In this talk, we will present new cooperation strategies for relay, broadcast, multiple access, and three way channels subject to the half duplex constraint. In particular, for the outage-limited relay channel, we will propose a dynamic decode and forward (DDF) strategy that achieves the optimal diversity-multiplexing tradeoff for a certain range of multiplexing gains. We will further argue that the gain offered by the DFF strategy is more significant in the cooperative broadcast channel. For the outage-limited multiple access channel, we will present a linear cooperation strategy that achieves the optimal tradeoff for all multiplexing gains. A modular cooperation strategy based on multi-casting with side information will be developed for the three way channel.
Our results reveal a fundamental difference between the half duplex cooperative multiple access and relay channels and highlight the fundamental role of ARQ feedback in facilitating cooperation in vector multiple access channels.
This is a joint work with Kambiz Azarian, Lifeng Lai, and Philip Schniter.