JP6254824B2 - COMMUNICATION DEVICE, DATA TRANSMISSION METHOD, AND DATA TRANSMISSION PROGRAM - Google Patents

Description

  The present invention relates to a communication system in which a plurality of communication devices are connected by a wireless network.

  In recent years, a wireless communication terminal has been installed at each power consumer, and these are connected so as to be able to communicate with a collection server owned by the power company, and automatic meter reading is performed to periodically collect power meter reading data at each power consumer The system is being realized. In constructing such an automatic meter reading system, application of a so-called multi-hop wireless network system in which packets are sequentially transferred through the wireless communication terminal (node) is being studied.

  For example, a wireless data collection system has been proposed in which a tree-type network is configured with wireless communication terminals as nodes, meter-reading data is collected and integrated into a higher-level wireless communication device, and further transferred to the higher-level side ( Patent Document 1).

  According to this technology, for example, if a tree is formed for each predetermined number of wireless communication terminals and meter reading data collected in the wireless communication device that is the root of each tree is collected, meter reading data is collected in a short time Will be able to.

JP 2000-187793 A

Here, many of the general wireless networks represented by IEEE 802.11 have CSMA / CA (Carrier) by autonomous distributed control (DCF) at each node (wireless communication terminal).
The wireless channel access method of Sense Multiple Access with Collision Aviation is used. In this CSMA / CA, in order to avoid the collision of frames as much as possible, it is determined whether or not to transmit a frame after checking the usage status of the radio channel. Specifically, a wireless communication terminal that wants to transmit a frame senses (detects) the usage status of the carrier, and the channel is used while other radio communication terminals detect radio waves transmitted. Judge that it is in the middle and stop sending. Then, when the radio waves transmitted by other wireless communication terminals are not detected, and it is not used (idle state) for a certain period of time, it is determined that no one is using the carrier (obtains the transmission right), and the frame Start sending.

  That is, each wireless communication terminal cannot transmit a frame when the channel is in use, and cannot transmit a frame unless the idle state continues for a certain period.

  Therefore, when the radio wave environment is disturbed or unexpected transmission interruption occurs, the wireless communication terminal cannot easily acquire the transmission right, and the frame that needs to be transmitted remains. Once the frame is retained, even if it is transmitted after the retention, the information transmitted by the delayed frame is outdated, and there may be inconveniences in the received wireless communication terminal or a system composed of wireless communication terminals. is there. In addition, due to the occurrence of a delay frame, a retransmission request frame, a retransmission frame, and the like are generated, a large amount of staying frames are generated, and further, traffic congestion is caused.

  Therefore, an object of the present invention is to reduce the occurrence of delay frames in a wireless communication terminal as much as possible in a multi-hop wireless network system.

A communication apparatus according to an aspect of the present invention is a communication apparatus that performs multi-hop communication with another communication apparatus in a wireless network system having a plurality of communication apparatuses, and transmits transmission data to be subjected to the multi-hop communication. An enqueue means for enqueuing in a transmission queue that is a FIFO queue, and when the transmission right of the transmission data is acquired, the transmission data is dequeued from the transmission queue, and the dequeued transmission data is transmitted to the other communication device. The transmission queue includes a first transmission queue and a second transmission queue, the enqueue unit enqueues the transmission data into the first transmission queue, and the data transmission unit includes: The transmission data is dequeued from the second transmission queue, and the transmission queue is dequeued from the second transmission queue. When transmission data is dequeued, the transmission data first enqueued in the first transmission queue is enqueued at the end of the second transmission queue, and the first transmission queue and the second transmission queue The queue further includes storage means for storing transmission data in the order of enqueue and storing pointer information indicating transmission data to be dequeued next, and the data transmission means includes the dequeued transmission data as the enqueue. Only when it is transmission data before a predetermined period has elapsed since being enqueued to the transmission queue by the means , and the pointer information indicates in each of the first transmission queue and the second transmission queue When the transmission data is dequeued, the pointer information is updated with information indicating the transmission data to be dequeued next, If serial pointer information is not updated the predetermined period or more, the information indicating the transmission data to which the pointer information is dequeued next transmission data shown, and performs parallel processing for rewriting the pointer information.

