3 may be assigned to the fully active state and other nodes 3 to the sleep-mixed state. This assignment may be performed for each intermittent standby cycle, or for multiple intermittent standby cycles. This assignment itself is performed by the CS2. In such a case, the number or ratio of one node 3 to be assigned to the fully active state and other nodes to be assigned to the sleep-mixed state is determined in advance. The CS2 assigns the fully active state or the sleep-mixed state to each node 3 for each intermittent standby cycle according to the predetermined number or ratio of nodes 3 in the fully active state and nodes 3 in the sleep-mixed state.

[0041] In the process of this allocation, CS2 detects and counts the number of nodes 3 subordinate to itself. Some nodes 3 move and go out of the wireless communication range of CS2, while others newly enter the wireless communication range of CS2. As such, the number and number of nodes 3 subordinate to CS2 change over time, so every time the above-mentioned allocation is performed, all nodes 3 subordinate to itself are detected and counted.

[0042] Here, if it is predetermined that the percentage of nodes 3 in the fully active state is 1 / 5 of the total and the percentage of nodes 3 in the sleep-mixed state is 4 / 5 of the total, then all newly detected nodes 3 subordinate to itself are assigned as fully active nodes 3 and sleep-mixed nodes 3, respectively. If there are 10 newly detected nodes 3, two will be assigned to the fully active nodes 3 and eight will be assigned to the sleep-mixed nodes 3, according to the predetermined percentages. Which nodes 3 are assigned to the fully active state and which nodes 3 are assigned to the sleep-mixed state may be based on any rule, or may be determined randomly. Similarly, if the fully active state and the sleep-mixed state are specified as numbers rather than percentages, the allocation will be performed accordingly.

[0043] In this way, even if the number of nodes 3 subordinate to CS2 changes over time as a result of node 3 moving, it is possible to assign a fully active state in which all nodes are in active periods, an active period AP and a sleep period SP are assigned, or a sleep mixed state in which all nodes are assigned sleep periods SP.

[0044] In the present invention, when allocating the fully active state or the sleep-mixed state, the allocation may be performed based on the rules described below.

[0045] 5 shows an example in which active periods AP and sleep periods SP are assigned to chronologically consecutive intermittent standby cycles for nodes 3-1 to 3-3. In this example, in the first intermittent standby cycle T1, only node 3-2 is in a fully active state, and the other nodes 3-1 and 3-3 are assigned a mixed sleep state. In this intermittent standby cycle T1, data frames can be sent, received, and waited for without omission through node 3-2 in a fully active state, and by putting the other nodes 3-1 and 3-3 to sleep, it is possible to achieve both low-latency operation and power saving.

[0046] After this intermittent standby period T1 ends, in the next intermittent standby period T2, one of the nodes 3-1 and 3-3 other than node 3-2 is assigned the fully active state. When selecting one node from nodes 3-1 and 3-3 to be placed in the fully active state, the node is selected randomly. In other words, the nodes 3-1 and 3-3 are selected randomly under a probability distribution with equal probability of selection. A probability distribution is set so that the nodes 3-1 and 3-3 have equal probability of selection at 50% each, and the nodes are selected randomly under that probability distribution. This random selection is performed under the control of CS2.

[0047] In the intermittent standby period T2, when the node 3-3 is selected, it is set to the fully active state, and the remaining nodes 3-1 and 3-2 are configured to be in the sleep-mixed state.

[0048] Similarly, after the intermittent standby period T2 ends, in the next intermittent standby period T3, one of the nodes 3-1 and 3-2 other than node 3-3 is set to the fully active state. Similarly, when selecting one node to be set to the fully active state from nodes 3-1 and 3-2, the node is selected randomly under a probability distribution with equal probability.

[0049] In the intermittent standby period T3, when the node 3-2 is selected, it is set to the fully active state, and the remaining nodes 3-1 and 3-3 are configured to be in the sleep-mixed state.

[0050] This type of processing operation is executed in the same way for each intermittent standby period T4 and thereafter. As shown in Fig. 5, in the short term, there is a possibility that a bias will occur in the ratio at which the fully active state is selected among nodes 3-1 to 3-3. On the other hand, if this processing operation is executed an infinite number of times for intermittent standby periods T, the ratio at which the fully active state is selected among nodes 3-1 to 3-3 will become approximately equal, as shown in Fig. 5. This is because the fully active state is selected randomly under a probability distribution with equal probability, and therefore, if this processing operation is repeated an infinite number of times, the ratio at which the fully active state is selected will theoretically converge to be approximately equal.

[0051] This allows both low-latency operation and power saving in the entire network to be achieved, as described above, and furthermore, the power consumption among the nodes 3-1 to 3-3 can be smoothed out while maintaining a balance.

[0052] In the above example, an example consisting of three nodes 3-1 to 3-3 was described, but this is not limited to this, and the same applies when the number of nodes 3 is four or more.When selecting a node 3 in a fully active state in the next intermittent standby period T, the selection will be made randomly under a probability distribution with equal probability.

[0053] Furthermore, the fully active state is not limited to a state consisting of one node 3, but may involve the selection of multiple nodes 3. In such a case, multiple other nodes 3 must also be assigned.

[0054] Furthermore, in this embodiment, if there is variation in the ratio at which the fully active state is selected among nodes 3-1 to 3-3 shown in Fig. 5, control may be performed to eliminate this variation. If node 3-3 has a lower ratio at which the fully active state is selected than nodes 3-1 and 3-2, node 3-3 may be randomly selected under a probability distribution that increases the probability that the fully active state will be selected. That is, based on the ratio at which nodes 3 are actually selected as fully active nodes 3, in order to eliminate this variation, a probability distribution may be reset so that nodes 3 with lower ratios are more likely to be selected, and nodes 3 may be randomly selected.

