JPS6036145B2 - Signal transmission method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a signal transmission system that can perform error-controlled and effective signal transmission in, for example, facsimile transmission.

Recently, facsimile transmission via narrowband lines such as telephone lines has been widely used.

In this case, signal errors may occur depending on the characteristics of the transmission path. Therefore, signal transmission has conventionally been carried out in which error control is performed by adding an error detection code or an error correction code to the transmission signal. Further, for a signal in which an error has occurred, a retransmission request signal is returned to retransmit the signal. Conventional devices that use this type of system, such as facsimile machines, retransmit the signal of the frame each time a frame with a signal error is detected, which takes a very long time to transmit. became. The present invention was developed in consideration of these circumstances, and its purpose is to retransmit frame information of high importance only when a transmission error is detected, and to retransmit frame information of low importance at all times. An object of the present invention is to realize and provide a signal transmission method that can shorten transmission time without retransmitting even if a transmission error is detected.

An embodiment of the method of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram of a signal transmission device, such as a facsimile device, to which the same embodiment is applied.

The device consists of a transmitting section 1, a receiving section 2, and a transmission line 3 such as a telephone line connecting these transmitting/receiving sections 1 and 2. In the transmitter 1, an image signal generation circuit 11
, and are sequentially stored in the memory 12. This memory 12 is a random access memory (
A retransmission request identification code is added to the encoded signal and stored in each address in a successive memory. In addition, the signals stored in this memory 12 are obtained by inserting -dimensional encoded signals every predetermined number of scanning lines, and for the remaining scanning line signals, sequential processing is performed using the correlation with the immediately preceding scanning line signal. It consists of a processed encoded signal. The signal stored in the memory 2 is read out in units of a predetermined number of bits and input to the code generation/addition circuit 13. This code generation/addition circuit 13 is, for example, a second
As shown in the figure, a block number and an error detection code are added to the information signal to form one frame signal of a predetermined bit length and output. Note that the retransmission request identification code is given as retransmission request corresponding information indicating the necessity of retransmission for a frame including a signal with high information importance such as a one-dimensional encoded signal. Further, this signal is given as a corresponding signal that does not require retransmission to a frame that includes a signal whose information importance is not so high, such as an encoded signal of a sequentially processed scanning line. Further, a block number is added as an identifiable value to each signal string constituting one frame, and various conventionally well-known error control codes such as parity and cyclic codes are appropriately used as error detection codes. Then, the signal train in the format shown in FIG. 2 outputted via the code generation/addition circuit 13 is transmitted via the interface circuit 14 from, for example, a 9600 bps modem via the forward channel of the transmission line 3. Note that this transmission is performed after synchronization is established. Further, a retransmission request signal sent back via the backward channel of the transmission line 3 is detected by a retransmission request detection circuit 15 via the interface circuit 14. This retransmission request detection circuit 1
5 determines the block number of the retransmission request signal sent back from the receiver 2, and stores the memory 1 corresponding to the block number.
2 read address is specified. The signal read out by this addressing is sent via the code generation/addition circuit 13 for signal retransmission. On the other hand, the receiving section 2 which receives the signal transmitted via the transmission line 3 is configured as follows. The signal received via the interface circuit 21 is input to an error detection and correction circuit 22 as well as to a retransmission request identification circuit 23. The error detection and correction circuit 22 detects errors in the information signal based on the previously added error detection code. If an error occurs in the information signal due to this error detection, the circuit 23 outputs a detection signal to the retransmission request identification circuit 23.
The retransmission request identification circuit 23 determines from the added retransmission request identification code whether the information signal of the frame in which the error occurred is of high importance requiring retransmission, or there is no need to perform error control even if retransmission is performed. It identifies items that are not very important. Then, when an error occurs in the information signal and the information signal is of high importance that requires retransmission to perform error control, the retransmission request identification circuit 23 energizes the retransmission request signal generation circuit 24. ing. This circuit 24 detects, for example, the frame in which the error occurred. The transmission line 3 is sent to the transmission line 3 at a speed of 50 bps, for example, via the interface circuit 21 using the retransmission request signal as a retransmission request signal.
is being sent back via the backward channel. Further, the error detection and correction circuit 22 performs error correction such as previous layer hold and average value interpolation on the information signal in which the error has occurred when the importance is not very high, and when the importance is high, is replaced by the retransmitted signal to perform error correction. Signals subjected to such error correction and information signals in which no errors occur are sequentially stored in the memory 25 based on the block number. The signals forming one image stored in this memory 25 are sequentially read out and used for signal recording. By the way, in such a device, signals with high information importance and signals with low information importance are classified as follows, and retransmission request identification codes are added.

