 cross-entropy (CE) to improve the per- formance of the energy detector-based spectrum sensing method. Chapter 9 covers gamified wearables in childhood obesity therapy driven by 5G wireless communication systems with special emphasis on Pacific Island Countries. Compared to the traditional methods, gamification has shown a new alternative model for healthcare. Due to the widespread use of mobile phones, laptops, and the like, the potential to use gamification in the control and prevention of obesity is enormous. With the increase in 5G network coverage the potential to use gamification increases many times. The mobile applications can not only be used to deliver health-related messages and physical activity components of any of the programs but can also be used to collect, compile, analyze and access the data easily at the click of the button. This chapter contains an overview of the literature and the design of the qualitative study conducted in Pacific Island countries. This chapter also summarizes various interventions that used gamified wearables conducted in these countries and the major limitations identified by these studies. It also highlights the recommendations given by researchers. In brief, these recommendations are realistic methods for obesity man- agement, enticing game strategy, challenging incentives, and constructive education. Chapter 10 covers the role of photonics in the realization of future 6G communica- tion systems. This chapter discusses the key enabling technologies of 6G communica- tion systems and the importance of photonics in realizing these 6G technologies. This chapter also presents the recent development of photonics for 6G communication. Chapter 11 covers the MIMO antenna for IoT and ISM band applications. In this chapter, authors describe a design of antenna that achieves specific important requirements. 5G communications are likely to include MIMO, which will necessi- tate antennas with a large number of elements. However, maintaining strong isolation between ports is difficul