JP2010062803A - Data transmission/reception device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a data transmission/reception device capable of keeping synchronization between client terminals without intermitting video stream data during transmission between the client devices even when communication between a management terminal and a client terminal is intermitted, and causing a new management terminal to emerge in a network, in a network system enabling direct communication between client terminals. <P>SOLUTION: In the client terminal, a reception condition of synchronization information and schedule information from the management terminal is managed; and when the information cannot be received for a certain period or more, its own device emerges as a candidate of a new management terminal, and starts operation as a new management terminal through approval of another client terminal. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a data transmission / reception apparatus, and more particularly to a data transmission / reception apparatus that transmits and receives data such as a video stream in a network system such as wireless communication or high-speed PLC (Power Line Communication).

  With recent increases in the speed of network systems such as wireless communication and high-speed PLCs, research has been conducted in various fields to construct home video networks using these systems. In order to transmit and receive video and audio data that requires real-time performance using wireless communication or a high-speed PLC, the transmission band of data to be transmitted in advance to transmit video and audio smoothly without interruption. It is necessary to transmit after securing the Therefore, a wireless LAN (Local Area Network) or the like adopts a TDMA (Time Division Multiple Access) method, and a method for transmitting data while ensuring a data transmission band in advance has been introduced. Specifically, for example, HiSWANA (High Speed Wireless Access Networking Type a: ARIB STD-T70 version 1.0) standardized by ARIB (Radio Industry Association) is available.

  Hereinafter, the outline of the TDMA system adopted in the HiSWANA standard will be briefly described. In the TDMA system adopted in HiSWANA, each terminal (data transmission / reception apparatus) in a network is managed by one terminal (data transmission / reception apparatus) called a management terminal. A terminal managed by the management terminal is called a client terminal.

  In order to manage time synchronization of the entire network, the management terminal broadcasts packet data called a beacon (beacon) signal (hereinafter referred to as BCH: Broadcast CHannel) at a predetermined cycle (a 2 ms cycle in HiSWANA). ).

  Upon receiving the BCH, each client terminal arranged in the network resets the reference time information in the terminal and starts preparation for receiving various control packets transmitted from the management terminal. After transmitting the BCH, the management terminal broadcasts packet data for network system control (hereinafter referred to as FCH: Frame CHannel) including the data transmission schedule of each client terminal connected to the network to each client terminal. To do.

  Data transmission and reception schedules (data transmission / reception slot information (transmission / reception start timing information, data transmission / reception time information, etc.)) of each client terminal connected to the network are added to the FCH and transmitted. When each client terminal receives the FCH, each client terminal detects the timing at which the terminal receives data and the timing at which the terminal transmits data.

  Following the transmission of the FCH, the management terminal transmits packet data of a transmission request reception notification (hereinafter referred to as ACH: Access feedback CHannel) to each client terminal. When transmission of the BCH, FCH, and ACH packet data from the management terminal is completed, each client terminal starts receiving and transmitting packet data based on the schedule notified on the FCH (hereinafter, between each terminal). The period during which data is transmitted and received is denoted as TCH).

  In the TDMA scheme, the management terminal schedules data transmission slots only for client terminals having data to be transmitted. Therefore, the client terminal having data to be transmitted needs to request the management terminal to allocate a slot for transmitting the data of the own terminal. In the TDMA system adopted in the HiSWANA standard, a transmission request is accepted from each client terminal, so that the transmission slot request request (bandwidth allocation request) from each terminal is received at the end of one Beacon period (hereinafter referred to as one frame). CSMA (Carrier Sense Multiple Access) period (hereinafter referred to as RCH: Random access CHannel period) is prepared.

  The management terminal notifies the terminal that has received the transmission slot request request during the RCH period that the bandwidth allocation request has been received on the ACH within the Beacon period of the next one frame.

  Next, a system configuration in a conventional data transmission / reception apparatus in which the above-described TDMA scheme based on the HiSWANA standard is applied to, for example, a high-speed PLC will be described.

  In general, in a data transmission / reception apparatus based on a wireless LAN or a high-speed PLC, data transmission / reception is performed via a management terminal when data transmission / reception is performed between client terminals. Specifically, when transmitting data from the first client terminal to the second client terminal, the first client terminal sends transmission data to the management terminal, and the management terminal that has received the data receives the second data Send the received data to the client terminal. In this case, although the data is transmitted from the first client terminal to the second client terminal, the limited bandwidth is used twice because it passes through the management terminal.

  In order to solve such a problem, there is a method of directly transmitting and receiving data between client terminals. That is, in the TDMA system, as described above, synchronization between the management terminal and each client terminal is ensured by the Beacon signal periodically output from the management terminal. Therefore, by extending the concept of scheduling, direct communication between synchronized client terminals becomes possible.

  In the following, as an example of direct communication between client terminals synchronized by the management terminal, the TV system in the bedroom that is the management terminal, the TV system in the child room that is the client terminal, and the living room that is also the client terminal An example in which three AV (Audio Visual) devices of a recorder are connected to a high-speed PLC, video stream data is transmitted from the recorder in the living room to the TV system in the child room, and video is displayed on the TV system in the child room I will give you.

  In this example, the BCH output from the TV system in the bedroom enables the TV in the children's room and the recorder in the living room to perform synchronized communication, and the living room by the FCH output from the TV system in the bedroom. The video data transmission timing of the recorder is scheduled, and the video data reception timing from the recorder in the living room is scheduled for the TV in the child room.

  However, in the above example, it is assumed that noise is generated on the transmission path of the high-speed PLC, and communication between the TV system in the bedroom and the TV system in the child room is interrupted. At this time, the TV system in the child room cannot receive control information such as BCH and FCH from the management terminal, cannot synchronize, and cannot receive the schedule data, so that the video display is interrupted or disturbed. .

  As described above, in the case of a network where control of direct communication between client terminals is performed by the management terminal, communication between the client terminals is transmitted when communication between the management terminal and the client terminal is interrupted due to a failure in the transmission path. There is a problem that data transmission / reception between these client terminals is interrupted even if there is no problem in the road.

  Here, in Patent Document 1, in an autonomous decentralized ad hoc network in which data is directly transmitted and received between client terminals that do not have a management terminal, communication apparatuses can communicate with each other without executing complicated synchronization processing between the communication apparatuses. Describes a communication system capable of executing communication processing.

  Patent Document 1 discloses that a communication system including a plurality of communication apparatuses that do not have a relationship between a control station and a controlled station has a predetermined cycle configured from a plurality of time frames for transmitting and / or receiving signals. Setting a superframe based on clock information of the own communication device; determining at least a time frame for transmitting a beacon signal in the superframe; and within a communication area capable of communicating with the own communication device Receiving a beacon signal transmitted by another existing communication device in a superframe period; and transmitting and / or receiving a signal described in the beacon signal from the other communication device. The time frame and at least the time frame for the communication device to transmit the beacon signal are stored in the time frame management table. There is a description relating to one having a step of allocating based on clock information of a communication device.

  However, in Patent Document 1, each client terminal assigns a beacon transmission position of its own communication device to a super frame in the control of the time frame management table, and a beacon signal is transmitted at a constant period. For this reason, since a terminal that does not transmit data also transmits a beacon signal at a constant period, there is a problem that an unnecessary transmission band is used.

  In particular, in a high-speed PLC, the symbol length of one OFDM symbol is often long, and when each client terminal connected to the network sends a beacon signal at a fixed period, overhead for synchronization (useless bandwidth use) ) Occurs. For example, even if one OFDM symbol length is 50 μs, the preamble is 4 symbols, and the payload is 1 symbol, a transmission band of at least 250 μs is used for beacon transmission per client terminal.

JP 2006-121332 A

  The present invention has been made to solve the above problems, and in a network system capable of direct communication between client terminals, even when communication between the management terminal and the client terminal is interrupted, An object of the present invention is to provide a data transmission / reception apparatus capable of maintaining synchronization between client terminals without interruption of video stream data being transmitted and enabling a new management terminal to be created in the network.

