Peter Martini

Link stability in mobile wireless ad hoc networks

We develop adaptive metrics to identify stable links in a mobile wireless networking environment based on the analysis of link durations in several different mobility scenarios. Our metrics only rely on online statistical evaluation of observed link durations. Neither do they require information on signal strength, radio conditions, or spacing of the mobile devices, nor do they depend on the availability of additional hardware such as GPS receivers or a synchronisation of the devices. We demonstrate the ability of the metrics to select stable links with a high probability in a wide range of scenarios.

Modelling mobility in disaster area scenarios

This paper provides a model that realistically represents the movements in a disaster area scenario. The model is based on an analysis of tactical issues of civil protection. This analysis provides characteristics influencing network performance in public safety communication networks like heterogeneous area-based movement, obstacles, and joining/leaving of nodes. As these characteristics cannot be modelled with existing mobility models, we introduce a new disaster area mobility model. To examine the impact of our more realistic modelling, we compare it to existing ones (modelling the same scenario) using different pure movement and link based metrics. The new model shows specific characteristics like heterogeneous node density. Finally, the impact of the new model is evaluated in an exemplary simulative network performance analysis. The simulations show that the new model discloses new information and has a significant impact on performance analysis.

Handoff support for mobility with IP over Bluetooth

The BLUEPAC (BLUEtooth Public ACcess) concepts present ideas for enabling mobile Bluetooth devices to access local area networks in public areas, such as airports, train stations and supermarkets. The proposed protocols support mobility on OSI layer 3. This paper concentrates on the necessary layer 2 protocol concepts for supporting mobility and handoffs between different access points. Furthermore, we present the necessary adaptations for allowing IP datagrams to be exchanged between the mobile Bluetooth devices and access points. The BLUEPAC protocol concepts have been implemented above a Bluetooth emulation system to test their feasibility. First results clearly showed the importance of minimizing the handoff duration to allow efficient operation of upper layer protocols such as TCP.

A Flexible Dynamic Partitioning Algorithm for Optimistic Distributed Simulation

The performance of distributed simulation depends very much on the partitioning of the simulation model among the participating hosts. Usually, when starting a simulation run, an initial partitioning is determined by taking into account the available computing resources as well as the expected workload and the communication structure of the simulation model. However, as hosts can be subject to background load or the model behavior can change in the course of the simulation, a dynamic partitioning mechanism is required to avoid inefficiencies. In this paper, we introduce a new dynamic partitioning algorithm for optimistic distributed simulation. The algorithm is generally applicable but can also be configured to meet the requirements of specific scenarios. It is based on performance estimates for both computation and communication workload, the calculation of which is completely platform-independent. Our experiments show that the algorithm has low overhead and reacts reliably to changes of both model behavior and external resources.

Modeling mobility in disaster area scenarios

This paper provides a model that realistically represents the movements in a disaster area scenario. The model is based on an analysis of tactical issues of civil protection. This analysis provides characteristics influencing network performance in public safety communication networks like heterogeneous area-based movement, obstacles, and joining/leaving of nodes. As these characteristics cannot be modeled with existing mobility models, we introduce a new disaster area mobility model. To examine the impact of our more realistic modeling, we compare it to existing ones (modeling the same scenario) using different pure movement and link-based metrics. The new model shows specific characteristics like heterogeneous node density. Finally, the impact of the new model is evaluated in an exemplary simulative network performance analysis. The simulations show that the new model discloses new information and has a significant impact on performance analysis.

Adaptive scatternet support for Bluetooth using sniff mode

Future applications of Bluetooth are likely to include ad-hoc networking. Therefore, it is desirable to interconnect multiple Bluetooth piconets to form a scatternet. Up to now, there is no extensive proposal for scatternet support available. We present and analyze an adaptive scheme for scatternet scheduling that is based on the sniff mode and thus does not require substantial modification of the current Bluetooth specification. The suitability of our approach is shown by first simulation results.

