Research On Rate-Compatible LDPC Coding For Free Space Optical Communication

LDPC codes have been widely used in wireless communication, and channel coding using LDPC is the standard in the fourth generation mobile communication. In FSO, LDPC codes also have good error correction capability; NASA uses LDPC codes as one of the standard codes in deep space communication.Studied the LDPC codes'error correction capabilities in atmospheric turbulence channel. Constructed rate-compatible LDPC codes by protogragh and parity split. After the best degree distribution of high rate protogragh was obtained by using differential evolution algorithm, constructed the LDPC matrix of high rate by modified PEG algorithm. Then the protograph of lower rate, which has the efficient encoding rate-compatible structure, was achieved by parity split. The results can be applied to error correction codes in the second ARQ system.Simulation showed the error rate curves under various rates. Results show that the rate-compatible LDPC codes constructed can fit different turbulence index channel.