Evolution Toward 5G Mobile Networks - A Survey on Enabling Technologies

In this paper, an extensive review has been carried out on the trends of existing as well as proposed potential enabling technologies that are expected to shape the fifth generation (5G) mobile wireless networks. Based on the classification of the trends, we develop a 5G network architectural evolution framework that comprises three evolutionary directions, namely, (1) radio access network node and performance enabler, (2) network control programming platform, and (3) backhaul network platform and synchronization. In (1), we discuss node classification including low power nodes in emerging machine-type communications, and network capacity enablers, e.g., millimeter wave communications and massive multiple-input multiple-output. In (2), both logically distributed cell/device-centric platforms, and logically centralized conventional/wireless software defined networking control programming approaches are discussed. In (3), backhaul networks and network synchronization are discussed. A comparative analysis for each direction as well as future evolutionary directions and challenges toward 5G networks are discussed. This survey will be helpful for further research exploitations and network operators for a smooth evolution of their existing networks toward 5G networks

Will SDN be part of 5G?

For many, this is no longer a valid question and the case is considered settled with SDN/NFV (Software Defined Networking/Network Function Virtualization) providing the inevitable innovation enablers solving many outstanding management issues regarding 5G. However, given the monumental task of softwarization of radio access network (RAN) while 5G is just around the corner and some companies have started unveiling their 5G equipment already, the concern is very realistic that we may only see some point solutions involving SDN technology instead of a fully SDN-enabled RAN. This survey paper identifies all important obstacles in the way and looks at the state of the art of the relevant solutions. This survey is different from the previous surveys on SDN-based RAN as it focuses on the salient problems and discusses solutions proposed within and outside SDN literature. Our main focus is on fronthaul, backward compatibility, supposedly disruptive nature of SDN deployment, business cases and monetization of SDN related upgrades, latency of general purpose processors (GPP), and additional security vulnerabilities, softwarization brings along to the RAN. We have also provided a summary of the architectural developments in SDN-based RAN landscape as not all work can be covered under the focused issues. This paper provides a comprehensive survey on the state of the art of SDN-based RAN and clearly points out the gaps in the technology.Comment: 33 pages, 10 figure

Xhaul: toward an integrated fronthaul/backhaul architecture in 5G networks

The Xhaul architecture presented in this article is aimed at developing a 5G integrated backhaul and fronthaul transport network enabling flexible and software-defined reconfiguration of all networking elements in a multi-tenant and service-oriented unified management environment. The Xhaul transport network vision consists of high-capacity switches and heterogeneous transmission links (e.g., fiber or wireless optics, high-capacity copper, mmWave) interconnecting remote radio heads, 5G points of attachment (5GPoAs, e.g., macro-and small cells), centralized-processing units (mini data centers), and points of presence of the core networks of one or multiple service provider(s). This transport network shall flexibly interconnect distributed 5G radio access and core network functions, hosted on network centralized nodes, through the implementation of a control infrastructure using a unified, abstract network model for control plane integration (Xhaul Control Infrastructure, XCI); and a unified data plane encompassing innovative high-capacity transmission technologies and novel deterministic-latency switch architectures (Xhaul packet Forwarding Element, XFE). Standardization is expected to play a major role in a future 5G integrated front haul/backhaul architecture for multi-vendor interoperability reasons. To this end, we review the major relevant activities in the current standardization landscape and the potential impact on the Xhaul architecture.This work has been partly supported by the Madrid Regional Government through the TIGRE5-CM program (S2013/ICE-2919) and the EU H2020 Xhaul Project (grant no. 671598)

High-capacity 5G fronthaul networks based on optical space division multiplexing

\u3cp\u3eThe introduction of 5G mobile networks, bringing multi-Gbit/s user data rates and reduced latency, opens new opportunities for media generation, transport and distribution, as well as for new immersive media applications. The expected use of millimeter-wave carriers and the strong network densification resulting from a much reduced cell size--which enable the expected performance of 5G--pose major challenges to the fronthaul network. Space division multiplexing (SDM) in the optical domain has been suggested for ultra-high capacity fronthaul networks that naturally support different classes of fronthaul traffic and further enable the use of analog radio-over-fiber and advanced technologies, such as optical beamforming. This paper discusses the introduction of SDM with multi-core fibers in the fronthaul network as suggested by the blueSPACE project, regarding both digitized and analog radio-over-fiber fronthaul transport as well as the introduction of optical beamforming for high-capacity millimeter-wave radio access. Analog and digitized radio-over-fiber are discussed in a scenario featuring parallel fronthaul for different radio access technologies, showcasing their differences and potential when combined with SDM.\u3c/p\u3

