Research On Peak To Average Power Ratio Suppression Of OFDM Communication System

Orthogonal Frequency Division Multiplexing (OFDM) receives more and more deployment in many wireless multi-carrier communication systems due to a variety of attractive performances such as its robustness to the frequency-selective channel and high spectrum efficiency.A main drawback of OFDM is high Peak to Average Power Ratio (PAPR/PAR). An excessive fluctuation of the symbol power demands adequate dynamic scope of such components as high power amplifier, AID converter and D/A converter, which leads to low efficiency of these parts. Once such a demand cannot be met, clipping distortion would be introduced and system performance degrades. In practical systems, the suppression of PAR is indispensable.The thesis shows the feasibility and necessity of research on PAPR suppression of OFDM on the basis of a thorough survey of OFDM technology. Based on the specification of IEEE 802.11a WLAN standard, a simulation system for physical layer is completed with Matlab 6.5, which includes such functions as transmitter and system performance evaluation. A scheme named Phase Scrambling is proposed for the suppression of PAPR. The modulating vectors for the subcarriers consist of the information-bearing components and the reduction components. The scrambling of the information components is optional and the scrambling of the reduction components is achieved by vector space scanning. A Differential Recursive scheme for PAPR suppression is put forward. The pseudo-randomized modulating vector to the subcarrier series is differentially phase-encoded between successive components in frequency domain, while recursion manipulates several samples in time domain.Research in the thesis gains the expected ends with ease of hardware implementation, realizing the design of wireless OFDM communication systems with low PAPR.