KR100334787B1 - Apparatus and method for combining symbol data in cdma communication system - Google Patents

Abstract

In a method for combining symbols received through a multipath in a code division multiple access communication system, extracting symbol data by despreading a signal received through a plurality of paths, and extracting a pilot signal to the symbol data Generating channel compensated symbol data by multiplying the channel compensation signal generated from the plurality of channel compensation signals, calculating energy of the channel compensated symbol data corresponding to the plurality of paths, and exceeding a reference energy value among the calculated energy values. An energy determiner for outputting symbol data, a valid path selector for outputting remaining symbol data except for symbol data having a different sign based on a code occupying a large number of symbol data from the energy determiner, and the valid path selector Including a channel combiner for accumulating and combining symbol data from And a gong.

Description

Apparatus and method for combining symbol data in code division multiple access communication system {APPARATUS AND METHOD FOR COMBINING SYMBOL DATA IN CDMA COMMUNICATION SYSTEM}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for combining symbol data in a code allocation access communication system, and more particularly, to an apparatus and method for combining symbol data by removing a fading component.

In general, in a code division multiple access (CDMA) communication system, a data signal d (t) transmitted from a base station is first divided into even (even) and odd (odd) through a 1: 2 demultiplexer (DEMUX). Divided into I, Q signals. The orthogonal codes corresponding to the I and Q signals are multiplied and spread modulated, and a pilot signal is added to only the I signal to be complex-noise spread. The signal is passed through a filter and then upconverted in frequency, and the transmitted signal is received by the terminal receiver through a padding channel. Therefore, the signal received by the terminal is represented by Equation 1 below.

Where "P" is a pilot signal, W ₀ is an orthogonal code corresponding to the pilot channel, W _d is a orthogonal code predetermined for orthogonal modulation, and PN (I) and PN (Q) are for orthogonal spreading. Represents an orthogonal code. On the other hand, (f (I) + jf (Q)) is a fading component. Therefore, the terminal must demodulate the symbol data having the maximum energy by combining signals of multipath to obtain the maximum energy. This ensures that the decode is guaranteed at the decoder. Previously, the maximum ratio combining method (ubg) is known as a combining method that can achieve maximum performance. The maximum ratio combining method is a method of multiplying received symbol data by a fading component to perform channel compensation, and combining only symbol data that exceeds a required energy among the channel compensated symbol data.

However, in the maximum ratio combining method, fading components are removed when the phases of the two components are the same in the process of multiplying the received symbol data by fading components, but otherwise, the fading components are not completely removed. To date, accurate phases cannot be compensated for. Therefore, symbol combining is performed in the presence of fading components. In this process, even the severely fading components are combined to reduce the symbol energy, making the meaning of symbol combining to obtain maximum energy uncolored.

Accordingly, an object of the present invention is to provide a symbol combining apparatus and method for combining symbol data by removing a fading component from a terminal in a code division multiple access communication system.

Another object of the present invention is to provide a symbol combining apparatus and method for selectively combining symbol data of each multipath component in a code division multiple access communication system to combine symbol data at a maximum ratio.

It is still another object of the present invention to provide a method for a path having symbol data whose sign is inverted due to severe fading, even if any symbol data received in a mobile communication system is determined to be sufficient energy to be combined with a symbol due to a conventional reception energy measurement problem. The present invention provides a symbol combining apparatus and method for excluding signals from symbol combining.

In order to achieve the above objects, a method of combining symbols received through a multipath in a code division multiple access communication system includes extracting symbol data by despreading a signal received through a plurality of paths, and piloting the symbol data. Multiplying the channel compensation signal generated from the signal to generate channel compensated symbol data, calculating energy of the channel compensated symbol data corresponding to the plurality of paths, and calculating a reference energy value among the calculated energy values. An energy determiner for outputting more than one symbol data, a valid path selector for outputting remaining symbol data except for symbol data having a different sign based on a code occupying a large number of symbol data from the energy determiner, and the valid path A channel combiner for accumulating and combining symbol data from the selector; The features.

1 is a diagram illustrating a terminal receiver structure of a code division multiple access communication system according to an embodiment of the present invention.

FIG. 2 is a diagram showing the configuration of a combiner for selective maximum rate symbol data combining in FIG. 1; FIG.

