CN104158550A - A method for constructing a code-rate-compatible protograph LDPC code based on deep space communication environment - Google Patents

Abstract

The invention discloses a method for constructing a code-rate-compatible protograph LDPC code based on deep space communication environment. The method includes: 1) obtaining multiple code-rate-compatible protographs based on row and column extension of an ARAPA proto matrix; 2) then executing extension four times on the obtained series of protographs in a PEG algorithm, to remove multiple edges and obtain the protograhs having no multiple edges; and 3) lastly executing extension several times on the above protographs in the PEG algorithm again, to obtain the code-rate-compatible protograph LDPC code having certain code length and having quasi-cyclic characteristic. This code-rate-compatible LDPC code constructed based on the matrix extension method has a lower decoding threshold and a lower error-code floor. Compared with code-rate-compatible LDPC code constructed based on AR4JA protographs, the code-rate-compatible LDPC code constructed based on the present method has the similar performance thereto, however has the lower decoding threshold and decoding calculation complexity, and has superior performance especially in the case of high code-rate, which can obtain the performance gain of about 0.2 dB in the case that BER is 10<-6>.

Description

A kind of code-rate-compatible protograph LDPC code constructing method based on deep space communication environment

Technical field

The present invention relates to deep space communication system channel coding technical field, particularly a kind of building method of code-rate-compatible protograph LDPC code.

Background technology

The feature such as deep space communication environment has long transmission distance, time delay is large, signal to noise ratio is low, the error rate is high, link rate is asymmetric and transmitted power is limited.Therefore, the chnnel coding of the applicable deep space communication environment of structure, high-performance, low complex degree becomes a key technology that ensures deep space communication system reliability and validity.Low-density checksum (Low-Density Parity-Check, LDPC) code has parallel decoding architecture, is more suitable for high-speed hardware and realizes, and error floor is lower, is considered to the best code of error-correcting performance up to now.2003, the aerodynamic experiment chamber (JPL) of NASA (NASA) has proposed protograph (protograph) LDPC code first, make up the higher deficiency of traditional LDPC code encoder complexity, the AR4JA code of its design was recommended the standard pattern of NASA as deep space communication in 2006 by CCSDS (Consultative Committee for Space Date Systems, CCSDS).

In recent years, researcher finds under changing environment condition, to introduce the protograph LDPC coding techniques of code-rate-compatible and can adaptively make corresponding adjustment according to channel circumstance in the time that deep space communication system is residing.Adopt the protograph LDPC code of code-rate-compatible, can, under the prerequisite guaranteeing service quality, adjust in real time its error correcting capability according to channel circumstance by adjusting code check, thereby realize the throughput maximization of channel, improved the efficiency of transmission of data.Consider from the angle of implementation complexity, code-rate-compatible protograph LDPC code is made up of a nested structure, and it can adopt the work of single encoded device/decoder in certain range of code rates, thereby greatly reduces the complexity of system.

At present, mainly contain based on the conventional method of protograph design code-rate-compatible LDPC codes: (1) punching (puncture), the protograph LDPC code of low code check is punched continuously and obtains the subcode of a series of high code checks.The people such as El-Khamy are at " Design of rate-compatible structured LDPC codes for hybrid ARQ applications " [Selected Areas in Communications, IEEE Journal on, 2009,27 (6): 965-973] in article, launch research for a kind of code-rate-compatible LDPC codes of asymptotic node punching algorithm (the progressive node puncturing algorithm) structure based on protograph.Although this method is simple, but exist very serious this defect of the rear high code check subcode of the gained decoding performance decline of punching.(2) method based on grand master pattern matrix-expand (extension), to the former modular matrix of high code check protograph LDPC code successively ranks expand and obtain the subcode of a series of low code checks.For the decoding performance severe exacerbation of high code check subcode in protograph punching process, the people such as Nguyen are at " The design of rate-compatible protograph LDPC codes " [Communications, IEEE Transactions on, 2012,60 (10): 2841-2850] a kind of method of the extended architecture code-rate-compatible protograph LDPC code based on AR4JA protograph has been proposed in article.Although this method can avoid subcode decoding performance in punching process to worsen this drawback,, in view of the feature of deep space communication, the code-rate-compatible protograph LDPC code that it adopts need possess more superior performance, lower decoding threshold and decoding computation complexity.Therefore, constructing a kind of code-rate-compatible protograph LDPC code that is suitable for deep space communication environment, high-performance, low complex degree becomes people in recent years and studies one of hot issue of code-rate-compatible LDPC codes application.

