Programmable soft-output Viterbi algorithm system and method
View Patent ↗In a particular embodiment, a channel detector is disclosed that includes a programmable look-up table (LUT) to relate user bits to channel bits. The programmable LUT is adapted to be implemented on a state trellis of arbitrary radix. The channel detector further includes a sectional precoder coupled to a channel and having access to the programmable LUT. The sectional precoder is adapted to map channel bits to user bits and vice versa using a programmable LUT.
1. An assembly comprising:
a postcoder adapted to assign user bit labels from one or more look-up tables (LUTs) to each branch of a trellis;
the one or more look-up tables (LUTs) providing a relation between channel bits and user bits; and
a detector component configured to receive an input signal including one or more input channel bits and provide an output including one or more output user bits wherein the detector component uses the postcoder to decode the input signal using the user bits determined from the one or more LUTs in the branches of the trellis.
2. The assembly of claim 1 , wherein the one or more LUTs defines a non-polynomial postcoder.
3. The assembly of claim 1 , wherein the detector component comprises a soft-output Viterbi algorithm (SOVA) detector adapted to calculate a path metric difference between possible states of the user bits using the postcoder and the one or more LUTS, based upon reliabilities of the user bits and adapted to update reliabilities of the user bits based on the path metric difference.
4. The assembly of claim 3 comprising an inner decoder configured to receive the user bits and the reliabilities of the user bits and output decoded user data using a message passing algorithm to interface with the SOVA detector.
5. The assembly of claim 1 wherein the postcoder is configured to select one of a plurality of LUTs stored in memory based upon operating conditions and the postcoder includes logic to select the one of the plurality of LUTs to decode the input signal.
6. The assembly of claim 1 , wherein the postcoder comprises logic adapted to access the one or more LUTs.
7. The assembly of claim 1 wherein the detector component forms a component of a magnetic recording channel wherein the input signal is received from a magnetic recording head.
8. The assembly of claim 1 , wherein the detector component includes a soft-output Viterbi algorithm (SOVA) detector adapted to operate using the user bit labels.
9. The assembly of claim 8 , wherein the SOVA detector uses the postcoder to compute reliabilities of the user bits.
10. The assembly of claim 1 , wherein the one or more LUTs are programmed to operating conditions associated with a read channel of the assembly.
11. A method comprising:
mapping user bits to channel bits via a precoder during a write operation using one or more look-up tables (LUTs);
receiving from a channel readback samples including one or more of the channel bits;
decoding the readback samples using a soft-output channel detector which interfaces with a postcoder;
assigning user bit labels to branches of a trellis using a postcoder map;
determining user bit decisions and their reliabilities for the readback samples based upon a likelihood path metric using the trellis and the postcoder map specified by the one or more LUTs; and
outputting the determined user bit decisions.
12. The method of claim 11 , wherein the postcoder comprises logic and a memory accessible to the logic, wherein the one or more LUTs are programmed in the memory.
13. The method of claim 11 , comprising providing the readback samples to a soft-output Viterbi algorithm (SOVA) detector and using the postcoder map to determine the user bit decisions.
14. A system comprising:
an input to receive a signal;
a channel detector coupled to the input, the channel detector comprising:
a memory including one or more look-up tables LUTs that provide a relation between channel bits and user bits programmed in the memory;
a postcoder having access to the memory and adapted to map the channel bits to the user bits and adapted to assign user bit labels from the one or more LUTs to each branch of a trellis;
a decoder adapted to iteratively decode one or more channel bits of the input signal into user bit decisions using the user bit labels from the postcoder in branches of the trellis; and
an output terminal to provide an output including the user bit decisions.
15. The system of claim 14 wherein the postcoder comprises a processor and instructions in the memory executable by the processor to map the channel bits to the user bits.
16. The system of claim 14 , wherein the postcoder comprises logic, and wherein the relation between the channel bits and the user bits is provided by the one or more look-up tables (LUTs) accessible to the logic to map the channel bits to the user bits.
17. The system of claim 16 , wherein the decoder comprises a soft-output Viterbi algorithm (SOVA) decoder.
18. The system of claim 16 , wherein the one or more LUTs include a plurality of LUTs that provide the relation between the channel bits and the user bits dependent upon a data track position on a rotating storage media.