10,551 research outputs found
A spatial Markov Queueing Process and its Applications to Wireless Loss Systems
We consider a pure-jump Markov generator that which can be seen as a generalization of the spatial birth-and-death generator, which allows for mobility of particles. Conditions for the regularity of this generator and for its ergodicity are established. We also give the conditions under which its stationary distribution is a Gibbs measure. This extends previous work in~\cite{Preston1977} by allowing particle mobility. Such spatial birth-mobility-and-death processes can also be seen as generalizations of the spatial queueing systems considered in~\cite{Serfozo1999}. So our approach yields regularity conditions and alternative conditions for ergodicity of spatial open Whittle networks, complementing the results in~\cite{SerfozoHuang1999}. Next we show how our results can be used to model wireless communication networks. In particular we study two spatial loss models for which we establish an expression for the blocking probability that might be seen as a spatial version of the classical Erlang loss formula. Some specific applications to CDMA (Code Division Multiple Access) networks are also discussed
Massive MIMO Extensions to the COST 2100 Channel Model: Modeling and Validation
To enable realistic studies of massive multiple-input multiple-output
systems, the COST 2100 channel model is extended based on measurements. First,
the concept of a base station-side visibility region (BS-VR) is proposed to
model the appearance and disappearance of clusters when using a
physically-large array. We find that BS-VR lifetimes are exponentially
distributed, and that the number of BS-VRs is Poisson distributed with
intensity proportional to the sum of the array length and the mean lifetime.
Simulations suggest that under certain conditions longer lifetimes can help
decorrelating closely-located users. Second, the concept of a multipath
component visibility region (MPC-VR) is proposed to model birth-death processes
of individual MPCs at the mobile station side. We find that both MPC lifetimes
and MPC-VR radii are lognormally distributed. Simulations suggest that unless
MPC-VRs are applied the channel condition number is overestimated. Key
statistical properties of the proposed extensions, e.g., autocorrelation
functions, maximum likelihood estimators, and Cramer-Rao bounds, are derived
and analyzed.Comment: Submitted to IEEE Transactions of Wireless Communication
Mixing Properties of CSMA Networks on Partite Graphs
We consider a stylized stochastic model for a wireless CSMA network.
Experimental results in prior studies indicate that the model provides
remarkably accurate throughput estimates for IEEE 802.11 systems. In
particular, the model offers an explanation for the severe spatial unfairness
in throughputs observed in such networks with asymmetric interference
conditions. Even in symmetric scenarios, however, it may take a long time for
the activity process to move between dominant states, giving rise to potential
starvation issues. In order to gain insight in the transient throughput
characteristics and associated starvation effects, we examine in the present
paper the behavior of the transition time between dominant activity states. We
focus on partite interference graphs, and establish how the magnitude of the
transition time scales with the activation rate and the sizes of the various
network components. We also prove that in several cases the scaled transition
time has an asymptotically exponential distribution as the activation rate
grows large, and point out interesting connections with related exponentiality
results for rare events and meta-stability phenomena in statistical physics. In
addition, we investigate the convergence rate to equilibrium of the activity
process in terms of mixing times.Comment: Valuetools, 6th International Conference on Performance Evaluation
Methodologies and Tools, October 9-12, 2012, Carg\`ese, Franc
Superprocesses as models for information dissemination in the Future Internet
Future Internet will be composed by a tremendous number of potentially
interconnected people and devices, offering a variety of services, applications
and communication opportunities. In particular, short-range wireless
communications, which are available on almost all portable devices, will enable
the formation of the largest cloud of interconnected, smart computing devices
mankind has ever dreamed about: the Proximate Internet. In this paper, we
consider superprocesses, more specifically super Brownian motion, as a suitable
mathematical model to analyse a basic problem of information dissemination
arising in the context of Proximate Internet. The proposed model provides a
promising analytical framework to both study theoretical properties related to
the information dissemination process and to devise efficient and reliable
simulation schemes for very large systems
Slow transitions, slow mixing and starvation in dense random-access networks
We consider dense wireless random-access networks, modeled as systems of
particles with hard-core interaction. The particles represent the network users
that try to become active after an exponential back-off time, and stay active
for an exponential transmission time. Due to wireless interference, active
users prevent other nearby users from simultaneous activity, which we describe
as hard-core interaction on a conflict graph. We show that dense networks with
aggressive back-off schemes lead to extremely slow transitions between dominant
states, and inevitably cause long mixing times and starvation effects.Comment: 29 pages, 5 figure
Analyzing wireless communication network vulnerability with homological invariants
This article explains how sheaves and homology theory can be applied to
simplicial complex models of wireless communication networks to study their
vulnerability to jamming. It develops two classes of invariants (one local and
one global) for studying which nodes and links present more of a liability to
the network's performance when under attack.Comment: Submitted to ICASSP 201
- …