Adaptive congestion control in infrastructure wireless LANs with bounded medium access delay

Due to the speed mismatch between wired and wireless networks, network congestion can easily occur at the fusion point (gateway or access point) that interconnects these two networks. In this paper we propose a congestion control scheme for TCP traffic retrieved by wireless LAN clients from the Internet, denoted as media access delay regulator (MADR). The proposed scheme is based on active queue management principles adapted for wireless media. MADR dynamically adapts the MAC layer queue size in order to maintain the average media access delay of packets entering the wireless LAN. The proposed congestion control scheme, MADR, extends the control principles of the PI controller which was first proposed as an AQM scheme for wired networks. Instead of using the reference queue size as the control target, we control the medium access delay of the AP, which reflects the congestion level of the wireless channel. We have implemented our scheme in OPNET simulator. The simulation results show that the proposed scheme maintains the average medium access delay under dynamic traffic patterns and varying channel capacity.