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

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RTS/CTS cannot resolve hidden nodes problem completely. A new MAC layer schema: <strong>the</strong> conservative CTS reply (CCR) can be used to solve <strong>the</strong> above problem [5]. Figure 2.13: Net throughput with 802.11b including RTS/CTS [17]. <strong>An</strong> experimental measurement was conducted to investigate effective TCP throughput and used analytical modeling to find MAC throughput in [45]. The experimental study indicated that <strong>the</strong> MAC throughput is around 15% to 20% higher than effective TCP throughput. The results showed that effective throughput is increased from 47% to 82% when data rate shifts from 11 Mbps to 1 Mbps. - 22 -
As highlighted in [46, 47], distance, buffer size and fragmentation have important effects on WLAN throughput. With increasing distance, signal power is attenuated gradually and packet loss rate is increased. The data buffer also plays a significant role in WLAN. The function <strong>of</strong> data buffer is used to keep packets which are from high layer protocols (e.g. network, TCP layer). Packets will be dropped when <strong>the</strong> buffer is full, thus, smaller buffer size would result in <strong>the</strong> lower throughput. Appropriate buffer size is between 64000-128000 bits in <strong>the</strong> IEEE 802.11b networks [10]. Small fragmentation (packet size) would have better throughput in higher radio interference environment. However, large fragmentation would provide higher throughput in a good radio propagation environment. As mentioned in [48], <strong>the</strong> low height <strong>of</strong> antenna and short distance between a receiver and a transmitter would cause significant path loss. The radio propagation <strong>of</strong> WLANs would be limited within quite short ranges because <strong>of</strong> <strong>the</strong> Fresnel zone (as shown in figure 2.14). <strong>An</strong>astasi et al. [49] pointed out that only when <strong>the</strong> height <strong>of</strong> both laptops is 1 meter from <strong>the</strong> ground and <strong>the</strong> distance between two laptops is more than 33 meters, <strong>the</strong> Fresnel Zone will touch <strong>the</strong> ground (refer figure 2.14). If <strong>the</strong> height <strong>of</strong> both laptops is ei<strong>the</strong>r 1.5 or 2 meters, <strong>the</strong> Fresnel zone will only touch <strong>the</strong> ground when <strong>the</strong> distance between laptops is greater than 73 meters and 131 meters. The communication range would increase if <strong>the</strong> Fresnel zone is kept at a level away from <strong>the</strong> ground. In addition, when any object (for example, table, chair and <strong>the</strong> ground) is located in <strong>the</strong> Fresnel zone, it results in diffraction and degrades <strong>the</strong> signal power. Therefore, <strong>the</strong> height <strong>of</strong> antenna has a significant impact on throughput in <strong>the</strong> IEEE 802.11b network. The throughput - 23 -
Page 1 and 2: An Investi
Page 3 and 4: 2.3.5 Signal <stro
Page 5 and 6: Attestation of Aut
Page 7 and 8: Abstract Wireless local area networ
Page 9 and 10: List of Abbreviati
Page 11 and 12: List of Figures Fi
Page 13 and 14: List of Tables Tab
Page 15 and 16: Chapter 1 Introduction There has be
Page 17 and 18: WLAN performance evaluation and ana
Page 19 and 20: Chapter 2 Background and Related Wo
Page 21 and 22: The IEEE 802.11 networks have two o
Page 23 and 24: The coverage of a
Page 25 and 26: 2.2.1 Physical Layer Figure 2.8 sho
Page 27 and 28: throughput significantly at higher
Page 29 and 30: DCF is designed to provide “best-
Page 31 and 32: Figure 2.11: Backof</strong
Page 33 and 34: modulation in [37]. According to si
Page 35: Figure 2.12: Net throughput <strong
Page 39 and 40: 2.3.2 Base Station Placement <stron
Page 41 and 42: gained an insight that this would m
Page 43 and 44: proposed to improve WLAN performanc
Page 45 and 46: specifications of
Page 47 and 48: dynamic and complicated. As argued
Page 49 and 50: In addition, we surveyed and review
Page 51 and 52: 4.1 Performance Metrics A stopwatch
Page 53 and 54: 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 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 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
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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
Page 163 and 164:
IEEE 802.11 b/g Access Point DWL-21
Page 165 and 166:
Standards • IEEE 802.11g • IEEE
Page 167 and 168:
1 Maximum wireless signal rate deri
Page 169 and 170:
Wireless 108G Standards • 802.11b
Page 171 and 172:
Wireless 108G Add 802.11g Wireless
Page 173:
2.4GHz Omni-Directional 7dBi Indoor
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