KR0155332B1 - Method of variable rate data transmission - Google Patents

Abstract

The present invention relates to a method for varying a data transmission rate in a CDMA mobile communication system. In particular, the present invention relates to a receiving end together with input information for transmitting a predetermined bit data rate information to be transmitted in a communication system having a variable data rate. In the transmission method, a first process of encoding data rate information of a predetermined bit to be transmitted using a cyclic convolutional code together with input information to be transmitted and transmitting the data rate information of a predetermined bit to the receiver; The second process of adjusting the coded block size of the cyclic convolutional code in subframe units for fast decoding and the data rate decoded by the Viterbi decoder at a time when the symbol string generated in the process is delayed by a predetermined data depth. Information to determine the data size of the current frame When the data transmission method is provided in a communication system to which the Viterbi data transmission method is applied, the third process includes: a ratio of about 1 / n in the case of a variable data transmission system using n data rates. It is possible to reduce the amount of Viterbi decoding, and even if an error of estimation of information transmission rate occurs, the ripple effect is lost.

Description

Data transmission method in a communication system using a variable data transmission method

1 is an exemplary embodiment of a communication system having a variable data rate.

2 is a diagram illustrating a case where a data rate of the next frame is transmitted in a communication system having a variable data rate.

3 is an exemplary embodiment of the present invention for transmitting data rate information in a communication system having a variable data rate.

The present invention relates to a method for varying a data transmission rate in a CDMA mobile communication system. In particular, the present invention relates to a data transmission rate to be transmitted in a variable data transmission system. The present invention relates to a data transmission method in a communication system using a variable data transmission method for simplifying the configuration of the system.

In general, in a communication system, the amount of information generated changes over time with information to be transmitted.

For example, in the case of a voice signal, the speaker's voice signal is encoded by a voice encoder, and the result of encoding is different for the case where the voice signal has many voiced sounds and the voiceless voice.

That is, the more voiced sounds, the more the data of the encoding result of the encoder is output, so that the amount of information of the transmission data increases accordingly.

In addition, in the case of a human voice, a voiced voice section, a voiceless voice section, and a voiceless section may be distinguished.

Therefore, in recent years, in order to improve the conventional rate fixing scheme, many schemes for constructing a speech encoder using a variable data rate scheme to use a characteristic in which the amount of information changes with time changes are proposed. .

The use of the voice encoder to which the variable data rate is applied is variable data rate speech because the rate of occurrence of the encoded data has a data reduction effect of about 60% than that of the conventional voice encoder to which the fixed data rate is applied. The use of encoders has greatly benefited voice communication systems.

In addition, since the necessity of using the source coder using the variable data rate method is generated not only in the case of speech but also in most information sources generated in the natural world such as a video signal, more information is transmitted within a constant bandwidth. In the communication system to be used, it can be said that the use of the coding scheme to apply the variable data rate as described above is absolute.

However, in the communication system using the variable data rate encoder as described above, a problem arises in that the data rate must be transmitted to the receiver side at the time of data transmission. In this case, if the transmission rate is not correctly transmitted to the receiving side or if the receiving side decodes the information about the transmission rate incorrectly, it is impossible not only to restore the currently transmitted data but also to decode the next frame. Is generated. In addition, if the decoder of the receiver is configured to estimate the transmission rate transmitted by the transmitter by performing decoding at all possible rates, the decoder has a complicated structure. As a result of this problem, there is a problem of difficulty in maintenance and production technology.

Looking at the above-mentioned problems in detail with reference to the accompanying drawings, look at the case of not transmitting the transmission rate as follows.

FIG. 1 illustrates a case of a general communication system using a convolutional encoder, and simplifies a communication block in a standard standard of digital cellular communication in Korea. In this case, the length of the information frame to be encoded is set to 20 msec, the constraint length of the convolutional code is 8, and the encoding rate of the source encoder is 8 kbps, 4 kbps, 2 kbps, 1 kbps according to the amount of input information. Assume that we code.

In the block diagram, the source coder encodes the above four data rates by using a Qualcomm Code Excited Linear Predication (QCELP).

Therefore, the length of one frame for each data rate is composed of 192 bits, 96 bits, 48 bits, and 24 bits, respectively, including a cyclic redundancy check (CRC) bit and a tail bit required in the convolutional encoder.

After the source coded data passes through a convolutional encoder having a rate of 1/2, it is converted into 384Symbol, 192Symbol, 96Symbol, and 48Symbol, and then modulated by a modulator and transmitted to the receiver.

After that, the receiver first demodulates the received symbol strings and then decodes them by a Viterbi decoder. In this case, since the data rate of the received data is not known, the receiver performs decoding on all four data rates and checks the CRC bits for each. The transmission rate of the data finally transmitted is determined.

The voice is restored by inputting the rate and the decoded information bit string determined by the above process to the source decoder.

In this case, the Viterbi decoder of the receiver can decode all the possible information rates and compare the CRCs to determine the transmission rate of the transmission frame. This causes a lot of complexity of the Viterbi decoder.

On the other hand, in order to reduce the complexity caused by the structure of the decoder that can be generated in the above technique, let's look at the case where the transmitting end is encoded in the current frame and transmitted in the current frame.

FIG. 2 shows a case in which the information rate is transmitted in addition to FIG. 1, and the CRC bit and the tail bit are added after encoding all input information of one frame by the source encoder.

