JP5967584B2 - Wireless communication system and wireless communication method thereof - Google Patents

Description

  The present invention impairs the advantages of the communication method in a wireless network that wirelessly collects (shares) data of distributed sensor nodes using the CI Flooding (Constructive-Interference Flooding) method using constructive interference. The present invention relates to a wireless communication system and a wireless communication method for improving the reliability of data communication.

  When a plurality of sensor nodes with wireless communication functions (hereinafter referred to as wireless nodes) are distributed in the field and data collected by each wireless node is collected through a wireless network, the power consumption of each wireless node is suppressed ( Because battery operation is performed in the field, it is necessary to reduce power consumption), thus preventing variation in power consumption between wireless nodes (aligning the timing of battery replacement) and increasing the probability of successful communication (distributed in the field) In order to increase the reachability of the sensor node by radio, a method called CI Flooding using constructive interference (hereinafter referred to as CI Flooding method) has been proposed (for example, Non-Patent Document 1). reference.).

  In the CI Flooding scheme, when one of the wireless nodes arranged in a distributed manner transmits data, another wireless node that has received the data transmits the same data in a broadcast manner immediately after receiving the data. In this case, constructive interference of radio signals (sending the exact same radio signal at the same timing to spatially strengthen the radio signals and reach more other nodes) is caused multiple times. By repeating, it is possible to share data with the entire wireless node group. In this method, since the transmission signals are exactly the same wireless signals, decoding is possible even if they are transmitted simultaneously from a plurality of wireless nodes. In addition, since retransmission is performed immediately upon reception of a signal, there is an advantage that back-off delay can be omitted and the layer implementation of the radio link is simplified.

  Incidentally, the CI Flooding method includes an expansion method (Non-Patent Document 2) separately from the normal method. In the normal method, in order to join / synchronize a new wireless node in a group of already communicating wireless nodes, the newly joined wireless node is always in a power-on state (standby state). ) Or randomly turn on the power and wait. However, in the former, an increase in standby power consumption due to long-term power supply is a problem, and in the latter, since already operating wireless nodes operate intermittently while sleeping, the probability of discovering each other cannot be expected.

  In addition, when two or more wireless nodes start communication when they enter each other's communicable area, long-term synchronization is established in scheduling to create a state in which they return from sleep at the same time. There is a research that evaluates the basic method for avoiding this and the relationship between the synchronization frequency and standby power consumption (basically a trade-off) (Non-Patent Document 3). However, this proposal assumes relatively short-cycle synchronization (such as a small network or encounter communication), and does not consider power saving in a long-term standby state such as standby power reduction before shipment.

F. Ferrari, “Efficient Network Flooding and Time Synchronization with Glossy”, IPSN’11, 2011. Chao GAO et al, “Efficient Collection Using Constructive-Interference Flooding in Wireless Sensor Networks”, IEICE 2011. Prabel Dutta et al, “Practical asynchronous neighbor discovery and rendezvous for mobile sensing applications, SenSys '08 Proceedings of the 6th ACM conference on Embedded network sensor systems.

  By the way, in recent years, when collecting (sharing) data of a wireless node using CI Flooding on a wireless network, when adding a new wireless node to the wireless node group, each new wireless node of the wireless node group Not only does it take time to complete the addition, but also there is a problem that power consumption due to mutual communication between them increases.

  Therefore, in view of the above points, the present invention can reliably add a new wireless node to the wireless node group within a finite time, and until the addition of a new wireless node is completed for each wireless node. An object of the present invention is to provide a wireless communication system and a wireless communication method capable of setting a trade-off between time and power consumption.

