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Cricket PowerPoint Presentation

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PowerPoint is the world's most popular presentation software which can let you create professional Cricket powerpoint presentation easily and in no time. This helps you give your presentation on Cricket in a conference, a school lecture, a business proposal, in a webinar and business and professional representations.

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Slide 1 - Cricket Tutorial on using cricket location system
Slide 2 - Cricket Tutorial on using cricket location system 2 Cricket Goals Research prototype build and then evaluate Useful mainly indoor environments walls, ceilings not too far Recognize spaces, not just physical position good boundary detection is important doors, floors, etc. Preserve user’s privacy Big-brother can be a bother user has choice to reveal location
Slide 3 - Cricket Tutorial on using cricket location system 2 Cricket Goals Research prototype build and then evaluate Useful mainly indoor environments walls, ceilings not too far Recognize spaces, not just physical position good boundary detection is important doors, floors, etc. Preserve user’s privacy Big-brother can be a bother user has choice to reveal location 3 Features Distributed architecture No wired infrastructure Easy deployment (no satellites) Low maintenance Users are not tracked Listeners are passive Large number of listeners w/o interference Integrates with a wide range of resource discovery systems
Slide 4 - Cricket Tutorial on using cricket location system 2 Cricket Goals Research prototype build and then evaluate Useful mainly indoor environments walls, ceilings not too far Recognize spaces, not just physical position good boundary detection is important doors, floors, etc. Preserve user’s privacy Big-brother can be a bother user has choice to reveal location 3 Features Distributed architecture No wired infrastructure Easy deployment (no satellites) Low maintenance Users are not tracked Listeners are passive Large number of listeners w/o interference Integrates with a wide range of resource discovery systems Cricket: Private location-support Beacon Listener space = “a1” space = “a2” Pick nearest to infer space No central beacon control or location database Passive Listeners + Active Beacons
Slide 5 - Cricket Tutorial on using cricket location system 2 Cricket Goals Research prototype build and then evaluate Useful mainly indoor environments walls, ceilings not too far Recognize spaces, not just physical position good boundary detection is important doors, floors, etc. Preserve user’s privacy Big-brother can be a bother user has choice to reveal location 3 Features Distributed architecture No wired infrastructure Easy deployment (no satellites) Low maintenance Users are not tracked Listeners are passive Large number of listeners w/o interference Integrates with a wide range of resource discovery systems Cricket: Private location-support Beacon Listener space = “a1” space = “a2” Pick nearest to infer space No central beacon control or location database Passive Listeners + Active Beacons 5 Finding the distance distance = speed * time want to find the distance we know the speed How do we figure out time? Radar: measure round-trip time cannot use it as it violates some goals
Slide 6 - Cricket Tutorial on using cricket location system 2 Cricket Goals Research prototype build and then evaluate Useful mainly indoor environments walls, ceilings not too far Recognize spaces, not just physical position good boundary detection is important doors, floors, etc. Preserve user’s privacy Big-brother can be a bother user has choice to reveal location 3 Features Distributed architecture No wired infrastructure Easy deployment (no satellites) Low maintenance Users are not tracked Listeners are passive Large number of listeners w/o interference Integrates with a wide range of resource discovery systems Cricket: Private location-support Beacon Listener space = “a1” space = “a2” Pick nearest to infer space No central beacon control or location database Passive Listeners + Active Beacons 5 Finding the distance distance = speed * time want to find the distance we know the speed How do we figure out time? Radar: measure round-trip time cannot use it as it violates some goals 6 Finding the distance Synchronized clocks receiver knows exactly when transmitter sent signal how about sending signal first to sync clocks and then 2nd signal?
Slide 7 - Cricket Tutorial on using cricket location system 2 Cricket Goals Research prototype build and then evaluate Useful mainly indoor environments walls, ceilings not too far Recognize spaces, not just physical position good boundary detection is important doors, floors, etc. Preserve user’s privacy Big-brother can be a bother user has choice to reveal location 3 Features Distributed architecture No wired infrastructure Easy deployment (no satellites) Low maintenance Users are not tracked Listeners are passive Large number of listeners w/o interference Integrates with a wide range of resource discovery systems Cricket: Private location-support Beacon Listener space = “a1” space = “a2” Pick nearest to infer space No central beacon control or location database Passive Listeners + Active Beacons 5 Finding the distance distance = speed * time want to find the distance we know the speed How do we figure out time? Radar: measure round-trip time cannot use it as it violates some goals 6 Finding the distance Synchronized clocks receiver knows exactly when transmitter sent signal how about sending signal first to sync clocks and then 2nd signal? 7 Finding the distance Use two different speed signals both start at same time d = s1 * t1 d = s2 * t2 We measure delay: m = t1 - t2 t2 = m * s1/(s2 - s1) d = m * s2 s1 /(s2 - s1)
Slide 8 - Cricket Tutorial on using cricket location system 2 Cricket Goals Research prototype build and then evaluate Useful mainly indoor environments walls, ceilings not too far Recognize spaces, not just physical position good boundary detection is important doors, floors, etc. Preserve user’s privacy Big-brother can be a bother user has choice to reveal location 3 Features Distributed architecture No wired infrastructure Easy deployment (no satellites) Low maintenance Users are not tracked Listeners are passive Large number of listeners w/o interference Integrates with a wide range of resource discovery systems Cricket: Private location-support Beacon Listener space = “a1” space = “a2” Pick nearest to infer space No central beacon control or location database Passive Listeners + Active Beacons 5 Finding the distance distance = speed * time want to find the distance we know the speed How do we figure out time? Radar: measure round-trip time cannot use it as it violates some goals 6 Finding the distance Synchronized clocks receiver knows exactly when transmitter sent signal how about sending signal first to sync clocks and then 2nd signal? 7 Finding the distance Use two different speed signals both start at same time d = s1 * t1 d = s2 * t2 We measure delay: m = t1 - t2 t2 = m * s1/(s2 - s1) d = m * s2 s1 /(s2 - s1) 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)
