New methods for transmit space-time processing combining diversity and beamforming

Orientador: João Marcos Travassos RomanoTese (doutorado) - Universidade Estadual de Campinas. Faculdade de Engenharia Eletrica e de ComputaçãoResumo: O presente trabalho trata da utilização, em transmissão, de um arranjo de antenas na estação rádio-base de um sistema de comunicação celular. Na recepção, as soluções para explorar o arranjo são atualmente bem estabelecidas na literatura. Por outro lado, na transmissão, o problema se mantém aberto. Duas abordagens são possíveis: explorar o arranjo de antenas em beamforming ou em diversidade. Essas duas abordagens se opõem pelas hipóteses sobre a correlação dos canais, o que implica um maior ou menor espaçamento entre as antenas, de acordo com o ambiente de propagação. Na prática, essas hipóteses são muito difíceis de se respeitar. Nesta dissertação, pretendemos tratar esta questão na sua globalidade, conciliando diversidade e beamforming para melhor explorar o arranjo de antenas. Consideramos o contexto monousuário, assim como o caso multiusuário. No caso monousuário, propomos uma estrutura de transmissão composta por uma técnica de diversidade de transmissão clássica aplicada a antenas virtuais diretivas e idealmente independentes. Essas antenas virtuais são fabricadas por meio de filtros puramente espaciais aplicados às antenas reais. O conjunto desses filtros é chamado precoder e se intercala entre a diversidade de transmissão e o arranjo de antenas utilizado em transmissão. Esse precoder desempenha um duplo papel, o de realizar o beamforming e o de criar a diversidade por meio de antenas virtuais idealmente independentes, conciliando assim diversidade de transmissão e beamforming em transmissão. Duas abordagens são propostas para se obter o precoder , uma baseada na minimização da variância da potência recebida pelo móvel e a segunda baseada diretamente na minimização da taxa de erro. Comparadas às técnicas clássicas, as novas técnicas apresentam melhores desempenhos. Em seguida, propomos uma extensão dessa estrutura ao contexto multiusuário, para o qual técnicas de diversidade de transmissão ainda não foram propostas na literatura. Propomos a adaptação conjunta dos precoders, buscando minimizar a potência total de transmissão, respeitando as BERs alvo dos usuários. De maneira análoga ao caso monousuário, os precoders permitem conciliar beamforming e diversidade de transmissão. Comparada às técnicas clássicas de beamforming multiusuário, a nova abordagem introduz diversidade de transmissão ao enlace, apresentando melhores desempenhosAbstract: This work deals with the use of an antenna array at the base station of a mobile communication system for transmission. In reception, solutions that exploit the antenna array are now well established. In transmission, however, the problem remains open. Two approaches are possible: exploit the array by using beamforming techniques or by using diversity techniques. These two approaches are based on opposing assumptions about the channels correlation, which implies a greater or smaller distance between antennas, depending on the environment. In practice, these assumptions are not verified. Here, we aim to deal with the problem as a whole for better exploiting the antenna array. This work treats the single-user case, as well as the multiuser scenario. In the single-user case, we propose a transmission scheme composed of a classical transmit diversity technique applied to virtual antennas, which are directive and ideally independent. These virtual antennas are produced by means of purely spatial filters applied to the real antennas. This set of filters is called precoder, and acts as the interface between the transmit diversity technique and the transmit antenna array. The precoder function is twofold; to beamform the transmit signal, and to create diversity by means of ideally independent virtual antennas, thus combining transmit diversity and transmit beamforming. We propose two approaches to obtain this precoder, one based on the minimization of the variance of the received power at the mobile, and the other directly based on the minimization of the error rate. Compared to more classical approaches, the performance of the new methods reveals their advantage. Then, we extend this scheme to a multiuser context, for which transmit diversity techniques have not yet been developed. We propose to jointly adapt the precoders by minimizing the total transmit power while satisfying the users¿ target BER. Similarly to the single-user case, the precoders allow to combine beamforming and transmit diversity. Compared to classical multiuser beamforming techniques, the new approach adds diversity to the link and obtains in return better performancesDoutoradoTelecomunicações e TelemáticaDoutor em Engenharia Elétric

Effects of peeling methods on the quality of cubiu fruits

Cubiu (Solanum sessiliflorum Dunal) is an Amazonian Basin native fruit. Its importance comes from its high contents of pectin. Currently, processing technologies are necessary for the substitution of the traditional system (small crops and small-scale processing) for a larger scale system and thus increase the use of biodiversity and promote the implementation of Local Productive Arrangements of agribusiness in the Amazon. This research aims to evaluate the methods of peeling cubiu. Ripe fruits were divided into lots (150 each) and subjected to the following treatments: immersion in 2.5% NaOH boiling solution for 5 minutes, exposure to water vapor, and immersion in water at 96 ºC for 5, 10, 15 and 20 minutes. The peel released during heat treatment and immediately removed under running tap water. In the control treatment, the fruits were manually peeled (unheated) with a stainless steel knife. The treatments were evaluated for completeness and ease of peeling, tissue integrity, texture, and peroxidase activity. The immersion in 2.5% NaOH boiling solution (5 minutes) stood out as the best treatment since it inhibited the enzymatic browning and intensified the natural yellow color of the cubiu fruit and easily and fully peeled the whole fruit more rapidly without damaging its tissues. This treatment was chosen as the most advantageous because it can promote simultaneous peeling and bleaching. Therefore, it is recommended for cubiu industrial processing

