Ralf Tönjes

Dynamic spectrum allocation in composite reconfigurable wireless networks

Future wireless systems are expected to be characterized by increasing convergence between networks and further development of reconfigurable radio systems. In parallel with this, demand for radio spectrum from these systems will increase, as users take advantage of high quality multimedia services. This article aims to investigate and review the possibilities for the dynamic allocation of spectrum to different radio networks operating in a composite reconfigurable wireless system. The article first looks into the current interest of regulators in this area, before describing some possible schemes to implement dynamic spectrum allocation and showing some example performance results. Following this, the technical requirements that a DSA system would have, in terms of reconfigurable system implementation, are discussed.

Survey of Context Provisioning Middleware

In the scope of ubiquitous computing, one of the key issues is the awareness of context, which includes diverse aspects of the users situation including his activities, physical surroundings, location, emotions and social relations, device and network characteristics and their interaction with each other. This contextual knowledge is typically acquired from physical, virtual or logical sensors. To overcome problems of heterogeneity and hide complexity, a significant number of middleware approaches have been proposed for systematic and coherent access to manifold context parameters. These frameworks deal particularly with context representation, context management and reasoning, i.e. deriving abstract knowledge from raw sensor data. This article surveys not only related work in these three categories but also the required evaluation principles.

Convergence of cellular and broadcast networks from a multi-radio perspective

The demand of both the new telecom industry and digital broadcasters for cost-efficient provisioning of mobile multimedia services faces the reality of scarce radio resources. Various digital mobile and broadcast radio technologies have been developed and specifically been optimized. However, existing and emerging multimedia services exhibit challenging requirements in terms of asymmetry, interactivity, real time, and multicast communication. This article describes an evolution of an IP-based infrastructure from todays networks toward a future multi-radio infrastructure, taking into account the implications on the end-user terminal. This multi-radio infrastructure enables the cooperation of existing radio networks to combine their spectrum-efficient capabilities, whereby high-quality mobile multimedia services shall be provided. Furthermore, the need for dynamic allocation of spectrum to radio services is motivated. The basic functionality and architecture of a multi-radio system are outlined, with a special emphasis on cooperation between different radio systems. Also, an evolution path for the convergence of broadcast and new telecom is described, starting from todays systems and leading to a fully coordinated system.

CityPulse: Large Scale Data Analytics Framework for Smart Cities

Our world and our lives are changing in many ways. Communication, networking, and computing technologies are among the most influential enablers that shape our lives today. Digital data and connected worlds of physical objects, people, and devices are rapidly changing the way we work, travel, socialize, and interact with our surroundings, and they have a profound impact on different domains, such as healthcare, environmental monitoring, urban systems, and control and management applications, among several other areas. Cities currently face an increasing demand for providing services that can have an impact on peoples everyday lives. The CityPulse framework supports smart city service creation by means of a distributed system for semantic discovery, data analytics, and interpretation of large-scale (near-)real-time Internet of Things data and social media data streams. To goal is to break away from silo applications and enable cross-domain data integration. The CityPulse framework integrates multimodal, mixed quality, uncertain and incomplete data to create reliable, dependable information and continuously adapts data processing techniques to meet the quality of information requirements from end users. Different than existing solutions that mainly offer unified views of the data, the CityPulse framework is also equipped with powerful data analytics modules that perform intelligent data aggregation, event detection, quality assessment, contextual filtering, and decision support. This paper presents the framework, describes its components, and demonstrates how they interact to support easy development of custom-made applications for citizens. The benefits and the effectiveness of the framework are demonstrated in a use-case scenario implementation presented in this paper.

A knowledge based approach to automatic image registration

The presented work addresses the problem of automatic control point matching for the registration of remotely sensed images. The inaccuracy of flight parameters and the sensor specific appearance of objects are the difficulties automatic registration suffers from. To overcome these problems the presented system uses prior knowledge to select appropriate structures for matching, i.e. control points, from a GIS and to extract their corresponding features from the sensor data. The knowledge is represented explicitly using semantic nets and rules. The best correspondence between the GIS data and the image is found by an A*-algorithm. The automatic control point matching is demonstrated for crossroads in aerial and SAR imagery.

