JPH04322519A - Power line carrier communication system and power line carrier communication equipment - Google Patents

Abstract

PURPOSE:To reduce the number of times of re-transmission considerably and to recover a communication error with single re-transmission. CONSTITUTION:This system is provided with an error correcting section 19 checking the field error of a reception frame, storing the result sequentially to a reception frame memory 20 and checking a frame error after one reception frame is completely stored, an acknowledge generating section 22 generating an affirmative acknowledge signal based on a reception frame deciding output, an acknowledge detecting section 23 detecting the affirmative acknowledge signal, and a transmission control section 24 sending the frame again for a time except the sum/subtraction of a time equipvalent to at least a field period with respect to a delay time for each integer number of multiple of an AC half period of a power line from a preceding transmission starting time when the affirmative acknowledge signal is not detected. By such constitution, the number of times of r-transmission is remarkably reduced to shorten the time till the communication success and the system is recovered by single re- transmission even in the case of a communication error caused at an interval shorter than a communication frame length due to the burst noise of a period equivalent to the frequency synchronously with the AC frequency.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power line communication system and a power line communication device, and more particularly to a power line communication system for a power line home bus system and a power line communication device used therein.

0002

2. Description of the Related Art An example of a conventional power line communication system is the power line home bus system reported in the Japan Electronics Machinery Association's Power Line Communication Investigation Committee Report (July 1988). A home bus system connects information and communication equipment such as telephones and personal computers with communication functions, housekeeping equipment such as security and energy controllers, and AV equipment such as satellite broadcasting and text broadcasting to a common transmission path. It is a control communication system that can be completed within the home and is organically connected. It is a system that allows anyone to select all kinds of information, both inside and outside the home, from anywhere, at any time. The power line home bus system uses power lines as this common transmission path.

FIG. 7 is a diagram showing the structure of a communication frame of a power line home bus system. In FIG. 7, the communication frame of the power line home bus system includes a synchronization signal AS, a text start code STX, a self address SA,
Destination address DA, control code CC, house code HC, data length BC, data field DF, frame check code FCC, text termination code E
It consists of each field of XT.

Each field also includes a start bit SB, data bits b0 to b7, as shown in FIG.
It consists of a parity bit PB and a stop bit TB.

Next, the operation will be explained.

Detection and correction of communication errors, that is, errors in the power line home bus system, is performed as follows. First, on the receiving side, an error check is performed using the even parity added on the transmitting side for each field. Furthermore, the transmitting side transmits a frame check code FCC with a two's complement value added to the sum of the self-address SA to the data field DF, and the receiving side sends the self-address of the received signal corresponding to this frame check code FCC. Error checking is performed using a checksum method that adds the sum from SA to data field DF.

[0007] If an error is detected on the receiving side,
By not sending anything from the receiver, it is considered a negative acknowledgment (NAC). In this case, on the sending side,
The retransmission frame number included in the control code CC of the communication frame is changed and a new frame check code F is added.
A communication frame containing a CC is being retransmitted.

[0008] Furthermore, if no error is detected on the receiving side, the communication is terminated by transmitting an acknowledgment frame from the receiving side.

[0009]

[Problems to be Solved by the Invention] In the conventional power line carrier communication system described above, when a communication error is detected, the number of the retransmitted frame is changed and the communication frame containing a new frame check code is retransmitted. If a communication error occurs in the retransmitted frame, it will be detected as an error again by the frame check on the receiving side.
This method has the disadvantage that the number of retransmissions increases and the time required for successful communication increases. In addition, if a communication error occurs at an interval shorter than the communication frame length due to burst noise with a period synchronized with the frequency of the AC flowing through the power line, there is a problem that the communication error cannot be recovered even if retransmission is repeated. There was a point.

An object of the present invention is to solve the above-mentioned drawbacks and problems, to significantly reduce the number of retransmissions, to shorten the time until communication is successful, and to improve communication using burst noise with a period synchronized with the frequency of alternating current. An object of the present invention is to provide a power line carrier communication system and a communication device that can recover from communication errors that occur at intervals shorter than a frame length by one retransmission.

