Patent ID: 8675783

Claim:
A method of determining a data value for a bit of interest in a received data signal, the method comprising: selecting a closest 0-bit symbol candidate, at the bit of interest, from a plurality of 0-bit symbol candidates using a symbol selection distance approximation; selecting a closest 1-bit symbol candidate, at the bit of interest, from a plurality of 1-bit symbol candidates using the symbol selection distance approximation; calculating a 0-bit distance and a 1-bit distance, wherein the 0-bit distance represents the distance between the received data signal and the selected closest 0-bit symbol candidate, and the 1-bit distance represents the distance between the received data signal and the selected closest 1-bit symbol candidate; calculating a log likelihood ratio for the bit of interest using i) the calculated 0-bit distance and ii) the calculated 1-bit distance; and determining the data value for the bit of interest based on the calculated log likelihood ratio; wherein locations of each of the received data signal, the plurality of 0-bit symbol candidates, and the plurality of 1-bit symbol candidates are identified by coordinates; wherein the symbol selection distance approximation, as applied to selecting the closest 0-bit symbol candidate, includes estimating first distances between the received data signal and the plurality of 0-bit symbol candidates using norm approximations of vectors from the coordinates of the received data signal to coordinates of the plurality of 0-bit symbol candidates, wherein the symbol selection distance approximation, as applied to selecting the closest 1-bit symbol candidate, includes estimating second distances between the received data signal and the plurality of 1-bit symbol candidates using norm approximations of vectors from the coordinates of the received data signal to coordinates of the plurality of 1-bit symbol candidates, wherein the vector between the coordinates of the received data signal and the coordinates of a 0-bit or 1-bit symbol candidate is represented as z k =z kI +jz kQ , wherein the norm approximation of ∥z k ∥ estimates ∥z k ∥=max{|z kI |,|z kQ |}+α·min{|z kI |,|z kQ |}, where α is 5/16, and wherein the first or second distances are calculated according to a non-iterative distance approximation according to: ∥z∥≈G ( z ), where G ⁡ ( z ) = ∑ k = 1 N ⁢ g ⁡ ( z k ) , where g ( z k )=max{| z kI |,|z kQ |}+α·min{| z kI |,|z kQ |}, k= 1 . . . N.