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Deus, Junior Getulio Antero de. "Sistemas FFH-CDMA codificados." [s.n.], 2002. http://repositorio.unicamp.br/jspui/handle/REPOSIP/260269.
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Orientador : Jaime PortugheisTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação
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Resumo: Neste trabalho é desenvolvido um estudo sobre um sistema FFH-CDMA cujo receptor de máxima verossimilhança (MV) não-quantizado necessita de uma não-linearidade de difícil implementação. Para um sistema FFH-CDMA não-codificado propomos a utilização de um único perceptron para a implementação da não-linearidade. Esta proposta demonstrou apresentar degradação desprezível quando comparada ao receptor de MV. O cálculo da probabilidade de erro par-a-par tanto para receptores quantizados quanto para não-quantizados, foi também realizado. Um sistema que utiliza um receptor de :MVnão-quantizado demonstrou possuir ganho considerável em termos do número de usuários simultâneos quando comparado a um sistema quantizado. Motivados por este fato, realizamos cálculos para a capacidade de canal por dimensão e para a taxa de corte de canal do sistema FFH-CDMA considerado. Os resultados mostraram ganhos significativos do sistema tanto em termos de número de usuários simultâneos, como também em termos de relação sinal-ruído (para a probabilidade e o número de usuários fixados). A partir de uma aproximação para a probabilidade de erro par-a-par, um critério de projeto dos codificadores é proposto. Alguns codificadores convolucionais que se adequam ao critério proposto podem ser encontrados da literatura. Resultados de desempenho obtidos através de simulação e de limitantes superiores para códigos convolucionais terminados encontrados na literatura, mostraram a eficiência do critério de projeto sugerido para os codificadores. A partir das expressões para a taxa de corte de canal pode-se obter valores otimizados para taxas de codificação. Nem todos estes valores se encontram na literatura. Sendo assim, um algoritmo de procura de codificadores foi desenvolvido de acordo com o critério de projeto sugerido. Vários codificadores foram encontrados que podem eventualmente ser utilizados em outras aplicações. Alguns codificadores obtidos comprovam que um sistema FFH-CDMA codificado, com uma treliça de 1024 estados, pode trabalhar bem próximo da taxa de corte de canal
Abstract: This work presents a study of FFH-CDMA systems whose maximum likelihood (ML) receiver uses a nonlinearity of difficult of implementation. For an uncoded FFH-CDMA system, we propose the use of an unique perceptron to approximate the optimum nonlinearity. The proposed perceptron has performance almost identical to ML detection. An unquantized FFH-CDMA system can support a considerable greater number of simultaneous active users than a quantized FFH-CDMA system. Motivated by this fact, we evaluated the normalized sum capacity and the channel cutoff rate of the considered system. The results have showed expressive gains of an unquantized FFH-CDMA system in terms of number of active users as well as in terms of signal-to-noise ratio. Starting from an approximation of the pairwise error probability, a design criterion is proposed. Performance results obtained through computer simulation and upper bounds for convolutional codes found in the literature, showed the effectiveness of the proposed design criterion. A search algorithm for finding codes based on this criterion was implemented. Some of the coders obtained give evidence that a coded FFH-CDMA system, with a trellis of 1024 states, can work near channel cutoff rate
Doutorado
Telecomunicações e Telemática
Doutor em Engenharia Elétrica
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Venkatasubramanian, Ramasamy. "Beamforming for MC-CDMA." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/31287.
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Orthogonal Frequency Division Multiplexing (OFDM) has recently gained a lot of attention and is a potential candidate for Fourth Generation (4G) wireless systems because it promises data rates up to 10Mbps. A variation of OFDM is Multi-Carrier CDMA (MC-CDMA) which is an OFDM technique where the individual data symbols are spread using a spreading code in the frequency domain. The spreading code associated with MC-CDMA provides multiple access technique as well as interference suppression.
Often times in cellular and military environments the desired signal can be buried below interference. In such conditions, the processing gain associated with the spreading cannot provide the needed interference suppression. This research work investigates multi-antenna receivers for OFDM and MC-CDMA systems; specifically this works investigates adaptive antenna algorithms for MC-CDMA for very different channel conditions. Frequency domain beamforming is studied in this research predominantly through simulation. As an alternative a time domain beamforming is also studied.
Time variations in the channel can disrupt the orthogonality between subcarriers. Minimum Mean Square Error (MMSE) detection coupled with MMSE beamforming is proposed for time varying channels. Semi-analytic results are derived to study the Bit Error Rate (BER) performance. These results show significant performance improvement in the presence of interference. Joint MMSE weights in space and frequency is also investigated and semi-analytic results are derived to study their BER performance.Master of Science
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LE, BOT MARIE. "Antennes adaptatives en CDMA." Paris, CNAM, 2001. http://www.theses.fr/2001CNAM0384.
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Ce rapport de these traite de la demodulation a la station de base multi-capteurs dans le cadre d'une communication radiomobile en cdma. Apres un rappel du systeme cdma, nous analysons le canal de propagation. Nous presentons le recepteur optimal (mlse) dans le cas general d'une modulation lineaire, puis applique au cdma. Nous valorisons alors le role des codes d'etalement dans la demodulation en les separant du traitement spatio-temporel, qui est adapte au canal et rejette les brouilleurs. Nous proposons deux facons differentes de mettre en uvre le mlse, qui tiennent compte de la coloration spatiale et temporelle du bruit. Ceci est tres important lorsque les signaux brouilleurs proviennent des memes secteurs geographiques, ou en cas d'eblouissement. L'analyse des performances est grandement facilitee par le developpement d'un critere simplifie, qui permet d'approcher correctement la probabilite d'erreur. Nous evaluons ainsi les performances des recepteurs obtenus par les deux methodes proposees, pour differentes applications, et nous montrons qu'elles augmentent la capacite cellulaire de maniere significative. Nous comparons ces resultats avec les performances du recepteur rake classique, qui est sous-optimal en presence de bruit colore. Nous fournissons egalement une borne de reference qui indique les performances ultimes qu'on peut esperer atteindre sans erreur de modele. Enfin nous nous interessons a l'estimation du canal, dont la precision a un impact decisif sur les performances des recepteurs. Nous developpons des techniques originales de rectification, qui prennent en compte la presence de trajets ponctuels ou diffus, d'un point de vue aussi bien spatial que temporel. Nous sommes ainsi capables d'affiner les estimations classiques du canal, au sens des moindres carres. Les performances sont evaluees en termes d'erreur quadratique moyenne d'estimation, et montrent l'efficacite de ces techniques.
