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Dissertations / Theses on the topic 'Multicarrier communication systems'
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Yap, K. S. "Multicarrier equalisation and synchronisation systems." Thesis, Queen's University Belfast, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269147.
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Huang, Hu, and 黃鵠. "Multicarrier DS/SFH-CDMA systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B31222705.
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Huang, Hu. "Multicarrier DS/SFH-CDMA systems /." Hong Kong : University of Hong Kong, 2000. http://sunzi.lib.hku.hk/hkuto/record.jsp?B22053839.
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Wang, Hao Chen Biao. "Transceiver design issues for wireless multicarrier communication systems." Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2004. http://wwwlib.umi.com/cr/syr/main.
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Hu, Bin. "Multicarrier DS-CDMA communication systems using smart antennas." Thesis, University of Southampton, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.430726.
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Zhang, Hongbing. "Wavelet Packet Based Multicarrier CDMA Wireless Communication Systems." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1081568890.
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Hau, Yan Kit Gary. "Multicarrier microwave amplifier for cellular communications." Thesis, University of Leeds, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289809.
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Vajipeyajula, Mani Kishore. "Clustered multicarrier systems for very wideband wireless communications." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 4.92 Mb., 53 p, 2005. http://wwwlib.umi.com/dissertations/fullcit/1428250.
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Tureli, Didem Kivanc. "Resource allocation for multicarrier communications /." Thesis, Connect to this title online; UW restricted, 2005. http://hdl.handle.net/1773/6068.
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Deumal, Herraiz Marc. "Multicarrier communication systems with low sensibility to nonlinear amplification." Doctoral thesis, Universitat Ramon Llull, 2008. http://hdl.handle.net/10803/9137.
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Actualment estem entrant a una nova era de la informació amb gran demanda de sistemes de comunicació sense fils. Nous serveis com dades i video requereixen transmissions fiables d'alta velocitat, fins i tot en escenaris d'alta mobilitat. A més a més, la dificultat d'assignar el limitat espectre radioelèctric juntament amb la necessitat d'incrementar el temps de vida de les bateries dels terminals mòbils, requereix el diseny de transceptors que usin la potència i l'ampla de banda disponibles de manera eficient. Les comunicacions multiportadora basades en OFDM són capaces de satisfer la majoria d'aquests requeriments. Però, entre altres reptes, reduir la sensibilitat a la amplificació no-lineal és un factor clau durant el diseny. En aquesta tesi doctoral s'analitza la sensibilitat dels sistemes multiportadora basats en OFDM a l'amplificació no-lineal i es consideren formes eficients per superar aquest problema. La tesi s'enfoca principalment al problema de reduir les fluctuacions de l'envolupant del senyal transmès. En aquest sentit es presenta també un estudi de les mètriques de l'envolupant del senyal, PAPR i CM. A més a més, basant-nos en l'anàlisis presentat es proposen noves tècniques per sistemes OFDM i MC-SS. Per MC-SS, també es tracta el diseny d'una tècnica de postprocessament en forma de detector multiusuari per canals no-lineals.Actualmente estamos entrando en una nueva era de la información donde se da una gran demanda de sistemas de comunicación inalámbricos. Nuevos servicios como datos y vídeo requieren transmisiones fiables de alta velocidad, incluso en escenarios de alta movilidad. Además, la dificultad de asignar el limitado espectro radioeléctrico junto con la necesidad de incrementar el tiempo de vida de las baterías de los terminales móviles, requiere el diseño de transceptores que usen eficientemente la potencia y el ancho de banda disponibles. Las comunicaciones multiportadora basadas en OFDM son capaces de satisfacer la mayoría de dichos requerimientos. Sin embargo, entre otros retos, reducir su sensibilidad a la amplificación no-lineal es un factor clave durante el diseño. En esta tesis se analiza la sensibilidad de los sistemas multiportadora basados en OFDM a la amplificación no-lineal y se consideran formas eficientes para superar dicho problema. La tesis se enfoca principalmente al problema de reducir las fluctuaciones de la envolvente. En este sentido también se presenta un estudio de las métricas de la señal, PAPR y CM. Además, basándonos en el análisis presentado se proponen nuevas técnicas para OFDM y MC-SS. Para MC-SS, también se trata el diseño de un detector multiusuario para canales no-lineales.
We are now facing a new information age with high demand of wireless communication systems. New services such as data and video require achieving reliable high-speed transmissions even in high mobility scenarios. Moreover, the difficulty to allocate so many wireless communication systems in the limited frequency band in addition to the demand for long battery life requires designing spectrum and power efficient transceivers. Multicarrier communications based on OFDM are known to fulfill most of the requirements of such systems. However, among other challenges, reducing the sensitivity to nonlinear amplification has become a design key. In this thesis the sensitivity of OFDM-based multicarrier systems to nonlinear amplification is analyzed and efficient ways to overcome this problem are considered. The focus is mainly on the problem of reducing the envelope fluctuations. Therefore, a study of the signal metrics, namely PAPR and CM, is also presented. From the presented analysis, several new techniques for OFDM and MC-SS are proposed. For MC-SS, the design of a post-processing technique in the form of a multiuser detector for nonlinearly distorted MC-SS symbols is also addressed.
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Zhang, Y. "Timing and frequency synchronization for multicarrier mobile communication systems." Thesis, University of Surrey, 2007. http://epubs.surrey.ac.uk/844076/.
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In this thesis, we study the timing and frequency synchronization and channel estimation for multicarrier mobile communication systems. Two typical multicarrier systems, MC-CDMA and OFDMA are considered. The sensitivity of multicarrier systems to the timing and frequency offsets are studied, and system performance is deduced by analytical methods. Analysis shows that both MC-CDMA and OFDMA are very sensitive to the timing and frequency offsets. The OFDMA system with the subband-based subcarrier assignment scheme is more sensitive to the synchronization errors of the reference user than that with interleaved subcarrier assignment scheme, while less sensitive to the synchronization errors of the interference users. We investigate the timing and frequency synchronization methods for multicarrier systems in both the downlink and uplink transmissions. The uplink case is more challenging because the uplink synchronization has to cope with independent frequency and timing offsets for each individual user. A novel timing and frequency offset estimation scheme for the uplink is proposed exploiting the principle of best linear estimation. The timing and frequency offsets are estimated by identifying the differential phases of the training pilots in frequency and time dimensions respectively. In contrast to other methods, the proposed scheme has moderate complexity and allows flexible subcarrier assignment schemes for the OFDMA system. The analysis and simulation results show that the proposed method performs well in the uplink channels. The initial synchronization tasks in the downlink including the cell identification, and the timing and frequency synchronization are studied. Several typical synchronization methods are presented and compared with each other. It shows that the MMSE method achieves the best performance for the timing estimation. In order to reduce the plateau of the metrics, a time domain smooth window is used with which a single peak is observed for all metrics. After the timing and frequency synchronization, a frequency domain correlation algorithm is applied for the cell identification. The overall performance of the initial synchronization was evaluated under multiple access interference, which gives the reference preamble power for designing the system. Finally, channel estimation algorithms are investigated. MMSE interpolation, FFT-based interpolation and polynomial interpolation methods are presented and compared with each other. Simulation results show that MMSE interpolation is superior to other methods in terms of MSE performance. However considering the trade-off between performance and complexity, the polynomial interpolation is a good approach. The effect of residual synchronization errors on channel estimation performance is studied. The modified channel estimation method to compensate residual synchronization errors is proposed. It shows that our compensation methods considerably improve the performance of channel estimators in imperfect synchronization conditions.
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Guvenkaya, Ertugrul. "Multidimensional Waveform Shaping in Multicarrier Systems." Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/5958.
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Constantly increasing demand for wireless communications in various applications has always led to new ways of modulating the radio frequency (RF) carrier signal by advancing waveform structure throughout generations. Although communication data rates are limited by the theoretical capacity, specific signaling designs for the signal that experiences natural and artificial effects in the transmission medium such as multipath fading channel, hardware impairments and multiuser environment promised better solutions in providing improved wireless access to various type of users and networks. Besides communication capacity, broadcasting nature of radio signals poses the information security as another main concern in wireless communications. In this dissertation, new advanced methods for improving signal statistics in multiple domains are studied. Instead of focusing on a single aspect, the waveform design approaches studied in this dissertation tackle with improving the orthogonal frequency-division multiplexing (OFDM)-based signaling in multiple perspectives such as out-of-band (OOB) emission reduction, peak-to-average-power ratio (PAPR) reduction, and secure transmission with minimum or no eect at the receiver side. Various concepts are coherently exploited while achieving aforementioned goals with minimal cost such as unexplored spaces in the signal space like (CP), guard band, multipath fading; multivariate nature of the multicarrier signals; time spreading and location uniqueness of the wireless channels. The proposed techniques are analyzed theoretically and performance results are presented including related previous works in the literature. It is worth noting that the methods presented in the dissertation can be easily applicable to conventional OFDM systems thanks to having no or minimal change in the receiver structure.
