Wireless Ad Hoc and Sensor Networks

Admission Controller Design for High-Speed Networks 171The CLR for the adaptive scheme is slightly higher than for adaptive withoverallocation and the PCR because the adaptive scheme is conservative;however, the CLR meets the target specification. The CLR resulting fromPCR is near zero as enough resources are a priori reserved. These resultsclearly show that the bandwidth assignment has to be accurate to admitnew sources. This chapter has demonstrated a novel scheme of assigningbandwidth, preventing congestion and a scheme for admitting sourcesbased on available capacity.4.7 ConclusionsThis chapter proposes a system theoretic approach to admission controllerdesign for high-speed networks. This admission controller explicitly computesthe equivalent bandwidth required to support each class of traffic,based on online observation of aggregate traffic flow obtained via NN-basedonline adaptive bandwidth estimation. The network buffer dynamics aremodeled as a nonlinear dynamical system and an adaptive NN algorithmis designed to estimate traffic flow. This adaptive NN approach does notrequire accurate information about network system dynamics or trafficrate. A novel weight tuning method was derived using rigorous mathematicalanalysis. In fact, the proposed adaptive estimator guarantees performance,as shown through the Lyapunov analysis.The bandwidth required to meet the QoS is then estimated and theavailable capacity is derived given the actual cell losses, latency, and theestimated traffic flow. This information, along with the intended PCR ofthe source to be admitted, predictive congestion indicator, and desiredQoS metrics, is used to construct the adaptive admission controller. Theadmission controller is expressed as a discrete-event state equation in“min”-“max” algebra and the dynamics of the buffer along with theadmission controller can be described as a hybrid system. The stability ofthe hybrid system is stated using nonsmooth Lyapunov function becausethe admission controller switches the operation of the buffer dynamics.The congestion and admission controllers operate at two different timescales.Results are presented to evaluate the performance of the proposedadmission controller with ON/OFF and bursty MPEG data. Based onthese results, it was concluded that the adaptive methodology generatesan accurate estimation of the bandwidth required and that needs to beassigned to the sources to meet the QoS. Accurately estimating the bandwidthonline along with the admission control will result in high networkutilization.