For example, when encoding a facsimile signal, one-dimensional encoding, in which information on only one scanning line is encoded, and sequential encoding, in which information on the current scanning line is encoded using information on the previous scanning line, are generally used. When an entire image is encoded only by the {}-dimensional encoding described above, the number of information bits becomes enormous because the correlation between scanning lines is not utilized. Therefore, it is possible to reduce the number of information bits more by performing sequential encoding. However, if a transmission error occurs during sequential encoding, the ripple effects will be very large, causing problems.Therefore, sequential encoding is adopted and primary encoded information is inserted for each multiple scanning line. It is preferable to minimize the spread of errors. In this case, the one-dimensional encoded scanning information has an initialization function,
The importance of this information is extremely high. Further, image signals have a very high correlation between signals of adjacent scanning lines, so even if an error occurs in several pixels, for example, if it is compensated for using the previous scanning line information, almost no problem will occur. In other words, it can be concluded that the importance of the initialization scan information is very high, and that the remaining scan information can be compensated for by other scan information. However, in this device, information that requires retransmission is added as a retransmission request identification signal and transmitted only to frames that include signals with high information importance that include one-dimensional encoded signals. There is.

The receiving unit 2 identifies the information importance from the retransmission request identification signal, and performs error control by retransmitting signals only for signals with high importance. Furthermore, for signals whose information importance is not so high, the receiving section 2 independently performs error correction to compensate for signal deterioration. In this way, according to the present device, error control by signal retransmission is performed only for signals with high information importance, so the number of signal retransmissions is significantly reduced compared to the conventional device.

Therefore, the time required to transmit one image signal can be shortened, and an improvement in transmission efficiency can be expected. Further, since there is no wasted time for signal retransmission, that is, time that does not have a very important meaning, it can be expected that signal errors will be reduced. Furthermore, since the code length constituting one frame is constant, a frame synchronization signal to indicate the beginning of a frame is not required, and the transmission time can be further shortened. Furthermore, in cases where there is a strong correlation between adjacent scanning line signals such as image signals, error compensation for signals with low information importance can be performed easily and effectively, which is a huge advantage. Become something. In this way, the present device can provide various special advantages such as effective error control, little deterioration in received image quality, and ability to transmit signals in a short time. Note that the present invention is not limited to the above embodiments.

For example, the format of the signal to be transmitted, the form of the retransmission request identification signal, etc. may be determined according to the specifications, and the transmission speed is not limited. Alternatively, the information signal may be encoded, and one frame of information to which an error detection code, retransmission request identification code, etc. are added may be stored in a memory with a specified address, and the signal may be read out from the same memory with speed conversion and transmitted. . Furthermore, the criteria for information importance may be set as appropriate by taking various conditions into consideration.

In short, the present invention can be implemented with various modifications without departing from the gist thereof.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a signal transmission device to which an embodiment of the present invention is applied, and FIG. 2 is a diagram showing an example of the format of a transmission signal. 1... Transmitting section, 2... Receiving section, 3...
...Transmission line, 11... Image signal generation circuit, 12... Memory, 13... Code generation addition circuit, 1
4... Interface circuit, 15... Retransmission request detection circuit, 21... Interface circuit, 22... Error detection and correction circuit, 23...
. . . Retransmission request identification circuit, 24 . . . Retransmission request signal generation circuit, 25 . . . Memory. Figure 2 Figure 1

Claims (1)

[Claims] 1. A signal having a predetermined bit length is transmitted with a retransmission request identification code added, and the receiving section detects an error in the signal and determines the retransmission request identification code to detect a signal error. 1. A signal transmission system characterized in that a retransmission request signal is issued only in the case of a signal in which an error occurs and a retransmission request is necessary, thereby retransmitting a signal in which an error has occurred. 2. The signal transmission according to claim 1, wherein a signal having a predetermined bit length constitutes one frame of an image signal, and the retransmission request identification signal has information as to whether or not the frame requires retransmission. method. 3 The retransmission request identification code is the information that requires retransmission for one frame signal with high information importance, and 1 with high information importance.
2. The signal transmission system according to claim 1, wherein the signal is added as retransmission unnecessary information to the frame signal.