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Sadler, David James. "Antenna array systems for wireless communication using multicarrier DS-CDMA." Thesis, Imperial College London, 2004. http://hdl.handle.net/10044/1/11477.
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Li, Cheng, and 李鋮. "Carrier frequency offset estimation for multicarrier communications." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B29725331.
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Tan, Jun. "Iterative decoding and multicarrier modulation for wireless communications." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/13274.
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Kanaras, I. "Spectrally efficient multicarrier communication systems : signal detection, mathematical modelling and optimisation." Thesis, University College London (University of London), 2010. http://discovery.ucl.ac.uk/766544/.
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This thesis considers theoretical, analytical and engineering design issues relating to non-orthogonal Spectrally Efficient Frequency Division Multiplexing (SEFDM) communication systems that exhibit significant spectral merits when compared to Orthogonal FDM (OFDM) schemes. Alas, the practical implementation of such systems raises significant challenges, with the receivers being the bottleneck. This research explores detection of SEFDM signals. The mathematical foundations of such signals lead to proposals of different orthonormalisation techniques as required at the receivers of non-orthogonal FDM systems. To address SEFDM detection, two approaches are considered: either attempt to solve the problem optimally by taking advantage of special cases properties or to apply sub-optimal techniques that offer reduced complexities at the expense of error rates degradation. Initially, the application of sub-optimal linear detection techniques, such as Zero Forcing (ZF) and Minimum Mean Squared Error (MMSE), is examined analytically and by detailed modelling. To improve error performance a heuristic algorithm, based on a local search around an MMSE estimate, is designed by combining MMSE with Maximum Likelihood (ML) detection. Yet, this new method appears to be efficient for BPSK signals only. Hence, various variants of the sphere decoder (SD) are investigated. A Tikhonov regularised SD variant achieves an optimal solution for the detection of medium size signals in low noise regimes. Detailed modelling shows the SD detector to be well suited to the SEFDM detection, however, with complexity increasing with system interference and noise. A new design of a detector that offers a good compromise between computational complexity and error rate performance is proposed and tested through modelling and simulation. Standard reformulation techniques are used to relax the original optimal detection problem to a convex Semi-Definite Program (SDP) that can be solved in polynomial time. Although SDP performs better than other linear relaxations, such as ZF and MMSE, its deviation from optimality also increases with the deterioration of the system inherent interference. To improve its performance a heuristic algorithm based on a local search around the SDP estimate is further proposed. Finally, a modified SD is designed to implement faster than the local search SDP concept. The new method/algorithm, termed the pruned or constrained SD, achieves the detection of realistic SEFDM signals in noisy environments.
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Sim, Zee Ang. "PAPR Reduction in Multicarrier Communication Systems Using Efficient Pulse Shaping Technique." Thesis, Curtin University, 2020. http://hdl.handle.net/20.500.11937/79917.
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Emerging multicarrier modulation schemes have been considered for the fifth generation (5G) communication systems. However, existing designs often suffer from a high peak-to-average power ratio (PAPR) in the transmitted signal. This thesis aims to (i) design pulse shaping filters to reduce the PAPR using computationally efficient optimisation approach (ii) investigate the performance of the multicarrier systems employing the designed filter and (iii) study the power utilisation efficiency of the nonlinear amplifier with the use of the designed filters.
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Hijazi, Samer L. "Multi-user detection for multi-carrier communication systems." Diss., Manhattan, Kan. : Kansas State University, 2006. http://hdl.handle.net/2097/147.
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Wong, Tat-tung, and 黃達東. "Multicarrier CDMA overlay for ultra-wideband wireless communications." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B29491198.
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Yim, Wan Hung. "All-digital multicarrier demodulators for on-board processing satellites in mobile communication systems." Thesis, University of Surrey, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.290415.
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Nagy, Amr. "Performance enhancement for filter bank multicarrier methods in multi-antenna wireless communication systems." Thesis, University of Strathclyde, 2018. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=30532.
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This thesis investigates filter bank based multicarrier modulation using offset quadrature amplitude modulation (FBMC/OQAM), which is characterised by a critically sampled FBMC system that achieves full spectral efficiency in the sense of being free of redundancy. As a starting point, a performance comparison between FBMC/OQAM and oversampled (OS) FBMC systems is made in terms of per-subband fractionally spaced equalisation in order to compensate for the transmission distortions caused by dispersive channels. Simulation results show the reduced performance in equalising FBMC/OQAM compared to OS-FBMC,where the advantage for the latter stems from the use of guard bands. Alternatively, the inferior performance of FBMC/OQAM can be assigned to the inability of a per-subband equaliser to address the problem of potential intercarrier interference(ICI) in this system. The FBMC/OQAM system is analysed by representing the equivalent transmultiplexed channel including the filter banks as a polynomial matrix. The formulated polynomial matrix is demonstrated as a tri-diagonal matrix plus two corner elements which indicates that the induced ICI is limited to the direct adjacent spectrally overlapped subchannels. Based on polynomial matrix algebra, an equaliser is proposed which considers the cross terms between subchannels rather than performing a per-subband equalisation. The proposed equaliser is obtained through the inversion of the channel polynomial matrix; due to its reduced-rank nature, this inversion requires the extension of pseudo-inversion principles to the domain of polynomial matrices, and the inclusion of a regularisation term for enhanced stability and system performance. Some numerical examples demonstrate the ability of the proposed equaliser to suppress both ISI and ICI. Furthermore, this thesis combines FBMC/OQAM with multi-antenna architectures. In this scenario, the FBMC/OQAM system will not only suffer from ISI and ICI but also from spatial or inter-antenna interference (IAI). The multiple input multiple-output (MIMO) channel including the filter bank system is formulated as a polynomial matrix. A polynomial matrix pseudo-inverse of the equivalent channel polynomial matrix is proposed to approximately eliminate ISI, ICI, and IAI. Examples and simulation results are presented to underpin the performance of the proposed architecture.
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Seo, Kyoungnam. "Multi-user interference reduction and throughput enhancement in OFDM-based multicarrier communication systems." [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0024948.
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Abdallah, Saeed. "Widely linear minimum variance channel estimation with application to multicarrier CDMA systems." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=112550.
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Conventional Minimum-Variance (MV) channel estimation is affected by two sources of error, namely the finite number of samples used to estimate the covariance matrix and the asymptotic bias due to interference and additive noise. On the other hand, widely linear (WL) filtering has been shown to improve the estimation of improper complex signals. Researchers have recently demonstrated that the application of WL processing principles can significantly improve the performance of subspace-based channel estimation algorithms. However, in contrast to MV estimation algorithms, subspace-based algorithms assume knowledge of the total number of users in the system, and must be coupled with sophisticated user enumeration algorithm at the expense of increased complexity. In this work, in an effort to combine the practical advantages of MV channel estimation algorithms with the performance of WL filters we propose a widely linear version of the MV channel estimator in the context of multicarrier(MC) CDMA systems employing real modulation. We use numerical simulations to demonstrate that the widely linear minimum-variance algorithm yields more accurate channel estimates compared to the conventional MV algorithm. By considering two simplified transmission/reception models, we also show analytically that the widely linear estimator on average reduces both types of error.
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Akho-Zahieh, Maryam Mahmoud. "Design and Analysis of Multicarrier Multicode Wavelet Packets Based CDMA Communication Systems with Multiuser Detection." University of Akron / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=akron1149006699.
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Zhang, Yifeng. "Wavelet packet based multicarrier modulation code division multiple access system." Ohio : Ohio University, 2000. http://www.ohiolink.edu/etd/view.cgi?ohiou1179861748.
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Zhang, Haijian. "Filter Bank based MultiCarrier (FBMC) for Cognitive Radio Systems." Thesis, Paris, CNAM, 2010. http://www.theses.fr/2010CNAM0763/document.
