Design and Experimentation of Rate Adaptation for IEEE 802.11n WLANs

MPhil Thesis Defence


Title: "Design and Experimentation of Rate Adaptation for IEEE 802.11n WLANs"

By

Mr. Arafet BEN MAKHLOUF


Abstract

The transition from wired to wireless networks have opened up new horizons 
for research. IEEE 802.11 Wireless Local Area Networks (WLANs) have become 
increasingly popular due to the recent availability of affordable devices 
providing multiple and high rate capabilities. Optimizing the performance 
of wireless networks for emerging network applications is an important and 
a highly challenging issue.

In the next generation WLAN standard, termed IEEE 802.11n, new PHY and MAC 
layer enhancements have been introduced. These improvements have given 
birth to high throughput and high data rates to keep up with current and 
upcoming Internet applications. In this thesis, we investigate various 
issues related to the new 802.11n and legacy standards. The fundamental 
problem is that 802.11 WLANs exhibit rich channel dynamics including 
random channel errors due to interference, mobility-induced channel 
variation, and contention from hidden stations. As a result, the 
throughput of IEEE 802.11 devices is affected due to the wireless channel 
conditions. In particular, rate control is a fundamental resource 
management issue for 802.11 devices; its goal is to optimize the link 
throughput in various wireless environments.

In this thesis, we concentrate on this important issue of rate adaptation 
for 802.11-based WLANs. All the IEEE 802.11 standards do not specify any 
algorithm for automatic rate control. The basic idea of rate adaptation is 
to estimate the current channel condition and dynamically select the best 
rate out of multiple available transmission rates. Many rate adaptation 
schemes have been proposed in recent years, some of them are not 
relatively easy to implement by requiring modifications or additions to 
the IEEE 802.11 standard. We present a novel rate control algorithm, which 
extends a legacy scheme with new features suitable for forthcoming 802.11n 
products. We also implement this scheme in real hardware devices and then 
evaluate their performance compared to the existing rate control 
mechanisms. The experiments prove that our rate adaptation algorithm 
allows the current wireless hardware to have a greater adaptability to a 
variety of channel conditions.

For future work, we will study other wireless networks such as IEEE 
802.11p for vehicular Ad-hoc networks and IEEE 802.16 mesh networks. We 
believe that the approach discussed in this thesis could also provide a 
flexible structure for various systems, and optimize the performance of 
the next generation of wireless networks.


Date:			Friday, 20 August 2010

Time:			10:00am – 12:00noon

Venue:			Room 5566
 			Lifts 27/28

Committee Members:	Prof. Mounir Hamdi (Supervisor)
 			Dr. Gary Chan (Chairperson)
 			Dr. Lin Gu


**** ALL are Welcome ****