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Graduate Exam Abstract


Zhi Zhang

Ph.D. Preliminary

April 30, 2008, 11:00am-1:00pm

Wagar 107B

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.<br> 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
Member 3: Dr. Mahmood R. Azimi-Sadjadi, ECE
Addional Members: NA

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Program of Study: