Wideband PowerLine Positioning for Indoor Localization

Ubicomp 2008Presenter: Vincent

Outline

• Overview• PLP background• Proposed Solution• Test environment• Wideband PLP Results• Conclusion

Overview

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

• PLP Limitations– Suboptimal frequency-pair selection.– Sensitivity to noise.– Temporal stability.

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

PLP Background

PLP Background

• Amplitudes create a unique signature at every physical location.

• Initial site survey required.

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

Classification 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.

8.5

MH

z, 9

.0

MH

z

8.5

MH

z, 1

1.0

MH

z

447

kHz,

11.

5 M

Hz

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.

How much noise exists?

How much noise exists?

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. (447kHz, 448kHz, 600kHz, 601kHz, 500kHz ~ 20MHz in 500kHz steps)

Test Environments• 66 surveyed grid-points

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

• 3 Levels of classification– Room– Sub-room– Grid

Measurement 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”

Wideband Results

Do you need 44 frequencies?

Wideband Noise Resistance

Narrowband, 2 Frequency Wideband, 44 Frequency

Wideband Temporal Stability

Conclusion

• PLP Limitations– Suboptimal frequency-pair selection.– Sensitivity to noise.– Temporal stability.

• Solution– replace the frequency-pair approach with a

wideband signal.