The present invention relates to a technique for increasing the rain margin at ground stations of a satellite communication system. In the present technique, spare TDMA time slots in each frame sequence are shared among all ground stations as required by stations experiencing a fade condition which exceed a predetermined power margin. Additional up-link power margin at a faded transmitter can be achieved by either increasing power transmission of a normal burst or by the use of spare time slots plus encoding and preamble field extension techniques for burst extension. Additional down-link power margin to a faded receiver is accomplished by either increased transmitter power transmission or by the use of burst extension and coding and field extension techniques. Apparatus for implementing framing, carrier and clock recovery and start of message detection using extended fields and coding techniques for other data at a transmitter and receiver and disclosed to overcome fade conditions.