Talks & Seminars
Title: Exploiting Physical Layer Information in Wireless System Design
Dr. Mythili Vutukuru, Movik Networks
Date & Time: March 6, 2013 15:00
Venue: CSE Department, Kanwal Rekhi Building, SIC 301
With wireless devices becoming ubiquitous, the problem of designing high performance and reliable wireless networks is of great importance today. The wireless physical layer (PHY) is characterized by a rapidly varying radio channel and a shared broadcast medium of communication. Higher layer networking protocols for wireless networks, such as bit rate adaptation and medium access control (MAC) protocols, have to account for the unique characteristics of the wireless PHY in their designs. In this talk, we describe designs of wireless systems that exploit the rich channel information available at the PHY and outperform traditional approaches that seek to abstract out the details of the PHY using a simple link abstraction. In particular, we describe the SoftRate bit rate adaptation protocol and the SoftCMAP MAC protocol. These protocols rely on an enhancement to the physical layer called SoftPHY. In contrast to today's PHY that delivers received frames and per-frame signal strength measurements to the link layer, SoftPHY streams bits to the link layer as soon as they are decoded and before the entire frame reception completes, and it computes and exports SoftPHY hints with each decoded bit. The SoftPHY hint of a bit indicates the PHY's confidence that the decoded bit is correct. We show that the SoftPHY hints of a received frame can be used to estimate the bit error rate (BER) of the wireless channel faster and with more accuracy than with existing methods. We develop the SoftRate bit rate adaptation protocol that uses this BER computed from SoftPHY hints to pick transmit bit rates and improves throughput by 2X over existing protocols. The streaming PHY interface enables the link layer to learn about the current transmission on the air by decoding headers before frame reception completes. The SoftCMAP and CMAP protocols make smart medium access decisions using this knowledge of ongoing transmissions along with a distributed map of conflicting transmissions, and improve aggregate network throughput by up to 50% by increasing the number of successful concurrent transmissions.
Speaker Profile:
Dr. Mythili Vutukuru obtained her B. Tech. from the Indian Institute of Technology, Madras, in 2004, and her M. S. and Ph. D. degrees from the Massachusetts Institute of Technology in 2006 and 2010 respectively. She has been working as a research engineer at Movik Networks, a startup in the telecom space, since 2010. Her research interests span wireless system design, communication protocols, and network security.
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