The Next Generation of Wireless: What You Need to Know About 802 11ac
The Internet era of wireless gigabit speeds is here. Data intensive programs from streaming services need the radio space to deliver content to multiple devices on the same network. Link referral services like Google equate faster speeds to more revenue. The IEEE (Institute of Electrical and Electronics Engineers) is hard at work building protocols to allow very high throughput gigabit speeds over wireless networks, and their first effort can be enjoyed now with 802.11ac capable hardware. The current generation "Wave 1" will be followed up with "Wave 2", expected to be released in the middle of this year with expanded features.
I recently viewed a fascinating video blog about what 802.11ac offers by Matthew Gast from Aerohive Networks. He explains what challenges are addressed by the new protocol and what direction the WiFi standard is headed (available on YouTube). If you don't have time to view all seven videos, here's a synopsis of what to expect with this update:
The 802.11ac protocol operates exclusively in the 5 GHz spectrum in an effort to stay out of the congested and channel-limited 2.4 GHz radio space. Users with 2.4 GHz devices can still access a WLAN with a dual-band radio. It utilizes 256-QAM modulation in order to squeeze more packets inside broadcasts, upgraded from the previous 64-QAM of 802.11n. Also increasing bandwidth are expanded 80 MHz channels, double from the previous 40 MHz channels of 802.11n.
You might be wondering why the protocol is named "ac" after the previous standard was given the letter "n". The answer is because there are not enough letters in the alphabet. The IEEE has gone through all the letters "o" through "z" during their development cycle, so they had to start again from the beginning with the "a" prefix.
Among other neat innovations of 802.11ac are dynamic bandwidth allocation, multiple-user multi-input multi-output (or MU-MIMO), and explicit beamforming. The protocol allows access points to allocate as much bandwidth as is available to a receiver at the time of transmit. As more clients connect, bandwidth is divvied up into 40 MHz and 20 MHz segments, and this is done on-the-fly on a per frame basis. MU-MIMO expands the spatial streams from four to eight, and it functions much like a switch broadcasting the same packets to multiple users simultaneously. This same functionality also expands the explicit beamforming capabilities pioneered by the 802.11n protocol. About every 10 milliseconds a null data packet, or NDP, is broadcasted to all connected clients, which in turn send back a grid of data called a "steering matrix" which tells the access point where the client is and where it's going. This allows the access points to tailor the broadcast to that specific client, which makes a huge difference in data rates at medium distances. All these features add up to give multiple users on the same network acceptable data rates at variable distances despite the high noise floor generated by so much energy.
The technology behind 802.11ac requires dependable receivers at both ends of the connection. At the time of this writing, such hardware comes at a high cost, so wholesale deployments will be uncommon. However the advantages are clear for users wanting bandwidth intensive wireless applications in homes or businesses. 802.11ac is only the beginning as Wave 2 will offer even higher bandwidth of 160 MHz channels. The upcoming successor 802.11ad protocol will move out of the 5 GHz spectrum altogether and occupy the high frequency 60 GHz radio space.
These are very exciting times for telecommunication technologies. The ability to offer gigabit data rates without the need to lay expensive cabling will open doors for new applications at businesses, schools and hospitals around the world. Soon tech-savvy users can stream 4K video to any device in any room they want. Surely there will be even grander applications that seemed like science fiction merely a decade ago as a result.