DECODE: Detecting Co-Moving Wireless Devices Gayathri - - PowerPoint PPT Presentation

DECODE: Detecting Co-Moving Wireless Devices

Gayathri Chandrasekaran, Mesut Ali Ergin, Marco Gruteser, Rich Martin (WINLAB, Rutgers University) Jie Yang and Yingying Chen (Department of ECE, Stevens Institute of Technology)

Co-Movement

Moving Together in Close Proximity

– (~ Few Meters)

Movement of

– Multiple Transmitters held by the same person – Multiple Radios attached on the same device.

Motivation

GSM <SIM ID> Wifi <MAC Address> Bluetooth <Bluetooth ID>

How to map different Transmitters to a Device or Person ?

• Friend Finder Application

Motivation: Social Network Mining

Dynamic Human Social Network. Viral Marketing (use pre-existing social networks to produce increases in brand awareness)

Localize and Estimate ?

(X1,Y1)

Localize and Estimate ?

Co- Mobile: Euclidean Distance < Threshold

TRIVIAL ?

Localize and Estimate ? Position Estimates Are Not Stable Co-Mobile Transmitters

Approach

Detect Co-Movement by Observing RSSI

– Co-Moving transmitters have Correlated fades – Dynamics of the environment are captured

Metric: Correlation Coefficient.

Properties of Co-Mobile Transmitters

Mobile: Small Scale Fading & Shadow Fading Different Small Scale Fading Similar Shadow Fading

Non- Co-Mobile Transmitters

Different Small Scale And Large Scale Fading

Correlation Co-Efficient

Pearson’s Product Moment Correlation Coefficient:- Determines the Linear Relationship between two Random Variables (Observed RSSI from 2 Devices) Ranges between [-1, +1] +1 - Strong Positive Correlation

• No Correlation
• 1 - Strong Negative Correlation

Experiment Goals

• 1. Quantify Co-Movement detection rates
• 1. Within Same Technology
• 2. Across Different Radio Technology
• 2. Quantify the Effect of Speed on the time

taken to detect co-movement

Experimental Setup

5

Detecting Co-Movement (Similar Radio - Wifi)

Impact of Speed on Co-Movement Detection Time

Threshold = 0.6 Conclusion: 50-100 Sec

• f Observation Required.

Impact of Speed on Co-Movement Detection Time

Other Observations

Sampling rates have a little effect Works with mixed radio technologies (in 2.4GHz band) motes, wifi Correlation Co-Efficient Threshold = 0.6 yields High Detection Rates and Low False Positives Detect Mobile Periods by Observing Variance(>3)

• f RSSI over time.

Note: It only needs a single measurement node (base station)

Conclusion and Future Work

Simple and effective technique to Detecting Co- Mobile transmitters through signal strength analysis ( 2 minutes of Observation ) Can work with just 1 receiver when the Localization infrastructure is Not in place Future Work - Would a similar technique work

• utdoors using cellular signal strength information

to detect co-moving cell phones?

QUESTIONS?

Thanks !

Determining Threshold (Τ)

Detecting Co-Movement (Different Radios)

Co-mobile Mote and Wifi

Mobility Detection using Variance.

Impact of Sampling Rate in Co-Movement Detection Time

DECODE System Design

Summary

Simple and effective technique to Detecting Co- Mobile transmitters through signal strength analysis ( 2 minutes of Observation ) Can work with just 1 receiver when the Localization infrastructure is Not in place Can Work Across radio Technologies Lesser Time with increased Speed. Insensitive to Sampling Frequency.

Future Work

Would a similar technique work outdoors using cellular signal strength information to detect co- moving cell phones? Application in Mind: Optimize phone Battery life by turning off the GPS for one of the Co-Mobile Devices. How to Extend this to Detect Static Co-Located Transmitters?