KR20070000929A - Method and apparatus for deciding a scaling factor for turbo decoder input data in cdma system - Google Patents

Abstract

A method and an apparatus for deciding a scaling factor for input data of a turbo decoder in a CDMA system are provided to reduce complexity of a receiver apparatus, by using the scaling factor obtained by simple calculation of a system constant and gain factors. According to an apparatus for deciding a scaling factor for input data of a turbo decoder in a CDMA(Code Division Multiple Access) system, a lake receiver generates input data by receiving a multiple path signal. A scaling factor calculation part(512) calculates the scaling factor for the input data by using gain factors used in transporting the input data and system constant values(516) of the lake receiver. An input data scaler(514) obtains an input value of the turbo decoder, corresponding to the input data by multiplying the input data by the scaling factor.

Description

METHODS AND APPARATUS FOR DECIDING A SCALING FACTOR FOR TURBO DECODER INPUT DATA IN CDMA SYSTEM}

1 is a diagram showing a transmission device of a communication system using a turbo code.

2 is a block diagram showing a configuration of a transmission data processor according to a preferred embodiment of the present invention.

3 is a block diagram showing a configuration of a reception data processor according to a preferred embodiment of the present invention.

4 is a view showing the configuration of a rake receiver according to a preferred embodiment of the present invention.

5 is a diagram showing the configuration of an apparatus for calculating a scaling factor according to a preferred embodiment of the present invention.

6 is a flowchart showing the operation of determining a scaling factor according to a preferred embodiment of the present invention.

The present invention relates to a code division multiple access (CDMA) system, and more particularly, to a method and apparatus for determining a scaling factor for input data of a turbo decoder.

The next-generation mobile communication terminal whose main purpose is to support high-speed data communication requires longer usage time than conventional terminals mainly for voice calls. Therefore, various methods for minimizing the power consumption of the terminal and using the power more efficiently have been studied in order to increase the continuous usable time by charging the battery once.

In next-generation mobile communication systems such as synchronous CDMA-2000 and asynchronous UMTS (Universal Mobile Telecommunication Service), channel encoding for forward error correction (FEC) is used for reliable transmission of multimedia data. use. Channel coding is known to show very good information recovery performance in terms of Bit Error Rate (BER) even at low Signal to Noise Ratio (SNR). The error can be corrected even if In the next generation mobile communication system, turbo coding has been mainly considered as an error correcting code having a performance close to the Shannon limit, which is known as a limit of error correcting capability. An iterative decoding algorithm is used to decode a codeword coded by a turbo code.

The turbo encoder has two constituent encoders that operate in parallel with the internal interleaver. One component encoder encodes information bits to generate first parity bits, and the other component encoder encodes information bits interleaved by the internal interleaver to generate second parity bits. All or part of the information bits and the parity bits are transmitted over a channel.

Soft values of the received bits are scaled, quantized and stored in a buffer to decode the turbo coded data. The information read from the buffer and the first parity bits are decoded by a first constituent decoder and the intermediate result comprising the information generated from the first constituent decoder corresponds to the interleaving used by the turbo encoder. Deinterleaved. The second component decoder decodes the intermediate result and the second parity bits, and the intermediate results including information generated from the second component decoder are likewise deinterleaved and stored. The stored intermediate result is used by the next iteration of the first component decoder. The iteration by the first and second component decoders is repeated several times until the final decoding result is obtained.

Turbo codes can achieve high coding gains, while decoding of turbo codes is very complex and often requires a large amount of complex computer computation. To minimize bit errors in codewords, turbo decoding is typically based on a MAP algorithm that operates by calculating a maximum a posteriori (MAP) probability for the coded data. The MAP algorithm is known as an optimal decoding algorithm for turbo codes, and various modifications have been developed to reduce the computational burden of the MAP algorithm. One such variant is the Log-MAP algorithm. The turbo decoder using the Log-MAP algorithm operates by inputting a Log Likelihood Ratio (LLR) of received bits including information bits and parity bits.

