Frame timing synchronization in a geostationary satellite system
View Patent ↗Aspects of the invention provide a system and method to allow inroute frame timing synchronization without the aid of hub signal loopback or satellite ephemeris data. Furthermore, it allows tracking and compensating of the satellite motion to allow multiple remotes to use TDMA on the inroute frequencies, while minimizing the aperture. Two main techniques proposed are CLT and polling based approaches, which are used in combination for an optimum solution. In CLT based approach, hub transmits remote specific timing correction feedback messages on the outroute on as needed basis. In polling based approach, the remotes derive their timing based on a per-beam average delay estimate broadcast by the hub and a measured local delay specific to each outroute stream from a remote. An aspect of the invention uses triangulation method to determine satellite position. Furthermore, an aspect of the invention uses hub burst arrival method instead of polling approach.
1. A method comprising:
determining, at at a first time, a first remote timing reference for data communications between a remote terminal and a hub terminal, wherein the data communications occur via one or more satellite channels between the remote terminal and a data communications satellite and one or more satellite channels between the data communications satellite and the hub terminal;
determining, at a second time, a second remote timing reference for the data communications;
determining a drift delay timing offset based on a difference between the first remote timing reference and the second remote timing reference resulting from a change in position of the satellite;
receiving an estimated propagation delay from the hub terminal; and
generating a third remote timing reference based on the a drift delay timing offset and the estimated propagation delay.
2. The method according to claim 1 , further comprising:
receiving a timing feedback message including an aperture offset time that reflects a timing delay offset between an expected burst receive time within a burst arrival aperture and an actual burst receive time within the burst arrival aperture,
wherein the generation of the third remote timing reference is further based on the timing delay offset.
3. A method comprising:
receiving a plurality of remote timing offsets, wherein each remote timing offset reflects a drift timing offset in data communications between a respective one of the remote terminals and a hub terminal, wherein the data communications occur via one or more satellite channels between the hub terminal and a data communications satellite and one or more satellite channels between the data communications satellite and the remote terminal, and wherein the drift timing offset results from a timing offset in the data communications resulting from a change in position of the satellite;
generating a beam time value for a respective beam of the data communications satellite that services the remote terminals, wherein the beam time value is generated based on at least a subset of the received remote timing offsets; and
transmitting the beam time value to all remote terminals serviced by the respective beam.
4. The method according to claim 3 , further comprising:
determining, by a one of the remote terminals, a first remote timing reference for the data communications at a first time between the one remote terminal and the hub terminal;
determining a second remote timing reference for the data communications at a second time between the one remote terminal and the hub terminal;
determining the drift timing offset of the one remote terminal based on a difference between the first remote timing reference and the second remote timing reference;
transmitting the respective remote timing offset, reflecting the drift timing offset of the one terminal, to the hub terminal.
5. The method according to claim 4 , further comprising:
receiving, by the one remote terminal, the beam time value;
determining frame timing for the data communications based on the beam time value and the first and second remote timing references.