CN101060339A - A Turbo coding and decoding device and method realized in SCDMA system - Google Patents

Abstract

The provided implementation method for Turbo code/decode scheme in SCDMA digital mobile communication system comprises: adding multi-frame data interlace device and a Turbo coder on the transmission end, and adding multi-frame data inverse-interlace device and a Turbo decoder on the receiving end. This invention changes little to current system, improves coding performance, and reduces error code rate.

Description

A kind of apparatus and method that in the SCDMA system, realize Turbo coding and decoding scheme

Technical field

The present invention relates to a kind of apparatus and method that in the TD-CDMA digital mobile communication system, realize Turbo coding and decoding scheme, relate in particular to a kind of apparatus and method that in the SCDMA digital mobile communication system, realize Turbo coding and decoding scheme.

Background technology

Turbo coding and decoding scheme is a kind of novel channel decoding scheme, because it has used randomness volume, decoding condition in celestial farming (Shannon) channel coding theorem well, has therefore obtained the almost decoding performance of approaching celestial agricultural theoretical limit.

The proposition of Turbo coding and decoding scheme has changed the traditional concept that people construct good sign indicating number, and the iteration thought of Turbo coding and decoding scheme also provides new approaches for the problem that solves the different communication field simultaneously.At present, Turbo coding and decoding scheme has obtained extensive use in fields such as deep space communication, (moving) satellite communication and multimedia communications.But for existing Turbo coding and decoding scheme, its application in terrestrial wireless communication system is rich in challenge most.Terrestrial wireless communication system is the system of power limited and limited bandwidth, simultaneously because declined, the influence of shade and multipath effect, it is complicated unusually that radio communication channel seems, and system requires than higher real-time, and these factors all make the application of Turbo coding and decoding scheme in terrestrial wireless communication system be subjected to serious challenge.Along with researcher's unremitting effort, Turbo coding and decoding scheme and convolutional encoding scheme together are widely applied in the third generation personal wireless communications system.

What adopt according to the regulation Turbo coding and decoding scheme of 3GPP is 1/3 bit rate, its coding is that, constraint length identical by 2 structures is 4, systematic recursive convolutional encoder (RSC) with generator matrix generates, the parallel level convolution code device (PCCC, ParallelConcatenated Convolutional Code) that adopts 8 state component sign indicating numbers to form.The structure of its Turbo code is the structure of eight state PCCC encoders.The transfer function of component code that is used for 8 states of PCCC encoder is:

$G\left(D\right)=[1,\frac{1+D^1+D^3}{1+D^2+D^3}]$

The encoder that is adopted for the 3GPP Turbo code shown in the above-mentioned formula, it mainly is designed for adapting to 3-G (Generation Three mobile communication system) data service and channel characteristics.

At present, the encoder that Turbo code adopted mainly is to design at the relatively long situation of certain concrete system and data block.And data block length is shorter in the common existing wireless communications system, also needs to consider delay problem simultaneously, therefore, when carrying out the Turbo coding and decoding, deciphers iterations accordingly and compares less.Primary Study shows that under the situation of identical complexity, Turbo code is compared with convolution code, and the additional gain that Turbo code can be contributed is more limited.Though P.Jung has carried out some further investigations and has proposed some following principle to the Turbo code under the short frame weaving length condition, does not also propose detailed mentality of designing at concrete wireless communication system in its research process.

The SCDMA system is a kind of advanced person's a 3-G (Generation Three mobile communication system), and its channel coding schemes is generally and does not carry out encoding or adopt the convolution code channel coding schemes at present.In order further to reduce the error rate of SCDMA system, need improve making it in the SCDMA system, to use to existing Turbo coding and decoding scheme.

Summary of the invention

Main purpose of the present invention is to provide a kind of apparatus and method that realize channel Turbo coding and decoding in the SCDMA system, thereby makes the SCDMA system obtain the better chnnel coding gain and the reduction error rate.

According to an aspect of the present invention, the invention provides a kind of channel Turbo Methods for Coding that in the SCDMA system, realizes, may further comprise the steps:

(1) a plurality of prewired parameters of SCDMA system initialization and preparation need the N frame data of transmission;

(2) one multiframe interleavers carry out data interlacing to the described N frame data that need to send;

(3) described multiframe interleaver takes out the data sequence that need send when former frame in the N frame data after interweaving and this data sequence is put into one by the mapping relations of the table that interweaves and sends buffering area;

(4) from send buffering area, take out data sequence and this data sequence sent into carry out the Turbo coding in the asymmetric Turbo encoder;

Data sequence after (5) one difference engines are encoded to Turbo carries out difference processing and a 4PSK modulator adopts the 4PSK modulation system that differentiated data sequence is modulated;

(6) data sequence of described 4PSK modulator after to difference and modulation carried out the modulation of two-dimentional Gray code, generates the two-dimensional modulation burst;

(7) one frequency multipliers carry out spread processing to the two-dimensional modulation burst;

(8) signal behind the spread spectrum is carried out pulse shaping filtering, subsequently filtered signal is delivered to the processing of carrying out radio frequency part in the SCDMA system channel, the spectrum CDMA signal of SCDMA system sends the most at last;

(9) turning back to the data sequence that step (3) need send next frame handles until handling whole N frame data.