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La radio cognitive (CR) est une radio entièrement reconfigurable qui permet de changer intelligemment ses paramètres de communication en réponse à l’activité des autres réseaux radios et demandes d’utilisateur. L’objectif ultime de la CR est de permettre à l’utilisateur secondaire (SU) d’utiliser la ressource de spectre disponible sans interférer sur l’utilisateur primaire (PU) en utilisant des trous de spectre. Par conséquent, la détection du PU est l’un des défis principaux dans le développement de la CR. Par rapport aux systèmes conventionnels de communication sans fil, le système CR introduit de nouveaux problèmes d’allocation de ressource (RA) en raison de l’interférence des canaux adjacents utilisés par le SU et le PU. Dans le contexte de la CR, la plupart des efforts ont été menés sur les systèmes de CR basés sur le multiplexage par division de fréquences orthogonales (OFDM). Toutefois, la technique de l’OFDM montre quelques points faibles dans l’application à cause des remontées significatives du spectre. Les modulations multiporteuses à base de bancs de filtre (FBMC) ont été récemment proposées pour des applications de CR. Dans cette thèse, trois points importants pour le développement d’un système de CR basé sur le FBMC sont discutés.Les trois points principaux peuvent être résumés ainsi: nous examinons premièrement les problèmes de détection de spectre des signaux OFDM et FBMC en employant le détecteur de signature de cyclostationnarité (CS). En outre, nous proposons une architecture de détection multi-bande basée sur le banc de filtre polyphasé (PFB), et montrons son avantage; deuxièmement, la comparaison entre l’OFDM et le FBMC du point de vue de l’efficacité spectrale est discutée; et enfin, nous proposons un algorithme stratégique d’allocation de ressource pour les systèmes cognitifs multi-cellulaires et multi-utilisateurs.Les algorithmes proposés dans cette thèse ont été testés par simulation. Les résultats numériques prouvent que le FBMC, par opposition à l’OFDM, pourrait réaliser une efficacité spectrale plus élevée et offre un avantage attrayant dans la détection de spectre. Les contributions de cette thèse ont accru l’intérêt d’appliquer FBMC dans les systèmes de CR à l’avenirCognitive Radio (CR) is a fully reconfigurable radio that can intelligently change its communicationvariables in response to network and user demands. The ultimate goal of CR is to allowthe Secondary User (SU) to utilize the available spectrum resource on a non-interfering basis to thePrimary User (PU) by sensing the existence of spectrum holes. Therefore, the detection of PU isone of the main challenges in the development of the CR technology. Moreover, compared to conventionalwireless communication systems, CR system poses new challenges to Resource Allocation(RA) problems because of the Cross-Channel Interference (CCI) from the adjacent channels used bySU to PU. In the CR context, most past efforts have been spent on Orthogonal Frequency DivisionMultiplexing (OFDM) based CR systems. However, OFDM technique exhibits some shortcomingsin application due to its significant spectrum leakage. Filter Bank based Multi-Carrier (FBMC), asanother promising Multi-Carrier Modulation (MCM) candidate, has been recently proposed for CRapplications. In this dissertation, three important issues in developing a FBMC based CR system arediscussed.The three prime issues can be summarized: we firstly survey the spectrum sensing problemsof OFDM and FBMC signals by using Cyclostationary Signature (CS) detector. Furthermore, wepropose a Polyphase Filter Bank (PFB) based multi-band sensing architecture, and argue for its advantage;secondly, the comparison of OFDM and FBMC from the spectral efficiency point of viewis discussed; and lastly, our emphasis is placed on the strategic resource allocation algorithms fornon-cooperative multi-cell CR systems.The overall proposed algorithms have been verified by simulation. Numerical results show thatFBMC, as opposed to OFDM, could achieve higher spectrum efficiency and attractive benefit inspectrum sensing. The contributions of this dissertation have heighten the interest in applying FBMCin the future CR systems
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Rowitch, Douglas Neal. "Convolutional and turbo coded multicarrier direct sequence CDMA, and applications of turbo codes to hybrid ARQ communication systems /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1998. http://wwwlib.umi.com/cr/ucsd/fullcit?p9835385.
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Bodinier, Quentin. "Coexistence of communication systems based on enhanced multi-carrier waveforms with legacy OFDM Networks." Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1S091/document.
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Les futurs réseaux sans fil devront être conçus pour répondre aux besoins hétérogènes de systèmes entièrement différents. De nouveaux services soumis à des contraintes variées coexisteront avec les utilisateurs actuels sur la même bande de fréquences. L'OFDM, la couche physique utilisée par les systèmes actuels, souffre d’un mauvais confinement spectral et ne permet pas cette coexistence. De nombreuses nouvelles formes d'onde avec une localisation spectrale améliorée ont donc été proposées. Nous étudions la coexistence de nouveaux systèmes basés sur ces formes d'onde avec des utilisateurs OFDM préexistant. Nous fournissons la première analyse théorique et expérimentale de l'interférence inter-système qui se produit dans ces scenarios. Nous appliquons ensuite cette analyse pour évaluer les performances de différentes formes d'ondes avancées et nous étudions finalement les performances d'un réseau où des utilisateurs cellulaires OFDM coexistent avec des paires D2D utilisant l'une des formes d'ondes améliorées étudiéesFuture wireless networks are envisioned to accommodate the heterogeneous needs of entirely different systems. New services obeying various constraints will coexist with legacy cellular users in the same frequency band. This coexistence is hardly achievable with OFDM, the physical layer used by current systems, because of its poor spectral containment. Thus, a myriad of multi-carrier waveforms with enhanced spectral localization have been proposed for future wireless devices. In this thesis, we investigate the coexistence of new systems based on these waveforms with legacy OFDM users. We provide the first theoretical and experimental analysis of the inter-system interference that arises in those scenarii. Then, we apply this analysis to evaluate the merits of different enhanced waveforms and we finally investigate the performance achievable by a network composed of legacy OFDM cellular users and D2D pairs using one of the studied enhanced waveforms
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Das, Sibasish. "Analysis and design of pilot-aided multicarrier systems over doubly selective channels with a local subcarrier processing constraint." Columbus, Ohio : Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1199305333.
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Strickland, Wilburn T. "A wideband multicarrier CDMA cellular communications system." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1998. http://handle.dtic.mil/100.2/ADA356571.
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Thesis (M.S. in Electrical Engineering) Naval Postgraduate School, September 1998.Thesis advisor(s): Tri T. Ha, R. Clark Robertson. "September 1998." Includes bibliographical references (p. 91). Also Available online.
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Zhang, Hongbing. "Wavelet packet based multicarrier CDMA wireless communication system." Cincinnati, Ohio : University of Cincinnati, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=ucin1081568890.
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Al-Attraqchi, Mohammed Hani Omar. "An enhanced multicarrier modulation system for mobile communications." Thesis, University of Newcastle upon Tyne, 2012. http://hdl.handle.net/10443/2215.
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The recent revolution in mobile communications and the increased demand on more efficient transmission systems influence the research to enhance and invent new modulation techniques. Orthogonal frequency division multiplexing with offset quadrature amplitude modulation (OFDM/OQAM) is one of the multicarrier modulations techniques that overcomes some of the weaknesses of the conventional OFDM in term of bandwidth and power efficiencies. This thesis presents a novel multicarrier modulation scheme with improved performance in mobile communications context. Initially, the theoretical principles behind OFDM and OFDM/OQAM are discussed and the advantages of OFDM/OQAM over OFDM are highlighted. The time-frequency localization of pulse shapes is examined over different types of pulses. The effect of the localization and the pulse choice on OFDM/OQAM performance is demonstrated. The first contribution is introducing a new variant of multicarrier modulation system based on the integration of the Walsh-Hadamard transform with the OFDM/OQAM modulator. The full analytical transmission model of the system is derived over flat fading and frequency selective channels. Next, because of the critical requirement of low implementation complexity in mobile systems, a new fast algorithm transform is developed to reduce the implementation complexity of the system. The introduced fast algorithm has demonstrated a remarkable 60 percent decrease in the hardware requirement compared to the cascaded configuration. Although, the problem of high peak to average power ratio (PAPR) is one of the main drawbacks that associated with most multicarrier modulation techniques, the new system achieved lower values compared to the conventional systems. Subsequently, three new algorithms to reduce PAPR named Walsh overlapped selective mapping (WOSLM) for a high PAPR reduction, simplified selective mapping (SSLM) for a very low implementation complexity and Walsh partial transmit sequence (WPTS), are developed. Finally, in order to assess the reliability of the presented system in this thesis at imperfect environments, the performance of the system is investigated in the presence of high power amplifier, channel estimation errors, and carrier frequency offset (CFO). Two channel estimations algorithms named enhanced pair of pilots (EPOP) and averaged enhanced pair of pilots (AEPOP), and one CFO estimator technique called frequency domain (FD) CFO estimator, are suggested to provide reliable performance.
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Pace, Howard. "An analysis of a broadband multicarrier CDMA cellular communications system." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1998. http://handle.dtic.mil/100.2/ADA354466.
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Thesis (M.S. in Electrical Engineering) Naval Postgraduate School, September 1998."September 1998." Thesis advisor(s): Tri T. Ha, R. Clark Robertson. Includes bibliographical references (p. 97). Also available online.
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Cheng, Hui. "New channel estimation and multiuser detection algorithms for multicarrier(MC)-CDMA communications systems." Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B35314321.
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Cheng, Hui, and 成慧. "New channel estimation and multiuser detection algorithms for multicarrier(MC)-CDMA communications systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B35314321.
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Awal, Mohammad abdul. "Efficient cqi feedback resource utilisation for multi-user multi-carrier wireless systems." Thesis, Paris 11, 2011. http://www.theses.fr/2011PA112223/document.
