JP7119750B2 - Wireless communication system, wireless communication device, and wireless communication program - Google Patents

Description

TECHNICAL FIELD The present invention relates to a wireless communication system, a wireless communication device, and a wireless communication program, and can be applied to, for example, a wireless multi-hop network.

In a wireless network system consisting of a plurality of wireless communication devices (hereinafter also referred to as "nodes") and a management device that manages each node, if each node cannot directly communicate with the management device, other nodes cannot directly communicate with each other. A form of multi-hop network that relays communications on behalf of This form of multi-hop network allows distant nodes to communicate with the management device.

In addition, it is often difficult to secure a power source depending on the environment in which the wireless network system is constructed (installed). In such an environment, a network can be constructed by operating nodes on battery power. When the node is operated by battery power, the node operates intermittently to improve the battery life. Intermittent operation is a power saving control technology in which a node periodically switches between a "sleep state" in which the node does not communicate and an "active state" in which the node communicates.

As an example of intermittent operation, the node is in a basic sleep state and becomes active at regular intervals to check whether there is data to receive. Communication between intermittent nodes requires that the data sending node send data when the receiving node is active. Therefore, the data transmitting node transmits a packet indicating that there is data to be transmitted (hereinafter also referred to as a "wakeup packet") only during the sleep period of the receiving node. The wakeup packet includes data transmission timing, and when the receiving node receives the wakeup packet, it becomes active based on the data transmission timing included in the wakeup packet and receives data. In communication between intermittently operating nodes in this way, compared to communication between non-intermittently operating nodes, it takes an extra sleep period (intermittent period) to transmit one packet.

By the way, when a node that newly participates in a multi-hop network (hereinafter also referred to as a "participating node") cannot directly communicate with the management device when joining (joining) the network, it sends a network participation request packet to the participating node. A node (hereinafter also referred to as a "parent node") to be relayed on behalf of is selected from among the nodes that have already joined the network.

In order to select such a parent node, a participating node broadcasts a packet (hereinafter also referred to as "adjacent node search packet") searching for its own peripheral nodes (hereinafter also referred to as "adjacent node"). . An adjacent node that receives the adjacent node search packet returns a response packet to the participating node. At this time, if the transmission timing of the response packet of the adjacent node coincides with that of another adjacent node, the packets collide and the participating node cannot receive the response packet. Therefore, each neighbor node waits a random time after receiving a neighbor search packet before sending a response packet in order to avoid collisions. The participating node then selects a parent node from among the received response packets.

Various methods are conceivable for selecting a parent node. For example, it is conceivable to select a node with the highest received signal strength (RSSI value) of a received packet. A joining node can determine the best parent node by collecting the response packets of all neighboring nodes and selecting a parent node among them. However, in order for all adjacent nodes to transmit response packets without collision, it is necessary to set a sufficiently long random waiting time for response packets in consideration of the high density of nearby nodes. Participating nodes must also wait up to the maximum random waiting time for response packets. In particular, when a node operates intermittently, it takes time to transmit one packet by the intermittent period, so the waiting time for response packets increases in proportion to the number of adjacent nodes and the intermittent period.

As described above, in a wireless network system composed of nodes that operate intermittently, there is a problem that it takes time to select a parent node of a participating node. As countermeasures against this problem, for example, the techniques described in Patent Documents 1 to 3 below can be cited.

The techniques described in Patent Literatures 1 and 2 relate to methods for selecting an optimal parent node in a multihop network. In the techniques described in Patent Literatures 1 and 2, the participating node receives information about the adjacent node transmitted from the adjacent node (the number of current child nodes, the number of hops to the management device, the RTT (Round Trip Timing) to the management device. ), etc.) and selects the most likely neighbor node as the parent node.

Further, in Patent Document 2, each node calculates the packet loss rate and SN ratio (Signal-to-Noise ratio) from the communication history with the adjacent node even after joining the network, and selects the optimal parent node from this information. change dynamically.

Patent Document 3 discloses a method of selecting a data communication partner (destination node or relay node). In the technique described in Patent Document 3, each node transmits an intermittent transmission signal at regular intervals. A node that transmits data waits for an intermittent transmission signal from a node within its direct communication range for a certain period of time, and selects a communication partner according to a radio selection rule that includes indicators such as remaining battery power from the source node of the received intermittent transmission signal. select. At this time, nodes that do not satisfy the minimum conditions of the radio selection rule are excluded from communication partner candidates.

The technique described in Patent Document 3 does not select the optimum communication partner, but rather selects a node that satisfies at least a certain condition from intermittent transmission signals received during a certain period of time. Different from the described technique.

