How Wi-Fi Works

http://www.verizoninternet.com/bookmark/how-wifi-works/

by sharjeelsayed • 9 years ago

308 92 9 years ago

verizoninternet.com

jonathanbull2• 9 years ago

Mirror: http://webcache.googleusercontent.com/search?q=cache:http://...

gruez• 9 years ago

google cache doesn't do the page justice. most of the value is in its visualizations.

jonathanbull2• 9 years ago

True, but better than the 503 I was receiving.

dotancohen3• 9 years ago

The cache now has the images, though it didn't when first posted. Honestly, the Google cache is _better_ than the original as it doesn't have the CPU-killing animations.

marmshallow• 9 years ago

The Archive of it is better https://web.archive.org/web/20170723145452/http://www.verizo...

dotancohen3• 9 years ago

These guys should do a followup "How Load Balancing Works".

sshanky• 9 years ago

This is beautiful, but probably still too complex for most of their customers. I wonder what their motive in putting this together was, as it must have been very expensive.

Rjevski• 9 years ago

Maybe the fact that as an internet provider it's their duty to explain how what they're selling works? Granted, "internet" doesn't mean Wi-Fi however their equipment includes a wireless access point so it's fair for them to provide documentation about how that works.

gist• 9 years ago

it's their duty

Not at all. No more than a car manufacturer has a 'duty' to explain how a car or a car engine works.

crispyambulance• 9 years ago

Yeah, it is beautiful.

Unlike their overcomplicated phone plans and billing statements which are deliberately obscure and their customer service which they run like a 2-bit boiler room operation.

lhuser123• 9 years ago

Specially obscure. Which is like scamming, because most people won't try to understand it.

joe5150• 9 years ago

it was nearly too complex for my pc! I had hardware acceleration disabled in Chrome and it completely pegged my CPU out. the animations barely worked until I re-enabled it, but then the page ran out of memory. I ended up having to look at it on my phone.

I'm not convinced the manipulable 3D modem rendered in-browser in realtime really added a lot of value for me, but it's pretty cool I guess.

princekolt• 9 years ago

"How Wi-Fi Works" --> 503 Service Unavailable

Seems about right.

Kenji• 9 years ago

Hahaha, I was about to post just that. Made me laugh. Reminds me of my time at university... during breaks and boring lectures, WiFi was impossible to use because of the load. You could probably measure how boring a lecture is by recording WiFi latency and stability parameters.

dzhiurgis3• 9 years ago

I've got that once it requested WebGL access and I've clicked "Never for this site". Refreshed and worked fine.

microwavecamera• 9 years ago

Verizon is trying to give you the authentic experience of how your WiFi works when you're on their network.

bdcravens3• 9 years ago

Speaking of how wifi works, I learned something interesting about wifi and Verizon's partner in many things, Comcast: Last night I notified my home Internet acting funny, and learned that the admin interface for my Comcast router had username "admin", password "password". SMH.

joshumax2• 9 years ago

If you want to hear something else scary, I dumped the firmware on my modem a little while back and started exploring it:

https://twitter.com/joshumax/status/860712276717748225

willstrafach2• 9 years ago

Did you need to do anything special to get shell access?

mnm2• 9 years ago

... which is "okay", since you can only access it (the admin web console) from within your wlan/lan (and not the internet) and ofc you can/should change it during setup

bdcravens3• 9 years ago

Most people (esp non-HNers) don't, they just let Comcast set it up. To make matters worse, they set the SSID to my last name, and the password was my address. Maybe that's one-off, but if standard, seems problematic.

mandeepj• 9 years ago

... which is "okay"

Nope. Anyone within range of your wifi router can connect to it and most possibly the first username and password that they will try is admin\admin or admin\password

rayiner2• 9 years ago

I mean, I just got a 10-gig router,[1] and the stock username/password was "ubnt"/"ubnt." It's always the installer's job to set up a new username/password.

[1] https://community.ubnt.com/t5/EdgeMAX-Stories/EdgeRouter-Inf...

jstimpfle• 9 years ago

Why not generate a long password and print it on the backside? My DSL provider can do it (for my DSL router)

hppycffee• 9 years ago

ISP's like spectrum discourage dispatching techs and opt for customer setup. And every model they give you has an 'admin/admin' or 'admin/password' setup.

plandis• 9 years ago

I think the difference here is that someone buying Ubiquiti is knowingly getting a slightly more in depth initial setup.

