## 6 Future Research Directions and Discussion
This will help to boost the use cases of 5G eMTC, 5G NB-IoT, and 5G RedCap IoT in utilizing the tremendous benefit of the 5G network. Hence, the 5G RedCap IoT end device (ED) can be used to support medium to High bandwidth IoT applications that cannot be supported with conventional IoT EDs (LoRaWAN, Sigfox, NB-IoT). The CBRS is mainly in the United States (US) which is currently with many use cases. Other countries could harness comparable services such as a private 5G network with an equivalent 5G mid-band spectrum to that of the CBRS spectrum. Also, a unified 5G and LPWAN-IoT architecture that will holistically support integration with emerging technologies and endogenous security is a possible new area of research. The authors believe that this unified architecture will go a long way to improve QoS/QoE and the security of smart cities and remote area applications in the 5G-LPWAN-IoT ecosystems. In addition, the joint consideration of QoS/QoE in an LPWAN-IoT application is a possible area of research. Moreover, as earlier seen in Table 5, some countermeasures are highlighted to address some security challenges. These countermeasures are not enough to fully secure LPWAN-IoT due to the increased rate of new attacks and security breaches on IoT applications. Hence, hardening the security standards or requirements such as Confidentiality, Integration, Authenticity, and Availability (CIAA) will eliminate security breaches and vulnerabilities. This will make it difficult for an attacker to launch an attack on LPWAN-IoT solutions. Therefore, CIAA hardening is a possible area of research to safeguard IoT solutions. For instance, new approaches such as Machine Learning (ML) using supervised, unsupervised, or reinforcement learning algorithms, including Artificial Intelligence (AI) approach such as Artificial Neural Network (ANN) can be used for improved security standard solutions. This type of security solution has the potential to detect and prevent security occurrences based on attacker behavioral activities. Also, SDN and NFV are emerging areas of security standard hardening. This approach will improve the LPWAN-IoT ecosystem because most of the security mechanisms will be leveraged on the software level, thereby saving the device energy and complexity. Research in these areas for 5G and LPWAN solutions is encouraged. Another possible area of research is in asymmetric cryptographic encryption algorithms for LPWAN-IoT. This is because most LPWANs are not supported by asymmetric encryptions due to their low computational complexity and low energy. Hence, lightweight asymmetric encryption is recommended for most non-cellular LPWAN security solutions This will provide stronger protection to massive MTC. In addition, massive MTC will enable ubiquitous IoT. Over 80% of the earth is not covered by the internet. Thus, greater proportions of the earth should be covered by the internet for ubiquitous IoT to be actualized. For example, the ocean and forest areas should be covered for ocean vessel and wildlife tracking respectively. One of the new technologiesthat will support ubiquitous IoT connectivity is the low earth orbit (LEO) satellite, which is usually from 300 km to 2500 km above the earth's surface. Researching on appropriate LPWAN jointly with LEO satellite for ubiquitous IoT connectivity is recommended as a very good area of research development. This will help for IoT availability even in the sea/ocean and remote rural areas. The LEO satellite constellation is a non-terrestrial network (NTN) solution, research in NTN is essential. Because compatibility issue abounds between the coexistence of terrestrial networks (TNs) with the non-terrestrial networks (NTNs) devices due to their dissimilarity physical (PHY) and media access (MAC) protocol layer properties. Hence, it is worthwhile to establish an appropriate frequency spectrum band for the TNs and NTNs devices. This will help to mitigate interference and the doppler effect caused by decibel (dB) isotropic losses.