CN1466270A - Method for raising performance of series cascade space time coding system - Google Patents

Abstract

This invention discloses a method for increasing serial cascade empty time coding system performance, in which, information series, a form bit series after coding foreign code and interleave process and a character stries is got after empty time coding to the said bit servity to be emitted by emitter antenna. At the receive end, the receive antenna processes the received character series by empty decoding to form bit series to be restored to information service a after deinterleave and foreign code decode keying in that the bit series is coded to character series applying lattice empty time code with parallel branches (PT-STTC) at the sending end, at the receive end, the character serial is decoded to bit series by PT-STTC.

Description

A kind of method that improves performance of series cascade space time coding system

Technical field

The present invention relates to the Space Time Coding technology, refer to a kind of method of utilizing the grid coding of being with parallel branch to improve performance of series cascade space time coding system especially.

Background of invention

In present wireless communication procedure, it is very important making full use of bandwidth and improving power system capacity.Space Time Coding is exactly a kind of many antenna arrays transmissions and reception technique of utilizing, improve the coding techniques of band system band utilance, it is according to the channel capacity theory of many antenna arrays, and when reception antenna number during greater than number of transmit antennas, approximately linear increases the capacity of system with the increase of number of transmit antennas.

Grid Space Time Coding (STTC, Space-Time Trellis Code) is a kind of of Space Time Coding, is to utilize multi-antenna technology, will encode and modulation combines, and can obtain a kind of technology of Space Time Coding preferably of coding gain and diversity gain simultaneously.Wherein, the speed that diversity gain decision STTC performance curve changes with signal to noise ratio, i.e. slope of a curve; Coding gain then determines the position of STTC performance curve in reference axis, and when signal to noise ratio fixedly time the, the corresponding frame error rate size of coding gain decision, coding gain is big more, and corresponding frame error rate is more little.Status number according to the STTC encoder can be divided into STTC two big classes: a class be the status number of STTC encoder more than or equal to the order of modulation that is adopted, then do not have parallel branch in the state transition diagram of such STTC, this type of STTC is commonly used at present arriving; Another kind of be status number less than order of modulation, exist parallel branch in the STTC encoder this moment.

N root transmitting antenna is arranged for one, m root reception antenna (establishing i root transmitting antenna is c at j transmission signal constantly for n, m) Space Time Coding system _j ⁱ, all n send signal and constitute vectorial c _t, then send the sign indicating number Matrix C _{N * N}By all N _fIndividual vector constitutes, wherein N _fIt is the signal number in the frame.If receiving terminal is E sending the misjudgement of sign indicating number Matrix C, then the matrix B of the difference of C and E formation (C E) is: $B(C,E)=\left[\begin{array}{cccc}{c}_1-e_1& c_2-e_2& ...& c_{N_f}-e_{N_f}\end{array}\right]=\left[\begin{array}{cccc}{c}_1^1-e_1^1& c_2^1-e_2^1& ...& c_{N_f}^1-e_{N_f}^{1n}\\ c_1^2-e_1^2& c_2^2-e_2^2& ...& c_{N_f}^2-e_{N_f}^2\\ ...& ...& ...& ...\\ c_1^n-e_1^n& c_2^n-e_2^n& ...& c_{N_f}^n-e_{N_f}^n\end{array}\right]---\left(1\right)$ According to present result of study, for quasistatic fading channel and fast fading channel, mainly (C E) decides the performance of STTC, B (C, order decision diversity gain E), and B (C, E) B by the difference matrix B ^H(C, determinant decision coding gain E).So, when selecting generator matrix, at first guarantee diversity gain, optimize coding gain again, then can obtain diversity gain and coding gain simultaneously.The quasistatic fading channel of being mentioned is meant that the channel fading factor remains unchanged in a frame, and in next frame a class channel of independent variation; Fast fading channel is the very fast class channel of channel fading factor variations.

