Structural Properties of Optimal Uplink Transmission Scheduling in Energy-Efficient Wireless Networks with Real-Time Constraints

It has been shown that the energy efficiency of wireless networks can be greatly improved by utilizing transmission control techniques, which dynamically adjust the transmission speed subject to real-time operating constraints. In this paper, we focus on the uplink transmission scheduling problem for minimizing the total transmission cost in the setting that multiple nodes share the spectrum and transmit to the same destination. Our formulation is more general than that in Uysal-Biyikoglu, E. and. Gamal, A.E., where the FlowRight algorithm is proposed, in the sense that we allow each individual task have its own deadline. We identify several structural properties of the optimal control to the two-node uplink scheduling problem, including: i) the optimal rates only change at known event times; ii) at each rate changing point, there exists an explicit relationship between the event type and the rate changing direction; and iii) at each rate changing point, the directions of rate change are reverse. These properties are helpful to establish an efficient decomposition approach towards solving the general transmission scheduling problem