  Multiple-input multiple-output (MIMO) technology applied with orthogonal
frequency division multiplexing (OFDM) is considered as the ultimate solution
to increase channel capacity without any additional spectral resources. At the
receiver side, the challenge resides in designing low complexity detection
algorithms capable of separating independent streams sent simultaneously from
different antennas. In this paper, we introduce an upper-lower
bounded-complexity QRD-M algorithm (ULBC QRD-M). In the proposed algorithm we
solve the problem of high extreme complexity of the conventional sphere
decoding by fixing the upper bound complexity to that of the conventional
QRD-M. On the other hand, ULBC QRD-M intelligently cancels all unnecessary
hypotheses to achieve very low computational requirements. Analyses and
simulation results show that the proposed algorithm achieves the performance of
conventional QRD-M with only 26% of the required computations.