The radio communication system according to the present invention has the following configuration.
(1) It is composed of a plurality of wireless nodes, and each wireless node is assigned a time slot for transmitting data, and each wireless node performs broadcast transmission of its own data within the time slot and receives other wireless data. In a wireless communication system that collects data transmitted from each wireless node at a predetermined wireless node by repeating the operation that the node immediately broadcasts the same data, the plurality of wireless nodes have already performed communication operations. The existing wireless node group and the new wireless node group to newly participate in the communication operation, and all the wireless nodes belonging to the existing wireless node group periodically transmit at the same first time interval, and The wireless nodes received in the communication slot and belonging to the new wireless node group are interchanged with the first time interval. When a signal of a wireless node belonging to the existing wireless node group can be received periodically at a second time interval that has a simple relationship, a signal indicating its presence is transmitted in the next communication slot. Let it be an aspect.

  (2) In (1), when the time unit of the communication slot is Ts, the parameter A is an arbitrary integer, and Ts and A are unified in all wireless nodes, the parameter K is set to the existing wireless node. An arbitrary integer set for each group, a parameter L is an arbitrary integer set for each new radio node, and the radio nodes of the existing radio node group transmit a signal every (KA-1) Ts The new wireless node receives every (A / L) Ts.

The wireless communication method according to the present invention has the following configuration.
(3) It is composed of a plurality of wireless nodes, and each wireless node is assigned a time slot for transmitting data, and each wireless node performs broadcast transmission of its own data within the time slot and receives other wireless data. In a wireless communication method in which data transmitted from each wireless node is collected by a predetermined wireless node by repeating an operation in which the node immediately broadcasts the same data, the plurality of wireless nodes have already performed a communication operation. The existing wireless node group and the new wireless node group to newly participate in the communication operation, and all the wireless nodes belonging to the existing wireless node group periodically transmit at the same first time interval, and Radio nodes received in the communication slot and belonging to the new radio node group are mutually connected with the first time interval. A mode in which a signal indicating its presence is transmitted in a next communication slot when a signal of a wireless node belonging to the existing wireless node group can be received periodically at a second time interval having the relationship To do.

  (4) In (3), when the time unit of the communication slot is Ts, the parameter A is an arbitrary integer, and Ts and A are unified in all wireless nodes, the parameter K is set to the existing wireless node. An arbitrary integer set for each group, a parameter L is an arbitrary integer set for each new radio node, and the radio nodes of the existing radio node group transmit a signal every (KA-1) Ts The new wireless node receives every (A / L) Ts.

  In the present invention, for example, when a new wireless node that is in a long-term standby state such as a factory-shipped state is introduced into a group of wireless nodes that have already been installed and are communicating with each other, the wireless node in the long-term standby state is intermittent By canceling sleep for a very short time and being able to receive surrounding radio waves, radio waves that are already in operation are detected, and wireless communication groups (wireless Node group).

  According to the present invention, a battery is incorporated at the time of manufacturing a wireless sensor node, and most of the time until sleep / shipping is started, and power consumption is suppressed as much as possible (battery consumption that can be operated in units of 10 years). The sleep scheduling and communication system that can automatically start sleep as soon as it is inserted and start operation as a wireless sensor node is realized.

  In realizing this, power consumption from manufacture to shipment of wireless sensors is suppressed as much as possible (by removing the power switch from the time of manufacture, manual power-on / off / on / off / Human errors such as forgetting to cut can be prevented), and when a sensor is introduced to the measurement site, a wireless sensor node is discovered and activated at an early stage. In addition, when considering the movement of sensor nodes, such as when using wireless sensor nodes for logistics tracking, sleep is automatically canceled only at the measurement site such as a logistics terminal, and other times when sleep is not required for wireless communication. It can also be used for applications that improve battery consumption (standby power consumption) by lengthening the time.

  As described above, according to the present invention, a new wireless node can be reliably added to the wireless node group within a finite time, and the time until the addition of a new wireless node is completed for each wireless node. It is possible to provide a wireless communication system and a wireless communication method capable of setting a trade-off between power consumption and power consumption.

