title: How can I get a channel width of WiFi under API level 23?
body: <p>I am building an app that scans Wi-Fi APs and prints gathered information.</p>
  
  <p>According to the Android docs, I can check <a href="http://developer.android.com/reference/android/net/wifi/ScanResult.html#channelWidth" rel="nofollow noreferrer">channel width of Wi-Fi after API level 23</a>, which is Android M.</p>
  
  <p>On the other hand, if I use API level lower than 23, I can't check that. You can see this by setting API level to 15, 21 or something in the link page above.</p>
  
  <p><a href="https://i.stack.imgur.com/2gog7.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/2gog7.png" alt="enter image description here"></a></p>
  
  <p>However, existing Wi-Fi device already supports 40, 80 and 160 MHz channels. The question is, that, how an Android device before Android M check whether an AP uses an wide channel?</p>
  
  <p>Does a manufacturer put some special and customized API into vanilla Android?</p>