Macro-assisted data-only carrier for 5G green cellular systems

As the commercial operation of 4G systems is speeding up worldwide to meet the increasingly explosive growth of mobile Internet in the 2020 era, a great many R&D efforts targeting the next generation wireless systems (5G) have been launched. With densely deployed small cells in a heterogeneous network, the excessive signaling overhead of conventional carrier design greatly degrades system performance. A new carrier designed for small cells in the next generation system will be highly beneficial toward a green communication network. In this article, we propose a macro-assisted data-only carrier for future 5G networks from a green prospective. With the help of macro base stations, control channel overhead, and cell-specific reference signals for small cells can be minimized to achieve a pure-data carrier. Under this architecture, key procedures are designed including small cell identification and access, synchronization, hand over, and small cell sleeping. Furthermore, to evaluate the potential of our proposed scheme, a complete system and link-level simulation platform according to the current 3GPP LTE standard is built. The simulation results show that our proposed systems, achieving significant performance enhancement of signaling overhead, can lead to more than 17 percent throughput improvement and 90 percent energy efficiency gain over the current LTE HetNet with on-off strategy implemented. The proposed scheme appears to be highly attractive as part of the future 5G green mobile networks.

Introduction

The fourth-generation (4G) mobile communication systems are commercially operated worldwide mainly based on Long Term Evolution (LTE) Release 8. As it evolved, LTE Release 9 was published in 2009 with the introduction of multimedia broadcast multicast services, home eNodeB (eNB), location-based services (LBS), and so on. The Third Generation Partnership Project (3GPP) Release 10, published in the beginning of 2011, made great progress through the introduction of carrier aggregation, multiple-input multiple-output (MIMO), and relaying. LTE Release 11 introduced the coordinated transmission and reception of base stations. LTE Release 12 (R12) mainly concentrated on small cell enhancement. However, there are still lots of open issues to be addressed. One of the most important topics in 5G networks is the ultra-dense network (UDN), where small cells will be ultra-densely deployed in hotspots. Thus, the downlink intercell interference will become much more serious, leading to huge energy consumption and intolerable delay. Although the concept of control and user plane (C/U) decoupling has been proposed for a long time, detailed approaches to splitting signals and channels are not discussed for the UDN scenario. In addition, existing new systems based on C/U splitting do not focus on the UDN scenario, and also face severe challenges in interference cancellation and energy saving. Thus, a new carrier designed for base stations in the ultra-dense scenario is vital for the next generation system to minimize interference and contribute to a “softer” and “greener” network [1].