98 research outputs found
Quasi-orthogonal space-frequency coding in non-coherent cooperative broadband networks
© 2014 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.So far, complex valued orthogonal codes have been used differentially in cooperative broadband networks. These codes however achieve less than unitary code rate when utilized in cooperative networks with more than two relays. Therefore, the main challenge is how to construct unitary rate codes for non-coherent cooperative broadband networks with more than two relays while exploiting the achievable spatial and frequency diversity. In this paper, we extend full rate quasi-orthogonal codes to differential cooperative broadband networks where channel information is unavailable. From this, we propose a generalized differential distributed quasi-orthogonal space-frequency coding (DQSFC) protocol for cooperative broadband networks. Our proposed scheme is able to achieve full rate, and full spatial and frequency diversity in cooperative networks with any number of relays. Through pairwise error probability analysis we show that the diversity gain of our scheme can be improved by appropriate code construction and sub-carrier allocation. Based on this, we derive sufficient conditions for the proposed code structure at the source node and relay nodes to achieve full spatial and frequency diversity.Peer reviewe
Timing and Carrier Synchronization in Wireless Communication Systems: A Survey and Classification of Research in the Last 5 Years
Timing and carrier synchronization is a fundamental requirement for any wireless communication system to work properly. Timing synchronization is the process by which a receiver node determines the correct instants of time at which to sample the incoming signal. Carrier synchronization is the process by which a receiver adapts the frequency and phase of its local carrier oscillator with those of the received signal. In this paper, we survey the literature over the last 5 years (2010â2014) and present a comprehensive literature review and classification of the recent research progress in achieving timing and carrier synchronization in single-input single-output (SISO), multiple-input multiple-output (MIMO), cooperative relaying, and multiuser/multicell interference networks. Considering both single-carrier and multi-carrier communication systems, we survey and categorize the timing and carrier synchronization techniques proposed for the different communication systems focusing on the system model assumptions for synchronization, the synchronization challenges, and the state-of-the-art synchronization solutions and their limitations. Finally, we envision some future research directions
IR-UWB and OFDM-UWB Transceiver Nodes for Communication and Positioning Purposes
RĂ©sumĂ© Ultra-wideband (UWB) a suscitĂ© l'intĂ©rĂȘt de chercheurs et de l'industrie en raison de ses nombreux avantages tels que la faible probabilitĂ© d'interception et de la possibilitĂ© de combiner la communication des donnĂ©es de positionnement dans un seul systĂšme. Il existe plusieurs UWB couche physique (PHY) prĂ©sentĂ©es initialement Ă la norme IEEE qui convergent en deux propositions principales: des porte-UWB ou Orthogonal Frequency-Division Multiplexing (OFDM-UWB), et Ă court d'impulsion porteuse Ă -UWB ou Impulse Radio-(IR-UWB). Une des plus grandes tĂąches difficiles pour les chercheurs est de nos jours la conception d'Ă©metteurs-rĂ©cepteurs UWB optimisĂ©s qui satisfont Ă des conditions rigoureuses, dont la simplicitĂ© caractĂ©ristiques large bande, Ă faible coĂ»t et de conception. Des Ă©tudes antĂ©rieures ont montrĂ© que les rĂ©cepteurs Ă conversion directe basĂ©e sur Wave-radio interfĂ©romĂštre (WRI) circuits reprĂ©sentent un bon candidat pour les applications UWB. Circuits IRG ont plusieurs avantages tels que l'exploitation Ă large bande, Ă faible coĂ»t et la simplicitĂ©. Des travaux antĂ©rieurs sur l'IRG circuit, cependant, a enquĂȘtĂ© sur le circuit de l'IRG sur la base du concept de porteuse unique signaux (par exemple, les signaux sinusoĂŻdaux). L'objectif de ce projet est de fournir les rĂ©sultats de conception, de simulation, de mise en oeuvre et le test d'un Ă©metteur-rĂ©cepteur WRI basĂ© sur ce que peut ĂȘtre utilisĂ© comme un noeud ou un pico-rĂ©seau dans un dĂ©tecteur sans fil / rĂ©seau de donnĂ©es. Nous allons passer par les Ă©tapes de conception et de mise en oeuvre de propositions UWB deux: IR-UWB et OFDM-UWB. Pour la proposition porteuse Ă nous concentrer sur la conception et la mise en oeuvre de l'Ă©metteur-rĂ©cepteur en intĂ©grant les
opĂ©rations de transmission / rĂ©ception dans un prototype unique, alors que pour la proposition des porte-nous concevoir et mettre en oeuvre l'Ă©metteur-rĂ©cepteur avec le circuit de l'IRG dans le rĂ©cepteur seulement utilisĂ© en tant que convertisseur abaisseur directe. RĂ©sultats expĂ©rimentaux, de simulation et d'analyse ont Ă©tĂ© obtenus et sont prĂ©sentĂ©s dans cette thĂšse.----------Abstract Ultra-wideband (UWB) technology has attracted interest from both researchers and the industry due to its numerous advantages such as low probability of interception and the possibility of combining data communication with positioning in a single system. There are several different UWB physical layer (PHY) proposals originally submitted to IEEE which converged into two main proposals: carrierâbased UWB or Orthogonal-Frequency Division Multiplexing (OFDMâUWB), and shortâpulse carrierlessâUWB or Impulse-Radio (IR-UWB). One of the biggest challenging tasks for researchers nowadays is the design of optimized UWB transceivers that would satisfy rigorous conditions, among which wideband characteristics, low-cost and design simplicity. Previous studies have shown that direct-conversion receivers based on Wave-Radio Interferometer (WRI) circuits represent a suitable candidate for UWB applications. WRI circuits have several advantages such as wideband operation, low cost, and simplicity. Previous works on WRI circuit, however, investigated the WRI circuit based on the concept of single-carrier signals (i.e., sinusoidal signals). The objective of this project is to provide the design, simulation, implementation and testing results of a WRI-based transceiver that can be utilized as a node or a piconet in a wireless sensor/data network. We will go through the design and implementation steps for both UWB proposals: IR-UWB and OFDM-UWB. For the carrierless proposal we will focus on designing and implementing the transceiver by integrating the transmitter/receiver operations in a single prototype, while for the carrierâbased proposal we will design and implement the transceiver with the WRI circuit in the receiver only utilized as a direct downconverter
