1,720,999 research outputs found
SUNSET: Simulation, Emulation and Real-life Testing of Underwater Wireless Sensor Networks
No full textA back-seat driver for remote control of experiments in underwater acoustic sensor networks
No full textThis paper presents a novel system to remotely control and reconfigure an heterogeneous underwater acoustic sensor network in scenarios with no direct access to all the underwater nodes after their deployment. The system uses the SUNSET framework to interact with and to operate the underwater network via single-hop and multi-hop acoustic transmissions. Users can remotely configure the underwater devices and the tests to run without the need to retrieve or bring to the surface the deployed nodes. The system allows the user to select different protocol stacks, protocol parameters and device behavior policies and to investigate the performance of several network configurations in an easy and fast way, avoiding that most of the experiment time is used to prepare the tests rather than to actually run the tests and collect the results. The presented mechanism has been successfully tested and validated during three in field campaigns, considering different underwater environments and communication devices. Our results show that the time to remotely control and reconfigure several batteries of tests for a variety of network configurations reduces to few tens of seconds, thus enhancing robustness and flexibility and significantly reducing the costs and logistic complexity of in field experiments. © 2013 IEEE
Comparing the SUNSET and DESERT frameworks for in field experiments in underwater acoustic networks
No full textThe emerging demand for pervasive underwater monitoring and control systems has significantly stimulated the research on network protocols for underwater acoustic sensor networks. In the last few years, several solutions have been proposed for this kind of networks at all layers of the protocol stack. However, to achieve a thorough understanding of the performance of these protocols running simulations is no longer enough and in field experiments are needed. Two different platforms, SUNSET and DESERT, have been recently developed and released open-source allowing to seamlessly simulate, emulate and test (at-sea) a variety of communication protocols. In this paper we compare the performance of these two frameworks, with a particular attention to their use during in field experimentation. Our tests show that when running simulations there is high compatibility and interoperability between the two systems. In actual underwater experiments, however, SUNSET represents a more mature, flexible and efficient solution. © 2013 IEEE
Performance evaluation of underwater MAC protocols: From simulation to real life testing
No full textEfficiently reconfigurable backbones for wireless sensor networks
No full textWe present the definition and performance evaluation of a protocol for building and maintaining a connected backbone among the nodes of a wireless sensor networks (WSN). Building backbones first, and then coping with network dynamics is typical of protocols for backbone formation. Rules for building the backbone, however, do not take into account the following network dynamics explicitly. This makes maintaining a connected backbone quite costly, especially in terms of reorganization time, overhead and energy consumption. Our protocol includes in the backbone forming operations a fail-safe mechanism for dealing with the addition and the removal of nodes, which are typical events in a WSN. More specifically, the network is kept partitioned into clusters that are cliques, i.e., nodes in each cluster are directly connected to each others. Therefore, removing a node does not disrupt a cluster, and adding one requires simple operations for checking node admission to the cluster. The protocol, termed CC ("double C", for clique clustering), comprises three phases, each designed to render the operations of the others swift and efficient. The first phase partitions the network into clusters that are cliques. Clusters are then joined to form a backbone that is provably connected. Finally, the third, more on-line phase, maintains the backbone connected in face of node additions and removals. We compare the performance of CC with that of DMAC, a protocol that has been previously proposed for building and maintaining clusters and backbones in presence of network dynamics. Our comparison concerns metrics that are central to WSN research, such as time for clustering and backbone reorganization, corresponding overhead, extent of the reorganization (i.e., number of nodes involved in it), and properties of the resulting backbone, such as its size, backbone route length, number of gateways and nodes per cluster. Our ns2-based simulation results show that the design criteria chosen for CC are effective in producing backbones that can be reconfigured quickly and with remarkably lower overhead. (c) 2007 Elsevier B.V. All rights reserved
Fail-safe hierarchical organization for wireless sensor networks
No full textThis paper presents the definition and evaluation of a new protocol for providing a wireless sensor network (WSN) with a hierarchical organization. Differently from previously proposed solutions, our protocol, termed CC ("double c," for clique clustering), includes in its operation a fail-safe mechanism for dealing with node failure or removal, which are typical of WSNs. More specifically, the network is partitioned into clusters that are cliques, i.e., nodes in each clusters are directly connected to each others. An efficient mechanism for building a connected backbone among the clique clusters is provided. Clustering, backbone formation and backbone maintenance are completely localized, in the precise sense that only nodes physically close to a failing node are involved in the reconfiguration process. We compare the performance of CC with that of DMAC, a protocol that has been previously proposed for building and maintaining clusters and backbones in presence of node removal. Our comparison concerns metrics that are central to WSN research, such as time for clustering and backbone reorganization, corresponding overhead (in bytes and transmission energy), backbone size, extent of the reorganization (i.e., the number of nodes involved in it), and backbone route length. Our ns2-based simulation results show that the design criteria chosen for CC are effective in producing backbones that can be reconfigured quickly (63% faster than DMAC's) and with remarkably lower overhead. © 2007 IEEE
Multiplexing data and control channels in random access underwater networks
No full textWe address random access networks with MAC protocols that use control packets such as RTS/CTS. These protocols reduce or eliminate collisions between data packets, but they typically remain prone to collisions between control and data packets. To avoid this type of collision, the data and control channels can be separated by multiplexing in the frequency domain. A small reduction in bandwidth is thus sacrificed in exchange for a reduced number of re-transmissions. This technique is investigated in conjunction with the distance-aware collision avoidance protocol (DACAP). Simulation results show that multiplexing offers some benefits to both throughput efficiency and energy consumption. ©2009 MTS
Towards an autonomous underwater vehicles test range: At-sea experimentation of bearing-only tracking algorithms
No full textUnderwater navigation performance of Autonomous Underwater Vehicles (AUVs) strongly affects the quality of the collected data. Scientific literature extensively addresses the AUV tracking and self-localisation problems. However, no standard evaluation methods for vehicle navigation exist. Therefore, the authors’ visionary perspective is to develop and implement an Underwater Test Range (UTR) to certify the vehicle compliance with long-term underwater navigation. This paper describes a first step along this research path represented by an in field validation of such conceived measurement network. Experiments are soundly based on extensive simulation analysis presented in previous works. In particular, an underwater network composed of acoustic modems with Ultra Short BaseLine capabilities is deployed as measurement rig. This setup, through bearing-only measurements, allows the tracking of an Autonomous Surface Vehicle (ASV) equipped with Differential GPS as position ground truth. Results show how the proposed methodology performs in a real marine scenario with challenging conditions due to shallow waters and magnetically noisy environment
Optimized Packet Size Selection in Underwater WSN Communications
No full textIn this paper, we investigate the effect of packet size selection on the performance of media access control (MAC) protocols for underwater wireless sensor networks, namely, carrier sense multiple access (CSMA) and the distance-aware collision avoidance protocol (DACAP). Our comparative analysis, conducted via ns-2 simulations, considers scenarios with varying, nonzero bit error rate (BER) and interference. We investigate metrics such as throughput efficiency (the ratio between the delivered bit rate and the offered bit rate), end-to-end packet latency, measured “per meter” to allow for different sizes of deployment areas, and the energy consumed to correctly deliver an information bit to the network collection point. Our results show the dependence of these metrics on the packet size, indicating the existence of an optimum. The optimum packet size is found to depend on the protocol characteristics, the bit rate, and the BER. For each protocol and scenario considered, we determine the packet size that optimizes throughput performance, and we show its effect on the normalized packet latency and on energy consumption
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