Making WiFi fast

Posted Nov 9, 2016 8:10 UTC (Wed) by Felix.Braun (guest, #3032)
Parent article: Making WiFi fast

Maybe WiFi can work in American houses built mainly out of wood with tons of space around each one. But in my experience a set of concrete walls will dampen the WiFi signal significantly even within a relatively small appartment. And if you live in a house with 15 other families then the 2.4 GHz band will become pretty crowded really fast. So it's Ethernet for me.

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Making WiFi fast

Posted Nov 9, 2016 9:08 UTC (Wed) by Sesse (subscriber, #53779) [Link] (8 responses)

Uhm, the solution to 2.4 GHz getting crowded is to… use 5 GHz. There's hardly any reason to use 2.4 GHz anymore, and 802.11ac doesn't even support it.

Making WiFi fast

Posted Nov 9, 2016 17:55 UTC (Wed) by spaetz (guest, #32870) [Link] (2 responses)

> There's hardly any reason to use 2.4 GHz anymore, and 802.11ac doesn't even support it.

Except that the HP laptop I just bought only supports 2.4GHz. Looking for 802.11n and Linux compatability, I failed to notice that a 500€ machine does not do 5GHz nowadays. It is a shame, really.

Making WiFi fast

Posted Nov 10, 2016 17:23 UTC (Thu) by kamil (guest, #3802) [Link]

Check if the WiFi in your laptop is upgradable. It's often on a separate mini-PCIe card that is trivial to replace with little more than a screwdriver, and the cards can often be found for under $/€20 on eBay and such.

Making WiFi fast

Posted Nov 11, 2016 0:08 UTC (Fri) by cesarb (subscriber, #6266) [Link]

> Looking for 802.11n and Linux compatability, I failed to notice that a 500€ machine does not do 5GHz nowadays.

There's a solution for that now: look for 802.11ac. Since 802.11ac is 5 GHz only, its presence means that the WiFi adapter can do 5 GHz.

Once 802.11ac becomes more popular, it should reduce the annoying tendency of offering professional-grade laptops with only 2.4 GHz WiFi.

Making WiFi fast

Posted Nov 10, 2016 3:04 UTC (Thu) by drag (guest, #31333) [Link] (4 responses)

2.4ghz is nice if you need longer distance. Different frequencies have different strengths.

Making WiFi fast

Posted Nov 10, 2016 8:33 UTC (Thu) by Sesse (subscriber, #53779) [Link] (3 responses)

They really don't. In empty space, they fade _exactly_ the same way (it's physics). And like I said in another comment, for most obstructions, they fade very similarly, too. The effects of “the band is seven times as wide” (really!) and “ambient noise tends to be about 3 dB lower on 5 GHz” drowns out these considerations in practice.

Making WiFi fast

Posted Nov 16, 2016 18:50 UTC (Wed) by mb (subscriber, #50428) [Link]

>They really don't. In empty space, they fade _exactly_ the same way (it's physics).

Except that my house consists of a little bit more matter than empty space and that the 5GHz signal certainly is a lot weaker than the 2.4 GHz signal after it passed a few walls.

Making WiFi fast

Posted Nov 18, 2016 7:11 UTC (Fri) by Sertorius (guest, #47862) [Link] (1 responses)

If you're going to make comments like that, please make sure you actually *know* the physics. The relevant equation in this case, the Friis path loss equation, has a lambda squared on the top, or if you prefer f squared on the bottom. So yes, path loss is significantly lower at lower frequencies; this is the reason that satellites use the lower of a pair of frequencies to transmit (because they are power-constrained); likewise frequency-division duplex phones will use the lower frequency channel for the uplink (again, power-constrained). This is also the best-case scenario; usually the path loss exponent is higher than 2 due to multipath fading (due to reflections).

Here's a graph if you aren't convinced.

