Date Added: Nov 2012
In many communication scenarios, such as in cellular systems, the energy cost is substantial and should be conserved, yet there is a growing need to support many real-time applications that require timely data delivery. To model such a scenario, in this paper, the authors consider the problem of minimizing the expected sum energy of delivering a message of a given size from a source to a destination subject to a deadline constraint. A relay is present and can assist after it has decoded the message. Causal Channel State Information (CSI), in the form of present and past SNRs of all links, is available for determining the optimal power allocation for the source and relay.