为了抑制因LED的非线性特性所导致的可见光通信系统中正交频分复用信号(OFDM)的峰均功率比出现上升的问题, 提出了一个频率调制恒定包络的OFDM技术。对来自源的串行输入比特序列进行并行转换, 将其映射到正交调幅星座点; 为了在电-光转换之前对OFDM信号进行频率调制, 将OFDM信号中的突变幅度应用到LED以产生恒定包络信号; 为保持LED处于其线性工作区域中, 通过逐步增加功率回退的方式选择最佳偏置点, 使LED进入非饱和状态。仿真结果表明, 方法的系统总衰减明显降低, 与其他类似方法相比, 其功率回退系统的误差向量幅度和比特误码率表现更佳, 系统整体性能改善明显。

In order to inhibit the effect of non-linearity of the LEDs leading to a significant increase in the peak to average power ratio of the Orthogonal Frequency Division Multiplexing (OFDM) signals in visible light communication, a frequency modulated constant envelope OFDM technology is proposed. Firstly, Parallel conversion of serial input bit sequence from the source, which is mapped to the quadrature amplitude modulation constellation points. Then, to modulate the frequency of the OFDM signal before the electro optical conversion, the amplitude of the mutation in the OFDM signal is applied to the LED to produce a constant envelope signal. Finally, to keep the LED in the linear region, the optimum bias point is selected by increasing power rollback step by step, making the LED into the unsaturated state. The simulation results show that the proposed method makes the total attenuation decrease significantly. Compared with other similar methods, the error vector magnitude and bit error rate performance in backoff system is better, the overall performance of the system has significantly improved.