In this demo, we demonstrate integration of cognitive radio capabilities, on the fly, with GSM base station (BTS) using OpenBTS architecture. The demonstration has following novel features: Cognitive sensing of the channel, in use by secondary user, while transmitting, On the fly shifting to free GSM subchannel without call drop, Works with existing GSM phones without any modification in hardware and software. Trials at IIT Hyderabad over the last one year has validated the viability of the system. © 2014 IEEE.