  The data transmission / reception apparatus according to claim 1 of the present invention is a data transmission / reception apparatus included in each of a plurality of terminals of a network system, wherein the plurality of terminals include a management terminal that manages other terminals, and the management A plurality of client terminals managed by a terminal, and transmission and reception of video data and control data between the plurality of terminals based on synchronization information and schedule information periodically output from the management terminal; The transmission / reception device confirms reception status information indicating whether the synchronization information and the schedule information have been normally received from the management terminal, and a control information detection unit that detects synchronization information and schedule information output from the management terminal And whether or not normal communication with the management terminal can be normally performed based on the reception status information. A control unit that generates reception status progress information, and when the control unit determines that continuous communication with the management terminal cannot be normally performed based on the reception status progress information, the management terminal communication failure A notification is generated and transmitted to another client terminal, and approval from the other client terminal as a candidate for a new management terminal replacing the management terminal is obtained, so that the own device starts operating as the new management terminal. To control.

  According to the data transmitting / receiving apparatus according to claim 1 of the present invention, when the client terminal determines that continuous communication with the management terminal cannot be normally performed based on the reception status progress information, the management terminal communication failure notification is generated. To the other client terminal and get approval from the other client terminal as a candidate for the new management terminal in place of the management terminal. A management terminal can be created.

<A. Embodiment 1>
<A-1. Network system configuration>
FIG. 1 is a diagram schematically showing a configuration of a high-speed PLC network system including a data transmitting / receiving apparatus according to Embodiment 1 of the present invention. In the following, the data transmitting / receiving apparatus is referred to as a terminal.

  As shown in FIG. 1, the high-speed PLC network system includes a management terminal 1 that manages the entire network, a client terminal A3, a client terminal B5, and a client terminal B7 connected to the PLC network system, and a power line 9 that also serves as a signal line. The management terminal 1, the client terminal A3, the client terminal B5, and the client terminal B7 and the power line 9 are electrically connected by power outlets 2, 4, 6, and 8, respectively.

  The configuration of the high-speed PLC network system shown in FIG. 1 is an example of a system configuration to which the data transmission / reception apparatus of the present invention can be applied. The data transmission / reception apparatus of the present invention includes a high-speed PLC network system having other configurations, The present invention can also be applied to other systems such as a network system using a wireless LAN and a network system using Ethernet (registered trademark). The data transmitting / receiving apparatus according to the present invention is connected to the TV system and DVD recorder via the Ethernet interface.

<A-2. Overview of network system operations>
Next, the schematic operation of the network system will be described with reference to FIG. 1, focusing on the operation of the management terminal 1 in the high-speed PLC network. In the first embodiment, a case will be described as an example where the TDMA method adopted in the HiSWANa standard described as the prior art is adopted as the MAC (Media Access Control) method.

<A-2-1. Operation of management terminal>
The management terminal 1 first broadcasts a Beacon signal (BCH: Broadcast CHannel) as synchronization information at a predetermined cycle in order to manage time synchronization of the entire network. After the BCH transmission, the management terminal 1 broadcasts data reception and data transmission timing information (FCH: Frame CHannel) of each client terminal in the high-speed PLC network. When an RCH (Random access CHannel) output from each client terminal is received in the previous frame after the FCH transmission, an ACH (Access feedback CHannel) for notifying the RCH transmission client terminal of normal reception is output.

  After the ACH transmission, the management terminal 1, the client terminal A3, the client terminal B5, and the client terminal C7 perform data transmission / reception between the client terminals based on the schedule transmitted on the FCH.

  In addition, the management terminal 1 is disconnected from the client terminal due to noise generated on the transmission path in the high-speed PLC network, and as a result, the terminal that was originally the client terminal is generated as a new management terminal. When this is confirmed, an operation of controlling the management terminal to become a client terminal is performed (details will be described later).

<A-2-2. Operation of client terminal>
Next, the operation of the client terminal will be described. When the client terminal receives the BCH output from the management terminal 1, the client terminal synchronizes the reference time in the client terminal based on the BCH.

  After the synchronization of the reference time, each client terminal sets the respective data transmission timing and data reception timing internally based on the FCH output from the management terminal 1, and starts data transmission and reception preparation. In the case of data transmission, when the transmission time based on the FCH approaches, the PLC transmission control unit (details will be described later) starts generating transmission data, and transmits the transmission data to the power line 9 at a predetermined timing. In the case of data reception, when the reception time based on the FCH is reached, a PLC reception control unit (details will be described later) demodulates the received data and performs a data reception operation such as error detection.

  When transmission / reception of data based on the schedule on the FCH is completed, each client terminal outputs a bandwidth allocation request to the management terminal 1 during the RCH period when it has transmission data.

  In addition, each client terminal monitors the communication status with the management terminal 1, and when it is determined that the communication is not normally performed, it occurs as a new management terminal candidate based on the data reception status of its own client terminal, A control for starting the operation as a new management terminal is performed by approval from another client terminal (details will be described later).

<A-3. Configuration of high-speed PLC terminal>
<A-3-1. Configuration of data transmitter / receiver>
Next, the configuration of the high-speed PLC terminal will be described with reference to FIGS.
FIG. 2 is a block diagram showing the configuration of the data transmitting / receiving apparatus 10 when the data transmitting / receiving apparatus according to the present invention is applied to a high-speed PLC terminal.

  As shown in FIG. 2, the data transmitter / receiver 10 includes a CPU (Central Processing Unit) 11, an Ethernet interface circuit 12, a bridge interface circuit 13, a bridge memory 14, a PLC modem circuit 15, a PLC transmission memory 16, and a PLC reception. A memory 17 and a CPU bus 18 are provided.

  Here, the bridge interface circuit 13 includes Ethernet frame data input from the Ethernet interface circuit 12, Ethernet frame data output to the Ethernet interface circuit 12, Ethernet frame data output to the PLC modem circuit 15, and the PLC modem circuit 15. This circuit bridges input Ethernet frame data.

  The bridge memory 14 is a memory in which the Ethernet frame input to the bridge interface circuit 13 is sorted and stored for each destination, and the PLC transmission memory 16 is transmitted via the power line 9 (FIG. 1). The PLC reception memory 17 is a memory for storing MAC frame data received via the power line 9.

  The Ethernet interface circuit 12 is a circuit for inputting Ethernet frame data from the outside to the data transmitting / receiving device 10 via the input terminal 20 and the output terminal 21 and outputting the data from the data transmitting / receiving device 10 to the outside. In this circuit, the frame data is transmitted to the outside through the output terminal 22 and the PLC frame input through the input terminal 23 is received.

  In general, in a high-speed PLC network, each terminal connected to the power line 9 (FIG. 1) uses the concept of a logical port, and the bridge interface circuit 13 uses a destination (the management terminal 1, the client terminal A3, the client in FIG. Data is distributed to each terminal B5 and client terminal C7) and queued in the bridge memory 14.

  Specifically, this is a process of distributing and storing Ethernet frame data input from the Ethernet interface circuit 12 in the bridge memory 14 for each destination.

<A-3-2. Configuration of PLC modem circuit>
FIG. 3 is a block diagram showing a configuration of the PLC modem circuit 15 in the data transmitting / receiving apparatus 10 shown in FIG.
As shown in FIG. 3, the PLC modem circuit 15 includes a PLC transmission control circuit 40 that generates a MAC frame data for PLC by connecting a plurality of Ethernet data input from the bridge interface circuit 13 via the input terminal 30, and an electric lamp. A PLC reception control circuit 50 that separates Ethernet frame data from the PLC MAC frame data received via the line 9 (FIG. 1) and outputs it to the bridge interface circuit 13 via the output terminal 31 is provided. The PLC transmission control circuit 40 exchanges MAC frame data for transmission with the PLC transmission memory 16, and the PLC reception control circuit 50 exchanges MAC frame data with the reception memory 17. Give and receive.

