KNOWS : Kognitive Networking Over White Spaces. Microsoft Research. White Spaces. Unused VHF & UHF Television Frequencies In the US, primarily the upper UHF "700-megahertz" band, covering television frequencies between 698 to 806 MHz (TV channels 52 to 69) The White Spaces Coalition
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Unused VHF & UHF Television Frequencies
In the US, primarily the upper UHF "700-megahertz" band, covering television frequencies between 698 to 806 MHz (TV channels 52 to 69)
The White Spaces Coalition
How should they discover
How should nodes connect?
Which mathematical tools should we use to reason about capacity & spectrum utilization?
How should the networked nodes react upon arrival of a primary user?
Which protocols should they use?
Version 1: Ad hoc networking in white spaces
Version 2: Infrastructure based networking (WhiteFi)
Version 3: Campus-wide backbone network (WhiteFi with Geolocation) -> Ongoing
Network Layer (TCP/IP)
location of TSB
(Spectrum Allocation Engine)
of TSB to map
app. req. to
Resource Allocation Matrix
Keeps track of
in overall throughput
...can we do better?
Raw (I, Q)
Determining the frequency and channel width of APs
UHF Rx Daughterboard
Serial Control Interface
Device Driver (Atheros)
SIFT: Signal Interpretation before Fourier Transform
How can Clients quickly find the AP…?
Tradition solution in Wi-Fi check all possible channels.
With SIFT, much faster algorithms become possible!
Jump cleverly across the spectrum, until you hit the AP
In most cases, SIFT takes 70% less time in discovery
Most benefit in rural areas
MSR lecture rooms have 20 microphones. Most mics on channels 46 or 47
Avg. over T
N pt. FFT
Worst case interference assumption is too conservative
100% detection at -114 dBm
Spectrum occupancy changes during the day and is location specific
Outdoor omni-directional VHF/UHF antenna (flat 2 dBi gain over 150 – 1000 MHz
Data packets over UHF
White Space Network Setup
Microphone testing in Anechoic Chamber
Subcarrier Suppression demo
Initial measurements & rudimentary database
Spectrum availability mirrors population density
Multi-core Software Radio Stack
Flexible RF Hardware
Latency critical radio control (AGC/PD)
Ongoing work in MSR Asia
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One possible detection solution: Beacons
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Lyrtech SFF SDR Development Platform
- Virtex-4 SX35 FPGA from Xilinx
- 0.2 – 1 GHz tunable , low-band RF
- Selectable bandwidth: 5 or 20 MHz
- Model based design
Allows us to carry out
PHY level innovations
DARPA’s XG program
Carnegie Mellon University, Virginia Tech., Berkeley Wireless Research Center, University of Kansas, Aachen, Rutgers, …
Conferences & Workshops
IEEE DySPAN, CrownCom, CogNet, CogWiNets, CWNets, …
Microsoft, Adaptrum, Motorola, Google, Phillips, HP, Dell, ….
"Multiuser detection can completely remove interference”
– Prof. Andrea Goldsmith (Stanford University)