Picture of Ram

Ram Ramanathan
Principal Scientist
Internetworking Research Department
BBN Technologies
10 Moulton Street, Cambridge
Massachusetts 02138, USA

 Phone : +1-617-873-2736
Fax : +1-617-873-6091
Email : ramanath AT bbn DOT com
Web : http://www.ir.bbn.com
[Contact] [Biography] [Projects] [Publications] [Professional Services] [Patents]

Bio

Ram Ramanathan is a Principal Scientist in the Internetworking Research Department at BBN Technologies.  His primary area of expertise is Mobile Ad Hoc Networking (MANET) in which he has had more than 14 years of advanced research and development experience. He has made significant contributions to several areas -- topology control, use of directional antennas, and scalable flat routing for MANETs.

Dr. Ramanathan's recent research areas include new MANET architectures, disruption tolerance, software radios, opportunistic spectrum access, topology control, beamforming antennas, and medium access control. Over the past few years, he has led several projects on advanced ad hoc networking for the Defense Advanced Research Projects Agency (DARPA). He has been the Principal Investigator for the DARPA project neXt Generation Communications (XG) which seeks to develop technologies for opportunistic spectrum access for cognitive radios. He was the co-Prinicpal Investigator of the DARPA project Utilizing Directional Antennas for Ad Hoc Networking (UDAAN), as part of which the first prototype ad hoc networking system with directional antennas was designed, simulated and field-demonstrated. Prior to that he was the PI for the DAWN project under the DARPA GloMo program. Currently, he is working on the DARPA WNAN program which seeks to build a very large MANET with Dynamic Spetrum Access and DTN support using inexpensive nodes each consisting of up to four frequency-agile radios.

Ram has served on the program committees of several top-tier conferences including ACM MobiCom, Mobihoc and IEEE Infocom, and is on the editorial board of IEEE Transactions on Mobile computing. He was the TPC co-chair of ACM Mobicom 2007. He has published over 40 refereed papers in international journals and conferences, including best paper award winning papers at IEEE MILCOM, IEEE INFOCOM, and ACM SIGCOMM. Ram received his Bachelor of Technology in Electrical Engineering from the Indian Institute of Technology, Madras, and received his M.S and Ph.D degrees in Computer and Information Sciences from the University of Delaware. respectively.

Projects

I have been involved in a number of exciting projects at BBN. Most of these have resulted in demonstrated prototypes. A brief summary of recent selected "large-ish" projects in my own words (and opinion, which may differ from person to person) is given below.  Click on the title for the project web page (in most cases not very up to date).


PIRANA (Adaptive Dynamic Open Source Intelligent Team) [2007-]

The goal of the PIRANA project is to build a large-scale MANET with very inexpensive nodes (by military standards), with up to four transceivers, each of which is highly frequency agile, and has a spectrum detector and simple MIMO capability. PIRANA will support multi-radio, multichannel dynamic spectrum access, unicast and multicast traditional and disruption tolerant routing and content based access. I am leading the Medium Access Control (MAC) part of this very large project which is funded under the DARPA Wireless Network After Next (WNAN) program. We are working towards a 40 radio demonstration in Dec 2008, a 100 radio demonstration in Dec 2009, and a 1000 radio demonstration in Dec 2010.


ADROIT (Adaptive Dynamic Open Source Intelligent Team) [2005-2007]

The goal of this project was to accelarate the use of software radios for wireless network research. As any frustrated  (mobile ad hoc) wireless network researcher can tell you, the lack of flexibility in radio firmware severely limits experimentation with MAC layer protocols. You have to live with what is in the radio (typically 802.11 for most researchers). ADROIT attempted to change that by significantly enhancing the open source GNU Radio software to send/receive packets, control parameters and many basic radio functions, except in software. The ADROIT system consists of the GNU USRP hardware, RX and TX chain software, a MAC framework for easy development of MAC protocols which is currently instantiated to a simple baseline, subnet layer routing based on Hazy Sighted Link State routing, and the standard IP stack above it. Unfortunately, this project did not run to its eventual completion for a number of reasons unrelated to the project itself. However, some groups have picked up whatever BBN did and are extending it. ADROIT was funded by DARPA IPTO and included BBN (prime), Kansas U., MIT, UCLA, and Eric Blossom as team members.


 SPINDLE (Disruption Tolerant Networking)  [2005 onwards]

This ongoing project is perhaps the largest funded effort on the topic of Delay/Disruption Tolerant Networking (DTN). The DTN idea, first put forth in this Internet Draft, seeks to provide data communications in so-called "intermittently connected" networks, where no end-to-end path may be available at any time. Conventional wired and MANET-based networks are designed around the assumption of having such an end-to-end path. A DTN utilizes "bundles" which can be persistently stored and handed over from node to node, so that as long as there is an end-to-end path "over time", the bundle can be delivered. SPINDLE is building on the DTNRG working group's work, helping define a flexible architecture, researching new adaptive routing algorithms, the use of content-based access in this environment, and late binding of names. My own work here is on routing for DTNs, from theory to design to experimentation. We began by asking two questions: In what way is a DTN fundmentally different from a MANET, and does it need fundamentaly different routing mechanisms? Can we design a simple, yet efficient DTN routing mechanism that works well in both MANETs and DTNs? Our state of research is represented by two recent conference papers, a formalism, and a protocol called PREP. SPINDLE is funded by DARPA ATO.



