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Design WLAN Politeknik Telkom 2008
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Design WLAN Step to design WLAN : 1. Location Survey 2. Topology 3. Distance calculating 4. Antenna design 5. Towering 6. Power calculation 7. Radio choosing
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Location survey Tools : Spectrum analyzer GPS Map Laptop Netstumbler (www.netstumbler.com)
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Netstumbler
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Coverage area vs number acces point AP = C Total C(AP) dimana : AP: Number of Access Point C(AP): coverage area of AP (maximum power) C Total: total of coverage area
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Antenna design Parameter of antenna quality : Impedance SWR Gain S/N
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Antenna design Software : MMANA-GAL http://mmhamsoft.amateur-radio.ca/
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MMANA-GAL
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MMANA-GAL vertical lobe
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MMANA-GAL horisontal lobe
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MMANA-GAL impedance vs frequency
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MMANA-GAL SWR vs frequency
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Towering Model of tower :
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Power calculation
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Parameter of power calculation : RX signal level (dBm) Free Space Loss (dB) SOM (dB)
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Power calculation Input parameter Free Space Loss : Frequency (MHz) Distance
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Power calculation Input parameter Rx Signal Level : TX Power (dBm) TX Cable Loss (dB) TX Antena Gain (dBi) Free Space Loss (FSL) RX Antena Gain (dBi) RX Cable Loss (dB
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Power calculation Input parameter SOM : Rx signal level Rx sensitivity
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Power calculation Example : Frequency = 2,45 GHz Distance between 2 station = 16 miles TX Power = 9,9 dBm TX Cable Loss = 5,1 dB TX Antena Gain = 24 dBi RX Antena Gain = 20 dBi RX Cable Loss = 3 dB RX Sensitivity = 15 dBm
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Power calculation Calculate : a. Free Space Loss b. Rx Signal level c. SOM (System Operating Margin)
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Reuse frequency
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EIRP EIRP (Effective Isotropic Radiated Power) EIRP (dBm) = TX Power (dBm) – TX Cable Loss (dB) + TX Antena Gain (dBi)
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EIRP TX Power Power Gain / Loss Result ing Power Anten na gain Resulti ng EIRP Lega l ? 1 Watt (+30 dBm) -1 dB loss via 1 m coax + 29 dBm +6 dBi +35 dBm Yes 100 mW (+20 dBm) +14 dB Amplifier +34 dBm +8 dBi +42 dBm No 25 mW (+14 dBm) +14 dB Amplifier +28 dBm +8 dBi +36 dBm Yes
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EIRP Example : A directional antenna 24 dBi has EIRP 36 dBm, cable loss 3 dB. Tx Power?
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EIRP Answer : EIRP (dBm)= TX Power (dBm) – TX Cable Loss (dB) + TX Antena Gain (dBi) 36 = TX (dBm) – 3 + 24 TX (dBm) = 36+3-24 = 15 dBm = 30 mW
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Channel of Wifi IEEE 802.11b Channel ID Channel Frekuensi F(t) MHz Alokasi Frekuensi Tiap Pancar (MHz) F(t )- 11MHzF(t) + 11 MHz 1241224012423 2241724062428 3242224112433 4242724162438 5243224212443 6243724262448 7244224312453
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Channel of Wifi IEEE 802.11b 8244724362458 9245224412463 10245724462468 11246224512473 12246724562478 13247224612483 14247724662488
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WiFi 802.11b Modulation : DSSS Width of spectrum : 22 MHz
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802.11b spectrum
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Overlapping channel
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3 non overlapping channel : Channel 1 = 2412 MHz Channel 6 = 2437 MHz Channel 11 = 2462 MHz
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Overlapping channel 4 non overlapping channel : Channel 1 = 2412 MHz Channel 5 = 2432 MHz Channel 9 = 2452 MHz Channel 13 = 2472 MHz
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