The order of modulation that adopts as a kind of STTC is 2 ^b, and its status number is 2 ^B-1The time, the parallel branch number is 2 in the state transition diagram of this STTC, this type of status number is less than order of modulation, and has the STTC of parallel branch in the state transition diagram, is the STTC (PT-STTC, STTC with paralleltransitions) that has parallel branch.Its shortest error event length is l=1, this moment corresponding B (C has only in E) row non-vanishing.So, according to right pair-wise error probability of dual-mode antenna in the quasistatic fading channel and the pair-wise error probability in the fast fading channel, can obtain the pair-wise error probability of the shortest error event under quasi-static channel opens and fast fading channel and be respectively:

P(C→E)≤λ ^-m(E _s/4N ₀) ^-m????????????????(2)

P (C → E)≤| c _t-e _t| ^-m(E _s/ 4N ₀) ^-m(3) wherein, λ is the shortest error event corresponding A (C, nonzero eigenvalue E).Usually, under the quasistatic fading channel, the matrix B of being on duty (C, E) during full rank, system can obtain maximum diversity gain mn; Under fast fading channel, (C E) has v row above when non-vanishing, the diversity gain mv that system can obtain to the matrix B of being on duty.And by (2), (3) formula as can be known, no matter be under the quasistatic flat fading channel, still under fast fading channel, the diversity gain that obtains when PT-STTC uses separately only is m, can't obtain the full diversity gain, thereby be difficult to obtain satisfactory performance.

Though adopt the Space Time Coding technology can improve the transmission rate of system,, should not use separately because its anti fading performance is poor slightly, therefore, often Space Time Coding and other error correcting code are united use at present, that is to say, adopt the series cascade system to finish the Space Time Coding process usually.The composition structure of this series cascade system comprises the two large divisions as shown in Figure 1: transmitter unit 10 and receiving element 11, and this transmitter unit 10 further comprises outer code coder 100, interleaver 101, Space Time Coding device 102 and transmitting antenna; Corresponding, decoder 112 and reception antenna when receiving element 11 further comprises outer code decoder device 110, deinterleaver 111, sky.In this system, be reference point with the interleaver, the code word of interleaver front is called outer sign indicating number, and the code word of interleaver back, promptly Space Time Coding is called ISN.The basic operation principle of this system is such: at transmitting terminal, form bit sequence u after the processing of information sequence a outer code coder 100 of process and interleaver 101, STTC encoder 102 to obtaining symbol sebolic addressing behind the bit sequence u coding, sends this symbol sebolic addressing by transmitting antenna more simultaneously; At receiving terminal, decoder 112 when reception antenna is delivered to sky with the symbol sebolic addressing of receiving is decoded into bit sequence, with the processing of this bit sequence through deinterleaver 111 and outer code decoder device 110, recovers the information sequence a that is sent again.

Because weighing one of topmost standard of Space Time Coding system is diversity gain, in above-mentioned processing procedure, in order to guarantee that the Space Time Coding system obtains the full diversity gain, generally select the STTC of coder state number for use greater than order of modulation, that is: the STTC of full rank is as ISN, such as: if system adopts quaternary PSK (QPSK) modulation, then adopt the status number of STTC encoder to equal 4 at least.And do not consider the PT-STTC of user mode number less than order of modulation, because according to the analysis of front, PT-STTC has non-full rank characteristic, can not obtain the full diversity gain.But, when adopting full rank STTC, because the coding and decoding complexity of STTC is exponential increase with the increase of status number, thereby the complexity that makes system is subjected to very big influence, make the optimization of system relatively more difficult, and the status number that will further reduce the STTC encoder is impossible, therefore, has seriously restricted the development of STTC coding.

Though the independent use of PT-STTC can not obtain the full diversity gain, the status number of PT-STTC is less than order of modulation, and from this angle, PT-STTC has important effect aspect the reduction complexity.So, how to make PT-STTC when reducing complexity, the problem that solves the gain of Space Time Coding full diversity becomes main goal in research.

Summary of the invention

In view of this, main purpose of the present invention is to provide a kind of method that improves performance of series cascade space time coding system, makes it when guaranteeing the full diversity gain of series cascade system, and the decoding complexity of STTC is reduced at least half.

For achieving the above object, technical scheme of the present invention is achieved in that

A kind of method that improves performance of series cascade space time coding system, at transmitting terminal, information sequence a carries out obtaining symbol sebolic addressing behind the Space Time Coding to this bit sequence through forming bit sequence after sign indicating number coding and the interleaving treatment outward, and this symbol sebolic addressing sends by transmitting antenna; At receiving terminal, decoding processing formed bit sequence when reception antenna passed through sky with the symbol sebolic addressing of receiving, this bit sequence recovers information sequence a through deinterleaving and outer code decoder processing again; Its key is: adopt the grid Space Time Coding (PT-STTC) with parallel branch that bit sequence is encoded to symbol sebolic addressing at transmitting terminal, adopt PT-STTC that symbol sebolic addressing is decoded as bit sequence at receiving terminal.

