JP5241874B2 - Multi-hop communication method and communication apparatus - Google Patents

Description

  The present invention relates to a multihop communication method and a communication apparatus, and more particularly to a technique for improving transmission performance.

  In Patent Literature 1, channel data transmitted via a virtual channel constructed between a source node and a destination node in a wireless communication network is transmitted using transmission resources specified before transmission of the channel data. It is described that the reservation control message is transmitted from the destination node after the transmission resource for the virtual channel is specified after being received by the destination node, and the reservation control message indicates the use of the specified transmission resource. It is disclosed that information about transmission resources designated for informing peripheral nodes is included.

  In Patent Document 2, when a power failure occurs in the power system, a predetermined transmitting station transmits a predetermined signal to a receiving station attached to each of the distributed power sources, and the receiving station that receives this signal distributes A communication network system (distributed power supply transfer cutoff system) that disconnects (cuts off) a power source from a power system is disclosed.

Special table 2008-500753 gazette JP 2009-240092 A

  In the distributed power transfer interruption system, power line communication (PLC) is used for communication (communication between a relay station and a slave station) in the last one mile part. However, when using power line communication, it is necessary to install a relay station for each pole transformer, especially when trying to deploy a distributed power transfer block system over a wide area, the cost of installing the relay station is a problem. It becomes.

  Therefore, for example, it is conceivable to perform multi-hop wireless communication between slave stations and expand the area covered by one relay station. However, the current multi-hop wireless communication technology has a large transmission delay due to route setting, session establishment, and the like, and it is difficult to complete transfer blocking within a specified time.

  The present invention has been made based on such a background, and an object thereof is to provide a multi-hop communication method and a communication apparatus that can improve transmission performance.

One aspect of the present invention for achieving the above object is a multi-hop communication method, in which a first communication device establishes a session with a second communication device and then communicates with the second communication device. Measures the no-communication time , which is the time during which no data is transmitted / received, and automatically detects that the no-communication time exceeds a preset first threshold time. A session maintenance signal, which is a signal for maintaining the session, is transmitted , and the first threshold time is longer than the time required for the session maintenance signal to reach the second communication device from the first communication device. In addition, the time is set to be shorter than the time for which the session times out .

  According to the present invention, the first communication device automatically transmits a session maintenance signal to the second communication device before the session times out and disconnects. Therefore, after the session is established, Even when data transmission / reception is not performed with the second communication device, the established session is maintained as it is. For this reason, the frequency with which a session is re-established is reduced, and the transmission performance of multi-hop communication can be improved.

  Another aspect of the present invention is the above multi-hop communication method, wherein the session maintenance signal is a command used to check the soundness of a communication path between the first communication device and the second communication device. To include.

  Thus, if the command for confirming the soundness of the communication path is transmitted as the session maintenance signal, the disconnection of the session can be prevented and the soundness of the communication path can be confirmed. When the first communication device and the second communication device communicate according to TCP / IP, the command is, for example, a PING command.

Another aspect of the present invention is the multi-hop communication method, wherein the first communication device broadcasts one hello packet to the plurality of second communication devices, and the plurality of second communication devices. each is to receive the hello packet transmitted the reply packet to the first communication device, the first communication device receives and stores the reply packet, the first communication device of the second communication device sends a session establishment request respectively, the each of the plurality of the second communication device receives the session establishment request sends a session establishment packet to the first communication device, the first communication device of said plurality The session is established for the plurality of second communication devices by receiving the session establishment packet sent from each of the two communication devices .

  Thus, the establishment of a session between the first communication device and the second communication device can be performed collectively for one or more second communication devices that have responded to the hello packet broadcasted by the first communication device. . Therefore, for example, by establishing a session in a time zone with a small amount of communication, the frequency of session establishment in the time zone where communication frequently occurs decreases, and transmission performance in a time zone where communication frequently occurs is improved. Can be made.

Another aspect of the present invention is the multi-hop communication method, wherein the first communication device is a time during which data transmission / reception is not performed with the second communication device other than the session maintenance signal. After a certain accumulated no-communication time exceeds a second threshold time (> time for session timeout), transmission of the session maintenance signal is stopped.

  As described above, the session is unnecessarily maintained for a long time by stopping the transmission of the session maintenance signal after the accumulated no-communication time exceeds a predetermined time (> time when the session times out). It is possible to prevent adverse effects such as a decrease in bandwidth and waste of resources.

  Another aspect of the present invention is the multi-hop communication method, wherein the second communication device is provided in a switch that controls connection / disconnection between an electric power system and a distributed power source, and the second communication device In addition, the switch is controlled in accordance with data received from the first communication device.

