Scheduling algorithm design in multiuser wireless networks

• Main Author: Chen, Yi
• Other Authors: Cai, Lin
• Language: English; en
• Published: 2016
• Subjects: Scheduling; Wireless Networks; Resource Allocation
• Online Access: http://hdl.handle.net/1828/7668

In this dissertation, we discuss throughput-optimal scheduling design in multiuser wireless networks. Throughput-optimal scheduling algorithm design in wireless systems with flow-level dynamics is a challenging open problem, especially considering that the majority of the Internet traffic are short-lived TCP controlled flows. In future wireless networks supporting machine-to-machine and human-to-human applications, both short-lived dynamic flows and long-lived persistent flows coexist. How to design the throughput-optimal scheduling algorithm to support dynamic and persistent flows simultaneously is a difficult and important unsolved problem. Our work starts from how to schedule short-lived dynamic flows in wireless systems to achieve throughput-optimality with queue stability. Classic throughput-optimal scheduling algorithms such as the Queue-length based Maxweight scheduling algorithm (QMW) cannot stabilize systems with dynamic flows in practical communication networks. We propose the Head-of-Line (HOL) access delay based scheduling algorithm (HAD) for flow-level dynamic systems, and show that HAD is able to obtain throughput-optimality which is validated by simulation. As the Transmission Control Protocol (TCP) is the dominant flow and congestion control protocol for the Internet nowadays, we turn our attention to the compatibility between throughput-optimal schedulers and TCP. Most of the existing throughput-optimal scheduling algorithms have encountered unfairness problem in supporting TCP-controlled flows, which leads to undesirable network performance. Motivated by this, we first reveal the reason of the unfairness problem, then study the compatibility between HAD and TCP with different channel assumptions, and finally analyze the mean throughput performance of HAD. The result shows that HAD is compatible with TCP. Since the assumption of an infinite buffer size in the existing theoretical analysis of throughput-optimality is not practical, we analyze the queueing behaviour of the proposed throughput-optimal scheduling algorithm to provide useful guidelines for real system design by using the Markov chain analytic model. We propose the analytic model for the queuing and delay performance for the HAD scheduler, and then further develop an approximation approach to reduce the complexity of the model. Finally, we propose a throughput-optimal scheduling algorithm for hybrid wireless systems with the coexistence of persistent and dynamic flows. Then, to generalize the throughput-optimal scheduling, the control function in the scheduling rule is extended from a specific one to a class of functions, so that the scheduling design can be more flexible to make a tradeoff between delay, fairness, etc. We show that the hybrid wireless networks with coexisting persistent flows and dynamic flows can be stabilized by our proposed scheduling algorithm which can obtain throughput-optimality. In summary, we solve the challenging problem of designing throughput-optimal scheduling algorithm in wireless systems with flow-level dynamics. Then we show that our algorithm can support TCP regulated flows much better than the existing throughput-optimal schedulers. We further analyze the queueing behaviour of the proposed algorithm without the assumption of infinite buffer size that is often used in the throughput-optimality analysis in the literature, and the result provides a guideline for the implementation of our algorithm. At last, we generalize the proposed scheduling algorithm to support different types of flows simultaneously in practical wireless networks. === Graduate === [e-mail]