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Venkat Padmanabhan


Principal Researcher
Microsoft Research


Contact Information

Microsoft Research India
#9, Lavelle Road,
Bengaluru 560 001
Tel: +91 (80) 6658-6004
Fax: +91 (80) 6658-6058

Brief Bio

I am a Principal Researcher at Microsoft Research India, where I founded the Mobility, Networks, and Systems group in 2007. I was previously with Microsoft Reseach Redmond for 8½ years. Before that, I obtained a Ph.D. in Computer Science from the University of California at Berkeley in September 1998. Professor Randy Katz was my advisor, having previously obtained an M.S. in Computer Science also from UC Berkeley in 1995 (advised by Professor Domenico Ferrari) and a B.Tech. in Computer Science and Engineering from the Indian Institute of Technology, Delhi in 1993.

My research interests lie broadly in mobile and networked systems. My current work centers on (a) the intersection of sensor systems and mobile computing, and on (b) efficient mobile communication. My past projects have spanned a range of areas, including network measurement, wireless networking, RFID, geolocation, network tomography, and peer-to-peer networking. The technologies developed in some of these projects (e.g., the ProbeGap bandwidth probing tool and the GeoCluster technique for learning IP-location mapping) have been transferred to Microsoft's product groups while others (e.g., the RADAR WLAN-based user localization system) have been made available through Microsoft's technology licensing program.

I am an INAE Fellow, IEEE Fellow, and ACM Distinguished Scientist. I have served both as General Co-Chair of the ACM SIGCOMM conference (in 2010 in New Delhi) and as Program Co-Chair (in 2012). At present, I am serving as the chair of the ACM SIGCOMM Technical Steering Committee. I have also served on the editorial board of ACM SIGCOMM Computer Communication Review, IEEE/ACM Transactions on Networking, and IEEE Transactions on Mobile Computing.

Awards and Honours

  • Keynote speaker, 2nd Workshop on Physical Analytics @ ACM MobiSys 2015
  • Keynote speaker, COMSNETS 2015
  • Keynote speaker, ACM/IFIP/USENIX Middleware 2010
  • Keynote speaker, IEEE International Conference on Internet Multimedia Systems Architecture and Applications (IMSAA), 2010
  • INAE Fellow, 2014, with the citation "for distinguished contributions to engineering"
  • IEEE Fellow, 2012, with the citation "for contributions to networked and mobile computing systems" [nomination through IEEE Computer Society]
  • ACM Distinguished Scientist, 2009
  • ACM SIGMOBILE Test-of-Time Paper Award, 2016
  • Best short paper award, ACM CoNEXT 2015
  • Best paper award, USENIX Annual Technical Conference, 2010
  • Best student paper award, USENIX Annual Technical Conference, 1995
  • Microsoft Achievement Award, 2006
  • President’s Runner-Up Award from the Microsoft Online Systems Division, 2013
  • Charles Fish Graduate Fellowship, UC Berkeley, 1993-1994
  • Eugene C. Gee and Mona Fay Gee Scholarship for Graduate Study, UC Berkeley, 1995 (declined)
  • Motorola Undergraduate Project Award, IIT Delhi, 1993
  • Shri Pyare Lal Murgai Scholarship, IIT Delhi, 1992-1993
  • Merit Prize in each semester at IIT Delhi, 1989-1993
  • Gold Medal in the National Physics Olympiad, India, 1989
  • National Talent Scholarship, India, 1987-1993

Research Highlights and Impact

My research has had a significant impact on the research and academic community, with my papers having received hundreds or thousands of citations (see Google Scholar for up-to-date information), and several follow-on efforts building on my work. Some of this research has also impacted Microsoft's products through technology transfer, and even the industry at large. Here are some highlights:

