LTE Advanced Versus LTE
The development of Long-Term Evolution (LTE) was the first step towards a fourth-generation (4G) radio access technology compatible with International Telecommunication Union (ITU) International Mobile Telecommunications (IMT)-Advanced . LTE-Advanced (LTE-A) was submitted in October 2009 as a candidate radio interface technology for 4G IMT-Advanced and in October 2010 the ITU decided that LTE-A is one of the first two technologies to meet the set requirements, besides IEEE's 802.16m . Although the Downlink (DL) of LTE already surpasses the requirements for a 4G technology, this is not true for the Uplink (UL) direction. Therefore, work on the next evolutionary step for LTE is ongoing in the 3rd Generation Partnership Project (3GPP) and the first backwards compatible version of LTE-A was already released at the end of December 2010 (Rel'10) .
This chapter is intended to give an introduction to the technological changes and enhancements introduced in LTE-A to further improve the performance of LTE. In Section 15.1 we discuss the performance requirements for a 4G radio access technology as set by the ITU. Furthermore, we compare these requirements with the performance targets defined by the 3GPP for LTE as well as LTE-A. The key enhancements for the LTE-A radio interface are briefly described in Section 15.2 and, moreover, an outlook on technologies considered ...