Process for improving GPS acquisition assistance data and server-side location determination for cellular networks

Abstract

This paper introduces a process for analyzing and improving the quality of the acquisition assistance data produced for Assisted GPS (A-GPS) positioning in cellular networks. An experimental test bed is introduced and a series of experiments and results are provided. The experiments validate the GPS acquisition assistance data in open-sky conditions. Accuracy results for initial testing of our server location determination engine in a range of different environments are also given with results of a long-term run. Acquisition assistance data provides the GPS handset with information that allows it to detect the GPS signals more quickly and allows detection of much weaker signals. It does this by providing information to the handset about where to look for the signals. The AGPS server is a mobile location server determining the location of devices within a cellular network. In order to measure the quality of the acquisition assistance data produced by the A-GPS server a piece of hardware has been developed called the “A-GPS Trainer”. This takes assistance data and uses it to lock on to the satellites. It then provides code phase measurements back to the server for it to do a location calculation. The trainer also reports on the amount of time it takes to lock on to the signals of the individual satellites. It can run multiple calculations over a period of time and report the results.