UMTS TDD vs UMTS FDD | Difference between UMTS TDD and UMTS FDD

This page compares UMTS TDD vs UMTS FDD and mentions difference between UMTS TDD and UMTS FDD topologies. It depicts UMTS TDD and FDD frame structures.

As we know TDD stands for Time Division Duplex and FDD stands for Frequency Division Duplex.
In TDD topology, same frequency is used for both uplink and downlink directions but they use different time slots for transmissions.
In FDD topology, different frequencies are used for both uplink and downlink directions but they both use same time slots for transmissions.


The figure-1 depicts simple TDD and FDD pictorially.
Refer advantages and disadvantages of TDD and FDD >>.


UMTS FDD frame

• The figure-2 depicts UMTS FDD frame structure.
• In UMTS FDD, both uplink and downlink uses separate frequency bands with duplex distance of 190 MHz between them.
• As shown, 1920 to 1980 MHz is used for uplink where as 2110 to 2170 MHz is used for downlink.
• The total BW(Bandwidth) of 60 MHz is divided into 12 divisions having 5 MHz BW for each channel.


UMTS TDD frame

• The figure-3 depicts UMTS TDD frame structure.
• In UMTS TDD, both uplink and downlink shares same frequency band at the same time period.
• The equipment requires to be switched between transmission and reception. Hence there is guard period between transmission and reception to avoid interference.
• UMTS uses either 1900 to 1920 MHz or 2010 to 2025 MHz for both uplink/downlink directions.

Refer use of FDD vs TDD >> in LTE wireless network.


UMTS tutorial covering UMTS Releases,UMTS frequency bands,UARFCN, UMTS multiple access,UMTS frame structure and UMTS network architecture. Follow following links.
UMTS tutorial  Architecture  Stack  channel types  Bands  UARFCN  Frame  Timers 

RF and Wireless Terminologies