  ADVANTAGE OF THE INVENTION According to this invention, the transfer interruption | blocking system for distributed power supplies which can control connection / disconnection between an electric power grid | system and a distributed power supply reliably using multihop communication is realizable.

  In addition, the subject which this application discloses, and its solution method are clarified by the column of the form for inventing, and drawing.

  According to the present invention, it is possible to improve transmission performance in multihop communication.

It is a figure explaining the schematic structure of the transfer interruption | blocking system 1 for distributed power supplies. 2 is a diagram illustrating a hardware configuration of a first communication device 10. FIG. 2 is a diagram illustrating a hardware configuration of a second communication device 20. FIG. It is a figure which shows the main functions with which the 1st communication apparatus 10 is provided. It is a figure which shows the main functions with which the 2nd communication apparatus 20 is provided. It is a flowchart explaining session establishment processing S600. 4 is an example of a hello packet 700. 4 is an example of a hello packet response 800. 3 is an example of a session establishment request 900. 4 is an example of a session establishment packet 1000. It is a flowchart explaining session maintenance processing S1100. 3 is an example of a session maintenance signal 1200. It is an example of the response 1300 of the session maintenance signal 1200. It is an example of a setting screen 1400.

Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings.
FIG. 1 shows a schematic configuration of a distributed power transfer interruption system 1 described as an embodiment. As shown in the figure, a distributed power transfer interruption system 1 includes a first communication device 10 attached to a power distribution facility 2 (such as a pole transformer) that constitutes a commercial power system 4, and a switch. 2 and a second communication device 20 attached to each of the one or more distributed power sources 5 connected to the commercial power system 4 via 3.

  The first communication device 10 includes an information processing device (not shown) provided in the central control station 6, predetermined communication means 7 (for example, the Internet, power line communication (PLC)), a dedicated line (power system). It communicates via a control information transmission system (CDT: Cyclic Digital data Transmission equipment, metal wire, optical fiber, etc.), wireless or wired public communication network). The first communication device 10 communicates with each of the second communication devices 20 by multi-hop wireless communication (hereinafter referred to as multi-hop communication).

  The switch 3 is connected to the commercial power system 4 of the distributed power source 5 or disconnected from the commercial power system 4 of the distributed power source 5 according to an instruction from the second communication device 20 attached to the switch 3 ( (Disconnection). When receiving the control signal from the central control station 6, the first communication device 10 performs multihop communication with the second communication device 20 and transmits the received control signal to the second communication device 20. The second communication device 20 controls the switch 3 according to the received control signal, and performs the connection or disconnection.

  FIG. 2 shows a hardware configuration of the first communication device 10. As shown in the figure, the first communication device 10 includes a central processing unit 11, a main storage device 12, an input device 13, a display device 14, a first communication interface 15A (first communication I / F), and a second communication interface. 15B (2nd communication I / F) and the time measuring device 16 are provided.

  The central processing unit 11 is configured using a CPU (Central Processing Unit), an MPU (Micro Processing Unit), and the like, and performs overall control of the first communication device 10. The main storage device 12 is configured using a RAM (Random Access Memory), a ROM (Read Only Memory), an NVRAM (Non Volatile RAM), and the like, and stores programs and data. The input device 13 is a user interface such as a numeric keypad or a touch panel, and accepts an operation input from the user. The display device 14 is a liquid crystal panel or the like, and outputs visual information.

  The first communication interface 15A performs multi-hop communication with the second communication device 20. The second communication interface 15B performs wired or wireless communication with an information processing apparatus provided in the central control station 6. The time measuring device 16 is configured using an RTC (Real Time Clock) or the like, and outputs date and time information (time stamp) such as the current date and time.

  FIG. 3 shows the hardware configuration of the second communication device 20. As shown in the figure, the second communication device 20 includes a central processing unit 21, a main storage device 22, a display device 23, and a communication interface 24.

  The central processing unit 21 is configured using a CPU or MPU, and performs overall control of the second communication device 20. The main storage device 22 is configured using RAM, ROM, NVRAM, and the like, and stores programs and data. The display device 23 is a liquid crystal panel or the like, and outputs visual information. The communication interface 24 (communication I / F) performs multi-hop communication with the first communication device 10 and the other second communication device 20.

  FIG. 4 shows main functions provided in the first communication device 10. As shown in the figure, the first communication device 10 includes a session establishment unit 151, a data transmission / reception unit 152, a no-communication time measurement unit 153, and an accumulated no-communication time measurement unit 154. These functions are realized by the hardware of the first communication device 10 or when the central processing unit 11 of the first communication device 10 reads and executes a program stored in the main storage device 12.

