Wireless Ad Hoc and Sensor Networks

106 Wireless Ad Hoc and Sensor NetworksS1 Link 1Link 1-1D1S2Link 2Link 1-2D2S3S4Link 3Link 4Router 1Link 0Router 2Link 1-3Link 1-4D3D4S5Link 5Link 6Link 1-5D5S6Link 1-6D6FIGURE 3.18End-to-end topology.shows the CLR with delay when additional delays were injected in thefeedback for different congestion control methods. From the figure, itis clear that the two-layer NN-based controller is more stable androbust compared to the adaptive ARMAX (rate-based) method whenfeedback delays were present. Here, the thresholding approach (witha value of 0.4) appears to be more stable as the rate adjustment dependsonly upon the magnitude of the buffer occupancy; however, duringcongestion, it performs unsatisfactorily in terms of CLR and delaycompared to the two-layer NN approach. Similar results were observedwhen more cross-traffic was used.Example 3.3.4: Fairness Test in the Presence of Cross-TrafficWe use two data traffic sources (elastic traffic), 1 VBR traffic source, and3 CBR traffic sources (inelastic). Elastic source rates are adjusted using thefeedback uk ( ) and fair share equation, Equation 3.15. The bottleneck buffersize is 25 cells. Congestion was created by cutting down the bandwidthof Link0 in Figure 3.18 as follows:Bandwidth of Link0 = 23,585 cells/sec,0 ≤ t < 3sec;= 18,868, cells/sec 3 ≤ t < 6sec;= 9,434 cells/sec, 6 ≤ t < 24sec; (3.34)= 18,868 cells/sec, 24 ≤ t < 27sec;= 23,585 cells/sec, 27 ≤ t.