Correlated lognormal interferers and outage probabilities

In this paper, three approaches that can be used to compute the distribution of a sum of correlated lognormal random variables (RV) were investigated. Specifically, Wilkinson's approach, an extension of Schwartz and Yeh's approach, and a cumulants matching approach were investigated and their accuracies compared. These techniques were used to compute the outage probability of a desired lognormal shadowed signal in the presence of multiple lognormal cochannel interferers. The outage results were presented as a function of the reuse factor, which is a key parameter in the design of any frequency reuse system. Simulation results for complementary distribution functions (CDF) of sums of lognormal RVs and for outage probabilities were used for verification and comparison. Overall, the results show that Wilkinson's method may be the best method to compute the CDF of sums of correlated RVs and hence the outage probability in correlated lognormal shadowed mobile radio environments. This is due to both its computational simplicity and accuracy over the range of parameters valid in practical applications.