JP4988475B2 - Congestion control method, radio communication system, and radio communication apparatus - Google Patents

Description

The present invention defines a predetermined period within a superframe period of a fixed period as an active period and the rest as a sleep period, and divides the active period into a plurality of time slots. The present invention relates to a congestion control method in a wireless communication system that uses and performs bi-directional communication in a time division manner. The present invention also relates to a wireless communication system and a wireless communication apparatus.
More specifically, the present invention relates to congestion control of communication that occurs when wireless communication devices (nodes) are densely present within a wireless communication range, and avoids communication contention while also reducing power consumption of a battery in the wireless communication node. It relates to media access control to be reduced.

  In ZigBee (registered trademark) as shown in Non-Patent Document 1 as a short-range wireless communication standard, a predetermined period within a certain period is defined as an active period (superframe period) with a beacon signal as a synchronization signal, and the rest is defined as a sleep period. The active period is divided into a plurality of time slots, and each of the plurality of wireless communication apparatuses performs bidirectional communication in a time division manner using each time slot. As another conventional example, Patent Document 1 discloses that each wireless communication node is an ad hoc communication system in which a large number of wireless communication nodes perform direct asynchronous wireless communication without passing through other nodes such as a base station and a control station. There has been proposed a method in which a reception section is provided immediately after a beacon signal to be transmitted and the remaining period is an unused period. Patent Document 2 proposes a method for determining a time slot for transmitting a beacon signal when a superframe period of a certain period is set using a beacon signal transmitted by each wireless communication node as a synchronization signal.

  In addition, as a method of assigning each time slot to a node, Patent Document 2 discloses a method of autonomously advertising its own slot use to an empty slot. According to this method, each node scans the specified time slot time to determine the used time slot and the empty time slot, and configures the table. It is possible to use. For example, if there is a node that no longer uses a time slot, the time slot is scanned as an empty time slot and is used by another node. If communication nodes using such a method exist densely within the wireless communication range and the number of nodes exceeds the number of time slots, there will be no available time slots, and there will be nodes that cannot communicate. come. In such a congested state, it is desirable that, for example, the transmitting node stops communication for a certain period of time to release time slots so that other nodes can use them sequentially. In this case, considering the characteristics of wireless communication, it is desirable to stop the transmission after confirming that the frame transmitted by itself has reached the other party. In such a case, it is conceivable to confirm the reception response (ACK, NACK) from the received node.

  When there are many nodes within the wireless communication range, especially when nodes using the same frequency communicate in a time-sharing manner, communication congestion may occur, avoiding communication contention. Providing access control is important. In addition, in the case of a node such as an active electronic tag that periodically outputs its information using a built-in battery as a power source, the collision is controlled by randomly changing the transmission timing with respect to a certain period. When the node density with respect to the wireless communication range is high, a communication impossible state due to a collision is caused. In such a case, it is possible to continue communication while avoiding temporary congestion by reducing the number of nodes to communicate until the congestion state is avoided. In such a case, it is important to determine which node stops transmission.

  However, in the case of a node that simply transmits its own information, such as an active electronic tag, it is difficult to determine the state of congestion itself, and there is no choice but to wait for avoidance of a physical congestion state due to node movement or the like. Also, in the case of a node that receives a command from a reader, such as a passive tag without a built-in battery, the reader, which is a specific node, manages the status and performs access control for each tag to control during congestion It can be performed. This is realized by performing transmission in order by confirming that the information transmitted by each tag is received by the reader. In this way, there is a method for avoiding congestion by notifying the node that transmits information to the node that transmits information at the time of congestion, thereby stopping communication and reducing the number of nodes that perform communication at the same time. Used. Confirming the reception of such information increases the reliability of information transmission, and at the time of congestion, confirms that information has been received compared to a method in which a node that has recognized congestion simply stops transmission for a certain period of time. It is considered that efficient information transmission can be performed by stopping transmission from the confirmed node.

  A conventional operation in the case of performing such a reception response will be described with reference to FIGS. FIG. 13 shows an operation in the case where three active wireless communication nodes A, B, and C each incorporating a battery transmit and receive a unicast frame in which a destination node is determined. Nodes A to C are nodes that are at a distance where they can communicate with each other. The frame F1 addressed to the node B (Dest B) output from the node A can be received by the nodes B and C, but the node B receives it by filtering the destination (Dest B) and confirms that it has been received. (ACK1) is transmitted. The reception of the frame F2 destined for node C (Dest C) output by the node B is confirmed by ACK2 from the node C. Here, the transmission of a new response confirmation frame at the time of congestion increases the amount of frames that need to be transmitted and also contributes to the congestion. For this reason, in Non-Patent Document 1, etc., the ACK frame is immediately returned as a very short frame, unlike the data frames F1 and F2. By such a method, the reception notification is made to the nodes A and B that transmitted the frames F1 and F2 without promoting congestion and without adding detailed information for identifying the frame returning the ACK. Yes.

