Hybrid Satellite-Terrestrial Communication Networks for the Maritime Internet of Things: Key Technologies, Opportunities, and Challenges

With the rapid development of marine activities, there has been an increasing number of maritime mobile terminals, as well as a growing demand for high-speed and ultra-reliable maritime communications to keep them connected. Traditionally, the maritime Internet of Things (IoT) is enabled by maritime satellites. However, satellites are seriously restricted by their high latency and relatively low data rate. As an alternative, shore & island-based base stations (BSs) can be built to extend the coverage of terrestrial networks using fourth-generation (4G), fifth-generation (5G), and beyond 5G services. Unmanned aerial vehicles can also be exploited to serve as aerial maritime BSs. Despite of all these approaches, there are still open issues for an efficient maritime communication network (MCN). For example, due to the complicated electromagnetic propagation environment, the limited geometrically available BS sites, and rigorous service demands from mission-critical applications, conventional communication and networking theories and methods should be tailored for maritime scenarios. Towards this end, we provide a survey on the demand for maritime communications, the state-of-the-art MCNs, and key technologies for enhancing transmission efficiency, extending network coverage, and provisioning maritime-specific services. Future challenges in developing an environment-aware, service-driven, and integrated satellite-air-ground MCN to be smart enough to utilize external auxiliary information, e.g., sea state and atmosphere conditions, are also discussed

Opportunistic Networks: Present Scenario- A Mirror Review

Opportunistic Network is form of Delay Tolerant Network (DTN) and regarded as extension to Mobile Ad Hoc Network. OPPNETS are designed to operate especially in those environments which are surrounded by various issues like- High Error Rate, Intermittent Connectivity, High Delay and no defined route between source to destination node. OPPNETS works on the principle of “Store-and-Forward” mechanism as intermediate nodes perform the task of routing from node to node. The intermediate nodes store the messages in their memory until the suitable node is not located in communication range to transfer the message to the destination. OPPNETs suffer from various issues like High Delay, Energy Efficiency of Nodes, Security, High Error Rate and High Latency. The aim of this research paper is to overview various routing protocols available till date for OPPNETs and classify the protocols in terms of their performance. The paper also gives quick review of various Mobility Models and Simulation tools available for OPPNETs simulation

On performance modeling of 3D mobile ad hoc networks

指導教員：姜 暁

Intelligent deployment strategies for passive underwater sensor networks

Passive underwater sensor networks are often used to monitor a general area of the ocean, a port or military installation, or to detect underwater vehicles near a high value unit at sea, such as a fuel ship or aircraft carrier. Deploying an underwater sensor network across a large area of interest (AOI), for military surveillance purposes, is a significant challenge due to the inherent difficulties posed by the underwater channel in terms of sensing and communications between sensors. Moreover, monetary constraints, arising from the high cost of these sensors and their deployment, limit the number of available sensors. As a result, sensor deployment must be done as efficiently as possible. The objective of this work is to develop a deployment strategy for passive underwater sensors in an area clearance scenario, where there is no apparent target for an adversary to gravitate towards, such as a ship or a port, while considering all factors pertinent to underwater sensor deployment. These factors include sensing range, communications range, monetary costs, link redundancy, range dependence, and probabilistic visitation. A complete treatment of the underwater sensor deployment problem is presented in this work from determining the purpose of the sensor field to physically deploying the sensors. Assuming a field designer is given a suboptimal number of sensors, they must be methodically allocated across an AOI. The Game Theory Field Design (GTFD) model, proposed in this work, is able to accomplish this task by evaluating the acoustic characteristics across the AOI and allocating sensors accordingly. Since GTFD considers only circular sensing coverage regions, an extension is proposed to consider irregularly shaped regions. Sensor deployment locations are planned using a proposed evolutionary approach, called the Underwater Sensor Deployment Evolutionary Algorithm, which utilizes two suitable network topologies, mesh and cluster. The effects of these topologies, and a sensor\u27s communications range, on the sensing capabilities of a sensor field, are also investigated. Lastly, the impact of deployment imprecision on the connectivity of an underwater sensor field, using a mesh topology, is analyzed, for cases where sensor locations after deployment do not exactly coincide with planned sensor locations

