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commit 159c29bd5f3d3bb0d40038ce5259bc86c4f91914
parent b28774daabc31655ddb718c0f37fda7d8d2ef104
Author: Paco Esteban <paco@onna.be>
Date:   Sat, 20 Jul 2019 18:06:08 +0200

new article draft

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diff --git a/content/long-wireless-links-and-monitoring.md b/content/long-wireless-links-and-monitoring.md @@ -0,0 +1,139 @@ +title: Long Wireless links and monitoring. +author: paco +date: 2019-07-19 +css: style.css + +XXmenuXX + +--------- +# Long Wireless links and monitoring. +2019-07-19 + +## Intro + +Some time ago I built 2 [P-t-P][1] links between some family members buildings. + +Thing is that my brother and my sister live in an area with no coverage from +traditional ISPs, but that is quite close (5.5km on a straight line, with no +obstacles) to my parent's which have good coverage (even FTTH) and plenty of +providers to choose from. + +This project has grown _organically_ so to speak, and the requisites kept +changing. + +That, and my lack of experience on the subject make all this far from an +optimal solution. + +In the end it has been working for almost 3 years now. This is an attempt to +document all the infrastructure and the bits and pieces used so I do not forget +about it and maybe it can be of use to somebody else. + +## First steps and research + +As I said, I knew nothing about this before tackling the project. I have some +solid knowledge about networking, but I knew little about long (for me) +wireless links, antennas, propagation and a bunch of other stuff I did not know +existed, so I had to do some research. + +If you want to do something like this, is better to plan ahead. See what the +requisites are and start digging. + +Some things to take into consideration are: + +* Budget. This is an important one in this scenario, as this is for personal + use only. +* Distance between the endpoints of the link. Modern hardware (more on my + choice later), can easily cover 10km or maybe more, but read the + manufacturer's datasheet and look for output power, antenna gain and + sensitivity. And always take their numbers with a grain of salt, as they + are usually tested on ideal conditions you won't encounter. You'll find + later a way to calculate the ideal numbers to have an estimate. +* Obstacles. There has to be perfect clear vision between endpoints. Wireless + communications, especially WiFi either on 2.4GHz or 5GHz, are very + sensitive to obstacles. Even partial cover can have a big impact on link + quality. And clear vision does not mean _"I can see a single point in the + distance"_, there's this thing called [Fresnel zone][2], under some + atmospheric conditions or spectrum saturation it will give you a lot of + trouble. +* Materials. Don't be cheap. This will have to resists the outdoor conditions + for as long as possible. +* Neighbours and regulations. There's the legal part (RF regulations in your + country and things like that) and the _"social"_ part, in this case my + family does not live in detached houses but on apartments, so that has to + be taken into consideration if there are any rules about this. +* Infrastructure. And by that I mean all the necessary to be able to install + the antennas, route the cables, install connectors, etc. I'm not only + talking about tools, but also access to the best spots to put the antennas, + etc. +* Antenna location. As a rule of thumb, the higher the better. But this + depends a lot on your particular situation. It deserves some thought. +* Spectrum saturation. Wifi is ubiquitous now. That may be a challenge for + any installation specially on urban areas. Ideally, you should check how + _crowded_ the spectrum is, but this is usually pretty difficult for + amateurs without special equipment. Some antennas have a built in spectrum + analyser, but it may perform badly. + +## Materials + +This is a list of materials I choose and why I choose them. It is short, as it +is really an easy installation. + +### Antennas + +I ended up using [Ubiquity PowerBeams][2] to create the 2 links. Four in +total, 2 for each link. + +I was looking for some reputable manufacturer trying to avoid problems in the +future. Also, I wanted something as simple as possible. This kind of antennas +have the _"emitter/receiver"_ and the antenna all in the same device. So no +special connectors to be crimped, virtually no losses on cables, just an easy +[PoE][4] setup from the house to the rooftop. + +Also, this antenna has an easy to setup web interface _and_ an SSH server that +leaves you in a busybox with some proprietary commands that are pretty handy +for automation and data collection. + +There are newer models now and other manufacturers. Do your research, read on +forums and all the usual stuff. I can say those work for this setup with minor +issues. + +If you know something about this subject you may be wondering why I did not use +something with a wider angle on the _"access point"_ side and use just 3 +antennas instead of 4. Truth is, I tried, but I had some problems with the 2nd +link giving poor performance. Not being an expert on this I can only guess +that the partial obstruction on the LOS (line of sight) path for the second +link was the cause of the poor performance, specially on bad weather days (WiFi +is pretty sensitive to heavy rain) and episodes of spectrum saturation. + +Creating a separate link with a dedicated pair of antennas improved the +situation a lot. + +### Cables + +As the antennas only need a network connection, we only need Ethernet cable. +Be sure that is CAT5e or better. + +Always use cable rated for outdoor use. Regular network cable will not last +long exposed to rain and the sun's UV. I went for [this one][5] because it was +available at the time on Amazon. + +### Connectors + +Don't go extra cheap on this, but anything with reasonable quality will do +here. The antennas are built in a way that the connectors are never exposed, +so this part is not that critical. + +### Antenna pole and other hardware + +I cannot say much about this. What to buy here depends a lot on your +particular setup. Remember that the higher the better for the antennas, and +remember wind is a thing ... you do not want it to fly away like a plastic bag. + +---- +[1]: https://en.wikipedia.org/wiki/Point-to-point_(telecommunications) +[2]: https://en.wikipedia.org/wiki/Fresnel_zone +[3]: https://www.ui.com/airmax/powerbeam/ +[4]: https://en.wikipedia.org/wiki/Power_over_Ethernet +[5]: https://www.konigelectronic.com/computer/networking/network-cable-reel-cat5e-futp-100-m-black-solid-55896639 + +Last updated: XXlastXX