TDMA frame design for a prototype underwater RF communication network

This document is the Accepted Manuscript version of the following article: Xianhui Che, Ian Wells, Gordon Dickers, and Paul Kear, ‘TDMA frame design for a prototype underwater RF communication network’, Ad Hoc Networks, Vol. 10 (3): 317-327, first available online 23 July 2011. The version of record is available online at doi: http://dx.doi.org/10.1016/j.adhoc.2011.07.002 © 2011 Elsevier B. V. All rights reserved.Very low frequency electromagnetic communication system is used in a small scale underwater wireless sensor network for coastal monitoring purposes, as recent research has demonstrated distinct advantages of radio waves compared to acoustic and optical waves in shallow water conditions. This paper describes the detailed TDMA and packet design process for the prototype sensor system. The lightweight protocol is time division based in order to fit the unique characteristics and specifications of the network. Evaluations are based on initial beach trial as well as modeling and simulations.Peer reviewe

TDMA frame design for a prototype underwater RF

Very low frequency electromagnetic communication system is used in a small scale underwater wireless sensor network for coastal monitoring purposes, as recent research has demonstrated distinct advantages of radio waves compared to acoustic and optical waves in shallow water conditions. This paper describes the detailed TDMA and packet design process for the prototype sensor system. The lightweight protocol is time division based in order to fit the unique characteristics and specifications of the network. Evaluations are based on initial beach trial as well as modeling and simulations

Field test of multi-hop image sensing network prototype on a city-wide scale

Open Access funded by Chongqing University of Posts and Telecommuniocations Under a Creative Commons license, https://creativecommons.org/licenses/by-nc-nd/4.0/Wireless multimedia sensor network drastically stretches the horizon of traditional monitoring and surveillance systems, of which most existing research have utilised Zigbee or WiFi as the communication technology. Both technologies use ultra high frequencies (mainly 2.4 GHz) and suffer from relatively short transmission range (i.e. 100 m line-of-sight). The objective of this paper is to assess the feasibility and potential of transmitting image information using RF modules with lower frequencies (e.g. 433 MHz) in order to achieve a larger scale deployment such as a city scenario. Arduino platform is used for its low cost and simplicity. The details of hardware properties are elaborated in the article, followed by an investigation of optimum configurations for the system. Upon an initial range testing outcome of over 2000 m line-of-sight transmission distance, the prototype network has been installed in a real life city plot for further examination of performance. A range of suitable applications has been proposed along with suggestions for future research.Peer reviewe

Re-Evaluation of RF Electromagnetic Communication in Underwater Sensor Networks

Most underwater wireless networks use acoustic waves as the transmission medium nowadays, but the chances of getting much more out of acoustic modems are quite remote. Optical links are impractical for many underwater applications. Given modern operational requirements and digital communications technology, the time is now ripe for re-evaluating the role of electromagnetic signals in underwater environments. The research presented in this article is motivated by the limitations of current and established wireless underwater techniques, as well as the potential that electromagnetic waves can offer to underwater applications. A case study is presented that uses electromagnetic technology in a small-scale underwater wireless sensor network. The results demonstrate the likely effectiveness of the designated network

Communication and control of autonomous underwater vehicles using radio frequency-acoustic hybrid MAC schemes

In shallow water subsea applications like control of AUVs, there is a growing demand of high-speed wireless communication links for transmitting data between AUVs and base station. Acoustic communication provide very low data rates and high propagation delays not suitable for high gain and high speed control of AUVs and on other hand radio communication is constrained by very high attenuation due to high conductivity and permittivity of water resulting in a very short working range. In this thesis, an Acoustic-RF hybrid communication system is proposed which uses acoustic link for long range communication and switches to Radio Frequency in close range. The system is tested on docking station model where AUVs get their location from transmitter at docking station and control the motors on AUVs to land on docking station. We show that this hybrid system solves the need of robust communication link as well as high data rate and low latency requirement of AUV communication. Three MAC schemes namely TDMA, Slotted ALOHA and Waiting Room are tested and compared in acoustic communication

