A Novel Modulation Scheme of Polar Codes

To improve the spectrum efficiency of high-order modulation polar codes, a novel modulation strategy, namely displacement of balanced modulation (DBM) is proposed in this paper. This algorithm can balance the performance between bit levels under the universal encoder and decoder by adding a shift mapping matrix. Simulation results show that the presented DBM algorithm can achieve almost the same performance as the multilevel coding (MLC) technique with more flexibility. To further reduce the computational complexity of the proposed DBM algorithm, a simplified algorithm called reduced-complexity DBM (RC-DBM) is also presented, where location-based reliability sorting construction with complexity O(n) instead of Gaussian approximation (GA) construction with complexity O(N logN) is used, and the computing process of DBM is replaced with the structure characteristics of polar codes. Simulation results show that the proposed RC-DBM algorithm has a tolerable performance loss compared to that of DBM.