locating in fingerprint space: wireless indoor localization with little human intervention
DESCRIPTION
Locating in Fingerprint Space: Wireless Indoor localization with Little Human Intervention. Zheng Yang, Chenshu Wu, and Yunhao Liu MobiCom 2012 - Sowhat 2012.08.20. Outline. Introduction System Design Evaluation Discussion Conclusion. Outline. Introduction System Design - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Locating in Fingerprint Space: Wireless Indoor localization with Little Human Intervention](https://reader036.vdocuments.mx/reader036/viewer/2022062520/56815f55550346895dce3290/html5/thumbnails/1.jpg)
LOCATING IN FINGERPRINT SPACE:WIRELESS INDOOR LOCALIZATION WITH LITTLE HUMAN INTERVENTION
Zheng Yang, Chenshu Wu, and Yunhao LiuMobiCom 2012
- Sowhat 2012.08.20
![Page 2: Locating in Fingerprint Space: Wireless Indoor localization with Little Human Intervention](https://reader036.vdocuments.mx/reader036/viewer/2022062520/56815f55550346895dce3290/html5/thumbnails/2.jpg)
OUTLINE Introduction
System Design
Evaluation
Discussion
Conclusion
![Page 3: Locating in Fingerprint Space: Wireless Indoor localization with Little Human Intervention](https://reader036.vdocuments.mx/reader036/viewer/2022062520/56815f55550346895dce3290/html5/thumbnails/3.jpg)
OUTLINE Introduction
System Design
Evaluation
Discussion
Conclusion
![Page 4: Locating in Fingerprint Space: Wireless Indoor localization with Little Human Intervention](https://reader036.vdocuments.mx/reader036/viewer/2022062520/56815f55550346895dce3290/html5/thumbnails/4.jpg)
MOTIVATION RSSI fingerprinting-based localization
Site survey Time-consuming Labor-intensive Vulnerable to environmental dynamics Inevitable
![Page 5: Locating in Fingerprint Space: Wireless Indoor localization with Little Human Intervention](https://reader036.vdocuments.mx/reader036/viewer/2022062520/56815f55550346895dce3290/html5/thumbnails/5.jpg)
OBJECTIVE
Wireless Indoor Localization Approach
RSSI Floor Plan User Movement
![Page 6: Locating in Fingerprint Space: Wireless Indoor localization with Little Human Intervention](https://reader036.vdocuments.mx/reader036/viewer/2022062520/56815f55550346895dce3290/html5/thumbnails/6.jpg)
OUTLINE Introduction
System Design
Evaluation
Discussion
Conclusion
![Page 7: Locating in Fingerprint Space: Wireless Indoor localization with Little Human Intervention](https://reader036.vdocuments.mx/reader036/viewer/2022062520/56815f55550346895dce3290/html5/thumbnails/7.jpg)
LIFS, SYSTEM ARCHITECTUREGeographical
dist.≠
Walking dist.RSSI + Distance
![Page 8: Locating in Fingerprint Space: Wireless Indoor localization with Little Human Intervention](https://reader036.vdocuments.mx/reader036/viewer/2022062520/56815f55550346895dce3290/html5/thumbnails/8.jpg)
MULTIDIMENSIONAL SCALING (MDS) Information visualization for exploring
similarities/dissimilarities in data
![Page 9: Locating in Fingerprint Space: Wireless Indoor localization with Little Human Intervention](https://reader036.vdocuments.mx/reader036/viewer/2022062520/56815f55550346895dce3290/html5/thumbnails/9.jpg)
STRESS-FREE FLOOR PLAN
MDS
Geographical distance ≠ Walking distance,Ground-truth floor plan –conflict with measured distance
Sample grids in a floor plan (grid length l = 2m)
Distance matrix D = [dij],dij = walking distance between point i and j
Stress-free floor plan – 2D & 3D
![Page 10: Locating in Fingerprint Space: Wireless Indoor localization with Little Human Intervention](https://reader036.vdocuments.mx/reader036/viewer/2022062520/56815f55550346895dce3290/html5/thumbnails/10.jpg)
FINGERPRINT SPACE – FINGERPRINT & DISTANCE MEASUREMENT Fingerprints and distance collection
Record while walking Footsteps every consecutive steps by accelerometer Set of fingerprints, F = {fi, i = 1~n}
Distance(footsteps) matrix, D’=[d’ij] Pre-processing
