JP2008263511A - Data transmitter-receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a data transmitter-receiver for performing retransmission control without failure even when an error occurs in transmission/reception data or data which is not required to be retransmitted. <P>SOLUTION: In receiving a NACK message, a transmitter terminal transmits a command for releasing a queue for PLCMAC frame data of a sequence number transmitted in the two cycles before in the next cycle (S63). In a receiver terminal that receives the command, a memory control circuit 506 for PLC reception, for example, receives an instruction of a CPU 11 and generates and outputs an ACK message to thereby notify that the terminal normally receives the command. When a management terminal 1 receives the ACK message (S64), the CPU 11 determines that the receiver can normally performs reception processing and instructs the a memory control circuit 409 for PLC transmission to complete transmission. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a data transmitter / receiver, and more particularly to a data transmitter / receiver in a network system such as wireless communication or high-speed PLC (Power Line Communication).

  In a network system such as wireless communication or high-speed PLC, the characteristics of the transmission path change from moment to moment. For this reason, generally, when an error occurs in a transmission packet on the transmission path, packet retransmission at the MAC (Media Access Control) layer level (hereinafter, referred to as retransmission) may be performed.

  In addition, in network systems such as wireless communication and high-speed PLC, a method of transmitting data using the TDMA (Time Division Multiple Access) method is introduced to transmit and receive data that requires real-time performance such as video and audio. It is being done. 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 signal (hereinafter referred to as BCH: Broadcast CHannel) at a predetermined cycle (2 ms cycle for 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 received 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 next Beacon cycle.

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

  In data communication using a power line, the characteristics of the transmission path change from moment to moment according to the operating conditions of the equipment connected to the power outlet. Therefore, in the conventional high-speed PLC modem, the modulation method applied to the data sent to the transmission line is switched in accordance with the changing transmission line characteristic.

  Further, in a high-speed PLC modem, similarly to a wireless LAN (Local Area Network), when a received packet is lost due to an error mixed in a transmission path, retransmission control is performed in the MAC layer. Therefore, in the high-speed PLC system, the SR (Selective Repeat) method or the Go-Back-N method is used as the retransmission control method in consideration of transmission efficiency and the like.

  On the other hand, in the Stop & Wait method, which is a retransmission method adopted in a wireless LAN or the like, a terminal that has received data immediately sends an ACK packet (notifies that data has been successfully received) to the transmitting terminal. Packet). In the case of a wireless LAN, a maximum 64 point OFDM modulation scheme is adopted as a modulation scheme in the physical layer and the symbol length is short. On the other hand, the modulation scheme in the physical layer used for high-speed PLC or the like employs a maximum of 1024 points OFDM modulation scheme and has a long symbol length. Therefore, in the high-speed PLC, compared with the wireless LAN, it takes time to demodulate the received data in the physical layer when data is received. Therefore, it is necessary to efficiently perform data communication. The transmission / reception schedule is determined in consideration of the data processing time in the layer. As a result, in a high-speed PLC that employs the TDMA scheme, the receiving terminal does not always send out the ACK packet immediately after reception.

  Specifically, when data is transmitted in multiple times to the same terminal within one frame period, each of the received MAC frame data from the receiving terminal to the transmitting terminal is received. Whether or not the MAC frame data is normally received is collectively reported using one ACK packet. On the other hand, when the Stop & Wait method, which is a retransmission method employed in a wireless LAN, is used in the high-speed PLC as described above, a transmission packet is created in consideration of the demodulation time of received data in the physical layer. It is necessary to increase the interval between the data and the ACK packet data, which reduces the data transmission efficiency. For example, when the OFDM symbol length is 50 μs and the processing time in the physical layer requires 4 OFDM symbols, the interval between the transmission packet data and the ACK packet data needs to be 200 μs or more.

  As described above, for example, when the TDMA method is adopted in the high-speed PLC, the SR method or the Go-Back-N method is used as the retransmission control method in order to increase the efficiency of transmission data.

  For example, Patent Documents 1 and 2 describe retransmission control using the SR method and the Go-Back-N method. Further, in Patent Document 3, a terminal that has received data uses a ACK / NACK packet to notify the terminal on the transmission side whether or not the data has been normally received, and notifies the terminal on the transmission side. Describes a method for performing retransmission control using the received ACK / NACK packet.

  In addition, when data that requires real-time performance such as voice or video is transmitted and received using a network using a wireless LAN, a high-speed PLC, or the like, retransmission control in the MAC layer may not be performed. In particular, in a high-speed PLC network that employs the TDMA system, as described above, a delay of one frame period or more may occur until an ACK packet is received. In particular, telephone-related applications such as VoIP (Voice over Internet Protocol) need to minimize the amount of packet delay.

  That is, in the MAC control method adopting the TDMA method adopted in HiSWANa or the like, when the transmitting terminal receives a NACK packet and then sends a retransmission packet, the transmission timing is at least about one frame period from the reception of the NACK packet. Is delayed. Specifically, since the bandwidth allocation for the retransmission packet is after the next frame period after receiving the NACK packet, the transmission timing is delayed by about one frame period. In particular, in high-speed PLCs, unlike OFDM, as described above, 1 OFDM symbol length is long. Therefore, considering the data transmission efficiency, the data length of 1 MAC frame data is 20 ms (about 10 times that of HiSWANa), for example. Long. Therefore, when an error occurs in the MAC frame data to which VoIP data is transmitted and retransmission control is performed, the packet is delayed by about two frame periods (about 40 ms). Therefore, even if the retransmission control in the MAC layer is used in the high-speed PLC, the retransmission packet is delayed by about two frame periods, and therefore there is a case where the retransmission control is not performed for data such as VoIP with severe restrictions on the data delay amount.

  Patent Document 4 describes a control method in the case where a packet that does not perform retransmission control such as VoIP exists in transmission data.

Japanese Patent Laid-Open No. 10-247901 JP 11-215192 A JP 2001-69156 A Japanese Patent Laid-Open No. 2005-64594

  Here, when the delivery confirmation control method using the ACK / NACK packet disclosed in Patent Document 3 is applied to the retransmission control method (SR retransmission control method) described in Patent Documents 1 and 2, the above VoIP that does not require retransmission, etc. When an error occurs in the transmission path in the packet including the packet, the receiving terminal determines that the PLC MAC frame data could not be received due to an error, sends a NACK packet, and performs SR retransmission control.

  That is, the receiving side terminal confirms the sequence number inserted in the PLCMAC header, and if the sequence number is found to be skipped, it is determined that the skipped data could not be received normally, and the next A NACK packet is output to the transmitting terminal at the transmission timing of the frame period, and a packet with a sequence number lost on the transmission path is waited for retransmission. store.

  At this time, since the terminal on the transmission side does not hold data for retransmission, it cannot be retransmitted even if a NACK packet is received. In this case, the receiving side terminal does not retransmit the retransmission-free PLC MAC frame data in which a receiving error has occurred from the transmitting side terminal, so that the reception waiting state continues, and the receiving frame buffer in the receiving side terminal overflows. There was a problem of causing.

  The present invention has been made to solve the above-described problems, and is a data transmission / reception apparatus that performs transmission / reception in a state where PLCMAC frame data that does not require retransmission, such as VoIP, and PLCMAC frame data that requires retransmission are mixed. Provides a data transmission / reception apparatus capable of performing retransmission control without failure even when an error occurs in transmission / reception data or data that does not require retransmission when the SR method is employed as a retransmission control method. For the purpose.

