les user data rates of 5 Gbps. Higher frequencies above 50 GHz offer more spectrum, which enables user data rates above 10 Gbps. The challenge with high spectrum is the short propagation. Millimeter wave signals attenuate fast, and the cell range is limited to a few hundred meters. The spectrum at 3.3-5.0 GHz is an attractive combination of high data rate and extensive coverage. The spectrum per operator is typically 100 MHz. The combina- tion of 100 MHz and 4x4 Massive Multiple Input Multiple Output (MIMO) gives a peak data rate of 2 Gbps. The coverage area of 3.3-5.0 GHz frequencies can be close to the 2 GHz band when combined with high-gain base station antennas and beamforming techniques. That spectrum uses TDD technology. Another mainstream TDD spectrum for 5G is 2.5 GHz. The spectrum at 1.5-2.6 GHz is widely used by Long Term Evolution (LTE) networks, especially for urban area coverage and capacity. The maximum spectrum per band is typically 2 X 20 MHz per operator. That spectrum is mostly FDD, while unpaired blocks at 2.3 and 2.6 GHz also use TDD technology. 5G deployment at these frequencies can be implemented by refarming from LTE to 5G. One motivation for refarming to 5G is that 5G is designed for massive MIMO. The spectrum below 1 GHz is essential for providing wide area coverage and deep indoor penetration. Therefore, low bands can be utilized for critical communications with ultra-high reliability in wide area networks, including rural cases too. FDD tech- nology has also a latency benefit compared to TDD since FDD supports simultane- ous transmission and reception. The total spectrum in sub-1 GHz bands is typically 2 X 20-30 MHz on two or three different spectrum blocks. Spectrum licensing can use a number of different models: exclusive licensing, shared licensing, or unlicensed spectrum; see Figure 4.2. 2G and 3G radios are only deployed on licensed spectrum, and LTE is also mostly deployed on licensed spectrum. The start- ing point in 5G is that it can utilize spectrum with any licensing model. Mo