Diploma thesis focuses on simultaneous transmission of selected photonic services by one single-mode optical fiber. The thesis deals with the problem of common transmission of multiple photonic services by one optical fiber using the wavelength division multiplex technology. Furthermore, the origin and influence of nonlinear phenomena accompanying the simultaneous transmission of photonic services are described. Except common data transmission with a bitrate of 10 Gbit/s, a common high-speed data signal transmission with a bitrate of 200 Gbit/s, accurate time transmission and high-power sensor signal are considered. During the aimultaneous transmission of selected photonic services, the measurement of the transmission parameters was performed for various variants of the simultaneous transmission arrangement. In particular, the influence of nonlinear phenomena and possible mutual interference of individual transmission channels at 50 and 100 GHz between signals was analyzed.

This thesis describes and models wirelesss transmission intereferences in real communication channels. A signal received on a fading channel is subjected to a multiplicative distortion and to the usual additive noise. Real channel adds to the signal noise and fadings. Gaussian noise is a result of channel awgn. Fadings is implicated by multipath propagation of signal in Rayleigh and Rician channels. Main goal of this project is to program BERsolve, which is created in tool GUIDE in Matlab. User program BERsolve makes it possible to analyse bit error rate and symbol error rate for some types of channel models, which are defined by standard COST207. BERsolve offers some other functions i.e. display time behaviour, constellation diagram and spectrum. This program provides us with an overview representation of problem by multipath interferences in communication channels.

The work explores ways to generate the OFDM signal and LDPC channel coding methods. Describes the creation of basic modules of the communication system in Matlab and simulation methods for atmospheric transmission environment, including effects of turbulence, attenuation along the route and weather conditions on the transmitted signal.

Most modern clock and data recovery circuits (CDR) are based on analog blocks that need to be redesigned whenever the technology process is to be changed. On the other hand, CDR based blind oversampling architecture (BO-CDR) can be completely designed in a digital process which makes its migration very simple. The main disadvantages of the BO-CDR that are usually mentioned in a literature are complexity of its digital circuitry and finite phase resolution resulting in larger jitter sensitivity and higher error rate. This thesis will show that those problems can be solved by designing a new algorithm of BO-CDR and subsequent optimization. For this task an FPGA was selected as simulation and verification platform. This enables to change parameters of the optimized circuit in real time while measuring on real links (unlike a simulation using inaccurate link models). The output of this optimization is a new BO-CDR algorithm with heavily reduced complexity and very low error rate. A new FPGA-based method of jitter measurement was developed (primary for CDR analysis), which enables a quick link characterization without using probing or additional equipment. The new method requires only a minimum usage of FPGA resources. Finally, new measurement equipment was developed to measure bit error distribution on FSO links to be able to develop a suitable error correction scheme based on ARQ protocol.