<A-3-3. Configuration of PLC transmission control circuit>
FIG. 4 is a block diagram showing a configuration of PLC transmission control circuit 40 shown in FIG.
As shown in FIG. 4, the PLC transmission control circuit 40 collects a plurality of Ethernet frame data input from the bridge interface circuit 13 via the input terminal 30 and a PLC header generation circuit 401 that generates a MAC header to be added to the PLC frame. Packet data generation circuit 402 for generating transmission data, encryption circuit 403 for encrypting data output from packet data generation circuit 402, Beacon frame data and schedule output from PLC network control data generation circuit 408 described later A selector 404 that switches between data, information on the occurrence of a new management terminal, and the like, and encrypted data output from the encryption circuit 403, and a PLC header generation circuit 401 at the head of the data output from the selector 404 Generated A header addition circuit 405 for adding a PLC MAC header, a selector 406 for switching between data output from the header addition circuit 405 and data output from a PLC transmission memory control circuit 409 described later, a PLC network described later Based on the control data generation circuit 408, a PLC transmission timing generation circuit 407, a PLC network control data generation circuit 408, a PLC transmission memory control circuit 409, and an output for generating a transmission timing of data output from the data transmitting / receiving device 10 to the PLC network. A CRC code adding circuit 410 for adding a CRC code (error detection code) to a PLC frame transmitted to the outside via the terminal 22 is provided.

  Here, the PLC network control data generation circuit 408 determines the data transmission timing based on the schedule data determined by the CPU 11 based on the output from the PLC control frame data storage circuit 505 (FIG. 5), which will be described later. And the reference time information of the terminal based on the information from the CPU 11, the ACK / NACK information indicating whether or not the received data has been normally received at the previous reception timing, the sequence number added to the data to be transmitted, and the BCH This is a circuit for generating data such as Beacon control data to be added to a control channel such as FCH and control information for newly generating a management terminal and outputting the data to the selector 404.

  The PLC transmission memory control circuit 409 generates a write control signal for storing the transmission frame used in the retransmission control in the PLC transmission memory 16 and is stored in the PLC transmission memory 16 in the retransmission. It is a circuit that generates a read control signal for reading the data being read.

<A-3-4. Configuration of PLC reception control circuit>
FIG. 5 is a block diagram showing a configuration of PLC reception control circuit 50 shown in FIG.
As shown in FIG. 5, the PLC reception control circuit 50 separates the MAC header from the received PLC frame and analyzes the contents thereof, and receives based on the CRC information added to the received PLC frame. Control of CRC decoding circuit 502 for detecting errors occurring in the PLC frame, encryption / decryption circuit 503 for decoding encrypted data output from the header analysis circuit 501, schedule information added to the PLC frame, etc. PLC information for temporarily storing PLC control frame information separated by PLC control frame separation circuit 504, PLC control frame separation circuit 504 for separating frame information, control information for newly generating a management terminal, and Ethernet frame information, etc. Control frame data storage circuit 505, PLC And a credit memory control circuit 506, PLC reception timing generating circuit 507 and the PLC network control data analyzing circuit 508. Note that the PLC header analysis circuit 501, the encryption / decryption circuit 503, and the PLC control frame separation circuit 504 constitute a control information detection unit that detects control frame information such as BCH and FCH.

  Here, the PLC reception memory control circuit 506 generates a control signal for temporarily storing the Ethernet frame information output from the PLC control frame separation circuit 504 in the PLC reception memory 17, and the CRC decoding circuit 502. This is a circuit that performs read control of Ethernet frame information stored in the PLC reception memory 17 based on an error detection result output from the network.

  The PLC reception timing generation circuit 507 generates a data reception timing from the PLC based on the analysis result output from the PLC network control data analysis circuit 508, and generates a header analysis circuit 501, a CRC decryption circuit 502, an encryption decryption circuit 503, This circuit is provided to the PLC control frame separation circuit 504 and the PLC reception memory control circuit 506.

  The PLC network control data analysis circuit 508 is a circuit that analyzes the schedule data based on the output from the PLC control frame data storage circuit 505 and instructs the PLC reception timing generation circuit 507 about the data reception timing.

  Also, the PLC network control data analysis circuit 508 analyzes the reception status of control information such as BCH and FCH from the management terminal, and when the BCH or FCH cannot be received, the transmission terminal added to the received PLC MAC header In addition to outputting the time information to the PLC reception timing generation circuit 507 so as to adjust the time in the receiving terminal based on the time information, and notifying the CPU 11, the reception status of the control information that causes the management terminal to newly occur Analyze.

<Transmission timing of data in A-4.1 frame>
In order to manage time synchronization of the entire PLC network, the management terminal 1 periodically outputs a Beacon signal using the BCH and schedule information using the FCH to manage the network as described in the related art.

FIG. 6 shows the transmission timing of various data in one frame.
As shown in FIG. 6, in one frame, after transmitting network management information in the order of BCH, FCH and ACH, n communication slots L1 to Ln are transmitted in the data transmission / reception period, and finally RCH is transmitted. It becomes.

  In the first embodiment, it is assumed that PLC network management information such as BCH is output in a cycle of 20 ms. Therefore, the PLC transmission control circuit 40 in the management terminal 1 generates a Beacon frame and schedule information at an interval of once every 20 ms.

  Further, in the first embodiment, as the Beacon frame information, the time information of the management terminal 1 when the Beacon frame is transmitted is transmitted as payload information.

  Specifically, the reference time information in the PLC network control data generation circuit 408 (FIG. 4) at the time of transmitting the Beacon frame is output to the selector 404 as payload information. On the other hand, when receiving the Beacon frame information, the client terminal on the receiving side synchronizes the internal reception reference time with the transmission reference time added to the Beacon frame. The management terminal 1 performs transmission of FCH (schedule information) following transmission of BCH.

  As shown in FIG. 6, the FCH includes preamble information for detecting the leading position of received data and a clock phase at the time of reception, and schedule information transmitted following the preamble information. In the schedule information, the transmission start time, the transmission time, and from which terminal (transmission terminal) to which terminal (reception terminal) data transmission correspond to each of the communication slots L1 to Ln provided in the data transmission / reception period. Terminal information indicating transmission / reception and information related to transmission / reception when data is transmitted / received.

  In Embodiment 1, it is assumed that MAC address (Media Access Control Address) information possessed by each terminal is used for transmitting terminal information and receiving terminal information. In addition to the MAC address information, for example, it may be a logical port number in the PLC network, or identification information determined privately in the network.

  As described above, the schedule information in the FCH is transmitted with the information added corresponding to each communication slot. Regarding the communication slot, the client terminal that starts transmission of the video stream uses the RCH time slot to transmit the bandwidth allocation request to the management terminal 1, so that the management terminal 1 transmits the video stream transmission request. A communication band is allocated to the terminal that has received. At this time, the management terminal 1 performs scheduling so that a band is fixedly allocated for data that requires real-time characteristics such as a video stream. The fixedly allocated band is referred to as a fixed band or fixed band allocation.

<A-5. Operation of management terminal>
Next, the operation of the management terminal 1 including the schedule information (FCH) generation flow will be described using the flowcharts shown in FIGS. 7 and 8 are connected to each other by the symbol (A) in FIG. 7 and the symbol (A) in FIG. Moreover, FIG. 8 and FIG. 9 are mutually connected by the symbol (B) in FIG. 8, and the symbol (B) in FIG. Furthermore, FIG. 9 and FIG. 7 are mutually connected by the symbol (C) in FIG. 9 and the symbol (C) in FIG.

  As shown in FIG. 7, when the management terminal 1 starts transmission / reception of data, the CPU 11 of the management terminal 1 determines whether or not a new management terminal has occurred (whether or not a BCH has been received from another terminal). Monitoring is started (step S11).