  • Indoor Localization: Worked on RADAR, the first system for indoor localization using the existing wireless LAN infrastructure. RADAR has spawned off much follow-on work in the research community, with our Infocom 2000 paper receiving nearly 8000 citations and being a recipient of the inaugural ACM SIGMOBILE Test-of-Time Paper Award in 2016. The method of fingerprinting invented in RADAR is the basis of many commercial WiFi-based indoor positioning systems. Followed up with more recent work at MSR India on making calibration for WiFi-based localization "zero-effort", through a combination of a modeling-based approach to reduce dependence on ground-truth data (EZ --- Mobicom 2010) and inertial tracking to generate ground truth data automatically (Zee --- Mobicom 2012). Transferred technology to Windows Phone.
  • Wireless performance: Worked on one of the earliest studies of TCP over error-prone wireless LAN links, while at Berkeley (Sigcomm 1996 paper, over 2200 citations, including the journal version), and subsequently on a novel framework for estimating the capacity of wireless mesh networks, while at MSR Redmond (Mobicom 2003 paper; over 1800 citations, including the journal version). More recently, at MSR India, shifted focus to cellular network performance and its impact on battery life, with work on signal-aware communication (Bartendr --- Mobicom 2010), application-aware radio management (Radio-Jockey --- Mobicom 2012), and implicit coordination through cellular load sensing (LoadSense/Peek-n-Sneak --- Mobicom 2013).
  • Web Data Transport: Worked on the persistent connection and pipelining optimizations to HTTP/1.0 during the early days of the World Wide Web, ideas which became part of the HTTP/1.1 standard (RFC 2616). Our WWW 1994 paper has over 450 citations (including the journal version). Also conducted one of the earliest studies of prefetching of Web content (CCR 1996 paper; over 780 citations). Subsequently, as part of my PhD thesis, worked on TCP-level solutions for Web data transport, including TCP Sessions and TCP Fast Start (Global Internet 1998 paper).
  • IP Geo-location: Designed a suite of novel techniques for geo-locating Internet hosts, using router labels obtained from traceroute (GeoTrace), delay measurements (GeoPing), and topology-aware clustering of web logs (GeoCluster). Published Sigcomm 2001 paper (over 520 citations), which to my knowledge, was the first paper in the academic literature on IP geo-location. Transferred technology to Microsoft ad Center.
  • Wireless Available Bandwidth Estimation: Developed the ProbeGap technique (IMC 2004 paper, nearly 175 citations) for lightweight yet accurate available bandwidth estimation in wireless LANs, where contention results in non-FIFO behavior across nodes. Transferred technology to Microsoft Windows. “ProbeGap” is now a term defined in the Windows Protocol Glossary on MSDN, alongside several well-known networking terms.
  • Resilient Peer-to-Peer Streaming: Proposed multi-tree-based structures for resilient P2P streaming, with multiple-description coding used to stripe content across the multiple trees, to limit disruption due to node churn. Published NOSSDAV 2002 paper (over 1200 citations) and ICNP 2003 paper (over 550 citations), which have influenced many follow-on proposals based on the multi-tree idea.
  • Smartphone-based Road and Traffic Monitoring: Developed Nericell, one of the earliest systems that used the then-anticipated sensing capabilities of smartphones for monitoring of road and traffic conditions, with particular focus on India. Published SenSys 2008 paper (over 825 citations). Nericell has inspired many follow-on efforts in India and abroad.

Some of my papers have also been included in course reading lists and research area reading lists at leading universities around the world. Here is a partial list: Berkeley, CMU, MIT, Stanford, Cornell, Harvard, Michigan, Princeton, Washington, Yale, UCL (UK), Bilkent University (Turkey), Boston University, Duke, Georgia Tech, Hong Kong University of Science and Technology, Institute for Systems and Robotics (Portugal), National Taiwan University, National University of Singapore, Purdue, Rutgers, Sun Yat-Sen University (China), UCLA, UC Santa Cruz, UCSD, UIUC, U Maryland, U Massachusetts, USC, UT Austin, U Virginia, U Waterloo (Canada), U Wisconsin.

Recent Publications

QProbe: Locating the Bottleneck in Cellular Communication
N. Baranasuriya, V. Navda, V. N. Padmanabhan, S. Gilbert
ACM CoNEXT, Heidelberg, Germany
December 2015
Received the best short paper award

DiversiFi: Robust Multi-Link Interactive Streaming
R. Kateja, N. Baranasuriya, V. Navda, and V. N. Padmanabhan
ACM CoNEXT, Heidelberg, Germany 
December 2015

Enabling Physical Analytics in Retail Stores Using Smart Glasses
S. Rallapalli, A. Ganesan, K. Chintalapudi, V. N. Padmanabhan, and L. Qiu
ACM Mobicom, Maui, HI, USA
September 2014

Demo: Tracking User Browsing on a Demo Floor
A. Ganesan, S. Rallapalli, K. Chintalapudi, V. N. Padmanabhan, and L. Qiu
Demo paper at ACM Mobicom, Maui, HI, USA
September 2014

Coordinating Cellular Background Transfers using LoadSense
A. Chakraborty, V. Navda, V. N. Padmanabhan, and R. Ramjee
ACM Mobicom, Miami, FL, USA
September-October 2013

Dhwani: Secure Peer-to-Peer Acoustic NFC
R. Nandakumar, K. K. Chintalapudi, V. N. Padmanabhan, and R. Venkatesan
ACM Sigcomm, Hong Kong
August 2013

MiG: Efficient Migration of Desktop VMs Using Semantic Compression
A. Rai, R. Ramjee, A. Anand, V. N. Padmanabhan, and G. Varghese
June 2013

Accurate Speed and Density Measurement for Road Traffic in India
R. Sen, A. Cross, A. Vashistha, V. N. Padmanabhan, E. Cutrell, and W. Thies
ACM DEV, Bengaluru, India
January 2013

Selected Publications

Zee : Zero-Effort Crowdsourcing for Indoor Localization
A. Rai, K. K. Chintalapudi, V. N. Padmanabhan, and R. Sen
ACM Mobicom, Istanbul, Turkey
August 2012

Indoor Localization Without the Pain
K. K. Chintalapudi, A. P. Iyer, and V. N. Padmanabhan
ACM Mobicom, Chicago, IL, USA
September 2010
Technology transferred to Microsoft Windows