A data transmission method according to another aspect of the present invention is a data transmission method used in a communication apparatus that performs multi-hop communication with another communication apparatus in a wireless network system having a plurality of communication apparatuses, An enqueue step for enqueuing transmission data subject to hop communication into a transmission queue that is a FIFO queue, and when the transmission right of the transmission data is acquired, the transmission data is dequeued from the transmission queue, and the dequeued transmission is performed. A data transmission step of transmitting data to the other communication device, wherein the transmission queue includes a first transmission queue and a second transmission queue, and in the enqueue step, the transmission data is transmitted to the first transmission queue. Enqueue to a queue, and in the data transmission step, the second transmission queue When the transmission data is dequeued from the second transmission queue, the transmission queue transmits the transmission data first enqueued in the first transmission queue to the last of the second transmission queue. The first transmission queue and the second transmission queue store storage data in the order in which they are enqueued and store pointer information indicating transmission data to be dequeued next. further wherein said at data transmission step, so that the transmission data dequeue, only transmits when after it is enqueued in the transmission queue in the enqueue step is the transmission data before the predetermined period of time has elapsed, the first The transmission data indicated by the pointer information is decoded in each of the transmission queue and the second transmission queue. Then, the pointer information is updated with information indicating transmission data to be dequeued next, and when the pointer information is not updated for the predetermined period or longer, the transmission data to be dequeued next to the transmission data indicated by the pointer information is updated. According to the information shown, the pointer information is rewritten in parallel .

A data transmission program according to another aspect of the present invention is a data transmission program used in a communication device that performs multi-hop communication with another communication device in a wireless network system having a plurality of communication devices, Enqueue means for enqueuing transmission data subject to multi-hop communication to a transmission queue that is a FIFO queue, and when the transmission right of the transmission data is acquired, the transmission data is dequeued from the transmission queue and dequeued The computer functions as data transmission means for transmitting transmission data to the other communication device, the transmission queue includes a first transmission queue and a second transmission queue, and the enqueue means transmits the transmission data to the first transmission queue. Enqueue to one transmission queue, the data transmission means from the second transmission queue The transmission queue dequeues transmission data, and when the transmission data is dequeued from the second transmission queue, the transmission queue first transmits the transmission data enqueued in the first transmission queue to the end of the second transmission queue. The first transmission queue and the second transmission queue store storage data in the order in which they are enqueued and store pointer information indicating transmission data to be dequeued next. The data transmission means transmits only when the dequeued transmission data is transmission data before a predetermined period of time has elapsed since being enqueued by the enqueue means into the transmission queue . When the transmission data indicated by the pointer information is dequeued in each of the transmission queue and the second transmission queue When the pointer information is updated with information indicating transmission data to be dequeued next, and the pointer information is not updated for the predetermined period or longer, information indicating transmission data to be dequeued next to the transmission data indicated by the pointer information is used. The pointer information is rewritten in parallel .

  Further, in the communication device described above, the transmission data is enqueued in the enqueue means, and data indicating that the transmission data is received from another communication device that is a transmission partner of the enqueued transmission data is transmitted. In the case where the data is not received before a predetermined retransmission period elapses from the time when the data is enqueued, further comprising communication control means for enqueuing the transmission data again in the enqueue means, and the predetermined period It is preferable that the period is longer than the retransmission period.

  According to the communication device, the data transmission method, and the data transmission program having such a configuration, the transmission data (frame) staying in the transmission queue for a predetermined period is not transmitted to other communication devices, so that a delay frame is generated. Is suppressed, and it is possible to prevent old information from being transmitted to other communication devices. In addition, when a retransmission frame corresponding to a delay frame or a frame requesting retransmission is transmitted / received, a large number of frames flow through the network. By not transmitting a delay frame, the number of frames flowing over the network is reduced as much as possible. It becomes possible.

  According to this configuration, it is possible to determine whether or not the user has stayed for a predetermined period by a simple method of checking the update time of the pointer information.

  The multi-hop wireless network system according to the present invention can minimize the generation of delay frames in a wireless communication terminal (communication device).

It is a figure which shows the usage example of the wireless network system for collecting meter-reading data from the terminal station of an electric power consumer. It is an example of the front view of the terminal station T. 1 is a diagram showing an outline of a wireless network system. It is a figure which shows the structural example of the functional block of a terminal station. It is a figure which shows the structural example of the functional block of gateway GW. It is a figure which shows the example of a structure and content of a transmission queue. FIG. 5 is a diagram for explaining a first method of queue management according to the first embodiment. 4 is a flowchart of an enqueue process according to the first embodiment. 3 is a flowchart of a transmission process according to the first embodiment. FIG. 10 is a diagram for explaining a second method of queue management according to the first embodiment. 3 is a flowchart of frame discard processing according to the first embodiment. 10 is a flowchart of frame discard processing according to the second embodiment.

<Embodiment 1>
The wireless network system of the embodiment is a multi-hop wireless network, and is a system for collecting meter reading data from each power consumer.

  FIG. 1 is a diagram illustrating a usage example of the wireless network system according to the embodiment. This wireless network system includes power consumers H1, H2,..., H12 (collectively referred to as power consumer H), and a terminal station T1 that is a power meter installed in each power consumer H. , T2,..., T12 (when collectively referred to as a terminal station T), gateways GWa, GWb, and GWc (when collectively referred to as gateway GW), a network 2, and a server device 1. In addition, the number of the electric power consumer H, the terminal station T, the gateway GW, and the server apparatus 1 is not restricted to these numbers.

