https://www.quora.com/What-is-the-difference-between-TD-LTE-and-FDD-LTE

https://www.quora.com/What-is-the-difference-between-2G-3G-and-4G-mobiles-as-well-as-networks

https://www.quora.com/How-do-2G-3G-4G-work-What-role-does-frequency-play-here-What-are-bands