PolyPoint: Accurate Indoor Localization via Trilateration
PolyPoint is a technology developed by Benjamin Kempke, Brad Campbell, Pat Pannuto, Ye-Sheng Kuo, and Prabal Dutta at the University of Michigan in 2015, showcasing accurate indoor localization using 802.15.4a and trilateration techniques. The system utilizes hardware with UWB transceivers, antenna diversity, and the Contiki embedded OS to achieve fine-granularity characterization of the multipath environment for precise localization. Through the Microsoft Indoor Localization Competition, PolyPoint demonstrates efficient ranging operations and range estimates calculation for enhanced positioning accuracy.
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Presentation Transcript
PolyPoint: Accurate 802.15.4a Indoor Accurate 802.15.4a Indoor Localization Localization Benjamin Kempke, Brad Campbell, Pat Pannuto, Ye-Sheng Kuo, and Prabal Dutta University of Michigan 2015 Microsoft Indoor Localization Competition April 15, 2015
PolyPoint: Localization via Trilateration (x3,y3,z3) (x2,y2,z2) (x1,y1,z1) 2
PolyPoint: Localization via Trilateration Tag 3
PolyPoint: Localization via Trilateration Tag 4
PolyPoint: Localization via Trilateration Tag 5
PolyPoint: Localization via Trilateration Tag 6
PolyPoint Node Hardware 802.15.4a UWB Transceiver Timed TX RX Timestamps UWB: fine- granularity characterization of the multipath environment Decawave DW1000 RF Switch 3 UWB antennas Atum (Cortex M3) 7
PolyPoint Node Hardware Enables antenna diversity Decawave DW1000 RF Switch 3 UWB antennas Atum (Cortex M3) 8
PolyPoint Node Hardware Enables antenna polarization diversity Decawave DW1000 RF Switch 3 UWB antennas Atum (Cortex M3) 9
PolyPoint Node Hardware Runs the Contiki embedded OS Schedules ranging operations Calculates range estimates Decawave DW1000 RF Switch 3 UWB antennas Atum (Cortex M3) 10
PolyPoint Node Hardware Offloads ranging measurements for trilateration processing Decawave DW1000 RF Switch 3 UWB antennas Atum (Cortex M3) USB 11
Ranging using Timestamps: Time-of-Flight Ranging Clock Offset Compensation: ferror =taf -tap ttf -ttp Time-of-Flight Calculation: ttof =(taf -tar)- ferror*(taf -ttr) Range Calculation: R=ttof *c 2 12
Estimating Actual Range from Multiple Time-of-Flight Measurements Ranging operations repeated 27 times Every combination of: 3 antennas @ the tag 3 antennas @ the anchor 3 UWB channels Best estimate of range: 10th percentile 13
Trilateration: From Range to Position Choose the three closest anchors Perform trilateration using the Non-linear Least Squares Method Minimize the function: 3 F(x,y,z) = ( ri-ri)2 i=1 Where: ri= (x-xi) 2+(y-yi)2+(z-zi) 2 14
PolyPoint Demonstrates Accurate Indoor Localization Using Inexpensive, Commercially- Available Hardware Ranging operations performed using timestamps provided by the DW1000 + 27 successive range measurements between the tag and each anchor + Antenna diversity avoids large ranging errors due to polarization mismatch + Frequency diversity avoids frequency-selective effects + Tag location derived using minimum least squares trilateration + Benjamin Kempke University of Michigan bpkempke@umich.edu PolyPoint: http://www.github.com/lab11/polypoint 15
