Oblivious Cooperation of Wireless Colocated Transmitters

We address a scenario where a source sends information to a remote destination and where a relay terminal is occasionally present in close proximity to the source, but without the source´s knowledge. We assume independent block fading channels from the source and the occasional relay to the destination, while the channel between the source and the relay is assumed additive Gaussian, due to their mutual proximity. The focus is on cooperative schemes which make efficient use of the relay when it is present, and maintain single user optimality when it is absent. One such scheme is shown to be block Markov decode-and-forward involving correlated transmissions of the source and the relay. The optimal correlation for this scheme is found by optimizing the outage performance of a 2X1 multiple-input single-output (MISO) link under certain constraints. Finally, quantization schemes involving various levels of side information are discussed.