Robust queue management for TCP-based large round trip time networks with wireless access link

Transport layer protocol (TCP) is used to avoid the congestion in the network by controlling the rate at which the source inject traffic to the network. In order to control their internal buffers and avoid overflow, the intermediate routers of a network send control signals (feedbacks). The source adjusts its transmission rate accordingly. Different control signals have proposed in the literature but the most widely used is performed by dropping the packet. When a packet is dropped, the source does not receive it acknowledgement and is notified of congestion at the network. Active queue management (AQM) is referred to the technique where intermediate routers by employing that can control and stabilize their internal routers and avoid network congestion. In many cases, an AQM technique defines the decision algorithm for dropping the packets of a source. In this paper, we consider the AQM in the network with one wireless access link. Active queue management is more complicated in the wireless networks than that in wired ones due to the changes in the link capacity and packet erasure in the communication channel. The main contribution of our study is to design a robust queue management based on two degree of freedom internal model control for a network consisting of a wireless link with variable capacity, packet loss, and large delay. Simulation results validate the analytical results through which it is proved that the procedure not only can restrict the fluctuations caused by the fading and packet error rate but also can control the queue length in the case of variation in the number of the users.