Cooperative MAC protocol with distributed relay selection using group-based probabilistic contention

For cooperative wireless networks, we propose a medium access control (MAC) protocol with distributed relay selection using group-based probabilistic contention and reparticipation. The relay with the minimum outage probability is selected in a distributed way. Based on the achievable outage probability, relay candidates are divided into multiple groups, and each relay candidate in a group uses a probability to send the acknowledgement (ACK) packet back to the source to contend for being selected. Each group is defined by a specified range of the outage probability. Relays in a group with lower outage probability range contend earlier. In addition, the relay candidate that does not send the ACK packet in the current time slot is assigned with a higher probability to contend in the next time slot. Once a relay candidate survives, the contention process is terminated. Thus, transmitting the unnecessary ACK packets for contention is avoided. Simulation results show that compared to the conventional scheme, the proposed one has a better performance in terms of the outage probability, shortens the contention period, and reduces the number of ACK packets for contention.