Disertační práce je zaměřena na měření a modelování kanálu uvnitř a vně vozidla pro komunikaci a lokalizaci. Pro účely vytvoření integrovaného inteligentního dopravního systému ITS (Intelligent transportation system) je důležitý odhad vlastnosti kanálů pro vnitřní a venkovní scénáře. Za tímto účelem je vhodné provést řadu činností, které jsou obsahem disertační práce: Simulace fyzické vrstvy 802.11p, její srovnávání s 802.11a, měření kanálu pro různé scénáře pro 802.11p a pro širokopásmový systém (UWB), vytvoření modelů kanálů pro 802.11p a UWB a výzkum vlastností lokalizace založené na měření v pásmu UWB. Výzkum komunikace vozidla s okolím založená na IEEE 802.11p standardu. Jedním z cílů disertační práce je ukázat rozdíly mezi standardy fyzické vrstvy IEEE 802.11a a IEEE 802.11p prostřednictvím simulace s použitím modelu kanálu HIPERPLAN/2. V práci je uvedena simulace přenosu signálu 802.11p kanálem ITU-R M.1225 s odlišným zpožděním a středním výkonem (pro chodce a vozidla). Vliv kanálu na signál je analyzován za použití simulace v prostředí MATLABu pomocí vyhodnocení chybovosti. Určení vlastností kanálů v kmitočtovém pásmu 5,8 GHz pro standard IEEE 802.11p a UWB. Experimenty byly prováděny pro vnitřní a vnější prostředí vozidla. Bylo zjištěno, že pro protokol 802.11p může být trend (dlouhodobý vývoj) profilu PDP (power delay profile) nejlépe aproximován pomocí modelu obsahujícího dvě klesající exponenciální funkce, na rozdíl od Saleh-Valenzuelova (S-V) modelu, který je více vhodný pro UWB systémy pracující v pásmu 3 až 11 GHz. Vytvoření odpovídající impulzní odezvy (CIR) s využitím trendu PDP. Informace o CIR byla použita pro simulaci 802.11p za účelem vyhodnocení chybovosti při použití Ricianova modelu. Výsledky odhadu BER ukazují vhodnost protokolu pro vnitřní a vnější prostředí bezdrátových aplikací. Výsledky simulací dále ukazují, že se chybovost zásadně nemění a proto je možné určit střední křivku BER pro celou sadu změřených dat. Určení vlivu malé změny polohy antény na vlastnosti kanálu. Práce ukazuje náhodnost parametrů UWB kanálu pro malé změny polohy antény okolo vozidla, zaparkovaného v podzemní garáži. Ztráty šířením jsou monotónně rostoucí se vzdáleností, avšak náhodně se mění v závislosti na úhlu a výšce antén, a proto je vyhodnocení vzdálenosti pomocí síly signálu pro tyto scénáře nevhodné. Na druhé straně může být pro spolehlivé určení vzdálenosti bez ohledu na úhel nebo výšku antény použita doba příchodu prvního svazku. Ověření vlivu změn konfigurace kanálu na parametry S-V modelu. Práce demonstruje závislost parametrů Saleh-Valenzuela modelu v na vzdálenosti a výšce antén, avšak ukazuje, že jejich průměrné hodnoty jsou blízké IEEE 802.15.3 standardu. Ověření možnosti lokalizace pomocí metody TOA (time of arrival). Vzdálenost mezi anténami byla určena z profilu PDP s využitím lineární závislosti vzdálenosti na zpoždění. Souřadnice vysílací antény byly nalezeny pomocí dvou přijímacích antén pomocí 2-D lokalizační techniky TOA. Porovnání vypočtených souřadnic s původními vykazuje chybu menší než 6%, což ukazuje vhodnost navrženého přístupu pro lokalizaci vozidel.

Orthogonal frequency division multiplexing (OFDM) has become a very popular method for high-data-rate communication. However, it is well known that OFDM is plagued by a large peak-to-average power ratio (PAPR) problem. This high PAPR results in overdesigned power amplifiers, which amongst other things leads to inefficient amplifier usage, which is undesirable. Various methods have been recommended to reduce the PAPR of an OFDM transmission; however, all these methods result in a number of drawbacks. In this thesis, a novel method called offset modulation (OM-OFDM) is proposed to control the PAPR of an OFDM signal. The proposed OM-OFDM method does not result in a number of the drawbacks being experienced by current methods in the field. The theoretical bandwidth occupancy and theoretical bit error rate (BER) expression for an OM-OFDM transmission is derived. A newly applied power performance decision metric is also introduced, which can be utilised throughout the PAPR field, in order to compare various methods. The proposed OM-OFDM method appears to be similar to a well-known constant envelope OFDM (CE-OFDM) transmission. The modulation, structural and performance differences between an OM-OFDM and a CE-OFDM method are discussed. By applying the power performance decision metric, the OM-OFDM method is shown to offer significant performance gains when compared to CE-OFDM and traditional OFDM transmissions. In addition, the OM-OFDM method is able to accurately control the PAPR of a transmission for a targeted BER. By applying the power performance decision metric and complementary cumulative distribution function (CCDF), the proposed OM-OFDM method is shown to offer further performance gains when compared to existing PAPR methods, under frequency selective fading conditions. In this thesis, the OM-OFDM method has been combined with an existing active constellation extended (ACE) PAPR reduction method. To introduce a novel method called offset modulation with active constellation extension (OM-ACE), to control the PAPR of an OFDM signal. The theoretical BER expression for an OM-ACE transmission is presented and validated. Thereafter, by applying the decision metric and CCDF, the OM-ACE method is shown to offer performance improvements when compared to various PAPR methods. The use of OM-OFDM for cognitive radio applications is also investigated. Cognitive radio applications require transmissions that are easily detectable. The detection characteristics of an OM-OFDM and OFDM transmission are studied by using receiver operating characteristic curves. A derivation of a simplified theoretical closed-form expression, which relates the probability of a missed detection to the probability of a false alarm, for an unknown deterministic signal, at various signal-to-noise ratio (SNR) values is derived and validated. Previous expressions have been derived, which relate the probability of a missed detection to the probability of a false alarm. However, they have not been presented in such a generic closed-form expression that can be used for any unknown deterministic signal (for instance OFDM and OM-OFDM). Thereafter, an examination of the spectrum characteristics of an OM-OFDM transmission indicates its attractive detection characteristics. The proposed OM-OFDM method is further shown to operate at a significantly lower SNR value than an OFDM transmission, while still offering better detection characteristics than that of an OFDM transmission under Rician, Rayleigh and frequency selective fading channel conditions. In addition to its attractive PAPR properties, OM-OFDM also offers good detection characteristics for cognitive radio applications. These aspects make OM-OFDM a promising candidate for future deployment. / Thesis (PhD)--University of Pretoria, 2012. / Electrical, Electronic and Computer Engineering / unrestricted

Ultra-wideband (UWB) communication technology offers inherent advantages such as the ability to coexist with previously allocated Federal Communications Commission (FCC) frequencies, simple transceiver architecture, and high performance in noisy environments. Spread spectrum techniques offer additional improvements beyond the conventional pulse-based UWB communications. This dissertation implements a multiple-access UWB communication system using a surface acoustic wave (SAW) correlator receiver with orthogonal frequency coding and software defined radio (SDR) base station transmitter. Orthogonal frequency coding (OFC) and pseudorandom noise (PN) coding provide a means for spreading of the UWB data. The use of orthogonal frequency coding (OFC) increases the correlator processing gain (PG) beyond that of code division multiple access (CDMA); providing added code diversity, improved pulse ambiguity, and superior performance in noisy environments. Use of SAW correlators reduces the complexity and power requirements of the receiver architecture by eliminating many of the components needed and reducing the signal processing and timing requirements necessary for digital matched filtering of the complex spreading signal. The OFC receiver correlator code sequence is hard-coded in the device due to the physical SAW implementation. The use of modern SDR forms a dynamic base station architecture which is able to programmatically generate a digitally modulated transmit signal. An embedded Xilinx Zynq ™ system on chip (SoC) technology was used to implement the SDR system; taking advantage of recent advances in digital-to-analog converter (DAC) sampling rates. SDR waveform samples are generated in baseband in-phase and quadrature (I & Q) pairs and upconverted to a 491.52 MHz operational frequency. The development of the OFC SAW correlator ultimately used in the receiver is presented along with a variety of advanced SAW correlator device embodiments. Each SAW correlator device was fabricated on lithium niobate (LiNbO3) with fractional bandwidths in excess of 20%. The SAW correlator device presented for use in system was implemented with a center frequency of 491.52 MHz; matching SDR transmit frequency. Parasitic electromagnetic feedthrough becomes problematic in the packaged SAW correlator after packaging and fixturing due to the wide bandwidths and high operational frequency. The techniques for reduction of parasitic feedthrough are discussed with before and after results showing approximately 10:1 improvement. Correlation and demodulation results are presented using the SAW correlator receiver under operation in an UWB communication system. Bipolar phase shift keying (BPSK) techniques demonstrate OFC modulation and demodulation for a test binary bit sequence. Matched OFC code reception is compared to a mismatched, or cross-correlated, sequence after correlation and demodulation. Finally, the signal-to-noise power ratio (SNR) performance results for the SAW correlator under corruption of a wideband noise source are presented.

