Adaptive soft-output detector for magnetic tape read channels

A method, comprising:

• minimizing variance of noise affecting a signal using an adaptive noise whitening filter, wherein the signal comprises data read from a magnetic tape medium using a tape channel;
• receiving the signal from the noise whitening filter at a soft detector;
• and
• updating one or more noise whitening coefficients used in the noise whitening filter to minimize the variance of noise affecting the signal using a noise whitening filter coefficient updater,
• wherein the noise whitening filter is configured to process the signal to minimize the variance of noise affecting the signal according to the following transfer polynomial:
• W(D)=1−(p1D+ . . . +pλ′Dλ′), where p1 . . . pλ′ are noise whitening coefficients,
• wherein the tape channel is characterized by a transfer polynomial F(D)=1+f1D+ . . . +fLDL where D is delay corresponding to bit duration, with 2L being a number of states of the tape channel,
• wherein the soft detector has a total of 2L+λ states, the noise whitening filter comprises 2λ′ states, and λ′ is greater than λ,
• wherein L represents a memory length of the tape channel, and
• wherein λ represents a memory length of the noise whitening filter.

A computer program product, comprising a computer readable storage medium having computer readable program code embodied therewith, the computer readable program code being readable/executable by a processor to cause the processor to:

• read, by the processor, data from a magnetic tape medium using a tape channel to produce a signal;
• pass, by the processor, the signal through an adaptive noise whitening filter to minimize variance of the noise affecting the signal output from the filter;
• pass, by the processor, the signal through a soft Dual-Max (DMAX) detector to calculate first soft information about each bit of the signal;
• send, by the processor, the first soft information to a soft decoder;
• pass, by the processor, the signal through the soft decoder to calculate second soft information about each bit of the signal;
• and
• send, by the processor, the second soft information to the soft DMAX detector,
• wherein one or more noise whitening coefficients used in the noise whitening filter are updated using a noise whitening filter coefficient updater,
• wherein the noise whitening filter is configured to process the signal according to the following transfer polynomial:
• W(D)=1−(p1D+ . . . +pλDλ), where p1 . . . pλ are the noise whitening coefficients, and where the tape channel is characterized by a transfer polynomial F(D)=1+f1D+ . . . +fLDL where D is delay corresponding to bit duration, L represents a memory length of the tape channel, and λ represents a memory length of the noise whitening filter.