1. A method of processing communications signals, comprising: receiving, at a receiver, a constellation which has a plurality of unused constellation points; using a plurality of lookup tables for indicating whether a particular constellation point is used and a corresponding codeword for the used constellation point; indexing the lookup tables using an integer u and an integer v; computing an initial estimate of the integer u and the integer v giving an integer ū and an integer v comprising: ⁢ v _ = 2 ⁢ ( y - y 0 ) / 3 u _ = x - x 0 - ( y - ) / 3 a normalized received symbol is ⁢ r = ( x , y ) , where (x,y) are the coordinates of the received symbol r and where (x0,y0) is a fixed perturbation for symbol r0 that could be used to minimize the maximum energy Eg; computing a modified Euclidean distance to an immediate constellation point neighbor that corresponds to the upper and lower integer of ū and ū; and from the distance to the immediate constellation point neighbor, computing a log-likelihood ratio value.