A Pedagogic Approach to Cascaded Fading Channels and Diversity in Wireless Systems

Abstract

College programs in electrical engineering offer courses in wireless communications. One of the complex topics of instruction in these courses is fading which deals with signal strength fluctuations. While many simple fading models exist, a cascaded approach to fading provides a general means to describe these fluctuations in wireless channels including keyhole and multi-hop relay channels. In this approach, the signal strength is expressed as the product of several random components. Such a methodology is complicated by the fact that the probability density functions of the signal-to-noise ratio cannot be expressed in simple forms. Furthermore, the study of diversity to mitigate fading is made difficult by the absence of analytical expressions for the densities, error rates and outages. To overcome these difficulties, a MATLAB-based simulation techniques is proposed and demonstrated. The beneficial effects of diversity in mitigating fading are established through density and distribution functions as well as quantitative measures of performance such as the error rates and outage probabilities. It is suggested that the MATLAB-based approach can provide a didactic means to facilitate the understanding of fading and fading mitigation.