  UAV-based base station (UBS) has played an important role in the air-ground
integration network due to its high flexibility and nice air-ground wireless
channels. Especially in Internet of Things (IoT) services, UBS can provide an
efficient way for data collection from the IoT devices. However, due to the
continuous mobility of UBS, the communication durations of devices in different
locations with the UBS are not only time-limited, but also vary from each
other. Therefore, it is a challenging task to analyze the throughput
performance of the UAV-based IoT network. Accordingly, in this paper, we
consider an air-ground network in which UAV flies straightly to collect
information from the IoT devices based on CSMA/CA protocol. An analytical model
analyzing the performance of this protocol in the network is proposed. In
detail, we set up the system model for the network, and propose a new concept
called quitting probability. Then, a modified Markov chain model integrating
the quitting probability is introduced to describe the transmission state
transition process and an accurately theoretical analysis of saturation
throughput is given. In addition, the effects of the network parameters are
discussed in the simulation section.
