Biblio

This paper investigates the secrecy outage performance of an energy harvesting-based dual-hop amplify-and-forward (AF) mixed radio-frequency/underwater optical wireless communication (RF/UOWC) system. A single-antenna source node (S) is considered, communicating with one legitimate destination node (D) with the aid of a multi-antenna AF relay (R) device. In this setup, the relay node receives the incoming signal from S via an RF link, which is subject to Nakagami-m fading, then performs maximal-ratio-combining (MRC) followed by a fixed-gain amplification, before transmitting it to the destination via a UOWC link, subject to mixture Exponential-Gamma fading. Assuming the presence of a malicious eavesdropper attempting to intercept the S- R hop, a tight approximate expression for the secrecy outage probability is retrieved. The derived results provide useful insights into the influence of key system parameters on the secrecy outage performance. Our analytical results are corroborated through computer simulations, which verifies their validity.

The past decade has seen a growing interest in underwater acoustic positioning networks (UAPNs) because of their wide applications in marine research, ocean monitoring, offshore exploration, and defense or homeland security. Efficient communication among all sensors and receivers is crucial so as to make positioning service available. Traditional UAPNs could locate only one target, that are growing obsolete due to increasing demands for multiple users working at the same time. Due to the demands for multiple users working simultaneously and narrow acoustic bandwidth, new efficient and reliable communication and networking protocols are required in design for UAPNs. In this paper, we aim to provide the procedure of communication design for UAPNs based on sonar equation and spread spectrum communication. What's more, signal design and performance analysis are supplied. The results show that the signal we designed have ideal correlation performance and high processing gain. The signal is suitable for multiple users UAPNs and thus show favorable potential in ocean engineering applications.

Key management is critical for the successful operation of a cryptographic system in wireless networks. Systems based on asymmetric keys require a dedicated infrastructure for key management and authentication which may not be practical for ad-hoc Underwater Acoustic Networks (UANs). In symmetric-key systems, key distribution is not easy to handle when new nodes join the network. In addition, when a key is compromised all nodes that use the same key are not secure anymore. Hence, it is desirable to have a dynamic way to generate new keys without relying on past keys. Physical Layer Security (PLS) uses correlated channel measurements between two underwater nodes to generate a cryptographic key without exchanging the key itself. In this study, we set up a network of two legitimate nodes and one eavesdropper operating in a shallow area off the coast of Portugal. We propose novel features based on the Channel Impulse Response (CIR) of the established acoustic link that could be used as an initial seed for a crypto-key generation algorithm. Our results show that the two nodes can independently generate 306 quantization bits after exchanging 187 probe signals. Furthermore, the eavesdropper fails to generate the same bits from her/his data even if she/he performs exactly the same signal processing steps of the legitimate nodes.

As the ocean covers 70% of the Earth's surface, it becomes inevitable to develop or extend underwater applications. Compared to Visible Light medium, Acoustic medium has been widely used to transmit the data from source to destination in underwater communication. Data transmission, however, has the limitation such as propagation delay, reliability, power constraints, etc. Although underwater MAC protocols have been developed to overcome these challenges, there are still some drawbacks due to the harsh underwater environment. Therefore, the selection mechanism for underwater multi-media communication is proposed inside Medium Access Control (MAC) layer. In this paper, the main focus is to select the appropriate medium based on the distance between nodes and transmission power. The result of performance evaluation shows that this multimedia approach can complement the existing underwater single medium communication. As a result, underwater multimedia mechanism increases the reliability and energy efficiency in data transmission.

The construction and improvement of the underwater acoustic network is the premise and guarantee for the development of the marine industry. Because the underwater nodes need to work for a long time, it is especially important to ensure that the nodes have a long standby capacity. In general, the node is in a low-power standby state waiting for a wake-up signal. When the node detects the wakeup signal, it will resume normal operation. In this paper, we propose a signal design based on the m-sequence. which can detect the hidden awakening signal in the complex environment with low SNR and small Doppler shift. Simulation and experimental data indicate that when the input SNR is as low as -11 dB and the signal has a small Doppler shift, the system can still achieve a detection probability of 100% and ensure that the false alarm probability is lower than 10-6.

