DOWNLOAD MY Ph.D Thesis - UNAM

Chapter 7Performance optimisation for the support of TCIS pperformance is yielded with at least one CS per signalling frame when the splittingtree algorithm is used.• The maximum number of active stations analysed was up to 680 instead of 180 inorder to cover the point when saturation is experienced and very low-data ratestreams are delivered.A) Performance analysis for mixed trafficIn this section, a performance comparison is provided when the PRA and QoS (with afixed-rate connection) mechanisms are used for the transmission of mixed traffic. Thesimulations were carried out using only the splitting tree algorithm and the mixed trafficconsisted of 9.7 kbps of VoIP traffic and 32 kbps of Internet traffic, as described inSection 5.3.3.It can be seen in Figure 7.15a that the delay characteristics for both traffic types weresimilar for the PRA mechanism, which supports approximately 80 stations. On the otherhand, with QoS not only an extended number of VoIP connections can be supported (upto 320), but also the mean access delay is reduced and ranged between ≈ 1 or 2 msbefore the system becomes unstable.This reduction in access was because the number of MCI frames transmitted in the 3msperiod was increased to 4 and this helped the NIUs to achieve a faster interaction withthe INA, and also because VoIP traffic had precedence over IP traffic at the headend.a) Mixed Traffic: Mean Access DelayMean Access Delay (ms)50454035302520151050Internet & VoIPTrafficPRAInternet TrafficQoS-FxdrateVoIP Traffic40 80 120 160 200 240 280 320b) Mixed Traffic: System ThroughputSystem Throughput (%)5550454035302520151050Internet TrafficPRAPRAQoS-FxdrateVoIP TrafficQoS-Fxdrate40 80 120 160 200 240 280 320umber of Active Stationsumber of Active Stations7-19Figure 7.15 – Mean access delay and system throughput vs. No. of active stations.Splitting tree algorithm with mixed traffic.