Turbo decoders using the Log-MAP algorithm require accurate information about the scale of the input bits. This scale information includes the variation and amplitude, or mean, of the input bits provided to the turbo decoder. If turbo decoding is performed based on incorrect information on the scale of the input bits, the decoding efficiency is greatly degraded. Moreover, the complexity of implementation is very high because N symbols to be input to the turbo decoder must be used for estimation of variance and average. Therefore, in order to obtain improved decoding efficiency in decoding the encoded data in the turbo decoder, a technique for obtaining more accurate scale information by simpler equations is required.

Accordingly, the present invention, devised to solve the problems of the prior art operating as described above, provides a method and apparatus for determining scale information for input bits of a turbo decoder using a Log-MAP algorithm.

The present invention provides a method and apparatus for more simply determining a scaling factor for input bits of a turbo decoder.

In order to achieve the above object, an embodiment of the present invention provides a method of determining a scaling factor for input data of a turbo decoder in a code division multiple access system.

Obtaining input data from the rake receiver,

Calculating a scaling factor for the input data using gain factors used to transmit the input data and system constant values of the rake receiver;

And multiplying the input data by the scaling factor to obtain an input value of a turbo decoder corresponding to the input data.

Another embodiment of the present invention is a device for determining a scaling factor for input data of a turbo decoder in a code division multiple access system,

A rake receiver for receiving a multipath signal and generating input data;

A scaling factor calculator configured to calculate a scaling factor for the input data using gain factors used to transmit the input data and system constant values of the rake receiver;

And an input data scaler for multiplying the input data by the scaling factor to obtain an input value of a turbo decoder corresponding to the input data.

Hereinafter, with reference to the accompanying drawings will be described in detail the operating principle of the preferred embodiment of the present invention. In the following description of the present invention, detailed descriptions of well-known functions or configurations will be omitted if it is determined that the detailed description of the present invention may unnecessarily obscure the subject matter of the present invention. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

1 shows a transmission apparatus of a communication system 100 using a turbo code. The communication system 100 is a CDMA system that conforms to CDMA standards such as synchronous CDMA2000 and asynchronous WCDMA (Wideband CDMA).

Referring to FIG. 1, in the transmitter 110, data in block units is transmitted from a data source 112 to a transmit data processor 114. The transmission data processor 114 generates the data as an analog signal through formatting, encoding, and modulation. The analog signal is provided to a transmitter 116, which filters, amplifies and frequency up-converts the analog signal to receive one or more via one or more antennas 118. To the device.

In the receiving device 150, the transmitted signal is received by the one or more antennas 152 with different delay times through multiple passes and provided to the receiver 154. The receiver 154 receives the multipath signals by rake combining and then amplifies, filters, and frequency down-converts the sample data. The received data processor 156 demodulates and decodes the sample data to recover the transmitted data. The recovered data is provided to the data analyzer 158.

2 is a block diagram showing the configuration of a transmission data processor 114 according to a preferred embodiment of the present invention.

Referring to FIG. 2, the CRC attacher 212 attaches CRC (Cyclic Redundancy Codes) to each transport block (TrBK) to transport channel (TrCH) data received from a data source and transmits the data. The TrBk concatenator / Code block segmentater 214 concatenates several transport blocks into one data and segments them into code blocks according to the input data size of the channel encoder 216. The code blocks are passed to a channel encoder 216.

A channel encoder 216 encodes the code blocks by using a turbo code, and a radio frame equalizer 218 dummyizes the encoded data to create a size of a transmission time interval (TTI) multiple. Insert symbols. The output data of the radio frame equalizer 218 is interleaved by the primary interleaver 220 and then separated into radio frame data of 10 ms by the radio segment generator 222. The rate matcher 224 performs rate matching to make the radio frame data the size of a physical channel (PhCH) frame. The rate-matched data generated for each transport channel forms one transport channel data by the transport channel multiplexer 226, and the physical channel generator 228 separates the multiplexed data into the size of each physical channel data. After the transfer to the secondary interleaver 230. The output data of the physical channel generator 228 is interleaved by the secondary interleaver 220 and then mapped and transmitted to the physical channel by a physical channel mapper 232.

