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Chapter 7Performance optimisation for the support of TCIS pB) Performance analysis for the splitting tree algorithmSimulations with the splitting tree algorithm, Figure 7.10a indicates that for pure VoIPtraffic optimum system performance may be obtained using the unsolicited grantmechanism. With this mechanism the network capacity is considerably increased to thehighest figure for this research at ≈ 170 connections. This equates to approximately 53%of the available channel capacity and produces mean access delays below 7 ms. Hence,this mechanism has been shown to match the requirements of CBR. The othermechanisms, with the exception of CPG, support the same number of connections equalto ≈ 145.Results for mixed traffic are shown in Figure 7.10b. It should be noted that discussionof the UGS mechanism is absent here since in a mixed traffic situation the constant bitrate requirements cannot be satisfied using this technique. From the figure we can alsoappreciate that the enhanced-reservation-request mechanisms are more effective withhigh traffic loads. For example, for traffic loads above 55% of the cc, the maximumnumber of Internet connections that can be supported was ≈ 45 with the CPGmechanism, compared with ≈ 41 with the PRA mechanism. For delay sensitiveapplications the number of connections supported resulted in ≈ 40, regardless of themechanism utilised.Mean Access Delay (ms)30027525022520017515012510075502503 Mbps Uptream9.6 9.7 Kbps kbps VoIPSpliting Splitting Tree CRAa) VoIP Traffic b) Mixed TrafficCPGEPRAPRA70 80 90 100 110 120 130 140 150 160 170umber of Active StationsPGUGS7-123 Mbps UpteamMixed TrafficSplitting Spliting Tree CRAPRAEPRACPG37 38 39 40 41 42 43 44 45 46 47umber of Active StationsFigure 7.10 – Bandwidth consumed by collisions vs. No. of active stations for VoIP andmixed traffic. Splitting tree algorithm with enhanced-reservation-request mechanisms.PG