Matthias Vodel

Wake-Up-Receiver Concepts - Capabilities and Limitations

A promising idea for optimising the power consumption of mobile communication devices represents the usage of an additional ultra-low-power receiver unit, which is able to control the main transceiver in order to reduce the standby power consumption of the overall system. Such a Wake-Up-Receiver (WuRx) unit senses the medium and switches on the communication interfaces in case of an external request. Otherwise, all system components for the network communication are completely switched off. Especially in the domain of resource-limited and embedded devices, WuRx technologies enable novel communication paradigms. But on the application layer, not all scenarios allow the efficient usage of such WuRx technologies. Dependent on environmental parameters, technological limitations and conceptual requirements, different strategies are necessary to ensure energy-efficient system operation. In this article, we present a critical analysis of the capabilities and the conceptual limitations of WuRx approaches. Therefore, we identify critical parameters for WuRx concepts, which limit the efficiency in real world scenarios. Our goal is to classify sufficient fields of application. Furthermore we evaluate the influences of these parameters on the system behaviour. In addition, we introduce heterogeneous energy harvesting approaches as an efficient way for the system optimisation. The proposed technologies are capable to be integrated into small-sized wireless sensor platforms and prolong the system uptime significantly. The presented simulation results are focusing on actual smart metering scenarios and wireless sensor networks. Based on these measurements, we were able to apply further optimisation steps within the system configuration on the application layer. In this context, we focus on application-specific key issues, like the trade-off between measurement quality and quantity, the usage of data buffering approaches and QoS capabilities.

SimANet – A Large Scalable, Distributed Simulation Framework for Ambient Networks

In this paper, we present a new simulation platform for complex, radio standard spanning mobile Ad Hoc networks. SimANet - Simulation Platform for Ambient Networks - allows the coexistence of multiple radio modules with different communication technologies and protocol stacks within one node, which can be used concurrently. By the usage of efficient data structures like Randomised Skip Quadtrees, SimANet allows the analysis and evaluation of large scale, heterogeneous network topologies in both static and dynamic simulation scenarios based on different movement models. The software design enables a modular extension with additional models for power consumption, communication complexity or barrier simulation. Furthermore, an integrated MPI library provides the possibility to run distributed test cycles on parallel computing systems. Thereby, special sliding time window algorithms avoid the typical disadvantage of a slow network interconnection structure and allow a dynamic load balancing on the available hardware resources during the runtime. With the main focus on the evaluation of abstract multi-interface, multi-standard communication concepts, we compare the functionality and the complexity of SimANet with well-known simulation tools like ns2-MIRACLE, ns2-NW-Node, OMNet++ and TeNS. Simulation results for different application scenarios estimate features like versatility, practicality or usability in large scale network topologies with up to 105 nodes.

Energy efficient handling of big data in embedded, wireless sensor networks

The development of wireless sensor networks has reached a point where each individual node of a network may store and deliver a massive amount of (sensor-based) information at once or over time. In the future, massively connected, highly dynamic wireless sensor networks such as vehicle-2-vehicle communication scenarios may hold an even greater information potential. This is mostly due to the increase in node complexity. Consequently, data volumes will become a problem for traditional data aggregation strategies traffic-wise as well as with regard to energy efficiency. Therefore, in this paper we suggest to call such scenarios big data scenarios as they pose similar questions and problems as traditional big data scenarios. Although the latter focus mostly on business intelligence problems. We then propose an aggregation strategy tied to technological prerequisites which enables the efficient use of energy and the handling of large data volumes. Furthermore, we demonstrate the energy conservation potential based on experiments with actual sensor platforms.

Data aggregation and data fusion techniques in WSN/SANET topologies - a critical discussion

WSN and SANET topologies generate huge amount of heterogeneous data, which has to be transmitted in a dynamically changing network infrastructure. Especially in the domain of wireless low-power applications, the energy-efficiency and the prioritisation of communication tasks is critical. Several research areas deal with this issue. They optimising the respective hardware components as well as the protocols within the PHY, MAC or network layer. But for an optimised media transport in the topology also the data management and the task scheduling on the application layer is essential. Here, the key challenge is to minimise the data amount without decreasing the information quality. Related research work in the field of data aggregation and data fusion offers interesting techniques for an efficient data handling. In this paper, we discuss usual ways for data aggregation, including the adapted communication process. We critically analyse the benefits in theory and compare these conceptual advantages with measured real-world results. The evaluation was done in two steps. The first one is based on simulation scenarios of typical WSN/SANET applications. In a second step, we implement a demonstrator platform for a respective real-world environment. The test bed configuration is similar to the simulation scenario and provides comparable data. Based on the results and the respective analysis, we propose feasible methods for optimising data aggregation techniques. We clarify, that these improvements are essential for an efficient usage in resource-limited, embedded sensor network environments.

Performance analysis of radio standard spanning communication in mobile Ad Hoc networks

In this paper, the feasibility and necessity of a new concept for radio standard spanning communication in mobile Ad Hoc networks (MANET) has been analysed. Past research approaches limited their solutions to the usage in a homogeneous topology on basis of a unique radio standard. The proposed concept offers the possibility to connect standardised radio modules on a hardware near layer by the usage of a dedicated Interface Block. Such an IFB allows the interoperability between tasks with incompatible protocols. For evaluating the conceptual advantages of this approach, different network topologies have been tested in a dedicated simulation environment. The scenario-based performance analysis includes the behaviour of the nodes both in static and in high-dynamic network topologies. Thereby, the main objective of verification is a qualitative evaluation of the power consumption in each node and in the entire topology. Furthermore, improvements of route paths and the connectivity level have been analysed. The degree of improvements in the analysed scenarios averages 15% and rises up to 35% in a random distributed, heterogeneous network topology with a high node density.

