A Multi-Hop 6LoWPAN Wireless Sensor Network for Waste Management Optimization

In the first part of this Thesis several Wireless Sensor Network technologies, including the ones based on the IEEE 802.15.4 Protocol Standard like ZigBee, 6LoWPAN and Ultra Wide Band, as well as other technologies based on other protocol standards like Z-Wave, Bluetooth and Dash7, are analyzed with respect to relevance and suitability with the Waste Management Outsmart European FP7 Project. A particular attention is given to the parameters which characterize a Large Scale WSN for Smart Cities, due to the amount of sensors involved and to the practical application requested by the project. Secondly, a prototype of sensor network is proposed: an Operative System named Contiki is chosen for its portability on different hardware platforms, its Open Source license, for the use of the 6LoW-PAN protocol and for the implementation of the new RPL routing protocol. The Operative System is described in detail, with a special focus on the uIPv6 TCP/IP stack and RPL implementation. With regard to this innovative routing proto col designed specifically for Low Power Lossy Networks, chapter 4 describes in detail how the network topology is organized as a Directed Acyclic Graph, what is an RPL Instance and how downward and upward routes are constructed and maintained. With the use of several AVR Atmel modules mounting the Contiki OS a real WSN is created and, with an Ultrasonic Sensor, the filling level of a waste basket prototype is periodically detected and transmitted through a multi-hop wireless network to a sink nodeope

EFFICIENT, LOCALITY-MAINTAINING NAMESPACE OPERATIONS IN A WRITE-OPTIMIZED FILE SYSTEM

There is a long-standing trade-off between good locality (fast directory traversals) and efficient namespace operations (efficient file or directory renames) in file systems. Traditional inode-based file systems have good rename performance but can fail to maintain locality, especially in the face of file system aging. On the other hand, full-path-indexed file systems ensure locality, however, renaming a directory needs to update all related full-paths, which is usually implemented as an expensive operation. No existing file system has both good locality and efficient namespace operations. This dissertation describes a new file system design that has both good locality and efficient namespace operations. In particular, we describe a novel synthesis of write-optimization, fullpath indexing, and operations on data structures. By directly manipulating the data structure, a full-path-indexed file system can efficiently update related full-paths in a rename. Moreover, with the technique, a full-path-indexed file system can clone a directory without traversing the directory. We implement this technique in BetrFS, a full-path-indexed, write-optimized, local file system for Linux. Compared to ext4, the widely used inode-based file system in Linux, the new version of BetrFS traverses the Linux source directory 9.47x faster and renames the same directory 1.09x faster. Meanwhile, the new version of BetrFS clones a directory faster than state-of-the-art file systems that support clones, such as Btrfs and XFS.Doctor of Philosoph