nto an approximately 20% increase in the range at the cell edge. In addition to improving cell edge performance, 2 X 2 uplink MIMO improves spectrum efficiency. Since 5G NR is mostly a TDD technology above 2 GHz, and TDD cells are likely to be configured in a highly asymmetrical configura- tion with priority given to downlink, improving spectrum efficiency is the key to delivering high cell capacity. In the initial-phase of Rel-15 deployment, mobile operators emphasized the need to estab- lish a framework for the dual-connectivity non-standalone mode of operation. In principle, network deployment with dual-connectivity NSA means that the 5G systems are overlaid by an existing LTE network. Dual-connectivity implies that the control and synchronization between the BS and the UE are provided by a 4G network, while the 5G network is a com- plementary radio access network tied to the 4G anchor. In this model, the 4G anchor estab- lishes the connection using the existing 4G network which later can be complemented with a 5G NR user-plane connection (see Fig. 5.26). The addition of the new radio, together with the existing LTE multi-band carrier aggregation mode, strains the system performance, size, and interference mechanisms, posing additional challenges to be resolved when designing the NR RF front-end. Depending on 1TX or 2TX carrier frequencies and their relative spac- ing, intermodulation distortion products may fall into the LTE anchor receiver frequency band and cause LTE receiver desensitization. A simplified view of NSA option-3a network topology is shown in Fig. 5.26, which is expected to be used in early rollouts of 5G networks, where the mobility is handled by LTE New Radio Access RF and Transceiver Design Considerations ((q)) ((p)) User plane Control plane NR (2TX/2RX) LTE (1TX/1RX) Primary cell Secondary cells (downlink and uplink) (downlink only) Figure 5.26 Non-standalone option-3a dual-connectivity network architecture [28]. anchors (control and user planes). This architecture leverages the LTE legacy 