Lockup detection and avoidance scheme for satellite communication network

Abstract

A mechanism for avoiding satellite transponder TWT saturation in an ALPC communication network detects the onset of a lockup condition through an avalanche detector. In response to avalanche detection, those links which have been identified as participating in a downlink fade have their ALPC attenuator settings placed at a minimum level, so that the operating point of the transponder TWT may be reduced below the avalanche threshold. Thereafter, as the fade recedes, those units whose ALPC attenuators have minimum power settings may be restored to normal operation. Because the orderwire which couples link quality data from a received terminal monitor unit to transmitter attenuator control units through the avalanche detection and recovery scheme may itself be impacted by a downlink fade, the foregoing scheme is augmented by a lockup detection and avoidance mechanism through which recovery from an actual lockup may take place. Transmit and receive terminal data is monitored and prescribed signal quality and ALPC attenuator setting data are correlated with one another. When a lockup condition has been detected, all of the links are effectively turned off to permit the TWT to recover from its saturation condition. Thereafter, those links which have not been identified as being in the path of a downlink fade are restored to normal service. When the fade recedes, those links which have had their power settings minimized for the presence of the fade are restored.