The channel encoder 216 of the transmission data processor 114 is composed of a turbo encoder. In order to decode the turbo code, the received data processor 156 uses a turbo decoder. The input of the turbo decoder using the Log-MAP algorithm is expressed by Equation 1 below.

는 상기 n번째 입력 비트가 겪은 통신 채널의 이득 a(n)의 평균 크기(amplitude)이고, d(n)는 송신한 정보 비트의 부호(+1 또는 -1)이고,

은 잡음의 분산이다.Where x (n) is a soft value representing the nth input bit of the turbo decoder

Is the average amplitude of gain a (n) of the communication channel experienced by the nth input bit, d (n) is the sign (+1 or -1) of the transmitted information bit,

Is the variance of noise.

(이하 스케일링 인자(scaling factor)라 칭함)으로 x(n)를 스케일링하여 x(n)의 LLR을 구하여야 한다. 상기 스케일링 인자를 구하기 위해 터보 복호기로 입력되기 이전의 x(n)를 이용하여

과

를 추정하는 것은, 매우 복잡한 계산을 필요로 한다. 따라서 본 발명의 바람직한 실시예에 따른 수신 데이터 처리기(156)는 CDMA 시스템에서 사용하는 레이크 수신기의 특성을 이용하여 스케일링 인자를 직접 계산한다.In order to obtain the optimal performance in the turbo decoder, as shown in Equation 1

LLR of x (n) should be obtained by scaling x (n) by a scaling factor (hereinafter, referred to as a scaling factor). Using x (n) before input to the turbo decoder to obtain the scaling factor

and

Estimating requires very complex calculations. Therefore, the reception data processor 156 according to the preferred embodiment of the present invention directly calculates the scaling factor by using the characteristics of the rake receiver used in the CDMA system.

3 is a block diagram showing the configuration of the reception data processor 156 according to the preferred embodiment of the present invention.

Referring to FIG. 3, the reception data processor 156 is provided with despread data with a minimum spreading factor from a rake receiver (not shown) of the receiver 154. The data is scaled by the input data scaler 314 using the scaling factor calculated at the scaling factor generator 312. The scaling factor generator 312 calculates the scaling factor using the system constants and the gain factors of the transmission channels instead of calculating the variance and the magnitude using the symbols input to the turbo decoder 332. Detailed operation of the scaling factor generator 312 will be described later.

The secondary dynamics calculator 316 despreads the scaled data with a spreading factor indicated by a transport format combination indicator (TFCI). Here the first despreading is performed by the rake receiver. The secondary deinterleaver 318 deinterleaves the data despread to each physical channel in response to the interleaving operation of the secondary interleaver 230, and the physical channel concatenator 320 is used for each physical channel. The deinterleaved data is connected to one physical channel data. The transport channel demultiplexer 322 multiplexes the physical channel data for each transport channel, and subsequent blocks are duplicated for each transport channel, but for the sake of convenience, only components related to one transport channel are described. Is shown.

The rate dematcher 324 performs rate dematching on the demultiplexed data to output a radio frame having a desired size, and a radio frame concatenation unit 326 is 10 ms units. Converts the radio frame into transmission channel data in TTI units. The primary deinterleaver 328 deinterleaves the transport channel data in response to the interleaving operation of the primary interleaver 220.

The radio frame equalizer 330 removes the symbols inserted by the radio frame equalizer 218 from the output data of the primary deinterleaver 328 to generate input data for channel decoding. Since the output of the radio frame equalizer 330 has been scaled by the input data scaler 314, it can be directly input to the turbo decoder 332 without further scaling.

The turbo decoder 332 turbo decodes the data from the radio frame inverse equalizer 330 to recover information bits, and the code block concatenation and transport block generator 334 outputs from the turbo decoder 332 in code block units. The information bits are separated into one data and then separated into transport blocks. The CRC checker 336 examines the CRCs of the transport blocks, and transmits data from which the CRC has been removed to the data analyzer 158 when a CRC error does not occur.

