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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
Chapter 6Optimisation of CRA using adaptive CSAs pIn addition, the CSA assigned on average 1.07 CSs (or 3.21 MSs) per successful requestas shown in Figure 6.6, instead of the optimum value of ‘2.718 MSs ≈ 0.89 CSs’.As a general observation, results presented for both CRAs showed that the optimalsystem performance depends on the Min. o. of CSs per signalling frame allocated. Forthe exponential backoff algorithm we found that the optimum value for this parameterwas 4 CSs for a maximum system throughput and 3 CSs for lower access delays. Forthe splitting tree algorithm this value appeared to be of 1 CSs.Average umber of ContentionSlots per Request7.57.03 Mbps Upstream6.564 Kbps kbps IPTree CRA6.05.55.04.54.0 CSs-03.5 CSs-13.0 CSs-22.5 CSs-32.0 CSs-41.5 CSs-51.0 CSs-60.518 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33umber of Active StationsFigure 6.6 – Average No. of CSs per reservation request vs. active stations.Splitting tree algorithm with a Simple-CSA.6-8
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I would like to thank all the peopl
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CHAPTER 6: OPTIMISATIO OF CRA ALGOR
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FIGURE 5.17 - SYSTEM THROUGHPUT VS.
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LIST OF TABLESTABLE 2.1 - NEXT GENE
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Chapter 1Introduction pBecause of h
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Chapter 1Introduction pA first step
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Chapter 1Introduction passumption i
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Chapter 1Introduction ppolynomial b
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Chapter 1Introduction pIn general,
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Chapter 1Introduction pminislots to
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Chapter 1Introduction pThe authors
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Chapter 1Introduction prate access
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Chapter 1Introduction p1.4 Overview
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Chapter 2OVERVIEW OF CURRENT CATVNE
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Chapter 2Overview of current CATV n
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Chapter 3THE DVB/DAVIC PROTOCOL3.1
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Chapter 3The DVB/DAVIC protocol pEu
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Chapter 3The DVB/DAVIC protocol pMA
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Chapter 3The DVB/DAVIC protocol pTh
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Chapter 3The DVB/DAVIC protocol p3.
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Chapter 4Simulation and analytical
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Chapter 7Performance optimisation f
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aChapter 7Performance optimisation
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Chapter 8Final conclusions p8.2 Gen
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Chapter 8Final conclusions pWe have
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Chapter 8Final conclusions pperform
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Chapter 8Final conclusions pslots i
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Chapter 8Final conclusions pfocused
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Chapter 8Final conclusions preserva
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Chapter 8Final conclusions pbandwid
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Chapter 8Final conclusions pThe opt
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Chapter 8Final conclusions p8.4 Fut
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Chapter 8Final conclusions pApplica
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Chapter 8Final conclusions pTCIS st
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Referencesp[17] I. Cidon, and M. Si
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Referencesp[50] N. F. Huang, C. A.
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Referencesp[85] V. Rangel, R. Edwar
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Referencesp[112] K. Sriram, “Meth
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APPEDIX A: GLOSSARYAALABRADSLATMBCB
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Appendix AGlossary pkbpsLANLLCMACMA
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Appendix AGlossary pUSBUWVDSLVoDVoI
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Appendix BProtocol stack and packet
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Appendix BProtocol stack and packet
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APPENDIX C: D VERIFICATION TEST FOR
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Appendix D Verification test p209 2
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Appendix EResults for a 6 Mbps upst
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Appendix FGuide to CD-ROM p IEEE802
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