KR100329972B1 - Data symbol detection apparatus and its method of communication system - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

The present invention relates to an apparatus for detecting data symbols in a communication system, a method thereof, and a computer-readable recording medium having recorded thereon a program for realizing the method.

2. The problem to be solved by the invention

The present invention provides a data symbol detection apparatus and method and method for reducing performance degradation due to nonlinear distortion and fading channel distortion at the transmitting end when detecting a data symbol at a receiving end of a DS / CDMA system using multiple spreading codes. To provide a computer-readable recording medium that records a program for realizing this.

3. Summary of Solution to Invention

The present invention provides a data symbol detection apparatus of a communication system, comprising: bit determining means for temporarily determining a reception symbol sequence transmitted from the outside; Generates a circular sequence from the reference sequence determined by the bit determining means, selects a new reference sequence by evaluating the similarity between the received symbol sequence and the weighted distortion sequence, and controls whether or not the sequence is output by comparing the old and new reference sequences. Sequence control means for performing; Distortion estimating means for estimating the distortion generated by the multicode and the nonlinear transfer characteristic by receiving the output signal of the sequence control means; And gain weighting means for calculating a sequence weight using the channel gain information transmitted from the distortion estimating means, and multiplying the calculated weight value by each symbol of the distortion sequence to output a multiplication value to the sequence control means. .

4. Important uses of the invention

The present invention is used in a communication system using a multi-code DS / CDMA method.

Description

Apparatus and method for detecting data symbol of communication system {DATA SYMBOL DETECTION APPARATUS AND ITS METHOD OF COMMUNICATION SYSTEM}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting data symbols in a multi-code CDMA communication system, a method thereof, and a computer-readable recording medium having recorded thereon a program for realizing the method. Data symbol detection apparatus for detecting data symbols at a receiving end of a communication system using a Direct Sequence / Code Division Multiple Access (hereinafter referred to as DS / CDMA) scheme, a method thereof, and a computer storing a program for realizing the method. The present invention relates to a recording medium which can be read by.

In general, a transmission method through modulation by spreading code for wireless communication is called a DS / CDMA method, and several codes may be used. Such a system using a transmission method is called a multicode DS / CDMA system.

On the contrary, a system for spreading modulation using one spreading code is a general DS / CDMA system and is called a single code DS / CDMA system corresponding to a system using multicode.

In addition, the DS / CDMA system exhibits better performance in a wireless channel than the frequency division multiple access (FDMA) and time division multiple access (CDMA) schemes due to its technical characteristics. Increasingly, due to the multipath characteristics of the radio channel, interference between transmitted symbols occurs and the transmission performance of the system is severely degraded.

Such transmission degradation occurs as a result of overlapping the previous and current symbols received at the receiver because the delay spread defined by the time difference between the first path and the last path of the multipath channel far exceeds the symbol interval. In this case, when high-speed data such as moving pictures are transmitted, inter-symbol interference becomes more severe and there is a problem that a function of a transmission system cannot be performed.

A conventional data symbol detection apparatus for solving the above-described problems will be described with reference to the general multi-code code division multiple access communication system of FIG.

As shown in FIG. 4, in the case of a multi-code CDMA transmitter, a cyclic redundancy code (CRC) generator 401 calculates a CRC parity bit for each transmitted data block having a B bit size using a cyclically generated polynomial. In order to detect a transmission error of the data block, the receiver adds a CRC bit after the data block. In this case, the channel encoder 402 provides redundancy with respect to the signal distortion generated in the transmission channel and performs signal processing to have the correction capability of the channel decoder 415. Usually, several bits are output for one bit input by the convolution code or the turbo code. The rate matching 403 outputs a constant bit rate by repeating or removing specific bits according to a predetermined rule for the input data block. The coded arbitrary bit rate is matched to a predetermined bit rate. The interleaver 404 is for distributing clustering errors occurring in the channel.

The multi-code spreader 405 is a multi-code CDMA modulator for direct sequence spread modulation using multiple spread codes. The data code generator 111, the serial / parallel converter 112, and the spread modulators 121 to 12k. ) And an adder 113.

Here, the data symbol generator 111 generates a data symbol from the input bits. In the case of Quadrature Phase Shift Keying (QPSK), 2 bits per symbol are available and mapping is performed by Gray code. The serial / parallel converter 112 converts an input symbol sequence into a low speed parallel sequence. Therefore, when using K channel codes, K parallel sequences are generated. The spreading modulators 121 to 12k spread the data symbols with the assigned channel codes. Walsh codes are used as the spreading codes, and subchannels are distinguished by them. The adder 113 adds the output of each spreading modulator 121 to 12k in units of chips so that a multilevel signal is output.