5 GHz is severely attenuated by relatively mild obstructions (such as gyprock/drywall or timber) that 2.4 penetrates very easily. If you have concrete or brick walls, you'll want an AP in every room.

The main benefits of 5 GHz are that you have a lot more non-overlapping channels, so it is easier to avoid interference - it is also good if you have a lot of users to support and want to have a LOT of short-range APs.

Making WiFi fast

Posted Nov 18, 2016 8:34 UTC (Fri) by zlynx (guest, #2285) [Link]

The 5GHz fade is also a great thing in apartment buildings. All of your neighbors have a WiFi router that they picked up somewhere and they managed to make it though the configuration wizard. So every single apartment is at 100% transmission power, all of the time. Having the walls cut that down (and having all of the extra channels) really helps.

Making WiFi fast

Posted Nov 9, 2016 9:36 UTC (Wed) by Cyberax (✭ supporter ✭, #52523) [Link] (6 responses)

Rapid 5GHz signal fading is a GOOD thing. You won't get a lot of noise from neighbors. So just install a couple of WiFi repeaters in rooms with bad reception.

Making WiFi fast

Posted Nov 9, 2016 12:26 UTC (Wed) by Sesse (subscriber, #53779) [Link] (5 responses)

5 GHz actually fades pretty similarly to 2.4 GHz for most materials (red brick being a notable counterexample). But in many jurisdictions, it starts out with a small (3 dB) penalty in allowed transmission strength.

Making WiFi fast

Posted Nov 9, 2016 19:18 UTC (Wed) by jonth (guest, #4008) [Link] (4 responses)

A small nitpick: fading!=attenuation.

One other observation I'd like to share: 20 years of experience in cellular comms has taught me is that you can't beat a wire.

Making WiFi fast

Posted Nov 10, 2016 1:39 UTC (Thu) by samroberts (subscriber, #46749) [Link] (3 responses)

Unless your goal is to decrease wiring!

Making WiFi fast

Posted Nov 11, 2016 0:13 UTC (Fri) by cesarb (subscriber, #6266) [Link]

Or your wire is broken. Wireless is much harder to cut.

(A coworker just found out that the Ethernet wire to one of the WiFi APs at work was broken, which explains network issues they were having.)

Making WiFi fast

Posted Nov 14, 2016 6:13 UTC (Mon) by eduard.munteanu (guest, #66641) [Link] (1 responses)

In practice, though, WiFi is often added on to the premises as an afterthought. Whoever set up the space didn't plan properly for networking, so WiFi gets used as a stop-gap measure. As with all last resort measures, it kinda sucks, not necessarily because there's something inherently wrong with WiFi.

Making WiFi fast

Posted Mar 9, 2019 1:29 UTC (Sat) by gdt (subscriber, #6284) [Link]

A reminder that wired connections also have downsides, mostly its inconvenience and cost.

A good RJ-45 jack is rated for 2,500 cycles. So wireless is a much better fit for high-traffic areas such as cafes and libraries. Patch leads are a small but ongoing expense, and staff and students don't like "BYO patch lead".

A wired port costs around $200 per wallport to cable. But this can blow out when a custom solution is required. Wiring a cafe table will cost more than than table.

Wireless networks work without any further action by the user. Once set up (which is far too hard) Eduroam connects your laptop or phone to the campus network the moment you go to use the device. No searching for a jack and patch lead. Wireless is so convenient that it's common to see a person sitting next to a wall port but using wireless.

Wired from modern devices is difficult. Using wired ethernet from a phone or tablet requires special cabling (a OTG cable) to the ethernet dongle. The dongle itself is a optional purchase. Cheaper dongles meant for laptops might not have driver support in a phone. Using wired ethernet from a recent laptop requires a USB-C/ethernet dongle, which means the laptop can't be powered whilst using the wired network. To have both power and wired networking requires a bulky and expensive "docking station".

We should be telling people who need network performance to use wired. But that may not end up being the bulk of the connections on a campus network.