I have a few questions related to WiFi routers/access points. Regardless of the WiFi technology implementation a,b,g,n,ac... I think the underlying protocol for channel assignments are similar, but please correct me if my understanding is wrong.

  1. If I have a single WiFi AP/Router setup at home, and I have multiple clients connected to it, i.e. my cellphone, my tablet, my chromecast etc, all of them will have independent WiFi channel assignments or separated? For example, will all my devices be assigned to WiFi channel 4 with all of them sharing the 20MHz bandwidth assuming 802.11g technology?

  2. Is all my devices connected will be limited by the 20MHz channel bandwidth, i.e. ~54Mbps between all my devices? This is regardless of my ISP internet speed for now.

  3. What parameters within the WiFi router/AP determines how many simulataneous devices that can be connected to it, before all the devices attached bogs everybody down? Is it only the data throughput of the channel?

Please help me out


closed as off-topic by Marcus Müller, Andy aka, Dmitry Grigoryev, brhans, Voltage Spike Apr 7 '17 at 17:19

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Questions on the use of electronic devices are off-topic as this site is intended specifically for questions on electronics design." – Marcus Müller, Andy aka, Dmitry Grigoryev, Voltage Spike
If this question can be reworded to fit the rules in the help center, please edit the question.

  • \$\begingroup\$ Wi-Fi uses multiple channels to increase the bandwidth. According to Wikipedia: "A Wi-Fi signal occupies five channels in the 2.4 GHz band. Any two channel numbers that differ by five or more, such as 2 and 7, do not overlap. The oft-repeated adage that channels 1, 6, and 11 are the only non-overlapping channels is, therefore, not accurate. Channels 1, 6, and 11 are the only group of three non-overlapping channels in North America and the United Kingdom. In Europe and Japan using Channels 1, 5, 9, and 13 for 802.11g and 802.11n is recommended". \$\endgroup\$ – Finbarr Apr 7 '17 at 9:45
  • \$\begingroup\$ And in any case, questions regarding the use of equipment are off-topic for this site. \$\endgroup\$ – Finbarr Apr 7 '17 at 9:45
  • \$\begingroup\$ The AP assigns the channels, the 802.11 spec (depending on what it is) determines the number of devices \$\endgroup\$ – Voltage Spike Apr 7 '17 at 17:19

First of all, WiFi channels are assigned mostly by hand, by selecting the channel for the access point. All devices need to use the same channel.

Next, the bandwidth of the channel is shared by all devices using time division multiple access scheme. Basically, only one device can use the channel at one time, others have to wait. This also includes all of your neighbors as well! So if they have devices on the same channel, they have to share it with you, or just cause interference.

You also need to separate the concept of the maximum speed on a channel and the maximum speed of the Internet access. On the layer where WiFi operates, devices don't know much about the Internet. It's sending data to the AP, what happens after the AP is magic that your WiFi card doesn't want to go into. So if your Internet speed is greater than the WiFi speed, the WiFi will the the bottleneck.

For number 3, the answer is it depends and it's very complicated. Basically, the big points are the data throughput, the signal strength and the numerous actual settings of the AP. As I mentioned previously, only one device can work on a channel at one time and each device needs to wait for the others. If you have a slow device, using older standard, it will take more air time than newer devices that are faster. If the signal strength is low, the device will reduce data rate, again taking more time. If you're using multicasting, then it can happen that the AP will send everything using very old standards, again taking lots of air time.

  • \$\begingroup\$ AndrejaKo - From my readings, WiFi technology would "listen before talking", thus, if there are multiple independent AP's in the same area on the same channels, then between them they would have to "coordinate" between each other? I would have thought that they would self interfere between each other unless there are some central controller? In another scenario, if there is a Single APs configured to say Channel 1, with multiple devices connected, how does the AP determine which device to send data to as priority? I.e. Tablet is on youtube and another computer is downloading a large file? \$\endgroup\$ – Faisal Apr 10 '17 at 14:04
  • \$\begingroup\$ @Faisal It's true that there's a listen before talking, but this creates something called "hidden node problem". Basically, if you listen, hear nothing, but someone is talking, what are you going to do? In general case, if all stations can hear each-other, then they will coordinate and share the channel. If they can't, then they'll jam each-other. If that happens, each will back off for a random period and retry, hoping that the collisions will not happen next time. \$\endgroup\$ – AndrejaKo Apr 10 '17 at 21:02
  • \$\begingroup\$ @Faisal For the multiple devices, you have a transmit buffer that stores the packets waiting to go out of the AP. AP just sends them in the order in the buffer. There are some exceptions and the packets do have their own priorities, but this is a very long and complicated topic and my feeling is that it doesn't really work all that well. \$\endgroup\$ – AndrejaKo Apr 10 '17 at 21:05
  • \$\begingroup\$ @Faisal Finally, about the central coordination, yes, that is one of the ways the technology is progressing. Unfortunately, it's a bit difficult to explain to people that they should share with others, so it's mostly limited to big installations where there's a central administration. Read up about the light AP concept. Basically, you have a bunch of "dumb" APs connected to a network using wired Ethernet. Then there's a "smart" central computer that does all the channel allocations, power level configurations, statistics collection and so on, in order to optimize performance. \$\endgroup\$ – AndrejaKo Apr 10 '17 at 21:08

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