Evaluating the Cloud-RAN architecture: functional splitting and switched Ethernet Xhaul

A hybrid cloud radio access network (H-CRAN) architecture has been proposed to alleviate the midhaul capacity limitation in C-RAN. In this architecture, functional splitting is utilized to distribute the processing functions between a central cloud and edge clouds. The flexibility of selecting specific split point enables the H-CRAN designer to reduce midhaul bandwidth, reduce latency, save energy, or distribute the computation task depending on equipment availability. Meanwhile, techniques for caching are proposed to reduce content delivery latency and the required bandwidth. However, caching imposes new constraints on functional splitting. In this study, considering H-CRAN, a constraint programming problem is formulated to minimize the overall power consumption by selecting the optimal functional split point and content placement, taking into account the content access delay constraint. We also investigate the trade-off between the overall power consumption and occupied midhaul bandwidth in the network. Our results demonstrate that functional splitting together with enabling caching at edge clouds reduces not only content access delays but also fronthaul bandwidth consumption and saves energy finding a compromise between these performance metrics.

With the emergence of cloud radio access network (C-RAN) architecture, latency in fronthaul (FH) network is a critical performance metric especially for ultra-reliable and low-latency communication applications. The stringent FH capacity and latency requirements of C-RAN can be relaxed by offloading some baseband functionalities to remote radio unit (RRU), referred to as functional splitting. This allows packetized FH network solutions such as ubiquitous Ethernet. In this paper, we calculate the FH latency in the uplink of a C-RAN system with massive MIMO-based RRUs and 3GPP functional Split 7, wherein MIMO equalization is done at the RRU. We derive tractable, closed-form expressions for the steady-state probabilities of queue length and sojourn time distribution at the output port of an Ethernet switch in the FH network. We first present these results for Poisson file arrivals from users in the network and exponential file size distribution. We then extend the results to general file size distribution. The numerical results show that the file size and spectral efficiency of the users are critical in determining the FH latency. Further, results show that switch speed can be decreased without incurring significant increase in FH latency revealing the possibility for statistical multiplexing gains.

Cloud Radio Access Networks (C-RAN) was proposed as a solution to overcome the challenges faced by the current Radio Access Networks (RAN). C-RAN was introduced as a change in the architecture of the Base station (BS). Fronthaul is a communication link between the BS entities of the proposed architecture. The change in BSs architecture places some technical challenges to utilize the benefits offered by C-RAN. Fronthaul capacity limitation and delay are the major bottlenecks of the C-RAN practical implementation. To prevail over these limitations, various C-RAN models in terms of functional splits are proposed. But none of the architectures is finalized among the industry and academia. In this paper, exhaustive literature is presented on the advantages offered by C-RAN architecture. To make full utilization of those advantages, different C-RAN architectures and fronthaul architectures were proposed. Fronthaul compression is crucial for bringing sustainability to C-RAN architecture. As part of the study, different compression techniques are discussed in this literature. Besides the theoretical study, various practical implementation of C-RAN testbeds is examined.

5G is coming with a promise to provide ubiquitous coverage with high data rate availability. To do so, densification of access points to enhance the system capacity is anticipated. For managing such densely populated network, 5G will be employing Centralized Radio Access Network (CRAN), where most of the Radio Access Network (RAN) functionalities are centralized in a central processing unit. This centralization reduces operational costs and eases implementation of advanced technologies, such as, Cooperative multipoint (CoMP) and enhanced inter-cell interference coordination (eICIC), in a cost efficient way. However, CRAN imposes stringent requirements on the fronthaul, i.e. the link connecting access points to the central unit, in terms of capacity and latency. Furthermore, future fronthaul networks are expected to rely on wireless technologies, since wired options are costly, not scalable and not always suitable for all scenarios. Therefore, meeting the expected requirements of fronthaul network utilizing capacity-limited wireless technologies may become an inescapable bottleneck. In this paper, we study different functional splits at the PHY layer in terms of data rate requirements and operational cost, and discuss the combination of different splits aimed at minimizing the overall cost and maximizing the centralization gains, while keeping the capacity requirements below the limit of the fronthaul.

