正交幅度调制(QAM)技术具有较高的功率效率和带宽利用率，已广泛应用于多种通信系统中．高阶 QAM 解映射搜索范围很大，复杂度高．为此，文中引入软判决贡献因子来衡量参考星座点对解映射的贡献，提出了缩小搜索范围的高阶 QAM 解映射算法;文中还讨论了算法的边界情况，研究了信道估计辅助的自适应搜索范围选择方案．仿真结果表明:在获得与全集合搜索范围相同的误码性能的前提下，文中所提算法大大减小了搜索范围，4096- QAM 和 1024- QAM 解映射搜索范围仅分别为全集合搜索范围的12．7% 和19．7%;文中算法能较好地平衡性能和解映射复杂度，具有较好的工程应用前景．

QAM (Quadrature Amplitude Modulation) is broadly used in various communication systems thanks toits high power efficiency and bandwidth utilization.High- order QAM,because of its wide search range,may resultin high demapping complexity.In order to solve this problem,a novel concept of soft- decision contribution factor isintroduced to evaluate the contribution of reference constellation to the demapping,and a demapping algorithm ofhigh- order QAM within shrunk search range is proposed.Then,some boundary conditions of the algorithm are dis-cussed,and an adaptive selection scheme of search range is finally presented with the assistance of channel estima-tion.Simulated results indicate that (1) the proposed algorithm downsizes the search range without any sacrifice of BER performance; (2) 4096- QAM and 1024- QAM respectively shrink their search range to 12.7% and 19.7% ofthat of the whole constellation; and (3) as the proposed algorithm makes good tradeoff between performance anddemapping complexity.it has a good prospect of engineering application.