Accordingly, the multicode spreader 405 provides a result of converting the symbol signal into a multilevel chip signal.

That is, since the data symbol detection unit 141 requires 512 sequences when the spreading code number K is 5, the symbol sequence and calculation amount to be used for the similarity evaluation when the spreading code number is increased for a higher data rate service are Since it increases exponentially, the number of sequences and the computational complexity increase.

A digital analog (D / A) converter 406 converts the baseband digital signal into an analog signal. The converted analog signal is balanced modulated by a radio frequency (RF) upconverter 407, and then converted into an intermediate frequency and a carrier frequency, respectively, and radiated through the power amplifier 408 and the antenna. The power amplifier 408 amplifies the output of the RF signal with a linear characteristic or a non-linear characteristic as an input / output response characteristic, but in the case of the nonlinear amplifier, it outputs a different signal level according to the input signal level due to its nonlinear characteristic. Equation 1 shows the input and output response characteristics of a general nonlinear power amplifier.

As can be seen from Equation 1, the level of the output signal in the level range 0 `` `` x '' <= `` 0.45 of the output signal is y = 2x, the level of the input signal 0.45 `` '' x `` <= '' 1 outputs y = x and input signal level range 0.45 `` `` x `` <= '' 1 outputs y = -0.2x signal level. As a result, the nonlinear characteristic of the power amplifier is that the transmission signal is deformed or damaged due to the power amplifier characteristics in terms of the signal size excluding the gain of gain of the power amplifier. Therefore, in the nonlinear power amplifier, since the input signal is output as variously modified signals, the output signal is distorted with respect to the input signal.

In the case of a multicode CDMA receiver, the function of each block corresponds to the inverse function of the corresponding block of the transmitter.

The data symbol detector 412 detects the original k transmitted symbols for the k received symbols that are the outputs of the RAKE demodulator 411. One method evaluates the similarity between k received symbols, i.e., the received symbol sequence and all transmittable symbol sequences, so that the transmittable symbol sequence having the largest similarity, that is, the least error between symbols, is used as the current received symbol sequence. Will output the decision.

For example, if the transmission symbol sequence And the receiving symbol sequence Assume that here, Denotes a data symbol input to the i-th spreading modulators 121 to 12k constituting the multi-code spreader 405 and is a complex signal composed of I and Q components, that is, a QPSK signal. Is an output symbol of the i &lt; th &gt; rake coupling parts 131 to 13k constituting the rake demodulator 411 which is the front end of the data symbol detector. Since there are 2 ^ 2 kinds of 2-bit symbols, a symbol sequence consisting of k symbols There is a branch. Therefore, transmittable symbol sequences That is, the transmission symbol sequence to be used for similarity evaluation to be. If k is 4, i.e., when the multicode CDAM transmitter uses 4 spreading codes in the multicode spreader 405, the symbol sequence to be evaluated is 256. Therefore, the data symbol detection process is as shown in Equation 2 below. Evaluate the similarity of meetings, and symbol sequence showing the smallest error among them Receive Symbol Sequence Outputs the transmit symbol sequence for.

On the other hand, since the transmitting end of the transmission signal output from the multi-code spreader 405 is not known how much distortion in the non-linear power amplifier, the data symbol detection unit 141 of the present invention to reproduce the non-linear characteristics of the non-linear power amplifier Used.

Here, the nonlinear characteristics of the nonlinear power amplifier are aggravated by unsafe operation of the nonlinear power amplifier, such as aging, shock, overheating, overcurrent, and unstable power supply. Such input / output response characteristics are distortions that affect the input signal. Thus, the performance of the system is extremely degraded when the nonlinear power amplifier is used, in addition to its input / output response characteristics, when serious fading occurs in the mobile radio channel.

A conventional data symbol detection apparatus for solving the above problems will be described with reference to the detailed configuration diagram of the general multi-code code division multiple access communication system of FIG.

As shown in FIG. 1, a detailed configuration diagram of a general multi-code code division multiple access communication system is described in more detail with respect to the configuration diagram of FIG. 4.

