Comparative performance between drop-out detection and Viterbi reliability metric erasure flagging

It is known that reliable symbol erasure flags can significantly enhance the decoded performance of an interleaved Reed-Solomon code on a digital magnetic recording channel. The author compares the improvement afforded by a drop-out detector erasure flagger to the improvement provided by an erasure flagger based on a class IV partial response Viterbi detector. It is shown that, in addition to being less complex, the drop-out detector is the superior erasure flagger when decoded performance is burst-error-limited and burst errors are a result of signal level drops. Although the proposed Viterbi erasure flagger is derived heuristically, it performs as well as the previously considered optimum method and, hence, the drop-out detector can be claimed to be superior to all such Viterbi flaggers under the assumptions of the present work