Wolfgang Kellerer

Wolfgang Kellerer
Technische Universität München | TUM

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224
Publications
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4,697
Citations

Publications

Publications (224)
Conference Paper
The introduction of Software-Defined Radio Access Networks (SD-RANs) in 5G, whose main feature is the possibility of decoupling the control plane from the data plane, and associating the former with a controller away from Base Stations (BSs), represents a paradigm shift in the way the network resources are allocated. This property provides an incre...
Conference Paper
5G networks have emerged as the only viable solution to render a satisfying level of performance to different types of services, each of them with very stringent traffic requirements. One of those services are Ultra-Reliable Low-Latency Communications (URLLC). A use case where these services are especially sensitive are vehicular networks. Therefor...
Conference Paper
Software-Defined Radio Access Networks (SD-RANs), introduced in 5G, represent a paradigm shift in the process of cellular network resource allocation. The decoupling of the control from the data plane, and associating the former with a controller away from Base Stations (BSs), has enabled an increased flexibility in allocating network resources whi...
Conference Paper
Mobility management in 5G, especially at higher frequencies, is challenging because the signal quality fluctuates significantly due to blockages of Line of Sight (LoS), shadowing and user mobility. As a result, users experience frequent handovers, which reduce the network capacity. In order to perform smooth network operation, the decisions when to...
Conference Paper
Software-Defined Networking (SDN) lays the foundation for the operation of future networking applications. The separation of the control plane from the programmable data plane increases the flexibility in network operation. One of the most used languages for describing the packet behavior in the data plane is P4. It allows protocol and hardware ind...
Conference Paper
Software-Defined Radio Access Networks (SD-RANs), introduced for the first time in 5G networks, symbolize a paradigm shift in the way the allocation of cellular network resources is performed. The main feature of SD-RAN is the possibility to decouple the control plane from the data plane, and associating the former with a controller that is located...
Conference Paper
Line of Sight (LoS) blockages are a common occurrence in densely deployed cellular networks, as is the case with 5G. This leads to a significant deterioration in the signal quality on the user side. Modeling LoS blockages is crucial for simulations to obtain reliable results, but also challenging since LoS might appear and disappear occasionally be...
Conference Paper
In the next-generation wireless networks, energy efficiency (EE) is a fundamental requirement due to the limited battery power and the deployment of various devices in hardly accessible areas. While a plethora of approaches have been proposed to increase users’ EE, there are still many unresolved issues stemming mainly from the limited wireless res...
Conference Paper
The ubiquitous spread of programmable data planes has been conditioned by the development and use of domain spe- cific languages. One such very convenient programming language is P4, which enables devices, like switches, to be configurable and protocol-independent, making it a perfect match for Software Defined Networks. Therefore, analyzing the me...
Conference Paper
Next generation radio access networks (RANs) envision softwarization and programmability as the main tools to provide the quality of service (QoS) requirements of emerging applications. Consequently, software-defined radio access networks (SD-RANs) have gained increased traction as a technology to foster network management and alleviate orchestrati...
Conference Paper
Full-text available
Centralized Software Defined Networking (SDN) controllers and Network Management Systems (NMS) introduce the issue of controller as a single-point of failure (SPOF). The SPOF correspondingly motivated the introduction of distributed controllers, with replicas assigned into clusters of controller instances replicated for purpose of enabling high ava...
Article
Full-text available
Wind energy is one of the most attractive and one of the fastest growing sources of green energy in the world. With the expansion of wind parks, there is a growing need for an efficient coordination of the diverse energy production systems, as well as a tighter coupling between the production and the consumer side of the grid. Current grid operator...
Conference Paper
Public Intelligent Transportation Systems (ITS) aim at enhancing daily travelling experience by providing safety, traffic efficiency and infotainment services. These services demand connection to a core network with content storage, centralized processing and decision capabilities. The proposed study focuses on the optical backhaul network planning...
Article
Flexibility is often claimed as a competitive advantage when proposing new network designs. However, most proposals provide only qualitative arguments for their improved support of flexibility. Quantitative arguments vary a lot among different proposals. A general understanding for flexibility is not yet clearly defined, leaving it to the reader to...
Article
The increasing popularity of mobile video streaming applications has led to a high volume of video traffic in mobile networks. As the base station, for instance, the eNB in LTE networks, has limited physical resources, it can be overloaded by this traffic. This problem can be addressed by using Scalable Video Coding (SVC), which allows the eNB to d...
