Wideband PowerLine Positioning for Indoor

LocalizationErich Stuntebeck (Georgia Tech) - Shwetak Patel (U.

Washington)Thomas Robertson (Georgia Tech) - Matthew

Reynolds (Duke) Gregory Abowd (Georgia Tech)

2

OverviewPatel et al. (UbiComp 2006) introduced PowerLine Positioning (PLP-I), a fingerprinting-based indoor localization system.

PLP-I Limitations

• Sub-optimal frequency-pair selection.

• Sensitivity to noise.

• Temporal stability.

Solution: replace the frequency-pair approach with a wideband signal.

3

PLP-I Background

S. Patel, K. Truong, G. Abowd. “PowerLine Positioning: A Practical Sub-Room-LevelIndoor Location System for Domestic Use”, UbiComp 2006.

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PLP Background

• Amplitudes create a unique signature at every physical location.

• Initial site survey required.

• K-Nearest-Neighbors used for post-site-survey mapping.

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PLP-I Status

•Works as expected in residential environments and is currently undergoing commercialization.

•Problems in commercial environments with lots of electrical equipment.

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Our Test Environments

Technology Square Research Building

Georgia Tech Aware Home

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Data Collection• 66 surveyed grid-points

on a best-effort 0.9m x 0.9m grid.

• 3 Levels of classification

• Room

• Sub-Room

• Grid

• 5 sweeps conducted over 2 months.

8Measurement Apparatus• Software radio used to record raw over-the-air

waveforms with a 64 MHz ADC.

• Broadband loop-antenna used for prototyping speed and flexibility.

• Necessary hardware has been reduced to portable size for deployments in the future.

Locator “tag”

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Signal Injection• One signal injector

located in the kitchen.

• 40 signals (pure unmodulated carrier waves) tested ranging from 500 kHz to 20 MHz, plus 447/448/600/601 kHz.

• All 44 tested frequencies injected in sequence from the indicated point.

10Classification

Results• KNN classification of 66

grid-points using a K value of 1.

• Frequency pairs chosen independently for each of the three granularities for worst and best cases.

• Test and training data captured several hours apart.

Patel et al. ’06 results67% accuracy @ 1m

8.5

MH

z, 9

.0 M

Hz

8.5

MH

z, 1

1.0

MH

z

447 k

Hz,

11.5

MH

z

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Noise Sensitivity

• How sensitive is two-frequency amplitude data to noise?

• Added zero-mean Gaussian noise.

• Trained on the original uncorrupted data and tested on the corrupted data.

2 dB

12How much noise

exists?

13How much noise

exists? 5 Datasets over 2 Months

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Proposed Solution

•Frequency pair approach suffers from poor performance and noise sensitivity.

•Proposed solution: wideband signaling

•Use all 44 tested frequency amplitudes for classification - 44 dimensional classifier space.

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Wideband Results

16Do you need 44

frequencies?

17Wideband Noise

Resistance

Narrowband, 2 Frequency Wideband, 44 Frequency

18Wideband Temporal

Stability

19Wideband Temporal

Stability

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Summary

PLP-I Limitations

• Sub-optimal frequency-pair selection.

• Sensitivity to noise.

• Temporal stability.

Solution: replace the frequency-pair approach with a wideband signal.

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Future Work

•Further experimentation on temporal stability and accuracy vs. wideband signal size / frequency component spacing.

•Other techniques for improvement in temporal stability?

•Adaptive solution - continually monitor powerline noise.

Wideband PowerLine Positioning for Indoor

LocalizationErich Stuntebeckeps@gatech.edu