Daniel Burgstahler

SMARTENERGY.KOM: An intelligent system for energy saving in smart home

Over the last twenty years, energy conservation has always been of great importance to individuals, societies and decision makers around the globe. As a result, IT researchers have shown a great interest in providing efficient, reliable and easy-to-use IT services which help users saving energy at home by making use of the current advances in Information and Communications Technology (ICT). Driven by the aforementioned motivation, we developed SMARTENERGY.KOM, our framework for realizing energy efficient smart homes based on wireless sensor networks and human activity detection. Our work is based on the idea that most of the user activities at home are related to a set of electrical appliances which are necessary to perform these activities. Therefore, we show how it is possible to detect the users current activity by monitoring his fine-grained appliance-level energy consumption. This relation between activities and electrical appliances makes it possible to detect appliances which could be wasting energy at home. Our framework is organized in two components. On one hand, the activity detection framework which is responsible for detecting the users current activity based on his energy consumption. On the other hand, the EnergyAdvisor framework which utilizes the activity detection for the purpose of recognizing the appliances which are wasting energy at home and informing the user about optimization potential.

Exploiting platform heterogeneity in wireless sensor networks by shifting resource-intensive tasks to dedicated processing nodes

Platform heterogeneity in wireless sensor networks is often seen as a major challenge for application development. Once embedded systems with different processor architectures, computational power, and memory are part of the same network, algorithms and applications must be adapted to this additional degree of complexity. As a result, current sensor network deployments are (with exception of the sink node) commonly comprised of devices of identical make and model. In this paper, we show how device heterogeneity may be exploited to improve the energy efficiency of the sensor network by shifting resource-intensive processing tasks to other nodes within the network. To this end, we analyze the energy demand for representative processing operations and wireless communications on six heterogeneous state-of-the-art sensor platform types. Based on the created models, we assess the achievable energy savings when tasks are shifted to more powerful processing nodes. Our results show that platform heterogeneity, although often being perceived as a hindrance to the easy deployment of applications, also serves as an enabler for increased energy efficiency of the network.

Impact of Time in Network Selection for Mobile Nodes

Today, mobile nodes use multiple Internet access networks inefficiently. State-of-the-art network selection strategies distribute data traffic to available networks, but ignore an important second dimension: time. Time selection offers the opportunity to plan usage of future-available networks for delay-tolerant data traffic. We hypothesize, that concurrent selection of network and time leads to synergy effects, which reduce transmission cost and boost connectivity performance. To assess data distribution to wireless networks and time, we propose a novel rating model for joint network and time selection. The proposed model rates the satisfaction of Quality-of-Service (QoS) application requirements and trades off conflicting optimization goals. Moreover, we analyze the impact of time in network selection and present three network selection schedulers, which differ in their time selection strategy. Evaluation of the results reveals a strong impact of time selection on network performance. This gives evidence, that our initial hypothesis holds and forward-looking scheduling strategies provide a substantial benefit over state-of-the-art approaches.

MoVeNet: Mobility Management for Vehicular Networking

Vehicle Internet access benefits from using heterogeneous multi-provider networks. However, such access suffers significantly from insufficient handover processes. Due to high vehicle speeds, handover happens frequently and is substantially impaired by high handover delays. To solve correlated issues, we propose MoVeNet, a client-controlled, distributed mobility management approach with three substantial characteristics. Firstly, it pools parallel resources of wireless multi-provider networks for efficient common use. Secondly, MoVeNet reduces overhead for mobility management due to publish-subscribe methods. Thirdly, it provides a low-latency option for critical data flows, which enables flow-wise trade-off between latency and overhead. The architecture splits control from data, introducing lightweight Data Agents, which provide protocol transparency towards communication partners. Data Agents are located near the optimal route to provide low-latency packet routes. Moreover, MoVeNet introduces a Control Agent, which offloads communication-intensive tasks from the mobile node to reduce signaling overhead. The result solves deficiencies of related approaches and satisfies typical requirements of modern mobility management protocols. As shown by simulation, MoVeNet reaches excellent handover performance even for the harsh environment of the connected vehicle scenario.

