JP2652398B2 - Data transmission method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a data transmission method.

[Prior Art] A data transmission method using a frame format of an HDLC (High Level Data Link Control) procedure is one of the data transmission methods that can transmit data bit-transparently and does not limit the content of transmission data. Yes, for example, it is used for exchanging transmission control procedure signals of a group 3 facsimile machine.

On the other hand, in wireless devices, transmission errors are more likely to occur if the state of the propagation path changes significantly. In general, protection against transmission errors is required more than in wired data transmission devices.

Recently, a wireless facsimile apparatus using a wireless apparatus as a transmission means has been put into practical use. This wireless facsimile apparatus has a transmission control procedure signal of the group 3 facsimile apparatus so as to realize a function equivalent to that of the group 3 facsimile apparatus. Is diverted as it is.

In the transmission control procedure of the group 3 facsimile apparatus, if the expected transmission control procedure signal cannot be received within a certain period, the transmission control procedure signal corresponding thereto is not responded.
When it is repeated a specified number of times (for example, three times),
At that point, the transmission control procedure is interrupted. On the side that transmits the transmission control procedure signal, if the transmission control procedure signal corresponding to the transmission control procedure signal is not responded within a certain period of time after transmitting the transmission control procedure signal, the same transmission control procedure signal is retransmitted. Send a signal.

As described above, when the wireless device is used as the transmission means, transmission errors may frequently occur. Therefore, when the wireless facsimile device exchanges transmission control procedure signals, the transmission errors may occur frequently. The time required for facsimile transmission may be prolonged due to repeated signal retransmission, or the transmission control procedure may be interrupted and image information transmission may not be possible.

For this reason, the radio facsimile apparatus uses the transmission control procedure signal format of the group 3 facsimile apparatus by extending the transmission control procedure signal format to an error correction code for detecting and correcting an error in transmission data. Is shown in FIG. 6 (a).

This frame format includes two flag sequences F1 and F2 each having a predetermined 8-bit pattern, an address field A having a predetermined 8-bit pattern (global address), a control field C having an 8-bit pattern unique to a facsimile apparatus, and a facsimile. 8 of transmission procedure signal
Facsimile control field FCF in which a bit pattern is arranged, facsimile information field FI in which various information added to the facsimile transmission procedure signal are arranged
F, frame check sequence in which a 16-bit CRC (Cyclic Redundancy Check) code for error detection from address field A to facsimile information field FIF is arranged
FCS, an error correction field ECF in which an error correction code for performing error correction of data from the address field A to the frame check sequence FCS is arranged, and a flag sequence F3 are sequentially arranged and formed, and an error correction field ECF is added. Part is standard group 3
This is a portion extended from the frame format of the transmission control procedure signal of the facsimile apparatus.

Now, in this frame format, the flag F used to separate frames has a bit pattern of "01111110" as shown in FIG. 6 (b).

In the HDLC procedure, the flag sequence F1, F2,
When five data "1" s are consecutive in the transmission data other than F3, the transmitting side performs a so-called "0" insertion process of inserting data "0" between the next bit data and the next bit data. , Transmission data is adjusted so that six or more data “1” do not continue.

For example, as shown in FIG. 6C, when there is 9-bit data of “011111110” in which seven data “1” s are continuous, as shown in FIG. Data “0” (indicated by adding “*”) is inserted between the eyes to change to 10-bit data “0111110110”.

On the other hand, on the receiving side, when five consecutive data “1” appear in the received data, a so-called “0” deletion process for removing data “0” of the next bit is performed, and “0” is performed. The bits increased by the insertion process are removed. Therefore, the data in FIG. 9D is restored to the original 9-bit data on the receiving side as shown in FIG.

From the above, in the conventional wireless facsimile machine,
When transmitting the transmission control procedure signal, the processing shown in FIG. 7 is performed.

First, a transmission control procedure signal to be transmitted is formed (Step 10
1), an error correction code is added thereto (process 102), and data is formed in the above-described frame format (process 103). Then, the frame data is subjected to “0” insertion processing (processing 104) and transmitted to the partner apparatus (processing 1).
05).

When the transmission control procedure signal is received, the processing shown in FIG. 8 is performed.

First, a signal is received (processing 201), a “0” deletion process is performed while determining a flag pattern from the received signal (processing 202), a frame is identified, and an error is detected by referring to the contents of the error correction field ECF. A correction process is performed (process 203), and the content of the transmission control procedure signal is determined based on the result (process 204), and a process corresponding to the determined content is performed (process 205).

