Lecture notes on turbo codes.

similarly βn(s) = 0 for s=S n otherwise β n (s) = -∞So we replace log and exp with maximum values. Thus we have thefollowing set of equations.Eα k (s) = max (e:s (e)=s) {α k-1 [s S (e) + π k [u(e);I] + π k [c(e);I]}, k=1,2..,nSβ k (s) = max (e:s (e)=s) {β k+1 [s E (e) + π k+1 [u(e);I] + π k+1 [c(e);I]}, k=n-1,… ,0π k (c;O) = max (e:c(e)=c)) {α k-1 [s S (e) + π k [u(e);I] + β k [s E (e)]}π k (u;O) = max (e:u(e)=u)) {α k-1 [s S (e) + π k [c(e);I] + β k [s E (e)]}Generally for serial concatenated codes:OUTER CODE- NON RECURSIVE or NON-Feed back , Non systematicINNER CODE- RECURSIVE SYSTEMATIC or Feed-back SystematicIt is seen that the performance of SCCC is usually better than that of PCCC.BERSCCCPCCCError Floor Effectin PCCCE b /N 017