KR101402251B1 - Encoding method and apparatus using a low density parity check code - Google Patents

Abstract

The present invention relates to an apparatus and method for encoding using a low-density parity-check code, in which an encoder determines channels requiring codeword processing based on the number of codewords to be processed for a predetermined period for each channel, It is possible to uniquely manage the information necessary for codeword processing such as the number of codewords by selecting the channel to be encoded using a predetermined method among the plurality of channels and encoding the information bit for the selected channel, It is possible to control the coding rate dynamically according to the coding high-line state, and it is possible to realize control with one LDPC coding unit and one perforation, thereby greatly reducing the scale of the circuit.

Description

TECHNICAL FIELD The present invention relates to an encoding method and apparatus using a low-density parity check code,

Fig. 1 is a block diagram showing a configuration of a conventional encoding circuit.

2 is a block diagram illustrating a general configuration of a transmitter and a receiver of a communication apparatus in which an information encoding apparatus according to the present invention is used.

3 is a block diagram showing the configuration of the encoding circuit 160, which is a characteristic component of the present embodiment.

4 is a block diagram showing the configuration of the control unit 320, which is a characteristic component of the present embodiment.

5 is a diagram illustrating an example of a lookup table according to an embodiment of the present invention.

6 is a diagram illustrating an example of puncturing timings according to an embodiment of the present invention.

The present invention relates to a coding method and apparatus using a low-density parity-check code for correcting an error occurring in a transmission path for transmitting high-speed data. More particularly, the present invention relates to a coding method and apparatus using a plurality of channels, To a coding method and apparatus using a low-density parity-check code capable of coping with changes appropriately.

In recent mobile communication, wireless LAN, etc., data transmission speed is increasing. In these fields, the frequency of error occurrence varies greatly depending on the state of the transmission path. Therefore, it is necessary for high-speed transmission to efficiently transmit data even when the state of the transmission path changes. Since the error correction capability is changed by changing the coding rate in the error correction technique, efficient data transmission can be achieved by appropriately selecting one of the plurality of coding rates according to the transmission path state. Accordingly, a study on an error correction technique such as LDPC (Low Density Parity Check Codes) (see, for example, Japanese Patent Laid-Open No. 2006-54575) has been actively conducted. At this time, the low density parity check code is a linear code defined by a check matrix having a very small number of elements of "1" in the matrix.

In addition, there is a mobile phone terminal that simultaneously transmits and receives voice and video signals from one mobile phone terminal, such as a video telephone. In such a mobile terminal, a coding rate with a smaller error is applied to the voice and a coding rate Can be applied. Or, in this case, only the audio is transmitted and the video is not transmitted. In such a case, the LDPC code processing may be performed by performing LDPC code processing on a plurality of channels such as voice and video with different coding rates, or dynamically changing the coding rate according to the channel line state.

Conventionally, as a method of processing data of a plurality of channels as described above at different coding rates, a plurality of coding circuits and decoding circuits corresponding to a plurality of coding rates are provided, respectively, and a plurality of channels are processed Was used.

Fig. 1 is a block diagram showing a configuration of a conventional encoding circuit.

The conventional encoding circuit includes encoding circuits 30-1 to 30-N corresponding to N encoding rates as shown in Fig. As shown in Fig. 1, the encoding circuit 30-1 includes an input buffer 33 for storing information bits of a plurality of channels, an input buffer 33 for storing information bits read from the input buffer 33 at a predetermined basic coding rate An LDPC coding unit 35 for coding a low density parity check code, a puncturing unit 36 for changing a coding rate by puncturing the codeword output from the LDPC coding unit 35, An output buffer unit 37 for outputting the codeword to the outside according to the length of the codeword whose coding rate has been changed after storing the codeword whose output coding rate has been changed in the memory and a coding rate adaptive to the line condition of the channel And a control unit 32 for controlling the channel setting unit 31 and the LDPC coding unit 35, the perforating unit 36 and the output buffer unit 37 for maintaining one channel setting value for each channel. The same applies to the other encoding circuits 30-2, ..., 30-N.