The conceptual diagram which shows an example of the radio | wireless communications system by CI Flooding expansion system as embodiment which concerns on this invention. The block diagram which shows the structure of the radio | wireless node of the said embodiment. The conceptual diagram which shows schematic structure of the radio | wireless communications system which concerns on the said embodiment. The figure which shows the operation example (when L = 1) by the setting of the parameter of the wireless node of the said embodiment. The figure which shows the operation example (in the case of L = 2) by the setting of the parameter of the wireless node of the said embodiment. The sequence diagram which shows the flow of the data transmission / reception between 1 node A of the existing wireless node group of the said embodiment, and the new wireless node 1. FIG. The figure which shows the example of parameter setting by the characteristic analysis for implement | achieving the specific target value of the said embodiment. The figure which shows the other parameter setting example by the characteristic analysis for implement | achieving the specific target value of the said embodiment.

Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiment described below is an example of the configuration of the present invention, and the present invention is not limited to the following embodiment.
FIG. 1 shows an example of a communication system according to the present embodiment. In the communication system according to the present embodiment, one or more wireless nodes N21 to N2m are newly provided separately from a plurality of existing wireless nodes N11 to N1n (n is a natural number of 2 or more) having a sensor function of collecting and transmitting data. (M is an arbitrary natural number) is added (hereinafter, an existing wireless node group (fixed network) is denoted as F, a new wireless node group is denoted as M, and individual wireless nodes are denoted as Ni). Each of these wireless nodes Ni transmits and receives signals using the CI Flooding method.

  Here, in this embodiment, each wireless node Ni has a time slot for transmitting data, and “each node transmits sensor data in the time slot and other wireless nodes that have received the sensor data By repeating the operation of “broadcast transmission of the same sensor data using the CI Flooding method immediately (regardless of time slot)”, the sensor data transmitted from each wireless node Ni is collected.

  The wireless node Ni holds the transmission data in association with the sequence number and transmits the data according to the sequence number within the time slot. When the wireless node Ni receives the transmission permission, the wireless node Ni transmits the sensor data of the instructed sequence number in the imslot.

  FIG. 2 is a block diagram showing a configuration of the wireless node Ni. The wireless node Ni includes a sensor 10, a wireless communication unit 11, a communication control unit 12, a data holding unit 13, a sensor input unit 14, a schedule management unit 15, and a time generation unit 16. The communication control unit 12 includes a transmission processing unit 17 and a transfer processing unit 18.

The sensor 10 performs predetermined sensing at the installation location, converts it into data, and transmits it. The wireless communication unit 11 is a wireless communication module, and wirelessly transmits and receives data to and from other wireless nodes. The communication control unit 12 manages the communication state of the wireless communication unit 11 and executes transmission / transfer processing according to a predetermined sequence.
Here, the transfer processing unit 18 of the communication control unit 12 is in charge of packet relay. In addition, the transmission processing unit 17 analyzes data from other wireless nodes, and sends necessary sensor data to the wireless communication unit 11. The data to be transmitted is a sequence number, sensor data to which the sequence number is assigned, and node identification information such as an ID in addition to this.

  The data holding unit 13 includes a database that holds sensor data of the sensor 10 together with a sequence number corresponding to time. The database records sensor data and also records a list of wireless nodes that have joined the fixed network if the wireless node has joined the fixed network. The data holding unit 13 preferably holds a certain amount of sensor data in preparation for packet dropping. The sensor input unit 14 receives the transmission data from the sensor 10 and sends it to the data holding unit 13. The schedule management unit 15 manages time slots. The time generation unit 16 is a clock and is used for setting the control timing of each processing unit.

The operation of the above configuration will be described with reference to the conceptual diagram shown in FIG. 3, and the operation example of this embodiment shown in FIGS.
FIG. 3 shows a schematic configuration of the communication system according to the present embodiment. FIG. 3A shows a newly added wireless node N21 added to the already operating (communication) wireless node group F (N11 to N16). The state of setting is shown. FIG. 4B is a waveform diagram showing the intermittent operation of the active wireless node, and FIG. 4C shows the synchronization of the newly participating wireless node by detecting the radio waves of the already operating wireless node group. Therefore, the state of intermittently releasing the sleep is shown.

