Asymptotic performance of M-ary signals on Rician fading diversity channels / by Hongwei Zhang.

In this thesis, we will study the average symbol error rate of M-ary signals on wireless Rician fading channels at high average signal-to-noise ratio (SNR) in both single-carrier and multicarrier orthogonal frequency division multiplexing (OFDM) systems. In the system discussed, diversity reception with maximal ratio combining (MRC) and equal gain combining (EGC) is adopted. A general theorem relates the asymptotic error rate to the multidimensional integral of the conditional error probability is presented. Two other theorems are presented for the special cases where the conditional error probability is function of the sum of received SNR's and the sum of received amplitudes corresponding to the cases using MRC diversity and EGC diversity respectively. Then theorems are provided to analyze the asymptotic error rate performance of M-ary signals including M-ary phase-shift keying (MPSK), M-ary pulse amplitude modulation (MPAM), and M-ary quadrature amplitude modulation (MQAM) signals in both single-carrier and multicarrier OFDM systems

Optical Communication

Optical communication is very much useful in telecommunication systems, data processing and networking. It consists of a transmitter that encodes a message into an optical signal, a channel that carries the signal to its desired destination, and a receiver that reproduces the message from the received optical signal. It presents up to date results on communication systems, along with the explanations of their relevance, from leading researchers in this field. The chapters cover general concepts of optical communication, components, systems, networks, signal processing and MIMO systems. In recent years, optical components and other enhanced signal processing functions are also considered in depth for optical communications systems. The researcher has also concentrated on optical devices, networking, signal processing, and MIMO systems and other enhanced functions for optical communication. This book is targeted at research, development and design engineers from the teams in manufacturing industry, academia and telecommunication industries

Performance analysis of MC-CDMA detection schemes for D2D communication

The wireless communication standard has gone to the era of Long Term Evolution which is also known as LTE. The requirements for transmission speed and communication quality become more and more rigorous and the number of wireless communication devices is increasing rapidly. The available spectrum for mobile wireless communication is getting congested. Therefore, more efficient spectrum utilization should be taken into consideration within the future development. New methods need to be implemented to increase the efficiency of spectrum utilization. To confront this obstacle, orthogonal frequency division multiplexing (OFDM) was developed in 1990’s and has been widely deployed in the LTE networks. Multicarrier code division multiple access technique (MC-CDMA) combines code division multiple access (CDMA) with OFDM to acquire advantages from both sides. With the continuous increase of mobile applications, the power consumption of mobile terminals is also increasing significantly. Then device-to-device (D2D) communication, which is a short distance communication technique from one device directly to another one, was invented. The data of users will be transmitted between devices directly without relying on the base station. D2D communication decreases the load of the base station, reduces the terminal power consumption, and improves the spectral efficiency. Due to these merits, D2D has become a significant research topic and various new related applications for D2D have been developed and tested in realistic circumstances. This thesis applies MC-CDMA into D2D communication and studies different detection schemes for MC-CDMA. The OFDMA cellular user signals appear as significant sources of interference to D2D communication. Three alternative detection schemes are investigated: equal gain combining (EGC), maximum ratio combining (MRC) and linear minimum mean square (LMMSE) equalization. MC-CDMA performance with these detection methods is evaluated based on MATLAB simulations using relevant channel and interference models to find out the best alternative for different D2D scenarios. At the end of this thesis, a conclusion is drawn of which MC-CDMA detection scheme will be a better choice for D2D communication according to the BER performances based on the simulation results on MATLAB

FSO通信システムの新高度化技術に関する研究

早大学位記番号:新7795早稲田大

Estudio, diseño e implementación del enlace ascendente de comunicaciones NVIS multiportadora de baja potencia y diversidad de polarización

