## 3 Architectures in the 5G and LPWAN-IoT and Smart Cities
### 5G Network Architecture
Spectrum bands include low-band (<1 GHz), mid-band (3-6 GHz), high-band (24-86 GHz), and ultra-high band (millimeter-wave band (30-300 GHz));
* 5G Core (5 GC): Leverages a service-based architecture comprising many interconnected Network Functions (NFs);
* 5 GC control plane: This includes Access and Mobility Management Function (AMF) and Session Management Function (SMF);
* 5G user plane: This includes User Plane Function (UPF);
* 5 GC Control and User Plane Separation (CUPS): This allows the centralized control plane functions while distributing user plane functions nearer to users for better performance;
* NG: This is the interface between base stations and 5G network functions servers;
* xn: This is the interface between base stations. Current challenges associated with 5G Architecture include backhaul design issues, QoS/QoE issues, emerging technologies integration issues, interference management issues, security and privacy issues, and ubiquitous connectivity issues. Hence, a reliable 5G network architecture should be able to address the stated challenges. For example, the backhaul design issues can be addressed by implementing a 5G architecture that supports diversified backhaul connectivity, that is, backhaul comprising a 5G low-band, mid-band, and high-band deployed at respective locations based on application needs. This is indeed a cost-effective architecture deployment solution; whereby backhaul resources are utilized where necessary. The emerging technologies integration issues can be addressed by proper integration of these emerging technologies such as Network Function virtualization (NFV), Software Defined Networks (SDN), Network slicing, Machine learning (ML)/Artificial intelligence (AI) in the 5G architecture in order to satisfy the various use cases of 5G network solution demand. This will help to improve the QoS/QoE of the network. Further discussion on this aspect is provided in Section 5. The interference management issues including cell edge interference especially in a dense network environment can be tackled with the use of multiple-input-multiple-output  
Figure 1: 5G Network Architecture. (MIMO) antennas in 5G architecture. This will help to offload some of the connections to the available massive MIMO antennas. Also, the cell edge interference problem can be overcome by implementing 5G jointly with a very long-range LPWAN. Detailed information on this is provided in Section 5. A reliable 5G architecture should have adequate support for security and privacy solutions. A key security concern is that of the physical (PHY) layer security, that is, security involving the device, channel, and over-the-air (OTA) interface. One of the measures to circumvent this PHY layer security is the integration of endogenous security in the 5G architecture. Further discussion on this is provided in Section 4. The problem of ubiquitous connectivity can be addressed by adequate integration of LEO satellite constellations jointly with LPWANs in the 5G architecture. This will help for global coverage of 5G and LPWAN-IoT connectivity. The next Section gives detailed information on this.