At this time, before the information bits are convolutionally coded, the source coder receives information about the coded data rate of the next frame and inserts the information bits into the beginning of the information string to be convolutionally encoded.

The information bit string thus constructed is encoded, modulated and transmitted to the receiver as shown in FIG.

The receiver transmits the symbol string after the demodulation process to the input of the Viterbi decoder. In this case, the Viterbi decoder needs to know the data size of the current frame to decode it. Therefore, decoding is performed using the data rate decoded in the previous frame (this is the data rate of the current frame), and the data rate of the next frame obtained in this decoding process is used in the decoding process of the next frame.

In this way, when the transmitting end encodes and transmits information on the data rate of the next frame, when an error of information on the data rate occurs at the receiving end, decoding of all frames from the next frame becomes impossible.

Accordingly, an object of the present invention for solving the above problems is to focus on the fact that the length of the information can be set to an arbitrary size unless additional information (Tail bit) is transmitted in the encoding process of the cyclic convolutional code. In a communication system using a variable data transmission method for transmitting the information of the current frame rate to the receiving end to simplify the complexity of the decoder provided on the receiving side and to accurately transmit the current frame rate. To provide a data transmission method.

A feature of the present invention for achieving the above object, in a method for transmitting the data rate information of a predetermined bit to be transmitted to the receiving end with the input information to be transmitted in a communication system having a variable data rate, a cyclic convolutional code A first step of encoding the data rate information of a predetermined bit to be transmitted together with the input information to be transmitted to the receiver by using the first information; Adjusting a coding block size of a cyclic convolutional code in units of subframes so as to decode data rate information of a predetermined bit as quickly as possible; And a third process used for Viterbi decoding of all subsequent Subframes using the data rate information decoded in the first Subframe adjusted in the above process.

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

First of all, the technical background used in the present invention is a cyclic convolutional encoder of a conventional transmission end convolutional encoder used as a function of a channel codec to cope with an error that may occur when decoding information on a data rate in a Viterbi decoder. Replace with

At this time, the cyclic convolutional encoder used is initialized and encoded by the initial state of the conventional convolutional encoder as a part of the input information to be encoded by initializing and encoding the initial state of the encoder as a part of the input information to be encoded. It is a convolutional code method that makes it equal to its final state (see Korean Patent Application No. 93-16054).

In other words, the cyclic convolutional encoder uses binary linear convolution operation while the conventional convolutional encoder uses binary cyclic convolution operation, and does not require additional tail bits. Any length can be encoded. In addition, the decoding method generally requires a considerable amount of calculation compared to the conventional decoding method, but as the reference patent shows as a reference, the decoding method requires an additional calculation amount of about 10% compared to the existing decoding calculation amount. Developed in

Considering that the conventional decoding method requires a large amount of traceback to save the memory of the Viterbi decoder when the length of the input information is quite long, the size of the input information is set not so large in the decoding method of the cyclic convolutional code. Therefore, since only one traceback operation is required to decode one coding block, the overall calculation amount can be reduced.

3 is a communication block diagram according to the method proposed by the present invention.

Basically, the circular convolutional coding method does not require an additional information code, that is, a tail bit, thus saving information as much as the size of the restriction.

At this time, the saved information bits are replaced with the information on the data rate of the current frame and transmitted, thereby making it possible to transmit the data without changing the overall amount of information.

In FIG. 3, the information bit of one frame generated by the source encoder is reconfigured into a 24-bit subframe.

At this time, the first subframe consists of 16 bits of information bits, 2 bits of data rate information of the local frame, and CRC 6 bits by 18 bits, and constitutes another subframe.

Each subframe configured as described above is cyclically convolutional coded for each subframe, modulated, and transmitted.

The receiving end demodulates the first subframe and checks the CRC to determine whether it is correctly demodulated, and if it is correctly decoded, the current data rate can be obtained.

Accordingly, this information can be used to determine how many subframes of the current decoded frame are included, and to decode all data of the current frame.

Even if the data rate of the current frame is incorrectly decoded by this method, a decoding error occurs only in the current frame and does not affect the next framing decoding.

In other words, it is possible to prevent the continuous decoding error caused by the decoding error at the same data rate as in the method shown in FIG.

As such, when the data rate of the current frame is transmitted from the transmitter, the receiver can use this information very usefully.

In particular, in the communication system as shown in FIG. 1, since a Viterbi decoding is required for all transmission rates, a large amount of calculation is required, but the calculation amount in the present invention may perform Viterbi decoding at one data transmission rate.

According to the present invention, a data transmission method in a communication system employing a variable data transmission method according to the present invention provides a Viterbi decoding at a ratio of about 1.1 / n for a variable data transmission system using n data rates. Computation can be reduced, and even if an error of estimation of information transmission rate occurs, the ripple effect is eliminated.

Claims (1)

In a communication system having a variable data rate, a method of transmitting data rate information of a predetermined bit to be transmitted to a receiving end together with input information to be transmitted, wherein the data rate information of a predetermined bit currently to be transmitted is transmitted using a cyclic convolutional code. A first step of encoding the input information to be transmitted and transmitting the same to the receiving end; Adjusting a coding block size of a cyclic convolutional code in units of subframes so as to decode data rate information of a predetermined bit as quickly as possible; And a third process used for Viterbi decoding of all subsequent Subframes using the data rate information decoded in the first Subframe adjusted in the above process. Data transfer method.