Thomas Michael Bohnert

Mobile Cloud Networking: Virtualisation of cellular networks

Virtualisation of cellular networks can be seen as a way to significantly reduce the complexity of processes, required nowadays to provide reliable cellular networks. The Future Communication Architecture for Mobile Cloud Services: Mobile Cloud Networking (MCN) is a EU FP7 Large-scale Integrating Project (IP) funded by the European Commission that is focusing on how cloud computing and network function virtualisation concepts are applied to achieve virtualisation of cellular networks. It aims at the development of a fully cloud-based mobile communication and application platform, or more specifically, it aims to investigate, implement and evaluate the technological foundations for the mobile communication system of Long Term Evolution (LTE), based on Mobile Network plus Decentralized Computing plus Smart Storage offered as one atomic service: On-Demand, Elastic and Pay-As-You-Go. This paper provides a brief overview of the MCN project and discusses the challenges that need to be solved.

WiMAX for Emergency Services: An Empirical Evaluation

WiMAX, as a Broadband Wireless Access technology for Metropolitan Area Networks, supporting fixed and mobile terminals, is very promising for Next Generation Networks. Emergency Services can also strongly benefit from WiMAX features, allowing the exploitation of novel application scenarios and business models. This paper presents a set of scenarios, such as Environmental Monitoring, Telemedicine and Fire Prevention, defined and implemented in several European testbeds, interconnected by the European research network GEANT 2, in the framework of the WEIRD project. In particular, we focus our attention on the scenario implemented in the Portuguese testbed - Fire Prevention - providing a detailed description about the testbed planning, implementation and evaluation.

A comment on simulating LRD traffic with pareto ON/OFF sources

Long-Range-Dependency (LRD) and Self-Similarity (SS) effects are synthetically generated by multiplexing ON/OFF sources with Pareto distributed ON and OFF times. Dependent on a myriad of parameters, however, it can be questioned if resulting traffic actually exhibits SS and LRD effects. In this paper we evaluate the robustness of these effects in simulator generated traffic to parameter settings. Using a typical simulation for performance evaluation, we measure the degree of SS and LRD.

Quality of service differentiation support in WiMAX networks

Ubiquitous broadband Internet access is an important requirement to satisfy user demands and support a new set of real time services and applications. WiMAX, a broadband wireless access solution for wireless metropolitan area networks, covering large distances with high throughputs, is a promising technology for next generation networks. Nevertheless, for the successful deployment of WiMAX based solutions, quality of service (QoS) is a mandatory feature that must be supported. In this paper, the lack of QoS support for WiMAX in NS2- NIST software is addressed. A QoS framework, composed by a packet classification mechanism and a scheduler, has been specified and implemented on the simulator, providing service differentiation over WiMAX networks. Furthermore, in order to validate the developed solutions, a set of QoS oriented scenarios have been simulated and the obtained results show that the implemented model is able to efficiently differentiate between the different traffic classes defined in the WiMAX model.

QoS management and control for an all-IP WiMAX network architecture: Design, implementation and evaluation

The IEEE 802.16 standard provides a specification for a fixed and mobile broadband wireless access system, offering high data rate transmission of multimedia services with different Quality-of-Service (QoS) requirements through the air interface. The WiMAX Forum, going beyond the air interface, defined an end-to-end WiMAX network architecture, based on an all-IP platform in order to complete the standards required for a commercial rollout of WiMAX as broadband wireless access solution. As the WiMAX network architecture is only a functional specification, this paper focuses on an innovative solution for an end-to-end WiMAX network architecture offering in compliance with the WiMAX Forum specification. To our best knowledge, this is the first WiMAX architecture built by a research consortium globally and was performed within the framework of the European IST project WEIRD (WiMAX Extension to Isolated Research Data networks). One of the principal features of our architecture is support for end-to-end QoS achieved by the integration of resource control in the WiMAX wireless link and the resource management in the wired domains in the network core. In this paper we present the architectural design of these QoS features in the overall WiMAX all-IP framework and their functional as well as performance evaluation. The presented results can safely be considered as unique and timely for any WiMAX system integrator.

