Hierarchical Routing in Low-Power Wireless Networks

Steen, M.R. van [Promotor

Gossip-Based Self-Management of a Recursive Area Hierarchy for Large Wireless SensorNets

A recursive multihop area hierarchy has a number of applications in wireless sensor networks, the most common being scalable point-to-point routing, so-called hierarchical routing. In this paper, we consider the problem of maintaining a recursive multihop area hierarchy in large sensor networks. We present a gossip-based protocol, dubbed PL-Gossip, in which nodes, by using local-only operations and by periodically gossiping with their neighbors, collaboratively maintain such a hierarchy. Since the hierarchy is a complex distributed structure, PL-Gossip introduces special mechanisms for internode coordination and consistency enforcement. Yet, these mechanisms are seamlessly integrated within the basic gossiping framework. Through simulations and experiments with an actual embedded protocol implementation, we demonstrate that PL-Gossip maintains the hierarchy in a manner that addresses all the peculiarities of sensor networks. More specifically, it offers excellent opportunities for aggressive energy saving and facilitates provisioning energy harvesting infrastructure. In addition, it bootstraps and recovers the hierarchy after failures relatively fast while also being robust to message loss. Finally, it can seamlessly operate on real sensor node hardware in realistic deployment scenarios and can outperform existing state-of-the-art hierarchy maintenance protocols. © 2010 IEEE

A Case for Hierarchical Routing in in Low-Power Wireless Embedded Networks

Hierarchical routing has often been mentioned as an appealing point-to-point routing technique for wireless sensor networks (sensornets). While there is a volume of analytical and high-level simulation results demonstrating its merits, there has been little work evaluating it in actual sensornet settings. This article bridges the gap between theory and practice. Having analyzed a number of proposed hierarchical routing protocols, we have developed a framework that captures the common characteristics of the protocols and identifies design points at which the protocols differ. We use a sensornet implementation of the framework in TOSSIM and on a 60-node testbed to study various trade-offs that hierarchical routing introduces, as well as to compare the performance of hierarchical routing with the performance of other routing techniques, namely shortest-path routing, compact routing, and beacon vector routing. The results show that hierarchical routing is a compelling routing technique also in practice. In particular, despite only logarithmic routing state, it can offer small routing stretch: An average of ~1.25 and a 99th percentile of 2. It can also be robust, minimizing the maintenance traffic or the latency of reacting to changes in the network. Moreover, the trade-offs offered by hierarchical routing are attractive for many sensornet applications when compared to the other routing techniques. For example, in terms of routing state, hierarchical routing can offer scalability at least an order of magnitude better than compact routing, and at the same time, in terms of routing stretch, its performance is within 10-15% of that of compact routing; in addition, this performance can further be tuned to a particular application. Finally, we also identify a number of practical issues and limitations of which we believe sensornet developers adopting hierarchical routing should be aware. © 2012 ACM

Proactive Gossip-Based Management of Semantic Overlay Networks

Much research on content-based P2P searching for file-sharing applications has focused on exploiting semantic relations between peers to facilitate searching. Current methods suggest reactive ways to manage semantic relations: they rely on the usage of the underlying search mechanism, and infer semantic relationships based on the queries placed and the corresponding replies received. In this paper we follow a different approach, proposing a proactive method to build a semantic overlay. Our method is based on an epidemic protocol that clusters peers with similar content. Peer clustering is done in a completely implicit way, that is, without requiring the user to specify preferences or to characterize the content of files being shared. In our approach, each node maintains a small list of semantically optimal peers. Our simulation studies show that such a list is highly effective when searching files. The construction of this list through gossiping is efficient and robust, even in the presence of changes in the network. Copyright © 2007 John Wiley & Sons, Ltd