  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 the terminal are included, and data transmission / reception is performed between the plurality of terminals based on schedule information output from the management terminal. The data transmitter / receiver determines a transmission timing and a reception timing of the data based on the schedule information, confirms whether or not the data is normally received, and is added to header information of the data, If the data cannot be received normally, the data is data that needs to be retransmitted based on retransmission necessity information that indicates whether the data needs to be retransmitted or data that does not require retransmission. A control unit that confirms whether the data does not require retransmission, and a control data generation unit that receives an instruction from the control unit and generates an ACK message and a NACK message, respectively, indicating whether or not the data has been normally received A transmission control unit that controls transmission of the data based on the transmission timing, and the data has been normally received. The data transmission / reception device includes: a reception control unit that stops processing for data given at the subsequent transmission timing until the data is normally received, and enters a reception waiting state. When functioning as a terminal, when the data is not normally received, the NACK message is output to the management terminal, and when the data transmitting / receiving apparatus functions as the management terminal, the transmission control unit In addition, when transmitting the data, the header information including the retransmission necessity information is added to the data, and the NACK message is received from the client terminal, and the data is the data that does not require retransmission. If there is, the header information Including by, and transmitted to the client terminal which outputs the NACK message, cancels the reception waiting state of the retransmission unnecessary data at the client terminal.

  According to the data transmitting / receiving apparatus according to claim 1 of the present invention, when the NACK message is received from the client terminal and the data is data that does not require retransmission, the reception waiting state of data that does not require retransmission is set. A release command to be released is included in the header information and transmitted to the client terminal that has output the NACK message, and the client terminal on the receiving side releases the data reception wait state for retransmission unnecessary data. If this is not possible, even if the data is data that does not need to be retransmitted, the receiving buffer in the receiving terminal does not overflow, and data transmission / reception can be performed without failure of the retransmission control method. it can.

<A-1. Network system configuration>
FIG. 1 is a diagram schematically showing a configuration of a high-speed PLC network system provided with a data transmitting / receiving apparatus according to an embodiment 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).

  FIG. 2 shows time allocation for transmission of various data within one frame period. Network management information is assigned in the order of BCH (Broadcast CHannel), FCH (Frame CHannel) and ACH (Access feedback CHannel). After transmission, n communication slots L1 to Ln are transmitted in the data transmission / reception period, and finally RCH (Random access CHannel) is transmitted.

<A-2. Overview of network system operations>
Next, a schematic operation of the network system will be described with reference to FIGS. 1 and 2 focusing on the operation of the management terminal 1 in the high-speed PLC network. In the 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 method.

<A-2-1. Operation of management terminal>
The management terminal 1 first broadcasts a Beacon signal (BCH) as synchronization information in 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) of each client terminal in the high-speed PLC network. When the RCH output from each client terminal is received in the previous frame after the FCH transmission, the ACH notifying that the RCH transmission client terminal has normally received is output.

  When the RCH is not received or when the RCH is not received normally, the ACH notifying that is broadcasted to determine that the terminal that has transmitted the RCH in the previous cycle has not been able to transmit normally. Then, RCH is transmitted again.

  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. Details of the FCH will be described later.

  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.

<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 corrects the reference time in the client terminal based on the BCH and synchronizes with the management terminal 1.

  After the correction of the reference time, each client terminal notifies the data transmission timing and data reception timing to the MAC unit (details will be described later) and the modem unit (details will be described later) based on the FCH output from the management terminal 1. To do.

  When receiving the notification of the data transmission timing and the data reception timing, the modem unit starts preparations for data transmission and reception based on the reference time information corrected by the BCH.

  Specifically, in the case of data reception, when the reception time based on FCH is reached, the PLC demodulation circuit unit (details will be described later) starts the data reception operation and detects the preamble information added in advance to the beginning of the data. To do. When the preamble information is detected at a predetermined timing, the PLC demodulation circuit unit detects the head of the received data based on the detected preamble information, demodulates the received data, and outputs the demodulated data to the MAC unit. On the other hand, when the preamble cannot be detected at a predetermined timing, the PLC demodulation circuit unit notifies the MAC unit that it could not be received.

  On the other hand, in the case of data transmission, when the transmission time based on FCH approaches, the MAC unit starts generating transmission data. When the generation of transmission data is completed in the MAC unit, it is output at the timing generated in the PLC modulation circuit unit. In the PLC modulation circuit unit, transmission data output from a PLC transmission control circuit (details will be described later) is subjected to digital modulation such as OFDM modulation, for example, and preamble information is added to the power line 9 (see FIG. Send transmission data to 1).

<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. 3 is a block diagram showing a 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. 3, the data transmitter / receiver 10 includes a CPU (Central Processing Unit) 11, an Ethernet interface circuit 12, a bridge circuit 13, a bridge memory 14, a PLC transmission control circuit 15, a PLC reception control circuit 16, and a PLC transmission. A memory 17, a PLC reception memory 18, a PLC modulation circuit 19, a PLC demodulation circuit 20, and a CPU bus 21 are provided.

  Here, the bridge circuit 13 includes the Ethernet frame data input from the Ethernet interface circuit 12, the Ethernet frame data output to the Ethernet interface circuit 12, the Ethernet frame data output to the PLC transmission control circuit 15, and the PLC reception control circuit 16. This is a bridge circuit that distributes and transfers Ethernet frame data input from each destination.

  The bridge memory 14 is a memory in which the Ethernet frame input to the bridge circuit 13 is sorted and stored for each destination, and the PLC transmission memory 17 sends out via the power line 9 (FIG. 1). The PLC reception memory 18 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 and outputting the data from the data transmitting / receiving device 10 to the outside via the input terminal 22 and the output terminal 23. The PLC transmission control circuit 15 Is a circuit for controlling transmission of frame data to the outside, and the PLC reception control circuit 16 is a circuit for controlling reception of frame data from the outside.

  The PLC modulation circuit 19 is connected to the CPU 11 via the CPU bus 21 and is controlled by the CPU 11 to perform modulation processing on the PLC MAC frame data output from the PLC transmission control circuit 15 and to output terminals. 24 is a circuit that sends out to the power line 9 via 24.

  The PLC demodulating circuit 20 is connected to the CPU 11 via the CPU bus 21 and the operation is controlled by the CPU 11 to demodulate data received from the power line 9 via the input terminal 25, and the PLC reception control circuit. 16 is a circuit for giving PLCMAC frame data to 16.