혹은

라 칭하며, 상기 제어 채널의 이득인자는

혹은

라 칭한다. 상기 이득인자들은 각 서비스(예를 들어 음성 서비스 혹은 패킷 데이터 서비스)에 대해 전송 가능한 데이터의 크기에 따라 미리 정의된다. 수신 장치는 상기 제어 채널을 통해 수신한 전송 파라미터에 따라 상기 데이터의 크기를 확인하고, 상기 전송 블록의 크기에 대응하는 상기 이득인자들 혹은 상기 이득인자들의 비

을 알 수 있다.As mentioned above, the scaling factor generator 312 calculates the scaling factor according to system constants and gain factors of the transmission channels. The gain factors are respectively set for a data channel (hereinafter referred to as DCH) carrying user data traffic and a control channel (hereinafter referred to as CCH) carrying control information indicating transmission parameters of the data channel. do. The gain factor of the data channel is

or

The gain factor of the control channel is called

or

It is called. The gain factors are predefined according to the size of data that can be transmitted for each service (eg voice service or packet data service). The receiving apparatus confirms the size of the data according to the transmission parameter received through the control channel, and the gain factors or ratios of the gain factors corresponding to the size of the transport block.

It can be seen.

4 illustrates a configuration of a rake receiver 410 according to a preferred embodiment of the present invention. As shown in FIG. 4, the rake receiver 410 includes L fingers 412 and 414 and a maximum ratio combiner corresponding to each of the multipaths. Maximum ratio combiner (MRC) 426. The fingers 412 and 414 both have the same configuration and show the internal configuration of the first finger 414. The finger 414 includes a data channel (DCH) despreader 416, a control channel (CCH) despreader 418, a channel estimator 420, a channel compensator 422, and a signal component selector 424. Here, the descrambler is included in each despreader 416, 418.

는 하기 <수학식 2>와 같다.P-th signal input from the p-th TTI to the rake receiver 410 configured as described above

Is as shown in Equation 2 below.

는 잡음이 없는 수신 신호이고

는 잡음이다. 입력 신호

는 수신기의 RF 유닛에서 AGC(Automatic gain control)을 통과한 신호이므로 동위상(In phase: I) 및 직교위상(Quadrature phase: Q) 신호성분 별로 일정한 에너지 값 rms²를 갖는다. 상기 rms는 상기 입력 신호

의 제곱근 평균(Root mean square)이다. 상기 <수학식 2>에서

와

는 하기 <수학식 3> 및 <수학식 4>와 같이 나타내는 복소수 값이다.In Equation 2, k is a time index,

Is the noise-free received signal

Is noise. Input signal

Since is a signal passing AGC (Automatic Gain Control) in the RF unit of the receiver has a constant energy value rms ² for each of the in-phase (I) and quadrature phase (Q) signal components. The rms is the input signal

Root mean square of. In Equation 2

Wow

Are complex values represented by Equations 3 and 4 below.

의 에너지의 대부분은 잡음 에너지이므로 상기 잡음

의 분산을 하기 <수학식 5>와 같이 근사화 할 수 있다.The input signal

Since most of the energy of the noise energy is noise

The variance of can be approximated as in Equation 5 below.

을 디스크램블링(Descrambling)하면 하기 <수학식 6>과 같다.The input signal

If descrambled (Descrambling) to the following equation (6).

는 2이다.Where s (k) means scrambling code and the size of s (k)

Is 2.