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La technologie OFDMA (Orthogonal frequency division multiple access) a été adoptée par les systèmes de télécommunications de 4ème génération (4G) comme technique de transmission et d'accès multiple pour ses performances supérieures en termes d'efficacité spectrale. Dans ce type de systèmes, l'adaptation dynamique du débit en fonction de la qualité du canal CQI (Channel Quality Indicator) constitue une problématique de recherche d'actualité qui attire l'attention de plusieurs acteurs académiques et industriels. Ce problème d'adaptation dynamique est encore plus complexe à gérer dans des environnements multi-utilisateurs hétérogènes et à ressources limitées tels que les systèmes OFDMA comme WiMAX Mobile et Long-term Evolution (LTE). Dans cette thèse, nous nous intéressons au problème d'allocation de ressources de l'information de feedback relative au CQI dans le cadre de systèmes OFDMA multi-porteuses multi-utilisateurs. Dans le but de réduire la charge (overhead) du feedback, nous proposons une méthode de prédiction du CQI basée sur l'exploitation de la corrélation temporelle de ce dernier et d'une solution inter-couches. L'objectif est de trouver des schémas d'allocation de ressources adaptatifs respectant les contraintes de qualité de service (QoS) applicatives.Nous proposons en premier lieu un algorithme de réduction de feedback PBF (Prediction Based Feedack) qui permet à la station de base (BS) à prédire certaines occurrences du CQI en se basant sur l'algorithme des moindres carrés récursif RLS (Recursive least-square). Les résultats de simulation montrent que l'outil de prédiction du CQI réduit sensiblement l'overhead du feedback et améliore par conséquent le débit de la liaison montante. Nous proposons, par la suite, une version opportuniste de PBF pour atténuer les éventuels effets de sur et sous estimations liées à l'algorithme de prédiction. Dans ce mécanisme, nous exploitons les informations inter-couches pour améliorer les performances des mécanismes de feedbacks périodiques dont PBF fait partie. L'approche opportuniste améliore sensiblement les performances du système pour les cas de mobilité élevée comparés aux cas de faible mobilité.Dans un second temps, nous proposons une plateforme (FEREP : feedback resource allocation and prediction) basée sur une approche inter-couches. Implémentée au niveau de la station BS, FEREP intègre les fonctionnalités de prédiction, d'adaptation dynamique du CQI et d'ordonnancement des demandes de feedback. Elle comporte trois modules. Le module FWA (feedback window adaptation) gère dynamiquement la fenêtre de feedbacks de chaque station mobile (MS) en se basant sur les messages ARQ (Automatic Repeat Request) reçus qui reflètent l'état actuel des canaux respectifs. Le module PBFS (priority-based feedback scheduling) effectue ensuite l'ordonnancement des feedbacks en tenant compte de la taille de la fenêtre de feedback, du profil de l'utilisateur sous la contrainte de la limitation des ressources globales du systèmes réservées au feedback. Afin de choisir les paramètres de transmission MCS (modulation and coding schemes), le module PBF (prediction based feedback) est utilisé pour les utilisateurs dont le feedabck n'a pas pu être ordonnancé dans la trame courante. Les résultats de simulation ont montré un gain significatif des performances de FREREP en comparaison à un mécanisme de référence, en particulier, sous de fortes contraintes de limitation des ressources du feedback.Le protocole ARQ génère un accusé de réception uniquement si l'utilisateur est sélectionné par l'ordonnanceur pour envoyer des données sur la liaison descendante. Dans le cas où la fréquence d'ordonnancement des utilisateurs sur le lien descendant est réduite, les messages ARQ s'en trouvent également réduits, dégradant par conséquent les performances de la plateforme FEREP proposée ci-dessus. En effet, dans ce cas la signalisation ARQ devient insuffisante pour adapter efficacement la fenêtre de feedback de chaque utilisateur. Pour pallier à ce problème, nous proposons l'algorithme DCRA (dynamic CQI resource allocation) qui utilise deux modes d'estimation de la fenêtre de feedback. Le premier est un mode hors-ligne basé sur des études empiriques permettant d'estimer la fenêtre moyenne optimale de feedback en utilisant les profils applicatif et de mobilité de l'utilisateur. Notre analyse de performance par simulation montre que la fenêtre de feedback peut être estimée en fonction de la classe de service des utilisateurs et de leurs profils de mobilité pour un environnement cellulaire donné. Le second mode de fonctionnement de DCRA effectue une adaptation dynamique de la fenêtre en temps réel dans le cas où la signalisation ARQ est suffisante. Une étude comparative avec les mécanismes DFS (deterministic feedback scheduling) et OFS (opportunistic feedback scheduling), a montré que DCRA arrive à réaliser un meilleur gain en ressources montantes grâce à la réduction de l'overhead des feedbacks, sans pour autant trop dégrader le débit descendant des utilisateurs. Du point de vue des utilisateurs, DCRA améliore les contraintes de QoS tels que le taux de perte de paquets et réduit la consommation énergétique des terminaux grâce à la réduction de feedbackOrthogonal frequency division multiple access (OFDMA) technology has been adopted by 4th generation (a.k.a. 4G) telecommunication systems to achieve high system spectral efficiency. A crucial research issue is how to design adaptive channel quality indicator (CQI) feedback mechanisms so that the base station can use adaptive modulation and coding (AMC) techniques to adjust its data rate based on the channel condition. This problem is even more challenging in resource-limited and heterogeneous multiuser environments such as Mobile WiMAX, Long-term Evolution (LTE) networks. In this thesis, we consider CQI feedback resource allocation issue for multiuser multicarrier OFDMA systems. We exploit time-domain correlation for CQI prediction and cross-layer information to reduce feedback overhead for OFDMA systems. Our aim is find resource allocation schemes respecting the users QoS constraints.Our study begins with proposing prediction based feedback (PBF) which allows the base station to predict the CQI feedbacks based on recursive least-square (RLS) algorithm. We showed that it is useful to use channel prediction as a tool to reduce the feedback overhead and improve the uplink throughput. Then, we propose an opportunistic periodic feedback mechanism to mitigate the possible under and over estimation effects of CQI prediction. In this mechanism, we exploited the cross-layer information to enhance the performance of periodic feedback mechanisms. The opportunistic mechanism improves the system performance for high mobility cases compared to low mobility cases.For OFDMA systems with limited feedback resource, we propose an integrated cross-layer framework of feedback resource allocation and prediction (FEREP). The proposed framework, implemented at the BS side, is composed of three modules. The feedback window adaptation (FWA) module dynamically tunes the feedback window size for each mobile station based on the received ARQ (Automatic Repeat Request) messages that reflect the current channel condition. The priority-based feedback scheduling (PBFS) module then performs feedback allocation by taking into account the feedback window size, the user profile and the total system feedback budget. To choose adapted modulation and coding schemes (MCS), the prediction based feedback (PBF) module performs channel prediction by using recursive least square (RLS) algorithm for the user whose channel feedback has not been granted for schedule in current frame. Through extensive simulations, the proposed framework shows significant performance gain especially under stringent feedback budget constraint.ARQ protocol receives users acknowledgement only if the user is scheduled in the downlink. The reduction in users scheduling frequency also reduces the rate of ARQ hints and degrades the performance of above contributions. In this case, it is difficult to exploit the ARQ signal to adapt the feedback window for that user. To address this issue, we propose a cross-layer dynamic CQI resource allocation (DCRA) algorithm for multiuser multicarrier OFDMA systems. DCRA uses two modes for feedback window estimation. The first one is an off-line mode based on empirical studies to derive optimal average feedback window based on user application and mobility profile. Our experimental analysis shows that the feedback window can be averaged according to users service class and their mobility profile for a given cell environment. DCRA performs a realtime dynamic window adaptation if sufficient cross-layer hints are available from ARQ signaling. DCRA increases uplink resource by reducing feedback overhead without degrading downlink throughout significantly compared to deterministic feedback scheduling (DFS) and opportunistic feedback scheduling (OFS). From the users perspective, DCRA improves QoS constraints like packet loss rate and saves users power due to feedback reduction
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Gutiérrez, González Ismael. "Adaptive Communications for Next Generation Broadband Wireless Access Systems." Doctoral thesis, Universitat Ramon Llull, 2009. http://hdl.handle.net/10803/9141.
