Validação Computacional tendo em vista a Interoperabilidade entre os Veículos Aéreos Não Tripulados

Nos dias de hoje, com o contínuo desenvolvimento e inovação no campo dos UAVs (Unmanned Aerial Vehciles), o mundo já tem como adquiridos os benefícios que estes sistemas podem fornecer. Os benefícios obtidos com a aplicação destes sistemas abrange tanto as forças armadas como industrias e organizações civis. Todas as nações e indústrias querem ter uma cota parte no futuro desta tecnologia. Diferentes UAVs foram desenvolvidos, mas estes, diferem em termos de arquitetura e protocolos de comunicação. Protocolos como o STANAG 4586, MAVLink, JAUS e ROS são só alguns exemplos. A proliferação de informação através destes sistemas e as suas consolas de comando e controlo é uma das principais preocupações, principalmente pelas forças armadas. Uma das principais prioridades é combinar forças de diferentes nações, principalmente pelos membros NATO. A necessidade de uma consola para cada tipo de sistema devido à falta de padronização apresenta assim um problema. É conhecida a necessidade de uma padronização em termos de arquitetura por camadas e de comunicação tendo em vista a interoperabilidade entre estes sistemas. Não existe nenhuma que esteja a ser implementada como documento padrão. Pretende-se que o STANAG 4586 seja o documento padrão para os membros NATO e, por conseguinte, todos os esforços estão direcionados em desenvolver sistemas que o consigam implementar. Os diferentes UAVs já existentes possuem o seu próprio protocolo de comunicação e a alteração de toda a sua estrutura não é fácil. A ideia de fazer uma conversão de linguagens como alternativa surge como uma solução teórica ótima. Utilizando um piloto automático que comunica com a sua consola através da linguagem MAVLink esta dissertação tem como objetivo desenvolver um programa computacional que converta as mensagens MAVLink em STANAG 4586 e estudar se o tempo de conversão é operacionalmente válido tendo em conta os requisitos operacionais dos sistemas.Nowadays, in the continuous technological development and innovation regarding UAVs (Unmanned Aerial Vehciles), the world has acknowledged the benefits that these systems bring to our environment. The profits received with the application of these robots cover almost all the fields regarding the armed forces, environmental and agriculture industries and civil protection organizations. Every nation and industry wants to take part in this future main technology. Different UAVs have been designed and developed that differ in terms of architecture and communication protocols. Frameworks like STANAG 4586, MAVLink , JAUS and ROS are some examples. The proliferation of information through these systems and their command and control consoles is one of the main concerns, mainly by armed forces. Combining forces from different nations, mainly by NATO members, in exercises and real time crisis fights are one of the primary priorities due to the benefits that they can combine. It’s known the necessity of a standard in terms of layered architecture and communication towards the interoperability between these systems. Many standards have been created trying to fulfil this gap but there isn’t one that is currently implemented as the main standard document. The STANAG 4586 is intended to be implemented as the main standard for NATO members and, therefore, all the efforts go towards to develop systems that implement these architecture and communication protocol. The different UAVs already created have their one communication protocol and the redesign of the entire architecture of the systems by one company isn’t easy and could not be convenient or affordable. The idea of doing a conversion of languages instead of redesign all the system architecture emerges as the optimal theoretical solution. Using a PIXHAWK autopilot that communicates to the Ground Control Station (GCS) through MAVLink it’s possible to develop computational software that converts MAVLink messages to the format of STANAG 4586. Starting from there, the objective is to check if it is viable for the protocol requirements and study the delay that the conversion introduces to the system in comparison with the channel without the conversion. The delay must not be inviable for the communication requirements between the GCS and the UAV

Minimum Codebook Size to achieve Maximal Diversity Order for RVQ based MIMO Systems

Multiple antenna systems provide both capacity and diversity gains relatively to single antenna based networks. These gains rely heavily on the availability of channel state information. In this manuscript we assume that the receiver has accurate channel information, which is quantized and fed back to the transmitter. Sufficient conditions for the feedback rate are provided that guarantee no loss of diversity due to channel quantization. Considering a K × M MIMO system, we show that to achieve a diversity of D = M – K + 1 which is the maximum allowable, a feedback channel with rate of log2(1 + D) bits per channel use is enough

Set optimization for efficient interference alignment in heterogeneous networks

To increase capacity and offload traffic from the current macro-cell cellular system operators are considering the deployment of small-cells. It is expected that both the small and macro-cells will coexist in the same spectrum resulting in unsustainable levels of interference. Interference alignment is considered as an effective method to deal with such interfer- ence. By using interference alignment the small-cells align their transmission along a common direction to allow the macro-cell receiver to completely remove it. It is clear that if the two systems have no limitations on the information that may be exchanged between them to perform the signal design, then the performance may be improved in comparison to the case of no or partial cooperation. However, this full cooperation strategy requires a high-rate connection between the macro and small-cells, which may not be available. To overcome this problem we consider that the alignment direction is selected from a finite set, known to both macro and small-cell terminals. We provide sufficient conditions for this set that guarantee full-diversity, at the macro- cell, and propose an efficient method to optimize the set elements. Results show that an alignment set with a description length of 1 bit is enough to achieve the same diversity as in the case where an infinite amount of information is exchanged between both systems. The proposed set optimization method achieves better performance than random vector quantization and similar performance to Grassmannian quantization

