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.
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.
12/14/2015
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.)
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).
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