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E-MiLi: Energy-Minimizing Idle Listening in Wireless Networks

Kang G. Shin
EECS Department, The University of Michigan
11am Friday, January 27th, 2012
International Center (CIP-115) 

WiFi interface is known to be a primary energy consumer in mobile devices, and idle listening (IL) is the dominant source of energy consumption in WiFi.  Most existing protocols, such as the 802.11 power-saving mode (PSM), attempt to reduce the time spent in IL by sleep scheduling.  However, through an extensive analysis of real-world traffic, we found more than 60% of energy is consumed in IL, even with PSM enabled.  

To remedy this problem, we propose E-MiLi (Energy-Minimizing idle Listening) that reduces the power consumption in IL, given that the time spent in IL has already been optimized by sleep scheduling.  Observing that radio power consumption decreases proportionally to its clock-rate, E-MiLi adaptively downclocks the radio during IL, and reverts to full clock-rate when an incoming packet is detected or a packet has to be transmitted.  E-MiLi incorporates sampling rate invariant detection (SRID), ensuring accurate packet detection and address filtering even when the receiver's sampling clock-rate is much lower than the signal bandwidth.  Further, it employs an opportunistic downclocking mechanism to optimize the efficiency of switching clock-rate, based on a simple interface to existing MAC-layer scheduling protocols.  We have implemented E-MiLi on the USRP software radio platform.  Our experimental evaluation shows that E-MiLi can detect packets with close to 100% accuracy even with downclocking by a factor of 16. When integrated with 802.11, E-MiLi can reduce energy consumption by around 44% for 92% of users in real-world wireless networks. 

This is joint work with Xinyu Zhang and was presented at  ACM MobiCom’11.
Bio: Kang Geun Shin is the Kevin and Nancy O'Connor Professor of Computer Science and Founding Director of the Real-Time Computing Laboratory in the Department of Electrical Engineering and Computer Science, The University of Michigan, Ann Arbor, Michigan.
At Michigan, he has supervised the completion of 70 PhDs and also chaired the Computer Science and Engineering Division at Michigan for three years starting 1991. From 1978 to 1982 he was on the faculty of Rensselaer Polytechnic Institute, Troy, New York.  He received the B.S. degree in Electronics Engineering  from Seoul National University, Seoul, Korea in 1970, and both the M.S. and Ph.D. degrees in Electrical Engineering from Cornell University, Ithaca, New York in 1976 and 1978, respectively.

His current research focuses on computing systems and networks as well as on embedded real-time and cyber-physical systems, all with emphasis on timeliness, security, and dependability. He has authored/coauthored more than 770 technical articles (more than 270 of which are published in archival journals) and more than 20 patents or invention disclosures. He has co-authored (with C. M. Krishna) a textbook ``Real-Time Systems,'' McGraw Hill, 1997. He has received numerous best paper awards from, for example, the 2011 ACM International Conference on Mobile Computing and Networking (MobiCom’2011), the 2011 IEEE International Conference on Autonomic Computing, the 2010 & 2000 USENIX Annual Technical Conference, the 2003 IEEE  IWQoS, and  the 1996 IEEE Real-Time Technology and Application Symposium. He also won the 2003 IEEE Communications Society William R. Bennett Prize Paper Award and the 1987 Outstanding IEEE Transactions on Automatic Control Paper Award. He has also received several institutional awards, including the Research Excellence Award in 1989, Outstanding Achievement Award in 1999, Service Excellence Award in 2000, Distinguished Faculty Achievement Award in 2001, and Stephen Attwood Award in 2004 from The University of Michigan (the highest honor bestowed to Michigan Engineering faculty); a Distinguished Alumni Award of the College of Engineering, Seoul National University in 2002; 2003 IEEE RTC Technical Achievement Award; and 2006 Ho-Am Prize in Engineering. He is Fellow of IEEE and ACM,  and overseas member of the Korean  Academy of Engineering.
Host: Dr. Guoliang Xing