  In this paper, we discuss the effects on throughput and fairness of dynamic
channel bonding (DCB) in spatially distributed high-density wireless local area
networks (WLANs). First, we present an analytical framework based on
continuous-time Markov networks (CTMNs) for depicting the behavior of different
DCB policies in spatially distributed scenarios, where nodes are not required
to be within the carrier sense range of each other. Then, we assess the
performance of DCB in high-density IEEE 802.11ac/ax WLANs by means of
simulations. We show that there may be critical interrelations among nodes in
the spatial domain - even if they are located outside the carrier sense range
of each other - in a chain reaction manner. Results also reveal that, while
always selecting the widest available channel normally maximizes the individual
long-term throughput, it often generates unfair situations where other WLANs
starve. Moreover, we show that there are scenarios where DCB with stochastic
channel width selection improves the latter approach both in terms of
individual throughput and fairness. It follows that there is not a unique
optimal DCB policy for every case. Instead, smarter bandwidth adaptation is
required in the challenging scenarios of next-generation WLANs.
