Joint sequence estimation of symbol and phase with high tolerance of nonlinearity

Abstract

A method and system for a sequence estimation in a receiver, such as for use when receiving a sample of a received inter-symbol correlated (ISC) signal corresponding to a transmitted vector of L symbols, with L being a integer greater than 1, and with symbol L being a most-recent symbol and symbol 1 being least recent symbol of the vector. A plurality of candidate vectors may be generated, wherein element L-m of each candidate vector holding one of a plurality of possible values of the symbol L-m, with m is an integer greater than or equal to 1, and elements L-m+1 through L of each candidate vectors holding determined filler values. A plurality of metrics may be generated based on the plurality of candidate vectors, and based on the generated plurality of metrics, a best one of the possible values of the symbol L-m may be selected.

1 - 20 . (canceled) 
     
     
         21 . A system comprising:
 a sequence estimation circuit operable to:
 generate a plurality of candidate vectors, wherein each of said plurality of candidate vectors comprises:
 a first element that holds a symbol selected during a previous iteration of said sequence estimation; 
 a second element that holds a symbol to be searched; and 
 a third element that holds a value calculated based on said first element, said second element, and a cost function; 
 
 calculate a plurality of branch metrics corresponding to the plurality of candidate vectors; and 
 select, based on said plurality of branch metrics, one of said plurality of candidate vectors to be output for use by another circuit. 
   
     
     
         22 . The system of  claim 21 , wherein:
 said plurality of candidate vectors consists of M, an integer, candidate vectors; and   each of said plurality of symbol values to be searched corresponds to a respective one of M values of an M-QAM constellation.   
     
     
         23 . The system of  claim 21 , wherein, as part of said calculation of said plurality of branch metrics, said sequence estimation circuit is operable to convolve each of said plurality of candidate vectors with a plurality of tap coefficients to generate a corresponding plurality of candidate partial response vectors. 
     
     
         24 . The system of  claim 23 , wherein, as part of said calculation of said plurality of branch metrics, said sequence estimation circuit is operable to apply a non-linearity model to each of said plurality of candidate partial response vectors to generate a corresponding one of a plurality of partial response reconstructed candidates. 
     
     
         25 . The system of  claim 24 , wherein, as part of said calculation of said plurality of branch metrics, said sequence estimation circuit is operable to calculate a Euclidean distance between each of said plurality of partial response reconstructed candidates and a corresponding one of a plurality of vectors generated from a signal whose values are to be estimated by said sequence estimation circuit. 
     
     
         26 . The system of  claim 21 , wherein said calculation is an inverse calculation. 
     
     
         27 . The system of  claim 26 , wherein said inverse calculation uses a model of non-linearity experienced by a signal whose values are to be estimated by said sequence estimation circuit. 
     
     
         28 . The system of  claim 21 , wherein:
 for any particular one of said plurality of candidate vectors, determining said value held by said third element of said particular one of said plurality of candidate vectors comprises insertion of a zero into said third element of said particular one of said plurality of candidate vectors to generate a zero-filled vector.   
     
     
         29 . The system of  claim 28 , wherein, as part of said determination of said value held by said third element, said sequence estimation circuit is operable to determine a contribution of a most-recent symbol of a received signal based on said zero-filled vector. 
     
     
         30 . The system of  claim 29 , wherein, as part of said determination of said contribution of said most-recent symbol of said received signal, said sequence estimation circuit is operable to perform a slicing operation. 
     
     
         31 . A method comprising:
 in a sequence estimation circuit of a receiver:
 generating a plurality of candidate vectors, wherein each of said plurality of candidate vectors comprises:
 a first element that holds a symbol selected during a previous iteration of said sequence estimation; 
 a second element that holds a symbol to be searched; and 
 a third element that holds a value calculated based on said first element, said second element, and a cost function; 
 
 calculating a plurality of branch metrics corresponding to the plurality of candidate vectors; and 
 selecting, based on said plurality of branch metrics, one of said plurality of candidate vectors to be output for use by another circuit. 
   
     
     
         32 . The method of  claim 31 , wherein:
 said plurality of candidate vectors consists of M, an integer, candidate vectors; and   each of said plurality of symbol values to be searched corresponds to a respective one of M values of an M-QAM constellation.   
     
     
         33 . The method of  claim 31 , wherein said calculation of said plurality of branch metrics comprises convolving each of said candidate vectors with a plurality of tap coefficients to generate a corresponding plurality of candidate partial response vectors. 
     
     
         34 . The method of  claim 33 , wherein said calculating said plurality of branch metrics comprises applying a non-linearity model to each of said plurality of candidate partial response vectors to generate a corresponding one of a plurality of partial response reconstructed candidates. 
     
     
         35 . The method of  claim 34 , wherein said calculating said plurality of branch metrics comprises calculating a Euclidean distance between each of said partial response reconstructed candidates and a corresponding one of a plurality of vectors generated from a signal whose values are to be estimated by said sequence estimation circuit. 
     
     
         36 . The system of  claim 31 , wherein said calculating comprises performing an inverse calculation. 
     
     
         37 . The method of  claim 36 , wherein said inverse calculation uses a model of non-linearity experienced by a signal whose values are to be estimated by said sequence estimation circuit. 
     
     
         38 . The method of  claim 31 , comprising:
 for any particular one of said candidate vectors, determining said value held by said third element of said particular one of said plurality of candidate vectors, wherein said determining comprises inserting a zero into said third element of said particular one of said candidate vectors to generate a zero-filled vector.   
     
     
         39 . The method of  claim 38 , wherein said determining said value held by said third element comprises determining a contribution of a most-recent symbol of a received signal based on said zero-filled vector. 
     
     
         40 . The method of  claim 39 , wherein said determining said contribution of said most-recent symbol of said received signal comprises performing a slicing operation.