We consider the use of energy harvesters, in place of conventional batteries
with fixed energy storage, for point-to-point wireless communications. In
addition to the challenge of transmitting in a channel with time selective
fading, energy harvesters provide a perpetual but unreliable energy source. In
this paper, we consider the problem of energy allocation over a finite horizon,
taking into account channel conditions and energy sources that are time
varying, so as to maximize the throughput. Two types of side information (SI)
on the channel conditions and harvested energy are assumed to be available:
causal SI (of the past and present slots) or full SI (of the past, present and
future slots). We obtain structural results for the optimal energy allocation,
via the use of dynamic programming and convex optimization techniques. In
particular, if unlimited energy can be stored in the battery with harvested
energy and the full SI is available, we prove the optimality of a water-filling
energy allocation solution where the so-called water levels follow a staircase
function.Comment: 27 pages, 6 figures, accepted for publications at IEEE Transactions
on Signal Processin
