57 research outputs found
Latency-Optimized and Energy-Efficient MAC Protocol for Underwater Acoustic Sensor Networks: A Cross-Layer Approach
Considering the energy constraint for fixed sensor nodes and the unacceptable long propagation delay, especially for latency sensitive applications of underwater acoustic sensor networks, we propose a MAC protocol that is latency-optimized and energy-efficient scheme and combines the physical layer and the MAC layer to shorten transmission delay. On physical layer, we apply convolution coding and interleaver for transmitted information. Moreover, dynamic code rate is exploited at the receiver side to accelerate data reception rate. On MAC layer, unfixed frame length scheme is applied to reduce transmission delay, and to ensure the data successful transmission rate at the same time. Furthermore, we propose a network topology: an underwater acoustic sensor network with mobile agent. Through fully utilizing the supper capabilities on computation and mobility of autonomous underwater vehicles, the energy consumption for fixed sensor nodes can be extremely reduced, so that the lifetime of networks is extended
Multifunction Radios and Interference Suppression for Enhanced Reliability and Security of Wireless Systems
Wireless connectivity, with its relative ease of over-the-air information sharing, is a key technological enabler that facilitates many of the essential applications, such as satellite navigation, cellular communication, and media broadcasting, that are nowadays taken for granted. However, that relative ease of over-the-air communications has significant drawbacks too. On one hand, the broadcast nature of wireless communications means that one receiver can receive the superposition of multiple transmitted signals. But on the other hand, it means that multiple receivers can receive the same transmitted signal. The former leads to congestion and concerns about reliability because of the limited nature of the electromagnetic spectrum and the vulnerability to interference. The latter means that wirelessly transmitted information is inherently insecure.
This thesis aims to provide insights and means for improving physical layer reliability and security of wireless communications by, in a sense, combining the two aspects above through simultaneous and same frequency transmit and receive operation. This is so as to ultimately increase the safety of environments where wireless devices function or where malicious wirelessly operated devices (e.g., remote-controlled drones) potentially raise safety concerns. Specifically, two closely related research directions are pursued. Firstly, taking advantage of in-band full-duplex (IBFD) radio technology to benefit the reliability and security of wireless communications in the form of multifunction IBFD radios. Secondly, extending the self-interference cancellation (SIC) capabilities of IBFD radios to multiradio platforms to take advantage of these same concepts on a wider scale.
Within the first research direction, a theoretical analysis framework is developed and then used to comprehensively study the benefits and drawbacks of simultaneously combining signals detection and jamming on the same frequency within a single platform. Also, a practical prototype capable of such operation is implemented and its performance analyzed based on actual measurements. The theoretical and experimental analysis altogether give a concrete understanding of the quantitative benefits of simultaneous same-frequency operations over carrying out the operations in an alternating manner. Simultaneously detecting and jamming signals specifically is shown to somewhat increase the effective range of a smart jammer compared to intermittent detection and jamming, increasing its reliability.
Within the second research direction, two interference mitigation methods are proposed that extend the SIC capabilities from single platform IBFD radios to those not physically connected. Such separation brings additional challenges in modeling the interference compared to the SIC problem, which the proposed methods address. These methods then allow multiple radios to intentionally generate and use interference for controlling access to the electromagnetic spectrum. Practical measurement results demonstrate that this effectively allows the use of cooperative jamming to prevent unauthorized nodes from processing any signals of interest, while authorized nodes can use interference mitigation to still access the same signals. This in turn provides security at the physical layer of wireless communications
Spectrum handoff strategy for cognitive radio-based Mac in industrial wirless sensor and actuator networks
In this thesis, a Cognitive Radio(CR)-based MAC for Industrial Wireless Sensor and Actuator Network (IWSAN) applications is proposed. IWSANs are typically used for closed-loop control applications, and they demand strict requirements in terms of time and robustness. Low latency and low error rates are required in order not to endanger persons or machinery. Moreover, these applications operate in industrial environments such as factories or transport scenarios (as aeronautics or railway) where multipath fading and shadowing are present due to metal surfaces. Furthermore, interference from other communication systems or industrial machinery is also common in these environments. The proposed MAC, based on the CR paradigm, is capable of ensuring time and robustness requirements in industrial channels.