Preferably, describedly in the SCDMA system, realize the described step (4) in the channel Turbo Methods for Coding and then may further comprise the steps:

(a) before carrying out the Turbo coding, the SCDMA system carries out initialization and setting according to the requirement of system to the parameter of asymmetric Turbo encoder;

(b) thus will send into the data sequence of carrying out the Turbo code interleaver of described asymmetric Turbo encoder after data interlacing obtains to interweave from sending a frame data sequence that buffering area takes out; Thereby will encode from first component coder that a described frame data sequence that sends the buffering area taking-up is sent into described asymmetric Turbo encoder simultaneously and generate first the verification of data sequences; Also will send into the multiplexer of described asymmetric Turbo encoder as system's dateout sequence simultaneously from a described frame data sequence that sends the buffering area taking-up;

(c) thus the second component encoder that the data sequence after described interweaving is sent into described asymmetric Turbo encoder encoded generate second the verification of data sequences;

(d) thus carrying out puncturing process in the residual matrix that first the verification of data sequences that described two component coders are exported respectively and second the verification of data sequences are sent into described asymmetric Turbo encoder simultaneously obtains to have deleted surplus the verification of data sequences and this sequence is sent in the multiplexer of described asymmetric Turbo encoder;

(e) thus described multiplexer carries out multiple connection and handles the data sequence that obtains behind the Turbo coding described surplus the verification of data sequences and the described system dateout sequence of having deleted that receives.

According to a further aspect in the invention, the invention still further relates to a kind of method that in the SCDMA system, realizes channel Turbo decoding, may further comprise the steps:

(a) the SCDMA system carries out system initialization and parameter setting;

(b) despreader is searched for Synchronous Processing and despreading processing to the spectrum CDMA signal that receives;

(c) signal of a phase difference device after to despreading carries out difference processing, to obtain differentiated signal;

Processing to the multiframe data interlacing when (d) a multiframe data deinterlacing device is encoded according to Turbo is handled with the signal after the acquisition deinterleaving the deinterleaving that differentiated signal carries out the multiframe data;

(e) signal of an asymmetric Turbo decoder after to deinterleaving carries out Turbo code decoding and handles the data sequence that obtains received signal.

Preferably, the described step (e) in the described method that in the SCDMA system, realizes channel Turbo decoding and then may further comprise the steps:

(1) before the Turbo decoding beginning, described asymmetric Turbo decoder is carried out parameter setting and initialization process;

(2) according to the rule of transmitting terminal residual matrix, the residual matrix module in the described asymmetric Turbo decoder is handled the data sequence before deciphering, and it is corresponding to make it satisfy the signal that encoder produced in signal that decoder receives and transmission stage;

(3) according to formula $D_k(I,J)=\frac{L_c}{2}((x_k+\frac{\mathrm{\Λ}\left(d_k\right)}{L_c})(2I-1)+y_k(2J-1)),$ Branch Computed metric in first decoder and second decoder, wherein, Λ (d _k) be prior probability, L _cFor channel is put letter reliability, x _kAnd y _kBe the input signal of decoder, corresponding respectively decoder receives the real part information and the imaginary part information of signal, if first round iteration, Λ (d _k) value be 0; Otherwise the external information that is last round of decoding output is through interweaving or the value of deinterleaving;

(4) according to formula $A_k^i\left(m\right)=D_k(i,p_k(i,m))+\underset{j=\mathrm{0,1}}{\max }\left(A_{k-1}^j(S_b^j\left(m\right)\right)$

$B_k^i\left(m\right)=D_{k+1}(j,p_{k+1}(j,S_f^i\left(m\right)))+\underset{j=\mathrm{0,1}}{\max }\left(B_{k+1}^j(S_f^i\left(m\right)\right)$

Calculate forward metrics and back to tolerance in first decoder and second decoder, wherein (i m) is illustrated in present condition m and the NextState of importing encoder under the i, wherein p to p _k(i, initial value m) are 0; S ^j(m) expression is transferred to the previous state of m by j, wherein, and S _b ^j(m), S _f ^j(m) the subscript b in, f represent respectively forward direction and back to the relation of recurrence, the relation of its position of expression;

(5) basis $L\left(d_k\right|R_1^N)=\underset{m=\mathrm{0,1},2^v-1}{\max }(A_K^1\left(m\right)+B_k^1\left(m\right))-\underset{m=\mathrm{0,1},2^v-1}{\max }(A_K^0\left(m\right)+B_k^0\left(m\right)),$ In first decoder and second decoder, calculate likelihood output respectively;

(6) judge whether iterations finishes,, then forward step (9) to and in second decoder, carry out hard decision if iterations has arrived; Otherwise, then carry out step (7) and continue to calculate external information;

(7) first decoders are according to formula $L_e\left(d_k\right)=L\left(d_k\right|R_1^N)-\mathrm{Lc}*x_k-\mathrm{\Λ}\left(d_k\right)$ Calculate the external information of first decoder;

(8) external information that calculates is sent in first interleaver interweaved, send into then in second decoder, information after second decoder interweaves this as prior information also to the received signal, comprise that real part information and imaginary part information carries out optimal decoding, generation is about the likelihood information of each bit in the information sequence after interweaving, give first decoder as prior information with external information wherein through deinterleaver then, forwarding step (2) again to handles, wherein, directly the real part information of the signal that receives is sent into the wherein input signal of first decoder as first decoder, for second decoder, the real part information of the signal that receives interweaves through one second interleaver earlier, and then second interleaver export interweave after sequence as the wherein input signal of second decoder;

(9) second decoders carry out hard decision to likelihood output, obtain Turbo code decode results L (d _k).

According to a further aspect in the invention, the invention still further relates to and a kind ofly can realize SCDMA system channel Turbo apparatus for encoding, described device comprises a multiframe interleaver and an asymmetric Turbo encoder.

Preferably, described asymmetric Turbo encoder comprises an interleaver, different and first component coder and second component encoder, a residual matrix and a multiplexer that is connected with described two component coders by described interleaver parallel cascade of structure each other.Input message sequence is sent into multiplexer, first component coder and interleaver respectively simultaneously, first component coder is encoded to information sequence, deliver in the second component encoder after interleaver interweaves to the information sequence information of carrying out and encode, the verification sequence of two component coders output is deleted surplus respectively at residual matrix, thereby described multiplexer carries out multiple connection and handles the data sequence that obtains behind the Turbo coding described surplus the verification of data sequences and the described system dateout sequence of having deleted that receives.Wherein, the generator matrix of described first component coder is that (7,5), generator polynomial are (1+D+D ², 1+D ²), described second component encoder generator matrix is that (13,17), generator polynomial are (1+D ²+ D ³, 1+D+D ²+ D ³).

