I work in the Water Industry were we use radio links for telemetry/SCADA purposes. In order to find a viable link, a desktop study is completed using “path profile” applications which is backed up by an actual on site radio test. Any help in the form of webinars, paperwork or courses would be most welcome.
you do not mention frequency. in the range 1-2GHz you could do worse than read the COST (COopération européenne dans le domaine de la recherche Scientifique et Technique) 231 reports that describe models you can apply (Okumura-Hata, Walfisch-Ikegami, etc.)
If not then you are looking at more conventional and inaccurate link budget.
An intro to a few common approaches.
https://www.irjet.net/archives/V5/i1/IRJET-V5I149.pdf
Or go to a specialist company to plan it for you.
megalithia will give you a terrain profile.
https://www.megalithia.com/elect/terrain.html
Mike.
Hi Mike, I had a look at the reports which give loads of info. on path loss and different models which is all good. At home, I use the Radio Mobile app. for path profiles which I believe uses the Longley Rice model.
I am also wondering about the actual on site radio test and what measurements to take. I can calculate Fade Margin and I think 20 dB is a good target to aim for. I can also get figures for system availability/reliability and again, I think well over 99% is a good target to aim for ?
Unfortunately I dont have any experience of doing this work and therefore want to be sure the figures I am getting are going to provide a link that is viable. Do you know of any documents/standards that I can refer to which give details on how to carry out the radio tests and what measurements to record etc.
Generally the fade margin to allow depends on how serious a link failure would be, both in the sense of what stops working, and how cleanly the system recovers when it comes back. There is also the thorny issue of interference to and from adjacent channel users in range and also co-channel users who are not supposed to be in range but may well be. 20dB may be a sensible first cut, but understand that when you write a level plan, you do so mainly so you know what you are changing.?
Also systems that can degrade gracefully to lower data-rates and or give a report link margin, so you can see if problems are imminent before they occur need less mollycoddling than those that give no warning and fail dead.
At 460MHz you may also need to consider that at certain times of year you will get tropospheric ducting - as a direct example I am aware of a project about 20 years ago to solve interference to southern water UHF telemetry from France that caused havoc, but only for a few days a year. Cunning use of directional antennas and an INCAN system helped in that case.
Channel sounding is a very sensible idea, but like an interference survey it needs to be over a long enough period to capture the SNR over a range of likely conditions - leaves on trees and thunderstorms are the sort of thing you need to wait for, they do not happen to order.
I'm not sure if CISPR have any ‘how to do channel sounding' papers but I can have a look.
The L_R model is well respected, but uses a sort of average roughness figure for terrain, so gets fooled by mountain ranges in planes and so on.
algorithm detail here.
https://www.its.bldrdoc.gov/media/50676/itm_alg.pdf
for most of the UK it will get you close.
Mike.
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