Research on decoding of LDPC codes in the PCM/FM reentry telemetry system

ZHANG Li-li, ZHAO Ze-mao, BAO Jian-rong
（College of Communication Engineering, Hangzhou Dianzi University, Hangzhou 310018, China）

Abstract: In the phase of decoding, when the SNR is lower than the decoding threshold, to continuously information iterative cant improve the BER performance of low density parity check（LDPC） codes. In order to solve this problem, an improved decoding method was proposed. In this method, the decoding was terminated once the results repeating, and the iterative times was decreased. LDPC codes and the new decoding method were applied to pulse code modulation/frequency modulation（PCM/FM） telemetry system, then complexity and the BER performance were analyzed. Simulations show that, under the PCM/FM telemetry system , the normalized min-sum algorithm using the improved decoding method shows excellent BER performance. Meanwhile, this algorithm is easy to hardware implementation.
Key words: pulse code modulation/frequency modulation（PCM/FM）; low density parity check（LDPC） codes; decoding; iterative times