Wherein, to another state, there are at least two parallel branchs from a state transitions of encoder in described PT-STTC.This grid Space Time Coding (PT-STTC) with parallel branch can be the two condition PT-STTC based on quaternary PSK (QPSK) modulation; Or be the four condition PT-STTC that modulates based on eight phase phase-shift keyings (8PSK).So, based on the two condition PT-STTC of QPSK modulation or based on the four condition PT-STTC of 8PSK modulation, during to another state, there are two parallel branchs from a state transitions of encoder.

In said method, outer code coding/decoding device adopts convolution code, or adopts Turbo code.Interleaver adopts random interleaver, or is the odd-even device.

Under the quasistatic fading channel, when using PT-STTC separately might be non-the set Г that constitutes of full rank error event _NonfullWith all possible errors event sets Γ that really can occur in the series cascade system that adopts PT-STTC _SCSTCommon factor be empty.

Under fast fading channel, adopt all possible errors event sets Γ that really can occur in the series cascade system of PT-STTC _SCSTMiddle minimum non-zero columns is v _MinMore than or equal to 2.

This method further comprises: to the PT-STTC based on QPSK modulation, when the list entries of encoder is u=(a ₀, b ₀, a ₁, b ₁, ..., a _L, b _L) time, (a _i, b _i) be the PT-STTC encoder at i input information constantly, set a in the list entries _i(i=0,1 ..., L) all equal zero.To PT-STTC, when the list entries of encoder is u=(a based on 8PSK modulation ₀, b ₀, c ₀, a ₁, b ₁, c ₁..., a _L, b _Lc _L) time, (a _i, b _i, c _i) be the PT-STTC encoder at i input information constantly, set a in the list entries _iAnd b _i(i=0,1 ..., L) all equal zero.

By such scheme as can be seen, key of the present invention is: in the series cascade space time coding system, adopt PT-STTC as ISN.

The method of raising performance of series cascade space time coding system provided by the present invention, because the status number of PT-STTC is less than order of modulation, adopt the ISN of PT-STTC, the coding and decoding complexity of system can be reduced at least half as the series cascade space time coding system.Simultaneously, owing to utilize the synergy of outer sign indicating number and interleaver to compensate some non-full rank error event of PT-STTC, guaranteeing the full diversity gain of system's Space Time Coding, thereby under the prerequisite of reduction system complexity, further improved the performance of whole system.

Description of drawings

Fig. 1 is the composition structural representation of series cascade space time coding system;

Fig. 2 is the state transition diagram based on the two condition PT-STTC of QPSK modulation;

Fig. 3 is the state transition diagram based on the four condition PT-STTC of 8PSK modulation;

Fig. 4 is the composition structural representation of series cascade grid Space Time Coding of the present invention system;

Fig. 5 a is the simulation performance curve chart that uses separately under the quasistatic fading channel based on the PT-STTC of QPSK;

Fig. 5 b is the simulation performance curve chart that uses separately under the quasistatic fading channel based on the PT-STTC of 8PSK;

Fig. 6 a is series cascade system simulation performance curve chart under the quasistatic fading channel of ISN for adopting the PT-STTC based on QPSK;

Fig. 6 b is series cascade system simulation performance curve chart under the quasistatic fading channel of ISN for adopting the PT-STTC based on 8PSK;

Fig. 7 a is series cascade system simulation performance curve chart under fast fading channel of ISN for adopting the PT-STTC based on QPSK;

Fig. 7 b is series cascade system simulation performance curve chart under fast fading channel of ISN for adopting the PT-STTC based on 8PSK.

Embodiment

Because there is parallel branch in the status number of PT-STTC less than order of modulation in the state transition diagram, the direct diversity gain that influences system of meeting, normally not adopted.But, in series cascade system shown in Figure 1, unite when PT-STTC and other error correcting code and to use when constituting series cascade space time coding, though the non-full rank characteristic of itself can not change, but the influence of outer sign indicating number can make the list entries of PT-STTC encoder change to some extent, that is: can to make the sequence that enters the STTC encoder only be a subclass of the possible sequence of institute to the redundant information introduced of outer sign indicating number, so, as long as the error event that this subclass correspondence code matrix constitutes is a full diversity, this series cascade system just can obtain the full diversity gain.As seen, in the series cascade system, adopting the empty time-code of full rank grid is its abundant inessential condition that obtains full diversity as ISN.This analysis makes the application of PT-STTC in the series cascade system become possibility, and then the possibility that improves diversity gain in fading channel is provided.

