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Conference Papers


Open list in Research Information System

MARVELO: Wireless Virtual Network Embedding for Overlay Graphs with Loops

H. Afifi, S. Auroux, H. Karl, Proc. of IEEE Wireless Communications and Networking Conference (WCNC), 2018


Scaling and Placing Bidirectional Services with Stateful Virtual and Physical Network Functions

S. Dräxler, S.B. Schneider, H. Karl, in: 4th IEEE International Conference on Network Softwarization (NetSoft 2018), 2018

Network function virtualization requires scaling and placement, deciding the number and the location of function instances. Current approaches are limited in flexibility and practical applicability. Specifically, we study dynamic, single-step, joint scaling and placement of network services with bidirectional flows traversing Physical or Virtual Network Functions (VNFs) and returning to their sources. We develop models to support stateful components and legacy network functions with fixed locations in these network services as well as the possibility of reusing VNFs across network services. We formalize the problem of jointly scaling and placing such network services as a mixed- integer linear program (MILP). We show that this problem is NP-complete and also present a heuristic algorithm to find good solutions in short time. In an extensive evaluation with realistic scenarios, we investigate the capabilities of the two approaches.


Let the state follow its flows: An SDN-based flow handover protocol to support state migration

M. Peuster, H. Küttner, H. Karl, in: 4th IEEE International Conference on Network Softwarization (NetSoft 2018), 2018

Dynamically steering flows through virtualized net- work function instances is a key enabler for elastic, on-demand deployments of virtualized network functions. This becomes par- ticular challenging when stateful functions are involved, necessi- tating state management. The problem with existing solutions is that they typically embrace state migration and flow rerouting jointly, imposing a huge set of requirements on the on-boarded VNFs, e.g., solution-specific state management interfaces. In this paper, we introduce the seamless handover proto- col (SHarP). It provides an easy-to-use, loss-less, and order- preserving flow rerouting mechanism that is not fixed to a single state management approach. This allows VNF vendors to implement or use the state management solution of their choice. SHarP supports these solutions with additional information when flows are migrated. Further, we show how SHarP significantly reduces the buffer usage at a central (SDN) controller, which is a typical bottleneck in existing solutions. Our experiments show that SHarP uses a constant amount of controller buffer, irrespective of the time taken to migrate the VNF state.


Containernet 2.0: A Rapid Prototyping Platform for Hybrid Service Function Chains

M. Peuster, J.. Kampmeyer, H. Karl, in: 4th IEEE International Conference on Network Softwarization (NetSoft 2018), 2018

Developing a virtualized network service does not only involve the implementation and configuration of the network functions it is composed of but also its integration and test with management solutions that will control the service in its production environment. These integration tasks require testbeds that offer the needed network function virtualization infrastructure~(NFVI), like OpenStack, introducing a lot of management and maintenance overheads. Such testbed setups become even more complicated when the multi point-of-presence~(PoP) case, with multiple infrastructure installations, is considered. In this demo, we showcase an emulation platform that executes containerized network services in user-defined multi-PoP topologies. The platform does not only allow network service developers to locally test their services but also to connect real-world management and orchestration solutions to the emulated PoPs. During our interactive demonstration we focus on the integration between the emulated infrastructure and state-of-the-art orchestration solutions like SONATA or OSM.


Understand your chains and keep your deadlines: Introducing time-constrained profiling for NFV

M. Peuster, H. Karl, in: IEEE/IFIP 14th International Conference on Network and Service Management (CNSM), IEEE/IFIP, 2018


Emulation-based Smoke Testing of NFV Orchestrators in Large Multi-PoP Environments

M. Peuster, M. Marchetti, G. Garcia de Blas, H. Karl, in: European Conference on Networks and Communications (EuCNC), 2018

Management and orchestration~(MANO) systems are the key components of future large-scale NFV environments. They will manage resources of hundreds or even thousands of NFV infrastructure installations, so called points of presence~(PoP). Such scenarios need to be automatically tested during the development phase of a MANO system. This task becomes very challenging because large-scale NFV testbeds are hard to maintain, too expensive, or simply not available. In this paper, we present a multi-PoP NFV infrastructure emulation platform that enables automated, large-scale testing of MANO stacks. We show that our platform can easily emulate hundreds of PoPs on a single physical machine and reduces the setup time of a test PoP by a factor of 232x compared to a DevStack-based test PoP installation. Further, we present a case study in which we test ETSI's Open Source MANO~(OSM) against our proposed system to gain insights about OSM's behaviour in large-scale NFV deployments.


Modelling Time-Limited Capacity of a Wireless Channel as aMarkov Reward Process

B. Shiferaw Heyi, H. Karl, Proc. of IEEE Wireless Communications and Networking Conference (WCNC), 2018


Distributed Placement of Virtualized Control Applications in Mobile Backhaul Networks

S. Auroux, H. Karl, Proc. of IEEE Wireless Communications and Networking Conference (WCNC), 2018

DOI


DeepCAS: A Deep Reinforcement Learning Algorithm for Control-Aware Scheduling

B. Demirel, A. Ramaswamy, D. Quevedo, H. Karl, 2018

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Generating Resource and Performance Models for Service Function Chains: The Video Streaming Case

S. Dräxler, M. Peuster, M. Illian, H. Karl, in: 4th IEEE International Conference on Network Softwarization (NetSoft 2018), IEEE, 2018, pp. 318--322

Understanding the behavior of the components of service function chains (SFCs) in different load situations is important for efficient and automatic management and orches- tration of services. For this purpose and for practical research in network function virtualization in general, there is a great need for benchmarks and experimental data. In this paper, we describe our experiments for characterizing the relationship between resource demands of virtual network functions (VNFs) and the expected performance of the SFC, considering the individual performance of the VNFs as well as the interdependencies among VNFs within the SFC. We have designed our experiments focusing on video streaming, an important application in this context. We present examples of models for predicting the interdependence between resource demands and performance characteristics of SFCs using support vector regression and polynomial regression models. We also show practical evidence from our experiments that VNFs need to be benchmarked in their final chain setup, rather than individually, to capture important interdependencies that affect their performance. The data gathered from our experiments is publicly available.


