A low-complexity noncoherent MAP detector for turbo-coded unitary space-time modulation scheme

Abstract

In non-coherent multiple-input multiple-output (MIMO) systems, the conventional noncoherent MAP detector is too complex to be performed if the number of labelling bits conveyed within one single coherence block is high. In order to overcome this difficulty, in this paper, we propose a noncoherent MAP (maximum a posteriori) detector with very low complexity for orthogonally designed USTM (unitary space-time modulation) schemes. In addition, we show that the detected soft values are independent of the extrinsic information fed back from the turbo decoder. As a result, iterative detection and decoding between the noncoherent detector and the turbo decoder can be avoided without performance degradation. Compared to the scheme using the exhaustive-search-based noncoherent MAP detector, the proposed scheme achieves the same error performance, and has a much lower detection complexity.