Companding Transform Technique Combined With Iterative Filtering For Reducing PAPR Of OFDM Signals

This dissertation mainly focuses on the companding transform method combinedwith iterative filtering approaches for the peak-to-average power ratio (PAPR) reductionof wireless orthogonal frequency division multiplexing (OFDM) signals. First of all, thedevelopment of PAPR reduction techniques as well as their potential application isbriefly introduced. The generalized system model and its corresponding theoreticalfoundation in mathematics were then illustrated, followed by the description for theprinciples of OFDM modulation. The effects of high PAPR on OFDM wirelesstransmission systems were subsequently elaborated and various state-of-art PAPRreduction methods were illuminated and analyzed in depth. Each method was alsocategorized in groups and a summary for each group was provided. Considering thedefect of the existing companding transform schemes, two iterative filtering methodsfor reducing signal PAPR were applied in this investigation. Two novel PAPR reductionschemes were proposed, namely, joint companding transform and iterative filteringoptimization scheme employing the linear and nonlinear companding function,respectively. Computer simulations were conducted, and the results illustrated that,compared with existing PAPR reduction schemes, the proposed schemes perform bettercomprehensively. It can be observed that two new schemes effectively reduce the PAPR,in the mean time, had little influence on the bit error rate (BER) as well as powerspectral density (PSD) performances in OFDM system. Moreover, the filter optimizingapproach made it feasible to further improve the PAPR and the BER performanceswithout any impact on the PSD. In addition, the companding and filtering parameterscan be adjusted in real-time during the iterative process, which effectively increases theadaptability and flexibility of the proposed schemes.