How can an orbit prediction module speed up the TTFF and help to authenticate the position?

Many GNSS applications require both, fast and trusted positioning. For example, in road toll collection this two requirements are extremely critical in order to provide fair road fee charges. One of the most effective measure to shorten the time to first fix is the usage of an assistance server to provide actual ephemeris and almanac information to the user. On the another hand, information from the assistance server can also be used as trusted reference data, which can help to detect spoofing attacks. The drawback is that a permanent connection to assistance server is required, in order to retrieve the latest ephemeris and almanac data. To overcome this problem the assistance server must be able to calculate and provide predicted orbits having a validity over a long period (e.g., up to 1-2 weeks). This paper describes a modular and cost-effective GNSS orbit prediction algorithm for reducing time to first fix as well as trusted positioning. The presented algorithm is implemented in the Positioning And Navigation Data Assistance Server, developed by TeleConsult Austria GmbH.