| 摘要 |
An assisted global positioning satellite (Assisted GPS) system has a GPS reference network node (260) that collects GPS satellite broadcast messages and prepares separate GPS assistance messages to be modulated by a base transceiver station (BTS) (202) on a cellular carrier signal (201) and sent to single or multiple handset (204). In a first preferred embodiment, instead of the handset (204) receiving standard ephemeris and clock correction data elements in a GPS assistance message, a compressed GPS assistance message containing XYZ information contains a GPS satellite's coordinate position modified according to the satellite clock correction. In a second preferred embodiment, there is a first type of compressed GPS assistance message containing subframe 1, 2, 3 data of a GPS satellite broadcast message and a second type of compressed GPS assistance message containing subframe 4, 5 data of a GPS satellite broadcast message. The compressed GPS assistance messages according to the second preferred embodiment lack redundant or predictable information in order to reduce the size of the compressed GPS assistance message. The first type can be updated at a different rate than the second type in order to reduce the traffic and yet keep the handset (204) up to date.
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