We present a novel rails approach so that future e-Science applications can effectively exploit future system architectures, including multi-core and many-core architectures, multiple network cards, multiple graphical processing units and hybrid hierarchical memory architectures. We define "rail" as the co-scheduling of two or more of these resources. This approach enables creation of parallel multi-rails through every aspect of an end system: from processing on the multi- and many cores, to generation of multiple data flows and streaming over multi-lane network interface card (NIC) connected via a parallel interconnect. We describe a novel open-source multi-rail toolkit and the evaluation of end-system parameters that impact the efficiency of such multi-rail systems, including Interrupt, Memory, Thread and Core Affinities -- key properties for achieving scalable performance.

Cellular networking has entered the paradigm of next generation networking, Software Defined Mobile Networking (SDMN) and Cloud Radio Access Networks (CRAN). This paradigm shift has compelled to improve future cellular networks by making them more efficient and smart. The improved, future cellular networks could have a profound impact on the commercial and research segments in terms of capital expenditure and operational expenditure by presenting a unified robust technology for data connectivity. In future, 5G cellular networks will be progressed with LTE that will facilitate this technological transformation. Future 5G demands reliance on more flexible and dynamic technologies such as static Radio Access Networks (RAN), otherwise resources will be depleting and will be unable to meet the surging demands including wireless transmission connectivity and providing an efficient network bandwidth. To address this problem, the paper presents a study exploring the amalgamation of Software Defined Network (SDN) and cloud computing achieve Cloud RAN or RAN-as-a-Service (RANaaS). This helps to overcome the problems associated with handling enormous matrix of connecting devices and nodes. This paper explores existing research geared towards the deployment of 5G networks through Remote Radio Heads (RRH) and Virtual Base Stations (VBSs) backed by SDN. Furthermore, this research survey is an effort to unearth the security implications and challenges of CRAN while adopting LTE and SDMN services in CRAN based 5G networks. The security challenges of conventional wireless networks are framed to emphasize on the need to migrate from traditional RAN to CRAN. Subsequently the possible mitigation techniques are also discussed. Furthermore, the role of SDN and its security artifacts are also explored to embed security within the CRAN architecture.

SG is set to be revolutionary and more flexible compared to the previous mobile network generations able to support services with diverse requirements. However, the wide range of use cases poses challenges to network resource allocation and management. Infrastructure providers to address the issues deriving from the requirements of a multi-service environment, adopt two key paradigms, network slicing and functional split options, in which the former controls the network resources and the latter relaxes the fronthaul constraints. Since the slices are deployed over a common and shared infrastructure functional split must dynamically adjust the demands of the service providers. As there is no one-split-fits-all option, we propose a mathematical framework for the optimal selection of functional split options per slice requests and the optimal slice size in terms of data-rate, that maximizes the infrastructure provider's total profits. Hence, a thorough analysis is performed and the optimal solutions are discussed with a comparison against hybrid network configurations.

Cloud Radio Access Network (C-RAN) has been proposed as a new paradigm shift in the Radio Access Network (RAN) technology as a part of the fifth generation Long-Term Evolution Advanced (LTE-A) networks to support better spectral and energy efficiency along with the high availability. In this paper, we discuss implementation details of a C-RAN Fronthaul with the help of USRP-based transceivers and LabView platform. To the best of our knowledge, this is the first implementation of a C-RAN architecture that functionally splits the radio resource head (RRH) and the baseband processing unit (BBU) at the physical layer (Split 8) and transfers the completely unprocessed raw signal elements from the RRH to the BBU pool at the cloud for signal processing. We explore TCP and UDP as alternate protocols for fronthaul data transfer to the cloud. In order to evaluate the performance of a C-RAN fronthaul and the interplay of different performance parameters for fronthaul data transfer, we observe various metrics like the receiver goodput and the latency and compare the performance between a C-RAN setup and a generic distributed RAN setup.We observe that TCP works better for Ethernet fronthauling compared to UDP, as it provides reliable data delivery. The analysis discussed in this paper gives insights about the implementation and performance of a C- RAN environment which is essential for designing efficient fronthauling and functional splits of a C-RAN architecture.