In the conventional encoding circuit having a plurality of channels and performing encoding with a plurality of encoding rates for each channel, the number of low density parity check code circuits corresponding to the plurality of encoding rates must be equal to the number of channels.

That is, in the conventional encoding circuit shown in FIG. 1, encoding circuits and decoding circuits corresponding to the encoding rate for each channel are included, which causes a problem that the circuit scale becomes large. Furthermore, since the coding rate is dynamically changed according to the line state of each channel and the number of codewords to be processed dynamically changes for a predetermined period each time the coding rate is changed, the control of the coding circuit becomes complicated. In addition, even when the number of encoding circuits corresponding to the number of channels is combined into one, the coding rate of each channel is changed dynamically, and the number of codewords to be processed for each channel changes dynamically.

Disclosure of Invention Technical Problem [8] The present invention provides a coding method and apparatus capable of reducing the size of a circuit while easily controlling a plurality of channels at different coding rates or changing a coding rate of a plurality of channels dynamically have. The present invention also provides a computer-readable recording medium for causing a computer to execute the above-described method.

According to an aspect of the present invention, there is provided an encoding apparatus for determining a channel for which codeword processing is required based on a number of codewords to be processed for a predetermined period for each channel, A control unit for controlling to select a channel to be encoded; And an encoding unit encoding an information bit for a channel selected by the controller, wherein the controller controls to discard parity bits required to be discarded based on the number of puncturing bits for the encoded information bits.

According to another aspect of the present invention, there is provided an encoding method comprising: determining channels to be codeword-processed based on a number of codewords to be processed for a predetermined period for each channel; Selecting a channel to be encoded using a predetermined method among the determined channels; Encoding an information bit for a channel selected by the controller; And discarding parity bits required to be discarded based on the number of puncturing bits for the encoded information bits.

According to another aspect of the present invention, there is provided a computer-readable recording medium storing a program for causing a computer to execute the encoding method.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the detailed description of the present invention, constituent elements having substantially the same functions are denoted by the same reference numerals, and redundant description will be omitted.

2 is a block diagram illustrating a general configuration of a transmitter and a receiver of a communication apparatus in which an information encoding apparatus according to the present invention is used.

The transmitter 100 includes a CPU 110 that controls the entire transmitting apparatus, a microphone 120 that converts voice to an electrical signal, a voice signal processing circuit 130 that processes voice signals, a camera that converts the image into an electrical signal A video signal processing circuit 150 for processing a video signal, a coding circuit 160 for coding a signal-processed audio signal and a video signal, and a transmission circuit 170 for transmitting a coded signal. The present embodiment is particularly characterized by the configuration and operation of the encoding circuit 160, which will be described in detail below with reference to FIG.

Meanwhile, the receiver 200 includes a receiving circuit 210 for demodulating and soft-decision a received signal, a decoding circuit 220 for decoding the demodulated signal, a CPU 230 for controlling the entire receiving apparatus, A video signal processing circuit 240 for processing a video signal, a voice signal processing circuit 250 for processing the decoded voice signal, a speaker 260 for externally outputting the processed voice signal, And a monitor 270 for displaying the image.

The data amount of the audio signal is smaller than the data amount of the video signal. However, in a mobile phone, it is required to transmit a voice signal at a stable coding rate with a lower error rate than a video signal. Therefore, it is necessary for one encoding circuit to correspond to a plurality of channels such as audio and video, and to operate each channel at a different encoding rate. Hereinafter, a description will be given of a method for changing the coding rate based on this viewpoint.

A result of detecting the error of the received data in the decoding circuit 220 of the receiver 200 or a result of detecting the error of the received data by the CRC (Cyclic Redundancy Check) of the upper layer in the video signal processing circuit 240 or the audio signal processing circuit 250 The CPU 230 determines the line state of the channel by using the result of detecting the error of the channel. When it is determined that the number of errors is large and the line status is bad, the CPU 230 lowers the number of puncturing bits of the parity bit, thereby lowering the coding rate and improving the error correction capability. On the other hand, when it is determined that the error is small and the line status is good, the CPU 230 increases the number of puncturing bits of the parity bit to increase the coding rate and increase the data transmission rate. At this time, the coding rate is adaptively determined according to the error frequency detected among the coding rates prepared in advance. At this time, the determined coding rate is transmitted to the transmitter 100 to make the transmitter 100 coincide with the sign. And performs the series of operations periodically in order to always operate at a coding rate adapted to the line state.

