KR100383737B1 - An apparatus for transmitting and receiving a signal in OFDM/CDMA system - Google Patents

Abstract

The present invention provides a transmission / reception apparatus of an OFDM / CDMA system for improving error control performance by using parallel concatenated convolutional coding and decoding in a transmission / reception apparatus of an orthogonal frequency division multiplexing / code division multiple access (OFDM / CDMA) system. A plurality of processors 110 for spreading a plurality of transmission data signals, converting the plurality of spread data signals to a serial signal, and then parallel convolutional convolutional encoding, and inputs each of the encoded serial data signals A plurality of serial / parallel converters 130 for converting and outputting a parallel carrier transmission path, an interleaver 150 for inputting parallel data signals output from each serial / parallel converter 130 and performing interleaving, and Input a parallel data signal, which is the output of the interleaver 150, modulate it into an orthogonal frequency division multiplexing signal, and then The transmission apparatus includes an OFDM modulator 170 for transmission to; And an OFDM demodulator 210, a deinterleaver 220, a parallel / serial converter 230, a PCCC decoder 240, a serial / parallel converter 250, and a despreader 260 corresponding to the transmitter. It is composed of a receiving device to improve the error control performance on the wireless transmission path.

Description

An apparatus for transmitting and receiving in an orthogonal frequency division multiplexing / signal division multiple access system

The present invention relates to a transmission / reception apparatus of an orthogonal frequency division multiplexing / signal division multiple access (OFDM / CDMA) system, and more particularly, to a parallel connection to a transmission and reception apparatus of an orthogonal frequency division multiplexing / signal division multiple access system. A transmission / reception apparatus of an orthogonal frequency division multiplexing / code division multiple access system for improving error control performance using convolutional encoding and decoding.

For a high speed multimedia service, a wireless transmission method having a high spectrum efficiency and a multiple access method are required. One of the methods suitable for high-speed data transmission in a wireless channel is a multicarrier transmission method. In the multi-carrier method, a plurality of subcarriers (subcarriers) are used for first-to-parallel conversion and then modulation for incoming data at high speed. At this time, orthogonality between carriers should be maintained. The multicarrier method in which orthogonality is maintained is referred to as orthogonal frequency division multiplexing (hereinafter, referred to as OFDM). In addition, a code division multiple access (hereinafter, referred to as CDMA) scheme is currently considered as a multiple access scheme suitable for high-speed data transmission in a wireless transmission path environment.

Deterioration of data transmitted in a wireless transmission path occurs due to fading or the like during transmission. Various error control codings have been proposed to detect and correct this. Up to now, convolutional coding and RS (Reed-Solomon) codes have been considered. Recently, parallel concatenated convolutional coding (hereinafter, abbreviated as PCCC) is a very good performance. Although it has been known, in the past studies, since the study of applying the PCCC to the OFDM / CDMA system has not been done at all, it is a situation that needs to be studied.

SUMMARY OF THE INVENTION The present invention has been made based on the above technical background, and its purpose is to increase the error control performance of an OFDM / CDMA system by applying parallel convolutional convolutional coding, thereby significantly reducing the probability of bit error when transmitting and receiving data over a wireless transmission path. Another object of the present invention is to provide a transmission / reception device of an OFDM / CDMA system.

That is, until now, the OFDM method has been applied to audio and video broadcasting systems, and is applied to a method for high-speed data transmission on a wireless transmission path, thereby making it a frequency selective fading channel. ) To reduce the fading deterioration by making a frequency flat fading channel environment. In addition, by applying a code division multiple access system as a multiple access method for high speed transmission, the flexibility of user allocation, robustness to external interference signals, security, And soft handoff. In addition, the PCCC is applied to the OFDM / CDMA system scheme to improve the high-speed data transmission capability on the wireless transmission path.

1 is a block diagram of a transmission apparatus of an orthogonal frequency division multiplexing / code division multiple access system according to an embodiment of the present invention;

FIG. 2 is a block diagram of a receiving device of an OFDM / CDMA system according to an embodiment of the present invention, and is a block diagram of a receiving device of the system.

