Title: Performance of Amplify-and-forward and Decode-and-Forward Relaying with Turbo Codes
Authors: Michael Souryal, Branimir Vojcic (Poster I, 16)

ABSTRACT

We compare the performance of amplify-and-forward (AF), decode-and-forward (DF) and a new hybrid DF/AF relaying protocol using practical turbo codes in Rayleigh fading channels. In the hybrid approach, the relay decodes and forwards if a CRC passes; otherwise, it amplifies and forwards. Hybrid DF/AF achieves diversity against fading without the need for feedback to the source or for channel state information at the source, and it avoids noise amplification when the source-relay transmission succeeds. Analytical approximations are derived for the frame error rate in block Rayleigh fading using a threshold signal-to-noise ratio model for the success/failure of a transmission, and they are shown to compare well with simulation results. While hybrid DF/AF has a clear advantage in AWGN, the three relaying protocols perform comparably in Rayleigh fading but with differing levels of complexity. Varying the location of the relay on a line between the source and destination, we find that the error rate is minimized when the relay is at the midpoint. This observation implies that in large networks, symmetric partnering, where two users relay for each other, is less advantageous than allowing each node to choose its most helpful relay.