Date Added: Jan 2012
In this paper, the authors first study the Decode-and-Forward strategy for secrecy in a single-relay network. They propose a suboptimal Decode-and-Forward with Zero Forcing (DF/ZF) strategy for which they obtain the optimal power control policy. Next, they consider the multiple relay problem. They propose three different strategies based on DF/ZF. The first strategy is a single-hop strategy in which all the relays decode the source message at the same time, then perform beamforming such that all the relays' signals are eliminated from the eavesdropper's observation (full zero-forcing).