FDD (Frequency Division Duplexing) and TDD (Time Division Duplexing) are two different methods used in mobile networks to enable two-way communication (uplink and downlink).

In FDD, the uplink and downlink transmissions are separated by different frequency bands. This allows for more efficient use of the available spectrum.

In TDD, the uplink and downlink transmissions are separated in the time domain, using the same frequency band.

FDD typically has lower latency than TDD. This is because the uplink and downlink transmissions can occur simultaneously, without the need for time-domain switching between them. This makes it suitable for applications that require low latency, such as real-time communications or gaming.

On the other hand, TDD can be more flexible in adapting to asymmetric uplink and downlink traffic patterns, which can be beneficial in certain use cases.