The present invention also provides a kind of device that can realize SCDMA system channel Turbo decoding again on the other hand according to of the present invention, and described asymmetric Turbo code translator comprises a multiframe deinterleaver and an asymmetric Turbo decoder.

Preferably, the described asymmetric Turbo decoder in the described Turbo code translator comprises a residual matrix module, first decoder, first interleaver, second decoder, deinterleaver and second interleaver that is connected with first decoder, second decoder respectively.Wherein, the residual matrix module is handled the data sequence before deciphering, it is corresponding to make it satisfy the signal that encoder produced in signal that decoder receives and transmission stage, first decoder to the received signal, comprise that real part information and imaginary part information deciphers, and the external information that calculates sent in first interleaver interweave, send into then in second decoder, information after second decoder interweaves this as prior information also to the received signal, comprise that real part information and imaginary part information carries out optimal decoding, generation is about the likelihood information of each bit in the information sequence after interweaving, give first decoder as prior information with external information wherein through deinterleaver then, carry out next round decoding, wherein, directly the real part information of the signal that receives is sent into the wherein input signal of first decoder as first decoder, for second decoder, the real part information of the signal that receives interweaves through one second interleaver earlier, and then second interleaver export interweave after sequence as the wherein input signal of second decoder.

Turbo code device for encoding and decoding and method that the present invention proposes, by adopting multiframe to interweave and asymmetric Turbo code compiling structure and Turbo code optimization Algorithm etc., existing SCDMA system is being changed under the little situation, for the SCDMA system has brought the excellent properties of Turbo code chnnel coding, make the SCDMA system obtain better chnnel coding gain and reduced the error rate.

Description of drawings

Below in conjunction with accompanying drawing the specific embodiment of the present invention is described in further detail.In the accompanying drawing:

Fig. 1: the signal processing flow of SCDMA system Turbo code device;

Fig. 2: the asymmetric Turbo code encoder of SCDMA system;

Fig. 3: the asymmetric Turbo code code device of SCDMA system;

Fig. 4: the asymmetric Turbo code decoder of SCDMA system;

Fig. 5: the asymmetric Turbo code code translator of SCDMA system;

Fig. 6: under quiescent conditions, the graph of a relation of three kinds of channel coding method bit error rates and signal to noise ratio;

Fig. 7: under mobile condition, the graph of a relation of three kinds of channel modulation mode bit error rates and signal to noise ratio;

Fig. 8: the signal processing flow of Turbo code transmitting terminal in the SCDMA system;

Fig. 9: the SCDMA system realizes Turbo code Methods for Coding schematic diagram;

Figure 10: SCDMA system Turbo code encoder method schematic diagram;

Figure 11: SCDMA system Turbo code receiving end signal handling process;

Figure 12: the method schematic diagram of Turbo code decoding in the SCDMA system;

Figure 13: SCDMA system Turbo code decoder method schematic diagram.

Embodiment

According to the feature and the business need of SCDMA system, the present invention proposes a kind of apparatus and method that in the SCDMA system, realize the Turbo coding and decoding.Simultaneously, based on the reality (being that every frame data length has only 96 bits) of the short-and-medium frame of SCDMA system, the present invention proposes the scheme that multiframe interweaves.By the multiframe data are carried out interweaving of data, make the SCDMA system both can obtain the gain that interweaves, can make the SCDMA system obtain the gain of time diversity again.At last, the situation that takies of and DSP resource lower to the signal to noise ratio (snr) thresholding based on the SCDMA system the present invention proposes the unsymmetric structure (structure that is the encoder in the Turbo code device for encoding and decoding has adopted the asymmetry structure) of Turbo code and Turbo code is optimized algorithm and is optimized to adapt to SCDMA system signal handling process and to the requirement of signal to noise ratio.

The apparatus and method that in the SCDMA system, realize the Turbo coding and decoding proposed by the invention, it realizes the main flow process of Turbo coding and decoding signal processing in the SCDMA system, as shown in Figure 1, its main contents can be divided into the launching phase of Turbo code coding and the reception stage of decoding.

From Fig. 1, can draw, in the SCDMA system, realize Turbo coding and decoding signal processing flow and existing base station handling process basically identical, just increased multiframe data interleaver and asymmetric Turbo encoder, in the receiver decoding process, increased multiframe data deinterlacing device and asymmetric Turbo decoder in modulation.

Figure 2 shows that described in the SCDMA system the Turbo device for encoding and decoding and the asymmetry Turbo coder structure of method, promptly first component coder is adopted different constraint lengths and generator polynomial respectively with the second component encoder.The present invention proposes asymmetry Turbo code compiling structure, and purpose is under low signal-to-noise ratio (SNR) condition of SCDMA system, and the SCDMA system can obtain relatively good Turbo code chnnel coding gain.

As can be seen from Figure 2, the Turbo encoder mainly is made up of two systematic recursive convolutional sign indicating number (RSC) first component coder, second component encoder and interleavers inequality in SCDMA system transmitting terminal, and two encoders by the interleaver parallel cascade together.The first component coder generator matrix is (7,5), and its generator polynomial is (1+D+D ², 1+D ²), second component encoder generator matrix is (13,17), its generator polynomial is (1+D ²+ D ³, 1+D+D ²+ D ³).

Realize that in the SCDMA system input message sequence of two component coders is identical in the Turbo cataloged procedure, length is the information sequence { U of N _kWhen sending into first component coder and encoding as the output { C of system ^sDirectly deliver to multiplexer, { U simultaneously _kPass through to deliver in the second component encoder after the interleaver information of carrying out interweaves and encode, the verification of two component coder outputs is respectively { C ^1pAnd { C ^2p, delete the surplus { C that obtains at residual matrix then ^p, the last and output sequence { C of system ^sCarry out differential modulation jointly.