From Radio Design to System Evaluations for Ultra-Reliable and Low-Latency Communication

S. Ali Ashraf, Y.E. Wang, S.. Eldessoki, B. Holfeld, D.. Parruca, M. Serror, J. Gross, Proceedings of 23th European Wireless Conference 2017, 17- 19.05.2017, 2017


Minimizing downtimes: Using dynamic reconfiguration and state management in SDN

A. Schwabe, E. Rojas, H. Karl, in: 2017 {IEEE} Conference on Network Softwarization, NetSoft 2017, Bologna, Italy, July 3-7, 2017, 2017, pp. 1--5

DOI


Joint Optimization of Scaling and Placement of Virtual Network Services

S. Dräxler, H. Karl, Z.A. Mann, in: Proceedings of the 17th IEEE/ACM International Symposium on Cluster, Cloud and Grid Computing (CCGrid 2017), 2017

Management of complex network services requires flexible and efficient service provisioning as well as optimized handling of continuous changes in the workload of the service.To adapt to changes in the demand, service components need to be replicated (scaling) and allocated to physical resources (placement) dynamically. In this paper, we propose a fullyautomated approach to the joint optimization problem of scaling and placement, enabling quick reaction to changes. We formalize the problem, analyze its complexity, and develop two algorithms to solve it. Extensive empirical results show the applicability andeffectiveness of the proposed approach.


Profile Your Chains, Not Functions. Automated Network Service Profiling in DevOps Environments

M. Peuster, H. Karl, in: IEEE Conference on Network Function Virtualisation and Software Defined Networks (NFV-SDN), 2017

Benchmarking and profiling virtual network functions (VNFs) generates input knowledge for resource management decisions taken by management and orchestration systems. Such VNFs are usually not executed in isolation but are often deployed as part of a service function chain (SFC) that connects single functions into complex structures. To manage such chains, isolated performance profiles of single functions have to be combined to get insights into the overall behavior of an SFC. This becomes particularly challenging in highly agile DevOps environments in which profiling processes need to be fully automated and detailed insights about a chain's internal structures are not always available. In this paper, we introduce a fully automatable, flexible, and platform-agnostic profiling system that allows to profile entire SFCs at once. This obviates manual modeling procedures to combine profiling results from single VNFs to reflect SFC performance. We use a case study with different SFC configurations to show that it is hard to model the resulting SFC performance based on single-VNF measurements and that performance interactions between real, non-trivial functions that are deployed in a chain exist.


Verification and validation framework for 5G network services and apps

M. Zhao, F. Le Gall, P. Cousin, R. Vilalta, R. Munoz, S. Castro, M. Peuster, S.B. Schneider, M. Siapera, E. Kapassa, D. Kyriazis, P. Hasselmeyer, G. Xilouris, C. Tranoris, S. Denazis, J. Martrat, in: 2017 IEEE Conference on Network Function Virtualization and Software Defined Networks (NFV-SDN), IEEE, 2017

DOI


A Coordination Architecture for Wireless Industrial Automation

I. Aktas, J. Ansari, S. Auroux, D. Parruca, M.D. Perez Guirao, B. Holfeld, Proceedings of 23th European Wireless Conference, 2017


A flexible multi-pop infrastructure emulator for carrier-grade MANO systems

M. Peuster, S. Dräxler, H. Razzaghi Kouchaksaraei, S. van Rossem, W. Tavernier, H. Karl, in: IEEE Conference on Network Softwarization, NetSoft 2017, Bologna, Italy, July 3-7, 2017, 2017, pp. 1--3

Developing a virtualized network service does not only involve the implementation and configuration of the network functions it is composed of but also its integration and test with management solutions that will control the service in its production environment. These integration tasks require testbeds that offer the needed network function virtualization infrastructure~(NFVI), like OpenStack, introducing a lot of management and maintenance overheads. Such testbed setups become even more complicated when the multi point-of-presence~(PoP) case, with multiple infrastructure installations, is considered. In this demo, we showcase an emulation platform that executes containerized network services in user-defined multi-PoP topologies. The platform does not only allow network service developers to locally test their services but also to connect real-world management and orchestration solutions to the emulated PoPs. During our interactive demonstration we focus on the integration between the emulated infrastructure and state-of-the-art orchestration solutions like SONATA or OSM.


SONATA: Service programming and orchestration for virtualized software networks

S. Dräxler, H. Karl, M. Peuster, H. Razzaghi Kouchaksaraei, M. Bredel, J. Lessmann, T. Soenen, W. Tavernier, S. Mendel-Brin, G. Xilouris, in: 2017 IEEE International Conference on Communications Workshops (ICC Workshops), IEEE, 2017

In conventional large-scale networks, creation and management of network services are costly and complex tasks that often consume a lot of resources, including time and manpower. Network softwarization and network function virtualization have been introduced to tackle these problems, aiming at decreasing costs and complexity of implementing new services, maintaining the implemented services, and managing available resources in service provisioning platforms and underlying infrastructures. To experience the full potential of these approaches, innovative development support tools and service provisioning environments are needed. To answer these needs, we introduce the architecture of the open-source SONATA system, a service programming, orchestration, and management framework. We present a development toolchain for virtualized network services, fully integrated with a service platform and orchestration system. We introduce the modular and flexible architecture of our system and discuss its main components and features, such as function- and service-specific managers that allow fine-grained service management, slicing support to facilitate multi-tenancy, recursiveness for improved scalability, and full-featured DevOps support.


SONATA: Service Programming and Orchestration for Virtualised Software Networks

S. Dräxler, H. Karl, H. Razzaghi Kouchaksaraei, M. Peuster, M. Bredel, J. Lessmann, T. Soenen, W. Tavernier, S. Mendel-Brin, G. Xilouris, in: Communications Workshops (ICC Workshops), 2017 IEEE International Conference on, 2017

DOI


Assessing Genetic Algorithms for Placing Flow Processing-aware Control Applications

S. Auroux, S. Scholz, H. Karl, in: Proc. European Wireless, 2017


E-State: Distributed state management in elastic network function deployments

M. Peuster, H. Karl, in: IEEE NetSoft Conference and Workshops, NetSoft 2016, Seoul, South Korea, June 6-10, 2016, 2016, pp. 6--10

Elastic deployments of virtualized network functions~(VNF) can automatically scale the amount of used resources in relation to their workload. This is often done by starting new VNF instances or stopping old ones. A problem of these scale operations is that most network functions are stateful and their internal state is not automatically migrated when traffic is redistributed in the deployment. As a result, mechanisms are needed to exchange or migrate internal network function state between VNF instances. This paper presents a state management framework that creates a logically distributed state store on top of elastically deployed virtual network functions. We also introduce a novel programming model that provides both a local and a global view of the state to each VNF instance. We discuss the integration of our framework into existing network function virtualization architectures and compare the performance of our prototype to a centralized and a distributed state store solution.