Slide 9 - Cricket Tutorial on using cricket location system 2 Cricket Goals Research prototype build and then evaluate Useful mainly indoor environments walls, ceilings not too far Recognize spaces, not just physical position good boundary detection is important doors, floors, etc. Preserve user’s privacy Big-brother can be a bother user has choice to reveal location 3 Features Distributed architecture No wired infrastructure Easy deployment (no satellites) Low maintenance Users are not tracked Listeners are passive Large number of listeners w/o interference Integrates with a wide range of resource discovery systems Cricket: Private location-support Beacon Listener space = “a1” space = “a2” Pick nearest to infer space No central beacon control or location database Passive Listeners + Active Beacons 5 Finding the distance distance = speed * time want to find the distance we know the speed How do we figure out time? Radar: measure round-trip time cannot use it as it violates some goals 6 Finding the distance Synchronized clocks receiver knows exactly when transmitter sent signal how about sending signal first to sync clocks and then 2nd signal? 7 Finding the distance Use two different speed signals both start at same time d = s1 * t1 d = s2 * t2 We measure delay: m = t1 - t2 t2 = m * s1/(s2 - s1) d = m * s2 s1 /(s2 - s1) 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) 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
Slide 10 - Cricket Tutorial on using cricket location system 2 Cricket Goals Research prototype build and then evaluate Useful mainly indoor environments walls, ceilings not too far Recognize spaces, not just physical position good boundary detection is important doors, floors, etc. Preserve user’s privacy Big-brother can be a bother user has choice to reveal location 3 Features Distributed architecture No wired infrastructure Easy deployment (no satellites) Low maintenance Users are not tracked Listeners are passive Large number of listeners w/o interference Integrates with a wide range of resource discovery systems Cricket: Private location-support Beacon Listener space = “a1” space = “a2” Pick nearest to infer space No central beacon control or location database Passive Listeners + Active Beacons 5 Finding the distance distance = speed * time want to find the distance we know the speed How do we figure out time? Radar: measure round-trip time cannot use it as it violates some goals 6 Finding the distance Synchronized clocks receiver knows exactly when transmitter sent signal how about sending signal first to sync clocks and then 2nd signal? 7 Finding the distance Use two different speed signals both start at same time d = s1 * t1 d = s2 * t2 We measure delay: m = t1 - t2 t2 = m * s1/(s2 - s1) d = m * s2 s1 /(s2 - s1) 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) 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
Slide 11 - Cricket Tutorial on using cricket location system 2 Cricket Goals Research prototype build and then evaluate Useful mainly indoor environments walls, ceilings not too far Recognize spaces, not just physical position good boundary detection is important doors, floors, etc. Preserve user’s privacy Big-brother can be a bother user has choice to reveal location 3 Features Distributed architecture No wired infrastructure Easy deployment (no satellites) Low maintenance Users are not tracked Listeners are passive Large number of listeners w/o interference Integrates with a wide range of resource discovery systems Cricket: Private location-support Beacon Listener space = “a1” space = “a2” Pick nearest to infer space No central beacon control or location database Passive Listeners + Active Beacons 5 Finding the distance distance = speed * time want to find the distance we know the speed How do we figure out time? Radar: measure round-trip time cannot use it as it violates some goals 6 Finding the distance Synchronized clocks receiver knows exactly when transmitter sent signal how about sending signal first to sync clocks and then 2nd signal? 7 Finding the distance Use two different speed signals both start at same time d = s1 * t1 d = s2 * t2 We measure delay: m = t1 - t2 t2 = m * s1/(s2 - s1) d = m * s2 s1 /(s2 - s1) 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) 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 Solution Carrier-sense + randomized transmission reduce chance of concurrent beacons Bounding stray signal interference envelop all ultrasonic signals with RF Listener inference algorithm Processing distance samples to estimate location
Slide 12 - Cricket Tutorial on using cricket location system 2 Cricket Goals Research prototype build and then evaluate Useful mainly indoor environments walls, ceilings not too far Recognize spaces, not just physical position good boundary detection is important doors, floors, etc. Preserve user’s privacy Big-brother can be a bother user has choice to reveal location 3 Features Distributed architecture No wired infrastructure Easy deployment (no satellites) Low maintenance Users are not tracked Listeners are passive Large number of listeners w/o interference Integrates with a wide range of resource discovery systems Cricket: Private location-support Beacon Listener space = “a1” space = “a2” Pick nearest to infer space No central beacon control or location database Passive Listeners + Active Beacons 5 Finding the distance distance = speed * time want to find the distance we know the speed How do we figure out time? Radar: measure round-trip time cannot use it as it violates some goals 6 Finding the distance Synchronized clocks receiver knows exactly when transmitter sent signal how about sending signal first to sync clocks and then 2nd signal? 7 Finding the distance Use two different speed signals both start at same time d = s1 * t1 d = s2 * t2 We measure delay: m = t1 - t2 t2 = m * s1/(s2 - s1) d = m * s2 s1 /(s2 - s1) 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) 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 Solution Carrier-sense + randomized transmission reduce chance of concurrent beacons Bounding stray signal interference envelop all ultrasonic signals with RF Listener inference algorithm Processing distance samples to estimate location 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
Slide 13 - Cricket Tutorial on using cricket location system 2 Cricket Goals Research prototype build and then evaluate Useful mainly indoor environments walls, ceilings not too far Recognize spaces, not just physical position good boundary detection is important doors, floors, etc. Preserve user’s privacy Big-brother can be a bother user has choice to reveal location 3 Features Distributed architecture No wired infrastructure Easy deployment (no satellites) Low maintenance Users are not tracked Listeners are passive Large number of listeners w/o interference Integrates with a wide range of resource discovery systems Cricket: Private location-support Beacon Listener space = “a1” space = “a2” Pick nearest to infer space No central beacon control or location database Passive Listeners + Active Beacons 5 Finding the distance distance = speed * time want to find the distance we know the speed How do we figure out time? Radar: measure round-trip time cannot use it as it violates some goals 6 Finding the distance Synchronized clocks receiver knows exactly when transmitter sent signal how about sending signal first to sync clocks and then 2nd signal? 7 Finding the distance Use two different speed signals both start at same time d = s1 * t1 d = s2 * t2 We measure delay: m = t1 - t2 t2 = m * s1/(s2 - s1) d = m * s2 s1 /(s2 - s1) 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) 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 Solution Carrier-sense + randomized transmission reduce chance of concurrent beacons Bounding stray signal interference envelop all ultrasonic signals with RF Listener inference algorithm Processing distance samples to estimate location 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 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!
