Performance Modelling and Control of Server Systems using Non-linear Control Theory

All service control nodes, for example SCPs, HLRs, and MSCs, are constructed as a server system with one or more servers that process incoming requests. Since service control nodes are sensitive to overload, admission control mechanisms are often implemented. In this paper, we model and analyse admission control mechanisms for server systems with control theoretic methods. We develop a nonlinear stochastic control theoretic model of a GI/G/1-system. Further, we show that this model can be used to design admission control mechanisms that behave well in the “real” system, that is the queuing system. We develop two types of controllers for the system, one PI-controller and one RST-controller, both commonly used in automatic control. Also, we discuss some of the limitations of previous work in this area, in which only deterministic and linear models have been used