  The session establishment unit 151 establishes a session with the second communication device 20. Note that the establishment of a communication path between the first communication device 10 and the second communication device 20, which is a precondition for establishing a session, is a protocol that realizes multi-hop communication between the two (for example, RIP ( It is performed dynamically or statically according to Routing Information Protocol (OSPF), Open Shortest Path First (OSPF), Border Gateway Protocol (BGP), and the like.

  The data transmission / reception unit 152 transmits / receives data to / from the information processing device of the central control station 6 or the second communication device 20. The session maintaining signal transmitting unit 1521 of the data transmitting / receiving unit 152 uses a signal for maintaining a session (hereinafter referred to as a session maintaining signal) between itself and the second communication device 20 that has established a session. Send.

  The no-communication time measuring unit 153 is a time period during which no data is transmitted / received since the session is established between itself and the second communication device 20 of the other party that has established the session (hereinafter referred to as no-communication). Time)).

  The accumulated no-communication time measuring unit 154 measures a time period during which data is not transmitted / received to / from the second communication device 20 other than the session maintenance signal (hereinafter referred to as accumulated no-communication time).

  FIG. 5 shows main functions of the second communication device 20. As shown in the figure, the second communication device 20 includes a data transmission / reception unit 251 and a data transfer unit 252. These functions are realized by the hardware of the second communication device 20 or by the central processing unit 21 of the second communication device 20 reading and executing a program stored in the main storage device 22.

  The data transmission / reception unit 251 transmits / receives data to / from the first communication device 10 or another second communication device 20. The session maintenance signal receiving unit 2511 of the data transmission / reception unit 251 receives a session maintenance signal transmitted from the first communication device 10 or another second communication device 20.

  The data transfer unit 252 transfers data sent from the first communication device 10 or another second communication device 20 to the first communication device 10 or another second communication device 20. The session maintenance signal transfer unit 2521 of the data transfer unit 252 receives the session maintenance signal sent from the first communication device 10 or another second communication device 20 as the first communication device 10 or another second communication device 20. Forward to.

= Description of processing =
Next, processing performed in the distributed power transfer cutoff system 1 having the above configuration will be described.

<Session establishment processing>
A session is established between the first communication device 10 and each second communication device 20 at a predetermined timing. For example, when the new distributed power source 5 is introduced into the distributed power source transfer cut-off system 1 or when the failure of the distributed power source 5 is recovered, the timing is changed from the information processing device of the central control station 6 to the switch 3. For example, when a control instruction is received.

  FIG. 6 is a flowchart for explaining a process (hereinafter referred to as a session establishment process S600) performed between the first communication apparatus 10 and the second communication apparatus 20 in establishing the session. As shown in the figure, first, the first communication device 10 broadcasts a hello packet 700 to all the second communication devices 20 (S611).

  FIG. 7 shows an example of the hello packet 700. As shown in the figure, the hello packet 700 includes information such as transmission source information 701 (for example, the network address of the first communication device 10) and destination information 702 (for example, the network address of the second communication device 20). It is included.

  When receiving the hello packet 700 (S612), the second communication device 20 transmits a reply packet to the received hello packet 700 (hereinafter referred to as a hello packet response 800) to the first communication device 10 (S613).

  FIG. 8 shows an example of the hello packet response 800. As shown in the figure, the hello packet response 800 includes transmission source information 801 (for example, the network address of the second communication device 20) and destination information 802 (for example, the network address of the first communication device 10). Contains information.

  Next, when receiving the hello packet response 800 sent from the second communication device 20, the first communication device 10 stores this (S614). Next, the first communication device 10 transmits a session establishment request 900 to one or more second communication devices 20 that have transmitted the hello packet response 800 (S615).

  FIG. 9 shows an example of the session establishment request 900. As shown in the figure, the session establishment request 900 includes transmission source information 901 (for example, the network address of the first communication device 10) and destination information 902 (for example, the network address of the second communication device 20). Contains information.

  When receiving the session establishment request 900 sent from the first communication apparatus 10 (S616), the second communication apparatus 20 transmits a session establishment packet 1000 as a response to the first communication apparatus 10 (S617).

  FIG. 10 shows an example of the session establishment packet 1000. As shown in the figure, the session establishment packet 1000 includes transmission source information 1001 (for example, the network address of the second communication device 20), destination information 1002 (for example, the network address of the first communication device 10), and the like. Information is included.

  When receiving the session establishment packet 1000 sent from the second communication device 20, the first communication device 10 stores this (S618).

