Nuno Pereira

Software maintenance can be seen as the act of correct errors in the software and/or the addiction of new features. This is one of the most difficult and frequent jobs of a software engineer and one of the most important and expensive parts of software development. Maintaining a software is very complex mainly because before making the change to the program, software engineers need to find the location, or locations, where the changes will be made; in other words, first they need to understand the program. Real applications are always huge and sometimes these programs are old or were written by other person and it is difficult to find the location where the change will be applied. There are various techniques to find these locations minimizing the time spent, but this phase of software development continues to be one of the most expensive and longer. The objective is to combine Program Comprehension techniques like comment analysis and SDG visualization, creating a tool easy to use, that can simplify and decrease the time spent understanding a program.

This book focuses on the design of a 3rd Order CT-S? M where the integrator stages of the filter are implemented with Bipolar-Junction Transistors (BJT) differential pairs. These circuits are fully analyzed and the design method is carefully explained. The design method is validated through experimental measurements of several prototype circuits.

This book outlines the most important characteristics of IEEE 802.15.4 and ZigBee and how they can be used to engineer Wireless Sensor Network (WSN) systems and applications, with a particular focus on Quality-of-Service (QoS) aspects. It starts by providing a snapshot of the most relevant features of these two protocols, identifying some gaps in the standard specifications. Then it describes several state-of-the-art open-source implementations, models and tools that have been designed by the authors and have been widely used by the international community. The book also outlines the fundamental performance limits of IEEE 802.15.4/ZigBee networks, based on well-sustained analytical, simulation and experimental models, including how to dimension such networks to optimize delay/energy trade-offs.