JP 2009-302694 A Japanese Patent Publication No. 2011-523830 JP 2015-179923 A

However, the techniques described in Patent Literatures 1 and 2 are both techniques related to indicators for selecting the optimal parent node, and in order to select the optimal parent node, wait for response packets from all adjacent nodes. That is the premise.

Also, the technology described in Patent Document 3 is considered to be able to quickly select a parent node that satisfies a certain condition by adjusting the intermittent transmission signal waiting time of the data transmission node. However, with the technique described in Patent Document 3, the selected parent node is not necessarily the optimal parent node, so depending on the selected parent node, communication quality may deteriorate compared to when the optimal parent node is selected. be done.

Therefore, in a network in which each node operates intermittently, there is a demand for a wireless communication system, wireless communication device, and wireless communication program that can reduce the time required to select a parent node and select a parent node with high communication quality.

A first aspect of the present invention provides a wireless communication system having a wireless communication device that requests connection to a network and performs wireless communication by intermittent operation, and a plurality of wireless relay devices that accept the connection of the wireless communication device. (1-1) a first communication means for transmitting a neighbor search packet for searching for the wireless relay device to a surrounding network and receiving a response packet to the neighbor search packet; (1-2) response reception waiting time calculation means for calculating a reception waiting time that is the reception waiting time of the response packet; and (1-3) the reception waiting time calculated by the response reception waiting time calculation means. (1-4) first storage means for storing the received response packet; (1-5) the device operating in either an intermittent or continuous mode ( 1-6 ) after transmitting the neighbor search packet, using the operation mode switching means to switch the operation state from intermittent operation to continuous operation; When the timer means of (1) notifies that the reception standby time has elapsed, the wireless relay device to be connected to is selected from among the wireless relay devices that are the transmission sources of the response packets received during the reception standby time. a first processing means for switching the operation state from continuous operation to intermittent operation using the operation mode switching means after selecting a connection destination; 2-1) a second communication unit that receives the neighbor search packet and transmits the response packet to the neighbor search packet; and (2-2) a transmission waiting time that is a waiting time until the response packet is transmitted. (2-3) second timer means for managing the elapse of the transmission waiting time calculated by the response transmission waiting time calculating means; (2-4) the second and second processing means for controlling the second communication means to transmit the response packet by a communication method in continuous operation when the timer means of No. 2 notifies that the transmission standby time has elapsed. It is characterized by

According to a second aspect of the present invention, a wireless communication device that requests connection to a network and performs wireless communication by intermittent operation: and receive a response packet to the neighbor search packet; 3) first timer means for managing elapse of the reception waiting time calculated by the response reception waiting time calculating means; ( 4) first storage means for storing the received response packet; ( 6 ) operation mode switching means for switching the operation state of the wireless communication device operating in either an intermittent operation state or a continuous operation state; is switched from intermittent operation to continuous operation, and when the first timer means notifies that the reception standby time has elapsed, the wireless relay device that is the transmission source of the response packet received during the reception standby time a first processing means for selecting the wireless relay device as a connection destination from among, and after selecting the connection destination, switching the operation state from continuous operation to intermittent operation using the operation mode switching means; It is characterized by

A wireless communication program according to a third aspect of the present invention requests a connection to a network and searches for a computer installed in a wireless communication device that performs wireless communication by intermittent operation (1) for a wireless relay device that accepts its own connection. a first communication means for transmitting a neighbor search packet to a surrounding network and receiving a response packet to the neighbor search packet; (3) first timer means for managing the elapse of the reception waiting time calculated by the response reception waiting time calculating means; (4) a second timer for storing the received response packet; (5) operation mode switching means for switching the operation state of the wireless communication device operating in either intermittent operation or continuous operation; ( 6 ) after transmitting the neighbor search packet, the operation When the operating state is switched from the intermittent operation to the continuous operation using the mode switching means, and when the first timer means notifies that the reception standby time has elapsed, the response received during the reception standby time. Selecting the wireless relay device as a connection destination from the wireless relay devices that are packet transmission sources, and after selecting the connection destination, switching the operation state from continuous operation to intermittent operation using the operation mode switching means . It is characterized by functioning as one processing means .

According to the present invention, in a network in which each node operates intermittently, it is possible to reduce the time required to select a parent node and select a parent node with high communication quality.

