International Business Machines Corporation

John Shabe

Joseph A Alvarez, Iii

Robert W Krug

John F Brennen

Bruce D Gobioff

A method and apparatus are disclosed for conducting broadcast, multipoint, and conference communications in a TDMA network at various data rates while simultaneously conducting point-to-point communications at other data rates, either between local ports or between geographically remote ports during time intervals within a TDMA burst, which are not necessarily predefined. The disclosed apparatus appends a direct destination address to each point-to-point port communication for transmission over a communications link, to directly address the intended destination port. The disclosed invention appends an indirect destination address to each broadcast communication transmitted over the communications link. A broadcast memory is provided at the receiving end of the communications link, for storing correlated direct addresses which are accessed by the indirect destination addresses, to directly address a plurality of intended destination ports. In this manner, both point-to-point and broadcast-type communications can be carried out for a variety of data rates, during time intervals which are not predetermined within the TDMA burst, and with a high degree of connectivity.

Time domain multiple access broadcasting, multipoint, and conferencing

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 station's normal traffic transmission operations can take place, with the transmit reference burst being periodically transmitted in the control portion of non-consecutive TDMA frames in order to achieve a long-term maintenance of synchronization between the secondary station and the reference station. The dual use of the traffic portion assigned to the secondary station for both the coarse adjustment of the transmit clocks of the station during the first phase and the transmission of normal traffic from this or other stations during the second phase of transmit acquisition for the station enables the use of a full power initial acquisition burst, while reducing the overall bandwidth requirements for the acquisition operation by completing the function with the transmit reference burst which requires substantially less bandwidth due to its narrower assigned interval and less frequent transmission.

Growing community of inventors

Darnestown, MD, United States of America

John Shabe