Frequency Division Duplex (FDD)


Definition - What does Frequency Division Duplex (FDD) mean?

Frequency division duplex (FDD) is a technique where separate frequency bands are used at the transmitter and receiver side.

Because the FDD technique uses different frequency bands for send and receive operations, the sending and receiving data signals don't interfere with each other. This makes FDD a better choice than Time Division Duplex (TDD) for symmetric traffic such as voice applications in broadband wireless networks.

Techopedia explains Frequency Division Duplex (FDD)

FDD is a technique where the transmitter and receiver operate at different carrier frequencies. For instance, in mobile wireless networks, one block of the electromagnetic spectrum is allocated for uplink, which carries data from mobile phones to a base station. A different block of the spectrum is allocated to downlink, carrying data from a base station to mobile phones.

This term is used in ham radio operations frequently, where operators contact a repeater station. The station in this situation sends and receives transmissions at the same time by altering the frequencies at which signals are transmitted and received.

Examples of FDD systems include the following:

  • Asymmetric digital subscriber line (ADSL) and very-high-bitrate digital subscriber line (VDSL)
  • Cellular systems, including the UMTS/WCDMA Frequency Division Duplexing mode and the CDMA2000 system
  • IEEE 802.16 WiMax Frequency Division Duplexing mode

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