The coding rate Rp is calculated as Rp = In / (N-Pn). Where N is the codeword length, In is the number of information bits, and Pn is the number of punctured bits of the parity bit.

In this embodiment, the puncturing bits are located in a continuous range from the head of the parity bit. Such a continuous range makes it possible to perform control more simply.

Hereinafter, the characteristic configuration of the present embodiment among the configurations shown in FIG. 2 will be mainly described. The configuration of the encoding circuit 160 is shown in FIG. 3 and FIG. 4, the configuration of the lookup table used in the encoding circuit 160 is shown in FIG. 5, and the puncturing timings are shown in FIG.

3 is a block diagram showing the configuration of the encoding circuit 160, which is a characteristic component of the present embodiment. 3, the encoding circuit 160 corresponds to the information encoding apparatus of the present invention. The encoding circuit 160 includes a channel setting unit 310, a control unit 320, N input buffer units 330-1, ..., 300 -N).

The channel setting unit 310 is a circuit for holding, for each channel, a channel setting value corresponding to a coding rate adapted to the line state of each channel. The control unit 320 is a circuit for controlling the entire coding circuit 160 according to the present embodiment. The control unit 320 will be described in detail below with reference to FIG. 4 and the like.

The input buffer units 330-1, ..., 330-N store information bits to be encoded As a memory, there are a plurality of channels (N channels). The selector 340 is a circuit for selecting and reading the information bits of the channel to be processed from the input buffer units 330-1 to 330-N. The LDPC encoding unit 350 encodes the information bits selected by the selection unit 340 at a single encoding rate. The perforation 360 is a circuit for discarding a parity bit in a range of consecutive periods for changing the coding rate of the information bit coded by the LDPC coding unit 350. [ The output buffer units 370-1 to 370-N are memories for storing the punctured codewords output from the perforating unit 360, and exist in a plurality of channels (N channels).

4 is a block diagram showing the configuration of the control unit 320, which is a characteristic component of the present embodiment.

The control unit 320 calculates the number of processed codewords, the number of punctured bits, and the length of the punctured codeword for a predetermined period with reference to the lookup table shown in FIG. 5 using the channel setting value input from the channel setting unit 310 as a key . 4, the control unit 320 is divided into three functional units: a round robin processing unit 400, a discard processing unit 500, and a codeword length processing unit 600. The look-up table will be described below with reference to FIG. 5 and the like. Hereinafter, each component of the control unit 320 will be described.

The round robin processing unit 400 performs a function of changing the order of processing of codewords that have not yet been processed for each channel. The round-robin processing is one of the parallel processing methods for load balancing. Each round processing is called sequential parallel processing. Once all of the allocated time has been used, processing is halted and returned to the end of the queue. At this time, a fragment of the CPU time allocated to each process is called a time quantum or a time slice. In round-robin processing, they are equal for each channel.

4, the round robin processing unit 400 of this embodiment includes N comparison units 410-1, ..., 410-N, a round robin circuit 420, and count-up And a control unit 430.

The comparison unit 410-1 includes a codeword process number calculation circuit 412, a codeword process completion number counter 414 and a comparison circuit 416. [ This also applies to the other comparators 410-2, ..., and 410-N.

The codeword process calculation circuit 412 is a circuit for calculating the " codeword process number ", which is the number of codewords to be processed within a certain period of time, with reference to the lookup table (FIG. 5). The codeword process completion number counter 414 is a circuit for counting the number of " codeword process completion ", which is the number of codewords processed.

The comparison circuit 416 compares the "codeword process number" from the codeword process calculation circuit 412 with the "codeword process completion count" from the codeword process completion counter 414 and, based on the comparison result, And outputs a processing request to the circuit 420.

The round robin circuit 420 is a circuit for selecting a processing request received from each channel in a round-robin manner, and outputs a processing channel number according to the selected channel.

