How far away is infinity? Using asymptotic analyses in multiple-antenna systems

Asymptotic theorems are very commonly used in probability. For systems whose performance depends on a set of random variables, asymptotic analyses are often used to simplify calculations and obtain results yielding useful hints at the behavior of the system when the parameters take on finite values. These asymptotic analyses are especially useful whenever the convergence to the asymptotic results is so fat that even for moderate parameter values they yield results close to the true values. The goal of this paper is to illustrate this principle through a number of examples taken from multiple-antenna systems.