A non-disruptive automated approach to update SDN applications at runtime

A. Marsico, R. Doriguzzi-Corin, M. Gerola, D. Siracusa, A. Schwabe, in: NOMS 2016 - 2016 IEEE/IFIP Network Operations and Management Symposium, IEEE, 2016

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MeDICINE: Rapid Prototyping of Production-Ready Network Services in Multi-PoP Environments

M. Peuster, H. Karl, S. van Rossem, in: IEEE Conference on Network Function Virtualization and Software Defined Networks (NFV-SDN), 2016

Virtualized network services consisting of multiple individual network functions are already today deployed across multiple sites, so called multi-PoP (points of presence) environments. This allows to improve service performance by optimizing its placement in the network. But prototyping and testing of these complex distributed software systems becomes extremely challenging. The reason is that not only the network service as such has to be tested but also its integration with management and orchestration systems. Existing solutions, like simulators, basic network emulators, or local cloud testbeds, do not support all aspects of these tasks. To this end, we introduce MeDICINE, a novel NFV prototyping platform that is able to execute production-ready network functions, provided as software containers, in an emulated multi-PoP environment. These network functions can be controlled by any third-party management and orchestration system that connects to our platform through standard interfaces. Based on this, a developer can use our platform to prototype and test complex network services in a realistic environment running on his laptop.


Monitoring and debugging using an SDK for NFV-powered telecom applications

S. v. Rossem, W. Tavernier, M. Peuster, D. Colle, M. Pickavet, P. Demeester, in: Proc. IEEE Conference on Network Function Virtualization and Software Defined Network (NFV-SDN), Demo Track, 2016


Empowering network operating systems with memory management techniques

R. Doriguzzi-Corin, D. Siracusa, E. Salvador, A. Schwabe, in: NOMS 2016 - 2016 IEEE/IFIP Network Operations and Management Symposium, IEEE, 2016

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Composition of SDN applications: Options/challenges for real implementations

A. Schwabe, P. A. Aranda-Gutierrez, H. Karl, in: Proceedings of the 2016 Applied Networking Research Workshop, {ANRW} 2016, Berlin, Germany, July 16, 2016, 2016, pp. 26--31

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Understand Your Chains: Towards Performance Profile-Based Network Service Management

M. Peuster, H. Karl, in: Fifth European Workshop on Software-Defined Networks, EWSDN 2016, Den Haag, The Netherlands, October 10-11, 2016, 2016, pp. 7--12

Allocating resources to virtualized network functions and services to meet service level agreements is a challenging task for NFV management and orchestration systems. This becomes even more challenging when agile development methodologies, like DevOps, are applied. In such scenarios, management and orchestration systems are continuously facing new versions of functions and services which makes it hard to decide how much resources have to be allocated to them to provide the expected service performance. One solution for this problem is to support resource allocation decisions with performance behavior information obtained by profiling techniques applied to such network functions and services. In this position paper, we analyze and discuss the components needed to generate such performance behavior information within the NFV DevOps workflow. We also outline research questions that identify open issues and missing pieces for a fully integrated NFV profiling solution. Further, we introduce a novel profiling mechanism that is able to profile virtualized network functions and entire network service chains under different resource constraints before they are deployed on production infrastructure.


Joint real-time scheduling and interference coordination for wireless factory automation

S. Auroux, D. Parruca, H. Karl, in: 27th IEEE Annual International Symposium on Personal, Indoor, and Mobile Radio Communications, {PIMRC} 2016, Valencia, Spain, September 4-8, 2016, 2016, pp. 1--6

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Reusability of software-defined networking applications: {A} runtime, multi-controller approach

R. Doriguzzi Corin, P. A. Aranda-Gutierrez, E. Rojas, H. Karl, E. Salvadori, in: 12th International Conference on Network and Service Management, {CNSM} 2016, Montreal, QC, Canada, October 31 - Nov. 4, 2016, 2016, pp. 209--215

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Demonstrating on-demand cell switching with a two-layer mobile network testbed

M. Peuster, H. Karl, A. Enrico Redondi, A. Capone, in: IEEE Conference on Computer Communications Workshops, INFOCOM Workshops 2016, San Francisco, CA, USA, April 10-14, 2016, 2016, pp. 1015--1016

Traditional cellular networks are forced to remain active regardless of the actual amount of traffic that is currently produced/requested, with a clear waste of energy. Two-layer mobile networks with separated signalling and data layers have been recently proposed for energy savings in future implementations. These networks are able to switch off unneeded data cells completely while maintaining full coverage with their signalling cells, thus saving energy. In this demonstration, we showcase a testbed that uses Wi-Fi access points to emulate small cells of the data layer and a publicly available cellular connection as the signalling layer. We use off-the-shelf Android smartphones with an ad-hoc networking management module and a MultiPath TCP-enabled kernel to manage the Wi-Fi and cellular interfaces simultaneously. The testbed is used to demonstrate the general feasibility of this layered architecture and to facilitate experiments with network-wide resource optimization.