Slide 14 - Cricket Tutorial on using cricket location system 2 Cricket Goals Research prototype build and then evaluate Useful mainly indoor environments walls, ceilings not too far Recognize spaces, not just physical position good boundary detection is important doors, floors, etc. Preserve user’s privacy Big-brother can be a bother user has choice to reveal location 3 Features Distributed architecture No wired infrastructure Easy deployment (no satellites) Low maintenance Users are not tracked Listeners are passive Large number of listeners w/o interference Integrates with a wide range of resource discovery systems Cricket: Private location-support Beacon Listener space = “a1” space = “a2” Pick nearest to infer space No central beacon control or location database Passive Listeners + Active Beacons 5 Finding the distance distance = speed * time want to find the distance we know the speed How do we figure out time? Radar: measure round-trip time cannot use it as it violates some goals 6 Finding the distance Synchronized clocks receiver knows exactly when transmitter sent signal how about sending signal first to sync clocks and then 2nd signal? 7 Finding the distance Use two different speed signals both start at same time d = s1 * t1 d = s2 * t2 We measure delay: m = t1 - t2 t2 = m * s1/(s2 - s1) d = m * s2 s1 /(s2 - s1) 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) 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 Solution Carrier-sense + randomized transmission reduce chance of concurrent beacons Bounding stray signal interference envelop all ultrasonic signals with RF Listener inference algorithm Processing distance samples to estimate location 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 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! 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
Slide 15 - Cricket Tutorial on using cricket location system 2 Cricket Goals Research prototype build and then evaluate Useful mainly indoor environments walls, ceilings not too far Recognize spaces, not just physical position good boundary detection is important doors, floors, etc. Preserve user’s privacy Big-brother can be a bother user has choice to reveal location 3 Features Distributed architecture No wired infrastructure Easy deployment (no satellites) Low maintenance Users are not tracked Listeners are passive Large number of listeners w/o interference Integrates with a wide range of resource discovery systems Cricket: Private location-support Beacon Listener space = “a1” space = “a2” Pick nearest to infer space No central beacon control or location database Passive Listeners + Active Beacons 5 Finding the distance distance = speed * time want to find the distance we know the speed How do we figure out time? Radar: measure round-trip time cannot use it as it violates some goals 6 Finding the distance Synchronized clocks receiver knows exactly when transmitter sent signal how about sending signal first to sync clocks and then 2nd signal? 7 Finding the distance Use two different speed signals both start at same time d = s1 * t1 d = s2 * t2 We measure delay: m = t1 - t2 t2 = m * s1/(s2 - s1) d = m * s2 s1 /(s2 - s1) 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) 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 Solution Carrier-sense + randomized transmission reduce chance of concurrent beacons Bounding stray signal interference envelop all ultrasonic signals with RF Listener inference algorithm Processing distance samples to estimate location 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 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! 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
Slide 16 - Cricket Tutorial on using cricket location system 2 Cricket Goals Research prototype build and then evaluate Useful mainly indoor environments walls, ceilings not too far Recognize spaces, not just physical position good boundary detection is important doors, floors, etc. Preserve user’s privacy Big-brother can be a bother user has choice to reveal location 3 Features Distributed architecture No wired infrastructure Easy deployment (no satellites) Low maintenance Users are not tracked Listeners are passive Large number of listeners w/o interference Integrates with a wide range of resource discovery systems Cricket: Private location-support Beacon Listener space = “a1” space = “a2” Pick nearest to infer space No central beacon control or location database Passive Listeners + Active Beacons 5 Finding the distance distance = speed * time want to find the distance we know the speed How do we figure out time? Radar: measure round-trip time cannot use it as it violates some goals 6 Finding the distance Synchronized clocks receiver knows exactly when transmitter sent signal how about sending signal first to sync clocks and then 2nd signal? 7 Finding the distance Use two different speed signals both start at same time d = s1 * t1 d = s2 * t2 We measure delay: m = t1 - t2 t2 = m * s1/(s2 - s1) d = m * s2 s1 /(s2 - s1) 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) 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 Solution Carrier-sense + randomized transmission reduce chance of concurrent beacons Bounding stray signal interference envelop all ultrasonic signals with RF Listener inference algorithm Processing distance samples to estimate location 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 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! 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
Slide 17 - Cricket Tutorial on using cricket location system 2 Cricket Goals Research prototype build and then evaluate Useful mainly indoor environments walls, ceilings not too far Recognize spaces, not just physical position good boundary detection is important doors, floors, etc. Preserve user’s privacy Big-brother can be a bother user has choice to reveal location 3 Features Distributed architecture No wired infrastructure Easy deployment (no satellites) Low maintenance Users are not tracked Listeners are passive Large number of listeners w/o interference Integrates with a wide range of resource discovery systems Cricket: Private location-support Beacon Listener space = “a1” space = “a2” Pick nearest to infer space No central beacon control or location database Passive Listeners + Active Beacons 5 Finding the distance distance = speed * time want to find the distance we know the speed How do we figure out time? Radar: measure round-trip time cannot use it as it violates some goals 6 Finding the distance Synchronized clocks receiver knows exactly when transmitter sent signal how about sending signal first to sync clocks and then 2nd signal? 7 Finding the distance Use two different speed signals both start at same time d = s1 * t1 d = s2 * t2 We measure delay: m = t1 - t2 t2 = m * s1/(s2 - s1) d = m * s2 s1 /(s2 - s1) 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) 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 Solution Carrier-sense + randomized transmission reduce chance of concurrent beacons Bounding stray signal interference envelop all ultrasonic signals with RF Listener inference algorithm Processing distance samples to estimate location 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 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! 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
Slide 18 - Cricket Tutorial on using cricket location system 2 Cricket Goals Research prototype build and then evaluate Useful mainly indoor environments walls, ceilings not too far Recognize spaces, not just physical position good boundary detection is important doors, floors, etc. Preserve user’s privacy Big-brother can be a bother user has choice to reveal location 3 Features Distributed architecture No wired infrastructure Easy deployment (no satellites) Low maintenance Users are not tracked Listeners are passive Large number of listeners w/o interference Integrates with a wide range of resource discovery systems Cricket: Private location-support Beacon Listener space = “a1” space = “a2” Pick nearest to infer space No central beacon control or location database Passive Listeners + Active Beacons 5 Finding the distance distance = speed * time want to find the distance we know the speed How do we figure out time? Radar: measure round-trip time cannot use it as it violates some goals 6 Finding the distance Synchronized clocks receiver knows exactly when transmitter sent signal how about sending signal first to sync clocks and then 2nd signal? 7 Finding the distance Use two different speed signals both start at same time d = s1 * t1 d = s2 * t2 We measure delay: m = t1 - t2 t2 = m * s1/(s2 - s1) d = m * s2 s1 /(s2 - s1) 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) 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 Solution Carrier-sense + randomized transmission reduce chance of concurrent beacons Bounding stray signal interference envelop all ultrasonic signals with RF Listener inference algorithm Processing distance samples to estimate location 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 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! 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
