Every new instalment in the alphabet soup of Wi-Fi standards promises to fling ones and zeros around your home or office faster than ever, and 802.11ac is no exception. While the speed boost is impressive when you're up close, 802.11ac's worth really shines through once you put some distance -- and perhaps a few walls -- between you and the Wi-Fi access point.
The 802.11ac standard offers a theoretical maximum throughput of 1300 Mbps, but we all know that theoretical maximums are to be taken with a grain of salt. In the real world it's likely to deliver file transfer speeds of 300 to 400 Mbps per second if you're near the Wi-Fi access point.
Tripling the real-world speeds of 802.11n is nothing to be sneezed at, although you're really only likely to notice the difference when shuffling large files around your local network rather than downloading files from the internet. Once you're online your internet connection is likely to be the bottleneck, or else you might be hampered by the speed at which the server on the other end can send files to you.
While 802.11n can run on either the 2.4GHz or 5GHz wireless band, 802.11ac only runs on 5GHz. The throughput boost is in part due to the use of wider channels in order to squeeze through more data -- like extra lanes on a freeway. With 802.11n you're relying on 20MHz channels, which can sometimes be combined to create a 40MHz channel for faster speeds.
The new 802.11ac standard relies on 80MHz channels by default and can handle 160MHz, although it's not supported by the current generation of 802.11ac hardware.
No upgrade is complete without the promise of something even better just around the corner. We should see "Wave 2" 802.11ac Wi-Fi access points in the next 12 months, delivering another speed boost thanks to support for 160MHz channels -- basically the eight-lane highway of Wi-Fi networking.
While 5GHz radio waves can deliver faster data speeds than 2.4 GHz, the laws of physics aren't without a sense of balance. The trade-off for the higher frequency is that such signals find it more difficult to penetrate solid objects such as walls. This means when you're running a dual-band Wi-Fi access point, generating both 5GHz and 2.4GHz networks, there's a crossover point as you move away where the supposedly slower 2.4GHz network actually outperforms the 5GHz network. A sports car might outpace a four-wheel drive on the freeway, but once they hit rough terrain the slower four-wheel drive handles the difficult conditions better.
Thankfully there are a few tricks that help reduce the impact of walls on Wi-Fi networks. One such trick is MIMO (Multiple-Input and Multiple-Output), which uses more than one antenna to basically split one fast lane into several slow lanes that cope better with obstructions and interference.
MIMO was introduced with 802.11g but continues to improve. Current 802.11ac gear supports up to three streams, while Wave 2 devices will raise this to four. Taking full advantage of these streams requires the end devices to feature multiple antennas, but this varies between gadgets.
Smartphones and tablets are just embracing two-stream MIMO, while notebooks are slowly making the move to four-stream MIMO. For now, Wi-Fi access points with four antennas will find that some of those antennas lie idle much of the time. The upcoming Wave 2 802.11ac gear promises to take advantage of these idle antennas thanks to Multi-User MIMO.
Single-User MIMO demands that every device wait its turn to talk to the Wi-Fi access point, which obviously slows things down when there are many connected devices. Multi-User MIMO can group MU-MIMO-compatible devices together and talk to them simultaneously, ensuring every device is served faster.
If you think of a Wi-Fi network like a McDonalds drive-through, with every connected device waiting to be served, MU-MIMO lets you open up extra drive-through lanes for compatible devices so several can be served at once. This means everyone gets served sooner and can then come back for more.
Thankfully you don't have to wait for Wave 2 devices to see a performance boost in difficult conditions. Some of today's 802.11ac Wi-Fi access points support ‘beamforming’, which lets the Wi-Fi network target distant devices. With some beamforming-compatible access points you'll even see a performance boost with end devices that don't support beamforming.
The motoring metaphors start to break down at this point. It's best to picture a traditional Wi-Fi access point as a light bulb, with light radiating out in circles. The further away you are, the less light reaches you -- especially if objects get in the way. Beamforming uses interference tricks to focus the signal, turning your light bulb into a torch so you can point it at devices, which are far away and deliver a stronger signal.
Up close you won't see a significant performance boost from beamforming, but as you put a few walls between yourself and the Wi-Fi access point, or perhaps go upstairs, it starts to make its presence felt. It can't work miracles, but beamforming can certainly make a difference in difficult wireless conditions.