In the transmitting terminal (404 to 406 of FIG. 4), the multi-code spreader 405 includes a data symbol generator 111 for modulating data bits into data symbols and a high-speed symbol string transmitted from the data symbol generator 111. FIG. A serial / parallel converter 112 for converting the signal into a plurality of low-speed symbol strings, spread modulators 121 to 12k for spread-modulating a signal transmitted from the serial / parallel converter 112 by a separate code, And an adder 113 for adding spread modulated signals by the spread modulators 121 to 12k.

The operation of the multicode spreader 405 having such a structure will be described below.

Data bits such as moving pictures are converted into digitally modulated symbols by the data symbol generator 111.

For example, in the case of a quadrature phase shift keying (QPSK) method in which data bits are modulated in phase, the data symbol generator 111 may generate? / 4 for the input bit '00' and 3π / 4 for the data bit '01'. For example, a data symbol having a size of 1 is output with a phase of -3π / 4 for data bit '11' and a phase of -π / 4 for data bit '10'.

In order to simplify signal processing, the normal bits are used as logic values '0' and '1' and logic values '1' and '-1', respectively.

The data symbols inputted to the serial / parallel conversion unit 112 are sequentially assigned k parallel branches.

Therefore, the symbol section input to the spreading modulators 121 to 12k has a T_s (= KT_d) which is much larger than the symbol section T_d of the data symbol.

The spreading modulators 121 to 12k have spreading codes having a unique length of N and multiply them by data symbols converted in parallel. One data symbol is output to N chip symbols T_c (= T_s / N) having smaller intervals through the spreading modulators 121 to 12k, which are usually configured as correlators.

As a result, in this process, the bandwidth W_s (= 1 / T_s) of the data symbol is spread over N times the bandwidth W_c (= 1 / T_c). This process is performed simultaneously in each of the spreading modulation units 121 to 12k.

The spread modulated signal output from each spread modulator 121 to 12k is added through the adder 113 in units of chip symbols.

In addition, the actual transmitting end includes a transmission processor and an antenna.

Among the receivers 410 to 413, the RAKE combiner 131 to 13k and the data symbol detector 141 (the same as 412 of FIG. 4) will be described in more detail.

The rake combiners 131 to 13k that receive signals transmitted through the L paths include L despreaders and one diversity combiner.

The data symbol detector 141 is configured to recover a transmission symbol from the demodulated symbol. The receiving end performs a function opposite to that of the transmitting end.

The operation of the receiver having such a structure will be described below.

First, the received signal is first input to the plurality of rake coupling parts 131 to 13k for demodulation. Each of the rake combiners 131 to 13k demodulates a corresponding data symbol.

For example, the first rake combining unit 131 demodulates the spread-modulated parallel data symbols through the first spreading modulation unit 121 of the transmitter.

This process is performed with the same spreading code as used at the transmitting end and despread for each of the L path components to obtain the maximum symbol energy. The despreading unit of the k-th Rake coupling unit 13k multiplies the received signal by the k-th spreading code and outputs it over N periods.

In addition, in order to obtain other L-1 path components of the same symbol, a predetermined delay time ( The same code delayed by) is used.

The L signal components despread for each path input to the diversity combiner are output through the maximum ratio combining multiplied by the channel gain estimated for each path.

The delay time and the estimated channel gain used through the rake coupling units 131 to 13k may be used as estimated from general channel estimation performed independently.

This process is the same for the remaining rake coupling portions 131 to 13k. The data symbols demodulated by the rake combiners 131 to 13k are recovered as symbols transmitted from the transmitter through the data symbol detector 141.

When k symbols, which are outputs of the Rake combiners 131 to 13k, are referred to as one symbol sequence, a symbol sequence having the least error between symbols is selected by evaluating the received symbol sequence with all transmittable sequences. Symbol detection is performed through the process.

This method shows the best performance in the channel where only noise is present. Another symbol detection method is a method of determining an original value (ie, +1 or -1) of a symbol for a symbol output from the rake coupling units 131 to 13k.

However, in the conventional case of detecting data symbols as described above, the performance of the multicode DS / CDMA system is significantly degraded when the distortion due to the nonlinear processing unit of the transmitting end is increased or when used in a fading channel. When more than one spreading code is used for the data rate, the number of sequences to be compared with the symbol sequences received by the data symbol detection unit 141 and the complexity of the calculations increase exponentially so that the conventional detection method can perform real-time processing. There was a problem that could not be.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the present invention is directed to performance degradation due to channel distortion due to nonlinear distortion and fading at the transmitting end when data symbols are detected at the receiving end of a DS / CDMA system using multiple spreading codes. An object of the present invention is to provide a data symbol detecting apparatus and method thereof, and a computer-readable recording medium having recorded thereon a program for realizing the method.

