The Five C’s of Reliable Wireless Internet: Congestion (part 4 of 6)

November 3, 2012

This is the fourth part of a six-part series on WiFi at events. Our next “C” of good wireless network design is congestion. Because radio frequency waves are not visible and they don’t take up physical space, it seems logical that there would be no limit to the number of signals that can effectively fly around at the same time. 

 

Unfortunately, this is not the case. WiFi has a distinct number of channels, very similar to the different channels on the radio you listen to in your car. If you have ever brought a MiFi device into a crowded trade show, chances are you had one heck of a time trying to connect to it (and stay connected). This is because there are only three non-overlapping channels on which a MiFi can transmit. 

 

So imagine that your MiFi device is like a radio station transmitting a song and your computer is a boombox listening to the song. You will be able to pick up the song crystal clear if you are located close to the radio station’s antenna and there are no other radio stations nearby broadcasting on the same frequency. 

 

But now assume you are transmitting at a trade show, where there are DOZENS of other people transmitting on the SAME station (from here on, we’ll call it a channel). Your computer will be listening for your song but all it will hear is garbled static.  This is what happens with your MiFi device on the trade show floor. But fear not, there is a solution. 

 

Without going into too much detail, older access points (including all MiFi devices on the market right now) have radios with the ability to transmit on three non-overlapping channels on the 2.4 GHz spectrum. However, newer access points can transmit on the 5 GHz spectrum with 21 non-overlapping channels If your access point has multiple radios, it’s possible that each radio can be configured to broadcast on a different channel (either on 2.4 or 5 GHz).

 

The important take away here is that simply putting more access points with more radios into a small space is not an effective method of providing a better network. Rather, it will likely lead to more problems due to channel congestion.

 

Nevertheless, this strategy of haphazardly increasing the number of access points is often times what venues do when they need to increase the capacity of their network. Rather than redesigning the network as a whole to ensure the most effective use of 24 different channels, they simply add more access points, introducing interference into their own network.

 

In the absence of an entire investigation into the channel setup, a good question to ask your venue is whether their access points broadcast solely on the older 2.4 GHz spectrum or both the 2.4 GHz and 5 GHz spectrums (giving you up to 24 distinct channels). Doing so will ensure that even if people bring their own WiFi emitting devices, you won’t all be competing for the same three channels.

 

Now that we’ve addressed coverage, capacity, and congestion, in the next installment we’ll address the fourth “C”, connectivity.

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