14 ms·
You should see 2.4 GHz noise floor when viewed from a spectrum analyzer in a densely populated, 5-floor, wood framed condo/apartment in a major urban area. Prot
by walrus01 6y ago
You should see 2.4 GHz noise floor when viewed from a spectrum analyzer in a densely populated, 5-floor, wood framed condo/apartment in a major urban area. Prototypical example would be some place in south lake union seattle.
https://archive.curbed.com/2018/12/4/18125536/real-estate-modern-apartment-architecture https://archive.curbed.com/2018/12/4/18125536/real-estate-mo...
https://crosscut.com/2015/04/the-new-seattle-where-everything-looks-the-same https://crosscut.com/2015/04/the-new-seattle-where-everythin...
a "one plus five" looks like this, structurally: https://1.bp.blogspot.com/-DZ2BLyticQE/VRMjELb1DYI/AAAAAAAAXHI/ic2uYMsuUhc/s1600/IMG_9409.JPG https://1.bp.blogspot.com/-DZ2BLyticQE/VRMjELb1DYI/AAAAAAAAX...
Since 2.4 GHz goes through wood fairly effectively to moderate distances, it's a total half duplex CSMA hell...
One possible mitigation if you have older 2.4 GHz only devices is to run your own wifi on a 20 MHz channel, sacrificing throughput for better SNR. As channel sizes get narrower it cuts through the noise floor a little bit better. And of course to use your own choice of the cleanest 5.x GHz channel for everything you care about.
- Lammy 6y agoThey propagate signal about as well as they propagate fire
- foota 6y agoMy understanding is that wood structures compare similarly to others in a fire: https://link.springer.com/article/10.1007/BF01095562 https://link.springer.com/article/10.1007/BF01095562
- Lammy 6y agoIt's not just the material but the arrangement https://en.wikipedia.org/wiki/One-plus-five#Criticism https://en.wikipedia.org/wiki/One-plus-five#Criticism e: The study you linked is also a decade older than the type of construction we're talking about :)
- manuel_w 6y agoFun fact: Wooden doors propagate fire less then metal doors. That's because metal doors just heat up and set what's behind the door on fire, while wooden doors consume the heat. The opposite side of the doors stays cooler than a metal door would.
- hyperbovine 6y agoSay wha? Hollow core steel doors are the industry standard fire rated door. You’ll find them in almost every commercial building in America.
- Uberphallus 6y agoWhile what gp says is true, it's also true that doors usually don't touch anything other than the frame. It's a bit like that antijoke: What's white and hurts when it falls on you from a tree? A fridge.
- walrus01 6y agowhen under construction and all the wood is exposed, they burn very effectively... https://www.cbc.ca/news/canada/british-columbia/bc-langley-fire-1.5994236 https://www.cbc.ca/news/canada/british-columbia/bc-langley-f... https://twitter.com/JSchenderling/status/1384384802715934721?s=19 https://twitter.com/JSchenderling/status/1384384802715934721...
- throwaway189262 6y agoNot sure why downvoted. For nearly a century large multi family wood structures were banned in most countries due to fire risk. These huge apartment buildings are all 2X4's, not timber framing. They're incredibly flammable. The only thing keeping them safe is fire sprinklers. There's been many infernos that burned the things to the ground when sprinklers failed.
- SilverRed 6y agoI wonder if future apts buildings will build RF blocking mesh in to the roof and floors and then have a phone signal repeater in each room.
- walrus01 6y agoin practical use it's really not necessary, since a lot of those apartments are small enough in square footage to be well covered by one $80 5.x GHz capable 2x2 or 3x3 802.11ac AP. You can still get 400-700Mbps speeds through a 5 GHz channel, such as around 5150MHz, on any dual band equipment. Although 5 GHz goes through wood framed walls/floors a tiny bit, it doesn't go very far, to the point where you might see your neighbor's 5 GHz AP at a signal of -87.
- sargun 6y agoFunnily enough, I seem to get 5 GHz interference from nearby buildings through glass. I’m very much looking forward to 6Ghz. I ran some 60Ghz radios for a bit, and that was great, as it was interference free, and a drywall layer would stop it. Unfortunately, the hardware failed, and I didn’t see mass adoption of 60Ghz elsewhere. I hope that tech like local optical or 60Ghz becomes viable.
- walrus01 6y agoYep that is definitely a thing, and you will see more of it coming in through glass in the 5725 to 5850 band, since APs can run at higher power in those frequencies. One possible mitigation is to choose the cleanest possible channel for your in home use in the bands where FCC-allowed equipment can only transmit at moderate powers (specifically disallowed for outdoor WISP 5 GHz equipment too), in the area of 5100 to 5300.
- yjftsjthsd-h 6y ago> I hope that tech like local optical or 60Ghz becomes viable Yeah, I was really fond of the prototypes a while back that used visible light; those would completely end contention in an apartment complex or office:)
- crimony 6y agoI clicked on those links to see Spectrum Analyser noise floor plots and was sorely disappointed.
