DETECTING DRIVER PHONE USE LEVERAGING CAR SPEAKERS
Jie Yang, Simon Sidhom, Gayathri Chandrasekaran, Tam Vu, Hongbo Liu, Nicolae Cecan, Yingying Chen, Marco Gruteser, Richard P. Martin
MobiCom 2011
- Sowhat 2011.10.24
INTRODUCTION
MOTIVATION
Cell Phone Distraction
Hands-free Phone Operation
Driving Mode• Route incoming calls to
voicemail• Delay incoming text
notification
Driver? Passenger?
INTRODUCTION
OBJECTIVE Classify phone use @ which seat
Bluetooth + Audio infrastructure
Phone Transmit Signal
Car Head Unit
Speaker Play
Signal
Phone Record
Processing
SYSTEM DESIGN
BEEP SIGNALUnobtrusivenessRobustness to Noise
Frequency Android developer phone 2 – 16~18kHz iPhone 3G – 18~20kHz
Length – 10ms
SYSTEM DESIGN
DETECT BEEP Sequential change-point detection
: sequence of recorded audio signal
Requirement: known distribution
Cumulative sum μ : mean value of noise from t0 to t1, time of
transmitting
> Threshold for W samples
EXPERIMENT
PHONES & CARS Phones
Android Developer Phone 2, Phone I iPhone 3G, Phone II
Cars Honda Civic Si Coupe, Car I Acura Sedan, Car II 2 channel sound system with fader system
EXPERIMENT
PROCEDURE Create Beep
4 beep audio files, For { Phone I, Phone II } x { 2 channel, 4 channel } Each file with 4 beeps for each channel
Create uniformly distributed white noise
Bandpass filter {16~18, 18~20} kHz
Transmit Laptop to car’s head unit via Bluetooth
Record Audio recorder app. on phone for offline analysis
RESULTS
COMPUTATIONAL COMPLEXITY Filtering, Short-time Fourier transform
n recorded samples, moving window size
After filtering,
Average processing time 0.5s for 2-channel 1s for 4-channel
CONCLUSION Driver mobile phone use detection system
Leverage existing infrastructure of car speaker for ranging via Bluetooth
Acoustic relative-ranging
Over 90% detection rate
DISCUSSION Strengthens
Clear motivation, system design description Real implement
Weakness Different setting for different hardware
not comparable How to set calibration value