Non Traditional Relay Channels: Diversity and Secrecy Gains

Summary form only given. In this talk, we report some of the recent results on non traditional relay channels. More specifically, the outage-limited relay channel is discussed first. Here, a simple implementation of the dynamic decode and forward relaying scheme is presented. This scheme achieved the optimal diversity-multiplexing tradeoff for multiplexing gains r les 0.5. In the second part of the talk, we impose a secrecy constraint on the relay channel by introducing an eavesdropper to the basic setup. Several cooperation strategies for enhancing the secrecy capacity are devised, and the corresponding achievable rate-equivocation region is characterized. Of particular interest is the novel noise-forwarding (NF) strategy, where the relay node sends codewords independent of the source message to confuse the eavesdropper. This strategy is used to illustrate the deaf helper phenomenon, where the relay is able to facilitate secure communications while being totally ignorant of the transmitted messages. Furthermore, NF is shown to increase the secrecy capacity in the reversely degraded scenario, where the relay node fails to offer performance gains in the classical setting.