  Then, the operation of confirming whether or not the BCH generation start timing has been reached is repeated (step S12). When the BCH generation start timing comes, the management terminal 1 generates a BCH for managing the PLC network (step S13), and the BCH transmission start timing. The operation of confirming whether or not has been reached is repeated (step S14). Then, at the BCH transmission start timing, the BCH is broadcast to each client terminal (step S15).

  When the above operation is completed, the RCH received up to the previous time is analyzed (step S16), and preparation for starting generation of schedule information (FCH) in the next operation is started.

  Then, the operation of confirming whether or not the FCH generation start timing has been reached is repeated (step S17). When the FCH generation start timing is reached, the management terminal 1 checks whether or not there is a client terminal for which fixed bandwidth allocation has been performed. However, if there is a client terminal to which the fixed bandwidth is assigned, the time slot for the fixed bandwidth is continuously assigned in step S19, and the process proceeds to step S20. If there is no client terminal to which the fixed bandwidth is allocated, the process proceeds to step S20 as it is.

  In step S20, it is confirmed whether or not there is a client terminal that has requested release of fixed-band time slot allocation in the previous frame. If there is such a release request, the management terminal 1 sends the request in step S21. The fixed bandwidth allocation for the issued client terminal is released, and the process proceeds to step S22 (FIG. 8). If there is no client terminal making a release request, the process proceeds directly to step S22.

  In step S22, the management terminal 1 confirms whether or not there is a new fixed bandwidth allocation request in the previous frame. When there is a new fixed bandwidth allocation request, check the time slot for the currently allocated fixed bandwidth and check whether a new fixed bandwidth can be allocated from the surplus state of the communication slot in one frame (Step S23). If there is no new fixed bandwidth allocation request, the process proceeds to step S26.

  If a new fixed bandwidth can be allocated, a fixed bandwidth is allocated to the client terminal that has newly requested a fixed bandwidth (step S24). On the other hand, if a new fixed band cannot be allocated, a fixed band allocation impossible notification (transmitted in the ACH) is generated for a client terminal that has newly requested a fixed band (step S25).

  Next, the CPU 11 of the management terminal 1 checks whether or not a bandwidth allocation request for a control command has been received from the client terminal (step S26). If there is a control command bandwidth allocation request, a control command time slot is allocated in step S27 and the process proceeds to step S28. If there is no request, the process proceeds to step S28.

  In the first embodiment, when a video stream or the like is transmitted, a control command other than the video stream is used in various cases such as when the user performs device control with a remote control or exchanges key information for copyright management. Is assumed to be exchanged. Therefore, when allocating a fixed bandwidth to a new terminal in step S24, after securing the bandwidth so that a bandwidth for a control command of at least one time slot can be allocated within at least one frame, a time slot for the new terminal is allocated. Shall be assigned.

  In step S28, the management terminal 1 assigns a management terminal transmission time slot for transmitting PLC network control information including BCH and FCH to each client terminal.

  Next, the CPU 11 of the management terminal 1 checks whether or not there has been a request for normal bandwidth allocation other than fixed bandwidth allocation (hereinafter referred to as normal bandwidth allocation) in the previous frame (step S29). If there is a new normal band allocation request, it is confirmed whether or not a normal band can be allocated (step S30). If there is no new normal bandwidth allocation request, the process proceeds to step S33.

  If new normal band allocation is possible, the normal band is allocated to the client terminal that has newly requested the normal band (step S31). On the other hand, if a new normal band cannot be allocated, a normal band allocation impossible notification (transmitted in the ACH) is generated for the client terminal that has newly requested the normal band (step S32).

  When the assignment of each time slot is completed, in step S33, the FCH is generated based on the time slot information of each client terminal including the assigned management terminal 1, and assigned by the management terminal 1 itself. Based on the time slot, the operation of confirming whether or not the FCH transmission start timing has been reached is repeated (step S34). When the FCH transmission start timing is reached, the FCH is transmitted to each client terminal as shown in FIG. 9 (step S35). .

  Then, the operation of confirming whether or not the ACH transmission start timing has been reached is repeated (step S36). When the ACH transmission start timing is reached, the management terminal 1 transmits the ACH generated in the time slot allocation to each client terminal (step S37). ).

  When the FCH frame is generated in step S33 (FIG. 8), fixed band allocation to each client terminal in the first embodiment is basically allocated to the same position in the frame. This is based on the following reason. In other words, the average data transmission rate of data such as video streams transmitted by fixed bandwidth allocation (same as audio data such as VoIP) is substantially constant. Therefore, even if the FCH frame transmitted from the management terminal 1 cannot be received due to the influence of peripheral device noise, if synchronization is ensured between the client terminals, data can be transmitted if transmitted based on the previously received schedule information. This is because it is possible to perform transmission and reception. As will be described in detail later, when communication with the management terminal 1 is interrupted while a video stream is being played back between client terminals, if the clock synchronization between the client terminals is established, the video is based on the previously received schedule information. This is because if the stream is transmitted, the reproduced image can be transmitted without being disturbed until a new management terminal occurs.

  When the transmission of the ACH to each client terminal is completed, the management terminal 1 and each client terminal perform data transmission / reception (TCH period) based on the schedule information (step S38). Then, the operation of confirming whether or not the RCH period for accepting the bandwidth allocation request from each client terminal has been reached is repeated (step S39). When the RCH period is reached, the RCH is received (step S40). It is maintained until the period ends (step S41).

  After the end of the RCH period, the CPU 11 of the management terminal 1 determines whether or not a new management terminal started to be monitored in step S11 (FIG. 7) has occurred between steps S12 to S41 (whether BCH has been received from another client terminal or not). (Step S42), and if it is determined that no new management terminal has occurred, it operates as the management terminal in the next transmission / reception, and the operations in step S11 and subsequent steps are repeated. On the other hand, if it is determined that a new management terminal has occurred, the operation as the management terminal is stopped and the operation as the client terminal is started in the next transmission / reception (step S43).

  Thereby, even after a new management terminal occurs, it is possible to prevent a situation in which the management terminal up to now continues to operate as a management terminal, and to prevent a plurality of management terminals from being confused.

  In addition, when a new management terminal occurs, other client terminals receive the BCH from the new management terminal, confirm the occurrence of the new management terminal, start the operation according to the new management terminal, and manage the current management terminal Is regarded as an unmanaged terminal.

  As a result, even if the management terminal up to now continues to operate as a management terminal, other client terminals follow the new management terminal, so even if a plurality of management terminals temporarily exist, it will be confused. There is nothing.

  The operations in steps S11 to S43 described above are operations performed mainly by the CPU 11 of the management terminal.

<A-6. Operation of client terminal>
Next, the data transmission / reception operation of the client terminal will be described with reference to FIGS. 10 and 11 are connected to each other by the symbol (A) in FIG. 10 and the symbol (A) in FIG. Moreover, FIG. 11 and FIG. 12 are mutually connected by the symbol (B) in FIG. 11 and the symbol (B) in FIG. Furthermore, FIG. 12 and FIG. 10 are mutually connected by the symbol (C) in FIG. 12 and the symbol (C) in FIG.

  As shown in FIG. 10, when a client terminal starts data transmission / reception, the CPU 11 of the client terminal initializes flag counters BCH, MISS, COUNT, and FCH, MISS, COUNT to 0 (step S101).

  The flag counter BCH / MISS / COUNT (details will be described later) is a counter that counts how many times the BCH from the management terminal 1 has not been received continuously. The flag counter FCH / MISS / COUNT (details will be described later) It is a counter that counts how many times the FCH from the terminal 1 has not been received continuously.

  These counters are arranged in the PLC reception control circuit 50 in the PLC modem circuit 15 shown in FIG. 3, and receive the BCH and FCH reception status data from the PLC network control data analysis circuit 508 (FIG. 5). , Controlled by the CPU 11.