1 is a block diagram showing the functional configuration of a wireless communication device according to an embodiment; FIG. 1 is a block diagram showing an example of the overall configuration of a radio communication system according to an embodiment; FIG. 3 is a block diagram showing the functional configuration of the radio relay device according to the embodiment; FIG. 4 is a flow chart showing the operation of the wireless communication device according to the embodiment (operation up to selection of a node that has already joined). 7 is a flowchart showing the operation of the operation state selection unit (processing for calculating operation switching information) according to the embodiment; FIG. 10 is an explanatory diagram showing transmission timings of response packets during response packet reception waiting time according to the embodiment; 6 is a flowchart showing the operation of the wireless relay device (joined node) according to the embodiment (operation when receiving a neighbor search packet);

(A) Main Embodiment Hereinafter, an embodiment of a wireless communication system, a wireless communication device, and a wireless communication program according to the present invention will be described in detail with reference to the drawings.

(A-1) Configuration of Embodiment (A-1-1) Overall Configuration FIG. 2 is a block diagram showing an example of the overall configuration of a wireless communication system according to an embodiment.

First, the configuration of the radio communication system 1 will be described.

In the radio communication system 1, a radio communication device 10, a plurality of radio relay devices 20 (20-1 to 20-k), and a base station 30 are arranged. Although the number of devices arranged in the radio communication system 1 is not limited, in the radio communication system 1 of this embodiment, at least one radio communication device 10 and a plurality of radio relay devices 20 (20- 1 to 20-k) and one base station 30 are arranged.

Also, in the wireless communication system 1, it is assumed that a multi-hop network is configured by the wireless relay device 20 and the base station 30, which are wireless communication devices that have already joined the network. Hereinafter, the wireless communication device 10, the wireless relay device 20, and the base station 30 are also collectively referred to as "nodes." A node (wireless communication device 10) that selects a connection destination in order to participate in the network of the wireless communication system 1 is called a "participating node", and a connected node (wireless relay device 20) that accepts connection from the participating node is called a "participating node". shall be referred to as a "subscribed node". An adjacent node that can directly communicate with a certain node is called an "adjacent node". Although the communication method (communication medium) between devices (between nodes) in the wireless communication system 1 is not limited, for example, various wireless LAN interface communication methods can be applied.

Next, an overview of features of the wireless communication system 1 of this embodiment will be described.

In this embodiment, the joining node changes its operating state from intermittent operation to always active continuous operation after sending the neighbor discovery packet. An adjacent node (joined node) of the joining node transmits a response packet by a communication method for non-intermittent operation (that is, a method of transmitting only data packets without transmitting wakeup packets). After waiting for a response packet for a certain period of time, the joining node selects the neighbor node with the highest path quality value from the received response packets as the parent node.

The path quality value represents the communication quality value between itself and the base station 30. For example, the link quality value on the route to the base station 30 (for example, a value calculated based on the RSSI value or the packet loss rate) ). Also, the waiting time of the response packet of the participating node is calculated from the probability that all neighboring nodes can transmit the response at the maximum node density assumed in the wireless communication system 1 . Furthermore, in consideration of battery life, the participating node may determine whether to change the operation state to continuous operation or continue to operate intermittently according to the number of trials of parent node selection.

Next, detailed configurations of the wireless communication device 10 (participating node) and the wireless relay device 20 (joined node) will be described. Since the base station 30 has the same configuration as the existing one, its explanation is omitted.

(A-1-2) Detailed Configuration of Wireless Communication Device 10 (Participating Node) FIG. 1 is a block diagram showing the functional configuration of the wireless communication device according to the embodiment. In FIG. 1 , the wireless communication device 10 has a communication section 11 , a processing section 12 , an operating state selection section 13 , a response reception waiting time calculation section 14 , a storage section 15 and a timer section 16 .

The wireless communication device 10 may be constructed, for example, by installing a program in a computer having a processor and memory. Also, the wireless communication device 10 may be partially or wholly configured using hardware (for example, a dedicated semiconductor chip, an electric circuit, or the like).

The communication unit 11 has means for transmitting and receiving radio signals. For example, the communication unit 11 demodulates a signal received by an antenna (not shown) and receives packets included in the signal. Also, the communication unit 11 modulates the packet sent from the processing unit 12, converts it into a radio signal, and starts transmitting the radio signal using an antenna (not shown).

The processing unit 12 has means for switching operation states (intermittent operation and continuous operation), generating various packets, and selecting a parent node.

First, the processing unit 12 needs to select a node that has already joined in order to participate in the network (wireless communication system 1). The operation state selection unit 13 is requested to provide information for switching (hereinafter, also referred to as "operation switching information").

