JPH05176001A - Data transmission device - Google Patents

Abstract

PURPOSE:To provide a data transmission device which allocates the code of short bit length to a transmission symbol with high generation frequency, executes encoding/decoding with variable length and reduces transmission information quantity. CONSTITUTION:When a transmission symbol with high generation frequency, which is detected by a variable length encoder 1, is not held in an adaptive code book 3, it is encoded, transmitted to a transmission line 2 and is held in the adaptive code book 3. When the detected transmission symbol is held in the adaptive code book 3, the code of short bit length is allocated to the symbol and is transmitted to the transmission line 2. The reception symbol is decoded from the code transmitted by a variable decoder 4. When the reception symbol is not held in an adaptive code book 5, the reception symbol is obtained, and it is held in the adaptive code book 5. When it is held in the adaptive code book 5, the reception symbol corresponding to it is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transmission device used for digital data communication such as digital car telephone, mobile telephone, packet communication and the like.

[0002]

2. Description of the Related Art In recent years, in digital data communication, it has been desired to reduce the amount of transmitted information by changing the rate.

A conventional data transmission device will be described below with reference to the drawings. FIG. 5 is a schematic block diagram showing a conventional data transmission device. In FIG. 5, reference numeral 51 denotes a fixed-length encoder that encodes a transmission symbol into a binary number having a fixed bit length and transmits the binary number to a transmission path 52, and 53 decodes a binary number having a fixed bit length received from the transmission path 52 into a reception symbol. It is a fixed-length decoder for converting into a fixed length.

The operation of the data transmission apparatus configured as described above will be described below.

First, the fixed-length encoder 51 encodes a transmission symbol into a binary number having a fixed bit length and transmits it to the transmission line 52. Next, the fixed length decoder 53 decodes the code received from the transmission path 52 into received symbols. For example, when there are 256 types of symbols to be transmitted, the number of bits of the transmission code is 8 bits.

As described above, the above-mentioned conventional data transmission apparatus can perform data communication by transmitting a code having a fixed bit length.

[0007]

However, in the above-mentioned conventional data transmission apparatus, since the fixed length code is transmitted to the transmission line, the transmission rate is fixed and the amount of transmission information can be reduced. I had the problem that I couldn't.

The present invention solves the above-mentioned conventional problems, and makes it possible to perform variable-length coding and decoding by allocating a code having a short bit length to a transmission symbol that frequently occurs. It is an object of the present invention to provide a data transmission device capable of reducing the amount of transmission information.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a holding means capable of holding a transmission symbol and a reception symbol having a high occurrence frequency, and the use of this holding means to reduce the occurrence frequency. A variable length coding means and a variable length decoding means capable of assigning a code having a short bit length to a high transmission symbol to perform coding and decoding are provided.

[0010]

Therefore, according to the present invention, the variable-length coding means detects a transmission symbol having a high frequency of occurrence, and if the transmission symbol is not held in the holding means, it is encoded and transmitted, and is also held. When the transmission symbol is held in the holding means, the transmission symbol is transmitted by allocating a code having a short bit length to the transmission symbol. On the other hand, when the received symbol is decoded from the code transmitted by the variable length decoding means and the received symbol is not held in the holding means, the received symbol is obtained and held in the holding means, and the received symbol is held in the holding means. , The received symbol corresponding to this can be obtained.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic block diagram showing a data transmission apparatus according to an embodiment of the present invention.

In FIG. 1, 1 is a variable-length encoder that encodes a transmission symbol into a transmission code having a variable bit length and transmits it to a transmission line 2, 3 is an adaptive codebook for holding transmission symbols, and 4 is a transmission line 2. The variable-length decoder 5 for decoding symbols from the variable-bit-length code from 4 is an adaptive codebook having the same contents as the adaptive codebook 3.

The above configuration will be described in more detail below together with the operation thereof. FIG. 2A is an explanatory diagram showing the initial values of the adaptive codebook, FIGS. 2B and 2C are explanatory diagrams when the adaptive codebook is updated, and FIG. 3 is an explanation of the processing procedure of the variable length encoder. FIG. 4 is a flowchart for explaining the processing procedure of the variable length decoder.