Detecting Black Hole Attacks in Tactical MANETs using Topology Graphs

Black hole attacks are a serious threat to communication in tactical MANETs. In this work we present TOGBAD a new centralised approach, using topology graphs to identify nodes attempting to create a black hole. We use well-established techniques to gain knowledge about the network topology and use this knowledge to perform plausibility checks of the routing information propagated by the nodes in the network. We consider a node generating fake routing information as malicious. Therefore, we trigger an alarm if the plausibility check fails. Furthermore, we present promising first simulation results. With our new approach, it is possible to already detect the attempt to create a black hole before the actual impact occurs.

Graph based Metrics for Intrusion Response Measures in Computer Networks

Keeping up with the timing constraints of real-time traffic in wireless environments is a hard task. One of the reasons is that the real-time stations have to share the same communication medium with stations that are out of the sphere-of control of the real-time architecture. That is, with stations that generate timing unconstrained traffic. The VTP-CSMA architecture targets this problem in IEEE 802.11 wireless networks. It is based on a Virtual Token Passing procedure (VTP) that circulates a virtual token among real-time stations, enabling the coexistence of real-time and non realtime stations in a shared communication environment. The worst-case timing analysis of the VTP-CSMA mechanism shows that the token rotation time is upper-bounded, even when the communication medium is shared with timing unconstrained stations. Additionally, the simulation analysis shows that the token rotation mechanism behaves adequately, even in the presence of error-prone communication channels. Therefore, the VTP-CSMA architecture enables the support of real-time communication in shared communication environments, without the need to control the timing behavior of every communicating device. A ring management procedure for the VTP-CSMA architecture is also proposed, allowing real-time stations to adequately join/leave the virtual ring. This ring management procedure is mandatory for dynamic operating scenarios, such as those found in VoIP applications.This contribution presents a graph based approach for modelling the effects of both attacks against computer networks and response measures as reactions against the attacks. Certain properties of the model graphs are utilized to quantify different response metrics which are well-kown from the pragmatic view of network security officers. Using these metrics, it is possible to (1) quantify practically relevant properties of a response measure after its application, and (2) estimate these properties for all available response measures prior to their application. The latter case is the basis for the selection of an appropriate reaction to a given attack. Our graph-based model is similar to those used in software reliability analysis and was designed for a scalable granularity in representing properties of the network and its components to be protected. Different examples show the applicability of the model and the resulting metric values.

Indoor tracking for mission critical scenarios: A survey

The availability of a reliable and precise tracking system for relief units operating in mission critical scenarios would drastically improve the situational awareness and thus facilitate the mission planning and accomplishment as well as increase the safety of human resources. Thus, the demand for such a system is very high both in the military and in the emergency and crisis intervention domain. While there are solutions like GPS for the localization in open areas, problems arise in urban scenarios and indoors due to insufficient or failed signal reception. For indoor use, multiple alternative localization concepts exist that are suited for different use cases and expose varying properties in precision, complexity and required preconditions. The deployment within mission critical scenarios implicates explicit restrictions and requirements so that only some of the techniques are adept or have the potential of being used here. This article identifies the commonly issued requirements to an indoor tracking in mission critical scenarios and introduces basic techniques for position estimation. Subsequently, existing indoor tracking systems specifically in the field of mission critical scenarios are reviewed with a focus on their capabilities in terms of reliability and accuracy. By doing so, an overview of current approaches in this field is given. Furthermore, the most adept techniques are classified with respect to the requirements within mission critical scenarios.

Human mobility in MANET disaster area simulation - a realistic approach

Disaster areas have been figured out as a typical usage scenario for mobile wireless ad-hoc networks (MANETs). In contrast to this, there are no specific mobility or traffic models for MANETs. We present a realistic approach to realize mobility in disaster areas based on tactical issues of civil protection. The new model is analyzed and compared to Gauss-Markov and random waypoint mobility models. Furthermore, we present first simulation results. The mobility model analysis as well as the simulation are based on two real disasters that occurred in Germany in 1999 and 2001. We show that disaster area scenarios have specific characteristics. Thus, they should be considered in MANET performance evaluation.