一种新的22n+1阶QAM星座图设计

该文研究了2²ⁿ⁺¹阶正交幅度调制(Quadrature Amplitude Modulation,QAM)的星座图,提出了一种可以根据格雷映射规则建立映射表的正方形QAM星座图。为了对比正方形星座图与十字形以及矩形星座图的性能,该文以32 QAM为例对3种星座图的信号功率效率进行了分析,并对三者的误码性能进行了仿真。仿真结果表明,与信道编码结合使用时,正方形星座图的误码性能优于十字形星座图和矩形星座图。而且,对于多载波通信系统,正方形星座图和十字形以及矩形星座图具有相同的信号功率效率。     

Coherent optical OFDM scheme with inter-carrier interference self-cancellation and common phase error compensation

Schemes integrating inter-carrier interference （ICI） self-cancellation and common phase error （CPE） com- pensation for coherent optical orthogonal frequency division multiplexing （CO-OFDM） systems are investi- gated. The purpose of our research is to counteract the impacts of laser phase noise and fiber nonlinearity. We propose two ICI self-cancellation-based CO-OFDM schemes, and adopt a pilot-aided decision feedback （DFB） loop for CPE compensation. The proposed schemes are compared with conventional CO-OFDM schemes at the same spectral efficiency. Simulations show that our schemes can not only enhance laser linewidth tolerance of the CO-OFDM system, but also present strong robustness against fiber nonlinearity.