Subsequently, the processing unit 12 notifies the response reception wait time calculation unit 14 of the operation switching information acquired from the operation state selection unit 13, and waits for the calculation (acquisition) of the reception wait time for the response packet to the neighbor search packet. A request is made to the time calculation unit 14 . The processing unit 12 requests the timer unit 16 to set a timer for the response reception waiting time acquired from the response reception waiting time calculation unit 14 .

Also, the processing unit 12 generates an adjacent search packet and requests the communication unit 11 to transmit the packet. Note that the neighbor search packet includes operating state information and a waiting time for receiving a response packet.

Upon receiving the response packet from the communication unit 11, the processing unit 12 requests the storage unit 15 to store the response packet received from the adjacent node. Further, when the processing unit 12 receives notification of the elapse of the reception waiting time from the timer unit 16, the processing unit 12 acquires a response packet from the storage unit 15 and selects a joined node to be connected (selects a parent node).

The operation state selection unit 13 has means for acquiring the parent selection failure count R from the storage unit 15 and using the acquired parent selection failure count R to calculate operation switching information. The parent selection failure count R is the number of retries from the transmission of the neighbor search packet without receiving even one response packet during the response packet reception waiting time after the neighbor search packet is transmitted. The operation state selection unit 13 notifies the processing unit 12 of the calculated operation switching information.

The response reception waiting time calculation unit 14 has means for calculating the reception waiting time of the response packet in response to a request from the processing unit 12 . The response reception waiting time calculation unit 14 acquires the maximum node density information M (the number of adjacent nodes) of the network system from the storage unit 15 and uses it. The response reception waiting time calculation unit 14 notifies the processing unit 12 of the calculated reception waiting time.

The storage unit 15 has means for storing the parent selection failure count R, the maximum node density information M of the network system, and the response packet (response packet information) transmitted from the adjacent node in response to the neighbor search packet. The maximum node density information M of the network system is determined in advance by the system administrator, for example.

The timer unit 16 has means for setting a timer for a time specified by the processing unit 12 and notifying the processing unit 12 when the specified time has passed.

(A-1-3) Detailed Configuration of Wireless Relay Device 20 (Joined Node) FIG. 3 is a block diagram showing the functional configuration of the wireless relay device according to the embodiment. In FIG. 3 , the radio relay device 20 has a communication section 21 , a processing section 22 , a response transmission waiting time calculation section 23 and a timer section 24 .

The wireless relay device 20 may be constructed by installing a program in a computer having a processor and memory, for example. Also, the wireless relay device 20 may be partially or wholly configured using hardware (for example, a dedicated semiconductor chip, an electric circuit, or the like).

The communication unit 21 has means for transmitting and receiving radio signals. For example, the communication unit 21 demodulates a signal received by an antenna (not shown) and receives packets included in the signal. Further, the communication unit 21 modulates the packet sent from the processing unit 22, converts it into a radio signal, and starts transmitting the radio signal using an antenna (not shown).

When the neighbor search packet is received from the communication unit 21, the processing unit 22 notifies the response transmission wait time calculation unit 23 of the operation switching information included in the neighbor search packet and the reception wait time of the response packet, and determines the transmission wait time of the response packet. is requested to the response transmission waiting time calculation unit 23 . The processing unit 22 requests the timer unit 24 to set the transmission waiting time acquired from the response transmission waiting time calculating unit 23 . Further, when the processing unit 22 receives the notification that the transmission waiting time has elapsed from the timer unit 24, the processing unit 22 generates a response packet and requests the communication unit 21 to transmit the packet. The response packet contains its own path quality value and the RSSI value when the neighbor search packet was received.

The response transmission waiting time calculation unit 23 has means for calculating the transmission waiting time of the response packet using the operation switching information received from the processing unit 22 and the reception waiting time of the response packet. The response transmission waiting time calculation unit 23 notifies the processing unit 22 of the calculated transmission waiting time of the response packet.

The timer unit 24 has means for setting a timer for a time specified by the processing unit 22 and notifying the processing unit 22 when the specified time has passed.

(A-2) Operation of Embodiment Next, the operation of the wireless communication system 1 of the embodiment having the configuration as described above will be described.

In the following, each device ( The operation of the participating node, the joined node) will be described with reference to FIGS. 4 to 7. FIG.

The operation of the participating node is step S101 (FIGS. 4 and 5), which will be described later. Also, the operation of the joined node is step S102 (FIG. 7), which will be described later.

[Step S101: Operation of Participating Node]
FIG. 4 is a flowchart showing the operation of the wireless communication device (participating node) according to the embodiment (operation up to selection of a joined node).

After the power is turned on, the participating node (processing unit 12) requests the operation state selection unit 13 to acquire information (operation switching information) as to whether to switch the operation state during the parent selection operation (S101-1). ).

