panels and four antenna elements per panel. However, the number of antenna panels required to achieve spherical coverage requirements and to mitigate blockage issues due to user interaction, such as head and hand proximity, is purely an original equipment manufacturer (OEM) implementation choice. In 3GPP RAN4, OEMs have presented simulation and measurement data across a large range of UE architectures, with two to four antenna panels, and four to eight antenna elements per panel, some using combinations of dipoles and antenna arrays [1-5]. Figure 12.8 (left) illustrates the two most common architectures used at 3GPP, using two and three antenna panels. For the FR1 subsystem, remote antennas such as D1, D2, and D3 (Figure 12.7) can be routed back to the RF transceiver either via printed circuit board (PCB) tracks or coaxial cables. In FR2, mmWave routing must be kept as short as possible as routing nmWave through the UE PCB material (e.g. FR4) would cause detrimental insertion losses. First-generation UEs therefore use the superheterodyne architecture illustrated in Figure 12.8 (right). FR2 waveforms are modulated at an intermediate frequency (IF) where PCB trace or coaxial cables losses are tolerable (10.56 GHz [6], 6.5 GHz [7]). The remote mmWave RF transceiver needs to be tightly connected to the antenna array and performs final up-conversion, phase shifting, and amplification for transmission and for reception. This is a radical change to FR1 legacy architectures, and Section 12.4.3 discusses some challenges associated with mmWave. 12.2.4.2 Impact of UL MIMO Operation UL MIMO is already part of the LTE specification, but in 5G the adoption of CP-OFDM for UL MIMO transmissions brings several additional benefits. In addition to removing RB length restrictions inherent to DFT-S-OFDM, CP-OFDM also offers a 1.6-3.9 dB uplink signal-to-noise ratio (SNR) gain for QPSK and an up to 5 dB gain for 64-QAM over DFT-S-OFDM (cf. Chapter 3, Table 3.5), thereby offsetting the penalty in the PAPR. For example, Section 12.3.4.2