Handling the Congestion Control Problemof TCP/AQM Wireless Networks with PID Controllers

Internet users rely on the good capabilities of TCP/IP networks for dealing with congestion. The network delay and the number of users change constantly, which might lead to transmission problems. Usually, they are handled following approaches such as Drop Tail or Random Early Detection (RED) algorithms. During the last few years, automatic control techniques are providing practical solutions. Moreover, if there are wireless links, congestion control is more difficult to detect. This chapter presents a methodology to design a PID controller with a linear gain scheduling that allows a network with wireless links to deal with control congestion under a variety of configurations. The technique is compared with a standard PID and several tests are carried out using linear and non-linear environments.