Cada dia el nombre de dispositius IoT (Internet of Things) és major, apareixent conseqüentment nous protocols i tecnologies radio enfocades a la comunicació d'aquesta mena de dispositius segons les seves necessitats. En el cas de dispositius RIoT (Remote Internet of Things) que es troben en zones molt allunyades d'infraestructures de telecomunicacions o que l'orografia no permet la visió directa entre transmissor i receptor, les comunicacions per satèl·lit i HF (High Frequency) són opcions que poden garantir l'enllaç. En el cas de les comunicacions HF, són una alternativa de baix cost degut a les característiques de propagació de les seves ones capaces de ser reflectides per la ionosfera abastant milers de quilòmetres. A pesar que la banda d'ús (3-30 MHz) es troba molt per sota de la satel·litària, són una opció vàlida per a l'amplada de banda requerida en dispositius RIoT. Respecte als estàndards de les comunicacions HF podem destacar el MIL-STD-188-110D i el STANAG 4539, els quals varien la modulació i l'amplada de banda segons la velocitat de bits requerida. Aquest tipus d'estàndards són genèrics per als subtipus d'enllaços HF: DX (Distance X) per a enllaços superiors a 250 km i NVIS (Near Vertical Incidence Skywave) per a enllaços menors a 250 km. A causa de les diferències en els paràmetres del canal entre tots dos subtipus d'enllaços, els estàndards actuals poden ser més robustos si es basen en un únic subtipus d'enllaç. Per això, a través d'aquesta tesi doctoral, s'ha caracteritzat el canal ionosfèric NVIS a la regió polar antàrtica amb la finalitat de definir un protocol de transmissió de la capa física el més delimitat a les característiques del canal. Amb tal propòsit, pel fet que les modulacions de banda estreta són susceptibles principalment al delay spread del canal es proposa l'ús de la modulació multiportadora OFDM (Orthogonal Frequency Division Multiplexing) a causa del seu disseny capaç d’evitar el delay spread. Amb el propòsit de verificar els resultats, s'ha provat la OFDM dissenyada en un escenari real, mantenint la velocitat de bit i amplada de banda dels estàndards per a poder comparar la robustesa de la comunicació. A més, pel fet que els estàndards no estan enfocats a transmissions de potències molt baixes, en dispositius RIoT la gestió energètica és de gran importància pel fet que es troben fora de la xarxa elèctrica i requereixen altes autonomies energètiques. Per això la recerca s'ha centrat també en l'anàlisi de les modulacions de banda estreta i de la modulació OFDM a molt baixes potències (menors de 6 W). Finalment, per a augmentar més la robustesa de la modulació, s'ha analitzat el comportament de les modulacions de banda estreta i la modulació OFDM fent ús de tècniques de diversitat de polarització com SC (Selection Combining) i EGC (Equal-Gain Combining) en un enllaç SIMO (Single Input Multiple Output) per a rebre les ones ordinària i extraordinària.Cada día el número de dispositivos IoT (Internet of Things) es mayor, apareciendo consecuentemente nuevos protocolos y tecnologías radio enfocadas a la comunicación de este tipo de dispositivos según sus necesidades. En el caso de dispositivos RIoT (Remote Internet of Things) que se encuentran en zonas muy alejadas de infraestructuras de telecomunicaciones o que la orografía no permite la visión directa entre transmisor y receptor, las comunicaciones por satélite y HF (High Frequency) son opciones que pueden garantizar el enlace. En el caso de las comunicaciones HF, son una alternativa de bajo coste debido a las características de propagación de sus ondas capaces de ser reflejadas por la ionosfera abarcando miles de kilómetros. A pesar de que la banda de uso (3-30 MHz) se encuentra muy por debajo de la satelital, son una opción válida para el ancho de banda requerido en dispositivos RIoT. Respecto a los estándares de las comunicaciones HF podemos destacar el MIL-STD-188-110D y el STANAG 4539, los cuales varían la modulación y el ancho de banda según la velocidad de bits requerida. Este tipo de estándares son genéricos para los subtipos de enlaces HF: DX (Distance X) para enlaces superiores a 250 km y NVIS (Near Vertical Incidence Skywave) para enlaces menores a 250 km. Debido a las diferencias en los parámetros del canal entre ambos subtipos de enlaces, los