<p>Cell Broadcast (CB) is a possible technical realisation of a global emergency alert system. It is a technique used for sending short text messages to all mobile stations (MSs) in a defined geographical area. An potential effect of using CB is the increase in battery consumption of the MS due to the fact that an extra channel has to be used to make the service available even when the network is otherwise congested. Another part of the service which leads to a potential problem is making CB messages available in different languages. Investigating these problems is the objective of this thesis and the studies it includes. During the first part of the thesis, we measured the battery consumption of MSs in different modes of operation in order to analyse how CB affects the amount of current drained. The tests showed that battery consumption increased only slightly when CB messages were being received at the MS. Although some of the results can be, and are, discussed, we believe that CB would have a small effect on the power consumption of an MS, particularly in a context where it would be used for emergency warning messages only. This mentioned, it would however be wishful to confirm the conclusions further through the realisation of long-term testing. The second part of the thesis deals with the investigation of the MSs’ support for CB messages with different coding schemes. Based on the investigation’s result, we have come to the conclusion that in the long term the usage of different coding schemes on the same channel is preferred. However, the usage of one, global, emergency channel is hard to realise since that requires a standardisation between all countries. In our opinion this may be achieved first in the long run and until then, the usage of separate channels seems to be necessary.</p>

Graduation date: 1999

Cell Broadcast (CB) is a possible technical realisation of a global emergency alert system. It is a technique used for sending short text messages to all mobile stations (MSs) in a defined geographical area. An potential effect of using CB is the increase in battery consumption of the MS due to the fact that an extra channel has to be used to make the service available even when the network is otherwise congested. Another part of the service which leads to a potential problem is making CB messages available in different languages. Investigating these problems is the objective of this thesis and the studies it includes. During the first part of the thesis, we measured the battery consumption of MSs in different modes of operation in order to analyse how CB affects the amount of current drained. The tests showed that battery consumption increased only slightly when CB messages were being received at the MS. Although some of the results can be, and are, discussed, we believe that CB would have a small effect on the power consumption of an MS, particularly in a context where it would be used for emergency warning messages only. This mentioned, it would however be wishful to confirm the conclusions further through the realisation of long-term testing. The second part of the thesis deals with the investigation of the MSs’ support for CB messages with different coding schemes. Based on the investigation’s result, we have come to the conclusion that in the long term the usage of different coding schemes on the same channel is preferred. However, the usage of one, global, emergency channel is hard to realise since that requires a standardisation between all countries. In our opinion this may be achieved first in the long run and until then, the usage of separate channels seems to be necessary.

abstract: Spectral congestion is quickly becoming a problem for the telecommunications sector. In order to alleviate spectral congestion and achieve electromagnetic radio frequency (RF) convergence, communications and radar systems are increasingly encouraged to share bandwidth. In direct opposition to the traditional spectrum sharing approach between radar and communications systems of complete isolation (temporal, spectral or spatial), both systems can be jointly co-designed from the ground up to maximize their joint performance for mutual benefit. In order to properly characterize and understand cooperative spectrum sharing between radar and communications systems, the fundamental limits on performance of a cooperative radar-communications system are investigated. To facilitate this investigation, performance metrics are chosen in this dissertation that allow radar and communications to be compared on the same scale. To that effect, information is chosen as the performance metric and an information theoretic radar performance metric compatible with the communications data rate, the radar estimation rate, is developed. The estimation rate measures the amount of information learned by illuminating a target. With the development of the estimation rate, standard multi-user communications performance bounds are extended with joint radar-communications users to produce bounds on the performance of a joint radar-communications system. System performance for variations of the standard spectrum sharing problem defined in this dissertation are investigated, and inner bounds on performance are extended to account for the effect of continuous radar waveform optimization, multiple radar targets, clutter, phase noise, and radar detection. A detailed interpretation of the estimation rate and a brief discussion on how to use these performance bounds to select an optimal operating point and achieve RF convergence are provided. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2018

