Wireless Ad Hoc and Sensor Networks

Congestion Control in ATM Networks and the Internet 113where the packet losses are defined because of overflows asck ( ) = max( 0, ek ( )). The dynamics of the buffer can be written in terms ofthe buffer occupancy errors as:ek ( + 1) = Sat [ f( x( k)) − x + Tu( k) + d( k)].pd(3.39)The objective is to select a suitable traffic rate uk ( ), such that the availablebandwidth can be exploited up to its peak packet rate (PPR).3.4.2 End-to-End Congestion Control SchemeDefine the traffic rate input, uk ( ), as1uk ( ) = (T x d − f ( x ( k )) + k v e ( k ))(3.40)where k v is a diagonal gain matrix, f( x( k))is the traffic accumulation atthe bottleneck link/egress buffer, and T is the measurement interval. Then,the error in buffer length system becomesek ( + 1) = Sat[ kek ( ) + dk ( )]pv(3.41)If an adaptive estimator is employed to estimate the bottleneck queueand hence the traffic accumulation, f ˆ(), ⋅ at the destination buffer, then thebuffer-length error is written as:ek ( + 1 ) = Sat[ kek ( ) + fˆ() ⋅ + dk ( )]pv(3.42)Then uk ( ) will be defined as1uk ( ) = (T x d − f ˆ( x ( k )) + k v e ( k ))(3.43)The proposed rate-based methodology uses packet-arrival rate at theingress node and packet-arrival rate at the egress node to estimate thenetwork traffic accumulation or flow. The estimated value and the packetaccumulation at egress node are together used to compute the rate uk ( ) bywhich the source has to reduce or increase its rate. If uk ( ) is a positivevalue, it indicates that the buffer space is available and the sources canincrease their rates, whereas if uk ( ) is negative, it indicates that there are