Harris Corporation

Gerald S Duggan

William C Adams, Jr

Charles R Patisaul

The possibility of overload (saturation-lockup) condition of an ALPC satellite communication network is avoided by a scheme that grants network entry (allocates TWT power) to each link one at a time. As each link is granted entry into the network, the corresponding TWT probability density function is computed and then integrated to obtain a TWT cumulative distribution function. The required rain margin M.sub.r for a specified availability is determined from the cumulative margin. The computed margin M.sub.r is set equal to the initial satellite TWT operating point change (multiplicative factor) MR.sub.1 due to rain fade, MF.sub.1 =M.sub.r to ensure that network stability considerations and rain fades equally constrain network performance. This result is then used to compute the value of the corresponding multiplicative factor MF.sub.2. These two factors, when expressed in decibels, may be added to the nominal (no rain) TWT operating point (also expressed in decibel notation) to predict the maximum TWT operating point value in response to rain stress at the specified system availability. This predicted maximum TWT operating point is then compared to the analytically determined value of the TWT stability point. If the TWT stability point is not exceeded for the current number of links then an additional link may be added, otherwise, the last link requesting entry into the network is denied access. After the maximum permissible number of terminals has been accommodated, the final actual values of TWT stability point, stability margin, and link availability are computed and the allocation process is terminated.

Optimal satellite TWT power allocation process for achieving requested

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.

Growing community of inventors

Indialantic, FL, United States of America

Gerald S Duggan