estándares actuales pueden ser más robustos si se basan en un único subtipo de enlace. Por ello, a través de esta tesis doctoral, se ha caracterizado el canal ionosférico NVIS en la región polar antártica con el fin de definir un protocolo de transmisión de la capa física lo más acotado a las características del canal. Con tal propósito, debido a que las modulaciones de banda estrecha son susceptibles principalmente al delay spread del canal se propone el uso de la modulación multiportadora OFDM (Orthogonal Frequency Division Multiplexing) debido a su diseño capaz de evitar el delay spread. Con el propósito de verificar los resultados, se ha probado la OFDM diseñada en un escenario real, manteniendo la velocidad de bit y ancho de banda de los estándares para poder comparar la robustez de la comunicación. Además, debido a que los estándares no están enfocados a transmisiones de potencias muy bajas, en dispositivos RIoT la gestión energética es de gran importancia debido a que se encuentran fuera de la red eléctrica y requieren altas autonomías energéticas. Por ello la investigación se ha centrado también en el análisis de las modulaciones de banda estrecha y de la modulación OFDM a muy bajas potencias (menores de 6 W). Por último, para aumentar más la robustez de la modulación, se ha analizado el comportamiento de las modulaciones de banda estrecha y la modulación OFDM haciendo uso de técnicas de diversidad de polarización como SC (Selection Combining) y EGC (Equal-Gain Combining) en un enlace SIMO (Single Input Multiple Output) para recibir las ondas ordinaria y extraordinaria.The number of IoT (Internet of Things) devices is increasing every day, and consequently new protocols and radio technologies are appearing focused on the communication of these types of devices according to their needs. In the case of RIoT (Remote Internet of Things) devices that are located in areas far away from telecommunications infrastructures or where the orography does not allow direct vision between transmitter and receiver, satellite and HF (High Frequency) communications are options that can guarantee the link. In the case of HF communications, they are a low-cost alternative due to the propagation characteristics of their waves, which are capable of being reflected by the ionosphere, covering thousands of kilometres. Although the band of use (3-30 MHz) is well below than the satellite, they are a valid option for the bandwidth required in RIoT devices. Regarding HF communications standards, we can highlight MIL-STD-188-110D and STANAG 4539, which vary the modulation and bandwidth according to the required bitrate. These standards are generic for HF link subtypes: DX (Distance X) for links above 250 km and NVIS (Near Vertical Incidence Skywave) for links below 250 km. Due to the differences in channel parameters between the two link subtypes, current standards can be more robust if they are based on a single link subtype. Therefore, through this PhD thesis, the NVIS ionospheric channel in the antarctic polar region has been characterised in order to define a physical layer transmission protocol as close as possible to the channel characteristics. For this purpose, due to the fact that narrowband modulations are mainly susceptible to the channel delay spread, the use of OFDM (Orthogonal Frequency Division Multiplexing) multicarrier modulation is proposed due to its design to avoid the delay spread. In order to verify the results, the designed OFDM has been tested in a real scenario, maintaining the bitrate and bandwidth of the standards in order to compare the robustness of the communication. Furthermore, since the standards are not focused on very low power transmissions, in RIoT devices energy management is of great importance because they are off-grid and require high energy autonomy. Therefore, the research has also focused on the analysis of narrowband modulations and OFDM modulation at very low powers (less than 6 W). Finally, to further increase the robustness of the modulation, the behaviour of narrowband modulations and OFDM modulation has been analysed using polarisation diversity techniques such as SC (Selection Combining) and EGC (Equal-Gain Combining) in a SIMO (Single Input Multiple Output) link to receive ordinary and extraordinary waves