This thesis presents a comprehensive investigation into improving wireless transmission rates and reliability through the implementation of Space Time Trellis Codes(STTC). The study focuses on enhancing the coding gain, diversity gain, and flexible transmission capabilities, which are crucial for Error-Correcting Codes (ECC)in wireless communications. Spectral efficiency, a primary concern, is achieved byincorporating Multiple-Input Multiple-Output (MIMO) techniques. This thesis discusses the encoding method and decoding algorithm for STTC systems. Then, the performance of MIMO using the Alamouti scheme is determined.Further, the benefits of Cognitive Radio (CR), an intelligent radio technology capable of automatically detecting the best available wireless channel in the spectrumat any given time, are utilized. Energy Detection (ED) is employed for SpectrumSensing (SS) to detect the presence of Primary Users (PUs). The thesis analyzes theperformance of Probability of Detection (PD) and Probability of False Alarm (PFA). Furthermore, the thesis evaluates the Bit Error Rate (BER) performance of STTCover an additive white Gaussian noise (AWGN) channel, considering different modulation schemes generated in MATLAB. Specifically, it investigates the performance ofSTTC-MIMO in terms of BER over Rayleigh channels with Quadrature AmplitudeModulation (QAM) for different combinations of transmitting and receiving antennas. The findings from this research contribute to advancing wireless communicationsystems by addressing the challenges of error correction, spectral efficiency, and reliable data transmission. The integration of STTC with MIMO and CR presents aprogressive approach towards maximizing the potential of wireless communicationtechnologies to cater to the increasing demands for seamless connectivity and superior performance. This research adds to the ongoing efforts of enhancing wirelesscommunication systems’ performance and efficiency, fostering advancements in wireless technology.

International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California / Bit errors often occur in a wireless communications link when impairments alter the transmitted signal. It is advantageous to be able to predict how well a system will tolerate transmission problems. This paper details laboratory performance measurements and comparisons in terms of evaluating configurations of a digital receiver for Feher patented Quadrature Phase Shift Keying (FQPSK-B) demodulation. The transmitted signal is subjected to calibrated levels of impairments while the receiver performance is monitored in real-time.

The significant advances in fiber-optic technology have broadened the optical network\'s reach into end-user business premises and even homes, allowing new services and technologies to be delivered to the customers. The next wave of innovation will certainly generate numerous opportunities provided by the widespread popularity of emerging solutions and applications such as tactile Internet, telemedicine and real time 3-D content generation, making them part of everyday life. Nevertheless, to support such an unprecedented and insatiable demand of data traffic, higher capacity and security, flexible bandwidth allocation and cost-efficiency have become crucial requirements for technologies candidate for future optical access networks. To this aim, optical code-division multiple-access (OCDMA) technology is considered as a prospective candidate, particularly due to features like asynchronous transmissions, flexible as well as conscious bandwidth resource distribution and support to differentiated services at the physical layer, to name but a few. In this context, this thesis proposes new mathematical formalisms for bit error rate, packet throughput and packet delay to assess the performance of flexible OCDMA networks capable of providing multiservice multirate transmissions according to users\' requirements. The proposed analytical formalisms do not require the knowledge a priori of the users\' code sequences, which means that the network performance can be addressed in a simple and straightforward manner using the code parameters only. In addition, the developed analytical formalisms account for a general number of distinct users\' classes as well as general probability of interference among users. Hence, these formalisms can be successfully applied for performance evaluation of flexible OCDMA networks not only under any number of users\' classes in a network, but also for most spreading codes