  It has been shown that using appropriate channel coding schemes in wireless
environments, transmission energy can be significantly reduced by controlling
the packet transmission rate. This paper seeks optimal solutions for downlink
transmission control problems, motivated by this observation and by the need to
minimize energy consumption in real-time wireless networks. Our problem
formulation deals with a more general setting than the paper authored by Gamal
et. al., in which the MoveRight algorithm is proposed. The MoveRight algorithm
is an iterative algorithm that converges to the optimal solution. We show that
even under the more general setting, the optimal solution can be efficiently
obtained through an approach decomposing the optimal sample path through
certain "critical tasks" which in turn can be efficiently identified. We
include simulation results showing that our algorithm is significantly faster
than the MoveRight algorithm. We also discuss how to utilize our results and
receding horizon control to perform on-line transmission scheduling where
future task information is unknown.
