利用单频时间掩模函数降低OFDM的功率峰均比

Reduction of peak-to-average-power ratio in OFDM systems using the single-frequency-temporal mask function

为了减小正交频分复用(OFDM)系统信号功率的峰均比(PAR),在对PAR分析的基础上,首先给出了子载波初始相位分配方案,得到了最优相位解,它比传统的相位方案减小0.4 dB.同时证明了在子载波数>100时,信号的峰值功率出现的时间位置除了有较小的“漂移”外几乎固定不变,提出了一种基于单频时间掩模函数的PAR降低方案.先利用本文给出的初始相位分配方案抑制PAR,再利用掩模函数屏蔽掉功率峰值出现的时刻,使系统的PAR显著降低.为了保证信号的连续性,在掩模时间段内将所有信号都调制到一个频率点上.仿真结果证明:当掩模时间与信号持续时间之比为0.05时,该方法在误码率和PAR之间达到最优折衷,在用户数>100时,PAR可收敛到1.5 dB.

An initial phasing scheme to reduce the peak-to-average-power ratio （PAR） in orthogonal frequency division multiplexing （OFDM） systems is proposed. The optimum phasing value is obtained by analyzing the signal peak of systems, and PAR can be decreased by 0. 4 dB compared to the traditional phasing scheme. We prove that the time-positions of peak powers, which have small “excursion”, are almost fixed when the number of sub-carriers exceeds 100 when using the initial phasing scheme. So the single-frequency-temporal mask function is adopted. The peak power is reduced first by using the proposed phasing scheme, and then masked by using this function again. In this way, the PAR is significantly reduced. All signals are modulated to the same frequency within the time gap of these masked positions in order to guarantee the signal continuity. Results of simulations show that with this scheme, the PAR can converge to 1.5 dB when the number of users exceeds 100.