Contribution to Research on Underwater Sensor Networks Architectures by Means of Simulation

El concepto de entorno inteligente concibe un mundo donde los diferentes tipos de dispositivos inteligentes colaboran para conseguir un objetivo común. En este concepto, inteligencia hace referencia a la habilidad de adquirir conocimiento y aplicarlo de forma autónoma para conseguir el objetivo común, mientras que entorno hace referencia al mundo físico que nos rodea. Por tanto, un entorno inteligente se puede definir como aquel que adquiere conocimiento de su entorno y aplicándolo permite mejorar la experiencia de sus habitantes. La computación ubicua o generalizada permitirá que este concepto de entorno inteligente se haga realidad. Normalmente, el término de computación ubicua hace referencia al uso de dispositivos distribuidos por el mundo físico, pequeños y de bajo precio, que pueden comunicarse entre ellos y resolver un problema de forma colaborativa. Cuando esta comunicación se lleva a cabo de forma inalámbrica, estos dispositivos forman una red de sensores inalámbrica o en inglés, Wireless Sensor Network (WSN). Estas redes están atrayendo cada vez más atención debido al amplio espectro de aplicaciones que tienen, des de soluciones para el ámbito militar hasta aplicaciones para el gran consumo. Esta tesis se centra en las redes de sensores inalámbricas y subacuáticas o en inglés, Underwater Wireless Sensor Networks (UWSN). Estas redes, a pesar de compartir los mismos principios que las WSN, tienen un medio de transmisión diferente que cambia su forma de comunicación de ondas de radio a ondas acústicas. Este cambio hace que ambas redes sean diferentes en muchos aspectos como el retardo de propagación, el ancho de banda disponible, el consumo de energía, etc. De hecho, las señales acústicas tienen una velocidad de propagación cinco órdenes de magnitud menor que las señales de radio. Por tanto, muchos algoritmos y protocolos necesitan adaptarse o incluso rediseñarse. Como el despliegue de este tipo de redes puede ser bastante complicado y caro, se debe planificar de forma precisa el hardware y los algoritmos que se necesitan. Con esta finalidad, las simulaciones pueden resultar una forma muy conveniente de probar todas las variables necesarias antes del despliegue de la aplicación. A pesar de eso, un nivel de precisión adecuado que permita extraer resultados y conclusiones confiables, solamente se puede conseguir utilizando modelos precisos y parámetros reales. Esta tesis propone un ecosistema para UWSN basado en herramientas libres y de código abierto. Este ecosistema se compone de un modelo de recolección de energía y unmodelo de unmódemde bajo coste y bajo consumo con un sistema de activación remota que, junto con otros modelos ya implementados en las herramientas, permite la realización de simulaciones precisas con datos ambientales del tiempo y de las condiciones marinas del lugar donde la aplicación objeto de estudio va a desplegarse. Seguidamente, este ecosistema se utiliza con éxito en el estudio y evaluación de diferentes protocolos de transmisión aplicados a una aplicación real de monitorización de una piscifactoría en la costa del mar Mediterráneo, que es parte de un proyecto de investigación español (CICYT CTM2011-2961-C02-01). Finalmente, utilizando el modelo de recolección de energía, esta plataforma de simulación se utiliza para medir los requisitos de energía de la aplicación y extraer las necesidades de hardware mínimas.Climent Bayarri, JS. (2014). Contribution to Research on Underwater Sensor Networks Architectures by Means of Simulation [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/3532

Design and Analysis of Free Space Optical Sensor Networks for Short-Range Applications

