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Chapter 7Performance optimisation for the support of TCIS pIn terms of throughput, Figure 7.8 shows the maximum system throughput achieved byeach mechanism. The PRA and RR achieve under ≈38% cc for VoIP traffic(Figure 7.8a) and under 47% of the cc for mixed traffic (Figure 7.8b). This is due tocontinuous contention access. The maximum achievable throughput is produced by theCPG mechanisms, which can be up to 52% and 61% of the channel capacity for VoIPand mixed traffic, respectively.All of the enhanced mechanisms achieve a higher system throughput than the PRAmechanism, lowering collision risk and reducing (or even avoiding) contention accesstransmissions, thereby allocating more bandwidth to the reservation access region.System Throughput (%)565350474441383532292623203 Mbps Upstream9.7 Kbps kbps VoIPBackoff CRAa) Voice TrafficCRRRRPRACPGPGEPRA70 85 100 115 130 145 160 175umber of Active Stations6260585654525048464442403 Mbps UsptreamMixed TrafficBackoff CRAb) Mixed TrafficCPGPG & EPRAPRACRR31 33 35 37 39 41 43 45 47umber of Active StationsRRFigure 7.8 – System throughput vs. No. of active stations for VoIP and mixed traffic.Exponential backoff algorithm with enhanced-reservation-request mechanisms.7-10