KR20010060970A - Symbol decoding device and method for use in a mobile telecommunication system - Google Patents

Abstract

PURPOSE: An apparatus and method for demodulating symbols in a mobile communication system is provided to enhance the performance of symbol demodulation. CONSTITUTION: A PN code despreader despreads I-arm received signals and Q-arm received signals and outputs the PN-despread I-arm and Q-arm signals. A user data orthogonal code accumulator(140) accumulates the I-arm PN-despread signals as much as the length of a user data orthogonal code and outputs I-arm user data symbols. A user data orthogonal code accumulator(150) accumulates the Q-arm PN-despread signals as much as the length of the user data orthogonal code and outputs Q-arm user data symbols. A buffer(180) buffers the I-arm user data symbols as much as a preset length. A buffer(190) buffers the Q-arm user data symbols as much as a preset length. A pilot orthogonal accumulator(120) accumulates the I-arm PN-despread signals as much as the length of a pilot orthogonal code and outputs I-arm pilot symbols. A pilot orthogonal accumulator(150) accumulates the Q-arm PN-despread signals as much as the length of the pilot orthogonal code and outputs Q-arm pilot symbols. A channel predictor(160) accumulates the I-arm pilot symbols of the previous section, the current section and the next section equal to the preset length and outputs an I-arm channel prediction value. A channel predictor(170) accumulates the Q-arm pilot symbols of the previous section, the current section and the next section equal to the preset length and outputs a Q-arm channel prediction value. A channel compensator(200) compensates the I-arm and Q-arm user data symbols buffered at the buffers(180,190) for the longest time according to the obtained channel prediction values and outputs the channel-compensated user data symbols.

Description

Symbol demodulation device and method in mobile communication system {SYMBOL DECODING DEVICE AND METHOD FOR USE IN A MOBILE TELECOMMUNICATION SYSTEM}

The present invention relates to an apparatus and method for symbol demodulation in a mobile communication system, and more particularly, to an apparatus and method for performing data symbol demodulation by compensating data symbols for demodulation using pilot channel symbols.

In general, in order to enable coherent symbol demodulation in a mobile communication channel environment, a transmitter transmits reference phase channel symbols simultaneously in addition to a channel carrying data symbol signals. The receiver performs data symbol demodulation by compensating for the data symbol signal channel by predicting the environment of the channel through which the data symbol signal is transmitted using the reference phase channel symbol. For example, in a mobile communication system of Code Division Multiple Access (hereinafter referred to as "CDMA"), the reference phase channel is called a pilot channel. At the receiving end of the CDMA mobile communication system, a channel predictor for predicting the pilot channel is provided. The channel predictor includes an Infinite Impulse Response (IIR) filter or a Finite Impulse Response (FIR) filter. It can be implemented as.

On the other hand, in recent years, a lot of research for the IMT (Internation Mobile Telecommunication) -2000 service has been actively conducted. In the mobile communication system for the IMT-2000 service, a common pilot channel used in the existing IS-95A (Common Pilot Channel) In addition, the auxiliary pilot channel may be transmitted simultaneously. In this case, it is preferable to use an FIR filter as a channel predictor to maintain orthogonality of two channels, where the minimum cumulative number of symbols of the FIR filter depends on the number of maximum auxiliary pilot channels that can be generated. For example, if the minimum number of symbols that can be accumulated is 4 symbols (128 chips per symbol), the symbol values on the pilot channel accumulated and predicted during 4 symbols are compensated for the current symbol. It should be noted that the accurate prediction time of the channel predictor is the time of accumulating 2 symbols based on the 4 symbol cumulative channel predictor. Therefore, when only 4 symbols are accumulated and the current symbol is compensated, a delay of about 2 symbols is generated, which may result in somewhat inaccurate channel prediction. That is, the performance of symbol demodulation may be degraded.

Accordingly, an object of the present invention is to provide an apparatus and method for symbol demodulation in a mobile communication system for improving the performance of symbol demodulation.

Another object of the present invention is to provide an apparatus and method for demodulating symbols in a mobile communication system for demodulating symbols through accurate channel prediction.

