Device Signal Strength Self-Calibration Using Histograms
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Introduction - Motivation Device Calibration - Device Diversity Device Signal Strength Self-Calibration - Manual Calibration Self-Calibration using Histograms - RSS Histograms - Self-Calibration Method Performance ∗ y ∗ Evaluation Christos Laoudias , Robert Pich´e and Christos Panayiotou - Measurement Setup - Experimental Results ∗KIOS Research Center for Intelligent Systems and Networks, University of Cyprus y Conclusions Tampere University of Technology, Tampere, Finland - Concluding Remarks International Conference on Indoor Positioning and Indoor Navigation, Sydney, Australia 15 November 2012 Outline Introduction - Motivation Introduction Device Calibration - Device Diversity - Manual Calibration Device Calibration Self-Calibration - RSS Histograms - Self-Calibration Method Self-Calibration Performance Evaluation - Measurement Setup Performance Evaluation - Experimental Results Conclusions - Concluding Remarks Conclusions International Conference on Indoor Positioning and Indoor Navigation, Sydney, Australia 15 November 2012 I Different devices do not report RSS values in the same way I The WiFi standard (IEEE 802.11) defines the RSS Indicator (1 byte integer) for measuring RSS in [0 255] I Each vendor's implementation is limited up to RSSImax I RSSI is mapped to power values in dBm internally by the device driver (proprietary information) I Even worse: same chipsets may not report the same RSS values due to different antennas or packaging I Using a new device for positioning is feasible, but the RSS values are not compatible with the radiomap I Best accuracy is guaranteed only if the user carries the same device during positioning, otherwise calibration is required I Existing calibration methods do not fit well in real-time positioning scenarios Motivation of our work I RSS is intended for determining the signal quality and not for positioning purposes Introduction - Motivation Device Calibration - Device Diversity - Manual Calibration Self-Calibration - RSS Histograms - Self-Calibration Method Performance Evaluation - Measurement Setup - Experimental Results Conclusions - Concluding Remarks International Conference on Indoor Positioning and Indoor Navigation, Sydney, Australia 15 November 2012 I Using a new device for positioning is feasible, but the RSS values are not compatible with the radiomap I Best accuracy is guaranteed only if the user carries the same device during positioning, otherwise calibration is required I Existing calibration methods do not fit well in real-time positioning scenarios Motivation of our work I RSS is intended for determining the signal quality and not for positioning purposes Introduction - Motivation I Different devices do not report RSS values in the same way Device Calibration I The WiFi standard (IEEE 802.11) defines the RSS - Device Diversity - Manual Calibration Indicator (1 byte integer) for measuring RSS in [0 255] Self-Calibration I Each vendor's implementation is limited up to RSSImax - RSS Histograms - Self-Calibration I RSSI is mapped to power values in dBm internally by Method the device driver (proprietary information) Performance Evaluation I Even worse: same chipsets may not report the same - Measurement Setup - Experimental RSS values due to different antennas or packaging Results Conclusions - Concluding Remarks International Conference on Indoor Positioning and Indoor Navigation, Sydney, Australia 15 November 2012 I Best accuracy is guaranteed only if the user carries the same device during positioning, otherwise calibration is required I Existing calibration methods do not fit well in real-time positioning scenarios Motivation of our work I RSS is intended for determining the signal quality and not for positioning purposes Introduction - Motivation I Different devices do not report RSS values in the same way Device Calibration I The WiFi standard (IEEE 802.11) defines the RSS - Device Diversity - Manual Calibration Indicator (1 byte integer) for measuring RSS in [0 255] Self-Calibration I Each vendor's implementation is limited up to RSSImax - RSS Histograms - Self-Calibration I RSSI is mapped to power values in dBm internally by Method the device driver (proprietary information) Performance Evaluation I Even worse: same chipsets may not report the same - Measurement Setup - Experimental RSS values due to different antennas or packaging Results Conclusions I Using a new device for positioning is feasible, but the RSS - Concluding Remarks values are not compatible with the radiomap International Conference on Indoor Positioning and Indoor Navigation, Sydney, Australia 15 November 2012 I Existing calibration methods do not fit well in real-time positioning scenarios Motivation of our work I RSS is intended for determining