E standard development, the operators were rolling out HSPA networks to upgrade their 2G and 2.5G, and early 3G infrastructure, thus they were not ready to embrace yet another paradigm shift in radio access and core network technologies. Therefore, 3GPP has continued to improve UMTS technologies by adding multi-antenna support at the base station, higher modulation order in the downlink, multi-carrier support, etc., to extend the lifespan of 3G systems. It is anticipated that the new releases of 3GPP standards (i.e., LTE/LTE-Advanced) will not be commercially available worldwide on a large scale until current operators' investments are properly returned. A comparison of 3GPP LTE-Advanced and IEEE 802.16m basic and advanced features and functionalities reveals that the two systems are very similar and may perform similarly under the same operating conditions. Therefore, there is effectively no technical or performance distinction between the two technologies. It will be shown throughout this book that the two radio access technologies are practically equivalent as far as user experience is concerned. Table 3 summarizes the major differences between IEEE 802.16m and 3GPP LTE-Advanced physical layer protocols. The features and functions listed in this table will be described in Chapters 9 and 10. In the course of design and development of the IEEE 802.16n standard, the author decided to write a book and to take a different approach than was typically taken in other books and journal articles. The author's idea was to take a top-down systems approach in describing the design and operation of the IEEE 802.16m, and to contrast the 3GPP LTE/LTE-Advanced and IEEE 802.16m/mobile WiMAX algorithms and protocols to allow readers to better understand both systems. The addition of the 3GPP LTE/LTE-Advanced protocols and system description further expanded the scope of the book to a systems approach to understanding the design and operation of 4th generation cellular systems. There has been no attempt anywhere in this book to c