NetIDE: All-in-one framework for next generation, composed SDN applications

P.A.A. Gutierrez, E. Rojas, A. Schwabe, C. Stritzke, R. Doriguzzi-Corin, A. Leckey, G. Petralia, A. Marsico, K. Phemius, S. Tamurejo, in: 2016 IEEE NetSoft Conference and Workshops (NetSoft), IEEE, 2016

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Placement of Services with Flexible Structures Specified by a YANG Data Model

S. Dräxler, H. Karl, in: Proceedings of the 2nd International IEEE Conference on Network Softwarization (NetSoft), 2016, pp. 184--192

Network function virtualization and software-defined networking allow services consisting of virtual network functions to be designed and implemented with great flexibility by facilitating automatic deployments, migrations, and reconfigurations for services and their components. For extended flexibility, we go beyond seeing services as a fixed chain of functions. We present a YANG model for describing the service structure in deployment requests in a flexible way that enables changing the order of functions in case the order of traversing them does not affect the functionality of the service. Upon receiving such requests, the network orchestration system can choose the optimal composition of service components that gives the best results for placement of services in the network. This introduces new complexities to the placement problem by greatly increasing the number of possible ways a service can be composed. In this paper, we describe a heuristic solution that selects a Pareto set of the possible compositions of a service as well as possible combinations of different services, with respect to different resource requirements of the services. Our evaluations show that the selected combinations consist of representative samples of possible structures and requirements and therefore, can result in optimal or close-to-optimal placement results.


HybridTE: Traffic Engineering for Very Low-Cost Software-Defined Data-Center Networks

P. Wette, H. Karl, in: Proceedings of the 4th European Workshop on Software Defined Networks (EWSDN 2015), 2015, pp. 1--7

The size of modern data centers is constantly increasing. As it is not economic to interconnect all machines in the data center using a full-bisection-bandwidth network, techniques have to be developed to increase the efficiency of data-center networks. The Software-Defined Network paradigm opened the door for centralized traffic engineering (TE) in such environments. Up to now, there were already a number of TE proposals for SDN-controlled data centers that all work very well. However, these techniques either use a high amount of flow table entries or a high flow installation rate that overwhelms available switching hardware, or they require custom or very expensive end-of-line equipment to be usable in practice. We present HybridTE, a TE technique that uses (uncertain) information about large flows. Using this extra information, our technique has very low hardware requirements while maintaining better performance than existing TE techniques. This enables us to build very low-cost, high performance data-center networks.


Anticipatory Download Scheduling in Wireless Video Streaming with Uncertain Data Rate Prediction

M. Dräxler, J. Blobel, H. Karl, in: 8th IFIP Wireless and Mobile Networking Conference, WMNC 2015, Munich, Germany, October 5-7, 2015, 2015, pp. 136--143

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Dynamic network reconfiguration in wireless DenseNets with the CROWD SDN architecture

S. Auroux, M. Draxler, A. Morelli, V. Mancuso, in: 2015 European Conference on Networks and Communications (EuCNC), IEEE, 2015

DOI


SmarterPhones: Anticipatory Download Scheduling for Wireless Video Streaming

M. Dräxler, J. Blobel, P. Dreimann, S. Valentin, H. Karl, in: Proceedings of the 2nd International Conference on Networked Systems (NetSys), 2015, pp. 1--8

Video streaming is in high demand by mobile users. In cellular networks, however, the unreliable wireless channel leads to two major problems. Poor channel states degrade video quality and interrupt the playback when a user cannot sufficiently fill its local playout buffer: buffer underruns occur. In contrast, good channel conditions cause common greedy buffering schemes to buffer too much data. Such over-buffering wastes expensive wireless channel capacity. Assuming that we can anticipate future data rates, we plan the quality and download time of video segments ahead. This anticipatory download scheduling avoids buffer underruns by downloading a large number of segments before a drop in available data rate occurs, without wasting wireless capacity by excessive buffering.We developed a practical anticipatory scheduling algorithm for segmented video streaming protocols (e.g., HLS or MPEG DASH). Simulation results and testbed measurements show that our solution essentially eliminates playback interruptions without significantly decreasing video quality.


On Network Application representation and controller independence in {SDN

P. A. Aranda-Gutierrez, H. Karl, E. Rojas, A. Leckey, in: 2015 European Conference on Networks and Communications, EuCNC 2015, Paris, France, June 29 - July 2, 2015, 2015, pp. 429--433

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Extending Hadoop's Yarn Scheduler Load Simulator with a highly realistic network & traffic model

P. Wette, A. Schwabe, M. Splietker, H. Karl, in: Proceedings of the 1st {IEEE} Conference on Network Softwarization, NetSoft 2015, London, United Kingdom, April 13-17, 2015, 2015, pp. 1--2

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An Architecture for Energy-aware On-demand Mobile Network Management

M. Peuster, H. Karl, in: Proceedings of the 5th Workshop on All Things Cellular: Operations, Applications and Challenges, 2015


SynRace: Decentralized Load-Adaptive Multi-path Routing without Collecting Statistics

A. Schwabe, H. Karl, in: Proceedings of the 4th European Workshop on Software Defined Networks (EWSDN 2015), 2015, pp. 37-42

Multi-rooted trees are becoming the norm for modern data-center networks. In these networks, scalable flow routing is challenging owing to vast number of flows. Current approaches either employ a central controller that can have scalability issues or a scalable decentralized algorithm only considering local information. In this paper we present a new decentralized approach to least-congested path routing in software-defined data center networks that has neither of these issues: By duplicating the initial (or SYN) packet of a flow and estimating the data rate of multiple flows in parallel, we exploit TCP’s habit to fill buffers to find the least congested path. We show that our algorithm significantly improves flow completion time without the need for a central controller or specialized hardware.


Error characterization of multi-access point WSNs in an aircraft cabin

J. Blanckenstein, C. Nardin, J. Klaue, H. Karl, in: {IEEE} International Conference on Communication, {ICC} 2015, London, United Kingdom, June 8-12, 2015, Workshop Proceedings, 2015, pp. 2363--2368

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Flexible reassignment of flow processing-aware controllers in future wireless networks

S. Auroux, H. Karl, in: 26th IEEE Annual International Symposium on Personal, Indoor, and Mobile Radio Communications, PIMRC 2015, Hong Kong, China, August 30 - September 2, 2015, 2015, pp. 1850--1855

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Topology model to generate realistic latency for simulations

A. Schwabe, H. Karl, in: 2015 IEEE International Conference on Communications, ICC 2015, London, United Kingdom, June 8-12, 2015, 2015, pp. 6122--6127

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Efficient flow processing-aware controller placement in future wireless networks

