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If I try to set up an hotspot in GNOME, I get the following message:

If you have a connection to the Internet other than wireless, you can use it to share your internet connection with others.

Switching on the wireless hotspot will disconnect you from <network name>.

It is not possible to access the internet through your wireless while the hotspot is active.

What are the technical reasons why I can't set up an Hotspot and be connected to the Internet at the same time?

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Question also cross-posted at Ask Ubuntu: askubuntu.com/questions/324515/… –  Kevin Bowen Jul 25 '13 at 19:59
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1 Answer 1

up vote 3 down vote accepted
  1. Uses the same antenna.
  2. Currently most software doesn't allow to be in client and AP mode at the same time.
  3. Wireless is a half-duplex protocol, except for some really new bleeding edge stuff. The radio can only transmit or receive at one time, it cannot do both at the same time.

Going with point 3, if any software was developed to allow both client and AP mode simultaneously the radio would first need to communicate like a client and then pass the data along as an AP. The latency would be undesirable, and the most likely cause that no one has made software to run both client and AP mode at the same time.

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However if you had a second radio (WIFI card) you could do this no problem. –  Tim Jul 25 '13 at 17:37
    
On that note, you can get a USB wifi adapter for less than $10. So go for it. –  bahamat Jul 25 '13 at 17:52
    
But, when in hotspot mode, I can accept more than one incoming connection at the same time. What makes incoming connections different from outgoing connections? Also "the radio can only transmit or receive": I cannot understand that. From a very high-level view, I can download and upload a file at the same time. –  user16538 Jul 25 '13 at 18:18
    
From liveqos.com/wp-content/uploads/2012/12/…: A wired Ethernet network is full duplex, meaning a device can send and receive, or upload and download, simultaneously. WiFi is half duplex, so if a client is sending data to the AP, the AP can not also send data to the same or any other client at the same time. For two-way communication, which includes most applications people typically use over the Internet, such as video or voice chat, this essentially halves your throughput when compared to a full duplex technology, such as a wired Ethernet connection. –  Tim Jul 25 '13 at 18:26
    
@bahamat "less than $10" $9.99. All right, all right... –  WChargin Aug 29 '13 at 5:17
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