FRAME ALIGNMENT

摘要

The invention is directed to frame alignment of a digital link which interconnects two entities. Frames in which overhead is interleaved with payload are considered. In accordance with a general inventive concept, the fame alignment is executed in two phases such that the actual frame alignment, in which a predetermined frame alignment word (FAW) is found, is preceded by a procedure called "column alignment". The idea with column alignment is to find the positions for the overhead columns or overhead bits of a pending frame of payload and interleaved overhead. During column alignment, the transmitting entity will send an easily detectable column alignement word (CAW) and the receiving entity will quickly recognize the overhead bit positions in the interleaved frame. When the positions for the overhead bits have been detected, the transmitting entity will start to send Normal Frames and the receiving entity will gain final frame alignment by finding the FAW in the overhead bit positions.