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L ocation B ased S ervices for Mobile Devices. Embedded Computing Seminar Shay Horovitz. Technologies. Location Technologies. GPS - Global Positioning System AGPS - Assisted GPS Cell ID Cell ID + Timing Advance Signal Strength Based AOA - Angle Of Arrival TOA - Time Of Arrival

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l ocation b ased s ervices for mobile devices

Location Based ServicesforMobile Devices

Embedded Computing Seminar

Shay Horovitz

location technologies
Location Technologies
  • GPS - Global Positioning System
  • AGPS - Assisted GPS
  • Cell ID
  • Cell ID + Timing Advance
  • Signal Strength Based
  • AOA - Angle Of Arrival
  • TOA - Time Of Arrival
  • TDOA - Time Difference of Arrival
  • EOTD - Enhanced Observed Time Difference
  • Keypad based (click the address yourself)
  • Camera based (taking pictures of signs)
  • Hybrid solutions
  • RF Fingerprinting (on phones that will support WLAN)
  • Mariners relied upon the sun for latitude, and clocks for longitude
  • With the launch of Sputnik in 1957, radio-based global positioning became a (theoretical) possibility
  • This was a very crude form of GPS using only one satellite (1960s)
    • Submarines used it
    • Could only be used every 35-45 minutes
    • Submarine had to be still
timation 1960s
TIMATION (1960s)
  • Another satellite (TIMATION I) was launched to enhance the TRANSIT system
  • Major innovation was the inclusion of an atomic clock
  • Submarines could now be in motion and use the system
  • In 1973, NAVSTAR began research & development
  • 1978 – the first 4 satellites were launched
  • Operated by the Department of Defense
    • Primary mission is to provide exact coordinates for land, sea & air-based military forces
    • Cost about $18,000,000,000 to develop… so far
there are three components of gps
There are three components of GPS
  • 1.) Space (e.g. satellites)
  • 2.) Control (i.e. a ground station at a known geographic location)
  • 3.) User
  • The GPS receiver precisely measures the time it takes a signal to travel from a satellite to the receiver
  • There are lots and lots of satellites
  • Anyone want to guess how many?
  • 6 orbital planes, included at 55 degrees to the equator, each with 4 satellites
    • 21 active satellites, 3 backups
  • Orbit the earth at 12,541 miles and have an orbital period of 11 hrs. 56 min.
how many points do you need
How many points do you need?
  • Using one satellite narrows the distance to a sphere around the satellite
  • Using two satellites, you’ll find your location within a circle (previous slide)
  • Using three satellites limits your location to only 2 points
    • Usually, it is possible to determine which point
  • Using four satellites confirms your location and gives you 2 readings for altitude
    • Usually you can determine which is correct
the importance of time
The importance of time
  • Both satellites and receivers generate Pseudo Random Noise (PRN)
    • A Link 1 (L1) carrier signal is generated at 1575.42 MHz and Link 2 (L2) carrier signal is generated at 1227.60 MHz
      • Carrier signals are modulated to produce coded signals, such as C/A code (at 1.023 MHz) and the P code (at 10.23 MHz)
    • The frequencies are frequency-modulated to produce step-functions
    • The codes repeat every millisecond
  • The satellites come with cesium or rubidium clocks
selective acquisition
Selective Acquisition
  • The US military was concerned about the possibility of terrorists or other unfriendly people using GPS to precisely guide a missile (or other unfriendly device)
  • The deliberately introduced errors in the time embedded in the signal
  • This caused locations to be up to 100m off
  • Turned off on 2 May 2000
  • GPS III system will launch
  • Should be even more accurate than the 8m accuracy limit currently in place
tech agps
Tech: AGPS
  • GPS has a slow time to fix unless it is permanently tracking satellites
  • To solve the inherent restrictions with GPS, Assisted GPS was proposed
  • Assisted GPS is based upon providing GPS satellite information to the handset, via the cellular network
tech agps21
Tech: AGPS
  • Assisted GPS gives improvements in
    • Time to First Fix
    • Battery Life
    • Sensitivity
    • Cost
  • Assistance Data
    • Satellite Position
    • Time information
    • Visible GPS List
    • Sensitivity
tech cell id
Tech: Cell ID
  • Cell ID: the cell that the mobile is connected to
  • Operator’s know where their cell sites are
  • Accuracy is dependent on cell density
  • Can be implemented both network based or device based
tech cell id timing advance ta
Tech: Cell ID + Timing Advance (TA)
  • TA is the time delay between the mobile and serving base station
  • Resolution is 500 meters
  • Serving cell identity and TA are available in networks
tech signal strength based
Tech: Signal Strength Based
  • Measure signal strength from the control channels of several Base Stations
  • If signal levels from 3 different BSs are known, it’s possible to calculate the location
tech aoa angle of arrival
Tech: AOA - Angle Of Arrival
  • Measure the angle of arrived signal between base station and mobile station
  • Location error increases as mobile is far from BSs
tech toa time of arrival
Tech: TOA - Time Of Arrival
  • Measure the time of arrived signal between base station and mobile station
  • Mobile station locates at the intersection point which will be made by more than 3 circles
tech tdoa time difference of arrival
Tech: TDOA – Time Difference Of Arrival
  • Measure the time difference of arrived signal between base station and mobile station : Minimum three base stations
  • Mobile station locates at the intersection point which will be made by more than 3 hyperbolas
tech eotd enhanced observed time difference
Tech: EOTD – Enhanced Observed Time Difference
  • Added device, LMU (Location Measurement Unit), whose location is known
  • LMU and mobile station measure the time difference of arrived signal from base station at the same time
  • Mobile station locates at the intersection point which will be made by more than 3 hyperbolas
tech keyboard based
Tech: Keyboard Based
  • You set your location!
  • Example: Navigation Software:
    • Manually set origin
    • Manually set destination
    • Approve when each step is completed to get the next step instructions
tech camera based
Tech: Camera Based
  • Take a picture of road signs and send by MMS to a server
  • 2D Barcodes
tech lamposts based
Tech: Lamposts Based
  • Last Mile, a British company plans to offer Internet & LBS using street lampposts…
  • A flash memory will be installed inside the lampposts and store info about local pubs, shops.
  • Cost: about £500 per lamppost
tech hybrid solutions based
Tech: Hybrid Solutions Based
  • Improve effectiveness
  • Extends the coverage of a solution e.g. AGPS
  • Common Hybrids
    • EOTD / AGPS
    • Cell ID / AGPS
  • Benefits of both systems realized increasing the accuracy and availability of any single method
tech rf fingerprint based
Tech: RF Fingerprint Based
  • Pinpointing wireless clients makes it easier to secure and manage wireless LANs
  • WLANs typically have used closest access point (closest AP) or triangulation technologies to track location
  • RF fingerprinting improves by taking into account the effects that a building or people will have on an RF signal - characteristics such as reflection, attenuation and multi-path
range of coverage
Range Of Coverage