[0011]

[Means for Solving the Problems] The power line carrier communication system of the first invention has a predetermined field cycle generated by adding control information, address information, and error check information to digital data from a first transmitting/receiving device. A first communication frame consisting of a plurality of fields is sent as an electrical signal to a power line, and a second transmitter/receiver receives the electrical signal on the power line, detects the first communication frame, and transmits the control information and address. a power line carrier for selectively extracting the digital data of the first communication frame based on the information, and returning an acknowledgment signal to the first transmitting/receiving device when confirming that the extracted digital data has been correctly received by an error check; In the communication system, when the first transmitting/receiving device cannot detect the acknowledgment signal, the first transmitting/receiving device transmits the digital data, the address information, and the error check information that are the same as the transmitted first communication frame. Adding or subtracting a second communication frame having at least the field period from the transmission start time of the first communication frame to a delay time of every integral multiple of a half period of the alternating current flowing through the power line. The feature is that the retransmission is performed at a retransmission time set within a time range excluding the time range in which the data is sent.

Further, the power line carrier communication device of the second invention is used in the power line carrier communication system of the first invention, and the first and second transmitting/receiving devices transmit the digital data and the control information. a transmission frame memory that stores control data and address data that is the address information; and adding the error check information including field error check data and frame error check data to the transmission frame memory output data output from the transmission frame memory. a transmission frame generation unit that generates a first transmission frame that is the first communication frame; a reception frame memory that receives and demodulates the first transmission frame and stores a reception frame; and the field error check data. The received frame is checked for field errors for each field, and if there is no error, the received frame is sequentially stored in the received frame memory, and when one frame of the received frame is completely stored in the received frame memory, the frame error is detected. an error correction unit that checks frame errors using check data; and an error correction unit that receives the output of the error correction unit and analyzes the address data and control data of the received frame to determine that the received frame is addressed to the local station, and receives the received frame; a received frame determination unit that outputs a frame determination output; an acknowledge generation unit that generates the acknowledgment signal based on the received frame determination output; an acknowledge detection unit that detects the acknowledgment signal; and a transmission control section that retransmits the second transmission frame, which is the second communication frame, at the retransmission time when no signal is detected.

[0013]

Embodiments Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a power line carrier communication device used in the power line carrier communication system of the present invention.

The power line carrier communication device of this embodiment is a spread spectrum power line home bus system, as shown in FIG.
As shown in FIG. 2, the transmitting/receiving devices 1 and 2 of the own device and the partner device, which are the same, are connected to a power line 3 which is a transmission path.

The transmitting/receiving device 1 includes a coupler 11 which is an interface circuit with the power line 3, and a transmitting frame memory 1.
2, the transmission frame generation section 13, the modulation section 14, and the PN
A signal generation unit 15, a driver 16, a receiver 17,
demodulation section 18, error correction section 19, received frame memory 20, received frame determination section 21, acknowledge generation section 22, acknowledge detection section 23, and transmission control section 2
4.

The transmission frame memory 12 stores digital data to be sent to the destination device and the address of the destination device. The transmission frame generation unit 13 has a function of generating a transmission frame and sending it as serial data to the modulation unit 14 when a transmission request occurs. The modulator 14 performs spread spectrum modulation on the transmission frame. P
The N signal generation section 15 has a function of generating a pseudorandom signal for spread spectrum modulation of a transmission frame. The driver 16 limits the spread spectrum modulated transmission frame from the modulator 14 to a predetermined band, and performs power amplification. Receiver 17 amplifies the received signal from combiner 11. The demodulator 18 demodulates the input received signal. The error correction unit 19 has a function of generating a correct received frame on the received frame memory 20 from demodulated received data. The received frame determination section 21 analyzes the address data and the control code, and sends the result to the acknowledge generation section 22.
It has the function to send to. The acknowledge generation unit 22 has a function of outputting an acknowledgment signal under the control of the received frame determination unit 21. The acknowledge detection section 23 is connected to the demodulation section 1
It has the function of detecting the demodulated acknowledgment signal from 8. The transmission control unit 24 has a function of controlling the completion of communication or retransmission based on the detection output of the acknowledgment signal from the acknowledge detection unit 23.