However, in the case of the unicast in which the destination is determined in this way, since there is one node that responds, the nodes B and C that have received the frames F1 and F2 immediately return an ACK frame (ACK1, ACK2). However, for a frame transmitted to an unspecified number of nodes such as broadcast, for example, if a plurality of nodes send back an ACK at the time of reception, an ACK collision occurs and it is difficult to confirm the reception. For this reason, in Patent Document 1, for example, as shown in FIG. 14, when transferring received frames F11, F12, and F13, a passive ACK that confirms the response by returning the frame that it transmitted is returned. Is used.
IEEE 802.15.4 JP 2004-228926 A (FIG. 2) JP 2006-121332 A (Abstract)

  However, in response confirmation using passive ACK for the broadcast, it is necessary to sequentially transfer frames transmitted by a certain node, and a frame having the same size as the transmitted data is used. In such a case, not only is congestion promoted, but response confirmation cannot be performed in a network that does not transfer broadcast frames, for example.

  In the present invention, it is possible to autonomously stop transmission using reception response information that does not promote congestion at the time of congestion in wireless communication that advertises its information to an unspecified number of wireless communication devices. Another object of the present invention is to provide a congestion control method, a wireless communication system, and a wireless communication apparatus that can autonomously determine the cancellation of a congestion state and resume transmission.

In order to achieve the above object, the present invention defines a predetermined period within a superframe period of a constant period as an active period and the rest as a sleep period, and divides the active period into a plurality of time slots, thereby providing a plurality of radio communication apparatuses. Each of which is a congestion control method in a wireless communication system that performs bidirectional communication in a time-sharing manner using each time slot,
Each of the plurality of wireless communication devices transmitting a frame including a reception response information field of a frame received from another wireless communication device in each of the plurality of time slots in each time slot period; and
Each of the plurality of wireless communication devices that have received the frame stops transmission of its own device in the next superframe period based on each reception response information in the field of the reception response information in the previous superframe period. A determination step for determining whether or not
It was set as the structure which has.
With this configuration, whether the reception response information of the frames received from each of the plurality of wireless communication devices in each time slot period is broadcast in each super frame period, and whether or not to stop transmission of the own device in the next super frame period Can be judged.

Further, the reception response information includes information indicating “no reception”, “normal reception”, or “error reception”,
The determination step determines whether or not the total number of “normal reception” and “error reception” information in the reception response information field in the previous superframe period exceeds a first threshold value, It is characterized by determining whether or not to stop transmission of the own apparatus in the next superframe period.
With this configuration, it is possible to determine whether or not to stop transmission of the own device in the next superframe period.

Further, the reception response information includes information indicating “no reception”, “normal reception”, or “error reception”,
The determination step determines whether the number of “normal reception” information in the reception response information field in the previous superframe period exceeds a second threshold, thereby determining whether the next superframe period It is characterized by determining whether or not to stop transmission of the own device.
With this configuration, it is possible to determine whether or not to stop transmission of the own device in the next superframe period.

Further, the reception response information includes information indicating “no reception”, “normal reception”, or “error reception”,
The determination step determines whether or not the number of “normal reception” information for the use time slot of the own node in the reception response information field in the previous superframe period exceeds a third threshold value. Then, it is determined whether or not to stop transmission of the own apparatus in the next superframe period.
With this configuration, it is possible to determine whether or not to stop transmission of the own device in the next superframe period.

In addition, when the transmission of the own node is stopped, the determination step resumes transmission of the own device in the next superframe period based on each reception response information in the reception response information field in the previous superframe period. It is characterized by determining whether to do.
With this configuration, it is possible to determine whether or not to resume transmission of the own device in the next superframe period.

In order to achieve the above object, the present invention defines a predetermined period within a superframe period of a constant period as an active period and the rest as a sleep period, and divides the active period into a plurality of time slots, thereby providing a plurality of radio communication apparatuses. Each of which is a wireless communication system that performs two-way communication in a time-sharing manner using each time slot,
Means for transmitting a frame including a reception response information field of a frame received from each of the plurality of time slots in each of the plurality of time slots, in each of the plurality of wireless communication apparatuses;
Each of the plurality of wireless communication devices that have received the frame stops transmission of its own device in the next superframe period based on each reception response information in the field of the reception response information in the previous superframe period. Judging means for judging whether or not
It was set as the structure which has.
With this configuration, whether the reception response information of the frames received from each of the plurality of wireless communication devices in each time slot period is broadcast in each super frame period, and whether or not to stop transmission of the own device in the next super frame period Can be judged.

