Studying On Channel Coding In LEO Satellite Communication Systems

LEO(low-earth-orbit) satellite communication has many advantages and it receives more and more recognition.The advantages contains:low height of the orbit,small path loss ,low power of transmitter and receiver,low delay,low cost.It would be the important filed of the personal communications.When the satellites communicate with the terminal on the earth,the signal will be interfered by noise and fading.It is necessary to use channal coding technology to reduce the bit errors.This paper studys on the three kinds of channel coding.They are convolutional codes for real-time speech, concatenated codes and LDPC codes for data communication.Chapters are arranged as following:Chapter 1 demonstrates the development of LEO satellite communication and some channel coding method.Then introduces the software and hardware of the DSP.Chapter 2 detailedly introduces the coding and decoding of convolutional codes,the coding gain in AWGN channel.Then it describes how to implement this code by software on DSP and viterbi coprocessor.In chapter 3 I explain the coding and decoding method of RS codes.Furthermore I illustrate how to use RS and convolutional codes to construct concatenated codes,which can offer more coding gain.Chapter 4 introduces the LDPC codes.Comparing the difference among the three decoding methods.The simulation shows the LDPC codes can offer high coding gain.In chapter 5 I study the implementation of the three codes in the satellite communicaion.In different channel conditions,some aspects must be considerd.I compare the performance of the three codes in rician channel in detail.There is a summary of the research work in this dissertation in the end.