Apparatus and method for network level synchronization in multiple low earth orbit (leo) satellite communications systems

Patent metadata

Field	Value
Publication number	US-2018013484-A1
Application number	US-201715688675-A
Country	US
Kind code	A1
Filing date	Aug 28, 2017
Priority date	Mar 19, 2014
Publication date	Jan 11, 2018
Grant date	—

Abstract

A method for synchronization of user terminal (UT) uplink data transmissions to a satellite in a satellite communications system is provided. The UT tracks frame timing and frequency of downlink data transmissions received by the UT from the satellite. The UT estimates a respective timing delay and frequency shift of the downlink data transmissions based on the tracked frame timing and frequency of the downlink data transmissions. The UT receives satellite ephemeris data broadcast by the satellite. The UT synchronizes uplink data transmissions to the satellite based on the estimated timing delay and frequency shift of the downlink data transmissions, the received satellite ephemeris data, and knowledge of a UT position and velocity vectors associated with any movement of the UT.

First claim

What is claimed is:

1 . A method for synchronization of user terminal (UT) uplink data transmissions to a satellite in a satellite communications system, comprising:
tracking, by the UT, of frame timing and frequency of downlink data transmissions received by the UT from the satellite; estimating a respective timing delay and frequency shift of the downlink data transmissions based on the tracked frame timing and frequency of the downlink data transmissions; receiving, by the UT, satellite ephemeris data broadcast by the satellite; and synchronizing uplink data transmissions by the UT to the satellite based on the estimated timing delay and frequency shift of the downlink data transmissions, the received satellite ephemeris data, and knowledge of a UT position and velocity vectors associated with any movement of the UT.

2 . A satellite user terminal (UT), comprising:
a receiver configured to receive downlink data transmissions from a satellite in a satellite communications network, and to receive satellite ephemeris data broadcast by the satellite; a transmitter configured to transmit uplink data transmissions to the satellite; and a processor configured to track frame timing and frequency of the downlink data transmissions received from the satellite, to estimate a respective timing delay and frequency shift of the downlink data transmissions based on the tracked frame timing and frequency of the downlink data transmissions, and to synchronize the uplink data transmissions to the satellite based on the estimated timing delay and frequency shift of the downlink data transmissions, the received satellite ephemeris data, and knowledge of a UT position and velocity vectors associated with any movement of the UT.

Assignees

• Hughes Network Systems Llc

Inventors

• Vasavada Yash
• Ravishankar Channasandra
• Arur Deepak
• Parr Michael

Classifications

• H04B7/185

  Space-based or airborne stations; {Stations for satellite systems}(H04B7/204 takes precedence) · CPC title

• H04B7/1851 Primary

  Systems using a satellite or space-based relay (H04B7/18508, H04B7/18521 take precedence; providing specific services H04B7/18523 - H04B7/18576) · CPC title

• H04B7/195

  Non-synchronous stations · CPC title

• H04W56/00

  Synchronisation arrangements · CPC title