  As shown in FIG. 3 (b), the wireless node group F that is already in operation performs intermittent communication operations, most of which are in a sleep state. Is available. Here, as shown in FIG. 3 (c), in the newly joining wireless node, in order to detect the radio wave of the already operating wireless node group and start synchronization, the sleep should be intermittently released. For example, even in the case of automatic participation, there is no need for manual power switch operation, and the problem of low battery encounters due to constant power-on (standby) and low encounter probability due to random power-on will be improved. Can do.

FIG. 4 and FIG. 5 show examples of operations by setting the parameters of the wireless node. FIG. 4 shows a case where L = 1 and FIG. 5 shows a case where L = 2.
Here, the parameter setting items of the wireless node are generally set as follows.
Ts: Slot time, fixed value
A: Arbitrary integer, fixed value
K: Arbitrary integer, value set for fixed network F
L: Arbitrary integer, set for each node
F: Sent every (KA-1) Ts, received at the next communication slot
M: Received every (A / L) Ts
More specifically, s is a communication slot number,
(s mod A) = int (mA / L) (* int (X) means truncation after the decimal point of X)
Where m is an integer satisfying 0 ≦ m <L / A
And

  In FIG. 4, (a) shows an example of communication slot usage of each wireless node when A = 5, K = 3, L = 1, and (b) shows A = 5, K = 4, and L = 1. Yes. In FIG. 4A, the existing wireless node group F transmits a signal with a KA-1 (= 14) period, and the new wireless node group M receives a signal with an A / L (= 5) period. The new wireless node group M is composed of new nodes 1 to 5, each having a different reception timing. If the new wireless node M tries to receive every A slot, and the existing wireless node group F is transmitting a signal at that time, the new wireless node M receives the signal of the node group F, and the existing wireless node group F in the next slot. Can participate in Group F. In FIG. 4, the new node 1 is “discovered” when the slot = 0 and the new node 5 is “discovered” when the slot = 15, and can participate in the existing wireless node group F. New nodes 2 to 4 are also discovered at some point in the subsequent communication slot. Similarly, in the case of FIG. 4B, the existing wireless node group F transmits a signal with a KA-1 (= 19) period, and the new wireless node group M receives a signal with an A / L (= 5) period. . Therefore, the new node 1 is “discovered” when the slot = 0, and the new node 5 is “discovered” when the slot = 19, and can join the existing wireless node group F.

  In FIG. 5, (a) shows an example of communication slot usage of each wireless node when A = 5, K = 3, L = 2, and (b) shows A = 5, K = 4, and L = 2. Yes. In this example, in the case of FIG. 5A, the existing wireless node group F transmits a signal with a KA-1 (= 14) period, and the new wireless node group M has an A / L (= 2.5) period. Receive a signal. The actual reception interval of M is adjusted according to the communication slot. As a result, new node 1 and new node 4 are “discovered” when slot = 0, and new node 3 and new node 5 are respectively discovered when slot = 14. In the case of FIG. 5B, the existing wireless node group F transmits a signal with a KA-1 (= 19) period, and the new wireless node group M receives a signal with an A / L (= 2.5) period. . As a result, new node 1 and new node 4 are “discovered” when slot = 0, and new node 3 and new node 5 are respectively discovered when slot = 19.

  FIG. 6 is a sequence diagram showing the flow of data transmission / reception between one node A in the existing wireless node group F and the new wireless node 1. In FIG. 6, the existing node A includes a wireless transmission unit A1, a wireless reception unit A2, a communication management unit A3, a data storage unit (database) A4, and a sensor A5. The new node M includes at least the wireless transmission unit M1 and the wireless reception unit. Assume that M2 and a communication management unit M3 are provided.