Survey on 5G Second Phase RAN Architectures and Functional Splits

The Radio Access Network (RAN) architecture evolves with different generations of mobile communication technologies and forms an indispensable component of the mobile network architecture. The main component of the RAN infrastructure is the base station, which includes a Radio Frequency unit and a baseband unit. The RAN is a collection of base stations connected to the core network to provide coverage through one or more radio access technologies. The advancement towards cloud native networks has led to centralizing the baseband processing of radio signals. There is a trade-off between the advantages of RAN centralization (energy efficiency, power cost reduction, and the cost of the fronthaul) and the complexity of carrying traffic between the data processing unit and distributed antennas. 5G networks hold high potential for adopting the centralized architecture to reduce maintenance costs while reducing deployment costs and improving resilience, reliability, and coordination. Incorporating the concept of virtualization and centralized RAN architecture enables to meet the overall requirements for both the customer and Mobile Network Operator. Functional splitting is one of the key enablers for 5G networks. It supports Centralized RAN, virtualized Radio Access Network, and the recent Open Radio Access Networks. This survey provides a comprehensive tutorial on the paradigms of the RAN architecture evolution, its key features, and implementation challenges. It provides a thorough review of the 3rd Generation Partnership Project functional splitting complemented by associated challenges and potential solutions. The survey also presents an overview of the fronthaul and its requirements and possible solutions for implementation, algorithms, and required tools whilst providing a vision of the evaluation beyond 5G second phase.info:eu-repo/semantics/submittedVersio

ADVANCED RADIO ACCESS NETWORK FEATURING FLEXIBLE PER-UE SERVICE PROVISIONING AND COLLABORATIVE MOBILE EDGE COMPUTING

Enriched by numerous technological advances, radio access networks (RANs) in the fifth mobile networks generation (5G)-and-beyond strive to meet the goals of both mobile network operators (MNOs) and end-users. While MNOs seek efficiency, resiliency, reliability and flexibility of their networks, end-users are more concerned with the variety and quality of the provided, state-of-the-art, reasonably priced services. This has resulted in a complex, multi-tier, and heterogeneous RAN architecture that is severely challenged to achieve and maintain a strict reliability requirement of seven-nines (i.e., 99.99999% network up-time) and to meet ultra-reliable, low latency communications (URLLC) requirements with a latency upper bound of 1 ms end-to-end roundtrip time. Based on the flexible function split concept and data-plane programmability, this dissertation makes several key contributions to the body of knowledge on advanced, service-oriented RANs in two key core components. The first core component pertains to improving fronthaul efficiency, resiliency, flexibility, and latency performance with a cross-layer integration of Analog-Option-9 function split in the flexible fronthaul paradigm. Within the folds of that, the novel cross-layer digital-analog integration is experimentally investigated to pave the way for promising analog technologies to find their niche in 5G-and-beyond. The second core component is related to the design of lightweight, fronthaul-positioned multi-access edge computing (MEC) units to host Cooperative-URLLC applications at the edge of the fronthaul. Hence, from the vertical perspective, the dissertation provides solutions to support general URLLC applications and the Cooperative-URLLC variation by shrinking and eliminating latency sources at the Top-of-RAN and Low-RAN segments of advanced RANs.Ph.D

Integrating Fronthaul and Backhaul Networks: Transport Challenges and Feasibility Results

In Press / En PrensaIn addition to CPRI, new functional splits have been defined in 5G creating diverse fronthaul transport bandwidth and latency requirements. These fronthaul requirements shall be fulfilled simultaneously together with the backhaul requirements by an integrated fronthaul and backhaul transport solution. In this paper, we analyze the technical challenges to achieve an integrated transport solution in 5G and propose specific solutions to address these challenges. These solutions have been implemented and verified with commercially available equipment. Our results confirm that an integrated fronthaul and backhaul transport dubbed Crosshaul can meet all the requirements of 5G fronthaul and backhaul in a cost-efficient manner.Special thanks to the 5G-Crosshaul and 5G-TRANSFORMER team, in particular to Jaime Jose Garcia Reinoso, Chenguang Lu, Daniel Cederholm and Jakub Kocur who helped during the experimentation. This work has been partially funded by the EU H2020 project "5G-TRANSFORMER: 5G Mobile Transport Platform for Verticals" (grant no. 761536)