The ICoN integrated communication and navigation protocol for underwater acoustic networks

Thesis (M. Eng. and S.B.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.Includes bibliographical references (p. 81-82).The deployment of autonomous underwater devices has increased dramatically in the last several years, presenting a strong and growing need for a network protocol to mediate acoustic communications between devices. This network protocol must also provide an infrastructure for acoustic navigation, while ensuring that provisions for communication and navigation do not interfere with each other. To approach this difficult problem, we begin with a discussion of the limitations of traditional networking protocols when subjected to the complexities introduced by the underwater acoustic environment. We then present ICoN, a proposed network protocol, designed to integrate acoustic communication and navigation and optimized to operate in the low-bandwidth, high-loss underwater environment. A working description of ICoN and a discussion of its features are followed by analysis of the protocol through simulation, indicating its potential for improved performance over traditional networking protocols. The simulation results are reinforced through real-world experimental validation of ICoN, which, though limited, appears to confirm the effectiveness of the new protocol. We conclude with possible future extensions to ICoN, discussing various methods that might increase its potency in dealing with more demanding underwater acoustic applications.by Rupesh R. Kanthan.M.Eng.and S.B

Network protocols and time synchronization for underwater acoustic networks

Ph.DDOCTOR OF PHILOSOPH

Effective Medium Access Control for Underwater Acoustic Sensor Networks

This work is concerned with the design, analysis and development of effective Medium Access Control (MAC) protocols for Underwater Acoustic Sensor Networks (UASNs). The use of acoustic waves underwater places time-variant channel constraints on the functionality of MAC protocols. The contrast between traffic characteristics of the wide-ranging applications of UASNs makes it hard to design a single MAC protocol that can be adaptive to various applications. This thesis proposes MAC solutions that can meet the environmental and non-environmental challenges posed underwater. Scheduling-based schemes are the most common MAC solutions for UASNs, but scheduling is also challenging in such a dynamic environment. The preferable way of synchronisation underwater is the use of a global scheduler, guard intervals and exchange of timing signals. To this end, single-hop topologies suit UASN applications very well. The Combined Free and Demand Assignment Multiple Access (CFDAMA) is a centralised, scheduling-based MAC protocol demonstrating simplicity and adaptability to the time-variant channel and traffic characteristics. It is shown to minimise end-to-end delay, maximise channel utilisation and maintain fairness amongst nodes. This thesis primarily introduces two novel robust MAC solutions for UASNs, namely CFDAMA with Systematic Round Robin and CFDAMA without clock synchronisation (CFDAMA-NoClock). The former scheme is more suitable for large-scale and widely-spread UASNs, whereas the latter is a more feasible MAC solution when synchronisation amongst node clocks cannot be attained. Both analytical and comprehensive event-driven Riverbed simulations of underwater scenarios selected based on realistic sensor deployments show that the two protocols make it possible to load the channel up to higher levels of its capacity with controlled delay performance superior to that achievable with the traditional CFDAMA schemes. The new scheduling features make the CFDAMA-NoClock scheme a very feasible networking solution for robust and efficient UASN deployments in the real world

Desenvolupament, proves de camp i anàlisi de resultats en una xarxa de sensors

The objective of this master thesis is to describe the problems of the underwater acoustic sensor network and make some experiments. The experiments carried out try to characterize the communication in underwater environments in order to be able to develop underwater sensor networks. In the first chapter we describe the motivations, features of aquatic environment, the difficulties of underwater acoustic channels, and the open questions in mobile underwater sensor network design. In the second chapter we try to describe the experiments, show the results and try to explain these results. And finally in the third chapter we explain the conclusions and the further works of this master thesis

Performance analysis of the carrier-sense multiple access protocol for future generation wireless networks