That is, according to the present invention, in detecting a data symbol at a receiving end of a DS / CDMA system using multiple spreading codes, a symbol sequence which is likely to be transmitted is generated as a sequence having the highest error probability from a reference sequence, and is transmitted nonlinearly. By using the characteristics and channel gain, we estimate the distortion sequence with the distortion caused during transmission and select the symbol sequence by evaluating the similarity with the received symbol sequence to reduce the performance degradation due to the nonlinear distortion and fading channel distortion. It is an object of the present invention to provide a data symbol detection apparatus which can be reduced, and a method thereof and a computer-readable recording medium having recorded thereon a program for realizing the method.

1 is a detailed block diagram of a general multi-code code division multiple access communication system having a conventional data symbol detection apparatus.

2 is a block diagram of an embodiment of a data symbol detection apparatus of a communication system according to the present invention;

3 is a flowchart of an embodiment of a data symbol detection method of a communication system according to the present invention;

4 is a block diagram of a general multi-code code division multiple access communication system equipped with a conventional data symbol detection apparatus.

Explanation of symbols on the main parts of the drawings

211: bit determination unit 212: sequence control unit

213: distortion estimator 214: gain weighting unit

The present invention for achieving the above object is a data symbol detection apparatus of a communication system, comprising: bit determining means for temporarily determining a reception symbol sequence transmitted from the outside; Generates a circular sequence from the reference sequence determined by the bit determining means, selects a new reference sequence by evaluating the similarity between the received symbol sequence and the weighted distortion sequence, and controls whether or not the sequence is output by comparing the old and new reference sequences. Sequence control means for performing; Distortion estimating means for estimating the distortion generated by the multicode and the nonlinear transfer characteristic by receiving the output signal of the sequence control means; And gain weighting means for calculating a sequence weight using the channel gain information transmitted from the distortion estimating means, and multiplying the calculated weight value by each symbol of the distortion sequence to output a multiplication value to the sequence control means. Characterized in that made.

In addition, the present invention provides a data symbol detection method applied to a data symbol detection apparatus of a communication system, wherein a received symbol sequence is input and original bit values of respective components of the received symbol sequence are received based on a predetermined threshold. A first step of evaluating similarity between the received symbol sequence and the weighted distortion sequence and selecting a new first reference sequence according to the evaluation result; Generate a circular sequence based on the first reference sequence, generate a distortion sequence for distortion estimation using multicode and nonlinear transfer characteristics, and calculate the channel gain using the measured path gain set to calculate the channel gain. Multiplying the distortion sequence by a value; A third step of evaluating the similarity between the received symbol sequence and the weighted distortion sequence and selecting a distortion sequence having a minimum distance according to an evaluation result and designating a circular sequence of the selected distortion sequence as a new second reference sequence; And a fourth step of outputting the first reference sequence according to whether the first and second reference sequences are the same.

In addition, the present invention, after receiving the received symbol sequence to the data symbol detection apparatus of a communication system having a processor, and determines the original bit value for each component of the received symbol sequence on the basis of a predetermined threshold, A first function of evaluating the similarity between the received symbol sequence and the weighted distortion sequence and selecting a new first reference sequence according to the evaluation result; Generate a circular sequence based on the first reference sequence, generate a distortion sequence for distortion estimation using multicode and nonlinear transfer characteristics, and calculate the channel gain using the measured path gain set to calculate the channel gain. A second function of multiplying a value and the distortion sequence; A third function of evaluating the similarity between the received symbol sequence and the weighted distortion sequence and selecting a distortion sequence having a minimum distance according to an evaluation result and designating a circular sequence of the selected distortion sequence as a new second reference sequence; And a computer-readable recording medium having recorded thereon a program for realizing a fourth function of outputting the first reference sequence, depending on whether the first and second reference sequences are the same.

The above objects, features and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a block diagram of an embodiment of a data symbol detection apparatus of a communication system according to the present invention.

