LOCATION BASED SERVICES  

PRESENTED BY

SACHIN RASTOGI

  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

  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.

       Location TechnologiesNetwork-based

Technologies that exploit the cellular infrastructure to obtain geo-location information.

Handset-basedLocation 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 positionThe base stations measure the signals

transmitted by the MU and relay them to a central site for processing.

Different types of location based servicesCGI(Cell global identity )ECGI(Enhanced cell global identity)

TRANGULATIONGPS(Global positioning system)AGPS(Assisted global positioning system)

                        CGICell 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 .

CGI + TA Cell Global Identity, CGI

A standard identifier for mobile phones cellsTA: within a cellCGI+TA: global

                        ECGIEnhanced 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).

               TRANGULATIONtriangulation

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.

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.

                         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

             How GPS works

Control Segment

Space Segment

User Segment

   Three Segments of the GPS   Three Segments of the GPS

Monitor Stations

GroundAntennas

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

Kwajalein Atoll

US Space Command

Control SegmentControl Segment

Hawaii

Ascension Is.

Diego Garcia

Cape Canaveral

Ground AntennaMaster Control StationMonitor Station

• 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

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.

AGPS(Assisted-GPS)

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AssistedThe assistance information received,or derived from, thewireless network isused to “aid” theWAG receiver byproviding data thatwould normally bederived by timeconsumingdemodulation ofGPS satellite signals– demodulation isdifficult andsometimesimpossible in certaincommon wirelessenvironments.

GPSA proven system forworld-widepositioning andnavigation used forpersonal,commercial,business, andgovernmentapplications.Commercialimplementationshave been in placefor close to 10years, though thesystem has been inplace over 20years

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AGPS Architecture

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Why AGPS??     Very rapid acquisition--100 to 1000 times

faster than conventional GPS.Extremely fast positioning in almost all

conditionsOperation 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 indoorsExcellent accuracy/reliability through

cooperation between MS client and server

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 handsetWAG splits the workload into a very efficient,

quick, and accurate client/server structure.

THANK YOU