The decoder architecture of the PCCC that realization reception stage Turbo deciphers in the SCDMA system proposed by the invention as shown in Figure 4.

As can be seen from Figure 4, the basic process of realization Turbo decoding is as follows in the SCDMA system:

According to the rule of transmitting terminal residual matrix, the residual matrix module in the described asymmetric Turbo decoder is handled the data sequence before deciphering, and it is corresponding to make it satisfy the signal that encoder produced in signal that decoder receives and transmission stage.Decoder comprises real part information X to the received signal _KWith imaginary part information Y _KDecipher, the real part information of the signal that first decoder and second decoder receive all is X _K, and the imaginary part information of the signal that first decoder and second decoder receive is respectively Y _K ¹And Y _K ², wherein, directly the real part information X of the signal that receives _kSend into the wherein input signal of first decoder as first decoder, for second decoder, the real part information X of the signal that receives _kInterweave earlier through one second interleaver, and then second interleaver export interweave after sequence X _π(k) as the wherein input signal of second decoder.At first first decoder carries out optimal decoding to the output of the first subcomponent encoder, produces about information sequence { d _kIn the likelihood information of each bit, and external information L that will be wherein _e ¹(d _k) give second decoder through interweaving, second decoder with this as prior information L _E2(d _k), optimal decoding is carried out in the output of the second subcomponent encoder, produce likelihood information about each bit in the information sequence after interweaving, incite somebody to action external information L wherein then _e ²(d _k) give first decoder as prior information L through deinterleaver _E1(d _k), carry out next round decoding.Like this, through iteration repeatedly, the external information of first decoder and second decoder tends towards stability, and the likelihood ratio asymptotic value approaches the maximum-likelihood decoding to whole codeword, at last to second decoder output likelihood value L (d _k) carry out hard decision, can obtain information sequence { d _kThe best estimate of each bit.

According to the characteristics of SCDMA system and the applicable cases of DSP resource, need do a compromise processing to the complexity and the performance of the Turbo coding and decoding that system adopted, so in the SCDMA system, adopt the MAX_LOG_MAP decoding algorithm to carry out Turbo decoding, and carry out the optimization of implementation algorithm according to the characteristics of the DSP of SCDMA system, below just the MAX_LOG_MAP among the present invention is done simple the derivation.

The MAX_LOG_MAP algorithm is to have done some to improve on the MAP of classics algorithm basis, and its concrete expression formula is as follows:

$A_k^m=\log \left({\mathrm{\α}}_k^m\right)=\log \left(\underset{j=0}{\overset{1}{\mathrm{\Σ}}}\exp \right\{\log \left({\mathrm{\α}}_{k-1}^{b(j,m)}\right)+\log \left(r_{k-1}^{j,b(j,b)}\right)\left\}\right)$

$B_k^m=\log \left({\mathrm{\β}}_k^m\right)=\log \left(\underset{j=0}{\overset{1}{\mathrm{\Σ}}}\exp \right\{\log \left({\mathrm{\γ}}_{k-1}^{j,m}\right)+\log \left({\mathrm{\β}}_{k+1}^{f(j,m)}\right)\left\}\right)$

$D_k^{i,m}=\log \left({\mathrm{\γ}}_k^{i,m}\right)=\log \left(\mathrm{Pr}(d_k=i,S_k=m,R_k)\right)$

$L\left(d_k\right|R_1^N)=\log \left(\frac{\underset{m}{\mathrm{\&Sigma;}}{\mathrm{\&alpha;}}_k^m{\mathrm{\&gamma;}}_{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="A20061007648500261.png,A20061007648500262.png"\; state="\{\{state\}\}">k</figure-callout>}}^{1,m}{\mathrm{\&beta;}}_{k+1}^{f(1,m)}}{\underset{m}{\mathrm{\&Sigma;}}{\mathrm{\&alpha;}}_k^m{\mathrm{\&gamma;}}_{\mathrm{<figure-callout\; id="0"\; label="k"\; filenames="A20061007648500261.png,A20061007648500262.png"\; state="\{\{state\}\}">k</figure-callout>}}^{0,m}{\mathrm{\&beta;}}_{k+1}^{f(0,m)}}\right)$

$=\log \underset{m}{\mathrm{\&Sigma;}}\exp \{\log \left({\mathrm{\&alpha;}}_k^m\right)+\log \left({\mathrm{\&gamma;}}_{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="A20061007648500261.png,A20061007648500262.png"\; state="\{\{state\}\}">k</figure-callout>}}^{1,m}\right)+\log \left({\mathrm{\&beta;}}_{k+1}^{f(1,m)}\right)\}$

$-\log \underset{m}{\mathrm{\&Sigma;}}\exp \{\log \left({\mathrm{\&alpha;}}_k^m\right)+\log \left({\mathrm{\&gamma;}}_{\mathrm{<figure-callout\; id="0"\; label="k"\; filenames="A20061007648500261.png,A20061007648500262.png"\; state="\{\{state\}\}">k</figure-callout>}}^{0,m}\right)+\log \left({\mathrm{\&beta;}}_{k+1}^{f(0,m)}\right)\}$

According to the Jacobian algorithm, promptly

log(e ^x+e ^y)＝max(x，y)+log(1+e ^-|x-y|)

If adopt approximate expression:

log(e ^x+e ^y)＝max(x，y)

Then obtain as follows through deriving:

$A_k^m\&ap;\max (A_{k-1}^{b(1,m)}+D_{k-1}^{1,b(1,m)},A_{k-1}^{b(0,m)}+D_{k-1}^{1,b(1,m)})$

