Airtel today announced that it has shutdown its 3G network in Kolkata, and only 4G network will be available in the city. It has refarmed the 900 MHz band spectrum being used for 3G to further strengthen its 4G network, which will be rolled out across the country in phased manner. It has deployed state-of-the-art L900 technology in the 900 MHz band to complement its 4G services in the 2300 Mhz and 1800 Mhz bands.