Here, the number of transmission symbols is an integer of 0 to 255, the size of adaptive codebooks 3 and 5 is 8, and the initial values of adaptive codebooks 3 and 5 are shown in FIG.
It is assumed that

First, assume that "36" is given as a transmission symbol. When the variable-length encoder 1 detects this transmission symbol "36" as a transmission symbol with a high frequency of occurrence, encoding is performed according to the processing procedure shown in FIG. The variable length encoder 1 first checks whether or not the transmission symbol "36" is held in the adaptive codebook 3 (step 11). Here, if it is found that it is not held (step 12), a transmission code is created and transmitted to the transmission line 2 (step 13). In this transmission code, the first bit is "1", and the next 8 bits are "00100100" which is a binary of "36".
It is a 9-bit code of 100 ″. Variable-length encoder 1
Next shifts the contents of the adaptive codebook 3 by one, writes the transmission symbol "36", and updates it to the contents of FIG. 2B (step 14). On the other hand, the variable length decoder 4 decodes the 9-bit code received from the transmission line 2 by the processing procedure shown in FIG. The variable length decoder 4 first checks the first bit of the reception code transmitted through the transmission line 2 (step 17). In this example, since the first bit is “1” and the symbol is not registered in the adaptive codebook 5, 8 bits following the first bit “1” of the received code.
The bit code is decoded to obtain the received symbol "36" (step 18). The variable length decoder 4 then shifts the contents of the adaptive codebook 5 by one and writes and updates the received symbol "36" (step 19).

Next, assume that "82" is given as a transmission symbol. When the variable-length encoder 1 detects this transmission symbol "82" as a transmission symbol with a high frequency of occurrence, it performs encoding according to the processing procedure shown in FIG. The variable length encoder 1 first checks whether or not the transmission symbol "82" is held in the adaptive codebook 3 (step 11). Here, if the transmission symbol "82" is held, the index value "4" is obtained (step 12). The variable-length encoder 1 then assigns a code having a short bit length to the held transmission symbols and transmits the transmission symbols. That is, the first bit is set to "0" and the next 3
Set the bit to the binary value "100" of the index value,
A 4-bit transmission code "0100" is created and transmitted to the transmission line 2 (step 15). The variable-length encoder 1 then moves and shifts the adaptive codebook 3 to index 0 of "82", and updates the adaptive codebook 3 to the contents of FIG. 2C (step 16). . on the other hand,
The variable length decoder 4 decodes the 4-bit code received from the transmission line 2 by the processing procedure shown in FIG. The variable length decoder 4 first checks the first bit of the reception code transmitted through the transmission line 2 (step 17). In this example, since the first bit is “0” and is held in the adaptive codebook 5, the 3-bit value “4” following the first bit “1” of the received code is obtained and the adaptive codebook 5 is obtained. Then, the content "82" of index 4 is read and used as a received symbol (step 20). The variable length decoder 4 then
The adaptive codebook 5 is updated as in step 16.

As described above, according to the above-described embodiment, the transmission symbols and the reception symbols having a high frequency of occurrence are held in the adaptive codebooks 3 and 5, and the adaptive codebooks 3 and 5 are used to make the variable length encoder. 1 and the variable length decoder 4 assign a code having a short bit length to a transmission symbol that frequently occurs and perform coding and decoding, so that the amount of information on the transmission path can be reduced.

[0019]

As described above, according to the present invention, the transmission symbol and the reception symbol having a high frequency of occurrence are held in the holding means, and the holding means is used to make the variable length coding means and the variable length decoding means. Since a code having a short bit length is assigned to a transmission symbol having a high occurrence frequency to perform encoding and decoding, the amount of transmission information can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic block diagram showing a data transmission device according to an embodiment of the present invention.

FIG. 2A is an explanatory diagram showing initial values of an adaptive codebook used in the same data transmission device. FIG. 2B is an explanatory diagram when the adaptive codebook used in the same data transmission device is updated. FIG. 2C is the same data transmission. Explanatory diagram when updating the adaptive codebook used for the device

FIG. 3 is a flowchart for explaining a processing procedure of a variable length encoder used in the data transmission device.

FIG. 4 is a flowchart for explaining a processing procedure of a variable length decoder used in the data transmission device.

FIG. 5 is a schematic block diagram showing a conventional data transmission device.

[Explanation of symbols]

 1 Variable Length Encoder 2 Transmission Line 3 Adaptive Codebook 4 Variable Length Decoder 5 Adaptive Codebook

Claims (1)

[Claims] 1. A holding unit capable of holding a transmission symbol and a reception symbol having a high occurrence frequency, and a code having a short bit length is assigned to the transmission symbol having a high occurrence frequency by using this holding unit for encoding and decoding. A data transmission apparatus including variable length coding means and variable length decoding means that can be realized.