  Based on the schedule information received in the previous transmission / reception operation, the CPU 11 of the client terminal repeatedly confirms whether or not the BCH reception time has been reached (step S102). When the BCH reception time is reached, the BCH from the management terminal The success or failure of reception is confirmed (step S103).

  If the BCH is successfully received from the management terminal, it is determined whether the received BCH is transmitted from the same terminal as the management terminal in the previous reception operation (step S104). In order to make this determination, the client terminal records terminal information of the management terminal every time BCH is received, and is used to determine whether or not the management terminal in the current reception operation is the same as the management terminal in the previous reception operation. To do.

  If it is determined in step S104 that BCH has been received from the same management terminal as the previous time, the reference time in the client terminal is synchronized based on the BCH from the management terminal (current management terminal) received this time (step S105). ), The flag counter BCH / MISS / COUNT is set to 0 (step S106).

  On the other hand, if it is determined in step S104 that BCH has been received from a different management terminal (newly generated management terminal) from the previous time, the reference time in the own client terminal is synchronized based on the BCH from the new management terminal received this time. Then, the flag counters BCH, MISS, COUNT and FCH, MISS, COUNT are set to 0 (step S108). Further, NEW · FLAG indicating whether or not the own client terminal is generated as a new management terminal is set to 0 (step S109).

  Here, NEW • FLAG is an operation reference flag that serves as a reference for determining whether or not to perform an operation as a candidate to become a new management terminal in the own client terminal. When this is set to 1, for example, The operation as a candidate to become a new management terminal is performed, and when set to 0, the operation as a candidate to become a new management terminal is not performed.

  In step S103, if the client terminal cannot normally receive the BCH from the management terminal, the synchronization control of the reference clock with the management terminal using the BCH is detected based on the BCH received up to the previous time. The reference time of the client terminal is corrected using the error information (step S110).

  This is because the BCH received up to the previous time is almost clock-synchronized between the management terminal and the client terminal (actually, a clock frequency error of several ppm or less exists), so that the BCH is restored even if error information is used. This is because the clock synchronization of the PLC network can be established if the time period until is not so long.

  As a result, even when the management terminal is disconnected from the PLC network during transmission / reception of a video stream between client terminals and the client terminal cannot receive network management information such as BCH and FCH, synchronization can be inherited and the network topology can be restored. Can be made.

  Since BCH could not be received normally, the flag counters BCH, MISS, and COUNT are incremented by one (step S111).

  Next, the CPU 11 repeatedly confirms whether or not the FCH reception time has been reached (step S112). When the FCH reception time is reached, the success or failure of reception of the FCH from the management terminal is determined in step S113 (FIG. 11). Check. If the FCH from the management terminal can be normally received, the schedule information is confirmed from the FCH (step S114), and the flag counters FCH, MISS, and COUNT are set to 0 (step S115).

  When the FCH from the management terminal cannot be normally received in step S113, the schedule information is confirmed based on the FCH received in the previous reception operation (step S116), and the flag counter FCH / MISS / COUNT is set to 1. Is incremented by one (step S117).

  Here, as described above, the fixed bandwidth allocation that the management terminal allocates to each client terminal is basically allocated at the same position in the frame. Therefore, if the period until the FCH is restored is not very long, The transmission of the video stream based on the schedule information based on the FCH can be performed without disturbing the reproduced image.

  After confirming the schedule information, the presence / absence of a reception slot is confirmed in step S118, and if there is a reception slot, reception time information corresponding to the reception slot is generated (step S119). On the other hand, if there is no reception slot, the process proceeds to step S123 in FIG.

  Then, the operation of confirming whether or not the reception time has been reached is repeated (step S120). When the reception time is reached, reception of the MAC frame is started (step S121), and data reception processing is performed. Next, in step S122, it is confirmed whether or not reception of the reception slot has been completed. If there are a plurality of reception slots and all reception operations have not been completed, the operation from step S120 is repeated, and the MAC frame reception operation is repeated. continue.

  On the other hand, when the reception of the reception slot is completed and the reception operation of the MAC frame is completed, the presence / absence of a transmission slot is confirmed from the schedule information in step S123 (FIG. 12). Transmission time information is generated (step S124). On the other hand, if there is no transmission slot, the process proceeds to step S128.

  Then, the operation of confirming whether or not the transmission time has been reached is repeated (step S125). When the transmission time is reached, transmission of the MAC frame is started (step S126), and data transmission processing is performed. Next, in step S127, it is confirmed whether or not the transmission of the transmission slot has been completed. If there are a plurality of transmission slots and all transmission operations have not been completed, the operations in step S125 and subsequent steps are repeated to perform the MAC frame transmission operation. continue.

  On the other hand, when the transmission of the transmission slot is completed and the transmission operation of the MAC frame is completed, the operation of confirming whether or not the RCH period has been reached is repeated in step S128, and when the RCH period is reached, the client terminal Then, a bandwidth allocation request operation (details will be described later) is performed (step S129).

  Then, the operation of confirming whether or not the RCH period has ended is repeated (step S130). When the RCH period ends, the client terminal waits until the next BCH reception time is reached (step 102).

  The operations in steps S101 to S130 described above are operations performed mainly by the CPU 11 of the client terminal.

<A-7. Live startup of new management terminal>
Next, the live startup operation and bandwidth allocation request operation of the new management terminal of the client terminal will be described with reference to FIGS. 13 are connected to each other by the symbols (A) to (C) in FIG. 13 and the symbols (A) to (C) in FIG. 14, and the symbols (D) in FIG. 13 and 15 are connected to each other by symbol (D), and FIG. 14 and FIG. 15 are connected to each other by symbol (E) in FIG. 14 and symbol (E) in FIG.

  As shown in FIG. 13, when the live startup operation and bandwidth allocation request operation of the new management terminal is started, the CPU 11 notifies the management terminal communication failure notification from other client terminals that may be transmitted from each client terminal during the RCH period. Whether or not (details will be described later) is received is managed (step S201).

  Next, it is checked whether or not the client terminal has transmitted a management terminal communication failure notification until the previous transmission / reception operation (step S202).

  That is, in step S202, it is confirmed whether NEW · FLAG is 1, and if NEW · FLAG is 0, that is, if a management terminal communication failure notification has not been transmitted before the previous transmission / reception operation, fixed bandwidth allocation The threshold parameter NEW / BORDER according to the above is set (step S203). If NEW • FLAG is 1, that is, if a management terminal communication failure notification has been transmitted before the previous transmission / reception operation, the process proceeds to step S223 (FIG. 15). Here, in the management terminal communication failure notification, the own client terminal cannot receive more than a certain amount of network management information such as BCH and FCH from the management terminal, and the own client terminal becomes a new management terminal candidate in place of the current management terminal. This is indicated to other client terminals.

  The threshold parameter NEW / BORDER is a reference value for setting a candidate to be a new management terminal when network management information such as BCH and FCH cannot be received from the current management terminal for a certain amount, and data is being received. In this case, control is performed such that a smaller value is set for a client terminal having a higher ratio of fixed bandwidth allocation, thereby ranking candidates for new management terminals.

  For example, the fixed bandwidth allocation is 50% for the client terminal A3, 30% for the client terminal B5, and 0% for the client terminal C7. The client terminal A3 is transmitting data, the client terminal B5 is receiving data, and the client When the terminal C7 is receiving data (with normal bandwidth allocation), the threshold parameter NEW / BORDER is set to 100 for the client terminal A3, 20 for the client terminal B5, 50 for the client terminal C7, etc. Control is performed so that the client terminal having a higher ratio of fixed bandwidth allocation during reception tends to be a candidate for a new management terminal.

  Next, based on the threshold parameter NEW / BORDER determined in step S203, the magnitude relationship between the flag counter BCH / MISS / COUNT and the threshold parameter NEW / BORDER is determined (step S204).

  If it is determined that the value of the flag counter BCH, MISS, COUNT is equal to or greater than the value of the threshold parameter NEW, BORDER, the process proceeds to step S206, where NEW, FLAG is set to 1, and the value of the flag counter BCH, MISS, COUNT is set. Is determined to be smaller than the value of the threshold parameter NEW · BORDER, the process proceeds to step S205.