$B_k^m\&ap;\max (B_{k+1}^{f(1,m)}+{\mathrm{<figure-callout\; id="1"\; label="D\; k"\; filenames="A20061007648500261.png,A20061007648500262.png"\; state="\{\{state\}\}">D</figure-callout>}}_k^{},B_{k+1}^{f(0,m)}+{\mathrm{<figure-callout\; id="0"\; label="D\; k"\; filenames="A20061007648500261.png,A20061007648500262.png"\; state="\{\{state\}\}">D</figure-callout>}}_k^{})$

$L\left(d_k\right|R_1^N)\&ap;\underset{m}{\max }(A_k^m+{\mathrm{<figure-callout\; id="1"\; label="D\; k"\; filenames="A20061007648500261.png,A20061007648500262.png"\; state="\{\{state\}\}">D</figure-callout>}}_k^{}+B_k^m)-\underset{m}{\max }(A_k^m+{\mathrm{<figure-callout\; id="0"\; label="D\; k"\; filenames="A20061007648500261.png,A20061007648500262.png"\; state="\{\{state\}\}">D</figure-callout>}}_k^{}+B_k^m)$

Wherein (j m) is illustrated in present condition m and imports under the j NextState of encoder f; (j is m) for transferring to the previous state of m state by input j for b; A _k ^m, B _k ^m, D _k ^{I, m}Expression is respectively forward metrics, back to tolerance and metastatic rate value; L (d _k| R ₁ ^N) be expressed as code element d _kThe posterior probability log-likelihood ratio.

According to the feature of Turbo decoding and the DSP characteristics of SCDMA system, the present invention has done optimization on some engineerings to the Turbo decoding scheme, wherein calculate the iterative process of forward metrics and reverse metrics according to the butterfly structure of Turbo code, also branched measurement value is simplified calculating, promptly do not handle for identical entry.Simultaneously, be used to calculate forward metrics and back to branched measurement value preserve, so only need to calculate separately forward metrics and back to the iterative value of measuring, amount of calculation and intermediate storage amount are significantly reduced.And to channel confidence level L _cCalculating, owing to SCDMA system itself need to calculate and to separate differentiated signal to noise ratio (snr) and make it become simpler.

The apparatus and method of the Turbo coding and decoding in the SCDMA proposed by the invention system, its main contents can be divided into the launching phase of Turbo code coding and the reception stage of decoding.

In the SCDMA system transmitting terminal Signal Processing process step of Turbo code coding as shown in Figure 8, it mainly may further comprise the steps:

(1) SCDMA system initialization parameter is prewired and be ready for sending data, and main prewired parameter comprises at least: the interleaver parameter of multi frame buffer district, every frame coded data length, Turbo code encoder, Turbo coding residual matrix and take the isoparametric setting of code rate;

(2) the N frame data that needs are sent carry out data interlacing according to interleaver interleave depth L.Its purpose mainly is to increase the Turbo code interleaver sizes by the N frame data, has also increased the effect of time diversity simultaneously, thereby better promotes the chnnel coding gain of Turbo code in the SCDMA system;

(3) interleaver from the N frame takes out the data sequence U that present frame need send, and being put into needs to send in the buffering area;

(4) from send buffering area, take out data sequence U, carry out the Turbo code cataloged procedure, also the back data flow of encoding is carried out residual matrix and multiplexer processing simultaneously according to asymmetric Turbo code coding structure proposed by the invention;

(5) data sequence after handling by Turbo code is carried out difference processing, because existing SCDMA system is adopted as the DQPSK modulation system, in order to carry out compatibility with existing system, the present invention still adopts the modulation system of DQPSK;

(6) the 4PSK modulator carries out two-dimentional Gray code modulation to differentiated data sequence V, generates the two-dimensional modulation burst that has only V/2 length;

(7) the two-dimensional modulation burst is carried out spread processing;

(8) signal behind the spread spectrum is carried out pulse shaping filtering, and then deliver to the processing of carrying out radio frequency part in the SCDMA system channel, finally the spectrum CDMA signal of SCDMA system is sent.

In step 4, be mainly concerned with the code device of asymmetry Turbo code proposed by the invention, the code device of following asymmetry Turbo code of specifically setting forth among the present invention to be mentioned in conjunction with Fig. 3, Fig. 9 and original data are carried out the code device handling process of Turbo code, its concrete steps are as follows:

(a) before Turbo code carries out, parameter to Turbo is carried out initialization and setting, and it specifically comprises at least, and interleaver interleave depth, first component coder and second component encoder initial condition are zero, the parameter settings such as length of residual matrix, encoder data;

(b) to carry out the data interlacing of N frame from the data sequence U that sends the buffering area taking-up;

(c) to first component coder, its constraint length is 3, and generator matrix is that (7,5) carry out the Turbo code cataloged procedure.It specifically is to be the information sequence { U of N with length _kWhen sending into first component coder and encoding as the output { C of system ^sDirectly deliver to multiplexer, the verification { C of its generation ^1p;

(d) with length be the information sequence { U of N _kTo generate information sequence by the Turbo code interleaver be { U _{π (k)};

(e) with sequence be the back information sequence { U that interweaves of N _{π (k)}, carrying out the second component encoder, its constraint length is 4, generator matrix is that (13,17) carry out the Turbo code cataloged procedure.It specifically is to be the information sequence { U of N with length _{π (k)}Deliver to the second component encoder and encode, generation be verified as { C ^2p;

(f) verification with two component coder outputs is respectively { C ^1pAnd { C ^2p, delete and obtain { C after surplus carrying out residual matrix ^p;

(g) will delete and obtain { C after surplus ^pExport { C with system ^sInformation behind the Turbo coding formed carries out the processing of back.

Above-mentioned is the elaboration of key step that the signal processing flow of Turbo code code device proposed by the invention and coding are realized, and the method for Turbo code encoder, in conjunction with Figure 10 as can be seen, its key step is roughly consistent with above-mentioned steps, just in above-mentioned step, increased the process that the N frame interweaves, and other processes are the same.

