along with their interworking with EV-DO are described. A section is dedicated to discuss key network interoperability challenges. Lastly, Fixed Mobile Convergence and the associated challenges are illustrated. 1.2.11 Chapter 12 Technology Management Chapter 12 discusses various aspects of technology management and their relevance to mobile communi- cations. The principles of TM like technology strategy, technology development, innovation management, cultural management, and SO on, are described. Lastly, a hypothetical case involving a startup 4G radio equipment manufacturer is used to illustrate these various principles. 1.2.12 Chapter 13 Recap and Future Outlook This chapter primarily focuses on eight topics - summarizing what has been discussed in the previous chapters, discussing 4G, justifying the enhanced mobile communications model presented in Chapter 1, briefly describing some key industry trends including Infrastructure Network Sharing, Convergence of Media and Mobile, Connecting the Next Billion Users and Renewal Energy, and finally providing a 30 000 foot view on the future of mobile communications. Reference 1. Asif, S.Z. (2007) Wireless Communications Evolution to 3G and Beyond, Artech House, Inc., Norwood, MA. OFDM and OFDMA Introduction The wireless communications industry is evolving from circuit switched systems to all IP packet centric platforms. A common theme for this evolution is the use of OFDM (Orthogonal Frequency Division Multiplexing) and associated multiple access technique called OFDMA (Orthogonal Frequency Division Multiple Access). A major difference between 3G and NGMN (Next Generation Mobile Networks) is that all 3G networks are based on CDMA while NGMN (like 3G-LTE and WiMAX) are based on OFDMA. Thus, it becomes important that we learn about OFDM first before we dive into NGMN. 1 Multi carrier modulation systems, of which OFDM is a key example, were first developed in the 1950s for military applications. However, the low cost implementation of OFDM only became possible with the a