Thought of the present invention utilizes the PT-STTC coding techniques to reduce system complexity just, utilize the characteristic of outer sign indicating number and interleaver to compensate the non-full rank error event of introducing by PT-STTC simultaneously, suppress non-full rank error event and in list entries, occur, thereby obtain the prerequisite decline low complex degree of full diversity in the assurance system.

Based on above-mentioned thought, respectively to the series cascade system that adopts PT-STTC under the quasistatic fading channel and the performance under fast fading channel analyze:

Under the quasistatic fading channel, to set when using PT-STTC separately, the set that institute might non-full rank error event formation is Г _NonfullBe set in when adopting PT-STTC in the series cascade system, all possible errors event sets that really can occur in the series cascade system are Γ _SCSTSo, Γ _NonfullAnd Γ _SCSTOnly may there be three kinds of relations: , and ≠ Ω, wherein Ω represents empty set; $\left(2\right)---{\mathrm{\&Gamma;}}_{\mathrm{SCST}}{\&Subset;\mathrm{\&Gamma;}}_{\mathrm{nonfull}};$ $\left(3\right)---{\mathrm{\&Gamma;}}_{\mathrm{SCST}}{\&cap;\mathrm{\&Gamma;}}_{\mathrm{nonfull}}=\mathrm{\&Omega;}.$ For these three kinds of relations, if set up (3), the equal full rank of the error event that really can occur in the series cascade system is described then, system shown in Figure 1 can obtain the full diversity gain.At this moment, the frame error rate of system shown in Figure 1 is: $P_f\&le;\underset{w=1}{\overset{{\mathrm{<figure-callout\; id="0"\; label="LR\; c"\; filenames="A0212353100162.png,A0212353100201.png"\; state="\{\{state\}\}">LR</figure-callout>}}_c^{}}{\mathrm{\&Sigma;}}}\underset{\mathrm{\&Lambda;}={\mathrm{\&Lambda;}}_{\min }}{\overset{{\mathrm{\&Lambda;}}_{\max }}{\mathrm{\&Sigma;}}}{\mathrm{\&Lambda;}}^{-m}A(r=2,\mathrm{\&Lambda;},w){(E_s/{4N}_0)}^{-2m}$ Wherein, A (r, Λ _i, be that order is the long-pending Λ of being of r, nonzero eigenvalue w) _iAnd the information sequence Hamming distance is all error event numbers of w, and its value will be united definite by outer sign indicating number and interleaver, and changes with the different of interleaver with outer sign indicating number; E _s/ 4N ₀Be signal to noise ratio.So, when being ISN with PT-STTC in the present invention, as long as select suitable outer sign indicating number and interleaver, because interleaver has the function to the input information displacement, assurance relation (3) is set up, and can make system obtain superior performance when reducing complexity.

Under fast fading channel, the performance of Space Time Coding system is relevant with its non-zero columns.Be set in the error event set Γ that really can occur in the series cascade system _SCSTMiddle minimum non-zero columns is v _Min, maximum non-zero columns is v _Max, so, the frame error rate of system shown in Figure 1 is: $P_f\underset{C}{\&le;\mathrm{\&Sigma;}}P\left(C\right)\underset{v=v_{\min }}{\overset{v_{\max }}{\mathrm{\&Sigma;}}}\underset{w=w_m}{\overset{{\mathrm{LR}}_{\mathrm{<figure-callout\; id="0"\; label="c"\; filenames="A0212353100162.png,A0212353100201.png"\; state="\{\{state\}\}">c</figure-callout>}}^0}{\mathrm{\&Sigma;}}}\underset{{\mathrm{\&Lambda;}}^{\&prime;}={\mathrm{\&Lambda;}}_{\min }^{\&prime;}}{\overset{{\mathrm{\&Lambda;}}_{\mathrm{MAX}}^{\&prime;}}{\mathrm{\&Sigma;}}}{\mathrm{\&Lambda;}}^{-m}{A}_E^{\&prime;}{(v,{\mathrm{\&Lambda;}}^{\&prime;},w)(E_s/{4N}_0)}^{-\mathrm{vm}}$ Wherein, A ' _E(v, Λ ', w) be have v row non-vanishing (v=1,2 ..., N _f), long-pending distance is all error event numbers of w for Λ ' and information sequence Hamming distance, Λ _Min' and Λ _Max' be minimum and the maximum among the Λ '.Equally,,, satisfying relation (3) and setting up, then v during with PT-STTC as long as select suitable outer sign indicating number and interleaver as ISN _Min〉=2, this moment, SCST can obtain the diversity gain of 2m at least, made system obtain superior performance.