S. Auroux, H. Karl, in: 2015 IEEE Wireless Communications and Networking Conference, WCNC 2015, New Orleans, LA, USA, March 9-12, 2015, 2015, pp. 1787--1792

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Energy-efficient clock synchronization using wake-up receivers

J. Blanckenstein, H. Karl, in: 22nd International Conference on Software, Telecommunications and Computer Networks, SoftCOM 2014, Split, Croatia, September 17-19, 2014, 2014, pp. 408--413

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Analytic quantification of outage probability and radiated power of cooperative base stations

M. Herlich, H. Karl, in: 12th International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks (WiOpt) 2014, IEEE, 2014

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Incorporating feedback from application layer into routing and wavelength assignment algorithms

P. Wette, H. Karl, in: 2013 IEEE Conference on Computer Communications Workshops (INFOCOM WKSHPS), IEEE, 2014

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Using Application Layer Knowledge in Routing and Wavelength Assignment Algorithms

P. Wette, H. Karl, in: Proceedings of the IEEE International Conference on Communications 2014, 2014, pp. 3270-3276

Preemptive Routing and Wavelength Assignment (RWA) algorithms preempt established lightpaths in case notenough resources are available to set up a new lightpath in aWavelength Division Multiplexing (WDM) network. The selectionof lightpaths to be preempted relies on internal decisions of theRWA algorithm. Thus, if dedicated properties of the networktopology are required by the applications running on the network,these requirements have to be known to the RWA algorithm.We present a family of preemptive RWA algorithms for WDMnetworks. These algorithms have two distinguishing features: a)they can handle dynamic traffic by on-the-fly reconfiguration,and b) users can give feedback for reconfiguration decisions andthus influence the preemption decision of the RWA algorithm,leading to networks which adapt directly to application needs.This is different from traffic engineering where the network is(slowly) adapted to observed traffic patterns.Our algorithms handle various WDM network configurationsincluding networks consisting of heterogeneous WDM hardware.To this end, we are using the layered graph approach togetherwith a newly developed graph model that is used to determineconflicting lightpaths.


Specifying and Placing Chains of Virtual Network Functions

S. Dräxler, M. Keller, H. Karl, in: Proceedings of the 3rd International Conference on Cloud Networking (CloudNet), 2014, pp. 7-13

Network appliances perform different functions on network flows and constitute an important part of an operator’s network. Normally, a set of chained network functions process network flows. Following the trend of virtualization of networks, virtualization of the network functions has also become a topic of interest. We define a model for formalizing the chaining of network functions using a context-free language. We process deployment requests and construct virtual network function graphs that can be mapped to the network. We describe the mapping as a Mixed Integer Quadratically Constrained Program (MIQCP) for finding the placement of the network functions and chaining them together considering the limited network resources and requirements of the functions. We have performed a Pareto set analysis to investigate the possible trade-offs between different optimization objectives.


Response Time-Optimized Distributed Cloud Resource Allocation

M. Keller, H. Karl, in: Proceedings of the SIGCOMM workshop on Distributed cloud computing, 2014, pp. 47--52

In the near future many more compute resources will be available at different geographical locations. To minimize the response time of requests, application servers closer to the user can hence be used to shorten network round trip times. However, this advantage is neutralized if the used data centre is highly loaded as the processing time of re- quests is important as well. We model the request response time as the network round trip time plus the processing time at a data centre.We present a capacitated facility location problem formal- ization where the processing time is modelled as the sojourn time of a queueing model. We discuss the Pareto trade-off between the number of used data centres and the resulting response time. For example, using fewer data centres could cut expenses but results in high utilization, high response time, and smaller revenues.Previous work presented a non-linear cost function. We prove its convexity and exploit this property in two ways: First, we transform the convex model into a linear model while controlling the maximum approximation error. Sec- ond, we used a convex solver instead of a slower non-linear solver. Numerical results on network topologies exemplify our work.


Template Embedding: Using Application Architecture to Allocate Resources in Distributed Clouds

M. Keller, C. Robbert, H. Karl, in: Proceedings of 7th International Conference on Utility and Cloud Computing (UCC), 2014, pp. 387--395

In distributed cloud computing, application deployment across multiple sites can improve quality of service. Recent research developed algorithms to find optimal locations for virtual machines. However, those algorithms assume to have either single-tier applications or a fixed number of virtual machines – a strong simplification of reality. This paper investigates the placement and scaling of complex application architectures. An application is dynamically scaled to fit both the current demand situation and the currently available infrastructure resources. We compare two approaches: The first one is based on virtual network embedding. The second approach is a novel method called Template Embedding. It is based on a hierarchical 1-allocation hub flow problem and combines applica- tion scaling and embedding in one step. Extensive experiments on 43200 network configurations showed that Template Embedding outperforms virtual network embedding in all cases in three metrics: success rate, solution quality, and runtime. This positive result shows that template embedding is a promising approach for distributed cloud resource allocation.


Flow processing-aware controller placement in wireless DenseNets

S. Auroux, H. Karl, in: 25th IEEE Annual International Symposium on Personal, Indoor, and Mobile Radio Communication, {PIMRC} 2014, Washington DC, USA, September 2-5, 2014, 2014, pp. 1294--1299

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Predicting mobile video inter-download times with Hidden Markov Models

F. Beister, H. Karl, in: IEEE 10th International Conference on Wireless and Mobile Computing, Networking and Communications, WiMob 2014, Larnaca, Cyprus, October 8-10, 2014, 2014, pp. 359--364

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MaxiNet: Distributed Emulation of Software-Defined Networks

P. Wette, M. Dräxler, A. Schwabe, F. Wallaschek, M.H. Zahraee, H. Karl, in: Proceedings of the 2014 IFIP Networking Conference (Networking 2014), 2014, pp. 1-9

Network emulations are widely used for testing novel network protocols and routing algorithms in realistic scenarios. Up to now, there is no emulation tool that is able to emulate large software-defined data center networks that consist of several thousand nodes. Mininet is the most common tool to emulate Software-Defined Networks of several hundred nodes. We extend Mininet to span an emulated network over several physical machines, making it possible to emulate networks of several thousand nodes on just a handful of physical machines. This enables us to emulate, e.g., large data center networks. To test this approach, we additionally introduce a traffic generator for data center traffic. Since there are no data center traffic traces publicly available we use the results of two recent traffic studies to create synthetic traffic. We show the design and discuss some challenges we had in building our traffic generator. As a showcase for our work we emulated a data center consisting of 3200 hosts on a cluster of only 12 physical machines. We show the resulting workloads and the trade-offs involved.


