Advanced technologies for LTE advanced

With the explosive growth in mobile data traffic fueled by smartphones and mobile applications, transition from the 3rd generation (3G) toward 4th generation (4G) cellular networks is progressing at an unprecedented pace. Since the first release (release 8) of the 3rd generation partnership project (3GPP) long-term evolution (LTE) standard in December 2008, LTE has become the de facto standard on the way toward 4G cellular networks. Accordingly, LTE networks have seen rapid growth since 2009 when only two networks were initially launched. The number quickly expanded over the next few years, currently reaching 89 networks across 45 countries [1]. From the users’ side, the number of global LTE subscribers is likely to surge more than five-fold to reach some 50 million in 2012 from 9 million in 2011, and is expected to exceed 560 million in 2016 [2]. 3GPP has been working on further evolution of the LTE, which is referred to as LTE Advanced (release 10 and beyond), to develop a true 4G standard. The LTE Advanced is targeted to fulfill or even surpass all the requirements of international mobile telecommunications-Advanced (IMT-Advanced) [3] which is an official definition of 4G made by international telecommunication union (ITU) in 2008. These requirements include peak data rates, peak spectral efficiency, cell spectral efficiency, and scalable bandwidth. There are a lot of technical challenges for successful standardization of the LTE Advanced that meets the ITU requirements and supports backward compatibility with the LTE. The key features of the LTE Advanced differentiated from the LTE include support for wider bandwidth, improved uplink performance, better energy efficiency, advanced multiantenna technology, advanced interference management, and self-organizing network. Accordingly, from the perspective of physical (PHY) and medium access control (MAC) layers, multihop relay, multicell multi-input multi-output (MIMO), carrier aggregation, and intelligent interference management are challenging areas to