Your grandma is getting a Comcast router and probably doesn't know it can be logged into and configured or how to do it.

fest• 9 years ago

ER-XG is quite far from home WiFi router though :)

UBNT's new-ish home router series (AmpliFi) doesn't have default username/password- it needs to be set-up before using. I do think it's possible to have an open-network default configuration, but the LCD will nag you to set-up the device, and the first step of the setup is choosing a password (both for management and WiFi).

Disclaimer: I work at UBNT.

oskenso• 9 years ago

Also there was a time when Verizon's modem/router had generated passwords based on the SSID https://aruljohn.com/fios/

JustSomeNobody• 9 years ago

Why can't it be "admin", "<random string of x number of nums chars etc>". Could even print it in the bottom of the device.

peterwwillis• 9 years ago

It's bad practice to assume things are set up properly by someone else. This applies to more than just computers, fwiw.

greedo• 9 years ago

My ISP just set me up with gigE fiber. The installer was a bit clueless, didn't really want to provide me with the gateway IP for the router. Then I looked at the wifi settings; a 2.4Ghz and 5 Ghz setup, both with SSIDs that included the provider's name as a prefix. The password was a 9 digit password, all numerical...

I called the support line and got through quickly to an admin who could change the password and SSID for me (unless you pay for a public IP, the mgmt interface is locked down). I mentioned that having such a short, all numerical password would mean that any access point they set up would be trivial to crack. Just wardrive looking for similarly named access points, and you'd be able to jump on their connection in just a few minutes. He didn't seem to care, which is too bad.

hatsunearu• 9 years ago

the radio stuff is pretty wrong; one glaring one is that PSK is pretty much not used anymore, it's all OFDM.

rayiner2• 9 years ago

OFDM is orthogonal to PSK (hah). PSK is a modulation--a way of representing bits on a carrier wave. Another type of modulation is QAM. OFDM is a way of combining multiple sub-carriers (each modulated with PSK or QAM) into one signal in order to deal with multi-path distortion: https://www.csie.ntu.edu.tw/~hsinmu/courses/_media/wn_11fall....

tankenmate• 9 years ago

Some systems even combine PSK and ASK (like QAM) but asymmetrically (called APSK), obviously though you start getting into diminishing returns; noise limiting the gains. Of course you are limited by Shannon's law. But depending on the transmission medium lower energy signals can be more resistant to noise, so you can use either probabilistic or dynamic symbol selection to reduce the effect noise has on the signal and hence increase the available error free bandwidth (error free symbol rate)[0].

[0] https://en.wikipedia.org/wiki/Constellation_shaping ; check the references and external links for more in depth explanations.

mrb2• 9 years ago

Still, hatsunearu is correct. The page is grossly wrong, absolutely no modern WiFi modulation technique uses 8-PSK. Have a look at http://mcsindex.com/ 11a/11n/11ac all use BPSK, QPSK, 16-QAM, 64-QAM, and (for 11ac only) 256-QAM.

notgood• 9 years ago

Just a reminder that Verizon its the biggest lobbyist against Net Neutrality[0] and if you do support it then it's probably wise to stay away from their services as far as possible.

[0] https://www.dailydot.com/layer8/lobbyists-net-neutrality-fcc...

mrb2• 9 years ago

As hatsunearu said, the radio modulation described is grossly incorrect. WiFi never uses 8-PSK (encoding 3 bits per symbol). 802.11n and 11ac encode 1/2/4/6/8 bits using a BPSK/QPSK/16-QAM/64-QAM/256-QAM symbol (256-QAM is for 11ac only). The modulation scheme is negotiated based on signal quality. Here is a quick reference: http://mcsindex.com/ (MCS = modulation coding scheme) On Linux you can find the MCS negotiated with "iw dev wlan0 link | grep -i mcs"

14 channels are defined in the 2.4GHz band. For example channel 6 is centered on 2437 MHz. Each channel is 20MHz wide and divided in 52 "data" subcarriers, each occupying a different frequency and spaced out by 312.5 kHz (52 × 312.5 kHz is less than 20 MHz because there are "control" subcarriers and additional spacing.) So 52 different symbols can be sent in parallel at the same time, which is what we call OFDM https://en.wikipedia.org/wiki/Orthogonal_frequency-division_... (basically, I'm simplifying!)

