超奈奎斯特(FTN)传输技术可有效提高无线光通信系统的传输速率,但其引入的码间干扰会极大影响系统的可靠性。针对此问题,设计了一种基于逐点消除的自适应预均衡算法。推导了4阶脉冲幅度调制下该算法的理论误码率和计算复杂度。仿真结果表明,该算法可以消除由FTN成型带来的码间干扰,其性能几乎等同于正交传输系统。系统的计算复杂度则随着加速因子的减小而增加,当加速因子小于0.4时,计算复杂度会出现快速上升。

Faster-than-Nyquist (FTN) transmission technology can effectively improve the transmission rate of free space optical communications. Unfortunately, the inter-symbol interference (ISI) introduced by FTN greatly affects the system reliability. To this issue, a point-by-point elimination adaptive pre-equalized algorithm is proposed. The theoretical bit error rate and computational complexity under 4 order pulse amplitude modulation are derived. The simulation results show that this algorithm can eliminate the ISI brought by FTN pulse shaping filter, and its performance is almost equal to that of orthogonal transmission system. In addition, the system computational complexity is inversely proportional to the acceleration constant. When the acceleration constant is less than 0.4, the computational complexity increases rapidly.