Limiting analysis of outage probabilities for diversity schemes in fading channels

Diversity schemes that exploit wireless channel variations in time, frequency, and space are an essential component for combating multipath fading in modern wireless communications systems. To evaluate performance and thereby design reliable and resource-efficient systems, designers require analytical tools that capture the salient, if not precise, characteristics of the fading channel model and diversity scheme employed. In this paper, we develop a simple and powerful way of characterizing performance of diversity schemes via limiting analysis of outage probabilities. As in other approaches to such an analysis, the two key parameters in our analysis are diversity order and coding gain, corresponding to the slope and intercept, respectively, in a plot of log-outage versus signal-to-noise ratio (SNR) in decibels (dB). Our approach allows for the characterization of a wide variety of diversity schemes operating over a broad class of fading channels, especially non-repetition diversity schemes such as parallel channel coding as well as multiuser diversity schemes such as cooperative diversity.