As described above, since the transmission control procedure signal is transmitted with the error correction code added thereto, transmission errors can be recovered to some extent, and efficient image information transmission can be performed.

However, such a conventional method has the following disadvantages.

That is, a transmission error may occur in all parts of the transmission data, and thus a data error may occur in the flag sequences F1, F2, and F3.

In this case, for example, as shown in FIG. 6 (f), when a data error occurs in the fifth bit (indicated by an arrow) of the flag sequence F2 and the bit is inverted, the flag pattern is not formed. F2 is not detected, so that the frame delimiter is not properly determined and the transmission control procedure signal cannot be received.

Also, as shown in FIG. 3D, a data error occurs in one of the five consecutive data "1" in a portion where the "0" insertion process is performed and the bit is increased by 1 bit. For example, if the fifth bit is bit-inverted as shown in FIG. 9G, it is erroneously determined that the bit increased by the “0” insertion processing is the original transmission data.

Also, as shown in FIG.
A data error occurs in the fourth bit of the 10-bit data, the bit is inverted, and “011111” is set on the receiving side as shown in FIG.
When the data “0011” is received, on the receiving side, since the data “1” that is continuous for 5 bits appears in the bit pattern, the next data “0” is a bit increased by the “0” insertion processing. And it is removed as shown in FIG.

In this way, if the original transmission data and the number of bits do not match, the transmission data is not properly separated, so that the error correction is not properly performed and the transmission control procedure signal is erroneously determined / recognized.

Furthermore, flag sequences F1, F2, F3
When a flag pattern is formed other than the part of, it is determined that it is any of the flag sequences F1, F2, F3,
Frame division is not performed properly.

As described above, in the related art, when a data error occurs in the flag sequences F1, F2, and F3, and a data error of a specific bit pattern cannot be corrected.

[Purpose] The present invention has been made to solve the problems of the related art, and has as its object to provide a data transmission method capable of always performing appropriate data transmission.

[Configuration] The present invention relates to a data transmission method for transmitting transmission data formed by adding a preamble formed by repeating a predetermined number of flags to the head of frame data partitioned by a flag composed of a specific bit pattern. Is to divide the transmission data into block data consisting of an integer multiple of the number of bits of the bit pattern constituting the flag, and after applying a predetermined 0 insertion process, add an error correction code to each block data; Thereafter, while transmitting without performing the 0 insertion processing, the receiving apparatus cuts out bit data in which the block data length and the error correction code length are combined while shifting one bit from the head of the received signal, and the bit data is flagged. And whether they match the bit pattern of the error correction code. When the setting is established, the subsequent received signal is cut out for each bit data including the block data length and the error correction code length, and the block data is error-corrected by referring to the error correction code for each cut-out bit data unit. Later, a predetermined 0 deletion process is performed,
This is to form received data.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a wireless facsimile apparatus according to one embodiment of the present invention.

As shown in FIG. 1, the wireless facsimile apparatus includes a facsimile apparatus 1 having a function of generating / recording image information,
It comprises a wireless device 2 having a transmission function, and a wireless interface circuit 3 for exchanging data between the facsimile device 1 and the wireless device 2, and the wireless interface circuit 3 is provided with a microphone 4 for talking. ing.

In the facsimile machine 1, the system control unit 11
The scanner 12 is for performing the overall control processing of the facsimile apparatus 1, the scanner 12 is for reading a transmission original at a predetermined resolution, and the plotter 13 is for recording and outputting an image at a predetermined resolution. It is.

The operation display unit 14 is for operating the facsimile apparatus, and the encoding / decoding unit 15 encodes and compresses the transmission image signal and decodes the reception image information to the original image signal. Yes, the communication control unit 16 is for performing facsimile transmission control procedure processing, and the modem 17 is
It modulates and demodulates digital data. Also modem
The 17 input / output signals are exchanged with the wireless device 2 via the wireless interface circuit 3.

These system control unit 11, scanner 12, plotter 1
3. The operation display unit 14, the encoding / decoding unit 15, and the communication control unit 16 exchange necessary data via the system bus 18.

FIG. 2 shows an example of transmission processing of a transmission control procedure signal when image data is transmitted between the wireless facsimile apparatuses having the above configuration.