According to above-mentioned analysis, for the assurance system obtains the full diversity gain, series cascade of the present invention system adopts structure shown in Figure 4, and itself and structure shown in Figure 1 are basic identical, comprise transmitter unit 40 and receiving element 41.Just adopting PT-STTC is ISN, and the Space Time Coding device 102 among Fig. 1 is replaced with PT-STTC encoder 402, and decoder 112 replaces with PT-STTC decoder 412 when empty; And when selecting for use PT-STTC to be ISN, adopting convolution code or Turbo code is outer sign indicating number, and interleaver adopts random interleaver or odd-even device.In the present embodiment, outer code coder 100 is replaced with encoder for convolution codes 400, outer code decoder device 110 replaces with Convolutional Decoder Assembly 410; Interleaver 101 replaces with random interleaver 401, and deinterleaver 111 replaces with RANDOM SOLUTION interleaver 411.

Fig. 2 has provided two kinds of PT-STTC with eight phase-shift keyings mutually (8PSK) based on QPSK respectively with Fig. 3, and Fig. 2 is the two condition PT-STTC based on the QPSK modulation, and Fig. 3 is the four condition PT-STTC based on the 8PSK modulation.Wherein, 0～7 among 0～3 among Fig. 2 and Fig. 3 represents the point in the signal constellation which respectively.In Fig. 2,0,1 is in 0 state, and 2,3 are in 1 state, if transmitting terminal has two antennas, then the STTC encoder can produce two symbols simultaneously when coding.When " 00/11 " on Fig. 2 right side is represented the PT-STTC encoder from 0 state transitions to 0 state, two corresponding parallel branchs; When " 02/13 " represents the PT-STTC encoder from 0 state transitions to 1 state, two corresponding parallel branchs; When " 20/31 " represents the PT-STTC encoder from 1 state transitions to 0 state, two corresponding parallel branchs; When " 22/33 " represents the PT-STTC encoder from 1 state transitions to 1 state, two corresponding parallel branchs.The numeral on Fig. 3 right side is implication like the representation class also, and only it is based on the transfer between the one of four states.

To PT-STTC based on the QPSK modulation, two condition PT-STTC promptly shown in Figure 2, the list entries that makes encoder is u=(a ₀, b ₀, a ₁, b ₁, ..., a _L, b _L), (a _i, b _i) be that the PT-STTC encoder is at i input information constantly, (a _i, b _i) four kinds of possible combinations 00,01,10,11, wherein a should be arranged _iDecision PT-STTC encoder is at i state constantly.Then as seen from Figure 2: have only a in the list entries of PT-STTC encoder _i(i=0,1 ..., when L) all equalling zero, that is: only comprising 00 and 01 combination, PT-STTC shows non-full rank characteristic.At this moment, adopt following measure to guarantee that the error pattern of these non-full ranks does not occur in the list entries of PT-STTC encoder: to select code check for use be 1/2 convolution code or Turbo code to sign indicating number 1), and interleaver is selected the odd-even device for use.2), select for use random interleaver also can guarantee the full diversity gain of series cascade system if outer sign indicating number is selected bigger convolution code or the Turbo code of the bigger or maximum free distance of constraint length for use.

To PT-STTC based on the 8PSK modulation, four condition PT-STTC promptly shown in Figure 3, the list entries that makes encoder is u=(a ₀, b ₀, c ₀, a ₁, b ₁, c ₁, ..., a _L, b _Lc _L), (a _i, b _i, c _i) eight kinds of possible combinations 000,001,010,011,100,101,110,111, wherein a should be arranged _iAnd b _iCommon decision PT-STTC encoder is at i state constantly, then as seen from Figure 3: have only a in the list entries of PT-STTC encoder _iAnd b _i(i=0,1 ..., when L) all equalling zero, that is: only comprising 000 and 001 combination, PT-STTC shows non-full rank characteristic.At this moment, adopt following measure to guarantee that the error pattern of these non-full ranks does not occur in the list entries of PT-STTC encoder: outside sign indicating number to select code check for use be 1/3 or 1/2 convolution code or Turbo code, interleaver is selected random interleaver for use.