In the process of designing the CR-based MAC for IWSAN applications, a comparison between several non-CR-based MACs and CR-based MACs has been carried out. This comparison, which allows stating the benefits of CR for these applications, is presented in this thesis. The performance of every MAC is determined theoretically using Network Calculus, and it is validated through OPNET simulations. CR solutions, due to their adaptability characteristics, are capable of avoiding interference and ensuring robustness in industrial environments. However, none of the selected MACs are capable of ensuring robustness without comprising time requirements, since interference is avoided but not in a bounded time. On the other hand, the MAC proposed in this thesis is capable of avoiding interference ensuring time and robustness requirements at the same time. This MAC is therefore suitable for IWSAN applications.
To ensure a deterministic behavior against interference, a novel handoff algorithm, which detects interference and hops to another channel, has been proposed. This algorithm has been designed to be used jointly with one of the evaluated MACs. The detection of the interference and the hop to another channel is done in a bounded time, because the proposed algorithm detects interference while the system is transmitting. The performance of this proposal is evaluated using Network Calculus and OPNET simulations, and the results are compared with the system without the proposed handoff algorithm. The comparison of the results shows how the evaluated MAC is only capable of ensuring both time and robustness requirements when the proposed handoff strategy is used.
Moreover, the spectrum sensing algorithm used to obtain information about the environment is delved and its performance is measured through MATLAB simulations. An energy detector has been chosen due to its simplicity. Also, a cyclostationary Modulation Classifier is presented and a simplification has been carried out allowing its implementation on real hardware. The Modulation Classifier is capable of distinguishing between OFDM, QPSK and GFSK signals. The performance of the algorithm is presented in this thesis for different signals and for different receiver impairments such as frequency offset, DC offset and I/Q imbalance.
Finally, a cognitive platform to validate the spectrum sensing algorithms is presented. This platform has been designed using a Xilinx Virtex 6 FPGA by a working group composed of researchers from IK4-Ikerlan and Mondragon Unibertsitatea. The platform, which uses both spectrum sensing algorithms, is an Ethernet-to-RF bridge. It has been designed to replace an Ethernet wired link by a wireless one for IWSAN applications. The proposed platform ensures a reliable communication link against interference. In the proposed implementation, the energy detector is used by the transmitter in order to find a free channel to transmit data, whereas the modulation classifier is used by the receiver in order to distinguish between the signal transmitted by the RF-Ethernet bridge and other signals. In this way the receiver can find the channel where the transmitter is carrying out the communication.En esta tesis se propone una MAC basada en el paradigma de la Radio Cognitiva (RC) para redes de sensores y actuadores inalámbricos industriales. Estas redes se suelen utilizar para aplicaciones de control en lazo cerrado, que exigen requisitos estrictos de tiempo y robustez. Para no poner en peligro la salud de las personas o la maquinaria es necesario que la red asegure una baja latencia y una tasa baja de errores. Además, al trabajar en ambientes industriales como fábricas o transportes (trenes, aviones, etc.), estas redes tienen que hacer frente a canales con mucho desvanecimiento por multitrayecto y efecto sombra debido a las superficies metálicas. También es común en estos entornos que haya interferencias de otros sistemas de comunicaciones o de la propia maquinaria industrial. La MAC propuesta en esta tesis es capaz de asegurar los requisitos temporales y de robustez demandados trabajando en este tipo de entornos.