Anticipatory power cycling of mobile network equipment for high demand multimedia traffic

M. Dräxler, P. Dreimann, H. Karl, in: IEEE Online Conference on Green Communications, OnlineGreenComm 2014, November 12-14, 2014, 2014, pp. 1--7

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Provider Competition in Infrastructure-as-a-Service

J. Künsemöller, S. Brangewitz, H. Karl, C. Haake, in: Proceedings of the 2014 IEEE International Conference on Services Computing (SCC), 2014, pp. 203-210

This paper explores how cloud provider competition influences instance pricing in an IaaS (Infrastructure-as-a-Service) market. When reserved instance pricing includes an on-demand price component in addition to a reservation fee (two-part tariffs), different providers might offer different price combinations, where the client’s choice depends on its load profile. We investigate a duopoly of providers and analyze stable market prices in two-part tariffs. Further, we study offers that allow a specified amount of included usage (three-part tariffs). Neither two-part nor three-part tariffs produce an equilibrium market outcome other than a service pricing that equals production cost, i.e., complex price structures do not significantly affect the results from ordinary Bertrand competition.


Using MAC addresses as efficient routing labels in data centers

A. Schwabe, H. Karl, in: Proceedings of the third workshop on Hot topics in software defined networking, HotSDN '14, Chicago, Illinois, USA, August 22, 2014, 2014, pp. 115--120

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Reactive Planar Spanner Construction in Wireless Ad Hoc and Sensor Networks

M. Benter, F. Neumann, H. Frey, in: Proceedings of the 32nd IEEE International Conference on Computer Communications (INFOCOM), 2013, pp. 2193-2201

Within reactive topology control, a node determines its adjacent edges of a network subgraph without prior knowledge of its neighborhood. The goal is to construct a local view on a topology which provides certain desired properties such as planarity. During algorithm execution, a node, in general, is not allowed to determine all its neighbors of the network graph. There are well-known reactive algorithms for computing planar subgraphs. However, the subgraphs obtained do not have constant Euclidean spanning ratio. This means that routing along these subgraphs may result in potentially long detours. So far, it has been unknown if planar spanners can be constructed reactively. In this work, we show that at least under the unit disk network model, this is indeed possible, by proposing an algorithm for reactive construction of the partial Delaunay triangulation, which recently turned out to be a spanner. Furthermore, we show that our algorithm is message-optimal as a node will only exchange messages with nodes that are also neighbors in the spanner. The algorithm’s presentation is complemented by a rigorous proof of correctness.


On Greedy Routing in Degree-bounded Graphs over d-Dimensional Internet Coordinate Embeddings

M. Autenrieth, H. Frey, in: Proceedings of the Conference on Networked Systems (NetSys), 2013, pp. 126-131

In this paper we will introduce a new d-dimensional graph for constructing geometric application layer overlay net-works. Our approach will use internet coordinates, embedded using the L∞ -metric. After describing the graph structure, we will show how it limits maintenance overhead by bounding each node’s out-degree and how it supports greedy routing using one-hop neighbourhood information in each routing step. We will further show that greedy routing can always compute a path in our graph and we will also prove that in each forwarding step the next hop is closer to the destination than the current node.


A topology-aware adaptive deployment framework for elastic applications

M. Keller, M. Peuster, C. Robbert, H. Karl, in: 17th International Conference on Intelligence in Next Generation Networks, {ICIN} 2013, Venice, Italy, October 15-16, 2013, 2013, pp. 61--69

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An evaluation testbed for adaptive, topology-aware deployment of elastic applications

M. Keller, C. Robbert, M. Peuster, in: Proceedings of the ACM SIGCOMM 2013 conference on SIGCOMM , 2013


A Local Heuristic for Latency-Optimized Distributed Cloud Deployment

M. Keller, S. Pawlik, P. Pietrzyk, H. Karl, in: Proceedings of the 6th International Conference on Utility and Cloud Computing (UCC) workshop on Distributed cloud computing, 2013, pp. 429-434

In Distributed Cloud Computing, applications are deployed across many data centres at topologically diverse locations to improved network-related quality of service (QoS). As we focus on interactive applications, we minimize the latency between users and an application by allocating Cloud resources nearby the customers. Allocating resources at all locations will result in the best latency but also in the highest expenses. So we need to find an optimal subset of locations which reduces the latency but also the expenses – the facility location problem (FLP). In addition, we consider resource capacity restrictions, as a resource can only serve a limited amount of users. An FLP can be globally solved. Additionally, we propose a local, distributed heuristic. This heuristic is running within the network and does not depend on a global component. No distributed, local approximations for the capacitated FLP have been proposed so far due to the complexity of the problem. We compared the heuristic with an optimal solution obtained from a mixed integer program for different network topologies. We investigated the influence of different parameters like overall resource utilization or different latency weights.


Energy-Efficient Assignment of User Equipment to Cooperative Base Stations

M. Herlich, H. Karl, in: ISWCS 2013, The Tenth International Symposium on Wireless Communication Systems, Ilmenau, Germany, August 27-30, 2013, 2013, pp. 1--5


CROWD: An SDN Approach for DenseNets

H. Ali-Ahmad, C. Cicconetti, A. de la Oliva, M. Draxler, R. Gupta, V. Mancuso, L. Roullet, V. Sciancalepore, in: 2013 Second European Workshop on Software Defined Networks, IEEE, 2013

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Adding Capacity-Aware Storage Indirection to Homogeneous Distributed Hash Tables

P. Wette, K. Graffi, in: 2013 Conference on Networked Systems, IEEE, 2013

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OpenNetInf - prototyping an information-centric Network Architecture

C. Dannewitz, M. Herlich, H. Karl, in: 37th Annual IEEE Conference on Local Computer Networks -- Workshops, IEEE, 2013

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Incorporating feedback from application layer into routing and wavelength assignment algorithms

