24.07.2008, Stefan Rührup

Beaconless Geographic Routing with Guaranteed Delivery in Wireless Networks

Beaconless geographic routing algorithms use position information for
routing in wireless ad hoc networks. They forward a message to the
location of the destination instead of a network address and need no
exchange of topology information. The basic principle of geographic
routing is greedy forwarding, where each node forwards the message to
the neighbor that minimizes the distance to the destination. This
requires the knowledge of the own position (GPS) and also the position
of the neighbors, which can be announced by exchanging beacon messages.
Beaconless routing does not require this information beforehand: The
forwarding node announces a message transmission and then its neighbors
contend for taking over this message. This kind of greedy forwarding
without beacons works well in dense networks, but fails in case of a
local minimum, i.e. if no neighbor is closer to the destination. There
are strategies to recover from such local minima, which, however,
require the knowledge of the neighborhood. We show that recovery from
local minima is possible with partial knowledge and how it can be
incorporated in the beaconless routing scheme. This enables a completely
reactive routing with guaranteed delivery based on position information.

17.07.2008, Jan Meyer

Garbage collection for sensor motes

The goal of this bachelor’s thesis is to provide Java garbage collection and its resulting benefits on sensor motes. In order to program motes, programmers would often have to learn
an unfamiliar language. To facilitate mote programming, it is an attractive alternative to
program in Java, which is already a widespread and often referred to as an easy to learn
language. Furthermore, the Java language comes with integrated garbage collection, which
disburdens the programmer from large parts of manual memory management. This thesis
examines common garbage collection techniques both in theory and practice.
This thesis emerged from the TakaTuka project, currently in development at the University
of Freiburg under the supervision of Prof. Dr. Christian Schindelhauer. Different algorithms
were chosen to be implemented and integrated into the TakaTuka virtual machine. Several
working garbage collectors are introduced, which are designed to run in environments
with very limited hardware resources and keep used memory to a minimum. The proposed
garbage collectors are written entirely in Java, but make use of several native methods written in C to manipulate low-level structures in memory and to provide functionality which is not possible to implement in pure Java. The collectors run without occupying a thread of
their own.
The most important desired goals to achieve in the described garbage collectors were:
• Garbage collection written entirely in Java
• Low memory requirements
• Garbage collection must be runnable even without thread support

(bachelor thesis)

10.07.2008, Hui Sheng

Die Simulation von 3MANET mit OMNet++

Dieser Vortrag betrifft die Simulation des Routingprotokolls (3MANET), das ein neues hybrides Routingprotokoll ist. Die Simulation wird in der Simulationsumgebung OMNet++ durchgeführt, welche die Generierung komplexer Modelle aus grundlegenden Einheiten unterstützt. Das Simulieren dieses Protokolls ist notwendig, um eine erfolgreiche Implementierung durchführen zu können.


26.06.2008, Damian Spyra

Radio drivers for sensor motes

In dieser Bachelorarbeit wurde ein Treiber für ein CC1000 Funkmodul der Firma Chipcon entwickelt, der die drahtlose Kommunikation zwischen Sensoreinheiten in einem Sensornetzwerk gewährleisten soll. Ziel der Arbeit war die Entwicklung eines Treibers, der später als ein Teil einer selbstentwickelten Java-Virtual-Machine auf einem Prozessor-Board dienen soll. Als Hardware-Plattform wurde das Mica2-Board der Firma Crossbow verwendet, das über ein Chipcon CC1000 Funkmodul und einen ATmega128L Mikrocontroller verfügt. Weiterhin beinhaltet diese Arbeit eine Beschreibung der technischen Funktionalität des CC1000 Funkmoduls sowie der Hardware-Komponenten mit welchen es kommuniziert. Für die Konfiguration und Initialisierung der Hardware-Komponente wurden Software-Routinen implementiert. Im Weiteren wurde ein Netzwerkprotokoll implementiert, das für die Aufgaben der physikalischen, der Verbindungs- und Teile der MAC-Schicht (Medium-Access-Control- Schicht) zuständig ist.

