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PRML detection using the patterns of run-length limited codes  

Lee Joo hyun (동국대학교 전자공학과 통신 및 정보저장 연구실)
Lee Jae jin (동국대학교 전자공학과 통신 및 정보저장 연구실)
Publication Information
The Journal of Korean Institute of Communications and Information Sciences / v.30, no.3C, 2005 , pp. 77-82 More about this Journal
Abstract
Partial response maximum likelihood (PRML) detection using the Viterbi algorithm involves the calculation of likelihood metrics that determine the most likely sequence of decoded data. In general, it is assumed that branches at each node in the trellis diagram have same probabilities. If modulation code with minimum and maximum run-length constraints is used, the occurrence ratio (Ro) of each particular pattern is different, and therefore the assumption is not true. We present a calculation scheme of the likelihood metrics for the PRML detection using the occurrence ratio. In simulation, we have tested the two (1,7) run-length-limited codes and calculated the occurrence ratios as the orders of PR targets are changed. We can identify that the PRML detections using the occurrence ratio provide more than about 0.5dB gain compared to conventional PRML detections at 10/sup -5/ BER in high-density magnetic recording and optical recording channels.
Keywords
PRML; Viterbi algorithm; run-length limited codes; recording systems; branch metric;
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