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

["Dave Farber" <farber () gmail com>]

Begin forwarded message:

> From: Dewayne Hendricks <dewayne () warpspeed com>
> Date: March 4, 2017 at 10:47:46 AM EST
> To: Multiple recipients of Dewayne-Net <dewayne-net () warpspeed com>
> Subject: [Dewayne-Net] 802.eleventy what? A deep dive into why Wi-Fi kind of sucks
> Reply-To: dewayne-net () warpspeed com
>
> 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 4x4 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 3x3 dual-band routers are suddenly jumping from "AC1700" to "AC1900.”
>
> [snip]
>
> Dewayne-Net RSS Feed: <http://dewaynenet.wordpress.com/feed/>



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