En el proceso de diseño de la MAC basada en RC para redes de sensores y actuadores inalámbricos industriales, se ha llevado a cabo una comparación de diferentes MACs diseñadas para estas redes. Se han evaluado tanto MACs basadas en RC como no basadas en ella, estableciendo las ventajas de la RC para estas aplicaciones. La evaluación se ha llevado a cabo haciendo un estudio teórico mediante Network Calculus, cuyos resultados se han validado mediante simulaciones en OPNET. Los resultados muestran como la RC es capaz de evitar interferencias y asegurar robustez en ambientes industriales. Sin embargo, ninguna de las MACs seleccionadas ha conseguido asegurar ambos requisitos, temporales y de robustez, al mismo tiempo; se puede evitar las interferencias pero no sin comprometer los requisitos temporales de la aplicación. Sin embargo, la MAC propuesta es capaz de evitar interferencias asegurando al mismo tiempo los requisitos temporales y de robustez. Por lo tanto, la MAC propuesta es apropiada para este tipo de redes.
Para asegurar el comportamiento determinista del sistema, se ha propuesto un novedoso algoritmo de handoff que es capaz de detectar una interferencia y saltar a otro canal. Este algoritmo se ha diseñado para ser utilizado conjuntamente con una de las MACs previamente evaluadas. La detección de la interferencia y el salto a otro canal se hace en un tiempo determinado de tiempo, ya que es posible detectar interferencias mientras el sistema está transmitiendo. Su rendimiento se ha evaluado mediante Network Calculus y simulaciones en OPNET, y se ha comparado con los resultados obtenidos con la MAC cuando no se utiliza el esquema propuesto. De la comparación se deduce que el esquema de handoff añade a la MAC la capacidad de asegurar a la vez los requisitos temporales y de robustez.
Además, en la tesis se explica el algoritmo de spectrum sensing que la MAC utiliza para obtener información del entorno, y su rendimiento se ha estudiado mediante simulaciones en MATLAB. Debido a su simplicidad, se ha optado por un detector de energía para este propósito. También se presenta un clasificador de modulaciones cicloestacionario. Este clasificador ha sido simplificado todo lo posible para posibilitar su implementación en hardware real. El clasificador de modulaciones es capaz de distinguir entre señales OFDM, QPSK y GFSK. Su rendimiento se detalla para diferentes señales y para diferentes deficiencias presentes en el receptor, como son offset de frecuencia, offset de continua o desequilibrios I/Q.
Por último, se presenta una plataforma cognitiva que se ha utilizado para validar los algoritmos de spectrum sensing. Un grupo de trabajo compuesto por investigadores de IK4-Ikerlan y Mondragon Unibertsitatea ha diseñado esta plataforma sobre una FPGA Virtex 6 de Xilinx. La plataforma, que utiliza los dos algoritmos de spectrum sensing, es un puente Ethernet-RF. Su objetivo es reemplazar un enlace cableado de Ethernet por uno inalámbrico para aplicaciones de redes de sensores y actuadores industriales. Gracias a los algoritmos de spectrum sensing, la plataforma es capaz de asegurar un enlace robusto ante interferencias. El detector de energía se utiliza en el transmisor para encontrar los posibles canales libres donde transmitir la información. Mientras que el clasificador de modulaciones se utiliza en el receptor para distinguir entre la señal del transmisor y otras posibles señales. Esto permite al receptor saber en qué canal de todos los posibles está el transmisor.Tesi honetan proposatzen da Irrati Kognitiboaren (IK) paradigman oinarritutako MAC bat industriako haririk gabeko sentsore eta eragingailuen sareetarako. Sare horiek begizta itxiko kontrol aplikazioetarako erabili ohi dira, denbora eta sendotasunaren aldetik baldintza ugari eskatzen dute eta. Pertsonen osasuna eta makinak arriskuan ez jartzeko, beharrezkoa da sareak latentzia eta hutsegite tasa txikiak bermatzea. Gainera, industri giroetan lan egiteko direnez, esaterako, lantegietan edo garraioetan (trenak, hegazkinak, etab.), sare horiek gai izan behar dira gainazal metalikoek eragiten dituzten ibilbide aniztunaren eta itzal efektuaren ondorioz asko barreiatzen diren kanalei aurre egiteko. Ingurune horien ohiko ezaugarria da, baita ere, beste komunikazio sistema batzuen edo industriako makinen beraien interferentziak egotea. Tesi honetan proposatzen den MACa gai da honelako inguruetan lan egiteko denborari eta sendotasunari dagokienez eskatzen dituen baldintzak ziurtatzeko.
