This book is an adaptation from PhD thesis and focus on ionospheric layer over Malaysia. Our current life very much depends on radio navigation and communication technology. The ionosphere which exists from 60 to 2000 km above the Earth surface can influence radio communications and Global Navigation Satellite System (GNSS). This layer is important in predicting the space weather, where any space weather event can affect the communication signals and disrupting power transmission which can result in significant economic losses. Due to that, this book discussed on basic knowledge on ionospheric layer over equatorial and find the model that can be used to study and predict the ionosphere for Malaysia.