Um esquema para entrega de mensagens codificadas em redes DTNS

Orientador : Prof. Dr. Luiz Carlos Pessoa AlbiniDissertação (mestrado) - Universidade Federal do Paraná, Setor de Ciências Exatas, Programa de Pós-Graduação em Informática. Defesa: Curitiba, 22/08/2014Inclui referênciasResumo: As redes tolerantes a atrasos e desconexões (DTN) são formadas por nos moveis ad hoc cujas características de mobilidade impõem serias restrições para o encaminhamento e entrega de mensagens. Uma característica importante das DTNs e a conectividade intermitente, resultado das frequentes desconexões causadas pela mobilidade e topologia esparsa. Nesses cenários, a entrega de mensagens torna-se um desafio, pois elas podem ser retidas por longos períodos ou nunca serem entregues ao destinatário. As propostas existentes para melhorar a taxa de entrega de mensagens nesses cenários alteram os protocolos de roteamento, fazendo verifica.ao de integridade a cada salto. Isso resulta em sobrecarga no roteamento e em um custo computacional muitas vezes impraticável. Este trabalho propõe um esquema, denominado EMCOD, que visa reduzir o tempo para entrega de mensagens e a sobrecarga de processamento, em redes caracterizadas por longos atrasos e que sofrem perdas de pacotes. O esquema utiliza codificação de rede e intercalação de dados para criação de mensagens menores que são encaminhadas pela rede. A reconstrução dos dados originais e feita a partir da recepção de algumas mensagens, não sendo necessário aguardar o recebimento de todas. Utilizando Reed-Solomon para codificação de dados, o EMCOD .e capaz de reduzir o tempo para recuperação dos dados originais em mais de 50%, em cenários que sofrem altas taxas de perdas de pacotes. A sobrecarga computacional adicionada pelo processo de codificação e compensada pela capacidade de recuperação dos dados originais, sem que seja necessário reenviar as mensagens perdidas. Devido a essa capacidade, e possível reduzir a sobrecarga na rede em mais de 60%, em cenários que possuem altos índices de perda de mensagens. O EMCOD altera a estrutura da camada de Agregação, mas não interfere no funcionamento das demais camadas. Assim, e possível realizar o roteamento das mensagens através de nos que não implementem o esquema proposto. Palavras-chave: DTN, codificação de rede, redução de tempo, baixa sobrecarga.Abstract: Delay and Disruption Tolerant Networks (DTN) are made up of mobile ad hoc nodes, and it is exactly that mobility that imposes major message routing and delivery restrictions. Another important characteristic of DTNs is its intermittent connectivity, resulting from frequent disconnections, which in turn are caused by mobility and scattered topologies. In these scenarios, message delivery becomes a challenge, considering they can be detained for long periods or never get delivered to its destination. Existing solutions to improve message delivery rates in such scenarios modify routing protocols to perform integrity verification with each hop. This results in routing overloads and, too often, unrealistic processing costs. This research proposes a schema, named EMCOD, that decreases message delivery times, and also minimizes processing overloads in networks burdened by long delays and packet losses. The schema uses data encoding and interleaving to create smaller messages, which are then routed through the network. The original data is then reassembled from some of the messages received, without the need to wait for the retrieval of all messages. Using Reed-Solomon codes to encode the data, EMCOD is capable of reducing original data retrieval times by more than 50%, in scenarios with high packet loss rates. The processing overload resulting from the encoding procedures is offset by the data retrieval capabilities, without the need to resend lost messages. This capability effectively decreases network overloads by more than 60%, in scenarios subject to high message loss rates. EMCOD modifies the structure of the Bundle Layer, without interfering with the remaining layers, making it possible to route the messages through nodes that don’t implement the proposed schema. Keywords: DTN, network encoding, time reduction, low overhead

Defense and traceback mechanisms in opportunistic wireless networks

 In this thesis, we have identified a novel attack in OppNets, a special type of packet dropping attack where the malicious node(s) drops one or more packets (not all the packets) and then injects new fake packets instead. We name this novel attack as the Catabolism attack and propose a novel attack detection and traceback approach against this attack referred to as the Anabolism defence. As part of the Anabolism defence approach we have proposed three techniques: time-based, Merkle tree based and Hash chain based techniques for attack detection and malicious node(s) traceback. We provide mathematical models that show our novel detection and traceback mechanisms to be very effective and detailed simulation results show our defence mechanisms to achieve a very high accuracy and detection rate

A Hybrid Routing Approach for Opportunistic Networks

With wireless networking technologies extending into the fabrics of our working and operating environments, proper handling of intermittent wireless connectivity and network disruptions is of significance. As the sheer number of potential opportunistic application continues to surge (i.e. wireless sensor networks, underwater sensor networks, pocket switched networks, transportation networks, and etc.), the design for an effective routing scheme that considers and accommodates the various intricate behaviors observed in an opportunistic network is of interest and remained desirable. While previous solutions use either replication or coding techniques to address the challenges in opportunistic networks, the tradeoff of these two techniques only make them ideal under certain network scenarios. In this paper, we propose a hybrid scheme, named H-EC, to deal with a wide variety of opportunistic network cases. H-EC is designed to fully combine the robustness of erasure coding based routing techniques, while preserving the performance advantages of replication techniques. We evaluate H-EC against other similar strategies in terms of delivery ratio and latency, and find that H-EC offers robustness in worst-case delay performance cases while achieving good performance in small delay performance cases. We also discuss the traffic overhead issues associated with H-EC as compared to other schemes, and present several strategies that can potentially alleviate the traffic overhead of H-EC schemes