As shown in FIG. 2, the data symbol detection apparatus of the present invention generates a circular sequence from a bit determining unit 211 that temporarily determines a reception symbol and a reference sequence transmitted through the bit determining unit 211. In addition, a new reference sequence is selected by evaluating the similarity between the received symbol sequence and the weighted distortion sequence, and the output signal of the sequence control unit 212 and the sequence control unit 212 for controlling whether or not the sequence is output through comparison between the old and new reference sequences. Using the distortion estimator 213 and the channel gain information transmitted from the distortion estimator 213 for estimating the distortion generated by the multicode and the nonlinear transfer characteristics, the weight of the sequence is calculated and the weight is calculated. A gain weighting unit 214 is provided for multiplying the value by each symbol of the distortion sequence and outputting the multiplication value to the sequence control unit 212.

Here, the bit determination unit 211 simultaneously performs the determination as the original bit value for each component of the received reception symbol sequence on the basis of a predetermined threshold value.

The sequence control unit 212 generates a circular sequence that differs from the reference sequence by only 1 bit, calculates a Euclidean distance between the received symbol sequence and the weighted distortion sequence, and calculates a circular sequence corresponding to the symbol sequence having the smallest result. The sequence is selected and the output of the sequence is determined by comparing the existing reference sequence with the new reference sequence.

Distortion estimator 213 is a multi-code spreader that spreads and modulates the circular sequence simultaneously with multi-codes, converts a multi-code signal in series, and outputs the multi-code spreader. A nonlinear processing unit having a nonlinear property and a plurality of spreading codes are used, and the multi-code despreading unit multiplies the signal sequence input from the multicode converting unit and each spreading code at the same time, accumulates each code, and outputs a demodulated symbol. do.

Incidentally, the " " mark between blocks in the drawing indicates that K symbols are transmitted in parallel.

The operation of the data symbol detection apparatus of the present invention having the above structure will be described in detail as follows.

First, referring to the terms generally used in the present invention, the output of the bit determination unit 211 which is a symbol sequence directly determined for the output of the RAKE demodulator and constituting the data symbol detector of the present invention is referred to as a reference sequence. The output of the RAKE coupling unit is called a reception symbol sequence, and the symbol sequence generated by the sequence control unit 212 constituting the data symbol detector of the present invention by a sequence different from the reference sequence by only one bit is called a circular sequence. The symbol sequence is a symbol sequence obtained by multiplying a nonlinear characteristic and a channel fading distortion component in a circular sequence, and performing a multicode spreading process, a nonlinear processing process, and a multimode despreading process. The output of the gain weighting unit 214 constituting the data symbol detector corresponds to a weighted distortion sequence. do. Here, the symbol sequence means a symbol sequence.

In addition, as provided by a separate channel estimator, this refers to the size of fading generated in the mobile radio channel, that is, the size of a received signal for a normalized transmission signal, and in the case of a multipath channel, a different size for each path. Since fading occurs, the presence of channel gains equal to the number of paths is referred to as channel gain, and a weight multiplied by the output of the distortion estimator 213 to consider channel fading as a result of the square of the channel gain. In other words, what is calculated in the gain weighting unit constituting the data symbol detector of the present invention is called a sequence weight.

The bit determining unit 211 temporarily determines the reception symbol sequence, that is, the output sequence of the rake coupler of FIG.

In order to facilitate signal processing according to the present invention, the bit corresponding to the logic value '0' is represented by '1', and the bit corresponding to the logic value '1' is represented by '-1'. Therefore, assuming that the symbol sequence input to the bit determining unit 211 is the reception sequence " z_1, z_2,..., Z_k ~~~~ (= Z) ", the channel sequence a_k and the Q channel component b_k The composed symbol is expressed as in Equation 3 below.

z_k = a_k + jb_k k = 1, ..., K

Here, the symbol z_k is determined to be '1' when larger than '0' for each component and '-1' when smaller than '0'. The symbol sequence determined in this manner, that is, the reference sequence, is transmitted to the sequence controller 212.

The sequence control unit 212 generates a circular sequence from the reference sequence, calculates an Euclidean distance between the 2K weighted distortion sequence input from the gain weighting unit 214 and the received symbol sequence, respectively, and has the smallest value. A weighted distortion sequence is selected, and a new reference sequence is determined by comparing whether the circular sequence corresponding to that before the distortion estimation of the selected sequence is identical to the reference sequence.

The circular sequence generation function, on the other hand, creates a sequence that is different from the reference sequence by only one bit, that is, a circular sequence. For example, the expression method is changed by the process of generating the circular sequence.

