Location based services


Angle of Arrival (AOA)
AOA requires a complex antenna array at each cell site. These antenna in principle work together to determine the angle (relative to the cell site) from which a cellular signal originated.

Enhanced Observed Time Difference
Enhanced Observed Time Difference (E-OTD) systems operate by placing location receivers, overlaid on the cellular network as a location measurement unit (LMU) at multiple sites geographically dispersed in a wide area. Each of these LMU has an accurate timing source. When a signal from at least three base stations is received by an E-OTD software enabled mobile and the LMU, the time differences of arrival of the signal from each BTS at the handset and the LMU are calculated. The differences in time are combined to produce intersecting hyperbolic lines from which the location is estimated.

E-OTD schemes offer greater positioning accuracy than cell of origin, between 50 and 125 meters, but have a slower speed of response, typically around five seconds, and require software modified handsets.

Assisted GPS (AGPS)
The last main category is assisted global positioning services (AGPS). AGPS can be accurate upto ten metres, but is expensive for the end-user as they would have to invest in a GPS-equipped handset. Besides this, GPS handset necessarily needs to be in sight of three or more satellites, hence making it’s implementation difficult in built areas and more so from indoor.

Flexible Architecture
The architecture being adopted today by many network operators is based upon mobile location center (MLC). The MLC separates the location technology to locate the device from the application the location information will be put into. Since many applications can function quite well with cell of origin information, network operators can deploy advanced location technology gradually and not wait for 100-percent coverage to offer new services.

With this flexible architecture in place, network operators can apply new applications.

Applications
The extent of horizontal coverage of LBS has virtually covered all the walks of life from selecting the restaurants to emergency services to aid in navigation, it is all there. Some of the fileds where network operator are moving in are:
  • The ability to pinpoint location is going to revolutionise customer billing in the wireless industry as carriers move from flat-rate billing to location-sensitive billing models. For an example, a family could receive better rates for residential location.

  • Fleet management using the remote tracking of taxis and trucks will be common place. One could know the proximity of their trucks or packages and in years to come even the precise location of their goods.

  • Roadside assistance and driving directions will become more prevalent with the availability of improved location service. It could later turn out to be turn-by-turn driving directions a complicated location service.

  • If you’re driving to the theatre and are low on gas, your handset will know there’s a gas station three blocks ahead on the right. It will display directions to the theatre and even indicate that you can upgrade your tickets to orchestra seating if you request it in the next few minutes.

  • On the leisure and sports sector, golfers would “tag” their ball with a satellite transmitter before and after each shot. The location data would be shot to a satellite and tracked. When users go back to their home they would be able to track their performance on a Web site, complete with maps of fairways marked with the flight of their ball.
References
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