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 of communicating from a remote to a hub by way of a satellite, the satellite being operable to bi-directionally communicate with the hub and the remote, the hub having assigned a timeslot for communication with the remote, the hub being operable to transmit a request for a drift delay to the remote by way of the satellite and to transmit an estimated propagation delay to the remote by way of the satellite, the drift value being based on a difference between an initial timing reference and a subsequent timing reference as a result of a change of position of the satellite, said method comprising:
determining, at the remote, a first remote offset time for communication with the hub by way of the satellite at a first time;
determining, at the remote, a second remote offset time for communication with the hub by way of the satellite at a second time;
determining, at the remote, a drift delay based on the first remote offset time and the second remote offset time;
receiving, at the remote, the request for the drift value;
transmitting, from the remote, the drift delay to the hub by way of the satellite; receiving, at the remote, the estimated propagation delay; and
generating, at the remote, a third remote offset time based on the second remote offset time and the estimated propagation delay.
2. The method of claim 1 , further comprising receiving, at the remote, a closed loop feedback message from the hub including aperture offset error information.
3. The method of claim 2 , wherein said generating, at the remote, a third remote offset time based on the second remote offset time and the estimated propagation delay comprises generating, at the remote, the third remote offset time based additionally on the aperture offset error information.
4. A remote for communicating with a hub by way of a satellite, the satellite being operable to bi-directionally communicate with the hub and said remote, the hub having assigned a timeslot for communication with said remote,
the hub being operable to transmit a request for a drift delay to said remote by way of the satellite and to transmit an estimated propagation delay to said remote by way of the satellite, the drift value being based on a difference between an initial timing reference and a subsequent timing reference as a result of a change of position of the satellite,
said remote comprising:
a communication portion operable to bi-directionally communicate with the satellite;
a timing portion operable to determine a first remote offset time for communication with the hub by way of the satellite at a first time and to determine a second remote offset time for communication with the hub by way of the satellite at a second time; and
a drift delay portion operable to determine a drift delay based on the first remote offset time and the second remote offset time;
wherein said communication portion is further operable to receive the request for the drift value,
wherein said communication portion is further operable to transmit the drift delay to the hub by way of the satellite,
wherein said communication portion is further operable to receive the estimated propagation delay, and
wherein said timing portion is further operable to generate a third remote offset time based on the second remote offset time and the estimated propagation delay.
5. The remote of claim 4 , wherein said communication portion is further operable to receive a closed loop feedback message from the hub including aperture offset error information.
6. The remote of claim 5 , wherein said timing portion is operable to generate the third remote offset time based additionally on the aperture offset error information.