A mathematical model of access control to allocate downlink bandwidth in high-density wireless LAN

In the IEEE 802.11 standards used for wireless local area networks (WLANs), an access point (AP) and stations (STAs) have opportunities to transmit the data frame in a basic service set (BSS) by carrier sense multiple access with collision avoidance (CSMA/CA). When there are a large number of STAs with high traffic in the BSS, the throughput from AP to a STA will deteriorate since its transmit opportunities are severely limited. We develop a mathematical model of access control to allocate bandwidth for the downlink from AP to STAs in the saturated traffic. The mathematical model enables us to derive a contention window (CW) size at AP with uniform backoff algorithm such that the downlink bandwidth is guaranteed even in the bidirectional saturated traffic. We show the validity of the CW size obtained from the mathematical model using a network simulator, ns3.