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SHEN, HANHONG. "SEMIBLIND MULTIUSER DETECTION FOR MC-CDMA." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1127324165.
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SHARMA, ANSHUL. "Performance Analysis of MC-CDMA and CI/MC-CDMA Using Interference Cancellation Techniques." University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1218826853.
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Jakubek, David Andrew. "Coherent/noncoherent detection of coherent optical heterodyne DPSK-CDMA and MFSK-CDMA signals." Thesis, Monterey, California. Naval Postgraduate School, 1991. http://hdl.handle.net/10945/28033.
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Haiou, Zheng, and Zhang Naitong. "ANALYSIS OF HYBRID FDMA/CDMA SYSTEMS IN RICIAN FADING." International Foundation for Telemetering, 1999. http://hdl.handle.net/10150/606808.
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International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, NevadaIn this paper, a hybrid frequency division multiple access/code division multiple access (FDMA/CDMA) system in a Rician fading channel is described and analysis. The performance of the hybrid system is compared with a wideband CDMA system, which occupies the same total bandwidth. The results show that for DPSK modulation with a RIKE receiver, a hybrid system can have a greater capacity with a strong direct path component or a high signal to noise ratio (SNR). Otherwise, a wideband system remains optimal.
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Cheung, Tze Chiu. "2GHz W-CDMA Radio Transceiver." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36411.
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A radio transceiver has been designed and built for a W-CDMA experimental system
operating at 2GHz. The radio is an RF front-end for mobile terminals. The radio provides
the functions of modulation and demodulation to enable transmitting and receiving digital
information through the air link. The radio comprises one transmitter in conjunction with
transmit power control (TPC), two independent receivers in conjunction with automatic
gain control (AGC) and automatic frequency control (AFC), and one common
synthesizer. Data exchange between the radio and the baseband processor takes place in
an 8-bit digital format. Digital-to-analog converters (DAC) at the transmitter and analog-
to-digital converters (ADC) at the receivers provide the interface between the radio and
the baseband processor. DACs are also used to convert the 7-bit command codes from the
processor to analog signals for the TPC, AGC and AFC. The radio transceiver is designed
to meet the stringent requirements imposed by the W-CDMA system. The 70dB TPC
enables the adaptive power control for combating the near-far problem. The high linearity
of the transmitter provides the use of linear modulation with less than 40dBc adjacent
channel power suppression. The 0.03125ppm tuning resolution of the AFC maximizes
the receiver sensitivity. The 80dB AGC produces a constant demodulated signal level to
the ADC regardless of the RF signal level. This thesis documents the design methodology
for this radio transceiver.Master of Science
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Duran, Omer Agah. "Multiuser Receivers For Cdma Downlink." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609953/index.pdf.
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In this thesis, multiuser receivers for code division multiple-access (CDMA) downlink are studied under frequency selective fading channel conditions. The receivers investigated in this thesis attempt to estimate desired symbol as a linear combination of chip-rate sampled received signal sequence. A common matrix-vector representation of signals, which is similar to the model given by Paulraj et. al. is constructed in order to analyze the receivers studied in this thesis.
Two receivers already well known in the literature are introduced and derived by using the common signal model. One of the receivers uses traditional matched filter and the other uses symbol-level linear minimum mean square error (MMSE) estimation. The receiver that uses traditional matched filter, also known as the conventional RAKE receiver, benefits from time diversity by combining the signal energy from multiple paths. The conventional RAKE receiver is optimal when multiple-access interference (MAI) is absent. Linear MMSE based receivers are known to suppress MAI and to be more robust to noise enhancement. The optimal symbol-level linear MMSE based receiver requires inversion of large matrices whose size is determined by either number of active users or spreading factor. These two parameters can be quite large in many practical systems and hence the computational load of this receiver can be a problem.
In this thesis, two alternative low-complexity receivers, which are chip-level linear MMSE equalizer proposed by Krauss et. al. and interference-suppressing RAKE receiver proposed by Paulraj et. al., are compared with the linear full-rank MMSE based receiver and with the conventional RAKE receiver in terms of bit-error-rate performance. Various simulations are performed to evaluate the performance of the receivers and the parameters affecting the receiver performance are investigated.
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Wan, William Ming. "Digital CDMA multi-carrier demodulator." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1996. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/MQ28260.pdf.
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Sorokine, Vladislav. "Gallager codes for CDMA applications." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ35329.pdf.
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Tanner, Rudolf. "Nonlinear receivers for DS-CDMA." Thesis, University of Edinburgh, 1999. http://hdl.handle.net/1842/1377.