After outer sign indicating number was fixing, the coding and decoding complexity of series cascade space time coding system shown in Figure 1 decided main complexity by selected STTC encoder.So, the status number of setting a certain STTC is 2 ^v, have 2 in the signal constellation which ^bIndividual signaling point, t at a time then is from a certain state s _i(i=0,1 ..., 2 ^v-1) 2 ^bBar branch considers the possible state of institute, and at a time t has 2 ^B+vBar branch.If the symbol numbers that sends in the frame is N _f, the institute that then produces might branch into Bar.Table 1 has provided based on the STTC grid complexity comparative result under the different conditions number of QPSK modulation.

Table 1

As can be seen from Table 1: for the QPSK modulation, the grid complexity of 4 state STTC is 2 times of two condition PT-STTC, and the grid complexity of 8 state STTC is 4 times of two condition PT-STTC, and 16 state STTC are 8 times of two condition PT-STTC; For the 8PSK modulation, the grid complexity of 8 state STTC is the twice of 4 state PT-STTC, and 16 state STTC are 4 times of 4 state PT-STTC.As seen, under the identical prerequisite of other conditions, in the series cascade system, adopt STTC can make system complexity reduce by one times at least with parallel branch.

Below by the contrast of several groups of simulation curves, can obviously find out series cascade system shown in Figure 1 after adopting PT-STTC, the superior part of its performance under quasistatic fading channel and fast fading channel.Selected simulation parameter is as follows in the present embodiment:

1) outer sign indicating number: the convolution code that provides in the employing table 2, for the situation that adopts STTC2 and STTC3 as ISN, the convolution code of employing is g with the generator polynomial of octal representation ₀=7, g ₁=5; For other situations, the convolution code of employing is g with the generator polynomial of octal representation ₀=17, g ₁=15.

2) length of information bit is 240, and random interleaver length is 720.

3) ISN: a few class STTC of providing of employing table 2 respectively, wherein, STTC2 and STTC3 are four condition, STTC5 is eight states, is the STTC that is not with parallel branch; PT-STTC1 is the two condition PT-STTC based on QPSK, and PT-STTC4 is the four condition PT-STTC based on 8PSK.In the table 2, when using STTC separately, with " STTCi (i=1,2 ..., 5) " expression; The corresponding employing " STTCi (i=1,2 ..., 5) " during the series cascade system of coding, with " SCSTi (i=1,2 ..., 5) " expression, such as: adopting PT-STTC1 is that the series cascade system of ISN correspondence is called SCST1.

Modulation system	?????????????????QPSK			????????8PSK
						Outer sign indicating number	????g 0＝17，g 1＝15	?????g 0＝7，g 1＝5		????g 0＝17，g 1＝15
ISN	????PT-STTC1	????STTC2	????STTC3	?PT-STTC4	?STTC5
						Interleaver	Random interleaver
The serially concatenated system	????SCST1	????SCST2	????SCST3	?SCST4	?SCST5

Table 2 in addition, all dotted lines are the performance curve in 21 time receivings in several picture groups, the performance curves that all solid lines then represent 22 to receive.

