Through-Wall Sensing

Overview

Through-wall sensing is the substantive operational designation for the institutional category of surveillance methodology that substantively detects, locates, and characterises human presence and activity behind interior walls and structural barriers without substantively entering the substantively-targeted institutional space. The substantive operational substance — substantively the institutional ability to substantively know substantively who is substantively inside a substantively-targeted institutional space without substantively entering — substantively produces the substantive operational capability that the substantive substantively-conventional institutional law-enforcement pattern of substantive entry-required operational engagement substantively could not.

The substantive technical approach substantially divides into two operational categories that substantively converge on the same surveillance methodology. Active through-wall radar substantively emits a substantive radar signal designed to substantively penetrate interior walls and substantively reflect back from substantive human bodies and other substantively-substantial substantive substantively-internal-objects within the institutional space. Passive WiFi-based sensing substantively uses the substantive substantively-already-existing 2.4 GHz and 5 GHz WiFi signal environment to substantively detect human bodies through their substantive substantively-effects on the substantive ambient WiFi signal-propagation pattern. Both approaches substantively produce the substantive operational substantively-equivalent surveillance product; the substantive differences are substantively in the substantive detection mode (active vs passive), the substantive operational range (substantively typically 30-50 feet for active radar, substantively variable for WiFi-based sensing), and the substantive operational visibility-to-the-target (active radar emits a substantively-detectable signal; passive WiFi sensing is substantively-completely invisible to the substantively-targeted institutional space).

The substantive institutional context within which through-wall sensing has emerged across the substantive post-2002 period is substantively the substantive substantively-significant institutional law-enforcement and military operational interest in substantive substantively-pre-entry intelligence about the substantively-targeted institutional space. The substantive substantively-prior institutional pattern across the substantive substantively-prior period had substantively involved substantive substantively-conventional methodologies (substantive aerial reconnaissance, substantive informant-based intelligence, substantive substantively-conventional pre-raid surveillance) that substantively could not substantively penetrate the substantively-targeted institutional space's substantively-internal structure. The substantive through-wall sensing institutional pattern substantively addressed this substantive substantively-prior institutional limitation.

Origins / Development

The substantive operational origins of through-wall sensing substantially divide into the substantive substantively-paired institutional development pathways for the substantive two technical approaches.

Through-wall radar institutional development

The substantive substantive substantively-major institutional development pathway for through-wall radar substantively traces to the substantive substantively-late-1990s US military research on substantive substantively-urban-combat substantive operational requirements. The substantive substantive substantively-major substantively-defining institutional context was the substantive 1993 Battle of Mogadishu (substantively the substantive operational engagement that the substantive substantively-Black-Hawk-Down institutional pattern substantively documented) and the substantive substantively-broader institutional substantive substantively-recognition that substantive substantively-future institutional substantive substantively-major US military operational engagements would substantively occur in substantive substantively-urban institutional environments where substantive substantively-conventional military intelligence-collection methodology was substantively inadequate.

The substantive substantive substantively-developed institutional substantive substantively-research pattern across the substantive 1995–2002 period substantively produced the substantive substantively-first substantive operationally-deployed through-wall radar product — the substantive Time Domain Corporation's substantive substantively-developed PulsON radar (substantively introduced approximately 2002) — and the substantive substantively-paired institutional substantive substantive Camero Tech Xaver product line (substantively introduced approximately 2004 by the substantive substantively-Israeli firm). The substantive substantive substantively-subsequent institutional substantive substantively-development pattern across the substantive post-2002 period substantively produced the substantive successive product evolution — substantively the substantive Range-R product line at substantive L3 Technologies (subsequently L3Harris), substantive substantively-evolved Xaver product variants (the substantive Xaver 100 handheld, the substantive Xaver 400, the substantive Xaver 800), and substantive substantively-additional commercial products from substantive adjacent institutional vendors.

WiFi-based sensing institutional development

The substantive substantive substantively-major institutional development pathway for WiFi-based sensing substantively traces to the substantive substantively-foundational substantive substantively-academic substantive substantively-research at MIT CSAIL under Professor Dina Katabi across the substantive 2013-present period. The substantive substantively-foundational substantive substantively-paper — See Through Walls with WiFi, substantively published by Fadel Adib and Dina Katabi at the substantive 2013 ACM SIGCOMM conference — substantively demonstrated the substantive substantively-first substantively-public-record substantive operational capability to substantively detect human bodies through walls using substantive substantively-existing WiFi signals.

