Wireless Link Calculations: Radio Mobile

Am taking a PhD course at ITU about Wireless Sensor Networks. Our first assignment is related to finding a link budget for two sites of interest: Zackenberg and Abisko. In Zackenberg we tackle a 21 Kilometer link between two points separated by water. In Abisko we tackle a 9.6 Kilometer link that has obstructions (mountains) in the middle.

Signal Behavior from Danneborg

Signal Behavior from Danneborg

I was not too worried about the Zackenberg link because I had already been there and knew that there was line of sight between the two points we were supposed to connect. But I have never been to Abisko and had now idea how to find out what the conditions were. I sincerely did not see how we could come up with anything descent by just using the GPS coordinates. And then I installed Radio Mobile.

Radio Mobile is an application that is made for window, so I had to use wine to make it work [1] (The instructions for windows are here). It does not work at its full potential when using wine: there are some labels that don’t appear correctly and the text areas are strange. But it’s not unusable :).

Radio Mobile needs the GPS coordinates from the two connecting sites and additional information about type of antennas, signal frequency, cable loss and connector loss (among others). Once you have input data you can create really nice images depicting the theoretical behavior of the wireless signal in the surrounding terrain. In the “signal behavior” figure we see that the signal grows weaker as the distance increases. We also see how the surrounding mountains prevent the signal from spreading completely into the valley.

2.5GHz Abisko

2.5GHz Abisko

There is another graph that can be created that depicts the conditions of a point to point connections. It contains lots of data about signal (like antenna gain, cable loss, antenna placement, Fresnel Zones…) and terrain. IMO, this type of graph is the one that most clearly describes the connection behavior between two points. In the case of Abisko the graph hints at a problem with 2.5GHz signals (figure 2.5GHz). There is connection at the peaks of the hills, but there is no connection at the end points. Notice how this is color coded on the terrain.

900MHz Abisko

900MHz Abisko

On the other hand, for 900Mhz the figure is completely different and hints at a better connection (figure 900MHz). Notice how all the hill is now green. Also notice how the Fresnel zone has grown.

And if all this was not enough, Radio Mobile has an additional feature to export to google earth format. This means that all the figures in this post can be seen in google earth. This give GREAT versatility as one can pan and zoom the terrain around the place of interest. One can also notice potentially important land marks like roads that are close to the link (giving further insight into the interference and other factors).

All in all, it is a REALLY AWESOME app!!!!

[1] Download the Radio Mobile files into a freshly created directory (file1, file2). Download the MSVBVM60.DLL file from the web (I just googled it) and put it in the newly created file. After you unzip the first two file, you should execute `wine rmwdlx.exe`.


About joelgranados

I'm fascinated with how technology and science impact our reality and am drawn to leverage them in order to increase the potential of human activity.
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