MQAM-OFDM系统中降低峰均比与残余载波频偏同步联合算法

摘要

针对OFDM系统对频偏敏感及峰均比高的问题,提出一种用MQAM调制值的共轭码对残余载波频偏进行跟踪的方法,该共轭码同时可以降低系统峰均比.用频域MQAM数值的共轭来调制导频子载波以抵消相位,降低系统的峰值功率.同时利用这种共轭关系估计残余载波频偏引起的相位旋转,在时域或频域进行纠正.仿真结果表明利用这种共轭码可有效的跟踪频偏,又使系统具有更低的峰均比.%A technique for the residual carrier frequency offset (CFO) tracking and the peak-to-average power ratio (PAPR) reduction in multilevel quadrature amplitude modulation (MQAM) based orthogonal frequency division multiplexing (OFDM) systerm is presented. The scheme is based on unknown pilot subcarriers modulated by the conjugate of the MQAM information data,cancelling their phases to reduce the maxim power. The conjugate code periodically inserted in the OFDM symbols allows the frequency tracking loop to estimate the phase offset using a derived formula. The simulation investigates the algorithm performance showing that the frequency can be precisely corrected and the PAPR can be reduced with several dB.