Summary of the invention

In prior art, at present, for the punching technical construction code-rate-compatible LDPC codes of protograph, exist this defect of decoding performance degradation of the rear high code check subcode of gained of punching, the design of the method based on the grand master pattern matrix-expand code-rate-compatible LDPC codes proposing for this defect, often need to expand by the protograph based on superior performance, but conventional method is mainly the extended architecture code-rate-compatible LDPC codes based on AR4JA protograph at present, there is the suboptimality of performance, the shortcomings such as higher decoding complexity, therefore urgently choose better than AR4JA protograph performance, decoding threshold and the lower protograph of decoding computation complexity are constructed code-rate-compatible protograph LDPC code to adapt to the deficiency of demand of deep space communication, the object of the present invention is to provide a kind of degradation that can overcome the rear high rate codewords decoding performance of punching, the code-rate-compatible protograph LDPC code constructing method based on deep space communication environment of lower decoding threshold and decoding computation complexity, technical scheme of the present invention is as follows: a kind of code-rate-compatible protograph LDPC code constructing method based on deep space communication environment, it comprises the following steps:

101, construct cumulative (ARAPA) protograph of lower the adding up-repeat of the average nodal number of degrees-cumulative-part of a kind of AR4JA of comparing protograph, and to being added up-repeat-cumulative (ARAPA) protograph of add up-part carries out matrix-expand, the former modular matrix of female code of selected ARAPA protograph is successively increased to a line check-node and a row variable node, obtain several protographs;

102, several protographs that then step 101 obtained adopt asymptotic limit growth (PEG) algorithm to carry out 4 times and expand, and obtain the protograph without heavy limit after copying-replacing;

103, the protograph without heavy limit again step 102 being obtained adopts asymptotic limit growth (PEG) algorithm to carry out several times expansion, can construct and obtain code-rate-compatible ARAPA protograph LDPC code.

Further, in step 103, selected ARAPA code is that one is based on cumulative-repeat-cumulative (ARA) yard protograph LDPC code that improvement obtains.

Further, when the ARAPA protograph based on 4/5 code check carries out 6 submatrix expansions, after carrying out altogether at twice expanding for 128 times, the information bit length of female code LDPC0, the subcode LDPC1 in step 103, LDPC2, LDPC3, LDPC4, LDPC5, LDPC6 is 1024, and code check is respectively 4/5,8/11,2/3,8/13,4/7,8/15,1/2.

Further, in step 101 in the corresponding Tanner figure of corresponding protograph, newly-increased variable node is only connected with newly-increased check-node, increase row newly in corresponding former modular matrix time, only there is nonzero element at newly-increased a line place at every turn, while determining the distribution of newly-increased every a line the inside nonzero element, the calculating of iterative decoding threshold value adopts PEXIT algorithm.

Further, the corresponding basis matrix B of the ARAPA protograph described in step 101 is as follows:

Further, under the deep space communication environment that the number of times that adopts asymptotic limit growth (PEG) algorithm to expand step in step 103 is recommended according to CCSDS, the standard code length of LDPC code is selected.

