Cell of Origin (COO)
This is the most natural way to start offering LBS because all handsets support this technology. COO uses the network base station cell area to identify the location of the caller. The accuracy depends upon the cell area and the accuracy can be up to 150 meters for an urban area. Although the accuracy is not high and cannot be applied for emergency usage it is popular amongst the operators, as it does not require any modifications in the handset or the network, hence it is comparatively cheap to deploy.
Time of Arrival (TOA)
Here the difference in the time of arrival of the signal from the mobile to more than one base station is used to calculate the location
of the device. The cost benefit analysis is not very much in favor of
the usage of this technology, as the cost of implementing this is
very high as compared to the enhancement in the performance. It
is expensive because of the large number of location measurement
units (LMUs) required. The accuracy of TOA is definitely better
than COO but again it is dependent on the visibility of the terminal
transmissions at LMU sites.
Angle of Arrival (AOA)
AOA is a system that calculates the angles at which a signal arrives at two base stations from a handset, using triangulation to find location. AOA works poorly in urban settings, where buildings interrupt signals.
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. This is the most accurate technique but
subject to the visibility of the base stations. The technique is subject
to degradation in places like buildings. In fact any geographical
hindrance that affects the signal will result in reduced accuracy.
Assisted GPS (AGPS)
The last main category assisted global positioning services (AGPS)
is an amalgamation of mobile technologies and GPS. AGPS can be
accurate up to ten meters, 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, where people spend a significant portion of their
time. A-GPS can help to provide rich services to the users like self-navigation
and emergency services because of its accuracy.
Cell of Origin is most accepted technology used by cell network
operators to find out location of the mobile device as it serves the
purpose and requires minimum investment. The next step in this
direction could be E-OTD for better accuracy but with SW
modifications in the mobile terminals. The third step could be A-GPS
capability with SW and HW modifications in mobile terminals.
GPS
Navigation and positioning are critical to so many activities and yet
the methods have always been quite cumbersome. Over the years all
kinds of technologies have tried to simplify the task but every one
has had some disadvantages.
The Global Positioning System a gift of the arms race has
changed navigation and position forever.
GPS is a worldwide radio navigation system consisting of 24
satellites and their ground stations. Imagine the world divided into
square meters with its unique address so we can literally point each
location on the earth.
The miracle here is the GPS receiver, which have now been
miniaturized to just a few integrated circuits and are economical.
The principals of GPS are quite simplistic in nature, yet this simple
solution to maintaining knowledge of the exact location of a vehicle
or troop of vehicles is currently being trusted by such relentless
industries as Police Forces, Hospitals and Fire Departments. Other
industries such as Taxi Cab Companies, Messenger Services, Cement
and Concrete suppliers, Construction Firms and Utility Companies
have also discovered the benefits of GPS, and they are finding
advantageous and profitable results as an outcome.
GPS is based on the concept of Trilateration. Trilateration is
a basic geometric principle that allows you to find one location if
you know its distance from other, already known locations.
Trilateration is at the very root of GPS. No fewer than 5
satellites are in view of any given spot on the Earth’s surface at any
given moment. In order to use the formula of trilateration it is only
necessary for three signals to be intercepted by a GPS receiver.
Using the information the satellites transmit to the receiver and by
calculating the time the signal took to reach the receiver, the receiver
is able to recognize its exact distance from the satellite. By collecting
signals from three of more satellites in carefully monitored orbit
the receiver computes its own spatial relationship to each satellite
in order to come up with a precise reading of its position on the
planet.
Thus for a GPS receiver to find your location, it has to determine two things:
- The location of at least three satellites above you
- The distance between you and each of those satellites
Geographic data
The next ingredient is the GIS data needed to facilitate LBS. It
provides the data to render man made structures like road network,
geocoded customer addresses and buildings and terrains like mountains
and rivers. GIS is also used to manage point-of-interest data such as
location of gas stations, restaurants, cinema halls, etc. Finally, GIS
information also includes information about the radio frequency
characteristics of the mobile network. This allows the system to
determine the serving cell site of the user or the wireless serving
boundaries.
The intensity or quality of GIS data needed is dependent in
the type of service to be provided to the user. A service that
determines navigation or pin pointing the ATM center requires a
database of rich GIS data. If a sophisticated system were to set up in
a developing nation it would not be wrong to say, how can one do
this? The data infrastructure in these countries is still infantile.
These data are either unknown or is inaccessible to potential users,
in and outside the government. Data availability, accessibility, quality,
documentation and dissemination are critical issues. Thus the non-availability
of correct and extensive GIS data often makes
implementation of not only something like a Navigation system
difficult but various Disaster management based services are also
hampered.
The GIS data needed should be updated and rich to be able to cater to various demands of LBS.
Control Center
The control center is another important element in LBS. It is the center of data management and dissemination of location services. The location data, geocoded data or map data need to be managed and manipulated to provide the various services based on the location to the user.
Retrieving and using Geocoding is of prime importance as it determines the latitude and longitude of an address. The technical requirements of geocoding services can vary from trivial to demanding. A trivial approach could mean getting the approximate location of an address in a street network.
Sophisticated mapping is needed to visualize location related data. Mapping requires spatial queries and visual algorithms. These operations require good geographic data. Sophisticated algorithm is again required for routing and navigation services. The applications need to scalable and robust to enable prompt and perfect services.
The control centers and the intensity of the work they perform are again dependent on the scale of user service provided by them.
Communication system
It is inevitable that communication plays a vital role in LBS. Messaging is required to convey the location to the control center and provide the service needed. The system could be based on various options like:
- Radio with dedicated channels
- Cellular telephony (SMS)
- Satellite communications (GSM)
The choice of one or another will depend on the level of service needed, the inclusion of voice communications and the relationship between channel occupation and cost.
While the ingredients are very much in place it is time to ponder whether all the ingredients are necessary for LBS. The needs of various kinds of location services provided could vary and so could vary the technology used or the ingredients. When choosing the most suitable technology the LBS providers need to categorize the application, service and customer segments.
We could consider Truck Management system and Friend Tracking system to analyze the ingredients needed.