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Contemporary electromagnetic spectrum reuse techniques: tv white spaces and D2D communications / TÃcnicas contemporÃneas de reuso do espectro electromagnÃtico: tv de espaÃos branco e comunicaÃÃes D2DCarlos Filipe Moreira e Silva 15 December 2015 (has links)
CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Over the last years, the wireless broadband access has achieved a tremendous success.
With that, the telecommunications industry has faced very important changes in terms
of technology, heterogeneity, kind of applications, and massive usage (virtual data tsunami)
derived from the introduction of smartphones and tablets; or even in terms of market structure
and its main players/actors. Nonetheless, it is well-known that the electromagnetic spectrum is
a scarce resource, being already fully occupied (or at least reserved for certain applications). Tra-
ditional spectrum markets (where big monopolies dominate) and static spectrum management
originated a paradoxal situation: the spectrum is occupied without actually being used!
In one hand, with the global transition from analog to digital Television (TV), part of the
spectrum previously licensed for TV is freed and geographically interleaved, originating the
consequent Television White Spaces (TVWS); on the other hand, the direct communications
between devices, commonly referred as Device-to-Device (D2D) communications, are attracting
crescent attention by the scientific community and industry in order to overcome the scarcity
problem and satisfy the increasing demand for extra capacity. As such, this thesis is divided in
two main parts: (a) Spectrum market for TVWS: where a SWOT analysis for the use of TVWS
is performed giving some highlights in the directions/actions that shall be followed so that its
adoption becomes effective; and a tecno-economic evaluation study is done considering as a
use-case a typical European city, showing the potential money savings that operators may reach
if they adopt by the use of TVWS in a flexible market manner; (b) D2D communications: where
a neighbor discovery technique for D2D communications is proposed in the single-cell scenario
and further extended for the multi-cell case; and an interference mitigation algorithm based
on the intelligent selection of Downlink (DL) or Uplink (UL) band for D2D communications
underlaying cellular networks.
A summary of the principal conclusions is as follows: (a) The TVWS defenders shall
focus on the promotion of a real-time secondary spectrum market, where through the correct
implementation of policies for protection ratios in the spectrum broker and geo-location
database, incumbents are protected against interference; (b) It became evident that an operator
would recover its investment around one year earlier if it chooses to deploy the network
following a flexible spectrum market approach with an additional TVWS carrier, instead of
the traditional market; (c) With the proposed neighbor discovery technique the time to detect
all neighbors per Mobile Station (MS) is significantly reduced, letting more time for the actual
data transmission; and the power of MS consumed during the discovery process is also reduced
because the main processing is done at the Base Station (BS), while the MS needs to ensure that
D2D communication is possible just before the session establishment; (d) Despite being a simple
concept, band selection improves the gains of cellular communications and limits the gains
of D2D communications, regardless the position within the cell where D2D communications
happen, providing a trade-off between system performance and interference mitigation. / Nos Ãltimos anos, o acesso de banda larga atingiu um grande sucesso. Com isso, a indÃstria
das telecomunicaÃÃes passou por importantes transformaÃÃes em termos de tecnologia,
heterogeneidade, tipo de aplicaÃÃes e uso massivo (tsunami virtual de dados) em consequÃncia
da introduÃÃo dos smartphones e tablets; ou atà mesmo na estrutura de mercado e os seus
principais jogadores/atores. PorÃm, à sabido que o espectro electromagnÃtico à um recurso
limitado, estando jà ocupado (ou pelo menos reservado para alguma aplicaÃÃo). O mercado
tradicional de espectro (onde os grandes monopÃlios dominam) e o seu gerenciamento estÃtico
contribuÃram para essa situaÃÃo paradoxal: o espectro està ocupado mas nÃo està sendo usado!
Por um lado, com a transiÃÃo mundial da TelevisÃo (TV) analÃgica para a digital, parte do
espectro anteriormente licenciado para a TV Ã libertado e geograficamente multiplexado para
evitar a interferÃncia entre sinais de torres vizinhas, dando origem a ÂespaÃos em branco na
frequÃncia da TV ou Television White Spaces (TVWS); por outro lado, as comunicaÃÃes diretas
entre usuÃrios, designadas por comunicaÃÃes diretas Dispositivo-a-Dispositivo (D2D), estÃ
gerando um crescente interesse da comunidade cientÃfica e indÃstria, com vista a ultrapassar
o problema da escassez de espectro e satisfazer a crescente demanda por capacidade extra.
Assim, a tese està dividida em duas partes principais: (a) Mercado de espectro eletromagnÃtico
para TVWS: onde à feita uma anÃlise SWOT para o uso dos TVWS, dando direÃÃes/aÃÃes a
serem seguidas para que o seu uso se torne efetivo; e um estudo tecno-econÃmico considerando
como cenÃrio uma tÃpica cidade Europeia, onde se mostram as possÃveis poupanÃas monetÃrias
que os operadores conseguem obter ao optarem pelo uso dos TVWS num mercado flexÃvel;
(b) ComunicaÃÃes D2D: onde uma tÃcnica de descoberta de vizinhos para comunicaÃÃes D2D Ã
proposta, primeiro para uma Ãnica cÃlula e mais tarde estendida para o cenÃrio multi-celular; e
um algoritmo de mitigaÃÃo de interferÃncia baseado na seleÃÃo inteligente da banda Ascendente
(DL) ou Descendente (UL) a ser reusada pelas comunicaÃÃes D2D que acontecem na rede celular.
