Packet Unloading Strategies for Buffer-Aided Multiuser Mixed RF/FSO Relaying

In this letter, a buffer-aided (BA) multiuser dual-hop mixed radio frequency (RF)/free space optical (FSO) communication system is considered. For this setup, multiple RF users communicate with a single decode-and-forward (DF) relay with storage capabilities where the relay multiplexes the received packets along a FSO link. We analyze the scenario where the relay is equipped with multiple buffers and we propose different strategies for unloading these buffers for the sake of generating the multiplexed FSO packet. Through a Markov chain analysis, we highlight on the different levels of tradeoff between outage probability, queuing delay and quality-of-service (QoS) differentiation that can be achieved by the proposed schemes.