The capacity of IEEE 802.11-based ad hoc networks is a critical issue because multi-hop communication requires additional capacity which is not available for transmitting application data. Furthermore, the distributed coordination function (DCF) of IEEE 802.11 causes various channel access problems which can lead to bad utilization of the channel capacity and to unfair capacity assignment for the connections in a network. In this paper we present an approach for calculating an upper bound capacity for a given fairness constraint. Our calculations can be used for networks with any node distribution, routing and traffic pattern. We also discuss the performance of the DCF in regard to the calculated upper bound capacity by simulating example scenarios. Our results show that a DCF is able to provide about 55% of the upper bound capacity.

The capacity of IEEE 802.11-based ad hoc networks is a critical issue because multi-hop communication requires additional capacity which is not available for transmitting application data. Furthermore, the distributed coordination function (DCF) of IEEE 802.11 causes various channel access problems which can lead to bad utilization of the channel capacity and to unfair capacity assignment for the connections in a network. In this paper we present an approach for calculating an upper bound capacity for a given fairness constraint. Our calculations can be used for networks with any node distribution, routing and traffic pattern. We also discuss the performance of the DCF in regard to the calculated upper bound capacity by simulating example scenarios. Our results show that a DCF is able to provide about 55% of the upper bound capacity.

The capacity of IEEE 802.11-based ad hoc networks is usually a critical issue because multi-hop communication requires additional capacity which is not available for transmitting application data. Further, the sharing of the available capacity among different connections should be fair. In this paper we present an approach for calculating an upper bound capacity for a given fairness constraint. Our approach can be used for networks with any node distribution, routing and traffic pattern. We also present simulation results for the upper bound capacity of an example scenario and compare it with the theoretical upper bound capacity calculated by Gupta and Kumar. Our results show that IEEE 802.11 provides a capacity which is considerable lower than the theoretical upper bound capacity

1 Prof Dr.-Ing. Klaus Jobmann, University of Hannover, Institut of Communications Engineering, Appelstr. 9a, 30167 Hannover, GERMANY, jobmann@ant.uni-hannover.de 2 Jr.-Prof. Dr.-Ing. Kyandoghere Kyamakya, University of Hannover, Institut of Communications Engineering, Appelstr. 9a, 30167 Hannover, GERMANY, kyandogh@ant.uni-hannover.de 3 Dipl.-Ing. Silke Feldmann, Institut of Communications Engineering, Appelstr. 9a, 30167 Hannover, GERMANY, feldmann@ant.uni-hannover.de 4 Dipl-Berufspäd. Dipl.-Ing (FH) Marc Krüger, Learning Lab Lower Saxony [L3S], Deutscher Pavillon 1.OG, Expo Plaza 1, 30539 Hannover, GERMANY, krueger@learninglab.de Abstract The Notebook -Seminar is a project-based learning scenario. An extensive project task has to be solved by a maximum of 20 students at the Institute of Communications Engineering (University Hannover) over a period of one semester. During this period, the students learn selected topics about communication technology (for example Bluetooth); thereby they acquire on one hand technical knowledge and on the other hand important methodological knowledge and soft-skills. These are for example how to work in teams, how to organize the work, or how to use the new media technologies for the engineering work. To develop these skills the “notebook-seminar” is organized with fixed learning tasks (information, planning, decision, carry out, control and assessment), specific learning tasks (e.g. producing a project plan), and learning support facilities (e.g. notebook).

Zusammenfassung: Das Notebook-Seminar stellte ein projektorientiertes Lernszenario dar, dass durch die Integration des Notebooks in die Lehre eine Verbesserung derselben erwirken soll. Methodischer Schwerpunkt ist das projektorientierte Lernen, welches neben der Vermittlung von Fachinhalten, auch die Vermittlung von fachübergreifenden Kompetenzen zum Ziel hat. Auf Basis einer ein Semester umfassenden Projektaufgabe werden Lernhandlungen von den Studierenden absolviert. Diese Lernhandlungen umfassen bestimmte Lernziele, die in Fach-, Methoden und Sozialkompetenz aufgeteilt sind. Diese Veröffentlichung beleuchtet die Vorgehensweise der Konzeption des NotebookSeminars anhand der Stellung des Notebooks im beruflichen Alltag. Anschließend wird das in die Praxis umgesetzte Konzept vorgestellt und die gemachten Erfahrungen, sowie die Ergebnisse der Evaluation diskutiert.

In the context of the UbiCampus project, the Notebook-seminar was developed in the Institute of Communications Engineering (Institut fur Allgemeine Nachrichtentechnik, IANT) at the University of Hannover. In this seminar the students worked in groups in order to provided a Bluetooth infrastructure for the rooms of the IANT. In this paper the Ubicampus project is described, as well as the most interesting results of the 3 groups that participated in the seminar.

Coloured Petri Nets are powerful models for different problems. This paper deals with the modelling of a Bluetooth communication network, piconet and scatternet. The developed Petri Net model is based on the Bluetooth Specification 1.1. The Petri Net model is structured in an hierarchical way. Thus, every part of the model, for example the channel model, is developed in a self-contained Petri Net. These parts are then connected to each other over predefined interfaces.The Petri Net model has been implemented using the tool Design/CPN. Simulation results that have been compared to empirical measurements confirm the accuracy of the model.

This paper presents the experimental evaluation of a Bluetooth-based positioning system. The method has been implemented in a Bluetooth-capable handheld device. Empirical tests of the developed considered positioning system have been realized in different indoor scenarios.The range estimation of the positioning system is based on an approximation of the relation between the RSSI (Radio Signal Strength Indicator) and the associated distance between sender and receiver. The actual location estimation is carried out by using the triangulation method. The implementation of the positioning system in a PDA (Personal Digital Assistant) has been realized by using the Software "Microsoft eMbedded Visual C++ Version 3.0".