Study On PAPR Reduction For OFDM System

As the information technology improving, the application of personal mobile communications booms, and the wireless communication technology becomes more closely to human life. Orthogonal frequency division multiplexing (OFDM) technology has become one of the most promising wireless technology and favored by many researchers, for its good resistance to multipath effects of capacity and high spectrum efficiency. The OFDM technology is facing a serious problem:a high peak to average power ratio (PAPR), and the issue directly affects the application of OFDM in the uplink of mobile communication systems.This project studied and analyzed the PAPR problem of OFDM system in-depth and summarize the existing typical PAPR reduction algorithms, such as:selected mapping (SLM), partial transmit sequences (PTS), nonlinear companding transform (NCT), constant envelope OFDM (CE-OFDM), single carrier frequency domain equalization (SC-FDE) as well as constellation extension (CE), etc.. In this paper, the basic principles of above algorithms and their characteristics comparisons are given, with emphasis on CE type algorithm. Although this kind of algorithm may increase the transmission power of the system, it has simple receiving terminal. The CE type schemes do not need to send additional information, and will not cause more noise.Thus, such algorithms have a high application potential.In the CE type methods, the complexity for searching the optimal mapping vector is high. The present search algorithms are all sub-optimal solution. This paper proposes a new sub-optimal search algorithm:joint search (JS) algorithm. Computer simulation results show that compared with existing algorithms, the proposed algorithm outperforms with low complexity. And the JS algorithm can balance the computational complexity and the PAPR suppression gain by flexible set the parameters:joint factors, to satisfy the actual application needs.