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The growing demand for capacity in wireless communications is the driving force behind improving established networks and the deployment of a new worldwide mobile standard. Capacity calculations show that the direct sequence code division multiple access (DS-CDMA) technique has more capacity than the time division multiple access technique. Therefore, most 3rd generation mobile systems will incorporate some sort of DS-CDMA. In this thesis DS-CDMA receiver structures are investigated from the view point of pattern recognition which leads to new DS-CDMA receiver structures. It is known that the optimum DS-CDMA receiver has a nonlinear structure with prohibitive complexity for practical implementation. It is also known that the currently implemented receiver in 2nd generation DSCDMA mobile handsets has poor performance, because it suffers from multiuser interference. Consequently, this work focuses on sub-optimum nonlinear receivers for DS-CDMA in the downlink scenario. First, the thesis reviews DS-CDMA, established equalisers, DS-CDMA receivers and pattern recognition techniques. Then the new receivers are proposed. It is shown that DS-CDMA can be considered as a pattern recognition problem and hence, pattern recognition techniques can be exploited in order to develop DS-CDMA receivers. Another approach is to apply known equaliser structures for DS-CDMA. One proposed receiver is based on the Volterra series expansion and processes the received signal at the chip rate. Another receiver is a symbol rate radial basis function network (RBFN) receiver with reduced complexity. Subsequently, a receiver is proposed based on linear programming (LP) which is especially tailored for nonlinearly separable scenarios. The LP based receiver performance is equivalent to the known decorrelating detector in linearly separable scenarios. Finally, a hybrid receiver is proposed which combines LP and RBFN and which exploits knowledge gained from pattern recognition. This structure has lower complexity than the full RBF and good performance, and has a large potential for further improvements. Monte-Carlo simulations compare the proposed DS-CDMA receivers against established linear and nonlinear receivers. It is shown that all proposed receivers outperform the known linear receivers. The Volterra receiver’s complexity is relatively high for the performance gain achieved and might not suit practical implementation. The other receiver’s complexity was greatly reduced but it performs nearly as well as an optimum symbol by symbol detector. This thesis shows that DS-CDMA is a pattern recognition problem and that pattern recognition techniques can simplify DS-CDMA receiver structures. Knowledge is gained from the DSCDMA signal patterns which help to understand the problem of a DS-CDMA receiver. It should be noted that from the large number of known techniques, only a few pattern recognition techniques are considered in this work, and any further work should look at other techniques. Pattern recognition techniques can reduce the complexity of existing DS-CDMA receivers while maintaining performance, leading to novel receiver structures.
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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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Iltis, Ronald A. "Localization Using CDMA-MIMO Radar." International Foundation for Telemetering, 2010. http://hdl.handle.net/10150/605975.
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ITC/USA 2010 Conference Proceedings / The Forty-Sixth Annual International Telemetering Conference and Technical Exhibition / October 25-28, 2010 / Town and Country Resort & Convention Center, San Diego, CaliforniaA MIMO radar system for target localization is presented which uses direct-sequence CDMA (DS-CDMA) waveforms. The received DS-CDMA signal at each antenna is expressed directly in terms of the target positions. The waveforms employed are Gold sequences, and hence are not exactly orthogonal. A generalized successive interference cancellation (GSIC) approach is used to resolve multiple scatterers and reduce clutter. Simulation results are presented which suggest the capability to detect weak scatterers in the presence of clutter using the cancellation method.
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Filho, Rivail Vilas Boas dos Santos. "Análise de sistemas CDMA ópticos." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/18/18133/tde-06102006-104349/.
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A evolução das redes ópticas para atender o crescimento da demanda por largura de banda tem estimulado a busca por uma maior eficiência na utilização da largura de faixa disponível. O sucesso da implementação prática da técnica de acesso múltiplo por divisão de código (CDMA) em sistemas de comunicações móveis também despertou o interesse por aplicações em redes ópticas (OCDMA). Atributos únicos tais como capacidade flexível sob demanda, segurança na comunicação e alta escalabilidade, incentivaram significativamente as pesquisas. Neste contexto, este trabalho apresenta, primeiramente, uma revisão de várias configurações OCDMA propostas na literatura para qualificar e quantificar códigos válidos, com ênfase nas propriedades de correlação. Em seguida, realiza uma modelagem de sistema óptico abrangendo os subsistemas principais de geração, transmissão e recepção de sinal. O impacto das degradações, referentes à fibra óptica e aos diversos dispositivos que constituem o sistema, é então avaliado e sua influência sobre o desempenho de algumas configurações de codificação é investigado. O conhecimento da forma e das condições de manifestação destas degradações poderá servir de base ao processamento de sinal óptico à luz dos esquemas de codificação. Uma discussão sobre qualidade de serviço (QoS) e sobre flexibilização da aplicação OCDMA em sistemas de comunicação óptica também são também abordadas.The evolution of optical networks verified in the last few years has been characterized by the search for better bandwidth utilization efficiency. The successful implementation of practical code division for multiple access techniques (CDMA) in mobile communications systems has stimulated new investigations on this topic, particularly in the optical domain (optical CDMA). This is justified due to some remarkable attributes of this technology, such flexibility in code design, capacity on demand, safety, and high scalability. In this context, this dissertation presents, initially, a comprehensive review of several code configurations for OCDMA proposed in the literature, with emphasis particularly on the correlation and users availability properties. Next, it describes the modeling of an optical system consisting of the following three subsystems: generation, transmission, and signal detection. The penalties imposed to the optical codes by the propagating medium, as well as by the devices employed in the system, are accounted for and their influence on the performance of some coding configurations is investigated. The knowledge of how and when these penalties will affect the system is crucial in optical signal processing based on codification schemes. Finally, this work also addresses some aspects related to quality of service (QoS) and flexibility of the OCDMA technology in optical communications systems.
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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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Woodward, Graeme Kenneth. "Adaptive detection for DS-CDMA." Thesis, The University of Sydney, 1999. https://hdl.handle.net/2123/27691.