  In general, in a high-speed PLC network, each terminal connected to the power line 9 (FIG. 1) uses a concept of a logical port, and the bridge circuit 13 uses a destination (management terminal 1, client terminal A3, client terminal in FIG. 1). B5 and client terminal C7) distribute data and queue them in 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 transmission control circuit>
FIG. 4 is a block diagram showing a configuration of PLC transmission control circuit 15 shown in FIG.
As shown in FIG. 4, the PLC transmission control circuit 15 includes a PLCMAC header generation circuit 401 that generates a PLCMAC header to be added to PLCMAC frame data, an Ethernet frame data that is input from the bridge circuit 13 via the input terminal 30, and a PLC network. Transmission data by collecting a plurality of ACK / NACK necessity flag information output from the control data generation circuit 408 and message information generated for exchanging information between the management terminal 1 and each client terminal. A packet data generation circuit 402 that outputs sequence number information to be inserted into the PLCMAC header to the PLCMAC header generation circuit 401, an encryption circuit 403 that encrypts data output from the packet data generation circuit 402, which will be described later You A selector 404 for switching between the Beacon frame data and schedule data output from the PLC network control data generation circuit 408 and the encrypted data output from the encryption circuit 403, and at the head of the data output from the selector 404 The header addition circuit 405 for adding the PLCMAC header generated by the PLCMAC header generation circuit 401, the data output from the header addition circuit 405, and the data output from the PLC transmission memory control circuit 409 described later are switched. PLC transmission for generating a transmission timing of data to be output from the data transmitting / receiving apparatus 10 to the PLC network based on the schedule information from the selector 406 and the PLC network control data generation circuit 408 and the setting information from the CPU 11 Imming generation circuit 407, PLC network control data generation circuit 408, PLC transmission memory control circuit 409, and CRC code addition circuit for adding a CRC code (error detection code) to PLC MAC frame data transmitted to the outside via output terminal 22 410.

  Here, the PLC network control data generation circuit 408 includes a sequence number added to data to be transmitted, reference time information of the terminal itself, flag information indicating whether BCH or FCH has been normally received at the previous reception timing, A circuit for generating and outputting an ACK / NACK message indicating whether or not received data has been normally received at the reception timing, Beacon control data to be added to a control channel such as BCH and FCH, schedule information within one frame period, etc. It is.

  The PLC transmission memory control circuit 409 generates a write control signal for storing the transmission PLC MAC frame data used in the retransmission control in the PLC transmission memory 17 and stores it in the PLC transmission memory 17 during the retransmission. This circuit generates a read control signal for reading the read data.

<A-3-3. Configuration of PLC reception control circuit>
FIG. 5 is a block diagram showing a configuration of the PLC reception control circuit 16 shown in FIG.
As shown in FIG. 5, the PLC reception control circuit 16 separates the PLCMAC header from the PLCMAC frame data input via the input terminal 31, and analyzes the content of the PLCMAC header analysis circuit 501, and converts the PLCMAC header data into the received PLCMAC frame data. CRC decoding circuit 502 for detecting an error generated in the received PLCMAC frame data based on the added CRC information, and encryption / decryption circuit 503 for decoding the encrypted data output from the PLCMAC header analysis circuit 501 PLC control frame separation circuit 504 for separating control frame information such as schedule information added to PLC MAC frame data, and PLC control frame data for temporarily storing PLC control frame information separated by PLC control frame separation circuit 504 And a memory circuit 505, PLC receiving memory control circuit 506 and the PLC reception timing generation circuit 507. The PLC MAC 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 reconstructs the Ethernet frame data output from the PLC control frame separation circuit 504, and once generates a control signal to be stored in the PLC reception memory 17, and the CRC. On the basis of the error detection result output from the decoding circuit 502, this is a circuit that performs read control of Ethernet frame data stored in the PLC reception memory 18.

  In addition, the PLC reception timing generation circuit 507 reads schedule data stored in the PLC control frame data storage circuit 505 or a storage circuit such as a memory accessible by the CPU 11 by the CPU 11 via the CPU bus 21, and outputs the data from the PLC. This is a circuit that generates data reception timing and supplies it to the PLCMAC header analysis circuit 501, CRC decryption circuit 502, encryption / decryption circuit 503, PLC control frame separation circuit 504, and PLC reception memory control circuit 506.

<A-4. Transmission operation>
Next, the operation at the time of transmission of the data transmitting / receiving apparatus 10 will be described using FIGS. 6 to 11 with reference to FIGS. In this embodiment, as in the conventional example, the TDMA method is adopted as the MAC control method in the PLC network.

First, an outline of the transmission operation will be described with reference to FIG.
The Ethernet frame data input via the input terminal 22 is separated and analyzed by the Ethernet interface circuit 12 based on the Ethernet MAC header information added to the data in advance, and input to the bridge circuit 13. Is done.

  When the Ethernet frame data is input from the Ethernet interface circuit 12, the bridge circuit 13 separates the priority information of the data from the Ethernet MAC header. Similarly, the destination port address is searched using the destination MAC address information. When the analysis of the MAC header information added to the Ethernet frame is completed, the bridge circuit 13 stores the received Ethernet frame data in the bridge memory 14 with the priority information and the detection result of the destination port. .

  The bridge circuit 13 also prioritizes the Ethernet frame data stored in the bridge memory 14 based on the destination port information output from the PLC transmission control circuit 15 in the data transmitting / receiving apparatus 10 and the Ethernet frame data request signal. Are output in the descending order and output to the PLC transmission control circuit 15.

<A-4-1. Operation of PLC transmission control circuit>
Next, the operation of the PLC transmission control circuit 15 in the management terminal 1 (FIG. 1) will be described with reference to FIG.

  In order to manage time synchronization of the entire PLC network, the management terminal 1 periodically outputs a Beacon frame on the BCH and schedule information on 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 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.

  In the 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 the embodiment, the MAC address information of each terminal is used for the terminal information on the transmitting side and the terminal information on the receiving side. 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.

  Also, the terminal information on the transmission side or the terminal information on the reception side is not necessarily required information, and only one of the information may be used.

  As for the communication slot, each client terminal having data transmits RCH information to the management terminal 1 in the same manner as in the conventional example, or in the case of a client terminal actually transmitting data, one of the PLC MAC frame data. A transmission slot is allocated by adding a band allocation request as message information to the transmission section.

<A-4-1-1. Generation of schedule information>
Next, a method for generating schedule information in the PLC transmission control circuit 15 will be described using the flowchart shown in FIG.

  When transmission / reception of data is started, the CPU 11 (FIG. 2) in the management terminal 1 confirms whether or not it is the generation start timing of the schedule information (step S10). If the generation start timing has not been reached, the generation start timing is reached. It waits until it reaches, and when it is the generation start timing, it proceeds to step S11.

  In step S11, the CPU 11 in the management terminal 1 transmits a ACK / NACK packet transmission band (time slot) for the transmission slot allocated by the previous frame data, and an ACK / NACK packet transmission for the data transmitted this time. Implement bandwidth allocation.

  When the time slot allocation for the ACK / NACK packet is completed, it is confirmed whether there is a retransmission request from each client terminal and a retransmission request to each client terminal (step S12).

  If there is no retransmission request, the process proceeds to step S14. If any retransmission request is present, a retransmission time slot is assigned to the retransmission data (step S13).

  When the allocation of the retransmission time slot is completed, the CPU 11 of the management terminal 1 checks whether or not there is a new communication requesting terminal that has requested the bandwidth allocation by the RCH (step S14).

  If there is no new communication request terminal, the process proceeds to step S16. If there is a new communication request terminal, the PLC network control data generation circuit 408 (FIG. 4) is controlled to transmit a time slot for transmission to that terminal. Is assigned (step S15).

  When the assignment of the transmission time slot to the new communication requesting terminal is completed, the CPU 11 of the management terminal 1 controls the PLC network control data generation circuit 408 to assign the transmission time slot of the management terminal 1 (step S16).

  Thereafter, a transmission time slot is assigned to each client terminal (step S17).