  The network 2 is a network managed by a network operating company such as an electric power company, and may be wired or wireless. The gateway GW is connected to the server device 1 that is provided in, for example, a main utility pole and managed by an electric power company or the like via the network 2.

  The terminal station T constitutes a node of a network using multihop and belongs to any gateway GW. The terminal station T has a function as an integrated watt-hour meter, and each meter reading data is sequentially transferred to the adjacent terminal station T and collected at the gateway GW to which the own apparatus belongs. The meter reading data collected in each gateway GW is transmitted to the server device 1 via the network 2. The terminal station T performs communication according to a wireless LAN (Local Area Network) standard, and performs one-to-one communication in an ad hoc mode as indicated by signals A1 to 4 and the like. Each gateway GW collects meter reading data of about several hundred terminal stations T.

  FIG. 2 is an example of a front view of the terminal station T. This terminal station T is configured by arranging a terminal block 6, a load switch 3000, a watt hour meter 2000, and a communication device 1000 to which each distribution line in the home of a power consumer is connected. The watt-hour meter 2000 reads the accumulated power amount every predetermined period, for example, every 5 minutes. The meter reading data is transmitted every 30 minutes by the communication apparatus 1000 toward the gateway GW to which the own apparatus belongs. The load switch 3000 performs an opening / closing operation in accordance with control data transmitted from the server device 1.

  Here, FIG. 3 shows an outline of the network using the multi-hop of the embodiment. A double circle indicates the gateway GW, and an identifier “GWa” or the like of the gateway GW is described inside the circle. A single circle indicates the terminal station T, and an identifier “T1” or the like of the terminal station T is described inside the circle. A broken line connecting the circles indicates that the gateways GW or the terminal stations T indicated by circles at both ends thereof detect (learn) each other's existence.

  The server device 1 and the gateway GW are connected by a network (communication line) 2, and the gateway GW and each terminal station are connected by multi-hop. In the network of the embodiment, the number of hops is at most several tens, preferably 10 hops or less.

  The network of the embodiment is generated by, for example, OLSR (Optimized Link State Routing) which is one of so-called proactive routing protocols in a multi-hop wireless network. As for the route between the gateway GW and each terminal station T, each device (gateway GW, terminal station T) periodically transmits and receives a message for exchanging route information while transmitting the presence of the device itself. Thus, each device constructs autonomously. Each gateway GW and each terminal station T is a routing table (route table) which is topology information of the entire network, for example, a terminal station T in the learned network and an adjacent network for transmitting data to the terminal station T. The terminal station T that is the transmission destination is stored in association with it.

  Since each device autonomously constructs an optimum route according to changes in surrounding radio wave conditions, etc., the upstream route from the terminal station T to the gateway GW and the downstream route from the gateway GW to the terminal station T The route may be different.

  The meter reading data is transmitted on the upstream route toward the gateway GW to which the terminal station T belongs. For example, in FIG. 3, the hatched terminal T with the identifier “T8” (hereinafter referred to as “terminal T8”) is transferred to the gateway GW with the identifier “GWa” (hereinafter referred to as “gateway GWa”). The upstream route is indicated by a solid arrow facing the gateway GW. The meter reading data transmitted by the terminal station T8 reaches the gateway GWa via the terminal station T6.

  In the embodiment, the destination of the terminal station T is a MAC (Media Access Control) address, and the gateway GW is an IP (Internet Protocol) address.

  Further, when transmitting control data to the terminal station T8, the server device 1 passes control data (command) to the gateway GWa to which the terminal station T belongs, and requests transmission to the terminal station T8. The control data is transmitted on the down route indicated by the solid arrow route toward the terminal station T8 in FIG. The control data transmitted by the gateway GWa reaches the terminal station T8 via the terminal station T1, the terminal station T3, and the terminal station T5.

  Also, each terminal station T in FIG. 3 periodically transmits to the surroundings (hereinafter referred to as “Hello message”) for the purpose of notifying the information held by itself. The terminal station T can collect the peripheral information by receiving the Hello message from the other terminal station T. In this message (packet), all destinations (broadcast addresses) as destinations, destinations of the own device as transmission sources, learning GW information, a list of identifiers of all gateway GWs learned by the own device, neighboring node information, As a list of identifiers (destination addresses) of adjacent terminal stations T (adjacent terminal stations) and other station information, the identifiers of the terminal stations T learned by the device itself and adjacent transmission destinations (next hops) for each terminal station T Etc. are included.

  Further, the gateway GW transmits data for time adjustment in all directions, and the terminal station that has received this data and performed time adjustment transmits the time information data held by itself to all directions. The terminal station T that has received the time information data sets the time, and further transmits the time information data in all directions. In this way, all terminal stations T perform time synchronization. This is because each terminal station T transmits meter-reading data at a fixed time or performs a predetermined process such as a process for stabilizing the network at a predetermined time.

  Thus, in the multi-hop wireless network of the embodiment, various data are constantly transmitted and received, and the above-mentioned data is a part. The data to be transmitted / received includes data desired to be transmitted without delay, such as meter reading data and time information data.

