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

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 .