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After reading some introductory explanations about the 802.11 standard, i obviously still have some fundamental problems of understanding. When every device connected in the network, shares the frequency with other devices (shared access medium) and only one device can communicate with the AP at the same time, how is it possible that two or more devices do things like streaming or downloading at the same time?

Reinmarius
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    yes, but AP can send first frame (packet) to device 1 and second frame (packet) to device 2, . This is basically the high level idea. – Effie Dec 14 '22 at 09:45
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    Ah, so it's similiar to how multitasking on a CPU works, right? – Reinmarius Dec 14 '22 at 09:48
  • yes. something like this. at the same time only one packet can be sent, but (1) each packet is addressed, so each device, including AP, can determine if it is the intended recipient, and (2) there is a mechanism of how devices determine when they can actually send. – Effie Dec 14 '22 at 09:50
  • you might want to read about Media Access Control in general, ALOHA, CSMA/CD, and CSMA/CA. All of this describe how many devices share the same communication channel. This should be enough background to understand how WiFI implements media access control. – Effie Dec 14 '22 at 09:51

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how is it possible that two or more devices do things like streaming or downloading at the same time?

"At the same time" as perceived by a human being is quite different from what really happens on the physical/technical level.

On the technical level, simultaneous communication in a wireless network isn't really possible.[*1] But it's also not possible with a wired network when multiple clients access the same resource or utilize the same (Internet) link.

The key is that a packet-switched network has an inherent multiplexing capability. Traffic is split into small packets and those are transferred sequentially but in rapid succession. Each packet can carry data for a different recipient or application.

Packets over gigabit Ethernet can easily exceed 100,000 packets per second and in theory, each packet could carry data for a different user or application. Basically, as long as the available bandwidth or other resources aren't exceeded you can run as much in parallel as you like.

So, even if nothing really happens "at the same time" it does look that way.

[*1] Ignoring technology like MU-MIMO and similar here.

Zac67
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