Compensation factor reduction in an unrolled decision feedback equalizer
AssigneePMC-Sierra US, Inc.
InventorMathieu GAGNON
Life of this patent
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Abstract
An unrolled decision feedback equalizer (DFE) as disclosed herein has a reduced number of compensation factors while keeping a suitable performance level for a given application. The KN possible DFE correction levels are reduced or compressed into fewer levels (R), merging together the levels that are the closest together where K represents the number of possible symbols in each baud, or the number of bits encoded into each baud, and N represents the DFE depth in number of bauds. A mapping function is then provided to convert the KN combinations of previous history bits into R sampler selections.
Claims22
A method of operating an unrolled Decision Feedback Equalizer (DFE) having a plurality of input samplers, the method comprising:
- a) creating a reduced set of compensation factors (R) based on an original set of compensation factors (KN) for the unrolled DFE, where R<KN, and where K represents number of bits encoded into each baud, and N represents the DFE depth in number of bauds;
- b) applying the reduced set of compensation factors as input sampler thresholds for the plurality of input samplers to generate a reduced set of unrolled DFE decisions, the number of input samplers being no more than R;
- and
- c) selecting an appropriate DFE decision from the reduced set of unrolled DFE decisions based upon previous bit values and in accordance with a mapping table, wherein step a) comprises:
- a0) merging the original set of compensation factors until their number reaches a pre-defined target R and keeping track of which levels in the original set of compensation factors were merged together;
- and
- a1) computing a mapping function to map between the previous bit values and the new input sampler thresholds;
- creating the mapping table based on the mapping function;
- and
- assigning values of a mapping table by assigning an increasing index value for each unique value of the unique index list.
A non-transitory machine readable medium having stored thereon statements and instructions for execution by a processor to perform a method of operating an unrolled Decision Feedback Equalizer (DFE) having a plurality of input samplers, the method comprising:
- a) creating a reduced set of compensation factors (R) based on an original set of compensation factors (KN) for the unrolled DFE, where R<KN, and where K represents number of bits encoded into each baud, and N represents the DFE depth in number of bauds;
- b) applying the reduced set of compensation factors as input sampler thresholds for the plurality of input samplers to generate a reduced set of unrolled DFE decisions, the number of input samplers being no more than R;
- and
- c) selecting an appropriate DFE decision from the reduced set of unrolled DFE decisions based upon previous bit values and in accordance with a mapping table, wherein step a) comprises:
- a0) merging the original set of compensation factors until their number reaches a pre-defined target R and keeping track of which levels in the original set of compensation factors were merged together;
- and
- a1) computing a mapping function to map between the previous bit values and the new input sampler thresholds;
- creating the mapping table based on the mapping function;
- and assigning values of a mapping table by assigning an increasing index value for each unique value of the unique index list.
A Decision Feedback Equalizer (DFE), comprising:
- a plurality (R) of input samplers;
- a compensation factors reduction module configured to create a reduced set of compensation factors (R) based on an original set of compensation factors (KN) for the unrolled DFE, where R<KN and where K represents number of bits encoded into each baud, and N represents the DFE depth in number of bauds;
- a mapping and ordering function configured to apply the reduced set of compensation factors as input sampler thresholds for the plurality of input samplers to generate a reduced set of unrolled DFE decisions, the number of input samplers being no more than R;
- and
- a mapping function configured to select an appropriate DFE decision from the reduced set of unrolled DFE decisions based upon previous bit values and in accordance with a mapping table, wherein the compensation factors reduction module is further configured:
- to merge the original set of compensation factors until their number reaches a pre-defined target R and keep track of which levels in the original set of compensation factors were merged together;
- and
- to compute a mapping function to map between the previous bit values and the new input sampler thresholds;
- to create the mapping table based on the mapping function;
- and to assign values of a mapping table by assigning an increasing index value for each unique value of the unique index list.
Dependencies are inferred from the claim text.