The count-up control unit 430 counts up the codeword completion count counter 414 in accordance with the coding process signal received from the LDPC coding unit 350 for the channel selected by the round robin circuit 420.

The round robin processing unit 400 adopts the above configuration. According to this configuration, the number of codewords to be processed within a predetermined period of time from each channel set value is obtained in advance through a lookup table (Fig. 5). If the number of codewords processed in each channel does not reach the number of codewords to be processed, And outputs a processing request to the robin circuit 420.

The information bits of the processing channel selected by the round robin circuit 420 are selectively read from the input buffer units 330-1 to 330-N and output to the LDPC encoding unit 350, Can be sequentially encoded. Further, even if the number of process codewords within a certain period of each channel is changed, the number of process codewords and the round robin circuit 420 can be easily controlled.

As shown in FIG. 4, the discard processor 500 includes N comparison units 510-1 to 510-N, a selection circuit 520, and a count-up control unit 530. The comparing unit 510-1 includes a puncturing bit number calculating circuit 512, a parity bit discarding counter 514 and a comparing circuit 516. [ This also applies to the other comparison units 510-2, ..., and 510-N.

The puncturing bit number calculation circuit 512 is a circuit for calculating the " number of puncturing bits " with reference to a lookup table (FIG. 5).

The parity bit discard counter 514 is a circuit for counting the " parity bit discard count " which is the discarded parity bit.

The comparison circuit 516 compares the number of " punctured bits " from the puncturing bit number calculation circuit 512 with the " number of parity bits discarded " from the parity bit discarding counter 514, And outputs a discarding request to the discarding device.

The selection circuit 520 outputs the discard request received from each channel to the perforator 360.

The count-up control unit 530 counts up the parity bit discard counter 514 in accordance with the encoding process signal from the LDPC encoding unit 350 for the channel selected by the round robin circuit 420 described above.

In this manner, the discard processor 500 generates a signal for each channel to request discarding of a continuous range of parity bits based on the number of puncturing bits per channel. And outputs the discard request signal of the processing channel selected by the round robin circuit 420 to the percussion unit 360 so that the coding rate can be controlled for each channel even if the coding rate of each channel is different.

The codeword length processing unit 600 includes codeword length calculation circuits 610-1..., 610-N as shown in FIG. The codeword length calculation circuit 610-1 calculates the codeword length by referring to the lookup table (FIG. 5), and outputs the calculated codeword length to the output buffer unit 370-1. This also applies to the other codeword length calculation circuits 610-2, ..., 610-N, and outputs the calculated codeword length to the corresponding output buffer units 370-2, ..., 370-N .

The codeword length processing unit 600 transfers the codeword length of the channel selected by the round robin circuit 420 to the output buffer units 370-2 to 370-N, , It is also possible to write the punctured codewords into the output buffer units 370-1, ..., 370-N corresponding to the respective channels.

The configuration of the control unit 320 has been described above with reference to FIG. By adopting such a configuration, it is easy for one controller 320 to encode a plurality of information bits of a channel at different coding rates for each channel.

5 is a diagram illustrating an example of a lookup table according to an embodiment of the present invention. As shown in Fig. 5, the look-up table is a table for defining the relationship of "number of processed codewords", "number of punctured bits", "codeword length after puncturing" and "coding rate" . The look-up table shown in FIG. 5 will be described in detail.

In channel setting value 0, the number of puncturing bits is 0, and this channel setting value 0 is regarded as a default. As described above, the coding rate Rp is calculated as Rp = In / (n-Pn). Where N is the code length, In is the number of information bits, and Pn is the number of punctured bits of the parity bit. The number of processed codewords = 6, the length of codes N = 1200, the number of punctured bits Pn = 0, the length of codeword after puncturing = 1200, the coding rate Rp = 1/2, do.

The channel setting value 1 is a case where the coding rate is slightly increased, and the coding rate Rp = 2/3. At this time, the number of processed codewords = 8, the length of codes N = 1200, the number of punctured bits Pn = 300, the length of codeword after puncturing = 900, and the number of information bits In = 600.

The channel setting value 2 is a case where the coding rate is further increased, and the coding rate Rp = 3/4. At this time, the number of processed codewords = 9, the length of codes N = 1200, the number of punctured bits Pn = 400, the length of codeword after puncturing = 800, and the number of information bits In = 600.

