Christian Wietfeld

RF Mesh Systems for Smart Metering: System Architecture and Performance

This paper describes the system architecture and the performance evaluation of a Radio Frequency (RF) mesh based system for smart energy management applications in the Neighborhood Area Network (NAN). The RF mesh system presented in this paper leverages the Industrial, Scientific and Medical (ISM) band at 902-928 MHz and is based on frequency hopping spread spectrum (FHSS). The performance evaluation is based on a geographical model of the deployment scenario and implements geographical routing combined with appropriate radio propagation models. The results show that the system is able to handle Smart Metering communication traffic with a high reliability provided potential coverage gaps are properly filled with repeater nodes. The proposed methodology allows the identification of coverage gaps, which may cause bottlenecks in the network, prior to deployment and therefore supports efficient and reliable deployment and operation of the system.

AirShield: A system-of-systems MUAV remote sensing architecture for disaster response

For clarification, containment and combat of large danger areas, fast and flexible survey of potentially contaminated areas is an emerging challenge. In this paper we present a project that focuses on incidents, that are caused by uncontrolled emissions of liquid or gaseous contaminants (e.g. explosive or toxic gases or liquids, biological, chemical or nuclear weapons). Instead of sending specially equipped forces with expensive transport and measurement devices into the contaminated area, our proposed system makes use of an autonomous, wireless connected swarm of Micro Unmanned Aerial Vehicles (MUAV), often simply known as drones, that are featured with lightweight mobile sensor systems. In this paper we will be particularly focusing on the complex communication system, which on the one hand has to organize the on-board-communication between the control systems of the MUAV and the sensors and on the other hand has to establish wireless connections to the mission control center on the ground as well as to neighboring MUAVs in the air via a mesh network.

Role-Based Connectivity Management with Realistic Air-to-Ground Channels for Cooperative UAVs

Ad-hoc aerial sensor networks leveraging MUAVs (Micro Unmanned Aerial Vehicles) are ideally suited to cost-efficiently explore unknown or hostile environments for example in case of incidents producing harmful gases or radiation. In this manuscript we present results on the investigations of communication-aware steering algorithms for cooperative MUAV swarms. The mission objective is to achieve a maximum spatial exploration efficiency with the simultaneous ability to self-optimize the communication links by exploiting controlled mobility. While our previous work has mainly considered the performance of the Air-to-Air mesh network, in this paper we focus on the Air-to-Ground-link connectivity control. To achieve appropriate communication links to a central sensor data sink even while exploring larger search areas, an agent-based role management strategy is used to provide suitable multi-hop connectivity. The novel algorithms are investigated for static as well as dynamically changing environments. Key results include a detailed realistic aerial channel characterization and network dimensioning analysis considering numbers of MUAVs and density of ground stations vs. exploration speed and sensor data latency.

An accurate and extensible mobile IPv6 (xMIPV6) simulation model for OMNeT

MIPv6 is the IPv6 based mobility management protocol and it is expected to become the mobility management protocol of choice for the Next Generation Wireless Access Networks. In order to develop the understanding of the protocols behavior, its suitability for deploying in a wireless environment and in order to be able to propose and develop appropriate improvements and optimizations, it is imperative to have an accurate, reliable and scalable simulation model for the MIPv6 protocol which is fully compliant to the IETF standards and specifications. This paper presents the logic, design and performance results of an extensible MIPv6 (xMIPv6) simulation model integrated into the INET20061020 framework for the OMNeT++ discrete event simulator.

Software-defined networking for Smart Grid communications: Applications, challenges and advantages

Future power systems are characterized by a high degree of complexity with a large number of intelligent devices, exchanging and processing both huge amounts of data and realtime critical information. Accordingly reliable, real-time capable and secure communication networks are required for enabling autonomous monitoring, management and control to guarantee stable power system operation. In this paper, we present and analyse a flexible and dynamic network control approach based on Software-Defined Networking (SDN) for meeting the specific communication requirements of both distribution and transmission power grid. Therefore a testbed is introduced, enabling the evaluation of multiple failure scenarios such as link disturbance and congestion by analysing corresponding fast recovery and prioritization solutions. The performance and robustness of the developed strategies is shown using highly-critical monitoring and control messages on basis of IEC 61850 and considering the mutual impact with low priority background traffic. Results indicate the advantages of SDN compared to traditional routing and Quality-of-Service mechanisms, providing a more reliable communication network, which is able to handle complex failure scenarios. In particular, SDN enables the integration of diverse network management functions and thus offers the power system new options for dealing with faults even in the case of overall outages. On the basis of these results, we demonstrate challenges and derive future benefits for a SDN-enabled Smart Grid communication network, holding the potential to evolve into a self-healing infrastructure.

