802.eleventy what? A deep dive into why Wi-Fi kind of sucks

802.eleventy what? A deep dive into why Wi-Fi kind of sucks
The good news is that it doesn’t have to suck, if you build it out properly.
By JIM SALTER
Mar 4 2017
https://arstechnica.com/information-technology/2017/03/802-eleventy-what-a-deep-dive-into-why-wi-fi-kind-of-sucks/

When wireless networking based around the 802.11b standard first hit consumer markets in the late nineties, it looked pretty good on paper. Promising “11 Mbps” compared to original wired Ethernet’s 10 Mbps, a reasonable person might have thought 802.11b was actually faster than 10Mbps wired Ethernet connections. It was a while before I was exposed to wireless networking—smartphones weren’t a thing yet, and laptops were still hideously expensive, underpowered, and overweight. I was already rocking Fast Ethernet (100 Mbps) wired networks in all my clients’ offices and my own house, so the idea of cutting my speed by 90 percent really didn’t appeal.

In the early 2000s, things started to change. Laptops got smaller, lighter, and cheaper—and they had Wi-Fi built in right from the factory. Small businesses started eyeballing the “11Mbps” that 802.11b promised and deciding that 10Mbps had been enough for them in their last building, so why not just go wireless in the new one? My first real exposure to Wi-Fi was in dealing with the aftermath of that decision, and it didn’t make for a good first impression. Turns out that “11Mbps” was the maximum physical layer bit rate, not a speed at which you could ever expect your actual data to flow from one machine to another. In practice, it wasn’t a whole lot better than dial-up Internet—in speed or reliability. In real life, if you had your devices close enough to each other and to the access point, about the best you could reasonably expect was 1 Mbps—about 125 KB/sec. It only got worse from there—if you had ten PCs all trying to access a server, you could cut that 125 KB/sec down to 1.25 KB/sec for each one of them.

Just as everybody got used to the idea that 802.11b sucked, 802.11g came along. Promising 54 screaming Mbps, 802.11g was still only half the speed of Fast Ethernet, but five times faster than original Ethernet! Right? Well, no. Just like 802.11b, the advertised speed was really the maximum physical layer data rate, not anything you could ever expect to see on a progress bar. And also like 802.11b, your best case scenario tended to be about a tenth of that—5 Mbps or so—and you’d be splitting that 5 Mbps or so among all the computers on the network, not getting it for each one of them like you would with a switched network.

802.11n was introduced to the consumer public around 2010, promising six hundredMbps. Wow! Okay, so it’s not as fast as the gigabit wired Ethernet that just started getting affordable around the same time, but six times faster than wired Fast Ethernet, right? Once again, a reasonable real-life expectation was around a tenth of that. Maybe. On a good day. To a single device.

When 802.11ac came to market in late 2013, the boxes in stores hysterically proclaimed faster and faster speeds, many of them several times higher than the fastest consumer wired networking available. As the years went by, it was 1.3 Gbps! 2.7 Gbps! 5.3 Gbps! But by then, I’d long since stopped paying attention. The marketers had gotten the bit between their teeth on day one and never let go. Wi-Fi is nowhere near as fast as wired; the marketing is all lies, lesson learned.

Having given up being excited about Wi-Fi a long time ago, I found it deeply weird when Wi-Fi mesh exploded on the market in 2016, and I wound up reviewing it in-depth.

Unpacking the marketing copy

Let’s say a wireless router offers you an “AC5300” router with “breakthrough tri-band Wi-Fi technology with amazing combined wireless speeds of up to 5,332 Mbps. Thanks to 4×4 data streams, that can be combined through beamforming and MU-MIMO technology to increase reliability and range.” (Actual ad copy from a modern router. It’s not just D-Link, though—Netgear, Linksys, ASUS, and TP-Link all do the same thing.) By now, we hopefully know that absolutely does not mean we’re going to connect a laptop and download things at 600+ MB/sec. But what does it mean?

Things get murky when we try to unpack that “AC5300” speed rating. The way these things are generated is by taking the maximum PHY rate of each radio in the router, multiplied by the maximum number of MIMO streams that radio supports, and adding them all together. The DIR-895L/R is a tri-band device and can transmit and receive on three different Wi-Fi channels at once: two 5 GHz channels and one 2.4 GHz channel. Assuming you don’t have any congestion from your neighbors’ networks, that means you can connect three devices—say, a laptop, a smartphone, and a tablet—all at once, to different radios and on different channels. So far, so good!

We have two 5 GHz radios with 80MHz wide channels and a 2.4 GHz radio with a 40 MHz wide channel, each of which supports up to four MIMO streams. Unfortunately, this doesn’t add up right—433 Mbps per 80 MHz wide 5GHz channel multiplied by four spatial streams comes out to 1,732 Mbps, and D-Link is claiming 2,166 Mbps per 5GHz radio. Where’s that extra 108.5 Mbps per stream coming from? You won’t find a straightforward answer to that question, but depending on your level of cynicism, it’s either “proprietary extensions to 802.11 that your device may or may not support enabling compression that your data may or may not be suitable for,” or “marketing lol.” This is a pretty standard practice now, and it’s the reason why some 3×3 dual-band routers are suddenly jumping from “AC1700” to “AC1900.”

[snip]

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