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

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5.7 Summary The ad-hoc mode has <strong>the</strong> advantage in forming a WLAN quickly without AP involved. However, <strong>the</strong> preliminary measurement results showed that ad-hoc mode is inappropriate in <strong>the</strong> crowded <strong>of</strong>fice environment due to insufficient signal coverage. Unlike <strong>the</strong> ad-hoc mode, <strong>the</strong> infrastructure mode uses APs to repeat and boost signals. Phase 1 results showed that RSS has a significant impact on WLAN throughput. The throughput was changing with varying RSS. However, <strong>the</strong> throughput was not only affected by signal strength, but also distance, obstructions, and radio propagation environment. Fur<strong>the</strong>rmore, a single AP would have sufficient signal coverage in this <strong>of</strong>fice; however, <strong>the</strong> signal strength and throughput would be inadequate in some locations <strong>of</strong> <strong>the</strong> <strong>of</strong>fice. The positions “I” and “L” could have better throughput coverage for both <strong>the</strong> “right-hand side” and <strong>the</strong> “left-hand side” <strong>of</strong> <strong>the</strong> <strong>of</strong>fice than o<strong>the</strong>r positions. However, <strong>the</strong> average throughput at positions “I” and “L” was lower than <strong>the</strong> estimated throughput. On <strong>the</strong> o<strong>the</strong>r hand, <strong>the</strong> positions “A”, “G” and “E-3M” would have better throughput and signal coverage on <strong>the</strong> “left-hand side” <strong>of</strong> <strong>the</strong> <strong>of</strong>fice. The positions “J”, “R” and “N-3M” would provide adequate signal strength and throughput on <strong>the</strong> “right-hand side” <strong>of</strong> <strong>the</strong> <strong>of</strong>fice. Phase 1 results gave us an implication for using an additional AP to provide sufficient throughput and signal strength in <strong>the</strong> <strong>of</strong>fice. Phase 2 results showed that end-to-end throughput was affected by position <strong>of</strong> APs and configuration <strong>of</strong> APs. The results showed that inter-AP throughput was much better - 92 -
when APs were placed at positions “E-3M” and “N-3M”. Phase 3 results showed that using E<strong>the</strong>rnet as distribution system would have much better end-to-end performance than using wireless distribution system in multiple hops WLAN environment. The “WDS with AP mode” has <strong>the</strong> advantage <strong>of</strong> having multiple functions in AP deployment and being cable free. However, <strong>the</strong> throughput between BSSs may be inadequate under high traffic condition. Capacity estimation is an important part <strong>of</strong> network design. The number <strong>of</strong> concurrent users and characteristics <strong>of</strong> application would have significant influence on network capacity. <strong>An</strong> accurate estimation <strong>of</strong> WLAN capacity not only save cost, but also efficiency <strong>of</strong> spatial utilization and sufficient performance. Site survey is <strong>the</strong> first step in WLAN design. Performing site survey would collect important information in terms <strong>of</strong> real radio propagation environment (for example, sources <strong>of</strong> potential interference, possible locations <strong>of</strong> AP). Moreover, a single AP deployment is simpler than <strong>the</strong> deployment <strong>of</strong> multiple APs. During AP deployment, in addition to maintaining <strong>the</strong> distance from <strong>the</strong> sources <strong>of</strong> interference, channel assignment and security mechanism are important issues in terms <strong>of</strong> WLAN performance. Although different AP configurations would provide higher flexibility <strong>of</strong> WLAN design, an appropriate AP configuration would ensure sufficient performance. - 93 -
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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
Page 55 and 56: Figure 4.1: WY building layout. - 4
Page 57 and 58: Figure 4.2 shows wireless configura
Page 59 and 60: 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: The following notes are needed to b
Page 109 and 110: Real and accurate results for AP pl
Page 111 and 112: Chapter 7 Summary and Conclusions W
Page 113 and 114: planning. Propagation measurement (
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
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AP at L RX Position Left-Hand Area
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Appendix D Phase 3 Experimental Res
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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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