Article
Software defined networking (SDN) has emerged as a promising paradigm for making the control of communication networks flexible. SDN separates the data packet forwarding plane, i.e., the data plane, from the control plane and employs a central controller. Network virtualization allows the flexible sharing of physical networking resources by multipl...
Conference Paper
Full-text available
Software-defined Networking (SDN) is a promising and powerful concept to introduce new dimensions of flexibility and adaptability in today's communication networks. In particular, the realization of Quality of Service (QoS) concepts becomes possible in a flexible and dynamic manner with SDN. Although concepts of QoS are well researched, they were n...
Article
Application-aware resource management is the approach to tailor access networks to have characteristics beneficial for the running applications and services. This is achieved through the monitoring and integration of key performance indicators from the application layer within the network resource management. The aim is to increase user-perceived q...
Conference Paper
Video content and, in particular, YouTube’s content account for the largest amount of today’s Internet traffic. However, little is known about the behavior of video streaming services for different kinds of network environments and under varying network conditions. Due to network operators’ lack of knowledge about the transmitted content, network r...
Article
The introduction of Software Defined Networking (SDN) and Network Functions Virtualization (NFV) has transformed the way networks will be built in the future. This development also applies to mobile networks and their evolution. How the SDN and NFV concepts will be integrated exactly is still an open research question with multiple approaches and t...
Article
The introduction of Network Functions Virtualization (NFV) and Software Defined Networking (SDN) to mobile networks enables operators to control and dimension their network resources with higher granularity and on a more fine-grained time scale. This dynamic operation allows operators to cope with the rapid growth of traffic and user demands, in ad...
Article
Access networks are continuously evolving to increase the bandwidth to their users. In order to be able to offer more than 100Mbps per user, Next Generation Optical Access (NGOA) Networks are being considered. These architectures offer new advantages, not only higher bandwidth per user but also a significant increase of client count (hundreds per p...
Article
With the rapid growth of user data, service innovation, and the persistent necessity to reduce costs, today's mobile operators are faced with severe challenges. In networking, two new concepts have emerged aiming at cost reduction, increase of network scalability and service flexibility, namely Network Functions Virtualization (NFV) and Software De...
Conference Paper
Nowadays, access networks connecting fixed users are independently planned from the mobile backhaul, which interconnects the base stations. This independence causes high capital expenditures due to the investment of having two networks instead of a single one. The recently proposed Hybrid PON architecture could be used to offer more bandwidth to th...
Conference Paper
Full-text available
Mobile services are evolving rapidly, moving from their conventional mobile voice to a wider portfolio such as Internet access, entertainment, health, and also location-based services. A wide range of on-board mobile services with very different requirements is also offered by automotive manufacturers. They rely on Mobile Network Operators (MNOs) t...
Article
Full-text available
The term Software Defined Networking (SDN) is prevalent in today's discussion about future communication networks. As with any new term or paradigm, however, no consistent definition regarding this technology has formed. The fragmented view on SDN results in legacy products being passed off by equipment vendors as SDN, academics mixing up the attri...
Conference Paper
Full-text available
The continuous increase of services bandwidth is forcing operators to upgrade their access networks. Fixed access networks are migrating from copper technology and GPON to new optical access networks, whereas mobile networks are migrating from 3G to 4G and in the near future to 5G. However, these migrations are being done in parallel and independen...
Conference Paper
Today's Internet does not provide an exchange of information between applications and networks, which may result in poor application performance. Concepts such as application-aware networking or network-aware application programming try to overcome these limitations. The introduction of Software-Defined Networking (SDN) opens a path towards the rea...
Conference Paper
Full-text available
Virtual Network Embedding (VNE) algorithms are used to find the best embedding of multiple Virtual Networks (VNs) with respect to a performance metric such as network utilization. However, most algorithms assume that the demands of the VNs are static over time. We focus on VNE algorithms for VNs whose demands are changing according to traffic patte...
Conference Paper
Mobile network operators experience a rapid increase of traffic in their networks that is mainly driven by the growing popularity of mobile video applications. They partly compensate this traffic increase by improved transmission technology and network densification. Supporting videos at high quality during peak traffic, however, does not scale eco...
Conference Paper
The recent initiative of Network Functions Virtualization (NFV) aims to deliver any data- plane processing or control-plane function in high volume data centers or network elements to decrease operational cost and increase deployment flexibility. In order to dynamically direct traffic flows between respective network elements, Software Defined Netw...
