{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Thiagarajan-VTrack - VTrack Accurate Energy-Aware Road...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
VTrack: Accurate, Energy-Aware Road Traffic Delay Estimation Using Mobile Phones Arvind Thiagarajan, Lenin Ravindranath, Katrina LaCurts, Sivan Toledo Jakob Eriksson Samuel Madden, Hari Balakrishnan Tel-Aviv University U. Illinois Chicago MIT CSAIL [email protected] [email protected] { arvindt,lenin,katrina,madden,hari } @csail.mit.edu Abstract Traffic delays and congestion are a major source of ineffi- ciency, wasted fuel, and commuter frustration. Measuring and localizing these delays, and routing users around them, is an important step towards reducing the time people spend stuck in traffic. As others have noted, the proliferation of commod- ity smartphones that can provide location estimates using a variety of sensors—GPS, WiFi, and/or cellular triangulation— opens up the attractive possibility of using position samples from drivers’ phones to monitor traffic delays at a fine spatio- temporal granularity. This paper presents VTrack, a system for travel time estimation using this sensor data that addresses two key challenges: energy consumption and sensor unreliability. While GPS provides highly accurate location estimates, it has several limitations: some phones don’t have GPS at all, the GPS sensor doesn’t work in “urban canyons” (tall buildings and tunnels) or when the phone is inside a pocket, and the GPS on many phones is power-hungry and drains the bat- tery quickly. In these cases, VTrack can use alternative, less energy-hungry but noisier sensors like WiFi to estimate both a user’s trajectory and travel time along the route. VTrack uses a hidden Markov model (HMM)-based map matching scheme and travel time estimation method that interpolates sparse data to identify the most probable road segments driven by the user and to attribute travel times to those segments. We present experimental results from real drive data and WiFi access point sightings gathered from a deployment on several cars. We show that VTrack can tolerate significant noise and outages in these location estimates, and still successfully iden- tify delay-prone segments, and provide accurate enough delays for delay-aware routing algorithms. We also study the best sampling strategies for WiFi and GPS sensors for different energy cost regimes. Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. SenSys’09, November 4–6, 2009, Berkeley, CA, USA. Copyright 2009 ACM 978-1-60558-748-6 ...$5.00 Categories and Subject Descriptors C.2 [ Computer Communication Networks ]: Distributed Applications General Terms Algorithms, Measurement Keywords GPS, Location, Localization, Traffic, Congestion, Mobile, Phone, Car, Transportation, Energy, Sensor 1 Introduction
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}