JPH04345364A - Transmission processing method for picture data - Google Patents

Abstract

PURPOSE:To attain a restoration to a normal transmission sequence in an FSK mode even when a synchronism is lost due to the intrusion of a noise on the transmission of picture data in a high speed MODEM mode, at the time of the transmission of the picture data by an ECM communication. CONSTITUTION:When the synchronism is lost due to the incapability of the reception of a synchronizing flag included in a frame on receiving the picture data for each block constituted of plural frames in the high speed MODEM mode, the high speed MODEM mode is forcedly switched to the FSK mode in order to wait the reception. Afterwards, at the time of receiving a transmission confirmation request signal at the tail of the picture data of one block, which is transmitted from a transmission side in the FSK mode, a retransmission request signal is transmitted to the transmission side in order to request the retransmission of the frame which can not be correctly received.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a method for transmitting and processing image data, and more specifically, even if synchronization is lost during reception of image data in high-speed modem mode, it is possible to restore the normal transmission sequence and transmit the image data. The present invention relates to a device characterized in that the transmission of the information is continued.

0002

[Prior Art] Recently, error correction mode communication (hereinafter referred to as E
Facsimile machines equipped with CM communication (described as CM communication) have been developed and come into use. What is ECM communication here?
Image data is transmitted from the transmitting side to the receiving side in blocks of 256 frames, and on the receiving side, a CRC code is attached to each frame and the frames are read until there are no CRC errors in the transmitted block of image data. A retransmission request is made in units of units, and when one block of image data is correctly received, it is printed out on recording paper, and then the next block is received. This operation is repeated, and the noise level of the telephone line is Error-free image data transmission can be performed even when the error is high.

FIGS. 3(a) and 3(b) show such EC
This is a time chart showing the transmission process of M communication. As shown in FIG.
00 BPS, 7200 BPS, etc.), one block of image data is transmitted, and at the end of one block of image data,
F that sends and receives control signals from the receiving side in high-speed modem mode
An RCP signal (control return signal) for transitioning to SK mode is added. On the receiving side,
As shown in FIG. 3(b), when the RCP signal is received after receiving the transmitted image data for each frame, the high-speed modem mode is switched to the FSK mode, and the transmitted image data from the transmitting side is switched from the high-speed modem mode to the FSK mode. When receiving an incoming post message command, if there is a frame with a CRC error, P
Since a PR signal can be returned to request retransmission of an error frame, error-free image data transmission can be performed by repeatedly performing retransmission until there are no CRC errors.

By the way, in such ECM communication, as shown in FIG. 4(a), noise is mixed into a part of the frame of image data on the transmitting side, and as a result, as shown in FIG. 4(b). As shown, when the synchronization flag becomes undeterminable on the receiving side, it waits for synchronization to be restored for a predetermined time T (about several seconds), and if synchronization is not restored within this predetermined time T, the line is forcibly cut off. It is supposed to be done.

However, once the synchronization is lost, it is almost impossible to recover the synchronization, so if the synchronization is lost due to the introduction of noise, the RCP added to the end of one block of image data The signal can no longer be recognized, and since the receiving side cannot switch to FSK mode, it is no longer able to receive post message commands, and in the end, the only recourse is to cut off the line, reducing the reliability of image data transmission. This was a contributing factor.

[0006]

[Problems to be Solved by the Invention] The present invention has been made in view of the above circumstances, and even if synchronization is lost due to noise mixed in during image data transmission in high-speed modem mode, it is possible to It is an object of the present invention to provide an image data transmission processing method in which the image data transmission sequence is continued by switching to the FSK mode, thereby improving reliability.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the present invention proposes a synchronization flag included in a frame while receiving image data for each block consisting of a plurality of frames in a high-speed modem mode. When synchronization is lost due to unreceivable reception, the system forcibly switches to FSK mode and waits for reception.After that, when a transmission confirmation request signal transmitted in FSK mode at the end of one block of image data is received from the transmitting side, , a retransmission request signal is sent to the transmitting side to request retransmission of the frame that could not be received correctly.

[0008]

[Operation] According to the method of the present invention, when the synchronization flag in the frame cannot be received due to factors such as noise and synchronization is lost during the reception of one block of image data consisting of frames in high-speed modem mode, In order to receive the transmission confirmation request signal, the receiving side forcibly switches to FSK mode and waits for reception, regardless of whether image data is being received. Then, when the transmission of one block of image data is completed and a transmission confirmation request signal is transmitted from the transmitting side in FSK mode, a retransmission request signal is sent to request retransmission of only the frames that could not be correctly received. Therefore, even if synchronization is lost and image data cannot be received, the image data transmission sequence can be continued in the FSK mode without interrupting the line.

