Pipelined decision-feedback unit in a reduced-state viterbi detector with local feedback
View Patent ↗A pipelined decision feedback unit (DFU) is disclosed for use in reduced-state Viterbi detectors with local feedback. The disclosed pipelined decision feedback unit improves the maximum data rate that may be achieved by the reduced state Viterbi detector by the pipelined computation of partial intersymbol interference-based estimates. A pipelined decision feedback unit is thus disclosed that computes a plurality of partial intersymbol interference based estimates, wherein at least one partial intersymbol interference-based estimate is based on a selected partial intersymbol interference-based estimate; and selects the selected partial intersymbol interference-based estimate from among partial intersymbol interference-based estimates for path extensions into a state.
1. A method for computing intersymbol interference-based estimates for a channel using reduced-state detection techniques, said channel having a channel impulse response, said method comprising the steps of:
selecting a partial intersymbol interference-based estimate from among previously computed partial intersymbol interference-based estimates for path extensions into a state; and
computing a plurality of new partial intersymbol interference based estimates, wherein at least one new partial intersymbol interference-based estimate is based on said selected partial intersymbol interference-based estimate, wherein said new partial intersymbol interference-based estimates are one or more of a partial intersymbol interference estimate and a partial intersymbol interference-free signal estimate and wherein one or more of said previously computed partial intersymbol interference-based estimates and said selected partial intersymbol interference-based estimates are stored in one or more of a pipeline register and a memory.
2. The method of claim 1 , where said selection is based on a decision from a corresponding state.
3. The method of claim 1 , wherein a partial intersymbol interference-based estimate that accounts for the intersymbol interference due to a plurality of channel coefficients of said channel impulse response is an intersymbol interference-based estimate.
4. The method of claim 3 , further comprising the step of computing a branch metric based on said intersymbol interference-based estimate.
5. The method of claim 4 , further comprising the step of selecting one of said computed branch metrics based on a decision from a corresponding state.
6. The method of claim 3 , wherein said intersymbol interference-based estimates are used to compute one dimensional error metrics.
7. The method of claim 6 , wherein a branch metric for a multi-dimensional symbol is computed based upon said one dimensional error metrics.
8. The method of claim 6 , wherein said one dimensional error metric is computed based on a sum of one or more partial intersymbol interference-based estimates and the intersymbol interference associated with at least one channel coefficient.
9. The method of claim 6 , wherein a one-dimensional error metric is selected among said computed one-dimensional error metrics based on at least one add-compare-select decision or at least one survivor symbol.
10. The method of claim 1 , wherein said computing step further comprises the step of adding said selected partial intersymbol interference-based estimate to intersymbol interference associated with at least one other channel coefficient.
11. The method of claim 10 , wherein said intersymbol interference associated with at least one other channel coefficient is defined by a corresponding state.
12. The method of claim 10 , wherein said intersymbol interference-based estimate associated with at least one other channel coefficient is given by a channel coefficient and a corresponding survivor symbol for an associated state.
13. A pipelined decision feedback unit for computing intersymbol interference-based estimates for a channel having a channel impulse response, comprising:
a multiplexer for selecting a partial intersymbol interference-based estimate from among previously computed partial intersymbol interference-based estimates for path extensions into a state;
processing elements for computing a plurality of new partial intersymbol interference based estimates, wherein at least one new partial intersymbol interference-based estimate is based on said selected partial intersymbol interference-based estimate, wherein said new partial intersymbol interference-based estimates are one or more of a partial intersymbol interference estimate and a partial intersymbol interference-free signal estimate and wherein one or more of said previously computed partial intersymbol interference-based estimates and said selected partial intersymbol interference-based estimates are stored in one or more of a pipeline register and a memory.
14. The pipelined decision feedback unit of claim 13 , wherein a partial intersymbol interference-based estimate that accounts for the intersymbol interference due to a plurality of channel coefficients of said channel impulse response is an intersymbol interference-based estimate.
15. The pipelined decision feedback unit of claim 14 , wherein said intersymbol interference-based estimates are used to compute one dimensional error metrics.
