ELIMINATING UNDETECTED ERRORS IN LDPC–CPM DECODERS

In error control coding, an undetected error occurs when the received code word passes the parity check even though errors are present. Such errors are a critical concern in many applications because a passed parity check at the receiver is taken to mean that the received code word is error free. In this paper, we outline the key operating principles and differences between the two constituent decoders in the system. Our high-level discussion reveals insights on two strategies that can be used in an LDPC–CPM decoder to eliminate undetected errors. The first is a brute-force approach of performing an additional decoding iteration to confirm (or rebut) a passed parity check. The second is a simple and elegant check-node-splitting approach that can be incorporated into the LDPC code itself. We provide numerical results and operating scenarios where these techniques are recommended for use.