The operation state selection unit 13 calculates operation switching information in accordance with the process of FIG. 5, which will be described later (S101-2). The response waiting time calculation unit 14 returns the calculated operation switching information to the processing unit 12 .

When the processing unit 12 acquires the operation switching information, the processing unit 12 notifies the operation switching information to the response reception waiting time calculating unit 14, and requests to calculate (acquire) the reception waiting time of the response packet for the neighbor search packet transmitted by itself. (S101-3).

Specifically, the response reception waiting time calculation unit 14 acquires the maximum node density information M of the network system from the storage unit 15 in order to calculate the reception waiting time of the response packet.

Next, the response reception waiting time calculator 14 calculates the reception waiting time of the response packet using, for example, the following equation (1).

Equation (1) above represents the probability (P) that a joined node can send a response packet to a joining node. P is calculated under the following two preconditions.

The first precondition is that the joined node selects the timing of transmitting the response packet in units of slots divided by the transmission time of the response packet as shown in FIG. Here, the transmission time of the response packet is obtained from the value obtained by dividing the size of the response packet by the data transmission rate and the intermittent operation period. When the operation switching information is "switch" (that is, the parent selection operation is executed in continuous operation), the intermittent operation period is "0".

The second precondition is that each node performs data communication by the CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) method. That is, even if a certain joined node attempts to transmit a response packet at the same timing (slot) as other x nodes, it can transmit the response packet with a probability of 1/(x+1).

Expression (1) will be explained based on the above preconditions. N in equation (1) indicates the maximum number of adjacent nodes, and slot indicates the number of slots that can be selected as the transmission timing of the response packet. The term in Σ on the right side of equation (1) is such that if a certain joined node selects a certain slot for response packet transmission, i out of the other N joined nodes transmit in the same slot. P is obtained by calculating the sum of all possible values of i (that is, from i to N).

The waiting time for receiving a response packet is determined by the slot value, and here the slot value (slot_n) is calculated so that P is 99% or more. The response packet reception waiting time that is finally obtained is "slot_n"×"response packet transmission time".

The response reception waiting time calculating unit 14 returns the calculated reception waiting time of the response packet to the processing unit 12 .

When the processing unit 12 acquires the reception waiting time of the response packet, it generates a neighbor search packet and transmits (for example, broadcasts) the packet via the communication unit 11 (S101-4). At this time, the neighbor search packet includes the operation switching information and the waiting time for receiving the response packet. The timer unit 16 sets a timer for the reception waiting time of the response packet.

If the operation switching information is "switch", the processing unit 12 switches the operation state of the node from intermittent operation to continuous operation (S101-5).

The timer unit 16 sets a timer for the waiting time for receiving the response packet, and when it times out (when the waiting time for receiving the response packet has elapsed), the process proceeds to step S101-9, which will be described later (S101-6).

On the other hand, when the processing unit 12 receives a response packet from the communication unit 11 until the waiting time for receiving the response packet has elapsed, the processing unit 12 receives the received response packet information (path quality value, RSSI value at the time of receiving the neighbor search packet, etc.). ) and the RSSI value at the time of receiving the response packet are stored in the storage unit 15 (S101-7, S101-8).

When the processing unit 12 receives from the timer unit 16 the notification that the waiting time for receiving the response packet has elapsed, the processing unit 12 acquires the received response packet from the storage unit 15, and calculates the path quality value and the RSSI value of the neighbor search packet included in each response packet. , from the RSSI value of the response packet, the path quality value is calculated when each subscribed node of the transmission source is selected as the connection destination (S101-9). Here, the link quality values of the joining node and the joined node are obtained from the above two RSSI values (the RSSI value of the neighbor search packet and the RSSI value at the time of receiving the response packet). The processing unit 12 selects the joined node with the highest path quality value as the connection destination (parent node).

Then, when the current operation state is continuous operation, the processing unit 12 switches the operation state from continuous operation to intermittent operation (S101-10).

Next, a supplementary description of the processing (calculation of operation switching information) in step S101-2 described above will be given. FIG. 5 is a flowchart illustrating the operation of the operation state selection unit (processing for calculating operation switching information) according to the embodiment.

Upon receiving the operation switching information acquisition request from the processing unit 12, the operation state selection unit 13 acquires the parent selection failure count R from the storage unit 15 in order to determine whether to switch the operation state (S101-2A). .

The operation state selection unit 13 determines whether or not the parent selection failure count R has been acquired from the storage unit 15 (whether or not the parent selection failure count R exists in the storage unit 15) (S101-2B).