  Next, the first communication device 10 starts measuring the above-described no-communication time for each session with one or more second communication devices 20 that have received the session establishment packet 1000 in S618 (S619).

  Subsequently, the first communication device 10 determines whether or not session establishment packets 1000 have been received from all the second communication devices 20 that have transmitted the hello packet response 800 in S614 (S620). If session establishment packets 1000 have been received from all the second communication devices 20 that have received the hello packet response 800 (S620: YES), the processing ends. On the other hand, if there is a second communication device 20 that has not yet received the session establishment packet 1000 (S620: NO), the process returns to S615.

  Note that an upper limit may be set for the number of retry transmissions of the session establishment request 900 or a timeout may be set for the waiting time of the session establishment packet 1000 so that the session establishment packet 1000 is not waited indefinitely. The session establishment process S600 is performed as described above.

<Session maintenance processing>
After the session establishment process S600 is performed, for each session established with the second communication device 20, the first communication device 10 approaches the above-described no-communication time to the time for which the session times out. Real-time monitoring is started, and if approaching, a session maintenance signal is transmitted to the second communication device 20 of the other party so that the session will not time out and disconnect. FIG. 11 is a flowchart illustrating the details of this processing (hereinafter referred to as session maintenance processing S1100). Hereinafter, it will be described with reference to FIG.

  The first communication device 10 determines in real time whether or not the no-communication time t exceeds a preset first threshold time T1 (idle time limit) for each session established between the second communication devices 20. Monitor (S1111). The first threshold time T1 (<time for session timeout) is set to a time longer than at least the time required for the session maintenance signal to reach the second communication device 20 from the first communication device 10.

  When it is detected that the no-communication time t exceeds a preset first threshold time T1 (S1111: YES), the first communication device 10 sends a session maintenance signal 1200 to the second communication device 20 of the other party of the session. Is transmitted (S1112).

  FIG. 12 shows an example of the session maintenance signal 1200. As shown in the figure, the session maintenance signal 1200 includes transmission source information 1201 (for example, the network address of the first communication device 10), destination information 1202 (for example, the network address of the second communication device 20), and the like. Information is included.

  When the first communication device 10 and the second communication device 20 are communicating according to TCP / IP (Transmission Control Protocol / Internet Protocol), a command used for checking the soundness of the communication path is used as the session maintenance signal 1200. (For example, a PING command) can be used. As described above, if the command used for confirming the soundness of the communication path is transmitted as the session maintenance signal 1200, the disconnection of the session can be prevented and the soundness of the communication path can be confirmed.

  When receiving the session maintenance signal 1200 from the first communication device 10 (S1113), the second communication device 20 transmits a response 1300 to the first communication device 10 (S1114). Then, the first communication device 10 receives the response 1300 sent from the second communication device 20 (S1115).

  FIG. 13 shows an example of the response 1300. As shown in the figure, the response 1300 includes source information 1301 of the response (for example, the network address of the second communication device 20) and destination information 1302 (for example, the network address of the first communication device 10). ) And other information. The session maintenance process S1100 is performed as described above.

  As described above, in the distributed power transfer cutoff system 1 according to the present embodiment, after the first communication device 10 establishes a session with the second communication device 20, the first communication device 10 establishes a session with the second communication device 20. Since the session maintenance signal 1200 is automatically transmitted to the second communication apparatus 20 before the session times out, the first communication apparatus after the session is established is measured. Even when data transmission / reception is not performed between 10 and the second communication device 20, an already established session is maintained. According to this, the frequency with which a session is re-established is reduced, and the transmission performance of multi-hop communication can be improved. In addition, since the session is maintained for a long period of time regardless of whether or not communication is performed between the first communication device 10 and the second communication device 20 in this way, the central control station 6 can quickly move to the second communication device 20. It is possible to reliably control the switch 3 by transmitting a control instruction.

  Embodiment described above is for making an understanding of this invention easy, and does not limit this invention. The present invention can be changed and improved without departing from the gist thereof, and the present invention includes the equivalents thereof.

  For example, a time during which data is not transmitted / received to / from the second communication device 20 other than the session maintenance signal 1200 (the accumulated no communication time described above) is a predetermined second threshold time T2 (> time when the session times out) After exceeding, transmission of the session maintenance signal 1200 from the first communication device 10 to the second communication device 20 may be stopped. By doing so, it is possible to prevent a reduction in bandwidth and waste of resources due to an unnecessarily maintained session over a long period of time. Instead of comparing the accumulated no-communication time and the second threshold time T2, the number of transmissions of the session maintenance signal 1200 within the accumulated no-communication time may be limited. When the accumulated no-communication time exceeds the second threshold time T2, the connection may be disconnected together with the session, or only the session may be disconnected and the connection may be maintained as it is. Thus, by maintaining the connection as it is, the establishment of the connection can be omitted at the next connection, and the communication efficiency can be improved accordingly.

