NSRC Wireless. How to make wireless work with really really limited means, limited budgets. How to build wireless infrastructure on a really really small budget. This will be about presenting some best practices some acceptable practices that might not be the best but they might work for you for certain purposes there'll also be some fun practices things that are educational worth doing even though you might not want to deploy them for the longer run for bigger projects this first picture here is an example from a workshop in south africa in 2005 if i remember correctly and while this is all taped together and definitely not the way you would want to do this for any real project this worked and this worked for six kilometers i think we could stretch it to 10 kilometers why does this work well here is a bit of a reference to the wireless foundations lecture here's a link budget and you can look through these items in the link budget you have a standard transmission of 20 dbm you have not so good cables and connectors you have antennas that we estimate and we'll get back to that at being around 10 dbs and if you're adding all of this up you end up with a 9 db link margin over a distance of say 10 kilometers now that's very tight that's not really enough for a stable link with margin for rainfall and so forth but it just about works and that was the purpose of what we did in this workshop back then let's get to maybe the most important question is it worth building your own wireless infrastructure is it worth engaging in do it yourself things um when is it worth it what parts are interesting now in general we have the three main elements here to look at the access points or wireless routers that's definitely something you will have in any wireless network you have a software layer you have the management systems the systems that help you maintain the network manage users manage bandwidth manage the whole network and you have as a relatively simple and maybe the most visible part antennas of course now aps and wireless routers you can in principle build these yourself many aps and wireless routers are de facto linux boxes they are modified specialized linux boxes you can build these yourself from general purpose embedded systems embedded boards embedded small computers by adding the radio card the wi-fi card however you will not be able to save a lot of money here it tends to be the other way around that the mass production simply because of the numbers um has led to wi-fi equipment being cheaper as a you know a small linux embedded board then a general purpose board that you could buy independently to then turn it into a wi-fi box so you shouldn't hope to to save a lot of money here it might still be interesting to do but it's not where you save on budget uh what might be worth it is looking into older gear that you find lying around somewhere repurposing gear with one big warning though you need to be aware of if you're trying to build a network out of things that you find here and there you will run into issues of maintaining this managing this imagine you have a network built out of 10 20 50 different pieces all different vendors all different models no unified interface to them this would be very very difficult to do the reason it's still interesting sometimes to do that is that you might have isolated parts of your network like a cafe hotspot a visitor's lounge or something where you can treat the system as fairly much standalone independent and for these things looking at older gear might still make sense and keep in mind that the newest and fastest and fanciest isn't always the best the reason i'm saying this very often we are struggling with transporting all the data that we're accumulating on the wireless network through our backhaul connections our uplink to our isp for example so sometimes using relatively old gear that naturally keeps the speeds down might be quite a relevant idea let me show you something here we have some old very old 20 years roughly these are the lynxes the famous blue boxes they got so famous because they were so nicely hackable they were the first that actually opened up their firmware which is essentially linux so they were forked into many many different ones and some of my oldest ones here like i said 20 years and they're still working and they're still doing certain jobs so you might look into finding such old gear to repurpose but repeating the warning be aware that you need to manage this maintain this somehow which will not be trivial if you have a mix of 10 20 different things speaking of management and software for that there is a lot you could actually do although not many people do it to use standard tools and elements tools that we're talking about for example in network management and monitoring and in general system administration you can use these tools to actually manage a variety of networking gear tools i'm thinking about here include things like snmp ssh remote procedure execution over ssh dhcp servers firewalls monitoring and many of these ingredients put together and most of them are open source and freely usable might actually help you maintaining and managing such improvised networks in the absence of a real enterprise management system with that let me come to the last and probably most popular field of doing your own do it yourself wireless the antennas whether it's worth doing that this depends a lot on your ambition level what you compare it with in terms of budget like is it worth saving ten dollars on something what means what does ten dollar mean to you how expensive is your labor cost if you needed to hire some someone to do something how much money can you save on what all these questions and they go into projects in many many different ways you can't compare one to the other it really depends on your um location your situation your budget your background your people your skills so there's no one good answer for that whether it's worth it in the relatively privileged world i'm talking to you from europe there's hardly a reason hardly a motivation to spend time on building your own antennas simply because the cost of an off-the-shelf antenna compared to the cost of labor doesn't make it attractive but that might be completely different depending on where you are and that decision obviously is up to you now what are we comparing what are we up against in terms of cost the small omni rubber duck antennas again let me show this kind of thing here right these are antennas that cost a dollar or two they're really really inexpensive they're also very weak that maybe two three db's at best um not they're not serious antennas they are small antennas for a local hotspot for a couple 10 meters or something strong outdoor omni antennas 20 30 50 patch panel antennas somewhat the same 20 30 dollars the really strong outdoor antennas fifty to hundreds of dollars so that becomes more interesting to consider replacing them by something you can build yourself if you're buying antennas and also if you're building your own and especially if you then want to compare the performance of these antennas always remember to check them to measure them to look at data sheets if it's purchased commercial antennas data sheets measurement protocols and so forth.
© Produced by Philip Smith and the Network Startup Resource Center, through the University of Oregon.
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