When the parent selection failure count R does not exist in the storage unit 15 (that is, when the attempt is made for the first time), the operation state selection unit 13 sets the parent selection failure count R to "0" (S101-2C). On the other hand, if the parent selection failure count R exists, the operating state selection unit 13 adds 1 to the current count (value) of the parent selection failure count R (S101-2D).

Next, the operation state selection unit 13 calculates (determines) whether the parent selection failure count R matches any of an in the following equation (2) ( _S101-2E ).

If the parent selection failure count R matches with any of an in formula (2), the operation state selection unit 13 selects "switching" as the operation switching information ( _S101-2F ). , the operation switching information is selected as "non-switching" (S101-2G).

From the above formula (2), "switching" occurs when the parent selection failure count R is, for example, "0", "2", "5", "9", . This means that each time the parent selection operation fails in , the number of parent selection operations is incremented by one with "non-switching".

[Step S102: Operation of Joined Node]
FIG. 7 is a flow chart showing the operation of the wireless relay device (joined node) according to the embodiment (operation when receiving a neighbor search packet).

Upon receiving the neighbor search packet via the communication unit 21, the joined node (processing unit 22) notifies the response transmission wait time calculation unit 23 of the operation switching information and the reception wait time of the response packet included in the neighbor search packet. Then, the response transmission waiting time calculator 23 is requested to calculate (acquire) the transmission waiting time of the response packet (S102-1).

The response transmission waiting time calculation unit 23 calculates the transmission waiting time of a response packet to be transmitted in response to the neighbor search packet (S102-2).

Specifically, the response transmission waiting time calculation unit 23 calculates the number of slots that can be selected as the transmission waiting time of the response packet from the response reception waiting time and operation switching information included in the neighbor search packet. The number of slots is obtained by dividing the response reception waiting time by the transmission time of the response packet (if the operation switching information is "non-switching", the intermittent operation cycle is also included in the transmission time). Next, one slot is randomly selected as the transmission timing of the response packet from among the determined number of slots.

The response transmission waiting time calculation unit 23 notifies the processing unit 22 of the “selected slot”דresponse packet transmission time” as the response packet transmission waiting time.

The processing unit 22 requests the timer unit 24 to set the transmission waiting time of the response packet in the timer, and upon receiving the time-out notification from the timer unit 24, executes the following processing (S102-3).

The processing unit 22 generates a response packet and transmits the packet from the communication unit 21 with the participation node as the destination (S102-4). At this time, if the operation switching information is "switching", the response packet is transmitted by the communication method in the continuous operation state (wake-up packet is not transmitted), and if the operation switching information is "not switching", it is transmitted by the intermittent operation. communication method.

(A-3) Effects of Embodiment According to this embodiment, the following effects are obtained.

In the wireless communication system 1 (a network in which each node operates intermittently), a participating node switches from intermittent operation to continuous operation only from the time it transmits a neighbor search packet until it selects a connected node that has already joined. Also, the joined node transmits a response packet to the neighbor discovery packet by the communication method of continuous operation state. This reduces the time required for the joining node to receive response packets from all adjacent joined nodes, thereby reducing the time required for parent node selection.

Further, this embodiment is characterized in that the reception wait time and the transmission wait time of the response packet are obtained from the probability that all adjacent nodes can transmit the response packet at the maximum node density assumed by the network system. As a result, the participating node can receive response packets from almost all neighboring nodes during the waiting time for receiving response packets, so that it is possible to select a parent node with high communication quality.

In this embodiment, based on the number of failures of the parent selection operation, the participating node determines whether to perform the parent selection operation in a continuous operation state or an intermittent operation state. It is characterized by reducing the frequency of implementation in the state. As a result, power saving performance can be improved, for example, by preventing wasteful power consumption when there are no joined nodes around the participating node.

(B) Other Embodiments The present invention is not limited to the above-described embodiments, and modified embodiments as exemplified below can also be mentioned.

(B-1) In the above embodiment, the response packet reception wait time and transmission wait time are calculated so that all adjacent joined nodes can transmit response packets (that is, the quality of the selected parent node is emphasized). However, it is not limited to this and may be calculated from other requirements of the wireless network system.

For example, in a system in which the parent node selection time is included in the requirements, the reception wait time and the transmission wait time may be determined so as to satisfy the requirements. Alternatively, in systems where node battery life is critical, there is a method to derive it from the battery life requirements. For example, the expected number of node restarts until the battery life of the participating node, the average number of neighbor search packet transmissions per startup, the average power consumption during normal operation, etc. A method of calculating and presetting the time is conceivable.