A novel architecture design for Radio Access Networks (RANs) to address critical elements in resource management and to achieve the 5G mobile network requirements is needed. Cloud Radio Access Network (C-RAN) and Software Defined Networking (SDN) / Network Function Virtualization (NFV) technologies are recognized as key enabling solutions for the future mobile networks. C-RAN is a new mobile network architecture, characterized by a redistribution of functionalities. More specifically, the baseband processing resources are centralized in remote locations, known as Base Band Unit (BBU) Pool, whereas the radio functionalities, known as Remote Radio Head (RRH), remain in edge locations. SDN focuses on decoupling control and data plane, while NFV performs the functionalities abstraction from the underlying hardware. In this paper, a hierarchical layered software-defined architecture for future 5G networks is proposed. We deploy a Next Generation Fronthaul Interface (NGFI) based architecture, in order to overcome issues related to massive MIMO deployment. Furthermore, in order to implement dynamically different functional splitting options, a virtualized Remote Aggregation Unit (RAU) is proposed. As further contribution, our solution aims to provide new features that facilitate SDN/NFV integration in wireless/mobile environments.

This paper suggests a control strategy of coordinating multiple dynamic-braking units during the transients ensuing major disturbances. The control strategy considered in this study is a two-level hierarchy. The proposed two-level structure results from the decomposition of the overall problem into parallel sub-problems. This allows the retention of the closed-loop controls associated with each subsystem, which together constitute the lower level (Level I). The central coordinating controller forms the upper level (Level II). The coordination of the local controllers by the central controller, accounts for nonlinear terms and interconnections, and yields the global optimization of the overall system transient performance. The local controllers are not dependent on one another and are robust to any changes in the network configuration, due to the feedback or closed-loop control formulation inherent in the proposed strategy. To ensure physical realizability of the local controllers, the input was restricted to locally measurable signals. The methodology was implemented into a prototype software program, which was tested on a single machine connected to a very large network approximated by an infinite bus, and then on the IEEE four-generator test system. These studies considered fault clearing times greater that the critical, assuring an unstable condition. The well-damped optimal state and control trajectories illustrate the successful solution of the problem, indicating that the technique is a valuable tool dealing with transient control problems for large-scale systems.

The rapid development and spread of communication technologies is now becoming a global information revolution. Customers have a need for communication services, which could be flexibly configured in accordance with their Quality of Experience (QoE) requirements. Realizing the close connection between customer experience and profitability, the service provider has been placing more and more attention on customer experience and QoE. The traditional quality of service management method based on SLA (Service Level Agreement) is not sufficient as a means to provide QoE-related contracts between service providers and customers. The current SLA method is mostly limited and focused on technical aspects of QoS (Quality of Service). Furthermore, they do not follow on the network the principles and semantic approach to the QoS specification for a communication service using QoE parameters. In this paper, we propose a customer-oriented quality of service management method for future IBN (Intent-Based Networking). It is based on a new QoE metric on a scale from 1 to 5, which allows one to take into account the commercial value of e-services for customers. Based on this approach, the network configuration and functionality of network equipment automatically changes depending on customer requirements. To implement the new method of service quality management, an algorithm for routing data packets in the network was developed, taking into account the current load of the forecast path. The algorithm of billing system functioning in conditions of customer-oriented quality management in telecommunication networks has been created. To investigate the effectiveness of the proposed method of service quality management with the traditional SLA method, we developed a simulation network model with the implementation of two approaches. By conducting a simulation, it was determined that the proposed method gives an average gain of 2–5 times for the criterion of the number of customers who require high quality of experience of the service.

