| 摘要 |
A satellite positioning system comprises a plurality of mobile clients that can move in and out of a wireless service area. Such area is more or less fixed and supported by a base station, e.g., a mobile telephone cell. The service area and/or the base station is associated with an identity code that can be queried. Each mobile client includes an autonomous GPS receiver that does not require aiding information to produce a position fix, but will produce such fix quicker and at higher sensitivity if aiding information is supplied. A local memory is used to store a limited number of cell-ID identity codes associated with previously determined positions for those sites. The mobile clients further include a cellular telephone that can support Internet access to a mobile aiding server. An ID-registration database is used to collect aiding information collected and contributed in the past by other mobile clients. Such database is co-located with the mobile aiding server and will supply requests for aiding information. When a mobile client enters a new service area and is required to produce a fix, it consults its own local memory and then the Internet server for information related to the particular cell-ID. Such aiding information includes the approximate position of the mobile client, and this reduces the position and Doppler uncertainties during a cold start. The range of positioning is extended when the signal is too weak to allow successful decoding of all navData by using the data bit phase, codephase, and a prior position estimate.
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