Defense Presentation

Zhi Zhang

Ph.D. Final
April 24, 2009, 9:30am-11:30am
Pathology 101
"Resource Management in QoS-Aware Wireless Cellular Networks "
Abstract:  Emerging broadband wireless networks which support highspeed packet data with heterogeneous quality of service (QoS) requirements demand more flexible and efficient use of the scarce spectral resource. Opportunistic scheduling exploits the time-varying, location-dependent channel conditions to achieve multiuser diversity. In this work, we study two resource allocation problems in QoS-aware wireless cellular networks. First we develop a rigorous framework to study opportunistic scheduling in multiuser OFDM systems. We derive optimal opportunistic scheduling policies under three QoS/fairness constraints for multiuser OFDM systems ---temporal fairness, utilitarian fairness, and minimum-performance guarantees. To implement these optimal policies efficiently, we provide a modified Hungarian algorithm and a simple suboptimal algorithm. We then propose a generalized opportunistic scheduling framework that incorporate multiple mixed QoS/fairness constraints, including providing both lower and upper bound constraints.
Next, taking input queues and channel memory into consideration, we reformulate the transmission scheduling problem as a Markov decision process (MDP) with fairness constraints. We in- vestigate the throughput maximization and the delay minimization problems in this context. We consider both discounted reward and average reward criteria. We derive and prove explicit dynamic programming equations for the above constrained MDPs, and give optimal scheduling policies based on those equations. Further more, we develop an efficient approximation method ---temporal fair rollout---to reduce the computational cost. An attractive feature of our proposed schemes is that they can easily be extended to fit different objective functions and other fairness measures.

Adviser: Dr. Edwin K. P. Chong
Co-adviser: NA
Non-ECE member: Dr. William S. Duff, Mechanical Engineering
Member3: Dr. Mahmood R. Azimi-Sadjadi, ECE
Member4: Dr. Peter M. Young, ECE
Additional member: NA

Publications:
-Z. Zhang, "Optimal selection and estimation of ? algorithm for space time variable correlation," in Proceedings of Future Telecommunications Conference 2001, Beijing, China, November 29–30, 2001, pp. 210–-213 (Ericsson best paper award).
-L. L. Scharf, E. K. P. Chong, L. T. McWhorter, and Z. Zhang, “Algebraic Equivalence of Block Conjugate Direction and Block Multistage Wiener Filters for Estimating Random Vectors,” Lake Louise Workshop on The Future of Signal Processing in the 21st Century, Lake Louise, AL, Canada, October 5–10, 2003.
-L. L. Scharf, E. K. P. Chong, and Z. Zhang, "Algebraic equivalence of matrix conjugate direction and matrix multistage filters for estimating random vectors," in Proceedings of the 43rd IEEE Conference on Decision and Control (CDC'04), Atlantis Resort, Paradise Island, Bahamas, December 14--17, 2004, pp. 4175--4179.
-Z. Zhang, Y. He, and E. K. P. Chong, "Opportunistic downlink scheduling for Multiuser OFDM systems," in Proceedings of the 2005 IEEE Wireless Communications and Networking Conference (WCNC'05), New Orleans, LA, March 13--17, 2005, pp. 1206--1212 (Invited paper).
-Z. Zhang, Y. He, and E. K. P. Chong, "Opportunistic scheduling for OFDM systems with fairness constraints," EURASIP Journal on Wireless Communications and Networking, special issue on Cognitive Radio and Dynamic Spectrum Sharing Systems, vol. 2008, Article ID 215939, 12 pages, 2008. doi:10.1155/2008/215939.
-Z. Zhang, S. Moola, and E. K. P. Chong, "Approximate stochastic dynamic programming for opportunistic fair scheduling in wireless networks," in Proceedings of the 47th IEEE Conference on Decision and Control, Cancun, Mexico, December 9--11, 2008, pp. 1404--1409.
-Z. Zhang, S. Moola, and E. K. P. Chong, "Opportunistic Fair Scheduling in Wireless Networks: An Approximate Dynamic Programming Approach," Journal of ACM Mobile Networks and Applications (MONET), under review, October, 2008.



Program of Study:
M517 - Intro-Mathematical Analysis
M560 - Linear Algebra
ST730 - Advanced Theory of Statistics
EE514 - Applications of Random Processes
EE520 - Optimization of Control & Comm
EE554 - Computer Architecture
EE612 - Robust Control Systems
EE614 - Principles of Digital Communications
EE752 - Advanced Topics in Signal Processing
EE799 - Dissertation