الفهرس 
Emergency Call Service Applications
POSITION LOCATION TECHNIQUESOnly 14 pages are availabe for public view
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Abstract
Wireless Position Location (PL) systems have received considerable
attenuation over the past few years. The potential applications provided by
these systems include emergency and safety services, location sensitive
billing, fraud detection, fleets management and cellular system design and
resources management.
Many PL techniques such as Angle of Arrival (AOA) and time-based
systems including the Time of Arrival (TOA) and the Time Difference of
Arrival (TDOA) techniques were discussed. Hyperbolic PL systems are
one such technology that can provide accurate PL information using the
existing cellular, Personal Communication Systems (PCS) infrastructure
and without requiring additional hardware/software implementation within
the Mobile Station (MS).
This thesis analyzes the performance of TDOA techniques in the
Global System of Mobile communications (GSM) based on Time Division
Multiple Access (TDMA). A comparison of different algorithms for
fmding the time difference estimates and for solving the hyperbolic
equations generated by those estimates has been made. Also the feasibility
and accuracy of TDOA techniques under systems conditions that might be
encountered in real satuations such as Additive White Guassian Noise
(AWGN), multi path, shadowing and path loss, power control, mobile
positions and number and configuration of base stations is investigated. All
results derived in this thesis are validated by simulation programs.
It was shown that the multi path either increases the PL accuracy or
decrease it, according to the power of LOS signal compared with the
multi path component Also the effect of path loss on the PL accuracy for
several path loss factors was demonstrated. The results showed that there is
degradation in PL accuracy at higher path loss factors. The effect of the
power control scheme on PL accuracy is also discussed. It is found that as a
mobile moves closer to the controlling base station, lower SNRs are
experienced at neighboring base stations which in tum results in inaccurate
TOOA estimates and poor PL performance. The effect of mobile positions
and the number and different arrangements of base stations for
macrocelJular and microcellular environments on TDOA accuracy is also
studied. It was Sh0W11 that redundant TDOA measurements can lead to
improved PL accuracy and the macrocellular can provide a better PL