Initial acquisition for TDMA systems with satellite switching

Initial acquisition in a TDMA system using satellite switching is examined. In order to have minimum distortion of the initial acquisition system, a time slot of approximately 3 microsec is reversed in the TDMA frame solely for initial acquisition (IA). General IA objectives and design parameters are given, and performance limiting effects are identified. Two representative IA systems requiring no additional equipment in the satellite are described. Analysis of these systems indicates that the required acquisition time is on the order of a few seconds only, which is necessary if many stations participate in the system and if the stations are organized in a superframe for IA. Coherent demodulation has to be used, and the phase-locked loops for carrier and clock recovery can lock on harmonics of the TDMA frame rate. A method is proposed whereby the IA performance can be improved simply by an additional terminal-pair on the satellite switching matrix and an IF amplifier.