(Bachelor Thesis)

Mohannad Zalloom

TakaTuka on SunSpot

SunSpot (Small Programmable Object Technology) is small wireless sensor mote programmed by Java, the idea of having Java programming language running on motes is the need of hight level programing language which is more understandable by the developers. Also separate them from low level hardware and let them focus on application features and functionalities. The mote (SunSpot) is unlike other motes, by having Squawk Java Virtual Machine which developed by Sun Microsystems specially for embedded systems and small devices. Squawk differ from other virtual machines that the core is
written mostly in Java.
TakaTuka is virtual machine (still in early stages) developed for embedded systems and also adapt the idea of having Java on motes. TakaTuka is coded to run on motes have AVR microcontrollers like mica2, but SunSpot motes has ARM9 microcontroller so TakaTuka should be modified to run also on motes contain ARM microcontrollers.
My Project will focus mainly on modifying and compiling TakaTuka to be able to run on motes having ARM microconrollers, this will be followed by running some applications testing TakaTuka.

(Master Thesis)

12.06.2008, Volker Poplavski

Implementation of a mobile Ad-Hoc-network using Landmark-Routing on single-board computers

3Manet is a mobile ad-hoc network implementation for PCs with WLAN-Interfaces. It is based on Landmark-Routing and is able to cope with large networks of multiple nodes. In this thesis a additional computing platform was made available for the the 3Manet routing protocol. The Gumstix single-board computer platform offers a high degree of mobility at low per unit costs and is therefore suited for large scale experiments in mobile ad-hoc- networking. The gumstix platform was evaluated for the use with 3Manet, the existing
3Manet software was implemented and adapted to the platform, furthermore a monitoring system was conceived and implemented to monitor network behaviour in real time.

(Diploma Thesis)

05.06.2008, Marek Talik

Delay Tolerant Networking in Mobile Robot Networks

Mobility in wireless networks can be helpful or harmful. It can cause temporary network interruption, but also help to deliver a packet, especially if there is some knowledge about future movement. Traditional protocols for end-to-end communication such as TCP fail in case of temporary network disconnection. Instead, various techniques have been proposed under the term "delay-tolerant networking".

One of the solutions is the Bundle Protocol proposed by the IETF research group on delay tolerant networking. The Bundle Protocol resides as an additional layer between TCP and the application layer. In general, this module offers functionality of “storing” packets when communication to destination is not possible and “forwarding” packets when path to destination is available. Though the Bundle protocol splits up the end-to-end communication into smaller parts between so-called bundle endpoints, a mechanism for selecting the next bundle endpoints is not specified. Here, the prediction of mobility patterns can be an solution.

In order to overcome some drawbacks existing in Bundle Protocol we propose a lightweight transport layer solution as a replacement for TCP.

05.06.2008, Christian Kretschmer

Delay Tolerant Routing in Wireles Ad hoc Networks

Multi-hop routing in networks with moving nodes represents a big challenge, because of changing links and temporary network partition. Conventional routing protocols for ad hoc networks can be descibed as either proactive or reactive. They try to maintain routing tables or discover a path to the destination by flooding the network. Both approaches have limitations in scenarios where network connection cannot be guaranteed.

In my introductory talk I will explain the basic routing strategies for wireless networks and how existing protocols address the problem of network partition.
The goal is to develop a routing protocol that supports immediate message delivery and also slow distribution of messages with in-network storage for temporary disconnected networks.

29.05.2008, Gayatri Tribhuvan

Topology Management in Peer-To-Peer Networks

(Kick-off presentation diploma thesis)

18.03.2008, Simon Zimmer

InSANe - Integrated Storage Area Network Extension

Prototyp eines Read-Write-Codierung-Systems in C++

Due to the exponential growth of data worldwide, efficient techniques have to be developed to maintain the data availability and integrity especially in storage area networks. Starting with Reed-Solomon Codes in 1960, the so called "Erasure resilent coding" have an undeniable role and are used in many different application areas like satellite communication, multimedia devices or RAID-Storage-Systems. Since hard disk drive failures are in order of business in large storage area networks, data recovery should not cause a downtime or not even a performance drop of the involved storage system. Therefore the erasure coding scheme should ensure data availability even under error conditions. While this is true for reading operations per definition, write operations will fail if not all drives are online. The Read-Write-Codes used in this diploma thesis overcome this problem by adding additional capabilities of write redundancy and online migration between different Read-Write-Coding schemata.

