Turbo Code Technology In The Hf Frequency Hopping System And Dsp Implementation

In digital communication system, since noise and interference can be inevitably introduced in communication channel, the channel encoding issues should be considered to achieve reliable communication. Due to the most approach to Shannon limit, Turbo code is specified as one of standard error correction codes in the 3th Generation mobile communication system. The paper expelains the principle of Turbo code, simulates its performance in frequency hopping communication system, and implements the decoding for Turbo code in TigerSHARC DSP TS201.The paper firstly introduces the status and effect of shortwave hopping communication system and states how Turbo code is presented and its development. Through the analysis of the capability of Turbo code, the theoretical basis of the subject of the paper is decided.The chapter two firstly explicits the encoding and decoding architecutre of Turbo code and expounds the SISO decoding algorithm based on Maximum a posteriori probability. then the detailed description of the principle of MAP algorithm is presented and its expression in log domain is discussed, finally the simplified Max-LogMap algorithm is given.The simulation result of Turbo code in FFH communication system is given in chapter3. First the performance of Turbo code is simulated in the case of different AWGN parameters, and the difference between Turbo code and the convolutional code, Reed Solomon code, concatenated code is studied. Second, the performance of Turbo code in rayleigh channel is studied and comparison between the performance of the convolutional code and that of concatenated code at the same condition is made. At last, the encoding gains of Turbo code in short wave rayleigh channel are studied and comparison between the performance of the convolutional code and that of concatenated code at the same condition is made.Chapter4 describes the realization of encoding technique for Turbo code on the platform TigerSHARC ADSP TS201. the hardware charicteristic of used DSP is depicted and calibration and overflow problems of numbers in the process are analyzed. And the implementation of LogMap algorithm is designed, and the memory resource occupied by the algorithm, decode delay and the performance are analyzed comprehensively.