Friendly Jammer Localization for Secrecy Enhancement

Abstract

This paper presents a joint resource sharing and jammer placement problem for a simple four node system including a source, a jammer and two untrusted users. Observing that the resource allocation involving subcarrier allocation, power allocation and jammer placement is complex due to their interdependence on each other, this work attempts to solve the problem in parts. First of all, key insights on optimal subcarrier allocation which is simply based on channel conditions is presented. Since, jammer has been introduced for secrecy performance improvement, the need for optimal power sharing between source and jammer is highlighted. Due to the consideration of sum power budget, the fraction in which power should be shared between signal and noise for maximizing sum secure rate is an important decision. Utilizing some key concepts, optimal power allocation based on alternating optimization is presented. Further, insights on optimal placement of jammer are presented to highlight whether jammer should be placed near the users or somewhere in between on the line joining the two users. All analytical concepts have been numerically verified and performance gain against bench-mark has been highlighted through simulation results.