Advantage of the present invention and beneficial effect are as follows:

The code-rate-compatible LDPC codes building method based on ARAPA protograph that the present invention proposes has been considered the time-varying characteristics of deep space communication environment lower channel, proposed a kind of building method of code-rate-compatible protograph LDPC code, its error correcting capability can adaptively be made corresponding adjustment according to channel circumstance.Adopt this code-rate-compatible protograph LDPC code under the prerequisite guaranteeing service quality, to adjust in real time its error correcting capability according to channel circumstance by adjusting code check, thereby to improve the throughput of channel.Based on this code-rate-compatible LDPC codes of constructing than the ARAPA protograph that AR4JA protograph performance is better, decoding threshold is lower and decoding computation complexity is lower, not only can overcome the degradation of the rear high rate codewords decoding performance of punching, and performance is better than traditional these shortcomings of code-rate-compatible LDPC codes based on AR4JA protograph structure, and can adapt to well deep space communication some about code check, code length relevant regulations and demand.This code-rate-compatible LDPC codes based on matrix-expand method construct has lower decoding threshold, lower error floor, in addition, ARAPA protograph is expanded at twice, make the check matrix of constructed code-rate-compatible LDPC codes there is accurate cycle characteristics, thereby can carry out decoding at a high speed.Compared with the code-rate-compatible LDPC codes of constructing based on AR4JA protograph, although the performance of the code-rate-compatible LDPC codes of this method structure is close with it, but it has lower decoding threshold and decoding computation complexity, especially in the time of high code check, there is more superior performance, be 10 at BER ^-6time can obtain the performance gain of about 0.2dB.

Brief description of the drawings

Fig. 1 is the structure flow chart of the code-rate-compatible LDPC codes based on ARAPA protograph in the present invention;

Fig. 2 is ARAPA protograph in the present invention;

Fig. 3 is the check matrix structure chart of the code-rate-compatible LDPC codes based on ARAPA protograph matrix-expand in the present invention;

Fig. 4 is the performance simulation figure of the code-rate-compatible ARAPA protograph LDPC code of 7 kinds of information bit length k=1024 in the present invention;

Fig. 5 is code-rate-compatible ARAPA protograph LDPC code and the relatively analogous diagram of code-rate-compatible AR4JA protograph codeword performance of 3 kinds of information bit length k=1024 in the present invention.

Embodiment

The invention will be further elaborated to provide an infinite embodiment below in conjunction with accompanying drawing.But should be appreciated that, these describe example just, and do not really want to limit the scope of the invention.In addition, in the following description, omitted the description to known features and technology, to avoid unnecessarily obscuring concept of the present invention.

Shown in Fig. 1-Fig. 3, for the structure of the LDPC code of the code-rate-compatible based on ARAPA protograph, the ranks that what the present invention chose is based on the former modular matrix of ARAPA expand to obtain the protograph of multiple code-rate-compatibles, then adopt PEG algorithm to carry out expanding for 4 times to remove heavy limit to obtained a series of protographs and obtain the protograph without heavy limit, finally again adopt PEG algorithm to carry out several times expansion to above-mentioned protograph, can obtain certain code length and there is the code-rate-compatible protograph LDPC code of accurate cycle characteristics.

Be illustrated in figure 1 the structure flow chart of the code-rate-compatible protograph LDPC code based on deep space communication environment in the present invention.Comprise the following steps:

First the expansion of the ranks based on the former modular matrix of ARAPA obtains the protograph of multiple code-rate-compatibles, then adopt PEG algorithm to carry out expanding for 4 times to remove heavy limit to obtained a series of protographs and obtain the protograph without heavy limit, finally, again adopt PEG algorithm to carry out several times expansion to above-mentioned protograph, can obtain a kind of high-performance, low complex degree, be applicable to certain code length of deep space communication environment and there is the code-rate-compatible protograph LDPC code of accurate cycle characteristics.

Specifically comprise the following steps:

1. adopt the ARAPA protograph of high code check, better performances to carry out matrix-expand: as shown in Figure 2, in Fig. 2, filled circles represents to import into the transmitted symbol of channel to the ARAPA protograph that this step is chosen; Open circles represents the code element of punching; The circle that comprises plus sige represents check-node.The corresponding basis matrix B of ARAPA protograph is as follows:

As shown in Figure 2, transmitted symbol number is N=4+2m, punching code element number P=1, and check-node is counted M=3, and the code check of this yard is:

$R=\frac{N+P-M}{N}=\frac{m+1}{m+2}---\left(2\right)$

Research shows, the coding of ARAPA protograph LDPC code is simple, and decoder has code-rate-compatible characteristic, and iterative decoding thresholding is low.In addition, it has linear code apart from characteristic, has reduced undetected errors, thereby error floor is lower.Compared with AR4JA code, ARAPA code with it performance is close, but because the average number of degrees of its node are lower than AR4JA code, thereby make its decoding computation complexity lower.