P. Wette, H. Karl, in: Proceedings of the 32nd IEEE International Conference on Computer Communications (INFOCOM), 2013, pp. 51-52

Preemptive Routing and Wavelength Assignment (RWA) algorithms preempt established lightpaths in case not enough resources are available to set up a new lightpath in a Wavelength Division Multiplexing (WDM) network. The selection of lightpaths to be preempted relies on internal decisions of the RWA algorithm. Thus, if dedicated properties of the network topology are required by the applications running on the network, these requirements have to be known to the RWA algorithm.Otherwise it might happen that by preempting a particular lightpath these requirements are violated. If, however, these requirements include parametersknown only at the nodes running the application, the RWA algorithm cannot evaluate the requirements. For this reason an RWA algorithm is needed which incorporates feedback from the application layer in the preemption decisions.This work proposes a simple interface along with an algorithm for computing and selecting preemption candidates in case a lightpath cannot be established. We reason about the necessity of using information from the application layer in the RWA and present two example applications which benefit from this idea.


Trade-off between latency and coverage in cooperative radio access networks

T. Hohenberger, M. Herlich, H. Karl, in: IEEE International Conference on Advanced Networks and Telecommunications Systems, ANTS 2013, Kattankulathur, India, December 15-18, 2013, 2013, pp. 1--6

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Cross-layer scheduling for multi-quality video streaming in cellular wireless networks

M. Dräxler, H. Karl, in: 2013 9th International Wireless Communications and Mobile Computing Conference, IWCMC 2013, Sardinia, Italy, July 1-5, 2013, 2013, pp. 1181--1186

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NetIDE: First Steps towards an Integrated Development Environment for Portable Network Apps

F. M. Facca, E. Salvadori, H. Karl, D. R. Lopez, P. Arranda Gutierrez, D. Kostic, R. Riggio, in: Second European Workshop on Software Defined Networks, EWSDN 2013, Berlin, Germany, October 10-11, 2013, 2013, pp. 105--110

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Which Flows Are Hiding Behind My Wildcard Rule? Adding Packet Sampling to OpenFlow

P. Wette, H. Karl, in: Proceedings of the ACM SIGCOMM '13, 2013, pp. 541-542

In OpenFlow [1], multiple switches share the same control plane which is centralized atwhat is called the OpenFlow controller. A switch only consists of a forwarding plane. Rules for forwarding individual packets (called ow entries in OpenFlow) are pushed from the controller to the switches. In a network with a high arrival rate of new ows, such as in a data center, the control trac between the switch and controller can become very high. As a consequence, routing of new ows will be slow. One way to reduce control trac is to use wildcarded ow entries. Wildcard ow entries can be used to create default routes in the network. However, since switches do not keep track of ows covered by a wildcard ow entry, the controller no longer has knowledge about individual ows. To nd out about these individual ows we propose an extension to the current OpenFlow standard to enable packet sampling of wildcard ow entries.


On the Quality of Selfish Virtual Topology Reconfiguration in IP-over-WDM Networks

P. Wette, H. Karl, in: Proceedings of the 19th IEEE International Workshop on Local and Metropolitan Area Networks (IEEE LANMAN), 2013, pp. 1 - 6

The process of planning a virtual topology for a Wavelength Devision Multiplexing (WDM) network is called Virtual Topology Design (VTD). The goal of VTD is to find a virtual topology that supports forwarding the expected traffic without congestion. In networks with fluctuating, high traffic demands, it can happen that no single topology fits all changing traffic demands occurring over a longer time. Thus, during operation, the virtual topology has to be reconfigured. Since modern networks tend to be large, VTD algorithms have to scale well with increasing network size, requiring distributed algorithms. Existing distributed VTD algorithms, however, react too slowly on congestion for the real-time reconfiguration of large networks. We propose Selfish Virtual Topology Reconfiguration (SVTR) as a new algorithm for distributed VTD. It combines reconfiguring the virtual topology and routing through a Software Defined Network (SDN). SVTR is used for online, on-the-fly network reconfiguration. Its integrated routing and WDM reconfiguration keeps connection disruption due to network reconfiguration to a minimum and is able to react very quickly to traffic pattern changes. SVTR works by iteratively adapting the virtual topology to the observed traffic patterns without global traffic information and without future traffic estimations. We evaluated SVTR by simulation and found that it significantly lowers congestion in realistic networks and high load scenarios.


The playground of Wireless Dense networks of the future

C. Cicconetti, A. Morelli, M. Dräxler, H. Karl, V. Mancuso, V. Sciancalepore, R. Gupta, A. de la Oliva, M. Isabel Sanchez, P. Serrano, L. Roullet, in: 2013 Future Network & Mobile Summit, Lisboa, Portugal, July 3-5, 2013, 2013, pp. 1--4


Efficiency of On-Path and Off-Path Caching Strategies in Information Centric Networks

M. Dräxler, H. Karl, in: 2012 IEEE International Conference on Green Computing and Communications, Conference on Internet of Things, and Conference on Cyber, Physical and Social Computing, GreenCom/iThings/CPSCom 2012, Besancon, France, November 20-23, 2012, 2012, pp. 581--587

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Coordinated multipoint multiuser-MIMO transmissions over backhaul-constrained mobile access networks

C. Choi, L. Scalia, T. Biermann, S. Mizuta, in: 2011 IEEE 22nd International Symposium on Personal, Indoor and Mobile Radio Communications, IEEE, 2012

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OpenNetInf - prototyping an information-centric Network Architecture

C. Dannewitz, M. Herlich, H. Karl, in: 37th Annual IEEE Conference on Local Computer Networks, Workshop Proceedings, Clearwater Beach, FL, USA, October 22-25, 2012, 2012, pp. 1061--1069

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Using OMNeT++ for energy optimization simulations in mobile core networks

M. Dräxler, F. Beister, S. Kruska, J. Aelken, H. Karl, in: International ICST Conference on Simulation Tools and Techniques, SIMUTOOLS '12, Sirmione-Desenzano, Italy, March 19-23, 2012, 2012, pp. 157--165

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Average and competitive analysis of latency and power consumption of a queuing system with a sleep mode

