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Chapter 6Optimisation of CRA using adaptive CSAs p6.2.2 Simple-CSA: Performance optimisation of the use of contentionslotsIn order to demonstrate the effects of the use of a simple contention slot allocator, anInternet traffic situation was analysed. The mean data rate per active station was set to64 kbps. The simulations were performed using both contention resolution algorithms.The Min. o. of CSs per signalling frame was ranged from 1 to 7 CSs for theexponential backoff algorithm. For the splitting tree algorithm this parameter wasranged from 0 to 6 CSs.6.2.2.1 Exponential backoff algorithm performance using a Simple-CSAWe have used Equation 4.43, (introduced in Section 4.4.3) to estimate the maximumupstream throughput for the exponential backoff algorithm.Smax_ exp_ backoffPksize=Pk + eCSsslotsThe term ‘eCSs’ in this equation, indicates that on average we need ‘e(=2.718)’contention slots to transmit a reservation request successfully, in order to get theoptimum system throughput, as suggested in [10]. Idles occur with a probability of 1/e ≈0.368, success occurs with a probability of 1/e and collisions occur with a probability of1-2/e ≈ 0.264. Thus in summary, 1 CSs for idle, 1 CSs for success and 0.718 CSs forcollisions are needed.On average the packet size for Internet traffic is 368.1 bytes [53], and the number ofdata slots requested per packet is 8.3. So using Equation 4.43 we have,Smax368.1== 52.2% ≈ 52%8.3*64 + 2.718*64Therefore, the maximum theoretical system throughput that can be achieved is ≈ 52%when large numbers of stations are transmitting.6-3
Chapter 6Optimisation of CRA using adaptive CSAs pFrom simulation results presented in Figures 6.1 and 6.2, it is apparent that with at least3 or 4 CSs per signalling frame (represented by CSs-3 and CSs-4 in these figures), notonly the lowest access delays are yielded, but also the highest system throughput isachieved.Mean Access Delay (ms)50045040035030025020015010050CSs -1CSs -2CSs -3CSs -4CSs -5CSs -6CSs -73 Mbps Upstream64 Kbps kbps IPBackoff CRA018 19 20 21 22 23 24 25umbe r of Active StationsFigure 6.1 – Mean access delay vs. No. of active stations.Exponential backoff algorithm with a Simple-CSA.System Throughput (%)52CSs -150CSs -248CSs -3CSs -446CSs -5CSs -644CSs -742403 M bps Upstream3864 Kbps kbps IPBackoff CRA3618 19 20 21 22 23 24 25 26 27 28 29 30umbe r of Active StationsFigure 6.2 – System throughput vs. No. of active stations.Exponential backoff algorithm with a Simple-CSA.6-4
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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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