Expansion is to choose a kind of high code check and well behaved code word as female code, then obtain the subcode of a series of low code checks by constantly increasing extra check bit, and matrix-expand is a kind of extended method proposing the earliest.The expansion process of this step successively increases a line (check-node) row (variable node) to the former modular matrix of female code of selected APAPA protograph, to obtain the protograph of a series of low code checks.A kind of code-rate-compatible check matrix structure of the ARAPA protograph matrix-expand based on 4/5 code check as shown in Figure 3.

2. a series of protographs that pair obtain adopt PEG algorithms to carry out 4 times and expand: the expanding method that this step is chosen according to people such as Hu X Y at " Regular and irregular progressive edge-growth tanner graphs " [Information Theory, IEEE Transactions on, the PEG algorithm of the amendment 2005,51 (1): 386-398] proposing in article carries out.The PEG algorithm of amendment is as follows:

In above-mentioned algorithm in the time that the degree of depth is l, the check-node set adjacent with variable node s (i, j) in expander graphs." meeting protograph expansion constraint " refers to and can only between same category node, replace.

The object that adopts PEG algorithm to carry out expanding for 4 times to obtained a series of protographs is to remove heavy limit to obtain the protograph without heavy limit.Some related requests according to deep space communication to adopted protograph LDPC code, carry out 4 times to above-mentioned protograph and copy-replace, and after also expanding, obtain the protograph without heavy limit.

3. again adopt PEG algorithm to carry out several times expansion to above-mentioned protograph: the standard code length of LDPC code under the deep space communication environment of recommending according to CCSDS, the number of times that in selected step 2, gained is expanded again without the protograph on heavy limit.Because the selected code check of protograph LDPC code of deep space application is 1/2,2/3,4/5, information bit length has k=1024, and 4096,16384, therefore can select 32,128,512 times the expansion number of times of above-mentioned protograph.

Below by embodiment, further illustrate by reference to the accompanying drawings the present invention, but the scope not limiting the present invention in any way.

Below elaborate the building method that utilizes the present invention to state, construct three kinds of code-rate-compatible protograph LDPC codes that are applicable to deep space communication, its information bit length is all k=1024, and code check is respectively 4/5,2/3,1/2.

1) first, the former modular matrix of the ARAPA based on 4/5 code check launches to expand the multiple code check protographs that obtain code-rate-compatible.As shown in Figure 2, its grand master pattern matrix B 4/5 is as follows for the ARAPA protograph of 4/5 code check:

$B_{4/5}=\left(\begin{array}{ccccccccccc}1& 0& 0& 0& 0& 0& 0& 0& 0& 1& 2\\ 0& 1& 3& 2& 1& 2& 1& 2& 1& 2& 1\\ 0& 1& 0& 1& 2& 1& 2& 1& 2& 1& 2\end{array}\right)---\left(3\right)$

In above-mentioned protograph basis matrix, last row of number of degrees maximum are as protograph punching node.For example, in order to obtain the code-rate-compatible protograph LDPC code of 1/2 to 4/5 range of code rates, therefore by the basis matrix of 4/5 code check is increased to a line one row at every turn, thereby obtaining a series of code-rate-compatible protograph LDPC code words, its code check is respectively:

$R=\frac{8}{10+n},n=\mathrm{1,2,3}...,6---\left(4\right)$

N represents line number that female code basis matrix newly increases and the sum of columns.

