India’s largest mobile operator Bharti Airtel kicked off LTE-FDD trials in Chennai yesterday and will extend them to Mumbai and Hyderabad by the end of the month.

It is offering existing 3G users a free upgrade to 4G.

The operator, which has 23 per cent market share, has already launched TD-LTE 4G services in 19 cities, but connection numbers are still low – just over 320,000. The company had 225 million total mobile connections at the end of Q1, according to GSMA Intelligence, 92 per cent of which are still based on 2G technology.

Airtel also announced a marketing deal with South Korea’s Samsung that calls for the companies to promote each other’s 4G offerings at their retail outlets.

Airtel said in March it plans to double its 4G base stations from 20,000 to more than 40,000 sites, with service to be expanded to Andhra Pradesh, Himachal Pradesh, North East and Punjab by the end of the year, the Economic Times said.

Meanwhile, rival Idea Cellular said despite increasing its capex to INR50-55 billion for fiscal 2016, it doesn’t have any immediate plans to launch 4G. The operator, the third largest Indian operator with a 16 per cent market share, has 4G spectrum in 10 regions or circles. Just 12 per cent of its 157 million connections are 3G.