Terminal scheduling method in satellite communication system

A terminal apparatus in a satellite communication system comprising:

• a receiver apparatus;
• a transmitting apparatus;
• a position and timing module;
• a processor, and
• a memory, wherein the memory comprises instructions to perform a method of operation of the terminal apparatus in the satellite communication system comprising:
• a) receiving and storing, by the terminal, ephemeris data including validity data received using the receiver apparatus;
• b) scheduling at least one wake up time based on the stored ephemeris data for transmitting data or for receiving updated ephemeris data, wherein the terminal enters a sleep state between scheduled wakeup times and is woken up at a scheduled wake up time;
• c) waking up the terminal at a scheduled wake up time and performing the following actions before going back to sleep;
• d) obtaining an estimate of the terminal's position and the global time from the position and timing module;
• e) determining, based upon the terminal's position and global time estimate, if the stored ephemeris data is valid, recently valid or invalid;
• f) if the stored ephemeris data is valid then either transmitting data to a satellite using the transmitting apparatus or attempting to receive updated ephemeris data from a satellite using the receiver apparatus;
• g) if the stored ephemeris data is recently valid, then estimating a set of possible satellite pass windows based on the stored ephemeris data and scheduling a set of warm wake up times during which the terminal is woken up to attempt to receive updated ephemeris data using the receiver apparatus;
• h) if the ephemeris data is invalid then the terminal is scheduled to go to sleep and periodically wake up and attempt to receive updated ephemeris data using the receiver apparatus with a period between wake up being less than an expected satellite pass duration, and if the attempt to receive updated ephemeris data was unsuccessful then the terminal goes back to sleep, and the terminal repeats this action h) until it successfully receives ephemeris data;
• i) wherein upon receiving updated ephemeris data in action f), g) or hi, the ephemeris data is stored and action b) is repeated.

A satellite communication system comprising a plurality of terminal apparatuses, and a plurality of satellites, wherein one or more of the satellites are configured to transmit ephemeris data for the plurality of satellites to the plurality of terminal apparatuses, wherein each of the terminal apparatuses comprises:

• a receiver apparatus;
• a transmitting apparatus;
• a position and timing module;
• a processor, and
• a memory, wherein the memory comprises instructions to perform a method of operation of the terminal apparatus in the satellite communication system comprising:
• a) receiving and storing, by the terminal, ephemeris data including validity data received using the receiver apparatus;
• b) scheduling at least one wake up time based on the stored ephemeris data for transmitting data or for receiving updated ephemeris data, wherein the terminal enters a sleep state between scheduled wakeup times and is woken up at a scheduled wake up time;
• c) waking up the terminal at a scheduled wake up time and performing the following actions before going back to sleep;
• d) obtaining an estimate of the terminal's position and the global time from the position and timing module;
• e) determining, based upon the terminal's position and global time estimate, if the stored ephemeris data is valid, recently valid or invalid;
• f) if the stored ephemeris data is valid then either transmitting data to a satellite using the transmitting apparatus or attempting to receive updated ephemeris data from a satellite using the receiver apparatus;
• g) if the stored ephemeris data is recently valid, then estimating a set of possible satellite pass windows based on the stored ephemeris data and scheduling a set of warm wake up times during which the terminal is woken up to attempt to receive updated ephemeris data using the receiver apparatus;
• h) if the ephemeris data is invalid then the terminal is scheduled to go to sleep and periodically wake up and attempt to receive updated ephemeris data using the receiver apparatus with a period between wake up being less than an expected satellite pass duration, and if the attempt to receive updated ephemeris data was unsuccessful then the terminal goes back to sleep, and the terminal repeats this action h) until it successfully receives ephemeris data;
• i) wherein upon receiving updated ephemeris data in action f), g) or h), the ephemeris data is stored and action b) is repeated.

A terminal apparatus in a satellite communication comprising:

• a receiver apparatus configured to receive ephemeris data transmitted by one or more satellites or a gateway in the satellite communication system, and configured to receive a beacon transmission from a gateway;
• a transmitting apparatus configured to transmit data to one or more satellites or a gateway in the satellite communication system;
• a position and timing module configured to estimate the terminal's position and the global time;
• a memory for storing the received ephemeris data;
• an alarm module configured to wake up the terminal apparatus from the sleep state to a wake state at one or more scheduled wake up times, and
• a scheduling module configured to schedule at least one wake up time based on the stored ephemeris data for transmitting data or for receiving updated ephemeris data, and to put the terminals into a sleep state upon completion of one or more terminal operations whilst in the wake state;
• and wherein upon wake up the scheduling module request the terminal's position and global time from the position and timing module, and is configured to determine, based upon the terminal's position and global time estimate, if the stored ephemeris data is valid, recently valid or invalid,
• and if the ephemeris data is valid, then the terminal is configured to either transmit data to a satellite or attempting to receive updated ephemeris data from a satellite,
• and if the stored ephemeris data is recently valid, then the scheduler is configured to estimate a set of possible satellite pass windows based on the stored ephemeris data and scheduling a set of warm wake up times during which the terminal is woken up to attempt to receive updated ephemeris data,
• and if the ephemeris data is invalid then the terminal is scheduled to go to sleep and periodically wake up and attempt to receive updated ephemeris data with a period between wake up being less than an expected satellite pass duration, and if the attempt to receive updated ephemeris data was unsuccessful then the terminal is configured to go back to sleep, and the terminal repeats operation until it successfully receives ephemeris data, and
• upon receiving updated ephemeris data, the ephemeris data is stored in the memory, and the scheduler schedules at least one wake up time based on the stored ephemeris data for transmitting data or for receiving updated ephemeris data and to put the terminal into a sleep state upon completion of one or more terminal operations whilst in the wake state.