Research On The Key Techniques Of OFDM System And The Implementation Based On DSP

Due to its high band-width efficiency, its robustness to multipath and pulse, its high transmission speed and its ability of flexible modulation on subcarriers in accordance with the channel conditions, Orthogonal Frequency Division Multiplexing (OFDM) has found its wide applications in high speed data transmission wireless systems, such as digital video broadcast, digital television, wireless local area network. Therefore, it must be of good theoretical and practical value to conduct research on these key problems of OFDM.In this paper, the high PAPR and Turbo code of OFDM systerm are researched thoroughly based on the analysis of the theory of OFDM technology. By simulating and comparing the proposed solutions, the appropriate solutions are gived and the Turbo coder and decoder are implemented on AD-TS101DSP. The main include:with the high PAPR problem, non-distorting technology and pre-distorting technology are studied in this dissertation . CR, MCT and PS are studied thoroughly. With the PS, according to the Shortcoming of the original implementing method using shaping matrix, this thesis deduces the formula and put forward a new method using DFT/IDFT and analyzes and simulates the the performance of the PS-OFDM systerms with the time deflection. the results indicate that the influence is little and the original channel estimate methods of OFDM systems are suitable for the PS-OFDM systerms. Furtherly, the paper simulates and analyzes the performance of the OFDM systerms with CR/MCT/PS methods to reduce the PAPR and gives the appropriate method to reduce the PAPR of OFDM systerms.To the Turbo code problem of the OFDM systerms, encoder, interleaver and iterative decoding algorithm (MAP/LOG-MAP/MAX-Log-MAP/SOVA) are studied in this dissertation. This paper simulates and analyzes the performance of the Turbo-OFDM systerms using grouping interleaver, random interleaver and S-interleaver. S-interleaves has better performance than other interleavers. Simultaneously, the performance of the Turbo-OFDM systerms with different decoding algorithm is simulated. Considering the performance, decoding complexity and implementing complexity, the paper puts forward an appropriate decoding algorithm to implement the practice systerms. Furtherly, the performance of the feedback Turbo-OFDM systerms is gived. The result indicate that feed back improves the performance of the systerms, the associated method including channel estimate, iterative decoding and chanel parameter is the a very important aspect of the futher.Based on performance and complexity, a digital communication system is carried out at the platform of ADSP-TS10lS, which includes Turbo code and the algorithm used SOVA algorithm.