Fronthaul-constrained cloud radio access networks: insights and challenges

Abstract

As a promising paradigm for fifth generation (5G) wireless communication systems, cloud radio access networks (C-RANs) have been shown to reduce both capital and operating expenditures, as well as to provide high spectral efficiency (SE) and energy efficiency (EE). The fronthaul in such networks, defined as the transmission link between a baseband unit (BBU) and a remote radio head (RRH), requires high capacity, but is often constrained. This article comprehensively surveys recent advances in fronthaul-constrained C-RANs, including system architectures and key techniques. In particular, key techniques for alleviating the impact of constrained fronthaul on SE/EE and quality of service for users, including compression and quantization, large-scale coordinated processing and clustering, and resource allocation optimization, are discussed. Open issues in terms of software-defined networking, network function virtualization, and partial centralization are also identified.

Dynamic Resource Allocation for Virtualized Wireless Networks in Massive-MIMO-Aided and Fronthaul-Limited C-RAN

“…However, in C-RAN, the limited capacity of the fronthaul links poses a severe constraint on the maximum number of served users over the coverage of interest [7], [8]. Besides, the optimal utilization of the BBU processing resources to control the network overload is important to reach the best performance design [9].…”

Communication recovery with emergency aerial networks

“…However, in cases where the EOC is located out of the FAR node range, there is a need for a more sophisticated solution [16]. In such cases, routing the traffic through aerial nodes positioned between FARs and the EOC and act as relays could solve this issue.…”

Recent Advances in Cloud Radio Access Networks: System Architectures, Key Techniques, and Open Issues

“…A novel logical structure of C-RANs comprising physical plane, control plane, and service plane is presented in [15], along with a coordinated user scheduling algorithm and parallel optimum precoding scheme. In [16], a comprehensive survey related to recent advances in fronthaul-constrained CRANs is discussed, mainly focusing on potential solutions to enhance SE and EE. In addition, the authors in [17] reviewed the key fronthaul compression techniques for the uplink and downlink of a C-RAN, together with simulation results to validate the performance improvement desired from the implementation of multiterminal fronthaul compression.…”