EP0035232A2
Expired / Lapsed
EP
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Method and apparatus for the initial acquisition of synchronization for a station in a TDMA satellite communication network
Assignee: International Business Machines Corp
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Filing: 1981-02-25
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Granted: —
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Expires: 2001-02-25
Abstract
Abstract A method and apparatus are disclosed for acquiring transmit synchronization at a secondary station with the periodic frame reference bursts from a reference station in a TDMA network in an improved manner to enable the use of full power initial acquisition bursts while also reducing the bandwidth required to complete the initial acquisition operation. During the first phase, the apparatus at the secondary station bursts an initial acquisition burst during a relatively wide interval in the traffic portion of a TDMA frame and measures a propagation delay factor. The apparatus then adds the propagation delay factor to the receive frame timing synchronized with the reception of the frame reference bursts at the secondary station to obtain a more accurate adjusted transmit frame timing. The more accurate frame timing is then employed in a second phase to burst a transmit reference burst from the secondary station during a relatively narrower interval in the control portion of periodic, non-consecutive ones of the TDMA frames and the apparatus measures a propagation delay correction factor. The propagation delay correction factor is then used to adjust the phase of the transmit frame timing so as to maintain the synchronization of the secondary station with the reference station. At the end of the second phase the secondary stations normal traffic transmission operations can take place, with the transmit reference burst being periodically transmitted in the control portion of non-TDMA frames in order to achieve a long-term of synchronization between the secondary the reference station. The dual use of the traf- assigned to the secondary station for both the of the transmit clocks of the station dur- phase and the transmission of normal traffic or other stations during the second phase of acquisition for the station enables the use of a full acquisition burst, while reducing the overall requirements for the acquisition operation by the function with the transmit reference burst substantially less bandwidth due to its nar- interval and less frequent transmission.
Inventors
- 👤 Joseph Anthony Alvarez, Iii
- 👤 John Shabe
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-28 04:22
CPC Classifications
H; H04; H04B; H04B7/00; H04B7/14; H04B7/15; H04B7/204; H04B7/212; H04B7/2125; H04B7/2126; H04B7/185; H04B7/18523; H04B7/24; H04B7/26; H04B7/2643
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
317 words
Method for achieving acquisition of synchronization with the ongoing operation of the network in a TDMA satellite communications network having a master station (3) and a plurality of subsidiary earth stations (2), each communicating through a satellite transponder (5) in a plurality of TDMA frames grouped in a superframe, each frame having a control portion and a traffic portion, by a'given station (2), characterized by the following steps: receiving (452, 464) from said master station (3) an asigned initial acquisition time slot in said traffic portion of said TDMA frame, transmitting (455, 468) consecutive initial acquisition bursts in the central portion of said assigned time slot in consecutive ones of said TDMA frames (Fig. 33), measuring (458) the round trip time (2Ti) of said initial acquisition bursts between said given station (2) and said satellite (5), adjusting (443), in response to said measurements, the transmission timing at said given station (2) for variations in said satellite's (5) relative distance, receiving (452, 464) from said master station an assigned transmit reference burst time slot which is narrower than said initial acquisition time slot, in said control portion of one of said plurality of TDMA frames in said superframe (Fig. 34) terminating (455, 468) the transmission of said initial acquisition burst and commencing transmission of said transmit reference burst in said control portion in said one of said TDMA frames to refine the local transmit timing in said given station, (Fig. 34) and transmitting (455, 468, 445, 444, 463) said trans- mitreference burst from said given station in said assigned time slot of said control field of said one of said TDMA frames on an interleaved basis with the transmission of transmit reference bursts by other earth stations in said network in said assigned time slot of said control field of other ones of said TDMA frames in said superframe, whereby the bandwidth of said TDMA frames is conserved.