5 m


100 m



300 m

Cell ID + TA

500 m

Cell ID


  • Network Optimization
  • In-Car & Personal Navigation and wayfinding
  • Emergency (E911)
  • Monitoring traffic flow using device location & optimization
  • Automated Mapping
  • Family Tracking/ Find-A-Friend
  • Find the Nearest Store/place
  • Tourist Information/Automated Guide
  • Live public transport info
  • Games
  • Fleet Management
  • Location-based Billing
  • Demographic Statistics
  • Target Marketing
  • Other applications
game glofun raygun
Game: Glofun RayGun
  • Location: US
  • Target: Ghost-Hunting!
  • Use of GPS for location of player
game ss k conqwest
Game: SS+K Conqwest
  • Location: 5 cities in the USA
  • Team-based treasure hunt in the urban jungle
  • 5 teams searching for treasure in the form of “printed codes” – 2d barcodes that can be captured by phonecam
  • 1 code=1$. First team to find $5000 worth codes wins and earns a $5000 scholarship for their school…
game blisterent swordfish
Game: Blisterent Swordfish
  • GPS based game
  • You play against a virtual school of Swordfish
  • See where’s the nearest school of virtual fish
game blisterent torpedo bay
Game: Blisterent Torpedo Bay
  • A-GPS based game
  • No GPS reception? - Predictive positioning…
  • Use of real map
  • 360 degrees view
game newtgames mogi
Game: NewtGames Mogi
  • Location: Tokyo, Japan
  • GPS based
  • Pick up virtual items spread on the whole of Japan
  • At a range of 400m, you’re able to collect an item
game mikoishi gunslingers
Game: Mikoishi GunSlingers
  • Location: Singapore
  • Cell-ID based
  • Multiplayer shooting game
hp labs city tags
HP Labs City Tags
  • Location: Bristol, UK
  • iPaq PocketPC with GPS, Wifi needed
  • Social interaction: Tag people
  • When got tagged, need to find a friend to free you
  • Take something from the cache
  • Leave something in the cache
  • Write about it in the logbook
developer toolkits
Developer Toolkits
  • Chips:
    • HammerHead
    • TI
    • Intel
  • APIs:
    • Sun J2ME Location API
    • Qualcomm BREW LBS API
chips market
Chips Market

