Low-complexity Location-aware Multi-user Massive MIMO Beamforming for High Speed Train Communications

Massive Multiple-input Multiple-output (MIMO) adaption is one of the primary evolving objectives for the next generation high speed train (HST) communication system. In this paper, we consider how to design an efficient low-complexity location-aware beamforming for the multi-user (MU) massive MIMO system in HST scenario. We first put forward a low-complexity beamforming based on location information, where multiple users are considered. Then, without considering inter-beam interference, a closed-form solution to maximize the total service competence of base station (BS) is proposed in this MU HST scenario. Finally, we present a location-aid searching-based suboptimal solution to eliminate the inter-beam interference and maximize the BS service competence. Various simulations are given to exhibit the advantages of our proposed massive MIMO beamforming method.Comment: This paper has been accepted for future publication by VTC2017-Sprin

Comparação do desempenho de arquiteturas híbridas para comunicações na banda das ondas milimétricas

Mestrado em Engenharia Electrónica e TelecomunicaçõesA proliferação massiva das comunicações sem os faz prever que o número de utilizadores aumente exponencialmente até 2020, o que tornar a necessário um suporte de tráfego milhares de vezes superior e com ligações na ordem dos Gigabit por segundo. Este incremento exigir a um aumento significativo da e ciência espectral e energética. Impõe-se portanto, uma mudança de paradigma dos sistemas de comunicação sem os convencionais, imposta pela introdução da 5a geração. Para o efeito, e necessário desenvolver novas e promissoras técnicas de transmissão, nomeadamente a utilização de ondas milimétricas em sistemas com um número massivo de antenas. No entanto, consideráveis desafios emergem ao adotar estas técnicas. Por um lado, este tipo de ondas sofre grandes dificuldades em termos de propagação. Por outro lado, a adoção de arquiteturas convencionais para sistemas com um número massivo de antenas e absolutamente inviável, devido ao custo e ao nível de complexidade inerentes. Isto acontece porque o processamento de sinal ao nível da camada f sica e maioritariamente feito em banda base, ou seja, no domínio digital requerendo uma cadeia RF por cada antena. Neste contexto as arquiteturas híbridas são uma proposta relativamente recente que visa simplificar a utilização de um grande número de antenas, dividindo o processamento entre os domínios analógico e digital. Para além disso, o número de cadeias RF necessárias e bastante inferior ao número total de antenas do sistema, contribuindo para obvias melhorias em termos de complexidade, custo e energia consumida. Nesta dissertação e implementada uma arquitetura híbrida para ondas milimétricas, onde cada cadeia RF está apenas conectada a um pequeno conjunto de antenas. E considerado um sistema contendo um transmissor e um recetor ambos equipados com um grande número de antenas e onde, o número de cadeias RF e bastante inferior ao número total de antenas. Pré-codificadores híbridos analógico/digital, recentemente propostos na literatura são utilizados e novos equalizadores híbridos analógico/digital são projetados. E feita uma avaliação de performance à arquitetura implementada e posteriormente comparada com uma outra arquitetura, onde todas as antenas estão conectadas a todas as cadeias RF.The expected massive proliferation of wireless systems points out an exponential increase in the number of users until 2020, which is needed to support up to one thousand times more tra c and connections in order of Gigabit per second. However, these goals require a signi cantly improvement in the spectral and energy e ciency. As a result, it is essential to make a paradigm shift in conventional wireless systems, imposed by the introduction of fth generation (5G). For this purpose, new and promising transmission techniques will be needed, namely the use of millimeter Waves (mmWave) in systems with a massive number of antenna elements. Nevertheless, considerable challenges emerge in the adoption of these techniques. On one hand, mmWave su er great di culties in terms of propagation. On the other hand, the using of conventional architectures for systems with a large number of antennas is absolutely impracticable because of the costs and the level of complexity. This happens because the signal processing in physical layer is mostly done in baseband, which means, that one RF chain for each antenna is required. In this context the hybrid architectures are a relatively recent proposal where the aim is to simplify the use of a large number of antenna elements, dividing the processing between the analog and digital domains. Moreover, the number of RF chains needed are much lower than the total number of antenna elements of the system, which contribute to obvious improvements in terms of complexity, costs and energy consumption. In this Dissertation a hybrid mmWave based architecture, where each RF chain is only connected to a small set of antennas, is implemented. It is considered a system comprising a transmitter and a receiver both equipped with a massive number of antennas and where the number of RF chains is much lower than the number of antennas. Hybrid analog/digital precoders recently proposed in the literature are used and a new hybrid analog/digital equalizer is designed. The implemented architecture is then evaluated and compared with other architecture, where all the antennas are connected to all RF chains

