56,008 research outputs found
Distributed Optimal Lexicographic Max-Min Rate Allocation in Solar-Powered Wireless Sensor Networks
Understanding the optimal usage of fluctuating renewable energy in Wireless Sensor Networks (WSNs) is
complex. Lexicographic Max-min (LM) rate allocation is a good solution, but is non-trivial for multi-hop
WSNs, as both fairness and sensing rates have to be optimized through the exploration of all possible
forwarding routes in the network. All current optimal approaches to this problem are centralized and
off-line, suffering from low scalability and large computational complexity; typically solving O(N2
) linear
programming problems for N-node WSNs. This paper presents the first optimal distributed solution to
this problem with much lower complexity. We apply it to Solar Powered WSNs (SP-WSNs) to achieve
both LM optimality and sustainable operation. Based on realistic models of both time-varying solar power
and photovoltaic-battery hardware, we propose an optimization framework that integrates a local power
management algorithm with a global distributed LM rate allocation scheme. The optimality, convergence,
and efficiency of our approaches are formally proven. We also evaluate our algorithms via experiments
on both solar-powered MicaZ motes and extensive simulations using real solar energy data and practical
power parameter settings. The results verify our theoretical analysis and demonstrate how our approach
outperforms both the state-of-the-art centralized optimal and distributed heuristic solutions
Distributed Optimal Lexicographic Max-Min Rate Allocation in Solar-Powered Wireless Sensor Networks
Understanding the optimal usage of fluctuating renewable energy in Wireless Sensor Networks (WSNs) is
complex. Lexicographic Max-min (LM) rate allocation is a good solution, but is non-trivial for multi-hop
WSNs, as both fairness and sensing rates have to be optimized through the exploration of all possible
forwarding routes in the network. All current optimal approaches to this problem are centralized and
off-line, suffering from low scalability and large computational complexity; typically solving O(N2
) linear
programming problems for N-node WSNs. This paper presents the first optimal distributed solution to
this problem with much lower complexity. We apply it to Solar Powered WSNs (SP-WSNs) to achieve
both LM optimality and sustainable operation. Based on realistic models of both time-varying solar power
and photovoltaic-battery hardware, we propose an optimization framework that integrates a local power
management algorithm with a global distributed LM rate allocation scheme. The optimality, convergence,
and efficiency of our approaches are formally proven. We also evaluate our algorithms via experiments
on both solar-powered MicaZ motes and extensive simulations using real solar energy data and practical
power parameter settings. The results verify our theoretical analysis and demonstrate how our approach
outperforms both the state-of-the-art centralized optimal and distributed heuristic solutions
Sensor Deployment for Network-like Environments
This paper considers the problem of optimally deploying omnidirectional
sensors, with potentially limited sensing radius, in a network-like
environment. This model provides a compact and effective description of complex
environments as well as a proper representation of road or river networks. We
present a two-step procedure based on a discrete-time gradient ascent algorithm
to find a local optimum for this problem. The first step performs a coarse
optimization where sensors are allowed to move in the plane, to vary their
sensing radius and to make use of a reduced model of the environment called
collapsed network. It is made up of a finite discrete set of points,
barycenters, produced by collapsing network edges. Sensors can be also
clustered to reduce the complexity of this phase. The sensors' positions found
in the first step are then projected on the network and used in the second
finer optimization, where sensors are constrained to move only on the network.
