An Overview of Cloud RAN: Architecture, Issues and Future Directions

摘要

Cloud radio access network (C-RAN) has been considered as one of the enabling network architectures towards the implementation of fifth generation (5G) wireless systems. Combining with advanced radio, wireless and computing techniques, C-RAN provides great potential to improve the network capacity, spectrum efficiency, energy efficiency and operational flexibility. Therefore, C-RAN has attracted considerable attention from both academia and industry. In this paper, we review the architecture and some of the key physical (PHY) layer signal processing issues of C-RAN. The functional split and limited-capacity fronthaul impose PHY layer issues and signal processing opportunities, e.g., channel state information acquisition, effective compress-and-forward methods and intelligent resource allocation schemes. Moreover, some emerging 5G techniques which can be supported by or integrated with C-RAN architecture, such as software-defined networking, heterogeneous networking, communication at millimeter wave frequencies and full-duplex radio are discussed. The challenges and future research directions are also presented, where mobile edge computing and caching, multi-dimensional resource management and PHY layer security and energy-efficient designs are highlighted.