Research On Constant Envelope OFDM Sub-Carrier Interference Suppression Technology

In recent years, there has been a great interest in researching and applying OFDM technology to high-speed wireless communications. However, conventional OFDM has a primary drawback that the OFDM signal has high peak-to-average power ratios (PAPR). The constant envelope OFDM (CE-OFDM) technique applies phase modulation to create ideal 0dB PAPR. In this thesis, the effect of zero-padding on the CE-OFDM system's inter-carrier interference(ICI) is studied, and the performance improvement of the CE-OFDM system by means of optimizing zero-padding is studied. The main contributions of this thesis are as follows.1. The performance of CE-OFDM system in the multipath channels is researched, and the effect of different values of modulation index on the performance of system is simulated and studied.2. Simulation results and theoretical analysis show that the phase modulation in the CE-OFDM system produces diversity gain and inter-carrier interference simultaneously, and the ICI degrades CE-OFDM system performance, and then the effect of different zero-padding patterns and oversampling factors on the performance of CE-OFDM system is analyzed.3. Under the condition of different values of oversampling factor, optimized zero-padding patterns are proposed through simulation and theoretical analysis. When the bit error rate(BER)is10-5, and oversampling factor is 8, the performance of CE-OFDM system with optimized zero-padding pattern increases about 6 dB compare with that of the system with original zero-padding pattern, and when oversampling factor is 4, the optimized zero-padding pattern outperforms the original zero-padding pattern by 2 dB.