Patent ID: 7072426

Claim:
An 8-ary PSK (Phase Shift Keying) demodulation apparatus for receiving an input signal R k (X k , Y k ) comprised of a k th quadrature-phase component Y k and a k th in-phase component X k , and for generating soft decision values Λ(S k,0 ), Λ(S k,1 ), and Λ(S k,2 ) for the input signal R k (X k , Y k ) by a soft decision means, comprising: a received signal analyzer for calculating a function Z k of the input signal R k (X k , Y k ) according to an equation Z k =|X k |−|Y k |, and determining a first parameter α and a second parameter β by the input signal; and a soft decision value output unit for calculating the soft decision values for the input signal R k (X k , Y k ), using the first parameter α, the second parameter β, and the received signal R k (X k , Y k ), according to Λ ⁡ ( s k , 2 ) = 2 ⁢ Y k + α · Z k , w ⁢ ⁢ h ⁢ ⁢ e ⁢ ⁢ r ⁢ ⁢ e ⁢ ⁢ α = { ⁢ 0 ⁢ i ⁢ ⁢ f ⁢ ⁢ Z k ≥ 0 ⁢ - 1 ⁢ i ⁢ ⁢ f ⁢ ⁢ Z k < 0 ⁢ ⁢ and ⁢ ⁢ Y k ≥ 0 ⁢ ⁢ 1 ⁢ i ⁢ ⁢ f ⁢ ⁢ Z k < 0 ⁢ ⁢ and ⁢ ⁢ Y k < 0 ⁢ ⁢ Λ ⁡ ( s k , 1 ) = 2 ⁢ X k + β · Z k , w ⁢ ⁢ h ⁢ ⁢ e ⁢ ⁢ r ⁢ ⁢ e ⁢ ⁢ β = { ⁢ 0 ⁢ i ⁢ ⁢ f ⁢ ⁢ Z k < 0 ⁢ - 1 ⁢ i ⁢ ⁢ f ⁢ ⁢ Z k ≥ 0 ⁢ ⁢ and ⁢ ⁢ X k < 0 ⁢ ⁢ 1 ⁢ i ⁢ ⁢ f ⁢ ⁢ Z k ≥ 0 ⁢ ⁢ and ⁢ ⁢ X k ≥ 0 Λ(S k,0 )=Z k where Λ(S k,i ) indicates a soft decision value corresponding to S k,i (i=0,1,2), and S k,i indicates an i th bit in a coded signal sequence mapped to a k th symbol.