as Frame Alignment Words (FAWs). Theoretically, the frame alignment words can be placed anywhere during the frame; however, in practice the FAWs are placed in a way that reduces the average time taken for the frame alignment process. Particularly, the framing strategy is called bunched (grouped) if all frame align- ment timeslots are concentrated at the beginning of each frame. By contrast, distributed framing refers to the case where the frame alignment words are spread during the frame. There is also a danger of simulating the framing pattern by information-carrying bits. One way to reduce this risk is to choose a framing pattern with a low correlation SO that it is impossible to imitate by shifting and infringement on random neighboring bits. Alterna- tively, it is possible to reject all the channels of the frame when the framing is lost at the receiver end. However, this might not be a good practical solution because it requires a return path to the sender SO that the receiver can send a Negative Acknowledgment (NACK) message. Especially if the size of the FAW is small compared to the frame size, the possibil- ity of such patter imitation is high, and requesting a new alignment word for every single imitation case might not be an efficient solution. Among all of the different alignment techniques, serial frame alignment is the most com- monly used. In this technique, when the alignment is lost, the system tries to find a FAW in the next coming frames (say two or three frames); if a FAW is found, then the system can return to the full-alignment state. Otherwise, the system enters the search mode. In the search mode, the system scans the incoming frames until it finds a valid FAW. However, to improve stability, the system does not enter full-alignment mode when it finds the first FAW during the scanning state; instead, it waits until a number of successive FAWs (say two or three) are received correctly. This mode is referred to as the waiting state. Losing any FAW during the waiting state returns the system to 