3 is a detailed block diagram of each processor of FIG. 1;

4 is a detailed block diagram of a parallel concatenated convolutional encoder of FIG. 3.

5 is a detailed block diagram of a parallel concatenated convolutional decoder of FIG. 2,

6 is a graph showing the bit error probability for the signal-to-noise ratio according to the number of iterative decoding as a simulation result of the OFDM / CDMA transmission / reception apparatus of the present invention.

※ Explanation of code for main part of drawing

110 processor 111 diffuser

112,230: bottle / serial converter 120: parallel convolutional weaving encoder

121,123: convolutional encoder 124: bypass output unit

130,250 Serial / Parallel Converter 150,122 Interleaver

170: OFDM modulator 210: OFDM demodulator

220: deinterleaver 240: parallel concatenated convolutional decoder

260 despreading unit

In order to achieve the above object, a transmission / reception apparatus of an OFDM / CDMA system according to the present invention multiplies a plurality of transmission data signals by a corresponding spreading sequence, and converts the plurality of spread data signals into a serial signal. And a plurality of processing means for performing parallel convolutional convolutional coding, a plurality of serial / parallel conversion means for converting and outputting serial data signals output from the respective processing means into a plurality of parallel carrier transmission paths, and the respective serial / parallel conversion means. An interleaving means for interleaving the outputted parallel data signal and then outputting the signal; and multiplying each subcarrier to maintain the orthogonality of the parallel data signal outputted from the interleaving means, modulating the signal into an orthogonal frequency division multiplexing signal, and transmitting the result in a wireless transmission path Transmission with orthogonal frequency division multiplexing modulation means Device; And orthogonal frequency division multiplexing demodulation means for demodulating the orthogonal frequency division multiplexing signal transmitted by the transmitting apparatus and received through the wireless transmission path based on the respective subcarrier signals and outputting the parallel data signal as the demodulation means. Deinterleaving means for performing deinterleaving corresponding to the interleaving process in the interleaving means on the demodulated and outputted parallel data signal; parallel / serial conversion for converting each deinterleaved parallel input data signal into a serial data signal Means for performing parallel convolutional convolutional decoding of the converted serial data signal and outputting the serial convolutional convolutional decoding means for converting the decoded serial data signal into a parallel data signal; Despread based on the corresponding despreading sequence And it is configured to include a receiving apparatus having a despreading means for estimating the target data.

The processing means of the transmitting device includes: a plurality of spreading means for spreading a plurality of transmission data signals based on respective corresponding spreading sequences; Parallel / serial conversion means for converting a plurality of signals output in parallel from the plurality of spreading means into serial data signals; And parallel concatenated convolutional encoding means for inputting the converted serial data signal, and performing parallel convolutional convolutional encoding on the output.

The parallel concatenated convolutional encoding means may include: a first convolutional encoder that performs convolutional encoding on the input data bit stream and then outputs the convolutional encoding; An interleaver for interleaving the input data bit stream; A second convolutional encoder that performs convolutional encoding on the data bit stream that is an output signal of the interleaver and then outputs the convolutional encoding; And an output unit which branches and outputs the input data bit stream as it is.

The parallel concatenated convolutional decoding means may further include: a metric calculator configured to calculate a metric with respect to an input data bit stream; A first convolutional decoder that convolutionally decodes input data and feedback data according to the calculated metric; A first interleaver for interleaving the output of the first decoder; A second interleaver for interleaving input data according to the calculated metric; A second convolutional decoder configured to convolutionally decode input data according to the output data of the first and second interleavers and the calculated metric; A deinterleaver deinterleaving the output of the second convolutional decoder to provide the feedback data of the first convolutional decoder; And a data determination unit that determines data bits according to the output of the second convolutional decoder.

