31,813 research outputs found
Disruptive events in high-density cellular networks
Stochastic geometry models are used to study wireless networks, particularly
cellular phone networks, but most of the research focuses on the typical user,
often ignoring atypical events, which can be highly disruptive and of interest
to network operators. We examine atypical events when a unexpected large
proportion of users are disconnected or connected by proposing a hybrid
approach based on ray launching simulation and point process theory. This work
is motivated by recent results using large deviations theory applied to the
signal-to-interference ratio. This theory provides a tool for the stochastic
analysis of atypical but disruptive events, particularly when the density of
transmitters is high. For a section of a European city, we introduce a new
stochastic model of a single network cell that uses ray launching data
generated with the open source RaLaNS package, giving deterministic path loss
values. We collect statistics on the fraction of (dis)connected users in the
uplink, and observe that the probability of an unexpected large proportion of
disconnected users decreases exponentially when the transmitter density
increases. This observation implies that denser networks become more stable in
the sense that the probability of the fraction of (dis)connected users
deviating from its mean, is exponentially small. We also empirically obtain and
illustrate the density of users for network configurations in the disruptive
event, which highlights the fact that such bottleneck behaviour not only stems
from too many users at the cell boundary, but also from the near-far effect of
many users in the immediate vicinity of the base station. We discuss the
implications of these findings and outline possible future research directions.Comment: 8 pages, 11 figure
Stochastic Geometry Modeling of Cellular Networks: Analysis, Simulation and Experimental Validation
Due to the increasing heterogeneity and deployment density of emerging
cellular networks, new flexible and scalable approaches for their modeling,
simulation, analysis and optimization are needed. Recently, a new approach has
been proposed: it is based on the theory of point processes and it leverages
tools from stochastic geometry for tractable system-level modeling, performance
evaluation and optimization. In this paper, we investigate the accuracy of this
emerging abstraction for modeling cellular networks, by explicitly taking
realistic base station locations, building footprints, spatial blockages and
antenna radiation patterns into account. More specifically, the base station
locations and the building footprints are taken from two publicly available
databases from the United Kingdom. Our study confirms that the abstraction
model based on stochastic geometry is capable of accurately modeling the
communication performance of cellular networks in dense urban environments.Comment: submitted for publicatio
A Survey of Cellular Automata: Types, Dynamics, Non-uniformity and Applications
Cellular automata (CAs) are dynamical systems which exhibit complex global
behavior from simple local interaction and computation. Since the inception of
cellular automaton (CA) by von Neumann in 1950s, it has attracted the attention
of several researchers over various backgrounds and fields for modelling
different physical, natural as well as real-life phenomena. Classically, CAs
are uniform. However, non-uniformity has also been introduced in update
pattern, lattice structure, neighborhood dependency and local rule. In this
survey, we tour to the various types of CAs introduced till date, the different
characterization tools, the global behaviors of CAs, like universality,
reversibility, dynamics etc. Special attention is given to non-uniformity in
CAs and especially to non-uniform elementary CAs, which have been very useful
in solving several real-life problems.Comment: 43 pages; Under review in Natural Computin
Downlink and Uplink Decoupling: a Disruptive Architectural Design for 5G Networks
Cell association in cellular networks has traditionally been based on the
downlink received signal power only, despite the fact that up and downlink
transmission powers and interference levels differed significantly. This
approach was adequate in homogeneous networks with macro base stations all
having similar transmission power levels. However, with the growth of
heterogeneous networks where there is a big disparity in the transmit power of
the different base station types, this approach is highly inefficient. In this
paper, we study the notion of Downlink and Uplink Decoupling (DUDe) where the
downlink cell association is based on the downlink received power while the
uplink is based on the pathloss. We present the motivation and assess the gains
of this 5G design approach with simulations that are based on Vodafone's LTE
field trial network in a dense urban area, employing a high resolution
ray-tracing pathloss prediction and realistic traffic maps based on live
network measurements.Comment: 6 pages, 7 figures, conference paper, submitted to IEEE GLOBECOM 201
Fractional diffusion emulates a human mobility network during a simulated disease outbreak
From footpaths to flight routes, human mobility networks facilitate the
spread of communicable diseases. Control and elimination efforts depend on
characterizing these networks in terms of connections and flux rates of
individuals between contact nodes. In some cases, transport can be
parameterized with gravity-type models or approximated by a diffusive random
walk. As a alternative, we have isolated intranational commercial air traffic
as a case study for the utility of non-diffusive, heavy-tailed transport
models. We implemented new stochastic simulations of a prototypical
influenza-like infection, focusing on the dense, highly-connected United States
air travel network. We show that mobility on this network can be described
mainly by a power law, in agreement with previous studies. Remarkably, we find
that the global evolution of an outbreak on this network is accurately
reproduced by a two-parameter space-fractional diffusion equation, such that
those parameters are determined by the air travel network.Comment: 26 pages, 4 figure
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