Jeff Duntemanns Drive-By Wi-Fi Guide

As Design Bleeds Into Implementation…

Purists insist that design and implementation are two separate tasks, and that design must always be completed before implementation begins. On the other hand, purists rarely do the actual work; mostly they just talk about it. This is true of software engineering, where I used to run into degreed 'design experts' constantly who had never written a line of code in their lives (it showed!) and it goes double for wireless networking.

In Wi-Fi work, the environment dominates the design. You're not pulling cables through a tidy plenum, and so your design is utterly dependent on what your space is built of, what's been piled up in it, and how it's all arranged. Your design will therefore be a starting point at best. Do not assume that you can draw a diagram, install three access points, and get everybody in the office connected, all on one arbitrary Wednesday before lunch.

It's better to work this way: Do your sketch, and then place one access point, running a cable back to your router/switch cabinet by just laying it on the floor. Then take a laptop and see what the shape of your field is for that single access point. You may find that you're getting better coverage than you guessed, or worse. Take your laptop into all the cubes and offices that your network must serve, and make sure you can connect everywhere. Mark down where you connect poorly, or can't connect at all- that's the space that may need to be covered by an additional access point, or where client adapters may need external antennas. (The antennas on laptop client adapters are notoriously bad-but this means that if you can connect in a location with a laptop, a client adapter with a real antenna will connect as well or probably better.) If you record enough readings to get a sense for the boundaries of the field, it may suggest where to place the subsequent access points.

Modify your design based on your actual wireless network field audits. Then deploy a second access point in the same way, and see how coverage has expanded. (This is a good weekend project, when staffers aren't around to trip over cables and waste your time asking questions.)

The process will be difficult, especially the first time you have to do it. After you get a little experience, your designs will come closer to the mark at the outset.

The point I'm making is that wireless network design is necessarily messy, heuristic, and incremental, and the design won't be finished until the network works.

I'll explain more about network field audits in Chapter 9, which is really about implementation. Between here and there, I'll be spending some time talking in detail about the hardware that makes up a Wi-Fi installation: Access points and wireless gateways, client adapters, and antennas.