  When the transmission time slot assignment is completed, the PLC network control data generation circuit 408 generates an FCH frame based on the assigned transmission time slot information (step S18).

  The FCH frame generated in the PLC network control data generation circuit 408 outputs the FCH frame to the selector 404 based on the timing information output from the PLC transmission timing generation circuit 407 (step S19).

  After outputting the FCH frame, the process returns to step S10 and waits until the next schedule generation start timing comes.

  Also, the PLC network control data generation circuit 408 outputs a schedule (transmission time slot information) of data to be transmitted to each client terminal in this frame period to the PLC transmission timing generation circuit 407 when transmitting the FCH frame. In the present embodiment, it is assumed that the transmission / reception timings of fixed slots such as BCH and FCH are set in advance in the PLC transmission timing generation circuit 407 and the PLC reception timing generation circuit 507 from the CPU 11. Further, the time slot information for data reception is set via the CPU 11 to a PLC reception timing generation circuit 507 (to be described later) in the PLC reception control circuit 16.

<A-4-1-2. Transmission operation of Ethernet frame data>
Next, the transmission operation of Ethernet frame data input from the bridge circuit 13 to the PLC transmission control circuit 15 will be described using the flowchart shown in FIG. 8 with reference to FIGS.

  In the management terminal 1, as described above, schedule information is output from the PLC network control data generation circuit 408 to the PLC transmission timing generation circuit 407 during FCH transmission.

  On the other hand, when each client terminal participating in the PLC network receives the FCH, each CPU 11 separates time slot information for its own device to transmit or receive data. It is set in the PLC transmission timing generation circuit 407 via the network control data generation circuit 408. Regarding the reception time slot, the CPU 11 directly sets a reception schedule in the PLC reception timing generation circuit 507 in the PLC reception control circuit 16 (FIG. 5).

  Since the transmission operation of the Ethernet frame data to the PLC network at the management terminal 1 and the client terminal is the same except for the operation of setting the time slot for transmission to the PLC transmission timing generation circuit 407, the transmission at the management terminal 1 Only the operation will be described with reference to FIG.

  When the generation of the MAC frame is started, the PLC transmission timing generation circuit 407 confirms the schedule information output from the PLC network control data generation circuit 408 and the destination terminal information to be transmitted next, and the number of bytes that can be transmitted based on the transmission time Is calculated (step S30). In the PLC network, as with the wireless LAN, since the PHY speed (PHY modulation / demodulation parameter) of transmission data differs for each connected client terminal, it is necessary to check the destination terminal information.

  When the calculation of the number of transmission bytes is finished, the PLC transmission timing generation circuit 407 stores the Ethernet frame data destined for the client terminal of the transmission destination stored in the bridge memory 14 for the bridge circuit 13 in descending order of priority. Request to notify the length.

  The PLC transmission timing generation circuit 407 calculates the number of connected Ethernet frames to be transmitted this time based on the byte number information of the Ethernet frame data output from the bridge circuit 13 (step S31).

  Here, in the embodiment, in order to efficiently transmit data over the PLC network, when generating PLCMAC frame data, a plurality of Ethernet frame data are concatenated to form one PLCMAC frame data.

  FIG. 9 schematically shows the connection process. As shown in FIG. 9, the PLC MAC frame data indicates how many message information and Ethernet frames for exchanging information between the management terminal 1 and each client terminal are connected as packet data following the PLC MAC header. One piece of PLCMAC frame data is generated by concatenating the concatenation information and a plurality of (F1 to Fn) Ethernet frames.

  The PLC MAC header includes terminal information for identifying a transmission source or a transmission destination, retransmission necessary / unnecessary bits indicating whether the PLC MAC frame data is a frame to be retransmitted or a frame not to be retransmitted, and packet data generation. The circuit 402 is configured by sequence number information assigned in the order of transmission for each PLC MAC frame data connected in the circuit 402.

  Here, the description returns to FIG. When the PLC transmission timing generation circuit 407 finishes calculating the number of connected Ethernet frames, it instructs the PLCMAC header generation circuit 401 to generate PLCMAC frame data. When the instruction to the PLC MAC header generation circuit 401 is completed, the PLC transmission timing generation circuit 407 waits until the data transmission time comes.

  On the other hand, the PLC network control data generation circuit 408 instructs the PLCMAC header generation circuit 401 to read a sequence number (referred to as SN) (step S321) and confirm the type of transmission data (step S322). Whether or not an ACK / NACK response is necessary is confirmed (step S323).

  If an ACK / NACK response is required, an ACK / NACK response flag is set in step S324. If an ACK / NACK response is not required, an ACK / NACK response flag is set in step S325. To reset.

  The PLCMAC header generation circuit 401 generates PLCMAC header information based on the above processing, and waits until the data transmission time.

  In addition, the process of step S321-S326 mentioned above is named generically the production | generation process (step S32) of PLCMAC header information.

  At the data transmission time, the PLC transmission timing generation circuit 407 instructs the PLCMAC header generation circuit 401 and the packet data generation circuit 402 to generate PLCMAC frame data for transmission based on the PLCMAC header information generated in step S32. In addition, the bridge circuit 13 is instructed to output Ethernet frame data, and the Ethernet frame data is connected based on the connection information (step S33).

  Specifically, the bridge circuit 13 reads and connects predetermined Ethernet frame data from the bridge memory 14 according to the data request instruction output from the PLC transmission timing generation circuit 407, and outputs it to the packet data generation circuit 402. In the packet data generation circuit 402, the Ethernet frame data read from the bridge memory 14 is temporarily stored in an internal memory (not shown) and converted into a block having a predetermined size (for example, 128 bits). Output to the encryption circuit 403.

  The encryption circuit 403 encrypts the data blocked in a predetermined size (step S34).

  Data encrypted by the encryption circuit 403 is input to the selector 404. The selector 404 switches and outputs the encrypted Ethernet frame data output from the encryption circuit 403 and PLC network control data such as BCH and FCH generated by the PLC network control data generation circuit 408. Specifically, for the data transmission / reception period shown in FIG. 6, the encrypted Ethernet frame data output by the encryption circuit 403 is selected and output, and during the BCH, FCH, ACH, and RCH periods, the PLC network control circuit 408 is selected. Selects and outputs PLC network control data of BCH, FCH, ACH, and RCH output by. Note that the select signal of the selector 404 is given from the PLC transmission timing generation circuit 407 as shown in FIG.

  The output of the selector 404 is input to the PLCMAC header addition circuit 405, and the PLCMAC header addition circuit 405 generates a PLCMAC header in front of the packet data output from the selector 404 based on the timing signal output from the PLC transmission timing generation circuit 407. The PLCMAC header information output from the header generation circuit 401 is added (step S35).

  In the present embodiment, the Ethernet frame data blocked in a predetermined size in the packet data generation circuit 402 is temporarily stored in a memory (not shown) provided in the PLCMAC header addition circuit 405. , It is restored to the size of Ethernet frame data.

  Similarly, the PLC MAC header addition circuit 405 adds a PLC MAC header to the PLC network control data output from the PLC network control data generation circuit 408.

  The PLC MAC frame data to which the PLC MAC header information is added is input to the selector 406 and the PLC transmission memory control circuit 409. The selector 406 switches between the output from the PLCMAC header addition circuit 405 and the output from the PLC transmission memory control circuit 409 based on the switching signal output from the PLC transmission memory control circuit 409. Details of the control of the PLC transmission memory control circuit 409 will be described later.

