16,609 research outputs found
Optimal Multiuser Scheduling Schemes for Simultaneous Wireless Information and Power Transfer
In this paper, we study the downlink multiuser scheduling problem for systems
with simultaneous wireless information and power transfer (SWIPT). We design
optimal scheduling algorithms that maximize the long-term average system
throughput under different fairness requirements, such as proportional fairness
and equal throughput fairness. In particular, the algorithm designs are
formulated as non-convex optimization problems which take into account the
minimum required average sum harvested energy in the system. The problems are
solved by using convex optimization techniques and the proposed optimization
framework reveals the tradeoff between the long-term average system throughput
and the sum harvested energy in multiuser systems with fairness constraints.
Simulation results demonstrate that substantial performance gains can be
achieved by the proposed optimization framework compared to existing suboptimal
scheduling algorithms from the literature.Comment: Accepted for presentation at the European Signal Processing
Conference 201
Optimal Scheduling and Power Allocation for Two-Hop Energy Harvesting Communication Systems
Energy harvesting (EH) has recently emerged as a promising technique for
green communications. To realize its potential, communication protocols need to
be redesigned to combat the randomness of the harvested energy. In this paper,
we investigate how to apply relaying to improve the short-term performance of
EH communication systems. With an EH source and a non-EH half-duplex relay, we
consider two different design objectives: 1) short-term throughput
maximization; and 2) transmission completion time minimization. Both problems
are joint scheduling and power allocation problems, rendered quite challenging
by the half-duplex constraint at the relay. A key finding is that directional
water-filling (DWF), which is the optimal power allocation algorithm for the
single-hop EH system, can serve as guideline for the design of two-hop
communication systems, as it not only determines the value of the optimal
performance, but also forms the basis to derive optimal solutions for both
design problems. Based on a relaxed energy profile along with the DWF
algorithm, we derive key properties of the optimal solutions for both problems
and thereafter propose efficient algorithms. Simulation results will show that
both scheduling and power allocation optimizations are necessary in two-hop EH
communication systems.Comment: Submitted to IEEE Transaction on Wireless Communicatio
OSCAR: A Collaborative Bandwidth Aggregation System
The exponential increase in mobile data demand, coupled with growing user
expectation to be connected in all places at all times, have introduced novel
challenges for researchers to address. Fortunately, the wide spread deployment
of various network technologies and the increased adoption of multi-interface
enabled devices have enabled researchers to develop solutions for those
challenges. Such solutions aim to exploit available interfaces on such devices
in both solitary and collaborative forms. These solutions, however, have faced
a steep deployment barrier.
In this paper, we present OSCAR, a multi-objective, incentive-based,
collaborative, and deployable bandwidth aggregation system. We present the
OSCAR architecture that does not introduce any intermediate hardware nor
require changes to current applications or legacy servers. The OSCAR
architecture is designed to automatically estimate the system's context,
dynamically schedule various connections and/or packets to different
interfaces, be backwards compatible with the current Internet architecture, and
provide the user with incentives for collaboration. We also formulate the OSCAR
scheduler as a multi-objective, multi-modal scheduler that maximizes system
throughput while minimizing energy consumption or financial cost. We evaluate
OSCAR via implementation on Linux, as well as via simulation, and compare our
results to the current optimal achievable throughput, cost, and energy
consumption. Our evaluation shows that, in the throughput maximization mode, we
provide up to 150% enhancement in throughput compared to current operating
systems, without any changes to legacy servers. Moreover, this performance gain
further increases with the availability of connection resume-supporting, or
OSCAR-enabled servers, reaching the maximum achievable upper-bound throughput
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