Further, the reception response information includes information indicating “no reception”, “normal reception”, or “error reception”,
The determination means determines whether the total number of “normal reception” and “error reception” information in the field of the reception response information in the previous superframe period exceeds a first threshold value, It is characterized by determining whether or not to stop transmission of the own apparatus in the next superframe period.
With this configuration, it is possible to determine whether or not to stop transmission of the own device in the next superframe period.

Further, the reception response information includes information indicating “no reception”, “normal reception”, or “error reception”,
The determination means determines whether or not the number of “normal reception” information in the field of the reception response information in the previous superframe period exceeds a second threshold value, so that the next superframe period It is characterized by determining whether or not to stop transmission of the own device.
With this configuration, it is possible to determine whether or not to stop transmission of the own device in the next superframe period.

Further, the reception response information includes information indicating “no reception”, “normal reception”, or “error reception”,
The determination means determines whether the number of “normal reception” information for the use time slot of the own node in the field of the reception response information within the previous superframe period exceeds a third threshold value. Then, it is determined whether or not to stop transmission of the own apparatus in the next superframe period.
With this configuration, it is possible to determine whether or not to stop transmission of the own device in the next superframe period.

In addition, when the transmission of the own node is stopped, the determination unit resumes transmission of the own device in the next superframe period based on each reception response information in the reception response information field in the previous superframe period. It is characterized by determining whether to do.
With this configuration, it is possible to determine whether or not to resume transmission of the own device in the next superframe period.

In order to achieve the above object, the present invention defines a predetermined period within a superframe period of a constant period as an active period and the rest as a sleep period, and divides the active period into a plurality of time slots, thereby providing a plurality of radio communication apparatuses. Each of the wireless communication devices in a wireless communication system that performs bidirectional communication in a time-sharing manner using each time slot,
Means for transmitting a frame including a reception response information field of a frame received from another wireless communication device in each of the plurality of time slots in each time slot period;
When receiving the frame, based on each reception response information in the field of the reception response information in the previous superframe period, a determination to determine whether or not to stop transmission of the own apparatus in the next superframe period Means,
It was set as the structure which has.
With this configuration, whether the reception response information of the frames received from each of the plurality of wireless communication devices in each time slot period is broadcast in each super frame period, and whether or not to stop transmission of the own device in the next super frame period Can be judged.

Further, the reception response information includes information indicating “no reception”, “normal reception”, or “error reception”,
The determination means determines whether the total number of “normal reception” and “error reception” information in the field of the reception response information in the previous superframe period exceeds a first threshold value, It is characterized by determining whether or not to stop transmission of the own apparatus in the next superframe period.
With this configuration, it is possible to determine whether or not to stop transmission of the own device in the next superframe period.

Further, the reception response information includes information indicating “no reception”, “normal reception”, or “error reception”,
The determination means determines whether or not the number of “normal reception” information in the field of the reception response information in the previous superframe period exceeds a second threshold value, so that the next superframe period It is characterized by determining whether or not to stop transmission of the own device.
With this configuration, it is possible to determine whether or not to stop transmission of the own device in the next superframe period.

Further, the reception response information includes information indicating “no reception”, “normal reception”, or “error reception”,
The determination means determines whether the number of “normal reception” information for the use time slot of the own node in the field of the reception response information within the previous superframe period exceeds a third threshold value. Then, it is determined whether or not to stop transmission of the own apparatus in the next superframe period.
With this configuration, it is possible to determine whether or not to stop transmission of the own device in the next superframe period.

If the determination means stops transmission of its own device, whether to restart transmission of its own device in the next superframe period based on each reception response information in the reception response information field in the previous superframe period It is characterized by determining whether or not.
With this configuration, it is possible to determine whether or not to resume transmission of the own device in the next superframe period.

