The High Par Problem In OFDM And Countermeasures

OFDM is a promising broadband communication technology, but OFDM is suffering from the high-PAR problem, which imposes high requirement on the linearity of the power amplifier. Therefore, how to mitigate the high-PAR problem is quite important. In this study, we deal with this problem from two perspectives: Firstly, also the passive way, we try to decrease the nonlinear distortion caused by the HPA through carefully constructing OFDM signal that would incur minimum distortion. Secondly, the active way, we seek to enhance the linearity of HPA by effective predistortion techniques. We hope that the performance of OFDM would improve with the proposed techniques.On the one hand, we try to mitigate the high-PAR problem by signal construction. While the conventional methods are oriented towards minimizing PAR to solve this problem, we develop a new performance criterion, which is closely associated with the specific characteristics of HPA. The purpose of the new criterion (i.e. the MMSE criterion) is to minimize the future nonlinear distortion after OFDM signal passing the HPA. The new criterion is shown to greatly outperform the conventional...