  The output of the selector 406 is input to the CRC code circuit 410. The CRC code circuit 410 adds a CRC code for detecting an error occurring in the PLC network when it is sent to the PLC network to the PLC MAC frame data to which the PLCMAC header is added output from the selector 406, and then adds the CRC code. A PHY header is added by a PHY header addition circuit (not shown) in the circuit 410 and output.

  The PLC MAC frame data to which the PHY header output from the CRC code circuit 410 in the PLC transmission control circuit 15 is added is subjected to digital modulation such as OFDM modulation in the PLC modulation circuit 19 shown in FIG. It becomes data.

  The transmission data subjected to digital modulation is subjected to a preamble addition circuit (not shown) in the PLC modulation circuit 19 by adding a predetermined number of symbols in front of the PLC MAC frame data to the power line 9 (FIG. 1). Sent out. When the transmission of the PLCMAC frame data to the power line 9 is completed, the packet data generation circuit 402 increments the sequence number (SN) by one in preparation for the next PLCMAC frame data generation (step S36), and the PLCMAC frame data End generation.

  In the above description, the timing for incrementing the sequence number in step S36 has been described as after the PLC MAC frame data is sent to the power line 9. However, in step S32, the sequence number is read in step S321, and then in step S326. The sequence number may be incremented during the period until the PLCMAC header is generated.

  Here, the operation of the PLC transmission memory control circuit 409 in the PLC transmission control circuit 15 will be described. This embodiment is characterized in that the presence or absence of retransmission control is set according to the type of PLC MAC frame data to be transmitted.

  Specifically, in the case of a packet such as VoIP that requires a delay amount to be kept below a predetermined time, even if retransmission control is performed, retransmission processing is not completed within the above time, so retransmission control is not performed. . Similarly, when only the protocol used for the MAC control of the PLC performed between the management terminal 1 and each client terminal such as ACK / NACK is transmitted, the retransmission control is not performed in the same manner. Therefore, in the present embodiment, the necessity of retransmission control is determined according to the type of Ethernet frame, and PLCMAC frame data that needs to be retransmitted is output from the PLCMAC header addition circuit 405 and then provided to the selector 406. At the same time, it is given to the PLC transmission memory 17 via the PLC transmission memory control circuit 409 and stored until the transmission is confirmed to be normal.

  If the normal transmission is not confirmed, the PLC transmission memory control circuit 409 reads the data from the PLC transmission memory 17 at the timing when the retransmission slot is given and outputs the data to the selector 406. Note that data that does not need to be retransmitted is discarded regardless of the transmission result when transmission is completed.

<A-5. Reception operation>
Next, with reference to FIG. 3 and FIG. 5, the operation at the time of reception when the data transmitting / receiving apparatus 10 is used as the client terminal A (FIG. 1) will be described using the flowchart shown in FIG.

  The PLC MAC frame data (digitally modulated) input to the PLC demodulation circuit 20 from the PLC network via the input terminal 25 is demodulated in the PLC demodulation circuit 20 and output to the PLC reception control circuit 16. The PLCMAC frame data (demodulated) input to the PLC reception control circuit 16 via the input terminal 31 is supplied to the PLCMAC header analysis circuit 501 and the CRC decoding circuit 502.

  Here, the PLC reception timing generation circuit 507 confirms whether or not the FCH has been normally received in step S40 shown in FIG.

  If the FCH is not normally received, the system waits until the FCH is normally received. If the FCH is normally received, the schedule information of the communication slot shown in FIG. If there is, the reception timing is generated (step S41), and the PLCMAC header analysis circuit 501, CRC decryption circuit 502, encryption / decryption circuit 503, PLC control frame separation circuit, and PLC reception so as to receive the PLCMAC frame data. To the memory control circuit.

  After receiving the PLCMAC frame data (step S42), the PLCMAC header analysis circuit 501 separates the MAC header portion from the PLCMAC frame data and analyzes the contents (step 43).

  Then, based on the destination information in the PLCMAC header, whether or not the data is addressed to the own device is checked (step S44), and the data addressed to the own device is received and is data to other client terminals Operates to discard the received data (step S56).

  Also, the PLCMAC header analysis circuit 501 reads the retransmission necessity / unnecessary bits and the sequence number information in the PLCMAC header and outputs them to the PLC reception memory control circuit 506.

  The PLCMAC frame data from which the PLCMAC header is separated is input to the encryption / decryption circuit 503, and it is confirmed whether or not it is encrypted data (step S45).

  If the data is encrypted, the data is decrypted (step S46). In step S47, it is confirmed whether the data can be decrypted normally. If the data is not decrypted, the received data is discarded (step S56). Is decoded to the PLC control frame separation circuit 504. In the case of non-encrypted data, it is output to the PLC control frame separation circuit 504 as it is.

  The PLC control frame separation circuit 504 separates PLC control frame information and message information added to the PLC MAC frame data (step S48) and stores them in the PLC control frame data storage circuit 505.

  Also, the PLC MAC frame data separated from the PLC control frame by the PLC control frame separation circuit 504 is output to the PLC reception memory control circuit 506 (step S49).

  Also, the CRC decoding circuit 502 confirms whether or not an error has occurred in the PLC MAC frame data during transmission based on the CRC information added to the received PLC MAC frame data at the time of transmission (step S55). Is detected (step S56), and if no error is detected, the process proceeds to step S45, and the detection result is output to the PLC reception memory control circuit 506.

  The PLC reception memory control circuit 506 reconstructs Ethernet frame data from the PLCMAC frame data output (separated) from the PLC control frame separation circuit 504 (step S50), and stores the control signal in the PLC reception memory 18 And whether or not the received PLCMAC frame data is normally received data is checked based on the error detection result output from the CRC decoding circuit 502 (step S51). If the data is normally received, the Ethernet frame data is stored in the PLC reception memory 18, and if the error is detected, the Ethernet frame data is discarded (step S56). If the error is also detected, the data is discarded (step S56).

  Also, in the PLC reception memory control circuit 506, whether or not the reconfigured Ethernet frame data is data that needs to be retransmitted based on the information on the requisite / unnecessary bits for retransmission given from the PLCMAC header analysis circuit 501. (Step S52), if the data needs to be retransmitted, the data is rearranged in units of PLCMAC frames in the order of transmission from the terminal on the transmission side based on the sequence number given from the PLCMAC header analysis circuit 501 ( In step S53), Ethernet frame data is read from the reception memory 18 and output to the bridge circuit 13 (step S54). If the data does not need to be retransmitted, the Ethernet frame data is read from the reception memory 18 without being rearranged and output to the bridge circuit 13 (step S54).

  When the output to the bridge circuit 13 is completed, it waits until reception of PLCMAC frame data starts.

<A-6. Conventional communication sequence in SR (Selective Repeat) method>
Next, a conventional communication sequence when the SR method is adopted will be described using FIG. 11 and FIG. In the following description, for the sake of simplicity, an example of data transmission from the management terminal 1 (FIG. 1) to the client terminal A3 (FIG. 1) is shown, and the BCH and FCH shown in FIG. Transmission / reception of PLC control frame information of ACH and RCH is omitted.