Conference Paper
Mobile devices, in particular smartphones, are battery powered. As their small size limits their energy capacity, an intelligent and energy-saving use of resources is crucial for the mobile user experience. Especially energy saving while sending and receiving data becomes important due to the always-on nature of smartphones. One solution for a soph...
Article
Interference is one of the most challenging problems in current cellular mobile access networks. Coordinated nultipoint transmission/ reception, and in particular joint processing, has proven to be a beneficial solution for interference management. Most research so far has investigated the requirements and gains on the wireless side but only superf...
Conference Paper
Full-text available
This paper presents a Quality of Experience (QoE) driven approach for multi-user resource optimization in Dynamic Adaptive Streaming over HTTP (DASH) over next generation wireless networks. Our objective is to enhance the user experience in adaptive HTTP streaming by jointly considering the characteristics of the media content and the available wir...
Article
Various technologies for optimizing video delivery in cellular networks have been presented in the past. QoE-based transport optimizations attempt to look for optimal solutions to provide the best overall user experience for a group of users to leverage constrained network bandwidth. However, the design of these optimizations varies widely. An attr...
Conference Paper
Providing smooth Handover (HO) for video applications over wireless networks is often difficult due to the different amount of available resources from cell to cell. In this paper, we propose a QoE-based scheme that statically or dynamically reserves resources in order to maintain unperceivable quality fluctuation during HO for video delivery in LT...
Article
Coordinated Multi-Point (CoMP) transmission and reception is a promising solution for managing interference and increasing performance in future wireless cellular systems. Due to its strict requirements in terms of capacity, latency, and synchronization among cooperating Base Stations (BSs), its successful deployment depends on the capability of th...
Conference Paper
Full-text available
Centralized approaches to solve resource allocation problems for wireless real-time multimedia communications have been intensively studied but require the availability of meta information about the multimedia content and channel information of all users. In this paper, we propose a Quality of Experience (QoE) driven bidding game for de-centralized...
Conference Paper
Managing interference by Coordinated Multi-Point (CoMP) transmission/reception is an effective mechanism to achieve high data rates in future cellular networks, like Long Term Evolution (LTE)-Advanced. For CoMP, sets of Base Stations (BSs) have to be selected to jointly serve User Equipments (UEs). These sets are typically selected based on wireles...
Conference Paper
Mounting capital and operational expenditure and reducing revenue per bit is straining the resources of mobile communication network operators. The future mobile communication networks will have to be dynamic; to adapt and re-adapt to the prevailing network conditions to increase operational efficiency. This paper presents the various use cases for...
Article
A protection scheme for passive optical networks (PONs) is proposed. It supports partial protection, relevant when reusing existing PON infrastructure for LTE-Advanced mobile network backhaul. We provide a protection level and cost analysis.
Article
Full-text available
The delivery of emerging, high performance mobile services is traditionally limited to the cellular operator home domain. Due to the centralized nature of service platforms, resource-demanding services suffer from long delays when a user is accessing them when roaming. With the globalization of our society, such data intensive services are enabled...
Article
Full-text available
Network virtualization is a relatively new research topic. A number of articles propose that certain benefits can be realized by virtualizing links between network elements as well as adding virtualization on intermediate network elements. In this article we argue that network virtualization may bring nothing new in terms of technical capabilities...
Article
Base station cooperation and infrastructure sharing are highly desirable features in future mobile access networks. We discuss the requirements they pose with regard to the optical network technologies which are likely to be deployed to support these upcoming mobile operator demands.
Article
It is currently difficult to provide advanced services with high quality when mobile users are roaming in a foreign network, since operators deliver services from platforms in their home networks. This paper presents a solution to support efficient access to services from a location close to the user. This is a key issue in the development of more...
Article
Full-text available
We address a multi-criteria Quality of Experience (QoE) driven optimization problem for multi-user wireless video delivery. The optimization is done in a cross-layer fashion by using parameterized models of application and link layer in order to determine the application data rate and the network resources that fulfill the criteria. Mean Opinion Sc...
Article
Full-text available
Mobile network operators, with decreasing revenue but high network performance requirements, are standing at a crossroads. Investing in 3GPP defined highly functional mobile networks and the consequent maintenance to sustain the market-driven network service quality standard results in high total cost of ownership unseen in fixed operators. Revenue...