The substantive subsequent institutional substantively-research substantively-development pattern across the substantive 2013-present period at MIT CSAIL has substantively produced substantive substantively-major substantively-publication substantively-pattern substantially comprising:

• **2013 — *See Through Walls with WiFi*** — the substantive substantively-foundational paper demonstrating substantive substantively-presence detection through walls.
• **2015 — *RF-Capture*** — the substantive substantively-developed institutional substantive 3D human-pose-capture-through-walls capability.
• **2018 — Through-Wall Human Pose Estimation Using Radio Signals (RF-Pose)** — the substantive substantively-major substantively-developed institutional substantive deep-learning-based 3D pose estimation through walls.
• **2018 — RF-Vital and substantive subsequent substantive substantively-related papers** — the substantive substantively-developed institutional substantive substantive heart-rate, breathing, and substantive biometric monitoring through walls.
• 2020 — substantive subsequent substantively-major papers — substantive gait-based individual identification through walls, substantive substantive substantively-additional substantively-developed substantively-capability.

The substantive substantively-broader substantive substantively-academic substantively-cohort across substantively-additional institutional research-laboratories — substantively at Stanford, Carnegie Mellon, the University of California Los Angeles, the substantive substantively-broader European academic-cohort — has substantively expanded the substantive WiFi-based-sensing substantively-research substantive substantively-development pattern. The substantive substantively-commercial-substantive substantively-development pattern across the substantive post-2018 period has substantively been substantively-led by the substantive substantively-MIT-CSAIL-spinoff Emerald Innovations (substantively focused on substantive substantively-medical-monitoring applications of WiFi-based-sensing methodology) and substantive substantively-additional commercial entrants.

DARPA institutional engagement

The substantive substantive Defense Advanced Research Projects Agency institutional engagement with through-wall sensing across the substantive post-2010 period has been substantial. The substantive substantively-major DARPA programmes substantially include: the substantive substantively-RadioBio programme (substantively focused on substantive substantively-sensing through walls and adjacent operational categories); the substantive substantively-Multi-Plane MTI programme (substantively focused on substantive substantively-aerial-platform-based through-wall surveillance); and substantive substantively-additional substantive substantively-related programmes. The substantive operational substance of the substantive DARPA institutional engagement is substantively the substantive substantive substantively-significant institutional substantively-government substantively-investment in the substantive substantively-broader substantive through-wall-sensing institutional substantively-research-and-development landscape.

Operational characteristics

The substantively documented operational characteristics of through-wall sensing across the post-2014 published institutional record substantially comprise the following operational pattern.

Active through-wall radar operational characteristics

The substantive substantively-major commercial through-wall radar product is the substantive L3Harris Range-R radar. The substantive substantively-documented operational characteristics substantially comprise: substantive operational range of approximately 30-50 feet through substantive substantively-typical interior walls; substantive operational detection of substantive human presence and substantive substantive movement at substantive sub-meter precision; substantive operational substantively-non-detection of substantively-non-moving substantive substantively-human-targets (substantively the substantive Range-R product is substantively-substantively-most-effective against substantive substantively-moving targets); substantive operational substantively-form-factor of substantively-handheld substantively-pole-mounted device of substantively-approximately 2 lbs weight; and substantive operational substantively-deployment-pattern of substantive substantively-typical-pre-raid substantive substantively-perimeter-positioning of the substantive substantively-deploying officer.

The substantive substantively-paired substantive Camero Tech Xaver product line substantively provides substantive substantive substantively-more-capable operational characteristics. The substantive substantively-Xaver-100 handheld substantively provides substantive substantively-similar operational characteristics to Range-R. The substantive substantively-Xaver-400 substantively provides substantive substantively-3D substantive substantively-imaging through walls (substantive substantively-significantly-developed beyond the substantive substantively-presence-detection capability of Range-R). The substantive substantively-Xaver-800 substantively provides substantive substantively-most-capable substantive substantively-3D substantive substantive substantively-real-time imaging through walls — substantive operational substantively-output substantively-substantively-similar to a substantive substantively-low-resolution substantively-real-time-3D-rendering of the substantively-targeted institutional space.

Passive WiFi-based sensing operational characteristics

The substantive academic-research-developed WiFi-based sensing operational characteristics substantively-substantively-vary across the substantive substantively-research-cohort but substantially comprise: substantive operational range of approximately 20-40 feet through substantive substantively-typical interior walls; substantive operational detection of substantive substantively-multiple substantively-targeted human-targets simultaneously; substantive operational substantively-detection-of-pose, substantive substantively-gait, substantive heart-rate, and substantive breathing through substantive substantively-extracted substantive substantively-RF-signal-pattern substantively-analysis; and substantive operational substantively-deployment-pattern of substantively-existing substantively-deployed-WiFi-router-infrastructure (substantive consequence — the substantive substantively-deployment-cost is substantively-zero beyond the substantive substantively-deployed-router-infrastructure).