Next, the operation of this embodiment will be explained.

FIG. 2 is a diagram showing the structure of a communication frame. In FIG. 2, the communication frame of the power line carrier communication system of this embodiment includes a synchronization signal AS and a text start code S.
TX, priority code PC, and own address S
A, a destination address DA, a control code CC, a data length BC, data fields D1 to Dn, and a frame check code FCC.

FIG. 2 also shows an acknowledgment signal frame that is returned when the receiving side confirms the communication frame. The acknowledgment signal frame is composed of a synchronization signal AS and an acknowledgment signal ACK.

Each field is composed of an 8-bit data section b0 to b7, a 1-bit parity bit PB, and a stop bit TB, as shown in FIG.

First, the stored address DA of the destination device and the transmission digital data DF are input from the transmission frame memory 12 to the transmission frame generation section 13 . When a transmission request is generated via the transmission control section 24, the transmission frame generation section 13 generates the transmission frame shown in FIG. 2 and sends it to the modulation section 14 as serial data. The modulator 14 uses the pseudorandom signal from the PN signal generator 15 to
Spread spectrum modulation of transmitted frames. Driver 1
6 limits the spread spectrum modulated transmission frame from the modulator 14 to a predetermined band, amplifies the power, and sends it to the power line 3 via the coupler 11.

The transmission signal from the transmitter/receiver 1 that has propagated through the power line 3 is received by the transmitter/receiver 2 . The received signal is input to the receiver 17 in the transmitting/receiving device 2 via the coupler 11 . The receiver 17 amplifies the input received signal and outputs it to the demodulator 18 and the PN signal generator 15. The pseudo-random signal from the PN signal generation unit 15 is synchronized by the synchronization signal AS of the received frame,
The signal is input to the demodulator 18 . The demodulation section 18 demodulates the input received signal and outputs it to the error correction section 19. The error correction unit 19 generates a correct received frame on the received frame memory 20 from the demodulated received data. The received frame for which error correction has been completed is sent to the received frame determination unit 21.
is output to. The received frame determining unit 21 analyzes the address data DA and the control code CC, and if it determines that the communication should be received by its own station, the acknowledgment generating unit 2
2 and outputs an acknowledgment signal ACK. The acknowledgment signal ACK is input to the modulation section 14, and is sent to the power line 3 via the coupler 11 as an acknowledgment signal frame through the same process as the operation after the modulation section 14 of the transmitting/receiving device 1 described above.

In the transmitter/receiver 1, the returned acknowledgment signal frame is input to the demodulator 18 via the coupler 11 and the receiver 17 to demodulate the acknowledgment signal ACK, and output to the acknowledge detector 23. do. The acknowledge detection section 23 detects the demodulated acknowledgment signal ACK from the demodulation section 18. When the acknowledgment signal ACK is detected, it is output to the transmission control section 24, and the transmission control section 24 completes the communication.

The transmission control unit 24 is an acknowledge detection unit 23
If the acknowledgment signal ACK is not input, the communication frame is retransmitted. FIG. 5 is a time chart for retransmission. In FIG. 5, a is an AC waveform with a period of 2T in a power line that is a transmission path, b is a burst noise that occurs in synchronization with the AC waveform, and c is one communication frame.
The timing relationship of the configuration fields in the second transmission,
d respectively indicate the timing relationship of the configuration fields in retransmission of the communication frame.

