Accurate Characterization and Low-Complexity MMSE Equalization of ISCI in Doubly-Dispersive Channels

this paper, we investigate the Inter Symbol and Carrier Interference (ISCI) of doubly-dispersive channels in highly dynamic scenarios from the continuous and discrete perspectives, respectively, and thoroughly analyze its impact on the performance of communications systems. Due to its robustness against the Doppler effect in time-varying channels, Orthogonal Time Frequency Space (OTFS) modulation has gained significant research interest, with many equalization algorithms proposed. However, existing studies either fail to fully account for ISCI or suffer from prohibitive complexity. In this study, we accurately quantify the ISCI of doubly-dispersive channels and provide an in-depth analysis from continuous and discrete channel models, respectively. Based on this, we propose a low-complexity Minimum Mean Square Error (MMSE) equalization to equalize ISCI in doubly-dispersive channels. The proposed algorithm demonstrates a reduction in complexity of the MMSE equalization fromO(M3N3)toO(MNL2bw), whereLbwdenotes the bandwidth of the time domain channel matrix. Concurrently, it has been demonstrated to significantly reduce the bit error rate (BER), thereby enhancing communication performance.