Novel Rateless Coded Selection Cooperation in Dual-Hop Relaying Systems

Selection cooperation is proposed for rateless coded relaying by developing a novel low-complexity protocol that exploits all source-destination, source-relay, and relay-destination link qualities for relay selection. The source or any decoding relay having a link to the destination with a gain greater than a preset threshold is a candidate for collaboration. When the number of candidates reaches a preset value, the best of them is selected for passing the source data to the destination. The source and relays are informed of the selected node by a broadcast feedback from the destination. Limited feedback is required only between the destination and the other nodes and merely for declaring success in decoding or selecting the next transmitting node. The system power and complexity are independent of the system parameters. Also, the system dispenses with internode synchronization at carrier or symbol levels, multireception combining, multiaccess interference, and multiuser detection. Assuming independent fading on different links, a general performance analysis of the new system is presented valid for any individual link fading model. It is shown through numerical results that the novel scheme is considerably more energy efficient, for diverse input conditions, than a more complex commensurate scheme previously proposed. Also, the energy efficiency is enhanced as the number of relays increases, such that despite an increase in the capacity, the energy expenditure diminishes.