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Adaptive techniques for detection of direct sequence code division multiple access (DS—CDMA) signals are
investigated. The goal is to improve CDMA system performance and capacity relative to conventional systems
by reducing interference between users. The techniques considered are adaptive versions of multiuser
receiver structures. Most multiuser receivers proposed to date suffer from overly high computational complexity
or impractical levels of assumed system knowledge. Adaptive techniques may be used to improve the
feasibility of certain classes of multiuser receivers. Receivers estimate system and environmental conditions
in lieu of having such knowledge a priori. Multiuser receiver structures are catalogued, concentrating on the
important class of minimum mean squared error (MMSE) receivers which are particularly suited to adaptive
implementation. A major limitation is their poor performance in non—stationary channel environments. One
motivation of this work is to explore ways to alleviate this. Transform domain techniques are considered as
an adjunct to current adaptive techniques and may be used for data pre—conditioning or complexity reduction
of receiver algorithms. Lattice structures are presented as a means of implementing such transforms. A combination
of time division multiple access and CDMA is investigated. This has the advantage of increasing the
CDMA chip rate while allowing smaller spreading gain. Improved tracking in fading channels and reduced
complexity filter structures result. This facilitates increased system capacity. The linear MMSE structure is
extended to non-linear decision feedback techniques. Under ideal conditions the multiuser MMSE decision
feedback filter is an ideal interference canceller. Its structure is amenable to adaptive implementation, for
which numerous algorithms are studied. Adaptive multiuser decision feedback structures are capable of
suppressing unknown sources of interference while simultaneously performing cancellation of known sources
of interference. Decision feedback is further extended to multistage multiuser decision feedback structures,
which are demonstrated to be capable of achieving greater increases in system capacity.
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Hu, Teck Hon 1965. "A multirate DS-CDMA system." Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/282425.
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A rapidly growing interest in third generation Personal Communication Networks has underlined the importance of wireless multimedia systems that can support voice, video, images, files, or any combinations thereof. In order to ensure satisfactory quality of service (QoS) for individual multimedia traffic, a new analysis with a new user model based on circuit-switched direct-sequence Code Division Multiple Access (DS-CDMA) system is presented. The new user model is introduced to allow users to transmit data at multiple bit rates and to switch to other bit rates at any time. To facilitate performance analysis, each traffic type with rate s is assumed a probability ps for user k. To ensure satisfactory QoS, a new power control scheme is further proposed for a multimedia circuit-switched DS-CDMA system. Specifically, a new closed-form power control function is introduced to ensure quality of service for each traffic type and to achieve a better overall throughput at the same time. Central to the new closed-form power control function is a parameter called the traffic exponent. By introducing this parameter, the difficulty in obtaining an optimal closed-form power control function is reduced which simplifies the information feedback process from the base station to the mobile stations.
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Kejík, Petr. "Optimalizace přístupu do CDMA sítí." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2011. http://www.nusl.cz/ntk/nusl-233541.
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The aim of this dissertation thesis is an optimization of access to CDMA networks. To be more specific, this thesis deals with an optimization of admission control in UMTS network. The first part of the thesis deals with the present progress of the particular topic. Thereinafter there is an analysis of admission control in UMTS system. An own UMTS simulation program was created in MATLAB. This program enables implementation and simulation of the selected admission control algorithms. The thesis is focused on load factor based, fuzzy logic based and genetic algorithms. The created UMTS simulator was used for the mutual comparison of all algorithms. The aims of this thesis are the suitable UMTS model design, evaluation and possible optimization of selected algorithms.
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Baudais, Jean-Yves. "Étude des modulations à porteuses multiples et à spectre étalé : analyse et optimisation." Phd thesis, INSA de Rennes, 2001. http://tel.archives-ouvertes.fr/tel-00009214.
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Les systèmes numériques de communications connaissent un essor considérable sous l'impulsion d'une demande de plus en plus pressante de mobilité, de diversité des services et d'intégration des applications multimédia les plus récentes. Les recherches présentées dans ce mémoire de thèse ont pour but l'étude de nouveaux systèmes de communications qui pourront s'appliquer aussi bien aux systèmes de radiocommunications mobiles qu'aux systèmes de communications à l'intérieur des bâtiments. L'élément nouveau est ici la combinaison de deux techniques : l'étalement de spectre permettant la mise en oeuvre d'un accès multiple à répartition de codes (AMRC) et les modulations à porteuses multiples (OFDM). Cettecombinaison permet de tirer partie de la robustesse et de l'efficacité spectrale de l'OFDM, et de la capacité d'accès multiple des techniques AMRC. Deux techniques associant l'OFDM et l'AMRC sont plus particulièrement analysées.
La première technique, l'AMRC à porteuses multiples est étudiée sur un canal de Rayleigh à trajets multiples. En réception, plusieurs techniques d'égalisation ou de traitement de diversité sont mises en oeuvre et une approche plus globale de la détection est proposée. Elle consiste à intégrer la fonction de désétalement dans le processus d'égalisation, permettant ainsi d'améliorer la fiabilité de la détection. Ces techniques d'égalisation sont insérées et combinées de différentes façons dans des structures d'annulation d'interférences.
Si le système AMRC à porteuses multiples est généralement proposé pour des liaisons synchrones ou quasi-synchrones, le système AMRC
multipilote peut être utilisé dans un contexte asynchrone. Les performances théoriques de ce système sont développées et comparées aux performances des systèmes AMRC à porteuse unique.
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Qin, Qin. "Linear Prediction Approach for Blind Multiuser Detection in Multicarrier CDMA Systems." University of Cincinnati / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1034355893.
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Xiao, Lin. "CDMA Bus lane : cross-layer protocol for Qos routing in CDMA based mobile ad hoc networks." Thesis, Queen Mary, University of London, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.498195.
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Alam, Fakhrul. "Simulation of Third Generation CDMA Systems." Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/36387.
