Wireless Ad Hoc and Sensor Networks

Admission Controller Design for High-Speed Networks 159or bandwidth allocation (Fahmy et al. 1998). The bandwidth at any timeinstant k can be shared fairly among n sources asii( ) = Bw( k),nBw ki=∑1PCRPCRi(4.23)orii( ) = Bw( k),nBw ki=∑1MCRMCRi(4.24)orBw ( k)=iIn ( k)ni=∑1iIn ( k)iBw( k),(4.25)where PCRi, MCRi, and Ini( k)denote the PCR, mean cell rate, and thecurrent intended rate of the source “i,” respectively. By contrast, fairnesscriteria can be used to allocate the bandwidth.4.5 Admission ControlHere the available capacity (bandwidth), congestion indicator, and bufferavailability are utilized to admit new sources while maintaining QoS.Figure 4.4 shows the AC with its peripheral schemes for multimedia highspeednetworks. The AC adopts several inputs: available capacity, availableresource estimator, a congestion indicator, and a target packet/cellloss ratio and outputs a decision signal to indicate acceptance or rejectionof the new source. The available capacity is calculated by subtracting thecurrent bandwidth usage from all existing sources from the maximumavailable bandwidth of the physical link.Available_capacity = Smax − Bwi( k)(4.26)where n is the number of existing sources. This available capacity isassumed to be utilized for admitting new sources. Other call admissioncontrol methods use equivalent-capacity-based algorithm. Theni=∑1