Tone Reservation Algorithms For Reducing PAPR Of OFDM Signals

Orthogonal Frequency Division Multiplexing(OFDM) technology has many advantages, such as high spectrum efficiency, the strong ability of resistance to frequency selective fading. As a result, it has become one of the main modulation techniques in modern wireless communication field. However, the issue of high Peak to Average Power Ratio(PAPR) of OFDM signals limits its wide application. If the PAPR is not covered by High Power Amplifier(HPA), nonlinear distortion will be produced and the performance is reduced. Although the large linear range of HPA can avoid nonlinear distortion, high cost makes it impossible to apply to the actual wireless system. Therefore, it’s necessary to make use of PAPR reduction techniques.PAPR reduction techniques are divided into three categories: predistortion techniques, coding techniques, probability techniques. Predistortion techniques can directly process OFDM signal and effectively suppress PAPR, but the techniques easily lead to signal distortion, and deteriorate Bit Error Rate(BER) and Power Spectral Density(PSD) performance; Though coding techniques don’t generate noise and distortion, but reduce the transmission rate; Probability techniques which reduce the chances of peak value appeared are the most popular PAPR reduction techniques, and Tone Reservation(TR) algorithms are part of the probability techniques.This dissertation mainly focuses on TR algorithms for PAPR reduction of wireless OFDM signals. First, it introduces the development and potential application and the evaluation criteria of PAPR reduction techniques; Secondly, it analyzes the principle and advantages and disadvantages of three kinds of PAPR reduction techniques, and elaborates the mathematical models of TR algorithms; Finally, it proposes two new algorithms by combining other PAPR reduction techniques to overcome the shortcoming that existing TR algorithms can not improve PAPR, BER and PSD simultaneously. The two algorithms are a combination of the TR algorithm based on Least Squares Approximation(LSA) and the Active Constellation Extension(ACE) algorithm based on Smart Gradient Projection(SGP), and a combination of TR algorithms based on Signal to Clipping Noise Ratio(SCR) and LSA. They are called the Sgp ACE-Lsa TR algorithm and the Lsa-Scr TR algorithm. The new proposed algorithms are analyzed in depth in the paper, and then the theoretical value and the computationcomplexity are understood.The paper simulates and verifies the algorithms by Matlab simulation software. Compared with the TR algorithm based on LSA, the first proposed algorithm can produce clipping signals with faster convergence, and other properties are optimum; since the second proposed algorithm can effectively reduce the PAPR and has little influence on BER as well as PSD, the algorithm also has a relatively good overall performance; during the iterative process, the parameters of the new algorithms can be adjusted in time, which can increase the adaptivity in the OFDM system.