Sensors incorporated into mobile devices provide unique opportunities to capture detailed environmental information that cannot be readily collected in other ways. We show here how data from networked navigational sensors on leisure vessels can be used to construct unique new datasets, using the example of underwater topography (bathymetry) to demonstrate the approach. Specifically, we describe an end-to-end workflow that involves the collection of large numbers of timestamped (position, depth) measurements from "internet of floating things" devices on leisure vessels; the communication of data to cloud resources, via a specialized protocol capable of dealing with delayed, intermittent, or even disconnected networks; the integration of measurement data into cloud storage; the efficient correction and interpolation of measurements on a cloud computing platform; and the creation of a continuously updated bathymetric database. Our prototype implementation of this workflow leverages the FACE-IT Galaxy workflow engine to integrate network communication and database components with a CUDA-enabled algorithm running in a virtualized cloud environment.

Underwater acoustic communications experiments often involve custom implementations of schemes and protocols for the physical and data link layers. However, most commercial modems focus on providing reliable or optimized communication links, rather than on allowing low-level reconfiguration or reprogramming of modulation and coding schemes. As a result, the physical layer is typically provided as a closed, non-reprogrammable black box, accessible by the user only through a specific interface. While software-defined modems would be the ultimate solution to overcome this issue, having access to the symbols transmitted by the modems using a proprietary modulation format already opens up a number of research opportunities, e.g., aimed at the cross-layer design and optimization of channel coding schemes and communication protocols. In this paper, we take the latter approach. We consider the commercial EvoLogics modem, driven by a custom firmware version that bypasses the channel coding methods applied by the modem, and allows the user to set the transmit bit rate to any desired value within a given set. This makes it possible to evaluate different coding schemes in the presence of different bit rates. Our results show that the custom firmware offers sufficient flexibility to test different configurations of the coding schemes and bit rates, by providing direct access both to correctly decoded and to corrupted symbols, which can be separated at the receiver for further processing. In addition, we show that the DESERT Underwater framework can also leverage the same flexibility by employing low-level physical layer access in more complex networking experiments.

Multi-modal communication methods have been proposed for underwater wireless networks (UWNs) to tackle the challenging physical characteristics of underwater wireless channels. These include the use of acoustic and optic technology for range-dependent transmissions. Software-defined networking (SDN) is an appealing choice for managing these networks with multi-modal communication capabilities, allowing for increased adaptability in the UWN design. In this work, we develop a simulation platform for software-defined underwater wireless networks (SDUWNs). Similarto OpenNet, this platform integrates Mininet with ns-3 via TapBridge modules. The multi-modal communication is implemented by equipping each ns-3 node with multiple net devices. Multiple channel modules connecting corresponding net devices are configured to reflect the channel characteristics. The proposed simulation platform is validated in a case study for oceanographic data collection.

This paper considers the use of Combined Free/Demand Assignment Multiple Access (CFDAMA) for Underwater Acoustic Networks (UANs). The long propagation delay places severe constraints on the trade-off between end-to-end delay and the achievable channel utilisation. Free assignment is shown to offer close to the theoretical minimum end-to-end delay at low channel loads. Demand assignment is shown to have a much greater tolerance to increasing channel load over virtually the entire channel utilisation range, but with longer delay. CFDAMA is shown to exhibit significantly enhanced performance with respect to minimising end-to-end delay and maximising channel utilisation.

In this paper, the mathematical framework of behavioral system will be applied to detect the cyber-attack on the networked control system which is used to control the remotely operated underwater vehicle ROV. The Intelligent Generalized Predictive Controller IGPC is used to control the ROV. The IGPC is designed with fault-tolerant ability. In consequence of the used fault accommodation technique, the proposed cyber-attacks detector is able to clearly detect the presence of attacker control signal and to distinguish between the effects of the attacker signal and fault on the plant side. The test result of the suggested method demonstrates that it can be considerably used for detection of the cyber-attack.

Real-time localization of mobile target has been attracted much attention in recent years. With the limitation of unavailable GPS signals in the complex environments, wireless sensor networks can be applied to real-time locate and track the mobile targets in this paper. The multi wireless signals are used to weaken the effect of abnormal wireless signals in some areas. To verify the real-time localization performance for mobile targets, experiments and analyses are implemented. The results of the experiments reflect that the proposed location method can provide experimental basis for the applications, such as the garage, shopping center, underwater, etc.