Performance of MIMO Schemes in Radio-over-fibre-based Distributed Antenna System

The research presented in this thesis has focused on the use of MIMO wireless communications in a RoF-based DAS to improve wireless coverage and capacity performance in an indoor environment. The aim is to analyse the practical issues that cause throughput to deteriorate when commercial MIMO APs are used in a RoF-DAS, and also to verify that improved performance - lower error rates and higher capacities - can be achieved by a large physical separation between the RAUs when specific multi-antenna scheme algorithms are used. The performance of an IEEE 802.11n MIMO-supported AP and IEEE 802.11g spatial-diversity-supported AP are investigated in a RoF-DAS when different fibre lengths are connecting the AP in the central unit to the RAUs, and when the RAUs are widely separated. The analysis indicates that for MIMO, the throughput drops rapidly due to severe ISI caused by differential delay when the fibre-length difference exceeds a certain distance, while for spatial diversity high throughputs can be maintained even at large fibre-length difference. Further, it was observed that largely separated RAU may lead to power imbalances and the throughput drops in specific wireless user's positions when the received power imbalance was above 12-15dB for MIMO-supported AP, while for spatial-diversity-supported AP the power imbalance does not affect the throughput. The majority of previous works on RoF-DAS for improving MIMO systems were based on commercial products and the specific algorithms used within these products are unknown. An investigation was carried out at microwave frequency with SIMO algorithms in RoF-DAS uplink, MISO and MIMO algorithms in RoF-DAS downlink, and compared with the performance of a SISO system. This investigation was later extended to millimetre-wave frequency where larger bands of frequency are available enabling the possibility of wider bandwidth and higher data rates. The result shows significantly reduced error rate and modestly increased capacity for a wireless 1x2 SIMO uplink using MRC algorithm and 2x1 MISO downlink using Alamouti STBC algorithm. Also, error rate was reduced for a wireless 2x2 MIMO downlink using the zero-forcing algorithm while, most importantly, greatly increased capacity was achieved through the spatial multiplexing gain

Técnicas de equalização para MIMO massivo com amplificação não linear

The dawn of the new generation of mobile communications and the trafic explosion that derives from its implementation pose great challenge. The milimeter wave band and the use of massive number of antennas are technologies which, when combined, allow the transmission of high data rate, functioning in zones of the electromagnetic spectrum that are less explored and with capability of allocation of dozens of GHz of bandwidth. In this dissertation we consider a massive MIMO millimeter wave system employing a hybrid architecture, i.e., the number of transmit and receive antennas are lower than the number of radio frequency chains. As consequence, the precoder and equalizers should be designed in both digital and analog domains. In the literature, most of the proposed hybrid beamforming schemes were evaluated without considering the effects of nonlinear amplifications. However, these systems face non-avoidable nonlinear effects due to power amplifiers functioning in nonlinear regions. The strong nonlinear effects throughout the transmission chain will have a negative impact on the overall system performance and thus its study and the design of equalizers that take into account these effects are of paramount importance. This dissertation proposes a hybrid iterative equalizer for massive MIMO millimeter wave SC-FDMA systems. The user terminals have low complexity, just equipped with analog precoders based on average angle of departure, each with a single radio frequency chain. At the base station it is designed an hybrid analog-digital iterative equalizer with fully connected architecture in order to eliminate both the multi-user interference and the nonlinear distortion caused by signal amplification during the transmission. The equalizer is optimized by minimizing the bit error rate, which is equivalent to minimize the mean square error rate. The impact of the saturation threshold of the amplifiers in the system performance is analysed, and it is demonstrated that the iterative process can efficiently remove the multi-user interference and the distortion, improving the overall system performance.O surgimento de uma nova geração de comunicações móveis e a explosão de tráfego que advém da sua implementação apresenta grandes desafios. A banda de ondas milimétricas e o uso massivo de antenas são tecnologias que, combinadas, permitem atingir elevadas taxas de transmissão, funcionando em zonas do espectro electromagnético menos exploradas e com capacidade de alocação de dezenas de GHz para largura de banda. Nesta dissertação foi considerado um sistema de MIMO massivo de ondas milimétricas usando uma arquitectura híbrida, i.e., o número de antenas para transmissão e recepção é menor que o número de cadeias de radiofrequência. Consequentemente, o pré-codificador e equalizadores devem ser projectados nos domínios digital e analógico. Na literatura, a maioria dos esquemas híbridos de beamforming são avaliados sem ter em conta os efeitos de não linearidade da amplificação do sinal. No entanto, estes sistemas sofrem inevitavelmente de efeitos não lineares devido aos amplificadores de potência operarem em regiões não lineares. Os fortes efeitos das não-linearidades ao longo da cadeia de transmissão têm um efeito nefasto no desempenho do sistema e portanto o seu estudo e projecto de equalizadores que tenham em conta estes efeitos são de extrema importância. Esta dissertação propõe um equalizador híbrido para sistemas baseados em ondas milimétricas para MIMO massivo com modulação SC-FDMA. Os terminais de utilizador possuem baixa complexidade, equipados apenas com pré-codificadores analógicos baseados no ângulo médio de partida, cada um com uma única cadeia de radiofrequência. Na estação base é projectado um equalizador iterativo híbrido analógico-digital com arquitectura completamente conectada de modo a eliminar a interferencia multi-utilizador e a distorção causada pela amplificação do sinal aquando da transmissão. O equalizador é optimizado minimizando a taxa de erro de bit, o que é equivalente a minimizar a taxa de erro quadrático médio. O impacto do limiar de saturação dos amplificadores no desempenho do sistema é analisado, e é demonstrado que o processo iterativo consegue eliminar de modo eficiente a interferência multi-utilizador e a distorção, melhorando o desempenho do sistema.Mestrado em Engenharia Eletrónica e Telecomunicaçõe

