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...[ Read more ]

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.