M. Herlich, H. Karl, in: Proceedings of the 3rd International Conference on Energy-Efficient Computing and Networking, e-Energy'12, Madrid, Spain, May 9-11, 2012, 2012, pp. 14

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Cooperating base station set selection and network reconfiguration in limited backhaul networks

M. Dräxler, T. Biermann, H. Karl, W. Kellerer, in: 23rd IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC 2012, Sydney, Australia, September 9-12, 2012, 2012, pp. 1383--1389

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Quantization techniques for accurate soft message combining

T. Volkhausen, K. Schinköthe, H. Karl, in: 2012 IEEE Wireless Communications and Networking Conference, WCNC 2012, Paris, France, April 1-4, 2012, 2012, pp. 575--580

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Energy Efficient Clustering using a Wake-up Receiver

J. Blanckenstein, J. Klaue, H. Karl, in: European Wireless 2012 - 18th European Conference 2012, April 18-20, 2012, Poznan, Poland., 2012


Efficient cooperative relaying in wireless multi-hop networks with commodity WiFi hardware

T. Volkhausen, K. Dridger, H. S. Lichte, H. Karl, in: 10th International Symposium on Modeling and Optimization in Mobile, Ad Hoc and Wireless Networks (WiOpt), Paderborn, Germany, May 14-18, 2012, 2012, pp. 299--304


Mobile WDM Backhaul Access Networks with Physical Inter-Base-Station Links for Coordinated Multipoint Transmission/Reception Systems

T. Biermann, L. Scalia, in: 2011 IEEE Global Telecommunications Conference - GLOBECOM 2011, IEEE, 2012

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On Local Separation of Processing and Storage in Infrastructure-as-a-Service

J. Künsemöller, H. Karl, in: Economics of Grids, Clouds, Systems, and Services - 9th International Conference, GECON 2012, Berlin, Germany, November 27-28, 2012. Proceedings, 2012, pp. 125--138

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Coding Opportunities from Similar Data in Wireless Cooperation Diversity Systems

T. Volkhausen, K. Schinköthe, H. Karl, in: IEEE 8th International Conference on Mobile Adhoc and Sensor Systems, MASS 2011, Valencia, Spain, October 17-22, 2011, 2011, pp. 146--148

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Improving CoMP cluster feasibility by dynamic serving base station reassignment

T. Biermann, L. Scalia, C. Choi, H. Karl, W. Kellerer, in: IEEE 22nd International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC 2011, Toronto, ON, Canada, September 11-14, 2011, 2011, pp. 1325--1330

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MDHT: A hierarchical name resolution service for information-centric networks

M. D'Ambrosio, C. Dannewitz, H. Karl, V. Vercellone, in: 2011 ACM SIGCOMM Workshop on Information-Centric Networking, ICN 2011, Toronto, ON, Canada, August 19, 2011, 2011, pp. 7--12

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Backhaul Design and Controller Placement for Cooperative Mobile Access Networks

T. Biermann, L. Scalia, J. Widmer, H. Karl, in: Proceedings of the 73rd IEEE Vehicular Technology Conference, VTC Spring 2011, 15-18 May 2011, Budapest, Hungary, 2011, pp. 1--5

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Power-efficient mobile backhaul design for CoMP support in future wireless access systems

L. Scalia, T. Biermann, C. Choi, K. Kozu, W. Kellerer, in: 2011 IEEE Conference on Computer Communications Workshops (INFOCOM WKSHPS), IEEE, 2011

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Segment-based packet combining in a cluster: To combine or not to combine?

A. Willig, D. Kipnis, H. Karl, in: 2010 Sixth International Conference on Intelligent Sensors, Sensor Networks and Information Processing, IEEE, 2011

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Multihop Performance of Cooperative Preamble Sampling MAC(CPS-MAC) in Wireless Sensor Networks

R. Azeem M. Khan, H. Karl, in: Ad-hoc, Mobile, and Wireless Networks - 10th International Conference, ADHOC-NOW 2011, Paderborn, Germany, July 18-20, 2011. Proceedings, 2011, pp. 145--149

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Backhaul network pre-clustering in cooperative cellular mobile access networks

T. Biermann, L. Scalia, C. Choi, H. Karl, W. Kellerer, in: 12th IEEE International Symposium on a World of Wireless, Mobile and Multimedia Networks, WOWMOM 2011, Lucca, Italy, 20-24 June, 2011, 2011, pp. 1--9

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Reducing power consumption of mobile access networks with cooperation

M. Herlich, H. Karl, in: 2nd International Conference on Energy-Efficient Computing and Networking 2011, e-Energy '11, New York, NY, USA - May 31 - June 01, 2011, 2011, pp. 77--86

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Designing optical metro and access networks for future cooperative cellular systems

T. Biermann, L. Scalia, H. Karl, in: Proceedings of the 14th International Symposium on Modeling Analysis and Simulation of Wireless and Mobile Systems, MSWiM 2011, Miami, Florida, USA, October 31 - November 4, 2011, 2011, pp. 265--274

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A Game-Theoretical Approach to the Benefits of Cloud Computing

J. Künsemöller, H. Karl, in: Economics of Grids, Clouds, Systems, and Services - 8th International Workshop, GECON 2011, Paphos, Cyprus, December 5, 2011, Revised Selected Papers, 2011, pp. 148--160

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The Trade-Off between Power Consumption and Latency in Computer Networks

M. Herlich, H. Karl, in: NETWORKING 2011 Workshops - International IFIP TC 6 Workshops, PE-CRN, NC-Pro, WCNS, and SUNSET 2011, Held at {NETWORKING} 2011, Valencia, Spain, May 13, 2011, Revised Selected Papers, 2011, pp. 273--280

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Energy efficiency model of network-coded cooperation in wireless sensor networks

D.H. Woldegebreal, H. Karl, in: Sensor Technologies and Applications (SENSORCOMM), 2010 Fourth International Conference on, 2010, pp. 513--520


Concept and Prototype for a Real-Time Enabled Publish/Subscribe System

M. Andree, A. Gebel, H. Karl, in: 10th IEEE International Conference on Computer and Information Technology, CIT 2010, Bradford, West Yorkshire, UK, June 29-July 1, 2010, 2010, pp. 737--742

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