Orientadores: Jose Marcos Travassos Romano, Cristiano Magalhães Panazio / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-09T08:52:54Z (GMT). No. of bitstreams: 1 Menezes_AlamSilva_M.pdf: 3586178 bytes, checksum: 0b475a352c1a0c8fc6c72a6a3c846f45 (MD5) Previous issue date: 2007 / Resumo: A presente dissertação apresenta um estudo da tecnologia dos rádios cognitivos bem como uma avaliação dos possíveis ganhos desta promissora técnica em relação aos atuais meios de acesso ao espectro eletromagnético. Numa segunda frente de trabalho, tratamos do problema de equalização cega no contexto de canais SIMO, com uma única entrada e múltiplas saídas. Propomos a predição linear multicanal como estrutura de equalização em sistemas OFDM e avaliamos por meio de simulações a viabilidade da técnica proposta / Abstract: In this work, we provide a study of the cognitive radio technology and the potential gains that this technique may provide with regard to current electromagnetic spectrum access techniques. In a second workphase, we deal with the problem of blind equalization in the context of single input multiple output channels (SIMO). We propose the use of a multichannel linear prediction structure to equalize OFDM systems and we assess its performance through numerical simulations / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica

The HF band of radio frequencies, from 3-30 MHz, is unique in its property that it is refracted by the ionosphere. This property allows long distance radio telecommunications around the world without requiring infrastructure. High frequency (HF) communication has been largely superseded by satellite and cellular technologies for day-to-day communications, due to the tight bandwidth constraints and technical difficulties inherent in using it. However there is still a need for HF communications devices where existing infrastructure is not available, such as in remote or polar locations, or in emergency situations due to natural disasters. This research is aimed at the development of an asymmetric HF communications link, with a battery-powered remote unit that transmits a small amount of data to a mains-powered base station. New technologies are identified and evaluated for use in the link, with the aim of reducing the power requirements of the remote unit. Error correction techniques are investigated. Low-density parity check (LDPC) codes, which are powerful codes used for forward error correction, are suggested for use in the link. Quasi-cyclic LDPC codes allow the low-power transmitter unit to use a computationally simple encoder based on feedback shift registers for generating the LDPC block codes cheaply. Semi-blind LDPC turbo equalisation is a powerful technique that can be used at the base station which utilises the structure of the LDPC code to encode the data stream. This equalises a received signal with a minimal amount of training data required, reducing the duty cycle of the remote unit. Hybrid automatic repeat request (HARQ) techniques are also investigated, which increase the throughput of a link when data repeats are required. A novel HARQ techniquewas created and proven to increase throughput in links with noise. As the proposed system may be deployed in remote locations, or locations where it might be difficult or undesirable to erect a proper HF antenna, a selection of buried antennas are characterised. A design for a remote unit is suggested. This unit was manufactured and used to test the capability of inexpensive, low power hardware to implement the proposed remote unit algorithms.

<p dir="ltr">This thesis discusses the use of a fiber optic system to synchronize GHz frequency radio-frequency signals over distances of up to 5 km and its future applications in quantum communications. The stability of the synchronization is assessed by an ‘identity gate’, where each radio-frequency signal drives a phase modulator, and the frequency profile of a continuous wave laser sent through both modulators indicates the stability of the RF signals relative to one another. Experimental results indicate that 19 GHz signals synchronized over 5.5 km drifted less than 1 ps over 30 minutes. This is superior to the radio-frequency synthesizers’ built in synchronization method and to other commonly used protocols. To illustrate an application, the system was employed in a quantum nonlocal modulation cancellation experiment. Joint spectral characterization of the biphotons shows that this synchronization scheme can be used for nodes in a quantum communications network. More specifically, possible future applications of this technology include use in a photonic quantum local area network at Oak Ridge National Laboratories.</p>

