At high linear recording densities, coping with electronics and media noise becomes increasingly difficult. We are developing new data detection schemes that shape the magnetic recording channel impulse response to a polynomial target with a few non-integer coefficients. As this polynomial is obtained via prediction theory, the sequence detection approach is termed noise predictive maximum likelihood (NPML) detection.
High data rates require an exceedingly rapid switching of the magnetization direction of the storage medium by reversing the current circulating in the write head. One approach to alleviate the problem is to restrict the length of alternating sequences of 1's and 0's by using mapping techniques to translate data into coded sequences of bits where 1's change to 0's and back again less frequently. The fundamental challenge of this constrained-coding process is to design high-rate codes such that the performance degradation due to rate loss is minimized.