An Investigation of the Impact of Signal Strength on Wi-Fi Link ...

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enhancement on PHY and MAC efficiency. We obtained valuable data in terms <strong>of</strong> conducting measurement study in <strong>the</strong> area <strong>of</strong> WLAN from previous researchers’ experiences. Especially, it is important to use <strong>the</strong> same equipment for measurements and deployment to avoid gaps between measurements and practical AP deployment. Radio interference is a serious problem influencing WLAN performance due to heavy load <strong>of</strong> ISM band. Occasionally, it is difficult to avoid radio interference but maintaining an appropriate distance from <strong>the</strong> sources <strong>of</strong> interference is an important guideline for AP deployment. Base station placement is related to signal coverage, spectral efficiency, performance and cost <strong>of</strong> WLAN deployment. In <strong>the</strong> multiple-hops WLAN, overlapping APs would provide adequate signal coverage for seamless roaming. If adjacent APs use an overlapping channel, it causes co-channel interference and degrades WLAN performance. Therefore, both signal coverage and appropriate channel assignment are <strong>the</strong> goals <strong>of</strong> base station placement. A variety <strong>of</strong> transmission overheads would result in a large gap between <strong>the</strong> <strong>the</strong>oretical data rate and throughput. It seems that <strong>the</strong>re is some misunderstanding about <strong>the</strong> data rate and throughput. Although <strong>the</strong> IEEE 802.11g has a higher data rate (54 Mbps) than <strong>the</strong> IEEE 802.11b (11 Mbps), <strong>the</strong> IEEE 802.11b has lower overheads (80% overhead for <strong>the</strong> IEEE 802.11g, while only 55% overhead for <strong>the</strong> IEEE 802.11b). A lack <strong>of</strong> understanding about data rate and throughput may cause inappropriate capacity - 98 -
planning. Propagation measurement (as discussed in chapter 3) is <strong>the</strong> research methodology used in <strong>the</strong> study. To gain a realistic and accurate RSS and throughput <strong>of</strong> WLAN in <strong>the</strong> obstructed <strong>of</strong>fice environment, it is difficult to use ei<strong>the</strong>r an analytical modeling or computer simulation. Thus, propagation measurement seems to be an appropriate methodology for optimal AP placement. In chapter 4, we discussed <strong>the</strong> design and planning <strong>of</strong> propagation study. The equipment used in <strong>the</strong> experiments is shown in section 4.2 and appendix E. The measurement environment including layout and main partition material are described. The detailed AP and wireless adapter configuration and scenarios are discussed. The measurement results are discussed in chapter 5. Our experimental measurements were divided into four phases. The preliminary measurement was done to understand <strong>the</strong> characteristics <strong>of</strong> WLAN equipment and <strong>the</strong> throughput <strong>of</strong> different AP configurations. The preliminary measurement results showed that ad-hoc mode cannot provide sufficient signal coverage in <strong>the</strong> <strong>of</strong>fice under consideration. It requires one or more APs to boost up <strong>the</strong> signal. Extensive measurements were performed with an AP in phase 1. RSS and throughput were collected from different locations <strong>of</strong> AP placement. While a single AP could cover <strong>the</strong> entire <strong>of</strong>fice, throughput was unacceptable in many measurement points. We required an additional AP to <strong>of</strong>fer sufficient throughput. Moreover, phase 2 measurement was carried out at two locations (“E-3M” and “N-3M”) that had better - 99 -
Page 1 and 2:
An Investi
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2.3.5 Signal <stro
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Attestation of Aut
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Abstract Wireless local area networ
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List of Abbreviati
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List of Figures Fi
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List of Tables Tab
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Chapter 1 Introduction There has be
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WLAN performance evaluation and ana
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Chapter 2 Background and Related Wo
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The IEEE 802.11 networks have two o
