Constructive interference as an information carrier by dual-layered MIMO transmission

We propose a bandwidth-efficient transmission scheme for multiple-input-multiple-output point-to-point and downlink channels. The bandwidth efficiency (BE) of spatial multiplexing (SMX) is improved by implicitly encoding information in the spatial domain based on the existence of constructive interference in the received symbols, which creates a differentiation in the symbol power. Explicitly, the combination of symbols received at a higher power level carries implicit information in the spatial domain in the same manner as that the combination of nonzero elements in the received symbol vector carries information for receive-antenna-based spatial modulation (RSM). The nonzero power throughout the received symbol vector for the proposed technique allows a full SMX underlying transmission, with the BE enhancement brought by the spatial symbol. Our simulation results demonstrate both significant BE gains and error probability reduction for our approach over the conventional SMX and RSM schemes

On the energy efficiency of spatial modulation concepts

Spatial Modulation (SM) is a Multiple-Input Multiple-Output (MIMO) transmission technique which realizes low complexity implementations in wireless communication systems. Due the transmission principle of SM, only one Radio Frequency (RF) chain is required in the transmitter. Therefore, the complexity of the transmitter is lower compared to the complexity of traditional MIMO schemes, such as Spatial MultipleXing (SMX). In addition, because of the single RF chain configuration of SM, only one Power Amplifier (PA) is required in the transmitter. Hence, SM has the potential to exhibit significant Energy Efficiency (EE) benefits. At the receiver side, due to the SM transmission mechanism, detection is conducted using a low complexity (single stream) Maximum Likelihood (ML) detector. However, despite the use of a single stream detector, SM achieves a multiplexing gain. A point-to-point closed-loop variant of SM is receive space modulation. In receive space modulation, the concept of SMis extended at the receiver side, using linear precoding with Channel State Information at the Transmitter (CSIT). Even though receive space modulation does not preserve the single RF chain configuration of SM, due to the deployed linear precoding, it can be efficiently incorporated in a Space Division Multiple Access (SDMA) or in a Virtual Multiple-Input Multiple-Output (VMIMO) architecture. Inspired by the potentials of SM, the objectives of this thesis are the evaluation of the EE of SM and its extension in different forms of MIMO communication. In particular, a realistic power model for the power consumption of a Base Station (BS) is deployed in order to assess the EE of SM in terms of Mbps/J. By taking into account the whole power supply of a BS and considering a Time Division Multiple Access (TDMA) multiple access scheme, it is shown that SM is significantly more energy efficient compared to the traditional MIMO techniques. In the considered system setup, it is shown that SM is up to 67% more energy efficient compared to the benchmark systems. In addition, the concept of space modulation is researched at the receiver side. Specifically, based on the union bound technique, a framework for the evaluation of the Average Bit Error Probability (ABEP), diversity order, and coding gain of receive space modulation is developed. Because receive space modulation deploys linear precoding with CSIT, two new precoding methods which utilize imperfect CSIT are proposed. Furthermore, in this thesis, receive space modulation is incorporated in the broadcast channel. The derivation of the theoretical ABEP, diversity order, and coding gain of the new broadcast scheme is provided. It is concluded that receive space modulation is able to outperform the corresponding traditional MIMO scheme. Finally, SM, receive space modulation, and relaying are combined in order to form a novel virtual MIMO architecture. It is shown that the new architecture practically eliminates or reduces the problem of the inefficient relaying of the uncoordinated virtual MIMO space modulation architectures. This is undertaken by using precoding in a novel fashion. The evaluation of the new architecture is conducted using simulation and theoretical results

Sobre a capacidade-soma e a probabilidade de bloqueio em canais de múltiplos usuários equipados com múltiplas antenas

Orientadores: Gustavo Fraidenraich, Behnaam AazhangTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: O uso de múltiplas antenas em comunicações sem fio permitiu, inicialmente, garantir que um sinal transmitido fosse recebido com maior energia, o que diretamente aumenta a probabilidade de sucesso na recuperação dos dados transmitidos. Posteriormente, foi possível aumentar a capacidade de uma comunicação sem fio utilizando múltiplas antenas transmitindo e recebendo ao mesmo tempo. Atualmente, os dispositivos móveis como telefones celulares e computadores pessoais já são equipados com múltiplas antenas garantindo uma flexibilidade entre taxas maiores, quando as condições são favoráveis, ou aumento da confiabilidade de recepção, em condições menos favoráveis. Além dos graus de liberdade trazidos com a utilização de múltiplas antenas para uma comunicação ponto-a-ponto, os benefícios para uma rede onde um ou mais elementos façam uso destas é notável. Neste trabalho, apresentamos um estudo sobre o impacto do uso de múltiplas antenas em diversos tipos de redes compostas por múltiplos usuários fazendo uso do canal sem fio ao mesmo tempo. Como será visto, em algumas situações o objetivo será reduzir a probabilidade de que ocorra uma falha na comunicação, havendo ou não interferência. Em outras situações, faremos um estudo da capacidade soma de vários usuários ao transmitirem ao mesmo tempo. Em todos os casos, o conhecimento ou não do canal no transmissor é fator determinante para decidir como os sinais serão distribuídos nas múltiplas antenas do transmissor e se estes estarão sujeitos a uma probabilidade de bloqueio ou uma determinada capacidade. Em todos os casos, para uma dada configuração da rede (número de transmissores, receptores), iremos obter a métrica adequada em função da relação sinal ruído e apresentaremos uma modelagem teórica do problema comparando os resultados propostos com simulações de forma a validar estes resultadosAbstract: The first use of multiple antennas in wireless communications aimed to the improvement of the reliability of a transmission by improving the signal to noise ratio at receiver. More energy of the desired signal means that the receiver has higher probability to correctly decode the transmitted signal. Later, it was possible to increase the capacity of a wireless communication by the use of multiple antennas to transmit and receive at the same time. Nowadays, even the inexpensive mobile devices such as smartphones and personal computers are equipped with multiple antennas that provide flexibility between more data rate in favourable channel situations and more reliability in poor channel conditions. Besides the degrees of freedom that multiple antennas provide in single user communication, it dramatically increases the network data rate. In this work, we study the impact of multiple antennas in several multi-user scenarios with concurrent transmission. Whenever is possible, we provide closed-form expressions or approximations for outage probability or sum capacity depending on the type of network. The derived expressions allow us to quantify the impact of the number of users and number of antennas in the performance of the network. We quantify either outage or sum capacity in terms of signal-to-noise ratio for channels under fading conditionsDoutoradoTelecomunicações e TelemáticaDoutor em Engenharia Elétrica10714/14-6CAPESBE