Practical considerations for extended V-BLAST: quantized parameters and imperfect channel estimation

Using multiple antennas at both the transmitter and receiver, BLAST exploits the multipath characteristics of a wireless channel to enable very large capacities. In an extended V-BLAST, those capacities are approached with single-dimensional coding and rate adaptation. However, such results require infinite precision for rate and power settings and perfect channel estimation. These assumptions are not practical due to a limited data rate of the feedback channel and a rapidly changing nature of a wireless channel. An algorithm for discretizing the rates and power control levels is proposed. We show that the loss in spectral efficiency due to rate and power control discretization is about 1-2 dB compared to that of an eigenmode transmission. We also consider the effects of imperfect channel estimation. We show that the performance loss is minimal when the channel estimation error is less than 2-3%.