Synchronization of tdma space division satellite system

Claim 2

In a communications satellite system of time division multiple access type utilizing a satellite having spot beam antennas, wherein a plurality of earth stations communicate by sending bursts of information sequentially through the spot beams of the satellite and each earth station is unable to receive its own signals and each station''s transmission includes a synchronizing signal, the method of synchronizing the information bursts of the stations in the system so that they do not overlap in the satellite, said method comprising the following steps: a. detecting at one station the synchronizing signals occurring during the same time frame of two or more other earth stations; b. comparing at said one station the time relationships of the synchronizing signals of each of said two or more stations, to a reference synchronizing signal; c. generating at said one station error signals representing the deviations between the respective time relationships between the reference signal and the synchronizing signals of said two or more stations, and a predetermined time relationship; d. transmitting to each of said two or more other stations said error signals; and e. controlling the time at which each of said two or more other stations transmit in response to said error signals.

Claim 3

The method of claim 1 wherein said error signals are transmitted to said two or more other stations by including said error signals in said one station''s transmissions through the satellite.

Claim 4

The method of claim 2 wherein said reference synchronizing signal is chosen to be the synchronizing signal from one of said other stations.

Claim 5

The method of claim 3 wherein the step of detecting synchronizing signals at said one station is performed every (2Td+a) seconds, where Td equals the round trIp time for a satellite transmission and a is a constant which is larger than the time variations caused by satellite motion and equipment delay.

Claim 6

The method of claim 3 wherein the step of detecting synchronizing signals at said one station is performed every Tf seconds when a pair of pulses have not been received during a frame, where Tf is the time for a complete sequence of bursts from said other stations.

Claim 7

In a communications satellite system of time division multiple access type utilizing a satellite having spot beam antennas, wherein a plurality of earth stations communicate by sending bursts of information sequentially through the spot beams of the satellite and each earth station is unable to receive its own signals and each station''s transmission includes a synchronizing signal, apparatus for synchronizing the information bursts of the stations in the system so that they do not overlap in the satellite, said method comprising the following steps: a. means for detecting at one station the synchronizing signals during a single time frame of two or more other earth stations; b. means for comparing at said one station the time relationship of, the synchronizing signals of each of said two or more stations, to a referenced synchronizing signal; c. means for generating at said one station error signals representing the deviations between the respective time relationship between the reference signal and synchronizing signals of said two or more stations, and a predetermined time relationship; d. means for transmitting from said one station to each of said two or more other stations said error signals; and e. means at each of said two or more other stations for controlling the time at which each of said two or more other stations transmit in response to said error signals.

Claim 8

In a communications satellite system of time division multiple access type utilizing a satellite having spot beam antennas, wherein a plurality of earth stations communicate by sending bursts of information sequentially through the spot beams of the satellite and each earth station is unable to receive its own signals and each station''s transmission includes a synchronizing signal, apparatus for synchronizing the information bursts of the stations in the system so that they do not overlap in the satellite, said method comprising the following steps: a. means for detecting at one station the synchronizing signals during a single time frame of two or more other earth stations; b. means for comparing at said one station the time relationship of, the synchronizing signals of each of said two or more stations, to a referenced synchronizing signal; c. means for generating at said one station error signals representing the deviations between the respective time relationship between the reference signal and synchronizing signals of said two or more stations, and a predetermined time relationship; d. means for transmitting from said one station to each of said two or more other stations said error signals; and e. means at each of said two or more other stations for controlling the time at which each of said two or more other stations transmit in response to said error signals.