1,135 research outputs found
Optimal Energy Allocation for Wireless Communications with Energy Harvesting Constraints
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
Communicating Using an Energy Harvesting Transmitter: Optimum Policies Under Energy Storage Losses
In this paper, short-term throughput optimal power allocation policies are
derived for an energy harvesting transmitter with energy storage losses. In
particular, the energy harvesting transmitter is equipped with a battery that
loses a fraction of its stored energy. Both single user, i.e. one
transmitter-one receiver, and the broadcast channel, i.e., one
transmitter-multiple receiver settings are considered, initially with an
infinite capacity battery. It is shown that the optimal policies for these
models are threshold policies. Specifically, storing energy when harvested
power is above an upper threshold, retrieving energy when harvested power is
below a lower threshold, and transmitting with the harvested energy in between
is shown to maximize the weighted sum-rate. It is observed that the two
thresholds are related through the storage efficiency of the battery, and are
nondecreasing during the transmission. The results are then extended to the
case with finite battery capacity, where it is shown that a similar
double-threshold structure arises but the thresholds are no longer monotonic. A
dynamic program that yields an optimal online power allocation is derived, and
is shown to have a similar double-threshold structure. A simpler online policy
is proposed and observed to perform close to the optimal policy.Comment: Submitted to IEEE Transactions on Wireless Communications, August
201
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