Philipp Sommer

• PhD
• Researcher at ABB

Energy-efficient location tracking with battery-powered devices using energy harvesting necessitates duty-cycling of GPS to prolong the system lifetime. We propose an energy- and mobility-aware scheduling framework that adapts to real-world dynamics to achieve optimal long-term tracking performance. To forecast energy, the framework uses an exponen...

Enabling Internet connectivity for mobile objects that do not have a permanent home or regular movements is a challenge due to their varying energy budget, intermittent wireless connectivity, and inaccessibility. We present a hardware and software framework that offers robust data collection, adaptive execution of sensing tasks, and flexible remote...

State-of-the-art trajectory compression methods usually involve high space-time complexity or yield unsatisfactory compression rates, leading to rapid exhaustion of memory, computation, storage and energy resources. Their ability is commonly limited when operating in a resource-constrained environment especially when the data volume (even when comp...

State-of-the-art trajectory compression methods usually involve high space-time complexity or yield unsatisfactory compression rates, leading to rapid exhaustion of memory, computation, storage and energy resources. Their ability is commonly limited when operating in a resource-constrained environment especially when the data volume (even when comp...

Context-aware services rely critically on accurate and energy-efficient location tracking. While GPS receivers offer high accuracy positioning, energy harvesting and storage constraints of battery-powered devices necessitate duty-cycling of GPS to prolong the system lifetime. Furthermore, real-world dynamics dictate that the GPS sampling strategy a...

The high energy consumption of GPS modules has kept long-term outdoor localisation with battery-powered devices an unsolved challenge. While low- power sensors can trigger GPS sampling to reduce energy consumption, validat- ing the long-term reliability of these sensors in unconstrained environments is challenging due to sensor drifts and the lack...

We present a simple model to study Lévy-flight foraging with a power-law step-size distribution [Formula: see text] in a finite landscape with countable targets. We find that different optimal foraging strategies characterized by a wide range of power-law exponent μopt, from ballistic motion (μopt → 1) to Lévy flight (1 < μopt < 3) to Brownian moti...

Long-term tracking of small-size animals with wireless sensor networks remains a challenge as only limited energy harvesting and storage is possible due to stringent size and weight constraints for animal collars.We present first experiences towards a perpetual monitoring system for free-living flying foxes. The highmobility of flying foxes require...

Long-term location tracking, where trajectory compression is commonly used, has gained high interest for many applications in transport, ecology, and wearable computing. However, state-of-the-art compression methods involve high space-time complexity or achieve unsatisfactory compression rate, leading to rapid exhaustion of memory, computation, sto...

Wireless sensor network platforms share the wireless communication channels with Wi-Fi and Bluetooth based networks, resulting in heavy use of these bands. As a consequence, platforms in wireless sensor networks need to carefully consider external interference to achieve reliable communication. In this paper, we present an experimental analysis of...

Clock synchronization is an enabling service for a wide range of applications and protocols in both wired and wireless networks. We study the implications of clock drift and communication latency on the accuracy of clock synchronization when scaling the network diameter. Starting with a theoretical analysis of synchronization protocols, we prove ti...

Flying-foxes (bats) are of scientific interest and management concern globally due to the amenity, crop and disease threat they pose. A management priority in Australia is the threat of Hendra virus transmission from flying-foxes to horses, subsequently putting humans at risk from this deadly virus. Simulation models can improve our capacity to pre...

Power management of mobile embedded devices remains im- portant with the slow growth of battery energy density rel- ative to computing power. Estimating the state of charge (SOC) of battery is key for scheduling power intensive tasks, yet current approaches either require dedicated hardware, use battery voltage as a loose indicator of SOC, or track...

Development of wireless sensor network applications remains a challenge, due to lack of visibility into the global network state. Debugging instrumentation using printf-like instructions affects the execution timing and non-intrusive approaches, such as JTAG, have not been used beyond a single node due to their high cost. This paper presents Minerv...

We present Twonet, a large-scale sensor network testbed with dual-radio nodes. Twonet has 100 Opal nodes with low-power 32-bit ARM CPU and 2.4 GHz and 900 MHz radios. These nodes are managed by a network of 20 Raspberry Pi nodes at tier 2 and a PC server at tier 1. These nodes together provide a robust testbed for public access. Twonet represents a...

The high popularity of wireless sensor networks has led to novel applications with diverse, and sometimes demanding, data communication requirements, for example, streaming camera images in surveillance applications. In response bulk-data transfer protocols were proposed that provide low latency and high throughput communication over multiple hops....

Long-term outdoor localisation with battery-powered devices remains an unsolved challenge, mainly due to the high energy consumption of GPS modules. The use of inertial sensors and short-range radio can reduce reliance on GPS to prolong the operational lifetime of tracking devices, but they only provide coarse-grained control over GPS activity. In...

Limited visibility into the global network state renders testing and debugging sensor network applications a challenging task. Existing debugging methods are often non-intrusive and require modifications of the binary image. Hardware based debugging instrumentation such as JTAG has not been widely used beyond a single node, mainly due to its relati...

