Those on the Lumia 830 are seeing an OS version update to 8.10.15148.160, with a firmware version of 02177.00000.15184.36003. The Lumia 1520's firmware version has been incremented to 02540.00019.15236.45004. With the update, it looks like a few users are able to see 4G connection speeds for cellular connectivity for the Lumia 1520 and the Lumia 930.

Both devices come with LTE bands that should theoretically work with Airtel's 1800MHz or 2100MHz frequency, although the rollout of 4G services is still in its nascent stages. Hyderabad is one such city where Airtel has commenced 4G services, and as it so happens we have a Lumia 930 with us. We'll let you know if the phone is able to connect to the carrier's 4G network in the city later this week. Until then, let us know if you're seeing any other improvements in the comments.

Lumia 830 discussion on Windows Central forums

Thanks everyone for the tips!