Pakedge Course 4 — Wireless Access Points

Think You Know Everything About Wireless? Think Again.
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Think you know everything about wireless? Think again. In fact, this is the lengthiest course in the PCNA syllabus, a fact they repeat numerous times throughout the class, with a ton of hands-on labs, and a Gone With the Wind-style intermission mid-course. Buckle up, people, knowledge is power, and it’s about to get all WAP-py up in here!

The best practice in implementing wireless networks is actually to NOT use wireless at all. Yup, go wired whenever possible for reliability, avoiding interference, and easing troubleshooting. Obviously this isn’t possible for every device — iPad, iPhone, Kindle, etc. — so understanding how wireless works, what affects it, and how to best implement in a project are important.

One thing that was new to me was that a Wi-Fi password is not a key to using the network, but a shared encryption key to unlocking and viewing the data. Because Wi-Fi uses radio waves, anyone can “listen in” on the signal, but encryption keeps them from being able to view the data.

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Another new point was that the most important ingredient for a strong Wi-Fi password is length. Length = Strength. (I’m resisting a “that’s what she said” joke here…) Minimum length of a WPA2 password is eight characters, which is 240 (2 to the 40th power), resulting in nearly 1.1 trillion possible combinations. Each additional character doubles the complexity of guessing a password, with a maximum length of 64 characters.

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Image Credit: XKCD by Randall Munroe
The problem with passwords is we’ve been taught to use bizarre combinations of symbols and numbers and upper and lower case letters that no one can remember. And special characters like * and # don’t foil computers, they only make it more difficult for humans, and a hard to remember password is more likely to be written down and more likely to get discovered. A far better method is to use three or four words a customer can easily remember. Like UseTheForceLuke or BeerTastesGreatAnytime.

There is a TON of time spent discussing — and measuring — the differences between 2.4 and 5 GHz Wi-Fi bands. In a nutshell you learn that 2.4 GHz has less attenuation through walls and obstructions and is supported by more devices, while 5 GHz delivers faster speeds, offers more channels, is less prone to interference, and is the band you want to use for most devices.

The other key difference is each Wi-Fi channel has a width, and wider channels can send more bits per second. Think of this as a freeway with more lanes allowing more traffic to flow at once; a 4-lane road is superior to a 1-lane. The 2.4 GHz channels have a width of 20 MHz, while the default bandwidth for 5 GHz is 80 MHz.

And how can you make sure your customer’s are using the 5G band? Easy, give the networks two different names like “Sciacca” for the 5G and “Sciacca-alternate” for the 2.4 GHz band. This is also super helpful for troubleshooting as you can manually select which band to connect to.

The Pakedge WK-1 WAP included with the PCNA class produces a sphere of Wi-Fi coverage that should cover a 2,000 square foot home, or generally suffice for a typical 2 story, 3 bedroom home. Obviously many of our jobs are much larger than this so understanding how to properly design and implement multi-WAP projects is key and the class offers several exercises to learn. The key to proper design is in determining necessary coverage and capacity.

Capacity was another concept that was new to me. It makes sense, but I didn’t realize that there was a limit to how many devices a WAP can support. A single Pakedge WAP supports about 50 devices* which is likely plenty for most homes, but what if you are doing a business or a large house that frequently hosts massive parties?

Large projects will also necessitate multiple WAPs to cover the entire home. Since one of the main sources of RFI (Radio Frequency Interference) are other nearby wireless networks, a key component of multi-WAP design is properly selecting channels for both 2.4 and 5 GHz to avoid adjacent or co-channel interference. Learning how to properly select from the three best channels — 1, 6, 11 — for 2.4 GHz and the wider channels in 5 GHz to allow for a full 80 MHz channel width will give your installs the best performance.

The problem with multi-WAP jobs is that people don’t stay put, and as they roam around the house, they transition from one WAP’s coverage to the next. Proper design can make this handoff as seamless as possible and this is where adjusting the WAP’s transmission power helps create proper roaming handoff points. This was new to me as it seemed logical to want MAX POWER on all WAPs, but this actually creates bad handoff zones. The class teaches how to measure and adjust transmission power to achieve a -70 dBm RSSI (Received Signal Strength Indication) at the edge of each WAP’s coverage area to prevent devices from getting stuck in the middle of two equally powered signals where they can end up jumping back and forth between the two.

The class also covers measuring a site’s background noise with MetaGeek’s WiSpy and installing and using iPerf to measure throughput on the wired and wireless network. A 40-question exam at the end tests your knowledge and prepares you to move on to course 5…Remote Monitoring & Management!

*Ted Haeger, Control4’s senior director of training and support commented: “50 connected devices is a guideline we provide; it’s not a hard limit. You could probably have well over 100 devices connected. With a switch, the electrical circuits of an Ethernet cable provide a physical means for detecting whether a device is still connected. Wireless devices don’t have that, so a WAP has to use a certain amount of transmission for maintaining connections. That means that there is some amount of wireless chatter that is simply connection maintenance overhead. As you load up more devices, maintaining connections demands more air time, which slows overall throughput.”

Check out Routers...Not Rooters, my rundown of Course 3, here.