Slide 19 - Cricket Tutorial on using cricket location system 2 Cricket Goals Research prototype build and then evaluate Useful mainly indoor environments walls, ceilings not too far Recognize spaces, not just physical position good boundary detection is important doors, floors, etc. Preserve user’s privacy Big-brother can be a bother user has choice to reveal location 3 Features Distributed architecture No wired infrastructure Easy deployment (no satellites) Low maintenance Users are not tracked Listeners are passive Large number of listeners w/o interference Integrates with a wide range of resource discovery systems Cricket: Private location-support Beacon Listener space = “a1” space = “a2” Pick nearest to infer space No central beacon control or location database Passive Listeners + Active Beacons 5 Finding the distance distance = speed * time want to find the distance we know the speed How do we figure out time? Radar: measure round-trip time cannot use it as it violates some goals 6 Finding the distance Synchronized clocks receiver knows exactly when transmitter sent signal how about sending signal first to sync clocks and then 2nd signal? 7 Finding the distance Use two different speed signals both start at same time d = s1 * t1 d = s2 * t2 We measure delay: m = t1 - t2 t2 = m * s1/(s2 - s1) d = m * s2 s1 /(s2 - s1) 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) 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 Solution Carrier-sense + randomized transmission reduce chance of concurrent beacons Bounding stray signal interference envelop all ultrasonic signals with RF Listener inference algorithm Processing distance samples to estimate location 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 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! 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 19 Cricket v1 Prototype
Slide 20 - Cricket Tutorial on using cricket location system 2 Cricket Goals Research prototype build and then evaluate Useful mainly indoor environments walls, ceilings not too far Recognize spaces, not just physical position good boundary detection is important doors, floors, etc. Preserve user’s privacy Big-brother can be a bother user has choice to reveal location 3 Features Distributed architecture No wired infrastructure Easy deployment (no satellites) Low maintenance Users are not tracked Listeners are passive Large number of listeners w/o interference Integrates with a wide range of resource discovery systems Cricket: Private location-support Beacon Listener space = “a1” space = “a2” Pick nearest to infer space No central beacon control or location database Passive Listeners + Active Beacons 5 Finding the distance distance = speed * time want to find the distance we know the speed How do we figure out time? Radar: measure round-trip time cannot use it as it violates some goals 6 Finding the distance Synchronized clocks receiver knows exactly when transmitter sent signal how about sending signal first to sync clocks and then 2nd signal? 7 Finding the distance Use two different speed signals both start at same time d = s1 * t1 d = s2 * t2 We measure delay: m = t1 - t2 t2 = m * s1/(s2 - s1) d = m * s2 s1 /(s2 - s1) 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) 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 Solution Carrier-sense + randomized transmission reduce chance of concurrent beacons Bounding stray signal interference envelop all ultrasonic signals with RF Listener inference algorithm Processing distance samples to estimate location 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 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! 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 19 Cricket v1 Prototype 20 Cricket Beacon LEDs Debug Switch = UP Green LED = Transmit Red LED = Carried Sensed Debug Switch = Down Green LED = Every 5th transmission At Startup LEDs flash version number Red on, Green flash count = Major # Green on, Red flash count = Minor # Power Switch Up = On Power Switch On Off Debug Switch Beacon ID
Slide 21 - Cricket Tutorial on using cricket location system 2 Cricket Goals Research prototype build and then evaluate Useful mainly indoor environments walls, ceilings not too far Recognize spaces, not just physical position good boundary detection is important doors, floors, etc. Preserve user’s privacy Big-brother can be a bother user has choice to reveal location 3 Features Distributed architecture No wired infrastructure Easy deployment (no satellites) Low maintenance Users are not tracked Listeners are passive Large number of listeners w/o interference Integrates with a wide range of resource discovery systems Cricket: Private location-support Beacon Listener space = “a1” space = “a2” Pick nearest to infer space No central beacon control or location database Passive Listeners + Active Beacons 5 Finding the distance distance = speed * time want to find the distance we know the speed How do we figure out time? Radar: measure round-trip time cannot use it as it violates some goals 6 Finding the distance Synchronized clocks receiver knows exactly when transmitter sent signal how about sending signal first to sync clocks and then 2nd signal? 7 Finding the distance Use two different speed signals both start at same time d = s1 * t1 d = s2 * t2 We measure delay: m = t1 - t2 t2 = m * s1/(s2 - s1) d = m * s2 s1 /(s2 - s1) 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) 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 Solution Carrier-sense + randomized transmission reduce chance of concurrent beacons Bounding stray signal interference envelop all ultrasonic signals with RF Listener inference algorithm Processing distance samples to estimate location 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 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! 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 19 Cricket v1 Prototype 20 Cricket Beacon LEDs Debug Switch = UP Green LED = Transmit Red LED = Carried Sensed Debug Switch = Down Green LED = Every 5th transmission At Startup LEDs flash version number Red on, Green flash count = Major # Green on, Red flash count = Minor # Power Switch Up = On Power Switch On Off Debug Switch Beacon ID 21 Cricket Beacon Antennas Receive Antenna For sensing transmission of other beacons Transmit Antenna Limit transmission distance Should not touch ultrasound Should not cover receive antenna Transmit antenna Receive antenna
Slide 22 - Cricket Tutorial on using cricket location system 2 Cricket Goals Research prototype build and then evaluate Useful mainly indoor environments walls, ceilings not too far Recognize spaces, not just physical position good boundary detection is important doors, floors, etc. Preserve user’s privacy Big-brother can be a bother user has choice to reveal location 3 Features Distributed architecture No wired infrastructure Easy deployment (no satellites) Low maintenance Users are not tracked Listeners are passive Large number of listeners w/o interference Integrates with a wide range of resource discovery systems Cricket: Private location-support Beacon Listener space = “a1” space = “a2” Pick nearest to infer space No central beacon control or location database Passive Listeners + Active Beacons 5 Finding the distance distance = speed * time want to find the distance we know the speed How do we figure out time? Radar: measure round-trip time cannot use it as it violates some goals 6 Finding the distance Synchronized clocks receiver knows exactly when transmitter sent signal how about sending signal first to sync clocks and then 2nd signal? 7 Finding the distance Use two different speed signals both start at same time d = s1 * t1 d = s2 * t2 We measure delay: m = t1 - t2 t2 = m * s1/(s2 - s1) d = m * s2 s1 /(s2 - s1) 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) 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 Solution Carrier-sense + randomized transmission reduce chance of concurrent beacons Bounding stray signal interference envelop all ultrasonic signals with RF Listener inference algorithm Processing distance samples to estimate location 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 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! 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 19 Cricket v1 Prototype 20 Cricket Beacon LEDs Debug Switch = UP Green LED = Transmit Red LED = Carried Sensed Debug Switch = Down Green LED = Every 5th transmission At Startup LEDs flash version number Red on, Green flash count = Major # Green on, Red flash count = Minor # Power Switch Up = On Power Switch On Off Debug Switch Beacon ID 21 Cricket Beacon Antennas Receive Antenna For sensing transmission of other beacons Transmit Antenna Limit transmission distance Should not touch ultrasound Should not cover receive antenna Transmit antenna Receive antenna 22 Listener LEDs Green Flash Received valid RF and ultrasound Red Flash Once Received Radio, but not ultrasound Red+Green Flash RF Error (e.g., parity error) Red and Green always on Listener not working correctly Power On Both LEDs flash together once Off On Power Switch
