Iterative Soft Cancellation With Element-Wise Extrinsic Information for Coded OTFS System

Orthogonal time-frequency-space (OTFS) modulation is able to improve the performance of the wireless communication system in a high-speed environment. This correspondence proposes an iterative soft cancellation receiver with element-wise extrinsic information for coded OTFS system. In calculating the soft estimates that are fed back to the iterative soft cancellation, existing full extrinsic information based method subtracts the entire a priori information from the a posteriori probability (APP) outputs from the decoder. In the proposed element-wise extrinsic information method, only the a priori information w.r.t the specific path (a single-element from the observation) in OTFS system is subtracted from the decoder's APP outputs. We show that the proposed approach outperforms existing a posteriori probability and full extrinsic information based iterative detection by 2 dB and 1 dB, respectively. Further, we apply extrinsic information transfer chart curve-fitting technique to optimize the code profile of the propose scheme. We demonstrate that the proposed scheme performs within 0.5 dB of the capacity limit of OTFS.