When the STTC that Fig. 5 a and Fig. 5 b have provided the STTC of employing QPSK modulation in the table 2 and adopted 8PSK to modulate uses separately, the performance curve under the quasistatic fading channel.Abscissa is the signal interference ratio (SNR) of each reception antenna among the figure, and ordinate is the error rate.Dextrosinistral curve is represented successively among Fig. 5 a: the independent PT-STTC1 of use of the curve representative sending and receiving end that adds fork on the dotted line is the performance curve in 21 time receivings, it is the performance curve in 21 time receivings that pure dotted line representative is used the STTC2 sending and receiving end separately, and it is the performance curve in 21 time receivings that the dotted line representative is used the STTC3 sending and receiving end separately; The independent PT-STTC1 of use of the curve representative sending and receiving end that adds fork on the solid line is the performance curve in 22 time receivings, it is the performance curve in 22 time receivings that pure solid line representative is used the STTC2 sending and receiving end separately, and it is the performance curve in 22 time receivings that the dotted line representative of the leftmost side is used the STTC3 sending and receiving end separately.Dextrosinistral curve is represented successively among Fig. 5 b: the independent PT-STTC4 of use of the curve representative sending and receiving end that adds square on the dotted line is the performance curve in 21 time receivings, and it is the performance curve in 21 time receivings that pure dotted line representative is used the STTC5 sending and receiving end separately; The independent PT-STTC4 of use of the curve representative sending and receiving end that adds square on the solid line is the performance curve in 22 time receivings, and it is the performance curve in 22 time receivings that pure solid line representative is used the STTC5 sending and receiving end separately.Can find out by Fig. 5 a and Fig. 5 b: since the influence of parallel branch, two kinds of PT-STTC that provide among the figure, that is: and PT-STTC1 and PT-STTC4 all can't obtain maximum diversity gain when using separately, and coding gain are the poorest.

When adopting method of the present invention, behind the ISN of PT-STTC as the series cascade system, its performance curve under the quasistatic fading channel is shown in Fig. 6 a and Fig. 6 b, and Fig. 6 a is for adopting the STTC performance curve of QPSK modulation, and Fig. 6 b is for adopting the STTC performance curve of 8PSK modulation.Abscissa is the signal interference ratio (SNR) of each reception antenna among the figure, and ordinate is the error rate.Dextrosinistral curve is represented successively among Fig. 6 a: the dotted line representative of the rightmost side is that series cascade systematic internal code sending and receiving end is the performance curve in 21 time receivings with STTC3, is that series cascade systematic internal code sending and receiving end is the performance curve in 21 time receivings from right number second dotted line representative with STTC2, and the curve representative that adds fork on the dotted line is that series cascade systematic internal code sending and receiving end is the performance curve in 21 time receivings with PT-STTC1; Pure solid line representative is that series cascade systematic internal code sending and receiving end is the performance curve in 22 time receivings with STTC2, the chain-dotted line representative is that series cascade systematic internal code sending and receiving end is the performance curve in 22 time receivings with STTC3, and the curve representative that adds fork on the solid line is that series cascade systematic internal code sending and receiving end is the performance curve in 22 time receivings with PT-STTC1.Dextrosinistral curve is represented successively among Fig. 6 b: pure dotted line representative is that series cascade systematic internal code sending and receiving end is the performance curve in 21 time receivings with STTC5, and adding the square representative on the dotted line is that series cascade systematic internal code sending and receiving end is the performance curve in 21 time receivings with PT-STTC4; Pure solid line representative is that series cascade systematic internal code sending and receiving end is the performance curve in 22 time receivings with STTC5, and adding the square representative on the solid line is that series cascade systematic internal code sending and receiving end is the performance curve in 22 time receivings with PT-STTC4.The slope of curve by Fig. 6 a and Fig. 6 b can be found out: the maximum diversity gain that can the acquisition system under the quasistatic fading channel provides as the SCST of ISN with PT-STTC, and have best anti fading performance.

By Fig. 6 a as can be known: in frame error rate is 10 ^-2, the reception antenna number is 1 o'clock, PT-SCST1 has nearly 2dB gain than the gain that SCST2 has about 0.3dB than SCST3.For among Fig. 6 a two two receive and series cascade system that Fig. 6 b provides modulates based on 8PSK, can release conclusion much at one.Obviously: under the quasistatic fading channel, adopt the SCST of PT-STTC not only can obtain the full diversity gain, its performance also improves to some extent than the SCST that adopts full rank STTC simultaneously.

When adopting method of the present invention, behind the ISN of PT-STTC as the series cascade system, its performance curve under fast fading channel is shown in Fig. 7 a and Fig. 7 b, and Fig. 7 a is for adopting the STTC performance curve of QPSK modulation, and Fig. 7 b is for adopting the STTC performance curve of 8PSK modulation.Abscissa is the signal interference ratio (SNR) of each reception antenna among the figure, and ordinate is the error rate.The definition of every curve and Fig. 6 a and Fig. 6 b are identical among Fig. 7 a and Fig. 7 b.So, the series cascade system for based on QPSK modulation, can be found out by Fig. 7 a: the diversity gain that obtains as the SCST performance of ISN with PT-STTC and adopt delay diversity much at one, but coding gain is more obvious.For the series cascade system based on the 8PSK modulation, can be found out by Fig. 7 b: the performance of SCST4 increases than SCST5, is 10 in frame error rate ^-2, when receiving terminal had only an antenna, SCST4 had the gain of about 0.8dB than SCST5; When receiving terminal had two antennas, then SCST4 can obtain the gain of nearly 2dB than SCST5.

