Low-complexity, highly-spectrally-efficient communications

1. A method comprising:

in a receiver:

receiving a single-carrier inter-symbol correlated (ISC) signal that was generated by passage of symbols through a non-linear circuit; and

generating estimated values of said symbols using a sequence estimation process and a model of said non-linear circuit, wherein said sequence estimation process comprises:

convolving each one of a plurality of candidate symbol vectors with a plurality of tap coefficients to generate a corresponding one of a plurality of first ISC vectors; and

generating a plurality of metrics, each one of said metrics corresponding to the result of a cost function calculated using one of said first ISC vectors and a second ISC vector.

2. The method of claim 1 , wherein said ISC signal is a partial response signal generated via a partial response filter.

3. The method of claim 1 , wherein said symbols are N-QAM symbols and N is an integer.

4. The method of claim 1 , wherein:

said generating said estimated values of said symbols comprises performing one or more iterations of said sequence estimation process; and

for each iteration of said sequence estimation process, the number of candidate symbol vectors considered is less than the maximum likelihood state space.

5. The method of claim 1 , wherein said plurality of tap coefficients are based on tap coefficients of a partial response filter.

6. The method of claim 5 , wherein said partial response filter comprises two or more filters jointly optimized such that communications between said two or more filters over a channel are more tolerant of non-idealities than communications between a pair of near zero positive ISI filters over said channel.

7. The method of claim 1 , wherein said sequence estimation process comprises:

selecting one of said candidate symbol vectors based on said plurality of metrics; and

outputting a symbol of said selected one of said candidate symbol vectors as one of said estimated values of said symbols.

8. The method of claim 1 , wherein said cost function is based on Euclidean distance.

9. The method of claim 1 , comprising:

generating an inter-symbol correlated feedback signal; and

controlling an equalizer of said receiver based on said feedback signal.

10. The method of claim 9 , comprising generating said inter-symbol correlated feedback signal by applying said model of said non-linear circuit to an inter-symbol correlated signal generated by said sequence estimation process.

11. The method of claim 1 , comprising:

generating an ISC feedback signal by applying said model of said non-linear circuit to an ISC signal generated by said sequence estimation process; and

recovering a carrier frequency of said received single-carrier ISC signal using said ISC feedback signal.

12. A system comprising:

circuitry that includes a sequence estimation circuit and a non-linearity modeling circuit, wherein:

said circuitry is operable to receive an inter-symbol correlated (ISC) signal that carries information bits and that passed through a non-linear circuit;

said information bits are mapped into N-QAM symbols and N is an integer;

said circuitry is operable to generate estimated values of said information bits using said sequence estimation circuit and using said non-linearity modeling circuit; and

an output of said non-linearity modeling circuit is equal to a corresponding input of said non-linearity modeling circuit modified according to a non-linear model that approximates the non-linearity of said non-linear circuit; and

said sequence estimation circuit comprises:

a convolution circuit operable to convolve each one of a plurality of candidate symbol vectors with a plurality of tap coefficients to generate a corresponding one of a plurality of first ISC vectors; and

a metric calculation circuit operable to generate a plurality of metrics, each one of said metrics corresponding to the result of a cost function calculated using one of said first ISC vectors and a second ISC vector.

13. The system of claim 12 , wherein:

said circuitry includes an equalizer;

said equalizer is controlled based on a signal generated via said non-linear modeling circuit.

14. The system of claim 12 , wherein:

said circuitry includes a carrier recovery circuit;

said carrier recovery circuit is controlled based on a signal generated via said non-linear modeling circuit.

15. A receiver comprising:

a partial response filter;

a timing pilot removal circuit;

a non-linearity modeling circuit;

an equalizer that operates based on a first partial response feedback signal;

a carrier recovery circuit that operates based on a second partial response feedback signal; and

a sequence estimation circuit operable to perform a sequence estimation process that comprises:

convolution of each one of a plurality of candidate symbol vectors with a plurality of tap coefficients to generate a corresponding one of a plurality of first inter-symbol correlated (ISC) vectors; and

generation of a plurality of metrics, each one of said metrics corresponding to the result of a cost function calculated using one of said first ISC vectors and a second ISC vector.

16. The receiver of claim 15 , comprising an N-QAM de-mapper, where N is an integer.

17. The receiver of claim 15 wherein said non-linearity modeling circuit is configured to model:

non-linearity in a transmitter from which said receiver is configured to receive a communication; and/or

non-linearity in said receiver.