A melhora na eficiência do uso do espectro de radiofrequência é fundamental para permitir um desempenho adequado dos diversos sistemas sem fio cuja complexidade e requerimentos aumentam a cada dia. O panorama atual de atribuição de canais é estático, tolerando assim, que o espectro de radiofrequência seja usado de forma desequilibrada, gerando com isso, problemas de coexistência em algumas faixas e subutilização de recursos em outras. Para contornar esse problema, tem sido proposta a ideia de introduzir algoritmos de cognição nos dispositivos sem fio, a fim de permitir um modelo de alocação dinâmico adicional. Neste, os usuários secundários equipados com rádios cognitivos podem utilizar de forma dinâmica os canais subutilizados de usuários primários. Um usuário primário tem prioridade de uso do canal como consequência da atribuição estática, porém, o uso do canal por um usuário secundário qualquer é oportunista e limitando ao tempo de inatividade do usuário primário em um determinado local. As redes de sensores sem fio trabalham em uma banda concorrida e são sistemas que podem melhorar seu desempenho utilizando um mecanismo de acesso dinâmico aos canais, possibilitando o aproveitamento dos períodos de inatividade de usuários primários ou aumentando sua capacidade de coexistência na banda de operação atual. Segundo a literatura pesquisada são vários os desafios existentes para conseguir um método distribuído de acesso dinâmico aos canais que considere as restrições de trocas de sinalizações, consumo de energia e complexidade dos dispositivos de uma rede de sensores sem fio. Neste contexto, propõe-se uma metodologia de sensoriamento e acesso dinâmico aos canais para uma rede de sensores sem fio considerando a simplicidade dos dispositivos. Como fatores de inovação, optou-se pela definição de uma política de sensoriamento por clusters que permite realizar uma aprendizagem cooperativa por reforço da situação dos canais de operação. Além disso, a definição de um mecanismo de acesso dinâmico aos canais fundamentado no padrão IEEE 802.15.4 permite comunicação e coordenação distribuída de forma assíncrona. O funcionamento da metodologia proposta é avaliado e comparado usando simulações e experimentos mediante um estudo de caso específico. As comparações são realizadas com métodos de seleção de canal: fixa, cega ou baseada em recompensas por acesso. Os resultados mostram a eficiência no acesso dinâmico aos canais com aumentos na taxa de entrega de mensagens e na capacidade de coexistir com as redes primárias. / The efficiency improvement of the use of radiofrequency spectrum is fundamental to allow more complex and more optimal wireless systems. The current channel allocation is static. It tolerates unbalanced use of the radiofrequency spectrum generating coexistence problems in some bands and underutilization of resources in other bands. The introduction of cognitive algorithms into wireless devices has been proposed to overcome that problem, in order to allow an additional dynamic allocation model. In this, the secondary users equipped with cognitive radios will be able to use dynamically the underutilized channels of primary users. A primary user has channel usage priority related to the static allocation, on the other hand, the use of the channel by any secondary user is opportunistic and limited to the inactivity time of the primary user in a specific place. Wireless sensor networks work in a competitive band. These systems can improve their performance using a dynamic access to the channels and consequently to enable the utilization of inactivity periods of primary users or to increase the coexistence capability at their current operation band. According to the researched literature, several challenges exist to find a distributed method for dynamic access to the channels considering the restrictions on control signaling, energy consumption and computational complexity of wireless sensor network devices. In this context, a methodology of sensing and dynamic access to the channels in a wireless sensor network considering the restrictions of the devices is proposed. As innovation, we opted for the definition of a sensing policy by clusters that allows the cooperative reinforcement learning of the situation of channels. In addition, a mechanism for dynamic access to the channels based on the IEEE 802.15.4 standard is defined to allow asynchronous and distributed coordination. The behavior of the proposed methodology is evaluated and compared using simulations and experiments through a specific case study. The comparisons are performed with channel selection methods: fixed, blind and access based. The results show good efficiency in the dynamic allocation of the channels, increasing the message delivery rate and the coexistence capability.

The world of information technology and communications is in a stage of continuous improvement. These new developments are accompanied by a very rapid data traffic growth, particularly for mobile wireless networks. An important effect is the increase of the consumed energy by the network, particularly the radio access section, i.e. the base station systems. This latter issue causes that operational costs associated to energy consumption become more significant for telecommunication operators. In addition to the question of the availability of energy, this problem has an ecological aspect, due to the CO2 emissions associated with the operation of the network but also an issue related to public health given the effects of electromagnetic radiation from wireless transmission. For these reasons, great research efforts in the so-called field of Green Radio are being done in the recent years. The aim of this thesis consisted of finding ways to reduce the energy consumption in wireless and mobile networks respecting the QoS levels assigned to users. After a study of the state of the art analysing the possible approaches, we proposed a set of energy efficient techniques supported on the cell breathing and hybrid cellular networks (macro/femtocells). Our proposed decision making mechanisms include distributed strategies and other features such as the use of a novel multimetric approach. In our work, we also take into account the energy consumption of mobile devices, an issue that to the best of our knowledge was not quite analysed so far. The use of renewable energy sources is also considered into our proposals. Our thesis work includes the study of the consequences of our radio resource management algorithms on the electromagnetic radiation taking into account the acceptable EM exposure thresholds. In the perspectives of future work, we can mention the improvement of our techniques with learning mechanisms and cognitive radio.