Hereinafter, a transmission / reception apparatus of an orthogonal frequency division multiplexing / code division multiple access (OFDM / CDMA) system according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of a transmission apparatus of an OFDM / CDMA system according to an embodiment of the present invention. As shown in the figure, a plurality of transmission data signals are spread based on respective corresponding spreading sequences, A plurality of processors 110 for converting a plurality of data signals into serial signals and then performing parallel concatenated convolutional coding; A plurality of serial-to-parallel converters (130) for converting and outputting serial data signals output from the processors (110) into a plurality of parallel carrier transmission paths; An interleaver 150 for inputting parallel data signals output from the serial / parallel conversion units 130 and interleaving the interleaved data; And inputting a parallel data signal output from the interleaver 150, multiplying each of the subcarriers to maintain mutual orthogonality with the input parallel data signal, modulating the parallel data signal into an orthogonal frequency division multiplexing signal, and transmitting the signal through a wireless transmission path. Is an orthogonal frequency division multiplexing (OFDM) modulator 170.

FIG. 2 is a block diagram of a reception device of an OFDM / CDMA system according to an embodiment of the present invention. As shown in the figure, OFDM transmitted by the transmission device of FIG. 1 and received through the wireless transmission path is illustrated in FIG. An orthogonal frequency division multiplexing (OFDM) demodulator 210 for demodulating the received signal based on the corresponding subcarrier signal and outputting the received signal as a parallel data signal; A deinterleaver 220 which performs deinterleaving corresponding to an interleaving process in the interleaver 150 of FIG. 1 with respect to the parallel data signal demodulated and output by the OFDM demodulator 210; A parallel-to-serial converter 230 for deinterleaving by the deinterleaver 220 and converting each data signal input in parallel into a serial data signal; A parallel convolutional convolutional decoder (PCCC decoder) 240 for inputting the serial data signal converted and output by the parallel / serial converter 230 to perform parallel concatenated convolutional decoding; A serial / parallel converter 250 for converting the serial data signal decoded by the PCCC decoder 240 into a parallel data signal; And a despreader 260 which despreads the parallel data signal converted by the serial / parallel converter 250 based on the corresponding despreading sequence and estimates the target data.

3 is a detailed block diagram of each of the above-described processors 110 of FIG. 1, and as shown in FIG. 1, a plurality of transmission data signals d ₁ (t) to d _M (t) are configured in parallel to each other. A plurality of diffusions 111 which are multiplied by the diffusion sequences c ₁ (t) to c _M (t) and then outputted; A parallel / parallel converter (112) for converting a plurality of data signals outputted from the plurality of spreaders (111) into parallel data signals; And a parallel concatenated convolutional encoder (PCCC encoder) 120 for inputting serial concatenated convolutional encoding by converting the serial data signal converted by the parallel / serial converter 112 and outputting the concatenated convolutional convolutional encoding.

FIG. 4 is a detailed block diagram of the PCCC encoder 120 of FIG. 3. As shown in FIG. 3, a first convolution is performed after convolutional encoding is performed on the input data bits u and then output v1. Encoder 121; An interleaver 122 for interleaving the input data bits u; A second convolutional encoder 123 performing convolutional encoding on the data bit u1 which is the output signal of the interleaver 122 and then outputting the result (v2); And a bypass output unit 114 for branching the input data bit u and outputting it as it is (v0).

FIG. 5 is a detailed block diagram of the PCCC decoder 240 of FIG. 2, and as shown in FIG. 2, a metric calculator (not shown) for calculating a metric for an input data bit stream (v0, v1, v2). Matrix Computation) 241; A first convolutional decoder 242 convolutionally decodes input data v0, v1 and feedback data according to the calculated metric; A first interleaver 243 for interleaving the output of the first convolutional decoder; A second interleaver 244 for interleaving input data v0 according to the calculated metric; A second convolutional decoder 245 for convolutionally decoding the output data of the first and second interleavers 243 and 244 and the input data v2 according to the calculated metric; A deinterleaver 246 for deinterleaving the output of the second convolutional decoder 245 and providing the feedback data of the first convolutional decoder 242; And a data decision unit 247 for determining a data bit u * according to the output of the second convolutional decoder 245.

