the OFDM robustness to fast fading and narrow-band cochannel interference, and makes it possible to achieve even better system spectral efficiency. Different numbers of sub-carriers can be assigned to different users, in view to support differentiated quality of service (QoS), i.e. to control the data rate and error probability individually for each user. OFDMA can be seen as an alternative to combining OFDM with time-division multiple access (TDMA) or time-domain statistical multiplexing communication. Low-data-rate users can send continuously with low transmission power instead of using a "pulsed" high-power carrier. Constant delay, and shorter delay, can be achieved. OFDMA can also be described as a combination of frequency-domain and time-domain multiple access, where the resources are partitioned in the time–frequency space, and slots are assigned along the OFDM symbol index, as well as OFDM sub-carrier index. OFDMA is considered as highly suitable for broadband wireless networks, due to advantages including scalability and use of multiple antennas (MIMO)-friendliness, and ability to take advantage of channel frequency selectivity. In spectrum sensing cognitive radio, OFDMA is a possible approach to filling free radio frequency bands adaptively. Timo A. Weiss and Friedrich K. Jondral of the University of Karlsruhe proposed a spectrum pooling system in which free bands sensed by nodes were immediately filled by OFDMA subbands. Usage OFDMA is used in: the mobility mode of the IEEE 802.16 Wireless MAN standard, commonly referred to as WiMAX, the wireless LAN (WLAN) standard IEEE 802.11ax (marketed as Wi-Fi 6 / Wi-Fi 6E), the IEEE 802.20 mobile Wireless MAN standard, commonly referred to as MBWA, MoCA 2.0, the downlink of the 3GPP Long-Term Evolution (LTE) fourth-generation mobile broadband standard. The radio interface was formerly named High Speed OFDM Packet Access (HSOPA), now named Evolved UMTS Terrestrial Radio Access (E-UTRA). the downlink and the uplink of the 3GPP 5G New Radio (5G NR) fifth-generation mobile network standard. 5G NR is the successor to LTE. the Qualcomm Flarion Technologies Mobile Flash-OFDM 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), a cognitive radio technology which uses white spaces in the television (TV) frequency spectrum, and the proposed access method for DECT-5G specification which aims to fulfill IMT-2020 requirements for high-throughput mobile broadband (eMMB) and ultra reliable low latency (URLLC) applications. See also Code-division