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Chapter 6Optimisation of CRA using adaptive CSAs pHaving a short value for the Min. o. of CSs per signalling frame, (e.g. 1 or even 2CSs), most of the bandwidth is allocated to the reservation access region, producing anincrease in the overall system performance. Larger values for this parameter (above 2CSs) are not required, because this algorithm efficiently resolves collisions. Defining alarge value for this parameter may result in many contention slots being unused, wastingbandwidth resources and therefore achieving a low system performance.Conversely, having at least 0 CSs per signalling frame may cause (on heavy loads)those stations with new incoming packets to wait until all the previous reservationrequests have been granted. Then, compete for contention access among all waitingstations. This increases considerably both the risk of collisions and the CRGC, resultingalso in a reduced performance.From Figure 6.5 the maximum system throughput obtained by using this algorithm wasapproximately 62%. The remaining bandwidth of 0.6%, (to get the 62.6% as estimated)was attributed, in this case, because the mean Pk size (registered by simulations) was of374 bytes with 8.42 slots requested per packet.System Throughput (%)6562595653504744413835CSs-0CSs-1CSs-2CSs-3CSs-4CSs-5CSs-63 Mbps Upstream64 Kbps kbps IPTree CRA18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33umber of Active StationsFigure 6.5 – System throughput vs. No. of active stations.Splitting tree algorithm with a Simple-CSA.6-7