US 7,321,643 B2
Soft decision decoder, and log likelihood ratio calculator and method thereof for enhanced performance in soft decision decoding
Dae-Ig Chang, Daejeon (Korea, Republic of); Dong-Weon Yoon, Daejeon (Korea, Republic of); and Nae-Soo Kim, Daejeon (Korea, Republic of)
Assigned to Electronics and Telecommunications Research Institute, (Korea, Republic of)
Filed on Sep. 12, 2003, as Appl. No. 10/662,195.
Claims priority of application No. 10-2002-0055302 (KR), filed on Sep. 12, 2002.
Prior Publication US 2004/0125883 A1, Jul. 01, 2004
Int. Cl. H04L 27/06 (2006.01)
U.S. Cl. 375—341  [375/340] 6 Claims
OG exemplary drawing
 
1. A soft decision decoder comprising:
a first log likelihood ratio calculator and a second log likelihood ratio calculator, for using a receive signal y with noise input from a receiver so as to perform soft decision decoding on a QAM (quadrature amplitude modulation) signal, the first log likelihood ratio calculator and the second log likelihood ratio calculator incorporating channel estimation errors in calculating a log likelihood ratio of a positive signal (x+) and a negative signal (x), respectively;
a subtractor for determining a difference between outputs of the log likelihood ratio calculators; and
a comparator for receiving a calculation result on the difference of the log likelihood ratios of the subtractor, and determining the QAM signal to be positive or negative according to a positive/negative state of the calculation result,
wherein each of the log likelihood ratio calculators comprises M adders for respectively adding M square values of M reference signals xi and a ratio ρ of a symbol noise bandwidth of a QAM signal and a channel estimation filter noise bandwidth.