A symbol demodulation apparatus of a mobile communication system according to the present invention for achieving these objects comprises: a data symbol buffer for buffering user data symbols; A channel predictor for accumulating pilot channel symbols for a minimum number of accumulators and outputting channel pilot values for predicting an environment of a channel to which user data symbols are transmitted; And a channel compensator for outputting a channel compensated user data symbol by compensating a symbol buffered for the longest time in the data symbol buffer according to the channel prediction value.

The channel predictor; A pilot channel symbol buffer for buffering pilot channel symbols corresponding to two previous, current and next sections of the user data symbol for channel compensation, an accumulator for accumulating pilot channel symbols stored in the pilot channel symbol buffer, And a gain controller that multiplies the average value of the pilot channel symbols accumulated by the accumulator by a specific gain value and outputs the channel predicted value. Such a channel predictor may be implemented with a finite field impulse response (FIR) filter.

The channel compensator; A multiplier for multiplying the longest buffered symbol in the data symbol buffer according to the channel prediction value to output a channel compensated user data symbol.

The data symbol buffer may buffer user data symbols corresponding to a length of a user orthogonal code, or buffer user data symbols corresponding to one-half of the minimum cumulative number of symbols.

In addition, the symbol demodulation device of the mobile communication system according to the present invention comprises: a despreader for despreading the P-I code of I-arm and Q-arm received signals; An I-arm and Q-arm data symbol buffer for buffering the PN despread I-arm and Q-arm user data symbols by a predetermined length, respectively; I-arm and Q-arm channels for predicting the environment of the channel through which the user data symbols are transmitted by accumulating PN despread I-arm and Q-arm pilot channel symbols of the previous section, the current section, and the next section by the set length, respectively. An I-arm and Q-arm channel predictor for outputting the predicted value; And a channel compensator for outputting channel compensated user data symbols by compensating the I-arm and Q-arm symbols buffered for the longest time in each data symbol buffer according to the channel prediction values.

Each channel predictor; A pilot channel symbol buffer for buffering pilot channel symbols in a previous section, a current section and a next section by the set length, an accumulator accumulating pilot channel symbols stored in the pilot channel symbol buffer, and a pilot channel accumulated by the accumulator And a gain controller that multiplies the average value of symbols by a specific gain value and outputs the channel prediction value. Each such channel predictor is implemented with a finite field impulse response (FIR) filter.

The channel compensator is implemented as a multiplier for complexly multiplying the I-arm and Q-arm symbols buffered for the longest time in the data symbol buffer according to the channel prediction value to output a channel compensated user data symbol.

The symbol demodulation device includes an I-arm and Q-arm pilot accumulator that accumulates the PN despread I-arm and Q-arm signal by a pilot orthogonal code length and outputs I-arm and Q-arm pilot symbols in symbol units, and the PN And an I-arm and Q-arm data accumulator for accumulating the despread I-arm and Q-arm signals by the length of the user data orthogonal code and outputting the I-arm and Q-arm user data symbols in symbol units.

1 is a view showing the configuration of a symbol demodulation device according to the present invention.

2 is a view showing in detail the configuration of the channel predictor shown in FIG.

DETAILED DESCRIPTION A detailed description of preferred embodiments of the present invention will now be described with reference to the accompanying drawings. It should be noted that reference numerals and like elements among the drawings are denoted by the same reference numerals and symbols as much as possible even though they are shown in different drawings. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

The symbol demodulation apparatus according to the present invention must first obtain user data symbols accumulated by a user orthogonal code length and channel prediction values for the symbols in order to more accurately compensate the channel for the user data symbols. A Walsh code may be used as the user orthogonal code. The channel prediction value is obtained after a specific number of pilot symbols are received from the time point at which the user data symbol to be compensated is received. This is because if the channel prediction value is obtained using both pilot symbols received in the previous section and pilot symbols to be further received in the current section and the next section, more accurate channel compensation can be performed for the user data symbols. That is, the symbol demodulation apparatus according to the present invention uses the pilot symbols received in the previous section and the pilot symbols to be received in the current section and the next section to compensate for the channel for one user data symbol currently received. Obtain In this case, the number of pilot symbols used to obtain a channel prediction value is determined by the minimum number of symbols that can be accumulated. Therefore, it is necessary to store user data symbols until channel prediction values for channel compensation are obtained, and then output and channel compensation when the channel prediction values are obtained. For this purpose, symbols of user data are stored in a buffer that can be implemented as a first-in first-out (FIFO).