3 is a diagram illustrating a symbol combining process of the symbol combiner of FIG.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. First, in adding the reference numerals to the components of each drawing, the same components have the same reference numerals as much as possible even if displayed on different drawings. In describing the present invention, when 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.

1 illustrates a terminal receiver structure for selectively combining symbol data of each multipath component in order to combine symbol data at a maximum ratio in a code division multiple access communication system according to an embodiment of the present invention. Here, since the configuration of the fingers for demodulating each multipath component is the same, only one finger will be described. On the other hand, in the embodiment of the present invention will be described on the assumption that it has four multipath components.

Referring to FIG. 1, the mixers 111 and 112 multiply the signals received through the terminal antenna, the carrier signal cos (wt) and the sin (wt) in which the carrier signal is phase shifted by 90 degrees, and output them by frequency downconversion.

Here, the signals downconverted through the mixers 111 and 112 are represented by Equation 2 below.

Where "P" is a pilot signal, W ₀ is an orthogonal code corresponding to the pilot channel, W _d is a orthogonal code predetermined for orthogonal modulation, and PN (I) and PN (Q) are for orthogonal spreading. Represents an orthogonal code.

The low pass filters 113 and 114 low pass filter the output signals of the corresponding mixers 111 and 112 and output them. The complex PN despreader 115 inputs the output signals of the low pass filters 113 and 114 and the PN code from a PN generator (not shown) to output the complex PN despread.

Here, the PN despread signal through the complex PN despreader 115 is represented by Equation 3 below.

The pilot signal separator 116 multiplies the output signal of the complex PN despreader 115 by an orthogonal code corresponding to the pilot signal to separate the pilot signal, which is an unmodulated signal, and outputs it to the channel estimator 117. Here, it is assumed that an orthogonal code corresponding to the pilot signal is W ₀ . Accordingly, the signal provided to the channel estimator 117 is expressed by Equation 4 below.

Since the pilot signal is +1 in Equation 4, the pilot signal obtained as in Equation 4 becomes a fading component.

The channel estimator 117 estimates the channel from the base station to the terminal by accumulating a signal as shown in Equation 4 for a predetermined time. The conjugate complex generator 118 conjugates and outputs the output signal of the channel estimator 117. That is, the conjugate complex generator 118 conjugates and outputs a signal obtained by accumulating the S ₄ (t) signal for a predetermined time.

On the other hand, mixers 119 and 120 multiply the output signal of the complex PN despreader 115 by a predetermined orthogonal code W _d and output it by orthogonal modulation. Here, the output signals of the mixers 119 and 120 are signals obtained by multiplying a data signal by a predetermined orthogonal code and present fading components. This is represented by the following equation (5).

The fading compensator 121 multiplies the outputs of the mixers 119 and 120 by the output of the conjugate complex generator 118 to output fading compensation. That is, fading compensation is performed by multiplying a signal having gain by accumulating the fading component of Equation 4 for a predetermined time and multiplying the signal obtained as in Equation 5 by the fading compensation. If this is expressed as an equation, Equation 6 below.

The gain value in Equation 6 may have an inverted value due to severe fading. The symbol combiner 122 inputs the final signals obtained from Equation 6 as shown in Equation 6, and outputs the combined symbols by excluding signals whose signals are inverted due to deep fading among the input signals. That is, the symbol combiner 122 performs symbol combining by removing a symbol having a severe fading component. In this way, an improved symbol energy value can be obtained.

Detailed configuration of the symbol combiner 122 is as shown in FIG. In order to obtain the maximum symbol energy, the symbol combiner 122 excludes symbol data whose sign is inverted by deep fading from symbol combining, even if symbol data having symbol energy exceeding a predetermined reference value among symbol data corresponding to each multipath component. Shows.

Referring to FIG. 2, the energy determiners 211 and 212 calculate energy of symbol data of each I and Q channel multiplied by fading components, respectively, and reference energy values (THIs) provided from an upper controller (not shown). , THQ). In this case, if the energy of the symbol data is equal to or greater than the reference energy value, it is determined that the lock is locked, and the symbol data is output to the valid path selector. If the energy of the symbol data is less than the reference energy value, the symbol data is set to 0 and output. At this time, the symbol data output from the energy determiner 211 is an A / D converting value from +1 to -1 and has a two's complement form of n bits.

