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Personalized Services Using Location Based Services (LBS) Wei-Meng Lee ( Technologist & Co-Founder Active Developer

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Presentation on theme: "Personalized Services Using Location Based Services (LBS) Wei-Meng Lee ( Technologist & Co-Founder Active Developer"— Presentation transcript:

1 Personalized Services Using Location Based Services (LBS) Wei-Meng Lee Technologist & Co-Founder Active Developer O’Reilly Emerging Technology Conference February 9-12, 2004

2 Agenda Motivation for LBS – E911
Location-Based Services – the fundamentals Location-Based Services – the techniques Telcos adopting LBS in the US LBS Applications Model Some Case Studies in Singapore Issues of LBS

3 * Singapore Location: About 140 kilometres north of the equator
It is 42 kilometers long and 23 kilometers across at its widest point Total area: sq km (slightly more than 3.5 times the size of Washington, DC ) Population 4,608,595 (July 2003 est.) *

4 Motivation for LBS – E911 The wireless Enhanced 911 (E911) rules seek to improve the effectiveness and reliability of wireless 911 service by providing 911 dispatchers with additional information on wireless 911 calls. Phase I requires carriers, upon appropriate request by a local Public Safety Answering Point (PSAP), to report the telephone number of a wireless 911 caller and the location of the antenna that received the call. Phase II requires wireless carriers to provide far more precise location information, within 50 to 100 meters in most cases.

5 Triangulation – Locating the caller
Triangulate from two angles – at least two reference points Triangulate from two points – at least three reference points Three-dimensional triangulation – at least four reference points

6 Triangulate from two angles
Two lines intersect at one point

7 Triangulate from two points
Two circles intersect at two points; a third circle is needed to remove the second point.

8 Three-dimensional Triangulation

9 Location Determination Technologies
Satellite-based, Network-based Network centric, Handset centric

10 Cell of Origin The tower transmitting the call is deemed to be the cell of origin. Good for densely populated area where towers are close together.

11 Useful for sparely populated area; less likelihood of interference.
Angle of Arrival (AOA) Measures the angle at which a cell phone’s signal arrives at two or more towers Useful for sparely populated area; less likelihood of interference.

12 Time Difference of Arrival (TDOA)
Measures the time at which a cell phone’s signal reaches at three or more towers Vendors using TDOA: Cell-Loc ( TruePosition (

13 Enhanced Observed Time Difference (E-OTD)
Measures the time at which signals from towers reaches the handset (requires changes to handsets and requires GSM). Vendor supporting E-OTD: Cambridge Positioning Systems (CPS) (

14 Global Positioning Systems
Uses 27 satellites (3 for backup) orbiting around the earth twice each day, emitting low-power radio waves in the frequency range of 1500MHz. Very costly to maintain – using GPS for LBS costs about $12 billion to build, staff, maintain and monitor. Lifespan: 7-15 years.

15 Three-dimensional Triangulation

16 Selective Availability
GPS was originally developed in the 1980s by the U.S. Department of Defense for military use. The U.S. Department of Defense introduced Selective Availability (SA) to degrade the signal accuracy so that civilian usage could be restricted. In May 2000, President Clinton announced that the U.S. would no longer degrade the accuracy of GPS. With SA turned off, the accuracy of the GPS data could be within 5 meters. In the second Gulf war against Iraq in 2003, the United States reportedly degraded the GPS system so that Iraq could not make use of GPS against U.S. forces. While this is good news for the military, it certainly affected all those who rely on GPS for their daily activities. So, if you arrived at the wrong destination using a GPS navigational system, now you know why!

17 Assisted-GPS (A-GPS) Handset broadcast request to towers
Location server tells handset which satellite to listen to Handset listens to GPS satellite Positional information combined with ranging information are sent back to the Location server Location server calculates the actual position and returns the coordinates to the handset, or application server Assisted-GPS (A-GPS)

18 Some A-GPS Phones

19 Comparing the different Location Determination Technologies
Cell-ID EOTD TDOA GPS AGPS Consistency Poor Average Very good Accuracy 100m – 20km 2D Positioning 100m-500m Good 5m-100m 3D Positioning Excellent 5m-50m TTFF 1s Very Good 5s 30s-15min 5-10s Need to modify handset? No Yes Network Efficiency Overall Cost Low High Moderate Summary * Source: SnapTrack (

20 Telcos adopting the various technologies
AT&T is adding GSM to its network as part of its migration to the third generation (3G), and implement E-OTD in its GSM network. VoiceStream, the largest GSM operator in the U.S., is also supporting EOTD. Sprint PCS, Alltel, U.S. Cellular, and Nextel Communications, have opted for a handset-based E-911 system using the satellite-based global positioning system (GPS). Verizon and Western Wireless plan to use a network-based system, using a combination of TDOA and AOA.

21 Video - How LBS Works

22 LBS Applications Model

23 Case Studies in Singapore
* Send Where am I? What’s around me? Weather forecast



26 Geo-Gaming “Our game technology enables producers to place virtual representations of products in specific geo-graphic areas. For example, a teen playing one of our games near a popular fast-food chain could find virtual “burgers” that could be consumed to provide extra energy or power to their game avatar.”


28 Some Potential LBS applications
Enhanced Shopping Experience Sending promotional information to your cell phone Informing you on the discounts you are entitled to Mapping Applications Traffic Monitoring Singapore has the Electronic Road Pricing (ERP) Warehousing Emergency services Tracking

29 Useful Links


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