  In FIG. 6, in the existing node A, in the data storage unit A4, sensor data is repeatedly acquired from the sensor A5 at a sensor data acquisition cycle and recorded in the database. In this state, a transmission instruction is repeatedly issued from the communication management unit A3 at a (KA-1) Ts cycle. When receiving the transmission instruction from the communication management unit A3, the wireless transmission unit A1 requests the sensor data of the database from the data storage unit A4. When the sensor data is provided from the data storage unit A4 in response to this request, the wireless transmission unit A1 receives the sensor data and transmits the packet by broadcast. It is also possible to transmit an empty packet only for adding a new node without transmitting sensor data.

  On the other hand, when the new wireless node M has received the sensor data transmission of the existing wireless node A, the wireless receiving unit M2 has repeatedly released the sleep in the (A / L) Ts cycle and is in a packet receivable state. Notifies the communication manager M3 of the reception. The communication management unit M3 instructs the wireless transmission unit M1 to transmit a network participation signal, and the wireless transmission unit M1 transmits a network participation signal according to the instruction.

  In the existing wireless node A, the communication management unit A3 designates a predetermined time slot after sending the sensor data transmission instruction, and the reception instruction is sent to the wireless reception unit A2. The wireless reception unit A2 can receive according to the instruction. It becomes. When receiving the network participation signal transmitted from the new wireless node 1 in this state, the wireless reception unit A2 sends a reception notification of the network participation signal to the communication management unit A3. The communication management unit A3 performs the participation process of the wireless node M, and registers the participation of the wireless node M in the database of the data storage unit A4. The data storage unit A4 newly registers the participation of the wireless node M in the database list and ends the series of processes.

In the above embodiment, examples of parameter setting by characteristic analysis for realizing a specific target value are shown in FIGS. In FIG. 7 and FIG. 8, D _F is a transmission-side duty cycle and is represented by D _F = 2 / (KA-1). 2 is for receiving in the slot after transmission. Power saving can be achieved by increasing K. D _M is a receiving-side duty cycle, and is represented by D _M = (Tp / Ts) (L / A). The speed can be increased by increasing L. T _R is the maximum time until discovery and is expressed by T _R = (K / L) A2Ts, and can be approximated as KA-1 = KA. Summing up these parameters, D _F · D _M · T _R = 2Tp (Tp = about 0.25ms). FIGS. 7 and 8 show examples of selection based on the characteristic analysis of A and Ts, respectively. To realize D _M = 0.1%, ATs = 250 ms, and to realize D _M = 0.2%, ATs = 125 ms. You can see that

  In this embodiment, when a new wireless node that is in a long-term standby state such as a factory-shipped state is introduced into a group of wireless nodes that are already installed and are communicating with each other, the wireless node in the long-term standby state is intermittent. By canceling sleep for a very short time and being able to receive surrounding radio waves, radio waves that are already in operation are detected, and wireless communication groups (wireless Node group).

  The problem of this embodiment is that (1) when a new wireless node is added to the wireless node group, it is guaranteed to be added within a finite time, and (2) within the multi-hop wireless node group. For example, a new node can be added anywhere, and (3) a trade-off between power consumption and discovery time (time until the addition of a new node is completed) for each wireless node so that the sensor can be applied to business in various fields. It is possible to set off, and (4) to improve power consumption efficiency.

  In the communication system according to the present embodiment, for example, a battery is incorporated at the time of manufacturing a wireless sensor node, and most of the time until sleep / shipping is started to suppress power consumption as much as possible (battery consumption that can be operated in units of 10 years). ), The sleep scheduling and communication system that can automatically start sleep as soon as it is introduced to the measurement site and start operation as a wireless sensor node is realized.

  In this system, the power consumption from manufacturing to shipping of the wireless node is minimized (by removing the power switch from the time of manufacture, it is possible to manually turn on / off the power at the time of shipping inspection or at the measurement site, and to enter / It is possible to prevent human error such as forgetting to cut), and to discover and activate wireless nodes at an early stage when they are introduced to the measurement site. In addition, when considering the movement of a wireless node, such as when using a wireless node for logistics tracking, sleep is automatically canceled only at the measurement site such as a distribution terminal, and during other movements where wireless communication is not required, the sleep time By extending the length, it can also be used for applications that improve battery consumption (standby power consumption).

