| 摘要 |
PURPOSE: A satellite-based location system employing knowledge-based sequential signal search strategy is provided to effectively reduce the area and code phase search ranges in which a GPS receiver searches for other satellite signals. CONSTITUTION: A flowchart(600) illustrating a sequential search technique used in accordance with one embodiment of the present invention. In step(605), WAG client receives a search message from its serving base station or WAG server. In the present invention, the search message includes, for each satellite detected by WAG server, information regarding the associated PN-j code, predicted frequency fj(r) at a reference point within the sector/cell where WAG client is currently located, code phase search range Rj(sect) including all possible phase shifts for a GPS signal transmitted by satellite and arriving within the sector/cell where WAG client is currently located, and orbital data including elevation angle alpha j and azimuth angle phi j. In step(610), WAG client selects a first satellite indicated in the search message to search. WAG client uses one or more criteria in a set of first satellite selection criteria to select the first satellite. In one embodiment, the set of first satellite selection criteria are as follows: maximize utilization of correlators; minimize search time; and maximize the amount of information regarding location of WAG client (or GPS receiver or antenna . The first criteria of maximizing utilization of correlators involves using as many of the available correlators to simultaneously search for a satellite. The second criteria of minimizing search time involves reducing the number of integrations to be performed by each correlator, e.g., each correlator performs one integration. Reducing the number of integrations to be performed by each correlator essentially means selecting a satellite having the smallest associated code phase search range Rj indicated in the search message.
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