  However, in a multi-hop wireless network, the communication environment may change due to weather or some trouble, and it may be difficult to acquire a transmission right, and a situation in which data cannot be transmitted may occur.

  The terminal station T of the present embodiment manages frames so that delay frames are not generated as much as possible in the entire network.

  Hereinafter, an embodiment according to the present invention will be described with reference to the drawings.

<Configuration>
FIG. 4 is a diagram illustrating a configuration example of functional blocks of the terminal station T. The terminal station T includes a communication device 1000, a watt-hour meter 2000, and a load switch 3000. A dashed arrow indicates that the gateway GW communicates with the gateway GW only at the terminal station T in the highest hierarchy.

  The communication apparatus 1000 includes a wireless communication control unit 1100 (communication control unit), a wireless communication unit 1200, a timer 1300, an in-flight communication control unit 1400, an interface 1410, an interface 1420, an external interface 1500, an input unit 1510, a link information storage unit 1800, And the electric energy information storage part 1900 is provided.

  The wireless communication control unit 1100 includes an enqueue unit 1110, a transmission queue 1120, and a frame transmission unit 1130 (data transmission unit), and has a function of controlling each functional unit such as the wireless communication unit 1200 to control wireless communication. Have. For example, periodically, when a message from another terminal station T is received, the route information stored in the link information storage unit 1800 is updated according to the received content. Also, every 30 minutes, the power amount stored in the power amount information storage unit 1900 is read, a frame of meter reading data addressed to the gateway GW to which the terminal station T belongs is created, and the transmission queue is instructed to the enqueue unit 1110 And so on. The timing for transmitting the meter reading data is detected by interruption from the timer 1300.

  Also, the wireless communication control unit 1100 transmits data indicating that it has been received from the communication partner, for example, ACK (for example, ACK () even after a predetermined retransmission period, for example, 3 seconds has elapsed since transmitting data to another communication device. If no (Acknowledgement) frame is received, it is determined that the data has not arrived, and the data is retransmitted.

  The enqueue unit 1110 has a function of receiving a frame from the wireless communication control unit 1100 and enqueuing it to the transmission queue 1120. The frame transmission unit 1130 dequeues the frame from the transmission queue 1120 when acquiring the transmission right of the frame, and performs wireless communication. A function of transmitting a frame via the unit 1200; The queue management performed by the transmission queue 1120, the enqueue unit 1110, and the frame transmission unit 1130 will be described in the section <Method for avoiding delayed frame generation>.

  The wireless communication unit 1200 has a function of communicating with another terminal station T (“terminal station T ′” in FIG. 4) or the gateway GW in an ad hoc mode according to the wireless LAN standard.

  The timer 1300 has a function of notifying the wireless communication control unit 1100 and the in-flight communication control unit 1400 of the time and also interrupting at a predetermined cycle. For example, the wireless communication control unit 1100 is interrupted every 30 minutes. For example, an in-flight communication control unit 1400 is interrupted every 5 minutes. The wireless communication control unit 1100 reads out and transmits the meter reading data for 30 minutes from the power amount information storage unit 1900 at the timing of interruption, and the in-flight communication control unit 1400 receives power for 5 minutes from the power meter 2000 at the timing of interruption. The power is acquired and stored in the power information storage unit 1900.

  The interface 1410 is an interface that receives meter reading data from the watt-hour meter 2000, and the interface 1420 is an interface that transmits control data to the load switch 3000.

  The in-flight communication control unit 1400 has a function of controlling communication with the watt-hour meter 2000 and the load switch 3000 via the interface 1410 and the interface 1420. The in-flight communication control unit 1400 has a function of periodically acquiring the received power amount from the watt-hour meter 2000 and storing it in the power amount information storage unit 1900.

  The external interface 1500 is an interface connected to an external setting tool or the like, and is used for setting initial values and the like when the terminal station T is initially set.

  The input unit 1510 has a function of accepting a user operation and storing data in the link information storage unit 1800 and the electric energy information storage unit 1900 or rewriting the stored data in accordance with the user operation. .

  The link information storage unit 1800 has a function of storing information necessary for data transmission / reception such as topology information of the entire network as shown in FIG.

  The electric energy information storage unit 1900 has a function of storing the electric energy acquired from the electric energy meter 2000 by the in-flight communication control unit 1400.

  FIG. 5 is a diagram illustrating a configuration example of functional blocks of the gateway GW. The gateway GW includes a wireless communication control unit 4100, a wireless communication unit 1200, a timer 1300, an external interface 1500, an input unit 1510, an external communication control unit 4000, a link information storage unit 1800, and a meter reading data storage unit 1850.