Full textAbstract:
Un dels aspectes claus en el disseny i gestió de les xarxes sense fils d'accés de banda ampla és l'ús eficient dels recursos radio. Des del punt de vista de l'operador, l'ample de banda és un bé escàs i preuat que s´ha d'explotar i gestionar de la forma més eficient possible tot garantint la qualitat del servei que es vol proporcionar. Per altra banda, des del punt de vista del usuari, la qualitat del servei ofert ha de ser comparable al de les xarxes fixes, requerint així un baix retard i una baixa pèrdua de paquets per cadascun dels fluxos de dades entre la xarxa i l'usuari. Durant els darrers anys s´han desenvolupat nombroses tècniques i algoritmes amb l'objectiu d'incrementar l'eficiència espectral. Entre aquestes tècniques destaca l'ús de múltiples antenes al transmissor i al receptor amb l'objectiu de transmetre diferents fluxos de dades simultaneament sense necessitat d'augmentar l'ample de banda. Per altra banda, la optimizació conjunta de la capa d'accés al medi i la capa física (fent ús de l'estat del canal per tal de gestionar de manera optima els recursos) també permet incrementar sensiblement l'eficiència espectral del sistema.L'objectiu d'aquesta tesi és l'estudi i desenvolupament de noves tècniques d'adaptació de l'enllaç i gestió dels recursos ràdio aplicades sobre sistemes d'accés ràdio de propera generació (Beyond 3G). Els estudis realitzats parteixen de la premissa que el transmisor coneix (parcialment) l'estat del canal i que la transmissió es realitza fent servir un esquema multiportadora amb múltiples antenes al transmisor i al receptor. En aquesta tesi es presenten dues línies d'investigació, la primera per casos d'una sola antenna a cada banda de l'enllaç, i la segona en cas de múltiples antenes. En el cas d'una sola antena al transmissor i al receptor, un nou esquema d'assignació de recursos ràdio i priorització dels paquets (scheduling) és proposat i analitzat integrant totes dues funcions sobre una mateixa entitat (cross-layer). L'esquema proposat té com a principal característica la seva baixa complexitat i que permet operar amb transmissions multimedia. Alhora, posteriors millores realitzades per l'autor sobre l'esquema proposat han permès també reduir els requeriments de senyalització i combinar de forma óptima usuaris d'alta i baixa mobilitat sobre el mateix accés ràdio, millorant encara més l'eficiència espectral del sistema. En cas d'enllaços amb múltiples antenes es proposa un nou esquema que combina la selecció del conjunt optim d'antenes transmissores amb la selecció de la codificació espai- (frequència-) temps. Finalment es donen una sèrie de recomanacions per tal de combinar totes dues línies d'investigació, així con un estat de l'art de les tècniques proposades per altres autors que combinen en part la gestió dels recursos ràdio i els esquemes de transmissió amb múltiples antenes.
Uno de los aspectos claves en el diseño y gestión de las redes inalámbricas de banda ancha es el uso eficiente de los recursos radio. Desde el punto de vista del operador, el ancho de banda es un bien escaso y valioso que se debe explotar y gestionar de la forma más eficiente posible sin afectar a la calidad del servicio ofrecido. Por otro lado, desde el punto de vista del usuario, la calidad del servicio ha de ser comparable al ofrecido por las redes fijas, requiriendo así un bajo retardo y una baja tasa de perdida de paquetes para cada uno de los flujos de datos entre la red y el usuario. Durante los últimos años el número de técnicas y algoritmos que tratan de incrementar la eficiencia espectral en dichas redes es bastante amplio. Entre estas técnicas destaca el uso de múltiples antenas en el transmisor y en el receptor con el objetivo de poder transmitir simultáneamente diferentes flujos de datos sin necesidad de incrementar el ancho de banda. Por otro lado, la optimización conjunta de la capa de acceso al medio y la capa física (utilizando información de estado del canal para gestionar de manera óptima los recursos) también permite incrementar sensiblemente la eficiencia espectral del sistema.
El objetivo de esta tesis es el estudio y desarrollo de nuevas técnicas de adaptación del enlace y la gestión de los recursos radio, y su posterior aplicación sobre los sistemas de acceso radio de próxima generación (Beyond 3G). Los estudios realizados parten de la premisa de que el transmisor conoce (parcialmente) el estado del canal a la vez que se considera que la transmisión se realiza sobre un sistema de transmisión multiportadora con múltiple antenas en el transmisor y el receptor. La tesis se centra sobre dos líneas de investigación, la primera para casos de una única antena en cada lado del enlace, y la segunda en caso de múltiples antenas en cada lado. Para el caso de una única antena en el transmisor y en el receptor, se ha desarrollado un nuevo esquema de asignación de los recursos radio así como de priorización de los paquetes de datos (scheduling) integrando ambas funciones sobre una misma entidad (cross-layer). El esquema propuesto tiene como principal característica su bajo coste computacional a la vez que se puede aplicar en caso de transmisiones multimedia. Posteriores mejoras realizadas por el autor sobre el esquema propuesto han permitido también reducir los requisitos de señalización así como combinar de forma óptima usuarios de alta y baja movilidad. Por otro lado, en caso de enlaces con múltiples antenas en transmisión y recepción, se presenta un nuevo esquema de adaptación en el cual se combina la selección de la(s) antena(s) transmisora(s) con la selección del esquema de codificación espacio-(frecuencia-) tiempo. Para finalizar, se dan una serie de recomendaciones con el objetivo de combinar ambas líneas de investigación, así como un estado del arte de las técnicas propuestas por otros autores que combinan en parte la gestión de los recursos radio y los esquemas de transmisión con múltiples antenas.
In Broadband Wireless Access systems the efficient use of the resources is crucial from many points of views. From the operator point of view, the bandwidth is a scarce, valuable, and expensive resource which must be exploited in an efficient manner while the Quality of Service (QoS) provided to the users is guaranteed. On the other hand, a tight delay and link quality constraints are imposed on each data flow hence the user experiences the same quality as in fixed networks. During the last few years many techniques have been developed in order to increase the spectral efficiency and the throughput. Among them, the use of multiple antennas at the transmitter and the receiver (exploiting spatial multiplexing) with the joint optimization of the medium access control layer and the physical layer parameters.
In this Ph.D. thesis, different adaptive techniques for B3G multicarrier wireless systems are developed and proposed focusing on the SS-MC-MA and the OFDM(A) (IEEE 802.16a/e/m standards) communication schemes. The research lines emphasize into the adaptation of the transmission having (Partial) knowledge of the Channel State Information for both; single antenna and multiple antenna links. For single antenna links, the implementation of a joint resource allocation and scheduling strategy by including adaptive modulation and coding is investigated. A low complexity resource allocation and scheduling algorithm is proposed with the objective to cope with real- and/or non-real- time requirements and constraints. A special attention is also devoted in reducing the required signalling. However, for multiple antenna links, the performance of a proposed adaptive transmit antenna selection scheme jointly with space-time block coding selection is investigated and compared with conventional structures. In this research line, mainly two optimizations criteria are proposed for spatial link adaptation, one based on the minimum error rate for fixed throughput, and the second focused on the maximisation of the rate for fixed error rate. Finally, some indications are given on how to include the spatial adaptation into the investigated and proposed resource allocation and scheduling process developed for single antenna transmission.
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Gomes, Baltar Leonardo [Verfasser], Josef A. [Akademischer Betreuer] Nossek, Paulo S. R. [Gutachter] Diniz, and Josef A. [Gutachter] Nossek. "Filter Bank based Multicarrier Systems for Wireless Communications / Leonardo Gomes Baltar ; Gutachter: Paulo S. R. Diniz, Josef A. Nossek ; Betreuer: Josef A. Nossek." München : Universitätsbibliothek der TU München, 2017. http://d-nb.info/1173898840/34.
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Carey, Daniel Jeffrey. "Statistical modelling and reduction of multiple access interference power in wideband DS-CDMA and MC-CDMA communications systems." Thesis, Queensland University of Technology, 2006. https://eprints.qut.edu.au/16342/1/Daniel_Carey_Thesis.pdf.
Full textAbstract:
With code division multiple access (CDMA) systems being the prominent multiple access scheme for the air interface for 3G cellular systems, most standardisation bodies have based their terrestrial cellular systems on DS-CDMA (W-CDMA, UMTS, cdma2000). With 4G systems fast approaching, bringing with them improved services and quality of service standards, there is growing interest in further investigating and developing more efficient multiple access techniques such as multicarrier CDMA (MC-CDMA) systems. MC-CDMA combines multicarrier modulation (MCM), namely OFDM, with CDMA profiting from the benefits of both multiplexing techniques; as such, MC-CDMA is emerging as a possible candidate for the air interface multiple access scheme for 4G cellular systems.
Multiple access interference (MAI) is a limiting factor of CDMA systems in terms of system capacity as orthogonally designed spreading sequences lose their orthogonality in the presence of timing misalignments amongst mobile subscribers in a cell; such is the case over the uplink channel. Ensuring orthogonal code properties minimises the MAI over synchronous environments, however, it is when the users are allowed to transmit asynchronously, as is the case over the uplink channel, that MAI inflicts significant performance degradation. In CDMA systems, all subscribers are active on the same frequency band simultaneously and signal separation is facilitated upon reception via the properties of the assigned spreading codes. Under asynchronous conditions the code properties alone do not provide the necessary separation and an additive MAI term remains in the detection process. In addition to the separation abilities of the spreading codes, a further method of deciphering the desired subscriber signal from the interfering subscriber signals is sought.
