Network coding has been successfully used in the past for efficient broadcasting in wireless multi-hop networks. Two coding approaches are suitable for mobile networks; random linear network coding (RLNC) and XOR-based coding. In this paper, we focus on the problem of multiple source broadcasting in mobile ad hoc networks. We make the observation that RLNC provides increased resilience to packet losses compared with XOR-based coding. We develop an analytical model that justifies our intuition. However, the model also reveals that combining RLNC with probabilistic forwarding, which is the approach taken in the literature, may significantly impact RLNC's performance. Therefore, we take the novel approach to combine RLNC with a deterministic broadcasting algorithm in order to prune transmissions. More specifically, we propose a connected dominating set-based algorithm that works in synergy with RLNC on the “packet generation level.” Since managing packet generations is a key issue in RLNC, we propose a distributed scheme, which is also suitable for mobile environments and does not compromise the coding efficiency. We show that the proposed algorithm outperforms XOR-based as well as RLNC-based schemes even when global knowledge is used for managing packet generations.

It has been observed that opportunistic networks exhibit a highly unbalanced traffic load distribution, mainly because of the heterogeneity in mobility and the greedy routing decisions, leading to packet drops due to storage constraints. The existing strategies rely either on fairness techniques or on diverting traffic to alternative routes in order to control congestion. The result is a dilemma between performance and fairness. In this work, we introduce a congestion control mechanism that provides a tunable trade-off between efficiency and fairness. We rely on the social preferences of the nodes for dynamically tuning the aforementioned trade-off. Our simulations show that the proposed algorithm achieves high delivery ratio, combined with low end-to-end delay and routing cost, without sacrificing fairness under high traffic load.

One of the dominant approaches in coping with the intermittent connectivity of opportunistic networks is packet replication. However, the need for a distributed operation forces the nodes carrying a message copy to make replication decisions without taking into account the replication state of other nodes. This strategy can lead to the creation of an excessive number of replicas thus exhausting the limited node resources such as energy and storage capacity. In this paper, we propose a simple yet efficient method which, without incurring any additional cost, allows nodes to share information about the replication process in order to avoid unnecessary replication. Our approach significantly reduces the routing cost without sacrificing delivery rate. Furthermore, it is generic in the sense that it can be implemented regardless of the utility metric used for making the replication decision. We validate the performance gains of our algorithm through analysis as well as extensive simulations.

Multiple Description coding (MD) has been proved to be very efficient for video multicast over random networks when combined with network coding. However, in the case where heterogeneous receivers are present in the network, the impact of the method is bounded by the fact that the solution to the inherent rate allocation problem is based on a compromise between low and high bandwidth receivers. To tackle this problem, we propose a novel video multicast scheme that enhances the combination of MD and network coding with a mechanism that allows all intermediate nodes to actively participate in MD coding by adjusting the size of the video descriptions. In this way, it is possible to tune the rate of the transmitted video stream in order to meet the needs of each receiver. The proposed method significantly improves the quality of the video delivered to all the receivers in the network, regardless of their heterogeneity.