Multimodal inroute timing synchronization system

Patent metadata

Field	Value
Publication number	US-11737041-B2
Application number	US-202217930800-A
Country	US
Kind code	B2
Filing date	Sep 9, 2022
Priority date	Feb 3, 2021
Publication date	Aug 22, 2023
Grant date	Aug 22, 2023

Abstract

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.

First claim

We claim as our invention:

1. A method for determining inroute frame timing for a burst, the method comprising:
receiving an appointment to transmit, on an inroute, at a start of a slot X of a frame number M;
establishing an arrival time of a Super Frame Numbering Packet (SFNP) comprising a frame number N;
calculating, based on a satellite ephemeris vector, a timing offset (T RO ) to be applied to the arrival time to compensate for a time varying gateway-satellite-terminal propagation delay based on a propagation time from gateway to satellite plus a propagation time from satellite to terminal (T HS +T SR );
setting a transmit instant as an end of the T RO after the arrival time;
adding to the transmit instant a duration of X slots and a duration of (M-N) frames; and
transmitting the burst, on the inroute from the terminal, at the transmit instant,
wherein a gateway receives the burst in the slot X within the frame number M of the inroute, and N is greater than or equal to M.

2. The method of claim 1 , wherein the transmit instant has an aperture size of 15 microseconds or less.

3. The method of claim 1 , further comprising determining a T RO reference (T RO-ref ) by requesting timing information from the gateway via an asynchronous burst, wherein the T RO-ref is used for the calculating.

4. The method of claim 1 , further comprising determining an estimated T RO (T RO-est ) via a ranging ALOHA session the T RO-est is used for the calculating.

5. The method of claim 1 , wherein the calculating updates the T RO based on a new satellite coordinate in a new SFNP.

6. The method of claim 1 , wherein the calculating is based on a timing feedback comprising an inroute burst timing offset.

7. The method of claim 1 , further comprising requesting a timing feedback when the terminal has been idle for longer than a timer threshold or when the SFNP indicates that the gateway requests a timing reacquisition.

8. The method of claim 1 , wherein the satellite ephemeris vector comprises an estimated Center-of-Box vector for a satellite location.

9. The method of claim 1 , further comprising predicting, a next inroute burst timing offset, based on previous timing feedbacks.

10. The method of claim 1 , wherein the appointment is received by the terminal via a Bandwidth Allocation Packet.

11. A method for handling an ephemeris outage when using ephemeris data for inroute timing, the method comprising:
transitioning to a Closed Loop Timing (CLT)-only mode when an outage duration is greater than zero;
using an ephemeris prediction data comprising ephemeris vectors beyond a usable period for the ephemeris prediction data;
calculating satellite-to-gateway delays for transmitting RF to the ephemeris vectors; and
sending, to a terminal, a SFNP comprising one of the ephemeris vectors and an associated satellite-to-gateway delay.

12. The method of claim 11 , wherein an outage duration is less than a temporary outage threshold, and the calculating is based on a last ephemeris vector in the ephemeris prediction data.

13. The method of claim 11 , wherein an outage duration is less than a short-term outage threshold, and the calculating is based on an ephemeris series comprising a 24 hour before a start of an outage and the ephemeris series is based on the ephemeris prediction data.

14. The method of claim 11 , wherein an outage duration is less than a long-term outage threshold, and the calculating is based on a straight-line satellite trajectory moving toward a Center-of-Box based on the ephemeris prediction data.

15. The method of claim 11 , wherein the calculating comprises smoothing a transition, using a weighted average, from the ephemeris predication data to a previous ephemeris predication data.

16. The method of claim 11 , further comprising:
acquiring new ephemeris prediction data; and
smoothing a transition, using a weighted average, from using the ephemeris vectors based on the calculating to valid vectors calculated based on the new ephemeris predication data.

17. A method for inroute timing acquisition by a terminal for communicating with a gateway via a satellite, the method comprising:
transmitting a burst from the terminal to the gateway;
receiving, at the terminal, an absolute timing of a burst arrival at the gateway;
calculating a timing offset time (TRO) based on the absolute timing; and
setting a transmit instant by adjusting a bandwidth allocation appointment with the TRO.

18. The method of claim 17 , wherein the bandwidth allocation appointment is based on a time of arrival of a Super Frame Numbering Packet (SFNP).

19. The method of claim 17 , wherein the calculating of the TRO is refined using ephemeris data.

20. The method of claim 17 , wherein the calculating of the TRO is refined using a timing correction feedback.

Assignees

• Hughes Network Systems
• Hughes Network Systems Llc

Inventors

• Regunathan Murali
• Wu Zheng
• Border John

Classifications

• H04W56/0045 Primary

  compensating for timing error by altering transmission time · CPC title

• H04B7/18528 Primary

  Satellite systems for providing two-way communications service to a network of fixed stations, i.e. fixed satellite service or very small aperture terminal [VSAT] system · CPC title

• H04W56/006

  using known positions of transmitter and receiver · CPC title

• H04W88/16

  Gateway arrangements · CPC title

• H04B7/2125

  Synchronisation · CPC title