H. Georg, S. C. Müller, C. Rehtanz and C. Wietfeld, "A HLA Based Simulator Architecture for Co-simulating ICT Based Power System Control and Protection Systems", 3rd IEEE International Conference on Smart Grid Communications (SmartGridComm 2012), Tainan City, Taiwan, Nov 2012.

Power systems and especially Smart Grids increasingly apply Information and Communication Technologies (ICT) for exchanging information over wide area networks. Here, the performance of the ICT has become crucial for the development of new Wide Area Monitoring, Protection And Control (WAMPAC) systems. In this context, simulations are a common way for evaluation, but power systems and communication networks are usually analysed with dedicated simulators. Therefore a combined simulation for analysing the dynamics and mutual impacts of both domains is needed. In this paper we present a generic hybrid simulation architecture based on the IEEE standard 1516 - High Level Architecture to enable a combined simulation of power systems and communication networks in an integrated simulation environment. First, we introduce our hybrid simulator architecture, along with the communication and synchronization process between sub-simulators. Secondly, we present our communication networks architecture for modelling the network traffic caused by the information transmitted by control and protection algorithms within the electrical transmission system. Finally, we introduce our modelling approach for mapping entities between the power systems and the communication networks. For this purpose, we introduce our concept of a Substation Data Processing Unit, which represents entities on substation level by providing an IEC 61850 based model for mapping logical functions for local process control, implementing decentralized protection and control algorithms and providing additional components for the power systems (e.g Phasor Measurement Units (PMUs)).

Subik, S. and Wietfeld, C., "Integrated PMR-Broadband-IP Network for Secure Realtime Multimedia Information Sharing",IEEE International Conference on Technologies for Homeland Security, Waltham, MA, USA, IEEE, Nov 2011.

In this paper, the authors present a novel solution for the integration of TETRA-based PMR and IP based wireless broadband networks through a novel inter-system interface. This solution enables secure group communications based on PMR standards using heterogeneous devices ranging from a traditional PMR device to smart phones such as the iPhone. Thereby a SmartPhone user will be enabled to leverage on one hand the multimedia data capabilities of 3G und 4G wireless networks (UMTS, LTE) while at the same time be part of a PMR group communication. In other words, any authorized Smart Phone can become part of a PMR communication group by simply downloading the appropriate, dedicated Application. As a key benefit, homeland security personnel can be included in the disaster response actions instantaneously, without necessarily carrying around a dedicated PMR device and without the need for PMR coverage. In contrast to existing solutions, the proposed interface solution prevents the reduction of the voice quality when bridging system boundaries by tandem encoding with a TETRA-over-IP (ToIP) interconnection. The presented solutions include different interconnection setups including Trunked Mode (TMO) and Direct Mode (DMO) capabilities. To enable the group communications services as known in PMR systems, a dedicated protocol, the Push-to-X protocol developed by CNI, is leveraged. The results of performance evaluations show that the speech quality is still acceptable even under harsh conditions. The proposed system therefore paves the way towards a future, high performance PMR based on LTE, while preserving backwards compatibility with existing PMR systems.

Daniel, K., Rohde, S. and Wietfeld, C., "Leveraging Public Wireless Communication Infrastructures for UAV-Based Sensor Networks",IEEE International Conference on Technologies for Homeland Security, Waltham, MA, USA, IEEE, Nov 2010.

Unmanned Aerial Vehicles (UAV) enable the in-depth reconnaissance and surveillance of major incidents. Uncontrolled emissions of liquid or gaseous contaminants in cases of volcanic eruptions, large fires, industrial incidents or terrorist attacks can be analyzed by utilizing UAVs. Hence, the use of cognitive Unmanned Aerial Systems (UAS) for distributing mobile sensors in incident areas is in general a significant value add for remote sensing, reconnaissance, surveillance and communication purposes. Police departments, fire brigades and other homeland security organizations will have access to medium and small size UAVs in the near future and will integrate UAVs in their work flow. In this paper we are focusing on the civilian concepts of operations (CONOPS) for UAVs, in particular for small-scale UAVs. We present viable concepts on system level for leveraging public wireless communication networks for UAV-based sensor networks with respect to existing constraints and user requirements.