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The goal for the next generation of mobile communications system is to seamlessly integrate a wide variety of communication services such as high speed data, video and multimedia traffic as well as voice signals. The technology needed to tackle the challenges to make these services available is popularly known as the Third Generation (3G) Cellular Systems. One of the most promising approaches to 3G is to combine a Wideband Code Division Multiple Access (WCDMA) air interface with the fixed network of Global System for Mobile communications (GSM). In this thesis a signal simulator was implemented according to the physical layer specification of the IMT-2000 WCDMA system. The data is transmitted in a frame by frame basis through a time varying channel. The transmitted signal is corrupted by multiple access interference which is generated in a structured way rather than treating it as Additive White Gaussian Noise (AWGN). The signal is further corrupted by AWGN at the front end of the receiver. Simple rake diversity combining is employed at the receiver. We investigate the bit error rate at both uplink and downlink for different channel conditions. Performance improvement due to error correction coding scheme is shown. The simulator developed can be an invaluable tool for investigating the design and implementation of WCDMA systems.Master of Science
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Rupf, Marcel. "Coding for CDMA channels and capacity /." Zürich, 1993. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=10398.
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Lundqvist, Henrik. "Error Correction Coding for Optical CDMA." Licentiate thesis, KTH, Microelectronics and Information Technology, IMIT, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1637.
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The optical fiber is a very attractive communication mediumsince it offers a large bandwidth and low attenuation and cantherefore facilitate demanding services such as high-qualityvideo transmission. As the reach of optical fiber is beingextended to the access network it is economically attractive toshare fibers between different users without adding activecomponents in the network. The most common multiple accessmethod for such passive optical networks is time divisionmultiple access (TDMA), but lately there has been an increasedinterest in using wavelength division multiple access (WDMA)and optical code division multiple access (OCDMA). This thesisevaluates forward error correction as a method to improve theperformance of passive optical networks, in particular OCDMAnetworks.
Most studies of OCDMA use simple channel models focusingonly on the multiple access interference. However, beat noiseis the main performance limitation for many implementations ofOCDMA. Beat noise occurs when multiple optical fields areincident on a receiver, because of the square-law detection. Tomake a realistic evaluation of OCDMA, channel models which takeinterference, beat noise and other noise types into account arestudied in this thesis. Both direct sequencing CDMA and fastfrequency hopping are considered as spreading methods. Anefficient simulation method was developed in order to simulatesystems with forward error correction (FEC) and soft decoding.The simulations show that the performance is significantlyoverestimated when the beat noise is neglected. In order todecrease the error rate without using overly complex equipmentthe bandwidth has to be increased. Simulation results show thatit is beneficial to use error correction codes in addition tospreading codes for the bandwidth expansion. The efficiency canbe further improved by using soft decoding; therefore maximumlikelihood decoding methods for the OCDMA channels aredeveloped and demonstrate a significant reduction in the errorrate. Frequency hopping and direct sequencing are also comparedwith each other, and the results show that temporally codedOCDMA is more sensitive to beat noise.
In addition, the performance of a low complexity softdecoding method for Reed-Solomon codes is evaluated. Softdecoding of Reed Solomon codes has not yet found practical usebecause the earlier proposed methods do not offer sufficientperformance gains to motivate the increased complexity. Thebit-level Chase-decoding algorithm evaluated here can be easilyimplemented using any algebraic decoder.
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Hakyemez, Serkan Ender. "Scheduling Algorithms For Wireless Cdma Networks." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12609050/index.pdf.
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In recent years the need for multimedia packet data services in wireless networks has grown rapidly. To overcome that need third generation (3G) mobile services have been proposed. The fast growing demands multimedia services in 3G services brought the need for higher capacity. As a result of this, the improvement on throughput, traffic serving performance has become necessary in 3G systems. Code
division multiple access (CDMA) technique is one of the most important 3G wireless mobile techniques that has been defined. The scheduling mechanisms used in CDMA plays an important role on the efficiency of the system. The power, rate and capacity parameters are variable and dependent to each other in designing a scheduling mechanism. The schedulers for CDMA decide which user will use the
frequency band at which time interval with what power and rate. In this thesis different type of algorithms used in time slotted CDMA are studied and a new algorithm which supports Quality of Service (QoS) is proposed. The performance
analysis of this proposed algorithm is done via simulation in comparison to selected CDMA schedulers.
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Katz, M. (Marcos). "Code acquisition in advanced CDMA networks." Doctoral thesis, University of Oulu, 2002. http://urn.fi/urn:isbn:9514268849.
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Abstract
The present dissertation deals with initial synchronization in Code Division Multiple Access (CDMA) networks. In the first part of this thesis an extensive and up-to-date review of the literature is presented. The basic theory of code acquisition as well as different techniques and structures used to achieve the initial synchronization are discussed. A survey of the most common theoretical approaches allowing performance characterization of the acquisition process is included. The effect of noise, interference, carrier Doppler, multipath propagation, fading and data modulation on system performance are reviewed. Advanced code acquisition approaches exploiting interference suppression techniques and multiple antennas are also described.
A summary of the results obtained within the area of code acquisition in CDMA networks is also embraced by this thesis. The distinctive assumption is to consider the actual variable effect of multiple access interference on the delay-domain search process, instead of the usual constant approximation. Three directions of research are followed. Models for code acquisition in quasi-synchronous and asynchronous CDMA networks are first developed and analysed. Closed-form expressions for the main performance figures of the acquisition process are derived and analysed. Results show a strong dependence of the mean acquisition time with the nature of the multiple access interference. In the second area of research the previous results are extended to consider code acquisition with a multi-branch (Rake) receiver in a multipath channel. A generic model for Rake receiver code acquisition is considered and developed, in which the synchronization takes place in two phases. The first detected path is allocated to the first finger during the initial synchronization phase, whereas the remaining fingers are successively allocated to other available paths in the postinitial synchronization phase. Performance measures for this acquisition process are also derived and analysed. Finally, based on the use of an antenna array and beamforming techniques, conventional delay-domain code acquisition is extended to the angular domain, resulting in a two-dimensional (delay-angle) search. This technique is found to be feasible, outperforming the synchronization approach exploiting a single-antenna. It is found that there exists an optimal number of antennas that minimises the mean acquisition time. Two-dimensional code acquisition is studied in a variety of scenarios, including single and multipath channels, fixed and fading channels, and with uniform and nonuniform spatial distributions of interference. Different two-dimensional search strategies are studied. A clear dependence of acquisition performance with the search strategy and the particular distribution of interference is pointed out. The performance of two-dimensional code acquisition is found to be seriously deteriorated by the presence of spatially nonuniform interference. Schemes based on search strategy and adaptive detector structures are considered and analysed to combat the performance degradation in the mentioned case. A comparative study of code acquisition exploiting multiple antennas is also presented.
