Date Added: May 2013
Wireless transmissions are prone to eves-dropping due to their broadcast nature. Providing security through physical layer mechanisms where the intended receiver gets the information reliably while the eavesdroppers get no information is an active area of recent research. Secrecy capacity results for fading channels have been widely reported. Also, secure wireless communications via cooperation is witnessing growing research interest. In particular, cooperation based on Amplify-and-Forward (AF) and Decode-and-Forward (DF) relaying protocols for secure communication has been investigated in the literature, assuming perfect and imperfect Channel State Information (CSI).