Wifi Design Cycle

I’m in the process of carrying out wifi improvement works on the campus, so I thought I’d write some pieces about our wifi equipment lifecycle and the processes I’m following.

Initial Survey
Pretty much everywhere has some wifi coverage. I’m therefore starting with an initial survey to find out what we currently have and inform what we need to change. Even if I know the coverage is terrible and I need to just start again, this survey is necessary to provide before and after documentation. It also shows how RF propagates through the building, which can help identify troublesome areas of attenuation that don’t show up on the plan. I try to identify where the available data points are at this stage, though it can be hard to be thorough about this.

The design stage is predictive, though it’s sense checked using the initial survey information.

Once there’s a new design, this gets deployed – this can be where some compromises occur as it turns out that ceiling cavity contains asbestos, or one of these data cables is damaged. Deployment is sometimes going to be done by me, sometimes by a contractor.

A repeat of the initial survey – validate the coverage is as expected, that APs are using sensible channels and we don’t have a Co-Channel Interference disaster, that 2.4GHz radios are on a sensible power setting or disabled as is appropriate. At this point there’s a loop back to design in the flowchart. If things are not looking as expected it’s back to the drawing board to find a remedy, then deploy physical or config changes and survey the area again. Recently I’ve carried out validation surveys in areas where I know an install compromise was made because the building structure wasn’t quite as expected. It was strangely satisfying to discover the original design was sound and the new AP position wasn’t working, so I had to come up with a different option.

This is an ongoing process, but it’s worth confirming the throughput for group of APs is in the expected range (hasn’t dropped horribly for a building) and retransmissions are at acceptable levels. We use Aruba Airwave which makes it easy to group APs into an area for graphing of basic metrics. When wifi is improved in a building we expect to see an increase in client count and throughput but that isn’t always the case. Improving coverage in a lab means tablets can be used for note taking; that might be one or two more devices, not something that’s going to impact the graph.

I also talk to the users. Let them know there’s been a change, if they don’t already know. Ask for feedback and encourage them to tell you if there’s an device they need to use that doesn’t work so well in some parts of the building. Hopefully the design and validation accounts for this, but…..  I’ll more to day about that in another post.

CWNA – Achievement unlocked

Just over a week ago I completed my journey towards becoming a Certified Wireless Network Administrator… well, as much as anyone completes any journey in IT, there’s always more to learn.

When I started working in my current job and it became clear nobody understood WiFi, or knew how to solve the problems we were having, I quickly found the CWNP website and the numerous references to CWNA. A year later I was on a CWNA course with Peter Mackenzie. Probably the best aspect of the course was not how much I learned but how much it cemented what I’d already picked up through reading and lab work.

Like most certifications getting a good score in the CWNA exam requires you to learn and remember stuff that in reality you’d look up. In the end I found the exam straight forward. I felt I knew pretty much all the answers (actually it turns out I didn’t know at least three of them), but this is not because it’s an easy exam. I’ve spent a lot of time reading the study guides, making sure I knew what was expected… and then, because I dithered so much between taking the course and sitting the exam CWNA-106 was retired…. so I started again with a new study guide. I was pleased with the end result, a score of 95%. Worth all that work.

I’d like to pursue more certifications, otherwise I’ll need to find something else to do with my evenings. Because I work almost exclusively with Aruba equipment at the moment, it makes sense to look at the ACMA and ACMP certs. I’m also going to go further with the CWNP certs, probably looking at the Analysis Professional next.

The fact CWNP is vendor neutral is particularly appealing. Whilst it’s great to have a certification in Cisco or Aruba wlan equipment (the only two I’d consider worthwhile), these can focus on platform specific commands, licensing requirements and model lineup. Whilst this is useful information it doesn’t teach you about WiFi. I much prefer the approach of understanding how a technology works, something I can apply to any platform, rather than being restricted to knowing how to do things with a particular vendor’s equipment.

Fundamentally, whilst all WiFi network vendors have their pros and cons, their specific technology solutions to problems, RF is RF and if you understand how 802.11 it helps enormously to make sense of why a vendor does something a certain way.