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Cricket ,[object Object]
Cricket Goals ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]
Features ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]
Cricket: Private location-support Beacon Listener Pick nearest to  infer  space No central beacon control or location database Passive Listeners + Active Beacons space = “a1” space = “a2”
Finding the distance ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]
Finding the distance ,[object Object],[object Object],[object Object]
Finding the distance ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]
Location Estimation •  Distance estimation via coupled RF and ultrasonic signals –  Beacons send information on the RF channel with concurrent ultrasonic pulse Beacon Listener Ultrasound (pulse) RF info
Uncoordinated Beacons Beacon A Beacon B t RF B RF A US B US A Incorrect distance •  Multiple beacon transmissions are uncoordinated •  Different beacon transmissions can interfere –  Causes inaccurate distance measurements at the listener
Multiple Beacons •  Beacon transmissions are uncoordinated •  Ultrasonic signals reflect heavily •  Ultrasonic signals are pulses (no data) These make the correlation problem hard and can lead to incorrect distance estimates Beacon A Beacon B t RF B RF A US B US A Incorrect distance Listener
Solution ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]
Bounding Stray Signal Interference •  Engineer RF range to be  larger  than ultrasonic range –  Ensures that if listener can hear ultrasound, corresponding RF will also be heard t RF A US A
Bounding Stray Signal Interference S   = size of space advertisement b   =  RF bit rate r   = ultrasound range v   = velocity of ultrasound (RF transmission time)  (Max. RF-US separation at the listener) S  r b  v •  No “unaccompanied” ultrasonic signal can be valid! t S/b r/v (max)
Bounding stray signal interference •  Envelop ultrasound by RF •  Interfering ultrasound causes RF signals to collide •  Listener does a block parity error check –  The reading is discarded... t RF A US A RF B US B
Problem: Closest Beacon May Not Reflect Correct Space I am at B Room A Room B
Correct Beacon Placement Room A Room B x x I am at A •  Position beacons to detect the boundary •  Multiple Beacons per space are possible
Implementation •  Cricket beacon and listener Micro- controller RF US Micro- controller RF US RS232
Cricket v1 Prototype Ultrasonic sensor RF antenna RF module (rcv) Atmel processor Listener Beacon RF module (xmit) RS232 i/f
Cricket v1 Prototype
Cricket Beacon LEDs ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Power Switch On Off Debug Switch Beacon ID
Cricket Beacon Antennas ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Transmit antenna Receive antenna
Listener LEDs ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Off  On Power Switch
Software Components Cricket Listener cricketd Application 1 Application 2 Application 3 Cricket Beacon 1 Cricket Beacon 2 Binary Data Over RF ASCII data over serial port 9600 baud ASCII data on TCP sockets (port 2947)
cricketd ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]
Cricket Listener Output ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],t dist duration
Speed of Sound ,[object Object],[object Object],[object Object],[object Object]
So where are you? ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]
So whre are you? ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]
Two beacons ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]
Orientation Orientation relative to B on horizontal plane Mobile device (parallel to horizontal plane) Beacons on ceiling Cricket listener with compass hardware
Hardware Design ,[object Object],[object Object],[object Object],[object Object],[object Object]

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Tutorial 8 Cricket

  • 1.
  • 2.
  • 3.
  • 4. Cricket: Private location-support Beacon Listener Pick nearest to infer space No central beacon control or location database Passive Listeners + Active Beacons space = “a1” space = “a2”
  • 5.
  • 6.
  • 7.
  • 8. Location Estimation • Distance estimation via coupled RF and ultrasonic signals – Beacons send information on the RF channel with concurrent ultrasonic pulse Beacon Listener Ultrasound (pulse) RF info
  • 9. Uncoordinated Beacons Beacon A Beacon B t RF B RF A US B US A Incorrect distance • Multiple beacon transmissions are uncoordinated • Different beacon transmissions can interfere – Causes inaccurate distance measurements at the listener
  • 10. Multiple Beacons • Beacon transmissions are uncoordinated • Ultrasonic signals reflect heavily • Ultrasonic signals are pulses (no data) These make the correlation problem hard and can lead to incorrect distance estimates Beacon A Beacon B t RF B RF A US B US A Incorrect distance Listener
  • 11.
  • 12. Bounding Stray Signal Interference • Engineer RF range to be larger than ultrasonic range – Ensures that if listener can hear ultrasound, corresponding RF will also be heard t RF A US A
  • 13. Bounding Stray Signal Interference S = size of space advertisement b = RF bit rate r = ultrasound range v = velocity of ultrasound (RF transmission time) (Max. RF-US separation at the listener) S r b v • No “unaccompanied” ultrasonic signal can be valid! t S/b r/v (max)
  • 14. Bounding stray signal interference • Envelop ultrasound by RF • Interfering ultrasound causes RF signals to collide • Listener does a block parity error check – The reading is discarded... t RF A US A RF B US B
  • 15. Problem: Closest Beacon May Not Reflect Correct Space I am at B Room A Room B
  • 16. Correct Beacon Placement Room A Room B x x I am at A • Position beacons to detect the boundary • Multiple Beacons per space are possible
  • 17. Implementation • Cricket beacon and listener Micro- controller RF US Micro- controller RF US RS232
  • 18. Cricket v1 Prototype Ultrasonic sensor RF antenna RF module (rcv) Atmel processor Listener Beacon RF module (xmit) RS232 i/f
  • 20.
  • 21.
  • 22.
  • 23. Software Components Cricket Listener cricketd Application 1 Application 2 Application 3 Cricket Beacon 1 Cricket Beacon 2 Binary Data Over RF ASCII data over serial port 9600 baud ASCII data on TCP sockets (port 2947)
  • 24.
  • 25.
  • 26.
  • 27.
  • 28.
  • 29.
  • 30. Orientation Orientation relative to B on horizontal plane Mobile device (parallel to horizontal plane) Beacons on ceiling Cricket listener with compass hardware
  • 31.