<A-6-1. If no error occurred during transmission>
First, a communication sequence when no error has occurred during data transmission will be described with reference to FIG.

  After transmitting the BCH, FCH, and ACH, the management terminal 1 generates PLC MAC frame data based on the MAC frame data generation flow described with reference to FIG. 8 and outputs the PLC MAC frame data to the PLC network.

  When receiving the PLCMAC frame data output from the management terminal 1, the client terminal A3 separates and analyzes the PLCMAC header and reads the sequence number.

  In FIG. 11, numbers indicated by M to M + 4 indicate sequence numbers assigned to the PLC MAC frame data, and one PLC MAC frame data is transmitted within one cycle. The transmission is not limited to one PLCMAC frame data per cycle, and a plurality of PLCMAC frame data may be transmitted per cycle.

  In FIG. 11, first, in period 1, PLC MAC frame data of sequence number M that needs to be retransmitted is transmitted from the management terminal 1 to the client terminal A3. Next, in cycle 2, PLC MAC frame data of sequence number M + 1 that does not require retransmission is transmitted from management terminal 1 to client terminal A3, and from client terminal A to management terminal 1 in cycle 1 In response to the received PLCMAC frame data of sequence number M, an ACK message of sequence number M indicating normal reception is transmitted as PLCMAC frame data.

  Similarly, in cycle 3, PLC MAC frame data of sequence number M + 2 that needs to be retransmitted is transmitted from management terminal 1 to client terminal A3, and from client terminal A3 to management terminal 1 in cycle 2 In response to the received PLCMAC frame data of sequence number M + 1, an ACK message of sequence number M + 1 indicating normal reception is transmitted as PLCMAC frame data.

  Further, in cycle 4, PLC MAC frame data of sequence number M + 3 that needs to be retransmitted is transmitted from management terminal 1 to client terminal A3, and received from management terminal 1 in cycle 3 from client terminal A3. The ACK message with the sequence number M + 2 indicating that the PLCMAC frame data with the sequence number M + 2 has been normally received is transmitted as PLCMAC frame data.

  Further, in cycle 5, PLC MAC frame data of sequence number M + 4 that needs to be retransmitted is transmitted from management terminal 1 to client terminal A3, and received from management terminal 1 in cycle 4 from client terminal A3. The ACK message with the sequence number M + 3 indicating that the PLCMAC frame data with the sequence number M + 3 has been normally received is transmitted as PLCMAC frame data.

  Finally, in cycle 6, there is no transmission from the management terminal 1 to the client terminal A3, and the PLC MAC frame data of sequence number M + 4 received in cycle 5 from the client terminal A3 to the management terminal 1 is normal. An M + 4 ACK message indicating reception is transmitted as PLC MAC frame data.

  As described above, when transmitting the PLC MAC frame data that needs to be retransmitted, the management terminal 1 completes the transmission by receiving the ACK message from the client A3 in the next cycle. At this time, the PLC MAC frame data that needs to be retransmitted is stored in the PLC MAC transmission memory 17 (FIG. 4) via the PLC transmission memory control circuit 409 (FIG. 4) prior to transmission.

  The data stored for retransmission is discarded from the transmission memory 17 by the PLC transmission memory control circuit 409 when an ACK message is received in the next cycle.

  Also, the PLCMAC frame data that does not need to be retransmitted is not stored in the PLCMAC transmission memory 17 but is discarded without receiving the ACK message.

<A-6-2. If an error occurs during transmission>
Next, a communication sequence when an error occurs in the transmission path during data transmission will be described with reference to FIG.

  In FIG. 12, first, in cycle 1, PLC MAC frame data of sequence number M that needs to be retransmitted is transmitted from management terminal 1 to client terminal A3. Next, in cycle 2, PLC MAC frame data of sequence number M + 1 that does not require retransmission is transmitted from management terminal 1 to client terminal A3, and from client terminal A to management terminal 1 in cycle 1 In response to the received PLCMAC frame data of sequence number M, an ACK message of sequence number M indicating normal reception is transmitted as PLCMAC frame data.

  At this time, the PLC MAC frame data of sequence number M + 1 transmitted from the management terminal 1 is affected by noise or the like in the transmission path and an error has occurred, and cannot be normally received by the client terminal A3. Since it is not known that the addressed data is being transmitted, the client terminal A3 waits for reception of the PLCMAC frame data of the next sequence number M + 1.

  Next, in period 3, PLC MAC frame data having a sequence number M + 2 that needs to be retransmitted is transmitted from the management terminal 1 to the client terminal A3. However, on the client terminal A3 side, due to the continuity of the sequence number, the sequence number When the PLC MAC frame data of M + 2 is normally received, the PLC MAC frame data of sequence number M + 1 cannot be normally received due to an error in the transmission path. Therefore, the PLC MAC frame data of sequence number M + 1 is normally received. It is managed as waiting to receive until it is received.

  In this way, by adopting a method of confirming the data reception status by the sequence number having continuity, the reception status can be confirmed relatively easily without significantly changing the apparatus configuration.

  When the SR method is adopted as the retransmission control method, data is transferred to the bridge circuit 13 in the order of the sequence number on the receiving side. In this case, since the PLC MAC frame data with the sequence number M + 1 is not received, even if the PLC MAC frame data with the sequence number M + 2 is normally received, the transfer is not immediately performed to the bridge circuit 13 (FIG. 3). It is temporarily stored in the PLC reception memory 18 as a waiting state.

  If the client terminal A3 normally receives the PLCMAC frame data with the sequence number M + 1, the client terminal A3 transmits the M + 1 ACK message to the management terminal 1 in the cycle 3, but the PLCMAC with the sequence number M + 2 Since it was found that M + 1 was not received for the first time when the frame data was received, the PLC MAC frame data of sequence number M + 1 could not be normally received in period 3 when it could be processed at high speed. Is transmitted to the management terminal 1, a NACK message of sequence number M + 1 is transmitted. If high-speed processing is impossible in period 3, a NACK message with sequence number M + 1 is transmitted in period 4.

  Next, in cycle 4, PLC MAC frame data of sequence number M + 3 that needs to be retransmitted is transmitted from management terminal 1 to client terminal A3, and is normally received by client terminal A3. Further, the client terminal A3 transmits, as PLCMAC frame data, an ACK message with a sequence number M + 2 indicating that the PLCMAC frame data with the sequence number M + 2 received in the cycle 3 has been normally received from the client terminal A3. Note that if the processing cannot be performed at high speed in the cycle 3, a NACK message with a sequence number M + 1 is also transmitted.

  At this time, the PLC MAC frame data with the sequence number M + 3 transmitted from the management terminal 1 to the client terminal A3 is managed as a transfer waiting state because the PLC MAC frame data with the sequence number M + 1 is not received, and the PLC reception memory 18 Once saved.

  Further, in cycle 5, PLC MAC frame data of sequence number M + 4 that needs to be retransmitted is transmitted from management terminal 1 to client terminal A3, and is normally received by client terminal A3. At this time, the PLC MAC frame data of sequence number M + 4 transmitted from the management terminal 1 to the client terminal A3 is managed as a transfer waiting state because it has not received M + 1, and is temporarily stored in the PLC reception memory 18. Also, the ACK message with the sequence number M + 3 received in the cycle 4 is transmitted as PLCMA MAC frame data from the client terminal A3 to the management terminal 1.

