Brief Description

The white spaces spectrum is fundamentally different from the ISM bands where Wi-Fi operates along three main axes. First, it exhibits spatial variation since a channel available at one node might be occupied by a primary user (TV, microphone) at another node in the network. Second, the spectrum is not contiguous. Some channels might be occupied by primary users hence causing the spectrum to be fragmented. Finally, there is temporal variation since an available spectrum might be occupied at a later time by a primary user, e.g. wireless microphone.

Given these challenges, we have researched several techniques to form networks over this part of the spectrum. In the first version of KNOWS we introduced the concept of Time Spectrum Blocks (TSB) as the fundamental unit over which two nodes could communicate.  We designed a control-channel based medium access control protocol, called CMAC, for enabling nodes with different spectrum views to access the medium. Associated with CMAC we proposed and evaluated an algorithm, called bSMART, for efficiently allocating the spectrum to different contending nodes.

In the second version of KNOWS, we looked at the problem of setting up a base station in the white spaces spectrum. In this system, called WhiteFi, we eliminated the need for a dedicated control channel. In addition, we proposed a new technique, called SIFT, that enables nodes to rapidly discover base stations operating at different center frequencies using different channel widths by analyzing signals in the time domain. We proposed and evaluated a new metric, called MChan, using which the base stations choose the "best" chunk of the spectrum to operate on, where the spectrum chunk can span multiple channels. We have prototyped this system on Windows.

Deployment History

Octber 22, 2009. Demonstrated network to a delgation from the Telecom Regulatory Authority of India (TRAI)  including Chariperson Dr. J. S. Sarma.

October 16, 2009.  Reached a significant and historic milestone! Successfully deployed WSN between buildings on Microsoft's Redmond Campus.  To the best of our knowledge this is the first urban WSN. 

Technologies being testing include:

• An opportunistic data network in the UHF and VHF bands
• Channel occupancy database service with real-time Longley-Rice RF propagation modeling over NASA Terrain Data
• Coexistence with wireless microphones
• Handling mobile clients
• Varying channel widths to accommodate varying needs of the application

July 15, 2009  Outdoor tests succeeded. Achieved communications with 1% BER between white spaces devices transmitting at 100 mW and separated by more than 0.5 Km.  Tests proved that enterprise wireless network coverage can be significantly enhanced with a combination of Wi-Fi & White-Fi.

July 6, 2009 Received FCC experimental license to test a deployment of a white space network.

June 30, 2009 Version 1 of our channel occupancy database came online

January 15, 2009 Demonstrated a fast channel discovery algorithm (a.k.a SIFT) and an efficient channel assignment algorithm (a.k.a. MCHAM) to achieve high throughput in a WSN

October 23, 2008 Happy birthday! the first white space network (WSN) is alive and kicking!  Successfully demonstrated a network of five nodes commuicating over the UHF white spaces. The network was built in our lab using the KNOWS hardware operating at 1 mW. We demonstrated (a) wireless microphone sensing, (b) Opportunistic networking, and (c) Variaible channel width  

Interns:

2009: Rohan Murty (Harvard), George Nychis (CMU), Hariharan Rahul (MIT), Xiaohui Wang (CMU)
2008: Rohan Murty (Harvard)
2007: Ramya Raghavendra (UCSB)
2006: Yuan Yuan (UMD)

Community Service

Outreach

• In June 2008 we organized an MSR networking summit on Cognitive Wireless Networking. The participants included experts from academia and industry in various fields of Computer Science and Electrical Engineering. More details can be found by clicking below:

Professional Service

• PC Co-Chair, ACM CoRoNet 2009
• Steering Committee Member, IEEE DySPAN (since inception in 2005)
• Patron Chair,  IEEE DySPAN 2010
• Program Committee Member, IEEE DySPAN 2005, 2007, 2008, 2010
• Guest Editor, IEEE Journal on Selected Areas in Communications, Special Issue on Advances in Cognitive Radio Networking and Communications (Submission date: Dec. 1, 2009; Publication 1st Quarter 2011)

University & Conference Support

• Rice University, White Space Mesh Networks
• University of Wisconsin, Spectrum Leasing Architecture
• IEEE DySPAN 2005, 2007 & 2008