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Latva-aho, M. (Matti). "Advanced receivers for wideband CDMA systems." Doctoral thesis, University of Oulu, 1998. http://urn.fi/urn:isbn:9514250397.
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Advanced receiver structures capable of suppressing multiple-access interference in code-division multiple-access (CDMA) systems operating in frequency-selective fading channels are considered in this thesis. The aim of the thesis is to develop and validate novel receiver concepts suitable for future wideband cellular CDMA systems. Data detection and synchronization both for downlink and uplink receivers are studied.
The linear minimum mean squared error (LMMSE) receivers are derived and analyzed in frequency-selective fading channels. Different versions of the LMMSE receivers are shown to be suitable for different data rates. The precombining LMMSE receiver, whichis also suitable for relatively fast fading channels, is shown to improve the performance of the conventional RAKE receivers signicantly in the FRAMES wideband CDMA concept. It is observed that the performance of the conventional RAKE receivers is degraded signicantly with highest data rates due to multiple-access interference (MAI) as well as due to inter-path interference.
Based on a general convergence analysis, it is observed that the postcombining LMMSE receivers are mainly suited to the high data rate indoor systems. The blind adaptive LMMSE-RAKE receiverdeveloped for relatively fast fading frequency-selective channels gives superior rate of convergence and bit error rate (BER) performance in comparison to other blind adaptive receivers based on least mean squares algorithms.
The minimum variance method based delay estimation in blind adaptive receivers is shown to result in improved delay acquisition performance in comparison to the conventional matched filter and subspace based acquisition schemes. A novel delay tracking algorithm suitable to blind least squares receivers is also proposed. The analysis shows improved tracking performance in comparison to the standard delay-locked loops.
Parallel interference cancellation (PIC) receivers are developed for the uplink. Data detection, channel estimation, delay acquisition, delay tracking, inter-cell interference suppression, and array processing in PIC receivers are considered. A multistage data detector with the tentative data decision and the channel estimate feedback from the last stage is developed. Adaptive channel estimation filters are used to improve the channel estimation accuracy. The PIC method is also applied to the timing synchronization of the receiver. It is shown that the PIC based delay acquisition and tracking methods can be used to improve the performance of the conventional synchronization schemes.
Although the overall performance of the PIC receiver is relatively good in the single-cell case, its performance is signicantly degraded in a multi-cell environment due to unknown signal components which degrade the MAI estimates and subsequently the cancellation efficiency. The blind receiver concepts developed for the downlink are integrated into the PIC receivers for inter-cell interference suppression. The resulting LMMSE-PIC receiver is capable of suppressing residual interference and results in good BER performance in the presence of unknown signal components.
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Ardebilipour, Mehrdad. "Acquisition techniques for mobile CDMA systems." Thesis, University of Surrey, 2000. http://epubs.surrey.ac.uk/843192/.
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The initial code Acquisition Techniques of Direct Sequence Spread Spectrum Systems for two categories of serial and parallel search strategies is investigated. A simple and economic scheme for coarse code acquisition of Reverse Link for UMTS (FDD-WCDMA) application is presented. The emphasis is on the performance of a new scheme (using a Surface Acoustic Wave Matched Filter) as a term of probability of false detection (pf) in code division multiple access (CDMA) systems. Knowledge of initial code uncertainty phases help to reduce the overhead of preamble on the access channel and a very simple scheme for acquisition to be determined. In the reverse link this uncertainty is due to the cell radius only. Acquisition time required for a simple serial search scheme may therefore be unacceptably large. On the other hand, for parallel acquisition using parallel branches in accordance with the chip uncertainty time region leads to a lot of hardware complexity. Initially, the effect of multiple access interference and spreading sequence length are determined for models applicable to the reverse link of a mobile communications system. Then the acquisition performance is derived using a model of a cellular mobile communication channel, which includes the effects of multiple access interference, adjacent cell interference, frequency selective Rician channel, shadowing, power control error, and vehicle speed. It is shown that the most significant factors in determining the acquisition performance are the acquisition observation interval, the number of users, and the specular to diffuse power ratio. Numerical results based on analysis of acquisition performance in mobile channel show that the proposed acquisition scheme is efficient, robust, fast and suitable for real time low cost implementation.
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Lim, Leycheoh. "Chip interleaving for CDMA cellular systems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ29414.pdf.
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Li, Haiyan. "Power control in cellular CDMA systems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0028/MQ27018.pdf.
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Wu, Xiao Wen. "Video transmission over wireless CDMA networks." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0026/MQ27027.pdf.
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Gao, Zhimin. "Radio location in urban CDMA macrocells." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0028/MQ51344.pdf.
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Lei, Sihong. "Capacity analysis for a CDMA system." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0025/MQ51740.pdf.
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Oyefuga, Oladipupo Olaseni. "Downlink optimisation for wideband CDMA systems." Thesis, Imperial College London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414589.
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Huang, Li-Ke. "Space-time DS-CDMA communication systems." Thesis, Imperial College London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.397681.
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Dimitriou, Nikos. "Call admission control for multimedia CDMA." Thesis, University of Surrey, 2000. http://epubs.surrey.ac.uk/930/.
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Dhomeja, Sheyam Lal. "CDMA communications over wireless infrared channels." Thesis, University of Southampton, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287004.
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Lee, Chin-Chun. "CDMA for cellular mobile radio systems." Thesis, University of Southampton, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240979.
