Synchronisation Issues in Non-coherent MIMO Systems

In this article, we identify some of the key problems that may be encountered when designing Non-Coherent (NC) Multiple-Input Multiple-Output (MIMO) DownLink (DL) synchronisation schemes for communicating over multi-path fading channels. Our main objectives are to illustrate the information theoretic features and to provide design guidelines for the initial synchronisation of NC MIMO systems. We conclude by outlining the relationships between the beneficial and detrimental design factors

Multiple Access Techniques for Next Generation Wireless: Recent Advances and Future Perspectives

The advances in multiple access techniques has been one of the key drivers in moving from one cellular generation to another. Starting from the first generation, several multiple access techniques have been explored in different generations and various emerging multiplexing/multiple access techniques are being investigated for the next generation of cellular networks. In this context, this paper first provides a detailed review on the existing Space Division Multiple Access (SDMA) related works. Subsequently, it highlights the main features and the drawbacks of various existing and emerging multiplexing/multiple access techniques. Finally, we propose a novel concept of clustered orthogonal signature division multiple access for the next generation of cellular networks. The proposed concept envisions to employ joint antenna coding in order to enhance the orthogonality of SDMA beams with the objective of enhancing the spectral efficiency of future cellular networks

Prototyping of Singular Value Reconstruction Precoding for Reliable Non-Orthogonal IoT Signals

Massive connectivity is one of the main research directions for beyond 5G. The cellular based narrowband IoT (NB-IoT), enabled by the orthogonal frequency division multiplexing (OFDM) signal, is an important technique. To evolve into the beyond 5G era, non-orthogonal concepts are preferred to re-shape the NB-IoT to provide higher spectral efficiency, wider coverage and lower power consumed services. This work investigates a non-orthogonal waveform in next generation IoT (NG-IoT) scenarios. Previous work has verified the advantages of zero forcing (ZF) precoding in interference mitigation but with some limitations. This work proposes a singular value reconstruction (SVR) precoding method, which can improve the precoding reliability and greatly reduce noise sensitivity. Simulations show significant spectral efficiency gain when compared with the previous work. An experiment platform is then configured in an over-the-air multiuser multiple input multiple output (MIMO) scenario to verify the practical feasibility of the precoding algorithm

Timing and Carrier Synchronization in Wireless Communication Systems: A Survey and Classification of Research in the Last 5 Years

Timing and carrier synchronization is a fundamental requirement for any wireless communication system to work properly. Timing synchronization is the process by which a receiver node determines the correct instants of time at which to sample the incoming signal. Carrier synchronization is the process by which a receiver adapts the frequency and phase of its local carrier oscillator with those of the received signal. In this paper, we survey the literature over the last 5 years (2010–2014) and present a comprehensive literature review and classification of the recent research progress in achieving timing and carrier synchronization in single-input single-output (SISO), multiple-input multiple-output (MIMO), cooperative relaying, and multiuser/multicell interference networks. Considering both single-carrier and multi-carrier communication systems, we survey and categorize the timing and carrier synchronization techniques proposed for the different communication systems focusing on the system model assumptions for synchronization, the synchronization challenges, and the state-of-the-art synchronization solutions and their limitations. Finally, we envision some future research directions

Recent Advances in Acquiring Channel State Information in Cellular MIMO Systems

In cellular multi-user multiple input multiple output (MU-MIMO) systems the quality of the available channel state information (CSI) has a large impact on the system performance. Specifically, reliable CSI at the transmitter is required to determine the appropriate modulation and coding scheme, transmit power and the precoder vector, while CSI at the receiver is needed to decode the received data symbols. Therefore, cellular MUMIMO systems employ predefined pilot sequences and configure associated time, frequency, code and power resources to facilitate the acquisition of high quality CSI for data transmission and reception. Although the trade-off between the resources used user data transmission has been known for long, the near-optimal configuration of the vailable system resources for pilot and data transmission is a topic of current research efforts. Indeed, since the fifth generation of cellular systems utilizes heterogeneous networks in which base stations are equipped with a large number of transmit and receive antennas, the appropriate configuration of pilot-data resources becomes a critical design aspect. In this article, we review recent advances in system design approaches that are designed for the acquisition of CSI and discuss some of the recent results that help to dimension the pilot and data resources specifically in cellular MU-MIMO systems