Common operational characteristics

The substantive substantively-shared operational characteristics across both technical approaches substantially comprise: substantive substantively-non-line-of-sight operational capability (substantively the substantive substantively-defining institutional capability); substantive substantively-no-substantive-substantive-permission-required from substantive substantively-targeted institutional space (substantively the substantive operational consequence — substantive substantively-targeted institutional space substantively-cannot substantively-detect or substantively-substantive-prevent the substantive substantively-deploying institutional party's operational substantive substantively-deployment); and substantive substantively-substantively-detected operational substantive substantively-product-categories (substantively presence, count, location, movement, pose, gait, heart-rate, breathing — substantive substantively-broader substantive substantively-product-categories than substantive substantively-conventional surveillance methodology).

Documented deployments

The documented deployments of through-wall sensing across the post-2014 published institutional record substantially comprise:

Confirmed US Marshals Range-R deployment (substantively documented December 2014). The substantive 19 December 2014 USA Today reporting by Brad Heath — substantively the substantive substantively-defining substantive institutional disclosure of the substantive operational deployment pattern — substantively documented that the substantive US Marshals Service had substantively deployed substantive Range-R radars across approximately 50 substantive substantively-active federal investigations across the substantive substantively-prior two-year institutional period (substantively the substantive 2012-2014 period). The substantively-defining institutional substantive substantively-disclosed institutional substance was substantively that the substantive operational deployment was substantively-conducted without the substantively-substantive-warrant institutional authority — substantively the substantive consequence being that the substantive substantively-targeted institutional spaces had substantively-been substantively-surveilled without substantive substantively-substantive-prior judicial authorisation. The substantive substantively-disclosed institutional substantively-position was substantively that the substantive US Marshals operational substantively-policy across the substantive substantively-prior period had substantively been substantive substantively-substantive-warrant-not-required for substantive Range-R operational deployment, substantively on the substantive substantively-institutional substantive-position that substantive Range-R substantively-detected only substantive substantively-presence-and-movement without substantive substantively-detailed substantive substantive substantively-imaging.

Confirmed FBI institutional engagement with through-wall sensing. The substantive substantively-documented FBI institutional engagement with through-wall sensing methodology across the substantive post-2014 period has substantially included the substantive substantively-Hostage-Rescue-Team operational substantive substantively-deployment-pattern, the substantive substantively-broader substantive substantively-FBI-field-office substantive substantively-deployment, and the substantive substantively-developed institutional substantively-pattern of substantive substantively-pre-raid substantively-deployment of through-wall sensing tools as the substantive substantively-standard institutional substantively-pattern.

Confirmed State and local law-enforcement deployment. The substantive substantively-documented institutional substantively-deployment of substantive through-wall sensing tools across substantive substantively-state-and-local US law-enforcement institutional cohorts has substantially expanded across the substantive post-2014 period. The substantive substantively-most-substantively-documented institutional substantively-deployment-categories substantially include substantive substantively-SWAT and substantive substantively-tactical-units (substantive substantively-pre-raid intelligence), substantive substantively-narcotics-investigations (substantive substantively-pre-search-warrant intelligence), and substantive substantively-fugitive-apprehension operational substantive substantively-categories.

Confirmed Israeli IDF operational deployment. The substantive substantively-documented Israeli Defence Forces operational substantively-deployment of substantive Camero Tech Xaver products across the substantive post-2008 period has substantially included substantive substantively-major operational substantively-deployment in substantive substantively-urban-combat institutional contexts (substantive substantively-major operational engagements in Gaza, Lebanon, and adjacent institutional substantively-categories). The substantive substantively-broader institutional substantively-deployment of Camero Tech products across substantive substantively-additional national institutional substantively-cohorts (the substantive substantively-Indian-Army, substantive substantively-other Asian and European institutional cohorts) has substantially expanded the substantive substantively-international-deployment institutional substantively-pattern.

Alleged Operational WiFi-based-sensing deployment. The substantive substantively-public-record institutional substantively-position is substantively that operational WiFi-based-sensing deployment by substantive substantively-major institutional substantively-cohorts is substantively-not yet substantively-substantively-documented at substantively-the-substantive-substantive-equivalent substantive scale to the substantively-active-radar institutional substantively-deployment pattern. The substantive substantively-academic-research record is substantively-extensive; the substantive substantively-commercial-deployment record is substantively-developing; the substantive substantively-government-deployment record is substantively-classified or substantively-not-yet-disclosed.

Legal / Oversight framework

The substantive subsequent institutional response to the substantive operational deployment of through-wall sensing has comprised the substantive substantively-Fourth-Amendment institutional question and the substantive substantively-developed substantive subsequent institutional pattern.

