title: Why does GSM use full-duplex while cell phones have only one antenna?
body: <p>According to <a href="http://gsmfordummies.com/intro/intro.shtml#fdma" rel="nofollow">this website</a>:</p>
  
  <blockquote>
    <p>Although GSM operates in duplex (separate frequencies for transmit and receive), the mobile station does not transmit and receive at the same time. A switch is used to toggle the antenna between the transmitter and receiver.</p>
  </blockquote>
  
  <p>What, then, is the advantage of using separate channels for two-way communication?  Communications can never go both ways at the same time; why have them separated (broadcast channels aside)?</p>