Key Challenges and Potential Applications of LTE- Advanced Hasibur Rashid Chayon 1 , Harikrishnan Ramiah 2 1,2 Department of Electrical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur, Malaysia 1 hasibur.rashid@siswa.um.edu.my 2 hrkhari@um.edu.my Abstract—Mobile technologies have been experiencing an extremely rapid evolution in the past decade. Third Generation Partnership Project (3GPP) initiated the Long Term Evolution (LTE) for the high complexity and limited capacity of the third generation (3G) cellular system. LTE is now established in most part of the world for its higher data rate and lower latency. However, it is necessary to upgrade the LTE system to cope up with the enormous current and future demands of mobile data traffic, new services, and applications. Researchers and standardizing bodies are putting a significant effort on LTE- Advanced (LTE-A) to meet that demands. This paper provides extensive views on the key challenges of LTE-A system. These challenges are considered as the major barrier to implement the LTE-A. Based on the user behavior and estimation of future demand, some potential future applications are also described. Keywords— LTE-A, Insufficient Bandwidth, Complex Devices, Massive MIMO, Internet of Things, Mobile Cloud, Ultra High Definition Video. I. INTRODUCTION 3GPP introduced LTE in Release-8 (Rel-8) as a fourth generation (4G) mobile communication technology which is based on Orthogonal Frequency Division Multiple Access (OFDMA) [1]. LTE has set a standard by obtaining maximum throughput of 300 Mbps in downlink, 150 Mbps in uplink and lower latency than 3G with some modification in Rel-9 [2]. However, the explosion of both smartphone subscription and the volume of mobile data force the researchers and the standardizing bodies to constantly upgrade the LTE system. Therefore, 3GPP continues its study and upgradation work to meet the user demand and the International Telecommunication Union (ITU) requirements. 3GPP launched LTE-A in Rel-10 to enhance the performance of LTE, which fulfills the requirements of International Mobile Telecommunication-Advanced (IMT-Advanced) set by ITU with major enhancement that includes peak data rate of 1 Gbps in downlink and 500 Mbps in the uplink [3]. Driven by the requirements of IMT-Advanced, LTE-A is required to provide various IP-based services and applications with wide range of data rates, different QoS requirements and various user mobility condition in multi-user environments. Moreover, LTE-A system has been developed to enhance the data rate up to 3Gbps and 1.5Gbps, respectively [4]. The requirements also include the spectral efficiency which can be 4.5 – 7 times higher in downlink and 3.5- 6 times higher in uplink than the Rel-6 specifications [5]. LTE-A is backward and forward compatible with LTE system which means LTE devices can work in LTE-A system and vice-versa [6]. Considering the increasing demand, 3GPP continued its effort through Rel-11, Rel-12 and Rel-13 [7]. LTE-A launched several new technologies to cope up with the requirements of the IMT-Advanced. LTE-A proposed carrier aggregation (CA), relay, self-organizing network (SON) and enhanced the performance of multiple input multiple output (MIMO) in Rel- 10 [8]. CA is most prominent technique in LTE-A which can enhance user throughput by using up to 100 MHz bandwidth with maximum 5 CCs [9]. Rel-11 improved several issues of Heterogeneous Network (HetNet) and previous basic technologies of LTE-A. Although the main contribution of Rel- 11 was to introduce cooperative multipoint transmission and reception (CoMP) which allow neighboring cells to cooperate each other for serving cell-edge users [10]. Later, Rel-12 developed further of the existing technologies as well as defined two ideas: Machine-Type communication (MTC) and Device-to-Device (D2D) communication. MTC allows machines to connect with other machines in a wide network whereas, D2D communication enables the users to communicate with other users without going through any conventional network. Although no conclusion and practical implementation have been made yet, 3GPP is working on the issues to overcome the challenges [11]. The efforts to develop the LTE-A architecture will be successful only if the above-mentioned technologies can support the existing and potential future applications. User behavior and their demands are changing rapidly. User prefers new ideas, faster, better quality and more efficient applications to fulfill their requirements. Therefore, developers and mobile operators are introducing new features and applications to overcome these challenges and most of these require higher data rate, low error rate, better Quality of Service (QoS) and lower latency. This paper describes primary challenges that will be the key issues to implement the LTE-A. Challenges include insufficient bandwidth, complex mobile devices, high attenuation and poor QoS of cell edge user, implementing CoMP, insufficient MIMO technology, poor resource allocation technique, implementing relay and Inter-cell interference(ICI) and mobility management in HetNets. After that, some future emerging applications that might use LTE-A technology is described. Finally, the paper ended with the conclusion.