Then the signal processing flow of the receiving terminal of Turbo code and the key step of realization of decoding are briefly described below.

As shown in Figure 1, the method that realizes Turbo decoding in the SCDMA system mainly be may further comprise the steps:

(a) before handling to received signal, the SCDMA system carries out initialization and parameter setting to system;

(b) despreader is searched for the processing of Synchronous Processing, despreading to the data that receive, and promptly the initial data that receives is carried out the relevant processing of despreading;

(c) signal of a phase difference device after to despreading carries out the difference processing of symbol, to obtain differentiated signal;

(d) according to the processing of transmitting terminal to the multiframe data interleaver, a multiframe data deinterlacing device is handled the deinterleaving that differentiated signal carries out the multiframe data;

(e) an asymmetric Turbo decoding is directly carried out Turbo code decoding processing to differentiated original signal;

(f) obtain the data sequence of received signal at last.

More than to realizing in the SCDMA system that the whole signal processing of Turbo code sets forth, below in conjunction with Fig. 5, Figure 12, elaborate the interpretation method of Turbo code device, described interpretation method specifically may further comprise the steps:

(1) parameter setting and the initialization process before the Turbo decoding beginning, its parameter is prewired to comprise the setting of decoder initial condition, Turbo code interleaver sizes and rule, Turbo code iterations and different channels attenuation factor and prewired at least;

(2) according to the processing of transmitting terminal to the multiframe data interlacing, described multiframe deinterleaver carries out the multiframe data deinterlacing to differentiated signal to be handled, to prepare that data are carried out the Turbo code process of decoding;

(3) according to the rule of transmitting terminal residual matrix, the residual matrix module in the Turbo decoder is handled the data sequence before deciphering, and it is corresponding to make it satisfy the signal that encoder produced in signal that decoder receives and transmission stage; The residual matrix module is a functions of modules in the Turbo code encoder, and is to receiving signal Y at receiving terminal _K, X _KDistribute to decoder 1Y according to encoder residual matrix module correspondence _K ¹, decoder 2 signal Y _K ²As: if current be the signal Y of decoder 1 _K ¹=Y _K, then giving decoder, and in the decoder 2

Two decoder X _KIdentical.In Fig. 4, exactly received signal is distributed to two decoders respectively according to odevity.Realize like this in the decoder with encoder in the function of residual matrix module.

(4) according to formula $D_k(I,J)=\frac{L_c}{2}((x_k+\frac{\mathrm{\&Lambda;}\left(d_k\right)}{L_c})(2I-1)+y_k(2J-1)),$ Branch Computed metric in first decoder and second decoder, D _K(I J) is branched measurement value from the i state to the j state; If first decoder, the then x in the formula _kAnd y _kCorresponding X _kAnd Y _K ¹, for the then corresponding X of second decoder _kAnd Y _K ¹Λ (d _k) be prior probability, if first round iteration, its value is 0; Otherwise the external information that is last round of decoding output is through interweaving or the value of deinterleaving, for first decoder and the second decoder Λ (d _k) be respectively Le ₁(dk) and Le ₂(dk).Because needing to calculate, SCDMA system itself separates differentiated signal to noise ratio, so to channel confidence level L _cCalculating be fairly simple problem.

(5) according to formula

$A_k^i\left(m\right)=D_k(i,p_k(i,m))+\underset{j=\mathrm{0,1}}{\max }\left(A_{k-1}^j(S_b^j\left(m\right)\right)$

$B_k^i\left(m\right)=D_{k+1}(j,p_{k+1}(j,S_f^i\left(m\right)))+\underset{j=\mathrm{0,1}}{\max }\left(B_{k+1}^j\left(S_f^i(m\right)\right)$

Calculate forward metrics and back to tolerance in first decoder and second decoder, wherein (i m) is illustrated in present condition m and the NextState of importing encoder under the i, wherein p to p _k(i, initial value m) are 0; S ^j(m) expression is transferred to the previous state of m by j, wherein, and S _b ^j(m), S _f ^j(m) the subscript b in, f represent respectively forward direction and back to the relation of recurrence, the relation of its position of expression;

(6) basis $L\left(d_k\right|R_1^N)=\underset{m=\mathrm{0,1},2^v-1}{\max }(A_K^1\left(m\right)+B_k^1\left(m\right))-\underset{m=\mathrm{0,1},2^v-1}{\max }(A_K^0\left(m\right)+B_k^0\left(m\right)),$ In first decoder and second decoder, calculate likelihood output respectively;

(7) judge whether iterations finishes,, then forward step (10) to and in second decoder, carry out hard decision that described iterations is recently determined by the noise of SCDMA system, is 4 iteration at present if iterations has arrived; Otherwise, then forward step (8) to and continue to calculate external information L _e(d _k);

(8) first decoders are according to formula $L_e\left(d_k\right)=L\left(d_k\right|R_1^N)-\mathrm{Lc}*x_k-\mathrm{\&Lambda;}\left(d_k\right)$ Calculate the external information L of first decoder ¹ _e(d _k);

(9) will calculate the external information L of first decoder ¹ _e(d _k) send into and send in second decoder after interweaving in first interleaver, the information after second decoder interweaves this is as prior information Le ₂(d _k) optimal decoding is carried out in the output of the second subcomponent encoder, simultaneously in the stage that second decoder begins to decipher, the real part information X that receives signal _kIn second interleaver, interweave earlier, and then the sequence X of second interleaver output _π(k) decipher as a wherein input of second decoder, produce likelihood information after second decoder for decoding, incite somebody to action external information L wherein then about each bit in the information sequence after interweaving _e ²(d _k) give first decoder as prior information Le through deinterleaver ₁(dk), forwarding step (3) again to handles;

(10) second decoders by hard decision, obtain Turbo code decode results L (d to likelihood output _k).