The valid path selectors 213 and 214 compare the MSB bits (sign bits) of the symbol data (n bits of two's complement form) output from the energy determiners 211 and 212 to set a signal having a different sign bit to 0 and rest Will print as is. That is, "0" to be excluded from symbol combining for symbol data having a different sign based on a sign that occupies a large number of symbol data transmitted from each finger (the signal is determined to be inverted due to deep fading). Set to.

The I-channel combiner 215 and the Q-channel combiner 216 accumulate and combine the symbol data output from the valid path selectors 213 and 214 in symbol units, and output the combined symbol data under the control of the time controller 217. The switch 218 multiplexes the outputs of the I-channel combiner 215 and the Q-channel combiner 216 under the control of the time controller 217.

The decimator 219 decimates the input long code and outputs it. A de-randomization part 220 exclusively adds the output of the switch 218 and the output of the decimator 219 to restore a signal encrypted by a long code at the time of transmission. Here, the long code is a code uniquely assigned to each subscriber and uniquely assigned to each subscriber. The reconstructed signal is transmitted to a decoder to undergo a decoding process.

Referring to the operation based on the configuration of FIG. 1 and FIG. 2, when a signal is received by the receiver of the terminal, the received signal is down-converted by the mixers 111 and 112 and converted into a baseband signal, and the low pass filters 113 and 114. It is lowpass from. The low-pass filtered signal is multiplied by a predetermined PNI and PNQ in a complex PN despreader 115 to PN despread, and the PN despread signal is multiplied by an orthogonal code corresponding to a pilot channel in pilot separator 116 to separate a pilot signal. do. The separated pilot signal is accumulated for a predetermined time in the channel estimator 117, and the accumulated signal is conjugated and complexed in the conjugate complex generator 118 to become a channel compensation signal. Meanwhile, the PN despread signal is multiplied by a predetermined orthogonal code corresponding to the data channel in the mixers 119 and 120 to demodulate the channel. The demodulated signal is multiplied by the channel compensation signal from the conjugate complex generator 118 in the fading compensator 121 to perform channel compensation. The signal output from the fading compensator 121 is symbol data of channel compensation. The energy determiners 211 and 212 calculate the symbol energy of the symbol data, and find the symbol data in which the energy is locked by comparing with the reference energy values THI and THQ. Here, the energy determiner 211 determines the energy of the symbol data corresponding to the I channel, and the energy determiner 121 determines the energy of the symbol data corresponding to the Q channel. Here, the energy determiners 211 and 121 output symbol data having an energy value greater than the reference energy value to the valid path selector 213 as it is, and symbol data smaller than the reference energy value is set to "0" to set the valid path. Output to selector213. By doing so, the symbol data which lost much energy due to fading is excluded from the symbol combination. The energy determiners 211 and 212 calculate energy by integrating and squaring a signal over a symbol period. At this time, the energy value of the symbol data whose sign is inverted due to deep fading exceeds the reference energy value, and thus it is determined that the energy is locked symbol data. However, the symbol data is inverted in sign due to deep fading. To obtain the maximum symbol energy, the symbol data inverted in the sign must be excluded from symbol combining. Accordingly, the valid path selectors 213 and 214 determine the symbols of the symbols output from the corresponding energy determiners 211 and 212, respectively, and determine symbol data having different codes based on the codes occupying a plurality of the symbols. Set symbol data to " 0 " and provide it to the channel combiner 215,216. Therefore, the channel combiners 215 and 216, which are substantially symbol-combined, may combine the remaining symbols except for the symbols that have lost much energy due to fading, thereby providing symbol data with a higher energy to the decoder.

3 illustrates a symbol combining process of the symbol combiner 122.

Referring to FIG. 3, the symbol combiner 122 receives symbol data from four fingers in step 311. The symbol combiner 122 calculates the energy of each of the symbol data in step 313, and compares the calculated energy value of each symbol data with a predetermined reference energy value in step 315. If the calculated energy value is greater than the predetermined energy value, it is selected as symbol data for symbol combining in step 319, and if it is smaller than the predetermined energy value, the corresponding symbol data is set to '0' in step 317. By doing so, symbol data satisfying a predetermined energy value are extracted. Then, the symbol combiner 122 checks each sign (MSB) of the symbol data satisfying the reference energy value in step 321, and has a symbol different from the symbol data having the same sign based on the sign occupying the majority. Separate into data. Here, the symbol data having another code is set to '0' to exclude from symbol combining in step 325, and the symbol data having the same code is selected as symbol data for symbol combining in step 323. In step 327, the symbol combiner 122 satisfies the reference energy value selected in step 323 and accumulates symbol data having the same reference numeral in symbol units to perform symbol combining. That is, except for symbol data whose sign is inverted due to deep fading, the symbol is combined to provide symbol data having a good energy value to the decoding end.