을 데이터 채널과 제어 채널의 채널화 코드(Channelization code)(즉 왈시 코드)

와

로 역채널화(Dechannelization)하면, 하기 <수학식 7>와 <수학식 8>과 같이 데이터 채널과 제어 채널의 신호들

와

로 분리된다. 상기 데이터 채널은, WCDMA 시스템의 경우 전용 물리 데이터 채널(Dedicated physical data channel: 이하 DPDCH라 칭함)을 의미하고, CDMA2000 시스템의 경우 기본 채널(Fundamental channel)과 부가 채널(Supplemental channel)을 의미한다. 또한 상기 제어 채널은, WCDMA 시스템의 경우 파일럿을 포함하는 DPCCH(Dedicated physical control channel)을 의미하고, CDMA2000 시스템의 경우 파일럿 채널을 의미한다.The descrambled signal of Equation 6

Is the Channelization code (i.e. Walsh code) of the data channel and the control channel.

Wow

When dechannelization is performed, the signals of the data channel and the control channel are expressed as in Equations 7 and 8 below.

Wow

To be separated. The data channel refers to a dedicated physical data channel (hereinafter referred to as DPDCH) in the case of a WCDMA system and a fundamental channel and a supplemental channel in the case of a CDMA2000 system. In addition, the control channel means a dedicated physical control channel (DPCCH) including a pilot in the case of a WCDMA system, and a pilot channel in the case of a CDMA2000 system.

Since the channel change can be regarded as little within the spreading factor SF _c representing the spreading code length of the control channel, despreaders despread using the spreading codes SF _d and SF _c of the data channel and the control channel ( The output signals of 416 and 418 may be represented by Equations 9 and 10 below.

은 송신 장치에서 보낸 트래픽 데이터 심볼로서 1 또는 -1의 값을 갖는다. 또한 m은 의 0과 (r-1) 사이의 값을 갖는 심볼 인덱스이며,

와

는 데이터 채널과 제어 채널의 잡음을 의미한다. 여기서

는 DCH 역확산기(416)가 트래픽 데이터를 역확산한 후 출력하는 신호의 크기 범위를 일정 수준으로 유지하기 위해 역확산된 신호에 곱해주는 상수 값으로서, 일반적으로 Truncation bit로 구현된다.In Equation (9), n is a discrete time index of a control channel symbol, r is SF _c / SF _d and represents the number of traffic data symbols per SF _c chips.

Is a traffic data symbol sent by the transmitting apparatus and has a value of 1 or -1. M is a symbol index with a value between 0 and (r-1)

Wow

Denotes the noise of the data channel and the control channel. here

DCH despreader 416 is a constant value that is multiplied by the despread signal to maintain the size range of the output signal after despreading the traffic data at a constant level, and is generally implemented as a truncation bit.

는 CCH 역확산기(418)가 제어 데이터를 역확산한 후 출력하는 신호의 크기 범위를 일정 수준으로 유지하기 위하여 맞춰 주기 위해 역확산된 신호에 곱해주는 상수 값으로서, 일반적으로 Truncation bit로 구현된다.In Equation 10, cch (n) is a control data symbol sent from the transmitting apparatus and has a value of 1 or -1. Also

The CCH despreader 418 is a constant value that is multiplied by the despread signal in order to fit the signal data to despread the control data to maintain a predetermined level range of the output signal, and is generally implemented as a truncation bit.

If the carrier to noise ratio (hereinafter referred to as C / N) in Equations 9 and 10 is sufficiently small, the variance of the noise of each channel is represented by Equations 11 and 8 12>.

과

은 하기 <수학식 13>와 같은 관계를 갖는다.Channel Gains in Equations 9 and 10

and

Has a relationship as shown in Equation 13 below.

는 데이터 채널을 위한 이득인자이고

는 제어 채널을 위한 이득인자이다.In <Equation 13>

Is the gain factor for the data channel

Is the gain factor for the control channel.

을 이용하여, 채널의 크기와 위상 변화를 나타내는 채널 추정값을 구한다. 상기 채널 추정값

을 하기 <수학식 14>와 같다.The channel estimator 420 despreads the signal of the control channel shown in Equation 10 above.

Using the equation, a channel estimate representing the channel size and phase change is obtained. The channel estimate

Equation 14 is as follows.

