An SwRI-developed tool enables signal analysts to scan an area's ...

A GoodScoutmAn SwRI-developed tool enables signalanalysts to scan an area’s radio spectrumand locate signal sources.By James H. NixonTourists who find themselvesin an exotic locale typicallyspend some time taking in thelocal sights and sounds to get abetter sense of the place and its people.Likewise, before military specialistscan operate safely in some remote andpotentially hostile part of the world, theyalso need a sense of the local environment’selectronic sights and sounds.An almost universal facet of moderncommunications is the unseen and silentchatter of wireless communications,both friendly and hostile. Unlike normalbroadcast radio or TV stations, thesources of this chatter don’t advertisetheir broadcast frequencies. It is up tosignal intelligence, or SIGINT, specialiststo detect the signals, locate theirsource and interpret their significanceto the mission at hand. Engineers atSouthwest Research Institute (SwRI)have been conducting research inantennas and geolocation for morethan 60 years. A newly developedsystem — dubbed Scout — is aportable, yet highly capable systemfor supporting radio frequency (RF)survey teams deploying to unchartedgeographic regions.Reading the signalsScout comprises a family ofwideband radio frequency survey anddirection-finding systems that operatein the high, very high and ultra-high(HF, VHF and UHF) frequency ranges.It provides a view into the types ofcommunications transmissions employedin the geographic region of interest. Ifa network of Scouts is deployed, thelocations of these transmitters can bedetermined using direction findingand radiolocation techniques. Suchsurveys are an important first step in6 Technology Today • Spring 2013

Photo courtesy DODD018916-2778James H. Nixon is director of the SIGINT SolutionsDepartment in SwRI’s Signal Exploitation and GeolocationDivision. He leads the design, development and deploymentof modern radio communications intelligence solutions. Hisexpertise includes wideband and narrowband signalacquisition and direction-finding systems.One aspect of the Scout system is an SwRI-developedfunction known as “Prospector,” whose user interface allowsthe operator to select from a stored display of radio frequencyactivity over the past 24 hours.understanding an adversary’s modesof communication and preparingmilitary and intelligence sources for theelectronic battlefield.SIGINT is derived from electronicsignals and systems used by adversariesfor communications systems, radarsand weapons systems. It provides a vitalwindow into the capabilities, actions andintentions of adversaries. A category ofSIGINT called communications intelligence,or COMINT, focuses on exploitingan adversary’s communications signals.These types of signals include voice,Morse code and many digitally codedsignals, such as those used by cellphones and data modems.Scout includes a radio antenna,special radio signal tuners and a numberof high-performance servers similar tothose used by information technologyTechnology Today • Spring 2013 7

An operator can select a single RF signal (lefttop photo) for analysis by Scout software(right bottom photo).D019013data centers and for scientific research.Once the radio spectrum is digitallyconverted to ones and zeros by thespecial wide-bandwidth radio receiverhardware, the digitized radio spectrum istransferred over a high-capacity local areanetwork to an array of computer servers.SwRI-developed software running onthese servers performs a number ofsignal processing steps needed to takethe raw RF environment and transformit to useful information. The first step inthis process is to automatically detectsignal events occurring anywherewithin the frequency coverage ofthe system. Once such energy hasbeen detected, the system builds asoftware radio receiver that filtersand isolates the new energy into anarrow-band channel.Adding a sense of directionThe Scout system canconstruct hundreds of thesechannels simultaneously. Oncethe new energy has been channelized,it is routed to one of manymission prosecutor softwareservices. Within these missionprosecutors,the channelis automaticallyanalyzedby SwRIdevelopedmodulation recognition software todetermine the general type of modulationemployed and ascertain whether theenergy comes from a voice, Morse codeor digital modem signal, and what kindsof digital modulation techniques arebeing employed. Additional processing isapplied to digitally modulated signals tofurther refine the identification process,ultimately resulting in a determination ofthe specific type of modem employed,and in some cases, the underlying dataprotocols in use.D019028Scout operates across the RFspectrum, as shown in this usageallocation chart.8Technology Today • Spring 2013

