The impact of channel estimation errors on space-time trellis codes paired with iterative equalization/decoding

The performance of space-time trellis codes paired with iterative equalization/decoding has been reported by Bauch and Naguib (see Wireless Communications and Networking Conference - WCNC´, p.261-265, 1999), by Liu, Fitz and Takeshita (see International Conference on Communications - ICC´, p.2800-2804, 2001), and by Gozali and Woerner (see PIMRC´, Feb. 2002) for MIMO frequency selective fading channels. Assuming perfect knowledge of channel state information at the receiver, the scheme has been shown to exploit multipath diversity in addition to spatial diversity and coding gain. We remove the assumption of ideal channel estimation and investigate the performance of the scheme in the presence of magnitude or phase error estimates. We show that the diversity advantage of the scheme relies heavily on accurate channel estimation and quantify the degradation associated with imperfect channel estimates. Results indicate that a phase error of up to 10 degrees or an amplitude error below 15% are tolerable, such that the diversity advantage of the scheme is maintained. Within these limits, the iterative process provides significant performance gains in the first and second iterations, while diminishing returns are observed for more than two iterations. Finally, we compare our simulation results with outage probability analysis bounds.