는 채널 추정기(420)를 통과한 잡음이다. 또한

는 채널 추정기(420)의 출력 범위를 일정 수준으로 유지하기 위한 상수 값이고

은 무선 채널을 통과하면서 틀어진 위상 왜곡 값이다. 만약 제어 채널이 Q 채널에 매핑된다면 상기

는 하기 <수학식 15>와 같고, 제어 채널이 I 채널에 매핑된다면 하기 <수학식 16>과 같다.In Equation 14 above

Is the noise that passed through the channel estimator 420. Also

Is a constant value for maintaining the output range of the channel estimator 420 at a constant level

Is the phase distortion value that passes through the wireless channel. If the control channel is mapped to the Q channel

Equation 15 is as follows, and if the control channel is mapped to the I channel, Equation 16 is shown.

는 무선 채널을 통과하면서 야기된 위상 및 크기의 왜곡 값을 나타낸다.here

Denotes a distortion value of phase and magnitude caused while passing through a wireless channel.

If the symbol energy to white noise E _s / N _o of the control data is sufficiently large, the channel estimation value of Equation 14 may be expressed as Equation 17 by omitting the noise.

에 상기 <수학식 17>의 채널 추정값을 곱하여 상기 역확산된 신호의 크기(Amplitude)와 위상을 보상한다. 신호성분 선택기(signal component selector)(424)는 데이터 채널이 I 채널에 매핑되는지 혹은 Q 채널에 매핑되는지에 따라, 상기 채널 보상된 신호의 I 성분 혹은 Q 성분을 검출하여 하기 <수학식 18> 혹은 <수학식 19>와 같은 신호를 출력한다. 하기 <수학식 18>은 데이터 채널이 I 채널에 매핑되는 경우를 나타낸 것이고, <수학식 19>는 데이터 채널이 Q 채널에 매핑되는 경우를 나타낸 것이다.The channel compensator 422 despreads the equation (9).

Multiply the channel estimation value of Equation 17 by to compensate for the amplitude and phase of the despread signal. The signal component selector 424 detects an I component or a Q component of the channel-compensated signal according to whether the data channel is mapped to the I channel or the Q channel. A signal as shown in Equation 19 is output. Equation 18 shows a case in which a data channel is mapped to an I channel, and Equation 19 shows a case in which a data channel is mapped to a Q channel.

는 각 핑거(412 또는 414)의 출력을 의미하며, A는

과 같이 정의되는 시스템 상수를 나타낸다. remind

Denotes the output of each finger 412 or 414, where A

Represents a system constant defined as

In Equations 18 and 19, the variance of noise is expressed by Equation 20 below.

는 채널 보상된 잡음을 의미한다.here

Denotes channel compensated noise.

,

, ...

을 출력하며, MRC(426)는 상기 핑거들(412, 414)의 출력들을 결합하여 하기 <수학식 21>와 같은 트래픽 데이터 심볼

을 출력한다.A total of L fingers 412, 414

,

, ...

The MRC 426 combines the outputs of the fingers 412 and 414 to represent a traffic data symbol as shown in Equation 21 below.

Outputs

는 MRC(426)의 출력 범위를 유지하기 위한 상수 값이다.In Equation 21, L is the number of multipaths

Is a constant value for maintaining the output range of the MRC 426.

의 평균을 구하면 하기 <수학식 22>과 같다.Input signal using Equation 21

The average of is given by Equation 22.

In addition, when the noise variance is obtained using Equation 20, Equation 23 is obtained.

When the scaling factor is obtained using Equation 22 and Equation 23, Equation 24 is obtained.

및

의 영향만을 받는다. In Equation 24, B and rms ² are system constants determined during modem design, and are defined as Equation 25 below.

And

Only affected by.

는 트래픽 데이터를 역확산하는 DCH 역확산기(416)의 상수 값이고

는 파일럿을 포함한 제어 데이터를 역확산하는 역확산기 (418)의 상수 값이며,

는 MRC(426)의 상수 값이다. 또한

는 채널 추정기(420)의 상수 값이고

는 제어 채널의 확산인자이다.As mentioned earlier,

Is a constant value of the DCH despreader 416 that despreads the traffic data

Is a constant value of the despreader 418 that despreads the control data including the pilot,

Is a constant value of the MRC 426. Also

Is a constant value of the channel estimator 420

Is the spreading factor of the control channel.