Knowledge for a Longer Life: Development Impetus for Energy-Efficient Smartphone Applications

In recent years, there has been a rapid growth in the spread of smartphones and thus in the utilization of mobile applications. Such applications require a substantial portion of the available energy. Since a short battery lifetime has a very negative impact for the user experience, application developers should have the skills and the knowledge to avoid energy-inefficient applications. In this paper, we present a comprehensive survey of approaches and methods to reduce the energy consumption and thus help software developers to improve their applications.

Empirical investigation of the effect of the door's state on received signal strength in indoor environments at 2.4 GHz

Due to the wide deployment of indoor wireless local area networks (WLANs), the indoor planning became a research of interest for IT as well as networking researchers. As a result of this wide deployment, many IT applications and services started relying on the ready implemented WLAN infrastructure. Therefore, there is a need for reliable propagation models which are able to predict the WLAN signal strength in indoor environments before starting the real world deployment which leads to an efficient and cost aware deployment process. In this paper we develop an empirical propagation model which focuses mainly on the effect of the door state on the propagated WLAN signal in indoor environments. The measurements were compared to other simulated results in literature. A new empirical parameter based on empirical measurements was introduced for a better estimation of the received signal strength (RSS).

Switching Push and Pull: An Energy Efficient Notification Approach

An increasing number of modern smartphone applications are dependent on information updates from the cloud. To realize such information updates mainly two communication approaches are common, namely push- and pull. Due to different communication patterns both approaches differ in their energy consumption and notification latency. The energy constrained nature of mobile devices entails a sensible selection of the appropriate notification approach. In this paper we provide an evaluation of the energy consumption of both communication approaches. Based on this we provide a transition approach that is able to use the best of both, low latency and low energy consumption. Our results show that energy savings of up to 7% of the total smartphone battery per day can be achieved by switching between both approaches, depending on the context.

Publish-subscribe-based control mechanism for scheduling integration in Mobile IPv6

Currently discussed handover protocols do not provide the means to allow holistic flow handover scheduling. However, flow scheduling leads to a performance boost resulting from efficient parallel network use and a match of network characteristics to application requirements. Mobile IPv6 with flow binding extension and route optimization fulfills most requirements. However, control data is redundantly transmitted to every communication partner. This forbids coordination of parallel data flows and, therefore, scheduling. We introduce a new publish-subscribe-based control data routing which makes Mobile IPv6 compatible with centralized flow scheduling and furthermore reduces overhead via the wireless channels. The result offloads computationally intensive tasks of scheduling to servers in the Internet and moves handover control to the same. The resulting handover protocol is an enabler for client-centric scheduling and paves the way towards this promising topic.

A concept for vehicle internet connectivity for non-safety applications

Internet access to multimedia content in vehicles today is only possible via cellular networks which offer insufficient bandwidth. By using additional V2X technology in a hybrid manner, vehicles can benefit from additional bandwidth to receive enhanced internet connectivity. We introduce a holistic concept that pursues the vision of an optimal use of available access networks in a vehicular environment combined with a managed resource utilization in a user-centric way to result in maximum user experience and economic efficiency. The resulting internet connection introduces further opportunities for value-added services that maximize Quality of Experience and allows further personalization.

Push vs. Pull: An Energy Perspective (Short Paper)

In many application scenarios, such as traffic guidance or ambient living, services need to notify mobile applications about status changes. Such notifications to mobile devices can be realized using two principal approaches, namely push- and pull-based. Apart from functional differences, the two options likely result in different energy consumption, which is an important aspect due to the battery constraints of contemporary mobile devices. This paper provides a detailed assessment of energy consumption in pull- and push-based notification scenarios, considering different payload sizes and notification intervals. Our results indicate that an educated choice among both options may, depending on the specific application scenario, facilitate energy savings of up to 19%.