In this paper, we investigate schemes for energy-efficient multi-hop broadcasting in large-scale dense Wireless Sensor Networks. We begin with an initial simplified study of the schemes for relay selection. Our first finding is that MPR-based (Multipoint Relay) mechanisms work poorly in a dense network while the recently proposed Multicast Protocol for Low power and Lossy Networks (MPL) protocol based on Trickle performs better. However, Trickle requires to overhear packet retransmissions in the vicinity, while sensor nodes try to avoid overhearing by periodically waking up and going to sleep to save energy.

In this paper, we study current routing issues in Low Power and Lossy Networks (LLNs) and propose two enhancements to the RPL routing protocol. First, we focus on the establishment and maintenance of the Destination Oriented Directed Acyclic Graph (DODAG) for upward traffic and propose a low overhead mechanism that guarantees the absence of loops and quickly reacts to topology changes using a link reversal algorithm. Second, we propose either proactive or on demand establishment of downward routes from the DODAG root to leaf nodes. Simulation results show that our enhancements reduce the convergence time, generate less routing messages, and improve the performance in a network subject to link failures.

We consider extended LANs composed of two different parts: a static one with hosts and routers, and a dynamic one with mobile hosts. We propose a scheme for interconnecting the two parts that builds on OLSR to establish compact routing tables, by aggregating addresses into prefixes whenever possible. Prefix advertisements imply possible conflicts of prefixes covering the same address ranges, thus we propose an extension to OLSR for solving this issue. We report on performance improvement measured on an experimental testbed.

Performance and reliability of content access in mobile networks is conditioned by the number and location of content replicas deployed at the network nodes. In this work, we design a practical, distributed solution to content replication that is suitable for dynamic environments and achieves load balancing. Simulation results show that our mechanism, which uses local measurements only, approximates well an optimal solution while being robust against network and demand dynamics. Also, our scheme outperforms alternative approaches in terms of both content access delay and access congestion.

Performance and reliability of content access in mobile networks is conditioned jointly by the number and location of content replicas deployed at the network nodes. The endeavour of this work is to address such an optimization problem with a distributed, lightweight solution that handles network dynamics. We devise a mechanism that lets nodes share the burden of storing and providing content, so as to achieve load balancing, and decide whether to replicate or drop the information so as to adapt to a dynamic content demand and time-varying topology. Simulation results show that our mechanism, which uses local measurements only, is: (i) extremely precise in approximating an optimal solution to content placement and replication; (ii) robust against network mobility; (iii) flexible in accommodating variation in time and space of the content demand.

We investigate the problem of spreading information contents in a wireless ad hoc network. In our vision, information dissemination should satisfy the following requirements: (i) it should result in a desirable distribution of information replicas in the network and (ii) the information should be evenly and fairly carried by all nodes in their turn. In this paper, we show that these goals can be achieved by simple cache-and-forward mechanisms inspired by well-known node mobility models, provided that a sufficient number of information replicas are injected into the network. The proposed approach works under different network scenarios, is fully distributed and comes at a very low cost in terms of protocol overhead.

In this work we define and study a new model for the caching problem in a heterogeneous wireless network under a flash-crowd scenario. Using non-cooperative game theory, we cast the caching problem as an anti-coordination game. We start by defining the social optimum in the general case and then focus on a two-player game to obtain insights into the design of efficient caching strategies. Based the theoretical findings, our current work focuses on the development of strategies to be implemented in a practical network setting.