Robust Optical Wireless Links over Turbulent Media using Diversity Solutions

Free-space optic (FSO) technology, i.e., optical wireless communication (OWC), is widely recognized as superior to radio frequency (RF) in many aspects. Visible and invisible optical wireless links solve first/last mile connectivity problems and provide secure, jam-free communication. FSO is license-free and delivers high-speed data rates in the order of Gigabits. Its advantages have fostered significant research efforts aimed at utilizing optical wireless communication, e.g. visible light communication (VLC), for high-speed, secure, indoor communication under the IEEE 802.15.7 standard. However, conventional optical wireless links demand precise optical alignment and suffer from atmospheric turbulence. When compared with RF, they suffer a low degree of reliability and lack robustness. Pointing errors cause optical transceiver misalignment, adversely affecting system reliability. Furthermore, atmospheric turbulence causes irradiance fluctuations and beam broadening of transmitted light. Innovative solutions to overcome limitations on the exploitation of high-speed optical wireless links are greatly needed.Spatial diversity is known to improve RF wireless communication systems. Similar diversity approaches can be adapted for FSO systems to improve its reliability and robustness; however, careful diversity design is needed since FSO apertures typically remain unbalanced as a result of FSO system sensitivity to misalignment. Conventional diversity combining schemes require persistent aperture monitoring and repetitive switching, thus increasing FSO implementation complexities. Furthermore, current RF diversity combining schemes may not be optimized to address the issue of unbalanced FSO receiving apertures.This dissertation investigates two efficient diversity combining schemes for multi-receiving FSO systems: switched diversity combining and generalized selection combining. Both can be exploited to reduce complexity and improve combining efficiency. Unlike maximum ratio combing, equal gain combining, and selective combining, switched diversity simplifies receiver design by avoiding unnecessary switching among receiving apertures. The most significant advantage of generalized combining is its ability to exclude apertures with low quality that could potentially affect the resultant output signal performance.This dissertation also investigates mobile FSO by considering a multi-receiving system in which all receiving FSO apertures are circularly placed on a platform. System mobility and performance are analyzed. Performance results confirm improvements when using angular diversity and generalized selection combining.The précis of this dissertation establishes the foundation of reliable FSO communications using efficient diversity-based solutions. Performance parameters are analyzed mathematically, and then evaluated using computer simulations. A testbed prototype is developed to facilitate the evaluation of optical wireless links via lab experiments

MIMO Systems

In recent years, it was realized that the MIMO communication systems seems to be inevitable in accelerated evolution of high data rates applications due to their potential to dramatically increase the spectral efficiency and simultaneously sending individual information to the corresponding users in wireless systems. This book, intends to provide highlights of the current research topics in the field of MIMO system, to offer a snapshot of the recent advances and major issues faced today by the researchers in the MIMO related areas. The book is written by specialists working in universities and research centers all over the world to cover the fundamental principles and main advanced topics on high data rates wireless communications systems over MIMO channels. Moreover, the book has the advantage of providing a collection of applications that are completely independent and self-contained; thus, the interested reader can choose any chapter and skip to another without losing continuity