When the start time of the first transmission of the communication frame shown in c is t0, on the receiving side, the synchronization signal AS and the text start code ST are generated by the burst noise shown in b.
X, priority code PC, data length BC,
Since each field of the data field D1 contains an error, the acknowledgment signal ACK is not returned. Therefore, the transmission control unit 24 on the transmitting side retransmits the retransmission communication frame shown in d at the following timing. That is,
When N is an integer, the retransmission start time is the half cycle T of the AC waveform from the previous time, that is, the first transmission start time t0.
This is the time obtained by adding the period of two fields of the communication frame to the delay time N times .

As shown in FIG. 4, the retransmission communication frames differ only in the retransmission frame number bit of the control code CC, and all other values are the same. Also, the frame check code FCC of the transmitted frame is the self address SA of the first transmitted frame and the other party's address D.
A, a control code CC, a data length BC, and an error check code (CRC) of a cyclic code detection method for data fields D1 to D3 are added.

FIG. 6 is a flowchart illustrating the operation of the error correction section 19.

When the error correction unit 19 of the transmitting/receiving device 2 receives one field's worth of received signals from the demodulating unit 18 (step S1), it uses the correlation value and parity bit PB of the demodulator to correct one field's worth of received signals. An error check is performed (step S2). If no error is detected, that field is normal and is stored in the reception frame memory 21 (step S3), and the error flag of that field is cleared (step S4). If an error is detected, an error flag for that field is set without storing it in the reception frame memory 21 (step S
5). The above steps are repeated for the remaining fields of one frame (step S6).

Next, after receiving one frame, the synchronization signal AS, text start code STX, priority code PC, self address SA, partner address DA, and control code CC stored in the reception frame memory 21 are
, data length BC, data fields D1 to Dn,
Check whether the data in each field is complete with the frame check code FCC (step S7)
. If there is an invalid field, the process advances to step S15 and the error correction operation is ended.

[0031] In step S7, the received frame memory 21
If all fields stored in C are valid, C
An RC error check is performed (step S8). At this time, the retransmission frame number bit of the control code CC is masked and is not subject to error checking. If a frame error is detected, all fields in which the field error flag is set, that is, fields that have not been updated in the received frame, are invalidated (steps S9 to S11), and the process proceeds to step 14 and ends.

If no frame error is detected, the received frame determination unit 21 determines the destination address D of the received frame.
A and the control code CC (step S12), and if it is determined that the communication frame is addressed to the own station, the acknowledge generation unit 22 is activated and an acknowledgment signal ACK is output (step S12). Finally, the process proceeds to step 14 and ends.

In FIG. 5, when the first received frame c is received, the data length BC
Then, each field of the data field D1 becomes an error field, and each error flag is set. Also, since the fields of self address SA, partner address DA, control code CC, data fields D2 and D3, and frame check code FCC are normal, they are stored in the reception frame memory 21, and the error flag of the field is cleared. At this point,
Since the contents of the receive frame memory 21 are not complete,
The acknowledgment signal ACK is not returned, and the retransmission communication frame d is retransmitted from the transmitting side.

The destination address DA, control code CC, data field D3, and frame check code FCC of the retransmission communication frame d received on the receiving side become error fields due to burst noise, and their respective error flags are set and stored in the reception frame memory. 21. Self-address SA of retransmission communication frame d,
Since the data length BC and each of the data fields D1 and D2 are normal, they are stored in the reception frame memory 21, and the error flag of that field is cleared. At this point, the contents of the reception frame memory 21, such as the self address SA, the other party's address DA, and the control code C
C, data length BC, data fields D1 to D3, and frame check code FCC. Furthermore, since the error check performed by masking the retransmission frame number bit of the control code CC is also successful, the error correction is completed.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and can be modified in various ways. For example, it is also possible to detect and correct field errors using the parity bit by configuring each field with 3 bits instead of 1 bit, as long as it does not depart from the spirit of the present invention. Of course.