Merge similar fingerprints (δij<ε)
Accelerometer readingTwice integration Distance: NoiceLocal variance threshold method Step count
Stride lengths vary? MDS tolerate measurement errors
![Page 11: Locating in Fingerprint Space: Wireless Indoor localization with Little Human Intervention](https://reader036.vdocuments.mx/reader036/viewer/2022062520/56815f55550346895dce3290/html5/thumbnails/11.jpg)
FINGERPRINT SPACE – FINGERPRINT SPACE CONSTRUCTION Adequate fingerprints & distance
1. 10x sample locations in stress-free floor plan2. First several days for training
d’ij unavailable d’ij = d’ik + d’kj
Shortest path update D’ all-pairs of fingerprints Floyd-Warshall algorithm
MDS Fingerprint space 2D & 3D
![Page 12: Locating in Fingerprint Space: Wireless Indoor localization with Little Human Intervention](https://reader036.vdocuments.mx/reader036/viewer/2022062520/56815f55550346895dce3290/html5/thumbnails/12.jpg)
MAPPING –CORRIDOR & ROOM RECOGNITION Corridor recognition (Fc)
Higher prob. on a randomly chosen shortest path Minimum spanning tree Betweenness Watershed
1. Size(corridor) / Size(all)2. Large gap of betweenness values
Room recognition (FRi) k-means algorithm
(k = number of rooms)
Classify fingerprints into the corridor or rooms
![Page 13: Locating in Fingerprint Space: Wireless Indoor localization with Little Human Intervention](https://reader036.vdocuments.mx/reader036/viewer/2022062520/56815f55550346895dce3290/html5/thumbnails/13.jpg)
Fingerprints collected near “doors”
PD = {p1, p2, …, pk}, stress-free floor planFD , fingerprint space
distance matrix D and D’ l = (lp1, lp2, …, lp k-1)l’ = (lf1, l’f2, …, l’f k-1)
cosine similarity
MAPPING –REFERENCE POINT
Near-door fingerprints, FD,labeled with real locations
1. Map near-door fingerprintsto real locations (FD → PD)
2. Map rooms to rooms
![Page 14: Locating in Fingerprint Space: Wireless Indoor localization with Little Human Intervention](https://reader036.vdocuments.mx/reader036/viewer/2022062520/56815f55550346895dce3290/html5/thumbnails/14.jpg)
Floor-level transformation Stress-free floor plan ≠ Fingerprint space
∵ translation, rotation, reflection Transform matrix,
xi = coordinate of fi ∈ FDyi = coordinate of pi ∈ PD
For fingerprint with coordinate xreal location = sample location closest to Ax + B
Room-level transformation Room by room Doors and room corners as reference point Transformation matrix
MAPPING –SPACE TRANSFORMATION
![Page 15: Locating in Fingerprint Space: Wireless Indoor localization with Little Human Intervention](https://reader036.vdocuments.mx/reader036/viewer/2022062520/56815f55550346895dce3290/html5/thumbnails/15.jpg)
OUTLINE Introduction
System Design
Evaluation
Discussion
Conclusion
![Page 16: Locating in Fingerprint Space: Wireless Indoor localization with Little Human Intervention](https://reader036.vdocuments.mx/reader036/viewer/2022062520/56815f55550346895dce3290/html5/thumbnails/16.jpg)
HARDWARE AND ENVIRONMENT 2 Google Nexus S phones Typical office building covering 1600m2
16 rooms,5 large – 142m2, 7 small, 4 inaccessible
26 Aps, 15 are with known location 2m x 2m grids, 292 sample locations
![Page 17: Locating in Fingerprint Space: Wireless Indoor localization with Little Human Intervention](https://reader036.vdocuments.mx/reader036/viewer/2022062520/56815f55550346895dce3290/html5/thumbnails/17.jpg)
EXPERIMENT DESIGN 5 hours with 4 volunteers Fingerprints recording – every 4~5 steps
(2~3m) Accelerometer –
work in different frequency based on detecting movement
600 user traces, with 16498 fingerprints Corridor, >500 paths
Small rooms, >5 pathsLarge rooms, >10 paths
Half of data used for training,half …………………... in operating phase
![Page 18: Locating in Fingerprint Space: Wireless Indoor localization with Little Human Intervention](https://reader036.vdocuments.mx/reader036/viewer/2022062520/56815f55550346895dce3290/html5/thumbnails/18.jpg)
