Patent ID: 6907084

Claim:
A method for processing symbols for a soft input decoder comprising the steps of: (a) receiving a modulation symbol having I and Q components; and (b) converting the received modulation symbol into a soft bit, b K , by calculating the following: b k = { log ⁢ ∑ G p ∈ Π + k ⁢ exp ⁡ ( - D Ip 2 ⁢ σ 2 ) - log ⁢ ⁢ ∑ G q ∈ Π - k ⁢ exp ⁡ ( - D Iq 2 ⁢ σ 2 ) k = 0 , 2 , 4 log ⁢ ∑ G p ∈ Π + k ⁢ exp ⁡ ( - D Qp 2 ⁢ σ 2 ) - log ⁢ ⁢ ∑ G q ∈ Π - k ⁢ exp ⁡ ( - D Qq 2 ⁢ σ 2 ) k = 1 , 3 , 5 where σ 2 is the noise variance associated with the channel, exp( ), II +k and II −k represent decoupled sets of constellation points associated with the I and Q components, D Ip and D Qp represent a distance metric, measurement, or calculation associated with the distance between the received modulation symbol and a grid or group of points in the given constellation, and G p and G q are constellation grids.