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PD1 PD2 Microcontroller Quad OpAmp Vision-Precision Ubiquitous Indoor Localization Using Conventional Lights Chi Zhang (UW-Madison), Xinyu Zhang (UC San Diego) Indoor Localizaton Discovery Navigaton Analytcs Interacton Current Practce: Wi-Fi Inaccurate Meters of error Fragile Easily afected by dynamics Future Promise: Visible Light Positoning Accurate Robust Ubiquitous Approach ①: Camera + Photogrammetry Narrow View Low Sensitiity Energy-Hungry Long Latency Approach ②: Photodiode + Intensity Model Model is Unrealistc Obstructon Breaks model Above All: Require Extra Beacon Hardware = Huge Retrofing Cost! Departure from the Regime Angle of Arrival (AoA) Database Reusing Existng Ligh ts 0 25 50 75 86 88 90 92 94 Intensity (dB) Frequency (kHz) Localizaton Resources Chi Zhang, Xinyu Zhang, “ Pulsar: Towards Ubiquitous Visible Light Localizaton”, ACM MobiCom’17 Chi Zhang, Xinyu Zhang, “ LiTell: Robust Indoor Localizaton Using Unmodifed Light Fixtures”, ACM MobiCom’16 http://dword1511.info AoA from Photodiodes Light Irradiate angle Incident angle (AoA) θ φ r 1 2 RSS 1 = P t A t (θ) α(r) A r1 (φ) RSS 2 = P t A t (θ) α(r) A r2 (φ) RSS = P t A t (θ) α(r) A r (φ) RSS 1 A r1 (φ 1 ) RSS 2 A r2 (φ 2 ) A c (φ) = = RSS 1 RSS 2 φ = A c -1 ( ) Prototype Light CF Light CF Light CF Light CF Light CF Light AoA 3D Location Orientation Gravity & Compass Spectrum Photodiode Database Photodiode Profile Light CF Light CF Landmark Location Light CF Light CF Vector Equation 3 Lights → 3D Locaton 4 Lights → 3D Locaton + Orientaton ÷ f -1 Retrofing is costly? Reuse existng lights! Intensity is unreliable? Enable photodiode-based AoA sensing! Visible Light: No Phase! Photodiodes: No Spatal Resoluton! Need New Tricks Accuracy: 10cm / 5° Oscillaton in Driver → High Frequency Flicker Ubiquitous Stable Manufacturing Error → Diversity in Oscillators Unique “Characteristc Frequency (CF)” Turn Existng Lights into Locaton Landmarks 4X 5X 2X How to Identfy Lights without Beacons? (Phone not to Scale) Obtain AoA from 2 Diferent Photodiodes
