Print ISSN: 1811-9212

Online ISSN: 2617-3352

Keywords : Model Predictive Control


Development of Model Predictive Controller for Congestion Control Problem †

Dr. Amjad J. Humaid; Dr. Hamid M. Hasan; Dr. Firas A. Raheem

IRAQI JOURNAL OF COMPUTERS, COMMUNICATIONS, CONTROL AND SYSTEMS ENGINEERING, 2014, Volume 14, Issue 3, Pages 42-51

Abstract— Nowadays congestion in computer networks is pointed out as an
important and a challenging problem. TCP (Transmission Control Protocol) has the
mechanism to avoid congestion in computer networks. TCP detects congestion by
checking acknowledgements or time-out processing and adjusts TCP window sizes of
senders. However, this control method shows low efficiency in communications
because it is based on a mechanism that avoid congestion after congestion once appears
in computer networks. TCP random early detection RED is another popular congestion
control scheme. The fundamental idea behind this control algorithm randomly drops the
incoming packets proportional to the average queuing length and to keep the queuing
length to a minimum. To achieve high efficiency and high reliability of communications
in computer networks, many control strategies based on advanced control theories have
been introduced to tackle the congestion problem. Model Predictive Control (MPC) is
the only practical control method that takes account of system constraints explicitly, and
the only ‘advanced control’ method to have been adopted widely in industry. MPC is a
model-based method which uses online optimization in real time to determine control
signals. The solution to optimization problem is usually formulated with the help of a
process model and measurements. At each control interval, an optimization algorithm
attempts to determine the plant dynamics by computing a sequence of control input
values satisfying the control specifications. In this work, a planning strategy based on
MPC will be developed for congestion control problem. A "preset controllers" approach
will be introduced for such application. The effectiveness of considered controller will
assessed in terms of how well it could show good tracking performance, maximizing the
utilization of the available bandwidth and to what extent it could cope with system
uncertainties.