  In particular, in Non-Patent Document 3, all wireless nodes are treated equally, but in the present embodiment, the existing wireless node group (fixed network) and the new wireless node (mobile node) are separated and fixed to the mobile node. Efficiency is achieved by targeting only discovery between networks. In addition, a scheduling scheme is designed so that a trade-off between power consumption and discovery time can be set for each fixed network and mobile node.

  As described above, according to the communication system of this embodiment, a new wireless node can be reliably added to the wireless node group within a finite time, and the addition of a new wireless node is completed for each wireless node. It is possible to set a trade-off between time to power consumption and power consumption.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some configurations may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different example embodiments may be combined as appropriate.

  The present invention can be applied to the information communication industry.

N11 to N1n ... existing wireless nodes,
N21 to N2m ... New wireless node,
F ... Existing wireless nodes,
M ... New wireless node group,
Ni: Individual wireless node,
10 ... sensor,
11 ... wireless communication unit,
12 ... Communication control unit,
13: Data holding unit,
14 ... sensor input section,
15 ... Schedule management department,
16: Time generation unit,
17 ... transmission processing unit,
18: Transfer processing unit.

Claims (4)

It consists of a plurality of wireless nodes, assigns a time slot for transmitting data to each wireless node, each wireless node performs broadcast transmission of its own data within the time slot, and other wireless nodes receiving the data immediately In a wireless communication system that collects data transmitted from each wireless node at a predetermined wireless node by repeating the operation of broadcasting the same data,
Dividing the plurality of wireless nodes into an existing wireless node group that is already performing communication operation and a new wireless node group that is newly participating in communication operation,
All wireless nodes belonging to the existing wireless node group periodically transmit at the same first time interval, and receive at the next communication slot,
The wireless nodes belonging to the new wireless node group periodically receive at a second time interval that is relatively prime to the first time interval, and receive signals of the wireless nodes belonging to the existing wireless node group If possible, a radio communication system that transmits a signal indicating its presence in the next communication slot. When the time unit of the communication slot is Ts, the parameter A is an arbitrary integer, and Ts and A are unified in all wireless nodes,
Parameter K is an arbitrary integer set for each existing wireless node group,
Parameter L is an arbitrary integer set for each new wireless node,
The wireless node of the existing wireless node group transmits a signal every (KA-1) Ts and receives it in the next slot,
The wireless communication system according to claim 1, wherein the new wireless node receives each (A / L) Ts. It consists of a plurality of wireless nodes, assigns a time slot for transmitting data to each wireless node, each wireless node performs broadcast transmission of its own data within the time slot, and other wireless nodes receiving the data immediately In a wireless communication method of collecting data transmitted from each wireless node by a predetermined wireless node by repeating the operation of broadcasting the same data,
Dividing the plurality of wireless nodes into an existing wireless node group that is already performing communication operation and a new wireless node group that is newly participating in communication operation,
All wireless nodes belonging to the existing wireless node group periodically transmit at the same first time interval, and receive at the next communication slot,
The wireless nodes belonging to the new wireless node group periodically receive at a second time interval that is relatively prime to the first time interval, and receive signals of the wireless nodes belonging to the existing wireless node group A radio communication method characterized by transmitting a signal indicating its presence in the next communication slot if it can be. When the time unit of the communication slot is Ts, the parameter A is an arbitrary integer, and Ts and A are unified in all wireless nodes,
Parameter K is an arbitrary integer set for each existing wireless node group,
Parameter L is an arbitrary integer set for each new wireless node,
The wireless node of the existing wireless node group transmits a signal every (KA-1) Ts and receives it in the next slot,
4. The wireless communication method according to claim 3, wherein the new wireless node receives every (A / L) Ts.

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