That is, the k-th symbol of the reference sequence is expressed by Equation 4 below.

r_k = r_i, k + jr_q, k

Here, if the reference sequence can be expressed as a vector "R = [r_1, i, r_1, q, r_2, i, r_2, q, ...., r_k, i, r_k, q]", the first element A vector having only a different value is expressed as "S (1) = [s_1, i, r_1, q, r_2, i, r_2, q, ...., r_k, i, r_k, q]".

Since all elements have a value of '1' or '-1', the elements s_1, i have values opposite to the elements r_1, i.

In the case of the vector S (2), only the second element of the vector R has a different value.

Therefore, there are 2K vectors different from the reference sequence by only one bit, and the sequence controller 212 generates 2K, i.e., a circular sequence, and sequentially outputs them to the distortion estimator 213.

The calculation and selection process of the sequence control unit 212 consists of evaluating how similar the 2K distortion sequences transmitted from the gain weighting unit 214 and the received symbol sequence, that is, the similarity between the sequences, are as follows.

If the input distortion sequence is " U_i (= u_1 ^ i, u_2 ^ i ..., u_k ^ i) &quot;, the Euclidean distance between this and the received symbol sequence is calculated as D_i = vert U_i -Z vert ^ 2. If you change this to the distance between symbols Is calculated.

The sequence controller 212 calculates the input 2K distortion sequences as described above and selects a distortion sequence having the smallest D value among them.

Subsequently, the sequence control unit 212 compares the circular sequence of the selected sequence with the reference sequence. If not, the sequence control unit 212 designates the selected circular sequence as a new reference sequence and repeats the above-described circular sequence generation process.

If the comparison result is the same, the already designated reference sequence is output and all memories of the sequence controller are initialized.

The distortion estimator 213 spreads and modulates the circular sequence simultaneously with multicode, converts a multicode signal in series, and outputs the multicode spreader, and a different form according to the size of an input signal input through the multicode spreader. Multi-code despreading using a non-linear processing unit and a plurality of spreading codes, which multiply the multi-code signal sequence inputted from the multi-code spreading unit and each spreading code at the same time, accumulate each code, and output a demodulated symbol. In this case, the nonlinear processing unit of the distortion estimator 213 has the same transmission characteristics as that of the nonlinear processing unit used in the transmitter of FIG. 1, and the description thereof will be replaced with the description of FIG. 1.

The multicode spreader and the multicode despreader of the distortion estimator 213 use the same spreading code as that used in the rake combining section of FIG.

Assume that the circular sequence is "S = [s_1, s_2, ..., s_k]".

If the kth spreading code of length N is "C_k = [c_1, ^ (k), c_2 ^ (k), ..., s_N ^ (k)]", then the spreading code set is represented by Equation 5 ]

Therefore, the circular sequence S input from the sequence control unit 212 is spread-modulated at the same time in the multi-code spreading unit by X = S · C by the code set C composed of K spreading codes. Where "X = [X_1, X_2, ..., X_N]" is spread through modulation As a signal formed as follows, the multi-code spreader sequentially outputs each of them.

The nonlinear processing unit processes the multicode signal input from the multicode spreader through its transfer characteristic and transmits the multicode signal to the multicode despreader.

In this case, the multicode despreader performs an inverse process processed by the multicode spreader, and the multicode despreader multiplies the k-th spreading code by each bit for N multicode signals input from the nonlinear processing unit. In addition, the multi-code despreader accumulates all of these to restore the k-th symbol, and the above process by the remaining spreading codes is performed for other symbols.

Accordingly, the multicode despreader simultaneously performs the above-described process and outputs the reconstructed symbol sequence, that is, the distortion sequence.

Through this process, since the distortion of the multicode signal due to the transmission characteristic of the nonlinear processing unit can be reproduced, the distortion estimation unit 213 enables accurate estimation of the distortion caused by the nonlinear processing unit of the transmitting end to the transmission symbol sequence. .

The gain weighting unit 214 is a process of multiplying the channel gain used in the reversibility combining unit of the receiver to consider distortion due to the radio channel. A channel gain estimated once every T_s is given from a channel estimator separately available for a receiver, and the gain weighting unit 214 multiplies the channel gain with respect to the distortion sequence transferred from the distortion estimator 213 and distorts the distortion. The value of channel gain for the sequence is determined by the number of multicode despreaders in the rake joint.