A capable, high-level scheduling concept for application-specific wireless sensor networks

The primary objective of wireless sensor networks is the monitoring of a system or area by measuring different kinds of sensor data. Dependent on the application scenario, a specific measurement scheduling scheme is preferred. Based on this scheduling, an optimisation of the available energy resources in each sensor node and accordingly in the whole network topology is possible. At the same time, an application-specific synchronisation of the measurement points ensures a maximum quality for the merged sensor information. One essential requirement for any kind of scheduling scheme is a synchronised time base in the entire network topology. In order to define capable measurement schemes for any kind of available sensor node hardware, lightweight synchronisation concepts are necessary. In this paper we present a scheduling concept for distributed, resource-limited sensor networks based on a capable time synchronisation approach. The concepts operate on the application layer and enable application-specific, energy-efficient sensor measurement schemes. For proof of concept, the approaches were implemented on a sensor node hardware platform. Several test scenarios evaluate the feasibility and clarify an excellent usability in wireless sensor network environments.

A capable, lightweight communication concept by combining Ambient Network approaches with Cognitive Radio aspects

In this paper, we present a feasible communication concept within the field of cognitive radios and ambient networking. The approach deals with the integration of different radio modules into an embedded communication platform. Basic idea is the simultaneous coexistence of multiple independent network interfaces, which allows us to combine the advantages of different communication technologies. At the same time we bypass the disadvantages of one single radio standard with its application specific design limitations. The result is a lightweight, radio standard spanning communication system, specially in the field of mobile ad hoc networks. The approach enables interesting new ways to create a reliable, heterogeneous network infrastructure. To avoid the influences of interferences in the topology, a special Link Management Unit identifies an increasing interference behaviour based on parameters like the packet loss rate, packet transmission time or fluctuations of the signal quality. With this knowledge base, we are able to adapt the transmission technology dynamically. Thus, the system takes an active influence on the local interference level in the network. Unlike other related research projects, this concept requires no special hardware devices and no complex software architecture. Instead, our approach focuses on standardised, low cost hardware components to realise an embedded communication platform. The presented paper analyses the feasibility with application-specific simulations and evaluate the results based on real world measurements with a designed prototype platform.

WRTA - Wake-Up-Receiver optimised routing and topology optimisation approach

In the domain of distributed embedded systems, available resources regarding computing power, energy, and memory are strongly limited. With focus on the energy resources, communication hardware and communication tasks represent critical consumers for most of the common application scenarios. Accordingly, optimised approaches for the communication have to be found, including routing, topology control, and scheduling. Wake-Up-Receivers (WuRx) represent a promising approach for minimising the energy consumption in wireless communication environments. To use the conceptual benefits of such technology, an adapted communication behaviour is required. Communication paradigm, communication protocols as well as the runtime behaviour must fit together. In this paper, we introduce a WuRx-optimised routing and topology optimisation approach - WRTA. We discuss the hardware integration as well as the adaptation of the communication task scheduling on application layer. The design matching process of all these aspects allows significant improvements of the energy-efficiency in typical sensor network scenarios. For achieving these goals, WRTA represents a lightweight protocol for data-centric WSN environments. The approach combines complex route path calculations and topology optimisation mechanisms, considering a given asynchronous communication environment. For proof of concept, we implement several heterogeneous test benches in both soft- and hardware. Hence, the presented simulation results as well as the respective real world measurements provide interesting results regarding the scalability and the efficiency. The analysis of the data shows minimum protocol overhead and outstanding characteristics regarding scalability and robustness. We clarify that application-specific adaptations & configurations within the overall system architecture are essential to ensure an reliable communication behaviour in energy self-sufficient WuRx environments.

Data aggregation in resource-limited wireless communication environments — Differences between theory and praxis

Multimodal Wireless Sensor Networks generate huge amount of heterogeneous data, which has to be transmitted in a dynamically changing network infrastructure. Especially in the domain of wireless low-power applications, the energy-efficiency and the prioritisation of communication tasks is critical. Several research areas deal with these issues. They are optimising the respective hardware components as well as the protocols within the PHY, MAC or network layer. But for an optimised media transport in the topology also the data management and the task scheduling on the application layer are essential. Here, the key challenge is to minimise the data amount without decreasing the information quality. Related research work in the field of data aggregation and data fusion offer interesting techniques for an efficient data handling. In this paper, we discuss usual ways for data aggregation, including the adapted communication process. We critically analyse the benefits in theory and compare these conceptual advantages with measured real-world results. The evaluation was done in two steps. The first one is based on simulation scenarios of typical WSN/SANET applications. In a second step, we implement a demonstrator platform for a respective real-world environment. The test bed configuration is similar to the simulation scenario and provides comparable data. Based on the results and the respective analysis, we propose feasible methods for optimising data aggregation techniques. We clarify, that these improvements are essential for an efficient usage in resource-limited, multimodal sensor network environments.

Dynamic channel management for advanced, energy-efficient sensor-actor-networks

Actual research projects in the fields of wireless communication systems focus on distributed, heterogeneous architectures for advanced sensor-actor-networks (SNETs). Each subsystem provides specific capabilities for measuring or manipulating its environment. At the same time, a huge amount of sensor, status and control data has to be transmitted over different network interfaces and communication standards. During the runtime, the number and the quality of communication channels is changing dynamically. Especially in wireless multi-hop scenarios with multiple radio standards, the maintenance of stable communication paths is critical.