Ofdm-based Non-distortion Of The Papr Suppression Of New Technologies

Owning to the high bandwidth efficiency and resistance to frequency-selective fading, Orthogonal Frequency Division Multiplexing (OFDM) has become one of most popular techniques for wirless communications in future. However, the inherent high Peak-to-Average Power Ratio (PAPR) in OFDM systems may cause the High Power Amplifier (HPA) to go into non-linear regions, and therefore produce nonlinear output and degrade the performance seriously.In order to avoid the non-linear distortion caused by high PAPR, it is necessary to reduce the PAPR and ensure the fluctuation of OFDM signals in the linear region of HPA. The PAPR reduction technologies consist of distorted methods and distortionless methods. Since the distorted methods would result in signal distortion and out-of-band radiation, we will focus on the distortionless methods: Tone Reservation (TR) and Partial Transmit Sequence (PTS). Finally, two novel PTS schemes with lower complexity are proposed.First of all, Chapter 1 introduces characteristics of the OFDM system, and summarizes the research topics in this dissertation.Chapter 2 introduces the definition of PAPR as well as its distribution in OFDM systems. And then the current poplular PAPR methods are discussed.Chapter 3 provides a detailed introduction of current TR schemes, and summarizes the computational complexity of these schemes. By simulating and comparing these TR schemes, the optimal TR scheme is concluded and then compared with Multiple Signal Representation (MSR) methods.Chapter 4 analyzes the correlation of all candidates in PTS, and then two novel PTS schemes with low complexity are proposed. These two PTS schemes either reduce the number of candidate signals or decrease the number of factor combination in each candidate signal to reduce the whole complexity in PTS. Simulation results show that they could make a desirable PAPR reduction performance near the same as that of conventional PTS while with lower complexity as that of conventional PTS. In the last chapter of this dissertation, we summarized whole thesis and pointed out the further research directions in PAPR reduction for OFDM systems.