Decision-feedback sequence estimation for time-reversal space-time block-coded transmission

In this correspondence, we consider three different decision-feedback sequence-estimation (DFSE) schemes originally proposed for single-input-single-output channels for time-reversal space-time block coding (TR-STBC). The first scheme is called unwhitened DFSE (U-DFSE) and performs reduced-state sequence estimation based on the output of the spatio-temporal matched filter (MF), typically employed in TR-STBC. The second approach improves upon U-DFSE by subtracting a bias term caused by anticausal interference from the U-DFSE metric. In the third scheme, the noise component in the output of the spatio-temporal MF is first whitened using a prediction-error filter and, subsequently, whitened DFSE (W-DFSE) is performed. As a relevant example, all three DFSE schemes are compared for the global system for mobile communications/enhanced data rates for GSM evolution (GSM/EDGE) system and typical channel profiles. Our results show that for binary modulation (as used in GSM) U-DFSE and its improved version can approach the performance of W-DFSE for the full range of delay spreads relevant for GSM and EDGE. On the other hand, for high-level modulation (as used in EDGE) only W-DFSE gives a satisfactory performance, if a low trellis complexity is desired.