NASA is planning to upgrade its network infrastructure to support missions for the 21st century. The first step is to increase the data rate provided to science missions to at least the 100 Mbps range. This is under way, using Ka-band 26 GHz, erecting an 18-meter antenna for the Lunar Reconnaissance Orbiter, and the planned upgrade of the Deep Space Network (DSN) 34-meter network to support the James Webb Space Telescope (JWST). The next step is the support of manned missions to the Moon and beyond. Establishing an outpost with several activities such as rovers, colonization, and observatories, is better achieved by using a network configuration rather than the current method of point-to-point. Another challenge associated with the Moon is communication coverage with the Earth. The Moon's South Pole, targeted for human habitat and exploration, is obscured from Earth view for half of the 28-day lunar cycle and requires the use of lunar relay satellites to provide coverage for the times when there is no direct view of the Earth. The future NASA and Constellation network architecture is described in the Space Communications Architecture Working Group (SCAWG) Report[l]. The Space Communications and Navigation (SCAN) Constellation Integration Project (SCIP) is responsible for coordinating Constellation requirements and has assigned the responsibility for implementing these requirements to the existing NASA communication providers: DSN, Space Network (SN), Ground Network (GN) and the NASA Integrated Services Network (NISN). The SCAWG Report provides a future architecture but does not provide implementation details. The architecture calls for a Netcentric system, using hundreds of 12-meter antennas, a ground antenna array, and a relay network around the Moon. The report did not use cost as a variable in determining the feasibility of this approach. As part of the SCIP Mission Concept Review and the second iteration of the Lunar Architecture Team (LAT), the focus is on cost, as well as communication coverage using operational scenarios. This approach maximizes use of existing assets and adds capability in small increments. This paper addresses architecture decisions such as the Radio Frequency (RF) signal and network (Netcentric) decisions that need to be made and the difficulty of implementing them into the existing Space Network and DSN. It discusses the evolution of the lunar system and describes its components: TDRSS, Earth-based ground stations, Lunar Relay, and surface systems.

A double-layered constellation for a future global satellite communications network connected by optical intersatellite links has been proposed. The constellation consists of lower layer satellites for mobile and personal satellite communications, and upper layer satellites for large- capacity fixed satellite communications and feeder links. Optical inter-satellite links, which can perform high-capacity communications with small terminals, are used for all intersatellite data transmission. Although a polar orbit constellation offers the merit of simpleness in network configurations, the inclined orbit constellation offers the potential for reducing the required number of satellites, improving link properties, and enhancing the coverage in middle and low latitudes, by selecting the most adequate inclination of the orbits. The optical inter- satellite link properties, coverage properties, and required number of satellites are evaluated for constellations using inclined orbits, and then compared with those of a polar orbit constellation. Three constellation types in each layer achieving continuous double coverage are assumed. For each constellation, the relations between these properties and the inclination of the orbits are examined. The basic parameters of optical inter-satellite links on satellite constellations using inclined orbits are also shown.

The role of transmission network design is diverse. Basically, it includes the preparation of transmission solutions for access and core (backbone) transmission networks. In the design of a transmission network, the engineer must have knowledge about existing transmission products and also operator budget analysis. For this reason, the transmission engineer might also act in early discussions with an operator and, in that case, support the marketing unit with technical competence within the area of transmission. In GSM/GPRS networks the user traffic is circuit switched through the GSM network and the signaling messages (including SMS) are transported on dedicated circuits, while the packet traffic is packet switched through the GPRS infrastructure. One of the most important parameters to consider is the design of GSM/PRS networks is the access radio topology. The network topology selection is an evaluation process, which incorporates business strategy, investment costs, technology roadmap, network redundancy and robustness, network evolution path, and the migration strategy from the current network to the planned target network. The topology selection produces a preferred network topology plan for the target network. The topology provides information about the network such as node/site location, geographical information, existing network infrastructure, and capacity, new node/site to be added, and new network configuration, such as new hub sites. The information contained in the topology plan allows the radio transmission network planner to formulate an expansion strategy to meet future cellular network growth (Figure 1). Cell plan is a graphical representation of the network which simply looks like a cell pattern on a map. However, there is a lot of work behind it, regarding the correct geographical position of the site, the antenna parameters and types, the dimensioning analysis regarding the offered and designed capacity and interference predictions. Such planning needs computer-aided analysis tools for radio propagation studies, for example, planning tools like TEMS CellPlanner Universal or NetHawk analyzer.

This article consists of a collection of slides from the author's conference presentation on photonics and future data center networking. Some of the specific topics discussed include: the special features of data centers, system architectures, and applications supported; network configuration; problems with current cabling infrastructures; the set up of a typical commercial data centers; workload considerations; data center challenges; and new technologies that will support data centers in the future.