In this paper, we present a model that estimates the time duration of routes formed by several intermediate nodes in mobile multi-hop ad-hoc networks. First, we analyze a 3-node route, where only the intermediate node is in movement while source and destination nodes remain static. From this case, we show how route duration is affected by the initial position of the intermediate node and the size of the region where it is located. We also consider a second case where all nodes of 3-node routes are mobile. Based on extensive analysis of these routes, we determine the PDF of route duration under two different mobility models. This PDF can be determined by either analytical or statistical methods. The main contribution of this paper is that the time duration of a route formed by N intermediate nodes can be accurately computed by considering the minimum route duration of a set of N routes of 3 nodes each. Simulation work was conducted using the NS-2 network simulator to verify the accuracy of the proposed model and to compare it with other proposals found in the literature. We show that our model is in better agreement with simulation results as compared with other models.Results from this work can be used to compute overhead signaling during route-maintenance of unicast and multicast routing protocols for mobile ad-hoc networks. Similarly, because route duration decreases with route length, this study can be used to scale the network size up/down.
In this work, we propose that packets travelling across a wireless sensor network (WSN) can be seen as the active agents that make up a complex system, just like a bird flock or a fish school, for instance. From this perspective, the tools and models that have been developed to study this kind of systems have been applied. This is in order to create a distributed congestion control based on a set of simple rules programmed at the nodes of the WSN. Our results show that it is possible to adapt the carried traffic to the network capacity, even under stressing conditions. Also, the network performance shows a smooth degradation when the traffic goes beyond a threshold which is settled by the proposed self-organized control. In contrast, without any control, the network collapses before this threshold. The use of the proposed solution provides an effective strategy to address some of the common problems found in WSN deployment by providing a fair packet delivery. In addition, the network congestion is mitigated using adaptive traffic mechanisms based on a satisfaction parameter assessed by each packet which has impact on the global satisfaction of the traffic carried by the WSN.
Localisation is a fundamental requirement for a monitoring and tracking system based on wireless sensor networks (WSN). In order to build an accurate set of measurements, sensor nodes must have information regarding their own position within a system of coordinates. When a considerable number of nodes are randomly scattered over a monitoring area, sensor nodes must be part of a self-organised system which provides a set of local position estimates. Nodes participate under very stringent conditions, for example, limited power supply and reduced computational capabilities. This work presents a GPS-free localisation method consisting of four stages that are executed only once during the network initialisation process. These stages are aimed to increase the overall system lifetime by reducing the signalling overhead commonly involved in distributed localisation procedures. The proposed localisation method turns the initial and complex node deployment to several smaller instances by dividing the network into clusters, which can be solved simultaneously based on local resources only. Simulation results show that this approach produces important savings in the involved overall complexity, which can translate into a trade-off between computational cost and localisation accuracy.
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