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I am answering some questions about my course of radio links and I came across with the question about explaining interference in fixed and mobile wireless systems. As far as I know ALL wireless system are susceptible to radio frequency interference (RFI), electrical interference and intermodulation (independently of the wireless system we are talking about). Thus my questions is what are the interferences you can encounter on the basis of fixed and mobile systems? Are they different?

I would appreciate if a book is also recommended to dive into details

Thanks!

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The question is quite broad - it could be improved through some context.

In general, consider that fixed antenna installations can be highly optimized. Distance and height can be used to minimize locally generated interference. Antenna directivity can be used to separate interfering signals from the desired signals. In a fixed application, long term interference can be located and often mitigated. Fixed antenna installations can generally take advantage of more space to install larger and more efficient antennas that result in more gain which may be used to improve the desired signal while minimizing interfering signals.

In a mobile application, the space and topology of the antenna installation is limited which often results in compromises. Directivity to avoid interference is often not practical while the antenna is moving so most mobile antenna installations are largely omnidirectional in the azimuth (horizontal compass) plane. Interfering sources come and go according to the location of the mobile antenna and the location of the interfering signal. It is not practical to mitigate these itinerant noise or interfering signal sources.

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  • $\begingroup$ I'd say that's exactly the answer I was looking for. Thank you so much! $\endgroup$
    – little_mice
    Commented May 31, 2018 at 12:16
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For fixed, licensed stations, such as commercial broadcast stations, part of obtaining that license requires establishing the coverage area of the transmitter, and determining that there will be no conflicts with other stations. Since the transmitter is fixed, it's feasible for some combination of geography and frequency to be exclusively reserved for that station.

But with mobile stations, some other transmitter on the same frequency can move into the same area. In some allocations, like the ISM bands in which WiFi operates, it's a free-for-all where everyone just has to deal with it. Other allocations are made to specific companies (cell phone networks) or government organizations (military, police) or purposes (aviation and maritime communication). Each allocation has specific rules for how to handle interference.

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