Worldwide Interoperability for Microwave Access (WiMAX) is currently one of the most widely used Telecommunication Protocol due to its high data rates. This book provides some basic understanding of WiMAX systems and different antenna techniques used in them. Chapter 1 is about introduction. It briefly discusses the history of wireless communication, different types of data networks, an overview of IEEE 802 Family Standards and 802.16 / WiMAX Standard. Chapter 2 is about the technical overview of WiMAX. It is divided into 3 parts. First part discusses the Physical layer of WiMAX. Second part discusses the MAC layer of WiMAX. Third part discusses the Network Architecture of WiMAX. Chapter 3 discusses about multiple antenna systems in WiMAX. It briefly discusses Diversity schemes (i.e Space Time Coding, Antenna Switching, Maximum Ratio Combining), Smart Antenna Systems and Multiple Input Multiple Output (MIMO) Systems. It also discusses short comings of classified MIMO theories and modern methods for MIMO systems. Chapter 4 discusses the MATLAB simulations based on these multiple antenna techniques. Chapter 5 is about conclusion and future work.