Slide 23 - Cricket Tutorial on using cricket location system 2 Cricket Goals Research prototype build and then evaluate Useful mainly indoor environments walls, ceilings not too far Recognize spaces, not just physical position good boundary detection is important doors, floors, etc. Preserve user’s privacy Big-brother can be a bother user has choice to reveal location 3 Features Distributed architecture No wired infrastructure Easy deployment (no satellites) Low maintenance Users are not tracked Listeners are passive Large number of listeners w/o interference Integrates with a wide range of resource discovery systems Cricket: Private location-support Beacon Listener space = “a1” space = “a2” Pick nearest to infer space No central beacon control or location database Passive Listeners + Active Beacons 5 Finding the distance distance = speed * time want to find the distance we know the speed How do we figure out time? Radar: measure round-trip time cannot use it as it violates some goals 6 Finding the distance Synchronized clocks receiver knows exactly when transmitter sent signal how about sending signal first to sync clocks and then 2nd signal? 7 Finding the distance Use two different speed signals both start at same time d = s1 * t1 d = s2 * t2 We measure delay: m = t1 - t2 t2 = m * s1/(s2 - s1) d = m * s2 s1 /(s2 - s1) 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) 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 Solution Carrier-sense + randomized transmission reduce chance of concurrent beacons Bounding stray signal interference envelop all ultrasonic signals with RF Listener inference algorithm Processing distance samples to estimate location 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 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! 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 19 Cricket v1 Prototype 20 Cricket Beacon LEDs Debug Switch = UP Green LED = Transmit Red LED = Carried Sensed Debug Switch = Down Green LED = Every 5th transmission At Startup LEDs flash version number Red on, Green flash count = Major # Green on, Red flash count = Minor # Power Switch Up = On Power Switch On Off Debug Switch Beacon ID 21 Cricket Beacon Antennas Receive Antenna For sensing transmission of other beacons Transmit Antenna Limit transmission distance Should not touch ultrasound Should not cover receive antenna Transmit antenna Receive antenna 22 Listener LEDs Green Flash Received valid RF and ultrasound Red Flash Once Received Radio, but not ultrasound Red+Green Flash RF Error (e.g., parity error) Red and Green always on Listener not working correctly Power On Both LEDs flash together once Off On Power Switch 23 Software Components
Slide 24 - Cricket Tutorial on using cricket location system 2 Cricket Goals Research prototype build and then evaluate Useful mainly indoor environments walls, ceilings not too far Recognize spaces, not just physical position good boundary detection is important doors, floors, etc. Preserve user’s privacy Big-brother can be a bother user has choice to reveal location 3 Features Distributed architecture No wired infrastructure Easy deployment (no satellites) Low maintenance Users are not tracked Listeners are passive Large number of listeners w/o interference Integrates with a wide range of resource discovery systems Cricket: Private location-support Beacon Listener space = “a1” space = “a2” Pick nearest to infer space No central beacon control or location database Passive Listeners + Active Beacons 5 Finding the distance distance = speed * time want to find the distance we know the speed How do we figure out time? Radar: measure round-trip time cannot use it as it violates some goals 6 Finding the distance Synchronized clocks receiver knows exactly when transmitter sent signal how about sending signal first to sync clocks and then 2nd signal? 7 Finding the distance Use two different speed signals both start at same time d = s1 * t1 d = s2 * t2 We measure delay: m = t1 - t2 t2 = m * s1/(s2 - s1) d = m * s2 s1 /(s2 - s1) 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) 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 Solution Carrier-sense + randomized transmission reduce chance of concurrent beacons Bounding stray signal interference envelop all ultrasonic signals with RF Listener inference algorithm Processing distance samples to estimate location 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 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! 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 19 Cricket v1 Prototype 20 Cricket Beacon LEDs Debug Switch = UP Green LED = Transmit Red LED = Carried Sensed Debug Switch = Down Green LED = Every 5th transmission At Startup LEDs flash version number Red on, Green flash count = Major # Green on, Red flash count = Minor # Power Switch Up = On Power Switch On Off Debug Switch Beacon ID 21 Cricket Beacon Antennas Receive Antenna For sensing transmission of other beacons Transmit Antenna Limit transmission distance Should not touch ultrasound Should not cover receive antenna Transmit antenna Receive antenna 22 Listener LEDs Green Flash Received valid RF and ultrasound Red Flash Once Received Radio, but not ultrasound Red+Green Flash RF Error (e.g., parity error) Red and Green always on Listener not working correctly Power On Both LEDs flash together once Off On Power Switch 23 Software Components 24 cricketd Background program (demon) that reads serial port and writes data to a socket Command line arguments (defaults work correctly on ipaq) -T k Version 3 Listeners (with LEDs) (default) -T c Version 2 Listeners (without LEDs) -S Socket port number (default is 2947) -p Serial port device name (default “/dev/ttySA0”) -s Baud rate of serial port (default is 9600) -h Help -D Debug level
Slide 25 - Cricket Tutorial on using cricket location system 2 Cricket Goals Research prototype build and then evaluate Useful mainly indoor environments walls, ceilings not too far Recognize spaces, not just physical position good boundary detection is important doors, floors, etc. Preserve user’s privacy Big-brother can be a bother user has choice to reveal location 3 Features Distributed architecture No wired infrastructure Easy deployment (no satellites) Low maintenance Users are not tracked Listeners are passive Large number of listeners w/o interference Integrates with a wide range of resource discovery systems Cricket: Private location-support Beacon Listener space = “a1” space = “a2” Pick nearest to infer space No central beacon control or location database Passive Listeners + Active Beacons 5 Finding the distance distance = speed * time want to find the distance we know the speed How do we figure out time? Radar: measure round-trip time cannot use it as it violates some goals 6 Finding the distance Synchronized clocks receiver knows exactly when transmitter sent signal how about sending signal first to sync clocks and then 2nd signal? 7 Finding the distance Use two different speed signals both start at same time d = s1 * t1 d = s2 * t2 We measure delay: m = t1 - t2 t2 = m * s1/(s2 - s1) d = m * s2 s1 /(s2 - s1) 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) 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 Solution Carrier-sense + randomized transmission reduce chance of concurrent beacons Bounding stray signal interference envelop all ultrasonic signals with RF Listener inference algorithm Processing distance samples to estimate location 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 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! 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 19 Cricket v1 Prototype 20 Cricket Beacon LEDs Debug Switch = UP Green LED = Transmit Red LED = Carried Sensed Debug Switch = Down Green LED = Every 5th transmission At Startup LEDs flash version number Red on, Green flash count = Major # Green on, Red flash count = Minor # Power Switch Up = On Power Switch On Off Debug Switch Beacon ID 21 Cricket Beacon Antennas Receive Antenna For sensing transmission of other beacons Transmit Antenna Limit transmission distance Should not touch ultrasound Should not cover receive antenna Transmit antenna Receive antenna 22 Listener LEDs Green Flash Received valid RF and ultrasound Red Flash Once Received Radio, but not ultrasound Red+Green Flash RF Error (e.g., parity error) Red and Green always on Listener not working correctly Power On Both LEDs flash together once Off On Power Switch 23 Software Components 24 cricketd Background program (demon) that reads serial port and writes data to a socket Command line arguments (defaults work correctly on ipaq) -T k Version 3 Listeners (with LEDs) (default) -T c Version 2 Listeners (without LEDs) -S Socket port number (default is 2947) -p Serial port device name (default “/dev/ttySA0”) -s Baud rate of serial port (default is 9600) -h Help -D Debug level 25 Cricket Listener Output Strings reported from Listeners When good RF and good ultrasound pulse heard: “$Cricket2,ver=3.0,space=MIT7,id=20,dist=4F,duration=1A” When only good RF heard, no ultrasound heard: “$Cricket2,ver=3.0,space=MIT7,id=20” When RF detected, but parity error detected: “$Cricket2,ver=3.0,err=rf”
