| There exists a fundamental trade-off between transmission energy and packet delay in wireless communications. In a static channel, a closed form solution of the optimal offline scheduling (vis-a-vis total transmission energy), assuming information of all packet arrivals, for a set of packets each subject to an individual delay constraint is derived. It is shown that when packet arrivals are identically and independently distributed, the optimal packet transmission durations (or, equivalently, transmission rates) exhibit a symmetry property, which leads to a simple and exact solution of the average packet delay. The delay performance for the optimal offline scheduling of a set of packets subject to a single transmission deadline is also analyzed and shown to be potentially unbounded. The problem of optimal offline scheduling is then extended to fading channels. The properties of the optimal offline transmission rates and the corresponding delay performance are also characterized. Heuristic online schedulers, assuming causal information only, are also studied. The properties of the optimal offline scheduling are demonstrated via simulations.; Delay-constrained energy-efficient packet transmission is then considered under a multihop link. For static channels, given an end-to-end delay constraint for each packet, the optimal offline scheduling over a multihop link is obtained. The transmission energy and average packet delay performance are analyzed and characterized. Extension to fading channels is also considered. It is further demonstrated via simulations that energy savings via multihopping are possible, but heavily depend on factors such as multihop resource orthogonalization mode, scheduling algorithms, delay constraints, SNR operation regions, and channel variations.; Packet transmission over wireless channels is subject to losses. Note that some applications can tolerate a small fraction of packet losses. Therefore, we initiate the study of proactive packet dropping, while satisfying the required maximum packet loss rate, to maximize transmission energy savings. The optimal and suboptimal packet dropping schemes are investigated under both the single transmission deadline model and the individual delay constraint model. It is found that proactive packet dropping yields substantial transmission energy savings, as evidenced via simulation results. |