  The wireless communication control unit 4100 has a function of controlling each functional unit to control wireless communication, and a function of causing the meter reading data storage unit 1850 to store meter reading data received from the terminal station T. The wireless communication control unit 4100 reads meter-reading data stored in the meter-reading data storage unit 1850 at a predetermined timing, transmits the data to the server device 1 via the external communication control unit 4000, and the external communication control unit 4000. The packet from the server device 1 received via the wireless communication unit 1200 is transmitted to the terminal station T via the wireless communication unit 1200.

  The wireless communication unit 1200, the timer 1300, the external interface 1500, the input unit 1510, and the link information storage unit 1800 are the wireless communication control unit 1100, the wireless communication unit 1200, the timer 1300, the external interface 1500, the input unit 1510, and the link of the communication device 1000. The information storage unit 1800 has the same function.

  The external communication control unit 4000 has a function of communicating with the server device 1.

  The meter-reading data storage unit 1850 has a function of storing meter-reading data transmitted from the terminal station T belonging to the gateway GW that is its own device.

  Each of the communication apparatus 1000 and the gateway GW of the embodiment can be configured using, for example, a computer, and software that programs a gateway GW determination method and the like stored in a storage unit (not shown) such as a hard disk, When executed by the CPU, the wireless communication control unit 1100 and the like described above are functionally configured in the computer.

<Delay frame generation avoidance method>
Here, a frame queue management and a method for avoiding the generation of a delayed frame will be described. First, the queue management of frames to be transmitted will be described with reference to FIG. The queue management is performed by the transmission queue 1120, the enqueue unit 1110, and the frame transmission unit 1130.

  The transmission queue 1120 includes a memory (storage means) that temporarily stores frames to be transmitted, and stores frames, addresses of the stored frames, stored order, and the like. The transmission queue 1120 has a function of managing one frame as one element as a FIFO (First In First Out) queue.

  The transmission queue 1120 has two queues: an AP queue 1121 that is a queue managed by an application, and a DR queue 1122 that is a queue managed by a so-called wireless driver. FIG. 6 is a schematic diagram of the AP queue 1121 and the DR queue 1122. One rectangle represents a frame, and a box containing a plurality of rectangles represents one element (frame, transmission data). Also, the smaller numerical value in the rectangle indicates that it has been queued first. That is, “F1” is the oldest frame and is first dequeued and transmitted. When “F1” is dequeued and transmitted from the DR queue 1122 and the queue is empty, “F7” is moved from the AP queue 1121 to the top of the DR queue 1122. The most recently enqueued frame is stacked on the top of the AP queue 1121 box.

  The enqueue unit 1110 enqueues frames at the end of the AP queue 1121 when enqueuing frames. That is, in FIG. 6, the enqueue unit 1110 stacks the frames on the top of the AP queue 1121, that is, connects them to the end of the queue.

  When the frame transmission unit 1130 dequeues the frame, the frame transmission unit 1130 takes out the frame first enqueued in the DR queue 1122. That is, in FIG. 6, the bottom frame of the box of the DR queue 1122 is taken out.

  Normally, the application side manages only the AP queue 1121. For example, only frames enqueued in the AP queue 1121 can be deleted. Further, when the DR queue 1122 has a free space, the wireless driver moves the frame from the AP queue 1121 to the DR queue 1122, and manages only the DR queue 1122. However, it is assumed that the enqueue unit 1110 and the transmission queue 1120 according to the embodiment can manage both the AP queue 1121 and the DR queue 1122.

  In the embodiment, a frame that stays in the AP queue 1121 or the DR queue 1122 for 3 seconds or more is discarded as invalid data. The discarded frame is retransmitted by the wireless communication control unit 1100 as necessary.

  For example, when communication conforming to the IEEE 802.11b standard is performed, it is rare that frames are not transmitted in units of seconds. Therefore, in the embodiment, the influence on the system of the entire network due to the delay of the frame such as time information is considered, and the actual queue time is observed, and the staying period (predetermined period) is 3 seconds. . This 3 seconds is a period from when the wireless communication control unit 1100 of the communication apparatus 1000 transmits data to another communication apparatus until it is retransmitted. That is, if the wireless communication control unit 1100 does not receive data indicating that it has been received from the communication partner even after waiting 3 seconds after enqueuing the data in the transmission queue, it determines that the data has not arrived, and again The same frame is enqueued (retransmitted) in the transmission queue.

  By setting the stagnation period to such a period, it is possible to avoid sending data that would have been retransmitted over the network, so that unnecessary frames are not sent over the network and traffic can be reduced as much as possible. It becomes possible. This residence period may be longer than the retransmission period (3 seconds). Moreover, you may change according to the content of the data to transmit. For example, if the data is important for freshness, such as time information, that is, if the data is received with a delay, the data may affect the processing. It is good also as not providing a residence period in the data which is not. Further, an allowable residence period may be set according to the priority of the frame.

  Two methods will be described as a method of discarding a frame whose residence time has exceeded 3 seconds. One is a method of giving a time stamp when enqueuing a frame. Based on this time stamp, the elapsed time is calculated at the time of dequeuing, and if it exceeds 3 seconds, it is discarded, and if it does not exceed, it is transmitted.

