1. LOCATION BASED SERVICES
PRESENTED BY
SACHIN RASTOGI

2. What is location based services ?
 Location services, wireless location services, mobile
location-based services
 Allow that mobile users (MUs) use services based in
their position or geographic location

3. Cont…..
 Location Based Services are services, which use the positioning information
about a mobile device in order to offer more personalized information. The
positioning information is useless if it is presented to the user as a raw set of
coordinates. It has to be combined with other information to become valuable
to the user. This kind of combination of information is exactly the main
purpose of LBS. There are some LBS categories: Public Safety Services,
Location Based Charging, Tracking Services, Enhanced Call Routing,
Information Services, and Advanced Network Services. Each one of these
services poses different positioning accuracy requirements. The main
positioning techniques in modern cellular telecommunications networks are:
Cell Global Identity (CGI), Cell Global Identity Timing Advance (CGI- TA),
Enhanced Cell Global Identity (E- CGI), Time Of Arrival (TOA), Observed
Time Difference Of Arrival (OTDOA), Observed Time Difference (OTD),
Enhanced Observed Time Difference (E- OTD) and Assisted GPS (A- GPS).
Each one of these methods offers different positioning accuracy.

4. Location Technologies
 Network-based
 Technologies that exploit the cellular infrastructure to
obtain geo-location information.
 Handset-based
 Location intelligence is stored within terminal
 Each of these groups may be divided into:
 The MU uses signal transmitted by the base stations to
calculate its own position
 The base stations measure the signals transmitted by the
MU and relay them to a central site for processing.

5. Different types of location based
services
CGI(Cell global identity )
ECGI(Enhanced cell global identity)
TRANGULATION
GPS(Global positioning system)
AGPS(Assisted global positioning
system)

6. CGI
Cell Global Identity (CGI) is a standard identifier for
mobile phones cells, providing means to geographically
locate connected mobile phones. If a cell phone is
connected to a GSM network then the position of that
particular cell phone can be determined using CGI of the
cell which is covering that cell phone. There is a series of
related technologies that were developed based on CGI
enhances the location precision: Cell Global Identity with
Timing Advance (CGI+TA), Enhanced CGI (ECGI), Cell ID
for WCDMA, Uplink Time Difference Of Arrival (U-
TDOA) and Any Time Interrogation (ATI), and the high
accuracy terminal based method Assisted Global
Positioning System .

7. CGI + TA
 Cell Global Identity, CGI
 A standard identifier for mobile phones cells
 TA: within a cell
 CGI+TA: global

8. ECGI
 Enhanced Cell ID provides the next-level of accuracy
over Cell ID through the use of Radio Frequency
parameters such as Timing Advance (TA) to estimate a
position within the cell-sector. In the GSM cellular
mobile phone standard, timing advance value
corresponds to a step change in an approximation of
the number of microseconds the signal from the
mobile phone requires to travel to the base transceiver
station (BTS—essentially the cell tower to which the
phone is connected at the time).

10. TRANGULATION
 triangulation
 Method of determining distance based on the
principles of geometry.
 A distance object is sighted from two well-
separated locations.
 The distance between the two locations and the
angle between the line joining them and the line to
the distant object are all that are necessary to
ascertain the object's distance.

11. Triangulation
Surveyors often use simple
geometry and trigonometry to
estimate the distance to a faraway
object. By measuring the angles
at A and B and the length of the
baseline, the distance can be
calculated without the need for
direct measurement.

12. GPS
The History of GPS
• Feasibility studies begun in 1960’s.
• Pentagon appropriates funding in 1973.
• First satellite launched in 1978.
• System declared fully operational in April, 1995

13. How GPS works

14. Control Segment
Space Segment
User Segment
Three Segments of the GPS
Monitor Stations
Ground
Antennas
Master Station
Feasibility studies begun in 1960’s.
Pentagon appropriates funding in 1973.
First satellite launched in 1978.
System declared fully operational in April,
1995

15. Kwajalein Atoll
US Space Command
Control Segment
Hawaii
Ascension Is.
Diego Garcia
Cape Canaveral
Ground AntennaMaster Control Station Monitor Station

17. • Military.
• Search and rescue.
• Disaster relief.
• Surveying.
• Marine, aeronautical and terrestrial navigation.
• Remote controlled vehicle and robot guidance.
• Satellite positioning and tracking.
• Shipping.
• Geographic Information Systems (GIS).
• Recreation.
User Segment

18. Four Basic Functions of GPS
• Position and coordinates.
• The distance and direction between any two
waypoints, or a position and a waypoint.
• Travel progress reports.
• Accurate time measurement.

19. AGPS(Assisted-GPS)

20. 20
Assisted
The assistance
information received,
or derived from, the
wireless network is
used to “aid” the
WAG receiver by
providing data that
would normally be
derived by timeconsuming
demodulation of
GPS satellite signals
– demodulation is
difficult and
sometimes
impossible in certain
common wireless
environments.
GPS
A proven system for
world-wide
positioning and
navigation used for
personal,
commercial,
business, and
government
applications.
Commercial
implementations
have been in place
for close to 10
years, though the
system has been in
place over 20
years

21. 21
AGPS Architecture

22. 22
Why AGPS??
 Very rapid acquisition--100 to 1000 times faster than
conventional GPS.
 Extremely fast positioning in almost all conditions
 Operation in difficult environments (blocked signals,
fading, etc.)
 Very sensitive for given acquisition time
 Can withstand >20 dB signal attenuation due to building
blockage, etc.
 Works indoors
 Excellent accuracy/reliability through cooperation
between MS client and server

23. How it Works?
 WAG receiver obtains aiding data from the server
and/or extracts key information from the wireless
network
 Using this aiding data, WAG receiver processes small
amounts of GPS satellite signals
 Then…
MS-Assisted: Sends data to Server for position
calculation
MS-Based: Calculates position in the handset
WAG splits the workload into a very efficient, quick, and
accurate client/server structure.

24. THANK YOU