the signal quality and not for positioning purposes Introduction - Motivation I Different devices do not report RSS values in the same way Device Calibration I The WiFi standard (IEEE 802.11) defines the RSS - Device Diversity - Manual Calibration Indicator (1 byte integer) for measuring RSS in [0 255] Self-Calibration I Each vendor's implementation is limited up to RSSImax - RSS Histograms - Self-Calibration I RSSI is mapped to power values in dBm internally by Method the device driver (proprietary information) Performance Evaluation I Even worse: same chipsets may not report the same - Measurement Setup - Experimental RSS values due to different antennas or packaging Results Conclusions I Using a new device for positioning is feasible, but the RSS - Concluding Remarks values are not compatible with the radiomap I Best accuracy is guaranteed only if the user carries the same device during positioning, otherwise calibration is required International Conference on Indoor Positioning and Indoor Navigation, Sydney, Australia 15 November 2012 Motivation of our work I RSS is intended for determining the signal quality and not for positioning purposes Introduction - Motivation I Different devices do not report RSS values in the same way Device Calibration I The WiFi standard (IEEE 802.11) defines the RSS - Device Diversity - Manual Calibration Indicator (1 byte integer) for measuring RSS in [0 255] Self-Calibration I Each vendor's implementation is limited up to RSSImax - RSS Histograms - Self-Calibration I RSSI is mapped to power values in dBm internally by Method the device driver (proprietary information) Performance Evaluation I Even worse: same chipsets may not report the same - Measurement Setup - Experimental RSS values due to different antennas or packaging Results Conclusions I Using a new device for positioning is feasible, but the RSS - Concluding Remarks values are not compatible with the radiomap I Best accuracy is guaranteed only if the user carries the same device during positioning, otherwise calibration is required I Existing calibration methods do not fit well in real-time positioning scenarios International Conference on Indoor Positioning and Indoor Navigation, Sydney, Australia 15 November 2012 Device Diversity Introduction - Motivation Device Calibration - Device Diversity - Manual Calibration Self-Calibration - RSS Histograms - Self-Calibration Method Performance Evaluation - Measurement Setup - Experimental Results Conclusions - Concluding Remarks Source: K. Kaemarungsi (2006) International Conference on Indoor Positioning and Indoor Navigation, Sydney, Australia 15 November 2012 I Limited Applicability: (i) User needs to be familiar with the indoor area and (ii) a considerable data collection effort is required Good News: Linearity between RSS values −20 −20 −30 −30 −40 −40 Introduction - Motivation −50 −50 Device Calibration −60 −60 - Device Diversity −70 −70 - Manual Calibration Mean RSS from HP iPAQ [dBm] −80 −80 Self-Calibration Mean RSS from Asus eeePC [dBm] - RSS Histograms −90 RSS pairs −90 RSS pairs Cloud center Cloud center - Self-Calibration Least−squares Fit Least−squares Fit Method −100 −100 −100 −90 −80 −70 −60 −50 −40 −30 −20 −100 −90 −80 −70 −60 −50 −40 −30 −20 Performance Mean RSS from HTC Flyer [dBm] Mean RSS from Samsung Nexus S [dBm] Evaluation - Measurement Setup - Experimental Results Manual Calibration: Collect several colocated RSS pairs at Conclusions I - Concluding Remarks known locations and estimate the linear coefficients through least squares (2) (1) ¯rij = α12¯rij + β12 International Conference on Indoor Positioning and Indoor Navigation, Sydney, Australia 15 November 2012 Good News: Linearity between RSS values −20 −20 −30 −30 −40 −40 Introduction - Motivation −50 −50 Device Calibration −60 −60 - Device Diversity −70 −70 - Manual Calibration Mean RSS from HP iPAQ [dBm] −80 −80 Self-Calibration Mean RSS from Asus eeePC [dBm] - RSS Histograms −90 RSS pairs −90 RSS pairs Cloud center Cloud center - Self-Calibration Least−squares Fit Least−squares Fit Method −100 −100 −100 −90 −80 −70 −60 −50 −40 −30 −20 −100 −90 −80 −70 −60 −50 −40 −30 −20 Performance Mean RSS from HTC Flyer [dBm] Mean RSS from Samsung Nexus S [dBm] Evaluation - Measurement Setup - Experimental Results Manual Calibration: Collect several colocated RSS pairs at Conclusions I - Concluding Remarks known locations and estimate the linear coefficients through least squares (2) (1) ¯rij = α12¯rij + β12 I Limited Applicability: (i) User needs to be familiar with the indoor area and (ii) a considerable data collection effort is required International Conference on Indoor Positioning and Indoor Navigation, Sydney, Australia 15 November 2012 Can we do it more efficiently? Introduction Objectives - Motivation Device Calibration - Device Diversity I Fully automatic approach