Testbeds are indispensable for debugging and evaluating wireless embedded systems. While existing testbeds provide ample opportunities for realistic, large-scale experiments, they are limited in their ability to closely observe and control the distributed operation of resource-constrained nodes - access to the nodes is restricted to the serial port...

Location awareness is a key requirement for many pervasive applications. Collaborative localization can improve accuracy and coverage indoors and improve power consumption by duty-cycling GPS outdoors. We use Bluetooth for collaborative localization of mobile personal devices. Specifically, we embed information in Bluetooth device names to improve...

Location awareness is a key requirement for many pervasive applications. Collaborative localization techniques are interesting because they help to improve accuracy and coverage indoors and improve power consumption by duty-cycling GPS outdoors. We use Bluetooth for collaborative localization of mobile personal devices. Specifically, we embed infor...

Analyzing foot pressure is helpful in clinical diagnosis. Possible applications include the diagnosis of back injuries, prevention of diabetic foot ulceration, and adaptation of insoles for orthopedic applications. Consequently, several approaches to measure foot pressure distributions exist. However, traditional systems exhibit one common drawback...

While the sun is important for our health, overexposure to sunlight carries significant health risks ranging from sunburn to skin cancer. Although people know about these risks, sunlight related skin damages have increased over the past decades. We have conducted a survey that sheds light on this phenomenon and suggests that the missing natural sen...

Having access to accurate position information is a key requirement for many wireless sensor network applications. We present the design, implementation and evaluation of SpiderBat, an ultrasound-based ranging platform designed to augment existing sensor nodes with distance and angle information. SpiderBat features independently controllable ultras...

Developing applications and protocols for wireless sensor networks is a time consuming and error prone task, which possibly includes many iterations of implementation and testing. While simulations will probably not replace testbed experiments completely, they are a time efficient tool for rapid prototyping of sensor networks. Writing code and test...

Sensor networks proved to be a useful research tool in the field of environmental monitoring. While first sensor de-ployments consisted of a relatively small number of static nodes, mobile sensor devices have attracted growing inter-est for large-scale sensing applications in recent years. In this paper, we present Ikarus, a novel participatory sen...

Having access to accurate position information is a key requirement for many wireless sensor network applications. We present SpiderBat, an ultrasound-based ranging platform for wireless sensor networks. It is designed to extend existing node platforms with ultrasound ranging capabilities. SpiderBat features four pairs of independently controllable...

Data gathering is one of the most common applications of wireless sensor networks. Such networks are an extremely useful tool for researchers in various domains since they allow for measurements in unaccessible locations, e.g., on mountains, glaciers or in animal habitats. At the same time, the deployment and maintenance of such sites is time consu...

Clock synchronization is one of the most basic building blocks for many applications in computer science and engineering. The purpose of clock synchronization is to provide the constituent parts of a distributed system with a common notion of time. While the problem of synchronizing clocks in distributed systems has already received con- siderable...

Having access to an accurate time is a vital building block in all networks; in wireless sensor networks even more so, because wireless media access or data fusion may depend on it. Starting out with a novel analysis, we show that or- thodox clock synchronization algorithms make fundamental mistakes. The state-of-the-art clock synchronization algo-...

We present YETI, an Eclipse plug-in providing support for TinyOS development. YETI provides features well-known from development environments for other languages such as syntax highlighting, code completion and error detection. Furthermore, it includes an additional set of tools which are designed to ease the TinyOS development process for both new...

Today's buildings account for a large fraction of our en-ergy consumption. In an effort to economize scarce fossil fu-els on earth, sensor networks are a valuable tool to increase the energy efficiency of buildings without severely reducing our quality of life. Within a smart building many sensors and actuators are interconnected to form a control...

Accurately synchronized clocks are crucial for many ap- plications in sensor networks. Existing time synchro- nization algorithms provide on average good synchro- nization between arbitrary nodes, however, as we show in this paper, close-by nodes in a network may be syn- chronized poorly. We propose the Gradient Time Syn- chronization Protocol (GTS...

We present YETI 1 , an Eclipse plug-in providing sup- port for TinyOS development. YETI provides features well- known from development environments for other languages such as syntax highlighting, code completion and error de- tection. Furthermore, it includes an additional set of tools which are designed to ease the TinyOS development process for...

Vehicular ad-hoc networks with inter-vehicular communica- tions are a prospective technology which contributes to safer and more ecient roads and oers information and enter- tainment services to mobile users. Since large real-world testbeds are not feasible, research on vehicular ad-hoc net- works depends mainly on simulations. Therefore, it is cru...

In this paper we argue that achieving symmetric errors is the key to an improved understanding of clock synchro-nization. We present a clock synchronization algorithm with drift compensation that implements this symmetric er-ror paradigm. The performance of the algorithm is evaluated by measurements in an indoor testbed using the TinyNode hardware...