THRESHOLD VALUE OF FINGERPRINT DISSIMILARITY
![Page 19: Locating in Fingerprint Space: Wireless Indoor localization with Little Human Intervention](https://reader036.vdocuments.mx/reader036/viewer/2022062520/56815f55550346895dce3290/html5/thumbnails/19.jpg)
STEP COUNT 5 ~ 200 footsteps
Error rate = 2% in number of detected steps
Accumulative error of long path Unobvious performance drop ∵ only use inter-fingerprint step counts
![Page 20: Locating in Fingerprint Space: Wireless Indoor localization with Little Human Intervention](https://reader036.vdocuments.mx/reader036/viewer/2022062520/56815f55550346895dce3290/html5/thumbnails/20.jpg)
FINGERPRINT SPACE 795 fingerprints when ε = 30
![Page 21: Locating in Fingerprint Space: Wireless Indoor localization with Little Human Intervention](https://reader036.vdocuments.mx/reader036/viewer/2022062520/56815f55550346895dce3290/html5/thumbnails/21.jpg)
CORRIDOR RECOGNITION
Refining Perform MST iteratively Sift low betweenness Until MST forms a single line
![Page 22: Locating in Fingerprint Space: Wireless Indoor localization with Little Human Intervention](https://reader036.vdocuments.mx/reader036/viewer/2022062520/56815f55550346895dce3290/html5/thumbnails/22.jpg)
ROOM RECOGNITION
![Page 23: Locating in Fingerprint Space: Wireless Indoor localization with Little Human Intervention](https://reader036.vdocuments.mx/reader036/viewer/2022062520/56815f55550346895dce3290/html5/thumbnails/23.jpg)
REFERENCE POINT MAPPING
![Page 24: Locating in Fingerprint Space: Wireless Indoor localization with Little Human Intervention](https://reader036.vdocuments.mx/reader036/viewer/2022062520/56815f55550346895dce3290/html5/thumbnails/24.jpg)
POINT MAPPING
• 96 percentile < 4m• Average mapping error = 1.33m
![Page 25: Locating in Fingerprint Space: Wireless Indoor localization with Little Human Intervention](https://reader036.vdocuments.mx/reader036/viewer/2022062520/56815f55550346895dce3290/html5/thumbnails/25.jpg)
LOCALIZATION ERROR Emulate 8249 queries using real data on LiFS Location error
Average,LiFS = 5.88mRADAR = 3.42m
Percentile of LiFS80 < 9m / 60 < 6m
Caused bysymmetric structure
Fairly reasonable!
Room error = 10.91%
![Page 26: Locating in Fingerprint Space: Wireless Indoor localization with Little Human Intervention](https://reader036.vdocuments.mx/reader036/viewer/2022062520/56815f55550346895dce3290/html5/thumbnails/26.jpg)
OUTLINE Introduction
System Design
Evaluation
Discussion
Conclusion
![Page 27: Locating in Fingerprint Space: Wireless Indoor localization with Little Human Intervention](https://reader036.vdocuments.mx/reader036/viewer/2022062520/56815f55550346895dce3290/html5/thumbnails/27.jpg)
DISCUSSION Global reference point
Last reported GPS locationLocations of APsSimilar surrounding sound signature…
Could be added in LiFS for more robust mapping Key for symmetric floor plans / multi-floor fuildings
Large open environment
![Page 28: Locating in Fingerprint Space: Wireless Indoor localization with Little Human Intervention](https://reader036.vdocuments.mx/reader036/viewer/2022062520/56815f55550346895dce3290/html5/thumbnails/28.jpg)
OUTLINE Introduction
System Design
Evaluation
Discussion
Conclusion
![Page 29: Locating in Fingerprint Space: Wireless Indoor localization with Little Human Intervention](https://reader036.vdocuments.mx/reader036/viewer/2022062520/56815f55550346895dce3290/html5/thumbnails/29.jpg)
CONCLUSION LiFS
Spatial relation of RSSI fingerprints + Floor plan Low human cost
Comments Clear architecture Not specific descriptions in evaluation
![Page 30: Locating in Fingerprint Space: Wireless Indoor localization with Little Human Intervention](https://reader036.vdocuments.mx/reader036/viewer/2022062520/56815f55550346895dce3290/html5/thumbnails/30.jpg)
THANKS FOR LISTENING ~