Wireless Ad Hoc and Sensor Networks

124 Wireless Ad Hoc and Sensor Networksretransmitted. Thus, when multiple packets are lost from a single windowof data, New-Reno can recover without a retransmission timeout, retransmittingone lost packet per round-trip time until all of the lost packetsfrom that window have been retransmitted.3.6.3 Performance MetricsTransmission delay, packet loss ratio, system power, and fairness wereused as the major measures of performance. The transmission delay isdefined as:Tc− ToTransmission delay = .(3.72)Twhere Tcand Todenote the time to complete the transmission by a source,with and without feedback, respectively.The network utilization is defined as:ocurrent throughputNetwork utilization = × 100%. (3.73)bandwidthPacket losses ck ( ) are defined as xk ( ) − x d , when xk ( ) > x d . The packetloss ratio (PLR) is defined as the total number of packets discarded at thereceiver because of buffer overflows divided by the total number of packetssent onto the network.total number of packets lossPLR = (3.74)total number of packetssent × 100%The system power is defined as,average throughputSystem power = (3.75)transmission delaySystem power metric encodes the throughput over delay as a singlemetric. Power appears to be a concise metric that can be used to comparedifferent congestion control schemes because, during congestion, higherthroughput results in higher delay.