Andreas Maeder

Cloud technologies for flexible 5G radio access networks

The evolution toward 5G mobile networks will be characterized by an increasing number of wireless devices, increasing device and service complexity, and the requirement to access mobile services ubiquitously. Two key enablers will allow the realization of the vision of 5G: very dense deployments and centralized processing. This article discusses the challenges and requirements in the design of 5G mobile networks based on these two key enablers. It discusses how cloud technologies and flexible functionality assignment in radio access networks enable network densification and centralized operation of the radio access network over heterogeneous backhaul networks. The article describes the fundamental concepts, shows how to evolve the 3GPP LTE architecture, and outlines the expected benefits.

Energy Efficiency Benefits of RAN-as-a-Service Concept for a Cloud-Based 5G Mobile Network Infrastructure

This paper focuses on energy efficiency aspects and related benefits of radio-access-network-as-a-service (RANaaS) implementation (using commodity hardware) as architectural evolution of LTE-advanced networks toward 5G infrastructure. RANaaS is a novel concept introduced recently, which enables the partial centralization of RAN functionalities depending on the actual needs as well as on network characteristics. In the view of future definition of 5G systems, this cloud-based design is an important solution in terms of efficient usage of network resources. The aim of this paper is to give a vision of the advantages of the RANaaS, to present its benefits in terms of energy efficiency and to propose a consistent system-level power model as a reference for assessing innovative functionalities toward 5G systems. The incremental benefits through the years are also discussed in perspective, by considering technological evolution of IT platforms and the increasing matching between their capabilities and the need for progressive virtualization of RAN functionalities. The description is complemented by an exemplary evaluation in terms of energy efficiency, analyzing the achievable gains associated with the RANaaS paradigm.

Towards a flexible functional split for cloud-RAN networks

Very dense deployments of small cells are one of the key enablers to tackle the ever-growing demand on mobile bandwidth. In such deployments, centralization of RAN functions on cloud resources is envisioned to overcome severe inter-cell interference and to keep costs acceptable. However, RAN back-haul constraints need to be considered when designing the functional split between RAN front-ends and centralized equipment. In this paper we analyse constraints and outline applications of flexible RAN centralization.

Mobile CDN enhancements for QoE-improved content delivery in mobile operator networks

With the popularity of YouTube and other video services (e.g., VoD), video content is becoming a dominant traffic type in mobile networks and will soon form the major bulk of the traffic. This poses a serious challenge to mobile network operators when it comes to delivering video content to multiple users in a wireless environment, where the quality of experience of each user must be met as per user expectation. To this end, mobile content distribution networks (mCDNs) are gaining attraction as one possibility to enable controllable and resource-efficient delivery of video content. In this article we motivate the deployment of mCDN serving point (mCSP) nodes in an mCDN infrastructure and describe its benefits for a mobile network operator who wishes to employ an mCDN system in their existing mobile network architecture. In this respect we highlight the key features and requirements of such an mCSP node and the advantages it offers. One particularly beneficial feature of our proposed mCSP node is to ensure fairness during the delivery of progressive video streaming services employed by the likes of YouTube, Daily Motion, and others. In this regard we first highlight the unfairness issue when delivering progressive video streaming services over TCP to multiple users over a wireless network infrastructure and its effect on the user perceived QoE. We then demonstrate, as a proof of concept, the effectiveness of employing application-level scheduling in an mCSP node to ensure fairness among multiple simultaneous progressive video sessions in scenarios where the backhaul link in a mobile network infrastructure may become congested.

Benefits and challenges of virtualization in 5G radio access networks

Future 5G deployments will embrace a multitude of novel technologies that will significantly change the air interface, system architecture, and service delivery platforms. However, compared to previous migrations to next-generation technologies, this time the implementation of mobile networks will receive particular attention. The virtualization of network functionality, the application of open, standardized, and inter-operable software, as well as the use of commodity hardware, will transform mobile-network technology. In this article we focus on the benefits, challenges, and limitations that accompany virtualization in 5G radio access networks (RANs). Within the context of virtualized RAN, we consider its implementation requirements and analyze its cost. We also outline the impact on standardization, which will continue to involve 3GPP but will engage new players whose inclusion in the discussion encourages novel implementation concepts.

