epends on LTE cell loading and transmission power. Ref- erence signals make 5% of LTE cell transmission power at full load or 50% at low load. We assume here 10% gain from lean carrier by assuming 50% loading in adjacent cells. When the load is low, the relative gain from lean carrier is higher especially for the cell edge users. Wideband carrier helps 5G performance when the spectrum is more than 20 MHz. LTE can utilize more spectrum than 20 MHz with multiple carriers, but there is a penalty in efficiency since each carrier must have common channels, and load balancing is needed between carriers. We assume here a modest 10% gain for the 100 MHz carrier compared to the 5 X 20 MHz case. The gain depends on the traffic type and network algorithms. Multiantenna MIMO performance depends on channel measurements, signaling capability, and algorithms. We assume here a 15-25% gain in 5G compared to LTE because of the more advanced MIMO codebook and calibration in 5G. Also, common channels can take advantage of beamforming in 5G. The total gain of 5G compared to LTE is then expected to be +30% for low band FDD and +60% for sub-6-GHz TDD with massive MIMO. In practice, the relative gain from 5G is higher with massive MIMO because many legacy LTE devices do not support massive MIMO. The expected spectral efficiency values for LTE and for 5G for typical antenna config- urations are shown in Table 10.20. We assume that the LTE X 2 spectral efficiency is 1.7 bps/Hz/cell based on live network experience. We further assume that 5G provides a 30-65% gain over LTE. We also assume that X 4 gives a 50% gain over 2 X 2, and mas- sive MIMO gives a 150% gain for LTE. These results illustrate that there can be up to six times higher spectral efficiency with 5G, massive MIMO, 4RX UEs, and 100 MHz carrier compared to LTE with 2x2 MIMO. 10 5G Performance 10.9.2 Downlink Spectral Efficiency with Different Antenna Configurations The 5G spectral efficiency depends on a number of assumptions: base station antenna solution, UE antenna solution,