Free space optical communication (FSOC) systems using direct detection and line of sight (LOS) laser links can provide spatially efficient and physically secure connectivity for wireless sensor networks. The FSOC system can be developed with low power microcontrollers so that the entire sensor system can be implemented on a single printed circuit board. Available data rates can range from kb/s to hundreds of Mb/s with the complete system consuming power only in the tens of mW. These features are advantageous for low-power communication networks over short distances in environments where LOS is available, and where radio frequency (RF) connectivity must be avoided because of interference or security issues. In particular, the faster data acquisition rates of FSOC systems are extremely attractive in applications where the sensor systems, or "motes", remain in sleep mode most of the time and need to transmit large amounts of data in extremely short bursts when they wake up. However, in order for directional FSO sensor networks to become viable short-range solutions, the networks must provide signal coverage over a wide field of view without strict optical alignment requirements, operate with efficient media access protocols that can handle network traffic in an efficient manner, and minimize random access times for the independent transmitting motes within the network. These challenges are the focus of this dissertation. In general, narrow optical beams used for FSOC require precise and complex pointing, acquisition, tracking and alignment methods. This dissertation addresses the challenge of alignment for FSO-based nodes by designing optical transceiver architectures with multiple narrow field of view (FOV) transmitters and a single, wide angle receiver. The architecture consists of rings of multiple transmitters surrounding a photodiode for light collection. Each ring is tilted at a different angle so that a wide transmission FOV can be obtained, thereby allowing point-multipoint communication. Depending on the number of transmitters and the transmitter's divergence angle, different FOVs can be tailored to fit the requirements of the target application. The developed transmitter design requires only a few milliwatts of transmission power from each transmitter to cover its respective FOV, which is sustainable with drive currents up to 10 milliamps using vertical cavity surface emitting lasers (VCSELs), making it a more practical strategy for a compact battery driven device. The other major challenge is designing the proper media access control (MAC) protocol, which provides nodes with addresses and channel access capability so that directional links between multiple nodes can be formed. The challenge lies in the fact that most nodes are blind to other nodes' transmissions because of their relatively narrow directional links. Because of this blindness, packet collisions are inevitable. Therefore, an efficient multiple access protocol needs to be designed for the FSOC system to ensure successful directional communication between the motes and cluster heads for data collection and relaying. While there are many protocols that allow multiple access and provide collision avoidance for traditional RF systems, these protocols are not optimized for FSOC systems consisting of multiple narrow FOV transmitters. Instead, a directional MAC (DMAC) protocol is developed from existing RF protocols, but modified for FSOC technology. It overcomes the limitations in FSOC communication resulting from directionality by setting up a master-slave network architecture where communication takes place between a sensing system, "mote", and a central control station, or "cluster head", which is designed with a multiple VCSEL transmitters. In this way, the physical transmitter sources of the cluster head become an integral part of the FSOC DMAC protocol. In this type of architecture, the master node, or cluster head, has the dual functionality of coordinating network traffic and aggregating data from all the slave nodes, or motes, that are within its field of view (FOV). Multiple cluster heads can form a directional network backbone, and can relay signals collected from a mote through other cluster heads, until the signal is delivered to its destination. In summary, this dissertation provides: 1) the design and implementation of small and inexpensive short-range FSOC systems that can be implemented using standard "off the shelf" components including a microcontroller and sensor device to form a complete standalone package; 2) development of a DMAC protocol that is optimized for the implemented FSOC system and target network applications; 3) network performance evaluation and optimization for the combined FSOC hardware, network architecture, and DMAC protocol. This is done through a series of hardware tests on an experimental prototype FSOC sensor network consisting of 10 motes and 1 cluster head and simulations of larger network sizes

State-of-the-Art System Solutions for Unmanned Underwater Vehicles

Unmanned Underwater Vehicles (UUVs) have gained popularity for the last decades, especially for the purpose of not risking human life in dangerous operations. On the other hand, underwater environment introduces numerous challenges in navigation, control and communication of such vehicles. Certainly, this fact makes the development of these vehicles more interesting and engineering-wise more attractive. In this paper, we first revisit the existing technology and methodology for the solution of aforementioned problems, then we try to come up with a system solution of a generic unmanned underwater vehicles