How Much Better is 802.11ax?

The new WiFi standard 802.11ax is expected to be ratified and released as a standard sometime next year. In the new industry nomenclature this now be called WiFi-6. A lot of the woes we have today with bandwidth in our home is due to the current 802.11ac standard that this will be replacing. 802.11ax will introduce a number of significant improvements that ought to improve home WiFi performance.

To understand why these improvements are important we need to first understand the shortcomings of the current WiFi protocols. The industry groups that developed the current WiFi standards had no idea that WiFi would become so prevalent and that the average home might have dozens of WiFi capable devices. The current problems all arise from a WiFi router trying to satisfy multiple demands for a data stream from multiple devices. Unlike cellular technologies, WiFi has no central traffic cop and every device in the environment can make an equal claim for connectivity. When a WiFi router has more demands for usage than it has available channels it pauses and interrupts all data streams until it chooses how to reallocate bandwidth. In a busy environment these stops and restarts can be nearly continuous.

The improvements from 802.11ax will all come from smarter ways to handle requests for connectivity from multiple devices. There is only a small improvement in overall bandwidth with a raw physical data rate of 500 Mbps compared to 422 for 802.11ac. Here are the major new innovations:

Orthogonal Frequency-Division Multiple Access (OFDMA). This improvement will likely have the biggest impact in a home. OFDMA can slice the few big existing WiFi channels into smaller channels, being called resource units. A router will be able to make multiple smaller bandwidth connections using resource units and avoid packet collision and the start/stop cycle of each device asking for primary connectivity.

Bi-Directional Multi-User MIMO. In the last few years we’ve seen home WiFi routers introduce MIMO, which uses multiple antennas to make connections to different devices. This solves one of the problems of WiFi by allowing multiple devices to download separate data streams at the same time without interference. But today’s WiFi MIMO still has one big problem in that the MIMO only work for downloading. Whenever there is a request for any device to use a channel for uploading, today’s MIMO pauses all the downloading streams. Bi-Directional MIMO will allow for 2-way data streams meaning that a request to upload won’t kill downstream transmissions.

Spatial Frequency Reuse. This will have the most benefit in apartments or in homes that have networked multiple WiFi routers. Today a WiFi transmission will pause for any request for connection, even for connections made to a neighbor’s router from the neighbor’s devices. Spatial Frequency Reuse doesn’t fix that problem, but it allows neighboring 802.11.ax routers to coordinate and to adjust the power of transmission requests to increase the chance that a device can connect to and maintain a connection to the proper router.

Target Wake Time. This will allow small devices to remain silent most of the time and only communicate at specific and pre-set times. Today a WiFi router can’t distinguish between a request from a smart blender and a smart TV, and requests from multiple small devices can badly interfere with the streams we care about to big devices. This feature will reduce, and distribute over time the requests for connectivity from the ever-growing horde of small devices we all have.

There’s no rush to go out and buy and 802.11ax router, although tech stores will soon be pushing them. Like all generations of WiFi they will be backwards compatible with earlier WiFi standards, but for a few years they won’t do anything differently than your current router. This is because all of the above features require updated WiFi edge devices that also contain the new 802.11ax standard. There won’t be many devices manufactured with the new standard even in 2019. Even after we introduce 802.11ax devices into our home we’ll continue to be frustrated since our older WiFi edge devices will continue to communicate in the same inefficient way as today.