In this thesis we propose a statistical model for both the probability density function (pdf) of the total MAI power and the corresponding bit-error rate (BER) observed during asynchronous CDMA transmission. The modelling offers the full statistic the MAI power and resulting BER, not just the first and second order statistics. In addition to statistically quantifying the MAI power, the thesis also proposes a technique for the successful reduction of MAI caused by asynchronous transmission. This interference reduction technique is derived from an ambiguity domain analysis of the asynchronous CDMA detection problem and its application to both the DS-CDMA and MC-CDMA multiplexing techniques is presented and the results show significant MAI reduction, and thus an improved the BER.
A methodology for the approximation of the total MAI power pdf and the resulting BER pdf is proposed for the asynchronous DS-CDMA and MC-CDMA techniques. This methodology is derived for the use of Walsh-Hadamard (WH) and Gold spreading sequences, however, it is applicable to any given set of deterministic spreading sequences. The total MAI power pdfs of both systems are statistically modelled as being Nakagamim distributed and the corresponding BER modelling is derived from the Nakagami-m formulation offering the full statistic of both the incurred MAI power and the achievable BER.
The proposed pdf acquisition methodology and statistical models can be used as analysis tools to assess the relative performances of the DS-CDMA and MC-CDMA techniques for a variety of communications environments. Here the asynchronous uplink channel is considered in the absence of fading and the results show a clear distinction between the BER performances of the MC-CDMA and DS-CDMA systems, for which the MC-CDMA system offers a superior performance for the purely asynchronous channel considered. The results suggest a higher resistance to MAI in the MC-CDMA technique in comparison to the DS-CDMA system for the considered transmission scenario.
Following ambiguity function analysis of the asynchronous CDMA detection problem, the concept of dual-frequency switching is introduced to the existing DS-CDMA and MC-CDMA techniques giving rise to the proposed dual-frequency DS-CDMA (DF/DSCDMA) and dual-frequency MC-CDMA (DF/MC-CDMA) schemes. Periodically switching the carrier frequency between dual frequency bands at consecutive symbol boundaries facilitates partial CDMA signal separation upon asynchronous reception. Such switching of the carrier frequency induces a separation in frequency between offset interference signals and the reference signal; this is equivalent to shifting the energy concentration of the interference signals away form the ambiguity domain origin (representing the decision variable of the matched filter). Further MAI reduction is demonstrated through careful design of the dual carrier frequencies.
The newly proposed DF systems clearly outperform the standard DS-CDMA and MC-CDMA systems when adopting equivalent spreading factors. The DF/DS-CDMA technique in particular achieves the most MAI reduction and in doing so, surpasses all other considered techniques to offer the best BER performance for the purely asynchronous channel considered. In terms of bandwidth usage, the DF/DS-CDMA band width is 1.5 times that of the DF/MC-CDMA system and from the BER results presented, one may argue that DF/MC-CDMA offers the better BER given the bandwidth usage. The multicarrier systems presented, MC-CDMA and DF/MC-CDMA, offer attractive BER performances for the bandwidth used and it is concluded that MC-CDMA is a genuine candidate for the uplink air interface multiple access scheme for future mobile cellular technologies.
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Carey, Daniel Jeffrey. "Statistical modelling and reduction of multiple access interference power in wideband DS-CDMA and MC-CDMA communications systems." Queensland University of Technology, 2006. http://eprints.qut.edu.au/16342/.
Full textAbstract:
With code division multiple access (CDMA) systems being the prominent multiple access scheme for the air interface for 3G cellular systems, most standardisation bodies have based their terrestrial cellular systems on DS-CDMA (W-CDMA, UMTS, cdma2000). With 4G systems fast approaching, bringing with them improved services and quality of service standards, there is growing interest in further investigating and developing more efficient multiple access techniques such as multicarrier CDMA (MC-CDMA) systems. MC-CDMA combines multicarrier modulation (MCM), namely OFDM, with CDMA profiting from the benefits of both multiplexing techniques; as such, MC-CDMA is emerging as a possible candidate for the air interface multiple access scheme for 4G cellular systems. Multiple access interference (MAI) is a limiting factor of CDMA systems in terms of system capacity as orthogonally designed spreading sequences lose their orthogonality in the presence of timing misalignments amongst mobile subscribers in a cell; such is the case over the uplink channel. Ensuring orthogonal code properties minimises the MAI over synchronous environments, however, it is when the users are allowed to transmit asynchronously, as is the case over the uplink channel, that MAI inflicts significant performance degradation. In CDMA systems, all subscribers are active on the same frequency band simultaneously and signal separation is facilitated upon reception via the properties of the assigned spreading codes. Under asynchronous conditions the code properties alone do not provide the necessary separation and an additive MAI term remains in the detection process. In addition to the separation abilities of the spreading codes, a further method of deciphering the desired subscriber signal from the interfering subscriber signals is sought. In this thesis we propose a statistical model for both the probability density function (pdf) of the total MAI power and the corresponding bit-error rate (BER) observed during asynchronous CDMA transmission. The modelling offers the full statistic the MAI power and resulting BER, not just the first and second order statistics. In addition to statistically quantifying the MAI power, the thesis also proposes a technique for the successful reduction of MAI caused by asynchronous transmission. This interference reduction technique is derived from an ambiguity domain analysis of the asynchronous CDMA detection problem and its application to both the DS-CDMA and MC-CDMA multiplexing techniques is presented and the results show significant MAI reduction, and thus an improved the BER. A methodology for the approximation of the total MAI power pdf and the resulting BER pdf is proposed for the asynchronous DS-CDMA and MC-CDMA techniques. This methodology is derived for the use of Walsh-Hadamard (WH) and Gold spreading sequences, however, it is applicable to any given set of deterministic spreading sequences. The total MAI power pdfs of both systems are statistically modelled as being Nakagamim distributed and the corresponding BER modelling is derived from the Nakagami-m formulation offering the full statistic of both the incurred MAI power and the achievable BER. The proposed pdf acquisition methodology and statistical models can be used as analysis tools to assess the relative performances of the DS-CDMA and MC-CDMA techniques for a variety of communications environments. Here the asynchronous uplink channel is considered in the absence of fading and the results show a clear distinction between the BER performances of the MC-CDMA and DS-CDMA systems, for which the MC-CDMA system offers a superior performance for the purely asynchronous channel considered. The results suggest a higher resistance to MAI in the MC-CDMA technique in comparison to the DS-CDMA system for the considered transmission scenario. Following ambiguity function analysis of the asynchronous CDMA detection problem, the concept of dual-frequency switching is introduced to the existing DS-CDMA and MC-CDMA techniques giving rise to the proposed dual-frequency DS-CDMA (DF/DSCDMA) and dual-frequency MC-CDMA (DF/MC-CDMA) schemes. Periodically switching the carrier frequency between dual frequency bands at consecutive symbol boundaries facilitates partial CDMA signal separation upon asynchronous reception. Such switching of the carrier frequency induces a separation in frequency between offset interference signals and the reference signal; this is equivalent to shifting the energy concentration of the interference signals away form the ambiguity domain origin (representing the decision variable of the matched filter). Further MAI reduction is demonstrated through careful design of the dual carrier frequencies. The newly proposed DF systems clearly outperform the standard DS-CDMA and MC-CDMA systems when adopting equivalent spreading factors. The DF/DS-CDMA technique in particular achieves the most MAI reduction and in doing so, surpasses all other considered techniques to offer the best BER performance for the purely asynchronous channel considered. In terms of bandwidth usage, the DF/DS-CDMA band width is 1.5 times that of the DF/MC-CDMA system and from the BER results presented, one may argue that DF/MC-CDMA offers the better BER given the bandwidth usage. The multicarrier systems presented, MC-CDMA and DF/MC-CDMA, offer attractive BER performances for the bandwidth used and it is concluded that MC-CDMA is a genuine candidate for the uplink air interface multiple access scheme for future mobile cellular technologies.
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Aquilué, de Pedro Ricardo. "Power line communications for the electrical utility: physical layer design and channel modeling." Doctoral thesis, Universitat Ramon Llull, 2008. http://hdl.handle.net/10803/9138.
Full textAbstract:
El món de les comunicacions per la xarxa elèctrica (CXE) pot ser dividit en tres grans tipus: CXE en baix voltatge (CXE-BV), en mig voltatge (CXE-MV) i en alt voltatge (CXE-AV). En aquests últims anys, les CXE-BV han atret una gran expectació, ja que les seves capacitats han fet d'aquesta tecnologia una bona opció com alternativa pel bucle local d'accés i pel desplegament de xarxes d'àrea local, focalitzades aquestes últimes en l'entorn domèstic. A més, les CXE-BV inclouen un conjunt d'aplicacions de baixa velocitat orientades a l'operador, com la lectura automàtica de comptadors (LAC), distribució de càrrega, facturació dinàmica, etc. Per altra banda, les CXE-MV i CXE-AV, històricament lligades a tasques de telecontrol i teleprotecció, s'estan començant a considerar com un canal de comunicacions eficient i fiable. El desenvolupament de sistemes digitals i els esforços d'estandardització estan fent d'aquests canals un medi atractiu per a que els operadors elèctrics ofereixin serveis de comunicacions, ja que no necessiten invertir en infraestructura perquè la xarxa elèctrica ja està desplegada.En aquesta Tesi s'introduiran i es comentaran les particularitats de les tres xarxes elèctriques, després, es mostraran al lector les solucions tecnològiques existents pels canals de BV basats en la norma Europea CENELEC així com pels canals d'AV, mostrant que els sistemes actuals de LAC ofereixen una diversitat freqüencial molt baixa i que els mòdems CXE-AV estan ancorats en estendards antiquats.
