Patent ID: 6661282
Filing Date: 2003-12-09
Classification: H04L

Abstract:
A 16-ary QAM (Quadrature Amplitude Modulation) demodulation apparatus for receiving an input signal Rk(Xk, Yk) comprised of a kth quadrature-phase component Yk and a kth in-phase component Xk, and for generating soft values &Lgr;(sk,0), &Lgr;(sk,1), &Lgr;(sk,2) and &Lgr;(sk,3) for the input signal Rk(Xk, Yk) by a soft decision means, comprising:a first soft value decider for deciding soft values &Lgr;(sk,0) and &Lgr;(sk,1) of first and second demodulated symbols among 4 demodulated symbols, according to the following equations, Zkâ€²=&LeftBracketingBar;Xk&RightBracketingBar;-2&it;aÎ›&af;(sk,1)=Xk+Î²&CenterDot;Zkâ€²,where&it;â€ƒ&it;Î²={0â€ƒ&it;if&it;â€ƒ&it;MSB&af;(Zkâ€²)=1-1if&it;â€ƒ&it;MSB&af;(Zkâ€²)=0&it;â€ƒ&it;and&it;â€ƒ&it;MSB&af;(Xk)=11if&it;â€ƒ&it;MSB&af;(Zkâ€²)=0&it;â€ƒ&it;and&it;â€ƒ&it;MSB&af;(Xk)=0Î›&af;(sk,0)=Zkâ€²where &Lgr;(sk,0) denotes the soft value of the first demodulated symbol, &Lgr;(sk,1) denotes the soft value of the second demodulated symbol, MSB is the most significant bit or sign bit, and â€œ2aâ€  denotes a distance between two demodulated symbols on the same axis of a mapping table; anda second soft value decider for deciding soft values &Lgr;(sk,2) and &Lgr;(sk,3) of third and fourth demodulated symbols among the 4 demodulated symbols, according to the following equations, Zk=&LeftBracketingBar;Yk&RightBracketingBar;-2&it;aÎ›&af;(sk,3)=Yk+Î±&CenterDot;Zk,where&it;â€ƒ&it;Î±={0â€ƒ&it;if&it;â€ƒ&it;MSB&af;(Zk)=1-1if&it;â€ƒ&it;MSB&af;(Zk)=0&it;â€ƒ&it;and&it;â€ƒ&it;MSB&af;(Yk)=11if&it;â€ƒ&it;MSB&af;(Zk)=0&it;â€ƒ&it;and&it;â€ƒ&it;MSB&af;(Yk)=0Î›&af;(sk,2)=Zkwhere &Lgr;(sk,2) denotes the soft value of the third demodulated symbol, &Lgr;(sk,3) denotes the soft value of the fourth demodulated symbol, and â€œ2aâ€  denotes the distance between two demodulated symbols on the same axis of a mapping table.