Navigation Performance Using Long-Term Ephemeris Extension for Mobile Device

Long-term ephemeris extension is needed in challenging environments in order to reduce the Time-To-First-Fixed (TTFF). It makes quick position fix possible for mobile devices while they are still acquiring the broadcast ephemeris. Based on the experiment results described in this paper, the median User Range Error (URE) for the extended ephemeris after one week and four weeks is 5.68m and 88.98m, respectively. Simulated signal obstruction experiments are also conducted to assess the position fix accuracy, availability and reliability based on different mean square positional error (MSPE) thresholds, prediction durations and obstruction scenarios. The results have shown 95.57% navigation availability at 99.28% reliability with one obstruction and 83.37% navigation availability at 97.12% reliability with two obstructions based on a user-defined MSPE of 50m after one week prediction.