为提升可见光双层叠加系统的通信性能, 提出了一种新型叠加编码系统。该系统在充分考虑远、近距离通信特点的基础上, 将迹正交编码与叠加系统相结合, 使双层信号满足迹正交特性,有效消除了层间干扰, 提升了信号间的欧氏距离, 并获得了一定的编码增益。针对此新型系统采用复杂度为线性的求和检测算法能够获得与最大似然(ML)检测算法相同的译码性能。通过推导基于ML检测时的理论误比特率(BER)闭式解, 分析了功率分配对各层传输BER性能的影响, 并给出了3类星座设计方案。仿真结果表明, 与现有双层叠加系统相比, 基于层间迹正交码编码的新型系统可有效改善系统的通信性能。

A novel overlapping code system is proposed to enhance the communication performance of double-layer overlay coding visible light communication system. With full consideration of the characteristics of far and near distance communication, the proposed system makes a creative combination of trace orthogonal coding and overlapping systems. This combination ensures the trace orthogonal property of two layers signals and therefore eliminates the interlayer interference. Moreover, an enhanced Euclidean distance and coding gain can be obtained to extract better performance. For this system, the same decoding performance can be obtained with the sum detection algorithm of linear complexity as well as with maximum-likelihood (ML) detection. The effect of different power allocations on system performance is analyzed by deriving the closed expression of bit error rate based on ML, and three constellation designs are then presented. Simulation results show that compared with existing double-layer overlapping systems, the new system based on layered trace-orthogonal coding can effectively improve communication performance.