This paper proposes a message structure for the L5 GEO data signal that can support more than 90 simultaneous L1/L5 satellite corrections. The proposal is similar to the existing L1 structure with 250 bit messages sent at one Hertz. It eliminates the need for fast clock corrections. It creates a new integrity information message capable of updating the status for 91 satellites in a single message. Further, it simplifies the satellite corrections by gathering all of the required information for each satellite into a single message. This structure has excellent flexibility as a service provider that wishes to correct fewer satellites (e.g. a single constellation) may update the satellite corrections more often for improved accuracy. The paper also examines optimal scheduling strategies and the handling of alerts. The proposed structure addresses many of the shortcomings of the current L1 structure while remaining very similar in nature. Thus, this proposal leverages the most successful aspects of the L1 Minimum Operational Performance Standards (MOPS) while adapting it to meet the goals set forth for dual-frequency multi-constellation use.
