Soft decode and forward improves cooperative communications

Mobile receivers can benefit from an increased spatial diversity through cooperation. Two relaying techniques are typically used: either amplify and forward (AF) or decode and forward (DF). This contribution presents a new technique, which combines the main advantages of both AF and DF. This technique amounts to a DF scheme where all operations are performed in a soft-input soft-output fashion. In particular, an encoding technique which uses soft values to incorporate reliability information is proposed. The resulting soft-DF relay can be seen as an analog signal-to-noise ratio enhancer. Simulations show that this soft-DF scheme outperforms both AF and DF