Um sumÃrio das principais conclusÃes à o seguinte: (a) Os defensores dos TVWS devem-se
focar na promoÃÃo do mercado secundÃrio de espectro electromagnÃtico, onde atravÃs da
correta implementaÃÃo de politicas de proteÃÃo contra a interferÃncia no broker de espectro e
na base de dados, os usuÃrios primÃrio sÃo protegidos contra a interferÃncia; (b) Um operador
consegue recuperar o seu investimento aproximadamente um ano antes se ele optar pelo
desenvolvimento da rede seguindo um mercado secundÃrio de espectro com a banda adicional
de TVWS, em vez do mercado tradicional; (c) Com a tÃcnica proposta de descoberta de vizinhos,
o tempo de descoberta por usuÃrio à significativamente reduzido; e a potÃncia consumida
nesse processo à tambÃm ela reduzida porque o maior processamento à feito na EstaÃÃo RÃdio
Base (BS), enquanto que o usuÃrio sà precisa de se certificar que a comunicaÃÃo direta Ã
possÃvel; (d) A seleÃÃo de banda, embora seja um conceito simples, melhora os ganhos das
comunicaÃÃes celulares e limita os das comunicaÃÃes D2D, providenciando um compromisso
entre a performance do sistema e a mitigaÃÃo de interferÃncia.
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Τεχνικές βελτιστοποίησης της ποιότητας των παρεχομένων υπηρεσιών (QoS) με έλεγχο κρίσιμων ηλεκτρικών και ηλεκτρομαγνητικών παραμέτρων στα σύγχρονα ασύρματα τηλεπικοινωνιακά συστήματαΦραίμης, Ιωάννης 01 October 2012 (has links)
Στην παρούσα διδακτορική διατριβή προτείνονται τεχνικές για την βελτιστοποίηση της ποιότητας των παρεχομένων υπηρεσιών στους χρήστες σύγχρονων ασύρματων τηλεπικοινωνιακών συστημάτων που ως τεχνολογίες πρόσβασης έχουν την πολλαπλή πρόσβαση ορθογωνικής διαίρεσης συχνότητας και την πολλαπλή πρόσβαση διαίρεσης κώδικα. Οι τεχνικές που αναπτύχθηκαν αφορούν επαναληπτικούς αλγόριθμους κατανομής των διαθέσιμων ραδιοπόρων και εφαρμόζοναι κυρίως στην κατερχόμενη των ασύρματων συστημάτων. Ως παράμετροι της ποιότητας των παρεχόμενων υπηρεσιών θεωρούνται: το ελάχιστο απαιτούμενο επίπεδο ρυθμού μετάδοσης των δεδομέων, ο ρυθμός των λανθασμέων bit, και η ελάχιστη απαιτούμενη ποσότητα ραδιοπόρων σε κάθε χρήστη. Η αξιολόγηση των τεχνικών που προτείνονται γίνεται μέσω δεικτών της απόδοσής τους, οι οποίοι είναι: η πιθανότητα παραβίασης της ποιότητας της υπηρεσίας, ο δείκτης δικαιοσύνης του συστήματος, ο ρυθμός μετάδοσης δεδομένων στα άκρα της κυψέλης και η χωρητικότητα της κυψέλης. Για την εξαγωγή των δεικτών αυτών είναι απαραίτητα στατιστικά δεδομένα, τα οποία συλλέγονται μέσα από μεγάλο αριθμό προσομοιώσεων. / This doctoral thesis proposes QoS optimization techniques in modern wireless telecommunication systems, whereby orthogonal frequency division multiple access and code division are used. The proposed techniques are iterative resource allocation algorithms which are mainly suitable for the downlink of wireless networks. The minimum required level of data rate, the bit error rate and the minimum number of resources per user are considered as quality of service parameters. The validation of the proposed techniques is done through the performance of performance metrics like the : the quality of service violation probability, the system fairness index, the cell-edge data rate and the cell capacity. Statistical data are required which are collected through extensive simulation
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Koexistence mobilních komunikačních systémů GSM-EDGE a UMTS / GSM-EDGE and UMTS Systems CoexistenceGleissner, Filip January 2009 (has links)
The dissertation thesis deals with the investigation of the coexistence of GSM–EDGE and UMTS systems with focus on the physical layer of the systems. The aim is to provide a set of recommendations for practical cooperation while the systems operate in both the separated and the common radio bands. A detailed description of signal processing of both the systems on the physical layer is presented. On the basis of this description, models of both systems were created and implemented in the MATLAB environment. The simulations are focused on the physical layer quality parameters, especially the bit error ratio evaluation for various ratios of useful signal power to noise power during the transmission over the radio channel. Simulation is also used to examine the quality of received useful signal while it is interfered by signals from the same and adjacent channels. The purpose is to determine the isolation between these adjacent channels, when the bit error ratio of the useful signal does not exceed a certain reference value. The simulation results are subsequently subjected to comparison with the results of the experimental measurements in laboratory conditions. Before the measurements are carried out, a study of possible interference types is performed. Consequently, the crucial parameters of the measuring equipment used are verified. From the results of simulations and measurements, the proposal of a minimum and recommended carrier separation between both the systems is presented in order to efficiently utilize the assigned frequency spectrum. Furthermore, for the cooperation in both the separated and the common radio bands, the necessary precautions are given for reaching the required isolation and thereby inter-system interference minimization.
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