Low-complexity Soft Output Algorithms for High-order Modulation
Dongliang Xiao · Radio and communications technology · 2012
The soft decision technique has been proved to be an efficient way to improve decoding performance in modern communication systems.The high-order modulation such as M-ary QAM and M-ary PSK can achieve high transmission rate without increasing the bandwidth.However,the accurate calculation expression of soft output algorithms via the log-sum approximation is of high computational complexity and traditional approximate algorithm has a great loss in performance.A low-complexity soft decision technique is proposed for two kinds of gray mapping modulation schemes,including 16QAM and 32PSK.Compared with the traditional method,the proposed algorithm is closer to the theoretical value under the simulation system with LDPC codes.