Can prove that by above-mentioned simulation result it is the ISN of series cascade system that the present invention adopts PT-STTC, not only under the quasistatic fading channel, can obtain the full diversity gain, performance is increased; And, can obtain to be not less than the diversity gain and the coding gain of the SCST system that adopts full rank STTC equally at fast fading channel.That is to say: no matter the present invention is under the quasistatic fading channel, still under fast fading channel, all can obtain effect preferably, and system complexity reduces half at least.

The above, all be being example based on the two condition PT-STTC of QPSK modulation with based on the four condition PT-STTC of 8PSK modulation, in actual applications, can be according to system or user's needs, select different PT-STTC arbitrarily, such as: based on eight state PT-STTC of 16QAM modulation or the like, and select corresponding outer sign indicating number and interleaver simultaneously.In a word, above-mentioned is preferred embodiment of the present invention only, is not to be used to limit protection scope of the present invention.

Claims (10)

1, a kind of method that improves performance of series cascade space time coding system, at transmitting terminal, information sequence a carries out obtaining symbol sebolic addressing behind the Space Time Coding to this bit sequence through forming bit sequence after sign indicating number coding and the interleaving treatment outward, and this symbol sebolic addressing sends by transmitting antenna; At receiving terminal, decoding processing formed bit sequence when reception antenna passed through sky with the symbol sebolic addressing of receiving, this bit sequence recovers information sequence a through deinterleaving and outer code decoder processing again; It is characterized in that: adopt grid Space Time Coding (PT-STTC) that bit sequence is encoded to symbol sebolic addressing at transmitting terminal, adopt PT-STTC that symbol sebolic addressing is decoded as bit sequence at receiving terminal with parallel branch.

2, method according to claim 1 is characterized in that: to another state, there are at least two parallel branchs from a state transitions of encoder in described PT-STTC.

3, method according to claim 1 is characterized in that: set the grid Space Time Coding (PT-STTC) with parallel branch and be the two condition PT-STTC based on quaternary PSK (QPSK) modulation; Or be the four condition PT-STTC that modulates based on eight phase phase-shift keyings (8PSK).

4, according to claim 2 or 3 described methods, it is characterized in that: based on the two condition PT-STTC of quaternary PSK (QPSK) modulation, or based on the four condition PT-STTC of eight phase phase-shift keyings (8PSK) modulation, to another state, all there are two parallel branchs from a state transitions of encoder.

5, method according to claim 1 is characterized in that: set outer code coding/decoding device and adopt convolution code, or adopt Turbo code.

6, method according to claim 1 is characterized in that: the setting interleaver is a random interleaver, or is the odd-even device.

7, method according to claim 1 is characterized in that: under the quasistatic fading channel, when using PT-STTC separately might be non-the set Г that constitutes of full rank error event _NonfullWith all possible errors event sets Γ that really can occur in the series cascade system that adopts PT-STTC _SCSTCommon factor be empty.

8, method according to claim 1 is characterized in that: under fast fading channel, adopt all possible errors event sets Γ that really can occur in the series cascade system of PT-STTC _SCSTMiddle minimum non-zero columns is v _MinBe not less than 2.

9, according to claim 1 or 3 described methods, it is characterized in that this method further comprises: to PT-STTC, when the list entries of encoder is u=(a based on QPSK modulation ₀, b ₀, a ₁, b ₁, ..., a _L, b _L) time, (a _i, b _i) be the PT-STTC encoder at i input information constantly, set a in the list entries _i(i=0,1 ..., L) all equal zero.

10, according to claim 1 or 3 described methods, it is characterized in that this method further comprises: to PT-STTC, when the list entries of encoder is u=(a based on 8PSK modulation ₀, b ₀, c ₀, a ₁, b ₁, c ₁, ..., a _L, b _Lc _L) time, (a _i, b _i, c _i) be the PT-STTC encoder at i input information constantly, set a in the list entries _iAnd b _i(i=0,1 ..., L) all equal zero.

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