PAR reduction techniques in OFDM

Abstract

Orthogonal frequency-division multiplexing (OFDM) is a modulation which uses multiple-carrier to transmit information. It uses multiple low speed carriers system instead of a high speed single carrier system. Hence, it has a better performance in multipath fading problem. However, OFDM has two major obstacles compared with a single carrier system --- sensitivity to synchronization error and high peak to average power ratio (PAPR). In this project, PAPR reduction techniques are studied. In order to verify the findings, Matlab has been used for simulations. In this project, there are some analyses of few PAPR reduction techniques such as conventional clipping, window clipping and peak cancellation. All of the techniques will have the error degradation problem since reducing the high peak of transmitted signal will normally cause distortion. Although the conventional clipping gives the best PAPR value, it will increase out of band radiation. On the other hand, widow clipping and peak cancellation can decrease out of band radiation. However, the PAPR reduction is not effective as conventional clipping. Also, it increases the probability of bit error.

In this project, an innovative peak replacement method is proposed. It is similar to windowing clipping since the reference points come from window function. However, it replaces the peak value with some reference points directly. Hence, it has simpler computational complexity.