Soft channel encoding; a comparison of algorithms for soft information relaying

Soft Decode and Forward using Soft-Input Soft-Output (SISO) BCJR encoder is a recent relaying technique. The main purpose of employing SISO BCJR encoder in the relay is to combine the benefits of traditional relaying techniques, i.e. “Decode and Forward” and “Amplify and Forward”. We propose a novel approach to derive the estimated BER of the overall system and the equivalent source-relay-destination channel SNR. We consider the loss of mutual information due to applying SISO BCJR encoder in the relay and compare it with the mutual information loss due to applying an equivalent convolutional encoder. We also propose a novel SISO encoder which outperforms existing SISO BCJR encoder.