Research On PAPR Mixed Reduction Based On OFDM Systems

Orthogonal frequency division multiplexing (OFDM) is a multi-carrier modulation technique with high data rate and high frequency efficiency, so it is robust to the multipath fading channel and fit for multimedia data transform. It has been regarded and used as one of the core technologies for the fourth generation communication network. However, high Peak-to-Average Power Ratio (PAPR) of the transmitted signal is a major drawback of OFDM system. Consequently, it is important to reduce PAPR of OFDM by an appropriate technique.First of all, the basic principle of OFDM is introduced, the distribution of PAPR is analyzed. Secondly, a PAPR reduction method based on the DFT property of the time domain circular convolution (TCM) and a linear companding transforem with two inflexion points (LCT) are studied. And in this thesis, a new method is proposed based on the TCM method and LCT method, which can reduce the PAPR a lot more. At the transmitter, the first of the OFDM signal processing method according to TCM, select the sequence with the minimum PAPR for transmission, in order to complete the first PAPR of OFDM signal processing and then with the help of the compression and expansion device through the second pair of reduce the PAPR of OFDM signal processing (LCT algorithm). After two lower PAPR treatments, the PAPR of the OFDM signal has been substantially improved. In the receiver, firstly through the anti-compression and expansion transform, as to restore the signal before compression and expansion, and then through the auxiliary information received TCM treatment to restore the original signal before all the transformations.And we discussed the PAPR performance of the new method and the two methods before combination under the different conditions. Based on the results of MATLAB simulations, the new method could reduce PAPR effectively, and achieve an excellent BER performance.