Remember this is for just 1 channel. So with 14 channels each composed of 52 subcarriers, we could have 728 symbols transmitted at the same time. If they are 256-QAM symbols that's basically 728 × 8 = 5824 bits being transmitted at the same time in the air. And they will all be received and demodulated independently. This high level of parallelism of OFDM is how WiFi can achieve very high throughput.

Then, with wide channels of 40 MHz, which basically aggregate two 20 MHz channels, we get a few more data subcarriers because we don't need as many control subcarriers so a few of them become used as data subcarriers. Hence a 40 MHz channel will have not 52 × 2 = 104 but actually 108 data subcarriers. And 802.11ac defines 80 MHz and 160 MHz channels with respectively 234 and 468 data subcarriers.

Let's calculate the maximum usable throughput of a single 802.11ac 160 MHz channel using 256-QAM modulation... It sends 468 symbols at the same time on 468 data subcarriers. Each symbol encodes 8 bits and takes in the best case 3.6us to be transmitted: 3.2us for the actual symbol + a short guard interval of 0.4us (the GI is normally 0.8us but can be a short GI of 0.4us if negotiated). The raw physical bitrate is:

1/3.6e-6 × 468 × 8 = 1.04 Gbit/s

However there is a mandatory error correction which is 5/6 in the best case so the actual usable bandwidth is:

1.04 × 5/6 = 866.67 Mbit/s

dzhiurgis3• 9 years ago

1.04 × 5/6 = 866.67 Mbit/s

This is bang on what most hardware is able to achieve.

I am curious Apple haven't jumped into 512-QAM yet. Partly stopped me from upgrading my fiber to 1Gb/s.

aexaey2• 9 years ago

Nobody uses 512-QAM for WiFi, and for some good reasons:

1) it's not part of any current or draft standard;

2) it only encodes 9 bits vs. 8 bits for 256-QAM. Plugging this into GP's formula gives us:

1/3.6e-6 × 468 × 9 × 5/6 = 975 Mbit/s

3) current WiFi QAM constellations are all square [1,2], and there is no way to arrange 512 points into a square.

4) that would require an unrealistically clean channel, and give no advantage over lower-order modulations otherwise [3]

[1] https://dsp.stackexchange.com/questions/31607/why-are-qam-co...

[2] http://www.radio-electronics.com/info/rf-technology-design/q...

[3] https://upload.wikimedia.org/wikipedia/commons/thumb/6/68/QA...

azernik• 9 years ago

Note that, although the 2.4GHz spectrum is formally divided into 12-14 channels (depending on local regulations), these are very narrow channels; in practice there are only 3 non-overlapping 20MHz-wide channels. This is a small fraction of the width of the 5GHz band.

aexaey2• 9 years ago

There are 3 non-overlapping 2.4Ghz channels (1,6,11) for 802.11b, because of the channel spectrum shape. Not only "b" uses 22Mhz channels with is just a bit too wide, but also, due to the way how single-carrier PSK modulation works, especially on older hardware, "b" has considerable amount of spurious emissions adjacent to the main carrier that widen it even more - could be seen here as smaller "hills" to the left and right [1],[2].

802.1g/n/ac can easily have 4 non-overlapping channels (1,5,9,13) because (thanks to OFDM) channel spectrum is much neater with rather square 20 (40) Mhz channels with practically no energy outside [3].

Yet, everybody's stuck with 1,6,11 channel scheme which is wasting precious bandwidth. [4] (middle graph) Notice gaps between the channels that could be eliminated by moving 6->5 and 11->9, and gap on the right where channel 13 can fit after that.

[1] https://villagetelco.org/2009/11/rf-hacking/

[2] http://ecee.colorado.edu/~ecen4242/wlanb/index_files/image02...

[3] http://rfmw.em.keysight.com/rfcomms/n4010a/n4010aWLAN/online...