X-MAC (Medium Access Control for XG) [2003-2005]

XG stands for neXt Generation Communications -- a DARPA program targeted toward dynamic or opportunistic spectrum access. This basically means a radio will snoop around over a wide range of spectrum (yes, including those licensed to other "primaries") and find "holes" in it and use them without interfering with the primaries. The motivation for such access comes from the fact that large portions are spectrum are allocated but never used. As part of the X-MAC project, we did a lot more than just a MAC. We led the vision for this whole program, which encompasses not only "spectrum agility" but also "policy agility", that is, a radio must be able to understand policies in some language (which we developed too), and change its access behavior accordingly. For example, we don't want to mess around with radio astronomy or public safety bands, even if those bands changed! Our framework made this possible. Our vision is described here.  We also built a very high fidelity simulation platform for evaluating a range of mechanisms to sense and access holes, and share it using a MAC.  This tech report gives details on some of our findings. More details on X-MAC and the follow on project called XAP (XG Architecture and Protocols) can be found here. X-MAC and XAP were funded by DARPA ATO. BBN had no subcontractors on this.



UDAAN (Utilizing Directional Antennas for Ad Hoc Networking) [2000-2003]

Before we started this project, most if not all work in MANETs used omni-directional antennas. Our preliminary investigations documented in this paper showed that directional antennas have a huge potential for improving performance. As part of UDAAN we developed a directional MAC protocol and neighbor discovery based on beamforming. We integrated this with routing and other technologies from previous projects and implemented the system on COTS hardware (modem that could house our MAC). The MAC was based on CSMA/CA but quite different from 802.11. It used directional carrier sensing and power aware NAVs. The design worked with both steerable and fixed beamforming. Along with a major defense contractor, we demonstrated our system using a mobile network of 20 SUVs equipped with fixed directional antennas. This project demonstrated, for the first time, a complete MANET system of non-trivial size that exploited directional antennas to give major performance improvement, inventing several novel techniques along the way. Part of our work is documented in this paper. UDAAN was funded by DARPA ATO and included BBN (prime), University of Illinois Urbana-Champaign, Stow Research. 



DAWN (Density- and Asymmetry Adaptive Wireless Network)

In many Mobile Ad Hoc Networks, there is a tension between resource consumption (spatial reuse, battery power, stealthiness) on one hand, and connectivity on the other. For example, increasing the transmit power of all nodes increases connectivity but may result poor spatial reuse. The DAWN project looked at topology control -- self-organizing, distributed algorithms for adaptively controlling the transmit powers of nodes so that the network is connected or biconnected while minimizing the maximum or average power. We also studies link asymmetry and routing in the presence of unidirectional MANET links, and jammer evasion. We built a testbed based on radios from Rooftop Networks (now Nokia Wireless Routers). This was the first real-life implementation of topology control. Our seminal work, presented in this paper, has been followed by hundreds of papers making topology control a research area unto itself. DAWN was funded by DARPA as part of its Global Mobile Information Systems (GloMo) program.


Selected Publications (Journal)

  1. J.B.D. Cabrera, R. Ramanathan, C. Guitierrez, R. Mehra, "Stable Topology Control for Mobile Ad Hoc Networks", IEEE Communications Letters, Vol. 11, No. 7,  July 2007, pp. 574-576.

  2. R. Ramanathan, J. Redi, C. Santivanez, D. Wiggins, S. Polit "Ad Hoc Networking with Directional Antennas: A Complete System Solution", Journal of Selected Areas in Communications, Jan. 2005.

  3. R. Ramanathan, J. Redi, "A brief overview of ad hoc networks: challenges and directions", IEEE Communications Magazine Vol. 40, Issue 5, May 2002

  4. S. Ramanathan, "A Unified Framework and Algorithm for Channel Assignment in Wireless Networks," Wireless Networks 5, (1999), pp 81-94.

  5. S. Ramanathan and M. Steenstrup, "Hierarchically-organized, multihop mobile networks for multimedia support," ACM/Baltzer Mobile Networks and Applications, Vol. 3, No. 1, pp 101-119.

  6. S. Ramanathan and M. Steenstrup, "A survey of routing techniques for mobile communications networks," ACM/Baltzer Mobile Networks and Applications, Vol. 1, No. 2, pp. 89-103.

  7. S. Ramanathan, "Multicast tree generation in networks with asymmetric links," IEEE/ACM Transactions on Networking, Vol. 4, No. 4, pp. 558-568.

