rization alone does not work, but beamforming solutions are required in 5G in order to benefit from the higher antenna gain. The relative link budgets on different frequencies are shown in Figure 10.23. The Okumura-Hata propagation model is applied to obtain the relative path loss values on different frequencies. The same maximum path loss assumed for the different bands. The results show that the coverage becomes shorter on higher frequencies. The gain from massive MIMO at 3.5 GHz is assumed to be 6 dB. The difference between the downlink and uplink is assumed to be 8 dB. The results show that 3.5 GHz with massive MIMO has a similar or better downlink coverage compared to the 1.8 GHz uplink. But the 5G uplink coverage even with massive MIMO is 4 dB shorter than with LTE1800. The next section takes a look at the uplink coverage improvements. Coverage difference 3500 + mMIMO 3500 MHz 2600 MHz 2300 MHz 2100 MHz 1800 MHz 800 MHz Downlink Uplink Figure 10.23 Relative link budgets on different frequencies. 10 5G Performance 10.6.3 Uplink Coverage Solutions The uplink coverage can be improved by using a lower band. There are a few different options for taking advantage of low band. The solutions are discussed in more detailed in the following subsections. 1) Low band LTE with dual connectivity 2) Low band 5G with carrier aggregation 3) Low band 5G with supplemental uplink 10.6.3.1 Low Band LTE with Dual Connectivity Dual connectivity is the first solution for improving the uplink coverage. First 5G devices are based on NSA and support dual connectivity between LTE and 5G radios. With split bearer in dual connectivity, the uplink can be mapped to either of the two systems. 5G can be configured as the primary entity in the split bearer case, and 5G radio is used for data transmission as much as possible. If the 5G uplink connection becomes weak and the throughput low, then the data volume in the uplink transmission buffer increases, and the UE will use LTE for the uplink data transmission. The high-level concept is shown