Abstract
In this paper an analysis of physical layer intruders, for direct sequence spread spectrum systems, is presented. Physical layer intruders are traditional jammers that do not have any intelligence as compared to smart jammers that have signal processing capability. The analysis is divided into two domains. In the first domain, different jammer architectures, their computational complexities and performance measurement in terms of bit error rates are explored. In the second domain, information theoretic perspective of jammers is developed. Expressions of channel capacity are developed and compared in the presence and absence of traditional and smart jammers. It is also shown that traditional jammers deteriorate channel capacities but for a smart jammer these can be made independent.