Determining type of Wifi connection in Android
If you can check Wi-Fi Link Speed It will give you an idea about the current connection.

"Maximum" link speed allowed is as follows- 


Link speed 866.5Mbps - 802.11ac
Link speed 300Mbps - 802.11n
Link speed 54Mbps - 802.g
Link speed 11Mbps - 802.b


Also Link speed varies by your signal strength. So check Link speed of connected router in wifi settings, and get a idea. For example link speed shows 86.7, it is 802.11n. If your speed is greater than 130Mbps, it's 802.11n otherwise not. Some standard values for 802.11n are 150Mbps (single stream router) &amp; 300Mbps (2 stream router).