"The mobile GPS semiconductor market is expected to exceed 180 million units in 2008 …" Will Strauss, president of Forward Concepts[http://www10.edacafe.com/nbc/articles/view_article.php?section=ICNews&articleid=223846]

hammerhead pmb 2520
HammerHead: PMB 2520
  • Single chip solution
  • A-GPS Implementation
  • Size: 80 mm2
  • Low Power
ti chip navilink 4 0 gps5300
TI Chip: NaviLink 4.0 GPS5300
  • Single chip solution
  • Smallest A-GPS (50 mm2)
  • Low Power, Power Management
  • Production: 2Q, 2006
intel s plans
Intel’s Plans
  • “Notebook chips will likely support location-based services by 2006, Intel says. “ PCWorld [http://www.itworld.com/Comp/2085/041025pentiumm/]
sun j2me lbs
  • Location API for J2ME (JSR 179)
  • A set of generic APIs for developing LBS
  • Can support GPS/A-GPS/Cell-ID/any other method [by implementing a location provider]
some interesting numbers
Some interesting numbers…
  • Most popular chipset – SiRF
  • Smallest modules:
    • SyChip GPS2020: 13x15x3.8
    • Trimble M-Loc MPM: 25x25x6.5
    • Fastrax iTrax02: 26x26x6.5
  • Smallest module with integrated Antenna – Axiom Swift A1: 41x41x11
use one
Use One?
  • Ready made External boxes with integrated antennas or separate
  • Support USB / RS232
  • Available as both PCMCIA and Compact Flash cards
gps building blocks 1
GPS Building Blocks 1
  • Antenna element
    • Cost: $3 to $300 (depends on single/double frequency reception & phase center stability)
    • Diameter: 2cm to 15cm
  • Low Noise Amplifier (LNA)
    • Amplifies GPS signals
    • Cost: $5 to $100 (depends on number of frequencies & quality of filters)
    • Power consumption: 20mW to 200mW
  • RF section
    • Converts received signal to digital form
    • Cost: $5 to $200 (depends on number of frequencies & quality of filters)
    • Size: 2-20 cm
    • Power consumption 100mW to 1 Watt
gps building blocks 2
GPS Building Blocks 2
  • Digital section
    • Processes the digital samples and provides tracking measures
    • Cost: $5 to $15
  • Microprocessor
    • Control the tracking elements based on measurements and doppler (range rate change)
    • Collects navigation data about the orbit and clock of each satellite
    • Compute position
    • Support interfaces to the user
    • Cost: $5 to $50
    • Power consumption: 200mW to 3W
gps building blocks 3
GPS Building Blocks 3
  • Processor Peripherals
    • Provide memory for program and data storage
    • Cost: $5 to $100 (depending on capacity and speed)
    • Power consumption: 100mW to 2W
  • I/O & Drivers
    • Serial/ Parallel/ USB/ Ethernet/ other comm ports
    • Cost: $2 to $20
    • Power consumption: 10mW to 100mW
  • Ronald Azuma et el., “Recent Advances in Augmented Reality”, IEEE Computer Graphics and Applications, vol.21, no.6, Nov/Dec 2001, pp.34-47
  • Mohammad S. Sharawi et el., “Investigation into the performance of EOTD for GSM users in Telematics applications”, Proceedings of SPIE, vol. 5084, Aug. 2003, pp.6-18
  • http://yona_n.tripod.com/gps/gps-survey.html#chips
  • EDN: http://www.edn.com/article/CA243219.html
  • GPSWorld: http://www.gpsworld.com/gpsworld/article/articleDetail.jsp?id=15100&pageID=1
  • HowStuffWorks: http://electronics.howstuffworks.com/gps.htm
  • http://www.symbian.com/developer/techlib/papers/messaging/LocalAwareness_LBS_01.pdf
  • http://www.terena.nl/conferences/tnc2005/core/getfile.php?file_id=453
  • LBS Market: http://www.trueposition.com/lrc/LBSLongTimeComing.pdf
  • LBS Forecast: http://mms.ecs.soton.ac.uk/mms2002/papers/4.pdf
  • Location Technologies: http://developer.openwave.com/omdtdocs/location_studio_sdk/pdf/Intro_to_Location_Technologies.pdf
  • GSM LBS: http://www.ftw.at/ftw/events/telekommunikationsforum/WS2001/WS01docs/020111.ppt
  • E-911: http://www.sss-mag.com/e911.html
  • Solutions: http://www.wirelessdevnet.com/channels/lbs/features/mobilepositioning.html
  • GPS Based games: http://www.glofun.com/
  • LBS in Europe: http://www.hottelecom.com/berginsight-lbs.html
Thank You

For Listening