  According to the present invention, transmission is autonomously stopped using efficient reception response information from a plurality of nodes in wireless communication that advertises its information to an unspecified number of wireless communication devices (nodes). It is possible to resume. As a result, congestion can be avoided autonomously only by nodes having the same function, and there is no need to use a specific control node separately. Further, by using reception responses from a plurality of nodes as reception responses for time slots, it is possible to reduce the additional information for reception responses and reduce the increase in the amount of transmission data. Furthermore, in order to stop transmission after confirming reception of the frame transmitted by the own node using reception responses from a plurality of nodes, transmission is performed after ensuring that there is a node that has received the frame transmitted by the own node. Can be stopped. In addition, it is possible to determine the state of congestion from information contained in a small number of frames received in time division multiplex communication that constitutes a plurality of time slots. In this case, all time slots are received and congestion is reduced. Since it is not necessary to make a determination, it is possible to reduce power consumption during congestion.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the wireless communication apparatus (node) type and system configuration in the present embodiment. This system includes a gateway (GW) 2 connected to an external network 1 (for example, the Internet) regardless of whether it is wired or wireless, can communicate with the external network 1 and can be supplied with commercial power, and the wireless communication node 3. It is composed of small wireless tags 3a and 3b driven by a battery. The wireless tags 3a and 3b can transmit and receive data and can exchange data in both directions, and are hereinafter also referred to as P2P (Point to Point) tags. The P2P tags 3a and 3b include a P2P-S tag 3a that is a P2P tag that is not supposed to move after installation (Stationary) and a P2P-M tag 3b that is a P2P tag that is moved by a person (Mobile), for example. There are two types.

  As shown in FIG. 1, each P2P tag 3a, 3b exchanges its own ID with the P2P tag 3a, 3b in its communicable range ad hoc. As described above, the P2P tags 3a and 3b exchange and accumulate IDs with each other by the moving P2P-M tag 3b, thereby maintaining the mutual contact history. Thereby, a person's action history can be accumulated in the P2P-M tag 3b, and a person's passage history at a certain point can be accumulated in the P2P-S tag 3a. For example, as an example of a specific application, it is conceivable to acquire human behavior and contact history in a city. In this case, the behavior and contact history of a person having the P2P-M tag 3b can be acquired by arranging the GW2 in a place where a commercial power source can be secured and arranging a large number of P2P-S tags 3a in other places. It becomes possible.

  Also, in such an application in which the wireless node 3 simply exchanges its own ID and leaves a contact history, the information transmitting side does not need to specify the receiving side, and the respective tags 3a, 3b Broadcasts its own ID, and the received tags 3a and 3b may store this.

  Next, FIG. 2 shows a configuration of the superframe period T_p in this embodiment. In the present invention, as shown in FIG. 2A, the superframe period T_p includes the active period Tact in which the tags 3a and 3b, which are the wireless communication nodes 3, transmit and receive frames, and the wireless units of the tags 3a and 3b (FIG. 7). And a sleep period (= T_p−Tact) during which the operation is stopped. The active period Tact is configured by a fixed-length time slot TS (number of time slots = 16) as shown in FIG. 2B, and each moving tag 3b periodically assigns each time slot TS in the active period Tact to random. And transmits its information in a frame in the selected time slot TS.

  FIG. 3 shows a response confirmation (ACK) sequence according to the present invention. FIG. 3 shows a state where three nodes A, B, and C broadcast their own frames F [A], F [B], and F [C]. In the present invention, the nodes A to C exchange and accumulate information when passing each other, and the accumulated information is transmitted only to a specific node (GW 2 in FIG. 1). For this reason, a frame received from a certain node is not transferred to another node. Therefore, the broadcast frames F [A], F [B], and F [C] are transmitted / received only between the nodes A to C that are in the communication range.

  In FIG. 3, each node A to C transmits its own information in frames F [A], F [B], and F [C] to a time slot TS randomly selected by each node A to C in a certain superframe period N-1. Indicates the state. However, node A and node C are examples in a place where direct communication is not possible. At this time, the frame F [A] transmitted from the node A is transmitted to the node B, the frame F [B] transmitted from the node B is transmitted to the nodes A and C, and the frame F [C] transmitted from the node C is transmitted to the node B. Assume that all are received normally.

  When the nodes A, B, and C transmit their own frames F [A: b], F [B: a, c], and F [C: b] in the next superframe period N, the respective frames F [A: b], F [B: a, c], F [C: b] The node information (a, b, c in []) received by itself in the previous superframe period N-1 Add and send. As a result, each of the nodes A, B, and C uses their own frames F [A] and F [B] transmitted in the previous superframe period N-1 based on the ACK information added together in the frames of the other nodes. , F [C] can be recognized. At the same time, with respect to the node B, by receiving the ACK information from the node A and the node C, the reception at the plurality of nodes A and C can be confirmed.

