Frame alignment in a digital carrier system-a tutorial

Four key timing parameters that are used as performance measures are defined; reframe time, false in-frame time, out-of-frame detection time, and misframe time. Several strategies that improve frame alignment performance are considered for the case of a burst frame alignment word (FAW). With a little modification, the same strategies could also be applied to the case of a distributed FAW. The probability generating function is introduced, and its derivation from a state transition diagram is presented. The probability generating function is used in the timing parameters estimation. As an example, the frame alignment of a SONET (synchronized optical network) STS-3 signal is discussed.<>