Also, for example, each time a participating node sends a neighbor discovery packet, the reception wait time required to meet the requirements is calculated each time from the node's operating time, remaining battery power, normal power consumption, etc. It is also possible to consider a method of obtaining Furthermore, a method is conceivable in which the participating node statically retains in advance the relationship between the battery life and the reception wait time at the time of transmitting the neighbor search packet, and determines the reception wait time using that information. When determining the reception waiting time from the battery life requirements, the reception waiting time for the response packet may differ depending on the participating node. The latency can be known (that is, this value can be used as the maximum latency to send response packets).

(B-2) In the above embodiment, the frequency of switching to the continuous action during the parent selection action by the participating node (action state selection unit 13) is gradually reduced each time the parent selection action fails (see FIG. 5 processing) has been described, but the present invention is not limited to this. For example, if the participating node repeats the parent selection operation by the continuous operation x times and the joined node of the connection destination is not selected, a method of switching to the intermittent operation from the next trial can be considered. Also, a method is conceivable in which the participating node predetermines a threshold for the remaining battery capacity of the node, and intermittently selects the parent when the remaining battery capacity is equal to or less than the threshold.

(B-3) In the above embodiment, no mention was made of the case where a plurality of neighbor search packets were received before the joined node sent the response packet. A conceivable method is to collectively transmit the responses to the . In this case, the joined node broadcasts the set of the address of each joining node and the RSSI value of the neighbor search packet in the response packet. Since this method can reduce the number of transmissions of response packets, it is expected to reduce the power consumption of already-joined nodes and suppress network congestion.

(B-4) In the above embodiment, the joined node always sends a response packet to the joining node, but the present invention is not limited to this. For example, if a node that has already joined detects that a node with better communication quality has sent a response packet during the response packet transmission wait time, it can cancel the transmission of its own response packet. Thereby, the joined node can prevent unnecessary response packets from being transmitted, and can further reduce the collision probability of the response packets.

(B-5) In the above embodiment, the operation in which the joining node waits for the waiting time for receiving the response packet and selects a joining node as a connection destination is shown, but the present invention is not limited to this. For example, a joining node may select a node as a connection destination upon receiving a response packet from a joined node that satisfies a certain path quality. As a result, the participating node can reduce the time required for parent node selection, especially when performing the parent selection operation in an intermittent operation state.

(B-6) In the above embodiment, an example is shown in which the participating node calculates the waiting time for receiving a response packet each time. A method of storing in the unit 15 is also conceivable.

DESCRIPTION OF SYMBOLS 1... Wireless communication system 10... Wireless communication apparatus 11... Communication part 12... Processing part 13... Operation state selection part 14... Response reception waiting time calculation part 15... Storage part 16... Timer part 20... Radio relay device 21 Communication unit 22 Processing unit 23 Response transmission waiting time calculation 24 Timer unit 30 Base station M Maximum node density information of network system R Parent selection failure count.

Claims (14)