More than be to the signal processing flow of realizing the Turbo code code translator in the SCDMA system and the elaboration that concrete steps are carried out.For the decode procedure of realizing Turbo code in the SCDMA system, in conjunction with Figure 13 as can be seen, the deinterleaving that has just increased the N frame data in its above-mentioned SCDMA system in the Turbo code translator key step is handled, and other process unanimities.

Increased N frame interleaver and deinterleaver in the key step just because of the Turbo code device for encoding and decoding in the SCDMA system, the performance of Turbo code in the SCDMA system is promoted greatly.

Fig. 6 is under the terminal quiesce condition, the comparison of the existing coded system of Turbo code chnnel coding proposed by the invention and SCDMA system.As can be seen from Figure 6, by Turbo code channel coding schemes of the present invention, the chnnel coding of acquisition gains significantly better than the existing channel coding method of existing SCDMA system, is 10 in the error rate ^-6The time, Turbo code channel coding schemes of the present invention is better than the scheme of existing convolution code, because the asymmetric Turbo code encoder that the present invention proposes, its status register is respectively 2,3, and realize that the status register of convolution chnnel coding is 6 in the existing SCDMA system, therefore, the complexity of Turbo code channel coding device proposed by the invention and method is less than the convolution code chnnel coding.Simultaneously Turbo code can also adopt the Turbo code coding structure of different constraint lengths according to the DSP of SCDMA system occupation condition flexibly in the realization of SCDMA system, with the performance of elevator system further.

Fig. 7 is under the terminal mobile condition, the comparison of the existing coded system of Turbo code chnnel coding proposed by the invention and SCDMA system.In the SCDMA system, its terminal is under the situation of v=60 kilometer/hour motion in speed, Turbo code channel coding device and method proposed by the invention, the performance of the chnnel coding of equally also doing well.Specifically as seen from Figure 7, under mobile condition, the performance of its Turbo code chnnel coding obviously is better than the performance of other two kinds of chnnel codings.

No matter under static still mobile condition, Turbo code apparatus and method in the SCDMA system proposed by the invention obviously are better than the channel coding schemes of existing SCDMA system, the while what is more important, owing to need mend 6 zero at the end in the convolution code chnnel coding of carrying out the SCDMA system, and for Turbo code of the present invention, owing to have only three status registers, even the end zero padding, also only need to mend 2 zero, therefore obviously improved the channel valid data transmission efficiency.

Claims (9)

1. in the SCDMA system, realize channel Turbo Methods for Coding for one kind, it is characterized in that, said method comprising the steps of:

(1) a plurality of prewired parameters of SCDMA system initialization and preparation need the N frame data of transmission;

(2) one multiframe interleavers carry out data interlacing to the described N frame data that need to send;

(3) described multiframe interleaver takes out the data sequence that need send when former frame in the N frame data after interweaving and this data sequence is put into one by the mapping relations of the table that interweaves and sends buffering area;

(4) from send buffering area, take out data sequence and this data sequence sent into carry out the Turbo coding in the asymmetric Turbo encoder;

Data sequence after (5) one difference engines are encoded to Turbo carries out difference processing and a 4PSK modulator adopts the 4PSK modulation system that differentiated data sequence is modulated;

(6) data sequence of described 4PSK modulator after to difference and modulation carried out the modulation of two-dimentional Gray code, generates the two-dimensional modulation burst;

(7) one frequency multipliers carry out spread processing to the two-dimensional modulation burst;

(8) signal behind the spread spectrum is carried out pulse shaping filtering, subsequently filtered signal is delivered to the processing of carrying out radio frequency part in the SCDMA system channel, the spectrum CDMA signal of SCDMA system sends the most at last;

(9) turning back to the data sequence that step (3) need send next frame handles until handling whole N frame data.

2. according to the described method of claim 1, it is characterized in that described step (4) and then may further comprise the steps:

(a) before carrying out the Turbo coding, the SCDMA system carries out initialization and setting according to the requirement of system to the parameter of asymmetric Turbo encoder;

(b) thus will send into the data sequence of carrying out the Turbo code interleaver of described asymmetric Turbo encoder after data interlacing obtains to interweave from sending a frame data sequence that buffering area takes out; Thereby will encode from first component coder that a described frame data sequence that sends the buffering area taking-up is sent into described asymmetric Turbo encoder simultaneously and generate first the verification of data sequences; Also will send into the multiplexer of described asymmetric Turbo encoder as system's dateout sequence simultaneously from a described frame data sequence that sends the buffering area taking-up;

(c) thus the second component encoder that the data sequence after described interweaving is sent into described asymmetric Turbo encoder encoded generate second the verification of data sequences;

(d) thus carrying out puncturing process in the residual matrix that first the verification of data sequences that described two component coders are exported respectively and second the verification of data sequences are sent into described asymmetric Turbo encoder simultaneously obtains to have deleted surplus the verification of data sequences and this sequence is sent in the multiplexer of described asymmetric Turbo encoder;

(e) thus described multiplexer carries out multiple connection and handles the data sequence that obtains behind the Turbo coding described surplus the verification of data sequences and the described system dateout sequence of having deleted that receives.

3. a method that realizes channel Turbo decoding in the SCDMA system is characterized in that, said method comprising the steps of:

(a) the SCDMA system carries out system initialization and parameter setting;

(b) despreader is searched for Synchronous Processing and despreading processing to the spectrum CDMA signal that receives;

(c) signal of a phase difference device after to despreading carries out difference processing, to obtain differentiated signal;

Processing to the multiframe data interlacing when (d) a multiframe data deinterlacing device is encoded according to Turbo is handled with the signal after the acquisition deinterleaving the deinterleaving that differentiated signal carries out the multiframe data;

(e) signal of an asymmetric Turbo decoder after to deinterleaving carries out Turbo code decoding and handles the data sequence that obtains received signal.

