What is the difference between FDD and TDD in 4G networks, and what is its relationship with dual 4G. Does dual 4G refer to the above two networks or China Unicom 4G?

TD and FDD are two communication modes of 4G. TD is a 4G mode independently developed in China, with a peak maximum rate of 100Mbps;

FDD is an international mainstream 4G communication technology, accounting for More than 90% of the world's 4G users have network speeds up to 150Mbps. At present, China Unicom 4G has adopted a hybrid experimental network model of TD and FDD, which can provide users with wider coverage and higher speeds.

Dual 4G refers to supporting both TD-LTE and FDD-LTE 4G standards. Currently, many 4G mobile phones can support TD-LTE in mainland China: roaming abroad can support FDD-LTE.