Based upon these RW-Codes I will present the results of my diploma thesis implementing such a prototype of a Read-Write-Coding-System in C++.

(Diploma Thesis)

14.02.2008, Sajid Sikandar

Mobility and Network Capacity in Ad hoc Networks

Communication is the main requirement why mobile ad-hoc networks are in
research on such a great scale. Not just communication but efficient
communication. There are several different possibilities on how to carry
out communication between the nodes of a MANET. Among other hurdles in
this issue mobility is right on top of the list, which makes the process
far complex. The research is being done to handle this problem, in fact
trying to turn mobility in the favor of communication. Yes, its’ true!
Mobility can be helpful.

In a normal MANET nodes communicate in pairs of source and destination
nodes. Due to direct communication between nodes, interference occurs,
causing failure to other transmissions. To avoid this, mobility is taken
into account in the form of relay nodes. Now the sources can drop their
packets to relay nodes that move around the network like other nodes and
deliver the packets to destinations node when encountered. This way
mobility increases the capacity of the network thus helps in
communication. We are working on a few algorithms based on the same
principle. These algorithms consist of different strategies to keep
track of other nodes in the network and to communicate between them.

24.01.2008, Faisal Aslam

A Java based environment for wireless sensor nodes

Most of the embedded system programmers have to deal with low level languages like assembly, C or NesC. These languages have limited design concepts, large development cycle, higher complexity, and are difficult to learn. In contrast, most schools tough Java as first programming language and many of well known design pattern exist for it. Therefore, java is easier to use, has smaller development cycle, and a large development community. Existing Java Virtual Machines (JVMs) are either too big to fit in small embedded devices, with few Kilo bytes of program memory or they compromise in Java semantics. Our aim is to design a new JVM which is small enough to fit in few Kilo bytes and has full Java support. For portability and ease of development we will develop most of JVM in Java. The resulting system will be tested on crossbow motes mica2 and will be later ported on almost all well known wireless sensor motes. We plan to write all the drivers in Java hence making it easier to develop drivers for future platforms. Our JVM will run on "bare metal" that implies that a device will not need an operating system to run Java.

10.01.2008, Amir Alsbih

Selbstverändernde Kryptoviren

Es werden die Ziele der Diplomarbeit erläutert: Die Grundidee des Virus, zu erwartende Problemstellungen und aktuelle Techniken der Herrsteller von Antivirensoftware.

(Kick-Off-Präsentation Diplomarbeit)

20.12.2007, Melinda Chulu

Modeling and Analysing Efficient and Secure Network Traffic Anonymization Algorithms

Many low-latency anonymous networks exist; many theoretical in nature and
some practically implemented. Much literature has been written on the capabilities
and advantages these systems provide and equally many papers on their weaknesses
and vulnerabilities, especially against a global passive adversary. Security, efficiency
and scalability are used as the examination criteria in this thesis. We look at many
well known variations of low-latency networks based on the idea of Chaum mixes.
We venture into the area of Private Information Retrieval in an effort to establish
whether the information theoretic security provided by the protocol can be combined
with the usability and acceptable latency in mixes to provide the ultimate low latency
anonymous system.
We then bring to light an Information theoretic secure yet efficient system that
was developed and proposed for adoption but since its inception has seen no further
work. One reason is that it was overshadowed by the hype TOR created at its
unveiling as the system that offered all the properties that an ideal low-latency
network should posses. But another more widely unknown reason is that the backlash
of the September 11th, 2001 terrorist attacks caused sponsors of such initiatives to
gradually withdraw their funding with the justification that anonymity was afforded
not only to well meaning users but to those with equally nefarious purposes.
However a prototype of this software is available as open source and should
afford if not a renewed practical interest in the system then at least a theoretical

(Master Thesis)

20.09.2007, Markus Beh

Mechanismen zur konsistenten Verteilung von Datenblöcke in unzuverlässigen Netzwerken

