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Base Station

Radio link between two remotely located Weather Stations using Wi-Fi Technology. - Sanjaya Gurung. Wi-Fi . Base Station. Remote Station. Objective. To set up wireless link between: - Discovery Park_WS and EESAT - GBC Weather Station and Natural Heritage Center

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Base Station

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  1. Radio link between two remotely located Weather Stations using Wi-Fi Technology - Sanjaya Gurung Wi-Fi Base Station Remote Station

  2. Objective • To set up wireless link between: - Discovery Park_WS and EESAT - GBC Weather Station and Natural Heritage Center • To collect data from all those stations via internet

  3. Introduction Wi-Fi • Wireless Fidelity: • - Wireless Technology operating in 2.4 GHz and 5 GHz frequency band • Wi-Fi lies in Microwave frequency range: • 0.3 – 300 GHz (UHF - SHF - EHF) • Wi-Fi covers IEEE 802.11 (WLAN Standard) • Standard: IEEE 802.11 b/g: 2.4 GHz • IEEE 802.11 a/n: 5 GHz

  4. EESAT-DP_WS, EESAT-NHC-GBC TWU

  5. EESAT – DP_WS

  6. NHC - GBC

  7. Radio Equipment • Ubiquity Networks Equipments NS2 • Nano Station Loco (Loco2) • NanoStation2 (NS2) • PowerStaion2 (PS2) Ethernet port Ext.Ant.

  8. Radio Equipment (Contd..) • Comparison between three radio equips. of Ubiquity Networks

  9. Radio Equipment (Contd..) • Data Rate Vs Receiver Sensitivity Data Rate Rx Sensitivity

  10. Line Of Sight propagation • Clear LOS Very good RSL Tx Rx No obstruction for direct wave in LOS path Best reception at Receiver side (best RSL)

  11. Line Of Sight propagation (Contd..) • Blocked LOS Very bad RSL Tx Rx Obstacle Other Obstacles: Buildings, high hills etc. lying between Tx and Rx antenna

  12. Line Of Sight Impairments Signal Attenuation Friis Transmission Formula Pr(dBm)=Pt(dBm) + Gt(dB) + Gr(dB) – {FSL(dB)+At(dB)+Ar(dB)} Transmitting antenna gain Receiving antenna gain Received power Transmitted power Total LOSS FSL(dB) = 20log(f) + 20log(d) + 32.44 MHz Km FSL = Free Space Loss At = Transmission line loss between Tx and Tx antenna Ar = Transmission line loss between Rx and Rx antenna

  13. Minimizing loss Signal Attenuation - Free Space Loss - Atmospheric Attenuation Free Space Loss FSL(dB) = 20log(f) + 20log(d) + 32.44 MHz Km f FSL d FSL

  14. Minimizing loss (Contd..) Atmospheric Attenuation e.g: Heavy rain of 150 mm/hr At low frequency f = 2.4 GHz, A = 0.02 dB/km At higher frequency f >= 10 GHZ, A = db/km f Atm. Attenuation e.g: Dense forest having wet leaves At low frequency f = 3.0 GHz, A = 0.4 dB/m So there’s a huge path loss if signal passes hundred meters through the forest.

  15. Radio Modeling EESAT – DiscoveryPark_WS

  16. Range Extension Transmission distance can be increased by following ways: • Choosing low frequency …. but f = 2.4 GHz fixed • Increasing Tx power • External high gain/highly directive antenna • Use of Repeater f d PTx d G d

  17. Repeater for longer transmission No sufficient power after this point R Tx 15 km 10 km Rx Repeater/ Signal Regenerator long link distance = 25 km (i.e. d > 15 km)

  18. Repeater for LOS blocked signal R Signal is blocked Repeater Tx Rx

  19. Minimizing Interference • Tx power • Channel selection • Polarization • Site selection

  20. Minimizing Interference (Contd..) • Tx power • - Minimize Tx power to avoid interfering another channel nearby Rx Sensitivity (Rxs) - 92 dBm 10 km A B Z PRx Pz nearby channel PTx 26 dBm(=400 mW) - 60 dBm - 85 dBm If Pz > Rxs … interference 23 dBm(=200 mW) - 70 dBm - 95 dBm If Pz < Rxs … no interference

  21. Minimizing Interference (Contd..) • Channel Selection • - Wisely selecting channel to reduce adjacent-channel interference Ch.1 Ch.6 Ch.11 Channel separation = 5 MHz 22 MHz Channel Bandwidth 3 non-overlapping (non-interfering) channels: Ch.1 = 2412 MHz Ch.6 = 2437 MHz Ch.11 = 2462 MHz

  22. Minimizing Interference (Contd..) • Polarization • - Proper antenna polarization setting will significantly reduce interference from neighbouring interfering channel H A B H V Y V X

  23. EESAT – DP_WS Test

  24. NS2 – Internet Connection Test EESAT_NS2 is connected to Router

  25. Research Questions • How to avoid Line Of Sight (LOS) problem? • What parameters should be taken into considerations while choosing sites? • How to select appropriate radio equipments • How to minimize interference: using highly directional antenna • Trade off between Gain and Complexity in Antenna Alignment

  26. Questions ? ?

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