Soft Iterative Detector and Semi-Blind Identification for LDPC-Coded MIMO Systems in Dispersive Fading Channels

摘要

In this paper, we propose a joint soft iterative detection scheme utilizing expectation maximization (EM) and low density parity check (LDPC) codes for multiple-input multiple-output (MIMO) orthogonal frequency division multi-plexing (OFDM) systems. A soft iterative MIMO detector is introduced, by exploiting soft-input soft-output in the detection and decoding, the tractable extrinsic information efficiently optimizes LDPC code algorithm. This novel semi-blind identification system consists of two components, namely EM estimator for channel coefficients and log-likelihood ratio (LLR) estimator for probability value. Meanwhile, a feedback loop with EM and LDPC is designed to improve the estimated accuracy over dispersive fading channels. Theoretical analysis and numerical simulations demonstrate that the proposed LDPC code-aided joint iterative detection scheme offers significant gains in reception performance and outperforms conventional algorithms over diverse channels with Doppler frequency shifts.