Conference Paper
Full-text available
We consider the joint upstreaming of live and on-demand user-generated video content over LTE using a Quality-of-Experience driven approach. We contribute to the state-of-the-art work on multimedia scheduling in three aspects: 1) we jointly optimize the transmission of live and time-shifted video under scarce uplink resources by transmitting a basi...
Conference Paper
The delivery of mobile services is traditionally limited to the cellular operator's home domain, except for a small set of standardized services. Due to the centralized nature of service platforms, resource demanding services suffer from long delays if a user is accessing them when roaming. In this paper we describe an architecture that supports a...
Conference Paper
Full-text available
The increasing popularity of user-generated content and the high quality upstreaming capabilities of mobile phones indicate a prevalence of video traffic in the uplink of next generation mobile networks. Need arises for optimizing the network resource allocation while preserving the user satisfaction. In this paper, we propose a service-centric app...
Conference Paper
Coordinated Multi-Point (CoMP) transmission/reception, and especially Joint Processing (JP), is a promising solution for managing interference in cellular mobile access networks. Its successful deployment, however, strongly depends on the capability of the backhaul infrastructure as strict capacity and latency requirements have to be fulfilled.
Conference Paper
Coordinated Multi-Point (CoMP) transmission/ reception is a promising solution for interference management in wireless cellular systems. Its successful deployment, however, strongly depends on the capability of the mobile backhaul network architecture to support the capacity, latency, and synchronization requirements of cooperation. In this paper,...
Conference Paper
Full-text available
A handful of proposals address the problem of bootstrapping a large DHT network from scratch, but they all forgo the standard DHT join protocols in favor of their own distributed algorithms that build routing tables directly. Motivating their algorithms, the proposals make a perfunctory claim that the standard join protocols are not designed to han...
Conference Paper
This paper proposes a novel approach for Quality of Experience (QoE) driven cross-layer optimization for wireless video transmission. We formulate the cross-layer optimization problem with a constraint on the temporal fluctuation of the video quality. Our objective is to minimize the temporal change of the video quality as perceivable quality fluct...
Article
Full-text available
We present NetServ, a node architecture for de-ploying in-network services in the next generation Internet. NetServ-enabled network nodes provide a common execution environment, where network services implemented as modules can be dynamically installed and removed. We demonstrate three such modules. MicroCDN is a dynamic content distribution networ...
Article
Full-text available
The evolution of the network architecture has been stagnant in recent time. Although cellular network architecture evolves at a faster pace to cope with rising traffic demand, it requires high CAPEX/OPEX in order to deploy new systems. Due to decreasing revenue per bit in any network servicing scenario, deploying a new network architecture is very...
Conference Paper
Base Stations (BSs) cooperation techniques, also referred to as Coordinated Multi-Point (CoMP) in the 3GPP terminology, promise significant performance gains in future 4G and beyond systems. The counterpart to such gains is represented by the challenging requirements that CoMP puts on the backhaul network, which may prevent the inclusion of certain...
Article
The optimization of overlay traffic resulting from applications such as BitTorrent is a challenge addressed by several recent research initiatives. However, the assessment of such optimization techniques and their performance in the real Internet remains difficult. Despite a considerable set of works measuring real-life BitTorrent swarms, several c...
Article
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Eyeball ISPs today are under-utilizing an important asset: edge routers. We present NetServ, a programmable node ar-chitecture aimed at turning edge routers into distributed ser-vice hosting platforms. This allows ISPs to allocate router resources to content publishers and application service pro-viders motivated to deploy content and services at t...
Article
Locality-awareness is considered as a promising approach to increase the efficiency of content distribution by peer-to-peer (P2P) networks, e.g., BitTorrent. It is intended to reduce the inter-domain traffic which is costly for Internet service providers (ISPs) and to simultaneously increase the performance from the viewpoint of the P2P users, i.e....
Article
Full-text available
In today's Internet, requirements of services regarding the underlying transport network are very diverse. In the future, this diversity will increase and make it harder to accommodate all services in a single network. A possible approach to keep up with this diversity in future networks is the deployment of isolated , custom tailored networks on t...
Conference Paper
In this paper, we apply a Quality of Experience (QoE) based Cross-Layer Optimization (CLO) framework for efficiently allocating the network resources for video delivery in LTE mobile networks. Conventionally, the objective function aims to maximize the average user-perceived quality of all users by jointly optimizing the application layer and the l...