ALPS: A Bluetooth and Ultrasound Platform for Mapping and Localization Patrick Lazik, Niranjini Rajagopal, Oliver Shih, Bruno Sinopoli, Anthony Rowe Electrical and Computer Engineering Department Carnegie Mellon University http://wise.ece.cmu.edu
Localization Approaches Range-Based (Distance) Kinect RADAR GPS Ultrasonic WiFi RFID 2 LIDAR Cellular Bluetooth Low-Energy Magnetic Field IMU VLC Audio Range-Free (Landmarks)
ALPS Smartphone Acoustic Ultrasonic Localization Ranging for Mobile Devices Uses near-ultrasound communication Commodity mobile hardware Provide accurate indoor localization Sub-meter, confined to rooms Time Difference of Arrival (TDOA) SenSys 2015 3
System Architecture Speaker Phone 4
Challenges Transmitting omnidirectional ultrasonic signals is difficult with standard speakers Installation and setup Obstructions (bodies) can block transmitters TDOA to TOF (RTAS 2015) Multipath signals cause measurement errors 5
Introducing ALPS Easily Deployable Ultrasonic Localization BLE, 802.15.4, Ultrasonic SenSys 2012 6 Come see our Demo!
ALPS Enhancements Embedded beacons Hardware Ultrasonic Horn Design Improved data transmission Simplified system setup Tracking with IMU data Multipath Detection 7
Original Hard-Wired Setup 8
BLE Antenna The ALPS Platform 802.15.4 Antenna Piezo Bullet Driver Battery Pack Horn 9 Back Microphone Front
The ALPS Platform TLV320 Audio Codec Microphone Atmega256RFR2 SoC RF Amplifier 10
Omnidirectional Sound Dispersion Ideally ALPS beacons should disperse ultrasound in omnidirectional manner Directivity pattern of speakers becomes more narrow as frequency increases 11
Omnidirectional Sound Dispersion 12
Omnidirectional Horn Design Horns increase the overall efficiency of driving elements A rotated horn will disperse sound omnidirectionally 13
Omnidirectional Sound Dispersion 14
Omnidirectional Horn Performance Evaluation criteria: Directional distortion: deviation from omnidirectionality Frequency distortion: flatness of frequency response 15
Omnidirectional Horn Performance 16
ALPS Enhancements Embedded beacons Improved data transmission Integration with BLE Simplified system setup Tracking with IMU data Multipath Detection 17
Transmitter Identification Originally modulated transmitter ID onto ultrasound carrier Long packet length, limited robustness Ultrasound is good for ranging BLE is better for data 18
System Architecture Beacon BLE Data Phone 19
The ALPS Platform 802.15.4 Antenna CC2460 SoC BLE Antenna 20
BLE TDMA Slot Synchronization τ tx0 Slot 0 Slot 1 a) τ tx1 τ tx2 τ tx3 τ tx4... b) c) τ rx0 21
BLE Synchronization Performance Typical TDMA slot length of 100ms 100ms advertisement interval 50ms advertisement interval 20ms advertisement interval 22
ALPS Enhancements Embedded beacons Improved data transmission Integration with BLE Simplified system setup Tracking with IMU data Multipath Detection 23
User Assisted Mapping and Setup Precise positioning of beacons, even in small installations is difficult Developed automated setup procedure for determining beacon locations and floorplan 24
User Assisted Mapping and Setup Beacon 25
Inter-beacon Ranging Beacon Inter-Node Ranging 26
Synchronize Receiver to Transmitters Beacon Inter-Node Ranging 27
Define Z Axis Beacon Inter-Node Ranging Beacon Ultrasound z Phone 28
Define X and Y Axis Beacon Inter-Node Ranging Beacon Ultrasound z y x Phone 29
Draw Floorplan Beacon Inter-Node Ranging Phone Beacon Ultrasound z y x 30
User-Assisted Mapping Performance 31
ALPS Enhancements Embedded beacons Improved data transmission Integration with BLE Simplified system setup Tracking with IMU data Multipath Detection 32
Tracking Use Case Insufficient Beacons SenSys 2015 Beacons blocked
ALPS Localization Performance Localization 12 True path Localization 10 8 y (m) 6 4 2 0-6 -4-2 0 2 4 6 8 10 x (m) 34
ALPS and PDR Performance Localization, PDR, both, with no obstacles 12 10 True path Dead Reckoning Localization Localization + Tracking 8 y (m) 6 4 2 0-6 -4-2 0 2 4 6 8 10 x (m) 35
ALPS with Obstacles Performance 12 True path Localization 10 8 y (m) 6 4 2 0-6 -4-2 0 2 4 6 8 10 x (m) 36
ALPS with Obstacles and PDR Performance 12 True path Localization Localization + Tracking 10 8 y (m) 6 4 2 0-6 -4-2 0 2 4 6 8 10 x (m) 37
ALPS and PDR Performance 38
ALPS Enhancements Embedded beacons Improved data transmission Integration with BLE Simplified system setup Tracking with IMU data Multipath detection 39
Multipath Detection Ultrasonic BLE True range Multipath range Signal propagation different Attenuation characteristics different 40
SVM Classifier Features and Accuracy Ratio of received ultrasound RSSI to TOF distance Ratio of received BLE RSSI to BLE distance RMS delay spread of received ultrasound signal 41
Impact of Training Samples of F ib and F us Performance 42
Conclusion Indoor localization systems need to be: Precise, cheap and simple to install ALPS has cheap hardware and supports a userassisted setup procedure Range based localization systems suffer from multipath ranging error ALPS incorporates a machine learning based LOS/ NLOS filtering approach 43
Questions 44