IKan oinarrituta haririk gabeko sentsore eta eragingailu industrialen sareetarako MACa diseinatzeko prozesuan, horrelako sareetarako aurkeztu diren hainbat MAC alderatu dira. IKan oinarritutako MACak zein bestelakoak ebaluatu dira, eta IKak aplikazio hauetarako dituen abantailak ezarri dira. Ebaluaziorako Network Calculus erabili da, zeinaren bidez azterketa teoriko bat egin baita, eta azterketaren emaitzak OPNETen simulazioak eginda baliozkotu dira. Emaitzek erakusten dutenez, IKa gai da industriako inguruneetan interferentziak ekidin eta sendotasuna ziurtatzeko. Halere, aukeratu diren MACetatik batek ere ez du lortu baldintza biak, denborari buruzkoa zein sendotasunari buruzkoa, aldi berean ziurtatzea; interferentziak ekidin daitezke, baina ez aplikazioaren denborari buruzko baldintzak arriskuan jarri gabe. Dena dela, proposatu den MACak portaera determinista bat ziurtatzen du interferentziekiko, eta aldi berean denborari eta sendotasunari buruzko baldintzak ere ziurtatzen ditu. Hortaz, MAC hau egokia da sare mota honetarako.
Sistemaren portaera determinista ziurtatzeko, handoff algoritmo berritzailea proposatu da, zeina interferentzia bat antzeman eta beste kanal bat igarotzeko gai den. Algoritmo hori aurretik ebaluatutakoa MACetako batekin batera erabiltzeko diseinatu da. Interferentzia antzeman eta beste kanal batera salto egitea denbora jakin batean egiten da, izan ere, sistema transmititzen ari dela antzeman baitaitezke interferentziak. Network Calculusen bitartez eta OPNETeko simulazioen bitartez ebaluatu da sistemaren errendimendua, eta proposatutako eskema erabiltzen ez denean MACak ematen dituen emaitzekin alderatu da. Alderaketa horretatik ondorioztatzen denez, handoff eskemak denborari eta sendotasunari buruzko baldintzak batera ziurtatzeko ahalmena ematen dio MACari.
Gainera, tesiak azaltzen du inguruneari buruzko informazioa eskuratzeko MACak erabiltzen duen spectrum sensing algoritmoa, eta bere errendimendua MATLABen simulazioak eginez aztertu da. Bere sinpletasuna dela eta, energia detektore bat aukeratu da asmo honetarako. Modulazio sailkatzaile zikloegonkor bat ere aurkezten da. Sailkapen hori ahalik eta gehien sinplifikatu da benetako hardwarean inplementatu ahal izateko. Modulazioen sailkatzaileak OFDM, QPSK eta GFSK seinaleak bereizi ditzake. Bere errendimendua hargailuan dauden seinale eta akats desberdinetarako zehazten da, esaterako maiztasunaren offset-a,zuzenaren offset-a edo I/Q desorekak.