As described above, the present invention locks the energy of symbol data received from each finger beyond the reference value, but excludes it from symbol combining when the sign is reversed by fading. That is, accurate decoding can be achieved by simply passing the symbol data decoding stage having an improved energy value than when combining symbol data whose energy value is conventionally locked.

As described above, in the code division multiple access communication system, even if the symbol data energy exceeds a reference value in the symbol combining process, the symbol symbol value can be improved by excluding from symbol combining when the sign is reversed by fading. This allows more accurate decoding to be performed at the rear end.

Claims (8)

An apparatus for combining symbols received via multipath in a code division multiple access communication system, A plurality of fingers extracting symbol data by despreading a signal received through one path; And a symbol combiner for symbol combining except symbol data whose sign is inverted by fading among the symbol data from the plurality of fingers. The method of claim 1, wherein the symbol combiner, An energy determiner for calculating energy of symbol data from the plurality of fingers and outputting symbol data exceeding a reference energy value among the calculated energy values; A valid path selector for outputting remaining symbol data except for symbol data having a different sign based on a code occupying a plurality of symbol data from the energy determiner; And a channel combiner for accumulating and combining symbol data from the valid path selector. The method of claim 1, The symbol data is n-bit data of the two's complement form. An apparatus for combining symbols received via multipath in a code division multiple access communication system, A fading component generator for extracting a pilot signal from a signal received through one path to generate a fading component, a channel demodulator for despreading the received signal to extract symbol data, and multiplying the symbol data and the fading component to compensate the channel A plurality of fingers including at least a fading compensator to An energy determiner for calculating energy of the channel compensated symbol data from the plurality of fingers and outputting symbol data exceeding a reference energy value among the calculated energy values; A valid path selector for outputting remaining symbol data except for symbol data having a different sign based on a code occupying a plurality of symbol data from the energy determiner; And a channel combiner for accumulating and combining symbol data from the valid path selector. The method of claim 4, wherein The symbol data is n-bit data having a two's complement form. An apparatus for combining symbols received via multipath in a code division multiple access communication system, First and second energy determiners for measuring energy of symbol data corresponding to corresponding I and Q channels and outputting only symbol data equal to or greater than a reference level; First and second valid path selectors for outputting the remaining symbol data except for symbol data having a different sign based on a code occupying a large number among the output symbol data from the corresponding first and second energy determiners; An I-channel and Q-channel combiner for accumulating and combining output symbol data from the corresponding first and second valid path selectors; A switch for multiplexing and outputting output symbol data from the I-channel combiner and the Q-channel combiner; And an encryption decoder which exclusively adds the output symbol data from the switch and a predetermined long code to output to the decoder. A method for combining symbols received over a multipath in a code division multiple access communication system, Receiving symbol data from a plurality of fingers, Calculating an energy value of each of the received symbols and comparing each calculated energy value with a predetermined reference energy value; Selecting symbol data as symbol data for symbol combining when the calculated energy value is greater than a predetermined reference energy value; Identifying signs of the selected symbol data and selecting remaining symbol data except for symbol data having a different sign based on a code occupying a plurality of symbols; And accumulating and combining the selected symbol data in symbol units. A method for combining symbols received over a multipath in a code division multiple access communication system, The energy determiner receives the symbol data from the plurality of fingers; Calculating an energy value of each of the received symbols and comparing each calculated energy value with a predetermined reference energy value; If the calculated energy value is greater than a predetermined reference energy value, output symbol data to an idle pass selector as it is, and if smaller than the predetermined reference energy value, setting and outputting symbol data to '0'; Checking the symbols of the symbol data output from the energy determiner by the idle path selector; A step of outputting symbol data having a different sign based on a code occupying a plurality of symbols of the symbol data as '0' and outputting the remaining symbol data to a channel combiner as it is; And combining the symbol data from the idle path selector by accumulating the symbol data in symbol units.