  Finally, in cycle 6, there is no transmission from the management terminal 1 to the client terminal A3, and the PLC MAC frame data of sequence number M + 4 received in cycle 5 from the client terminal A3 to the management terminal 1 is normal. An ACK message of sequence number M + 4 indicating that it has been received is transmitted as PLC MAC frame data.

  In the conventional communication sequence as described above, the management terminal 1 receives the NACK message notifying that the PLC MAC frame data of the sequence number M + 1 was not successfully transmitted in the cycle 3 or the cycle 4, but the sequence number The M + 1 PLC MAC frame data cannot be retransmitted because it is discarded immediately after the transmission in period 2 is completed as data that does not need to be retransmitted. On the other hand, since the PLC MAC frame data of sequence number M + 1 cannot be normally received on the client terminal A3 side, the sequence number M + 2 and the subsequent M + 3 and M + 4 stay in the PLC reception memory 18 in a transfer waiting state. Become.

<A-7. Communication sequence according to the present invention>
Next, a communication sequence when the SR method is adopted as a retransmission control method in the TDMA method in the data transmitting / receiving apparatus according to the present embodiment will be described.

  In the data transmission / reception apparatus according to the present embodiment, retransmission is performed in the PLC transmission memory control circuit 409 in the PLC transmission control circuit 15 so that reception data does not stay in the PLC reception memory 18 (FIG. 5) and the capacity is exceeded. The transmission control of unnecessary data is configured.

  Hereinafter, transmission control of retransmission unnecessary data will be described using the flowchart shown in FIG.

  In the management terminal 1 (FIG. 1) serving as the transmission side terminal, after generating the PLC MAC frame data based on the MAC frame data generation flow described with reference to FIG. 8, it is sent to the power line 9. As shown in step S60 of FIG. 13, when the PLC MAC frame data that does not require retransmission is transmitted, the data is not required for retransmission. Therefore, the PLC transmission memory control circuit 409 discards the transmission data from the PLC transmission memory 17. This is performed (step S61).

  Whether or not an ACK message corresponding to the sequence number of the transmitted PLCMAC frame data (including the sequence number as part of the data) can be received from the transmission destination terminal (client terminal A3) in the next cycle Confirmation is performed (step S62), and if reception of the ACK message is confirmed, transmission is completed. Up to this point, the conventional communication sequence is the same.

  On the other hand, when a NACK message is received from the transmission destination terminal or when no message is received, it can be determined that the PLC MAC frame data transmitted in the previous cycle has not normally reached the transmission destination terminal, and transmission It is expected that the previous terminal is in a reception waiting state. However, because the PLC MAC frame data that does not require retransmission is discarded after transmission, it cannot be retransmitted.

  For this reason, when the NACK message is received or when no message is received, the PLCMAC of the sequence number transmitted in the next cycle (the previous cycle: a natural number starting from n = 2) in the next cycle. A command for canceling reception of frame data is transmitted from the transmitting terminal (step S63). For example, the command may be configured so that the PLC transmission memory control circuit 409 outputs the command in response to an instruction from the CPU 11.

  Upon receiving this command, the receiving-side terminal, for example, receives an instruction from the CPU 11, and the PLC reception memory control circuit 506 generates and outputs an ACK message in response thereto, thereby notifying that the command has been normally received.

  When the management terminal 1 receives the ACK message (step S64), the CPU 11 determines that the reception process is normally performed on the reception side, and instructs the PLC transmission memory control circuit 409 to complete the transmission. To do.

  On the other hand, if the ACK message cannot be received, it is determined that the command for canceling the reception wait cannot be normally transmitted to the client terminal A3 on the receiving side, and the reception wait cancel command is transmitted in the next cycle (step S63). ). The management terminal 1 on the transmission side continues this operation until an ACK for the reception wait release command is returned, and completes a series of transmission operations by receiving the ACK.

  In this way, by repeatedly transmitting the reception wait release command, even if the reception wait release command is lost on the transmission line, the reception wait release command is received at the client terminal A3 on the receiving side. Therefore, it is possible to reliably give a reception wait release command.

  When the reception waiting release command is repeatedly transmitted, the number (n) of the cycle in which the PLCMAC frame data of the sequence number to be released from the second transmission is incremented by one, Will be sent.

  Next, the operation when the client terminal A3 (FIG. 1) serving as the receiving terminal receives the above-described reception wait release command will be described with reference to the flowchart shown in FIG.

  When the client terminal A3 cannot normally receive the retransmission-free PLC MAC frame data and is in a reception waiting state (step S70), the client terminal A3 waits for reception of a reception waiting release command from the management terminal 1 (step S71). . When the reception wait release command is received, it is checked whether or not the sequence number of the data to be released included in the reception wait release command matches the PLCMAC frame data waiting for reception (step S72). ).

  If the sequence numbers coincide with each other, the reception of the PLCMAC frame data corresponding to the sequence number is released (step S73). Further, the bridge circuit waits for the reception of the PLCMAC frame data of the sequence number. 13 starts transfer processing for the next sequence number in the waiting state for transfer to 13 (step S74).

  Thereafter, for example, in response to an instruction from the CPU 11, the PLC reception memory control circuit 506 generates and outputs an ACK message for this, thereby notifying that the command has been received normally (step S75).

  In step S72, even if the sequence number included in the reception wait release command is the sequence number of data that has already been confirmed to be received, or is not the sequence number of data that should be released from reception wait, An ACK for the PLC MAC frame data including the command is returned (step S75).

  With this process, even when an erroneous sequence number is included in the reception wait cancel command, the reception wait can be canceled and the transfer process can be prevented from being delayed.

  Next, a sequence for eliminating the retention of received data in the PLC reception memory 18 (FIG. 5) of the receiving client terminal by using the reception waiting release command will be described with reference to FIG.

  First, in cycle 1, PLC MAC frame data of sequence number M that needs to be retransmitted is transmitted from management terminal 1 to client terminal A3. Next, in cycle 2, PLC MAC frame data of sequence number M + 1 that does not require retransmission is transmitted from management terminal 1 to client terminal A3, and from client terminal A to management terminal 1 in cycle 1 In response to the received PLCMAC frame data of sequence number M, an ACK message of sequence number M indicating normal reception is transmitted as PLCMAC frame data.

  At this time, the PLC MAC frame data of sequence number M + 1 transmitted from the management terminal 1 is affected by noise or the like in the transmission path, and an error has occurred. The client terminal A3 cannot receive normally, and the client terminal A3 does not receive the error. Since it is not known that the data addressed to the machine is being transmitted, the client terminal A3 waits for reception of the PLCMAC frame data of the next sequence number M + 1.

  Next, in cycle 3, PLC MAC frame data of sequence number M + 2 that needs to be retransmitted is transmitted from management terminal 1 to client terminal A3. On the client terminal A3 side, PLC MAC frame data of sequence number M + 2 is normal. Since the PLCMAC frame data with the sequence number M + 1 cannot be normally received due to an error in the transmission path, it remains in a reception waiting state until the PLCMAC frame data with the sequence number M + 1 is normally received. to manage.

