Johannes Lessmann

Advanced wireless and optical technologies for small-cell mobile backhaul with dynamic software-defined management

This article discusses novel wireless and optical technologies to address the radical new challenges of small cell mobile backhaul (MBH). Specifically, we examine 60 GHz and 70-80 GHz millimeter-wave technologies for high-capacity last mile and pre-aggregation backhaul, and orthogonal frequency-division multiple access passive optical networks as the optical technology complement for enabling flexible cost-efficient hybrid backhaul coverage. Flexible high-capacity hybrid millimeter wave/optical MBH network operation is next verified via network simulations in the context of a demanding, urban small-cell backhaul application. Finally, a novel software defined networking tool called the backhaul resource manager is introduced for automated dynamic resource provisioning and capacity-aware path computation that improves fairness, network utilization and end-to-end user quality of experience. The introduction of the novel wireless, optical, and software-defined technologies thus has the potential to truly revolutionize the future MBH network.

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.

Fronthaul and backhaul requirements of flexibly centralized radio access networks

Cloud radio access networks promise considerable benefits compared to decentralized network architectures, but they also put challenging requirements on the fronthaul and backhaul network. Flexible centralization can relax these requirements by adaptively assigning different parts of the processing chain to either the centralized baseband processors or the base stations based on the load situation, user scenario, and availability of fronthaul links. In this article, we provide a comprehensive overview of different functional split options and analyze their specific requirements. We compare these requirements to available fronthaul technologies, and discuss the convergence of fronthaul and backhaul technologies. By evaluating the aggregated fronthaul traffic, we show the benefits of flexible centralization and give guidelines on how to set up the fronthaul network to avoid over- or under-dimensioning.

SoftEPC — Dynamic instantiation of mobile core network entities for efficient resource utilization

Existing mobile network infrastructures, for example the Evolved Packet Core (EPC), are based on mission specific, specialized network nodes/entities that are interconnect via standardized interfaces in a static manner, each providing a specific service/function. One common practice adopted by many Mobile Network Operators (MNOs) in order to cater to increasing traffic demand is the over provisioning of network and processing resources. However, this approach results in increased CAPEX and OPEX and in view of future load forecasts this approach is no longer considered feasible or economical. In this paper we address this specific issue and propose the concept of softEPC, which leverages the recent advances in cloud technology concept such as Infrastructure as a Service (IaaS) and virtualization techniques in the realm of mobile networks. A softEPC is considered as a virtual network of Evolved Packet Core (EPC) functions over a physical transport network topology. This will enable the on-demand and load-aware dynamic instantiation of network functions and services at appropriate locations in response to the actual traffic demand. The main objective of this approach is to increase the utilization of network resources by flexibly and dynamically placing the network functions/services where most appropriate to provide optimum service and where resources are available to increase the number of services provided to mobile users. The benefits and gains of this approach will be demonstrated by means of simulation results.

IEEE 802.21: Media independence beyond handover

The IEEE 802.21 standard facilitates media independent handovers by providing higher layer mobility management functions with common service primitives for all technologies. Right after the base specification was published, several voices rose up in the working group advocating to broaden the scope of IEEE 802.21 beyond handovers. This paper aims at updating the reader with the main challenges and functionalities required to create a Media Independence Service Layer, through the analysis of scenarios which are being discussed within the working group: 1) Wireless Coexistence, and 2) Heterogeneous Wireless Multihop Backhaul Networks.

Rope ladder routing: Position-based multipath routing for wireless mesh networks

In this paper, we present a novel multipath structure called rope-ladder which combines the advantages of path, node and link protection schemes. We also propose a position-based multipath routing protocol in order to efficiently construct rope-ladders in wireless networks. By design, the paths which are constructed by our protocol are closely together which allows to quickly switch back and forth between them in cases of node or link failures. Hence, the size of loss gaps (i.e. the number of consecutively lost packets) can be minimized. Previous works mostly confine themselves to overall packet loss comparisons. However, the loss gap size is crucial to ensure high quality for gap-sensitive traffic like voice flows. Our multipath structure can also tolerate failures of multiple consecutive nodes on the primary path, and has a superior path diversity and path lifetime compared to even perfect braids. We evaluate the performance of our protocol using analysis and simulations1.

