ter "Feasibility of LDM to Serve User-IoT Pairs in the Future Wireless Network" presents a transmission framework where the Layer division multiplexing (LDM) layer serves IoT-user pairs. LDM is considered as a potential technology that can enhance network capacity by taking advantage of this inherent heterogeneity of future wireless networks. The IoT devices are served using an LDM upper layer (UL), and the users are served using a lower layer (LL). The authors have developed a physical layer model incorporating LDM and tested its performance for the intended usages scenario. Both UL and LL performance show the capability to serve IoT devices and users to justify the proposed transmission scenario. The chapter "Wide Band THz Antenna Design Using Salp Swarm Algorithm for 6G Communications Systems" provides a complete framework for circular Preface polarized antenna design in the low THz band. THz communications have the poten- tial to provide an order of magnitude capacity improvement and thus considered to be an attractive candidate for 6G wireless networks. The presented optimization framework is based on a recently introduced swarm intelligence algorithm, namely the Salp Swarm Algorithm (SSA). The numerical results show that the SSA has been successfully applied in designing antenna with wide band operation and circular polarization. Conclusions Moving from 5G to B5G, the expectations are increasing about what the current and future generations of wireless communication can do for a wide range of applications. It is believed that the students, professionals, practitioners, and academic and industrial researchers who desire to work in the latest development of 5G and beyond technologies will need this book. The volume Reviews 5G network design methodologies as well as offers an in-depth analysis to understand future wireless networks Focuses on different emerging technologies and their applications under 5G and Provides state-of-the-art solutions to the theoretical and practical challenges in network design, ope