  Next, the structure of the frame F exchanged by each tag (node 3) is shown in FIG. Each node 3 generates a fixed-length frame F that can be transmitted in one time slot TS. Specifically, it responds to the reception of the frame F from each field of the number (Slot Number) of the time slot TS transmitted by itself, the type (Type) of Node 3 and its own ID number (ID), and other nodes. The ACK field notifies the transmission side node of the reception state. The present invention is characterized in that the frame F that transmits its own information includes reception response information of a frame received from another node 3 in another time slot TS. Specifically, the ACK field includes fields indicating the time slots TS1 to TS16 of the superframe SF defined by the system, and the reception status in each time slot TS1 to TS16 is stored as ACK information.

In the present invention, unlike a method such as an individual response using the ID of the transmitting side node or a passive ACK for notifying reception by transmitting a frame of the transmitting side node, an ACK field having a fixed length for a specified time slot Thus, its own reception information is provided to all other transmission source nodes received in the previous superframe period N-1. Therefore, 16 × 16 reception situations are provided in one superframe period T_p. Each piece of information in the ACK field for each time slot is composed of 2 bits, and the state is shown as follows.
00: No reception
10: Received in error state
11: Received in normal state,

  “10: Received in error” includes a case where the received frame F is discarded due to a bit error or a frame error, or a case where the frame F cannot be correctly received due to a collision. This is not an ACK that specifies individual nodes in this way, but a notification of the reception status for a fixed time slot. Thus, the frame length can be kept fixed with respect to the amount of ACK, and at the same time, notification can be made with a very small amount of information.

Next, a method for generating the ACK field will be described with reference to FIG. FIG. 5 illustrates a method of generating an ACK field using the timings of two superframe periods N−1 and N in a certain node 3. FIG. 5 shows a case where the node 3 transmits the frame F in “time slot: 3” in the Nth superframe period. At this time, in the ACK field of the frame F transmitted by the node 3, the states of all the time slots received by itself in the previous superframe period N-1 are described for each time slot. For example, “Time slot: 1” (hereinafter referred to as TS1) received a frame normally (= 11),
・ TS2 receives the frame normally in the same way (= 11),
・ There is no frame reception in TS3 (= 00),
...
・ In TS6, the frame was received but could not be received correctly (= 10)
...
It is shown that. Thus, in the superframe period N, the reception status of each time slot in the previous superframe period N-1 is always notified to the other nodes 3 in the area.

  FIG. 6 shows a confirmation method using the ACK field at the time of superframe reception. After receiving one superframe period N (all time slots TS = all frames), grasp the time slot reception status of each node 3 in the previous superframe period N-1 from the frame F that was successfully received. Can do. Each node 3 holds the slot number used for transmission in the previous superframe period N-1 and confirms the corresponding TS portion (TS7 in FIG. 6) of the ACK field, thereby transmitting the previous frame transmitted by itself. It becomes possible to know the reception state at the other node 3 of F. Considering that the node 3 moves, there is a possibility that the reception information for the frame F transmitted by the other node 3 may be included, but the ID of the node 3 that transmitted the corresponding information can be confirmed at the same time. If the information is from a new node that is not the node received by itself during the previous superframe period N-1, the corresponding ACK information may be excluded.

  Next, the configuration of the node 3 of the present invention will be described with reference to FIG. The node 3 of the present invention includes a radio unit 11 having a transmission unit 11a and a reception unit 11b, a control unit 12, an ID storage unit 13, a clock 14, and a power supply unit 15. The transmission unit 11a has a function of transmitting a frame F including its own ID to the outside via radio. In the node 3 of the present invention, frame transmission in the transmission unit 11a is performed by periodically broadcasting its own ID. The receiving unit 11b has a function of receiving a frame including an ID transmitted from the other node 3 in the same manner.

  The control unit 12 has a function of controlling the operation of the node 3. The function of the control unit 12 will be described in detail with reference to FIG. The ID accumulation unit 13 has a function of accumulating IDs of other nodes 3 received by the reception unit 11b. In addition, when ID is accumulate | stored in ID storage part 13, the time information at that time may be recorded with ID. Also, its own ID information is recorded in the same manner. The clock 14 has a function of outputting a clock signal for grasping the timing of frame transmission in the transmission unit 11a and frame reception in the reception unit 11b. The power feeding unit 15 is a power source built in the node 3 so that the node 3 can move to an arbitrary place. For example, the power feeding unit 15 is a battery mounted in the casing of the node 3.

