Bandit-Based Relay Selection in Cooperative Networks over Unknown Stationary Channels

In this paper, we propose low-complexity relay scheduling mechanisms with the aid of a multi-armed bandit (MAB) framework. More specifically, this MAB framework is used for relay scheduling, based only on observing the acknowledgements/negative-acknowledgements (ACK/NACK) of packet transmissions. Hence, a bandit-based opportunistic relay selection (BB-ORS) mechanism is developed, recovering eventually the performance of classical opportunistic relay selection (ORS) when channel state information (CSI) is available without requiring any CSI. In addition, a distributed implementation of BB-ORS is presented, herein called d-BB-ORS, where distributed timers are used at the relays for relay selection, thus reducing the signaling overhead significantly. BB-ORS is compared to optimal scheduling with full CSI and the negligible performance gap is compensated by the low-complexity low-overhead implementation, while it surpasses the performance of ORS with outdated CSI.