© 2005 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or forcreating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtainedfrom the IEEE.For more information, please see www.ieee.org/portal/pages/about/documentation/copyright/polilink.html.MOBILE AND UBIQUITOUS SYSTEMSwww.computer.org/pervasiveMobiscopes for Human SpacesTarek Abdelzaher, Yaw Anokwa, Péter Boda, Jeff Burke, Deborah Estrin,Leonidas Guibas, Aman Kansal, Samuel Madden, and Jim ReichVol. 6, No. 2April–June 2007This material is presented to ensure timely dissemination of scholarly and technicalwork. Copyright and all rights therein are retained by authors or by other copyrightholders. All persons copying this information are expected to adhere to the terms andconstraints invoked by each author's copyright. In most cases, these works may not bereposted without the explicit permission of the copyright holder.20PERVASIVEcomputingPublished by the IEEE Computer Society■ 1536-1268/07/$25.00 © 2007 IEEEMobiscopes for Human SpacesAmobiscope is a federation of distrib-uted mobile sensors into a taskablesensing system that achieves high-density sampling coverage over awide area through mobility. Mobis-copes affordably extend into regions that static sen-sors cannot, proving especially useful for applica-tions that only occasionally require data from eachlocation. They represent a newtype of infrastructure—virtual inthat a given node can participatein forming more than one mobis-cope, but physically coupled tothe environment through carri-ers, including people and vehi-cles. Mobiscope applicationsinclude public-health epidemio-logical studies of human expo-sure using mobile phones andreal-time, fine-grained automo-bile traffic characterization usingsensors on fleet vehicles. Althoughmobility has proven critical inmany scientific applications, suchas Networked InfomechanicalSystems for science observato-ries,1we focus on the challengesand opportunities mobiscopespose in human spaces.Mobiscopes complement sta-tic sensing systems by address-ing the fundamental limitationscreated by fixed sensors. Systemdesigners can’t always place sensing devices withsufficiently high spatial density to accurately sample the field of spatially varying phenomena,making it impossible to satisfy the spatial band-limiting guarantees that traditional sampling cri-teria require. Covering large areas can be chal-lenging because of the need for long dwell times,the unavailability of wired power, the impracti-cality of battery replacement, the inability of anyentity to install devices across the entire area, andthe expense of purchasing and maintainingenough devices. Equally important, target sensortypes might be unavailable or unaffordable in theform of autonomous instruments, further moti-vating mobile, human-in-the-loop instruments.For example, city-scale air quality measure-ments—which typically use costly mass spec-trometers to measure pollutants—are expensivewhen using fixed-sensor infrastructures but couldbe substantially cheaper and could cover muchlarger areas if sensors were mounted on mobilenodes (for example, cars). This combination of application demand andincreasingly powerful wireless and sensing tech-nology suggests that it’s time to consider a generalarchitecture for mobiscopes. To understandwhat’s needed to build a unified system, we con-sider several broad classes of mobiscope. We dis-cuss common architecture challenges, existingsolutions, and major areas for future work.Classes of mobiscopesEarly mobiscopes arose directly from widelyavailable sensing modalities in networked devices.Examples include image sensors in mobilephones, GPS in phones and vehicles, and theincreasingly diverse telemetry available in vehi-cles. We consider these as representatives of twobroad categories of mobiscope.Mobiscopes extend the traditional sensor network model, introducingchallenges in data management and integrity, privacy, and networksystem design. Researchers need an architecture and generalmethodology for designing future mobiscopes.BUILDING A SENSOR-RICH WORLDTarek AbdelzaherUniversity of Illinois at Urbana-ChampaignYaw AnokwaUniversity of WashingtonPéter BodaNokia Research CenterJeff Burke and Deborah EstrinUniversity of California, Los AngelesLeonidas GuibasStanford University Aman KansalMicrosoft ResearchSamuel MaddenMassachusetts Institute of Technology Jim ReichPalo Alto Research CenterVehicular mobiscopesOne category is vehicular applicationsfor traffic and automotive monitoring,2where a subset of equipped vehicles sensesvarious surrounding conditions such astraffic, road conditions, or weather. Thesemobiscopes exploit the spatial oversam-pling often provided by dense vehicle traf-fic to produce useful information beforeall vehicles can send data. However, evenwhen vehicular instrumentation achievesnearly 100 percent market penetration,subsampling the data intelligently willprevent network congestion and savestorage and processing space. Initial probe applications have alreadybeen deployed commercially. For exam-ple, Inrix (www.inrix.com) uses anon-ymous GPS data to provide real-timetraffic measurements for freeways andlocal streets. Vehicular mobiscopes canquery for certain traffic types. For exam-ple, the EZCab application uses vehicle-to-vehicle communication to find avail-able taxi cabs.3The probe-car conceptcan extend to other applications, such asaugmenting the number of NavTeq orTeleAtlas vehicles used for street map-ping or increasing the update frequencyof Microsoft’s street-level imagery cap-ture for Virtual Earth. Probe cars canalso acquire high-density maps of road-ways and measure road conditions,weather, and pollution using sensorsbuilt into cars and phones. Handheld mobiscopesThe second emerging category ismobiscopes that use handheld devices.Coarse-grained location information caninform studies ranging from the healthimpact of exposure to highway toxins toan individual’s use of transportation sys-tems. Researchers have proposed auto-mated image and acoustic capture toprovide user feedback on diet, exercise,and personal interaction as well as toidentify and share real-time informationabout civic hazards and hotspots. Aninteresting example is civic participationduring a crisis, where individuals couldexercise a