(Received November 25, 2003; accepted January 7, 2004; published July 29, 2004)
In this paper, we propose a modified calculation method of the branch metric in partial response maximum likelihood (PRML) detection for high-density optical storage systems. The scheme is related to the relative probability of the run-length limited code. Hence, we also present the relative probabilities of the 17PP coded sequences for 2nd-, 3rd- and 4th-orders of PR targets. The modified PRML detection using the relative probability of the 17PP coded sequence has better bit error rate (BER) performance than conventional PRML detection.
KEYWORDS:17PP code, modified PRML, relative probability, branch metric calculation, optical recording system