Decision feedback equalizer utilizing symbol error rate biased adaptation function for highly spectrally efficient communications
One or more embodiments describe a decision feedback equalizer utilizing symbol error rate biased adaptation function for highly spectrally efficient communications. A method may be performed in a decision feedback equalizer (DFE). The method may include determining values of tap coefficients used by the DFE based. The tap coefficients may be determined based on an error signal that is based on an estimated inter-symbol-correlated (ISC) signal. The tap coefficients may be determined based on a set of error vector(s), where each error vector in the set represents a difference between estimated symbols generated in the receiver and expected symbols. Determining the values of the tap coefficients may include using a symbol error rate function that estimates the actual symbol error rate in the receiver, wherein the symbol error rate function receives as input the set of error vector(s).
1. A method comprising
performing by circuitry for use in a receiver, said circuitry comprising a decision feedback equalizer (DFE) and a feed forward equalizer:
determining values of tap coefficients used by the DFE based on:
an error signal that is based on an output of the feed forward equalizer and an estimated inter-symbol-correlated (ISC) signal; and
a set of error vector(s), where each error vector in the set of error vector(s) represents a difference between estimated symbols generated in the receiver and expected symbols;
determining a frequency of occurrence of each of a plurality of error vectors in the receiver; and
selecting a most-frequently occurring subset of the plurality of error vectors as the set of error vector(s).
2. The method of claim 1 , wherein the ISC signal is a partial response signal.
3. The method of claim 2 , wherein the ISC signal is generated by a sequence estimation circuit.
4. The method of claim 1 , comprising determining the values of the tap coefficients using a symbol error rate function that includes one or more terms that represent the Euclidian distance of each error vector in the set of error vector(s).
5. The method of claim 1 , comprising, as part of said determining the values of the tap coefficients, seeking a minimum of a symbol error rate function.
6. The method of claim 1 , wherein one or more error vectors in the set of error vector(s) represent(s) distance(s) between symbol paths of transmitted values.
7. The method of claim 1 , wherein the expected symbols are the symbols as sent by a transmitter.
8. The method of claim 1 , wherein the expected symbols are the symbols as determined by an error correction unit.
9. A system comprising:
circuitry that includes a decision feedback equalizer (DFE) and a feed forward equalizer, wherein the circuitry is operable to:
determine values of tap coefficients used by the DFE based on:
an error signal that is based on an output of the feed forward equalizer and an estimated inter-symbol-correlated (ISC) signal; and
a set of error vector(s), where each error vector in the set of error vector(s) represents a difference between estimated symbols generated in the circuitry and expected symbols;
determine a frequency of occurrence of each of a plurality of error vectors in the circuitry; and
select a most-frequently occurring subset of the plurality of error vectors as the set of error vector(s).
10. The system of claim 9 , wherein the circuitry is operable to determine the values of the tap coefficients using a symbol error rate function that includes one or more terms that represent the Euclidian distance of each error vector in the set of error vector(s).
11. The system of claim 10 , wherein the determination of the values of the tap coefficients includes seeking a minimum of the symbol error rate function.
12. The system of claim 9 , wherein one or more error vectors in the set of error vector(s) represent(s) distance(s) between symbol paths of transmitted values.
13. A decision feedback equalizer (DFE) in a receiver, the decision feedback equalizer comprising:
a plurality of tap coefficients that are determined, at least in part, based on a function that seeks to minimize the mean square of an error signal and, at least in part, based on a set of error vector(s), wherein:
each error vector in the set of error vector(s) represents a difference between estimated symbols generated in the receiver and expected symbols;
circuitry of the receiver is operable to determine a frequency of occurrence of each of a plurality of error vectors in the receiver; and
the circuitry is operable to select a most-frequently occurring subset of the plurality of error vectors as the set of error vector(s).
14. The decision feedback equalizer of claim 13 , wherein the expected symbols are the symbols as sent by a transmitter.
15. The decision feedback equalizer of claim 13 , wherein the expected symbols are the symbols as determined by an error correction unit such that the symbols as sent by a transmitter need not be known to the receiver.
16. The decision feedback equalizer of claim 15 , wherein the one or more error vectors in the set of error vector(s) are dynamically computed by determining the difference between the estimated symbols generated in the receiver and the expected symbols.
17. The method of claim 1 , comprising adapting tap coefficients of said feed forward equalizer based on the error signal.
18. The system of claim 9 , wherein tap coefficients of said feed forward equalizer adapt based on the error signal.