Design WLAN

Politeknik Telkom 2008

Design WLAN

Step to design WLAN :1. Location Survey2. Topology3. Distance calculating4. Antenna design5. Towering6. Power calculation7. Radio choosing

Location survey

Tools :Spectrum analyzerGPSMapLaptopNetstumbler (www.netstumbler.com)

Netstumbler

Coverage area vs number acces point

AP = C Total C(AP) dimana :AP : Number of Access PointC(AP) : coverage area of AP (maximum

power)C Total : total of coverage area

Antenna design

Parameter of antenna quality :ImpedanceSWRGainS/N

Antenna design

Software :

MMANA-GAL

http://mmhamsoft.amateur-radio.ca/

MMANA-GAL

MMANA-GAL vertical lobe

MMANA-GAL horisontal lobe

MMANA-GAL impedance vs frequency

MMANA-GAL SWR vs frequency

Towering

Model of tower :

Power calculation

Power calculation

Parameter of power calculation :RX signal level (dBm)Free Space Loss (dB)SOM (dB)

Power calculation

Input parameter Free Space Loss :Frequency (MHz)Distance

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

Power calculation

Input parameter SOM :Rx signal levelRx sensitivity

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

Power calculation

Calculate :a. Free Space Lossb. Rx Signal levelc. SOM (System Operating Margin)

Reuse frequency

EIRP

EIRP (Effective Isotropic Radiated Power)

EIRP (dBm) = TX Power (dBm) – TX Cable Loss (dB) + TX Antena Gain (dBi)

EIRP

TX Power

Power Gain / Loss

Resulting

Power

Antenna gain

Resulting EIRP

Legal ?

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

EIRP

Example :A directional antenna 24 dBi has EIRP 36

dBm, cable loss 3 dB. Tx Power?

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

Channel of Wifi IEEE 802.11b

Channel ID

Channel Frekuensi F(t) MHz

Alokasi Frekuensi Tiap Pancar (MHz)

F(t )- 11MHz F(t) + 11 MHz

1 2412 2401 24232 2417 2406 24283 2422 2411 24334 2427 2416 24385 2432 2421 24436 2437 2426 24487 2442 2431 2453

Channel of Wifi IEEE 802.11b

8 2447 2436 2458

9 2452 2441 2463

10 2457 2446 2468

11 2462 2451 2473

12 2467 2456 2478

13 2472 2461 2483

14 2477 2466 2488

WiFi 802.11b

Modulation : DSSSWidth of spectrum : 22 MHz

802.11b spectrum

Overlapping channel

Overlapping channel

3 non overlapping channel :Channel 1 = 2412 MHzChannel 6 = 2437 MHzChannel 11 = 2462 MHz

Overlapping channel

4 non overlapping channel :Channel 1 = 2412 MHzChannel 5 = 2432 MHzChannel 9 = 2452 MHzChannel 13 = 2472 MHz