  Next, the function of the control unit 12 in the embodiment of the present invention will be described with reference to FIG. Specifically, the control unit 12 includes a time slot adjustment unit 21, a frame analysis unit 22, a frame generation unit 23, an ACK generation unit 24, and a congestion control unit 25. The time slot adjustment unit 21 has a function of adjusting the synchronization of time slots including the synchronization of the superframe period, and receiving the frame F and transmitting the generated frame F to the randomly selected time slot TS. is doing. The frame analysis unit 22 analyzes the reception state in each time slot TS, acquires the ID information from the received frame F and notifies the ID storage unit 13 of the ID information from the ACK generation unit 24 and the congestion control unit 25 It has a function.

  Based on the information from the frame analysis unit 22, the ACK generation unit 24 generates an ACK field to be added to the frame F to be transmitted next time. The congestion control unit 25 determines congestion based on information from the frame analysis unit 22, and performs frame transmission stop determination and frame transmission restart determination results to the frame generation unit 23 and the time slot adjustment unit 21. Specifically, the processing described in the flowchart described later is performed. The frame generation unit 23 generates a frame F from its own ID, time slot information to be transmitted, and ACK field information notified from the ACK generation unit 24.

  Next, the operation at the time of congestion will be described. When many nodes 3 are crowded within the wireless communication range, for example, when a person holding the node 3 is waiting for a signal at an intersection, the time slot in the superframe period with respect to the number of nodes that can communicate within the communication range There are cases where the number is small. In such a case, even if access control by CSMA (Carrier Sense Multiple Access) is performed, a frame cannot be received due to a collision, or a node 3 that continuously obtains transmission opportunities and transmits the transmission opportunities many times. There is a possibility that a node 3 or the like that cannot be obtained and cannot transmit a frame may occur due to timing. In the present invention, when congestion occurs, congestion is avoided by reducing the number of nodes 3 that transmit the frame F. For this reason, in each node 3, it becomes necessary to control the timing at which the transmission of the frame F is stopped and the timing at which the transmission is restarted at the time of congestion.

  9 to 11 are flowcharts showing the processing in the congestion control unit 25. First, as shown in FIG. 9, in the congestion control unit 25, when operating in the shortened time slot mode at the time of congestion based on the information from the frame analysis unit 22 (Yes in step S1), a transmission return determination process (step S2). ) Is performed in the normal time slot mode (No in step S1), a transmission stop determination process (step S3) is performed.

  The transmission stop determination process (step S3) will be described in detail with reference to FIG. When reception of one superframe n is completed, it is determined whether or not the number of time slots that the node 3 has received normally (= 11) and received error (= 10) in the corresponding superframe n exceeds the congestion threshold A (Step S11). If the congestion threshold A is not exceeded (No in step S11), it is determined that the congestion state is not yet reached, and normal operation is performed.

  If the congestion threshold A is exceeded (Yes in step S11), the ACK field of the frame F that is normally received (= 11) is checked next, and the number of slots used by the own node and other nodes indicated by the ACK field is the congestion threshold. It is determined whether or not B is exceeded (step S12). If the congestion threshold B has not been exceeded (No in step S12), it is possible that there is a temporary set of nodes 3 at the time of passing, and congestion determination is not performed yet, and normal frame transmission operation is performed.

  If the congestion threshold B is exceeded (Yes in step S12), the number of normal receptions (= 11) for the time slot transmitted by itself in the previous superframe period from the ACK field of all frames that were normally received (= 11) in the same manner Is checked (step S13), and if reception is confirmed at a threshold value C or more (Yes in step S13), frame transmission in the next superframe is stopped (step S14), and the time slots constituting the superframe are further changed. The mode is changed to the shortened time slot operation mode to be shortened (step S15). If reception of the threshold value C or higher is not confirmed (No in step S13), the frame is transmitted as usual in order to exchange its own information although it is congested.

  The shortened time slot operation mode is to reduce power consumption by reducing the number of received time slots until congestion is avoided when the transmission stops during congestion. In a congested state, this means that there are many partners that exchange information with each other, and that the number of nodes that exchange and store information of a certain node 3 also increases. In a situation where the nodes 3 are gathered at a high density, it is considered that the movement of the node 3 itself is relatively small, and transmission / reception between the same nodes 3 is considered to increase when the congestion state continues. . For this reason, with regard to the node 3 that has stopped transmitting its own frame in a congested state, reducing the information that it receives and accumulates until the congested state is eliminated is Effective means.

  Next, the transmission return determination process (step S2) when the transmission is stopped and the operation is performed in the shortened time slot operation mode will be described in detail with reference to FIG. In the shortened time slot mode, the surrounding congestion state is determined using the ACK field of the frame F received first. If the number of used slots indicated by the ACK field of the frame F that has been normally received first (= 11) is less than or equal to the congestion threshold D (Yes in step S21), it is determined that the congestion state has been avoided, and from the next superframe period Transmission of the own frame F is resumed (step S22), and the mode is changed to the normal time slot operation mode (step S23). If it is not equal to or less than the congestion threshold D (No in step S21), it is assumed that the congestion state is still present, the subsequent time slot is not used, the sleep mode is entered, and the same processing is repeated in the next superframe.