A case for CDN-as-a-service in the cloud: A Mobile Cloud Networking argument

Content Distribution Networks are mandatory components of modern web architectures, with plenty of vendors offering their services. Despite its maturity, new paradigms and architecture models are still being developed in this area. Cloud Computing, on the other hand, is a more recent concept which has expanded extremely quickly, with new services being regularly added to cloud management software suites such as OpenStack. The main contribution of this paper is the architecture and the development of an open source CDN that can be provisioned in an on-demand, pay-as-you-go model thereby enabling the CDN as a Service paradigm. We describe our experience with integration of CDNaaS framework in a cloud environment, as a service for enterprise users. We emphasize the flexibility and elasticity of such a model, with each CDN instance being delivered on-demand and associated to personalized caching policies as well as an optimized choice of Points of Presence based on exact requirements of an enterprise customer. Our development is based on the framework developed in the Mobile Cloud Networking (MCN) EU FP7 project, which offers its enterprise users a common framework to instantiate and control services. CDNaaS is one of the core support components in this project as is tasked to deliver different type of multimedia content to several thousands of users geographically distributed. It integrates seamlessly in the MCN service life-cycle and as such enjoys all benefits of a common design environment, allowing for an improved interoperability with the rest of the services within the MCN ecosystem.

Multi-Class Measurement Based Admission Control for a QoS Framework with Dynamic Resource Management

The advent of a Premium Service (PS) featuring Internet is still pending, mainly due its difficult deployment. But do we really need Quality of Service like PS? Likely no. We are therefore investigating an alternative QoS model, which is more flexible to deploy at the expense of looser QoS guarantees. We call it a Better-than-Best-Effort (BBE) service. What distinguishes our approach from traditional ones is dynamic resource management based on measurements and ruled by Perceptual QoS. What yet has been missing was Admission Control (AC) and in this paper we present our latest advance. Based on the existence of measurements taken by the queueing module, we developed a Measurement Based AC algorithm. Design goal was simplicity and general applicability in terms of independence from statistical assumptions. Likely the most interesting finding is that even a very simple design proofed to be reasonably effective for our BBE service, mainly due to a cross-layer design, i.e. cooperation between dynamic resource management on queuing level and AC. This is the conclusion a comprehensive simulative performance evaluating.

Cooperative Diversity for Virtual MIMO System in the Presence of Spatial Correlated Fading Model

In the existing papers on cooperative diversity, the fading channels are idealistically assumed to be Rayleigh fading channel. Taking into account the realistic propagation environments in the presence of spatial fading correlation, the performance of cooperative protocols using distributed space-time block code (DSTBC) in the two-ring scattering model is analyzed. The time division multiple access scheme is proposed with half duplex mode. Cooperative scheme is proposed, because cooperative diversity can combat the fading correlation by spatial decorrelation which is produced by independent multipaths and scattering paths between source nodes (SNs) and destination nodes (DNs). Cooperative relaying is shown to increase the link stability (or, alternatively, decrease the link outage probability) significantly. Therefore, the outage capacity and average bit error rate (BER) of cooperation are presented by applying various cooperative schemes in the correlated channel. Based on theoretical analyses and simulation results, the cooperative diversity yields significant performance gain in correlated channel, i.e., reducing the spatial correlation of each path and enhancing the overall performance of virtual MIMO system by high quality of cooperative interuser channel.

On evaluating a WiMAX access network for isolated research and data networks using NS-2

IEEE 802.16 is yet a very recent technology and released hardware does frequently only support standards partially. The same applies to public available simulation tools, in particular for NS-2. As the latter is the de-facto standard in science and as we use it for our research in the context of the WEIRD project, we evaluate the of IEEE 802.16 support for NS-2. We present several general but also specific issues, which are important in order to carry out reliable research based on these tools. In particular, we show in much detail where modules deviate significantly and even fail totally.

Performance Evaluation and Traffic Modeling

Mobile and wireless communication systems are becoming more and more complex, making understanding the interaction of different technologies on different layers a very difficult task. The introduction of sophisticated techniques on the physical layer that react to changes of the wireless channel on small timescales requires new paradigms for modeling, simulating, and analyzing current and future wireless networks. Investigating the relationship of new physical layer techniques, application-specific requirements and performance measures will become a major research topic for future wireless networks. A continuous change in the methodology for evaluating the network performance takes place in the Internet. In the past, network performance was mainly evaluated using concretely measurable values like packet loss rate, delay, or jitter. The current trend in the Internet goes toward application-specific quality measures that judge more the subjective experience of the end user than they do network parameters. In the terminology, this is expressed as the change from quality of service (QoS-Quality of Service (QoS)) to quality of experience (QoE). For wireless networks this leads to interesting consequences, as currently the traffic requirements for MAC layer connections are mainly formulated in terms of QoS parameters. Accomplishing the change from QoS to QoE also in the definition of connection parameters is a future challenge for wireless networks, for which the first approaches are presented.