개의 소수 비트(Fractional bit)를 사용한다면, 상기 <수학식 25>는 하기 <수학식 26>과 같이 변형된다.If you want to represent an input value below the decimal point in the turbo decoder,

If the number of fractional bits (Fractional bits) are used, Equation 25 is modified as in Equation 26.

및

를 상기 <수학식 26>에 대입하여 스케일링 인자를 구하고, 상기 스케일링 인자를 이용하여 트래픽 데이터를 스케일링한다. 바람직한 실시예로서, 스케일링 인자 생성기(312)는, 상기 이득인자들

및

에 따른 모든 스케일링 인자 값들을 테이블로 생성하고, 수신된 데이터에 해당하는 스케일링 인자 값을 상기 테이블로부터 신속하게 획득할 수 있다.Upon receiving the traffic data and the control data, the receiving device obtains the gain factors corresponding to the data.

And

Is substituted into Equation 26 to obtain a scaling factor, and the traffic data is scaled using the scaling factor. In a preferred embodiment, scaling factor generator 312 is provided with the gain factors.

And

It is possible to generate all the scaling factor values according to the table, and to quickly obtain the scaling factor values corresponding to the received data from the table.

In other cases, the receiving device includes a scaling factor calculator 512, as shown in FIG.

및

를 획득하여, 상기 <수학식 26>에 의해 스케일링 인자를 계산한다. 상기 시스템 상수 값들은 레이크 수신기로 입력되는 신호의 크기를 나타내는 rms와 레이크 수신기의 설계 특성에 따른 상수 값들의 조합 B 및 터보 복호기의 소수 비트에 의해 결정되는

이다. 입력 데이터 스케일링기(514)는 i번째 데이터 채널의 입력 데이터 x(i)에 상기 스케일링 인자를 곱하여 스케일링된 데이터 y(i)를 생성한다. Referring to FIG. 5, the scaling factor calculator 512 receives system constant values 516 and gain factors of traffic data and control data through a control channel.

And

Is obtained, and the scaling factor is calculated by Equation 26. The system constant values are determined by a combination of rms representing the magnitude of the signal input to the rake receiver and the fractional bits of the turbo decoder and the combination B of the constant values according to the design characteristics of the rake receiver.

to be. The input data scaler 514 multiplies the scaling factor by the input data x (i) of the i-th data channel to produce scaled data y (i).

The scaled data y (i) is input data of the turbo decoder 332 via the devices 316 to 330 shown in FIG. Since the devices 316 to 330 only perform rearrangement, puncturing / repeating, or classifying each symbol of the scaled data y (i), the soft values of the scaled symbols are determined by the devices 316 to 330. Passed through 330 is input to the turbo decoder 332 undeformed.

6 is a flowchart illustrating an operation of determining a scaling factor according to an exemplary embodiment of the present invention.

및

를 읽어오면서, 변수 i를 0으로 초기화한다. 604단계에서 스케일링 인자 계산부는 미리 알고 있는 시스템 상수 값들을 이용하여 상기 <수학식 26>에 의해 스케일링 인자(Scale_Factor)를 계산한다. 606단계에서 입력 데이터 스케일링기는 입력 데이터 x(i)에 상기 스케일링 인자(Scale_Factor)를 곱하여 스케일링된 데이터 y(i)를 생성한다. 608단계에서 상기 변수 i는 1만큼 증가되며, 610단계에서 수신 장치는 상기 변수 i가 터보 복호기(332)의 입력 데이터 크기 N보다 작은지 확인한다. 상기 변수 i가 상기 N보다 작으면 다음 데이터 채널의 입력 데이터를 스케일링하기 위하여 606단계로 복귀하고, 그렇지 않으면 동작을 종료한다.Referring to FIG. 6, in step 602, a scaling factor calculator calculates gain factors of currently received traffic data and control data.

