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
  • GPS
  • geolocation
  • DOA
  • AOA
Date of Defense 1997-08-06
Availability unrestricted
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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