Slide 26 - Cricket Tutorial on using cricket location system 2 Cricket Goals Research prototype build and then evaluate Useful mainly indoor environments walls, ceilings not too far Recognize spaces, not just physical position good boundary detection is important doors, floors, etc. Preserve user’s privacy Big-brother can be a bother user has choice to reveal location 3 Features Distributed architecture No wired infrastructure Easy deployment (no satellites) Low maintenance Users are not tracked Listeners are passive Large number of listeners w/o interference Integrates with a wide range of resource discovery systems Cricket: Private location-support Beacon Listener space = “a1” space = “a2” Pick nearest to infer space No central beacon control or location database Passive Listeners + Active Beacons 5 Finding the distance distance = speed * time want to find the distance we know the speed How do we figure out time? Radar: measure round-trip time cannot use it as it violates some goals 6 Finding the distance Synchronized clocks receiver knows exactly when transmitter sent signal how about sending signal first to sync clocks and then 2nd signal? 7 Finding the distance Use two different speed signals both start at same time d = s1 * t1 d = s2 * t2 We measure delay: m = t1 - t2 t2 = m * s1/(s2 - s1) d = m * s2 s1 /(s2 - s1) 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) 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 Solution Carrier-sense + randomized transmission reduce chance of concurrent beacons Bounding stray signal interference envelop all ultrasonic signals with RF Listener inference algorithm Processing distance samples to estimate location 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 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! 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 19 Cricket v1 Prototype 20 Cricket Beacon LEDs Debug Switch = UP Green LED = Transmit Red LED = Carried Sensed Debug Switch = Down Green LED = Every 5th transmission At Startup LEDs flash version number Red on, Green flash count = Major # Green on, Red flash count = Minor # Power Switch Up = On Power Switch On Off Debug Switch Beacon ID 21 Cricket Beacon Antennas Receive Antenna For sensing transmission of other beacons Transmit Antenna Limit transmission distance Should not touch ultrasound Should not cover receive antenna Transmit antenna Receive antenna 22 Listener LEDs Green Flash Received valid RF and ultrasound Red Flash Once Received Radio, but not ultrasound Red+Green Flash RF Error (e.g., parity error) Red and Green always on Listener not working correctly Power On Both LEDs flash together once Off On Power Switch 23 Software Components 24 cricketd Background program (demon) that reads serial port and writes data to a socket Command line arguments (defaults work correctly on ipaq) -T k Version 3 Listeners (with LEDs) (default) -T c Version 2 Listeners (without LEDs) -S Socket port number (default is 2947) -p Serial port device name (default “/dev/ttySA0”) -s Baud rate of serial port (default is 9600) -h Help -D Debug level 25 Cricket Listener Output Strings reported from Listeners When good RF and good ultrasound pulse heard: “$Cricket2,ver=3.0,space=MIT7,id=20,dist=4F,duration=1A” When only good RF heard, no ultrasound heard: “$Cricket2,ver=3.0,space=MIT7,id=20” When RF detected, but parity error detected: “$Cricket2,ver=3.0,err=rf” 26 Speed of Sound Listener reports distance and duration in 15.625 KHz counter cycles ( 64 microseconds each). Assume speed of sound is 344.49 m/s then 22.047 mm/cycle For 343.75 m/s = 22 mm/cycle Need to subtract 36 units for delay from end of RF to start of US transmission.
Slide 27 - Cricket Tutorial on using cricket location system 2 Cricket Goals Research prototype build and then evaluate Useful mainly indoor environments walls, ceilings not too far Recognize spaces, not just physical position good boundary detection is important doors, floors, etc. Preserve user’s privacy Big-brother can be a bother user has choice to reveal location 3 Features Distributed architecture No wired infrastructure Easy deployment (no satellites) Low maintenance Users are not tracked Listeners are passive Large number of listeners w/o interference Integrates with a wide range of resource discovery systems Cricket: Private location-support Beacon Listener space = “a1” space = “a2” Pick nearest to infer space No central beacon control or location database Passive Listeners + Active Beacons 5 Finding the distance distance = speed * time want to find the distance we know the speed How do we figure out time? Radar: measure round-trip time cannot use it as it violates some goals 6 Finding the distance Synchronized clocks receiver knows exactly when transmitter sent signal how about sending signal first to sync clocks and then 2nd signal? 7 Finding the distance Use two different speed signals both start at same time d = s1 * t1 d = s2 * t2 We measure delay: m = t1 - t2 t2 = m * s1/(s2 - s1) d = m * s2 s1 /(s2 - s1) 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) 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 Solution Carrier-sense + randomized transmission reduce chance of concurrent beacons Bounding stray signal interference envelop all ultrasonic signals with RF Listener inference algorithm Processing distance samples to estimate location 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 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! 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 19 Cricket v1 Prototype 20 Cricket Beacon LEDs Debug Switch = UP Green LED = Transmit Red LED = Carried Sensed Debug Switch = Down Green LED = Every 5th transmission At Startup LEDs flash version number Red on, Green flash count = Major # Green on, Red flash count = Minor # Power Switch Up = On Power Switch On Off Debug Switch Beacon ID 21 Cricket Beacon Antennas Receive Antenna For sensing transmission of other beacons Transmit Antenna Limit transmission distance Should not touch ultrasound Should not cover receive antenna Transmit antenna Receive antenna 22 Listener LEDs Green Flash Received valid RF and ultrasound Red Flash Once Received Radio, but not ultrasound Red+Green Flash RF Error (e.g., parity error) Red and Green always on Listener not working correctly Power On Both LEDs flash together once Off On Power Switch 23 Software Components 24 cricketd Background program (demon) that reads serial port and writes data to a socket Command line arguments (defaults work correctly on ipaq) -T k Version 3 Listeners (with LEDs) (default) -T c Version 2 Listeners (without LEDs) -S Socket port number (default is 2947) -p Serial port device name (default “/dev/ttySA0”) -s Baud rate of serial port (default is 9600) -h Help -D Debug level 25 Cricket Listener Output Strings reported from Listeners When good RF and good ultrasound pulse heard: “$Cricket2,ver=3.0,space=MIT7,id=20,dist=4F,duration=1A” When only good RF heard, no ultrasound heard: “$Cricket2,ver=3.0,space=MIT7,id=20” When RF detected, but parity error detected: “$Cricket2,ver=3.0,err=rf” 26 Speed of Sound Listener reports distance and duration in 15.625 KHz counter cycles ( 64 microseconds each). Assume speed of sound is 344.49 m/s then 22.047 mm/cycle For 343.75 m/s = 22 mm/cycle Need to subtract 36 units for delay from end of RF to start of US transmission. So where are you? Telnet to cricketd (on correct port) Get names of beacons within range Get distances from beacons Lookup beacon location in database Or use beacon name (longer transmission) Triangulate (compensate for temp)
