Professor of Electrical and Computer Engineering
City University of Hong Kong
Seminar: Random Access: Packet-Based or Connection-Based?
Abstract: Random access provides a simple and elegant solution for multiple users to share a common channel. With random access, each user determines when to access the network in a distributed manner. Due to its simplicity in concept and low implementation cost, random access has found wide applications to various wireless networks such as Long Term Evolution (LTE) cellular networks and WiFi networks, and is expected to play an increasingly important role in the next-generation Machine-to-Machine (M2M) communications networks to facilitate the massive access of machine-type devices.
In general, random access protocols can be divided into two categories: packet-based and connection-based. Different from the conventional packet-based random access where each data packet needs to contend for channel access, with connection-based random access, a connection is first established before the data packet transmission. As the length of a connection request is typically smaller than that of a data packet, the transmission failure time can be reduced, though at the cost of extra overhead caused by connection establishment. Intuitively, there exists a critical threshold of the data packet transmission time, only above which establishing a connection is beneficial. Characterization of such a threshold is of crucial importance to practical access protocol design, which, nevertheless, has long remained elusive. In this talk, I will introduce our recently proposed unified analytical framework for sensing-free (Aloha) and sensing-based (CSMA) random access, and show how to characterize the threshold of data packet transmission time for beneficial connection establishment based on it. The practical implications of the analysis to the optimal access design of M2M communications will also be discussed.
About the speaker: Dr. Lin Dai was born in Wuhan, China. At the age of 15, she excelled in the national college examination and was admitted into the "Special Class for Gifted Teenagers" at Huazhong University of Science and Technology. She received her BS degree from Huazhong University of Science and Technology, and the MS and PhD degrees from Tsinghua University, all in Electronic Engineering.She was a postdoctoral fellow at The Hong Kong University of Science and Technology and University of Delaware. Since 2007, she has been with City University of Hong Kong, where she is currently a full professor. She has broad interests in communications and networking theory, with special interests in wireless communications. Her recent research work focuses on modeling, performance analysis and optimal access design of next-generation mobile communication systems.
Host: Cong Shen, assistant professor of electrical and computer engineering