A context provisioning framework to support pervasive and ubiquitous applications

Acquisition and dissemination of user and environment context information is critical in development and deployment of context-aware systems. It is fundamental to the success of such systems that they have access to a scaleable, robust and flexible context provisioning framework capable of working across all types of devices and networks. In this paper, we present the design, implementation and experiences of developing a context management system that incorporates these ideas. It is based on a consumer-provider broker model, where providers employ a common context representation format, decoupling various entities involved in the production and consumption of context information. We demonstrate how the idea of independent context providers can aid in end-to-end working of a context management framework. One of the major advantages compared to other approaches is the extendibility of the system. By progressively adding Context Providers to legacy mobile communication systems, new context domains can be added. The system is able to evolve constantly and support a variety of emerging context-aware services and applications.

Challenges for Quality of Data in Smart Cities

Smart cities use multimodal information coming from heterogeneous sources, including various types of the Internet of Things (IoT) data such as traffic, weather, pollution, and noise data. The smart city data usually have different quality of information (QoI). QoI of each data source mainly depends on three factors: (1) errors in measurements or precision of the data collection devices, (2) noise in the environment and quality of data communication and processing (including network-dependent quality of service parameters), and (3) granularity of the observations and measurements in both spatial and temporal dimensions. Furthermore, various environments have different requirements that will determine the efficacy of using the data in the smart city applications; some systems have energy restrictions; and some wireless networks could rely on low bandwidth or intermittent connectivity. Most smart city applications also have to deal with huge volumes of data, with high velocity, dynamicity, and a variety of types of data. The QoI issues become more challenging when various data with different QoI are going to be integrated into an application to extract higher-level information and/or to provide actionable information to other services and applications. In some of the current smart city frameworks, the underlying information model is based on semantic

Effect of caching in a broker based context provisioning system

Caching is a well-established mechanism used in distributed systems for improving overall performance. In this paper, we analyse the effect of using a context cache in a broker-based context provisioning system. An experiment is carried out using a simulation based on our framework architecture of context consumers, context broker and context providers exchanging different types of context data over time. The results show notable improvement in the context query response time.

Advanced Multicast and Broadcast Content Distribution in Mobile Cellular Networks

Recently 3GPP (Third Generation Partnership Project) has standardised MBMS (Multimedia Broadcast Multicast Services) enabling broadcast and multicast transmissions over GPRS (General Packet Radio Service) and UMTS (Universal Mobile Telecommunications System). Hence it makes an efficient usage of radio resources possible. 3GPP and 3GPP2 introduced the specification of IMS (IP Multimedia Subsystem) and MMD (Multimedia Domain), receptively, which both are responsible for resource, admission and charging control. It allows for cost efficient and flexible provision of enriched multimedia services over IP networks. Up to now the controlling IMS and MBMS are separated subsystems sharing no common interfaces. This paper introduces both systems and depicts ongoing standardisation activities regarding their interworking. Finally, it proposes a service provision architecture and describes required signalling flows which enable the provision of multicast streaming using the MBMS specifications not only as access bearer technology. Thus, we present a step towards the evolution of IMS enabling it with multicast and broadcast capabilities.

Flow-control for multi-access systems

Future wireless communication systems will be characterised by an integration of different access technologies. Such systems will feature a user-friendly coordination of the complementary access technologies to access personalized services in a seamless manner via the currently most suitable access. Efficient resource management will provide cost effective bandwidth. These systems need a flow-control functionality to select always the best suitable access system for a certain traffic flow in different environments. This paper lists requirements and describes a flow control functionality that controls the forwarding of individual traffic flows over different access systems in a multi-access scenario. In addition, examples are presented and discussed as to how this advanced multimedia flow-control can be embedded both in a co-operative and in an integrated multi-access system architecture, providing thereby guidelines for standardization and future products.