For example, the minimum cumulative number of symbols is 4, the currently received user data symbol is UDS1, the pilot symbol is PS1, the next pilot symbol to be received is PS2, the previously received pilot symbol is PS-1, Assuming that the previously received pilot symbol is PS-2, the channel prediction value for channel compensation for the user data symbol UDS1 includes the pilot symbols PS-2 and PS-1 received in the previous two symbol intervals, and It is obtained using the pilot symbol PS1 received in the symbol period and the pilot symbol PS2 to be received in the next symbol period.

1 is a view showing the configuration of a symbol demodulation device according to the present invention.

Referring to FIG. 1, the symbol demodulation device according to the present invention includes elements 140, 150, 180, and 190 for processing a received user data symbol, and a channel compensator 200 for compensating a channel for the user data symbol. Components 120,130, 10,170 that provide channel prediction values for the channel compensation operation of the compensator 200. Here, an example will be described in which the symbol demodulation apparatus according to the present invention outputs channel compensated user data demodulation symbols by channel compensating I arm and Q arm user data symbols.

In FIG. 1, the pseudo noise (PN) code despreader 110 despreads the I-arm received signal and the Q-arm received signal according to the PN code, and outputs the PN despread I-arm signal and the Q-arm signal. The PN code despreader 110 may be implemented as a multiplier that multiplies the received signal by the PN code.

The user data orthogonal code accumulator 140 accumulates the I-arm PN despread signal by the length of the user data orthogonal code, and outputs an I-arm user data symbol. The user data quadrature accumulator 150 accumulates the Q-arm PN despread signal by the length of the user data orthogonal code, and outputs a Q-arm user data symbol.

The buffer 180 buffers the I-arm user data symbols by a preset length. The buffer 190 buffers the Q-arm user data symbols by a preset length. Herein, the preset length may be determined as 1/2 of the minimum number of cumulable symbols or as long as the length of the user data orthogonal code. For example, in the case where the set length is determined to be 1/2 of the minimum cumulative number of symbols, the buffers are assumed to be 4 symbols (when the length of the orthogonal code per symbol is 128 chips). 180, 190 buffers two user data symbols. At this time, if the length of orthogonal code per symbol is reduced, the size of the buffer should be increased by the inverse. For example, if the length of an orthogonal code per symbol is 64 chips, the buffers 180 and 190 should be able to store 4 symbol user data symbols.

The pilot orthogonal code accumulator 120 accumulates the I-arm PN despread signal by a pilot orthogonal code length and outputs an I-arm pilot symbol. The pilot quadrature accumulator 150 accumulates the Q-arm PN despread signal by a pilot orthogonal code length and outputs a Q-arm pilot symbol.

The channel predictor 160 accumulates the previous section I-arm pilot symbols by the set length and the I-arm pilot symbols of the current section and the next section by the set length to predict an environment of a channel on which the I-arm user data symbol is transmitted. It outputs the I-arm channel prediction value. The channel predictor 170 accumulates the previous period Q-arm pilot symbols by the set length and the Q-arm pilot symbols of the current period and the next period by the set length to predict an environment of a channel on which the Q-arm user data symbol is transmitted. It outputs the Q-arm channel prediction value for. Each of these channel predictors 160 and 170 includes a buffer 162, a pilot symbol accumulator 164, and a gain controller 166 as shown in FIG.

The channel compensator 200 compensates the longest buffered I-arm and Q-arm user data symbols in the buffers 180 and 190 according to channel prediction values obtained by the channel predictors 160 and 170, respectively, and outputs channel compensated user data symbols. The channel compensator 200 complex-multiplies the I-arm and Q-arm symbols buffered for the longest time in the buffers 180 and 190 according to channel prediction values obtained by the channel predictors 160 and 170, respectively, and outputs channel compensated user data symbols. It can be implemented as multipliers.

