VSAT Inroute Timing Synchronization Using Ephemeris Offset
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current systems face challenges in accurately determining inroute timing synchronization due to time-varying gateway-satellite-terminal propagation delays, leading to inefficiencies and increased overhead in aperture sizes, especially when ephemeris data is unavailable.
Innovation Solution
A method that uses ephemeris-based timing to calculate and compensate for time-varying propagation delays by receiving a satellite ephemeris vector, calculating a timing offset, and adjusting the transmit instant to ensure precise burst transmission, even in Temporary Outage Mode or Short-Term Outage Mode, thereby reducing aperture sizes and improving resiliency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ephemeris data is unavailable and the system transitions to TOM or STOM modes, then the system maintains timing synchronization capability, but the aperture size increases to 25-55 microseconds reducing inroute efficiency
Solution Approach 1:
The patent changes the timing calculation parameters by introducing TRO (terminal offset time) computation that dynamically adjusts transmission timing based on satellite ephemeris data, gateway location, and terminal location. This allows the system to maintain precise timing synchronization even in outage modes, reducing the aperture size from 25-55 microseconds to 10 microseconds and thereby improving inroute efficiency while maintaining reliability
Solution Approach 2:
The system performs preliminary timing offset calculation using available ephemeris data before actual transmission occurs. By pre-computing the TRO value based on satellite position, gateway position, and terminal position, the system prepares accurate transmission timing in advance, allowing it to maintain efficiency even when operating in TOM or STOM modes without requiring larger apertures
2Device complexity
If the system uses traditional timing synchronization without TRO calculation, then the system is simpler to implement, but timing precision deteriorates due to time-varying propagation delays
Solution Approach 1:
The patent implements a feedback mechanism where the gateway sends SFNP (superframe numbering packet) messages containing satellite ephemeris data to terminals. The terminal uses this feedback information to calculate TRO and adjust its transmission timing accordingly. This closed-loop feedback system continuously compensates for time-varying propagation delays, maintaining high timing precision without requiring overly complex implementation
Solution Approach 2:
The patent replaces traditional mechanical timing synchronization methods with computational approaches. Instead of relying on fixed timing tables or simple delay compensation, the system uses satellite ephemeris data, gateway location, and terminal location to computationally determine the precise timing offset TRO. This substitution of computational methods for mechanical approaches achieves high precision while keeping the system relatively simple to implement
3Productivity
If the aperture size is reduced to improve inroute efficiency, then the timing precision requirement increases, but this may reduce resiliency when ephemeris data is unavailable
Solution Approach 1:
The patent implements dynamic timing adjustment where the TRO value is continuously updated based on current satellite ephemeris data, gateway location, and terminal location. This dynamic approach allows the system to adapt to changing propagation conditions in real-time, maintaining both high timing precision for reduced aperture size and resiliency by recalculating TRO whenever new ephemeris data becomes available, even in TOM or STOM modes
Data Source
AI summary
A method and system for determining inroute frame timing for a Very Small Aperture Terminal (VSAT) includes receiving an appointment to transmit, on an inroute, at a start of a slot X of a frame number M; establishing, at a VSAT, an arrival time of a super frame numbering packet (SFNP) including a satellite ephemeris vector and a frame number N; calculating, at the VSAT, a timing offset (TRO) to be applied to the arrival time to compensate for a time varying gateway-satellite-terminal propagation delay (THS+TSR); setting a transmit instant as an end of the TRO after the arrival time; adding to the transmit instant a duration of X slots and a duration of (M−N) frames; and transmitting a burst, on the inroute from the VSAT, at the transmit instant. In the method, the calculating is based on computing THS+TSR from the satellite ephemeris vector, a gateway transmits the SFNP and receives the burst in the slot X within the frame number M of the inroute, and N is greater than or equal to M. A method and system for using ephemeris data for inroute timing is disclosed.