Interaction patterns for resilient intermittently-connected static sensor networks

Abstract

Abstract-We study systems of static and mobile sensors in which the participating nodes are disconnected. At any given time, only selected groups of nodes are able to interact. In this paper, we restrict attention to pairwise interactions of static nodes placed on a regular grid. Nodes must agree on a schedule that specifies when and in what order these interactions take place. Our focus is the impact this interaction schedule has on systemwide properties, such as information propagation and resiliency. We show how interaction schedules with varying properties can be built from simple patterns and we discuss the choice of suitable patterns on sample illustrative scenarios. I. CONTEXT AND PROBLEM DEFINITION A. Energy constraints and intermittent connectivityThe lifespan of a sensor network is typically determined by the amount of available energy in the nodes and the rate with which the energy is consumed. Technological constraints and cost make it difficult to increase the amount of energy in the nodes. Communication is one of the most significant energy consuming activities of a sensor node. A common method to extend the lifespan of a sensor network is to have the sensors spent a significant percentage of time in low energy consumption (sleep) mode [1]. Depending on the "depth" of the sleep mode, a node might be capable of sensing but it is not capable of sending or receiving. When a node is fully awake, it can send and transmit but consumes a significant amount of power which drastically reduces its lifespan.The overall objective is to satisfy the requirements of a network's mission while minimizing the amount of energy consumed. To this end, we aim to reduce the energy cost of communication by reducing the time spent in the fully awake mode and by limiting the overhead and interference. More specifically, we eliminate the need for media access control (MAC) at runtime by orchestrating the exchanges between agents offline before deployment in a way that only two agents take part in any one exchange. Furthermore, these exchanges are scheduled (in time and possibly communication channel) so that no other node within the interference range can transmit at the same time. In such a scheme, nodes can transmit without a prior channel arbitration that is normally required to address the hidden terminal problem. This is especially important in networks with high propagation latency, such as B. A network model based on scheduled meetingsThe nature of the networks described above leads to a model in which nodes interact in local groups and do not attempt to reach specific nodes outside their group through long distance mechanisms like multi-hop routing. There are other scenarios in which this form of communication-group based and local only-is appropriate, including cases where nodes are mobile. In this paper, we focus on pairwise meetings of static sensor nodes laid out on a regular grid, but the model we propose is more general and can be applied to non regular topologies, possibly with meetings of more than two nodes...

Local Algorithms for Robust Mission Realization in Large-Scale Disconnected Networks

“…To properly describe and evaluate our algorithms, we have defined a model of interaction and cooperation [1]. In this section, we only introduce aspects of the model relevant to the paper.…”

“…Similarly, agents in our model work independently and only interact when needed, for instance to confirm their observations with neighbors or to propagate information. This form of "disconnected network" presents multiple benefits, especially in terms of communication overhead and energy consumption (see [1] for details). In this model, agents need to take proactive steps to enable communication, like moving closer to a neighbor, aiming an orientable antenna, waking up from power-saving modes, etc.…”