[0009]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a flowchart of the image data transmission processing method of the present invention.
The operation will be explained with reference to the time charts of the transmitting side and receiving side shown in (B). (2) The transmitting side and the receiving side are switched to high-speed modem mode, and transmission of image data is started by ECM communication. (See step 100 in FIG. 1). ■On the receiving side, start the frame monitoring timer,
The operation of resetting the frame monitoring timer after receiving one frame of image data is repeated until an RCP signal (control return signal) is received, thereby receiving one block of image data. However, due to factors such as noise, it takes time T1 (in this example, it is set to several seconds) until the frame monitoring timer times out.
When one frame of image data cannot be received normally, it is assumed that synchronization has been lost and reception of the transmitted image data is stopped. (Figure 1 steps 101 to 105
, see FIGS. 2(a) and (b)). ■On the receiving side, after receiving an RCP signal after successfully receiving one block of image data, or after stopping image data reception due to loss of synchronization, it starts the post message monitoring timer and enters FSK mode. During the time T2 (set to approximately 3 minutes in this embodiment) until the post message monitoring timer times up after switching to , it is determined whether or not a post message command, which is a transmission confirmation request signal, is transmitted from the sending side. to monitor. (See steps 106 to 108, 118 in FIG. 1, and (a) and (b) in FIG. 2). ■If a post message command is transmitted from the sending side before the post message monitoring timer times up (until time T2 has elapsed), the post message monitoring timer is reset, and if there is an error frame that could not be received correctly, , sends a PPR signal (error retransmission request signal) to request retransmission of the error frame. Thereafter, the operation of switching to high-speed modem mode, receiving an error frame, and returning to the process of (2) above is repeated until there are no more error frames. In this way, 1
When the image data for a block is correctly received, an MCF signal (message confirmation signal) is returned in response to the post message command, after which printing processing is performed, and when there is image data for the next block, the process described in ① above is performed. By repeating the operation of returning to , image data for each block is sequentially received. (Figure 1 steps 108 to 113, 11
5 to 117, see (a) and (b) of FIG. 2). ■However, if a post message command is not transmitted from the sending side before the post message monitoring timer times up (before time T2 has elapsed), it is assumed that an error has occurred on the sending side, and the receiving side disconnects the line. Cut off. (See steps 108, 118, 114 in FIG. 1).

[0010]The operation when one block of image data is normally received without any noise or the like is the same as shown in the time charts of FIGS. 3(a) and (b) above. Therefore, the explanation of the operation will be omitted.

As described above, according to the image data transmission processing method of the present invention, when the receiving side loses synchronization due to noise, etc., the post message transmitted from the transmitting side is switched to the FSK mode. It waits for the reception of a command (transmission confirmation request signal), and when a post message command is transmitted, it continues the image data transmission sequence by requesting retransmission of the frame that could not be received correctly. .

0012

[Effects of the Invention] As can be understood from the above explanation, according to the image data transmission processing method of the present invention, even if synchronization is lost on the receiving side due to noise etc., FSK mode can be forced. By switching to , waiting for reception, and receiving a transmission confirmation request signal transmitted from the sending side, it is possible to retransmit the frame of image data that could not be received correctly and restore the normal transmission sequence. This eliminates the possibility of the line being cut off without being restored, and the reliability of image data transmission can be improved.

[Brief explanation of drawings]

FIG. 1 is a flowchart illustrating the method of the present invention.

FIGS. 2(a) and 2(b) are time charts for explaining the method of the present invention.

FIGS. 3(a) and 3(b) are time charts illustrating operations when one block of image data is normally transmitted.

FIGS. 4(a) and 4(b) are time charts illustrating the conventional operation when synchronization is lost due to mixing of noise or the like during transmission of one block of image data.

[Explanation of symbols]

PPR signal Retransmission request signal

Claims (1)

[Claims] Claim 1: While receiving image data for each block consisting of multiple frames in high-speed modem mode, if synchronization is lost due to inability to receive the synchronization flag included in the frame, the system is forcibly switched to FSK mode. After waiting for reception, when a transmission confirmation request signal transmitted in FSK mode at the end of one block of image data was received from the transmission side, a retransmission request signal was sent to the transmission side and could not be received correctly. An image data transmission processing method comprising requesting frame retransmission.