Lewandowski, A., Koester, V. and Wietfeld, C. , "Performance Evaluation of AODV- and OLSR-meshed IP-enabled IEEE802.15.4", The Third International Conference on Advances in Mesh Networks (Mesh 2010), Venice/Mestre, Italy, IARIA/IEEE (awarded with the Best Paper Award), July 2010.

Safety critical applications of IEEE 802.15.4 networks require autonomous network reconfiguration and dynamic meshing in case of node failures or changing environmental influences. In contrast to the classical approach of wireless sensor networks, this paper focuses on the development of enhanced network services like multimedia transmissions in a gas concentration monitoring scenario. Thus, using IEEE 802.15.4 reduces the energy consumption in comparison to Wi-Fi networks. Therefore, this paper demonstrates the application of Ad-hoc On Demand Distance Vector (AODV) and Optimized Link State Routing (OLSR) on IEEE 802.15.4 nodes based on an IP layer - instead of relying on the standard ZigBee configuration. The new network configuration is evaluated for handover processes between mobile and stationary nodes. The time delay, maximum throughput and generated overhead is compared between the two routing protocols for different node constellations. Finally, the lifetime of the node is evaluated in comparison to the ordinary IEEE 802.15.4 configuration and IEEE 802.11. Concluding, the application of AODV and OLSR for power-constrained IEEE 802.15.4 nodes is proposed.

Tran, T. and Wietfeld, C., "Approaches for Optimizing the Performance of a Mobile SAML-based Emergency Response System",The 13th IEEE Enterprise Distributed Object Computing Conference Workshops (EDOC), Auckland, New Zealand, IEEE, Vol. 1, pages: 148-156, Sept 2009, Best Paper Award in MTECS.

The fast access of essential and latest information from anytime and anywhere is crucial for the success of fire mission planning and is still a challenge, if requirements such as high performance, security and simplicity have to be met concurrently. However, the secure access to the distributed information of public authorities like building plans or medical patient data is currently mostly available via the traditional time-consuming post. Due to this problem a mobile integrated solution is developed, which allows a secure and holistic access to relevant information. The solution is based on the Security Assertion Markup Language (SAML) architecture which specifies an XML based standard for exchanging authentication and authorization data. Unfortunately, the performance of this approach is not applicable for time-critical mobile applications because of the SAML specific communication procedures. Thus, this paper presents two approaches for boosting the performance and shows the results of performance evaluation for the required validation. Moreover, an analytic model is introduced for identifying the SAML specific processing time.

Niehoefer, B., Burda, R., Wietfeld, C., Bauer, F. and Lüert, O., "GPS Community Map Generation for Enhanced Routing Methods based on Trace-Collection by Mobile Phones",1st International Conference on Advances in Satellite and Space Communications (SPACOMM), Colmar, France, IEEE Computer Society, Digital Object Identifier 10.1109/SPACOMM.2009.31, pages: 156 - 161, July 2009, Best Paper Award.

The paper describes a map generation system which relies on random individual contributions of GPS traced movements. In a typical use case, mobile phone users would join a specific community to contribute their movements along streets, roads or pathways in form of so called traces. Neither contributing subscribers nor the map generation need to have an a priori knowledge of the charted area. The approach presented here comprises the trace recording, the upload process to a common server and the processing algorithm for map generation. The problem of noisy data, resulting from GPS inaccuracies and random movements is addressed and countermeasures are proposed. One major perspective of this paper is the decomposition of a map into reasonable segments. In this context, the filter mechanism applied to the raw data is a key component for the deduction of precise street maps. Furthermore, the proof of concept is given and a guideline for a lower limit of active subscribers to achieve an operational system is derived.