Definition

OFDMA (orthogonal frequency-division multiple access)

Contributor(s): Laura Fitzgibbons and James Bowen

Orthogonal frequency-division multiple access (OFDMA) is a feature of Wi-Fi 6 (802.11ax) that allows access points to serve multiple clients at the same time. OFDMA follows a set of rules created for the transmission of data between more than one terminal (any device at the end of a transmission channel, such as a computer or phone) over a transmission medium (such as a wireless network).

An example of how OFDMA works is when two phones send data over the same phone line. A time-interval may be assigned to each phone, and they will take turns sending their signal over the line at each assigned interval. However, these time frames are imperceptibly small, making the data transfer seem to happen simultaneously and seamlessly.

OFDMA is an updated version of frequency-division multiplexing (FDM) technology used to divide packets of information into separate bands that are carried by separate signals. This form of communication is an upgrade that parallels the switch of internet carriers to Wi-Fi 6 wireless, as well as the upgrade of phone carriers to 4G and 5G LTE. Instead of the traditional analog modulation used in multiplexing, OFDMA uses carrier signal waves, called subcarriers, to move small bits of information in a more streamlined fashion.

Advantages and disadvantages of OFDMA

Implementing OFDMA can provide the following advantages: 

  • Higher diversity and efficiency of frequency
  • Provides lower interference between cells.
  • More flexibility as channels and sub-channels can be toggled on and off.
  • Better coverage over networks.

However, potential disadvantages include:

  • The diversity of frequencies is conditional on how subcarriers are assigned to users, and can thus become very complex.
  • Requires extra power because it is always on and ready to send a transmission.
  • Has a higher sensitivity than other channel types.
This was last updated in May 2019

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What do you find to be the biggest advantage to OFDMA when compared to OFDM?
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