Claim 2
Dependent Claim
317 words
Method for achieving acquisition of synchronization with the ongoing operation of the network in a TDMA satellite communications network having a master station (3) and a plurality of subsidiary earth stations (2), each communicating through a satellite transponder (5) in a plurality of TDMA frames grouped in a superframe, each frame having a control portion and a traffic portion, by a'given station (2), characterized by the following steps: receiving (452, 464) from said master station (3) an asigned initial acquisition time slot in said traffic portion of said TDMA frame, transmitting (455, 468) consecutive initial acquisition bursts in the central portion of said assigned time slot in consecutive ones of said TDMA frames (Fig. 33), measuring (458) the round trip time (2Ti) of said initial acquisition bursts between said given station (2) and said satellite (5), adjusting (443), in response to said measurements, the transmission timing at said given station (2) for variations in said satellite's (5) relative distance, receiving (452, 464) from said master station an assigned transmit reference burst time slot which is narrower than said initial acquisition time slot, in said control portion of one of said plurality of TDMA frames in said superframe (Fig. 34) terminating (455, 468) the transmission of said initial acquisition burst and commencing transmission of said transmit reference burst in said control portion in said one of said TDMA frames to refine the local transmit timing in said given station, (Fig. 34) and transmitting (455, 468, 445, 444, 463) said trans- mitreference burst from said given station in said assigned time slot of said control field of said one of said TDMA frames on an interleaved basis with the transmission of transmit reference bursts by other earth stations in said network in said assigned time slot of said control field of other ones of said TDMA frames in said superframe, whereby the bandwidth of said TDMA frames is conserved.
Claim 3
Dependent Claim
170 words
A method for acquiring transmit synchronization at a secondary station (2) with the periodic frame reference bursts from a reference station (3) in a TDMA network in accordance with claim 1 further characterized by the following steps: bursting (457) an initial acquisition burst from said secondary station (2) during a relatively wide interval in the traffic portion of a TDMA frame and measuring (458) a propagation delay factor (2Ti), adding (443, 426) said propagation delay factor (2Ti) to the receive frame timing (422) synchronized with the reception of said frame reference bursts at said secondary station (2) to obtain a finely adjusted transmit frame timing (91), bursting (465, 467) a transmit reference burst from said secondary station (2) during a relatively narrow interval in the control portion of perioaic, non-consecutive ones of said TDMA frames and measuring a propagation delay correction factor (410) and adjusting the phase (408) of said transmit frame timing with said correction factor to maintain synchronization of said secondary station (2) with said reference station (3).
Claim 4
Dependent Claim
286 words
Method according to claim 2 for acquiring transmit acquisition of synchronization at a secondary station (2) in a TDMA satellite communication network having a reference station (3) transmitting periodic frame reference bursts defining the beginning of consecutive TDMA frames, each frame having a control signal portion and a traffic portion, a plurality of said frames grouped into periodic superframes, characterized by the following steps: synchronizing (406) a receive clock at said secondary station (2) by starting a receive frame when said frame reference burst is received, adding (443, 426) an estimated satellite round trip propagation delay factor to the start of said receive frame during a first phase of transmit acquisition to start a transmit frame, to coarsely synchronize a transmit clock (91), bursting (455. 457) an initial acquisition burst from said secondary station (2) during an assigned relatively wide interval in said traffic portion of a plurality of consecutive ones of said TDMA frames, measuring (458) a round trip propagation delay factor for said initial acquisition bursts, adding (443, 426) said round trip propagation delay factor to the start of said receive frame to start said transmit frame (91), to finely adjust said transmit clock, bursting (466) a transmit reference burst from said secondary station (2) during an assigned relatively narrow interval in said control portion of one of said frames in said periodic superframes, during a second phase of transmit acquisition, measuring (410) a round trip propagation delay factor for said transmit reference bursts with said transmit clock and deriving a correction factor therefrom, and adjusting (408) the speed of said transmit clock with said correction factor to maintain a precise synchronization of said transmit clock with the transmit clock at said reference station.
