How many devices can one 802.11n standard access point control?

Expert Mike Jude reveals the technical and theoretical limitations of 802.11n access points as more enterprises upgrade to the new standard.

We are upgrading to the 802.11n standard soon, and I'm wondering how many devices one access point can control following the upgrade.

Based on the 11n standard, you can logically control up to 255 devices. But in practice, a single access point (AP) would have a problem handling that many. As the number of devices increases, the overhead on the AP also grows. This degrades AP performance and limits the absolute throughput per device. So, in practice, manufacturers set AP capacity limits that are lower than the 225-device ceiling.

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The real question, however, is this: How many devices can access a single AP before performance starts to degrade? The answer: Not that many. A rule of thumb is that, above 16 devices, performance begins to worsen noticeably. In any case, it is important to consider that Wi-Fi is not like cellular wireless: Generally, the amount of intelligence in the wireless router is not sufficient enough to provide a lot of contention management. This is both a virtue as well as a liability for Wi-Fi. It is cheap because it is less complex, but it is less capable as a result. The advantage, however, is that it is relatively straightforward to just place lots of APs in a given area, and by paying attention to things like coverage and overlap, achieve a relatively seamless user experience.

Fortunately, tools do exist to make coverage considerations somewhat less like rule of thumb. Simulation software can give you a sense of dead zones and what kind of performance you'll get at your location. The software is relatively expensive, however, and it may not get a lot of use after installation. If you know you are going to be expanding or modifying your Wi-Fi coverage in the future, simulation software can be a good investment. On the other hand, if you are planning a fairly static environment, purchasing the software may not be economically justifiable.

This was last published in November 2013

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