Distributed Relay Selection with Reduced Modulation-Order Signal Forwarding and Energy Harvesting

We proposed a new relay-selection (RS) scheme that operates in a completely distributed manner without the need for any channel state information at the transmitter (CSIT). Based on the information extracted from the received signals sent by the source, an antenna at the selected relay is used to forward signals. Notably, the modulation order of the forwarded symbols was reduced, which benefits the end-to-end error-rate performance. The results showed that in several scenarios, this distributed RS (D-RS) provides a lower error rate than the network with one relay, even using CSIT for enhancing the transmit diversity. Thanks to the use of the D-RS, we demonstrated that the unselected relays harvest radio-frequency energy from the forwarded signals toenergize the relay operation and prolong the lifetime of the network.