Asymptotic Outage Analysis of Large Size Correlated MIMO Systems

Current multi-input-multi-output (MIMO) capacity analysis focuses on the optimization of ergodic capacity, i.e., mean of capacity, if the capacity in random channels is considered as a random variable. In addition to ergodic capacity, outage probability is another important criteria of MIMO systems, as already stated by many researchers. However, it is not easy to optimize outage probability, because it is in fact a function of outage capacity. Different from previous outage analysis, in this work we are particularly interested in the relationship between outage probability and outage capacity, when outage capacity is asymptotically low, which is called asymptotic outage. Analogous to deep fading, the proposed asymptotic outage is the major exponent of error event. Moreover, it is convenient to optimize the proposed asymptotic outage, in contrast to conventional outage analysis. Detailed study is conducted in large size (number of antenna elements goes to infinity) MIMO systems, accompanied with a recently proposed correlated MIMO channel model, virtual channel representation. It is interesting to find that logarithm of asymptotic outage probability scales linearly with respect to logarithm of asymptotic outage capacity. Even more importantly, it is found that asymptotic outage performance degrades (higher outage probability) when channel correlation decreases.