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Chapter 5Upstream channel capacity and characterisation p5.4.2 Capacity in terms of active stationsHere, an analysis of the scalability of the cable network in terms of number of activestations is presented. For this analysis we have now considered a low trafficconfiguration per station to find out the maximum number of stations that could besupported. The analysis starts with a small network size of 20 stations, then we increasethe number of stations (in steps of 20) until the maximum network capacity has beenexceeded.The traffic load generated by each station was a single-Ethernet packet of 1518 byteswith an exponential distributed inter-arrival rate of 1 pk/sec or 12.14 kbps. Thesimulations were performed for each contention resolution algorithm.Figure 5.3 depicts a linear system throughput until the knee with respect to the numberof active stations. We can appreciate a slight increase in system performance whenusing the splitting tree algorithm. The maximum system throughput achieved was ≈61% and ≈ 65% of the cc for the exponential backoff algorithm and the splitting treealgorithm, respectively.Channel Capacity (%)10090807060504030201003 Mbps UpstreamEthernet frames (1518-bytes)12.14 Kbps kbps per stationBackoff & Tree AlgorithmThroughput-Backoff AlgorithmThroughput-Tree AlgorithmUtilisation - Backoff AlgorithmUtilisation - Tree Algorithm20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340umber of Active StationsFigure 5.3 - System throughput and utilisation vs. No. of active stations, exponentialbackoff and splitting tree algorithm.5-12