The expansion that the grand master pattern basis matrix of 4/5 code check is listed as through 6 a line one, finally can obtain the code-rate-compatible protograph LDPC code of 7 kinds of code checks.As shown in Figure 3, the protograph basis matrix of a kind of 1/2 code check finally obtaining is as follows for the code-rate-compatible check matrix structure of the ARAPA protograph matrix-expand based on 4/5 code check:

$B_{9\&times;17}=\left(\begin{array}{ccccccccccccccccc}1& 0& 0& 0& 0& 0& 0& 0& 0& 1& 2& 0& 0& 0& 0& 0& 0\\ 0& 1& 3& 2& 1& 2& 1& 2& 1& 2& 1& 0& 0& 0& 0& 0& 0\\ 0& 1& 0& 1& 2& 1& 2& 1& 2& 1& 2& 0& 0& 0& 0& 0& 0\\ 0& 0& 0& 0& 0& 0& 1& 1& 1& 1& 1& 1& 0& 0& 0& 0& 0\\ 0& 0& 0& 0& 0& 1& 1& 1& 1& 1& 2& 0& 1& 0& 0& 0& 0\\ 0& 0& 0& 0& 1& 1& 1& 1& 1& 1& 2& 0& 0& 1& 0& 0& 0\\ 0& 0& 1& 0& 0& 0& 1& 1& 1& 1& 2& 0& 0& 0& 1& 0& 0\\ 0& 0& 1& 0& 0& 1& 1& 0& 1& 0& 2& 0& 0& 0& 0& 1& 0\\ 0& 0& 1& 0& 0& 0& 1& 0& 1& 0& 1& 0& 0& 0& 0& 0& 1\end{array}\right)---\left(5\right)$

The grand master pattern basis matrix that above-mentioned former modular matrix has comprised other 6 high code checks.For guaranteeing that the code word of high code check is embedded among the code word of low code check, when each newly-increased row, only there is nonzero element at newly-increased a line place, in the time determining the distribution of newly-increased every a line the inside nonzero element, can be by launch search taking decoding gate limit value as standard, thus the protograph of the code-rate-compatible of better performance obtained.

For the people such as convenient and Nguyen are at " The design of rate-compatible protograph LDPC codes " [Communications, IEEE Transactions on, 2012, the code-rate-compatible protograph LDPC code comparison of 60 (10): 2841-2850] constructing in article, the ranks expansion process of former modular matrix is herein identical with it, and the newly-increased element distribution of corresponding line is identical in expansion process each time.

Decoding threshold is the key factor of weighing a protograph performance, and low decoding gate limit value means lower error floor and the coding gain of Geng Gao.Therefore, table 1 has provided the iterative decoding threshold value of the code-rate-compatible protograph LDPC code under each code check designing herein, the calculating of iterative decoding threshold value adopts the people such as Liva at " Protograph LDPC codes design based on EXIT analysis " [Global Telecommunications Conference, 2007.GLOBECOM'07.IEEE.IEEE, 2007:3250-3254] the PEXIT algorithm that proposes in article.

The iterative decoding thresholding of table 1 code-rate-compatible ARAPA

Can find by table 1, herein the iterative decoding thresholding of this class code-rate-compatible protograph LDPC code of design apart from channel capacity all in 0.5dB.

As a comparison, table 2 has provided the iterative decoding threshold value of the rate compatible codes based on AR4JA protograph under corresponding multiple code checks of people's designs such as Nguyen.

The iterative decoding thresholding of table 2 code-rate-compatible AR4JA

Data Comparison by table 1 with table 2, has illustrated that this class rate compatible codes of design has lower decoding gate limit value herein, thereby has more been conducive to reduce error floor (error floor).

In the corresponding Tanner figure of LDPC code, the average number of degrees of node have often determined the decoding computation complexity of such LDPC code.For with code-rate-compatible AR4JA code contrast, table 3 has provided 7 kinds of code-rate-compatible ARAPA protographs of design herein and the average nodal number of degrees of variable node and the average number of degrees of check-node of code-rate-compatible AR4JA protograph.

