ti-user multi-antenna concepts and techniques, dynamic QoS control, mobility management and handover between heterogeneous radio interfaces (vertical and horizontal), robust packet transmission, error detection and correction, multi-user detection, and interference cancellation. Systems beyond IMT-Advanced may further utilize sophis- ticated schemes including software defined radio and reconfigurable RF and baseband processing, adaptive radio interface, mobile ad hoc networks, routing algorithms, and cooperative communication. In response to this demand, the IEEE 802.16 Working Group began the development of a new amendment to the IEEE 802.16 standard (i.e., IEEE 802.16m) in January 2007 as an advanced interface to meet the requirements of ITU-R/IMT-Advanced for the fourth-generation of cellular systems. The 3rd Generation Partnership Project started a similar effort in 2008 to upgrade the UMTS standards and to further enhance its family of LTE technologies. Preface Many articles, book chapters, and books have been published on the subject of mobile WiMAX and 3GPP LTE, varying from academic theses to network operator analyses and manufacturers' appli- cation notes. By their very nature, these publications have viewed these subjects from one particular perspective, whether it is academic, operational, or promotional. A very different and unique approach has been taken in this book; a top-down system approach to understanding the system operation and design principles of the underlying functional components of 4th generation radio access networks. This book can be considered as the most up-to-date technical reference for the design of 4G cellular systems. In this book, the protocol layers and functional elements of both the IEEE 802.16m- and 3GPP LTE-Advanced-based radio access and core networks are described. While the main focus of the book (as will be understood from the title) is to provide readers with an in-depth understanding of the IEEE 802.16m radio access system design, and to demonstrate the operation of