Does the number of connected devices—regardless of activity

The question is not whether max speed is the same for more people, which it obviously is not. What I don't know if the number of devices alone, even when idle, kills your bandwith.

I've noticed our office Wi-Fi is rather slow and the explanation from IT is that there are so many smartphones etc. However most of the time most of them are not actually downloading anything. All the computers are using wired ethernet. Access points are properly managed with non-conflicting bands as far as I can tell.

So will you get worse downloads with access points supporting 20 devices as opposed to 2 even if the other connected devices are not doing anything? Does it depend on the tech ie 802.11 g/n/ac?

I tried searching, failed. And to be clear, this is not about a real network problem but more of a “how things work” type of question. In this case, very specifically about the number of passive—yet still connected— devices present degrading the performance of any active device(s).

Barleyman

Posted 2016-04-29T12:52:42.507

Reputation: 271

Answers

I spoke with a person who actually designs Wi-Fi hardware on low level signal processing et al.

The simple answer is: "No, the number of devices connected to an AP have little to no effect if they're not doing anything".

Longer answer gets a bit involved but basically Wi-Fi physical layer is entirely asynchronous technology and the clients do not "say" anything much "often" unless they want something. Obviously "often" is in machine terms, to put things into perspective the client Wi-Fi chip has only about 76us to react during a transaction so almost all of the low level functionality is handled in dedicated hardware even for host-based solutions. But very little real overhead is created by idle clients.

Wrt several devices taxing the network, it is more pronounced in a near-far case where the clients cannot "hear" each other. In this case they can both (or several of them) access the AP at the same time causing stalls and resynchronization, not very different from old-school coaxial ethernet collision issues. But if you have a room full of guys with their Android phones connected to the same AP, they can "hear" the band is in use and wait for their turn.

Barleyman

Posted 2016-04-29T12:52:42.507

Reputation: 271

Yes but having more devices on wireless can increase interference that reduces the range thus reduces the connection speed that can be negotiated. I tested this by reconnecting all devices to 5ghz and i watched my 2.4ghz band increase steadily by 5db to the test device i had stationed. I needed to free up my 2.4ghz band for some legacy devices with poor range. Doing that worked. Prior 6 months and the baby monitor was lagging. Now it has been working fine for 4 months. – ldrrp – 2019-10-04T14:10:36.337

This is a broad topic and dependent on the network equipment and devices connected. In most cases, WiFi is not its own Internet connection, it shares an Internet connection with the entire network.

Theoretically, just having devices connected to WiFi does not slow the speed. But the more devices connected and doing something, the bandwidth has to be shared, thus affecting the speed.

The phone may look idle, but they are not always as it appears. Even idle smartphones are often using the WiFi in the background to update/sync all the apps that are running. Especially those with settings to only do certain tasks when connected to WiFi, like Apple's cloud backup.

This article discusses the other performance issues of WiFi radio interference causing issues.

Additional data about running background applications - What is Eating Up Battery Life On My SmartPhone: A Case Study.

CharlieRB

Posted 2016-04-29T12:52:42.507

Reputation: 21 303

Wired WAN access is more than an order of magnitude faster so the bottleneck is not there. So according to what you're saying having n devices connected won't kill the wifi bandwith as long as they're idle? Does this also apply to the venerable 802.11g? I know that does not have a lot of bandwith to toss around to start with. – Barleyman – 2016-04-29T13:54:41.200

1No. What I am saying is, what appear to be idle devices may be using bandwidth in the background. There really is no way for us to give you a definitive answer for the reasons I outlined in my answer. – CharlieRB – 2016-04-29T14:08:07.100

I see it was a mistake to bring a real life example into this.. – Barleyman – 2016-04-29T14:22:28.767

1No reason to get upset. There are just too many factors involved for us to be able to solve it for you. Each network is unique and has its own set of issues. There is no quick easy answer to give you. – CharlieRB – 2016-04-29T14:25:20.233

It's more of a theoretical question / curiosity. Resolving the real bottleneck would be a rather simple excercise of getting more modern routers and/or analyzing traffic. I just checked and with more than a dozen people in the office, most of who probably have at least one wireless device, I got about 60% of ideal speed. So if the number of devices causes a static bandwith load, it does not appear to be a huge one. – Barleyman – 2016-04-29T15:20:36.330

Sorry. I thought this was an actual problem. This is why I have responded the way I have; site guidelines state "You should only ask practical, answerable questions based on actual problems that you face. Chatty, open-ended questions diminish the usefulness of our site and push other questions off the front page." Not trying to be a jerk, but this site just isn't suited for theoretical/hypothetical/curiosity type questions.

