Research On Optimization Of Adaptive LDPC Code In Satellite Communication System

Chanel code is an important measure to improve the effectiveness and the reliability of adaptive satellite communication systems. How to choose the channel code is critical, while LDPC code is a kind of channel code used wildly. As the onboard resource is limited, we should consider both the rate compatibility and complexity of LDPC codes. Under this background, we do some research works on adaptive coding and decoding algorithm.In chapter one, we introduce the background and the research status of adaptive coding and decoding.In chapter two we study LDPC coding algorithms. First of all, the basic theory of LDPC code is the principle of LDPC, the parity check matrix of LDPC and so on. Based on the 802.16 e standard, we construct the parity check matrix by using PEG method. And based on this newly constructed matrix as the mother matrix, we come up with an improved rate-compatible algorithm. In the end of this chapter we introduce the LDPC coding algorithm over GF(q).The chapter three mainly studies about decoding method of the LDPC. Firstly introduce the BP algorithm, the improved BP algorithm: Min-Sum algorithm. Then the Self-Corrected algorithm and Normalized Min-Sum, Offset Min-Sum algorithm are analyzed. Then we propose an improved Min-Sum decoding algorithm. Furthermore,, we studies the LDPC decoding algorithm over GF(q) and analyze its BP algorithm and MES algorithm.The chapter four studies the adaptive coding method on LDPC code. We decide the MCS based on the maximum throughput of the system. As the bit error rate of the system can’t be guaranteed. Then we come up with the new MCS algorithm which combined with HARQ.