Hypotheses generation based on multidimensional slicing
A sequence estimation circuit of a receiver may receive a sample of an inter-symbol correlated (ISC) signal corresponding to a time instant when phase and/or amplitude of the ISC signal is a result of correlation among a plurality of symbols of a transmitted symbol sequence. The sequence estimation circuit may calculate a residual signal value based on the sample of the ISC signal and based on a survivor sequence. The sequence estimation circuit may generate one or more branch vector hypotheses based on the residual signal value, where each of the hypotheses comprises a plurality of symbols. The sequence estimation circuit may generate an estimate of one or more of the plurality of transmitted symbols based on the one or more branch vector hypotheses.
1. A system comprising:
a front end circuit operable to receive a sample of an inter-symbol correlated (ISC) signal, said sample corresponding to a time instant when phase and/or amplitude of said ISC signal is a result of correlation among a plurality of symbols of a transmitted symbol sequence; and
a sequence estimation circuit operable to:
linearize said sample of said ISC signal;
calculate a residual signal value based on said linearized sample and based on a survivor sequence; and
generate one or more decisions for of one or more of said plurality of transmitted symbols based on said residual signal value.
2. The system of claim 1 , comprising nonlinearity modeling circuitry, wherein:
said linearization comprises application of an estimate of an inverse of a non-linear model generated by said nonlinearity modeling circuitry; and
said non-linear model is a model of nonlinearity experienced by said ISC signal in one or more of:
a transmitter from which said ISC signal originated;
a channel through which said ISC signal passed en route to said sequence estimation circuit; and
a front-end of a receiver.
3. The system of claim 1 , wherein each of said one or more decisions for one or more of said plurality of transmitted symbols is a hard decision.
4. The system of claim 1 , wherein:
each of said one or more decisions for one or more of said plurality of transmitted symbols is a soft-decision; and
said soft decision is weighted based on said residual signal value.
5. The system of claim 1 , wherein said one or more symbols of said transmitted symbol sequence are N-QAM symbols and N is an integer.
6. The system of claim 1 , wherein said generation of said one or more decisions is based on a multidimensional partial lattice.
7. The system of claim 2 , wherein said sequence estimation circuit is configured to, subsequent to said linearization and prior to said calculation of said residual signal value, filter said sample of said ISC signal.
8. The system of claim 6 , wherein said multidimensional partial lattice is based on:
a symbol constellation used to generate said transmitted symbol sequence; and
a subset of tap coefficients of a filter that models a composite response experienced by said transmitted symbol sequence en route to said sequence estimation circuit.
9. A system comprising:
a front end circuit operable to receive a sample of an inter-symbol correlated (ISC) signal, said sample corresponding to a time instant when phase and/or amplitude of said ISC signal is a result of correlation among a plurality of symbols of a transmitted symbol sequence; and
a sequence estimation circuit operable to:
calculate a residual signal value based on said sample and based on a survivor sequence;
generate one or more branch vector hypotheses based on said residual signal value, wherein:
each of said one or more branch vector hypotheses comprising a plurality of symbols; and
a quantity of branch vectors hypotheses in said one or more branch vector hypotheses is determined per sample of said ISC signal such that different quantities of branch vectors hypotheses may be generated for consecutive samples of said ISC signal; and
generate an estimate of one or more of said plurality of symbols or said transmitted symbol sequence based on said one or more branch vector hypotheses.
10. The system of claim 9 , wherein:
said quantity of branch vector hypotheses is a first quantity for a sample of said ISC signal corresponding to a residual signal value that is a first distance from a center of a lattice;
said quantity of branch vector hypotheses is a second quantity for a sample of said ISC signal corresponding to a residual signal value that is a second distance from said center of said multidimensional partial lattice;
said first quantity is greater than said second quantity; and
said first distance is greater than said second distance.
11. The system of claim 9 , wherein said quantity of branch vector hypotheses in said one or more branch vector hypotheses is determined based on a signal-to-noise ratio.
12. The system of claim 9 , wherein said quantity of branch vector hypotheses in said one or more branch vector hypotheses is determined based on an amount of non-linear distortion experienced by said ISC signal.
13. The system of claim 9 , wherein:
said estimate of said one or more of said plurality of symbols of said transmitted symbol sequence is a soft-decision; and
said soft decision is weighted based on said residual signal value.
14. The system of claim 9 , wherein said plurality of symbols of said transmitted symbol sequence are N-QAM symbols and N is an integer.
15. The system of claim 9 , wherein said generation of said estimate is based on a multidimensional partial lattice.
16. The system of claim 15 , wherein said multidimensional partial lattice is based on:
a symbol constellation used to generate said transmitted symbol sequence; and
a subset of tap coefficients of a filter that models a composite response experienced by said transmitted symbol sequence en route to said sequence estimation circuit.