WiFi Alliance Expands "Certified" AC Standards

The WiFi Alliance just made it easier for IT directors to pick out client devices with the latest and greatest 802.11ac Wave 2 capabilities. The latest revision to the "Certified" stamp for 802.11ac indicates wireless gear with some key new operating standards.

Multi-User, Multiple Input, Multiple Output (MU-MIMO)
This Wave 2 AC feature improves upon Single User MIMO technology, which allows one client device to communicate wirelessly with an access point across multiple spatial streams at the same time. Before MIMO, client devices could only transmit on one radio spatial stream at a time.

Image from ontheflywifi.net

Multi-user MIMO now allows multiple client devices to simultaneously transmit and receive data from a compliant access point, which is an important innovation to meet the increased density and demand more and more wireless clients are placing on wireless networks. Most mobile devices these days only have enough antennas in them to communicate across 1 or 2 spatial streams. However, access points often have 3 or 4 spatial streams available. MU-MIMO allows an access point to use all of those spatial streams to serve data requests from more devices at once. Moving forward, 802.11ac "Certified" devices will support Multi-user MIMO.

160 MHz Channels
The 802.11ac standard allows devices to utilize significantly larger channel bandwidths. While 802.11n only permitted 20 MHz and 40 MHz channels on the 5 GHz band, with 802.11ac, 80 MHz, and 160 MHz sized-channels are possible. The bigger the channel, the higher the data transfer rate.

The previous version of the Certified stamp for 802.11ac only guaranteed use with 80 MHz channels. The new version promises compatibility for 160 MHz channels.

Image from meraki.cisco.com

However, it's worth noting that the leading WiFi experts still only recommend 20 MHz channels be used in high-density areas, because the 5 GHz frequency band has room for significantly more channels at that size. When you crank things up to 180 MHz, there are only two non-overlapping channels available, and your data transmissions are subject to much more interference, which in turn slows down your transfer rates. While it's nice to know the "Certified" AC stamp means 160 MHz is supported, the actual use-cases for channels of that size are going to be very rare -- even if you can manage to find a clean RF environment to use them in.

Four Spatial Streams
The latest "Certified" indicator from the WiFi Alliance means the device can operate on four spatial streams, a boost from the three promised previously. That means a potential 33% boost in transfer speeds over the same devices communicating with only three spatial streams.

When it comes to designing your network infrastructure, it's important to remember that the slowest device in a data chain will act as a bottle neck within that chain, and WiFi is no exception. Having 802.11ac Wave 2 access points throughout your building won't impact a performance boost over Wave 1 APs if your client devices aren't also rated for Wave 2 features. While Wave 2 clients are still few and far between (the technology is still fairly new), this new certification standard for 802.11ac from the WiFi Alliance will make it easier for IT to ensure their wireless devices are all firing on the same cylinders.