  In the present embodiment, as described with reference to FIG. 6, session establishment between the first communication device 10 and one or more second communication devices 20 is performed all at once. The communication device 10 may establish a session with each of the second communication devices 20 individually.

  In the present embodiment, the mechanism for maintaining the session between the first communication device 10 and the second communication device 20 has been described. However, the same mechanism is used between the second communication device 20 and another second communication device 20. If applied to the multi-hop communication, the session between the second communication devices 20 can be automatically maintained.

  Further, the first communication device 10 or the second communication device 20 may be provided with a user interface for allowing the user to set the first threshold time T1 or the second threshold time T2. FIG. 14 shows an example of a user interface (hereinafter referred to as a setting screen 1400). As shown in the figure, the setting screen 1400 includes a setting field 141 for the first threshold time T1, a setting field 142 for the second threshold time T2, and the like.

  Further, the above mechanism can be applied to various wireless communication systems other than the distributed power transfer cutoff system 1. For example, the present invention can be applied to multi-hop communication (such as an inter-vehicle communication system) for in-vehicle terminals.

  Moreover, the above mechanism is the high-precision position detection system currently disclosed by Unexamined-Japanese-Patent No. 2004-184078, Unexamined-Japanese-Patent No. 2005-351877, Unexamined-Japanese-Patent No. 2005-351878, Unexamined-Japanese-Patent No. 2006-23261, for example. It can be applied to. That is, the high-accuracy position detection systems disclosed in these documents receive radio waves transmitted from each of the mobile terminals by a plurality of antennas of the base station, and carry out the mobile from the phase difference of the received waves received by each antenna. If the present invention is provided for multi-hop communication performed between the mobile terminals, the transmission performance of multi-hop communication performed between the mobile terminal and the base station can be improved. Can be improved.

DESCRIPTION OF SYMBOLS 1 Transfer interruption | blocking system 3 for distributed power supplies 3 Switch 4 Commercial power system 5 Distributed power supply 10 1st communication apparatus 20 2nd communication apparatus 1200 Session maintenance signal

Claims (7)

After the first communication device establishes a session with the second communication device, it measures a non-communication time , which is a time during which data transmission / reception is not performed with the second communication device, and the non-communication Upon detecting that the time exceeds a preset first threshold time , a session maintenance signal that is a signal for automatically maintaining the session is transmitted to the second communication device ,
The first threshold time is set to be longer than the time required for the session maintenance signal to reach the second communication device from the first communication device and shorter than the time for the session to time out. A multi-hop communication method. The multi-hop communication method according to claim 1,
The session maintenance signal includes a command used for confirming soundness of a communication path between the first communication device and the second communication device. The multi-hop communication method according to claim 2,
The first communication device and the second communication device communicate according to TCP / IP (Transmission Control Protocol / Internet Protocol), and the command is a PING command. The multi-hop communication method according to claim 1,
The first communication device broadcasts one hello packet to the plurality of second communication devices ,
Wherein each of the plurality of the second communication device receives the hello packet transmitted the reply packet to the first communication device,
The first communication device receives and stores the reply packet;
The first communication device transmits a session establishment request to each of the second communication devices;
Wherein each of the plurality of the second communication device receives the session establishment request sends a session establishment packet to the first communication device,
The first communication device establishes the session for the plurality of second communication devices by receiving the session establishment packet sent from each of the plurality of second communication devices. Communication method. The multi-hop communication method according to claim 1,
The first communication device has a second threshold time (> time for session timeout) that is a time during which data is not transmitted / received to / from the second communication device other than the session maintenance signal. The multi-hop communication method is characterized in that transmission of the session maintenance signal is stopped after exceeding. The multi-hop communication method according to claim 1,
A switch for controlling connection / disconnection between a power system and a distributed power source is provided with the second communication device, and the switch is provided in the second communication device according to data received from the first communication device. A multi-hop communication method characterized by controlling. A communication device that performs multi-hop communication, and after establishing a session with another communication device, measures a non-communication time , which is a time during which no data is transmitted to or received from the other communication device. When it is detected that the no-communication time exceeds a preset first threshold time , a session maintenance signal that is a signal for automatically maintaining the session is transmitted to the other communication device. ,
The first threshold time is set to be longer than the time required for a session maintenance signal to reach the other communication device from the communication device and shorter than the time for the session to time out. A communication device.

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