System design and validation of multi-band OFDM wireless communications with multiple antennas
[no abstract
Cooperative Radio Communications for Green Smart Environments
The demand for mobile connectivity is continuously increasing, and by 2020 Mobile and Wireless Communications will serve not only very dense populations of mobile phones and nomadic computers, but also the expected multiplicity of devices and sensors located in machines, vehicles, health systems and city infrastructures. Future Mobile Networks are then faced with many new scenarios and use cases, which will load the networks with different data traffic patterns, in new or shared spectrum bands, creating new specific requirements. This book addresses both the techniques to model, analyse and optimise the radio links and transmission systems in such scenarios, together with the most advanced radio access, resource management and mobile networking technologies. This text summarises the work performed by more than 500 researchers from more than 120 institutions in Europe, America and Asia, from both academia and industries, within the framework of the COST IC1004 Action on "Cooperative Radio Communications for Green and Smart Environments". The book will have appeal to graduates and researchers in the Radio Communications area, and also to engineers working in the Wireless industry. Topics discussed in this book include: âą Radio waves propagation phenomena in diverse urban, indoor, vehicular and body environmentsâą Measurements, characterization, and modelling of radio channels beyond 4G networksâą Key issues in Vehicle (V2X) communicationâą Wireless Body Area Networks, including specific Radio Channel Models for WBANsâą Energy efficiency and resource management enhancements in Radio Access Networksâą Definitions and models for the virtualised and cloud RAN architecturesâą Advances on feasible indoor localization and tracking techniquesâą Recent findings and innovations in antenna systems for communicationsâą Physical Layer Network Coding for next generation wireless systemsâą Methods and techniques for MIMO Over the Air (OTA) testin
Cooperative Radio Communications for Green Smart Environments
The demand for mobile connectivity is continuously increasing, and by 2020 Mobile and Wireless Communications will serve not only very dense populations of mobile phones and nomadic computers, but also the expected multiplicity of devices and sensors located in machines, vehicles, health systems and city infrastructures. Future Mobile Networks are then faced with many new scenarios and use cases, which will load the networks with different data traffic patterns, in new or shared spectrum bands, creating new specific requirements. This book addresses both the techniques to model, analyse and optimise the radio links and transmission systems in such scenarios, together with the most advanced radio access, resource management and mobile networking technologies. This text summarises the work performed by more than 500 researchers from more than 120 institutions in Europe, America and Asia, from both academia and industries, within the framework of the COST IC1004 Action on "Cooperative Radio Communications for Green and Smart Environments". The book will have appeal to graduates and researchers in the Radio Communications area, and also to engineers working in the Wireless industry. Topics discussed in this book include: âą Radio waves propagation phenomena in diverse urban, indoor, vehicular and body environmentsâą Measurements, characterization, and modelling of radio channels beyond 4G networksâą Key issues in Vehicle (V2X) communicationâą Wireless Body Area Networks, including specific Radio Channel Models for WBANsâą Energy efficiency and resource management enhancements in Radio Access Networksâą Definitions and models for the virtualised and cloud RAN architecturesâą Advances on feasible indoor localization and tracking techniquesâą Recent findings and innovations in antenna systems for communicationsâą Physical Layer Network Coding for next generation wireless systemsâą Methods and techniques for MIMO Over the Air (OTA) testin
Modulation and Multiple Access Techniques for Ultra-Wideband Communication Systems
Two new energy detection (ED) Ultra-Wideband (UWB) systems are proposed in this dissertation. The first one is an ED UWB system based on pulse width modulation (PWM). The bit error rate (BER) performance of this ED PWM system is slightly worse than ED pulse position modulation (PPM) system in additive white Gaussian noise (AWGN) channels. However, the BER performance of this ED PWM system surpasses that of a PPM system in multipath channels since a PWM system does not suffer cross-modulation interference (CMI) as a PPM system. In the presence of synchronization errors, the BER performance of a PWM system also surpasses that of a PPM system. The second proposed ED UWB system is based on using two pulses, which are the different-order derivatives of the Gaussian pulse, to transmitted bit 0 or 1. These pulses are appropriately chosen to separate their spectra in frequency domain.The receiver is composed of two energy detection branches and each branch has a filter which captures the signal energy of either bit 0 or 1. The outputs of two branches are subtracted from each other to generate the decision statistic and the value of this statistic is compared to a threshold to determine the transmitted bits. This system is named as acf{GFSK} system in this dissertation and it exhibits the same BER performance as a PPM system in AWGN channels. In multipath channels, a GFSK system surpasses a PPM system because it does not suffer CMI. And the BER performance of a GFSK system is better than a PPM system in the presence of synchronization errors. When a GFSK system is compared to a PWM system, it will always achieve approximately 2 dB improvement in AWGN channels, multipath channels, and in the presence synchronization errors. However, a PWM system uses lower-order derivatives of the Gaussian pulse to transmit signal, and this leads to a simple pulse generator. In this dissertation, an optimal threshold is applied to improve PPM system performance. The research results show that the application of an optimal threshold can e
A two phase framework for visible light-based positioning in an indoor environment: performance, latency, and illumination
Recently with the advancement of solid state lighting and the application thereof
to Visible Light Communications (VLC), the concept of Visible Light Positioning
(VLP) has been targeted as a very attractive indoor positioning system (IPS) due to
its ubiquity, directionality, spatial reuse, and relatively high modulation bandwidth.
