30,756 research outputs found
The Outage Probability of a Finite Ad Hoc Network in Nakagami Fading
An ad hoc network with a finite spatial extent and number of nodes or mobiles
is analyzed. The mobile locations may be drawn from any spatial distribution,
and interference-avoidance protocols or protection against physical collisions
among the mobiles may be modeled by placing an exclusion zone around each
radio. The channel model accounts for the path loss, Nakagami fading, and
shadowing of each received signal. The Nakagami m-parameter can vary among the
mobiles, taking any positive value for each of the interference signals and any
positive integer value for the desired signal. The analysis is governed by a
new exact expression for the outage probability, defined to be the probability
that the signal-to-interference-and-noise ratio (SINR) drops below a threshold,
and is conditioned on the network geometry and shadowing factors, which have
dynamics over much slower timescales than the fading. By averaging over many
network and shadowing realizations, the average outage probability and
transmission capacity are computed. Using the analysis, many aspects of the
network performance are illuminated. For example, one can determine the
influence of the choice of spreading factors, the effect of the receiver
location within the finite network region, and the impact of both the fading
parameters and the attenuation power laws.Comment: to appear in IEEE Transactions on Communication
Sequential Decision Algorithms for Measurement-Based Impromptu Deployment of a Wireless Relay Network along a Line
We are motivated by the need, in some applications, for impromptu or
as-you-go deployment of wireless sensor networks. A person walks along a line,
starting from a sink node (e.g., a base-station), and proceeds towards a source
node (e.g., a sensor) which is at an a priori unknown location. At equally
spaced locations, he makes link quality measurements to the previous relay, and
deploys relays at some of these locations, with the aim to connect the source
to the sink by a multihop wireless path. In this paper, we consider two
approaches for impromptu deployment: (i) the deployment agent can only move
forward (which we call a pure as-you-go approach), and (ii) the deployment
agent can make measurements over several consecutive steps before selecting a
placement location among them (which we call an explore-forward approach). We
consider a light traffic regime, and formulate the problem as a Markov decision
process, where the trade-off is among the power used by the nodes, the outage
probabilities in the links, and the number of relays placed per unit distance.
We obtain the structures of the optimal policies for the pure as-you-go
approach as well as for the explore-forward approach. We also consider natural
heuristic algorithms, for comparison. Numerical examples show that the
explore-forward approach significantly outperforms the pure as-you-go approach.
Next, we propose two learning algorithms for the explore-forward approach,
based on Stochastic Approximation, which asymptotically converge to the set of
optimal policies, without using any knowledge of the radio propagation model.
We demonstrate numerically that the learning algorithms can converge (as
deployment progresses) to the set of optimal policies reasonably fast and,
hence, can be practical, model-free algorithms for deployment over large
regions.Comment: 29 pages. arXiv admin note: text overlap with arXiv:1308.068
A Unifying Framework for Local Throughput in Wireless Networks
With the increased competition for the electromagnetic spectrum, it is
important to characterize the impact of interference in the performance of a
wireless network, which is traditionally measured by its throughput. This paper
presents a unifying framework for characterizing the local throughput in
wireless networks. We first analyze the throughput of a probe link from a
connectivity perspective, in which a packet is successfully received if it does
not collide with other packets from nodes within its reach (called the audible
interferers). We then characterize the throughput from a
signal-to-interference-plus-noise ratio (SINR) perspective, in which a packet
is successfully received if the SINR exceeds some threshold, considering the
interference from all emitting nodes in the network. Our main contribution is
to generalize and unify various results scattered throughout the literature. In
particular, the proposed framework encompasses arbitrary wireless propagation
effects (e.g, Nakagami-m fading, Rician fading, or log-normal shadowing), as
well as arbitrary traffic patterns (e.g., slotted-synchronous,
slotted-asynchronous, or exponential-interarrivals traffic), allowing us to
draw more general conclusions about network performance than previously
available in the literature.Comment: Submitted for journal publicatio
Networking Behavior in Thin Film and Nanostructure Growth Dynamics
Thin film coatings have been essential in development of several micro and
nano-scale devices. To realize thin film coatings various deposition techniques
are employed, each yielding surface morphologies with different characteristics
of interest. Therefore, understanding and control of the surface growth is of
great interest. In this paper, we devise a novel network-based modeling of the
growth dynamics of such thin films and nano-structures. We specifically map
dynamic steps taking place during the growth to components (e.g., nodes, links)
of a corresponding network. We present initial results showing that this
network-based modeling approach to the growth dynamics can simplify our
understanding of the fundamental physical dynamics such as shadowing and
re-emission effects
- …