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RF Situational Awareness with Low-Cost Signal Samplers

Description:

TECHNOLOGY AREA(S): Sensors 

OBJECTIVE: Develop and demonstrate a low SWaP-C network of RF spectrum awareness monitors that are able to navigate within, sense, share, and collectively characterize the local RF environment. 

DESCRIPTION: Global positioning system (GPS) and Global Navigation Satellite System (GNSS) based receivers tasked to operate in urban areas do so in an increasingly densely populated RF environment. Due to the availability of low-power consumer-level jamming devices, and the complex reflection/attenuation nature of urban environments, the RF spectrum can vary widely both temporally and spatially. Recently, extremely low-cost digital video broadcast decoding devices containing the Realtek 2832U demodulator chip were found to allow access to raw inphase/quadrature (I/Q) 8-bit sample streams [1]. Capable of tuning ~50-1800 MHz, these sub-$20 USB dongles enable software receiver processing of significant portions of the radio-navigation bands. A real-time GPS navigation solution has been demonstrated using this minimal hardware [2].Utilizing an array of these sensing nodes will allow for a characterization of the local RF environment including localizing interference sources. Although each individual node captures and process only 2 MHz of spectrum [3] instantaneously, their low-cost and frequency agility, schemes of sweep patterns and/or multiple co-located nodes can be used to effectively cover large portions of spectrum. Spectrum snapshots (e.g. Fast Fourier Transform results or small amounts of raw signal samples) and location data can be conveyed to a master node in order to synthesize the RF environment characterization. In such a system, the various SatNav constellation band plans can be highlighted and selected for navigation based on sensed spectrum conditions. Both ground and airborne nodes should be considered for this effort. 

PHASE I: Study of algorithms and approaches that characterize the RF environments from distributed, frequency agile, narrow-band nodes. This includes determining types and amounts of data required to be transferred from multiple sensing nodes to a master node. Also required is a survey of RF propagation in urban areas to determine number of nodes required for situational awareness. 

PHASE II: Develop a test plan and demonstrate RF environment characterization using a constellation of prototype nodes in a dense, urban area. Localize several strong signal sources for which location truth can be determined. Deliver RF sensing solution including communication infrastructure to government. Document design and test results in a final report. 

PHASE III: Complete integration of receiving nodes and transmitting elements with custom circuit layouts. Ruggedize system, analyze power requirements, and determine suitable portable power sources. 

REFERENCES: 

1. http://spectrum.ieee.org/geek-life/hands-on/a-40-softwaredefined-radio; 2. C. Fernández-Prades, J. Arribas, P. Closas, Turning a Television Into a GNSS Receiver, Proceedings of ION-GNSS+ Conference, September 2013, Nashville, TN. (http://ion.org/gnss/abstracts.cfm?paperID=405); 3. http://sdr.osmocom.org/trac/wiki/rtl-sdr; 4. Sarang Thombre, M. Zahidul H. Bhuiyan, Patrik Eliardsson, Björn Gabrielsson, Michael Pattinson, Mark Dumville, Dimitrios Fryganiotis, Steve Hill, Venkatesh Manikundalam, Martin Pölöskey, Sanguk Lee, Laura Ruotsalainen, Stefan Söderholm, Heidi Kuusniemi

KEYWORDS: GPS, Software Radio, Spectrum Sensing, Situational Awareness 

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