Wireless Ad Hoc and Sensor Networks

Admission Controller Design for High-Speed Networks 157In the next section, the estimated traffic accumulation is used to obtainthe current bandwidth usage and the future bandwidth requirement forall classes of traffic. Finally, the aggregate bandwidth required to meet theestimated traffic and target QoS will be derived for all classes of trafficfor the next measurement interval. In the next section, using the aggregatebandwidth along with the physically available one, the available bandwidthis obtained and allocated fairly among sources.4.4 Bandwidth Estimation, Allocation, and AvailableCapacity DeterminationAssume that all the packets are transmitted at regularly spaced intervalsto the buffer and consider that at the moment the new measurementinterval starts, a new aggregate bandwidth value is being assigned. If thetraffic that is being accumulated at the next measurement interval isknown, then the additional bandwidth required to meet the packet/cellloss requirement can be determined as:( f ˆ( x( k)) − fˆ( x ( k−1)))∆Bw( k)=T(4.18)where ∆Bw( k)is the additional bandwidth required to process the newdata, f ˆ( x( k))and ˆ( ( )) are the traffic estimates at the instants k andk−1, respectively. Further, the following equation relates the additionalbandwidth required to satisfy the target CLR as:f x k− 1∆Bw kActual cell losses( ) =TCLR * T(4.19)where TCLR represents the target or desired packet/cell loss ratio. Inorder to ensure that sufficient bandwidth is assigned to meet the delayrequirement in the next measurement interval, the bandwidth requiredto meet the delay is given byxk ( )∆Bw( k)= τ(4.20)where xk ( ) is the current buffer occupancy and τ the target call transferdelay.Equation 4.18 shows that additional bandwidth needs to be assigned totransmit the data queued in the ingress switch buffer to its destination.