Performance and sensitivity analysis of maximum-likelihood sequence detection on magnetic recording channels

The results of a study comparing the performance of maximum-likelihood sequence detection (MLSD) for various magnetic-recording schemes are presented. The schemes considered are: run-length limited (RLL) coding, nonreturn to zero (NRZ) recording, and partial-response class IV (PR-IV) and extended partial-response class IV (EPR-IV) signaling. The MLSD of RLL-coded and NRZ recording systems provides bounds on the performance that can be achieved, respectively, by peak detection systems and by partial-response schemes more complex than PR-IV and EPR-IV. Performance of PR-IV and EPR-IV signaling with MLSD is compared with the obtained bounds: the gain in recording density over peak detection provided by these partial-response schemes is established, and the merit of using more complex partial-response systems is determined. The sensitivity of the PR-IV and EPR-IV systems to various parameters is examined