That is, "g_1, g_2, ..., g_L" is the channel gain of each path estimated by the channel estimator, and the sum of their squares corresponds to the symbol energy.

Thus, the gain weighting unit 214 The channel gain calculated as follows is multiplied by each symbol of the distortion sequence to produce a distortion sequence having a gain, which is transmitted to the sequence controller 212.

3 is a flowchart illustrating an embodiment of a data symbol detection method of a communication system according to the present invention.

As shown in FIG. 3, in the data symbol detection method for a multicode DS / CDMA communication system, a received symbol sequence Z is received from a rake demodulator in order to recover a transmitted symbol first (301). The symbol sequence inputted to the detector is determined by the bit determiner 211 as '1' or '-1', respectively, and this determination is made for each component of every symbol and given a threshold for the determination, and is determined temporarily. The specified sequence is designated as the reference sequence R (302).

After generating a circular sequence (303), which is assumed to have been transmitted using the generated reference sequence as a seed, the distortion is configured using multicode and nonlinear transfer characteristics, and the distortion shown in the symbol sequence is generated. 304. In this case, the channel gain is multiplied to consider the channel distortion (305).

The Euclidean distance (D) is calculated to evaluate the similarity between the input received symbol sequence and the output sequence multiplied in the multiplication process (305). Here, 2K distance values are calculated.

Next, a distortion sequence having the smallest value D among them is selected and its circular sequence is designated as the new reference sequence R _s (307).

The reference sequence R_s having the minimum reference sequence R and D is compared with each other (308). If the reference sequence R_s is the same, the reference sequence R is output (309), and then the reception symbol is detected to detect the next received symbol sequence. Repeated from the sequence input process (301). At this time, the symbols of the reference sequence are output in series.

If the comparison result is not the same in the comparison process 308, it repeats from the circular sequence generation process (303).

Through the process as described above, it is possible to improve the determination error due to bit determination, and also significantly reduce the number of prototype sequences used for similarity evaluation in the symbol detection process.

That is, it is a symbol sequence used for evaluating the similarity with the received symbol sequence, and it is possible to improve the accuracy of symbol detection in consideration of the nonlinear input / output response characteristics and the channel fading characteristics of the power amplifier which is the source of distortion, and also to all symbol sequences that can be transmitted. By evaluating the similarity sequentially from the most probable symbol sequence to the lowest symbol sequence, the optimal symbol sequence can be detected before the comparison of all transmittable symbol sequences. Even for spreading codes that are increased for services, real-time processing can be performed without requiring exponentially increasing number of symbol sequences and computational complexity.

For example, if the number of multicodes K is 4, the general detection method should generate and process 2 ^ 2K circular sequences, but in the case of using the present invention, it is possible to generate only 2KN_r (N_r &lt; 32). .

In fact, N_r is less than or equal to '10'. The result is that the circular sequence generation process shown in the present invention is generated in order from the symbol sequence with the largest error occurrence.

This can be seen from the fact that the probability that one symbol sequence is changed to another symbol sequence is the largest in one case and the smallest in all other cases.

The method of the present invention as described above may be implemented as a program and stored in a computer-readable recording medium (CD-ROM, RAM, ROM, floppy disk, hard disk, magneto-optical disk, etc.).

Although the technical idea of the present invention has been described in detail according to the above preferred embodiment, it should be noted that the above-described embodiment is for the purpose of description and not of limitation. In addition, those skilled in the art will understand that various embodiments are possible within the scope of the technical idea of the present invention.

As described above, the present invention estimates a distortion sequence having distortion caused during transmission by using multicode, nonlinear transfer characteristics, and channel gain, and selects a symbol sequence by evaluating similarity with a received symbol sequence. In the case of distortion and channel distortion due to propagation characteristics, it is possible to improve the performance of a multicode DS / CDMA communication system by reducing an error of a received symbol, and to generate and process a circular sequence with the highest error probability first. This can significantly reduce the number of sequences and the complexity of computation.

That is, the present invention can improve the accuracy of symbol detection by considering the nonlinear input / output response characteristics and the channel fading characteristics of a power amplifier which is a source of distortion as a symbol sequence used for evaluating the similarity with a received symbol sequence. Rather than evaluating all symbol sequences, the similarity is evaluated sequentially from the most probable symbol sequence to the lowest one, so that the optimal symbol sequence can be detected before comparing and evaluating all transmittable symbol sequences. Spreading codes that are increased for high data rate services can be processed in real time without requiring exponentially increasing symbol sequence numbers and computational complexity.

