Evaluation of New Message Structures for Navigation Message Authentication

The current Galileo E1-B message will incorporate features to support navigation message authentication (NMA). The aim of this paper is to propose a future navigation message structure for satellite navigation systems incorporating NMA capabilities and providing stand-alone positioning. Based on signatures sizes ensuring high security strength, a message structures is presented, which offers short authentication times between consecutive events. To achieve frequent authentication events, high data rates are envisaged (up to 1000 sps). A dedicated subframe for the clock and ephemeris data (as in the CNAV-2 message) is foreseen to provide stand-alone information for positioning. The paper illustrates a future message structure for satellite navigation, where authentication on data level can be introduced most efficiently with respect to the authentication error rate (AER) and the time between two authentication events. For this purpose advanced forward error correction (FEC) schemes as Turbo and Super-Orthogonal Turbo Codes (SOTC) with different coding rates are assessed and their performance is compared to the data demodulation thresholds given by the message structures on GPS L1C (CNAV-2) and Galileo E1-B (I/NAV).