Resilient Wireless Sensor Networks Using Topology Control: A Review

Wireless sensor networks (WSNs) may be deployed in failure-prone environments, and WSNs nodes easily fail due to unreliable wireless connections, malicious attacks and resource-constrained features. Nevertheless, if WSNs can tolerate at most losing k − 1 nodes while the rest of nodes remain connected, the network is called k − connected. k is one of the most important indicators for WSNs’ self-healing capability. Following a WSN design flow, this paper surveys resilience issues from the topology control and multi-path routing point of view. This paper provides a discussion on transmission and failure models, which have an important impact on research results. Afterwards, this paper reviews theoretical results and representative topology control approaches to guarantee WSNs to be k − connected at three different network deployment stages: pre-deployment, post-deployment and re-deployment. Multi-path routing protocols are discussed, and many NP-complete or NP-hard problems regarding topology control are identified. The challenging open issues are discussed at the end. This paper can serve as a guideline to design resilient WSNs

Fault-tolerant relay deployment for k node-disjoint paths in wireless sensor networks

Ensuring that wireless sensor networks (WSNs) are robust to failures requires that the physical network topology will offer alternative routes to the sinks. This requires sensor network deployments to be planned with an objective of ensuring some measure of robustness in the topology, so that when failures occur that routing protocols can continue to offer reliable delivery. Our contribution is a solution that enables fault-tolerant WSN deployment planning by judicious use of a minimum number of additional relay nodes. A WSN is robust if at least one route to a sink is available for each remaining sensor node after the failure of up to k-1 nodes. In this paper, we define the problem for increasing WSN reliability by deploying a number of additional relay nodes to ensure that each sensor node in the initial design has k node-disjoint paths to the sinks. We present GRASP-ARP, a centralised offline algorithm to be run during the initial topology design to solve this problem. We have implemented this algorithm and demonstrated in simulation that it improves the efficiency of relay node placement for k node-disjoint paths compared to the most closely related published algorithms

A fault-tolerant relay placement algorithm for ensuring k vertex-disjoint shortest paths in wireless sensor networks

Wireless sensor networks (WSNs) are prone to failures. To be robust to failures, the network topology should provide alternative routes to the sinks so when failures occur the routing protocol can still offer reliable delivery. Our contribution is a solution that enables fault-tolerant WSN deployment planning by judicious use of a minimum number of additional relays. A WSN is robust if at least one route with an acceptable length to a sink is available for each sensor node after the failure of any nodes. In this paper, we define the problem for increasing WSN reliability by deploying a number of additional relays to ensure that each sensor node in the initial design has k length-bounded vertex-disjoint shortest paths to the sinks. To identify the maximum k such that each node has k vertex-disjoint shortest paths, we propose Counting-Paths and its dynamic programming variant. Then, we introduce GRASP-ARP, a centralised offline algorithm that uses Counting-Paths to minimise the number of deployed relays. Empirically, it deploys 35% fewer relays with reasonable runtime compared to the closest approach. Using network simulation, we show that GRASP-ARP’s designs offer a substantial improvement over the original topologies, maintaining connectivity for twice as many surviving nodes after 10% of the original nodes have failed

Fault-tolerant relay deployment based on length-constrained connectivity and rerouting centrality in wireless sensor networks

Wireless Sensor Networks (WSNs) are prone to failures. To be robust to failures, the network topology should provide alternative routes to the sinks so when failures occur the routing protocol can still offer reliable delivery. We define l-CRC, a new centrality index which measures a node’s importance to connectivity and efficient delivery in the network. We then use this centrality index to concentrate on the most important nodes, providing alternative paths around the nodes with high centrality. Varying l-CRC allows us to trade off cost for robustness. We introduce GRASP-ABP, a local search algorithm for initial robust topology design. We evaluate the algorithm empirically in terms of the number of additional nodes it suggests and its runtime. We then evaluate the robustness of the designs against node failures in simulation, and we demonstrate that the centrality-based GRASP-ABP’s designs are able to offer reliable delivery, comparable to competitor algorithms, but with fewer additional relays and faster runtime

Robotic Wireless Sensor Networks

In this chapter, we present a literature survey of an emerging, cutting-edge, and multi-disciplinary field of research at the intersection of Robotics and Wireless Sensor Networks (WSN) which we refer to as Robotic Wireless Sensor Networks (RWSN). We define a RWSN as an autonomous networked multi-robot system that aims to achieve certain sensing goals while meeting and maintaining certain communication performance requirements, through cooperative control, learning and adaptation. While both of the component areas, i.e., Robotics and WSN, are very well-known and well-explored, there exist a whole set of new opportunities and research directions at the intersection of these two fields which are relatively or even completely unexplored. One such example would be the use of a set of robotic routers to set up a temporary communication path between a sender and a receiver that uses the controlled mobility to the advantage of packet routing. We find that there exist only a limited number of articles to be directly categorized as RWSN related works whereas there exist a range of articles in the robotics and the WSN literature that are also relevant to this new field of research. To connect the dots, we first identify the core problems and research trends related to RWSN such as connectivity, localization, routing, and robust flow of information. Next, we classify the existing research on RWSN as well as the relevant state-of-the-arts from robotics and WSN community according to the problems and trends identified in the first step. Lastly, we analyze what is missing in the existing literature, and identify topics that require more research attention in the future

Integrated placement and routing of relay nodes for fault-tolerant hierarchical sensor networks

In two-tiered sensor networks, using higher-powered relay nodes as cluster heads has been shown to lead to further improvements in network performance. Placement of such relay nodes focuses on achieving specified coverage and connectivity requirements with as few relay nodes as possible. Existing placement strategies typically are unaware of energy dissipation due to routing and are not capable of optimizing the routing scheme and placement concurrently. We, in this thesis, propose an integrated integer linear program (ILP) formulation that determines the minimum number of relay nodes, along with their locations and a suitable communication strategy such that the network has a guaranteed lifetime as well as ensuring the pre-specified level of coverage (ks) and connectivity (kr). We also present an intersection based approach for creating the initial set of potential relay node positions, which are used by our ILP, and evaluate its performance under different conditions. Experimental results on networks with hundreds of sensor nodes show that our approach leads to significant improvement over existing energy-unaware placement schemes