Research On The Analysis And Simulations Of Tracking And Data Relay Satellite System Links Based On LDPC Codes

The low-density parity-check code (LDPC) is a kind of asymptotic good linear codes that can approach Shannon capacity with low complexity iterative decoding. This sort of code was originally proposed by Dr. Gallager in 1962, which had not attracted a large amount of interest at that time. However, after decades of years, it is now rediscovered by Mackay and Neal, along with the enhancement of computer ability and the development of some relative theory such as graph theory, BP algorithm, turbo codes and so on.LDPC codes and turbo codes are similar in many aspects, both can extremely approach to the Shannon limits by their unique ways. LDPC codes are relatively easy to be characterized, and can outperform turbo codes with sufficiently long block lengths. Moreover, because of the parallel decoding algorithm, the decoding delay of LDPC is little than that of turbo code. In recent years, LDPC codes have attracted the worldwide attentions in information theory and channel coding communities due to its impressive performance and great potentials in applications.This thesis presents comprehensive studies on the theory of LDPC codes and two kinds of irregular LDPC codes. A new construction algorithm for the parity-check matrix of an irregular LDPC code, which is based on PEG (Progressive Edge-Growth) algorithm, has been proposed. This algorithm can shortened the practical processing delay in the construction with the simplified the PEG algorithm. Simulation results show that the error correcting capability of LDPC codes is better than turbo codes over the Additive White Gaussian Noise (AWGN) or Rayleigh fading channels. Finally, in order to investigate the performance of applications of LDPC codes for the satellite communications, this paper analysis the characteristics of forward and reverse links of Tracking and Data Relay Satellite System by US standards and calculate the link lengths, received power, interference noise power, background noise power and so on. After that, A TDRSS (Tracking and Data Relay Satellite System) model was built on OPNET (Optimized Network Engineering Tools), the network with LDPC codes and turbo codes has been simulated. The simulation results also show that the LDPC codes and turbo codes are both suitable for satellite communications and even for deep space communications.