  The other is to periodically observe the fluctuation of the pointer managing the transmission queue and discard the frame according to the fluctuation.

<First method>
First, the first method will be described with reference to FIG. FIG. 7 shows an AP queue 1121a and a DR queue 1122a, which are transmission queues 1120a of the first method. As shown in the AP queue 1121a and the DR queue 1122a in FIG. 7, the time is associated with each queued frame and stored. For example, the time stamp “T1” in FIG. 7 indicates the time when the frame “F1” was enqueued. In FIG. 7, it is described that it is queued together with (included in) the frame, but it may be stored in another memory so that the correspondence with the frame can be understood.

  If the difference between the time of the time stamp of the dequeued frame and the current time (time when dequeued) exceeds 3 seconds when dequeued, the frame is discarded without being transmitted.

  Here, the operation of the communication apparatus 1000 that performs queue management according to the first method will be described with reference to FIGS. 8 and 9. FIG. 8 is a flowchart of the enqueue process performed by the enqueue unit 1110, and FIG. 9 is a flowchart of the transmission process performed by the frame transmission unit 1130.

  First, the enqueue process will be described with reference to FIG.

  The wireless communication control unit 1100 passes the frame to be transmitted to the enqueue unit 1110 and requests enqueue.

  Upon receiving the request, the enqueue unit 1110 acquires the current time from the timer 1300 (step S10), and adds a time stamp to the frame received from the wireless communication control unit 1100 (step S11). Specifically, the time acquired from the timer 1300 is set at a predetermined position in the frame received from the wireless communication control unit 1100. The enqueue unit 1110 enqueues the frame with the time stamp at the tail end of the AP queue 1121 (step S12), and notifies the wireless communication control unit 1100 that it has been enqueued.

  Next, the transmission process will be described with reference to FIG.

  The frame transmission unit 1130 always performs carrier sense, confirms that the carrier is free, and determines that the transmission right of the frame has been acquired if the idle state continues for a predetermined period (step S20). The frame transmission unit 1130 that has acquired the transmission right reads the first enqueued frame from the DR queue 1122a (step S21). If there is no frame to be read, the transmission process is terminated. If a frame is read, the oldest frame among the frames queued in the AP queue 1121a is moved to the tail end of the DR queue 1122a.

  The frame transmission unit 1130 that has read the frame acquires the current time from the timer 1300 (step S22), and calculates the difference between the acquired current time and the time of the time stamp assigned to the read frame, that is, the elapsed time. calculate. When the elapsed time does not exceed the stayable period (3 seconds) (step S25: No), the transmission is performed via the wireless communication unit 1200 (step S24), and the transmission process is terminated. On the other hand, when the elapsed time is equal to or longer than the retention period (step S25: Yes), the transmission process is terminated without discarding the transmission.

<Second method>
Next, the second method will be described with reference to FIG. FIG. 10 shows the DR queue 1122b among the transmission queues 1120b of the second method. In FIG. 10, the DR queue 1122 is described as an example, but the same applies to the AP queue 1121.

  As shown in the diagram on the right side of FIG. 10, the queue is composed of one continuous memory area. Here, a case where up to six frames are queued will be described. A rectangle described as “Buf (i)” (i = 0, 2,..., 5) indicates an area in which one frame is stored, and the frames are stored in order from “Buf (0)”. , “Buf (5)” is stored in “Buf (0)”.

  The memory area is managed by two pointers, ptr1 and ptr2. ptr1 (pointer information) indicates the start address of the memory area of the frame to be dequeued next. ptr2 indicates the address of the memory area of the frame to be enqueued next, that is, the start address of the empty area. That is, the area from ptr2 to ptr1 is an empty area. In FIG. 10, the Buf area where the frame is stored is hatched.

  A case where one frame is dequeued and one frame is enqueued from the DR queue 1122b shown in the figure above the white arrow is shown below. A dotted arrow indicates a correspondence between the Buf area and the frame. For example, in the above figure, the frame “F1” is stored in the region “Buf (3)”, and the frame “F2” is stored in the region “Buf (4)”.

  In the figure above the white arrow, ptr1 indicates the start address of the area “Buf (3)” where the frame “F1” to be dequeued next is stored, and ptr2 indicates “Buf (1) of the free area. "Indicates the head address. From this state, it is assumed that the frame “F1” is dequeued and the frame “F5” is enqueued.

  In the figure below the white arrow, since the frame “F1” is dequeued, ptr1 indicates the head address of the area “Buf (4)” in which the frame “F2” is stored. If the frame “F5” is enqueued, ptr2 indicates the start address of the area “Buf (2)” next to the area “Buf (1)” in which the frame “F5” is stored. .

