A comprehensive review on coordinated multi-point operation for LTE-A

Abstract

With the enormous increase in application demands and user's data rate, high Quality of Service (QoS) has attracted significant attention from the mobile operators and academia in the past few years. Coordinated Multi-Point (CoMP) operation system provides a valid solution to enhanced throughput and coverage performance by reducing the interference, especially for cell-edge users. In CoMP operation, multiple Base Stations (BS) coordinate with each other in such a way that the user's information signal from neighboring evolved Node B (eNB) reduces interference or even can be combined to improve received signal quality. CoMP transmission is depending on the sharing coordination information via backhaul links, usually, consist of user's feedback that explains channel condition. This paper provides a brief vision into the CoMP technology including its architecture, sets, and promising approaches that can be employed in the future network. It discussion extends to the deployment scenarios in which CoMP schemes will likely be most beneficial in the modern backhaul designs available today. The study also covers the most well-known CoMP types such as coordinated scheduling and beamforming, joint transmission and dynamic point selection in detail along with its issues and current possible solutions. Most of the ideas presented are presently being studied and may diverge throughout the standardization work. In addition, a range of practical issues is identified and addressed in the deployment of CoMP in Heterogeneous Network (HetNet) and Multiple Input Multiple Output (MIMO) system, such as backhaul traffic, synchronization, and feedback design. This article provides an insight into the current research problem and also suggested the most challenging research gaps that may be useful for future research. It is shown that CoMP leads to both network throughput and capacity expansion in Long Term Evolution Advanced (LTE-A) network and can significantly provide more enhancements in spectrum efficiency and network performance gain with better cooperative coordination strategies.

Introduction

After the advancement of the 3G group of measures, the Third Generation Partnership Project (3GPP) began dealing with Long Term Evolution (LTE) frameworks aimed to Release 8 (Rel-8) standard [1]. Being the principal cell framework in the light of Orthogonal Frequency Division Multiple Access (OFDMA), it spoke to a notable achievement regarding accomplishing maximum rates of 300 Mbps and 75 Mbps for downlink and uplink, respectively [2], [3]. In order to take care of the developing demands for rapid and various remote broadband services, the fundamental goal of International Mobile Telecommunication-Advanced (IMT-A) is now, to achieve 1 Gbps and 500 Mbps maximum rates for DL and UL respectively [4]. In LTE-A network, the main objective is to achieve greater network capacity as compared to LTE network. The main motive is to maximize the system throughput at minimum cost and to satisfy the necessities set by the International Telecommunication Union (ITU) for IMT-A Standard. However, both LTE Rel-8 and Rel-9 releases did not meet the IMT-A necessities set up by the ITU for 4G frameworks [5]. The initial acknowledged 4G framework whose institutionalization was started in Rel-10 by 3GPP has been conceived as the subsequent actions of 3GPP to meet those prerequisites [6]. Due to the demands of mobile users for administrations applications and remotely open cloud stage, the advancement in data traffic was dynamically progressed. At that point, Rel-11 and then Rel-12 began and further upgrades were incorporated to the essential advances produced for Rel-10 LTE-A [7], [8].

The trend of growing demand for high QoS at the UE needs more advanced mitigation techniques to reduce interference and increase the overall network throughput. Research and development teams of telecom operators are working on finding higher data rates network solutions to meet the high data traffic requirement. These data rates are comparatively high when the users are nearer to eNBs because of high received signal strength indicator (RSSI) value. This value indicates the efficient Channel Quality Indicator (CQI) with better Modulation and Coding Scheme (MCS) and high Signal-to-Interference-plus-Noise Ratio (SINR) [9], [10]. Clearly, the most difficult part is to serve the users who are at the cell boundaries, not just because of the greater separation from the eNB, but also, they are affected by high interference such as Inter-Cell Interference (ICI) causes due to the signals coming from the adjacent sector of the same cell and Co-Channel Interference (CCI) which occurs because of the reuse of same frequency in the adjacent cells [11]. As a result, CoMP is the optimal solution proposed in 3GPP Release 9 [12], which gives resolution for supporting cell-edge completion while keeping the coordination complexity at a minimum level. Mostly, the users who are at cell-edges are able to receive or send data from various eNBs. As indicated by the standards of CoMP [13], if the received signals coming from various interferer cells are well coordinated, it does not only increase the User Equipment's (UE) data rate but also enhances the overall network performance with better coverage area. So as to avoid a collision while performing the scheduling and resource management for the cell-edge user, CoMP must have strict synchronization among various geographically isolated eNBs (as shown in Fig. 1). Inter-site (soft) and Intra-site (softer) were the earlier application of CoMP for handoff methodology with regards to Code Division Multiple Access (CDMA) innovations [14], [15]. However, with the rise of the wireless mobile network system, it also became very useful to manage the systems for Group Cell Theory (GCT) [16] and Distributed Antenna Systems (DAS) [17], [18]. For MIMOOrthogonal frequency-division multiplexing (MIMOOFDM) based system, CoMP is a universal structure of coordination and collaboration procedures [19]. It gives resource scheduling techniques that depend on MIMO system in developing wireless network innovations [20].

The remainder of this paper is organized as follows. In Section 2 we first describe the CoMP features which includes CoMP architecture, scenarios, and its sets. While Section 3 illustrates the CoMP types along with their characteristics, advantages, drawbacks and related issues with possible suggested solutions for both DL and UL followed by its summary. After this, all current research challenges of CoMP network are discussed in Section 4. Finally, the conclusion is drawn in Section. 5.