ble power for the uplink transmission compared to the SC-FDMA waveform. However, even if the resulting transmission power is less, the better link performance with multi-antenna multi-stream transmission makes OFDMA a better choice when the link budget has some margin. The other aspect is interference management in Time Division Duplex (TDD) net- works. This is clearly easier to handle if both uplink and downlink use the same multiple access solution. The principle of OFDMA is shown in Figure 6.1, and more information on OFDMA fundamentals is given in [1] and the references therein. The uplink direction uses SC-FDMA (DFT-S-OFDMA) for the cases when the trans- mission power is limited and the use of uplink multi-stream transmission is not possible. OFDMA is intended to be used when the link budget allows the use of features like Transmitter Figure 6.1 OFDM principle. Serial to Cyclic Modulator Parallel Extension frequency Receiver total radio BW (up to 400 MHz) Remove Serial to Cyclic Parallel Extension Demodulator Equalizer 6.2 5G Multiple Access Principle Transmitter UE 1 Cyclic Modulator Extension Remove Transmitter UE 2 Cyclic frequency Extension Cyclic Modulator Extension radio bandwidth (up to 400 MHz) eg total radio BW Demodulator Equalizer Figure 6.2 SC-FDMA principle. higher-order modulation and uplink Massive Multiple Input Multiple Output (MIMO) transmission. 5G will fall back to SC-FDMA operation when there is not enough link quality for multi-stream operation. The SC-FDMA principle is illustrated in Figure 6.2. The same principle used in LTE is maintained, with only one symbol at a time sent using SC-FDMA transmission. The FFT/IFFT pair at the transmitter side allows the transmis- sion to be placed accurately and without filtering complexity in the correct place within the carrier (following the grants given by the gNB). Compared to LTE, the new 5G radio needed to be possible to be operated with: Higher frequency bands, with the Release 15 frequency range reaching up to 52.6 GHz and studies in Release