2 research outputs found
Algoritmos adaptativos para conformação de feixe e controle de potĂȘncia aplicados a sistemas de comunicaçÔes mĂłveis
Tese (doutorado) - Universidade Federal de Santa Catarina, Centro TecnolĂłgico, Programa de PĂłs-Graduação em Engenharia ElĂ©trica, FlorianĂłpolis, 2015.Neste trabalho de pesquisa sĂŁo desenvolvidos novos algoritmos adaptativos aplicados a sistemas de comunicaçÔes mĂłveis que efetuam simultaneamente a conformação de feixe e o controle de potĂȘncia de transmissĂŁo. Inicialmente, uma nova estratĂ©gia de controle de potĂȘncia Ă© formulada visando calcular, em cada iteração do processo de conformação de feixe, o correspondente nĂvel de potĂȘncia de transmissĂŁo. Tal estratĂ©gia Ă© utilizada no desenvolvimento de um novo algoritmo de conformação de feixe com controle de potĂȘncia aplicado a sistemas com sinal de referĂȘncia. Em seguida, dois novos algoritmos de conformação de feixe, chamados adaptive projection constrained stochastic gradient (AP-CSG) e quadratic AP-CSG (QAP-CSG), sĂŁo desenvolvidos a partir do mĂ©todo do gradiente estocĂĄstico usando uma restrição de projeção adaptativa. AlĂ©m disso, partindo da modelagem estocĂĄstica dos algoritmos AP CSG e QAP CSG, uma nova abordagem, chamada adaptive combination of vector projections (ACVP), Ă© proposta, originando um novo algoritmo, denominado sigmoid based ACVP (SB ACVP). Os algoritmos obtidos apresentam mais baixa complexidade computacional e proporcionam maiores valores de razĂŁo sinal-interferĂȘncia-mais-ruĂdo (SINR Ă signal to interference plus noise ratio) do que seus concorrentes atĂ© entĂŁo discutidos na literatura, permitindo, assim, valores menores de potĂȘncia de transmissĂŁo quando implementados em conjunto com algoritmos de controle de potĂȘncia. AnĂĄlises estocĂĄsticas sĂŁo tambĂ©m apresentadas com o objetivo de avaliar o comportamento mĂ©dio dos algoritmos propostos. Resultados de simulação numĂ©rica corroboram a eficĂĄcia dos novos algoritmos desenvolvidos e validam seus modelos estocĂĄsticos.Abstract : This research work presents new adaptive algorithms, which perform both beamforming and power control for mobile communication systems. Initially, a new power control strategy is formulated aiming to update the transmission power at each iteration of the beamforming process. Such a strategy is used to devise a new joint beamforming and power control algorithm based on reference signals. Next, two new beamforming algorithms, called adaptive projection constrained stochastic gradient (AP CSG) and quadratic AP CSG (QAP CSG), are developed from the stochastic gradient method by using an adaptive-projection constraint. Moreover, based on the stochastic modeling of the AP CSG and QAP CSG algorithms, a new approach, named adaptive combination of vector projections (ACVP), is proposed, giving rise to a new algorithm, termed sigmoid based ACVP (SB ACVP). The proposed algorithms exhibit lower computational burden and provide higher signal-to-interference-plus-noise ratio (SINR) values than the competing ones from the literature, thereby leading to lower transmission power levels when they are jointly implemented with power control algorithms. Stochastic analyses are also presented in order to evaluate the mean behavior of the proposed algorithms. Numerical simulation results are shown confirming the effectiveness of the developed algorithms and the accuracy of the proposed models
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Investigation, Design and Implementation of MIMO Antennas for Mobile Phones. Simulation and Measurement of MIMO Antennas for Mobile Handsets and Investigations of Channel Capacity of the Radiating Elements Using Spatial and Polarisation Diversity Strategies.
The objectives of this work were to investigate, design and implement Multiple-Input Multiple-Output (MIMO) antenna arrays for mobile phones. Several MIMO antennas were developed and tested over various wireless-communication frequency bands. The radiation performance and channel capacity of these antennas were computed and measured: the results are discussed in the context of the frequency bands of interest.
A comprehensive study of MIMO antenna configurations such as 2 Ă 1, 3 Ă 1, 2 Ă 2 and 3 Ă 3, using polarisation diversity as proposed for future mobile handsets, is presented. The channel capacity is investigated and discussed, as applying to Rayleigh fading channels with different power spectrum distributions with respect to azimuth and zenith angles. The channel capacity of 2 Ă 2 and 3 Ă 3 MIMO systems using spatial polarisation diversity is presented for different antenna designs. The presented results show that the maximum channel capacity for an antenna contained within a small volume can be reached with careful selection of the orthogonal spatial fields. The results are also compared against planar array MIMO antenna systems, in which the antenna size considered was much larger.
A 50% antenna size reduction method is explored by applying magnetic wall concept on the symmetry reference of the antenna structure. Using this method, a triple dual-band inverted-F antenna system is presented and considered for MIMO application. Means of achieving minimum coupling between the three antennas are investigated over the 2.45 GHz and 5.2 GHz bands.
A new 2 2 MIMO dual-band balanced antenna handset, intended to minimise the coupling with the handset and human body was proposed, developed and tested. The antenna coupling with the handset and human hand is reported in terms the radiation performance and the available channel capacity.
In addition, a dual-polarisation dipole antenna is proposed, intended for use as one of three collocated orthogonal antennas in a polarisation-diversity MIMO communication system. The antenna actually consists of two overlaid electric and magnetic dipoles, such that their radiation patterns are nominally identical but they are cross-polarised and hence only interact minimally