Slide 28 - Cricket Tutorial on using cricket location system 2 Cricket Goals Research prototype build and then evaluate Useful mainly indoor environments walls, ceilings not too far Recognize spaces, not just physical position good boundary detection is important doors, floors, etc. Preserve user’s privacy Big-brother can be a bother user has choice to reveal location 3 Features Distributed architecture No wired infrastructure Easy deployment (no satellites) Low maintenance Users are not tracked Listeners are passive Large number of listeners w/o interference Integrates with a wide range of resource discovery systems Cricket: Private location-support Beacon Listener space = “a1” space = “a2” Pick nearest to infer space No central beacon control or location database Passive Listeners + Active Beacons 5 Finding the distance distance = speed * time want to find the distance we know the speed How do we figure out time? Radar: measure round-trip time cannot use it as it violates some goals 6 Finding the distance Synchronized clocks receiver knows exactly when transmitter sent signal how about sending signal first to sync clocks and then 2nd signal? 7 Finding the distance Use two different speed signals both start at same time d = s1 * t1 d = s2 * t2 We measure delay: m = t1 - t2 t2 = m * s1/(s2 - s1) d = m * s2 s1 /(s2 - s1) 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) 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 Solution Carrier-sense + randomized transmission reduce chance of concurrent beacons Bounding stray signal interference envelop all ultrasonic signals with RF Listener inference algorithm Processing distance samples to estimate location 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 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! 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 19 Cricket v1 Prototype 20 Cricket Beacon LEDs Debug Switch = UP Green LED = Transmit Red LED = Carried Sensed Debug Switch = Down Green LED = Every 5th transmission At Startup LEDs flash version number Red on, Green flash count = Major # Green on, Red flash count = Minor # Power Switch Up = On Power Switch On Off Debug Switch Beacon ID 21 Cricket Beacon Antennas Receive Antenna For sensing transmission of other beacons Transmit Antenna Limit transmission distance Should not touch ultrasound Should not cover receive antenna Transmit antenna Receive antenna 22 Listener LEDs Green Flash Received valid RF and ultrasound Red Flash Once Received Radio, but not ultrasound Red+Green Flash RF Error (e.g., parity error) Red and Green always on Listener not working correctly Power On Both LEDs flash together once Off On Power Switch 23 Software Components 24 cricketd Background program (demon) that reads serial port and writes data to a socket Command line arguments (defaults work correctly on ipaq) -T k Version 3 Listeners (with LEDs) (default) -T c Version 2 Listeners (without LEDs) -S Socket port number (default is 2947) -p Serial port device name (default “/dev/ttySA0”) -s Baud rate of serial port (default is 9600) -h Help -D Debug level 25 Cricket Listener Output Strings reported from Listeners When good RF and good ultrasound pulse heard: “$Cricket2,ver=3.0,space=MIT7,id=20,dist=4F,duration=1A” When only good RF heard, no ultrasound heard: “$Cricket2,ver=3.0,space=MIT7,id=20” When RF detected, but parity error detected: “$Cricket2,ver=3.0,err=rf” 26 Speed of Sound Listener reports distance and duration in 15.625 KHz counter cycles ( 64 microseconds each). Assume speed of sound is 344.49 m/s then 22.047 mm/cycle For 343.75 m/s = 22 mm/cycle Need to subtract 36 units for delay from end of RF to start of US transmission. So where are you? Telnet to cricketd (on correct port) Get names of beacons within range Get distances from beacons Lookup beacon location in database Or use beacon name (longer transmission) Triangulate (compensate for temp) So whre are you? Beacon name may tell you room That may be enough May want to know relative movements As you walk around the room No climbing on tables Can you do it using two beacons? Can you do it without calibration?
Slide 29 - Cricket Tutorial on using cricket location system 2 Cricket Goals Research prototype build and then evaluate Useful mainly indoor environments walls, ceilings not too far Recognize spaces, not just physical position good boundary detection is important doors, floors, etc. Preserve user’s privacy Big-brother can be a bother user has choice to reveal location 3 Features Distributed architecture No wired infrastructure Easy deployment (no satellites) Low maintenance Users are not tracked Listeners are passive Large number of listeners w/o interference Integrates with a wide range of resource discovery systems Cricket: Private location-support Beacon Listener space = “a1” space = “a2” Pick nearest to infer space No central beacon control or location database Passive Listeners + Active Beacons 5 Finding the distance distance = speed * time want to find the distance we know the speed How do we figure out time? Radar: measure round-trip time cannot use it as it violates some goals 6 Finding the distance Synchronized clocks receiver knows exactly when transmitter sent signal how about sending signal first to sync clocks and then 2nd signal? 7 Finding the distance Use two different speed signals both start at same time d = s1 * t1 d = s2 * t2 We measure delay: m = t1 - t2 t2 = m * s1/(s2 - s1) d = m * s2 s1 /(s2 - s1) 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) 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 Solution Carrier-sense + randomized transmission reduce chance of concurrent beacons Bounding stray signal interference envelop all ultrasonic signals with RF Listener inference algorithm Processing distance samples to estimate location 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 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! 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 19 Cricket v1 Prototype 20 Cricket Beacon LEDs Debug Switch = UP Green LED = Transmit Red LED = Carried Sensed Debug Switch = Down Green LED = Every 5th transmission At Startup LEDs flash version number Red on, Green flash count = Major # Green on, Red flash count = Minor # Power Switch Up = On Power Switch On Off Debug Switch Beacon ID 21 Cricket Beacon Antennas Receive Antenna For sensing transmission of other beacons Transmit Antenna Limit transmission distance Should not touch ultrasound Should not cover receive antenna Transmit antenna Receive antenna 22 Listener LEDs Green Flash Received valid RF and ultrasound Red Flash Once Received Radio, but not ultrasound Red+Green Flash RF Error (e.g., parity error) Red and Green always on Listener not working correctly Power On Both LEDs flash together once Off On Power Switch 23 Software Components 24 cricketd Background program (demon) that reads serial port and writes data to a socket Command line arguments (defaults work correctly on ipaq) -T k Version 3 Listeners (with LEDs) (default) -T c Version 2 Listeners (without LEDs) -S Socket port number (default is 2947) -p Serial port device name (default “/dev/ttySA0”) -s Baud rate of serial port (default is 9600) -h Help -D Debug level 25 Cricket Listener Output Strings reported from Listeners When good RF and good ultrasound pulse heard: “$Cricket2,ver=3.0,space=MIT7,id=20,dist=4F,duration=1A” When only good RF heard, no ultrasound heard: “$Cricket2,ver=3.0,space=MIT7,id=20” When RF detected, but parity error detected: “$Cricket2,ver=3.0,err=rf” 26 Speed of Sound Listener reports distance and duration in 15.625 KHz counter cycles ( 64 microseconds each). Assume speed of sound is 344.49 m/s then 22.047 mm/cycle For 343.75 m/s = 22 mm/cycle Need to subtract 36 units for delay from end of RF to start of US transmission. So where are you? Telnet to cricketd (on correct port) Get names of beacons within range Get distances from beacons Lookup beacon location in database Or use beacon name (longer transmission) Triangulate (compensate for temp) So whre are you? Beacon name may tell you room That may be enough May want to know relative movements As you walk around the room No climbing on tables Can you do it using two beacons? Can you do it without calibration? Two beacons Put them along the wall Come very close to one of them Now know distance between them Given distances from both Before and now (d1,d2) & (e1,e2) Can find relative movement Two solutions! No problem, why? Ex. Doom virtual world
