Virtualized Cloud Radio Access Network for 5G Transport

Abstract

Current Radio Access Networks (RANs) need to evolve to handle diverse service requirements coming from the growing number of connected devices and increasing data rates for the upcoming 5G era. Incremental improvements on traditional distributed RANs cannot satisfy these requirements, so the novel and disruptive concept of cloud-RAN (CRAN) has been proposed to decouple digital units (DUs) and radio units (RUs) of base stations (BSs), and centralize DUs into a central office, where virtualization and cloud computing technologies are leveraged to move DUs in the "cloud". However, separating RUs and DUs requires low-latency and high-bandwidth connectivity links, called "fronthaul", as opposed to traditional backhaul links. Hence, design of the 5G transport network, i.e., the part of the network that carries mobile data traffic between BSs and the core network and data centers, is key to meet the new 5G mobile service requirements and effectively transport the fronthaul traffic. Today, consensus has not yet been achieved on how the fronthaul traffic will be transported between RUs and DUs, and how virtualization of network resources will occur from radio network segment to the centralized baseband processing units. In this article, we present a new 5G architecture called virtualized-CRAN (V-CRAN) moving towards a cell-less 5G network architecture. We leverage the concept of a "virtualized-BS" (V-BS) that can be optimally formed by exploiting several enabling technologies such as softwaredefined radio (SDR) and Coordinated Multi-Point (CoMP) Transmission/Reception. V-BS can be formed on a per-cell basis or peruser basis by allocating virtualized resources on demand. For the fronthaul solution, our approach exploits the passive optical network (PON), where a wavelength can be dynamically assigned and shared to form "virtualized" PON (VPON). Several use cases of V-CRAN are presented to show how network architecture evolution can enhance system throughput, energy efficiency, and mobility management.

Optimum Functional Splits for Optimizing Energy Consumption in V-RAN

“…Alabbasi et al [13] investigated processing delay in the same dual-site processing, and they highlighted the minimum delay at a specific functional split decision. Wang et al [14] discussed several enabling technologies such as; software-defined radio (SDR) and coordinated multipoint (CoMP) transmission/reception to exploit virtualized base stations per cell/ per user basis in different functional splits in V-RAN. Alabbasi and Wang et al [15] discussed the optimal processing functional split by studying the interplay between energy efficiency and midhaul bandwidth in the same dualsite processing.…”

Flying to the Clouds: The Evolution of the 5G Radio Access Networks

“…Additionally, in this scenario, the processing resources of a BBU cannot be shared among other RRHs. Wang et al (2017) propose an alternative means to improve the system by making use of technologies, such as coordinated multipoint (CoMP), to reduce the interference and increase the throughput. However, this solution has two main drawbacks: (1) it applies stringent delay constraints for control and signalling to guarantee on-time coordination between BS (NGMN Alliance 2015), and (2) it is not designed to deal with the processing capabilities of distributed BSs.…”

Sliced-RAN: Joint Slicing and Functional Split in Future 5G Radio Access Networks

“…Virtualization and slicing have become two major concepts of future 5G networks. Given the importance of SDN as an enabler for both virtualization [11] and slicing [12], some recent works have been focused on RAN virtualization platforms and slicing designs. Foukas et al propose FlexRAN in [13], a flexible and programmable software-defined RAN (SD-RAN) platform.…”