Why does the speed of wi-fi drop sharply when one computer is actively working?

Question

WiFi

At home there is a wi-fi point and several computers + ipad and mobile. When skype works on one computer (and one sound, no video; it's even worse when there are videos), the speed drops by 90% on the rest.
Moreover, the speed of the Internet from a torrent can reach 1-1.5 Mbps, i.e. one skype sound should take less than the whole channel.
Moreover, it is surprising that watching the same video or the same Skype on other devices does not cause big problems for other devices with a decrease in speed
. What are the causes of this problem and what are the solutions?

Answer 1

Answer: the router needs to be flashed with a fresh firmware (if there is a revision on their dlink.com website, then it is better to take it, and not the one on dlink.ru). If possible, change the connection to the provider to static.