Research Of Peak-To-Average Power Ratio Reduction In OFDM Systems

Orthogonal Frequency Division Multiplexing (OFDM) is an attractive technique for multi-carrier parallel transmission scheme due to its high bandwidth efficiency and good capability to resist multi-path interference. So it has been widely used in several areas such as Asymmetrical Digital Subscriber Line (A DSL), Local-Area Digital Audio Broadcasting (DAB), High Definition TV (HDTV) and Wireless Networks (WLAN) and become the fourth-generation mobile communication core technology. However, it has an inherent weakness of high Peak-to-Average Power Ratio (PAPR) of the transmitted signal. This weakness makes a high request for the linearity of high-power amplifier in transmitter and amplifier in receiver, and increases the complexity of A/D and D/A converter. Thus, high PAPR value of OFDM transmitted signal has been one of the main obstacles during its putting into practice. The method of PTS to reducing PAPR of OFDM is studied in this paper.Firstly, the basic OFDM principle is studied in this paper. The reason and impairment of high Peak-to-Average Ratio in OFDM system are analyzed, and then the status quo of reducing PAPR is summarized. The principle of signal scrambling technique is introduced, and SLM and PTS technique are analyzed in detail. A specific scheme is proposed to reduce the PAPR by using the standard arrays of extended hamming code. With Monte Carlo simulation, the effect on PAPR reduction of this scheme is testified. And then the algorithm of using Riemann Sequences to reduce the PAPR was proposed. The main idea of the algorithm is to select row vectors of the normalized Riemann matrix as phase vectors. Some results were obtained by Monte Carlo simulations, and it was proved that this algorithm has better performance for reducing the PAPR of OFDM signals, the computational complexity is reduced and the bandwidth efficiency is improved. Finally the two approaches are simulated by using MATLAB, and the results of simulation show that these methods can effectively reduce the OFDM system of the PAPR.