Algoritmos de processamento espacial para enlaces de comunicação sem fio

Orientador : João Marcos Travassos RomanoDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de ComputaçãoMestrad

A Hybrid Single-Carrier/Multicarrier Transmission Scheme with Power Allocation

<p>Abstract</p> <p>We propose a flexible transmission scheme which easily allows to switch between cyclic-prefixed single-carrier (CP-SC) and cyclic-prefixed multicarrier (CP-MC) transmissions. This scheme takes advantage of the best characteristic of each scheme, namely, the low peak-to-average power ratio (PAPR) of the CP-SC scheme and the robustness to channel selectivity of the CP-MC scheme. Moreover, we derive the optimum power allocation for the CP-SC transmission considering a zero-forcing (ZF) and a minimum mean-square error (MMSE) receiver. By taking the PAPR into account, we are able to make a better analysis of the overall system and the results show the advantage of the CP-SC-MMSE scheme for flat and mild selective channels due to their low PAPR and that the CP-MC scheme is more advantageous for a narrow range of channels with severe selectivity.</p

Nouvelles méthodes de traitement d'antenne en émission alliant diversité et formation de voie

Ce document traite de l'utilisation en émission d'un réseau d'antennes à la station de base d'un système de communication radio-mobile. On recherche des méthodes qui allient diversité et formation de voie pour mieux exploiter le réseau d'antennes. Dans ce but, on propose un schéma de transmission composé d'un précodeur intercalé entre la diversité de transmission et le réseau d'antennes. A partir de ce schéma, on propose deux méthodes pour obtenir ce précodeur dans le cas mono-utilisateur, une basée sur la minimisation de la variance de la puissance reçue et la deuxième basée directement sur la minimisation du taux d'erreur. On traite aussi le cas multi-utilisateur, dans lequel on propose l'adaptation conjointe des précodeurs pour minimiser la puissance totale d'émission, tout en respectant les TEB cibles des utilisateurs. Comparées aux techniques classiques, les nouvelles méthodes permettent d'allier diversité et formation de voie et obtient en retour des meilleures performances.This work deals with the use of an antenna array at the base station of a mobile communication system for transmission We search for techniques to combine diversity and beanforming to better exploit the antenna array. In this context, we propose propose a transmit scheme composed of a precoder acting as an interface between the transmit diversity and the antenna array. We propose two approaches to obtain this precoder, one based on the minimization of the variance of the received power at the mobile, and the other directly based on the minimization of the error rate. We also consider the multi-user case, for which we propose the joint adaptation of the precoders to minimize the total transmit power, while satisfying the users' target BERs. Compared to classical techniques, the new approaches combine diversity and beamforming and obtain in return better performances.PARIS-CNAM (751032301) / SudocSudocFranceF

A Fast Algorithm for Joint Downlink Beamforming

Downlink Beamforming and Power Control are techniques used to improve the capacity or the quality of service in wireless systems. In this paper we propose a fast iterative algorithm for joint downlink beamforming and power control. The performance of this algorithm is compared with decoupled strategies through simulations. Results show that the fast algorithm outperforms the decoupled strategies and has a low computational complexity

Adding Diversity to Multi-User Downlink Beamforming by using BER Constraints

Abstract — In this work, we propose a novel structure and criterion for joint transmit diversity and multi-user downlink beamforming. The proposed structure can be seen as an extension of the purely spatial downlink beamforming and is a transformation that, for each user, transforms K real antennas into L virtual antennas, with L ≤ K. Classical transmit diversity is then applied to these virtual antennas. We propose a design criterion to optimize the precoders in order to find the best tradeoff between minimizing the interference generated towards the other users and maximizing the channel diversity for the desired user. This criterion is based on the minimization of the total transmit power subjected to a target BER constraint for each user. Applied to a multiple-antenna transmitter, the proposed technique outperforms the purely-spatial downlink beamformer by about 5 dB for a target BER of 10 −2 and by 9 dB for 10 −3 in a simple scenario

Adaptive LCMV Beamforming Avoiding DOA Estimation for Packet-Like Wireless Systems

A new adaptive LCMV solution that avoids DOA estimation for uplink beamforming is proposed. The use of the uplink channel covariance matrix (UCCM) instead of DOA estimation is shown to be a suitable alternative for constraints selection. The resulting LCMV adaptive solutions are then based on the LMS and RLS versions with the UCCM estimation. The new method is then evaluated for packed-like wireless systems through computational simulations