And

Initialize variable i to 0, reading. In operation 604, the scaling factor calculator calculates the scaling factor Scale_Factor using Equation 26 using system constant values known in advance. In operation 606, the input data scaler multiplies the input data x (i) by the scaling factor Scale_Factor to generate scaled data y (i). In step 608, the variable i is increased by 1, and in step 610, the receiving device checks whether the variable i is smaller than the input data size N of the turbo decoder 332. If the variable i is smaller than N, the process returns to step 606 to scale the input data of the next data channel, otherwise the operation ends.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by those equivalent to the scope of the claims.

In the present invention operating as described in detail above, the effects obtained by the representative ones of the disclosed inventions will be briefly described as follows.

The present invention does not calculate complex noise variance and input signal size in calculating the LLR value, which is an input value for obtaining optimal decoding performance, in the turbo decoder using the Log-MAP algorithm. By using the scaling factor obtained by this, the complexity of the receiving device is drastically reduced.

Claims (8)

A method of determining a scaling factor for input data of a turbo decoder in a code division multiple access system, Obtaining input data from the rake receiver, Calculating a scaling factor for the input data using gain factors used to transmit the input data and system constant values of the rake receiver; And multiplying the input data by the scaling factor to obtain an input value of a turbo decoder corresponding to the input data. The method of claim 1, wherein the input data, The multipath signals received through the data channel and the control channel are despread with the despread codes of the data channel and the control channel, respectively, and are generated by the maximum ratio combining (MRC) of the despread signals. Said method. The method of claim 1, wherein the system constant values, A product constant (B) of system constant values for maintaining the output ranges of the data channel despreader, control channel despreader, channel estimator, and maximum ratio combiner constituting the Rake receiver, and the spreading code of the control channel; According to the number of decimal bits (f) used in the turbo decoder to represent values below the decimal point

And a magnitude (rms) of a received signal input to the rake receiver. The method as claimed in claim 1, wherein the scaling factor is calculated as in the following equation.

remind

Is a system constant value for maintaining the output range of the data channel despreader that despreads the traffic data,

Is a system constant value for maintaining the output range of the control channel despreader that despreads the control data including the pilot,

Is a system constant value to maintain the output range of MRC,

Is a constant value to maintain the output range of the channel estimator,

Is the spreading factor of the control channel,

Wow

Is the gain factor of the control channel and data channel. An apparatus for determining a scaling factor for input data of a turbo decoder in a code division multiple access system, A rake receiver for receiving a multipath signal and generating input data; A scaling factor calculator configured to calculate a scaling factor for the input data using gain factors used to transmit the input data and system constant values of the rake receiver; And an input data scaler for multiplying the input data by the scaling factor to obtain an input value of a turbo decoder corresponding to the input data. The method of claim 5, wherein the rake receiver, Despreaders including a data channel despreader and a control channel despreader for despreading multipath signals received through a data channel and a control channel into despread codes of the data channel and the control channel, respectively; And a maximum ratio combiner for generating the input data by maximum ratio combining (MRC) the despread signals. The method of claim 6, wherein the system constant values, The system constant values for maintaining the output ranges of the data channel despreader, the control channel despreader, the channel estimator and the maximum ratio combiner, respectively, and the chip length of the spreading code of the control channel (B), and the turbo Depending on the number of decimal bits (f) used by the decoder to represent values below the decimal point

And a magnitude (rms) of a received signal input to the rake receiver. 6. The apparatus as claimed in claim 5, wherein the scaling factor is calculated as in the following equation.

remind

Is a system constant value for maintaining the output range of the data channel despreader that despreads the traffic data,

Is a system constant value for maintaining the output range of the control channel despreader that despreads the control data including the pilot,

Is a system constant value to maintain the output range of MRC,

Is a constant value to maintain the output range of the channel estimator,

Is the spreading factor of the control channel,

Wow

Is the gain factor of the control channel and data channel.

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