  In the second method of the embodiment, when the address indicated by ptr1 is not changed for 3 seconds, it is determined that the first frame to be dequeued next is retained, and the first frame is discarded. That is, the address indicated by ptr1 is set as the start address of the next area. For example, in the lower diagram of FIG. 10, when ptr1 is not changed for 3 seconds or more, the address indicated by ptr1 is changed from the start address of the area “Buf (4)” to the start address of the area “Buf (5)”. Rewrite (update). By updating ptr1, the area “Buf (4)” becomes a free area. That is, the frame “F2” stored in the area “Buf (4)” is discarded.

  In the above description, ptr1 indicates (stores) the start address of the region “Buf (i)”, but ptr1 stores the index of the region “Buf (i)”, that is, the value of “i”. It is good to keep it.

  Here, the operation of the communication apparatus 1000 that performs queue management by the second method will be described with reference to FIG.

  When frame transmission section 1130 performs carrier sense and determines that it has acquired the right to transmit a frame, frame transmission section 1130 reads the first enqueued frame from DR queue 1122b and transmits it through radio communication section 1200. The frame transmission unit 1130 performs a frame discarding process in parallel with the process of transmitting this frame. The enqueue unit 1110 performs a process of enqueuing the frame passed from the wireless communication control unit 1100 to the tail end of the AP queue 1121.

  FIG. 11 is a flowchart of the frame discarding process performed by the frame transmitting unit 1130.

  The frame transmission unit 1130 periodically checks whether ptr1 in FIG. 10, that is, the pointer indicating the head address of the next dequeued frame has been rewritten (step S30), for example, at a period of 0.1 second.

  Specifically, the address indicated by the current pointer is acquired (step S31) and compared with the address of the pointer stored in the working memory. If the address indicated by the current pointer is different from the address stored in the working memory (step S32: No), the current time is obtained from the timer 1300 (step S35), and the current pointer and the current time are Is stored in the work memory (step S36), and the process returns to step S30. Note that the initial value of the pointer address stored in the working memory is a value such as 0 that is not indicated by the pointer in normal operation.

  In step S32, when the address indicated by the current pointer is the same as the address stored in the work memory (step S32: Yes), the current time is acquired from the timer 1300 and stored in the work memory. When the difference from a certain time is smaller than 3 seconds (step S33: No), the process returns to step S30. If the difference between the current time and the stored time is 3 seconds or more, it is determined that the pointer has not been updated for 3 seconds or more (step S33: Yes), and the pointer is moved, that is, the next The frame is updated with the stored address (step S34), and the process returns to step S30.

  Although the pointer and the current time are stored in step 36 in the flowchart, a new pointer and the time at that time may be stored when the frame is dequeued.

<Embodiment 2>
In the first embodiment, as a method of avoiding the occurrence of a delayed frame, the frame staying for a predetermined period is discarded. However, in the second embodiment, if the number of frames connected to the queue exceeds a predetermined number, for example, When the queue overflows and cannot be enqueued, all the enqueued frames are discarded.

  Once the frames that have stayed are discarded and newly queued, the flow of frames throughout the network is improved. In other words, if one communication device 1000 overflows, it can be predicted that the surrounding communication device 1000 overflows, and the surrounding communication devices 1000 discard the frame almost all at once. This increases the possibility of eliminating congestion.

The operation of the communication apparatus 1000 that performs queue management according to the second embodiment will be described with reference to FIG. FIG. 12 is a flowchart of the enqueue process performed by the enqueue unit 1110.
The wireless communication control unit 1100 passes the frame to be transmitted to the enqueue unit 1110 and requests enqueue.

  The enqueue unit 1110 that has received the request, when the number of frames currently queued is a threshold value, for example, the maximum value of frames that can be queued (step S40: Yes), the AP queue 1121 and the DR queue All the frames queued at 1122 are discarded (step S41). Then, the enqueue unit 1110 enqueues the frame passed from the wireless communication control unit 1100 into the AP queue 1121 (step S42), and ends the process.

  On the other hand, when the number of frames currently queued is smaller than a threshold, for example, the maximum number of frames that can be queued (step S40: No), the frame passed from the wireless communication control unit 1100 is stored in the AP queue 1121. Enqueuing is performed (step S42), and the process is terminated.

  In the second embodiment, all the queued frames are discarded, but a predetermined number of frames may be discarded. Also, a predetermined number of frames may be discarded.

  In order to express the present invention, the present invention has been properly and fully described through the embodiments with reference to the drawings. However, those skilled in the art can easily change and / or improve the above-described embodiments. It should be recognized that this is possible. Therefore, unless the modifications or improvements implemented by those skilled in the art are at a level that departs from the scope of the claims recited in the claims, the modifications or improvements are not covered by the claims. To be construed as inclusive.