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The coverage of a
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2.2.1 Physical Layer Figure 2.8 sho
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throughput significantly at higher
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DCF is designed to provide “best-
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Figure 2.11: Backof</strong
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modulation in [37]. According to si
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Figure 2.12: Net throughput <strong
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As highlighted in [46, 47], distanc
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2.3.2 Base Station Placement <stron
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gained an insight that this would m
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proposed to improve WLAN performanc
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specifications of
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dynamic and complicated. As argued
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In addition, we surveyed and review
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4.1 Performance Metrics A stopwatch
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Model: DWL-G132 Specification: Sta
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Figure 4.1: WY building layout. - 4
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Figure 4.2 shows wireless configura
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4.4.2 Wireless Adapter Configuratio
Page 61 and 62: 4.4.3 AP Operation Mode Two APs (D-
Page 63 and 64: meeting room with different distanc
Page 65 and 66: Scenario 4 In figure 4.12, two APs
Page 67 and 68: “(H-3.5m)F-H” is the</s
Page 69 and 70: Figure 4.16: Phase 2 measurement: A
Page 71 and 72: performed the prop
Page 73 and 74: The receiver sensitivity is an impo
Page 75 and 76: In table 5.1, the
Page 77 and 78: Ethernet connectio
Page 79 and 80: sufficient signal coverage and thro
Page 81 and 82: throughput decreases along with low
Page 83 and 84: In table 5.1, when RSS is larger th
Page 85 and 86: (for example, measurement point “
Page 87 and 88: AP at Position “R” Figure 5.13
Page 89 and 90: The measurement results indicated t
Page 91 and 92: 5.2.2 Throughput An</strong
Page 93 and 94: impact on RSS and throughput. Resul
Page 95 and 96: The throughput of
Page 97 and 98: The RSS of “WDS
Page 99 and 100: The average throughput of</
Page 101 and 102: The average data size of</s
Page 103 and 104: 5.6.1 SOHO Environment Due to <stro
Page 105 and 106: The following notes are needed to b
Page 107 and 108: when APs were placed at positions
Page 109 and 110: Real and accurate results for AP pl
Page 111: Chapter 7 Summary and Conclusions W
Page 115 and 116: deployment. Many WLANs are deployed
Page 117 and 118: placement in indoor wireless system
Page 119 and 120: Communications, vol. 2, no. 5, pp.
Page 121 and 122: [56] J. K. L. Wong, M. J. Neve, and
Page 123 and 124: eceived signal strength of<
Page 125 and 126: Appendix A Preliminary Experimental
Page 127 and 128: 2. AP Mode Measurement in t
Page 129 and 130: 7. The Ad-Hoc Mode Measurement on <
Page 131 and 132: Appendix B Phase 1 Experimental Res
Page 133 and 134: (P-1.5m)O-P 32.78 -86 193.6 0.453 N
Page 135 and 136: 3. Access Point at Position “E-3M
Page 137 and 138: (C-5m)C-D 21.63 -83 46.8 1.875 NLOS
Page 139 and 140: J 9.00 -44 8.2 10.703 LOS (J-1.5m)J
Page 141 and 142: 7. Access Point at Position “H”
Page 143 and 144: Figure B.2: Throughput map for AP a
Page 145 and 146: 60 40 20 0 -20 -40 -60 -80 -100 Acc
Page 147 and 148: (N-3m)N-O 15.00 -72 15.6 5.626 NLOS
Page 149 and 150: (C-3m)C-D 14.32 -74 13.6 6.453 NLOS
Page 151 and 152: Figure B.8: Throughput map for AP a
Page 153 and 154: 60 40 20 0 -20 -40 -60 -80 -100 Acc
Page 155 and 156: AP at A RX Position Left-Hand Area
Page 157 and 158: AP at L RX Position Left-Hand Area
Page 159 and 160: Appendix D Phase 3 Experimental Res
Page 161 and 162: TX at 2M from E-3M Data File: 153.6
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IEEE 802.11 b/g Access Point DWL-21
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Standards • IEEE 802.11g • IEEE
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1 Maximum wireless signal rate deri
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Wireless 108G Standards • 802.11b
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Wireless 108G Add 802.11g Wireless
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2.4GHz Omni-Directional 7dBi Indoor
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