What is 802.11ax WiFi, and will it really deliver 10Gbps? (updated)

 

 Wireless standards tend to get proposed, drafted, and finally accepted at what seems like a glacial pace. It’s been roughly 17 years since we began to see the first 802.11b wireless routers and laptops. In the intervening time, we’ve only seen three more mainstream standards take hold since then: 802.11g, 802.11n, and now 802.11ac. (I’m leaving out some lesser-used ones like 802.11a for the purposes of this story.)
Now a new standard looms over the horizon. And if you thought that your new 802.11ac router’s maximum speed of 1,300Mbps was already fast, think again. With 802.11ac fully certified and out the door, the Wi-Fi Alliance is looking at its successor, 802.11ax — and it looks pretty enticing. While you may have a hard time getting more than 400Mbps to your smartphone via 802.11ac, 802.11ax should deliver real-world speeds above 2Gbps. And in a lab-based trial of technology similar to 802.11ax, Huawei hit a max speed of 10.53Gbps, or around 1.4 gigabytes of data transfer per second. Clearly, 802.11ax is going to be fast. But what is it exactly?

What is 802.11ax WiFi?

The easiest way to think of 802.11ax is to start with 802.11ac — which allows for up to four different spatial streams (MIMO) — and then to massively increase the spectral efficiency (and thus max throughput) of each stream. Like its predecessor, 802.11ax operates in the 5GHz band, where there’s a lot more space for wide (80MHz and 160MHz) channels.
With 802.11ax, you get four MIMO (multiple-input-multiple-output) spatial streams, with each stream multiplexed with OFDA (orthogonal frequency division access). There is some confusion here as to whether the Wi-Fi Alliance and Huawei (which leads the 802.11ax working group) mean OFDA, or OFDMA. OFDMA (multiple access) is a well-known technique (and is the reason LTE is excellent for what it is). Either way, OFDM, OFDA, and OFDMA refer to methods of frequency-division multiplexing — each channel is separated into dozens, or even hundreds, of smaller subchannels, each with a slightly different frequency. By then turning these signals through right-angles (orthogonal), they can be stacked closer together and still be easily demultiplexed.
According to Huawei, the use of OFDA increases spectral efficiency by 10 times, which essentially translates into 10 times the max theoretical bandwidth, but 4x is seeming like more of a real-world possibility.

This lovely diagram shows you North America’s 5GHz channels, and where those 20/40/80/160MHz blocks fit in. As you can see, at 5GHz, you won’t ever get more than two 160MHz channels (and even then, only if you live in the boonies without interference from neighbors).

How fast is 802.11ax?

Let’s say we take the more conservative 4x estimate, and assume a massive 160MHz channel. In that case, the maximum speed of a single 802.11ax stream will be around 3.5Gbps (compared with 866Mbps for a single 802.11ac stream). Multiply that out to a 4×4 MIMO network and you get a total capacity of 14Gbps. If you had a smartphone or laptop capable of two or three streams, you’d get some blazing connection speeds of 1GB per second or more.
In a more realistic setup with 80MHz channels, we’re probably looking at a single-stream speed of around 1.6Gbps, which is still a reasonable 200MB/sec. If your mobile device supports MIMO, you could be seeing 400 or 600MB/sec. And in an even more realistic setup with 40MHz channels (such as what you’d probably get in a crowded apartment block), a single 802.11ax stream would net you 800Mbps (100MB/sec), or a total network capacity of 3.2Gbps. (Read: How to boost your WiFi speed by choosing the right channel.)

802.11ax range, reliability, and other factors

So far, neither the Wi-Fi Alliance nor Huawei has said much about 802.11ax’s other important features. Huawei says “intelligent spectrum allocation” and “interference coordination” will be employed, but most modern WiFi hardware already does that.
It’s fairly safe to assume that working range will stay the same or increase slightly. Reliability should improve a little with the inclusion of OFDA, and with the aforementioned spectrum allocation and interference coordination features. Congestion may also be reduced as a result, and because data will be transferred between devices faster, that frees the airwaves for other connections.
Otherwise, 802.11ax will work in roughly the same fashion as 802.11ac — just with massively increased throughput. As we covered in our Linksys WRT1900AC review, 802.11ac is already pretty great. 802.11ax will just take things to the next level.

Do we need these kinds of speeds?

The problem, as with all things WiFi, isn’t necessarily the speed of the network itself — it’s congestion, and more than that even, it’s what the devices themselves are capable of. For example, even 802.11ax’s slowest speed of 100MB/sec is pushing it for a hard drive — and it’s faster than what the eMMC NAND flash storage in most smartphones can handle as well. Best-case scenario, a modern smartphone’s storage tops out at around 90MB/sec sequential read, 20MB/sec sequential write — worst case, with lots of little files, you’re looking at speeds in the single-megabyte-per-second range. Obviously, for the wider 80MHz and 160MHz channels, you’re going to need some desktop SSDs to take advantage of 802.11ax’s max speeds.
Not every use-case requires you to read or write data to a slow storage medium. But even so, alternate uses like streaming 4K video still fall short of these multi-gigabit speeds. Even if Netflix begins streaming 8K in the next few years (and you thought there wasn’t enough to watch in 4K!), 802.11ax has more than enough bandwidth. And the bottleneck isn’t your WiFi there; it’s your internet connection. The current time frame for 802.11ax certification is 2018 — until then, upgrading to 802.11ac (if you haven’t already) should be a nice stopgap.