Aquest treball es mou per les tres topologies de la xarxa, particularment, en aplicacions orientades a la banda CENELEC, en mesura i modelat de canal, i en mesura i disseny del nivell físic per sistemes CXE-BV, CXE-MV i CXE-AV respectivament. Els sistemes actuals que exploten la banda CENELEC ofereixen mecanismes d'explotació de la diversitat freqüencial del canal molt limitats o nuls, donant lloc a una baixa robustesa en front a interferències i soroll de fons acolorit. Aquest treball proposa un esquema de modulació multiportadora que, mantenint una complexitat baixa, ofereix unes altes prestacions permetent un bon nivell d'explotació de la selectivitat freqüencial. Per al que a CXE-MV respecta, aquesta Tesi desenvolupa un model de canal determinístic-estadístic pels anells urbans de distribució de potència i, finalment, en sistemes CXE-AV, aquest treball proposa, basat en mesures de canal i proves de camp, un nivell físic de banda ampla capaç de incrementar la velocitat de comunicació mentre manté una baixa densitat espectral de potència limitant així la interferència a altres sistemes.
PARAULES CLAU: Power line communications (PLC), low voltage (LV), medium voltage (MV), high voltage (HV), automatic meter reading (AMR), orthogonal frequency division multiplexing (OFDM), multicarrier spread spectrum (MC-SS), communication system design, channel measurements, channel modeling, scattering parameters.
El mundo de las comunicaciones por la red eléctrica (CRE) puede ser dividido en tres grandes tipos: CRE en bajo voltaje (CRE-BV), en medio voltaje (CRE-MV) y en alto voltaje (CRE-AV). En estos últimos años, las CRE-BV han atraído una gran expectación, ya que sus capacidades han hecho de esta tecnología una buena opción como alternativa para el bucle local de acceso y para el despliegue de redes de área local, focalizadas estas últimas en el entorno doméstico. Además, las CRE-BV incluyen un conjunto de aplicaciones de baja velocidad orientadas al operador como la lectura automática de contadores (LAC), distribución de carga, facturación dinámica, etc. Por otro lado, las CRE-MV y CRE-AV, históricamente ligadas a tareas de telecontrol y teleprotección, se están empezando a considerar como un canal de comunicaciones eficiente y fiable. El desarrollo de sistemas digitales y los esfuerzos de estandarización están haciendo de estos canales un medio atractivo para que los operadores eléctricos ofrezcan servicios de comunicaciones, ya que no necesitan invertir en infraestructura porque la red eléctrica ya está desplegada.
En esta Tesis se introducirán y se comentarán las particularidades de las tres redes eléctricas, luego, se mostrarán al lector las soluciones tecnológicas existentes para los canales de BV basados en la norma Europea CENELEC así como para los canales de AV, mostrando que los sistemas actuales de LAC ofrecen una diversidad frecuencial muy baja y que los módems CRE-AV están anclados en estándares anticuados.
Este trabajo se mueve por las tres topologías de red, particularmente, en aplicaciones orientadas a la banda CENELEC, en medida y modelado de canal, y en medida y diseño del nivel físico para sistemas CRE-BV, CRE-MV y CRE-AV respectivamente. Los sistemas actuales que explotan la banda CENELEC ofrecen mecanismos de explotación de la diversidad frecuencial del canal muy limitados o nulos, dando lugar a una escasa robustez frente a interferencias y ruido de fondo coloreado. Este trabajo propone un esquema de modulación multiportadora que, manteniendo una complejidad baja, ofrece unas altas prestaciones permitiendo un buen nivel de explotación de la selectividad frecuencial. Por lo que a CRE-MV respecta, esta Tesis desarrolla un modelo de canal determinístico-estadístico para los anillos urbanos de distribución de potencia y, finalmente, en sistemas de CRE-AV, este trabajo propone, basado en medidas de canal y pruebas de campo, un nivel físico de banda ancha capaz de incrementar la velocidad de comunicación mientras mantiene una baja densidad espectral de potencia limitando así la interferencia a otros sistemas.
PALABRAS CLAVE: Power line communications (PLC), low voltage (LV), medium voltage (MV), high voltage (HV), automatic meter reading (AMR), orthogonal frequency division multiplexing (OFDM), multicarrier spread spectrum (MC-SS), communication system design, channel measurements, channel modeling, scattering parameters.
The world of Power line communications (PLC) can be divided into three main types: low voltage PLC (LV-PLC), medium voltage PLC (MV-PLC) and high voltage PLC (HV-PLC). These last years, LV-PLC has attracted a great expectation since its wideband capabilities has made this technology a suitable choice for last-mile access and in-home communications. Moreover, LV-PLC also includes a utility oriented low frequency and low speed applications, such as automatic meter reading (AMR), load distribution, dynamic billing and so on. On the other hand, MV-PLC and HV-PLC, historically oriented to teleprotection and telecontrol tasks, are being considered as a reliable communication channel. The development of digital equipment and the standardization efforts are making those channels an attractive medium for electrical utilities telecommunications services, since the network, as well as in LV-PLC, is already deployed.
In this PhD dissertation, the three different PLC topologies are reviewed and the different communications techniques in such channels exposed. Then, a deep technological review of existing AMR solutions for the European CENELEC band, as well as HV-PLC systems is given, showing that existing AMR systems deliver low frequency diversity and HV-PLC systems are anchored in old fashioned standards.
This work walks around the three topologies, specifically, CENELEC band utility oriented applications, channel measurement and modeling and channel measurement and physical layer design, regarding LV-PLC, MV-PLC and HV-PLC respectively. Existing CENELEC compliant systems deliver low or none frequency diversity mechanisms, yielding in a low robustness against colored noise and interference. This work propose a multicarrier based physical layer approach that, while keeping the complexity low, delivers high performance allowing a great level of frequency diversity. Focusing on MV-PLC, a hybrid deterministic-statistical channel model for urban underground rings is developed and, finally, in HV-PLC systems, this work proposes, based on measurements and field tests, a wideband physical layer in order to increase data rate while keeping low both the power spectral density and possible interference to other systems.
KEYWORDS: Power line communications (PLC), low voltage (LV), medium voltage (MV), high voltage (HV), automatic meter reading (AMR), orthogonal frequency division multiplexing (OFDM), multicarrier spread spectrum (MC-SS), communication system design, channel measurements, channel modeling, scattering parameters.
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Povalač, Karel. "Sledování spektra a optimalizace systémů s více nosnými pro kognitivní rádio." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2012. http://www.nusl.cz/ntk/nusl-233577.
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The doctoral thesis deals with spectrum sensing and subsequent use of the frequency spectrum by multicarrier communication system, which parameters are set on the basis of the optimization technique. Adaptation settings can be made with respect to several requirements as well as state and occupancy of individual communication channels. The system, which is characterized above is often referred as cognitive radio. Equipments operating on cognitive radio principles will be widely used in the near future, because of frequency spectrum limitation. One of the main contributions of the work is the novel usage of the Kolmogorov – Smirnov statistical test as an alternative detection of primary user signal presence. The new fitness function for Particle Swarm Optimization (PSO) has been introduced and the Error Vector Magnitude (EVM) parameter has been used in the adaptive greedy algorithm and PSO optimization. The dissertation thesis also incorporates information about the reliability of the frequency spectrum sensing in the modified greedy algorithm. The proposed methods are verified by the simulations and the frequency domain energy detection is implemented on the development board with FPGA.
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Hsueh, Chung-Huei, and 薛仲輝. "Frequency Synchronization Techniques for Orthogonal Multicarrier Communication Systems." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/75679506729179890541.
Full textAbstract:
碩士國立高雄第一科技大學
電腦與通訊工程所
91
In orthogonal multicarrier communication system, if carrier frequency between the local oscillators at the transmitter and at the receiver unsynchronize, the intercarrier interference (ICI) will produce and system performance will be degraded. Thus frequency synchronization of orthogonal multicarrier communication system is very important. Several methods use to solve frequency synchronization problem or alleviate ICI in orthogonal frequency division multiplexing (OFDM) system are presented in this thesis. A simple method performs repeated coding in frequency domain to alleviate ICI significantly, called ICI self-cancellation scheme. However, the phase rotation caused by frequency offset cannot be solved by this method alone. Another method uses statistical property to estimate frequency offset, called maximum likelihood estimation (MLE). The MLE could get accurate estimated result even in the small SNR environment. However, the estimate range of MLE cannot be larger than 50% of subcarrier spacing, this is a restriction of MLE. A method that combines the ICI self-cancellation scheme and MLE without more redundant data is called capacity-efficient scheme for ICI self-cancellation. This method can be use to solve phase rotation problem caused by frequency offset. A new method that can also solve phase rotation problem are proposed in this thesis, this method combines the ICI self-cancellation scheme and the decision feedback frequency estimation. Finally, the simulation results of these methods are presented, and the conclusions are also given in this thesis.
