Editing Orthogonal frequency-division multiplexing (section)

=== OFDM extended with multiple access ===
{{Main|Orthogonal frequency-division multiple access}}
OFDM in its primary form is considered as a digital modulation technique, and not a multi-user [[channel access method]], since it is used for transferring one bit stream over one communication channel using one sequence of OFDM symbols. However, OFDM can be combined with [[multiple access]] using time, frequency or coding separation of the users.

In [[orthogonal frequency-division multiple access]] (OFDMA), [[frequency-division multiple access]] is achieved by assigning different OFDM sub-channels to different users. OFDMA supports differentiated [[quality of service]] by assigning different number of subcarriers to different users in a similar fashion as in [[CDMA]], and thus complex packet scheduling or [[medium access control]] schemes can be avoided. OFDMA is used in:
* the mobility mode of the [[IEEE 802.16]] Wireless MAN standard, commonly referred to as WiMAX,
* the [[IEEE 802.20]] mobile Wireless MAN standard, commonly referred to as MBWA,
* the [[3GPP Long Term Evolution]] (LTE) fourth generation mobile broadband standard downlink. The radio interface was formerly named High Speed OFDM Packet Access (HSOPA), now named Evolved UMTS Terrestrial Radio Access ([[E-UTRA]]).
* the [[5G NR|3GPP 5G NR]] (New Radio) fifth generation mobile network standard downlink and uplink. 5G NR is the successor to LTE. 
* the now defunct [[Qualcomm]]/[[3GPP2]] [[Ultra Mobile Broadband]] (UMB) project, intended as a successor of [[CDMA2000]], but replaced by LTE.
OFDMA is also a candidate access method for the [[IEEE 802.22]] ''Wireless Regional Area Networks'' (WRAN). The project aims at designing the first [[cognitive radio]]-based standard operating in the VHF-low UHF spectrum (TV spectrum).
* the most recent amendment of [[802.11]] standard, namely [[802.11ax]], includes OFDMA for high efficiency and simultaneous communication.

In [[multi-carrier code-division multiple access]] (MC-CDMA), also known as OFDM-CDMA, OFDM is combined with CDMA spread spectrum communication for coding separation of the users. Co-channel interference can be mitigated, meaning that manual [[fixed channel allocation]] (FCA) frequency planning is simplified, or complex [[dynamic channel allocation]] (DCA) schemes are avoided.