Millimetre-wave radio-over-fibre supported multi-antenna and multi-user transmission

In this thesis, various features of the RoF supported mmW communication for future wireless systems have been analysed including photonic generation of mmW for MIMO operation, performance analysis of mmW MIMO to achieve spatial diversity and spatial multiplexing with analog RoF fronthaul, and multi-user transmission in the 60 GHz-band using multiplexing-over-fibre transport and frequency-selective antenna. A low cost mmW generation system for two independent MIMO signals has been presented, consisting of a single optical Phase Modulator (PM). The different aspects of experimental analysis on RoF-supported mmW MIMO in this thesis, which were not considered before, include use of specific MIMO algorithm to understand the amount of improvement in coverage and data rate for a particular MIMO technique, performance comparison with SISO at several user locations, and verification of optimum RAU physical spacing for a particular transmission distance with the theoretical results. The results show that flexible and wider RAU spacings, required to obtain optimum performance in a mmW MIMO system, can be achieved using the proposed analog RoF fronthaul. The investigation was extended to verification of a method to individual measurement of mmW channel coefficients and performing MIMO processing, which shows that mmW channels are relatively static and analysis can be extended to much longer distances and making projections for N×N MIMO. For mmW multi-user transmission, a novel low cost, low complexity system using single RoF link and single RF chain with single transmitting antenna has been presented and characterized, which was based on large number of RF chains and multiple antenna units previously. The setup involves generation and RoF transport of a composite SCM signal, upconversion at the RAU and transmission of different frequency channels towards spatially distributed users using a frequency-selective Leaky-Wave-Antenna (LWA), to convert Frequency Division Multiplexing (FDM) in to Spatial Division Multiple Access (SDMA). Analysis on low user-signal spacing for the SCM shows the feasibility to serve a large number of users within a specific transmission bandwidth and experimental demonstration to achieve sum rate of 10Gb/s is shown by serving 20 users simultaneously. Furthermore, investigation on SNR degradation of high bandwidth signals due to beamsteering effect of the LWA and theoretical calculations of the sum data rate for different number of users is performed, which shows that the proposed system can provide much higher sum rates with high available SNR. It was also experimentally demonstrated that improvement in coverage and spectral efficiency is obtained by operating multiple LWAs using single RF chain. Finally, an experimental demonstration of a DWDM-RoF based 60 GHz multi-user transmission using single LWA is presented to show the feasibility to extend the setup for a multiple RAU based system, serving each at distinct optical wavelength and performing direct photonic upconversion at the RAU for low cost mmW generation

Performance investigation of spatial modulation systems under realistic channel models

In order to fulfil the explosive demand for convenient wireless data access, novel wireless technologies such as the multiple-input-multiple-output (MIMO) have widely been used to improve the link reliability and capacity of wireless communication systems. In recent years, a new MIMO technology named the spatial modulation (SM) has attracted signi cant research interest due to its reported enhancement on the system performance with the reasonable system complexity. Before a new technology comes into real use, it is necessary to comprehensively evaluate its performance under different scenarios. In this thesis, we investigate the performance of SM systems under some important realistic scenarios for future wireless communications, such as the vehicle-to-vehicle (V2V), the high-speed train (HST), and the massive MIMO scenarios. Firstly, the bit error rate (BER) performance of SM systems under a novel threedimensional (3D) geometry based stochastic model (GBSM) for V2V MIMO channels is investigated by both theoretical analysis and system simulations. The impacts of vehicle tra c density (VTD), Doppler effect, and 3D feature on the BER performance of SM systems are thoroughly studied. In addition, other MIMO technologies, such as the vertical Bell Labs layered space-time (V-BLAST), the Alamouti scheme are compared with SM under different simulation settings. Secondly, the BER performance of SM systems is studied under a non-stationary wideband HST GBSM considering the non-ideal channel estimation case. The timevarying behaviour of the channel and its impact on the performance of SM systems are comprehensively investigated. The accurate theoretical BER expression of SM systems under a non-stationary wideband HST channels with non-ideal channel estimation is derived. A novel statistic property named stationary interval in terms of the space-time correlation function (STCF) is introduced in order to clearly explain all theoretical and simulation results. Thirdly, the performance of SM systems is evaluated under a Kroneck-based massive MIMO channel model. As a massive MIMO system employs large numbers of antennas, antenna elements are distributed over a wide range. Thus, different antenna elements may observe different sets of clusters. How this phenomenon affects the performance of SM systems is investigated by considering a survival probability of clusters, which abstracts the birth-death process of each cluster in the channel model. Moreover, the performance of SM systems is also compared with that of other MIMO technologies under the massive MIMO channel model. In summary, all research works in this thesis have considered realistic MIMO channel models, which are meaningful for the test, performance evaluation, and implementation of SM technology for future advanced wireless communications systems