The ARAPA of table 3 code-rate-compatible and the average number of degrees of AR4JA node

Known by the Data Comparison in table 3, the variable node of code-rate-compatible ARAPA protograph and the average number of degrees of check-node, all be less than the variable node of code-rate-compatible AR4JA protograph and the average number of degrees of check-node, the decoding computation complexity of the code-rate-compatible AR4JA code that the decoding computation complexity of the code-rate-compatible ARAPA code of design designs lower than people such as Nguyen has herein been described.

2) then, the ARAPA protograph based on above-mentioned 7 kinds of code checks adopts PEG algorithm to launch 4 times and expands the protograph obtaining without heavy limit.Also above-mentioned protograph is carried out to 4 copy-replacement operators and can obtain the protograph without heavy limit.Expanding method according to people such as Hu X Y at " Regular and irregular progressive edge-growth tanner graphs " [Information Theory, IEEE Transactions on, the PEG algorithm of the amendment 2005,51 (1): 386-398] proposing in article carries out.The object that adopts PEG algorithm to carry out expanding for 4 times to obtained a series of protographs is to remove heavy limit to obtain the protograph without heavy limit.

3) last, again adopt PEG algorithm to carry out 32 times to the above-mentioned protograph without heavy limit and expand, can obtain information bit length k=1024 and there is the code-rate-compatible protograph LDPC code of accurate cycle characteristics.

Next, provide the performance simulation result based on 7 kinds of code-rate-compatible LDPC codes of ARAPA protograph structure in the embodiment of the present invention.Emulation is carried out under additive white Gaussian noise (AWGN) channel in deep space communication, adopts the mode of BPSK to modulate, and adopts BP algorithm to carry out decoding, greatest iteration time is set and equals 100.

Fig. 4 is in deep space communication under awgn channel, the performance simulation result of the code-rate-compatible ARAPA protograph LDPC code of 7 kinds of information bit length k=1024.As can be seen from the figure in embodiments of the invention, bit error rate (BER) performance curve of 7 kinds of code-rate-compatible LDPC codes based on ARAPA protograph from right to left, along with the reduction of code check, performance is become better and better, and the BER curve of protograph LDPC code under each code check has good " waterfall " characteristic, be low to moderate 10 at BER ^-6, there is not error floor in place.And in these 7 kinds of code checks, comprising 1/2,2/3,4/5 these 3 kinds of code checks that deep space communication is selected, the message length of k=1024 also meets the code length requirement of deep space communication about LDPC code.

For the advantage of the code-rate-compatible LDPC codes building method based on ARAPA protograph of the present invention under deep space communication channel is described, the code-rate-compatible LDPC codes of AR4JA protograph structure and the code-rate-compatible LDPC codes based on ARAPA protograph structure of the present invention's proposition that the present invention has chosen the deep space application of recommending based on CCSDS contrast.

Fig. 5 is in deep space communication under awgn channel, information bit length k=1024 in the embodiment of the present invention, and code check is respectively code-rate-compatible code word and the code-rate-compatible AR4JA protograph codeword performance emulation comparative result of the selected code check of 1/2,2/3,4/5 these 3 kinds of deep space communications.In the embodiment of the present invention under the condition of equal code check, code length and extended mode, the performance of the code-rate-compatible LDPC codes of 4/5 and 2/3 code check based on ARAPA protograph structure is all better than traditional code-rate-compatible LDPC codes based on AR4JA protograph structure, only, in the time that code check is 1/2, the performance of code-rate-compatible ARAPA code is slightly worse than code-rate-compatible AR4JA code.In addition, because the APAPA short code of this code-rate-compatible is low to moderate 10 in the error rate ^-6time there is not wrong platform, the long code of so this code-rate-compatible also there will not be mistake platform under this error rate.Simultaneously, this simulation result has also illustrated the high rate codewords of this code-rate-compatible ARAPA, more traditional code-rate-compatible AR4JA code has larger advantage, is more and more inclined to and adopts the LDPC code of high code check, middle long code to agree with mutually to meet this trend of transfer of data day by day increasing severely with deep space communication in recent years.