Asymmetric Uplink-Downlink Assignment for Energy-Efficient Mobile Communication Systems

Mobile operators are facing increasing energy prices to operate their networks. At the same time, the demand for broadband wireless access is steadily increasing, driven by the success of smart phones and new services like machine-to-machine communication. In this paper we propose and evaluate a novel asymmetric user assignment scheme, which enables operators to save energy, while satisfying the capacity demands. The main innovation is to separate the association of users to base stations in uplink and downlink, such that in macro/micro overlay scenarios parts of the radio access network can be switched off. Based on system-level simulations we show that our scheme enables energy savings of up to 15% and 60% over typical macro and micro cell deployments, respectively. We further discuss its technical feasibility and implications on the system design. All numerical results are obtained in accordance with the guidelines and requirements of IMT-Advanced systems.

Energy Saving Enhancement for LTE-Advanced Heterogeneous Networks with Dual Connectivity

In this paper, we consider the use of heterogeneous networks with close integration between the cells, using dual connectivity and fiber optic backhaul. The energy efficiency of such a network is evaluated in comparison with some of the existing traffic offloading mechanisms. We try to enhance the mechanisms taking the system energy efficiency, and user quality of experience based on the offloaded traffic type into account. Detailed evaluations of the offloading mechanism is done using LTE-Advanced heterogeneous network settings, with dual connectivity architecture assumptions and scenarios. Based on the performance results in terms of energy efficiency, system power consumption and throughput, it is shown that the considered scheme provides significant energy savings, as well as provides the network operator the flexibility to offload traffic depending on tradeoffs between competing network priorities.

Joint RAN/backhaul optimization in centralized 5G RAN

This paper provides an overview of joint radio access network (RAN) and backhaul (BH) optimization methods in dense small cell networks, assuming a heterogeneous backhaul and centralization by Cloud RAN. The main focus is on the design of novel MAC (medium access control) and RRM (radio resource management) schemes for constrained, non-ideal backhaul which can influence the RAN performance. In this context, we provide some key technology approaches which incorporate the RAN/BH awareness at the cloud and exploit the benefits of Cloud-RAN by dynamically adapting to BH constraints.

Computationally Aware Sum-Rate Optimal Scheduling for Centralized Radio Access Networks

In a centralized or cloud radio access network, certain portions of the digital baseband processing of a group of several radio access points are processed at a central data center. Centralization improves the flexibility, scalability, and utilization of computational assets. However, the performance depends critically on how the limited data processing resources are allocated to serve the needs of the different wireless devices. As the processing load imposed by each device depends on its allocated transmission rate and channel quality, the rate- allocation aspect of the scheduling should take into account the available computing resources. In this paper, two computationally aware schedulers are proposed that have the objective of maximizing the system sum-rate while satisfying a constraint on the offered computational load. The first scheduler optimally allocates resources and is implemented according to a water-filling algorithm. The second scheduler is suboptimal, but uses a simpler and intuitive complexity-cut-off approach. The performance of both schedulers is evaluated using an LTE- compliant system level simulator. It is found that both schedulers avoid outages that are caused by an overflow of computational load (i.e., computational outages) at the cost of a slight loss of sum-rate.

5G multi-RAT multi-connectivity architecture

The 5th generation of mobile networks is envisioned to unify different access types under one system in order to enable efficient and performant operations. We propose a radio network architecture for tight integration of multiple radio access technologies supporting traffic steering, link selection, and aggregation of traffic flows from and to different sources. This enables the radio network architecture to support better throughput, and increased reliability with different levels of mobility. Specifically, we propose a common user plane and control plane across different radio technologies utilizing similar principles, such that the joint operation of radio technologies can be optimized.