Emily H. Qi

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.

Energy efficient and scalable device-to-device discovery protocol with fast discovery

Device-to-device (D2D) discovery is an important step toward numerous applications of device-to-device communications. However, the design of D2D discovery protocols also faces the challenges of distributed nature, energy efficiency, scalability, and fast discovery. In this paper, we propose a D2D discovery protocol called synced distributed protocol that can efficiently resolve these challenges. The key idea behind our protocol is to group devices in a neighborhood such that devices in a group will take turns to announce the existence of other devices in a group. Hence, a device can reduce the period of announcing its existence and have the advantages of energy efficiency and scalability. Further, the transmissions from other devices in the group still guarantee fast discovery. We validate our protocol design by analysis and simulations. Specifically, we prove that our proposed protocol will function correctly in a static environment with minor assumptions and simulate our protocol in the OPNET 802.11n model. Simulation results confirm that our algorithm is scalable and can achieve low duty cycle and fast discovery. For mobile environment, we propose enhanced techniques and use simulation to show that the enhanced techniques has the benefits of increasing the group size.

Augmenting wireless LAN technology for Wi-Fi PAN

The penetration of Wi-Fi in mobile and consumer electronic devices is increasing at a rapid pace. This increasing adoption in devices other than portable computers enables new usage models for end users. People want to view, listen, share and print their media anytime and anywhere. This paper looks at what new usages a Wi-Fi PAN can enable, its architecture, its components and its core technologies.

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.