Bukatzeko, spectrum sensing-eko algoritmoak baliozkotzeko erabili den plataforma kognitibo bat aurkezten da. IK4-Ikerlaneko eta Mondragon Unibertsitateko ikertzailez osatutako lantalde batek diseinatu du plataforma hori Xilinxen Virtex 6 FPGA baten oinarrutz. Plataformak spectrum sensing-eko bi algoritmo erabiltzen ditu eta Ethernet-RF zubi bat da. Bere helburua da Etherneteko kable bidezko lotura bat haririk gabeko batekin ordeztea industriako sentsore eta eragingailuen sareetan aplikatzeko. Spectrum sensing-eko algoritmoei esker, plataformak lotura sendoa bermatu dezake interferentziak gertatzen direnean. Energia detektorea transmisorean erabiltzen da informazioa transmititzeko erabilgarri egon daitezkeen kanalak aurkitzeko. Modulazioen sailkatzailea, berriz, hargailuan erabiltzen da transmisorearen seinalea eta egon daitezkeen beste seinale batzuk bereizteko. Horri esker, hargailuak badaki posible diren kanal guztietatik non dagoen transmisorea
Secure protocols for wireless availability
Since wireless networks share a communication medium, multiple transmissions
on the same channel cause interference to each other and degrade the
channel quality, much as multiple people talking at the same time make for
inefficient meetings. To avoid transmission collision, the network divides
the medium into multiple orthogonal channels (by interleaving the channel
access in frequency or time) and often uses medium access control (MAC)
to coordinate channel use. Alternatively (e.g., when the wireless users use
the same physical channel), the network users can emulate such orthogonal
channel access in processing by spreading and coding the signal. Building
on such orthogonal access technology, this dissertation studies protocols that
support the coexistence of wireless users and ensure wireless availability.
In contrast to other studies focusing on improving the overall e fficiency
of the network, I aim to achieve reliability at all times. Thus, to study the
worst-case misbehavior, I pose the problem within a security framework and
introduce an adversary who compromised the network and has insider access.
In this dissertation, I propose three schemes for wireless availability:
SimpleMAC, Ignore-False-Reservation MAC (IFR-MAC), and Redundancy
O ffset Narrow Spectrum (RONS). SimpleMAC and IFR-MAC build on MAC
protocols that utilize explicit channel coordination in control communication.
SimpleMAC counters MAC-aware adversary that uses the information being
exchanged at the MAC layer to perform a more power e fficient jamming
attack. IFR-MAC nulli ffies the proactive attack of denial-of-service injection
of false reservation control messages. Both SimpleMAC and IFR-MAC
quickly outperform the Nash equilibrium of disabling MAC and converge to
the capacity-optimal performance in worst-case failures. When the MAC
fails to coordinate channel use for orthogonal access or in a single-channel
setting (both cases of which, the attacker knows the exact frequency and time
location of the victim's channel access), RONS introduces a physical-layer, processing-based technique for interference mitigation. RONS is a narrow
spectrum technology that bypasses the spreading cost and eff ectively counters
the attacker's information-theoretically optimal strategy of correlated
jamming
Wireless Sensor System for Recycling
The motivation of this thesis was to research and design a prototype model of a wireless sensor network application, to be used as an automated detection infrastructure in recycling environment. The initial idea was to measure the level of the surface in a recycling container and transmit the information through a wireless communication system. The prototype is an initial step for recycling companies for building an automated detection network.
Background of the research strongly supports the accomplished prototype. Study includes description of wireless environment with its problems and challenges. It proceeds with consideration of suitable wireless standards and considers most convenient sensor methods for recycling environment. Eventually document presents the prototype combining the studied entities.
As a result, the prototype has two main operating parts: the wireless communication network and sensors. The network was realized with ZigBee standard by using two radio chips as communication nodes. Second communication node is attached to a recycling container and combined with two ultrasound sensors. This node includes a soft-ware algorithm, which is polling the state of the sensors regularly and deciding if the container is full. The node proceeds to transmission of the information to other communication node. This node is connected to computer and will transmit the information to be used by the recycling organization.fi=Opinnäytetyö kokotekstinä PDF-muodossa.|en=Thesis fulltext in PDF format.|sv=Lärdomsprov tillgängligt som fulltext i PDF-format
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