If the digital signal is recognizedby the system, it is thendemodulated and decoded toextract the underlying data beingcommunicated. Even signals thatare not part of the Scout signal-ofinterestlibrary are catalogued. Thisinformation can help the userdiscover new signals of interest. Ifthe unit is equipped with theradio direction-finding option, aline of bearing is computed fromthe Scout’s location to the radiotransmitter. Moreover, a numberof Scouts can be networkedtogether and the various lines ofbearing can be triangulated so thatthe radio transmitter’s estimatedlocation can be computed.The final results are stored in adatabase. Web browser-basedtools are provided with the systemto allow any authorized user onthe Scout network access to thecollection results.Record now, playback laterScout also supports manualsearch and user-driven signaldiscovery operations. Theautomatic RF environmentcataloguing operation requiresthat the user already know manydetails about the signals ofinterest. In many cases the typesof signals are known, and the automaticsearch capability will confirm that theyexist in the geographic region of interest.However, if an adversary deploys anewly invented signal waveform, theautomatic system may not identifythose emissions or characterize them inenough detail to assist the user. For thesesituations, the SwRI team developeda graphical user interface (GUI) tool,called Prospector, which is deployedwith Scout to enable the operator tovisualize the RF environment and searchfor interesting and unique signal activity.This is accomplished by storing thelast 24 hours of RF spectrum on Scout’sinternal hard drive. An operator who seesan interesting signal event can simplydraw a box around the signal and Scoutconstructs a software radio on the spotthat channelizes the signal and presentsthe waveform in another SwRI-developedtool called Tass. Tass provides a multitudeof signal analysis tools that enable thebreakdown of signal structures, includingdemodulation of fundamental modulationschemes. Scout’s ability to store theD018916-2860entire radio-frequency environmenton disk and channelize any part of thespectrum at will is akin to having “TiVo®on steroids” — except that instead ofstoring only your favorite channels, Scoutstores everything on the RF spectrum,enabling the operator to reconstruct anykind of signal event after the fact.Combining capabilities of earlier systemsOriginally developed to replacea now-retired system, Scout not onlyexceeds its predecessor’s capabilities inautomatic detection of known signals ofinterest, but also has a fully integrateddirection-finding capability. The waysignals are described in Scout is compatiblewith U.S. Department of Defenseformats, enabling Scout to leverage newsignals as they are developed by others.Additionally, 24 hours of RF environmentstorage and a GUI enable the userto manually scour the last 24 hours ofRF activity and reconstruct and locate asignal event. This capability was previouslyperformed by other systems thatwere separate from Scout’s predecessor.An SwRI engineer prepares aScout system for operation. Theunit is much more compact thanearlier systems.Scout does a job thatpreviously required a numberof systems from multiplevendors. By combiningautomatic search and signalidentification functionswith a manual search tool,Scout reduces the hardwareresources required to supportRF survey missions and alsoreduces the cost.Scout is based on commerciallyavailable, high-performanceservers widely used indata centers across the globe. All of thesignal processing required to supportthe operating modes consists of softwarerather than expensive special-purposeprocessing components such as thosedeveloped for the aerospace industry. Thiscombination of commodity hardware anda software-defined framework gives Scoutan unprecedented level of scalability andexpandability. Leveraging the commercialcomputer market allows the use of thelatest computer technology with minimalrisk of obsolescence and keeps costseconomical, while taking advantage of thelatest breakthroughs in the globally drivencomputer market.Although Scout’s primary applicationis in support of U.S. and allied military, lawenforcement and intelligence communities,potential commercial applicationscould include surveying other types ofradio spectrum signals, such as electromagneticinterference emissions fromindustrial and power distribution sources.Questions about this article? ContactNixon at (210) 522-2619 orjim.nixon@swri.org.Technology Today • Spring 2013 9