  In step S205, the magnitude relationship between the flag counter FCH, MISS, COUNT and the threshold parameter NEW, BORDER is determined. If the value of the flag counter FCH, MISS, COUNT is determined to be greater than or equal to the value of the threshold parameter NEW, BORDER, In step S206, NEW / FLAG is set to 1, and when it is determined that the value of the flag counter FCH / MISS / COUNT is smaller than the value of the threshold parameter NEW / BORDER, the process proceeds to step S207 and NEW / FLAG is set to 0. Set to.

  When the setting of NEW / FLAG is completed, whether the management terminal communication failure notification has been received from the other terminal during this RCH period based on the management result of the management terminal communication failure notification from the other client terminal implemented in step S201 It is confirmed whether or not (step S208).

  If the management terminal communication failure notification from another terminal has not been received, the process proceeds to step S209, where it is confirmed whether NEW / FLAG in the client terminal is set to 1, and NEW / FLAG is 1 Is set, a management terminal communication failure notification is generated (step S210).

  Thereafter, the generated management terminal failure notification is broadcasted to another client terminal (step S211), and in step S212 (FIG. 14), the live startup operation and the bandwidth allocation requesting operation of the new management terminal are terminated and waits.

  If it is confirmed in step S208 that a management terminal communication failure notification has been received from another terminal, the process proceeds to step S219 (FIG. 14), and NEW / FLAG is not set to 1 in step S209. If confirmed, the process proceeds to step S213 (FIG. 14).

  In step S213, it is determined whether or not a request for fixed bandwidth allocation is made to the current management terminal in accordance with transmission data held by the own client terminal. When making a fixed bandwidth allocation request, a fixed bandwidth allocation request is generated (step S214), and the fixed bandwidth allocation request is transmitted (step S215). If no fixed bandwidth allocation is requested, the process proceeds to step S216.

  Similarly, it is determined whether or not a normal band allocation request is to be made (step S216). If a normal band allocation request is to be made, a normal band allocation request is generated (step S217), and the normal band allocation request is issued. Transmit (step S218). When normal bandwidth allocation is not requested and when the bandwidth allocation request is completed, the live startup operation and bandwidth allocation request operation of the new management terminal is terminated and waits (step S212).

  If it is determined in step S208 that a management terminal communication failure notification has been received from another client terminal during the current RCH period, an operation of approving the client terminal that has transmitted the management terminal communication failure notification as a new management terminal is performed. carry out.

  That is, the flag counters BCH, MISS, COUNT and FCH, MISS, COUNT are initialized to 0 (step S219), and NEW, FLAG are set to 0 (step S220).

  Thereby, only the client terminal that has transmitted the management terminal communication failure notification first can become a new management terminal, and a plurality of new management terminals can be prevented from being confused.

  Next, a new management terminal approval notification is generated (step S221), and the new management terminal approval notification is transmitted to the client terminal that has transmitted the management terminal communication failure notification (step S222). When the transmission of the notification is completed, the live startup operation and bandwidth allocation requesting operation of the new management terminal is terminated and waits (step S212).

  In step S202, when it is confirmed that the management terminal communication failure notification has been transmitted before the previous transmission / reception operation, that is, the management terminal communication failure notification is generated and transmitted before the previous transmission / reception operation at the own client terminal. If (Steps S210 and S211) have been performed, the following operations are performed.

  That is, based on the management result of the management terminal communication failure notification from the other client terminal implemented in step S201, the management terminal failure notification is transmitted through the operations of steps S201 to S211 in the previous transmission / reception operation, and then the other It is confirmed whether a management terminal communication failure notification is received from the client terminal (step S223).

  If the management terminal communication failure notification has not been received from the other client terminal, the management terminal communication failure notification is generated again (step S224), and the generated management terminal failure notification is broadcast to the other client terminal. (Step S225).

  Since the management terminal communication failure notification is transmitted from the client terminal during the RCH period in which each client terminal makes a bandwidth allocation request, depending on the transmission timing, the management terminal communication failure notification and the bandwidth allocation request collide with each other. May not be able to broadcast. Therefore, by generating and transmitting the management terminal communication failure notification again, there is an effect of notifying each client terminal that a new management terminal candidate has occurred as much as possible.

  When the management terminal communication failure notification is transmitted, there is a notification of approval of the new management terminal from each client terminal (that is, the other client terminal performs the operations of steps S208 and S219 to S222). Therefore, the number of new management terminal approval notifications received from other client terminals is managed (step S226). In step S227, it is confirmed whether or not the new management terminal approval notification has reached a predetermined number.

  When the new management terminal approval notification reaches a certain number, the operation as the new management terminal is started as follows. That is, the flag counters BCH, MISS, COUNT and FCH, MISS, COUNT are initialized to 0 (step S228), NEW, FLAG is set to 0 (step S229), and then the operation as a new management terminal starts (step S229). S230).

  On the other hand, if it is confirmed in step S223 that the management terminal communication failure notification has been received from the other client terminal since the previous management terminal failure notification was transmitted, NEW based on a predetermined fixed probability. Control for setting FLAG to 0 is performed (step S231).

  That is, basically, the management terminal failure notification is not transmitted simultaneously from a plurality of client terminals. This is because, in step S208, when the own client terminal receives a management terminal failure notification from another client terminal, the own client terminal controls not to transmit the management terminal failure notification. However, although the other client terminal broadcasts the management terminal failure notification due to the transmission timing of the management terminal failure notification during the RCH period or the collision between the management terminal communication failure notification and the bandwidth allocation request, etc., the own client Since the management terminal failure notification could not be received by the terminal, it is conceivable to broadcast the management terminal failure notification from the own client terminal.

  Assuming such a case, in step S223, an operation of withdrawing a candidate for a new management terminal with a certain probability is performed. By performing this operation, it is possible to obtain an effect of preventing a plurality of new management terminals from occurring in a situation in which a management terminal failure notification is transmitted from a plurality of terminals.

  The operations in steps S201 to S231 described above are operations performed mainly by the CPU 11 of the client terminal.

<A-8. Effect>
As described above, according to the data transmitting / receiving apparatus of the first embodiment, the client terminal manages network management such as BCH and FCH by leaving the management terminal while the video stream is being transmitted / received between the client terminals. Even when the information cannot be received, the client terminal that is receiving data can quickly occur as a new management terminal, inherit synchronization, and restore the network topology.

  In addition, when transmitting a video stream, a fixed bandwidth is allocated and fixed bandwidth allocation within one frame is scheduled to be at the same position, so the video stream is based on the previously received schedule information and reference time information. Thus, there is an effect that the video stream can be transmitted without interruption even in the absence of a management terminal until a new management terminal occurs.

<B. Second Embodiment>
The data transmitting / receiving apparatus according to the second embodiment of the present invention will be described below.
The data transmission / reception apparatus according to the second embodiment is different only in operations related to the occurrence of the new management terminal described in the first embodiment.

  That is, in the first embodiment, when the client terminal cannot receive the network management information such as BCH and FCH from the current management terminal, it is generated as a new management terminal candidate, The operation starts as a new management terminal instead of the management terminal. On the other hand, in the second embodiment, when the client terminal cannot receive the network management information such as BCH and FCH from the current management terminal, it is generated as a new management terminal candidate. When the network management information can be received more, it is characterized in that it performs an operation to withdraw from becoming a candidate for a new management terminal. That is, even if one client terminal cannot communicate with the current management terminal, if another client terminal can communicate with the current management terminal, control is performed so that a new management terminal does not occur. By such control, it is possible to prevent the management terminal from changing frequently and destabilizing the synchronous communication of the PLC network.

