Research

Of late I am working on projects related to white space networking, energy conserving PC architecture, mobile systems and network management. In the past, I have worked on mesh networks and various other wireless system architectures.

White Space Networking (Cognitive Radios, SDRs, ...)

We are working on two fronts. First, on a system (hardware + software) capable of operating in the UHF TV bands. The goal is to efficiently utilize the available spectrum without interfering with licensed users. Second, we are exploring a more powerful WLAN architecture with variable channel widths in the ISM bands, in contrast to existing systems based on IEEE 802.11 that use channels of fixed width. There are several benefits of this new architecture, including better load balancing in enterprise WLANs. More details on this project can be found here.

• "White Space Networking with Wi-Fi like Connectivity", Paramvir Bahl, Ranveer Chandra, Thomas Moscibroda, Rohan Murty, Matt Welsh. To appear in ACM SIGCOMM, Barcelona, August 18-20, 2009
• "Load-Aware Spectrum Distribution in Wireless LANs", Thomas Moscibroda, Ranveer Chandra, Yunnan Wu, Sudipta Sengupta, Paramvir Bahl, Yuan Yuan. Proceedings of  IEEE ICNP, Orlando, October 19-22, 2008
• "A Case for Adapting Channel Width in Wireless Networks", Ranveer Chandra, Ratul Mahajan, Thomas Moscibroda, Ramya Raghavendra, Paramvir Bahl. Proceedings of ACM SIGCOMM, Seattle, August 17-22, 2008
• "Load Aware Channel-Width Assignments in Wireless LANs", Paramvir Bahl, Ranveer Chandra, Thomas Moscibroda, Yunnan Wu, Yuan Yuan. Microsoft Research Tech Report, MSR-TR-2007-79, June 2007
• "Allocating Dynamic Time-Spectrum Blocks in Cognitive Radio Networks", Yuan Yuan, Paramir Bahl, Ranveer Chandra, Thomas Moscibroda, Yunnan Wu. Proceedings of ACM MobiHoc, Montreal, Canada, September 9-14, 2007
• "A Hardware Platform for Utilizing the TV Bands with a Wi-Fi Radio", Srihari Narlanka, Ranveer Chandra, Paramvir Bahl, John Ian Ferrell. Proceedings of IEEE LANMAN, Princeton, June 10-13, 2007
• "KNOWS: Kognitiv Networking Over White Spaces", Yuan Yuan, Paramvir Bahl, Ranveer Chandra, Philip A. Chou, Ian Farrel, Thomas Moscibroda, Srihari Narlanka, Yunnan Wu. Proceedings of IEEE DySpan, Dublin, April 17-20, 2007.

Network Management (eXpose, DAIR, Sherlock, ...)

With the increasing complexity of enterprise networks, there is a pressing need for efficient approaches to detect, localize, diagnose and repair faults in the network. I have worked on several aspects of network management as part of a bigger project, called NetHealth. Sherlock uses dependency analysis to localize faults that impact end-users, DAIR helps IT administrators locate regions of poor WLAN coverage and performance, and WiFiProfiler enables users to collaborately diagnose Wi-Fi problems.

• "Whats Going On? Extracting Communication Rules in Edge Networks", Srikanth Kandula, Ranveer Chandra, Dina Katabi. Proceedings of ACM SIGCOMM, Seattle, August 17-22, 2008
• "Towards Highly Reliable Enterprise Network Services via Inference of Multi-level Dependencies", Paramvir Bahl, Ranveer Chandra, Albert Greenberg, Srikanth Kandula, David A. Maltz, Ming Zhang. Proceedings of ACM SIGCOMM, Kyoto, Japan, August 27-31, 2007
• "A Location-based Management System for Enterprise Wireless LANs", Ranveer Chandra, Jitendra Padhye, Alec Wolman, Brian Zill. Proceedings of USENIX NSDI, Cambridge, April 11-13, 2007.
• "Discovering Dependencies for Network Management", Paramvir Bahl, Paul Barham, Richard Black, Ranveer Chandra, Moises Goldszmidt, Rebecca Isaacs, Srikanth Kandula, Lun Li, John MacCormick, David A. Maltz, Richard Mortier, Mike Wawrzoniak, Ming Zhang. Proceedings of HotNets-V, Irvine, November 29-30, 2006.
• "WiFiProfiler: Cooperative Diagnosis in Wireless LANs", Ranveer Chandra, Venkata N. Padmanabhan, Ming Zhang. Proceedings of ACM/USENIX MobiSys, Uppsala, June 19-22, 2006.
• "Enhancing the Security of Corporate Wi-Fi Networks Using DAIR", Paramvir Bahl, Ranveer Chandra, Jitendra Padhye, Lenin Ravindranath, Manpreet Singh, Alec Wolman, Brian Zill. Proceedings of ACM/USENIX MobiSys, Uppsala, June 19-22, 2006.
• "Architecture and Techniques for Diagnosing Faults in IEEE 802.11 Infrastructure Networks", Atul Adya, Paramvir Bahl, Ranveer Chandra, Lili Qiu. Proceedings of ACM Mobicom, Philadelphia, September 26-30, 2004.

Green Computing

I am working on ways to reduce the energy consumption of PCs and mobile phones. Somniloquy (NSDI 2009) provides a way to let PCs go to sleep mode without losing network connectivity. Cell2Notify is a notification architecture for mobile phones that allows devices to turn on Wi-Fi only when needed, thereby increasing their battery lifetime. This is an active project, and expect to see more information soon.

