Performance losses in V-BLAST due to fading

New insights into the information theoretic aspects of multiple antenna systems have led to the development of numerous blind and training-based schemes that exploit the high data rate capacities of diversity systems. One such popular training-based spatial multiplexing technique is the Vertical Bell Labs Layered Space Time Architecture (V-BLAST). The common practice in the literature is to assume that the channel remains constant over some time interval, whose duration is proportional to the coherence time of the channel. This is not often true since the channel is continuously varying, although the variation is slow in some cases. For our analysis, the channel coefficients are modeled as a first-order autoregressive process. We then show that even in slow fading channels, the performance losses are considerable. One surprising and rather non-intuitive result is that the performance losses are higher at higher average signal-to-noise ratios. We have simulated V-BLAST with such a channel model to confirm the validity of our analysis.