Design and Network Topology-Specific Renewal-Theoretic Analysis of a MAC Protocol for Asymmetric Full-Duplex WLANs

The asymmetric network model, in which the access point (AP) is full-duplex (FD) capable while the other nodes are only half-duplex (HD) capable, is motivated by early-stage deployments of FD-capable networks. We propose a medium access control (MAC) protocol called asymmetric FD MAC (AFD-MAC) for this model. It leverages features such as random back-off and carrier sensing of the widely-used 802.11 HD MAC protocol, and it introduces two signals to exploit the FD capability of the AP. We also develop a general, network topology-specific renewal-theoretic analysis that characterizes the saturation throughput of AFD-MAC. It captures the differences in the statistical properties of the nodes and the AP due to differences in their duplexing capabilities or the number of hidden nodes. AFD-MAC can increase the throughput by a factor as large as two and can reduce head-of-line delay by a factor more than half compared to the conventional 802.11 HD MAC protocol. The gains depend on the ratio of the uplink to downlink packet lengths, network topology, and the extent of self-interference cancellation. A contrarian insight that emerges is that hidden nodes can enable the network to exploit its asymmetric FD capability.