IPSs, in general, have 4 major components (1) a modulation, (2) a multiple access
scheme, (3) a channel measurement, and (4) a positioning algorithm. A number of
VLP approaches have been proposed in the literature and primarily focus on a fixed
combination of these elements and moreover evaluate the quality of the contribution
often by accuracy or precision alone.
In this dissertation, we provide a novel two-phase indoor positioning algorithmic
framework that is able to increase robustness when subject to insufficient anchor luminaries
and also incorporate any combination of the four major IPS components.
The first phase provides robust and timely albeit less accurate positioning proximity
estimates without requiring more than a single luminary anchor using time division
access to On Off Keying (OOK) modulated signals while the second phase provides a
more accurate, conventional, positioning estimate approach using a novel geometric
constrained triangulation algorithm based on angle of arrival (AoA) measurements.
However, this approach is still an application of a specific combination of IPS components.
To achieve a broader impact, the framework is employed on a collection
of IPS component combinations ranging from (1) pulsed modulations to multicarrier
modulations, (2) time, frequency, and code division multiple access, (3) received signal
strength (RSS), time of flight (ToF), and AoA, as well as (4) trilateration and
triangulation positioning algorithms.
Results illustrate full room positioning coverage ranging with median accuracies
ranging from 3.09 cm to 12.07 cm at 50% duty cycle illumination levels. The framework
further allows for duty cycle variation to include dimming modulations and results
range from 3.62 cm to 13.15 cm at 20% duty cycle while 2.06 cm to 8.44 cm at a
78% duty cycle. Testbed results reinforce this frameworks applicability. Lastly, a
novel latency constrained optimization algorithm can be overlaid on the two phase
framework to decide when to simply use the coarse estimate or when to expend more
computational resources on a potentially more accurate fine estimate.
The creation of the two phase framework enables robust, illumination, latency
sensitive positioning with the ability to be applied within a vast array of system
deployment constraints
Modulation and Multiple Access Techniques for Ultra-Wideband Communication Systems
Two new energy detection (ED) Ultra-Wideband (UWB) systems are proposed in this dissertation. The first one is an ED UWB system based on pulse width modulation (PWM). The bit error rate (BER) performance of this ED PWM system is slightly worse than ED pulse position modulation (PPM) system in additive white Gaussian noise (AWGN) channels. However, the BER performance of this ED PWM system surpasses that of a PPM system in multipath channels since a PWM system does not suffer cross-modulation interference (CMI) as a PPM system. In the presence of synchronization errors, the BER performance of a PWM system also surpasses that of a PPM system. The second proposed ED UWB system is based on using two pulses, which are the different-order derivatives of the Gaussian pulse, to transmitted bit 0 or 1. These pulses are appropriately chosen to separate their spectra in frequency domain.The receiver is composed of two energy detection branches and each branch has a filter which captures the signal energy of either bit 0 or 1. The outputs of two branches are subtracted from each other to generate the decision statistic and the value of this statistic is compared to a threshold to determine the transmitted bits. This system is named as acf{GFSK} system in this dissertation and it exhibits the same BER performance as a PPM system in AWGN channels. In multipath channels, a GFSK system surpasses a PPM system because it does not suffer CMI. And the BER performance of a GFSK system is better than a PPM system in the presence of synchronization errors. When a GFSK system is compared to a PWM system, it will always achieve approximately 2 dB improvement in AWGN channels, multipath channels, and in the presence synchronization errors. However, a PWM system uses lower-order derivatives of the Gaussian pulse to transmit signal, and this leads to a simple pulse generator. In this dissertation, an optimal threshold is applied to improve PPM system performance. The research results show that the application of an optimal threshold can e
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