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Oon, Tik bin. "Multiple access interference cancellation for CDMA." Thesis, University of Southampton, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242678.
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Yan, Kai. "Genetic algorithm assisted CDMA multiuser detection." Thesis, University of Southampton, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343015.
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Shakya, Indu Lal. "High capacity CDMA and collaborative techniques." Thesis, University of Sussex, 2008. http://sro.sussex.ac.uk/id/eprint/7619/.
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The thesis investigates new approaches to increase the user capacity and improve the error performance of Code Division Multiple Access (CDMA) by employing adaptive interference cancellation and collaborative spreading and space diversity techniques. Collaborative Coding Multiple Access (CCMA) is also investigated as a separate technique and combined with CDMA. The advantages and shortcomings of CDMA and CCMA are analysed and new techniques for both the uplink and downlink are proposed and evaluated. Multiple access interference (MAI) problem in the uplink of CDMA is investigated first. The practical issues of multiuser detection (MUD) techniques are reviewed and a novel blind adaptive approach to interference cancellation (IC) is proposed. It exploits the constant modulus (CM) property of digital signals to blindly suppress interference during the despreading process and obtain amplitude estimation with minimum mean squared error for use in cancellation stages. Two new blind adaptive receiver designs employing successive and parallel interference cancellation architectures using the CM algorithm (CMA) referred to as ‘CMA-SIC' and ‘BA-PIC', respectively, are presented. These techniques have shown to offer near single user performance for large number of users. It is shown to increase the user capacity by approximately two fold compared with conventional IC receivers. The spectral efficiency analysis of the techniques based on output signal-to interference-and-noise ratio (SINR) also shows significant gain in data rate. Furthermore, an effective and low complexity blind adaptive subcarrier combining (BASC) technique using a simple gradient descent based algorithm is proposed for Multicarrier-CDMA. It suppresses MAI without any knowledge of channel amplitudes and allows large number of users compared with equal gain and maximum ratio combining techniques normally used in practice. New user collaborative schemes are proposed and analysed theoretically and by simulations in different channel conditions to achieve spatial diversity for uplink of CCMA and CDMA. First, a simple transmitter diversity and its equivalent user collaborative diversity techniques for CCMA are designed and analysed. Next, a new user collaborative scheme with successive interference cancellation for uplink of CDMA referred to as collaborative SIC (C-SIC) is investigated to reduce MAI and achieve improved diversity. To further improve the performance of C-SIC under high system loading conditions, Collaborative Blind Adaptive SIC (C-BASIC) scheme is proposed. It is shown to minimize the residual MAI, leading to improved user capacity and a more robust system. It is known that collaborative diversity schemes incur loss in throughput due to the need of orthogonal time/frequency slots for relaying source's data. To address this problem, finally a novel near-unity-rate scheme also referred to as bandwidth efficient collaborative diversity (BECD) is proposed and evaluated for CDMA. Under this scheme, pairs of users share a single spreading sequence to exchange and forward their data employing a simple superposition or space-time encoding methods. At the receiver collaborative joint detection is performed to separate each paired users' data. It is shown that the scheme can achieve full diversity gain at no extra bandwidth as inter-user channel SNR becomes high. A novel approach of ‘User Collaboration' is introduced to increase the user capacity of CDMA for both the downlink and uplink. First, collaborative group spreading technique for the downlink of overloaded CDMA system is introduced. It allows the sharing of the same single spreading sequence for more than one user belonging to the same group. This technique is referred to as Collaborative Spreading CDMA downlink (CS-CDMA-DL). In this technique T-user collaborative coding is used for each group to form a composite codeword signal of the users and then a single orthogonal sequence is used for the group. At each user's receiver, decoding of composite codeword is carried out to extract the user's own information while maintaining a high SINR performance. To improve the bit error performance of CS-CDMA-DL in Rayleigh fading conditions, Collaborative Space-time Spreading (C-STS) technique is proposed by combining the collaborative coding multiple access and space-time coding principles. A new scheme for uplink of CDMA using the ‘User Collaboration' approach, referred to as CS-CDMA-UL is presented next. When users' channels are independent (uncorrelated), significantly higher user capacity can be achieved by grouping multiple users to share the same spreading sequence and performing MUD on per group basis followed by a low complexity ML decoding at the receiver. This approach has shown to support much higher number of users than the available sequences while also maintaining the low receiver complexity. For improved performance under highly correlated channel conditions, T-user collaborative coding is also investigated within the CS-CDMA-UL system.
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Mozaffaripour, M. "Multiuser detection for mobile CDMA systems." Thesis, University of Surrey, 2003. http://epubs.surrey.ac.uk/844233/.
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The goal for the third generation (3G) of mobile communications system is to seamlessly integrate a wide variety of communication services such as high-speed data, video and multimedia traffic as well as voice signals for transmission on a Wideband Code Division Multiple Access (WCDMA) air interface. CDMA suffers from interference and in this thesis multiuser detection for the mobile uplink has been considered. A thorough comparative study for different multiuser detection methods is done. RAKE-IC as an architecture for mixing the ideas of RAKE receiver, and parallel Interference Cancellation, are introduced. The basic concept is to maximize the signal to noise ratio of all users in the system by using adaptive algorithms. The structure of RAKE-IC has been extended to multi-stages and several adaptive algorithms are implemented. An iterative method for interference cancellation has been considered and its convergence issue has been analytically studied. An improvement in convergence using the Rayleigh-Ritz theorem is proposed which in consequence increases the convergence speed in synchronous scenarios. Using analytical methods another improvement using the Gershgorin theorem has been proposed which does not impose a great complexity in the system, yet works well even in asynchronous environments. A suboptimum search algorithm for correcting the reliable detected information has been introduced with the property that its structure can be combined well with the iterative detectors. This combination achieves a better performance than partial parallel interference cancellation method even in rather low interference regions of operation. The structure of the sub-optimum search algorithm has been extended to multiple stages and its performance in terms of bit error rate has been analytically derived in closed form that shows good agreement with the simulation results. Considering the power profile of the users and by sacrificing a little performance, the suboptimum search structure has been further simplified. Key words: Multiuser Detection, WCDMA and Interference Cancellation.
