| It is known that the orthogonal frequency division multiplexing (OFDM) modulation is very suitable for high-speed wireless transmission systems due to its bandwidth efficiency and ability in coping with multipath fading. However, the large peak-to-average power ratio (PAPR) of an OFDM signal limits the application of OFDM to a certain degree.; The research focus of this thesis is on the study of some new PAPR reduction schemes for OFDM systems. In the first part of the thesis, we investigate the peak windowing method, the clipping method, and a combination of the two techniques with an emphasis on the performance assessment of the transmitted OFDM signal using the combination scheme. We start with the review of the two typical signal distortion techniques and point out their advantages and shortcomings. We then propose a combination scheme for the two techniques in order to overcome their drawbacks. In the proposed combination scheme, a weighting function is used to remove instantaneous signal peaks and then a hard-limiting is utilized for the reduction of the overall peak powers. A modified IDFT interpolation is developed and employed in the combination scheme to improve the interpolation precision of the time-domain OFDM signal. (Abstract shortened by UMI.)... |