Αυτή η εργασία περιγράφει το όραμα των I-centric επικοινωνιών (ατομοκεντρικών) - ένα νέο παράδειγμα για μελλοντικά συστήματα τηλεπικοινωνιών. Ο κύριος στόχος αυτής της προσέγγισης είναι να εξετάσει την ανθρώπινη επικοινωνιακή συμπεριφορά. Η εργασία αυτή εστιάζει στην εννοιολογική ολοκλήρωση όλων των πτυχών των ατομοκεντρικών επικοινωνιών. Εξετάζοντας την επικοινωνιακή συμπεριφορά του ανθρώπου, είναι προφανές, ότι οι άνθρωποι συχνά αλληλεπιδρούν με ένα σύνολο αντικειμένων στο περιβάλλον τους. Σύμφωνα με αυτήν την άποψη, μια προσέγγιση είναι να μη δημιουργηθούν συστήματα επικοινωνίας που βασίζονται σε εξειδικευμένες τεχνολογίες αλλά να βασίζονται στην ανάλυση του μεμονωμένου χώρου επικοινωνίας. Το αποτέλεσμα θα είναι ένα σύστημα επικοινωνιών που προσαρμόζεται στις απαιτήσεις κάθε ατόμου (ατομοκεντρικό). Το σύστημα επικοινωνιών θα ενεργεί σύμφωνα με τις απαιτήσεις του ανθρώπου, που απεικονίζουν τις πρόσφατες ενέργειές του ώστε να προσαρμόζεται αυτόματα σε αυτές. Οι ατομοκεντρικές υπηρεσίες προσαρμόζονται στους μεμονωμένους χώρους επικοινωνίας και τις καταστάσεις. Σε αυτό το πλαίσιο το «I», σημαίνει το εγώ ή το άτομο, και Centric σημαίνει προσαρμογή στις απαιτήσεις του «εγώ» και το περιβάλλον του ατόμου. Οι παραπάνω λογικές απαιτούν νοημοσύνη στην παροχή υπηρεσιών προκειμένου να προσωποποιηθούν, να προσαρμοστούν στις περιστασιακές και περιβαλλοντικές συνθήκες και να ελέγχουν το μεμονωμένο χώρο επικοινωνίας. Ένα ατομοκεντρικό σύστημα επικοινωνιών παρέχει τη νοημοσύνη που απαιτείται για τη διαμόρφωση του χώρου επικοινωνίας του κάθε ατόμου που προσαρμόζεται στα ενδιαφέροντα, το περιβάλλον, και τις προτιμήσεις του. Η εργασία εισάγει το όραμα των ατομοκεντρικών επικοινωνιών, που ακολουθείται από την ανάπτυξη ενός προτύπου αναφοράς για τις ατομοκεντρικές επικοινωνίες. Από τη στιγμή που το όραμα και το πρότυπο αναφοράς είναι γενικές έννοιες, εισάγεται στη συνέχεια ένα αρχιτεκτονικό πλαίσιο για τις ατομοκεντρικές επικοινωνίες. Αυτό το πλαίσιο χρησιμοποιείται για να σχεδιαστεί και να υλοποιηθεί ένα ατομοκεντρικό σύστημα επικοινωνιών. / This thesis describes the vision of I-centric communications – a new paradigm for future telecommunication systems. The main objective of this approach is to consider the human communication behaviour. The focus of this thesis is on the conceptual integration of all aspects of I-centric communications. Looking at the communication behaviour of human, it is obvious, that human beings frequently interact with a set of objects in their environment. Following this view, a new approach is not to build communication systems based on specific technologies, but on the analysis of the individual communication space. The result is a communication system that adapts to the demands of each individual (I-centric). The communication system will act on behalf of human’s demands, reflecting recent actions to enable self-adaptation. I-centric Services adapt to individual communication spaces and situations. In this context ‘I’ means I, or individual, ‘Centric’ means adaptable to I requirements and the individual’s environment. The rationales above require intelligence in service provisioning in order to personalize, adapt to situational and environmental conditions, to monitor and to control the individual communication space. I-centric communications system will provide the intelligence required for modelling the communication space of each individual adapting to its interests, environment, and preferences. The thesis introduces the vision of I-centric communications, followed by the development of a reference model for I-centric communications. Since both, the vision and the reference model, are general, an architectural framework for I-centric communications is introduced later on. This framework is used to design and implement an I-centric communications system.