21,146 research outputs found
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
Smart Meter Privacy with an Energy Harvesting Device and Instantaneous Power Constraints
A smart meter (SM) periodically measures end-user electricity consumption and
reports it to a utility provider (UP). Despite the advantages of SMs, their use
leads to serious concerns about consumer privacy. In this paper, SM privacy is
studied by considering the presence of an energy harvesting device (EHD) as a
means of masking the user's input load. The user can satisfy part or all of
his/her energy needs from the EHD, and hence, less information can be leaked to
the UP via the SM. The EHD is typically equipped with a rechargeable energy
storage device, i.e., a battery, whose instantaneous energy content limits the
user's capability in covering his/her energy usage. Privacy is measured by the
information leaked about the user's real energy consumption when the UP
observes the energy requested from the grid, which the SM reads and reports to
the UP. The minimum information leakage rate is characterized as a computable
information theoretic single-letter expression when the EHD battery capacity is
either infinite or zero. Numerical results are presented for a discrete binary
input load to illustrate the potential privacy gains from the existence of a
storage device.Comment: To be published in IEEE ICC201
On Resource Allocation in Fading Multiple Access Channels - An Efficient Approximate Projection Approach
We consider the problem of rate and power allocation in a multiple-access
channel. Our objective is to obtain rate and power allocation policies that
maximize a general concave utility function of average transmission rates on
the information theoretic capacity region of the multiple-access channel. Our
policies does not require queue-length information. We consider several
different scenarios. First, we address the utility maximization problem in a
nonfading channel to obtain the optimal operating rates, and present an
iterative gradient projection algorithm that uses approximate projection. By
exploiting the polymatroid structure of the capacity region, we show that the
approximate projection can be implemented in time polynomial in the number of
users. Second, we consider resource allocation in a fading channel. Optimal
rate and power allocation policies are presented for the case that power
control is possible and channel statistics are available. For the case that
transmission power is fixed and channel statistics are unknown, we propose a
greedy rate allocation policy and provide bounds on the performance difference
of this policy and the optimal policy in terms of channel variations and
structure of the utility function. We present numerical results that
demonstrate superior convergence rate performance for the greedy policy
compared to queue-length based policies. In order to reduce the computational
complexity of the greedy policy, we present approximate rate allocation
policies which track the greedy policy within a certain neighborhood that is
characterized in terms of the speed of fading.Comment: 32 pages, Submitted to IEEE Trans. on Information Theor
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