7,815 research outputs found
Energy-delay bounds analysis in wireless multi-hop networks with unreliable radio links
Energy efficiency and transmission delay are very important parameters for
wireless multi-hop networks. Previous works that study energy efficiency and
delay are based on the assumption of reliable links. However, the unreliability
of the channel is inevitable in wireless multi-hop networks. This paper
investigates the trade-off between the energy consumption and the end-to-end
delay of multi-hop communications in a wireless network using an unreliable
link model. It provides a closed form expression of the lower bound on the
energy-delay trade-off for different channel models (AWGN, Raleigh flat fading
and Nakagami block-fading) in a linear network. These analytical results are
also verified in 2-dimensional Poisson networks using simulations. The main
contribution of this work is the use of a probabilistic link model to define
the energy efficiency of the system and capture the energy-delay trade-offs.
Hence, it provides a more realistic lower bound on both the energy efficiency
and the energy-delay trade-off since it does not restrict the study to the set
of perfect links as proposed in earlier works
Low Power Dynamic Scheduling for Computing Systems
This paper considers energy-aware control for a computing system with two
states: "active" and "idle." In the active state, the controller chooses to
perform a single task using one of multiple task processing modes. The
controller then saves energy by choosing an amount of time for the system to be
idle. These decisions affect processing time, energy expenditure, and an
abstract attribute vector that can be used to model other criteria of interest
(such as processing quality or distortion). The goal is to optimize time
average system performance. Applications of this model include a smart phone
that makes energy-efficient computation and transmission decisions, a computer
that processes tasks subject to rate, quality, and power constraints, and a
smart grid energy manager that allocates resources in reaction to a time
varying energy price. The solution methodology of this paper uses the theory of
optimization for renewal systems developed in our previous work. This paper is
written in tutorial form and develops the main concepts of the theory using
several detailed examples. It also highlights the relationship between online
dynamic optimization and linear fractional programming. Finally, it provides
exercises to help the reader learn the main concepts and apply them to their
own optimizations. This paper is an arxiv technical report, and is a
preliminary version of material that will appear as a book chapter in an
upcoming book on green communications and networking.Comment: 26 pages, 10 figures, single spac
Energy-Delay Tradeoff and Dynamic Sleep Switching for Bluetooth-Like Body-Area Sensor Networks
Wireless technology enables novel approaches to healthcare, in particular the
remote monitoring of vital signs and other parameters indicative of people's
health. This paper considers a system scenario relevant to such applications,
where a smart-phone acts as a data-collecting hub, gathering data from a number
of wireless-capable body sensors, and relaying them to a healthcare provider
host through standard existing cellular networks. Delay of critical data and
sensors' energy efficiency are both relevant and conflicting issues. Therefore,
it is important to operate the wireless body-area sensor network at some
desired point close to the optimal energy-delay tradeoff curve. This tradeoff
curve is a function of the employed physical-layer protocol: in particular, it
depends on the multiple-access scheme and on the coding and modulation schemes
available. In this work, we consider a protocol closely inspired by the
widely-used Bluetooth standard. First, we consider the calculation of the
minimum energy function, i.e., the minimum sum energy per symbol that
guarantees the stability of all transmission queues in the network. Then, we
apply the general theory developed by Neely to develop a dynamic scheduling
policy that approaches the optimal energy-delay tradeoff for the network at
hand. Finally, we examine the queue dynamics and propose a novel policy that
adaptively switches between connected and disconnected (sleeping) modes. We
demonstrate that the proposed policy can achieve significant gains in the
realistic case where the control "NULL" packets necessary to maintain the
connection alive, have a non-zero energy cost, and the data arrival statistics
corresponding to the sensed physical process are bursty.Comment: Extended version (with proofs details in the Appendix) of a paper
accepted for publication on the IEEE Transactions on Communication
Gossip Algorithms for Distributed Signal Processing
Gossip algorithms are attractive for in-network processing in sensor networks
because they do not require any specialized routing, there is no bottleneck or
single point of failure, and they are robust to unreliable wireless network
conditions. Recently, there has been a surge of activity in the computer
science, control, signal processing, and information theory communities,
developing faster and more robust gossip algorithms and deriving theoretical
performance guarantees. This article presents an overview of recent work in the
area. We describe convergence rate results, which are related to the number of
transmitted messages and thus the amount of energy consumed in the network for
gossiping. We discuss issues related to gossiping over wireless links,
including the effects of quantization and noise, and we illustrate the use of
gossip algorithms for canonical signal processing tasks including distributed
estimation, source localization, and compression.Comment: Submitted to Proceedings of the IEEE, 29 page
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