• "Somniloquy: Augmenting Network Interfaces to Reduce PC Energy Usage", Yuvraj Agarwal, Steve Hodges, Ranveer Chandra, James Scott, Victor Bahl, Rajesh Gupta. Proceedings of USENIX NSDI, Boston, April 21-23, 2009
• "Somniloquy: Maintaining Network Connectivity While Your Computer Sleeps", Yuvraj Agarwal, Steve Hodges, James Scott, Ranveer Chandra, Victor Bahl, Rajesh Gupta. no. MSR-TR-2008-42, pp. 14, Microsoft Research, March 2008
• "Wireless Wakeups Revisited: Energy Management for VoIP Over Wi-Fi Smartphones", Yuvraj Agarwal, Ranveer Chandra, Alec Wolman, Paramvir Bahl, Kevin Chin, Rajesh Gupta. Proceedings of ACM/USENIX MobiSys, Puerto Rico, June 11-14, 2007

Mesh Networks

I have worked on networking issues in layer 2 and layer 3 (unicast + multicast) in wireless mesh networks. The details of this project are available on our group's Mesh Networking page.

• "Context Based Routing: Technique, Applications and Experience", Saumitra M. Das, Yunnan Wu, Ranveer Chandra, Y. Charlie Hu. Proceedings of USENIX NSDI, San Francisco, April 16-18, 2008.
• "Routing with a Markovian metric to promote local mixing", Yunnan Wu, Saumitra M. Das, Ranveer Chandra. Proceedings of IEEE INFOCOM Minisymposium, Anchorage, Alaska, May 6-12, 2007.
• "Routing with a Markovian metric to promote local mixing", Yunnan Wu, Saumitra M. Das, Ranveer Chandra. Microsoft Research Tech Report, MSR-TR-2006-158, November 2006.
• "Optimizing the Placement of Integration Points in Multi-hop Wireless Networks", Ranveer Chandra, Lili Qiu, Kamal Jain, Mohammad Mahdian. Proceedings of IEEE ICNP, Berlin, October 6-8, 2004.
• "SSCH: Slotted Seeded Channel Hopping for Capacity Improvement in IEEE 802.11 Ad-Hoc Wireless Networks", Paramvir Bahl, Ranveer Chandra,John Dunagan. Proceedings of ACM Mobicom, Philadelphia, September 26-30, 2004.
• "A Mesh based Robust Topology Discovery Algorithm for Hybrid Wireless Networks", Ranveer Chandra, Christof Fetzer, Karin Hogstedt. AT&T Labs Tech Report and Proceedings of Informatics, 1st International Conference on Ad-hoc Networks and Wireless, Toronto, Vol. 16, pp 1-16, September 20-22, 2002.
• "Providing a Bidirectional Abstraction for Unidirectional Ad Hoc Networks", Venugopalan Ramasubramanian, Ranveer Chandra, Daniel Mosse. Proceedings of IEEE INFOCOM 2002, New York, June 23-27, 2002.
• "Anonymous Gossip: Improving Multicast Reliability in Mobile Ad-Hoc Networks", Ranveer Chandra, Venugopalan Ramasubramanian, Kenneth P. Birman. Proceedings of the 21st International Conference on Distributed Computing Systems(ICDCS), Phoenix, April 16-19, 2001.

Rethinking the Design of Wireless Systems

Wi-Fi is designed as a convenient replacement for the wire, and its design mostly attempts to mimic the behavior of the Ethernet. For example, a Wi-Fi card needs to associate to an Access Point (AP) before it can send data packets, which is similar to the action to plugging the Ethernet cable in the wall. Furthermore, Wi-Fi restricts a card to associate to at most one AP. In my opinion, the wireless medium has a number of powerful properties and wireless networks should be treated differently from traditional wired networks. I have built some systems that try to break away from these constraints in Wi-Fi networks as part of VirtualWiFi and WiFiAds projects. 

• "Opportunistic Use of Client Repeaters to Improve Performance of WLANs",Paramvir Bahl, Ranveer Chandra, Patrick P. C. Lee, Vishal Misra, Jitendra Padhye, Dan Rubenstein, Yan Yu. Proceedings of ACM CoNEXT (Best Paper Award), Madrid, December 9-12, 2008
• "Designing High Performance Enterprise Wi-Fi Networks", Rohan Murty, Jitendra Padhye, Ranveer Chandra, Alec Wolman, Brian Zill. Proceedings of USENIX NSDI, San Francisco, April 16-18, 2008
• "Wi-Fi Neighborcast: Enabling Communication Among Nearby Clients", Ranveer Chandra, Jitendra Padhye, Lenin Ravindrananth. Proceedings of ACM HotMobile, Napa Valley, February 25-26, 2008.
• "BeaconStuffing: Wi-Fi Without Associations", Ranveer Chandra, Jitendra Padhye, Lenin Ravindrananth, Alec Wolman. Proceedings of IEEE HotMobile, Tucson, February 26-27, 2007.
• "A Virtualization Architecture for Wireless Network Cards", Ranveer Chandra. Ph.D. Thesis, Cornell University, September 2005 (Nominated by Cornell for the ACM best dissertation award)
• "MultiNet: Connecting to Multiple IEEE 802.11 Networks Using a Single Wireless Card", Ranveer Chandra, Paramvir Bahl, Pradeep Bahl. Proceedings of IEEE Infocom 2004, Hong Kong, March 7-11, 2004.