JP2001111645A - Method for processing variable length data frame and method for recovering variable length data frame - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method that can surely detect frame even when missing of data takes place. SOLUTION: A data stream is divided into data in seven bits, a parity bit in one bit is added to each data divisions, data in eight bits are used for one word, a set of a plurality of words is used for one frame, the respective parity bits are PN coded and the PN-coded parity bits are transmitted. Even when missing data take place on the way of transmission, a demodulator side can surely detect the frame through PN decoding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, a method of processing variable-length data used in digital data transmission, and more particularly to a method of improving data reproducibility against data loss during transmission. About.

[0002]

2. Description of the Related Art For example, JPE is known and well-known as one of techniques for digitally compressing a color still image.
In the G (Joint Photograhic Coding Experts Group) method or the like, a variable-length data frame whose length changes depending on the size of data to be processed is used.
In the case of transmitting digital image data or the like including such a variable-length data frame, for example, via a wireless line, the wireless line may be temporarily interrupted due to a change in radio wave propagation conditions and the like. In such a case, it is difficult to detect a segment of data that could not be received on the receiving side.

[0003]

Heretofore, there has been no satisfactory method for coping with a data loss in a variable-length data frame as described above. The present invention has been made in view of the above circumstances, and provides a variable length data frame processing method and a variable length data frame data reproduction method capable of reliably detecting a frame even when data is lost. It is another object of the present invention to provide a method for processing variable-length data frames and a method for reproducing data of variable-length data frames, which can reliably reproduce data and have high reliability.

[0004]

In order to achieve the object of the present invention, a method for processing a variable-length data frame according to the present invention comprises the steps of dividing a data sequence constituting a variable-length data frame into a first predetermined number of bits; The data string is defined by adding a 1-bit parity bit to the data constituting each unit, and setting the predetermined number of bits and the 1-bit parity bit for the predetermined number of bits as one word. Is a predetermined number of words, and further, after each of the parity bits is PN-encoded,
The whole is configured to be one frame.

In this processing method, variable-length data is configured in an appropriate bit unit, and a parity bit PN-encoded for each bit is added.
Even if data is lost during transmission, the data can be easily reproduced on the demodulation side due to the nature of the PN code.
It is intended to provide a more reliable variable length data frame.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of processing a variable-length data frame and a method of reproducing data of a variable-length data frame according to an embodiment of the present invention will be described below with reference to FIGS. The members, arrangements, and the like described below do not limit the present invention, and can be variously modified within the scope of the present invention. First, an X-bit data sequence is assumed as a variable-length data frame to be subjected to the variable-length data frame processing method according to the present invention (see FIG. 1A). Next, this data string is
In consideration of the length and the like, the data is divided into units of a predetermined number of bits n. Here, in order to facilitate understanding, a description will be given below of an example in which a data string is divided in units of 7 bits.

After the data string is divided in 7-bit units from the head, a 1-bit parity bit is added to each of the 7-bit units (see FIG. 1B). In addition,
The parity bit may be either odd parity or even parity, and is not limited here. In this way, the data string is 7 bits +
One bit parity, that is, 8 bits, is replaced by a set of a plurality of these. Next, 8 bits composed of the 7 bits + 1 bit parity are defined as one word, and a predetermined number, for example, a set of 31 (words) is defined as one frame for convenience (see FIG. 2).

Then, each parity bit of 31 words constituting one fullem is converted into a PN (Pseudorando).
m Noise) after encoding. Here, PN encoding of parity bits is equivalent to performing so-called information spreading, so that even if some data is lost during transmission, demodulation on the receiving side is possible. is there. Here, in the PN encoding, for example, an M-sequence code having a 31-bit length is generated, and the parity bit is PN-encoded by multiplying the 31-bit M-sequence code by a parity bit. You can do it.

On the other hand, in the demodulation of the data string processed as described above, the original data string can be reproduced by performing an operation opposite to the above operation on the received signal. That is, as a result of the processing on the transmission side, as described above, the arrangement of the received data sequence is obtained by PN-encoding the 7 bits that are a part of the original data sequence from the beginning and the parity bits for the 7 bits. 31 PN codes are arranged in the order of 31 sets. Therefore, first, a 7-bit signal is extracted from the head of the received data sequence, and the subsequent 31 bits are subjected to PN decoding to reproduce the original 1-bit parity. Then, the presence or absence of the previously extracted 7-bit error can be determined from the parity bit. Such processing is sequentially repeated for the above-mentioned 31 sets, and from the obtained data, an original data string of (7 bits × 31) bits is obtained by removing each 1-bit parity bit. Can be done.

Here, in the PN decoding, a 31-bit length M-sequence code is generated in the same manner as described above for the PN encoding, and the 31-bit length M-sequence code and the received 31-bit code are used. This is done by multiplying the data with Also, if data is lost in the PN-encoded 31-bit data due to, for example, some failure during transmission, the corresponding parity bit cannot be correctly reproduced.
The detection of the beginning of the next word following the N-encoded part is
It can be easily performed by the special feature of the PN code. Therefore, for 7-bit data corresponding to an incorrect parity bit, unlike the related art, even if the reliability is not guaranteed,
This eliminates the case where the delimiter of the variable-length data frame is lost and the subsequent data reproduction becomes difficult.

[0011]

As described above, according to the present invention,
A variable-length data frame is configured with a predetermined number of bits and parity bits as a unit, thereby making the configuration equivalent to a fixed frame.Furthermore, since each parity bit is PN-encoded, the Even if there is a loss of data, etc., the frame can be reliably detected, and demodulation becomes easy. In particular, the present invention has an effect that highly reliable data reproduction can be realized even in a case where data is lost due to a propagation state such as transmission via a wireless line.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram for explaining a method of processing a variable-length data frame according to an embodiment of the present invention, wherein FIG.
Is an explanatory view conceptually showing a data string to be processed, FIG.
FIG. 1B is an explanatory diagram exemplifying a case in which the data string shown in FIG. 1A is configured with 7 bits and a 1-bit parity for the data string as a unit.

FIG. 2 is an explanatory diagram conceptually showing a final configuration of a data string to which a method of processing a variable-length data frame according to an embodiment of the present invention has been applied.

[Explanation of symbols]

 P: parity bit

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Claims (4)

[Claims] 1. A data sequence forming a variable-length data frame is divided by using a first predetermined number of bits as a unit, and one bit of parity bit is added to the data forming each unit. And the parity bit of 1 bit for the predetermined number of bits are 1
A method for processing a variable-length data frame, wherein the data string is made up of a predetermined number of words as words, and the whole parity bit is PN-encoded to form one frame as a whole. 2. The PN encoding of parity bits is performed by generating an M-sequence code having a second predetermined number of bits and multiplying the M-sequence code having the second predetermined number of bits by a parity bit. 2. The method according to claim 1, wherein the variable-length data frame is processed. 3. A variable-length data frame data reproducing method for reproducing data of a variable-length data frame processed by the variable-length data frame processing method according to claim 2, wherein: Extracting a predetermined number of bits of 1 and then extracting a second predetermined number of bits, the number of times corresponding to the predetermined number of words, is repeated for the data of the second predetermined number of bits. Are respectively subjected to PN decoding to reproduce the original 1-bit parity bit, and the remaining data obtained by removing the reproduced 1-bit parity bit is used as an original data sequence. Data reproduction method for variable length data frames. 4. The PN decoding generates an M-sequence code having a second predetermined number of bits, and the M-sequence code having the second predetermined number of bits and a second predetermined bit extracted from the variable length data frame. 4. The data reproducing method for a variable-length data frame according to claim 3, wherein the method is performed by multiplying a number of data.