[4] https://www.codify.com/wp-content/uploads/2009/07/Central-Ro...

arikrak• 9 years ago

I was looking at this and thought it looked nice but then my computer froze so maybe they overdid the 3D graphics a bit?

blocker_chain• 9 years ago

Lol I had the same thoughts

dotancohen3• 9 years ago

Try the Google cache, it now has the images but not the animations: http://webcache.googleusercontent.com/search?q=cache:http://...

andrenotgiant2• 9 years ago

This is (good) SEO linkbait. Someone at Verizon got $10k to spend getting it created by saying it will boost organic search traffic to Verizon. Right now (during link-building phase) they keep the page completely separate from rest of site. Later, (after most links are created) they'll change it. Not sure whether the goal is just to generally build authority to VerizonInternet, or to get this URL ranking for wifi keywords. (Seems more likely the former.)

ejo3• 9 years ago

That page probably cost a lot more than 10K.

moondev• 9 years ago

Absolutely. They did a great job too

vxNsr• 9 years ago

Would it be accurate to assume this is gonna be used as ammo in the net neutrality debate of the next few weeks?

srtjstjsj3• 9 years ago

Are you saying they'll change the content later, and won't lose seojuice for that?

srtjstjsj3• 9 years ago

The promoted embed snippet actually points to a different URL: http://www.verizoninternet.com/bookmark/guides/how-wifi-work... which contains a bunch of site gunk for their "bookmark" blog, where they post a lot of content (and probably some net "neutrality" articles coming soon?)

Piccollo• 9 years ago

Why did CSS stop working

pier25• 9 years ago

I had to disable the ad blocker to get the nice web gl graphics.

From a front end perspective I think this it's awesome. No so sure about the content though.

nvahalik• 9 years ago

Can someone explain the natural resonance of walls of talked about with regards to 5Ghz?

deepsun2• 9 years ago

Does anyone know, if I'm on a WPA2-PSK wi-fi, do other devices that are also on the same network can "sniff" my traffic. For unprotected networks it's obvious, but what about protected?

m-j-fox2• 9 years ago

It wouldn't be a good system if they could. You have to worry more about wired Ethernet which can also be encrypted but rarely is.

GrayShade• 9 years ago

As far as I know, they can [1]. Once you're connected to the network you can sniff out everything from clients that connect after you.

The standard response to this is that you're safe since the eavesdropper needs to know the shared key. You can look into setting up WPA2-Enterprise if you're worried about that. FreeRADIUS doesn't seem particularly hard to configure.

[1] https://superuser.com/a/156969

ryan-c• 9 years ago

Yes, other devices on the same network (using WPA2-PSK) can sniff your traffic. It's possible to prevent this with WPA2-Enterprise.

detaro2• 9 years ago

Yes, if you know the PSK (=password) and can capture the initial handshake (which is easy, since you can just force-disconnect a client so it has to do a new one) you can decrypt it. (If I remember correctly, Wireshark has this built in, so you can try it for yourself if you are curious)

voltagex_2• 9 years ago

I'm assuming you mean a malicious device can force a deauth on another client (or more usually, all other clients) and then capture the packets as they reconnect. If so, is there a way to detect this? Is there any way to protect against this? I'm assuming client isolation makes it more difficult.

Magnets• 9 years ago

Each client uses a different session encryption key but that is negotiated using the shared PSK.

srtjstjsj3• 9 years ago

website crashes chrome on windows after a few seconds.

KozmoNau7• 9 years ago

TL;DR: It doesn't.

anilakar• 9 years ago

Stopped reading at "Wi-Fi antennas send information". Antennas don't send anything, they just match the impedance of the feedline into that of the medium.

Yizahi• 9 years ago

In my experience it doesn't. My every attempt at improving this shit ends up in laying more wires everywhere.

Ajedi32• 9 years ago

Getting a 404 now. Any idea where the page went? (Here's an archive link: https://web.archive.org/web/20170723145452/http://www.verizo...)

glenneroo• 9 years ago

Are you sure it was a 404? I'm getting a 503 (Service Temporarily Unavailable). Not that it really matters...

founderguy• 9 years ago

Pretty sure that domain isn't owned by Verizon. Looks like an authorized seller creating content to try to build authority.

andrenotgiant2• 9 years ago

Looks like it is actually owned by Verizon, see email contact on WHOIS http://whois.domaintools.com/verizoninternet.com

Web1Dollar• 9 years ago

wi-Fi is a best device! but is can work slow than wire. https://www.webhostingonedollar.com/ visit for getting more detail about hosting plan.

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