functions, nomadic wireless access systems, and other wireless systems with high commonality and seamless interworking. The capabilities and evolution of IMT-2000 systems is illustrated in Figure 1-2. As it appears from the figure, the services and performance of the systems noticeably increase as the systems evolve from one generation to another. CHAPTER 1 Introduction to Mobile Broadband Wireless Access The International Telecommunication Union (ITU)¹ framework for the future development of IMT-2000 and systems beyond IMT-2000 encompasses both the radio access, i.e., IMT-Advanced systems initiative, and the core network, i.e., Next Generation Networks (NGN) project. However, it is recognized that, in the future, the evolution of technologies and redistribution of traditional func- tions between radio access networks and core networks in practical systems may blur this distinction. Table 1-1 shows the service requirements for IMT-Advanced systems [11]. There are four user experience classes where each is further divided into a number of service classes based on the intrinsic characteristics of corresponding services, such as required throughput and latency to ensure the QoS requirements for each class are met. The service class requirements can be translated into system requirements, which are directly mapped to data transport over a wireless network. As a result, a limited number of QoS attributes, such as data throughput, packet delay and/or delay variations (often referred to as jitter), bit/packet error rate are defined. Examples of applications corresponding to each service class are provided in Table 1-1. In this table, the interactive gaming services mainly involve data transferred between multiple users that are con- nected to a server, or directly between the equipment of multiple users. Real-time communication with low delay and low jitter is required for interactive gaming. Multimedia refers to media that uses multiple forms of information content and information processing (e.g., text, audio, graphic