In this chapter, we review the channel usage techniques employed by 5G/5G-Advanced, Wi-Fi 6/7, and Bluetooth 5/6. In the cases of 5G and Wi-Fi channel, usage is via multi-carrier-based multiple-access techniques where multi-carrier implies communication via a plurality of radio-frequency carriers and multiple accesses implies two-way communication between a central station and multiple surrounding stations. First, we review orthogonal frequency division multiplexing (OFDM). OFDM is a multi-carrier technique that lends itself to form the basis of multiple-access techniques. One such technique is employed by both 5G and Wi-Fi, namely orthogonal frequency division multiple access (OFDMA). Another such technique is employed optionally by 5G, namely discrete Fourier transform spread OFDM (DFTS-OFDM). Having reviewed OFDM, next addressed are OFDMA and DFTS-OFDM. In the case of Bluetooth, channel usage is via frequency hopping spread spectrum (FHSS). This technique is therefore introduced.