In TN, I experienced limited 4G+ too. Only a few towers provide 4G+ these days when I travel. Not sure what criteria Airtel has to enable CA. Distance from the tower is certainly not an issue. I live and travel literally next to Airtel towers almost every week.
@pothi Airtel in Chennai and RoTN has been swapped from Huawei to Ericsson so no 4G+ anywhere even B40 CA works rarely 1/100 sites but in Chennai B40 alone is still Huawei so B40 CA works normally in Chennai