Patent ID: 7492830

Claim:
A receiving device comprising: an estimation unit for estimating a transmitted symbol from signals received using a plurality of antennas according to a status of channels which transmit signals from a transmitting device; a likelihood calculation unit for calculating a likelihood of the transmitted symbol estimated by said estimation unit; and an iterative unit for giving information indicating the likelihood to said estimation unit and for causing said estimation unit and said likelihood calculation unit to repeatedly execute the estimation and the calculation, respectively; wherein said estimation unit estimates the transmitted symbol using the information indicating the likelihood in a second and subsequent estimation, and said likelihood calculation unit calculates a log likelihood ratio of an estimated transmitted symbol and updates the log likelihood ratio obtained in a previous iterative cycle for every iterative cycle according to: L ( i + 1 ) ⁡ ( x k ) = L ( i ) ⁡ ( x k ) + Δ ⁢ ⁢ L ⁡ ( x k ) { L ( i ) ⁡ ( x k ) = L ⁡ ( x k / x ^ k ( i ) ) Δ ⁢ ⁢ L ⁡ ( x k ) = 1 ⁢ n ⁢ P ⁡ ( x ^ k / x k = + 1 ) P ⁡ ( x ^ k / x k = - 1 ) ⁢ ⁢ P ⁡ ( x ^ k / x k = b ) ∝ exp ⁡ ( - ( x ^ k - μ k ⁡ ( b ) ) 2 σ k 2 ⁡ ( b ) ) ⁢ ⁢ { μ k ⁡ ( b ) = E ⁢ { x ^ k / x k = b } σ k 2 ⁡ ( b ) = Cov ⁡ ( x ^ k , x ^ k / x k = b ) where “ΔL (x k )” is defined by a logarithm of a ratio of a probability when a symbol transmitted from a k-th transmitting antenna is “+1” and a probability when the symbol transmitted from the k-th transmitting antenna is “−1”, “μ k ” is a mean value of estimated values of symbols transmitted from the k-th transmitting antenna, and “σ k 2 ” is a variance of the estimated values of the symbols transmitted from the k-th transmitting antenna.