with good correlation properties. The packet throughput expression is derived assuming Poisson, binomial and Markov chain approaches for the composite packet arrivals with the latter defined as benchmark. Then, it is shown via numerical simulation the Poisson-based expression is not appropriate for a reliable throughput estimate when compared to the benchmark (Markov) results. The binomial-based throughput equation, by its turn, provides results as accurate as the benchmark. In addition, the binomial-based throughput is numerically more convenient and computationally more efficient than the Markov chain approach, whereas the Markov-based one is computationally expensive, particularly if the number of users is large. The bit error rate (BER) expressions are derived considering gaussian and binomial distributions for the multiple-access interference and it is shown via numerical simulations that accurate performance of flexible OCDMA networks is only obtained with the binomial-based BER expression. This thesis also proposes and investigates a network architecture for Internet protocol traffic over flexible OCDMA with support to multiservice multirate transmissions, which is independent of the employed spreading code and does not require any new optical processing technology. In addition, the network performance assumes users transmitting asynchronously using receptors based on intensity-modulation direct-detection schemes. Numerical simulations shown that the proposed network performs well when its users are defined with high-weight code or when the channel utilization is low. The BER and packet throughput performance of an OCDMA network that provides multirate transmissions via multicode technique with two codes assigned to each single user is also addressed. Numerical results show that this technique outperforms classical techniques based on multilength code. Finally, this thesis addresses a new breakthrough technology that might lead to higher levels of security at the physical layer of optical networks. This technology consists in the generation of deterministic chaos from a commercial free-running vertical-cavity surface-emitting laser (VCSEL). The chaotic dynamics is generated by means of mechanical strains loaded onto an off-the-shelf quantum-well VCSEL using a simple and easily replicable holder. Deterministic chaos is then achieved, for the first time, without any additional complexity of optical feedback, parameter modulation or optical injection. The simplicity of the proposed system, which is based entirely on low-cost and easily available components, opens the way to the widespread use of commercial and free-running VCSEL devices for chaos-based applications. This off-the-shelf and cost-effective optical chaos generator has the potential for not only paving the way towards new security platforms in optical networks like, for example, successfully hiding the user information in an unpredictable, random-like signal against eventual eavesdroppers, but also for influencing emerging chaos applications initially limited or infeasible due to the lack of low-cost solutions. Furthermore, it leads the way to future realization of emerging applications with high-integrability and -scalability such as two-dimensional arrays of chaotic devices comprising hundreds of individual sources to increase requirements for random bit generation, cryptography or large-scale quantum networks. / Os avanços relacionados a tecnologia fotônica ampliaram o alcance das redes de comunicação óptica tanto em instalações de estabelecimentos comerciais quanto em residências, permitindo que novos serviços e tecnologias fossem entregues aos clientes. A próxima onda de inovação certamente gerará inúmeras oportunidades proporcionadas pela popularidade de soluções emergentes e aplicações como a Internet tátil, a telemedicina e a geração de conteúdo 3-D em tempo real, tornando-os parte da vida cotidiana. No entanto, para suportar a crescente demanda de tráfego atual, uma maior capacidade e segurança, alocação flexível de largura de banda e custo-eficiência tornaram-se requisitos cruciais para as tecnologias candidatas a futuras redes de acesso óptico. Para este fim, a tecnologia de acesso múltiplo por divisão de código óptico (OCDMA) é considerada um candidato em potencial, particularmente devido a características como transmissões assíncronas, distribuição flexível de banda larga e suporte a serviços diferenciados na camada física, para citar apenas alguns. Neste contexto, esta tese propõe novos