QoS provisioning in Wi-Fi networks capacity modeling and resource control /

by Hui, Jie.

Hui, Jie. QoS Provisioning in Wi-Fi Networks: Capacity Modeling and Resource Control. (Under the direction of Professor Michael Devetsikiotis). The ubiquitous Wireless Fidelity (Wi-Fi) networks, and their increasing quality of service (QoS) requirements for emerging applications, motivate extensive studies of QoS provisioning in such networks. Two tasks, namely, capacity modeling and resource control, are crucial in solving the problem: A performance model is first needed to predict the network QoS metrics from the network settings. We propose a new unified analytical model to study the saturation throughput and delay performance of 802.11e Enhanced Distributed Coordination Function (EDCA), which is easier to apply than the most current ones. In order to find usable mathematical models for most cases where analytical models are not feasible, we first advocate the application of metamodeling techniques to Wi-Fi performance studies and formulate a general metamodeling framework for such purpose. The results in three case studies support the validity of our methodology: our saturation capacity metamodel for 802.11 Distributed Coordination Function (DCF) displays an interesting log-linear relationship between capacity and number of users; our voice over Wi-Fi admission capacity metamodel gives a much tighter bound than bounds existing in the literature; and, finally, our throughput metamodel for a simple ad-hoc network, for the first time, characterizes the cross-layer effects between MAC and network layer schedulers. Our work, therefore, points out a new direction for future performance studies of Wi-Fi networks. Then, based on the performance models we derive, resource control schemes of input parameters can be designed to achieve certain level of QoS outputs in some cases. For example, we are able to design a Weighted Round Robin (WRR) scheduler at the MAC layer to control the share of the radio resources, by applying our analytical model to a special case of EDCA configuration. Furthermore, based on our fitted metamodel for the capacity of voice over Wi-Fi, a more practical admission control scheme is composed. QoS Provisioning in Wi-Fi Networks: Capacity Modeling and Resource Control by Jie Hui A dissertation submitted to the Graduate Faculty of North Carolina State University in partial satisfaction of the requirements for the Degree of Doctor of Philosophy Department of Electrical and Computer Engineering Raleigh 2005 Approved By: Dr. Arne Nilsson Dr. Steve Roberts Dr. Michael Devetsikiotis Chair of Advisory Committee Dr. Wenye Wang ii To my parents for their everlasting unconditional love for me, staying beside me in this past tough year and supporting me meal by meal; To my husband for traveling overseas to accompany and support me; To the light of my life, my dear son Mark. Part of this Ph.D. work was done when he was inside me and kicking me. The last piece was made when he called his daddy as mom and cried to his grandparents for milk. Thank him, I appreciate life more. To my sister, wish her a happy birthday today. iii Biography Jie Hui was born in Shanxi, China. She received the B.S. degree in Electrical Engineering from the Xi’an Jiaotong University, Xi’an, China, in 1996, and the M.S. degree in Electrical Engineering from Institute of Space Electronic Equipment, Shanghai, China, in 1999. From 2000 to July 2001, she worked with 3G R & D center of ZTE Corp. in Shenzhen China as a system and software engineer. From August 2001 to August 2005, she has been pursuing her Ph.D. degree in Computer Engineering specializing in wireless networking in the department of Electrical and Computer Engineering of North Carolina State University. Her research interests include QoS provisioning for multimedia over Wi-Fi, medium access control, cross-layer control and optimization, modeling, performance evaluation and efficient simulation of wireless networks. iv