Study of SMS air interface delay in strong and weak signal environments

SMS has the potential to support time-sensitive applications that provide access to information and services in developing countries. In this paper we present a series of tests of SMS air interface delay in strong and weak signal environments. We initially establish time delay baselines for three different sizes of SMS messages. Comparing different size messages in strong and weak signal environments tells us that the time delay in a weak signal environment increases in comparison to the strong signal on average by 0.5 seconds and the standard deviation doubles. Introducing fast fading by making the sending device mobile, the average air interface delay increases slightly but the standard deviation triples compared to the stationary case. The distribution function of the time delay has thicker tails than a normal distribution and we develop a novel distribution model that provides a good fit to the empirical data and provides useful insights about system performance.