Selected Publications (Conferences)

  1. R. Ramanathan, F. Tchakountio, "Channel Access over Path Segments for Ultra Low Latency MANETs," Proc. IEEE MILCOM 2007, Orlando, October 2007.

  2. R. Ramanathan, P. Basu, R. Krishnan, "Towards a Formalism for Routing in Challenged Networks," Proc. CHANTS 2007, Montreal, September 2007.

  3. R. Ramanathan, R. Hansen, P. Basu, R. Hain, R. Krishnan, "Prioritized Epidemic Routing for Opportunistic Networks," Proc. MobiOpp 2007, Puerto Rico, June 2007.

  4. R. Ramanathan, "Challenges: A Radically New Architecture for Next Generation Mobile Ad Hoc Networks", Proc. ACM MOBICOM 2005,  Cologne, Germany, August 2005.

  5. C. Santivanez, R. Ramanathan, C. Partridge, R. Krishnan, M. Condell, S. Polit, "Opportunistic Spectrum Access: Challenges, Architecture, Protocols," in Proc. ACM WICON 2006, Boston, 2006.

  6. E.L. Lloyd, R. Liu, M.V. Marathe, R. Ramanathan, S.S. Ravi, "Algorithmic Aspects of Topology Control Problems for Ad Hoc Networks," Proc. ACM MOBIHOC 2002,  Lausanne, Switzerland, June 2002.

  7. J. Redi, R. Ramanathan, "Utilizing Directional Antennas for Ad Hoc Networking," Proc. IEEE MILCOM 2002,  Anaheim, California, USA, 2001 (Received Best Paper Classified Paper award).

  8. R. Ramanathan, "On the performance of ad hoc networks using beamforming antennas", Proc. ACM MOBIHOC 2001,  Long Beach, California, USA, October 2001.

  9. C. Santivanez, R. Ramanathan, I. Stavrakakis, "Making Link-State Routing Scale for Ad Hoc Networks", Proc. ACM MOBIHOC 2001,  Long Beach, California, USA, October 2001.

  10. R. Ramanathan, "Making Ad Hoc Networks Density Adaptive", Proc. IEEE MILCOM 2001,  Tysons Corner, Virginia, October 2001.

  11. F. Tchakountio, R. Ramanathan, ""Tracking Highly Mobile Endpoints",  Proceedings of ACM Workshop on Wireless Mobile Multimedia (WoWMoM), July 2001, Rome, Italy.

  12. R. Ramanathan and R. Hain, "Topology Control of Multihop Radio Networks using Transmit Power Adjustment", Proc. IEEE INFOCOM,  Tel Aviv, Israel, Mar 2000.

  13. R. Krishnan, R. Ramanathan and M. Steenstrup, "Optimization Algorithms for Large Self-Structuring Networks, IEEE INFOCOM '99, New York, USA, March 1999.

  14. K. Kasera and S. Ramanathan, "A Location Management Protocol for Hierarchically Organized Multihop Mobile Networks," in Proceedings of the IEEE ICUPC, San Diego, 1997.

  15. S. Ramanathan, "A Unified Framework and Algorithm for (T/F/C)DMA Channel Assignment in Wireless Networks," in Proceedings of the IEEE INFOCOM 1996, Kobe (Japan), 1997

  16. S. Ramanathan, "Multicast Tree Generation in Networks with Asymmetric Links," in Proceedings of the IEEE INFOCOM 1996, San Francisco, CA, 1997 (Received Best Paper Award from among 590 submissions) 

  17. S. Ramanathan, "Scheduling Algorithms for Multihop Radio Networks," in Proceedings of ACM SIGCOMM, 1992, Baltimore, MD, 1992 (Received Best Student Paper Award)

Book Chapters, Tech Reports and Misc

  1. R. Ramanathan, F. Tchakountiou, "Ultra Low-Latency MANETs", BBN Technical Memorandum TM-2023

  2. XG Working Group "The XG Vision, Request for Comments, Version 2.0.

  3. R. Ramanathan, "Antenna Beamforming and Power Control for Ad Hoc Networks," in Mobile Ad Hoc Networking, S. Basagni et al. (eds), IEEE Press/Wiley, 2004.

  4. PhD Thesis: "Scheduling Algorithms for Multihop Radio Networks", Dept. of Computer and Information Sciences, University of Delaware. Advisor: Prof. Errol Lloyd. (Received the Alan Colburn Prize for Best 1992 Dissertation in Engineering and Sciences at the University of Delaware)

Selected Patents

Tutorials

Along with Mineo Takai and Nitin Vaidya, I presented a tutorial at the ACM MobiHoc 2003 Conference, entitled "Directional Antenna Systems in Ad Hoc Networks". My parts of the tutorial are here: Part 1 of the tutorial, and Part 5 of the tutorial. Part 2 and 4 were given by Mineo Takai and part 3 was given by Nitin Vaidya. You can access them by going to their websites.

Professional Services