What Will 802.11ax Bring To Your Airspace?

Experts predict uplink scheduling and OFDMA optimizations together will improve performance by up to 3 times for certain use cases.

istock 874849032
Wenjie Dong
tom Aruba

Tom Hollingsworth, Blog Contributor

The industry is on the cusp of a new wireless protocol. It's been almost 10 years since 802.11ac was proposed, and five years since final ratification. 802.11ac has been built upon to deliver speeds past 1 Gpbs and has become the preferred method of wireless connectivity for computers and mobile devices alike.

However, 802.11ac exposes many of the problems we have with Wi-Fi coverage that is just faster. As Wi-Fi has become the primary method of connectivity for a range of devices we've seen how the protocol breaks down under certain conditions. We've seen how the accumulation of little issues can keep our speeds down and how simply making things bigger and faster won't fix them. That's why 802.11ax is taking a much firmer hand in directing wireless traffic.

Making Lanes For Data

One of the biggest changes in 802.11ax is the addition of Orthogonal Frequency-Division Multiple Access (OFDMA). That's a fancy acronym that describes the way that 802.11ax handles sub-channel communications. We've seen that the explosion of wireless devices in the past years has meant that there are many, many more devices trying to talk to an access point (AP) at any one given time. This means that there are a lot of clients waiting in line to deliver and receive data.

In 802.11ac and earlier protocols any transmission has to use the entire channel to transmit or receive. That doesn't mean much if you have a relatively skinny 20 MHz channel width. But if you've cranked the radio all the way up to 160 MHz, you're sending eight times the data but still using the entire channel no matter the size of the packet. This is inefficient and wastes valuable time that could be used by other clients.

802.11ax changes things by dividing those channels into a collection of subchannels. This allows data to be transmitted in parallel across a series of smaller channels instead of taking an entire wide channel for small things like acknowledgment (ACK) frames and such. For small packets, this means that a client can transmit and only use the necessary amount of bandwidth for their frame. This means they get off the air faster and can let the AP utilize those other subchannels for other clients.

For larger packet sizes, splitting things into a group of parallel transmissions saves transmission times versus sequential transmission. Research indicates that this could be up to three times faster for simple parallel versus sequential transmission. An increase in speed of 3x is nothing to sneeze at!

The best part is that these changes are in both the 5 GHz and 2.4 GHz spectrum. 802.11ac focused only on 5 GHz and left users of the older 2.4 GHz spectrum out in the cold. With 802.11ax, we're going to see improvements across the board. Much like the older 802.11n standard, even clients that don't support 802.11 ax should see an improvement thanks to better handling of transmission and such. This should really be helpful to the exploding Internet of Things (IoT) market, since most of those devices rely on inexpensive 2.4 GHz radios.

Waiting For Your Turn

The other thing that makes 802.11ax much more efficient is the idea of uplink scheduling. This is a method that allows the AP to decide who can transmit, what times they can transmit, and which channel/subchannels they can use. The analogy that is frequently used is of the air traffic control system in commercial flight. By having someone monitor and schedule takeoffs and landings you can serve a much larger flight schedule than if planes got to choose their own times.

Wireless clients are greedy by nature. They want to send their data right away and get a response as soon as possible. The interrupt-driven nature of communications makes it difficult for an AP to serve a large number of clients without eventually grinding to a halt due to the large amount of crosstalk and interruptions.

With uplink scheduling, the wireless AP can make sure that those interruptions don't happen very often. The scheduling algorithm on the AP can give clients a transmission window for sending large payloads. It can also choose when to answer client requests as well as sending partial acknowledgments to keep the clients happy while waiting for payload delivery.

Uplink scheduling also means that you can save battery power as well. By telling the client when they can transmit, the AP can also instruct the client to power down their radio until that time. Even if they schedule has the radio powered off and not transmitting for a few seconds those few seconds add up over the course of the day. Just like OFDMA, the little optimizations add up to make things better overall.

The future of 802.11ax is coming sooner than you think. APs and client radios should be out in the early part of 2018 ahead of ratification of the standard. That means you still have some time to take in what's being proposed and decide what your upgrade strategy is going to be. If you have a lot of high density clients or have many clients that still operate in the 2.4 GHz spectrum the move to 802.11ax should be an easy "yes". As for the rest, it's going to take time and research to find out if 802.11ax is going to give you the control you want at the price that's right.

Ready to Learn More About 802.11ax?

Get an in-depth understanding of 802.11ax in this whitepaper.

Visit our 802.11ax page

802.11ax white paper



Copyright © 2018 IDG Communications, Inc.