Sangeetha L. Bangolae

Performance study of fast BSS transition using IEEE 802.11r

The mass deployment of IEEE 802.11 based wireless local area networks (WLAN), and increased sales in portable devices supporting WLAN, have resulted in an urgent need to support real time applications while wireless users are on the move. This critical support necessitates research into current WLAN roaming capabilities. This paper discusses how WLAN roaming capabilities are affected by new standards such as security (IEEE 802.11i) and quality of service (IEEE 802.11e), and describes the new IEEE 802.11r standard, which was developed to address issues faced by real time applications that implement the security and quality of service enhancements. The performance evaluation of 802.11r prototype and the 802.11i baseline mechanisms show that a voice application using 802.11r can achieve significantly shorter transition time and reduced packet loss during AP-AP transition, and can therefore realize a noticeable improvement in voice quality.

BSS transition optimizations and analysis for VoIP over WLAN

Voice over IP (VoIP) is emerging as a critical application for IEEE 802.11 Wireless Local Area Networks (WLANs). However, the limited range of the IEEE 802.11 radio forces frequent transitions from one access point to another. Moreover, the introduction of IEEE 802.11i security and IEEE 802.11e Quality of Service (QoS) has increased the average transition time from ms to seconds, leaving mobile users with the unenviable dilemma of choosing good security and QoS while sacrificing real-time performance, or gaining acceptable real-time performance at the expense of security and QoS. Thus, optimizations to device transitioning that will provide an acceptable balance of latency, security, and QoS are needed to enable VoIP. This paper analyzes WLANs MAC layer transition procedure and optimizations being considered by IEEE 802.11 Working Group to improve transition times while retaining good security and QoS. The transition time improvements proposed in this paper are achieved through discovery phase optimizations and transition phase optimizations. The selective scanning and smart AP selection algorithms are designed to optimize the discovery phase to enable the mobile device to better exploit its ambient radio resource environment. The transition phase optimization seeks to accelerate device transition without compromising security. The paper then identifies security flaws in the current design and proposes simple corrections. Finally, experiment results for transition optimization are explained that demonstrate a significant increase in transition efficiency.