The code-rate-compatible LDPC codes building method based on ARAPA grand master pattern matrix-expand of above the present invention being stated is described in detail and illustrates.Above-mentioned concrete implementation can be used for helping to understand core concept of the present invention.The feature that the present invention becomes while maintaining close ties with deep space communication system channel, the performance suboptimality of considering the degradation of the high rate codewords decoding performance that punching technology produces and expanding based on AR4JA grand master pattern matrix ranks, high these drawbacks of decoding complexity, the present invention proposes a kind of code-rate-compatible LDPC codes building method based on ARAPA grand master pattern matrix-expand, with punching, expanding the implementation of these traditional code-rate-compatibles compares, the performance suboptimality that this method can effectively overcome the degradation of the rear high rate codewords decoding performance of punching and expand based on AR4JA grand master pattern matrix ranks, high these drawbacks of decoding complexity.Compared with traditional code-rate-compatible LDPC codes based on AR4JA protograph structure, code-rate-compatible APAPA code has lower decoding gate limit value, lower decoding computation complexity, especially in the time of high code check, there is more superior performance, can be for being more and more inclined to the volume of transmitted data day by day increasing severely to meet it among the deep space communication of the LDPC code that adopts high code check, middle long code.

These embodiment are interpreted as being only not used in and limiting the scope of the invention for the present invention is described above.After having read the content of record of the present invention, technical staff can make various changes or modifications the present invention, and these equivalences change and modification falls into the inventive method claim limited range equally.

Claims (6)

1. the code-rate-compatible protograph LDPC code constructing method based on deep space communication environment, is characterized in that comprising the following steps:

101, construct a kind of cumulative ARAPA protograph of lower the adding up-repeat of the average nodal number of degrees-cumulative-part of the AR4JA of comparing protograph, and the cumulative ARAPA protograph of the add up-repetition obtaining-cumulative-part is carried out to matrix-expand, the former modular matrix of female code of selected ARAPA protograph is successively increased to a line check-node and a row variable node, obtain several protographs;

102, several protographs that then step 101 obtained adopt asymptotic limit growth PEG algorithm to carry out 4 times and expand, and obtain the protograph without heavy limit after copying-replacing;

103, the protograph without heavy limit again step 102 being obtained adopts asymptotic limit growth PEG algorithm to carry out several times expansion, can obtain having the code-rate-compatible ARAPA protograph LDPC code of quasi-cyclic.

2. the code-rate-compatible protograph LDPC code constructing method based on deep space communication environment according to claim 1, is characterized in that: in step 103, selected ARAPA code is a kind ofly to improve based on cumulative-repeat-cumulative ARA code the protograph LDPC code obtaining.

3. the code-rate-compatible protograph LDPC code constructing method based on deep space communication environment according to claim 1, it is characterized in that: when the ARAPA protograph based on 4/5 code check carries out 6 submatrix expansions, after carrying out altogether at twice expanding for 128 times, the information bit length of female code LDPC0, the subcode LDPC1 in step 103, LDPC2, LDPC3, LDPC4, LDPC5, LDPC6 is 1024, and code check is respectively 4/5,8/11,2/3,8/13,4/7,8/15,1/2.

4. the code-rate-compatible protograph LDPC code constructing method based on deep space communication environment according to claim 1, it is characterized in that: in step 101 in the corresponding Tanner figure of corresponding protograph, newly-increased variable node is only connected with newly-increased check-node, increase row newly in corresponding former modular matrix time, only there is nonzero element at newly-increased a line place at every turn, while determining the distribution of newly-increased every a line the inside nonzero element, the calculating of iterative decoding threshold value adopts PEXIT algorithm.

5. the code-rate-compatible protograph LDPC code constructing method based on deep space communication environment according to claim 1, is characterized in that: corresponding basis matrix B is as follows for the ARAPA protograph described in step 101:

6. the code-rate-compatible protograph LDPC code constructing method based on deep space communication environment according to claim 1, is characterized in that: under the deep space communication environment that the number of times that adopts asymptotic limit growth PEG algorithm to expand step in step 103 is recommended according to CCSDS, the standard code length of LDPC code is selected.