We all know that WiFi is not the ideal technology. We have to face a lot of problems during daily usage of this technology, e.g. weak signal, interferences, low throughput and high latency. Wireless communication is very challenging, especially when we have a thick wall between our computer and router or we have a lot of electronic devices. I was always wondering what the maximum range of WiFi technology is. Our homes are not conducive to the propagation of WiFi signal. But, how does it looks in case of an open space?
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Let’s get to the point, I found information that the guys from Wroclaw University of Technology in Poland achieved a stable WiFi connection at 250 km distance!!! This is the record in Poland. How they did it? At first, they tried at 2 km distance, the second attempt was for 100 km, and finally they have decided to do this at 250 km. They have used MikroTik 5 GHz WiFi modules and 32 dBi parabolic antennas.

Unfortunately they did not public more details 🙁 Did they use amplifiers? Did they exceed the allowable maximum EIRP level? Let’s do some calculations. These calculations are approximate, but they give a view of the whole situation.

  • Free Space Loss: about 155 dB (it was the radio-line, so we can use this simple propagation model)
  • Minimum receiver power: about -75 dBm (we do not what they used, so it is a assumption)
  • Transmitter power, higher than: -75 dBm – 32 dB – 32 dB + 155 dB = 16 dBm

I do not include a lot of factors, so calculation accuracy is approx. +/- 1.5  – 3 dB. We can see that, the EIRP was higher than 48 dBm. It is very high value, but they used very directional antennas, so they (probably) did not interference others systems. In case of directional antennas, the signal is radiated in only one direction. What was the most challenging in this experiment? In my opinion, antennas pointing, they had to do this very precisely.

How did they test the connection? It is very interesting, because they have used Skype.. Just a reminder, Skype requires Internet connection, so one of used computers had to have mobile Internet access and acted as the gateway for the second computer. Personally, I would be more satisfied by iperf logs.

 

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