802.11ac "Gigabit Wi-Fi": What You Need to Know
The 802.11ac Wi-Fi standard is not yet finalized, but draft 802.11ac equipment will soon be available. Get ready with this primer.
Fri, April 27, 2012
PC World — Your 802.11n wireless network and devices are about to become passA(c). Although the official 802.11ac specification won't be finalized until sometime in 2013, wireless equipment will soon appear on store shelves sporting the faster wireless protocol.
It's been almost five years since 802.11n wireless routers and devices became available--also well ahead of the specification actually getting ratified. Now, IEEE is finalizing the 802.11ac standard. 802.11ac is also referred to as "gigabit Wi-Fi" and will be capable of significantly faster data transfer speeds than the current 802.11n.
Here's what you should know about the next generation Wi-Fi:
802.11n works in both 5GHz and 2.4GHz frequency ranges. 802.11ac will be purely 5GHz. The higher frequency has less range when dealing with walls and other obstacles, but there is also far less interference in the 5GHz range. Many household devices ranging from cordless phones, to baby monitors, to microwave ovens can degrade the wireless signal in the 2.4GHz range.
802.11ac uses wider channels to move more data. 802.11n relies on 40MHz channels. 802.11ac doubles that to 80MHz by default, with an option to use 160MHz channels. Coupled with QAM (check out this Wikipedia reference for a more detailed explanation of QAM) encoding that's four times more efficient than 802.11n, the new Wi-Fi standard will be capable of transferring data at 433Mbps.
More Spatial Streams
There are twice as many spatial streams available in 802.11ac as there are in 802.11n. With eight spatial streams--each capable of a theoretical 433Mbps--802.11ac devices that use eight antennas can reach speeds up to nearly 7Gbps.
Signals reflected off different angles and surfaces arrive at the device out of phase from each other and cancel each other out. Beamforming resolves the phase conflicts for a stronger signal and more stable throughput. 802.11n is capable of beamforming, but the technique is rarely used. Beamforming is still optional in 802.11ac, but will likely be used much more commonly in 802.11ac devices.
Although 802.11n has been around for years, there are still many routers and wireless devices in use that rely on the older 802.11b and 802.11g protocols. As we transition to 802.11ac, there will still be 802.11b-g devices, and it will take years for 802.11n to be replaced as the dominant Wi-Fi technology.
802.11ac will support fallback to older Wi-Fi standards to enable backwards compatibility. Some devices may only be capable of 5GHz, which means they'd only be able to revert to 802.11n. However, many devices will most likely still be dual-band, and be capable of switching to 2.4GHz and connecting with 802.11b or 802.11g if necessary.
Keep in mind that the 802.11ac specification is not yet finalized. Equipment and devices that come out this year will be based on the draft, and there is no guarantee they'll work with other proprietary draft 802.11ac equipment, or that they'll be fully compatible with the official 802.11ac standard once it's finalized.