ATM framing acquisition

There are two kinds of framing strategies in asynchronous transfer mode (ATM) networks: special word framing (SWF) and cell delineation framing (CDF). A simple design for the realization of cell delineation framing is proposed. In contrast to SWF which may include many cells to a frame, the CDF technique has only one cell per frame. Both framing methods detect the frame boundary using correlation. The SWF method directly compares the incoming data with a known special word. In contrast, the proposed CDF technique uses a sliding window cycle redundancy check (CRC) for the previous 40 b to produce an 8-b syndrome byte. This syndrome byte will be zero in all bit positions when a 5-byte cell header is positional within the 40-b window. The authors describe the concept and framing acquisitions model for CDF, and give a practical framing receiver design. The mathematical analysis and the synchronization performance are considered.