Claims (8)

An apparatus for detecting data symbols in a communication system, Bit determining means for temporarily determining a reception symbol sequence transmitted from the outside; Generates a circular sequence from the reference sequence determined by the bit determining means, selects a new reference sequence by evaluating the similarity between the received symbol sequence and the weighted distortion sequence, and controls whether or not the sequence is output by comparing the old and new reference sequences. Sequence control means for performing; Distortion estimating means for estimating the distortion generated by the multicode and the nonlinear transfer characteristic by receiving the output signal of the sequence control means; And Gain weighting means for calculating a sequence weight using the channel gain information transmitted from the distortion estimating means, multiplying the calculated weight value by each symbol of the distortion sequence and outputting a multiplication value to the sequence control means; Apparatus for detecting data symbols in a communication system comprising a. The method of claim 1, The bit determining means, And determining the original bit value for each component of the received symbol sequence on the basis of a predetermined threshold value simultaneously. The method according to claim 1 or 2, The sequence control means, Generate a circular sequence with a different number of bits from the reference sequence, calculate the Euclidean distance between the received symbol sequence and the weighted distortion sequence, and select the new one as the new reference sequence. And determining whether to output the sequence by comparing the sequence with the new reference sequence. The method of claim 3, wherein The distortion estimating means, A multicode spreader for spreading and modulating the circular sequence simultaneously with multicode and converting a multicode signal in series, and a nonlinear processing unit having different nonlinear properties according to the magnitude of an input signal input through the multicode spreader. And a multicode despreader that uses a plurality of spreading codes, multiplies the multicode signal sequence inputted from the multicode spreader and each spreading code at the same time, accumulates each code, and outputs a demodulated symbol. Apparatus for detecting data symbols in communication systems. A data symbol detection method applied to a data symbol detection apparatus of a communication system, After receiving the received symbol sequence and determining the original bit value for each component of the received symbol sequence on the basis of a predetermined threshold value, the similarity between the received symbol sequence and the weighted distortion sequence is evaluated and a new value is generated according to the evaluation result. 1 step of selecting a reference sequence; Generate a circular sequence based on the first reference sequence, generate a distortion sequence for distortion estimation using multicode and nonlinear transfer characteristics, and calculate the channel gain using the measured path gain set to calculate the channel gain. Multiplying the distortion sequence by a value; A third step of evaluating the similarity between the received symbol sequence and the weighted distortion sequence and selecting a distortion sequence having a minimum distance according to an evaluation result and designating a circular sequence of the selected distortion sequence as a new second reference sequence; And A fourth step of outputting the first reference sequence according to whether the first and second reference sequences are the same Data symbol detection method of a communication system comprising a. The method of claim 5, The first step is, A fifth step of receiving the received symbol sequence; A sixth step of determining an original bit value for each component of the received symbol sequence based on the predetermined threshold value; And A seventh step of selecting a new first reference sequence according to an evaluation result by evaluating the similarity between the received symbol sequence and the weighted distortion sequence; Data symbol detection method of a communication system comprising a. The method according to claim 5 or 6, The fourth step, An eighth step of comparing whether the first and second reference sequences are identical; A ninth step of outputting the first reference sequence if the first and second reference sequences are the same as a result of the comparison in the eighth step; And A tenth step of proceeding to the second step if the first and second reference sequences are not identical as a result of the comparison of the eighth step Data symbol detection method of a communication system comprising a. In the data symbol detection apparatus of a communication system having a processor, After receiving the received symbol sequence and determining the original bit value for each component of the received symbol sequence on the basis of a predetermined threshold value, the similarity between the received symbol sequence and the weighted distortion sequence is evaluated and a new value is generated according to the evaluation result. A first function of selecting one reference sequence; Generate a circular sequence based on the first reference sequence, generate a distortion sequence for distortion estimation using multicode and nonlinear transfer characteristics, and calculate the channel gain using the measured path gain set to calculate the channel gain. A second function of multiplying a value and the distortion sequence; A third function of evaluating the similarity between the received symbol sequence and the weighted distortion sequence and selecting a distortion sequence having a minimum distance according to an evaluation result and designating a circular sequence of the selected distortion sequence as a new second reference sequence; And A fourth function of outputting the first reference sequence according to whether the first and second reference sequences are the same A computer-readable recording medium having recorded thereon a program for realizing this.