| Frequency hopping communication belongs to the category of spread spectrum communication.Because of its anti-interference and confidentiality,frequency hopping communication system has received great attention and application in military communications.Transmission reliability is also one of the requirements for communication,in order to guarantee the transmission quality,the Forward Error Correction is often used to protect the transmission information in FH communication.Low-density parity-check code is a special kind of linear block codes.Gallager made a comprehensive study and introduction on LDPC codes in his paper published in 1963.The research showed that the performance of LDPC codes is almost better than other coding methods over many channels.But due to the limitations of computing ability at that time,LDPC codes didn’t receive too much attention.The LDPC code with larger code length performs well and is a good code close to Shannon limit.After being rediscovered,LDPC codes are more and more widely used,and the decoding algorithm of LDPC codes is based on belief propagation which can operate parallelly,and the decoding speed is faster than Turbo codes whose decoding method uses serial decoding.The emphasis of this paper is the physical implementation of frequency hopping communication system and the performance analysis of LDPC codes in frequency hopping system.This paper introduces the basic concepts of LDPC codes,including the generation method of LDPC construction matrix,coding and decoding algorithms and optimization methods.In the methods of constructing matrix,this paper introduces many construction methods,and then gives an optimized construction matrix based on Gallager’s construction method.In decoding algorithms,this paper introduces the Probability BP decoding algorithm emphatically.This paper then introduces the design of FH communication system,and introduces the overall design and key technologies of FH communication system.Then this paper introduces the physical implementation of FH system,and makes a detailed design description of data link layer.Finally,performance analysis of the combination of LDPC and FH communication system is given based on the MATLAB simulation system. |