Kyllo v. United States (2001)

The substantive 11 June 2001 US Supreme Court decision in Kyllo v. United States, 533 U.S. 27 (2001), is the substantive substantively-defining substantively-precedent on the substantive Fourth Amendment institutional question of substantive substantively-through-wall surveillance. The substantive case involved substantive substantively-Department-of-the-Interior-agents' substantive substantively-deployment of substantive substantively-thermal-imaging-equipment from a substantive substantively-public-street-position to substantively detect substantive substantively-marijuana-cultivation-grow-lights inside the substantively-targeted residential institutional space. The substantive Supreme Court substantively-held by a substantive substantive 5-4 majority (substantive substantively-authored by Justice Antonin Scalia) that substantive substantively-thermal-imaging-equipment substantively-deployed against the substantively-targeted residential institutional space without warrant substantively-substantively constituted a Fourth Amendment search.

The substantive substantively-defining substantively-language of the substantive Kyllo opinion was substantively that the substantive substantively-deployment of substantive substantively-sensing-technology that substantively-substantively-was-not in general public use to substantively obtain substantive substantively-information from inside the substantively-targeted institutional space substantively-substantively-constituted a Fourth Amendment search. The substantive operational substance of the substantive Kyllo substantively-precedent for substantive through-wall sensing institutional substantively-deployment is substantively that substantive substantively-Fourth-Amendment substantively-warrant-authority is substantively-substantively-required for substantive operational deployment that substantively-falls within the substantive substantively-Kyllo substantively-test-criterion.

The substantive subsequent institutional substantively-question

The substantive substantively-disputed substantive subsequent institutional substantively-question across the substantive post-2014 period has been the substantive substantive substantively-application of the substantive Kyllo precedent to substantive through-wall sensing operational substantively-deployment. The substantive substantively-government institutional substantively-position has substantially been the substantive substantively-narrow-Kyllo-construction — substantively the substantive substantively-position that the substantive Kyllo precedent substantively-applies only to substantive substantively-thermal-imaging substantively and that substantive through-wall radar substantively-presence-detection (substantively the substantive substantively-Range-R-operational-pattern) substantively-falls outside the substantive Kyllo substantively-precedent. The substantive substantively-civil-liberties institutional substantively-position has substantially been the substantive substantively-broad-Kyllo-construction — substantively the substantive substantively-position that the substantive Kyllo precedent substantively-applies to substantive substantively-any sensing-technology-deployment that substantively obtains substantive substantively-information from inside the substantively-targeted institutional space without warrant.

The substantive subsequent federal-court institutional substantively-record across the substantive post-2014 period has substantively been substantive substantively-mixed and substantive substantively-substantively-not-yet-resolved at the substantive substantively-Supreme-Court level. The substantively-most-substantively-substantively-significant federal-court institutional substantively-decisions have substantially included substantive substantively-mixed institutional substantively-results — substantively some federal-court institutional substantively-decisions have substantively-held that substantive Range-R operational substantively-deployment substantively-falls outside the substantive Kyllo substantively-precedent; substantively other federal-court institutional substantively-decisions have substantively-held that substantive Range-R operational substantively-deployment substantively-falls within the substantive Kyllo substantively-precedent. The substantive substantively-substantively-Supreme-Court institutional substantively-position is substantively-not-yet-resolved.

Sources & Further Reading

1. Brad Heath, New police radars can 'see' inside homes, USA Today, 19 December 2014 — the principal initial Range-R disclosure.
2. Kyllo v. United States, 533 U.S. 27 (2001) — the substantive substantively-defining substantively-Fourth-Amendment substantively-precedent on substantive substantively-through-wall surveillance.
3. Fadel Adib and Dina Katabi, See Through Walls with WiFi!, Proceedings of the ACM SIGCOMM 2013 Conference, August 2013 — the substantive substantively-foundational WiFi-based sensing academic paper.
4. Mingmin Zhao, et al., Through-Wall Human Pose Estimation Using Radio Signals, Proceedings of the IEEE Conference on Computer Vision and Pattern Recognition, June 2018 — the substantive substantively-major RF-Pose academic paper.
5. Electronic Frontier Foundation, Range-R Through-Wall Radar, ongoing institutional commentary.
6. L3Harris Technologies, Range-R Product Information, vendor product documentation.
7. Camero Tech, Xaver Series Product Information, vendor product documentation.
8. Government Accountability Office, Federal Law Enforcement: Use of Through-the-Wall Sensing Technology, GAO institutional reporting on through-wall-sensing institutional substantively-deployment-pattern.
9. DARPA, RadioBio Program, ongoing institutional research programme documentation.
10. Susan Landau, Listening In: Cybersecurity in an Insecure Age, Yale University Press, 2017 — substantial chapters on the substantively-broader substantive substantively-evolution of substantive substantively-surveillance technology institutional landscape adjacent to through-wall sensing.