Es wird auf das Problem der Verteilung einer Reihe zusammengehöriger Datenblöcke im Kontext vernetzer Systeme eingegangen. Wesentlich ist hierbei die Annahme unzuverlässiger Kommunikationsverbindungen. Vor diesem Hintergrund werden spezielle Mechanismen benötigt die eine konsistente Verteilung der Datenblöcke erlauben.
Es wird ein Verfahren vorgestellt werden, das diesen Anforderungen gerecht wird. Basierend auf redundanten Read-Write-Kodierungen erlaubt es eine Verteilung zusammengehöriger Datenblöcke auch über unzuverlässige Kommunikationskanäle (z.B. dem Internet).


30.07.2007, Atef Abdel Rahman

Implementation of a Massively Parallel Wireless Sensor Network

In this work wireless sensor networks consisting of a very large number of sensor nodes are considered. Furthermore, it is assumed that the network is to be deployed at a remote region and works for a long duration without any human intervention. During the experiments carried out useful experimental (log) data is collected. This log data has to be communicated to a central computer or base station so that it could be analyzed and used by humans. The collecting data  during the experiment saves power and network bandwidth. It is desirable to store data temporarily in the memory of the sensor nodes during the experiment and collect it after the end of experiment or after a fixed time period. Our objective is to show such an offline strategy to get the log data from the sensor nodes perserves energy. This strategy requires little memory, computation and human intervention. Furthermore, it is independent from the type, the number of sensor nodes used as well as the kind of sensing data gathered. The logging application has no dependency on data collected. It should be dynamic and change the provided display depending upon data available. Since a sensor has only small memory, memory reserved for logging. The logging application uses priority based log overwriting when the amount of log data collected exceeds memory reserved for data logging. The time complexity of the used strategy is $O(log(n))$, where $n$ is the number of fixed sized log blocks called entry in the memory.  A priority based linked list is used to store the log data. Each element of this linked list contains a FIFO queue having log entries corresponding to priority of linked list elements. A new log element is added at the end of the corresponding FIFO queue with right priority. To dynamically displayed data, the Extensible Markup Language (XML) and Extensible Stylesheet Language (XSL) are used. With XML and XSL dynamic HTML is generated.  The XML format definded is independent from the log data collected. XSL makes sure to display the data without consideration its size. In summary, the logging application collects log data independent of the developed sensor hardware and the type of experiments carried out using  sensor memory and computational resources efficiently.

(Diploma Thesis)

14.06.2007, Olaf Flaschel

Network Protocols for Large-Scale Mobile Ad Hoc Networks

Most of today's laptops are equipped with a built-in WLAN device. These
devices can run in one of two modes, infrastructure mode or ad hoc mode.
Both of them have their disadvantages. In infrastructure mode all communication
goes through an access point. This makes the network vulnerable
to a single point of failure, and additionally, the access point is an intrinsic
bottleneck for communication in the network. In ad hoc mode participants
can only communicate with other participants that are in radio range of
their WLAN device. Mobile Ad Hoc Networks (MANETs) are determined
to solve these problems. They use ad hoc network protocols to build up
infrastructure independent, self-configuring wireless networks. Exsisting ad
hoc network protocols often scale poorly and or have performance problems
when nodes change positions frequently.
The purpose of this project thesis is the implementation of a hybrid ad
hoc network protocol called 3MANET that is both scalable and robust towards
high node mobility. Embedded into IPv6, 3MANETs routing layer
is based on a combination of landmark routing and the hierarchical layer
graph. Therefore, landmark addresses should be short and routing tables
small. Weighted consistent hashing is used for landmark address look-up
and to distribute landmark addresses evenly among nodes in the network.
Together with the landmarking system a graph metric based on link failure
probabilities ensures that short stable routes are preferred. Finally, a
message box system is provided to distribute control information between

24.05.2007, Frederik Löser

Design and Implementation of Routing and Packet-Forwarding in a Large-Scale Mobile Ad Hoc Network

There are lots of different kinds of technologies using wireless transmission
for communication purposes. However, most of these technologies have the
drawback that they are dependent on some kind of infrastructure. Therefore,
it will be the case that communication is not possible anymore if the
respective infrastructure is suddenly out of order for unknown reasons. One
possible solution to manage such kind of situation and to reestablish
communication could be the construction of a mobile ad hoc network. In this
diploma thesis a hybrid routing protocol called 3MANET is presented that
enables routing and packet forwarding in a large scale mobile ad hoc network.

