Introduction to CDMA2000 standard【荐】.pdfVIP

CHAPTER 1 INTRODUCTION TO CDMA2000 STANDARDS EVOLUTION 1.1 INTRODUCTION The ongoing growth in demand for high-speed packet data services and multimedia applications over mobile wireless networks has set new system requirements and ob- jectives for the next generation of air interface protocols and network architectures. Although the channelization, signaling, and access protocols of second- generation (2G) cellular systems were designed to efficiently support symmetric circuit switched data and voice traffic, most of the new data applications are IP based with highly asymmetric and packet-switch traffic. This asymmetric and bursty nature of multimedia packet data traffic along with the variability of data rates and packet sizes and complexity of quality of service (QoS) management makes conventional voice-oriented channelization and access protocols of 2G systems inefficient. The third generations of radio access technologies, commonly known as 3G systems, are expected to use new physical and logical channelization schemes with enhanced media and link access control protocols. Also, to maximize the spectrum efficiency, the physical layer designs must utilize advanced coding, link adaptation, and diversity schemes as well as power and interference control mechanisms. In the late 1990s, these observations and requirements motivated major efforts and studies in the International Telecommunication Union (ITU) and other regional standardization groups to define and harmonize a common set of specifications for new International Mobile Telecommunications standards referred to as IMT2000 systems. In Europe the IMT2000 is also referred to as Universal Mobile Telecom- munication Services (UMTS). ITU activities on IMT2000 are comprised of international standardization, including frequency spectrum and technical specifications for radio