Presentations

You can download our August 31, 2009 keynote on "White Space Networking - Past, Present, and Future" (PPT, 19.35 MB)

We have delivered several high-profile keynote talks and distinguished lectures on the topic of White Space and Cognitive Networking around the world.  Here are some of the venues where we have delivered some keynotes:

Keynotes:

• The 7th IEEE/IFIP International Conference on Embedded and Ubiquitous Computing (EUC 2009), Vancouver, Canada, August 31, 2009 (Speaker: Bahl)
• The Fifth Euro-NGI Conference on Next Generation Internet Networks, July 2, 2009 (Speaker: Bahl)
• The Sixth International Conference on Wireless On-demand Network Systems and Services, Salt Lake City, Utah, February 2, 2009 (Speaker: Bahl)
• Workshop on Wireless Broadband Access for Communities and Rural Developing Regions, December 11, 2008 (Speaker: Bahl)
• Second IFIP International Symposium on Wireless Communications and Information Technology in Developing Countries, October 7, 2008 (Speaker: Bahl)
• IEEE Secon SDR Workshop, June 2008 (Speaker: Chandra)
• MSR’s Cognitive Wireless Networking Summit, Snoqualmie, Washington, USA, June 4, 2008 (Speaker: Bahl)
• First International Workshop on Cognitive Dynamic Systems and Their Applications 2008, May 27, 2008 (Speaker: Bahl)
• Intel's Communications Internal Senior Leadership Conference (ICOMM 2008), April 9, 2008 (Speaker: Bahl)
• The Third International Conference on Communication System Software and Middleware (COMSWARE 2008), January 8, 2008 (Speaker: Bahl)
• The Ninth International Conference on Distributed Computing and Networking (ICDCN), January 6, 2008 (Speaker: Bahl)
• IEEE DySPAN 2007 (Speaker: Khaki)

Lectures:

• Illinois Wireless Summer School, August 4, 2009 (Urbana, Illinois, USA)
• Microsoft Research India Summer School on Networking 2009, June 18, 2009 (Bangalore, India)
• SDForum Emerging Technology SIG, February 11, 2009 (Palo Alto, California, India)
• Workloads of the Future Workshop, GSRC UC Berkeley, November 2007
• Illinois Wireless Systems Symposium 2007

Seminars:

• Joint CS/ECE Colloquium, Purdue University, April 2009
• Networking Seminar, University of Washington, February 25, 2009
• Computer Science Department Seminar, University of California Los Angeles, February 10, 2009
• Networking, Communications and DSP Seminar, UC Berkeley, February 2008
• Colloquium, Boeing Phantom Labs, November 2007

FCC Panels

We were invited by the FCC to particpate on a few panels.

• Panel on "Broadband Spectrum: A Looming Crisis?" FCC's National Broadband Plan -- Field Hearing on Mobile Broadband, San Diego, CA, Oct. 8, 2009 (Participant: Bahl) {Click to read our talking points}
• Panel on "Innovating in Spectrum Access—Technological Advances and Other Approaches to Facilitate More Productive Spectrum Use" FCC’s National Broadband Plan -- Spectrum Workshop, Washington D.C. Sept. 17, 2009 (Participant: Chandra)

Sample Press Articles

• WhiteFi: Broadcasting wireless Internet over TV airwaves, Nick Eaton, Seattle Post Intelligencer, August 31, 2009
• WiFi on steroids? First “WhiteFi” prototypes hit testing stage, Nate Anderson, Ars technica, August 27, 2009
• Microsoft 'White-Fi' to solve interference worries in white space, Marguerite Reardon, cnet.com, August 19, 2009
• Wi-Fi via White Spaces, Erica Naone, MIT’s Technology Review, August 18, 2009
• SDF White Space Networking DJCline.com, February 13, 2009
• Revisiting old technology could bring broadband to masses by Barry Bateman, Pretoria News, Tshwane, South Africa, October 9, 2008 (also available here: IOL Technology)
• Inside Microsoft Research: The Cutting Edge on Display by Nancy Gohring, IDG News, March 4, 2008 (Appeared on PC World, The Standard, etc.)