LiteGreen: Saving Energy in Networked Desktops Using Virtualization
T. Das, P. Padala, V. N. Padmanabhan, R. Ramjee, and K. G. Shin
June 2010
Received the best paper award

Nericell: Rich Monitoring of Road and Traffic Conditions using Mobile Smartphones
P. Mohan, V. N. Padmanabhan, and R. Ramjee
ACM SenSys, Raleigh, NC, USA
November 2008

Bandwidth Estimation in Broadband Access Networks
K. Lakshminarayanan, V. N. Padmanabhan, and J. Padhye
ACM/USENIX Internet Measurement Conference, Taormina, Sicily, Italy
October 2004
PostScript, PDF
Technology transferred to Microsoft Windows (ProbeGap)

An Investigation of Geographic Mapping Techniques for Internet Hosts
V. N. Padmanabhan and L. Subramanian
Proceedings of ACM SIGCOMM 2001, San Diego, CA, USA
August 2001
Technology transferred to Microsoft adCenter

RADAR: An In-Building RF-Based User Location and Tracking System
P. Bahl and V. N. Padmanabhan
Proceedings of IEEE Infocom 2000, Tel-Aviv, Israel
March 2000
PostScript, PDF
Received the ACM SIGMOBILE Test-of-Time Paper Award in 2016
(This is an updated version of Microsoft Research Technical Report MSR-TR-99-12, February 1999 (PostScript, PDF))

A Comparison of Mechanisms for Improving TCP Performance over Wireless Links
H. Balakrishnan, V. N. Padmanabhan, S. Seshan, and R. H. Katz
Proceedings of the ACM SIGCOMM 1996, Stanford, CA, USA
August 1996

File system Logging versus Clustering: A Performance Comparison
M. Seltzer, K. Smith, H. Balakrishnan, J. Chang, S. McMains, and V. N. Padmanabhan
Proceeding of the Winter 1995 USENIX Technical Conference, New Orleans, LA, USA
January 1995
Received the Best Student Paper Award

Improving HTTP Latency
V. N. Padmanabhan and J. C. Mogul
The Second International World Wide Web Conference, Chicago, IL, USA
The Second International World Wide Web Conference, Chicago, IL, USA
Cited in the context of persistent connections in the HTTP/1.1 standard (RFC 2616)

Teaching and Mentoring

I have worked with several excellent students during and after their internships at Microsoft Research. The list below is of interns I worked with while at Microsoft Research Redmond; the interns from my period at Microsoft Research India are listed on the MNS group webpage:

I have held affiliate faculty appointments in the Electrical Engineering and Computer Science & Engineering departments at the University of Washington. I taught a graduate networking class in the CSE department in Spring 2001. I am on the advisory board for the Wireless Communications Technology program at UW Extension. I have also served on student thesis committees at UW and elsewhere:

Professional Service and Leadership

Editorial board service:

Chair positions:

Program committee membership:

  • ACM/USENIX MobiSys: 2007, 2011
  • ACM SIGCOMM: 2004, 2007, 2011, 2012 (co-chair), 2013, 2016
  • NSDI: 2010, 2015
  • Workshop on Physical Analytics: 2014 (co-chair), 2015, 2016
  • CoNEXT: 2006, 2009
  • ACM SIGMETRICS: 2003, 2008
  • COMSNETS: 2009
  • COMSWARE: 2008
  • ACM Mobicom: 2000, 2001, 2002
  • IEEE Infocom: 2001, 2002, 2005
  • ACM HotNets: 2005, 2011
  • ACM Internet Measurement Conference: 2002, 2005 (co-chair)
  • ACM NOSSDAV: 2000, 2002, 2003, 2004 (co-chair)
  • International Workshop on Peer-to-Peer Systems (IPTPS): 2007
  • International Conference on Distributed Computing Systems (ICDCS): 2005
  • SPIE/ACM Multimedia Computing and Networking (MMCN): 2002, 2003
  • IEEE International Conference on Network Protocols (ICNP): 2002, 2003
  • International World Wide Web Conference (WWW): 2002, 2003, 2006
  • ACM Workshop on Wireless Mobile Multimedia (in conjunction with ACM Mobicom): 1999, 2000
  • Performance and Architecture of Web Servers (in conjunction with ACM SIGMETRICS): 2000, 2001

Press Coverage

Here are some articles on research projects I have been involved with.

ProbeGap (2005): PC World
Suremail (2006): Computerworld, Computerworld, InformationWeek
COMBINE (2007): The Hindu, Business Line
Nericell (previously known as TrafficSense, 2008): PC World, Seattle Post-Intelligencer, ComputerWorld Canada, The Economic Times, Deccan Chronicle, Rediff
SixthSense (2008): Ubergizmo, ComputerWorld Canada
LiteGreen (2010): InfoWorld, Virtualization.Info
SpecNet (2011): NetworkWorld, The Register, Engadget
Dhwani (2013): Computerworld, EETimes India, The Register, RFID Journal, Ubergizmo, ...

There is also a Microsoft Research article which did a profile of the research group I lead some years ago.

Here are some videos featuring my projects:

BARWAN Project, UC Berkeley
Mobile Communications Research at Microsoft