actical because of the inefficiency of the protocol. As a result, the cRAN architecture in Figure 11.14 becomes impractical. To take full advantage of the large number of antenna elements in mmWave and FD-MIMO antennas, the advanced antenna arrays in 5G will need to execute some of the BBU-like functions in the antennas. This will make the overall configuration more analogous to the sRAN architecture in Figure 11.15, which is a strong match for implementation in the extended AIC architecture. 11.5.2.2 Dual Connectivity Another characteristic of mmWave spectrum is that these signals are far more easily blocked by obstacles, SO that turning a hand-held device from one position to another could rapidly block the mmWave signal. To overcome constant interruptions while using mmWave spectrum, 5G will use a technology called dual connectivity, shown in Figure 11.18. This allows a device to be simulta- neously connected to multiple parts of a 5G network, or even to be simultaneously connected to a 5G network and an LTE network. For example, a connection using a traditional cellular frequency would provide a robust and reliable anchor for services and signaling. A second simultaneous con- nection to a 5G mmWave frequency can then be used opportunistically to provide high speed and high capacity. This ability of the network to simultaneously use multiple connections between a device and different components of the network is an essential aspect of the 5G network design. Control Plane 5G + LTE Data Plane macro FIGURE 11.18 Dual connectivity. Network Access Dual connectivity can benefit significantly from an implementation based on the new archi- tecture. The separation of control plane and data plane functions aligns with the use of different frequency bands and even radio technology generations (LTE VS. 5G) for control and data. Also, SDN is ideally suited to handle the dynamic switching of traffic between different sites and parts of the network, while balancing traffic needs and priorities across multiple sites and techn