Robert L. Cloke

One-pairs codes for partial response magnetic recording

We consider a new constraint on stored data in partial response digital magnetic recording. The one-pairs constraint is an upper bound on the maximum number of symbols between pairs of ones in a coded sequence and can be considered as an alternative to the widely used (0, G/I) constraint. The constraint limits quasi-catastrophic error propagation and guarantees the occurrence of superior timing corrections in partial response class IV (PR4) and extended PR4 (EPR4) magnetic recording systems. In this paper we give low complexity rate 8/9, 16/17, and 24/25 block codes, derive the capacity of this constraint, and compute the power spectral density for maxentropic codes. The codes achieve greater than 95% of channel capacity and the 24/25 code has smaller than expected error propagation.

Codes for improved timing recovery in PR4 and EPR4 magnetic recording

We consider an alternative to the widely-used (0,G/I) constraint in partial response digital magnetic recording systems. The new one-pairs constraint is an upper bound on the maximum number of symbols between pairs of ones in a coded sequence. Codes for the one-pairs constraint can be used to limit quasi-catastrophic error propagation and improve timing recovery in Class-IV partial response (PR4) and Extended PR4 (EPR4) magnetic recording systems. Rate 4:5, 8:9, 16:17, and 24:25 block and finite state codes are discussed and compared with well-known rate 8:9 and 16:17 block codes. The new codes have improved one pairs statistics, low complexity, and for the 24:25 code, reduced error propagation.

Capacity, power spectral density, and codes for the one-pairs constraint

We consider a new constraint for improved timing recovery in partial response digital magnetic recording. The one-pairs constraint is an upper bound on the maximum number of symbols between pairs of ones in a coded sequence and can be considered as an alternative to the widely-used (0,G/I) constraint. We derive the capacity of this constraint, compute the power spectral density for maxentropic one-pairs constrained codes and give rate 16/17 and 24/25 block codes for this constraint.