Parameter uncertainties and variations as well as input or state delays are crucial factors in the analysis and control of packet flows using the Internet Protocol (IP) suite, of which the Transmission Control Protocol (TCP) is one of the core protocols. The main TCP task is to provide reliable, order and error–checked delivery of streams of octets between programs running on interconnected computers. In this paper an Active Queue Management (AQM) robust control strategy for TCP data transfer is proposed. It is based on the second–order model with delayed input obtained from the linearization of an efficient and commonly used nonlinear fluid–based model. To guarantee a satisfactory behavior of the adopted feedback control structure, a fractional–order PI controller is proposed. In particular, a method for determining the parameter regions where a P I λ controller ensures a given modulus margin (inverse of the H ∞ norm of the sensitivity function) is presented. The suggested graphically–based technique is simple to apply and ensures robustness against disturbances and unmodelled dynamics.
On robust fractional order PI controllers for TCP packet flow
VIARO, Umberto
2014-01-01
Abstract
Parameter uncertainties and variations as well as input or state delays are crucial factors in the analysis and control of packet flows using the Internet Protocol (IP) suite, of which the Transmission Control Protocol (TCP) is one of the core protocols. The main TCP task is to provide reliable, order and error–checked delivery of streams of octets between programs running on interconnected computers. In this paper an Active Queue Management (AQM) robust control strategy for TCP data transfer is proposed. It is based on the second–order model with delayed input obtained from the linearization of an efficient and commonly used nonlinear fluid–based model. To guarantee a satisfactory behavior of the adopted feedback control structure, a fractional–order PI controller is proposed. In particular, a method for determining the parameter regions where a P I λ controller ensures a given modulus margin (inverse of the H ∞ norm of the sensitivity function) is presented. The suggested graphically–based technique is simple to apply and ensures robustness against disturbances and unmodelled dynamics.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
