Soft-Feedback Time-Domain Turbo Equalization for Single-Carrier Generalized Spatial Modulation

Abstract

In this paper, a new class of soft-decision feedback aided time-domain turbo equalizer (TDTE) based on the minimum mean-square error criterion is proposed for broadband single-carrier (SC) generalized spatial modulation (GSM) systems. First, a time-domain soft-decision feedback (TDSDF) aided TDTE is proposed, which operates on a vector-by-vector basis. In order to provide a flexible tradeoff between complexity and performance, time-invariant filter coefficients are derived to provide a low-complexity approximate solution to the proposed TDSDF-TDTE. Furthermore, a soft-feedback interference cancelation (SFIC) aided TDTE is proposed for SC-GSM systems with a lower complexity, where the computation of the second-order moment of matrices is completely avoided. Finally, bi-directional soft-decision feedback aided TDTEs are proposed by using a time-reversed TDSDF-TDTE/SFIC-TDTE in conjunction with a ordinary TDSDF-TDTE/SFIC-TDTE so as to harvest time-reverse diversity and to mitigate the error propagation. An extrinsic information transfer chart based analysis and bit error rate simulation results are presented to demonstrate the superior performance of the proposed soft-decision feedback aided TDTEs as opposed to the original TDTEs, while achieving a lower complexity.