Patent ID: 7430704

Claim:
A method for detecting signals affected by intersymbol interference (ISI), the method including the steps of: providing a path memory in the form of a trellis admitting survivor paths comprising a first and a second stage, said first stage including a shift register exchange with a given number of states and a given length λ, outputting from said first stage at time k-λ, where λ is said given length: a) a first state S Ak k-λ on the survivor path for a best state A k at time k, while keeping track of a parity for the best state at time k-λ for each of the survivor paths in said path memory, and b) a second state S Bk k-λ on the survivor path for another state B k having a same ISI state as said best state A k and an opposite parity state, configuring said second stage as a two-state shift register exchange having a respective memory length Λ, including respective first and second registers, storing in said respective first and second registers the survivor paths leading to respective first σ 0 k and second σ 1 k states, said respective first state being equal to said first state S Ak λ on said best survivor path, whereby said respective first register contains the backend of said best survivor path, while said respective second register contains the backend of an alternative survivor path, said alternative survivor path being for an alternative state at time k with the same ISI state as said best state and the opposite parity state.