Outage capacities of space-time architectures

This paper considers non-ergodic multi-input multi-output (MIMO) fading channels. We compare the outage capacities yielded by the optimal unconstrained system and some recently proposed space-time architectures for i.i.d. Gaussian inputs. All the systems considered here are known to yield outage capacities having the same (maximum) rate of growth with the signal-to-noise ratio (SNR). For each system, an asymptotically tight lower bound on the outage capacity is derived. The analysis reveals that the diagonal BLAST architecture with the zero-forcing front end is asymptotically optimal with respect to the outage capacity. Another space-time architecture is shown to be optimal at all SNR with respect to the outage capacity.