Performance analysis of coded V-BLAST with optimum power and rate allocation

Several optimization strategies for instantaneous rate and/or power allocation in the coded V-BLAST are studied analytically. Outage probabilities and system capacities of these strategies in a spatial multiplexing system are compared under generic settings. Since the conventional waterfilling algorithm is suboptimal for the coded V-BLAST, a recently-proposed "fractional waterfilling" algorithm is studied, which simultaneously maximizes the system capacity and minimizes the outage probability. A comparative, closed-form performance analysis of this and other algorithms is presented, including bounds on the outage probability and its low-outage approximations. The fractional waterfilling algorithm attains the full MIMO channel diversity and outperforms the other algorithms by a wide margin.