What do TDD and FDD mean

　　TDD (Time Division Duplex) is one of the duplex technologies used in mobile communication technology, corresponding to FDD. It is a technique that timely distinguishes wireless channels and continues uplink operations in the downlink operation of the frame period.

　　FDD is a full duplex communication technology used in mobile communication systems, corresponding to TDD. FDD uses two independent channels to transmit information downwards and upwards respectively. In order to prevent mutual interference between adjacent transmitters and receivers, there is a guard frequency between the two channels.

　　1 slot=0.5 ms

　　1 subframe=1 ms

　　1 frame (wireless frame)=10ms

　　1 half frame=5 ms (TDD only)

　　TDD Special Subframe

　　DwPTS: Downlink Pilot Time Slot

　　GP: Guard Period Protection Interval

　　UpPTS: Uplink Pilot Time Slot

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