The second step can be performed on-line, in a distributed fashion, by sensors
moving in the real environment, and can make use of the full network as well as
of the collapsed one. The adoption of a less constrained initial optimization
has the merit of reducing the negative impact of the presence of a large number
of local optima. The effectiveness of the presented procedure is illustrated by
a simulated deployment problem in an airport environment
Sequential learning without feedback
In many security and healthcare systems a sequence of features/sensors/tests are used for detection and diagnosis. Each test outputs a prediction of the latent state, and carries with it inherent costs. Our objective is to {\it learn} strategies for selecting tests to optimize accuracy \& costs. Unfortunately it is often impossible to acquire in-situ ground truth annotations and we are left with the problem of unsupervised sensor selection (USS). We pose USS as a version of stochastic partial monitoring problem with an {\it unusual} reward structure (even noisy annotations are unavailable). Unsurprisingly no learner can achieve sublinear regret without further assumptions. To this end we propose the notion of weak-dominance. This is a condition on the joint probability distribution of test outputs and latent state and says that whenever a test is accurate on an example, a later test in the sequence is likely to be accurate as well. We empirically verify that weak dominance holds on real datasets and prove that it is a maximal condition for achieving sublinear regret. We reduce USS to a special case of multi-armed bandit problem with side information and develop polynomial time algorithms that achieve sublinear regret
Decentralised Control of Adaptive Sampling in Wireless Sensor Networks
The efficient allocation of the limited energy resources of a wireless sensor network in a way that maximises the information value of the data collected is a significant research challenge. Within this context, this paper concentrates on adaptive sampling as a means of focusing a sensor’s energy consumption on obtaining the most important data. Specifically, we develop a principled information metric based upon Fisher information and Gaussian process regression that allows the information content of a sensor’s observations to be expressed. We then use this metric to derive three novel decentralised control algorithms for information-based adaptive sampling which represent a trade-off in computational cost and optimality. These algorithms are evaluated in the context of a deployed sensor network in the domain of flood monitoring. The most computationally efficient of the three is shown to increase the value of information gathered by approximately 83%, 27%, and 8% per day compared to benchmarks that sample in a naive non-adaptive manner, in a uniform non-adaptive manner, and using a state-of-the-art adaptive sampling heuristic (USAC) correspondingly. Moreover, our algorithm collects information whose total value is approximately 75% of the optimal solution (which requires an exponential, and thus impractical, amount of time to compute)
Sequential learning without feedback
In many security and healthcare systems a sequence of features/sensors/tests are used for detection and diagnosis. Each test outputs a prediction of the latent state, and carries with it inherent costs. Our objective is to {\it learn} strategies for selecting tests to optimize accuracy \& costs. Unfortunately it is often impossible to acquire in-situ ground truth annotations and we are left with the problem of unsupervised sensor selection (USS). We pose USS as a version of stochastic partial monitoring problem with an {\it unusual} reward structure (even noisy annotations are unavailable). Unsurprisingly no learner can achieve sublinear regret without further assumptions. To this end we propose the notion of weak-dominance. This is a condition on the joint probability distribution of test outputs and latent state and says that whenever a test is accurate on an example, a later test in the sequence is likely to be accurate as well. We empirically verify that weak dominance holds on real datasets and prove that it is a maximal condition for achieving sublinear regret. We reduce USS to a special case of multi-armed bandit problem with side information and develop polynomial time algorithms that achieve sublinear regret
Sustainable Cooperative Coevolution with a Multi-Armed Bandit
This paper proposes a self-adaptation mechanism to manage the resources
allocated to the different species comprising a cooperative coevolutionary
algorithm. The proposed approach relies on a dynamic extension to the
well-known multi-armed bandit framework. At each iteration, the dynamic
multi-armed bandit makes a decision on which species to evolve for a
generation, using the history of progress made by the different species to
guide the decisions. We show experimentally, on a benchmark and a real-world
problem, that evolving the different populations at different paces allows not
only to identify solutions more rapidly, but also improves the capacity of
cooperative coevolution to solve more complex problems.Comment: Accepted at GECCO 201
Providing Long-Term Participation Incentive in Participatory Sensing
Providing an adequate long-term participation incentive is important for a
participatory sensing system to maintain enough number of active users
(sensors), so as to collect a sufficient number of data samples and support a
desired level of service quality. In this work, we consider the sensor
selection problem in a general time-dependent and location-aware participatory
sensing system, taking the long-term user participation incentive into explicit
consideration. We study the problem systematically under different information
scenarios, regarding both future information and current information
(realization). In particular, we propose a Lyapunov-based VCG auction policy
for the on-line sensor selection, which converges asymptotically to the optimal
off-line benchmark performance, even with no future information and under
(current) information asymmetry. Extensive numerical results show that our
proposed policy outperforms the state-of-art policies in the literature, in
terms of both user participation (e.g., reducing the user dropping probability
by 25% to 90%) and social performance (e.g., increasing the social welfare by
15% to 80%).Comment: This manuscript serves as the online technical report of the article
published in IEEE International Conference on Computer Communications
(INFOCOM), 201
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