Cognitive Agent Mobility for Aerial Sensor Networks

For efficient sensor coverage of large industrial and incident areas, fast and flexible strategies for collecting sensor data through an autonomous, wirelessly connected swarm of (Micro) Unmanned Aerial Vehicles (MUAVs) are still an emerging challenge. Deploying multiple MUAVs which stably carry sensing equipment in hostile environments yields cost efficiency and reducing the risk to human life. The use of an aerial ad hoc sensor network based on MUAV agents promises more timely and accurate information by fusing measurements from different types of sensors. In this paper, we examine agent-based mobility algorithms that target high spatial coverage distribution, high total coverage, and high-quality communication links. For these key figures, the performance of the different novel mobility algorithms is evaluated. We particularly focus on channel aware mobility and on self-organizing mesh topologies of MUAV-based sensor swarms with respect to communication constraints.

Comparison of User Mobility Pattern Prediction Algorithms to increase Handover Trigger Accuracy

The estimation of correct triggers for handover in cellular networks belongs to the critical tasks for accurate network operation. The importance of seamless handover even rises according to the increasing number of available radio access technologies, demanding for a reliable vertical handover. To aid the handover process, mobility prediction technologies gain interest and provide the possibility to prepare for handover in advance. The approaches presented here feature prediction of macro-mobility as an additional measure to aid handover decisions. The prediction is based on statistical data gained from the observation of movement across multiple cells. One of the main features lies in a generic user centric calculation of the most likely next hop during user movement, compared to network specific technological methods

Hybrid simulation of power systems and ICT for real-time applications

With the rise of smart grid technologies, the interdependencies of ICT and power systems become increasingly important in both transmission and distribution networks. For the design of time-critical applications, simulation tools for an integrated analysis of these domains are needed. In the case of electrical transmission systems, high-performance ICT solutions and fast controllable power equipment enable a new era of dynamic power system operation whereas applications for this purpose need to be investigated with a special focus on their real-time performance. This paper presents a novel, modular co-simulation environment for comprehensive analysis of mutual effects, taking into account communication networks, IT processing and power system response. This hybrid simulation environment has been developed with a focus on the evaluation of the real-time performance of wide-area monitoring, protection and control (WAMPAC) applications, nonetheless, it is applicable to a variety of smart grid applications in transmission and distribution networks. The simulator architecture takes into account various standards from different areas of research - such as IEEE 1516-2000 (High-Level Architecture), IEC 61850, OPC and CIM - in order to provide a highly flexible simulation environment and to enable development of applications close to industrial implementation.

Comparison of the communication protocols DLMS/COSEM, SML and IEC 61850 for smart metering applications

Communication technology plays an increasingly important role in the growing automated metering infrastructure (AMI) market. This paper presents a thorough analysis and comparison of four application layer protocols in the smart metering context. The inspected protocols are DLMS/COSEM, the Smart Message Language (SML), and the MMS and SOAP mappings of IEC 61850. The focus of this paper is on their use over TCP/IP. The protocols are first compared with respect to qualitative criteria such as the ability to transmit clock synchronization information. Afterwards the message size of meter reading requests and responses and the different binary encodings of the protocols are compared.

A Distributed and Autonomous Beacon Scheduling Algorithm for IEEE 802.15.4/ZigBee Networks

The need for high reliability wireless communication has triggered the interest in mesh networks recently. Even though IEEE 802.15.4/ZigBee offers basic meshing capabilities, it still lacks tight synchronization of the whole network by means of beacons in this topology mode. However, the goal of an energy efficient operation requires a close synchronization for effective duty cycle management. Beacon scheduling mechanisms for the cluster-tree topology on centralized basis are known, but extensions to meshing have not been defined. Therefore, this paper introduces a distributed beacon scheduling (DBS) algorithm to overcome this deficiency while addressing robustness and performance during reconfiguration, too. The results show the applicability of the approach by extensive simulations even for large networks of several thousand nodes in wireless mesh networks (WMNs) based on IEEE 802.15.4/ZigBee.