Networking Over White Spaces (KNOWS)

Established: December 19, 2008

The next generation of wireless networks will include software defined radios, cognitive radios, and multi-radio systems which will co-exist harmoniously while operating over a very wide range of frequencies. Under the umbrella of the KNOWS project we are revisiting “classical” wireless networking problems and designing new solutions that incorporate and build upon recent advances in software and hardware technologies for networking over the recently opened white spaces spectrum.

Brief Description

The WhiteFiService APIs and web front-end can be accessed by clicking here.
Check out deployment pictures by clicking here.

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 MCham, 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.

  • 2009:




  • We have deployed base stations on two different buildings within the Microsoft campus in Redmond, WA. These base stations operate over the white spaces, and provide coverage to nearly all of campus. We have also deployed a mobile client on a Microsoft shuttle, which bridges packets from white spaces to Wi-Fi within the shuttle, thereby providing Internet connectivity to existing laptops. As part of the deployment, we have also built a research prototype of a white space database, which is hosted at:

    Deployment History

    August 14, 2010. Demonstrated shuttle network and techniques on avoiding MIC interference to FCC Chairman Genachowski and Managing Director Steven VanRoekel.

    April 29, 2010. Demonstrated shuttle network and techniques on avoiding MIC interference to a delegation from the FCC. The ex-parte is available here.

    March 10, 2010. Demonstrated shuttle network to a delegation from Infocomm Development Authority of Singapore (IDA)

    February 2, 2010. Demonstrated shuttle network to a delegation from Agência Nacional de Telecomunicações Brazil (ANATEL) Brazil including Max Martinhão, the General Manager for Radio Frequency Spectrum in Brazil

    January 14, 2010. Demonstrated network to a delegation from Fisher Communications, Inc. (KOMO TV-ABC & KUNP TV—Univision) including Senior Vice President of Operation Robert I. Dunlop

    January 11, 2010. Demonstrated network to a delegation from the State Administration of Radio, Film, and Television (SARFT) China including Deputy Director General of Science and Technology China, Mr. Wang Lian

    Octber 22, 2009. Demonstrated network to a delegation 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. (Click here for deployment pictures)

    Technologies tested 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

  • Community Service


    • 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

    University & Conference Support

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

    We made a presentation to the FCC Chairman Genachowski when he visited us on Microsoft’s Redmond Campus on August 14, 2010 to see our White-Fi Deployment — “White Space Networking – Status Update

    For a technical description, you can download talks we have given in different venues worldwide:

    We have delivered several talks and lectures on the topic of White Space and Cognitive Networking around the world.




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

    We have also demonstrated our white space system to spectrum regulators from various countries, including delegations from:

    • Federal Communications Commission (FCC) Chairman Genachowski and Managing Director Steven VanRoekel on August 14, 2010 and separately to another delegation on April 29, 2010
    • Infocomm Development Authority of Singapore (IDA) on March 10, 2010
    • Agência Nacional de Telecomunicações Brazil (ANATEL), Brazil including Max Martinhão, the General Manager for Radio Frequency Spectrum in Brazil on February 2, 2010
    • State Administration of Radio, Film and Television (SARFT), China including Deputy Director General of Science and Technology China, Mr. Wang Lian on January 11, 2010
    • Telecom Regulatory Authority of India (TRAI), including its chairperson Dr. J. S. Sarma on October 22, 2009
  • Sample Press Articles



Portrait of Ranveer Chandra

Ranveer Chandra

Managing Director, Research for Industry Partner Manager, Networking Research CTO, Agri-Food

Portrait of Thomas Moscibroda

Thomas Moscibroda

Distinguished Engineer Azure Core

Portrait of Victor Bahl

Victor Bahl

Technical Fellow & Chief Technology Officer, Azure for Operators

Portrait of Tusher Chakraborty

Tusher Chakraborty

Research Software Engineer II