Supporting PHY-layer security in multi-link wireless networks using friendly jamming

Friendly jamming is a PHY-layer technique used to secure wireless communications. Unlike previous efforts that fix the placement of the friendly jamming devices, in this paper we consider small- scale multi-link wireless networks, e.g., peer-to- peer or multihop, and jointly optimize the powers and locations of the friendly jamming devices so as to minimize the total jamming power while simultaneously achieving a given secrecy constraint. We use distributed MIMO techniques and incorporate the necessary conditions to ensure nullification of the friendly jamming signals at legitimate receivers. Two optimization strategies are explored: per-link and network-wide. Our optimization framework is based on formulating a signomial programming problem using condensation techniques to approximate the problem as a geometric program, which can then be transformed into a convex problem. We also consider the secrecy-aware routing problem for multihop networks and propose a routing metric based on the total jamming power along the path. Simulations show that our proposed schemes outperform previous schemes in terms of energy efficiency (55%-99% power saving). Moreover, our formulation ensures protecting legitimate transmissions by nullifying friendly jamming signals at legitimate receivers.