If you thought that your new
802.11ac router’s max speed of 1,300Mbps was pretty crazy, think
again: With 802.11ac fully certified and out the door, the Wi-Fi
Alliance has started looking at its successor, 802.11ax — and boy do the
early draft specs and transfer speeds look good. While you will
probably be hard pushed to get more than 400Mbps to your smartphone via
802.11ac, 802.11ax should be into the 2Gbps+ range. In a lab-based trial
of technology similar to 802.11ax, Huawei recently hit a max speed of
10.53Gbps, or around 1.4 gigabytes of data transfer per second. 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 so darn awesome). I suspect OFDA is just an alternative name for the same thing. In any case, OFDM/OFDA/OFDMA refer to methods of frequency-division multiplexing — basically, each channel is separated into dozens/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. The Wi-Fi Alliance, speaking to GigaOm, says they’re targeting just a 4x increase in speed.
How fast is 802.11ax?
If we go for the more conservative 4x estimate, and assume a massive 160MHz channel, max speed of a single 802.11ax stream will be around 3.5Gbps (866Mbps for a single 802.11ac stream). Multiplying that out to a 4×4 MIMO network you get a total capacity of 14Gbps. If you had a smartphone or laptop capable of two or three streams, you’d be looking at some sickening connection speeds (7Gbps equates to around 900 megabytes per second; 10.5Gbps equates to 1344MB/sec).In a more realistic setup with 80MHz channels, we’re probably looking at a single-stream speed of around 1.6Gbps — or a very reasonable 200MB/sec. Again, if your mobile device supports MIMO, you could be seeing 400 or 600MB/sec.
In a much more realistic setup with 40MHz channels (i.e. 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.
802.11ax range, reliability, and other factors
So far, neither the Wi-Fi Alliance or Huawei has said a lot about 802.11ax’s other important features. Huawei says that “intelligent spectrum allocation” and “interference coordination” will be used — but that I think most modern WiFi hardware already does that.It’s fairly safe to assume that the range will stay the same or increase slightly. Reliability should improve a little with the inclusion of OFDA, and with the aforementioned spectrum allocation/interference coordination features. Congestion might also be reduced (by the same aforementioned features), and because data will be transferred between devices faster, freeing the airwaves for other connections.
For the most part though, don’t expect any major changes with 802.11ax except for massively increased throughput.
we need these kinds of speeds?
As you may have already noticed, even 802.11ax’s slowest speed of 100MB/sec is pushing it for a hard drive — and, incidentally, it’s a lot faster than the eMMC NAND flash storage in most smartphones can handle, too. Best-case, 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 range. Obviously, for the wider 80MHz and 160MHz channels, you’re going to need some SSDs (or an array of SSDs) to take advantage of 802.11ax’s max speeds.Of course, not every use-case requires you to read or write data to a slow storage medium, though — but even so, alternate uses like streaming 4K video, still fall way short of these multi-gigabit speeds. Even if Netflix starts doing 8K in the next few years, 802.11ax has more than enough bandwidth — and anyway, the bottleneck isn’t your WiFi, it’s your internet connection. The current time frame for 802.11ax certification is 2018 — and I’m pretty sure that most of us will still be rocking sub-300Mbps internet connections by then.
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