Claim 5
Dependent Claim
371 words
A TDMA satellite communications network having a master station (3) and a plurality of subsidiary earth stations (2), each communicating through a satellite transponder (5) in a plurality of TDMA frames grouped in a superframe, each frame (Fig. 34) having a control porticn and a traffic portion, and an apparatus for achieving acquisition of synchronization with the ongoing operation of the network, by a secondary station in accordance with claims 1 - 3 characterized by receiving means (452, 464) at said secondary station (2), for receiving from said master station (3) an assigned initial acquisition time slot in said traffic portion of said TDMA frame, transmission means (455, 468) connected to said receiving means, for transmitting consecutive initial acquisition bursts in the central portion of said assigned time slot in consecutive ones of said TDMA frames, (Fig. 33) delay measuring means (458) connected to said receiving means, for measuring the round trip time (2Ti) of said initial acquisition bursts between said secondary station (2)and said satellite (5), timing adjustment means (443) connected to said measuring means, for adjusting, in response to said measurements, the transmission timing at said secondary station for variations in said satellite's relative distance, said receiving means (4 52 , 464 ) receiving from said master station an assigned transmit reference burst time slot which is narrower than said initial acquisition time slot, in said control portion of one of said plurality of TDMA frames in said superframe,(Fig. 34) said transmission means (455, 468) terminating the transmission of said initial acquisition burst and commencing transmission of said transmit reference burst in said control portion in said one of said TDMA frames, (Fig. 34, frame 3) phase adjustment means (410) connected to said transmission means to control transmitting said transmit reference burst from said secondary station in said assigned time slot of said control field of said one of said TDMA frames on an interleaved basis with the transmission of transmit reference D ursts by other earth stations in said network in said assigned time slot of said control field of other ones of said TDMA frames in said superframe to refine the local transmit timing in said secondary station, whereby the bandwidth of said TDMA frame is conserved.
Claim 6
Dependent Claim
208 words
An apparatus for acquiring transmit synchronization at a secondary station with the periodic frame reference bursts from a reference station in a TDMA network, according to claim 4, characterized by a first transmission means (455, 451) at said secondary station (2), for bursting an initial acquisition burst during a first phase from said secondary station during a relatively wide interval in the traffic portion of a TDMA frame and measuring (458) a propagation delay factor, a timing adjustment means (443, 426) connected to said first transmission means, for adding said propagation delay factor to the receive frame timing synchronized with the reception of said frame reference bursts at said secondary station to obtain a finely adjusted transmit frame timing, (91) a second transmission means (466.) connected to said timing adjustment means, for bursting a transmit reference burst after said first phase from said secondary station (2) during a relatively narrow interval in the control portion of periodic, non-consecutive ones of said TDMA frames and measuring (410) a propagation delay correction factor, a phase adjustment means (408) connected to said second transmission means, for adjusting the phase of said transmit frame timing with said correction factor to maintain synchronization of said secondary station (2) with said reference station (3).
Claim 7
Dependent Claim
330 words
Apparatus for acquiring transmit acquisition of synchronization at a secondary station in a TDMA satellite communication network according to claim 5, characterized by a receive clock synchronizing means (406, 422) for synchronizing a receive clock at said secondary station by starting a receive frame when said frame reference burst is received, a delay estimating means (32, 402') connected to said receive clock synchronzing means, for adding an estimated satellite round trip propagation delay factor to the start of said receive frame during a first phase of transmit acquisition to start a transmit frame, to coarsely synchronize a transmit clock (91), a first transmission means (456, 451) connected to said elay estimating means, for bursting an initial acquisition burst from said secondary station (2) during an assigned relatively wide interval in said traffic portion of a plurality of consecutive ones of said TDMA frames; a delay measuring means (458) connected to said first transmission means, for measuring a round trip propagation delay factor (2Ti) for said initial acquisition bursts, a timing adjustment means (443, 426) connected to said delay measuring means, for adding said round trip propagation delay factor to the start of said receive frame to start said transmit frame, to finely adjust said transmit clock, a second transmission means (466) connected to said timing adjustment means, for bursting a transmit reference burst from said secondary station (2) during an assigned relatively narrow interval in said control portion of one of said frames in said periodic superframes, during a second phase of transmit acquisition, a phase measuring means (410) connected to said second transmission means, for measuring a round trip propagation delay factor for said transmit reference bursts with said transmit clock and deriving a correction factor therefrom, and a phase adjustment means (408) connected to said phase measuring means, for adjusting the phase of said transmit clock with said correction factor to maintain a precise synchronization of said transmit clock with the transmit clock at said reference station (3).
References Cited (Backward Citations)
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