This paper combines FMEA and n2 approaches in order to create a methodology to determine risks associated with the components of an underwater system. This methodology is based on defining the risk level related to each one of the components and interfaces that belong to a complex underwater system. As far as the authors know, this approach has not been reported before. The resulting information from the mentioned procedures is combined to find the system's critical elements and interfaces that are most affected by each failure mode. Finally, a calculation is performed to determine the severity level of each failure mode based on the system's critical elements.

On account of large and inconsistent propagation delays during transmission in Underwater Wireless Sensor Networks (UWSNs), wormholes bring more destructive than many attacks to localization applications. As a localization algorithm, DV-hop is classic but without secure scheme. A secure localization algorithm for UWSNs- RDV-HOP is brought out, which is based on reputation values and the constraints of propagation distance in UWSNs. In RDV-HOP, the anchor nodes evaluate the reputation of paths to other anchor nodes and broadcast these reputation values to the network. Unknown nodes select credible anchors nodes with high reputation to locate. We analyze the influence of the location accuracy with some parameters in the simulation experiments. The results show that the proposed algorithm can reduce the location error under the wormhole attack.

In this paper, we propose a theoretical framework to investigate the eavesdropping behavior in underwater acoustic sensor networks. In particular, we quantify the eavesdropping activities by the eavesdropping probability. Our derived results show that the eavesdropping probability heavily depends on acoustic signal frequency, underwater acoustic channel characteristics (such as spreading factor and wind speed) and different hydrophones (such as isotropic hydrophones and array hydrophones). Simulation results have further validate the effectiveness and the accuracy of our proposed model.

Due to the trend of under-ocean exploration, realtime monitoring or long-term surveillance of the under-ocean environment, e.g., real-time monitoring for under-ocean oil drilling, is imperative. Underwater wireless sensor networks could provide an optimal option, and have recently attracted intensive attention from researchers. Nevertheless, terrestrial wireless sensor networks (WSNs) have been well investigated and solved by many approaches that rely on the electromagnetic/optical transmission techniques. Deploying an applicable underwater wireless sensor network is still a big challenge. Due to critical conditions of the underwater environment (e.g., high pressure, high salinity, limited energy etc), the cost of the underwater sensor is significant. The dense sensor deployment is not applicable in the underwater condition. Therefore, Autonomous Underwater Vehicle (AUV) becomes an alternative option for implementing underwater surveillance and target detection. In this article, we present a framework to theoretically analyze the target detection probability in the underwater environment by using AUVs. The experimental results further verify our theoretical results.

Cognitive acoustic (CA) is emerging as a promising technique for spectrum-efficient Underwater Acoustic Networks (UANs). Due to the unique features of UANs, especially the long propagation delay, the busy terminal problem and large interference range, traditional spectrum decision methods used for radio networks need an overhaul to work efficiently in underwater environment. In this paper, we propose a dynamic spectrum decision algorithm called Receiver-viewed Dynamic Borrowing (RvDB) algorithm for Underwater Cognitive Acoustic Networks (UCANs) to improve the efficiency of spectrum utilization. RvDB algorithm is with the following features. Firstly, the spectrum resource is decided by receiver. Secondly, the receivers can borrow the idle spectrum resource from neighbouring nodes dynamically. Finally, the spectrum sensing is completed by control packets on control channel which is separated from data channels. Simulation results show that RvDB algorithm can greatly improve the performance on spectrum efficiency.

In this paper, a multi-channel medium access control (MAC) protocol is proposed to overcome the Large Interference Range Collision (LIRC) problem in underwater acoustic sensor networks (UWASNs), which has been known to occur when a handshaking based MAC protocol is jointly used with a power control. The proposed scheme divides the frequency band into two separate channels each used for control and data packets transmission. Considering the acoustic signal attenuation characteristics, higher frequency is used for data and lower frequency is used for control. And then, the data transmission power is controlled to escape the LIRC problem and simultaneously to save as much as possible. Furthermore with the separated channels, we can also reduce control-data packet collisions.

