Introduction -- Section A - Introduction to Heterogenous Networks & Critical Issues -- Heterogeneous networks -- Challenges in the deployment of heterogeneous wireless networks -- Load balancing in heterogeneous wireless networks -- Critical interface management in heterogeneous wireless networks -- Network selection and interface management in heterogeneous IoT environment -- Section - B Heterogeneous Sensor Networks -- Heterogeneous wireless sensor network structure -- Critical routing protocols and clustering algorithms for HWSNs -- Energy efficient protocol for heterogeneous wireless sensor networks -- Management platform for heterogeneous wireless sensor networks -- Heterogeneous wireless sensor network deployment and topologies -- Section-C Real-Time Performance Issues in Heterogeneous Networks -- Heterogeneous and multi-task wireless sensor networks -- Multi-level scheduling for heterogeneous wireless sensor networks -- Critical localization criteria in heterogeneous wireless sensor networks -- Critical security issues in heterogeneous wireless sensor networks -- Section - D Applications of Heterogeneous Networks in Diverse Fields -- Criticality of HWSNs in smart cities -- Implementation of heterogeneous wireless network for industrial applications -- Mobile healthcare applications over heterogeneous networks -- Convergence of Heterogeneous Wireless Networks for 5G and Beyond -- Conclusion.