Title page for ETD etd-82597-03345

Type of Document

Master's Thesis

Author

Aatique, Muhammad

Author's Email Address

aatique@qualcomm.com

URN

etd-82597-03345

Title

Evaluation of TDOA Techniques for Position Location in CDMA Systems

Degree

Master of Science

Department

Electrical Engineering

Advisory Committee

Advisor Name	Title
Woerner, Brian D.	Committee Chair
Reed, Jeffrey Hugh	Committee Member
Tranter, William H.	Committee Member

Keywords

GPS
geolocation
DOA
AOA

Date of Defense

1997-08-06

Availability

unrestricted

Abstract

The Federal Communications Commission (FCC) has adopted regulations requiring
wireless communication service providers to provide position location (PL)
information for a user requesting E-911 service. The Time Difference of Arrival
(TDOA) technique is one of the most promising position location techniques for
cellular-type wireless communication systems. The IS-95 Code Division Multiple
Access (CDMA) system is a popular choice for the companies deploying new
cellular and PCS systems in North America. Hence, the feasibility of TDOA
techniques in CDMA systems is an important issue for position location in the
wireless systems of the future.
This thesis analyzes the performance of TDOA techniques in the CDMA systems. A
comparison and assessment of different algorithms for finding the time
difference estimates and for solving the hyperbolic equations generated by
those estimates has been made. This research also considers a measure of
accuracy for TDOA position location method which is shown to be more suitable
for CDMA systems and more closely matches to the FCC requirements. Among the
other contributions is a proposed method to perform cross-correlations to
identify only the desired user's TDOA in a multiuser environment.
This thesis also evaluates the feasibility and accuracy of TDOA techniques
under varying system conditions that might be encountered in real situations.
This includes varying conditions of Additive White Gaussian Noise (AWGN), Multiple
Access Interference (MAI), power control and loading. The effect of the mobile
position and of different arrangement of base stations on TDOA accuracy is also
studied. Performance comparison in AWGN and Rayleigh fading channels is made.
The feasibility of using increased power levels for the 911 user in combination with interference cancellation
is also studied. The effect of using a single stage of parallel interference
cancellation at neighboring cell sites has also been explored. Non-ideal
situations such as imperfect power control in CDMA operation has also been
investigated in the context of position location. This thesis also suggests amethod to correct TDOA estimation errors in CDMA.
It is shown that this improvement can give greatly improved performance even
under worst-case situations. Performance comparison of results with and without
that modification has also been made under various conditions.

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