- walrus01 6y agoat the cheap end, looks something like this: https://help.ui.com/hc/en-us/articles/204950584-airMAX-Using-airView-to-Find-the-Best-Channel https://help.ui.com/hc/en-us/articles/204950584-airMAX-Using... you can see how bad 2.4 GHz is using an old ubiquiti rocket m2 802.11n 2x2 radio ($70) and a small $85 omni 2x2 antenna. https://www.youtube.com/watch?v=QNxXyP6QOqo https://www.youtube.com/watch?v=QNxXyP6QOqo or any of the older 802.11n 2.4 GHz based ubiquiti products such as the nanostation loco m2 mentioned in the video
- sushisource 6y agoWhy are your first two links just about buildings looking the same? I was thinking they'd spectrum visualizations per your lead-in which would be really fascinating to see...
- walrus01 6y agoprobably not the best links, they're meant to be reference to a construction style of putting five wood framed floors on top of a concrete first level/foundation, called a "five over one". Then when the wood walls are divided up into 450 to 750 sq ft apartments, it's a LOT of individual 2.4 GHz APs all packed into a dense noisy space, with only wood between them. https://www.google.com/search?channel=fs&client=ubuntu&q=five+over+one+construction https://www.google.com/search?channel=fs&client=ubuntu&q=fiv... cheap 2.4 GHz spectrum analyzer: https://www.youtube.com/watch?v=wc47pkUsLe8 https://www.youtube.com/watch?v=wc47pkUsLe8
- petre 6y agoI guess one could tape their walls in aluminium foil.
- danuker 6y agoWelcome to the space age!
- greesil 6y agohttps://www.amazon.com/Y-Shield-Shielding-Paint-liter-size/dp/B0025Z8GAY https://www.amazon.com/Y-Shield-Shielding-Paint-liter-size/d...
- Redoubts 6y agoOr conducting paints! https://www.lessemf.com/paint.html https://www.lessemf.com/paint.html (Warning, literal tin foil hat site)
- galangalalgol 6y agoI've got the opposite problem, a big old house with dense old pine shiplap full of nails covered with sheetrock. My wifi can't cover the house. Any recommendations for good router/APs with large range or maybe repeaters?
- kozak 6y agoI chuckle when Americans say that their "5 over 1" buildings "all look the same". This is nowhere near the level of sameness that I'm accustomed to see here in Eastern Europe. To my eye, these buildings look very distinct from each other.
- wffurr 6y agoRun Ethernet for everything you care about; problem solved. If only wired ethernet was considered standard wiring like coax and power outlets, and installed during construction.
- ajdude 6y agoI recommend just running conduit to everything during your next renovation, that way you could easily upgrade down the road. I wish conduit was used for all of these coax lines in my house.
- michaelt 6y ago20 years ago, I heard people online saying they were running their cat5e cable in conduits for ease of upgrading. Reasonable enough, after the 10-megabit to 100-megabit to 1-gigabit upgrades of the preceding decade. Not once, since then, have I heard of any of them pulling new cables.
- walrus01 6y agothere is a pretty good chance that 20-30 meters of cat5e utp in a house will test successfully for 2.5GBaseT today, not that even one percent of consumers will have such a switch.
- throw0101a 6y agoOfficially 2.5G can run up to 100m on Cate 5e: * https://en.wikipedia.org/wiki/Ethernet_over_twisted_pair#Variants https://en.wikipedia.org/wiki/Ethernet_over_twisted_pair#Var... So I wouldn't be surprised if 5GigE, and maybe even 10, could be done on shorter runs.
- klyrs 6y agoI still want a mainframe in my basement and HDMI ports in my walls for thin-client laptops...
- ortusdux 6y agoI did my undergrad in Seattle and had this issue. I eventually made 10 or so unprotected wifi printers spit out the "how to turn off wifi printing" page of their manuals. Definitely cleared up a bit of 2.4ghz room.
- pomian 6y agoInteresting reading. The results, and the issues with housing, remind one of the post war building boom in Central Europe, Communist enforced 'blocks'. We would visit from Canada and marvel how everything was the same. Obviously a very efficient use of planning and construction. Almost assembly line. Actually impressive how many people they had to house, quickly. The amount of design work that went into the community was more impressive. Years later, I could appreciate how everything was coordinated to have nearby playgrounds - so that you could watch your kids from your apartment. Schools, grocery stores, medical clinics, were all nearby in a logical efficient pattern. ( Communist system though, meant there was little to eat, or buy, or drugs, in those facilities.) The wiring, (and plumbing) was all prebuilt into the concrete walls and floors, ready to be connected, upon assembly. The ideas and designs were great. Of course, the actually performance, and construction, were prone to the usual Communist era woes of graft, theft, and shortages. To get back to the topic, phone wires were installed, but phones were not available for another 20 years. Imagine if Ethernet wiring was installed that way?