DOWNLOAD MY Ph.D Thesis - UNAM

More documents

Recommendations

Info

Chapter 8Final conclusions pIn the multiple node scenario analysis, the DVB/DAVIC protocol proved again veryinefficient due to the excessive number of reservation requests, collisions,retransmissions and DVB MAC and PHY protocol overheads.Table 8.1 presents the maximum system performance and bandwidth characterisationsfor the six different packet sizes considered.In this scenario the maximum system throughput achieved was ≈ 34.5% of the cc whenpacket sizes of 64 bytes were considered. Increasing the packet size can significantlyimprove the performance with maximum system throughput up to ≈ 65% of the cc.Results for channel utilisation were higher than for throughput results with a deviationof 54% to 24% for minimum and maximum size Ethernet packets, respectively. Themajor source of performance inefficiency was the extensive protocol overhead involvedat the MAC (ATM encapsulation) and PHY (FEC) layers, which can be as high as 35%and 23% of the upstream channel capacity for 64-byte and 1518-byte packets,respectively. A second significant factor degrading system performance is thebandwidth consumed for the transmission of successful requests, which accounted for ≈12% when minimum size Ethernet packets are transmitted. Furthermore, collisions alsocontribute to system inefficiency with up to 8% of the cc.Chapter 6 introduced three novel contention slots allocators (Simple-CSA, Variable-CSA and Fixed-CSA). These techniques were studied because the DVB/DAVICprotocol specification did not define any mechanism for the allocation of contentionTable 8.1 – Summary of maximum system performance andbandwidth characterisation.BandwidthPacket Size (bytes)Characterisation (%) 64 128 256 512 1024 1518Maximum Throughput 34.5 51.3 56.2 62.9 63.4 64.6Maximum Utilisation 89.1 90.1 90.5 89.8 88.9 88.5Deviation 54.6 38.8 34.3 26.9 25.5 23.9Supported Streams 25.0 48.0 54.0 60.0 60.0 63.0Request Collided 8.3 4.1 1.3 0.4 0.1 0.1Request Successful 11.8 8.5 4.6 2.6 1.3 0.9MAC&PHY overhead 34.5 26.2 28.4 23.9 24.1 23.0Bandwidth unused 10.9 9.9 9.5 10.2 11.1 11.58-7
Chapter 8Final conclusions pslots into the signalling frames. Here it is most likely that unscheduled slots are assignedto contention access).In an analysis for the IEEE 802 protocol (reported in [94] and [96]) it was pointed outthat the performance of multi-access reservation protocols heavily depends on theoverall structure and the capacity assigned to the reservation and contention accessregions. Therefore, in this chapter we have demonstrated that the performance of theDVB/DAVIC can be improved if these techniques are used.The first strategy studied was the Simple-CSA. Here the minimum number of contentionslots per signalling frame was ranged from 1 to 7 using the exponential backoffalgorithm and from 0 to 6 using the splitting tree algorithm. When the exponentialbackoff algorithm was used it was found that by allocating at least 3 or 4 CSs persignalling frame, not only lower access delays were yielded but also an increase insystem throughput was achieved. Larger values (e.g. 5, 6 and 7 CSs) caused a waste ofbandwidth because more CSs are allocated than the number of CSs required to resolvecollisions. Similarly, a low system performance is also obtained when short values (e.g.1 and 2 CSs) are considered. Here the system inefficiency is attributed to an increasednumber of collisions, due to a reduction of slots for contention access. Results for thesplitting tree algorithm revealed that optimal system performance is achieved byallocating at least 1 CS per signalling frame. The increase in performance is achievedbecause an extra slot is reserved in the next signalling frame when a collision happens.This extra slot (is split into three minislots that carry shortened reservation requests) andis used only by the stations that caused the collision, so that new arrivals do not competewith backlogged stations for contention access. The increase in system throughput isachieved because by allocating at lest 1 CSs in each signalling frame, more slots can bescheduled for data transmissions.8-8
