Research On Peak To Average Power Reduction Techniques For OFDM System

For its high bandwidth efficiency, inherent resistance to inter-symbol interference and frequency-selective fading, Orthogonal Frequency Division Multiplexing (OFDM) which is widely used in wireless LAN, mobile communication and high definition television(HDTV), is considered to be one of the core techniques of the 4th generation mobile communication.However, high Peak-to-Average Power Ratio(PAPR)of the OFDM signal, one of the major drawbacks of OFDM, directly results in signal distortion when it is entering into the nonlinear region of the power amplifier, greater complexity of digital-analog, analog-digital conversions in system and the system's requirement to a better power amplifier which still will work in low efficiency status. Therefore, OFDM system must take appropriate PAPR reduction techniques in practical applications, making signal changes in a suitable range.After analyzing PAPR reduction techniques of current OFDM system, the paper proposes some new algorithms and verifies their performances based on the clipping algorithm.First of all, the paper introduces the OFDM techniques'history, development and application, providing an overview of research and development of PAPR reduction techniques. Secondly, based on discussing the characteristics of wireless channel, the basic principles and link's architecture of OFDM system, the paper not only makes a thorough analysis of some critical techniques of OFDM system, but also explains the advantages of OFDM compared to the others. Then, a probability study and analysis is made about the PAPR of OFDM. Furthermore, there is a systematic introduction on variety of current PAPR reduction techniques'principles with a comprehensive compaprison about the technical features. Especially, some drawbacks in various current techniques are paid attention increasingly, like great BER in clipping, big complexity in frequency filter and a lack of use of sub-carriers OFDM in tone reservation algorithm. Due to these defects, a new algorithm, sub-carriers fixing which brings low BER, is proposed and studied. This paper creates a model for the new algorithm by means of MATLAB simulation. The simulation result shows that the new algorithm improves the performance of OFDM system effectively with low cost of complexity, which is contributed to the application. Finally, the summary is proposed pointing out that the new algorithm has its own technical superiority but still needs a further improvement, in the meanwhile, providing a clear direction for future research and thinking.