The growing demand for always being connected and reachable anywhere, at any time has led to the continuous progression of various mobile devices/mobile nodes (MNs) and Radio Access Technologies (RATs) over the past years. The availability of handover services such as intersystem handover enables MNs to change traffic channels between RATs seamlessly in Heterogeneous Wireless Networks (HWNs). However, supporting intersystem handover in HWNs comes with the challenges of delay, packet loss, service degradation, ping-pong effect, among many others. This is because the existing handover algorithms have failed to predict the future values of the Received Signal Strength (RSS) needed for rapid handover processes. As a result, in this book, we designed an Intelligent Intersystem Handover (IIH) algorithm by integrating Grey Prediction Theory (GPT), Multiple-Attribute Decision Making (MADM), Fuzzy Analytic Hierarchy Process (FAHP), and Multi-Objective Optimization Ratio Analysis (MOORA).