SS/TDMA Steady-State Synchronization: Analysis and Operation During Deep Signal Fades

An analysis of SS/TDMA steady-state synchronization is presented, in which the need for reliable sync maintenance during periods of deep signal fades, beyond the point of communications outage, is considered. The time required for sync-maintenance measurements, together with impact on guard time requirements, will lead to degradation of SS/TDMA transmission efficiency. The need to ensure a sufficiently low rate of occurence of errors in the syncmaintenance measurements also impacts transmission efficiency. A generalized formulation relating the degree of immunity to signal fading, degradation in transmission efficiency, and rate of occurrence of measurement errors is developed. Numerical results are obtained for a typical satellite communications system of current interest. It is shown that sync-maintenance systems can be designed to operate reliably during severe signal fades, orders of magnitude beyond the point of communication outage, at the expense of minimal degradation of transmission efficiency. For this level of performance it is shown that, with proper choice of parameters, virtually error-free syncmaintenance operation can be achieved. Numerical values of typical design parameters are presented.