Dynamic Decode and Forward Relaying for Broadcast Transmissions by Relay-Unaware Source

In this paper, we consider a broadcast transmission from a source to multiple destinations with an OFDM-based system. In order to improve the broadcast services of a cellular system, we consider the use of relays with Dynamic Decode and Forward protocols allowing the source to ignore the existence of relays in the system. A new algorithm executed at the relay is proposed. It allows for maximizing the diversity order at the destinations side by selecting the best relaying protocol and modulation size as function of the relay correct decoding time. No feedback is assumed on any link between the source, relays and destinations.