Cycle Slip Detection and Correction Through Classification of Modulation Code Failures

In high-density recording systems, synchronization might be lost due to increased noise and/or inaccurate sampling/filtering. In such, long bursts of errors occur due to bits either erased from or inserted into the bit stream. At low signal-to-noise ratios, such bit slips (also known as cycle slips) lead to excessive post-error correction code (post-ECC) failures. In order to reduce the rate of the post-ECC failures, cycle slips should be detected and corrected. In the past, the majority of the research was concentrated on iterative joint timing recovery and error decoding methodologies. In this study, we propose to detect and correct cycle slips using a decoding failure analysis of maximum transition run (MTR) codeword sequences in conjunction with a general-purpose classification algorithm. First, noncyclic properties of constrained coding are identified by realizing that MTR codewords render invalid more often if bit shifts happen. Later, we present a method to use such invalid codewords to help detect and correct cycle slips. Finally, some numerical results are presented to show the effectiveness of the proposed detection/correction scheme using MTR codes and the support vector machines. It is demonstrated that such a combination has the potential for BER and post-ECC failure rate performance improvements by eliminating cycle slips for the generalized partial response channels.