Patent ID: 7346833

Claim:
In an iterative decoder, an iterative decoding method for decoding received digital data elements representing source data elements coded according to a turbo coding scheme, the iterative decoding method comprising: computing a set of branch metrics for the received digital data elements based upon at least one received digital data element; computing a set of forward recursive metrics based upon the set of branch metrics according to an approximation: A k ⁡ ( m ) = log [ α k ⁡ ( m ) ] = max m ′ ⁢ { Γ ⁡ ( u k , c k , m ′ , m ) + A k - 1 ⁡ ( m ′ ) } - H A k ; computing a set of backward recursive metrics based upon the set of branch metrics according to an approximation: B k ⁡ ( m ′ ) = log [ β k ⁡ ( m ′ ) ] = max m ⁢ { Γ ⁡ ( u k , c k , m ′ , m ) + B k + 1 ⁡ ( m ) } - H B k ; ⁢ and computing a set of output extrinsic Log Likelihood Ratio (LLR) values based upon the set of backward metrics and the set of forward metrics according to an equation: Λ ⁡ ( d k ) = log ⁡ [ ∑ e : u ⁡ ( e ) = d k = + 1 ⁢ ⅇ { A k - 1 ⁡ ( m ′ ) + Γ 1 ⁡ ( c k , m ′ , m ) + B k ⁡ ( m ) } ] - log ⁡ [ ∑ e : u ⁡ ( e ) = d k = 0 ⁢ ⅇ { A k - 1 ⁡ ( m ′ ) + Γ 0 ⁡ ( c k , m ′ , m ) + B k ⁡ ( m ) } ] ; and outputting the set of output extrinsic Log Likelihood Ratio (LLR) values.