Ankara : The Department of Electrical and Electronics Engineering and the Graduate School of Engineering and Science of Bilkent University, 2013.Thesis (Ph. D.) -- Bilkent University, 2013.Includes bibliographical references leaves 115-127.Variants of the carrier-sense multiple access (CSMA) protocol has been employed in many communications protocols such as the IEEE 802.11 and Ethernet standards. CSMA based medium access control (MAC) mechanisms have been recently proposed for other communications scenarios such as sensor networks and acoustical underwater networks. Despite its widespread use, the performance of the CSMA protocol is not well-studied from the perspective of these newly encountered networking scenarios. We here investigate the performance of the CSMA protocol from the point of three different aspects: throughput in networks with large propagation delay, short-term fairness for delay sensitive applications in large networks and energy efficiency-throughput trade-off in networks with battery operated devices. Firstly, we investigate the performance of the CSMA protocol for channels with large propagation delay. Such channels are recently encountered in underwater acoustic networks and in terrestrial wireless networks covering larger areas. However, a mathematical model of CSMA performance in such networks is not known. We propose a semi-Markov model for a 2-node CSMA channel and then extend this model for arbitrary number of users. Using this model, we obtain the optimum symmetric probing rate that achieves the maximum network throughput as a function of the average propagation delay, ¯d, and the number of nodes sharing the channel, N. The proposed model predicts that the total capacity decreases with ¯d −1 as N goes to infinity when all nodes probe the channel at the optimum rate. The optimum probing rate for each node decreases with 1/N and the total optimum probing rate decreases faster than ¯d −1 as N goes to infinity. Secondly, we investigate whether the short-term fairness of a large CSMA network degrades with the network size and density. Our results suggest that (a) the throughput region that can be achieved within the acceptable limits of shortterm fairness reduces as the number of contending neighboring nodes increases for random regular conflict graphs, (b) short-term fair capacity weakly depends on the network size for a random regular conflict graph but a stronger dependence is observed for a grid topology. We also present related results from the statistical physics literature on long-range correlations in large systems and point out the relation between these results and short-term fairness of CSMA systems. Thirdly, we investigate the energy efficiency of a CSMA network proposing a model for the energy consumption of a node as a function of its throughput. We show that operating the CSMA network at a very high or at a very low throughput is energy inefficient because of increasing carrier-sensing and sleeping costs, respectively. Achieving a balance between these two opposite operating regimes, we derive the energy-optimum carrier-sensing rate and the energy-optimum throughput which maximize the number of transmitted bits for a given energy budget. For the single-hop case, we show that the energy-optimum total throughput increases as the number of nodes sharing the channel increases. For the multi-hop case, we show that the energy-optimum throughput decreases as the degree of the conflict graph of the network increases. For both cases, the energy-optimum throughput reduces as the power required for carrier-sensing increases. The energy-optimum throughput is also shown to be substantially lower than the maximum throughput and the gap increases as the degree of the conflict graph increases for multi-hop networks.Köseoğlu, MehmetPh.D

Design, Analysis, and Performance Evaluation for Handshaking Based MAC Protocols in Underwater Acoustic Networks

Ph.DDOCTOR OF PHILOSOPH

TIME DOMAIN MEDIUM ACCESS CONTROL PROTOCOLS FOR UNDERWATER ACOUSTIC NETWORKS

Ph.DDOCTOR OF PHILOSOPH

Adapting Deep Learning for Underwater Acoustic Communication Channel Modeling

The recent emerging applications of novel underwater systems lead to increasing demand for underwater acoustic (UWA) communication and networking techniques. However, due to the challenging UWA channel characteristics, conventional wireless techniques are rarely applicable to UWA communication and networking. The cognitive and software-defined communication and networking are considered promising architecture of a novel UWA system design. As an essential component of a cognitive communication system, the modeling and prediction of the UWA channel impulse response (CIR) with deep generative models are studied in this work. Firstly, an underwater acoustic communication and networking testbed is developed for conducting various simulations and field experiments. The proposed test-bed also demonstrated the capabilities of developing and testing SDN protocols for a UWA network in both simulation and field experiments. Secondly, due to the lack of appropriate UWA CIR data sets for deep learning, a series of field UWA channel experiments have been conducted across a shallow freshwater river. Abundant UWA CIR data under various weather conditions have been collected and studied. The environmental factors that significantly affect the UWA channel state, including the solar radiation rate, the air temperature, the ice cover, the precipitation rate, etc., are analyzed in the case studies. The obtained UWA CIR data set with significant correlations to weather conditions can benefit future deep-learning research on UWA channels. Thirdly, a Wasserstein conditional generative adversarial network (WCGAN) is proposed to model the observed UWA CIR distribution. A power-weighted Jensen–Shannon divergence (JSD) is proposed to measure the similarity between the generated distribution and the experimental observations. The CIR samples generated by the WCGAN model show a lower power-weighted JSD than conventional estimated stochastic distributions. Finally, a modified conditional generative adversarial network (CGAN) model is proposed for predicting the UWA CIR distribution in the 15-minute range near future. This prediction model takes a sequence of historical and forecast weather information with a recent CIR observation as the conditional input. The generated CIR sample predictions also show a lower power-weighted JSD than conventional estimated stochastic distributions