Fraunhofer Institute for Beijing University of Posts and Telecommunications Telecommunications Heinrich-Hertz-Institut Beijing, China Berlin, Germany A. Wolfgang Wolfgang Zirwas Chalmers University of Technology Nokia Siemens Networks Gothenburg, Sweden Munich, Germany C 2009 by Taylor & Francis Group, LLC Chapter 1 Introduction Borko Furht and Syed Ahson Mobile users are demanding higher data rate and higher quality mobile commu- nication services. The 3rd Generation Mobile Communication System (3G) is an outstanding success. The conflict of rapidly growing users and limited bandwidth resources requires that the spectrum efficiency of mobile communication systems be improved by adopting some advanced technologies. It has been proved, in both theory and in practice, that some novel key technologies such as MIMO (multiple input, multiple output) and OFDM (orthogonal frequency division multiplexing) improve the performance of current mobile communication systems. Many coun- tries and organizations are researching next-generation mobile communication systems, such as the ITU (International Telecommunication Union), European Commission FP (Framework Program), WWRF (Wireless World Research Forum), Korean NGMC (Next-Generation Mobile Committee), Japanese MITF (Mobile IT Forum), and China Communication Standardization Association (CCSA). International standards organizations are working for standardization of the E3G (Enhanced 3G) and 4G (the 4th Generation Mobile Communication System), such as the LTE (long term evolution) plan of the 3rd Generation Partnership Project (3GPP) and the AIE (air interface of evolution)/UMB (ultramobile broadband) plan of 3GPP2. The 3GPP LTE release 8 specification defines the basic functionality of a new, high-performance air interface providing high user data rates in combination with low latency based on MIMO, OFDMA (orthogonal frequency division multiple access), and an optimized system architecture evolution (SAE) as main enablers. At the same time, in the near future increasing numbe