– CharlieRB – 2016-04-29T15:25:55.710

Let us continue this discussion in chat.

– Barleyman – 2016-04-29T16:43:12.737

I'm asking here because I don't know enough about the topic. But wouldn't the number of devices on a network increase the chance of a collision and as such inherently slow down the network? So even if it isn't doing anything at any given time there are more devices that can be? – prateek61 – 2016-05-01T15:02:30.400

@prateek61 This is not a forum. Please do not ask your own questions in the answer area or in comments. Use the [Ask Question] button at the top of the page to post your own question. Thank you. – CharlieRB – 2016-05-02T11:58:10.420

I'm not asking as a question but asking you to expand on your answer. Sorry if that was not clear. If you don't know, no worries! – prateek61 – 2016-05-02T12:08:55.880

Just like I trying to get the OP to understand, this is a very broad topic to which specific answers can only be given if all factors are know (equipment, devices, network infrastructure, etc.). Therefore, I can not answer your question. – CharlieRB – 2016-05-02T13:01:56.697

@prateek61 "How things work" questions are apparently not approved.. – Barleyman – 2016-05-03T08:47:49.117

1@Barleyman This is really simple. Read the guidelines in the [help]. If you do not like or agree, then do not use this free site. No one is forcing you to use this site. Although, if you choose to use it correctly, it might be useful for you. – CharlieRB – 2016-05-03T13:28:08.293

I will add to the good answer of @CharlieRB, that yes the signal strengh is shared and we can’t guess what those devices do on the network, but the radius of the signal can be impacted too if a device use too much strengh or if the router try to serve multiples device on the outer end of the signal, your device will get performance issue. That fact will impact your device performance.

Don’t get me wrong, this is not a problem because of the router, cheap or not, as the same problem arise on LTE network.

The fact you have more device just modulate more eradictly how the signal strengh can be, just plan more AP or better location for your AP to be more in range of the most users.

yagmoth555

Posted 2016-04-29T12:52:42.507

Reputation: 258

1The signal is shared, but not the signal strength. The WiFi antenna radiates the signal. Whatever can pick up the signal can use it. A receiving device doesn't suck up the signal from the surrounding area like a black hole. So you can't have a device using too much of the signal strength. Similarly, any devices at the "outer end" of the signal range will have a harder time using the signal. but multiple devices don't affect that. – fixer1234 – 2018-06-01T04:10:45.540

@fixer1234 from https://www.cisco.com/c/en/us/support/docs/wireless-mobility/wireless-lan-wlan/82068-omni-vs-direct.html. An antenna is a passive device which does not offer any added power to the signal. Instead, an antenna simply redirects the energy it receives from the transmitter. The redirection of this energy has the effect of providing more energy in one direction, and less energy in all other directions.

– yagmoth555 – 2018-06-01T10:07:10.960

That's true, but it only describes the pattern of what goes out. Any receiver will pick up whatever is there regardless of what other receivers are doing. One receiver doesn't suck up the signal around it and reduce what's available to other receivers. – fixer1234 – 2018-06-01T10:16:36.863

@fixer1234 I agree, I badly wrote my answer then, will edit. My point was more the antenna can focus on a zone more than another, thus impacting device there, but yes I agree the device dont act like a blackhole – yagmoth555 – 2018-06-01T10:47:04.677

-1

No if its really ide it will not make diff. but these days mobiles r never idel most of internet features run when they are connected to internet on both Android and ios. Specially backup and all those things so you cannot say phone is in idle condition but if just assume that they are not using internet then the speed will not decrease only the Wi-Fi strength of your modem will be affected and that also depend on the quality of your modem or Wi-Fi router

fateh

Posted 2016-04-29T12:52:42.507

Reputation: 11

1Welcome to Super User. The site's purpose is a knowledge base of answers, so posts should be in the kind of language and format you would find in a reference source. Tweet abbreviations aren't really suitable. Can you clean up your answer to make it actual English words and sentences? Thanks. – fixer1234 – 2018-01-20T22:06:35.117

Does the number of connected devices—regardless of activity—kill Wi-Fi speed?

Answers