Performance analysis of low complexity soft detection for BICM MIMO system

We consider in this paper high spectral efficiency bit interleaved coded modulation (BICM) MIMO system where, after serial to parallel conversion and per antenna coding, spatial data streams are simultaneously transmitted by using an antenna array. We carry out the performance analysis of an earlier proposed detection algorithm for such system which is based on the combination of linear and non linear detection techniques. This algorithm employs linear MMSE filters to detect the streams which have seen good channel realizations and therefore enjoy higher signal-to-noise-ratios (SNRs). In the performance analysis, we show that the detection of these streams suffer from the loss of diversity order. These streams, after being detected, are subsequently stripped off leading to the max log MAP detection of the streams which have seen comparatively poor realizations of the channel and consequently have lower SNRs. We further show that these streams are benefited from the additional diversity order in the detection. Key idea is therefore to lower the detection complexity at the cost of reduced diversity order for the streams benefiting from good channel realizations and to enhance diversity order at the cost of increased detection complexity for the streams suffering from poor channel realizations.