  FIG. 12 shows an example of the reception status of each time slot. First, in FIG. 12 (a), as described in FIG. 6, each node 3 responds to the response information of frames received from other nodes 3 in each of a plurality of time slots (no reception). 0: 00, normal reception: 11, error reception: 10) frame F including the ACK field is transmitted. FIG. 12B shows that the number of used time slots (normal reception: 11, error reception: 10) is large. When each node determines this and stops transmission, the number of used time slots (normal reception: 11, error reception: 10) decreases as shown in FIG. 12 (c), and each node 3 determines this. Transmission can be resumed.

  As described above, in order to determine whether the congestion is eliminated, it is possible to reduce the operation by using the information of the ACK field included in a certain received frame F, instead of receiving all the time slots and checking the used time slots. It becomes possible to determine the state of congestion over time, and to realize power saving during congestion.

  Note that each functional block used in the description of the above embodiment is typically realized as an LSI which is an integrated circuit. These may be individually made into one chip, or may be made into one chip so as to include a part or all of them. The name used here is LSI, but it may also be called IC, system LSI, super LSI, or ultra LSI depending on the degree of integration. Further, the method of circuit integration is not limited to LSI's, and implementation using dedicated circuitry or general purpose processors is also possible. An FPGA (Field Programmable Gate Array) that can be programmed after manufacturing the LSI or a reconfigurable processor that can reconfigure the connection and setting of circuit cells inside the LSI may be used. Further, if integrated circuit technology comes out to replace LSI's as a result of the advancement of semiconductor technology or a derivative other technology, it is naturally also possible to carry out function block integration using this technology. For example, biotechnology can be applied.

  The present invention can autonomously stop transmission by using a response confirmation that does not promote congestion at the time of congestion in wireless communication that advertises its information to an unspecified number of nodes. Has the effect of autonomously judging the cancellation of the congestion state and restarting transmission, and is a small battery-powered node of a wireless communication network, especially an electronic tag system with small exchange data, and other networks It can be applied to equipment.

Explanatory drawing which shows the wireless node classification and system configuration in the embodiment of the present invention Explanatory drawing which shows the structure of the super-frame period and time slot in embodiment of this invention Explanatory drawing which shows the operation | movement sequence of the response confirmation in embodiment of this invention Explanatory drawing which shows the structure of the frame in embodiment of this invention Explanatory drawing which shows the production | generation timing of the ACK field in embodiment of this invention Explanatory drawing which shows the response confirmation method using the ACK field in embodiment of this invention The block diagram which shows the structure of the radio | wireless communication node in embodiment of this invention The block diagram which shows the structure of the control part of FIG. 7 in detail FIG. 8 is a flowchart for explaining the processing of the congestion control unit in FIG. FIG. 9 is a flowchart illustrating in detail the transmission stop determination process of FIG. FIG. 9 is a flowchart for explaining the transmission return determination process in FIG. 9 in detail. The figure explaining a series of control operation at the time of congestion in embodiment of this invention The figure explaining the operation | movement of the reception response with respect to the unicast frame in the conventional system The figure explaining the operation | movement of the reception response with respect to the broadcast frame in the conventional system.

Explanation of symbols

3 node 21 time slot adjustment unit 22 frame analysis unit 23 frame generation unit 24 ACK generation unit 25 congestion control unit

Claims (15)

