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Chapter 7Performance optimisation for the support of TCIS pa) G.711 PerformanceResults presented in Figure 7.16a revealed that the maximum number of streamssupported with a frame size of 10 ms is about 27 stations, which achieves a maximumsystem throughput at approximately 50% of the channel capacity (Figure 7.16b).Increasing up to three the number of frames per audio packet not only results in a gainof about 10% on system throughput, but also in an increased number of VoIP streamssupported (up to 45 stations).The maximum system capacity is yielded when header suppression is considered,achieving up to 53 VoIP connections, regardless of the frame size. However, themaximum system throughput of about 60% of the cc is only produced with a frame sizeof 10 ms. The other frame size achieves a reduced capacity at approximately 56% of thecc. This is because with a frame size of 30 ms, the VoIP packet size to be transmitted isof 248 bytes that requires an additional (8-byte) AAL5 header plus 32 bytes of paddingstuff. This extra padding is used to get an entire AAL5-PDU multiple of 48 bytes, whichresults in a waste of bandwidth and degrades the system throughput as indicated inFigure 7.16b.Mean Access Delay (ms)109876543210a) G.711: Mean Access Delay b) G.711: System ThroughputFs-10msFs-30msFs-30ms+HSFs-10ms+HS15 20 25 30 35 40 45 50 55umber of Active StationsSystem Throughput (%)646158555249464340Fs-30msFs-10ms+HSFs-30ms+HSFs-10ms40 43 46 49 52 55 58 61 64Offered Load (%)Figure 7.16 – Mean access delay and system throughput.Splitting tree algorithm and VoIP traffic (G.711 at 64 kbps).7-22