Article on TDD and FDD LTE FDD vs TDD LTE

Time Division Duplex (TDD)

In TDD, both Uplink and Downlink transmissions are arranged one after the other on time scale. Both uplink and downlink transmissions will take place at same RF carrier frequency(Fc).

Separation by Slots

  • UL and DL are separated by time in terms of slots
  • A slot can be either UL, DL, or a ‘special’ slot
    • ‘Special’ Slot a transitional slot between DL and UL slots intended to give time for the transceiver to switch direction. Some symbols in the special slot can still be used for DL or UL transmissions

As of today (June 2022), We do not support a mix of FDD and TDD within a single baseband, nor do we support different TDD patterns in a single Baseband


  • in TDD, the same Frequency Band is used by both Tx and Rx path at different time instants
  • In FDD system, different Frequency Bands Fc1 and Fc2 are used by transmit and receive paths at same time instant