Importance Sampling simulation of concatenated block codes

An importance sampling (IS) simulation of block codes based on the serial or parallel concatenation of simple codes is considered. At very low bit error rates, traditional Monte Carte simulations cannot be performed due to the very long simulation time that would be required. IS techniques can be very helpful in these cases. It is shown how IS can be applied to evaluate the performance of optimal MAP bit-per-bit decoders, and of non-optimal (turbo-like) iterative decoders.