In a wireless communication system having a wireless communication device that requests connection to a network and performs wireless communication by intermittent operation, and a plurality of wireless relay devices that accept connections from the wireless communication device,
The wireless communication device
a first communication means for transmitting a neighbor search packet for searching for the wireless relay device to a surrounding network and receiving a response packet to the neighbor search packet;
response reception waiting time calculation means for calculating a reception waiting time that is the reception waiting time of the response packet;
first timer means for managing the elapse of the reception waiting time calculated by the response reception waiting time calculating means;
a first storage means for storing the received response packet;
operation mode switching means for switching the operation state of the wireless communication device operating in either an intermittent operation state or a continuous operation state;
After transmitting the neighbor search packet, the operating state is switched from the intermittent operation to the continuous operation using the operation mode switching means, and when the first timer means notifies that the reception standby time has elapsed, the Selecting the wireless relay device as a connection destination from the wireless relay devices that are transmission sources of the response packets received during the reception standby time, and after selecting the connection destination, the operation using the operation mode switching means. a first processing means for switching the state from continuous operation to intermittent operation;
The wireless relay device
a second communication means for receiving the neighbor search packet and transmitting the response packet to the neighbor search packet;
response transmission waiting time calculation means for calculating a transmission waiting time that is a waiting time until the response packet is transmitted;
a second timer means for managing the elapse of the transmission waiting time calculated by the response transmission waiting time calculating means;
a second processing means for controlling the second communication means to transmit the response packet by a communication method in continuous operation when the second timer means notifies that the transmission waiting time has elapsed; A wireless communication system comprising: The wireless communication device further comprises operation state selection means for determining whether or not to switch the operation state to a continuous operation state after transmitting the neighbor search packet,
The first processing means selects the wireless relay device as a connection destination while keeping the operation state intermittent operation when the operation state selection means determines not to switch the operation state. a series of processes to
The neighbor search packet includes operation information indicating that the operation state is intermittent operation,
2. The wireless communication system according to claim 1, wherein the second processing means controls the second communication means to transmit the response packet in an intermittent communication mode based on the operation information. . 3. The operation state selecting means reduces the frequency of switching the operation state to the continuous operation state as the number of failures in the series of operations for selecting the wireless relay device to be connected increases. A wireless communication system as described. 3. The operation state selection means according to claim 2, wherein when a series of operations for selecting the wireless relay device to be connected to is failed a predetermined number of times, the operation state selection means does not switch the operation state to the continuous operation state. wireless communication system. wherein the operation state selection means does not switch the operation state to continuous operation when the remaining battery level of the wireless communication device at the time of transmission of the neighbor search packet is below a predetermined threshold. Item 3. The wireless communication system according to item 2. The wireless communication system according to any one of claims 1 to 5, wherein said reception waiting time and said transmission waiting time are calculated using the number of neighboring nodes at maximum node density of the network. 7. The wireless communication system according to claim 6, wherein the reception standby time and the transmission standby time are calculated from a probability value that the wireless relay device can transmit the response packet at the maximum node density. . The radio communication system according to any one of claims 1 to 5, wherein said reception waiting time and said transmission waiting time are calculated based on time requirements of said radio communication system. The wireless communication system according to any one of claims 1 to 5, wherein said reception standby time and said transmission standby time are calculated from battery life requirements required for said wireless communication system. The first processing means transmits the response packet from the wireless relay device satisfying a predetermined communication quality even before the first timer means notifies that the reception waiting time has elapsed. The wireless communication system according to any one of claims 1 to 9, wherein the wireless relay device to be connected is selected at the time of reception. The wireless communication device is a plurality,
The wireless relay device further has a second storage means for storing the received neighbor search packet,
2. The second processing means controls to transmit the response packets to the plurality of neighbor search packets received during the transmission standby time as one response packet. 11. The wireless communication system according to any one of 10. the second communication means intercepts the response packet transmitted by the other wireless relay device;
12. The second processing means according to any one of claims 1 to 11, characterized in that, when receiving the response packet from another wireless relay device having better communication quality than itself, the second processing means cancels transmission of the response packet. 1. A wireless communication system according to claim 1. In a wireless communication device that requests connection to a network and performs wireless communication by intermittent operation,
a first communication means for transmitting a neighbor search packet for searching for a wireless relay device that accepts its own connection to a surrounding network and receiving a response packet to the neighbor search packet;
response reception waiting time calculation means for calculating a reception waiting time that is the reception waiting time of the response packet;
first timer means for managing the elapse of the reception waiting time calculated by the response reception waiting time calculating means;
a first storage means for storing the received response packet;
operation mode switching means for switching the operation state of the wireless communication device operating in either an intermittent operation state or a continuous operation state;
After transmitting the neighbor search packet, the operating state is switched from the intermittent operation to the continuous operation using the operation mode switching means, and when the first timer means notifies that the reception waiting time has elapsed, the Selecting the wireless relay device as a connection destination from the wireless relay devices that are transmission sources of the response packets received during the reception standby time, and after selecting the connection destination, the operation using the operation mode switching means. and first processing means for switching a state from continuous operation to intermittent operation. A computer installed in a wireless communication device that requests connection to a network and performs wireless communication by intermittent operation,
a first communication means for transmitting a neighbor search packet for searching for a wireless relay device that accepts its own connection to a surrounding network and receiving a response packet to the neighbor search packet;
response reception waiting time calculation means for calculating a reception waiting time that is the reception waiting time of the response packet;
first timer means for managing the elapse of the reception waiting time calculated by the response reception waiting time calculating means;
a first storage means for storing the received response packet;
operation mode switching means for switching the operation state of the wireless communication device operating in either an intermittent operation state or a continuous operation state;
After transmitting the neighbor search packet, the operating state is switched from the intermittent operation to the continuous operation using the operation mode switching means, and when the first timer means notifies that the reception waiting time has elapsed, the Selecting the wireless relay device as a connection destination from the wireless relay devices that are transmission sources of the response packets received during the reception standby time, and after selecting the connection destination, the operation using the operation mode switching means. A wireless communication program characterized by functioning as first processing means for switching a state from continuous operation to intermittent operation.

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