<B-1. Live startup of new management terminal>
Next, the live startup operation and bandwidth allocation request operation of the new management terminal of the client terminal will be described using the flowcharts shown in FIGS. As described above, in the data transmitting / receiving apparatus according to the second embodiment, only the live startup operation of the new management terminal described as step S129 in FIG. 12 is different, and other operations are the same as those in the first embodiment. 16 and FIG. 17 are connected to each other by the symbol (A) in FIG. 16 and the symbol (A) in FIG. 17, and the symbol (B) in FIG. 17 and the symbol (B) in FIG. 17 and FIG. 19 are connected to each other. Symbols (C) to (E) in FIG. 17 and symbols (C) to (E) in FIG. 18 are connected to each other. Furthermore, FIG. 16 and FIG. 19 are mutually connected by the symbol (F) in FIG. 16 and the symbol (F) in FIG.

  As shown in FIG. 16, when the live startup operation and bandwidth allocation request operation of the new management terminal is started, the CPU 11 notifies the management terminal communication failure notification from other client terminals that may be transmitted from each client terminal during the RCH period. Is managed (step S301).

  Next, it is managed whether or not a management terminal normal operation notification (details will be described later) is received from other terminals that may be transmitted from each client terminal during the RCH period (step S302).

  Next, it is checked whether or not the client terminal has transmitted a management terminal communication failure notification until the previous transmission / reception operation (step S303).

  That is, in step S303, it is confirmed whether NEW · FLAG is 1, and if NEW · FLAG is 0, that is, if a management terminal communication failure notification has not been transmitted before the previous transmission / reception operation, fixed bandwidth allocation is performed. The threshold parameter NEW / BORDER according to the above is set (step S304). If NEW • FLAG is 1, that is, if a management terminal communication failure notification has been transmitted before the previous transmission / reception operation, the process proceeds to step S328 (FIG. 19).

  Next, based on the threshold parameter NEW / BORDER determined in step S304, the magnitude relationship between the flag counter BCH / MISS / COUNT and the threshold parameter NEW / BORDER is determined (step S305).

  If it is determined that the value of the flag counter BCH, MISS, COUNT is equal to or greater than the value of the threshold parameter NEW, BORDER, the process proceeds to step S307 and NEW / FLAG is set to 1, and the value of the flag counter BCH, MISS, COUNT Is determined to be smaller than the value of the threshold parameter NEW · BORDER, the process proceeds to step S306.

  In step S306, the magnitude relationship between the flag counter FCH / MISS / COUNT and the threshold parameter NEW / BORDER is determined. In step S307, NEW / FLAG is set to 1, and when it is determined that the value of the flag counter FCH / MISS / COUNT is smaller than the value of the threshold parameter NEW / BORDER, the process proceeds to step S308 and NEW / FLAG is set to 0. Set to.

  When the setting of NEW / FLAG is completed, in step S309 (FIG. 17), from the other client terminal during the current RCH period, based on the management result of the management terminal communication failure notification from the other client terminal implemented in step S301. It is confirmed whether or not a management terminal communication failure notification has been received.

  If the management terminal communication failure notification from another terminal has not been received, the process proceeds to step S310, where it is confirmed whether NEW / FLAG in the client terminal is set to 1, and NEW / FLAG is 1 Is set, a management terminal communication failure notification is generated (step S311).

  Thereafter, the generated management terminal failure notification is broadcasted to other client terminals (step S312), and the live startup operation and the bandwidth allocation requesting operation of the new management terminal are terminated and waited in step S313 (FIG. 19).

  If it is confirmed in step S309 that a management terminal communication failure notification has been received from another terminal, the process proceeds to step S320 (FIG. 18), and NEW / FLAG is not set to 1 in step S310. If confirmed, the process proceeds to step S314.

  In step S314, it is determined whether or not a request for fixed bandwidth allocation is to be made to the current management terminal according to transmission data held by the own client terminal. When making a fixed bandwidth allocation request, a fixed bandwidth allocation request is generated (step S315), and the fixed bandwidth allocation request is transmitted (step S316). If no fixed bandwidth allocation is requested, the process proceeds to step S317.

  Similarly, it is determined whether or not a normal band allocation request is to be made (step S317). When a normal band allocation request is to be made, a normal band allocation request is generated (step S318), and the normal band allocation request is issued. Transmit (step S319). When normal bandwidth allocation is not requested and when the bandwidth allocation request is completed, the live startup operation and bandwidth allocation request operation of the new management terminal is terminated and waits (step S313).

  If it is determined in step S309 that a management terminal communication failure notification has been received from another client terminal during the current RCH period, the client terminal that has transmitted the management terminal communication failure notification is approved as a new management terminal, Or the operation | movement which notifies that the present management terminal is working normally to the terminal which transmitted the management terminal communication failure notification is implemented.

  That is, in step S320 (FIG. 18), it is confirmed whether or not the flag counter BCH / MISS / COUNT in the own client terminal is 0. If it is 0, the own client terminal normally BCH from the current management terminal. Therefore, the management terminal normal operation notification indicating that is generated (step S321), and is transmitted to the terminal that has transmitted the management terminal communication failure notification (step S322).

  On the other hand, if the flag counter BCH, MISS, or COUNT is not 0, it is checked in step S323 whether the flag counter FCH, MISS, or COUNT is 0. Since the FCH has been normally received, a management terminal normal operation notification indicating that fact is generated (step S321), and is transmitted to the terminal that has transmitted the management terminal communication failure notification (step S322).

  When the management terminal normal operation notification is transmitted, since the current management terminal is operating normally, the bandwidth allocation request in steps S314 to S319 is performed, and the live startup operation and the bandwidth allocation request operation of the new management terminal are completed. And waits (step S313).

  If the flag counters BCH, MISS, and COUNT are not 0 and the flag counters FCH, MISS, and COUNT are not 0, the flag counters BCH, MISS, and COUNT and FCH, MISS, and COUNT are initialized to 0 (step S324). , NEW · FLAG is set to 0 (step S325). Further, a new management terminal approval notification is generated (step S326), and the new management terminal approval notification is transmitted to the client terminal that has transmitted the management terminal communication failure notification (step S327). When the transmission of the notification is completed, the live startup operation and the bandwidth allocation request operation of the new management terminal are terminated and waits (step S313).

  An operation when it is confirmed in step S303 (FIG. 16) that the management terminal communication failure notification has been transmitted before the previous transmission / reception operation will be described.

  That is, based on the management result of the management terminal normal operation notification from the other client terminal implemented in step S302 (FIG. 16), in step S328 (FIG. 19), after the previous management terminal failure notification was transmitted, Check whether a management terminal normal operation notification has been received from the client terminal.

  If the management terminal normal operation notification has not been received from the other client terminal, the previous management based on the management result of the management terminal communication failure notification from the other client terminal implemented in step S301 (FIG. 16). After transmitting the terminal failure notification, it is confirmed whether or not a management terminal communication failure notification has been received from another client terminal (step S329).

  If the management terminal communication failure notification has not been received from the other client terminal, the management terminal communication failure notification is generated again (step S330), and the generated management terminal failure notification is broadcast to the other client terminal. (Step S331).

  When the management terminal communication failure notification is transmitted, there is a notification of new management terminal approval from each client terminal or a notification of normal operation of the management terminal (that is, the other client terminal generates a new management terminal approval notification in steps S309 to S326 and S327, Transmission, or generation and transmission operations of the management terminal normal operation notification in steps S309 to S321 and S322 are performed). Therefore, the number of new management terminal approval notifications received from other client terminals is managed (step S332). In step S333, it is confirmed whether the new management terminal approval notification has reached a predetermined number.

  When the new management terminal approval notification reaches a certain number, the operation as the new management terminal is started as follows. That is, the flag counters BCH, MISS, COUNT and FCH, MISS, COUNT are initialized to 0 (step S334), NEW, FLAG is set to 0 (step S335), and then the operation as a new management terminal is started (step S335). SS336).

