Research On PAPR Reduction Techniques For OFDM System

OFDM (Orthogonal frequency Division Multiplexing) is an attractive technique for wireless high-bit-rate transmission due to the minimizing effects of frequency-selective fading and its high bandwidth efficiency. But OFDM has the high PAPR (Peak-to-Average-Power Ratio) which is its inherent disadvantage. These large peaks cause saturation in high-powered amplifier, leading to the lower transmitted efficiency, and increasing the complexity of A/D and D/A convertor. Therefore, the high PAPR limits the practical applications of OFDM.Whereas these problems, this paper carries on research towards the various algorithms of lowering the PAPR of OFDM signals, and uses MATLAB to complete the simulation about the problem. By analyzing the simulation results, it shows the advantages and disadvantages of these algorithms which are applied in our OFDM system. Surrounding the problem, the following works have been done: Chapter Three discusses companding transform of the signal pre-distortion techniques, compares the traditional companding transform with improved companding transform. It has proved that the improved companding is superior to the traditional companding at all points. A detailed discussion about the two typical methods of probability techniques: SLM (Selective Mapping) and PTS (Partial Transmit Sequence) is introduced in Chapter Four, it uses simulation to carry on the comparison to the two methods, points out their respective merits and shortcomings. For the large computation complexity of PTS, an improved method: Iterative-Algorithm has been proposed. This improved PTS method achieves a good compromise between performance and computation complexity. Chapter Five introduces clipping technique to reduce the PAPR, compares hard-clipping and soft-clipping, and combines clipping with the PTS to optimize the performance of the system. Finally, the summary to the full text is carried on in chapter Six.