Next, the operation of the present invention will be described.

First, in the transmitting apparatus of FIG. 1, when N users exist in the system, the user's data is input to each of the processors 110 and subjected to spreading, parallel / serial conversion, and parallel concatenated convolutional coding. 3 a plurality of the input data signal as shown in _{[d 1 (t) ~d M} (t)] is the spreading sequence through each diffusion unit 111 of the processor _{(110) [c 1 (t} ) Multiplied by ˜c _M (t)], the spread data signal is input to the parallel / serial converter 112 in parallel, converted into a serial data signal, and then input to the PCCC encoder 120. Parallel concatenated convolutional coding and output (S _i : S ₁ , S ₂ , ..., S _k ).

Each serial data signal S ₁ , S ₂ ,..., S _k output from the PCCC encoder 120 of each processor 110 is input to the serial / parallel converter 130 to provide parallel data. Is converted into a signal. Subsequently, each parallel data signal output from the serial / parallel converter 130 is inputted to the interleaver 150 to be interleaved to convert a burst error into a random error. The parallel data signal outputted from 150 is input to the OFDM modulator 170 and multiplied with each corresponding subcarrier to be modulated into an OFDM transmission signal maintaining mutual orthogonality, and then transmitted through a wireless transmission path.

In the above-described signal processing of the transmitting apparatus, as shown in FIG. 3, the PCCC encoder 120 inputs an input data signal u in parallel by two parallel encoders 121 and 123 so that one data is received. Since one data bit v0 and two parity bits v1 and v2 are output for the bit input, the coding rate is 1/3.

Next, in the reception apparatus of FIG. 2, the OFDM transmission signal modulated and transmitted by the OFDM modulator 170 of the transmission apparatus is received through the wireless transmission path, and the received OFDM reception signal is first received. The OFDM demodulator 210 is demodulated based on the corresponding subcarriers and then output as a parallel data signal. The parallel data signal, which is the output of the OFDM demodulator 210, is input to the deinterleaver 220 and deinterleaved and output. The deinterleaving corresponds to an inverse interleaving process in the interleaver 150 of the transmitter. It is a process.

Subsequently, the parallel data signal deinterleaved and output by the deinterleaver 220 is input to the parallel / serial converter 230 to perform a parallel-to-parallel conversion process in the serial / parallel converter 130 of the transmitter. Conversely, the serial data signal is converted and output, and the converted output serial data signal is input to the PCCC decoder 240 to perform parallel concatenated convolutional decoding.

The serial data signal decoded by the PCCC decoding unit 240 is input to the serial / parallel conversion unit 250 to be inversely parallel to the parallel-to-serial conversion process in the parallel / serial converter 112 of the transmitting device. The parallel data signal is converted into a data signal and outputted, and the outputted parallel data signal is input to the despreader 260, and each of the input parallel data signals is multiplied with each corresponding despreading sequence to despread and estimated target data. Is output.

In the above-described signal processing of the reception apparatus, the PCCC decoder 240 calculates a metric for the inputs of the two decoders 242 and 245 by the metric calculator 241 as shown in FIG. 5. The decoding is performed by the two parallel decoders 242 and 245. At this time, the outputs of the decoders 242 and 245 are fed back to the inputs of the other decoders 242 and 345 to perform repeated decoding. By iterative decoding, the performance of the parallel concatenated convolutional encoder is superior to other encoders.

FIG. 6 is a graph showing the bit error probability for the signal-to-noise ratio (Eb / No) according to the number of iterative decoding as a simulation result of the OFDM / CDMA transmission / reception apparatus of the present invention. The number of subcarriers is 512, the processing gain is 128, the transmission bandwidth is 1.25 MHz, the number of users is 10, the interleaver size of the PCCC encoder is 1000, and the carrier spacing is 2.441 kHz. It was set as. Then, when the generator polynomial is expressed in octal notation, a recursive convolutional code given by "(21,37)" is used. Maximum a posteriori (MAP) is used as the decoding algorithm. Simulation results of the present invention under such conditions. As can be seen in Figure 6, as the number of iterative decoding is increased to 2, 4 and 8 it can be seen that the bit error probability is significantly reduced.