(Master Thesis)

21.02.2007, Christian Schindelhauer

3-Nuts: An extremely robust Peer-to-Peer Overlay based on randomized graphs.

14.02.2007, Frederik Löser

First presentation of master thesis: 3MANET

08.02.2007, Arne Vater

EgoFish: Topology Management in Peer-to-Peer Networks

In recent years, peer-to-peer networks evolved from simple server-based file-sharing systems to a variety of decentralized networks. While the most frequently used application is still file-sharing, other such as distributed databases, distributed computing or multiplayer gaming are promising applications. To enable elementary functions such as routing, searching and data distribution, peer-to-peer networks use an overlay topology. This overlay topology is the main distinguishing feature of current peer-to-peer systems and is critical for their efficiency, cost and robustness. However, in general such topologies do not consider the locality of two peers, when being build up. Locality describes, how similar two peers are with respect to the peer-to-peer network's application. E.g. two nodes with databases of similar subjects may be close-by in the topology.
In this work, we develop a theoretical basis and research methods to build up locality based topologies for peer-to-peer networks. The goal is a locality based overlay topology, which is distributed built and maintained by local operations of peers, and which converges to the optimal global topology.

24.01.2007, Christian Hornkamp

Mobile Sensornetzwerke in der Büroumgebung

Es wurde mit Hilfe der Mote-Technologie experimentell ein mobiles Sensornetzwerk untersucht. Im Vortrag werden Netzwerk-HArdware und das speziell darauf angepasste Betriebsystem vorgestellt. Ausserdem wird eine kurze Einführung in die Programmiersprache des Betriebsystems TinyOS gegeben. Weiterhin werden zwei Implementierungen für ein mobiles Szenario vorgestellt und deren praktische Ergebnisse besprochen.


17.01.2007, Faisal Aslam

Sensor Networks

More S-MAC and C-MAC improvements.

10.01.2007, Faisal Aslam

Sensor Networks

Improvement proposals on the S-MAC and C-MAC protocols.

20.12.2006, Atef Abdel Rahman

Implementation of a Massively Parallel Wireless Sensor Network

First presentation of diploma thesis.

13.12.2006, Chia Ching Ooi

Smart Teams

Overview on Smart Teams research project.

22.11.2006, Faisal Aslam

Sensor Networks

Overview on wireless sensor network protocols

31.10.2006, Markus Beh

RW-Codes for Distributed File Systems

First presentation of diploma thesis.

15.11.2006, Christian Schindelhauer


A new Peer-to-Peer Network using network coding for high data availability and fast data distribution

31.10.2006, Markus Beh

RW-Codes for Distributed File Systems

First presentation of diploma thesis.

25.10.2006, Arne Vater

SIGCOMM 2006 (3)

Summary of the ACM SIGCOMM conference 2006 in Pisa (12. - 14.09.2006).
Part three.

18.10.2006,  Faisal Aslam

Wireless Sensors

A not so small demonstration of Wireless sensors.

13.10.2006, 9:30 am, Arne Vater

SIGCOMM 2006 (2)

Summary of the ACM SIGCOMM conference 2006 in Pisa (12. - 14.09.2006).
Part two.

29.09.2006, 10 am, Arne Vater

SIGCOMM 2006 (1)

Summary of the ACM SIGCOMM conference 2006 in Pisa (12. - 14.09.2006).
Part one.

20.09.2006, Christian Schindelhauer

Worst Case Mobility Models

Presentation of the paper: Worst Case Mobility in Ad Hoc Networks, by Christian Schindelhauer, Tamas Lukovszki, Stefan Rührup, Klaus Volbert, appeared on SPAA 2004

08.08.2006, Christian Schindelhauer

In this Oberseminar we present the research goals, the fundings, the methods and the projects of the research group.