Why a particular LTE band is TDD or FDD?

Hi Everyone.

I am searching for a basic question answer:

Why a particular LTE band is TDD or FDD?

For example why L2300 is TDD and L1800 is FDD.

It is about your mobile operator’s buying.
For example our operator has 800, 1800 FDD 2600 TDD in my country.

This is per operator selection for band division and as per 3GPP it standard to use:
High frequency band for TDD
Low frequency band for FDD

For example, all frequency bands in FR2 are in TDD mode.

  1. Reducing DL radio resource consumption.
  2. TDD Can reduce the waste of uplink bandwidth resources when uplink traffic volume is small.