Bell Labs, Murray Hill, NJ
Tuesday, July 2, 2013, 11:00 am, CEPSR 414
Abstract:
We use fluid limits to explore the
(in)stability properties of wireless networks with backlog-based
random-access algorithms. While relatively simple and inherently
distributed in nature, suitably designed backlog-based access schemes
provide the striking capability to match the optimal throughput
performance of centralized scheduling mechanisms in a wide range of
scenarios. The type of activation rules for which throughput optimality
has been established, may however yield excessive backlogs and delays.
More aggressive/persistent access schemes have the potential to improve
the delay performance, but do not offer any universal maximum-stability
guarantees.
In order to gain qualitative insight and investigate the (in)stability
properties of more aggressive/persistent activation rules, we examine
fluid limits where the system dynamics are scaled in space and time. In
some situations, the fluid limits have smooth deterministic features
and maximum stability is maintained, while in other scenarios they
exhibit rather erratic random characteristics. In the latter regime,
more aggressive access schemes continue to provide maximum stability in
some networks, but may persistently drive the system into inefficient
states and cause instability in others. Simulation experiments are
conducted to illustrate and validate the analytical results.
Bio: Phil Whiting received his BA degree from the University of Oxford, his MSc from the University of London and his Ph. D. was in queueing theory from the University of Strathclyde. After a post-doc at the University of Cambridge, Phil's interests centered on wireless. In 1993 Phil participated in the Telstra trial of Qualcomm CDMA in South Eastern Australia. He then joined the Mobile research Centre at the University of South Australia Adelaide. He was a Member of Technical Staff at Bell Labs from January 1997 to June 2013. He is now a research fellow at MacQuarie University, Sydney Australia. His main interests are the mathematics of wireless networks, particularly stochastic models for resource allocation, information and coding theory. Phil's current research includes lazy maxweight scheduling, CSMA networks, HetNets and the theory of random matrices.