Wireless Ad Hoc and Sensor Networks

Admission Controller Design for High-Speed Networks 169CLR10 −332.5PCR2Two-layer NNTwo-layer NN1.5with over allocationTwo-layer NN1with buffer control0.5Target CLR026 28 30 32 34 36 38 40 42×Buffer length (cells)20Delay (msec)15PCR10Two-layer NNTwo-layer NNwith over allocation5Two-layer NNwith buffer controlTarget CLR026 28 30 32 34 36 38 40 42Buffer length (cells)FIGURE 4.9Prediction error at Switch 1 for several schemes in which the cell loss ratio and delay aresmall when peak cell rate is used.PCR of all the sources, then all sources are admitted irrespective of themethod used. However, a large amount of bandwidth is wasted when thePCR-based scheme is used. Although a small prediction error similarly isobserved (blue), the selection of overallocation factor is done by trial anderror whereas NN scheme in “red” generated a small error.In Figure 4.9 and Figure 4.10, the CLR and transmission delay are givenfor several schemes in which the CLR and delay are small when PCR isused, compared to all other schemes. Although the two-layer NN methodproduces slightly higher CLR and delay than PCR, it meets the target QoSrequirement.In the second case, when the available bandwidth is not equal to thePCR of all sources, several new sources are rejected by the other methods,whereas our adaptive method admitted more sources, resulting in highnetwork utilization. The improved performance is the result of accuratebandwidth estimation. Here, the sources are queued until the sufficientbandwidth is available. Figure 4.11 shows the comparison between theavailable bandwidth’s being PCR of all the sources and its being PCR ofone ON/OFF source at Switch 2. As expected, fewer sources are admitted.