Relatório de Estágio na Spot of Brands

O presente relatório descreve as atividades desenvolvidas ao longo do estágio, no âmbito da unidade curricular “Estágio e Relatório” do segundo ano do Mestrado em Marketing e Negócios Internacionais, do Instituto Superior de Contabilidade e Administração de Coimbra. O estágio curricular teve lugar na empresa Spot Of Brands, uma agência de comunicação e marketing sediada na Mealhada, e foi realizado de Novembro a Abril de 2023, com a duração de 960 horas. Os principais objetivos deste estágio curricular foram consolidar os conhecimentos que adquiri na parte letiva do mestrado, vivenciar a realidade da profissão e ganhar experiência no mercado de trabalho, para ter uma melhor preparação para a introdução e inserção no mesmo. No decorrer do meu estágio, desempenhei tarefas na área do marketing digital, como o social media marketing e o marketing de conteúdo e tarefas na área do design, nomeadamente design gráfico e web design. Em termos estruturais, o relatório está dividido em quatro partes, sendo o primeiro capítulo constituído pela revisão da literatura, no segundo capítulo é feita a apresentação da empresa, no terceiro capítulo são apresentadas as atividades desenvolvidas durante o estágio e no último é feita a conclusão

Intrinsic secrecy of EGT and MRT precoders for proper and improper modulations

This paper makes an information theoretical analysis of the intrinsic secrecy level of M-QAM and M-PSK modulation schemes considering the use of equal gain transmission and maximum ratio transmission precoding techniques. In addition to the analysis of the conventional proper M-QAM and M-PSK constellations, a recently proposed family of improper versions of the M-QAM and M-PSK modulation schemes is also evaluated. With the exception of proper M-PSK, which verifies always full secrecy for the considered precoders, the main results show that for low order constellations, the amount of intrinsic secrecy provided by the combination of the precoder and modulation scheme is significant and, therefore, can be exploited in the design of a full secrecy solution. The theoretical derivations provided in this paper can be directly applied to quantify the minimal entropy that a secret key must have to fully secure the exchange of information for these transmission schemes.publishe

A cooperative jamming technique to protect a two-user broadcast channel with confidential messages and an external eavesdropper

This work addresses the security of a two-user broadcast channel. The challenge of protecting a broadcast channel is associated with the necessity of securing the system, not only against eavesdropping attacks originating from external nodes, but also to ensure that the inside users do not eavesdrop on each other’s information. To address this issue, the present work proposes a cooperative jamming scheme that provides protection against eavesdropping attacks carried out simultaneously by inside users and external eavesdroppers. To achieve this goal, the developed scheme combines real interference alignment with a blind cooperative jamming technique defined in the literature. An information theoretical analysis shows that positive secure degrees of freedom are achievable using the proposed solution.publishe

Quasi-orthogonal SFBC for monostatic MIMO ISAC scenarios

This paper studies the performance of the quasi-orthogonal Tirkkonen spatial-frequency block code (SFBC) for integrated sensing and communication (ISAC) scenarios. The considered scenario is a MIMO monostatic ISAC base station (BS), where transmitter and radar antenna arrays are co-located enabling the virtual array concept. The quasi-orthogonal Tirkkonen SFBC is encapsulated in an OFDM waveform, the radar processing is performed over the resulting OFDM frame. The performance in terms of radar and communication metrics of Tirkkonen SFBC is presented and compared with orthogonal Alamouti SFBC and the spectrally interleaved waveform approach, widely used in radar-like scenarios. The resulting Mean Square Error (MSE) of the Angle of Arrival (AoA) is chosen as the radar metric while the bit-error-rate (BER) is used to present the communication performance. The results show that Tirkkonen is a good candidate for future ISAC scenarios.publishe

Two-stage estimation algorithm based on interleaved OFDM for a cooperative bistatic ISAC scenario

This paper considers a cooperative bistatic scenario for integrated sensing and communication (ISAC) paradigm, where transmitter and receiver base stations (BS) are connected through the front-haul to a central unit (CU), enabling cooperation. A multiple-input multiple-output (MIMO) configuration is considered in combination with orthogonal frequency division multiplexing (OFDM). The communication and radio-sensing functions are performed in orthogonal sets of sub-carriers, where the sub-carriers allocated to radio-sensing are distributed among antennas in an interleaved way. The interleaved frame structure is exploited in the design of a new parameter estimation method. The proposed method is a two-stage algorithm to estimate the delay/Doppler shift and angular position of objects (paths) in the channel. First, the multiple signal classification (MUSIC) algorithm estimates the angle-of-arrival (AoA) of the paths. Then, the delay, Doppler shift and angle-of-departure (AoD) are jointly estimated for each AoA combining an extended search over the AoD domain and a two-dimensional periodogram. The simulations show that the delay, Doppler shift and AoA are estimated correctly, while the estimation of the AoD may report error, although it can be compensated.publishe

Geografia e fotografia: contribuições para a análise das territorialidades cíclicas

Trabalho de Conclusão de Curso (Graduação)Este trabalho tem como objetivo principal demonstrar a importância da fotografia na pesquisa geográfica, em especial quanto ao estudo dos territórios. No presente trabalho foi realizada pesquisa bibliográfica de autores geógrafos e fotógrafos, assim como, pesquisa de campo realizado por meio de registros fotográficos. Como resultado tem-se a importância da história da fotografia e a evolução das técnicas fotográficas e como a popularização da fotografia influenciou o estudo geográfico; a conceitualização de territorialidades do ponto de vista da Geografia e seus elementos característicos; a constatação da relação entre fotografia e Geografia; a constatação por meio da análise de registros fotográficos dos pontos de observação predeterminados da territorialidade cíclica e das multiterritorialidades. Por meio dos resultados alcançados neste trabalho foi possível concluir que a fotografia é um instrumento de grande importância para o estudo geográfico, visto que por meio de seus registros possibilita a análise e leitura dos territórios