Patent ID: 7609615

Claim:
A method of performing channel compensation and symbol demodulation on a received signal in an Orthogonal Frequency Division Multiplexing (OFDM) system, the method comprising: generating a channel-compensated signal by multiplying a fast Fourier transform (FFT) received signal by an estimated channel impulse response; calculating the power of the estimated channel impulse response; and setting the power of the estimated channel impulse response as a reference point value defining a minimum distance between signal points in a signal constellation used for modulation of the FFT received signal, and deciding soft metric values for channel decoding of the channel-compensated signal using the reference point value, I-channel and Q-channel signal components of the channel-compensated signal, and a multiple of the reference point value corresponding to the distance of a signal point closest to the origin to each axis in the signal constellation, wherein 16-ary Quadrature Amplitude Modulation (16QAM) is used and the channel-compensated signal modulates the deciding of soft metric values which comprises deciding soft metric values for the channel-compensated signal by Z k =  Y k  - 2 ⁢ a ⁢ ⁢ Λ ⁡ ( s k , 2 ) = SY k + AZ k , ⁢ where ⁢ ⁢ A = { 0 , if ⁢ ⁢ MSB ⁡ ( Z k ) = 1 - 1 , if ⁢ ⁢ MSB ⁡ ( Z k ) = 0 and ⁢ ⁢ MSB ⁡ ( Y k ) = 1 1 , if ⁢ ⁢ MSB ⁡ ( Z k ) = 0 and ⁢ ⁢ MSB ⁡ ( Y k ) = 0 ⁢ ⁢ Λ ⁡ ( s k , 0 ) = Z k ⁢ ⁢ and Z k ′ =  X k  - 2 ⁢ a ⁢ ⁢ Λ ⁡ ( s k , 3 ) = SX k + BZ k ′ , ⁢ where ⁢ ⁢ B = { 0 , if ⁢ ⁢ MSB ⁡ ( Z k ′ ) = 1 - 1 , if ⁢ ⁢ MSB ⁡ ( Z k ′ ) = 0 and ⁢ ⁢ MSB ⁡ ( X k ) = 1 1 , if ⁢ ⁢ MSB ⁡ ( Z k ′ ) = 0 and ⁢ ⁢ MSB ⁡ ( X k ) = 0 ⁢ ⁢ Λ ⁡ ( s k , 1 ) = Z k ′ where Y k and X k denote the Q-channel signal component and the I-channel signal component of the channel-compensated signal, respectively, (S k,3 ), (S k,2 ), (S k,1 ) and (S k,0 ) denote the soft metric values, a comprises the reference point value, S denotes the multiple of the reference point value corresponding to the distance of a signal point closest to the origin to each axis in the signal constellation, equal to the minimum distance between signal points, and k denotes a symbol index.