4. method according to claim 3 is characterized in that, described step (e) and then may further comprise the steps:

(1) before the Turbo decoding beginning, described asymmetric Turbo decoder is carried out parameter setting and initialization process;

(2) according to the rule of transmitting terminal residual matrix, the residual matrix module in the described asymmetric Turbo decoder is handled the data sequence before deciphering, and it is corresponding to make it satisfy the signal that encoder produced in signal that decoder receives and transmission stage;

(3) according to formula $D_k(I,J)=\frac{L_c}{2}((x_k+\frac{\mathrm{\&Lambda;}\left(d_k\right)}{L_c})(2I-1)+y_k(2J-1)),$ Branch Computed metric in first decoder and second decoder, wherein, Λ (d _k) be prior probability, L _cFor channel is put letter reliability, x _kAnd y _kBe the input signal of decoder, corresponding respectively decoder receives the real part information and the imaginary part information of signal, if first round iteration, Λ (d _k) value be 0; Otherwise the external information that is last round of decoding output is through interweaving or the value of deinterleaving;

(4) according to formula $A_k^i\left(m\right)=D_k(i,p_K(i,m))+\underset{j=\mathrm{0,1}}{\max }\left(A_{k-1}^j\left(S_b^j\left(m\right)\right)\right)$

$B_k^i\left(m\right)=D_{k+1}(j,p_{k+1}(j,S_f^i\left(m\right)))+\underset{j=\mathrm{0,1}}{\max }\left(B_{k+1}^j\left(S_f^i\left(m\right)\right)\right)$

Calculate forward metrics and back to tolerance in first decoder and second decoder, wherein (i m) is illustrated in present condition m and the NextState of importing encoder under the i, wherein p to p _k(i, initial value m) are 0; S ^j(m) expression is transferred to the previous state of m by j, wherein, and S _b ^j(m), S _f ^j(m) the subscript b in, f represent respectively forward direction and back to the relation of recurrence, the relation of its position of expression;

(5) basis $L\left(d_k\right|R_1^N)=\underset{m=\mathrm{0,1},2^v-1}{\max }(A_K^1\left(m\right)+B_k^1\left(m\right))-\underset{m=\mathrm{0,1},2^v-1}{\max }(A_K^0\left(m\right)+B_k^0\left(m\right)),$ In first decoder and second decoder, calculate likelihood output respectively;

(6) judge whether iterations finishes,, then forward step (9) to and in second decoder, carry out hard decision if iterations has arrived; Otherwise, then carry out step (7) and continue to calculate external information;

(7) first decoders are according to formula L _e(d _k)=L (d _k| R ₁ ^N)-Lc* χ _k-Λ (d _k) calculate the external information of first decoder;

(8) external information that calculates is sent in first interleaver interweaved, send into then in second decoder, information after second decoder interweaves this as prior information also to the received signal, comprise that real part information and imaginary part information carries out optimal decoding, generation is about the likelihood information of each bit in the information sequence after interweaving, give first decoder as prior information with external information wherein through deinterleaver then, forwarding step (2) again to handles, wherein, directly the real part information of the signal that receives is sent into the wherein input signal of first decoder as first decoder, for second decoder, the real part information of the signal that receives interweaves through one second interleaver earlier, and then second interleaver export interweave after sequence as the wherein input signal of second decoder;

(9) second decoders carry out hard decision to likelihood output, obtain Turbo code decode results L (d _k).

5. can realize SCDMA system channel Turbo apparatus for encoding for one kind, it is characterized in that described device comprises a multiframe interleaver and an asymmetric Turbo encoder.

6. Turbo code device according to claim 5, it is characterized in that, described asymmetric Turbo encoder comprises an interleaver, different and first component coder and second component encoder by described interleaver parallel cascade of structure each other, a residual matrix and a multiplexer that is connected with described two component coders, wherein, input message sequence is sent into multiplexer respectively simultaneously, first component coder and interleaver, first component coder is encoded to information sequence, deliver in the second component encoder after interleaver interweaves to the information sequence information of carrying out and encode, the verification sequence of two component coders output is deleted surplus respectively at residual matrix, thereby described multiplexer carries out multiple connection and handles the data sequence that obtains behind the Turbo coding described surplus the verification of data sequences and the described system dateout sequence of having deleted that receives.

7. Turbo code device according to claim 6 is characterized in that, the generator matrix of described first component coder is that (7,5), generator polynomial are (1+D+D ², 1+D ²), described second component encoder generator matrix is that (13,17), generator polynomial are (1+D ²+ D ³, 1+D+D ²+ D ³).

8. the device that can realize SCDMA system channel Turbo decoding is characterized in that described asymmetric Turbo code translator comprises a multiframe deinterleaver and an asymmetric Turbo decoder.

9. code translator according to claim 8, it is characterized in that, described asymmetric Turbo decoder comprises a residual matrix module, first decoder, first interleaver, second decoder, deinterleaver and respectively with first decoder, second interleaver that second decoder connects, wherein, the residual matrix module is handled the data sequence before deciphering, it is corresponding to make it satisfy the signal that encoder produced in signal that decoder receives and transmission stage, first decoder to the received signal, comprise that real part information and imaginary part information deciphers, and the external information that calculates sent in first interleaver interweave, send into then in second decoder, information after second decoder interweaves this as prior information also to the received signal, comprise that real part information and imaginary part information carries out optimal decoding, generation is about the likelihood information of each bit in the information sequence after interweaving, give first decoder as prior information with external information wherein through deinterleaver then, carry out next round decoding, wherein, directly the real part information of the signal that receives is sent into the wherein input signal of first decoder as first decoder, for second decoder, the real part information of the signal that receives interweaves through one second interleaver earlier, and then second interleaver export interweave after sequence as the wherein input signal of second decoder.

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