Abstract: The disclosed communication unit functions to detect a signal by detecting the zero crossing of a current sample (and prior samples) and determining a sample value for each sample, and to determine an estimated bit value of a previous sample based on upper and lower node metrics. In the preferred embodiment a two-state decoder is used. Using prior sample values, the possible upper and lower node path distance metrics are first determined, then path difference metrics are determined for each node based on the path distance metrics. The difference metrics are then compared against a threshold, preferably zero, to determine the estimated bit value (or which surviving path to use) in decoding a prior sample.

Abstract: The disclosed communication unit includes synchronization circuitry having a sync sequence match detector and a decode detector. Upon matching a received sync sequence or word with a known sync sequence, the sync word (or, e.g., the block containing the received sync sequence) is decoded to determine whether the block is correctable (or more generally, whether the signal quality is above a threshold). When a match is found and the sequence/block is correctable, an appropriate sync indication is outputted. Additional information, such as color code matching of consecutive sync words, may also be used before determining synchronization has been achieved.