||The mobile location positioning technology has been developed and widely used in recent years. After the US FCC mandates the E911 emergency service to be provided by all wireless service providers, the European Commission also starts to work out the E112 relative standards and regulations. Therefore positioning will be one of the essential features in cellular phones. The current main stream technology is to build-in a GPS chip for satellite positioning or via network based wireless location sending back result to the handset. The prior solution requires modifying the handset and increases bill of material (BOM) cost, and the later one has lower accuracy problem and requires additional data transmission fee to users.|
The main purpose of this thesis is to implement a positioning algorithm on a CDMA compatible cellular phone. In the condition of no hardware modification, but only modifying the firmware, the handset measures time difference of the base stations’ broadcast signal and locate the 2D position via trilateration method. Besides, there are 3 main issues are resolved in our implementation. First, when the measured signal is interfered by NLOS (Non-Sight-of-Light) effect, we utilize a sliding window to look up the minimum value and adopt a smoothing method to improve the NLOS effect. Second, for the implementation of algorithm on the embedded system, we simplify the complex matrix computation to use only 2 x 2 matrix form instead of k x k matrix in order not to overrun the system ability. When the number of the received BS signals, k, is greater than 3, all location estimates of the combinations are computed. Then these estimates are either directly averaged or weighted summed to compute a final estimate. In order to evaluate the system performance, we ran the static and dynamic tests on the live network. The results show the static tests can pass the FCC’s requirement.
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