FIG. 2 is a diagram illustrating a configuration of channel predictors 160 and 170 illustrated in FIG. 1. Here, the case of the channel predictor 160 will be described as an example, but the operation of the channel predictor 170 is the same.

Referring to FIG. 2, the buffer 162 stores the I-arm pilot symbols of the previous section by a preset length (half of the minimum number of cumulative minimum symbols) output from the pilot orthogonal code accumulator 120 and the set length. Sequentially buffer the I-arm pilot symbols in the current section and the I-arm pilot symbols in the next section. Pilot symbol accumulator 164 accumulates I-arm pilot channel symbols stored in the buffer 162. The gain controller 166 multiplies the average value of the I-arm pilot channel symbols accumulated by the accumulator 164 by a specific gain value and outputs the I-arm channel prediction value. The channel predictor 160 may be implemented as a finite impulse response (FIR) filter.

As described above, the symbol demodulation apparatus according to the present invention first obtains an output value of the channel predictor in a state in which the pilot symbol and the symbol to be demodulated are buffered, respectively. This channel prediction value is obtained by accumulating all the values of the buffers storing the pilot symbols and multiplying the averaged value by a constant gain. The symbol demodulation is performed by performing a channel compensation by complex multiplying the channel prediction value and the value stored in the buffer of the FIFO structure for the longest time accumulated by the length of the user orthogonal code. The update period of the channel prediction value is in a pilot symbol unit, and the symbol to be demodulated may be output in a shorter period than the pilot symbol unit. In this case, the channel prediction value may still use the channel prediction value in the previously output pilot symbol unit.

As described above, the present invention provides a buffer and a user data symbol for storing pilot channel symbols in order to resolve a mismatch between a user data symbol for channel compensation and an accurate prediction time of a channel predictor in symbol demodulation operation of a mobile communication system. A buffer for storing is provided prior to channel compensation.

Accordingly, the present invention has an advantage of enabling channel compensation of user data symbols at an accurate prediction time point, and also has an advantage of improving symbol demodulation performance.

Claims (22)