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Khanfouci, Mourad. "Séquences chaotiques pour les systèmes CDMA." Paris 11, 2005. http://www.theses.fr/2005PA112019.
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Nous nous sommes intéressés dans cette thèse au problème général de l'optimisation des performances d'un système de communication numérique, accès multiple par répartition des codes (CDMA) par un choix ou encore une synthèse des séquences d'étalement. Après avoir décrit brièvement les approches classiques, basées essentiellement des constructions dans le corps des symboles binaires ainsi qu'une optimisation des paramètres de corrélation maximaux associés, nous nous sommes concentrés sur des approches plus récentes, basées sur une minimisation des statistiques d'ordre 2 de l'interférence inter- utilisateurs. Notre travail s'est alors naturellement articulé en trois grandes parties. Dans la première partie nous avons décrit les séquences d'étalement optimales pour le système lorsqu’un récepteur conventionnel est considéré. Nous avons proposé une implémentation de ces séquences par le biais de séquences chaotiques Markoviennes linéaires par parties. Dans la deuxième partie de cette thèse, nous avons considéré les performances de ces séquences pour des systèmes CDMA en lien asynchrone et munis de détecteurs multi- utilisateurs linéaires. Nous avons alors montré, que les séquences (10,2)-Markoviennes retenues dans la première partie du travail amélioraient nettement les performances du système. Dans la dernière partie de notre thèse nous avons discuté l'emploi des séquences d'étalement chaotiques (10,2)-Markoviennes dans un contexte de systèmes CDMA asynchrones multicodes. Nous avons alors montré que les performances des séquences (10,2)-Markoviennes sont alors clairement supérieures à celle des solutions classiques adoptées pour les systèmes multicodesThe research presented in this dissertation concerns the spreading sequences optimization issues of the asynchronous DS-CDMA communication systems. After the descrption of the main classicla sequences families, based on linear feedback shift registers and optimized by the means of the minimization of maximal correlation parameters, defined on the sequence set, we have proposed a new spreading sequences design methodology that relies on the minimization of the second order statistics of the multiple access interference. We have proposed an implementation of the optimal sequences by the means of quantized chaotic (10,2)-Markovian sequences. The thesis is organized into three main topics. In the first one, we have proposed and validated the (10,2)- Markovian sequences by intensive C++ object oriented programming. In the second, we have illustrated the performances of the proposed sequences design for asynchronous DS-CDMA systems employing a linear multiuser detection front end. In the third, we have illustrated the error performances of multicode DS-CDMA systems employing the (10,2)- Markovian sequences as channelization codes. The results of the work are showing that the proposed sequences are superior to the classical spreading/channelization solutions both in terms of error performances and capacity, evaluated in terms of the available users for a target bit error rate
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Abdi, Moussa. "Détection multi-utilisateurs en mode CDMA." Paris, ENST, 2002. http://www.theses.fr/2002ENST0027.
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Phasouliotis, Antonis. "Multicarrier CDMA systems with MIMO technology." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/multicarrier-cdma-systems-with-mimo-technology(87853579-fae7-45cb-b243-abe731f2c786).html.
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The rapid demand for broadband wireless access with fast multimedia services initiated a vast research on the development of new wireless systems that will provide high spectral efficiencies and data rates. A potential candidate for future generation wireless systems is multi-carrier code division multiple access (MC-CDMA). To achieve higher user capacities and increase the system data rate, various multiple-input multiple-output (MIMO) technologies such as spatial multiplexing and spatial diversity techniques have been proposed recently and combined with MC-CDMA.This research proposes a chip level coded ordered successive spatial and multiuser interference cancellation (OSSMIC) receiver for downlink MIMO MC-CDMA systems. As the conventional chip level OSIC receiver [1] is unable to overcome multiple access interference (MAI) and performs poorly in multiuser scenarios, the proposed receiver cancels both spatial and multiuser interference by requiring only the knowledge of the desired user's spreading sequence. Simulation results show that the proposed receiver not only performs better than the existing linear detectors [2] but also outperforms both the chip and symbol level OSIC receivers. In this work we also compare the error rate performance between our proposed system and MIMO orthogonal frequency division multiple access (MIMO OFDMA) system and we justify the comparisons with a pairwise error probability (PEP) analysis. MIMO MC-CDMA demonstrates a better performance over MIMO OFDMA under low system loads whereas in high system loads, MIMO OFDMA outperforms MIMO MC-CDMA. However if all users' spreading sequences are used at the desired user receiver, MIMO MC-CDMA performs better than MIMO OFDMA at all system loads.In the second part of this work, user grouping algorithms are proposed to provide power minimisation in grouped MC-CDMA and space-time block code (STBC) MC-CDMA systems. When the allocation is performed without a fair data rate requirement, the optimal solution to the minimisation problem is provided. However when some fairness is considered, the optimal solution requires high computational complexity and hence we solve this problem by proposing two suboptimal algorithms. Simulation results illustrate a significantly reduced power consumption in comparison with other techniques.
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Wu, Xiao Wen Carleton University Dissertation Engineering Systems and Computer. "Video transmission over wireless CDMA networks." Ottawa, 1997.
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Li, Haiyan Carleton University Dissertation Engineering Systems and Computer. "Power control in cellular CDMA systems." Ottawa, 1997.
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Agashe, Parag. "Selective cancellation of interference for CDMA." Thesis, This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-11182008-063200/.
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Abdi, Moussa. "Détection multi-utilisateurs en mode CDMA /." Paris : École nationale supérieure des télécommunications, 2003. http://catalogue.bnf.fr/ark:/12148/cb390325301.
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