GW gateway T terminal station H power customer 1 server device 2 network 1000 communication device 1100 wireless communication control unit (communication control means)
1110 Enqueue unit 1120 Transmission queue (storage means)
1130 Frame transmission unit (data transmission means)
1200 Wireless communication unit 1300 Timer 1400 In-flight communication control unit 1500 External interface 1800 Link information storage unit 1900 Electric energy information storage unit 2000 Electric energy meter 3000 Load switch 4000 External communication control unit

Claims (4)

In a wireless network system having a plurality of communication devices, a communication device that performs multi-hop communication with other communication devices,
Enqueue means for enqueuing transmission data to be subjected to the multi-hop communication into a transmission queue that is a FIFO queue;
A data transmission unit that dequeues the transmission data from the transmission queue and transmits the dequeued transmission data to the other communication device when the transmission right of the transmission data is acquired;
The transmission queue has a first transmission queue and a second transmission queue,
The enqueue means enqueues the transmission data into the first transmission queue,
The data transmission means dequeues the transmission data from the second transmission queue,
The transmission queue is configured to enqueue the transmission data first enqueued in the first transmission queue at the end of the second transmission queue when the transmission data is dequeued from the second transmission queue. And
The first transmission queue and the second transmission queue further include storage means for storing transmission data in the order of enqueue and storing pointer information indicating transmission data to be dequeued next.
It said data transmission means,
Only when the dequeued transmission data is transmission data before a predetermined period has elapsed since being enqueued by the enqueue means into the transmission queue ,
When the transmission data indicated by the pointer information is dequeued in each of the first transmission queue and the second transmission queue, the pointer information is updated with information indicating transmission data to be dequeued next, and the pointer information is A communication device characterized in that, when it is not updated for a predetermined period or longer, processing for rewriting the pointer information is performed in parallel with information indicating transmission data dequeued next to the transmission data indicated by the pointer information . The transmission data is enqueued in the enqueue means, and the data indicating that the transmission data is received from another communication device that is the transmission partner of the enqueued transmission data, from the time when the transmission data is enqueued, A communication control means for enqueuing the transmission data again in the enqueue means if not received before a predetermined retransmission period elapses;
The communication apparatus according to claim 1, wherein the predetermined period is a period longer than the retransmission period. In a wireless network system having a plurality of communication devices, there is a data transmission method used in a communication device that performs multi-hop communication with another communication device,
An enqueue step for enqueuing transmission data to be subjected to the multi-hop communication into a transmission queue that is a FIFO queue;
A data transmission step of dequeueing the transmission data from the transmission queue and transmitting the dequeued transmission data to the other communication device when the transmission right of the transmission data is acquired;
The transmission queue has a first transmission queue and a second transmission queue,
In the enqueue step, the transmission data is enqueued in the first transmission queue,
In the data transmission step, the transmission data is dequeued from the second transmission queue,
The transmission queue is configured to enqueue the transmission data first enqueued in the first transmission queue at the end of the second transmission queue when the transmission data is dequeued from the second transmission queue. And
The first transmission queue and the second transmission queue further include storage means for storing transmission data in the order of enqueue and storing pointer information indicating transmission data to be dequeued next.
In the data transmission step ,
Only when the dequeued transmission data is transmission data before a predetermined period has elapsed since being enqueued in the transmission queue in the enqueue step ,
When the transmission data indicated by the pointer information is dequeued in each of the first transmission queue and the second transmission queue, the pointer information is updated with information indicating transmission data to be dequeued next, and the pointer information is A data transmission method comprising: performing parallel processing of rewriting pointer information using information indicating transmission data dequeued next to transmission data indicated by the pointer information when the pointer information is not updated for a predetermined period or longer . In a wireless network system having a plurality of communication devices, a data transmission program used in a communication device that performs multi-hop communication with another communication device,
Enqueue means for enqueuing transmission data to be subjected to the multi-hop communication into a transmission queue that is a FIFO queue;
When the transmission right of the transmission data is acquired, the computer functions as a data transmission unit that dequeues the transmission data from the transmission queue and transmits the dequeued transmission data to the other communication device,
The transmission queue has a first transmission queue and a second transmission queue,
The enqueue means enqueues the transmission data into the first transmission queue,
The data transmission means dequeues the transmission data from the second transmission queue,
The transmission queue is configured to enqueue the transmission data first enqueued in the first transmission queue at the end of the second transmission queue when the transmission data is dequeued from the second transmission queue. And
The first transmission queue and the second transmission queue further include storage means for storing transmission data in the order of enqueue and storing pointer information indicating transmission data to be dequeued next.
It said data transmission means,
Only when the dequeued transmission data is transmission data before a predetermined period has elapsed since being enqueued by the enqueue means into the transmission queue ,
When the transmission data indicated by the pointer information is dequeued in each of the first transmission queue and the second transmission queue, the pointer information is updated with information indicating transmission data to be dequeued next, and the pointer information is A data transmission program characterized in that, when it is not updated for a predetermined period or longer, processing for rewriting the pointer information is performed in parallel with information indicating transmission data to be dequeued next to the transmission data indicated by the pointer information .

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