PAPR Reduction Techniques with Hybrid SLM Partial Transmit Sequence Algorithm for OFDM System

In recent time, the demand for multimedia data services has grown up rapidly. One of the most promising multi-carrier system, Orthogonal Frequency Division Multiplexing (OFDM) forms basis for all 4G wireless communication systems due to its large capacity to allow the number of subcarriers, high data rate and ubiquitous coverage with high mobility. OFDM is significantly affected by peak-to-average-power ratio (PAPR). In general; the high peak-to-average power ratio (PAPR) of transmitted signals for OFDM systems reduces the system efficiency and hence increases the cost of the radio frequency (RF) power amplifier. This thesis emphasis mainly on the PAPR reduction of OFDM system using partial transmits sequence (PTS) and pre-coding techniques. Some other techniques such as amplitude clipping have low-complexity; on the other hand, they suffer from various problems such as in-band distortion and out-of-band expansion. Signal companying methods have low-complexity, good distortion and spectral properties; however, they have limited PAPR reduction capabilities.

A modified hybrid algorithm is developed to obtain better PAPR reduction performance and reduce computational complexity compared with the conventional hybrid scheme. This proposed algorithm combines selected mapping (SLM) with partial transmit sequence (PTS) strategies, and further employs linear addition and exchange of various PTS sub-blocks to create more alternative OFDM signal sequences. As a result, with the same numbers of IFFT and phase rotation sequences, our proposed algorithm has the potentials to provide better PAPR reduction performance with lower computational complexity.