Page 6 and 7:
I would like to thank all the peopl
Page 10:
CHAPTER 6: OPTIMISATIO OF CRA ALGOR
Page 13 and 14:
FIGURE 5.17 - SYSTEM THROUGHPUT VS.
Page 15 and 16:
LIST OF TABLESTABLE 2.1 - NEXT GENE
Page 17 and 18:
Chapter 1Introduction pBecause of h
Page 19 and 20:
Chapter 1Introduction pA first step
Page 21 and 22:
Chapter 1Introduction passumption i
Page 23 and 24:
Chapter 1Introduction ppolynomial b
Page 25 and 26:
Chapter 1Introduction pIn general,
Page 27 and 28:
Chapter 1Introduction pminislots to
Page 29 and 30:
Chapter 1Introduction pThe authors
Page 31 and 32:
Chapter 1Introduction prate access
Page 33 and 34:
Chapter 1Introduction p1.4 Overview
Page 35 and 36:
Chapter 2OVERVIEW OF CURRENT CATVNE
Page 37 and 38:
Chapter 2Overview of current CATV n
Page 39 and 40:
Page 41 and 42:
Page 43 and 44:
Page 45 and 46:
Page 47 and 48:
Page 49 and 50:
Page 51 and 52:
Page 53 and 54:
Page 55 and 56:
Chapter 3THE DVB/DAVIC PROTOCOL3.1
Page 57 and 58:
Chapter 3The DVB/DAVIC protocol pEu
Page 59 and 60:
Chapter 3The DVB/DAVIC protocol pMA
Page 61 and 62:
Chapter 3The DVB/DAVIC protocol pTh
Page 63 and 64:
Page 65 and 66:
Page 67 and 68:
Chapter 3The DVB/DAVIC protocol p3.
Page 69 and 70:
Chapter 4Simulation and analytical
Page 71 and 72:
Page 73 and 74:
Page 75 and 76:
Page 77 and 78:
Page 79 and 80:
Page 81 and 82:
Page 83 and 84:
Page 85 and 86:
Page 87 and 88:
Page 89 and 90:
Page 91 and 92:
Page 93 and 94:
Page 95 and 96:
Page 97 and 98:
Page 99 and 100:
Page 101 and 102:
Page 103 and 104:
Page 105 and 106:
Chapter 5Upstream channel capacity
Page 107 and 108:
Page 109 and 110:
Page 111 and 112:
Page 113 and 114:
Page 115 and 116:
Page 117 and 118:
Page 119 and 120:
Page 121 and 122:
Page 123 and 124:
Page 125 and 126:
Page 127 and 128:
Page 129 and 130:
Page 131 and 132:
Page 133 and 134:
Page 135 and 136:
Page 137 and 138:
Page 139 and 140:
Page 141 and 142:
Page 143 and 144:
Chapter 6Optimisation of CRA using
Page 145 and 146:
Page 147 and 148:
Page 149 and 150:
Page 151 and 152:
Page 153 and 154:
Page 155 and 156:
Page 157 and 158:
Page 159 and 160:
Page 161 and 162:
Page 163 and 164: Chapter 6Optimisation of CRA using
Page 171 and 172: Chapter 7PERFORMANCE OPTIMISATION F
Page 173 and 174: Chapter 7Performance optimisation f
Page 201 and 202: aChapter 7Performance optimisation
Page 209 and 210: Chapter 8Final conclusions p8.2 Gen
Page 211 and 212: Chapter 8Final conclusions pWe have
Page 213: Chapter 8Final conclusions pperform
Page 217 and 218: Chapter 8Final conclusions pfocused
Page 219 and 220: Chapter 8Final conclusions preserva
Page 221 and 222: Chapter 8Final conclusions pbandwid
Page 223 and 224: Chapter 8Final conclusions pThe opt
Page 225 and 226: Chapter 8Final conclusions p8.4 Fut
Page 227 and 228: Chapter 8Final conclusions pApplica
Page 229 and 230: Chapter 8Final conclusions pTCIS st
Page 231 and 232: Referencesp[17] I. Cidon, and M. Si
Page 233 and 234: Referencesp[50] N. F. Huang, C. A.
Page 235 and 236: Referencesp[85] V. Rangel, R. Edwar
Page 237 and 238: Referencesp[112] K. Sriram, “Meth
Page 239 and 240: APPEDIX A: GLOSSARYAALABRADSLATMBCB
Page 241 and 242: Appendix AGlossary pkbpsLANLLCMACMA
Page 243 and 244: Appendix AGlossary pUSBUWVDSLVoDVoI
Page 245 and 246: Appendix BProtocol stack and packet
Page 247 and 248: Appendix BProtocol stack and packet
Page 249 and 250: APPENDIX C: D VERIFICATION TEST FOR
Page 251 and 252: Appendix D Verification test p209 2
Page 253 and 254: Appendix EResults for a 6 Mbps upst
Page 255: Appendix FGuide to CD-ROM p IEEE802
show all

DOWNLOAD MY Ph.D Thesis - UNAM

Create successful ePaper yourself

Delete template?

Save as template?