Hidden-Node-Free MAC Protocol Design for FD WLANs

In this chapter, we provide a comprehensive investigation of the HN problem that arises in the FD WLANs with mutiple APs. In particular, we first provide the fundamental conditions that guarantee successful receptions for all the FD transmission cases, and propose an ellipse interference model and an ellipse carrier-sensing model to capture the interference relations and the carrier-sensing mechanism in FD WLANs, respectively. We further establish the hidden-node-free design in FD WLANs. Specifically, we show the sufficient conditions on the carrier-sensing power threshold that can eliminate hidden-node collisions. We show that compared with half-duplex CSMA networks, the FD network needs a much smaller carrier-sensing power threshold to prevent HN collisions, which leads to poor network spatial reuse. This motivates us to further propose a new MAC protocol with a full-duplex enhanced carrier-sensing (FECS) mechanism. The FECS-MAC enables the secondary carrier sensing before starting the secondary transmission. We show that with the secondary carrier-sensing design, the required carrier-sensing power threshold can be increased while keeping the network hidden-node free.