  On the other hand, if it is confirmed in step S329 that the management terminal communication failure notification has been received from the other client terminal since the management terminal failure notification was transmitted last time, NEW based on a predetermined fixed probability. Control is performed to set FLAG to 0 (step S337), and the live start-up operation and bandwidth allocation request operation of the new management terminal is terminated and waits (step S313).

  In step S328, if a management terminal failure notification is received from another terminal since the previous management terminal failure notification was transmitted, NEW / FLAG is set to 0 (step S338), and a new management terminal is generated. The operation and the bandwidth allocation request operation are terminated and waited (step S313).

  That is, by performing an operation to withdraw that it is a candidate for a new management terminal, even if the client terminal is a candidate for a new management terminal, the other client terminals can be normally BCH, When network management information such as FCH can be received, it can be controlled not to occur as a new management terminal.

  The operations in steps S301 to S338 described above are operations performed mainly by the CPU 11 of the client terminal.

<B-2. Effect>
As described above, according to the data transmitting / receiving apparatus of the second embodiment, the client terminal manages network management such as BCH and FCH by leaving the management terminal while the video stream is being transmitted / received between the client terminals. Even if it is a condition that a new management terminal occurs when information cannot be received, if it is notified that the current management terminal is operating normally by another client terminal, the new management terminal will be By preventing it from occurring, it is possible to prevent the synchronous communication of the PLC network from becoming unstable due to frequent switching of the management terminal.

  In addition, when transmitting a video stream, a fixed bandwidth is allocated and fixed bandwidth allocation within one frame is scheduled to be at the same position, so the video stream is based on the previously received schedule information and reference time information. Thus, there is an effect that the video stream can be transmitted without interruption even in the absence of a management terminal until a new management terminal occurs.

<C. Modification>
In the first and second embodiments described above, the case where the present invention is applied to a high-speed PLC terminal has been described as an application example of the present invention. However, the application of the present invention is not limited to this, and a wireless LAN or UWB (Ultra Wideband) is applied. ), Or other transmission systems that employ a TDMA system or a data transmission / reception system having a mechanism for transmitting and receiving data by allocating a fixed band to a video stream.

  In addition, the reference time correction on the reception client terminal side to which the fixed bandwidth is allocated is performed using the reference time information on the transmission client terminal side added to the MAC header. However, the present invention is not limited to this. Since the reference clock is substantially synchronized with the reference clock of the management terminal, it is also possible to perform data transmission / reception using a time slot to which a fixed bandwidth is assigned without performing reference time correction.

  Furthermore, although the case where the decision of leaving the management terminal from the PLC network could not be received by the BCH or FCH has been described, the present invention is not limited to this. The same effect can be obtained if configured to make the determination. Moreover, although the case where the video stream is transmitted in fixed band allocation has been described, the present invention is not limited to this, and the present invention may be applied to audio or voice.

It is a figure which shows the structure of the high-speed PLC network system to which the data transmission / reception apparatus concerning this invention is applied. It is a block diagram explaining the structure of the data transmitter / receiver which concerns on this invention. It is a block diagram which shows the structure of the PLC modem circuit in the data transmitter / receiver based on this invention. It is a block diagram which shows the structure of the PLC transmission control circuit in a PLC modem circuit. It is a block diagram which shows the structure of the PLC reception control circuit in a PLC modem circuit. It is a figure which shows the structure of the data format in 1 frame, and the schedule data in FCH at the time of performing data transmission / reception with the data transmission / reception apparatus using high-speed PLC. 6 is a flowchart illustrating a data transmission / reception operation in one frame when the data transmission / reception apparatus according to Embodiment 1 is used as a management terminal. 6 is a flowchart illustrating a data transmission / reception operation in one frame when the data transmission / reception apparatus according to Embodiment 1 is used as a management terminal. 6 is a flowchart illustrating a data transmission / reception operation in one frame when the data transmission / reception apparatus according to Embodiment 1 is used as a management terminal. 4 is a flowchart for explaining a data transmission / reception operation in one frame when the data transmission / reception apparatus according to the first embodiment is used as a client terminal. 4 is a flowchart for explaining a data transmission / reception operation in one frame when the data transmission / reception apparatus according to the first embodiment is used as a client terminal. 4 is a flowchart for explaining a data transmission / reception operation in one frame when the data transmission / reception apparatus according to the first embodiment is used as a client terminal. 6 is a flowchart for explaining a new management terminal raw activation operation and a bandwidth allocation request operation when the data transmitting / receiving apparatus according to the first embodiment is used as a client terminal. 6 is a flowchart for explaining a new management terminal raw activation operation and a bandwidth allocation request operation when the data transmitting / receiving apparatus according to the first embodiment is used as a client terminal. 6 is a flowchart for explaining a new management terminal raw activation operation and a bandwidth allocation request operation when the data transmitting / receiving apparatus according to the first embodiment is used as a client terminal. 10 is a flowchart for explaining a new management terminal live activation operation and a bandwidth allocation request operation when the data transmitting / receiving apparatus according to the second embodiment is used as a client terminal. 10 is a flowchart for explaining a new management terminal live activation operation and a bandwidth allocation request operation when the data transmitting / receiving apparatus according to the second embodiment is used as a client terminal. 10 is a flowchart for explaining a new management terminal live activation operation and a bandwidth allocation request operation when the data transmitting / receiving apparatus according to the second embodiment is used as a client terminal. 10 is a flowchart for explaining a new management terminal live activation operation and a bandwidth allocation request operation when the data transmitting / receiving apparatus according to the second embodiment is used as a client terminal.

Claims (6)

A data transmitting / receiving apparatus included in each of a plurality of terminals of a network system, wherein the plurality of terminals include a management terminal that manages other terminals and a plurality of client terminals managed by the management terminal, and the management terminal Transmission and reception of video data and control data between the plurality of terminals based on synchronization information output more regularly and schedule information,
The data transmission / reception device includes:
A control information detector for detecting synchronization information and schedule information output from the management terminal;
Check whether the synchronization information and the schedule information have been normally received from the management terminal or not, and whether or not communication with the management terminal has been normally continued based on the reception status information. And a control unit for generating reception status progress information,
The controller is
When it is determined by the reception status progress information that communication with the management terminal cannot be normally continued, a management terminal communication failure notification is generated and transmitted to another client terminal, and the management terminal transmits the management terminal to the management terminal. A data transmission / reception apparatus that controls an own device to start operation as the new management terminal by obtaining approval as a candidate for a new management terminal that replaces. The data transmission / reception device includes:
A timing generation unit that generates timing information including data reception timing based on the schedule information detected by the control information detection unit;
The controller is
When at least one of the synchronization information and the schedule information cannot be received, the timing generator is controlled based on the schedule information received up to the previous time, and the clock detected based on the schedule information received up to the previous time The data transmitting / receiving apparatus according to claim 1, wherein the reference time is corrected using the error information. The controller is
When the own device has not issued the management terminal communication failure notification and has received the management terminal communication failure notification from the other client terminal, the new terminal is notified to the transmission source of the management terminal communication failure notification. The data transmitting / receiving apparatus according to claim 1, which transmits a new management terminal approval notification for approving occurrence as a management terminal. The controller is
When the own device is the management terminal, it is determined that any of the client terminals has occurred as the new management terminal on behalf of the own device by receiving the synchronization information from the client terminal; The data transmission / reception apparatus according to claim 1, wherein the data transmission / reception apparatus controls the own apparatus so as to operate as: The controller is
The operation according to the new management terminal is started by receiving the synchronization information from the new management terminal when the own apparatus is the other client terminal, and the management terminal is regarded as a non-management terminal. The data transmitting / receiving apparatus according to 1. The controller is
Even if the management terminal communication failure notification is received from the other client terminal, the management terminal indicates that the management terminal is operating normally when the synchronization information is received in its own device. The data transmission / reception apparatus according to claim 1, wherein a normal operation notification is generated and transmitted to a transmission source of the management terminal communication failure notification.

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