First, the transmitting side forms a transmission control procedure signal (Step 30).
1) Form frame data in the same frame format as the transmission control procedure signal specified for the group 3 facsimile apparatus (process 302).

Here, the frame data formed at this time is, as shown in FIG. 3 (a), a non-standard function for transmitting a transmission control procedure signal for setting a non-standard function of the facsimile machine 1. A binary information frame comprising a frame FNS, a called terminal identification frame FCD for transmitting identification information of a called station (called station), and a digital identification frame FDI for transmitting a standard transmission control procedure signal B
Called F.

The non-standard function frame FNS, the called terminal identification frame FCD, and the digital identification frame FDI are each configured as shown in FIG. In this figure, the same parts as those in FIG. 6 (a) have the same names.

This frame format consists of two flag sequences F1, F
2. An address field A, a control field C, a facsimile control field FCF, a facsimile information field FIF, a frame check sequence FCS, and a flag sequence F3 are sequentially arranged.

At the beginning of the binary information frame BF, a preamble PA formed by repeating the flag sequence F by a certain number is added in order to synchronize the receiving side.

Note that the non-standard function frame FNS and the called terminal identification frame FCD that constitute the binary information frame BF do not necessarily constitute data frames of all transmission control procedure signals, and may include only the digital identification frame FDI. .

When the frame data is configured in this manner, the above-described “0” insertion processing is performed on the data of each frame constituting the binary information frame BF excluding the flag sequences F1, F2, and F3 (processing 303). ).

As a result, the non-standard function frame FNS, the called terminal identification frame FCD, and the digital identification frame FDI have a larger data amount than the original data amount as shown in FIG. 3B.

Next, the transmission data after the “0” insertion processing is separated from the head including the preamble PA by 8 bits corresponding to the bit length of the flag pattern, and the error correction code ECC is applied to each 8-bit data. (Block code) is added (process 301). The error correction code ECC is generated in the target 8-bit data.
It is assumed that it is 8 bits long and has the ability to correct up to bit errors.

As a result of this processing 304, as shown in FIG. 3 (c), the preamble PA portion has a form in which the flag F and the error correction code ECC are alternately repeated, and the binary information frame BF has 8 bits from the beginning. Error correction code EC for each data
This is a mode in which C is added.

Each frame of the binary information frame BF originally has a length of a multiple of 8 bits, but the number of bits may increase due to the “0” insertion processing, and the length may not be a multiple of 8 bits.

Therefore, the last 8-bit data is a remainder obtained by dividing the number of data after the “0” insertion processing by 8 by 8
The data "0" is added by the number of the results obtained by subtracting from the data.

For example, when the number of data after the “0” insertion processing is larger than a multiple of 8 by 2, FIG. 3 (b)
As shown in (1), the last two bits of the flag sequence F3 of the digital identification frame FDI are left (that is, the remainder is 2). Therefore, six data "0" are added to the two bits to form the last 8-bit data, and an error correction code ECC is added to the 8-bit data.

In this way, the transmission data formed by adding the error correction code ECC every 8 bits is transmitted to the partner device (process 305).

FIG. 5 shows a processing example when the transmission control procedure signal transmitted in this manner is received.

First, the receiving side receives a signal (process 401), cuts out 16-bit data from the beginning of the signal, and determines whether the 16-bit data is a flag F and an error correction code ECC corresponding to the flag F. Pattern recognition (processing 40
2). Since the error correction code ECC is a block code and the target flag F is a fixed bit pattern, the error correction code ECC corresponding to the flag F has a fixed bit pattern. Thereby, the flag F and the flag F
Since the 16-bit data combined with the error correction code ECC corresponding to
The flag F can be found by the pattern recognition process of FIG.

When the extracted 16-bit data does not match the bit pattern of the 16-bit data including the flag F and the error correction code ECC corresponding to the flag F (the result of determination 403 is N
O), the received signal is shifted by one bit (process 404), and the process 40
Returning to 2, the 16-bit data from the next bit is cut out and the same pattern recognition processing is performed.

By this processing loop, 16-bit data combining the flag F and the error correction code ECC corresponding to the flag F is found, and if the result of the determination 404 is YES, the data of the received signal is read 16 bits at a time starting from the next bit. , And for each 16-bit data, the first half of the 8-bit data is subjected to error correction processing, and the second half of the 8-bit error correction code
This is performed with reference to the ECC (process 405).