Distributed detection with data fusion has gained great attention in recent years. Collaborative detection improves the performance, and the optimal sensor deployment may change with time. It has been shown that with data fusion less sensors are needed to get the same detection ability when abundant sensors are deployed randomly. However, because of limitations on equipment number and deployment methods, fixed sensor locations may be preferred underwater. In this paper, we try to establish a theoretical framework for finding sensor positions to maximize the detection probability with a distributed sensor network. With joint data processing, detection performance is related to all the sensor locations; as sensor number grows, the optimization problem would become more difficult. To simplify the demonstration, we choose a 1-dimensional line deployment model and present the relevant numerical results.

Multiple-input multiple-output (MIMO) techniques have been the subject of increased attention for underwater acoustic communication for its ability to significantly improve the channel capabilities. Recently, an under-ice MIMO acoustic communication experiment was conducted in shallow water which differs from previous works in that the water column was covered by about 40 centimeters thick sea ice. In this experiment, high frequency MIMO signals centered at 10 kHz were transmitted from a two-element source array to a four-element vertical receive array at 1km range. The unique under-ice acoustic propagation environment in shallow water seems naturally separate data streams from different transducers, but there is still co-channel interference. Time reversal followed by a single channel decision feedback equalizer is used in this paper to compensate for the inter-symbol interference and co-channel interference. It is demonstrated that this simple receiver scheme is good enough to realize robust performance using fewer hydrophones (i.e. 2) without the explicit use of complex co-channel interference cancelation algorithms such as parallel interference cancelation or serial interference cancelation. Two channel estimation algorithms based on least square and least mean square are also studied for MIMO communications in this paper and their performance are compared using experimental data.

Currently, the coastal communication is mainly provided by satellite networks, which are expensive with low transmission rate and unable to support underwater communication efficiently. In this work, we propose a communication architecture for coastal network based on long term evolution (LTE) cellular networks in which a cellular network architecture is designed for the maritime communication scenario. Some key technologies of next-generation cellular networks such as device-to-device (D2D) and multiple input multiple output (MIMO) are integrated into the proposed architecture to support more efficient data transmission. In addition, over-water nodes aid the transmission of underwater network to improve the communication quality. With the proposed communication architecture, the coastal network can provide high-quality communication service to traffics with different quality-of-service (QoS) requirements.

The Earth is a water planet. The ocean is used for nature resource exploitation, fishery, etc., and it also plays critical roles in global climate regulation and transportation. Consequently, it is extremely important to keep track of its condition. And thus ocean observation systems have received increasing attentions.

In this work, a bi-directional transceiver with a maximum throughput of 24 kbps is presented. The spatio-temporal shallow water channel characteristics between a projector and a hydrophone array are analyzed in a seawater tank, and a methodology to maintain a 10−4 probability of bit error with prior knowledge of the channel statistics is proposed. Also, it is found that flow generated in the sea water provides a realistic representation of time-varying propagation conditions, particularly for the reverse link communication link at 22.5 kHz.

The local minima has been deemed as a challenging issue when designing routing protocols for 3D underwater sensor networks. Recently, harmonic potential field method has been used to tackle the issue of local minima which was also a major bottleneck in path planning and obstacle avoidance of robotics community. Inspired by this, this paper proposes a harmonic potential field based routing protocol for 3D underwater sensor networks with local minima. More specifically, the harmonic potential field is calculated using harmonic functions and Dirichlet boundary conditions are used for the local minima, sink(or seabuoy) and sending node. Numerical results show the effectiveness of the proposed routing protocol.

The ability to obtain reliable, long-term visual data in marine habitats has the potential to transform biological surveys of marine species. However, the underwater environment poses several challenges to visual monitoring: turbidity and light attenuation impede the range of optical sensors, biofouling clouds lenses and underwater housings, and marine species typically range over a large area, far outside of the range of a single camera sensor. Due to these factors, a continuously-recording or time-lapse visual sensor will not be gathering useful data the majority of the time, wasting battery life and filling limited onboard storage with useless images. These limitations make visual monitoring difficult in marine environments, but visual data is invaluable to biologists studying the behaviors and interactions of a species. This paper describes an acoustic-based, autonomous triggering approach to counter the current limitations of underwater visual sensing, and motivates the need for a distributed sensor network for underwater visual monitoring.

In this work, we develop an underwater relay network model for an unmanned cruise system. By introducing the underwater cruise, we analyze end-to-end outage performance for collecting data from a sensor node. Based on theoretical derivation of the outage probability, we further analyze the optimized location and data rate for relaying.