In the symbol demodulation device of the mobile communication system, A data symbol buffer for buffering user data symbols, A channel predictor for accumulating pilot channel symbols for the minimum number of accumulators and outputting channel pilot values for predicting an environment of a channel to which user data symbols are transmitted; And a channel compensator for outputting channel compensated user data symbols by compensating for the longest buffered symbol in the data symbol buffer according to the channel prediction value. The channel predictor of claim 1, A pilot channel symbol buffer buffering pilot channel symbols corresponding to the previous two sections, the current section, and the next section for the user data symbol for channel compensation; An accumulator for accumulating pilot channel symbols stored in the pilot channel symbol buffer; And a gain controller multiplying an average value of the pilot channel symbols accumulated by the accumulator by a specific gain value and outputting the channel predicted value. The symbol demodulation device of claim 2, wherein the channel predictor is implemented by a finite length pulse response (FIR) filter. The symbol demodulation device of claim 1, wherein the channel compensator is implemented as a multiplier for multiplying the longest buffered symbol in the data symbol buffer according to the channel prediction value and outputting a channel compensated user data symbol. The symbol demodulation device of claim 1, wherein the data symbol buffer buffers user data symbols equal to a length of a user orthogonal code. The symbol demodulation device of claim 1, wherein the data symbol buffer buffers user data symbols corresponding to one half of the minimum cumulative number of symbols. In the symbol demodulation device of the mobile communication system, A despreader for despreading the P-I and P-arm signals; An I-arm and Q-arm data symbol buffer for buffering PN despread I-arm and Q-arm user data symbols by a predetermined length, respectively; I-arm and Q-arm channels for predicting the environment of the channel through which the user data symbols are transmitted by accumulating PN despread I-arm and Q-arm pilot channel symbols of the previous section, the current section, and the next section by the set length, respectively. I-arm and Q-arm channel predictors for outputting prediction values, And a channel compensator for outputting channel compensated user data symbols by compensating the I-arm and Q-arm symbols buffered for the longest time in each data symbol buffer according to the channel prediction values. The method of claim 7, wherein each channel predictor, A pilot channel symbol buffer for buffering pilot channel symbols of a previous section, a current section, and a next section by the set length; An accumulator for accumulating pilot channel symbols stored in the pilot channel symbol buffer; And a gain controller multiplying an average value of pilot channel symbols accumulated by the accumulator by a specific gain value and outputting the channel predicted value. 9. The symbol demodulation apparatus of claim 8, wherein each channel predictor is implemented by a finite field impulse response (FIR) filter. 8. The channel compensator of claim 7, wherein the channel compensator is implemented with multipliers that complex-multiply the I-arm and Q-arm symbols buffered for the longest time in the data symbol buffer according to the channel prediction value and output the channel compensated user data symbol. Symbol demodulation device. 10. The method of claim 7, further comprising I-arm and Q-arm pilot accumulators that accumulate the PN despread I-arm and Q-arm signals by a pilot orthogonal code length to output I-arm and Q-arm pilot symbols in symbol units. Symbol demodulation device characterized in that. 8. The method of claim 7, further comprising accumulating the I-arm and Q-arm data accumulators for accumulating the PN despread I-arm and Q-arm signals by user data orthogonal code lengths and outputting I-arm and Q-arm user data symbols in symbol units. Symbol demodulation device comprising a. A symbol demodulation method in a mobile communication system having a pilot channel and a user data channel, (A) buffering user data symbols in a data symbol buffer, (B) accumulating pilot channel symbols for the minimum number of symbols that can be accumulated and outputting channel prediction values for predicting an environment of a channel to which user data symbols are transmitted; And (c) outputting a channel compensated user data symbol by compensating for the longest buffered symbol in the data symbol buffer according to the channel prediction value. The method of claim 13, wherein (b) is, Buffering pilot channel symbols corresponding to the previous two sections, the current section, and the next section of the user data symbol for channel compensation in a pilot channel symbol buffer; Accumulating pilot channel symbols stored in the pilot channel symbol buffer; And multiplying an average value of the accumulated pilot channel symbols by a specific gain value to output the channel prediction value. 15. The symbol demodulation method of claim 14, wherein the step (c) multiplies the longest buffered symbol in the data symbol buffer according to the channel prediction value to output a channel compensated user data symbol. 15. The method of claim 14, wherein in the step (a), buffering user data symbols equal to a length of a user orthogonal code is buffered. 15. The method of claim 14, wherein in step (a), buffering user data symbols corresponding to one half of the minimum cumulative number of symbols is buffered. A symbol demodulation method in a mobile communication system having a pilot channel and a user data channel, (A) the process of despreading the PN code of the I-arm and Q-arm received signals; (B) buffering the PN despread I-arm and Q-arm user data symbols into user data symbol buffers of a predetermined length, respectively; I-arm and Q-arm channels for predicting the environment of the channel through which the user data symbols are transmitted by accumulating PN despread I-arm and Q-arm pilot channel symbols of the previous section, the current section, and the next section by the set length, respectively. (C) outputting the predicted value, And (d) outputting channel compensated user data symbols by compensating the I-arm and Q-arm symbols buffered for the longest time in each data symbol buffer according to the channel prediction values. The method of claim 18, wherein (c) is, Buffering pilot channel symbols of a previous section, a current section, and a next section by the set length; Accumulating pilot channel symbols stored in the pilot channel symbol buffer; And multiplying an average value of the pilot channel symbols accumulated by the accumulator by a specific gain and outputting the channel predicted value. 19. The method of claim 18, wherein in step (d), the I-arm and Q-arm symbols buffered for the longest time in the data symbol buffers are complex-multiplied according to the channel prediction value to output a channel compensated user data symbol. Symbol demodulation method. 19. The symbol demodulation method of claim 18, further comprising accumulating the PN despread I-arm and Q-arm signals by a pilot orthogonal code length and outputting I-arm and Q-arm pilot symbols in symbol units. . 19. The symbol of claim 18, further comprising accumulating the PN despread I-arm and Q-arm signals by the length of the user data orthogonal code and outputting the I-arm and Q-arm user data symbols in symbol units. Demodulation method.