16. The pipelined decision feedback unit of claim 15 , wherein a branch metric for a multi-dimensional symbol is computed based upon said one dimensional error metrics.
17. The pipelined decision feedback unit of claim 15 , wherein said one dimensional error metric is computed based on a sum of one or more partial intersymbol interference-based estimates and the intersymbol interference associated with at least one channel coefficient.
18. The pipelined decision feedback unit of claim 15 , wherein one of said one dimensional error metrics is selected based on either at least one add-compare-select decision or at least one survivor symbol.
19. The pipelined decision feedback unit of claim 13 , wherein said processing elements include an adder or subtractor to add or subtract said selected partial intersymbol interference-based estimate to intersymbol interference associated with at least one other channel coefficient.
20. A pipelined decision feedback unit for computing intersymbol interference-based estimates for a channel having a channel impulse response, comprising:
at least one functional unit for computing one or more new partial intersymbol interference-based estimates, wherein said new partial intersymbol interference-based estimates are either partial intersymbol interference estimates or partial intersymbol interference free signal estimates, wherein said functional unit comprises:
at least one multiplexer for selecting one or more partial intersymbol interference-based estimates from among previously computed partial intersymbol interference-based estimates for path extensions into a state;
at least one pipeline register for storing a partial intersymbol interference-based estimate; and
at least one adder for adding a value that accounts for intersymbol interference associated with at least one channel coefficient.
21. The pipelined decision feedback unit of claim 20 , wherein said at least one multiplexer is driven by an add-compare select decision.
22. The pipelined decision feedback unit of claim 20 , wherein said partial intersymbol interference-based estimates are computed using survivor symbols.
23. The pipelined decision feedback unit of claim 20 , wherein a partial intersymbol interference-based estimate that accounts for intersymbol interference associated with any higher order taps is based upon an output of at least one other functional unit.
24. The pipelined decision feedback unit of claim 20 , wherein said path extensions are determined based on a trellis.
25. The pipelined decision feedback unit of claim 20 , wherein a plurality of said functional units are connected together using a register exchange architecture.
26. The pipelined decision feedback unit of claim 20 , wherein said value that accounts for intersymbol interference associated with at least one channel coefficient is defined by a corresponding state.
27. The pipelined decision feedback unit of claim 20 , wherein said value that accounts for intersymbol interference associated with at least one channel coefficient is computed based on at least one corresponding survivor symbol for an associated state.
28. The pipelined decision feedback unit of claim 20 , wherein said at least one multiplexer uses only add-compare select decisions to select said partial intersymbol interference-based estimates.
29. The pipelined decision feedback unit of claim 20 , which is employed in a reduced-state detector, where a survivor memory unit is implemented according to a trace back architecture.
30. A pipelined decision feedback unit for computing intersymbol interference-based estimates for a channel having a channel impulse response, comprising:
a plurality of multiplexers configured in a register exchange configuration for selecting partial intersymbol interference-based estimates from among previously computed partial intersymbol interference-based estimates for path extensions into a state;
a plurality of arithmetic circuits for computing a plurality of new partial intersymbol interference-based estimates, wherein said new partial intersymbol interference-based estimates are based on said selected partial intersymbol interference-based estimate and are either partial intersymbol interference estimates or partial intersymbol interference free signal estimates; and
a plurality of registers for storing partial intersymbol interference-based estimates.
31. A filter circuit, comprising:
at least one multiplexer for selecting a value from among a plurality of input values;
at least one pipeline register for storing said selected value; and
an adder for adding a value that accounts for a current filter tap, wherein a plurality of said filter circuits are configured in a plurality of rows and columns, where the inputs into the multiplexer of at least one filter circuit are connected to at least two filter circuits of a preceding column associated with said configuration.
32. The filter circuit of claim 31 , wherein two columns correspond to different filter taps.
33. The pipelined decision feedback unit of claim 14 , wherein a branch metric is computed based on said intersymbol interference-based estimate.