In this way, the 8-bit data for which the error correction has been completed is arranged in the receiving order, and the bit sequence formed by the above-mentioned “0” is determined while judging the flag pattern.
A deletion process is performed (process 406) to obtain the original transmission data.

Then, the preamble PA is separated from the transmission data, each frame data constituting the digital information frame BF is identified, and the content of the transmission control procedure signal arranged in each frame data is identified (processing
407), and performs processing corresponding to the transmission control procedure signal obtained by the identification (processing 408).

In this way, while shifting one bit at a time, the flag F and the corresponding error correction code
After finding ECC, after that, extract 16 bits of data, correct errors for each, and preamble PA
And a digital information frame BF is taken out to determine the received transmission control procedure signal.

Therefore, according to the present embodiment, first, the preamble
Error correction code ECC is also added to PA, and a bit pattern that combines the error correction code ECC and the flag F that composes the preamble PA is found by pattern recognition processing, so erroneous detection of preamble PA flag F is suppressed. Yes, it can be detected reliably.

As a result, since the subsequent data can be reliably separated, the digital information frame BF
Can be taken out, whereby the transmission control procedure signal can be reliably recognized.

By the way, in the above-described embodiment, the error correction code is added for each 8-bit data having the same number of bits of the flag F. However, the delimiter of this data may be set to an integral multiple of 8 bits. In such a case, it is necessary to select an error correction code having a capability of correcting at least one bit error for the data word.

In the above-described embodiment, the present invention is applied to a wireless facsimile apparatus. However, the present invention can be similarly applied to other data transmission apparatuses.

In the above embodiment, the length of the error correction code is set to 8
Although the number of bits is set, a code having at least one bit error correction capability for a target data word may be used, and the length of the code is not limited to this.

[Effects] As described above, according to the present invention, transmission data formed by adding a preamble formed by repeating a predetermined number of flags to the beginning of frame data partitioned by a flag composed of a specific bit pattern is transmitted. In the data transmission method, the transmission device divides the transmission data into block data consisting of an integral multiple of the number of bits of a bit pattern constituting a flag, and applies a predetermined 0 insertion process to each block data. The error correction code is added to the received signal, and then the data is transmitted without performing the 0 insertion process. And the bit data matches the bit pattern of the flag and error correction code If this determination is satisfied, the received signal thereafter is cut out for each bit data that is the sum of the block data length and the error correction code length, and the error correction code is referred to for each cut out bit data unit. After the block data is error-corrected, a predetermined 0-deletion process is performed to form the received data, so that the delimiter of the frame data can be appropriately determined. As a result, appropriate data transmission is always performed. The result is that you can do it.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a wireless facsimile apparatus according to one embodiment of the present invention, FIG. 2 is a flowchart showing an example of transmission processing, FIG. 3 is a schematic diagram showing an example of transmission data, and FIG. FIG. 5 is a schematic diagram showing an example of a format, FIG. 5 is a flowchart showing an example of a reception process, and FIG.
Is a schematic diagram showing a conventional frame format, FIG. 2B is a schematic diagram showing a bit pattern of a flag sequence, and FIGS. 2C to 2J are schematic diagrams for explaining a conventional problem.
FIG. 7 is a flowchart showing a conventional example of transmission processing, and FIG.
FIG. 2 is a flowchart showing a conventional example of the receiving process. 1 facsimile device, 2 radio device, 3 radio interface circuit, 11 system control unit, 16 communication control unit.

Claims (1)

(57) [Claims] 1. A data transmission method for transmitting transmission data formed by adding a preamble formed by repeating a predetermined number of flags to the head of frame data partitioned by a flag composed of a specific bit pattern, wherein the transmitting device comprises: The transmission data is divided into block data consisting of an integral multiple of the bit number of the bit pattern constituting the flag, and after applying a predetermined 0 insertion process, an error correction code is added to each block data, and then On the other hand, while transmitting without performing the insertion process, the receiving apparatus cuts out bit data in which the block data length and the error correction code length are combined while shifting one bit from the head of the received signal, and the bit data is flag and error. It is determined whether or not it matches the bit pattern of the correction code. Then, after the received signal is cut out for each bit data in which the block data length and the error correction code length are combined and each block data unit cut out is referred to the error correction code to correct the block data, A data transmission method, wherein a predetermined zero deletion process is performed to form received data.