Slide 30 - Cricket Tutorial on using cricket location system 2 Cricket Goals Research prototype build and then evaluate Useful mainly indoor environments walls, ceilings not too far Recognize spaces, not just physical position good boundary detection is important doors, floors, etc. Preserve user’s privacy Big-brother can be a bother user has choice to reveal location 3 Features Distributed architecture No wired infrastructure Easy deployment (no satellites) Low maintenance Users are not tracked Listeners are passive Large number of listeners w/o interference Integrates with a wide range of resource discovery systems Cricket: Private location-support Beacon Listener space = “a1” space = “a2” Pick nearest to infer space No central beacon control or location database Passive Listeners + Active Beacons 5 Finding the distance distance = speed * time want to find the distance we know the speed How do we figure out time? Radar: measure round-trip time cannot use it as it violates some goals 6 Finding the distance Synchronized clocks receiver knows exactly when transmitter sent signal how about sending signal first to sync clocks and then 2nd signal? 7 Finding the distance Use two different speed signals both start at same time d = s1 * t1 d = s2 * t2 We measure delay: m = t1 - t2 t2 = m * s1/(s2 - s1) d = m * s2 s1 /(s2 - s1) 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) 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 Solution Carrier-sense + randomized transmission reduce chance of concurrent beacons Bounding stray signal interference envelop all ultrasonic signals with RF Listener inference algorithm Processing distance samples to estimate location 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 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! 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 19 Cricket v1 Prototype 20 Cricket Beacon LEDs Debug Switch = UP Green LED = Transmit Red LED = Carried Sensed Debug Switch = Down Green LED = Every 5th transmission At Startup LEDs flash version number Red on, Green flash count = Major # Green on, Red flash count = Minor # Power Switch Up = On Power Switch On Off Debug Switch Beacon ID 21 Cricket Beacon Antennas Receive Antenna For sensing transmission of other beacons Transmit Antenna Limit transmission distance Should not touch ultrasound Should not cover receive antenna Transmit antenna Receive antenna 22 Listener LEDs Green Flash Received valid RF and ultrasound Red Flash Once Received Radio, but not ultrasound Red+Green Flash RF Error (e.g., parity error) Red and Green always on Listener not working correctly Power On Both LEDs flash together once Off On Power Switch 23 Software Components 24 cricketd Background program (demon) that reads serial port and writes data to a socket Command line arguments (defaults work correctly on ipaq) -T k Version 3 Listeners (with LEDs) (default) -T c Version 2 Listeners (without LEDs) -S Socket port number (default is 2947) -p Serial port device name (default “/dev/ttySA0”) -s Baud rate of serial port (default is 9600) -h Help -D Debug level 25 Cricket Listener Output Strings reported from Listeners When good RF and good ultrasound pulse heard: “$Cricket2,ver=3.0,space=MIT7,id=20,dist=4F,duration=1A” When only good RF heard, no ultrasound heard: “$Cricket2,ver=3.0,space=MIT7,id=20” When RF detected, but parity error detected: “$Cricket2,ver=3.0,err=rf” 26 Speed of Sound Listener reports distance and duration in 15.625 KHz counter cycles ( 64 microseconds each). Assume speed of sound is 344.49 m/s then 22.047 mm/cycle For 343.75 m/s = 22 mm/cycle Need to subtract 36 units for delay from end of RF to start of US transmission. So where are you? Telnet to cricketd (on correct port) Get names of beacons within range Get distances from beacons Lookup beacon location in database Or use beacon name (longer transmission) Triangulate (compensate for temp) So whre are you? Beacon name may tell you room That may be enough May want to know relative movements As you walk around the room No climbing on tables Can you do it using two beacons? Can you do it without calibration? Two beacons Put them along the wall Come very close to one of them Now know distance between them Given distances from both Before and now (d1,d2) & (e1,e2) Can find relative movement Two solutions! No problem, why? Ex. Doom virtual world 30 Orientation
Slide 31 - Cricket Tutorial on using cricket location system 2 Cricket Goals Research prototype build and then evaluate Useful mainly indoor environments walls, ceilings not too far Recognize spaces, not just physical position good boundary detection is important doors, floors, etc. Preserve user’s privacy Big-brother can be a bother user has choice to reveal location 3 Features Distributed architecture No wired infrastructure Easy deployment (no satellites) Low maintenance Users are not tracked Listeners are passive Large number of listeners w/o interference Integrates with a wide range of resource discovery systems Cricket: Private location-support Beacon Listener space = “a1” space = “a2” Pick nearest to infer space No central beacon control or location database Passive Listeners + Active Beacons 5 Finding the distance distance = speed * time want to find the distance we know the speed How do we figure out time? Radar: measure round-trip time cannot use it as it violates some goals 6 Finding the distance Synchronized clocks receiver knows exactly when transmitter sent signal how about sending signal first to sync clocks and then 2nd signal? 7 Finding the distance Use two different speed signals both start at same time d = s1 * t1 d = s2 * t2 We measure delay: m = t1 - t2 t2 = m * s1/(s2 - s1) d = m * s2 s1 /(s2 - s1) 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) 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 Solution Carrier-sense + randomized transmission reduce chance of concurrent beacons Bounding stray signal interference envelop all ultrasonic signals with RF Listener inference algorithm Processing distance samples to estimate location 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 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! 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 19 Cricket v1 Prototype 20 Cricket Beacon LEDs Debug Switch = UP Green LED = Transmit Red LED = Carried Sensed Debug Switch = Down Green LED = Every 5th transmission At Startup LEDs flash version number Red on, Green flash count = Major # Green on, Red flash count = Minor # Power Switch Up = On Power Switch On Off Debug Switch Beacon ID 21 Cricket Beacon Antennas Receive Antenna For sensing transmission of other beacons Transmit Antenna Limit transmission distance Should not touch ultrasound Should not cover receive antenna Transmit antenna Receive antenna 22 Listener LEDs Green Flash Received valid RF and ultrasound Red Flash Once Received Radio, but not ultrasound Red+Green Flash RF Error (e.g., parity error) Red and Green always on Listener not working correctly Power On Both LEDs flash together once Off On Power Switch 23 Software Components 24 cricketd Background program (demon) that reads serial port and writes data to a socket Command line arguments (defaults work correctly on ipaq) -T k Version 3 Listeners (with LEDs) (default) -T c Version 2 Listeners (without LEDs) -S Socket port number (default is 2947) -p Serial port device name (default “/dev/ttySA0”) -s Baud rate of serial port (default is 9600) -h Help -D Debug level 25 Cricket Listener Output Strings reported from Listeners When good RF and good ultrasound pulse heard: “$Cricket2,ver=3.0,space=MIT7,id=20,dist=4F,duration=1A” When only good RF heard, no ultrasound heard: “$Cricket2,ver=3.0,space=MIT7,id=20” When RF detected, but parity error detected: “$Cricket2,ver=3.0,err=rf” 26 Speed of Sound Listener reports distance and duration in 15.625 KHz counter cycles ( 64 microseconds each). Assume speed of sound is 344.49 m/s then 22.047 mm/cycle For 343.75 m/s = 22 mm/cycle Need to subtract 36 units for delay from end of RF to start of US transmission. So where are you? Telnet to cricketd (on correct port) Get names of beacons within range Get distances from beacons Lookup beacon location in database Or use beacon name (longer transmission) Triangulate (compensate for temp) So whre are you? Beacon name may tell you room That may be enough May want to know relative movements As you walk around the room No climbing on tables Can you do it using two beacons? Can you do it without calibration? Two beacons Put them along the wall Come very close to one of them Now know distance between them Given distances from both Before and now (d1,d2) & (e1,e2) Can find relative movement Two solutions! No problem, why? Ex. Doom virtual world 30 Orientation 31 Hardware Design http://nms.lcs.mit.edu/projects/cricket http://nms.lcs.mit.edu/cricket/fab Need user & password http://nms.lcs.mit.edu/cricket/distrib Need user & password
 

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