Mobile and Wireless Communications

Mobile and Wireless Communications have been one of the major revolutions of the late twentieth century. We are witnessing a very fast growth in these technologies where mobile and wireless communications have become so ubiquitous in our society and indispensable for our daily lives. The relentless demand for higher data rates with better quality of services to comply with state-of-the art applications has revolutionized the wireless communication field and led to the emergence of new technologies such as Bluetooth, WiFi, Wimax, Ultra wideband, OFDMA. Moreover, the market tendency confirms that this revolution is not ready to stop in the foreseen future. Mobile and wireless communications applications cover diverse areas including entertainment, industrialist, biomedical, medicine, safety and security, and others, which definitely are improving our daily life. Wireless communication network is a multidisciplinary field addressing different aspects raging from theoretical analysis, system architecture design, and hardware and software implementations. While different new applications are requiring higher data rates and better quality of service and prolonging the mobile battery life, new development and advanced research studies and systems and circuits designs are necessary to keep pace with the market requirements. This book covers the most advanced research and development topics in mobile and wireless communication networks. It is divided into two parts with a total of thirty-four stand-alone chapters covering various areas of wireless communications of special topics including: physical layer and network layer, access methods and scheduling, techniques and technologies, antenna and amplifier design, integrated circuit design, applications and systems. These chapters present advanced novel and cutting-edge results and development related to wireless communication offering the readers the opportunity to enrich their knowledge in specific topics as well as to explore the whole field of rapidly emerging mobile and wireless networks. We hope that this book will be useful for students, researchers and practitioners in their research studies

Uncoded space-time labeling diversity with three transmit antennas: symbol mapping designs and error performance analysis.

Doctoral Degrees. University of KwaZulu-Natal, Durban.Abstract available in PDF.Publications on page iii

Cooperative Radio Communications for Green Smart Environments

The demand for mobile connectivity is continuously increasing, and by 2020 Mobile and Wireless Communications will serve not only very dense populations of mobile phones and nomadic computers, but also the expected multiplicity of devices and sensors located in machines, vehicles, health systems and city infrastructures. Future Mobile Networks are then faced with many new scenarios and use cases, which will load the networks with different data traffic patterns, in new or shared spectrum bands, creating new specific requirements. This book addresses both the techniques to model, analyse and optimise the radio links and transmission systems in such scenarios, together with the most advanced radio access, resource management and mobile networking technologies. This text summarises the work performed by more than 500 researchers from more than 120 institutions in Europe, America and Asia, from both academia and industries, within the framework of the COST IC1004 Action on "Cooperative Radio Communications for Green and Smart Environments". The book will have appeal to graduates and researchers in the Radio Communications area, and also to engineers working in the Wireless industry. Topics discussed in this book include: • Radio waves propagation phenomena in diverse urban, indoor, vehicular and body environments• Measurements, characterization, and modelling of radio channels beyond 4G networks• Key issues in Vehicle (V2X) communication• Wireless Body Area Networks, including specific Radio Channel Models for WBANs• Energy efficiency and resource management enhancements in Radio Access Networks• Definitions and models for the virtualised and cloud RAN architectures• Advances on feasible indoor localization and tracking techniques• Recent findings and innovations in antenna systems for communications• Physical Layer Network Coding for next generation wireless systems• Methods and techniques for MIMO Over the Air (OTA) testin