[0055] This allows the power consumption between the nodes 3 to be further balanced and smoothed out.

[0056] In this case, other than selecting between the fully active state and the sleep mixed state based on the above-mentioned method between the nodes 3, when allocating for each intermittent standby cycle, if the proportion of the sleep period SP in one node 3 is increased, the proportion of the sleep period SP in the other nodes 3 is decreased, which is also included in the present invention. Conversely, if the proportion of the sleep period SP in one node 3 is decreased, the proportion of the sleep period SP in the other nodes 3 is increased, which is also included in the present invention.

[0057] For example, as shown in FIG. 5, the proportion of the sleep period SP of node 3-2 increases during the transition from intermittent standby cycle T1 to intermittent standby cycle T2. In this case, during the transition from intermittent standby cycle T1 to intermittent standby cycle T2, the sleep period SP of node 3-3, another node 3, is reduced, thereby increasing the active period AP. When there are two or more other nodes 3, the node 3 for which the sleep period SP is reduced may be selected randomly under a probability distribution with equal probability. Conversely, when the proportion of the sleep period SP of one node 3 is reduced, the proportions of the sleep period SP of the other nodes 3 are increased. Similarly, when there are two or more other nodes 3, the node 3 for which the proportion of the sleep period SP is increased may be selected randomly under a probability distribution with equal probability.

[0058] Furthermore, in the present invention, when at least one node 3 is assigned a sleep period, the other nodes 3 may be any nodes that are assigned an active period for a time period corresponding to the sleep period.

[0059] 6, for example, a sleep period SP is included in the intermittent standby cycle T1 in node 3-1. In such a case, an active period AP is allocated in node 3-2 during the time corresponding to that sleep period. In this way, when a sleep period SP is included in one node 3-1, the other node 3-2 can allocate the entire time corresponding to that sleep period SP to an active period AP, thereby enabling transmission, reception, and standby of data frames without omission.

[0060] Alternatively, for example, if the intermittent standby cycle T2 includes a sleep period SP in node 3-2, the time corresponding to the sleep period SP may be shared between node 3-1 and node 3-2 to fill in the active interval AP. Two or more nodes 3 may be allocated active periods during the time corresponding to the sleep period SP.

[0061] Furthermore, as shown in FIG. 7, the intermittent standby cycle T2 may include a total sleep period in which all nodes 3-1 to 3-3 simultaneously enter a sleep state. In this intermittent standby cycle T2, the period other than the total sleep period is an active period AP. In the example shown in FIG. 7, this active period AP is distributed among nodes 3-1 to 3-3. The active period AP allocated outside the total sleep period may be allocated to one or more nodes. The proportion of the total sleep period in the intermittent standby cycle is set to be equal to or less than the proportion of a preset maximum allowable total sleep period. This maximum allowable total sleep period is preset within a range of 0 to 1 / 2 the length of the intermittent standby cycle. This is because if the total sleep period is too long, it becomes difficult to transmit and receive data frames and to wait for them without any omissions. A maximum allowable total sleep period of 0 means that the total sleep period is 0. In other words, at each timing in the intermittent standby cycle, one or more nodes 3-1 to 3-3 are always in an active period. [Explanation of symbols]

[0062] 1. Wireless communication systems 2 CS 3 nodes

Claims

1. In a wireless communication system in a network in which data frames are transmitted and received between two or more nodes arranged around a collection control station based on time division multiple access (TDMA), each of the nodes is assigned an active period during which the node can transmit and receive the data frame and a sleep period during which the node does not operate, in successive intermittent standby periods; the active period and the sleep period are assigned to the nodes, each of which is different in time series from the other; When at least one node is assigned the sleep period, the other one or more nodes are assigned the active period for a time period corresponding to the sleep period. A wireless communication system comprising:

2. In a wireless communication system in a network in which data frames are transmitted and received between two or more nodes arranged around a collection control station based on time division multiple access (TDMA), each of the nodes is assigned an active period during which the node can transmit and receive the data frame and a sleep period during which the node does not operate, in successive intermittent standby periods; the active period and the sleep period are assigned to the nodes, each of which is different in time series from the other; In the intermittent standby cycle, a total sleep period in which all nodes simultaneously suspend operation and an active period in which one or more nodes are active are allocated, and the proportion of the total sleep period in the intermittent standby cycle is set to be equal to or less than a proportion of a preset maximum allowable total sleep period. A wireless communication system comprising:

3. The collection control station assigns a plurality of newly detected nodes to one node to which the predetermined active period and the predetermined sleep period are assigned and to other nodes to which only the active period is assigned, depending on the number or ratio of the one node and the other nodes.

3. The wireless communication system according to claim 2, wherein:

4. In a wireless communication system in a network in which data frames are transmitted and received between two or more nodes arranged around a collection control station based on time division multiple access (TDMA), each of the nodes is assigned an active period during which the node can transmit and receive the data frame and a sleep period during which the node does not operate, in successive intermittent standby periods; the active period and the sleep period are assigned to the nodes, each of which is different in time series from the other; When performing allocation for each intermittent standby cycle, if the ratio of the sleep period in one node is increased, the ratio of the sleep period in one or more other nodes is decreased, and if the ratio of the sleep period in one node is decreased, the ratio of the sleep period in one or more other nodes is increased. A wireless communication system comprising:

5. When there are a plurality of the one or more other nodes, any one of the other nodes that decreases the proportion of the sleep period or increases the proportion of the sleep period is selected with equal probability.

5. The wireless communication system according to claim 4, wherein:

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