and Positioning of Mobiles in Telecommunication
positioning technology has become an important area of research, for emergency
as well as for commercial services. Mobile positioning in cellular networks will
provide several services such as, locating stolen mobiles, emergency calls, different
billing tariffs depending on where the call is originated, and methods to predict
the user movement inside a region. The evolution to location-dependent services
and applications in wireless systems continues to require the development of more
accurate and reliable mobile positioning technologies. The major challenge to
accurate location estimation is in creating techniques that yield acceptable performance
when the direct path from the transmitter to the receiver is intermittently blocked.
This is the Non-Line-Of-Sight (NLOS) problem, and it is known to be a major source
of error since it systematically causes mobile to appear farther away from the
base station (BS) than it actually is, thereby increasing the positioning error.
FOR MOBILE TRACKING
Recent demands from new applications require positioning capabilities of mobile
telephones or other devices. The ability to obtain the geo-location of the Mobile
Telephone (MT) in the cellular system allows the network operators to facilitate
new services to the mobile users. The most immediate motivation for the cellular
system to provide MT position is enhanced in accident emergency services. The
positioning of the mobile user could provide services like
Emergency service for subscriber safety.
¢ Location sensitive billing.
¢ Cellular Fraud detection.
¢ Intelligent transport system services.
¢ Efficient and effective network performance and management.
Tracking Curve Method
The method proposed by us for tracking the location
of a mobile telephone using curves connecting the points where circles intersect
one another, the circles radii being the distances between BSs and the mobile
telephone. The steps involved are:
Each base station nearer to a mobile telephone receives a predetermined signal
from the mobile telephone and calculates the distance between the mobile telephone
and the base station and the variances of time arrival of the signal at the base
b. A circle is drawn to have a radius being the distance and the
coordinates of the base station being the center of the circle;
c. A pair
of the first and the second base stations is selected among the base stations.
A several location tracking curves connecting two intersection points between
the selected circles corresponding to the first and the second base stations are
drawn. One of the location tracking curves is selected using the variances of
the first and the second base stations;
d. The steps c. and d. are repeated
for the other pairs of the base stations;
e. The intersection points are obtained
among the location tracking curves selected in step d. and e. and,
location of the mobile telephone is determined using the coordinates of the intersection
points obtained in step e.
several location tracking curves are parts of circles with centers near to the
base station with smaller variances between the first and the second base stations.
The circles formed by the location tracking curves have the centers on a line
connecting the coordinates of the first and the second base stations. The larger
variances between the variances of the first and the second base stations are
compared to the variances of the several location tracking curves, and one of
the location tracking curves is selected according to the comparison result. The
location coordinates of the mobile telephone are determined by averaging the coordinates
of the intersection points obtained in step (f).