Reference station failure in a TDMA system

Claim 2

In a TDMA system having multiple stations and a frame format comprising one burst of transmitted data from each operating station in a non-overlapping sequence, a burst from a single station in the sequence being designated the reference burst, a method for preventing failure of system synchronization as a result of loss of a reference indication, said method at a local station comprising, a. monitoring bursts received from all stations to detect the presence of a reference signal identifying one of the received bursts as a reference burst, b. transmitting, during the local station burst time, a ''''lost'''' signal identifying that the reference station is lost when said reference signal has not been detected for a preset time period, c. monitoring bursts received from all stations to detect the presence of ''''lost'''' signals, and d. preventing any alteration of the local station burst transmit time relative to the other stations for a period of time following detection of ''''lost'''' signals in a predetermined number of received bursts.

Claim 3

The method as claimed in claim 1 further comprising, a. monitoring said received bursts to detect whether or not the local station burst occupies the second position within the frame relative to the reference burst, and b. transmitting a reference signal identifying said local station as the reference station following detection of ''''lost'''' signals in a predetermined number of received bursts and detection of said local station burst as occupying said second position within the frame.

Claim 4

The method as claimed in claim 2 further comprising, a. transmitting a pre-established code signal to cause all stations to resynchronize their bursts on the local station burst, said code signal being transmitted following detection of ''''lost'''' signals in a predetermined number of received bursts and detection of said local station burst as occupying said second position within the frame.

Claim 5

In a TDMA system having multiple stations and a frame format comprising one burst of transmitted data from each operating station in a non-overlapping sequence, a burst from a single station in the sequence being the reference burst, apparatus for preventing failure of system synchronization as a result of loss of a reference indication, said apparatus at a local station comprising, a. reference signal monitoring means for monitoring bursts received from all stations to detect the presence of a reference signal identifying one burst as a reference burst, b. means, connected to said monitoring means, for transmitting, during the local station burst time, a ''''lost'''' signal identifying that the reference station is lost when said reference signal has not been detected for a preset time period, c. ''''lost'''' signal monitoring means for monitoring bursts received from all stations to detect the presence of ''''lost'''' signals, and d. means, connected to said ''''lost'''' signal monitoring means, for preventing any alteration of the local station burst transmit time for a period of time, in response to the detection of ''''lost'''' signals in a predetermined number of received bursts.

Claim 6

In a TDMA system having multiple stations and a frame format comprising one burst of transmitted data from each operating station in a non-overlapping sequence, a burst from a single station in the sequence being the reference burst, apparatus for preventing failure of system synchronization as a result of loss of a reference indication, said apparatus at a local station comprising, a. reference signal monitoring means for monitoring bursts received from all stations to detect the presence of a reference signal identifying one burst as a reference burst, b. means, connected to said monitoring means, for transmitting, during the local station burst time, a ''''lost'''' signal identifying that the reference station is lost when said reference signal has not been detected for a preset time period, c. ''''lost'''' signal monitoring means for monitoring bursts received from all stations to detect the presence of ''''lost'''' signals, and d. means, connected to said ''''lost'''' signal monitoring means, for preventing any alteration of the local station burst transmit time for a period of time, in response to the detection of ''''lost'''' signals in a predetermined number of received bursts.

Claim 7

The apparatus as claimed in claim 4 further comprising, a. position detection means for monitoring said received bursts to detect whether or not the local station burst occupies the second position within the frame relative to the reference burst, and b. means, connected to said position detecting means, for transmitting a reference signal identifying said local station as the reference station in response to the detection of ''''lost'''' signals in a predetermined number of received bursts and detection of said local station burst as occupying said second position within the frame.

Claim 8

The apparatus as claimed in claim 5 further comprising, a. means, connected to said position detection means, for transmitting a pre-established code signal to cause all stations to resynchronize their bursts on the local station burst in response to the detection of ''''lost'''' signals in a predetermined number of received bursts and detection of said local station burst as occupying the second position within the frame.

Claim 9

In a TDMA communications system having multiple transmit/receive stations, a satellite transponder serving as a communication link for said stations, wherein each station transmits one burst of data per frame synchronized with respect to one said burst identified as a reference burst, the method of preventing failure of system synchronization as a result of loss of a reference indication, said method comprising, a. monitoring, at all stations, all received bursts for the presence of a reference signal identifying that the burst containing the reference signal is the reference burst, b. transmitting a ''''lost'''' signal from each station, during each said station''s burst, which has not detected the presence of a reference signal for a predetermined time period, c. monitoring, at all stations, all received bursts for the presence of ''''lost'''' signals, and d. preventing alteration of the burst transmit time with respect to all other bursts at each station at which lost signals were detected in a predetermined number of monitored bursts.

Claim 10

In a TDMA communications system having multiple transmit/receive stations, a satellite transponder serving as a communication link for said stations, wherein each station transmits one burst of data per frame synchronized with respect to one said burst identified as a reference burst, the method of preventing failure of system synchronization as a result of loss of a reference indication, said method comprising, a. monitoring, at all stations, all received bursts for the presence of a reference signal identifying that the burst containing the reference signal is the reference burst, b. transmitting a ''''lost'''' signal from each station, during each said station''s burst, which has not detected the presence of a reference signal for a predetermined time period, c. monitoring, at all stations, all received bursts for the presence of ''''lost'''' signals, and d. preventing alteration of the burst transmit time with respect to all other bursts at each station at which lost signals were detected in a predetermined number of monitored bursts.