A predetermined period within a superframe period of a certain period is defined as an active period, and the rest is defined as a sleep period. The active period is divided into a plurality of time slots, and each of the plurality of wireless communication apparatuses uses each time slot. A congestion control method in a wireless communication system that performs bi-directional communication by division,
Each of the plurality of wireless communication devices transmitting a frame including a reception response information field of a frame received from another wireless communication device in each of the plurality of time slots in each time slot period; and
Each of the plurality of wireless communication devices that have received the frame stops transmission of its own device in the next superframe period based on each reception response information in the field of the reception response information in the previous superframe period. A determination step for determining whether or not
A congestion control method. The reception response information includes information indicating “no reception”, “normal reception”, or “error reception”,
The determination step determines whether or not the total number of “normal reception” and “error reception” information in the reception response information field in the previous superframe period exceeds a first threshold value, The congestion control method according to claim 1, wherein it is determined whether or not to stop transmission of the own device in a next superframe period. The reception response information includes information indicating “no reception”, “normal reception”, or “error reception”,
The determination step determines whether the number of “normal reception” information in the reception response information field in the previous superframe period exceeds a second threshold, thereby determining whether the next superframe period 3. The congestion control method according to claim 1, wherein it is determined whether or not to stop transmission of the own device. The reception response information includes information indicating “no reception”, “normal reception”, or “error reception”,
The determination step determines whether or not the number of “normal reception” information for the use time slot of the own node in the reception response information field in the previous superframe period exceeds a third threshold value. The congestion control method according to any one of claims 1 to 3, wherein it is determined whether or not to stop transmission of the own apparatus in a next superframe period.   In the determination step, when the transmission of the own node is stopped, based on each reception response information in the reception response information field in the previous superframe period, whether to restart transmission of the own device in the next superframe period The congestion control method according to any one of claims 1 to 4, wherein it is determined whether or not. A predetermined period within a superframe period of a certain period is defined as an active period, and the rest is defined as a sleep period. The active period is divided into a plurality of time slots, and each of the plurality of wireless communication apparatuses uses each time slot. A wireless communication system that performs two-way communication in division,
Means for transmitting a frame including a reception response information field of a frame received from each of the plurality of time slots in each of the plurality of time slots, in each of the plurality of wireless communication apparatuses;
Each of the plurality of wireless communication devices that have received the frame stops transmission of its own device in the next superframe period based on each reception response information in the field of the reception response information in the previous superframe period. Judging means for judging whether or not
A wireless communication system. The reception response information includes information indicating “no reception”, “normal reception”, or “error reception”,
The determination means determines whether the total number of “normal reception” and “error reception” information in the field of the reception response information in the previous superframe period exceeds a first threshold value, The wireless communication system according to claim 6, wherein it is determined whether or not to stop transmission of the own device in a next superframe period. The reception response information includes information indicating “no reception”, “normal reception”, or “error reception”,
The determination means determines whether or not the number of “normal reception” information in the field of the reception response information in the previous superframe period exceeds a second threshold value, so that the next superframe period 8. The wireless communication system according to claim 6, wherein it is determined whether or not to stop transmission of the own device. The reception response information includes information indicating “no reception”, “normal reception”, or “error reception”,
The determination means determines whether the number of “normal reception” information for the use time slot of the own node in the field of the reception response information within the previous superframe period exceeds a third threshold value. The wireless communication system according to claim 6, wherein it is determined whether or not to stop transmission of the own device in a next superframe period.   Whether the determination means restarts transmission of the own device in the next superframe period based on each reception response information in the reception response information field in the previous superframe period when transmission of the own node is stopped The wireless communication system according to claim 6, wherein it is determined whether or not. A predetermined period within a superframe period of a certain period is defined as an active period, and the rest is defined as a sleep period. The active period is divided into a plurality of time slots, and each of the plurality of wireless communication apparatuses uses each time slot. The wireless communication device in a wireless communication system that performs bidirectional communication in a division,
Means for transmitting a frame including a reception response information field of a frame received from another wireless communication device in each of the plurality of time slots in each time slot period;
When receiving the frame, based on each reception response information in the field of the reception response information in the previous superframe period, a determination to determine whether or not to stop transmission of the own apparatus in the next superframe period Means,
A wireless communication device. The reception response information includes information indicating “no reception”, “normal reception”, or “error reception”,
The determination means determines whether the total number of “normal reception” and “error reception” information in the field of the reception response information in the previous superframe period exceeds a first threshold value, 12. The wireless communication apparatus according to claim 11, wherein it is determined whether or not transmission of the own apparatus is interrupted in a next superframe period. The reception response information includes information indicating “no reception”, “normal reception”, or “error reception”,
The determination means determines whether or not the number of “normal reception” information in the field of the reception response information in the previous superframe period exceeds a second threshold value, so that the next superframe period 13. The wireless communication apparatus according to claim 11 or 12, wherein it is determined whether or not to stop transmission of the own apparatus. The reception response information includes information indicating “no reception”, “normal reception”, or “error reception”,
The determination means determines whether the number of “normal reception” information for the use time slot of the own node in the field of the reception response information within the previous superframe period exceeds a third threshold value. The wireless communication apparatus according to claim 11, wherein it is determined whether or not to stop transmission of the own apparatus in a next superframe period.   Whether the determination means restarts transmission of the node in the next superframe period based on each reception response information in the field of the reception response information in the previous superframe period when transmission of the own device is stopped The wireless communication apparatus according to claim 11, wherein it is determined whether or not.