Chennai is more reliable than calcutta. the stuff really works well but the controllers for some unknown reason are asked not to rely on the info. So still stuck with HF. Chennai is getting a new radar in a few weeks and i hope they start using cpdlc regularly.
Calcutta has the latest equip but the bureaucracy has not got the official approval to use it.
Typical slow admin process we see in india, thanks to the blokes in the DGCA.