As described in detail above, an apparatus for transmitting / receiving an orthogonal frequency division multiplexing / signal division multiple access (OFDM / CDMA) system according to the present invention applies the OFDM scheme as a method for high-speed data transmission on a wireless transmission line. Reduces fading degradation by making the frequency selective fading channel into a frequency flat fading channel environment, and applies the code division multiple access system as a multiple access method for high speed transmission. This provides the advantages of flexibility of user allocation, robustness to external interference, security, and soft handoff. PCCC is applied to OFDM / CDMA system to improve bit error probability The creation of the effect of improving the high-speed data transfer capabilities.

Claims (4)

A plurality of processing means for multiplying a plurality of transmission data signals by a corresponding spreading sequence, converting the spread plurality of data signals to a serial signal, and then performing parallel convolutional convolutional encoding on the plurality of transmission data signals, and the serial data signal outputted from the respective processing means A plurality of serial / parallel conversion means for converting and outputting a plurality of parallel carrier transmission paths, interleaving means for interleaving and outputting parallel data signals outputted from the respective serial / parallel conversion means, and parallel data signals outputted from the interleaving means. A transmission device comprising orthogonal frequency division multiplexing modulation means for multiplying each subcarrier to maintain mutual orthogonality, modulating the quadrature frequency division multiplexing signal, and transmitting the result in a radio transmission path; And Orthogonal frequency division multiplexing demodulation means for demodulating the orthogonal frequency division multiplexing signal transmitted by the transmitting apparatus and received through the wireless transmission path based on the respective subcarrier signals and outputting the parallel data signal, and demodulation by the demodulation means. Deinterleaving means for performing deinterleaving corresponding to the interleaving process in the interleaving means with respect to the parallel data signal, and parallel / serial conversion means for converting each deinterleaved parallel input data signal into a serial data signal. Parallel convolutional convolutional decoding means for parallel convolutional convolutional decoding of the converted serial data signal, and outputting the serial / parallel conversion means for converting the decoded serial data signal into a parallel data signal; Despread based on the despread sequence Transmitting / receiving apparatus of orthogonal frequency division multiplexing / code division multiple access system, characterized in that configured by a receiving apparatus having a despreading means for estimating W target data. The method of claim 1, The processing means of the transmission device, A plurality of spreading means for spreading the plurality of transmission data signals based on respective corresponding spreading sequences; Parallel / serial conversion means for converting a plurality of signals output in parallel from the plurality of spreading means into serial data signals; And And a parallel concatenated convolutional encoding means for inputting the converted serial data signal, and performing parallel convolutional convolutional encoding on the converted serial data signal. 12. A transmission / reception apparatus for an orthogonal frequency division multiplexing / signal division multiple access system, comprising: The method of claim 2, The parallel concatenated convolutional coding means, A first convolutional encoder that performs convolutional encoding on the input data bit stream and then outputs the convolutional encoding; An interleaver for interleaving the input data bit stream; A second convolutional encoder that performs convolutional encoding on the data bit stream that is an output signal of the interleaver and then outputs the convolutional encoding; And And an output unit for branching the input data bit stream and outputting the same as it is. 2. The transmission / reception apparatus of an orthogonal frequency division multiplexing / code division multiple access system. The method of claim 1, The parallel concatenated convolutional decoding means, A metric calculator for calculating a metric for the input data bit stream; A first convolutional decoder that convolutionally decodes input data and feedback data according to the calculated metric; A first interleaver for interleaving the output of the first decoder; A second interleaver for interleaving input data according to the calculated metric; A second convolutional decoder configured to convolutionally decode input data according to the output data of the first and second interleavers and the calculated metric; A deinterleaver deinterleaving the output of the second convolutional decoder to provide the feedback data of the first convolutional decoder; And And a data determiner configured to determine data bits according to the output of the second convolutional decoder.