TDD or FDD is the duplexing technique which is used in the communication world for exchanging information.
To understand TDD and FDD, we have started with,
Half duplex communication where when one party talks the other party has to listen, further to extend this we have introduced,
FULL DUPLEX COMMUNICATION, where both parties can talk and listen simultaneously.
FDD:-
Frequency-division duplexing is a method for establishing a full-duplex communications link that uses two different radio carrier frequencies for transmitting( UPLINK) and receiving ( DOWNLINK) Both the channels are separated by a defined offset frequency, which is also known "Guard Band"
TDD:-
Time division duplexing is a technique by which the Uplink and the Downlink transmissions are carried over the same frequency by using synchronized time intervals also called as "Guard period"
We have also mentioned, the factor which will help Telecom operator to decide which technique can be deployed.
LOW LATENCY
EQUIPMENT COSTS
DISTANCE PREFERABILITY
UNBALANCED TRAFFIC
SPECTRAL EFFICIENCY
MAC LAYER COMPLEXITIES
Below is the link for all the fundamentals,
https://www.youtube.com/playlist?list=PLE6yE0jB6BTOY6Z1DKEkQ8yZ8fFPUiCD8
Reference:
Images - Google images, Openclipart
Music - Bensound, Google youtube audio library
Content - Radio - Electronics Websites, Wikipedia, and other web sources.