  Non-orthogonal space-time block codes (STBC) with {\em large dimensions} are
attractive because they can simultaneously achieve both high spectral
efficiencies (same spectral efficiency as in V-BLAST for a given number of
transmit antennas) {\em as well as} full transmit diversity. Decoding of
non-orthogonal STBCs with large dimensions has been a challenge. In this paper,
we present a reactive tabu search (RTS) based algorithm for decoding
non-orthogonal STBCs from cyclic division algebras (CDA) having large
dimensions. Under i.i.d fading and perfect channel state information at the
receiver (CSIR), our simulation results show that RTS based decoding of
$12\times 12$ STBC from CDA and 4-QAM with 288 real dimensions achieves $i)$
$10^{-3}$ uncoded BER at an SNR of just 0.5 dB away from SISO AWGN performance,
and $ii)$ a coded BER performance close to within about 5 dB of the theoretical
MIMO capacity, using rate-3/4 turbo code at a spectral efficiency of 18 bps/Hz.
RTS is shown to achieve near SISO AWGN performance with less number of
dimensions than with LAS algorithm (which we reported recently) at some extra
complexity than LAS. We also report good BER performance of RTS when i.i.d
fading and perfect CSIR assumptions are relaxed by considering a spatially
correlated MIMO channel model, and by using a training based iterative RTS
decoding/channel estimation scheme.