formalismos matemáticos para a taxa de erro de bits, taxa de transferência de pacotes e atraso de pacotes para avaliar o desempenho de redes OCDMA flexíveis capazes de fornecer transmissões em múltiplas qualidades de serviço (QoS) de acordo com as necessidades dos usuários. Os formalismos analíticos propostos não requerem o conhecimento a priori das sequências de código dos usuários, o que significa que o desempenho da rede pode ser abordado de forma simples e direta usando apenas os parâmetros de código. Além disso, os formalismos analíticos desenvolvidos representam um número geral de classes de usuários distintos, bem como a probabilidade geral de interferência entre os usuários. Portanto, esses formalismos podem ser aplicados com sucesso na avaliação de desempenho de redes OCDMA flexíveis não apenas em qualquer número de classes de usuários em uma rede, mas também para a maioria dos códigos de espalhamento com boas propriedades de correlação. A expressão de taxa de transferência de pacotes é derivada assumindo aproximações de Poisson, binomial e de cadeia de Markov para as chegadas de pacotes compostos, com a última definida como benchmark. Em seguida, é mostrado via simulação numérica que a expressão baseada em Poisson não é apropriada para uma estimativa confiável de taxa de transferência quando comparada aos resultados de benchmark (Markov). A equação de taxa de transferência binomial, por sua vez, fornece resultados tão precisos quanto o benchmark. Além disso, a taxa de transferência binomial é numericamente mais conveniente e computacionalmente eficiente quando comparada com abordagem de Markov, enquanto esta última é computacionalmente dispendiosa, particularmente se o número de usuários é grande. As expressões de taxa de erro de bit (BER) são derivadas considerando distribuições gaussianas e binomiais para a interferência de acesso múltiplo e é mostrado por meio de simulações numéricas que o desempenho exato de redes OCDMA flexíveis é obtido somente com a expressão binomial de BER. Esta tese também propõe e investiga uma arquitetura de rede para o tráfego de protocolo de Internet sobre OCDMA flexível com suporte a transmissões de QoS e de múltiplas taxas, que é independente do código de espalhamento empregado e não requer qualquer nova tecnologia de processamento óptico. Além disso, o desempenho da rede assume que os usuários transmitem de forma assíncrona usando receptores baseados em esquemas de detecção direta de modulação de intensidade. As simulações numéricas mostraram que a rede proposta possui melhor desempenho quando seus usuários são definidos com peso de código alto ou quando a utilização do canal é baixa. O desempenho da BER e da taxa de transferência de pacotes de uma rede OCDMA que fornece transmissões de múltiplas taxas por meio de uma técnica multi-código com dois códigos atribuídos a cada usuário é também abordado. Os resultados numéricos mostram que esta técnica supera as técnicas clássicas baseadas no código de comprimento múltiplo. Finalmente, esta tese aborda uma nova tecnologia que pode levar a níveis mais elevados de segurança na camada física de redes ópticas. Esta tecnologia consiste na geração de caos determinístico a partir de um laser de emissão superficial com cavidade vertical (VCSEL). A dinâmica caótica é gerada através da aplicação de forças mecânicas em um VCSEL comercial usando um suporte simples e facilmente replicável. O caos determinístico é então alcançado, pela primeira vez, sem qualquer complexidade adicional de realimentação óptica, modulação de parâmetros ou injeção óptica. A simplicidade do sistema proposto, o qual se baseia inteiramente em componentes de baixo custo e que são facilmente encontrados, abre o caminho para o uso de dispositivos VCSEL comerciais para aplicações baseadas em caos. Este gerador de caos óptico tem o potencial não só de pavimentar o caminho para novas plataformas de segurança em redes ópticas, como, por exemplo, ocultar com êxito as informações do usuário em um sinal imprevisível e aleatório contra eventuais invasores, como também tem o potencial de influenciar aplicações de caos emergentes inicialmente limitadas ou inviáveis devido à falta de soluções de baixo custo. Além disso, ele conduz o caminho para a realização futura de aplicações emergentes com alta integridade e escalabilidade, tais como matrizes bidimensionais de dispositivos caóticos que compreendem centenas de fontes individuais para aumentar as necessidades de geração de bit aleatória, criptografia ou redes quânticas de grande escala.