In the example of the look-up table of FIG. 5, the channel setting value 3 is defined as a case of channel unused.

This embodiment is configured as described above. Next, the operation of this embodiment will be described.

The control unit 320 refers to the lookup table with the " channel setting value " input from the channel setting unit 310 as a key to determine the number of "processed codeword number", "number of punctured bits", and "codeword length after puncturing" I ask. These values are input to the codeword process number calculation circuit 412, the puncture bit number calculation circuit 512 and the codeword length calculation circuits 610-1 to 610-N shown in Fig.

Next, the round robin processing unit 400 compares the values of the " codeword process count " and " codeword process completion counter " in the comparison circuit 416 for each channel. (420).

The round robin circuit 420 sequentially selects the processing requests from the respective channels in a round robin manner. The selection unit 340, the output buffer units 370-1, ..., and 370-N shown in FIG. 3 and the control unit 320 (the count up control unit 430), the count-up control unit 530, and the selection circuit 520).

The selector 340 selectively reads the information bits from the input buffer units 330-1 to 330-N according to the " processing channel number " and transfers the read information bits to the LDPC encoder 350 .

The LDPC encoder 350 encodes the information bits transmitted from the selector 340 at a basic coding rate and delivers the generated codewords to the perforator 360. [ Further, the "encoding processing signal" indicating the operation of the encoding circuit is outputted to the count-up control unit 430 shown in FIG.

The count-up control unit 430 that has received the "encoding processing signal" counts up the "codeword process completion counter" corresponding to the channel currently being processed.

In addition, in the discarding processing unit 500, the count-up control unit 530 counts up the " parity bit discard count " corresponding to the currently processed channel when the " encoding process signal " The comparison circuit 516 compares the values of the " number of punctured bits " and " number of discarded parity bits " And outputs a discard request to the perforator 360 until the " parity bit discard number " matches the " perforation bit number ".

6 is a diagram illustrating an example of puncturing timings according to an embodiment of the present invention. 6 (a) shows a coding process signal from the LDPC coding unit 350 to the control unit 320. In FIG. The puncturing timing in the encoding process signal period will be described as follows.

The puncturing unit 360 discards the codeword received from the LDPC encoding unit 350 while the discard request is being output from the control unit 320 (Fig. 6 (b)). 6 (c) shows an input data enable signal of the perforation 350, and a coder is input to the perforation 360 during this period (Fig. 6 (d)). Specifically, the output data enable signal (FIG. 6 (e)) indicating the data validity is not output, and the data is discarded to the output buffer unit 370 (FIG. 6 (f)). Here, it is assumed that the parity bits are arranged at the head of the codeword.

Next, the output buffer unit 370 stores the codeword output from the perforator 360 in the memory, and outputs the codeword to the outside of the coding circuit 160. [ Quot; length after puncturing " output from the codeword length processing unit 600 shown in Fig.

As described above, the information encoding apparatus (the encoding circuit 160 or the transmitter 100 including the encoding circuit 160) according to the present embodiment has been described. Such an information encoding apparatus can utilize a computer as an information encoding apparatus by inputting a computer program for realizing the above function into a computer. Such a computer program can be distributed to the market in the form recorded on a predetermined recording medium (for example, a CD-ROM) or in the form of a download through an electronic network.

Although the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to these examples. It will be apparent to those skilled in the art that various changes or modifications can be made within the scope of the claims, and they are understood to fall within the technical scope of the present invention as a matter of course.

For example, in the above-described embodiment, the look-up table which is a table for defining these relations as the means for obtaining the "number of processed codewords", "the number of punctured bits" However, the present invention is not limited to this. The control unit 320 can acquire the " number of processed codewords ", " number of punctured bits ", and " length of codeword after puncturing " It is also possible to refer to different lookup tables for each of the " number of processed codewords ", " number of punctured bits ", and " length of codeword after puncturing ".

In the above embodiment, the round robin process (round robin circuit 400), which is one method of parallel processing for load distribution, has been described as the switching means of the processing channel. However, the present invention is not limited to this, Can be adopted. For example, a processing technique (referred to as a burst process or the like) for moving to the processing of the next channel after completing the processing of one channel may be adopted.

