[CPCC] REMINDER: SEMINAR: QoS Provisioning in WLANs 2/22 10 AM EG 3161

[Ender Ayanoglu]

                              CPCC SEMINAR

             Quality of Service Provisioning in Wireless LANs

                                   by

                             Dr. Inanc Inan

                        February 22, 2010, Monday
                                 10 AM
                        Engineering Gateway 3161


                                  ABSTRACT

Recent years have witnessed a remarkable growth of Wireless Local Area
Networks (WLANs). The IEEE 802.11 standard specifies the Physical
(PHY) layer and the Medium Access Control (MAC) layer algorithms for
WLANs. Due to the specific design of MAC layer algorithms, IEEE 802.11
WLANs can only provide best effort services and do not have
Quality-of-Service (QoS) support for multimedia applications. Therefore,
recently, a new QoS-enhanced standard, IEEE 802.11e, has been developed.
The IEEE 802.11e standard introduces the Hybrid Coordination Function
(HCF) containing two medium access mechanisms: a contention-based channel
access, namely Enhanced Distributed Channel Access (EDCA), and a
polling-based channel access, namely HCF Controlled Channel Access (HCCA).

In this talk, we propose various analytical models for accurate
performance analysis of the EDCA function. As we discuss, the proposed
analytical frameworks can also address the multimedia capacity
estimation problem.  Based on this observation, we design simple
admission control algorithms that enable comprehensive QoS support in
the next-generation WLAN.

We first present two analytical models for capacity estimation of EDCA
in saturation (at arbitrarily high load). The first model we propose
is a Discrete-Time Markov Chain (DTMC) which incorporates an accurate
Contention Window (CW) and Arbitration Interframe Space (AIFS)
differentiation for any number of active Access Categories (ACs). The
second model we propose uses the fact that random access schemes
present cyclic behavior. The analysis shows that a station- and
AC-specific cycle time exists for the EDCA function. Validating the
theoretical results via simulations, we show that both models
accurately capture EDCA saturation performance, and are more accurate
than the models that miss accurate handling of the protocol details.

Next, we propose an analytical model for capacity estimation of EDCA
function which incorporates an accurate CW, AIFS, and Transmit
Opportunity (TXOP) differentiation at any traffic load. The proposed
model is shown to capture the effect of MAC layer buffer size on the
performance. Analytical and simulation results are compared to
demonstrate the accuracy of the proposed approach for varying traffic
loads, EDCA parameters, and MAC layer buffer space. The model can
directly be employed in an EDCA admission control algorithm.

For multimedia capacity analysis of the EDCA function, we also propose
another analytical framework. This framework utilizes the results of
saturation analysis in the capacity estimation. A simple admission
control method is proposed. We show that the proposed admission
control algorithm maintains satisfactory user-perceived quality for
coexisting voice and video connections in an infrastructure Basic
Service Set (BSS) and does not present over- or under-admission
problems of previously proposed models in the literature.

                         SPEAKER'S BIOGRAPHY

Inanc Inan received the B.S. degree from the Middle East Technical
University, Ankara, Turkey, in June 2001, the M.S. degree from Bilkent
University, Ankara, Turkey, in September 2003, and the Ph.D. degree
from University of California, Irvine, in September 2007, all in
electrical engineering.

He was a CPCC Fellow during 2004-2007. He was with Wireless Networking
division of Conexant Systems Inc. during Summer 2006. Since July 2007,
he has been working as a research scientist at Wionics Research - Realtek
Group, concentrating mainly on MAC, link, and transport layer protocol
research and development for UWB wireless networks. His current research
interests include analytical network modeling and simulation, QoS
provisioning, fair and efficient resource allocation, protocol and
algorithm design for wireless networks.