[0036]

Effects of the Invention As explained above, the power line carrier communication system and communication device of the present invention, when an acknowledgment signal cannot be detected, By retransmitting at a retransmission time set within a time range that excludes the time range that is obtained by adding or subtracting at least the field period from the delay time, the number of retransmissions can be significantly reduced and communication can be successful. This has the effect of shortening the time required for communication to occur, and also being able to recover from communication errors that occur at intervals shorter than the communication frame length due to burst noise with a period synchronized with the AC frequency with a single retransmission. .

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a power line carrier communication system and a power line carrier communication device of the present invention.

FIG. 2 is a diagram showing the structure of a communication frame of the power line carrier communication system of the present embodiment.

FIG. 3 is a diagram showing the structure of fields of a communication frame of the power line carrier communication system of the present embodiment.

FIG. 4 is a diagram showing the structure of a control code field of a communication frame.

FIG. 5 is a time chart in the case of retransmission of communication frames.

FIG. 6 is a flowchart illustrating an example of the operation of an error correction section of the transmitting/receiving device.

FIG. 7 is a diagram showing the structure of a communication frame of a conventional power line carrier communication system.

FIG. 8 is a diagram showing a field configuration of a communication frame of a conventional power line carrier communication system.

[Explanation of symbols]

1, 2 Transmitting/receiving device 3. Electric light line 11 Coupler 12 Transmission frame memory 13 Transmission frame generation unit 14 Modulation section 15 PN signal generation section 16 Driver 17 Receiver 18 Demodulation section 19 Error correction section 20 Receive frame memory 21 Received frame determination unit 22 Acknowledge generation section 23 Acknowledge detection section 24 Transmission control section

Claims (2)

[Claims] Claim 1: A first communication frame consisting of a plurality of fields with a predetermined field period, which is generated by adding control information, address information, and error check information to digital data from a first transmitting/receiving device, as an electrical signal. At the same time, a second transmitting/receiving device receives the electric signal on the power line, detects the first communication frame, and selectively converts the digital data of the first communication frame based on the control information and address information. Extract to
In a power line carrier communication system in which an acknowledgment signal is returned to the first transmitting/receiving device when it is confirmed that the extracted digital data has been correctly received through an error check,
When the first transmitting/receiving device cannot detect the acknowledgment signal, the first transmitting/receiving device sends a first communication frame having the same digital data, the address information, and the error check information as the transmitted first communication frame. The range of time obtained by adding or subtracting at least the field period from the transmission start time of the second communication frame to the delay time for each integral multiple of the half period of the alternating current flowing through the power line. A power line carrier communication system characterized by retransmission at a retransmission time set within a time range excluding. 2. The power line carrier communication device used in the power line carrier communication system according to claim 1, wherein the first and second transmitting/receiving devices transmit the digital data, the control data that is the control information, and the address that is the address information. a transmission frame memory for storing data, and a transmission frame memory that adds the error check information including field error check data and frame error check data to the transmission frame memory output data output from the transmission frame memory, and adds the error check information including field error check data and frame error check data to the transmission frame memory output data output from the transmission frame memory, a transmission frame generation unit that generates a certain first transmission frame; a reception frame memory that stores a reception frame obtained by receiving and demodulating the first transmission frame; and a reception frame memory that stores the reception frame obtained by receiving and demodulating the first transmission frame; A field error check is performed, and if there is no error, the received frame is sequentially stored in the received frame memory, and when one frame of the received frame is completely stored in the received frame memory, a frame error check is performed using the frame error check data. a correction unit; and a reception frame determination unit that receives the output of the error correction unit, analyzes the address data and the control data of the reception frame, determines that the reception frame is addressed to the local station, and outputs a reception frame determination output. an acknowledge generation unit that generates the acknowledgment signal based on the reception frame determination output; an acknowledge detection unit that detects the acknowledgment signal; and when the acknowledge detection unit does not detect the acknowledgment signal, the second A power line carrier communication device comprising: a transmission control unit that retransmits a second transmission frame that is a communication frame at the retransmission time.