  In this case, even if the PLC MAC frame data of sequence number M + 2 is normally received, it is not immediately transferred to the bridge circuit 13 (FIG. 3), but temporarily stored in the PLC reception memory 18 as a transfer waiting state. Further, since it can be seen that the PLC MAC frame data of sequence number M + 1 has not been received at the time of receiving the PLC MAC frame data of sequence number M + 2 at client terminal A3. Transmits a NACK message of sequence number M + 1 to notify the management terminal 1 that the PLC MAC frame data of sequence number M + 1 has not been successfully received.

  If high-speed processing is impossible in cycle 3, a NACK message with sequence number M + 1 is transmitted in cycle 4.

  In the management terminal 1, if the ACK message for the PLC MAC frame data having the sequence number M + 1 is not received in the period 3 or the NACK message is received according to the flow described with reference to FIG. Since the PLC MAC frame data of M + 1 is expected to be waiting to be received, in period 4, the PLC MAC frame of sequence number M + 1 is added to the PLC MAC frame data of sequence number M + 3 that needs to be retransmitted from the management terminal 1 to the client terminal A3. Transmit including frame data reception wait release command.

  When the client terminal A3 normally receives the reception wait release command, it waits for reception of the PLCMAC frame data of the sequence number M + 1 that is in the reception standby state according to the flow described with reference to FIG. Next, the data of the next sequence numbers M + 2 and M + 3 are sequentially transferred to the bridge circuit 13.

  Further, the client terminal A3 transmits an ACK message with a sequence number M + 2 indicating that the PLC MAC frame data with the sequence number M + 2 received in the cycle 3 has been normally received to the management terminal 1 in the cycle 4.

  With the above operation, the state where the reception data is retained in the PLC reception memory 18 is eliminated.

  Next, in cycle 5, when the PLC MAC frame data of the sequence number M + 4 that needs to be retransmitted is transmitted from the management terminal 1 to the client terminal A3 and is normally received at the client terminal A3, the management terminal 1 sends it to the client terminal A3. Since the transmitted PLCMAC frame data with the sequence number M + 4 has completed the transfer of data up to the sequence number M + 3, the PLCMAC frame data with the sequence number M + 4 is immediately transferred to the bridge circuit 13.

  The client terminal A3 transmits the ACK message with the sequence number M + 3 received in the cycle 4 to the management terminal 1 as PLCMA MAC frame data. In the management terminal 1, when an ACK message with sequence number M + 3, which is PLCMAC frame data including a reception release waiting command with sequence number M + 1, is returned from client terminal A3, a series of transmissions of PLCMA MAC frame data with sequence number M + 1 is performed. Complete the operation.

  Finally, in cycle 6, there is no transmission from the management terminal 1 to the client terminal A3, and the PLC MAC frame data of sequence number M + 4 received in cycle 5 from the client terminal A3 to the management terminal 1 is normal. An ACK message of sequence number M + 4 indicating that it has been received is transmitted as PLC MAC frame data.

  By using the communication sequence described above, it is possible to prevent the data from staying in the PLC reception memory 18 at the client terminal A3 and causing the memory capacity to be exceeded when the data that does not require retransmission can be normally received.

It is a figure which shows the structure of the high-speed PLC network system to which the data transmission / reception apparatus which concerns on this invention is applied. It is a figure which shows the structure of the data format in 1 frame at the time of performing data transmission / reception with the data transmission / reception apparatus using high-speed PLC. 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 transmission control circuit in the data transmitter / receiver based on this invention. It is a block diagram which shows the structure of the PLC reception control circuit in the data transmitter / receiver based on this invention. 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. 4 is a flowchart illustrating generation of PLCMAC frame data for transmission in the embodiment of the data transmitting / receiving apparatus according to the present invention. 5 is a flowchart for explaining an operation of transmitting Ethernet frame data in the embodiment of the data transmitting / receiving apparatus according to the present invention. It is a figure which shows schematically the structure of the data format of PLCMAC frame data. It is a flowchart explaining the operation | movement at the time of reception when using the data transmission / reception apparatus which concerns on this invention as a client terminal. It is a figure which illustrates notionally the operation | movement when it can communicate normally without a communication error. It is a figure which illustrates notionally operation | movement when a communication error generate | occur | produces and a reception waiting state generate | occur | produces. 6 is a flowchart illustrating a sequence for transmitting a reception wait release command when data that does not require retransmission is transmitted in the embodiment of the data transmitting / receiving apparatus according to the present invention. 6 is a flowchart for explaining a sequence when a reception waiting release command is received in the embodiment of the data transmitting / receiving apparatus according to the invention. In the embodiment of the data transmitting / receiving apparatus according to the present invention, when a reception waiting state occurs, it is a diagram conceptually explaining the operation when the reception waiting is canceled by a reception waiting release command.

Claims (4)

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 that are managed by the management terminal,
Transmission / reception of data between the plurality of terminals is executed based on schedule information output from the management terminal,
The data transmission / reception device includes:
Based on the schedule information, determine the transmission timing and reception timing of the data,
Confirms whether the data has been received normally, and is added to the header information of the data. If the data has not been received normally, the data that needs to be retransmitted or retransmitted A controller that confirms whether the data is data that requires retransmission or data that does not require retransmission, based on retransmission necessity information that indicates whether the data does not require retransmission.
A control data generation unit that generates an ACK message and a NACK message, each indicating whether the data has been normally received or not, upon receiving an instruction from the control unit;
A transmission control unit that controls transmission of the data based on the transmission timing;
If the data has not been received normally, a reception control unit that waits for reception and stops processing for data given at the later transmission timing until the data is received normally, and
When the data transmitter / receiver functions as the client terminal and the data is not normally received, the data transmitter / receiver outputs a NACK message to the management terminal,
When the data transmission / reception device functions as the management terminal, the transmission control unit adds the header information including the retransmission necessity information to the data when transmitting the data, and from the client terminal, When a NACK message is received and the data is the data that does not require retransmission, the header information includes a release command for canceling the reception waiting state of the data that does not require retransmission, and the NACK message is output. A data transmission / reception apparatus that transmits to the client terminal and releases the waiting state for receiving the data that does not require retransmission at the client terminal. A sequence number indicating continuity is added to the header information of the data,
The data transmission / reception device includes:
A header analysis unit that analyzes the header information and reads the sequence number;
When the data transmitter / receiver functions as the client terminal,
The controller is
When the continuity of the sequence number read by the header analysis unit can be confirmed, it is determined that the data has been normally received,
If the continuity of the sequence number could not be confirmed, it is determined that the data could not be received normally, and stored in the received data storage unit via the reception control unit, and the reception control unit If the control enters the reception waiting state and receives the release command from the management terminal, it indicates that reception of the data waiting for reception is canceled and the release command has been received normally. The data transmitting / receiving apparatus according to claim 1, wherein the ACK message is transmitted at a next transmission timing.   When the data transmission / reception device functions as the management terminal, after transmitting the cancellation command to the client terminal that has output the NACK message, the data transmission / reception device normally transmits the cancellation command from the client terminal that has output the NACK message. The data transmission / reception apparatus according to claim 2, wherein transmission of the release command is repeated until the ACK message indicating that the reception has been successfully received. When the data transmitter / receiver functions as the client terminal,
When the sequence number included in the release command is not the sequence number of the data to be released from the reception waiting state, the ACK message indicating that the release command has been successfully received is The data transmission / reception apparatus according to claim 2, wherein transmission is performed at the transmission timing of

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