Reliance Jio's Group Chief Technology Officer Jagbir Singh and Bharti Airtel's Chief Technology Officer for Mobile Networks Shyam Prabhakar Mardikar have resigned from their companies. Singh had joined Jio before the soft launch of 4G services and had previously worked with Samsung and Airtel. Mardikar joined Airtel in August 2012 for his second stint with the telecom major.