The encoding method according to the present invention determines channels requiring codeword processing based on the number of codewords to be processed for a predetermined period for each channel, selects a channel to be encoded by using a predetermined method among the determined channels, Information bits necessary for codeword processing such as the number of codewords and the number of puncturing bits are managed by discarding parity bits required to be discarded based on the number of puncturing bits for the encoded information bits It is possible to easily control the encoding of a plurality of channels such as voice and video at different coding rates or to change the coding rate dynamically according to the line state of each channel. So that the scale of the circuit can be remarkably reduced.

Claims (15)

Obtaining a number of information bits to be processed by the control unit for a predetermined period for a plurality of channels; Selecting one of the plurality of channels using a predetermined method based on the number of the obtained information bits; Encoding an information bit corresponding to the selected channel at a predetermined coding rate; Determining a number of puncturing bits and a coding rate of the selected channel by referring to a lookup table; And And changing a coding rate of the encoded information bits to the determined coding rate by discarding a predetermined parity bit from the encoded information bits based on the determined number of puncturing bits. The method of claim 1, wherein selecting the channel comprises: Determining a channel to be encoded among the plurality of channels according to the obtained number of information bits; And Wherein the controller selects a channel to be encoded using the round robin method among the determined channels. delete 2. The method of claim 1, wherein determining the number of information bits comprises: Wherein the control unit refers to a lookup table to obtain the number of information bits for the plurality of channels. The method according to claim 1, Calculating a length of a punctured codeword by referring to a lookup table; And Further comprising the step of storing the punctured codeword using the obtained codeword length after the puncturing. A controller for obtaining a number of information bits to be processed for a predetermined period for a plurality of channels and selecting any one of the plurality of channels using a predetermined method based on the number of information bits obtained; An encoding unit encoding an information bit corresponding to the selected channel at a preset encoding rate; And And changing the coding rate of the encoded information bit to a coding rate of the selected channel by discarding a predetermined parity bit from the encoded information bit based on the number of puncturing bits of the selected channel, Wherein the controller determines a number of puncturing bits and a coding rate of the selected channel by referring to a lookup table. 7. The apparatus of claim 6, wherein the control unit Determining channels to be coded in the plurality of channels according to the determined number of information bits, and selecting a channel to be coded using the round robin method among the determined channels. delete 7. The apparatus of claim 6, wherein the control unit Wherein the lookup table is referenced to obtain the number of information bits for the plurality of channels. The method according to claim 6, Wherein the controller calculates a codeword length after puncturing by referring to a lookup table, And an output buffer unit for storing the punctured codeword according to the obtained codeword length after the puncturing. An input buffer unit for storing information bits for a plurality of channels; A selector for selectively reading a predetermined information bit among the stored information bits; A coding unit for generating a codeword by performing coding with a predetermined coding rate on the read information bits; A cantilever for changing a coding rate of the encoded information bits to a coding rate of the selected channel by discarding a predetermined parity bit from the coded information bits based on the number of puncturing bits of the selected channel; An output buffer unit for storing the codeword with the changed coding rate and outputting the codeword to the outside according to the length of the codeword whose coding rate is changed; And And a control unit for controlling the selection unit, the encoding unit, the perforation and the output buffer unit, The control unit And determines a number of puncturing bits and a coding rate of the selected channel by referring to a lookup table. A control unit configured to obtain the number of information bits to be processed for a predetermined period of time for the plurality of channels and to select any one of the plurality of channels in the selection unit using a predetermined method based on the number of the obtained information bits And a channel selection unit for selecting one of the plurality of channels. 12. The apparatus of claim 11, wherein the control unit Determines channels to be coded from among the plurality of channels according to the obtained number of information bits, and selects a channel to be coded using the round robin method among the determined channels. 12. The apparatus of claim 11, wherein the control unit Wherein the lookup table is referenced to obtain the number of information bits for the plurality of channels. delete A computer-readable recording medium storing a program for causing a computer to execute the method according to any one of claims 1, 2, 4, and 5.

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