Improving Wireless Physical Layer Security Via Cooperating Relays
PHYsical (PHY) layer security approaches for wireless communications can prevent eavesdropping without upper layer data encryption. However, they are hampered by wireless channel conditions: absent feedback, they are typically feasible only when the source-destination channel is better than the source-eavesdropper channel. Node cooperation is a means to overcome this challenge and improve the performance of secure wireless communications. This paper addresses secure communications of one source-destination pair with the help of multiple cooperating relays in the presence of one or more eavesdroppers. Three cooperative schemes are considered: Decode-and-Forward (DF), Amplify-and-Forward (AF), and Cooperative Jamming (CJ). For these schemes, the relays transmit a weighted version of a re-encoded noise-free message signal (for DF), a received noisy source signal (for AF), or a Common Jamming signal (for CJ).