Cost-Efficient Wireless Mobile Backhaul Topologies: An Analytical Study

Wireless communication technologies such as microwave radios are used to provide high-speed mobile backhaul connectivity for radio access networks in cases in which wire-based alternatives, e.g. cable or fiber, are not readily available and cannot be deployed in an economic or timely manner. Current mobile backhauls are predominantly deployed in tree or ring topologies, which simplify traffic management. Yet, with the increasing demand on backhaul capacity and the immense cost pressure on mobile backhaul solutions, meshed wireless mobile backhauls have been identified as a promising evolution. While traffic management in wireless mesh networks have been studied extensively in the literature, so far there is no quantitative analysis comparing the different topology options, i.e. mesh, ring and tree, regarding network performance and deployment cost. This paper fills this gap by studying the minimum cost problem of connecting a set of base station/gateway sites using different topologies while supporting both time- and space-varying traffic demands. Furthermore, we consider the additional constraint of resilience to single link failures. The evaluation results show that meshed wireless backhaul topologies are a cost-effective alternative to trees and rings, in particular in the face of spatial and temporal fluctuation of traffic demand and protection against link failures.

Resource optimization in realistic mobile backhaul networks

This paper proposes a resource management system that allows maximizing the traffic which can be served by a given mobile backhaul network. It does so by means of a novel path optimization algorithm that consists of an offline component (based on predicted traffic demand information) and an online component (for excess traffic). As opposed to previous traffic engineering approaches, which usually assume a fluid traffic model, our algorithm explicitly takes flow classification and thus splitting granularity into account. To improve network utilization, we introduce t time slots and allow m traffic matrices, where the number of m depends on the QoS classes to be differentiated. The algorithm is able to compute a highly efficient resource allocation for each QoS class (also taking availability requirements into account) and avoids re-routing of QoS-sensitive traffic. We present a novel Genetic Algorithm for solving the offline problem. Evaluation is done using synthetic as well as real mobile backhaul data from European operators.

Policy-Based and QoE-Aware Content Delivery Using Q-Learning Method

AbstractWith the increasing popularity of various video services, video content is becoming a dominant traffic type in mobile networks. This poses a serious challenge to mobile network operators as well as service providers when it comes to delivering video content in a controllable and resource-efficient way to multiple users. Meeting various quality of experience and quality of service requirements is a difficult task especially in a wireless environment where several different priority based user classes can be included. This paper proposes an intelligent and context-aware application level fair scheduler, which is based on reinforcement learning and which can dynamically adjust relevant scheduling parameters in reaction to specific events or context information. nThe implemented Q-learning method is analyzed with reference to the delivery of progressive video streaming services employed by the likes of YouTube, Daily Motion, etc. In this regard, we study the performance observed by the end users in a scenario where the backhaul link in a mobile network infrastructure may become congested. Using the application level scheduler to intelligently orchestrate between multiple concurrent flows will minimize the number of buffer starvation events and thus enable smooth playback in cases where a pure TCP based delivery would fail. We also demonstrate the effectiveness of the Q-learning based scheduler to provide service separation between the user classes and fairness within a user class.

On the benefits of time-varying routing in realistic mobile backhaul networks

Since traffic load in mobile networks typically changes significantly over time, time-varying routing, where routing changes in certain time intervals, seems an obvious solution. Yet multiple researchers have claimed independently in the past, that time-varying routing does not lead to worthwhile benefits given its overhead. In this paper, we study this issue in a systematic way. We argue that previous claims are due to focusing on too narrow optimization metrics and demonstrate the poor expressiveness of such metrics using real mobile backhaul topologies. We propose a novel traffic engineering metric, capacity variation, and on that basis, prove that time-varying routing can in fact have great benefits, particularly in terms of infrastructure CAPEX costs. A quantitative evaluation on the benefits is provided based on real mobile backhaul data from a European operators.