Adaptive transmission of variable-rate data over a fading channel for energy-efficiency

This paper cxplorcs the adaptation of transmission rate and power jointly 10 the data generation rate and channel fading, far minimizing transmission energy. The optimal ofeinr adaptation problem iproluod,whichpmvid~s.lowcFbound onthe-ns mission enecgy A heuristic Online algorithm, Look-nhesd Water-filling, is developed for sdspting to the queue state as weU PI the channel state, and is r h m through simulations to achieve lranrmission anergy per high rate streaming video session. When the required rate drops, for example because the rate web session where switches to a lowere px the transmitter by any pr.otira~, that is, idle a significant fraction of time and transmit unnecessarily fast the rest of the time, which is wastefUl in terms Of energy. packet close to optimal. AS the packet ~ r r i v d rate is within Schemes that adapt solely to the channel state can maxknown limits, the avorage energy pr packet used by Lwk-ahead Water-filling is rignifieaolly lower than that achieved by optimal adaptation to the channel only (water-filling in time). The delay per packet Is larger, but i s almost constant for all data arrival rates. The results can be generalired to multi-access and bmadrsst fading channels.