Multiple Access Techniques for Next Generation Wireless: Recent Advances and Future Perspectives

The advances in multiple access techniques has been one of the key drivers in moving from one cellular generation to another. Starting from the first generation, several multiple access techniques have been explored in different generations and various emerging multiplexing/multiple access techniques are being investigated for the next generation of cellular networks. In this context, this paper first provides a detailed review on the existing Space Division Multiple Access (SDMA) related works. Subsequently, it highlights the main features and the drawbacks of various existing and emerging multiplexing/multiple access techniques. Finally, we propose a novel concept of clustered orthogonal signature division multiple access for the next generation of cellular networks. The proposed concept envisions to employ joint antenna coding in order to enhance the orthogonality of SDMA beams with the objective of enhancing the spectral efficiency of future cellular networks

MIMO Systems: Principles, Iterative Techniques, and advanced Polarization

International audienceThis chapter considers the principles of multiple-input multiple-output (MIMO) wireless communication systems as well as some recent accomplishments concerning their implementation. By employing multiple antennas at both transmitter and receiver, very high data rates can be achieved under the condition of deployment in a rich-scattering propagation medium. This interesting property of MIMO systems suggests their use in the future high-rate and high-quality wireless communication systems. Several concepts in MIMO systems are reviewed in this chapter. We first consider MIMO channel models and recall the basic principles of MIMO structures and channel modeling. We next study the MIMO channel capacity and present the early developments in these systems concerning the information theory aspect. Iterative signal detection is considered next; it considers iterative techniques for space-time decoding. As the capacity is inversely proportional to the spatial channel correlation, MIMO antennas should be sufficiently separated, usually by several wavelengths. In order to minimize antennas' deployment, we present advanced polarization diversity techniques for MIMO systems and explain how they can help to reduce the spatial correlation in order to achieve high transmission rates. We end the chapter by considering the application of MIMO systems in local area networks, as well as their potential in enhancing range, localization, and power efficiency of sensor networks

Implementação de pré-codificador SM-MIMO para 4G/LTE em plataforma SDR

Mestrado em Engenharia Eletrónica e TelecomunicaçõesThe main goal of this dissertation is the development and evaluation of new techniques to be used in new generation of wireless comunication devices. It focuses on the usage of multiple antennas (MIMO), precoding and the usage of spatial multiplexing in disregard of diversity techniques. This makes possible to increase data rates considerably. Throughout the document, are shown several multiplexing techniques, theoretical information about wireless propagation, and multiple antennas techniques. It was proposed and implemented a spatial multiplexing system. Firstly it was implemented in Matlab, with two precoders tested: Zero Forcing (ZF) and Minimum Mean Square Error (MMSE). Subsequently a System Generator implementation (this time with only ZF equalizer) was made in order to make possible the migration to FPGAs. Both implementations were tested and validated, we also concluded that ZF based pre-coder had a lower Bit Error Rate for the same Signal to Noise Ratio (SNR).O tema central deste trabalho de dissertação centra-se no desenvolvimento e teste de novas técnicas para utilização em comunicações sem-fios de nova geração. Foca-se no uso de várias antenas, técnicas de pré-codificação e no uso de multiplexagem espacial em detrimento de diversidade, de forma a aumentar a largura de banda. Ao longo do documento são apresentadas várias técnicas de multiplexagem, bem como bases teóricas de propagação de sinais rádio e técnicas baseadas no uso de várias antenas no emissor e recetor (MIMO). Foi proposto um sistema de pré-codificação baseado em diversidade espacial. A implementação e teste do bloco pré-codificador SMMIMO foi realizada em primeiro lugar usando um simulador Matlab para efeito de comparação. Foram implementados dois equalizadores: Zero Forcing (ZF) e Minimum Mean Square Error (MMSE); posteriormente procedeu-se à implementação em System Generator de um pré-codificador com equalização ZF, de forma a ser possível a sua implementação em FPGAs. Esta implementação foi igualmente validada por comparação com o bloco implementado em Matlab