1. The essentials of building wireless networks
Sebastian Büttrich, NSRC
edit: March

2. Some essential elements
Radio physics
Site survey
IP Planning (subnet! subnet! subnet!)
Link budget
Antennas … (sectorize! sectorize! sectorize!)
Layer thinking

3. Site Survey
No matter what network you are building, core infrastructure or edge access, a site survey is mandatory
Results of the site survey are the basis for your technology and process decisions

4. Site Survey A site survey includes
Spectrum Analysis, wireless scan – check for conflicts and interference
Power/Electricity conditions
Wired network conditions
Environmental conditions
Social / human factors … who are my neighbours?
Documentation of everything!

5. Site Survey
think holistic! networking is more than ping!

6. Link Budget
A link budget is mandatory for all long links – point to point, point to multipoint
Not relevant for a “hotspot”
A link budget is simply adding up all gains and losses (in dB!) and telling you if what you have in the end is enough for a working link

7. Link Budget Radio output TX Radio sensitivity RX Cables on both sides
Antennas on both sides
And a lot of Free space FSL [dB]= C + 20 * Log(D) + 20 * Log(F)
D distance, and F frequency [MHz]. C = 36.6 if D [miles] / 32.5 if D [kilometers]
(Hopefully no) amplifiers

8. Complete link budget – ex. 1
Transmit output dBm
Cable + Connectors dB
Antenna TX dBi
FSL (50 km / 31.1 miles at 2.4 Ghz) dB
Antenna RX dBi
Cable + Connectors dB
Receive Sensitivity dBm (subtract!)
TOTAL dB margin

9. Complete link budget – ex. 1

10. Complete link budget – ex. 2
Transmit output dBm
Cable + Connectors dB (low quality cabling)
Antenna TX dBi (an omni)
FSL (1 km / miles at 2.4 Ghz) dB
Antenna RX dBi (patch antenna
Cable + Connectors dB (bad again :)
Receive Sensitivity dBm (subtract!)
TOTAL dB margin

11. Complete link budget – ex. 2

12. Antennas!

13. Layers!

14. That was it ... Thank you! sebastian@nsrc.org http://nsrc.org
Sebastian Büttrich, NSRC