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Carvajal, Rodrigo. "EM-based channel estimation for Multicarrier communication systems." Thesis, 2013. http://hdl.handle.net/1959.13/938545.
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Research Doctorate - Doctor of Philosophy (PhD)This thesis addresses the general problem of channel estimation in Multicarrier communication systems. This estimation problem, inter-alia, includes the joint estimation of channel noise variance, carrier frequency offset and phase noise bandwidth. A general state-space model is developed for multicarrier systems that represents any modulation scheme, by separating the signals into their real and imaginary parts. The approach presented in this thesis relies on the statistical representation of the signals of interest. The approach is valid for any statistical representation. In particular, we present a linear and Gaussian structure associated with the transmitted signal, which is exploited by utilizing the Kalman filter. For nonlinear signals, nonlinear filtering is carried out by utilizing sequential Monte Carlo techniques. The estimation problem is solved by using Maximum Likelihood (ML) and Maximum a Posteriori (MAP) estimation, for which the Expectation-Maximization (EM) algorithm is considered. For ML estimation, a novel selection of hidden variables and parameters is proposed, whilst the maximization step is carried out by concentrating the cost in one variable (carrier frequency offset). For MAP estimation, the prior terms are expressed as variance-mean Gaussian mixtures. In this case, the channel estimate can be obtained in closed form within the EM framework. In the maximization step of the EM algorithm, the cost function is also concentrated in one variable (carrier frequency offset). For sparse channel estimation, an l1-norm regularization is considered. An Elastic Net penalty is also considered, which accounts for the different nature that communication channels can exhibit in a variety of environments. It is also shown that the utilization of variance-mean Gaussian mixtures present a general method for MAP estimation, which encompasses different penalizations and optimization methods, such as the Lasso, Group-Lasso, and local-linear/local-quadratic approximation for the Lasso, among others. The MAP estimation approach proposed in this thesis is illustrated with not only examples in MC communication systems, but also for sparse estimation with quantized data. Finally, it is also shown that the estimation of the channel noise variance is not straightforward, and that some modifications to the standard methods should be considered. It is shown that, in the proposed MAP estimation approach, those modifications can be included in a simple manner. The thesis also considers the impact of different levels of training on the overall parameter estimation problem. In particular, it is shown that the estimates of phase noise bandwidth are generally poor, and, hence, that high levels of training are required to obtain accurate channel estimates.
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"Code time division multiple access for multicarrier communication systems." 2004. http://library.cuhk.edu.hk/record=b5891853.
Full textAbstract:
Huang Yi.Thesis (M.Phil.)--Chinese University of Hong Kong, 2004.
Includes bibliographical references (leaves 97-98).
Abstracts in English and Chinese.
Abstract --- p.i
摘要 --- p.iii
Acknowledgments --- p.iv
Contents --- p.v
Chapter Chapter 1 --- Introduction --- p.1
Chapter 1.1 --- CTDMA for Multicarrier Communication Systems --- p.2
Chapter 1.2 --- Contributions of This Thesis --- p.4
Chapter 1.3 --- Outline of This Thesis --- p.6
Chapter Chapter 2 --- Multicarrier Communication Systems --- p.8
Chapter 2.1 --- Multicarrier Modulation (MCM) Scheme versus Single Carrier Modulation (SCM) Scheme --- p.9
Chapter 2.2 --- Orthogonal Frequency Division Multiplexing (OFDM) Systems --- p.12
Chapter 2.3 --- Multicarrier CDMA --- p.16
Chapter Chapter 3 --- Data Rate Guaranteed CTDMA for Multicarrier Communication Systems --- p.21
Chapter 3.1 --- Code Time Division Multiple Access (CTDMA) --- p.22
Chapter 3.2 --- Mathematical Programming --- p.28
Chapter 3.3 --- Near Optimal CTDMA Approach --- p.32
Chapter 3.4 --- Ad Hoc CTDMA Approach --- p.48
Chapter 3.5 --- Lower Bound on Optimization --- p.61
Chapter 3.6 --- Performance Evaluation --- p.64
Chapter Chapter 4 --- Code Assignment for Multicarrier Communication Systems with Quantized Feedback --- p.73
Chapter 4.1 --- Code Assignment for Fully Loaded Systems --- p.74
Chapter 4.2 --- Random Orthogonal Codes --- p.76
Chapter 4.3 --- Wireless Fading Channel Model --- p.78
Chapter 4.4 --- Performance Evaluation of One-to-one Assignment --- p.80
Chapter 4.5 --- Code Assignment for Non-fully Loaded Systems --- p.89
Chapter 4.6 --- Performance Evaluation of Multiple-to-one Assignment --- p.90
References --- p.97
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Kim, Tae Yoon. "Rate-robustness tradeoffs in multicarrier wireless communications." Thesis, 2006. http://hdl.handle.net/2152/2919.
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Shankar, Kumar K. R. "Performance Analysis Of Multicarrier DS-CDMA Systems." Thesis, 2004. http://etd.iisc.ernet.in/handle/2005/1200.
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Liang, Hsin-Ying, and 梁新潁. "PAPR Reduction Algorithms With Error Correction Capability in Multicarrier Communication Systems." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/54635133445467477479.
Full textAbstract:
博士國立中興大學
電機工程學系所
96
This dissertation mainly focuses on reducing PAPR in a BPSK OFDM system, a 16-QAM OFDM system, and a BPSK WHT-OFDM system. First, this dissertation tries to improve two unsolved issues of the EC-SLM technique used in a BPSK OFDM system: how to select the PAPR control bits and extend the EC-SLM technique into the high-order modulation system. By combining the EC-SLM technique with cyclic codes, called Cyclic-SLM, this method is proposed to provide the selection of PAPR control bits. To extend the EC-SLM technique used in a BPSK OFDM system into a 16-QAM OFDM system, this dissertation combines a 16-QAM block coded modulation codes with the EC-SLM technique, called BCM-SLM. Next, this dissertation proposes a new scheme called EC-PTS to improve error correction capability of the original PTS technique. Comparing the EC-PTS technique with the original PTS technique, EC-PTS not only has error correction capability but also has no need to transmit the side information for recovering the input data block in the receiver. In addition, we propose a method by combining the EC-PTS technique with a 16-QAM block coded modulation codes, to extend the EC-PTS technique into the high-order modulation system; we call this method BCM-PTS. Finally, this dissertation discovers a lot of Golay complementary sequences in a BPSK WHT-OFDM system and depicts the structure of these sequences by graphic forms. Moreover, this dissertation also provides the proofs about the general expression of these Golay complementary sequences in a BPSK WHT-OFDM system.
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Liao, Chia-Hui, and 廖佳慧. "Ant Colony Optimization Inspired Resource Allocation for Multiple Access Multicarrier Communication Systems." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/42646438266748109719.
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Hong, Chi-Fu, and 洪啟富. "Single-Carrier and Multicarrier Frequency-Hopping Spread Spectrum for Wireless Communication Systems." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/80170202880701805835.
Full textAbstract:
碩士國立中興大學
電機工程學系
87
Recently, much research and development of code-division multiple access (CDMA) communication systems has been encouraged for commercial applications such as personal communications, indoor wireless local area network (LAN), and mobile radio communications. There are two basic types of CDMA techniques, namely direct-sequence CDMA (DS-CDMA) and frequency-hopping CDMA (FH-CDMA). To reduce the effects of selective and multi-path fading, there has been much interest in FH-CDMA communication systems because of their frequency diversity and resistance to the near-far problem. In this thesis, we propose a multicarrier scheme using ''one-hit'' multicarrier FH patterns to increase user capacity in an MFSK/FH-CDMA system. In previous work on multicarrier systems, it has been assumed that the hopping frequencies of N disjoint subbands are identical. We consider the FH patterns without this assumption. These FH patterns have cross-correlation of no greater than one in order to minimize mutual interference. Our results show that the proposed scheme performs better than the conventional one in both non-fading and fading channels. Furthermore, a new construction of FH patterns, concatenated prime codes, has been provided for MFSK/FH-CDMA systems. We have constructed P*P-1 FH patterns with length P*P and maximum cross-correlation of two. These P*P-1 FH patterns can be partitioned into P+1 groups, and the maximum cross-correlation in each group can be reduced to one. For this characteristic, we assign FH patterns in the same group first to the users with in the system to gain optimal performance. Owing to the low cross-correlation property, the new designed codes will be usef ul in future wireless communication systems.