Long-Term Evolution (LTE) is the fourth generation (4G) wireless communications standard and its evolution is paving the path for the fifth generation (5G) technology. LTE is also considered for supporting public safety networks, Machine-to-Machine (M2M) communications, and many other applications. Hence, it is critical to ensure that the LTE system performs effectively even in harsh signaling environments. Unfortunately, LTE is vulnerable to intentional interference at the physical layer. We define the term LTE control channel spoofing, which refers to the case when an adversary sets a fake LTE-like base station (evolved NodeB or eNodeB) that transmits a partial or full LTE downlink frame to deceive LTE devices and hinder them from attaching to a real cell. Based on analyzing the initial cell selection process in the LTE specifications, we identify three different level of LTE control channel spoofing. We have built a testbed to demonstrate the feasibility of such an attack. The experimental results show that LTE control channel spoofing can cause permanent denial of service for LTE devices during the cell selection process. We propose effective mitigation techniques to enhance the immunity of LTE systems against all the three forms of LTE control channel spoofing, and ensure that it is secure and available when and where needed. Moreover, the commercial success of LTE and the resulting growth in mobile data demand have motivated cellular network operators to strive for new innovations. LTE-Unlicensed has been recently proposed to allow cellular network operators to offload some of their data traffic by accessing the unlicensed 5 GHz frequency band. There are three variants of LTE-Unlicensed that have been proposed in the industry. These variants differ in their operational features, but they enhance the capacity of LTE and represent a big milestone in its evolution toward 5G. However, LTE-Unlicensed faces several challenges when operating in the 5 GHz bands, as this spectrum is mainly occupied by Wi-Fi and by various radar systems. Therefore, we analyze the algorithms proposed in the industry for the LTE-Unlicensed and Wi-Fi coexistence, and we develop a new spectrum sharing technique for the coexistence between LTE-Unlicensed and radar systems. In order to analyze LTE-Unlicensed and Wi-Fi coexistence, we first explain the technical details of each of the three variants of LTE-Unlicensed, and we provide a comparative analysis of them in terms of their operational features. Then we develop an unbiased and objective evaluation of their proposed coexistence mechanisms with Wi-Fi systems, and numerically compare their performance. In order to emphasize the need for developing a new spectrum sharing technique for the coexistence between LTE-Unlicensed and radar systems, we first present the different regulatory requirements for the 5 GHz unlicensed bands in several world regions, and we perform a comprehensive survey on the different radar types within the 5 GHz sub-bands. Then we develop a novel spectrum sharing technique based on chance-constrained stochastic optimization to allow the LTE-Unlicensed eNodeB to share the spectrum efficiently with a radar system. The optimization problem is formulated to guarantee the minimum performance criteria for the radar operation, and at the same time allows the LTE-Unlicensed eNodeB to control its transmit power to maximize the performance for the serving LTE-Unlicensed device. A mathematical model is used to transform the stochastic optimization problem into a deterministic one, and an exhaustive search is used to solve the resulting optimization problem. Due to the power control mechanism resulting from the proposed algorithm, numerical results show a significant reduction in the protection distance required between the radar and the LTE-Unlicensed network for the two to coexist, as the proposed algorithm can allow the two systems to operate effectively with a protection distance of only 3.95% of the one imposed by the regulations.

The newly defined NB-IoT standard currently lacks a toolkit and simulator. In order to develop algorithms for this new standard there is a need for channels and signals as reference during tests. MATLAB is commonly used for testing LTE signals and therefore the toolkit was developed in this environment. The toolkit focuses primarily on the Layer 1-relevant functionality of NB-IoT, the grid generation, encoding, rate-matching and modulation of channels. The simulator focuses on testing the developed toolkit in a virtual LTE NB-IoT environment. The virtual environment attempts to emulate a base station and a terminal. The path followed is scheduling, channel processing, grid generation, QPSK and OFDM modulation through a modeled channel, OFDM demodulation, channel estimation, equalisation, QPSK demodulation and reversal of channel processing. The simulator tests primarily the NPDSCH channel implementations. Measurements of bit error and block error rates were made and it was concluded that they follow the expected trends. More testing is required to validate the remaining channels. A sector equaliser and an interpolating equaliser were tested by measuring block error rate and checking constellation diagrams and it was concluded that the performance of the interpolation equaliser is more consistent. In order to improve the equalisation further the noise estimation must be reworked.

Long Term Evolution (LTE) is becoming the first choice of operators when constructingthe new network infrastructure, because of its high throughput and lowlatency. Although the LTE can offer high speed data service as a benefit of widebandapplication, the large bandwidth also results in huge control signaling cost.This thesis studies how the available radio resources should be allocated todifferent users for the particular purpose. Three proposals are presented in thisthesis. The first two aim at maximizing the overall net capacity. The factors ofchannel conditions and control signaling cost are considered in the first proposalwhereas power control is supplemented as an additional factor in the second one.The third proposal aims at achieving a tradeoff between subframe efficiency andaverage data rate. Channel conditions and control signaling cost are taken intoconsideration.Resource blocks scheduling under a control signaling cost constraint is feasiblewith the knowledge of the channel condition of users. This is obtained from channelstate information directly. The first proposal studies how this scheduling isdone. The second proposal takes power allocation scheme into account. In termsof computational complexity, the methods of internal water-filling and externalwater-filling are described in the second proposal. The simulation results illustratethat the net capacity in the first proposal can be enhanced by about 5% -60% in the second proposal. The exact percentage of increase depends on differentcontrol signaling penalty.The third proposal discusses how to implement flexible subframe length underthe Rayleigh fading channel condition in the LTE system. The objective is toachieve subframe efficiency as high as possible, while maintaining the maximumaverage data rate. The simulation results illustrate that the optimal subframelength depends on control signaling cost penalty as well as on Doppler frequency.Finally, the fairness of the first proposal is compared with the improved versionsof Round Robin, Dynamic Allocation and Proportional Fair scheduling algorithms.The simulation results show that Round Robin and Dynamic Allocationoutperform the first proposal under a certain condition. / LOLA (Achieving Low Latency in Wireless Communication) is funded by EU FP7 (European Community’s Seventh Framework Programme).

This master thesis analyzes the effect of Carrier Frequency Offsets (CFO) on LTEuplink transmission, which is the main cause of ICI (Inter Carrier Interference) andMAI (Multiuser Access Interference). A model of the LTE uplink is required toconduct the study and is implemented in MATLAB, in compliance with 3GPPspecifications. The model can generate uplink signal as generated by the UE, (UserEquipment) and it supports multiple channel bandwidths described by the 3GPP.The channel estimation is done with the help of block type pilots. The model is usedto simulate the experimental conditions. The presence of CFO results in poor systemperformance. Therefore, many algorithms have been proposed for the CFOcancellation such as Successive Interference Cancellation (SIC), Parallel InterferenceCancellation (PIC) and Inverse Interference Matrix Cancellation. As the topic is verybroad, I investigate the performance of Inverse Interference Matrix Cancellationalgorithm. Compared with the other CFO cancellation algorithms this algorithm candirectly estimate the interference components from the inverse pilot matrix, thusthere is no need for CFO estimation. Simulation results show that the algorithm isvery effective in the presence of CFO. The channel estimation technique used is theLeast Square (LS) method and frequency selective channel is used for simulation.Performance graphs are plotted in terms of BER (Bit Error Rate) against differentvalues of SNR (Signal to Noise Ratio).

Le trafic de données mobiles augmente de façon permanente. Afin d'éviter une saturation, les opérateurs doivent décharger le réseau cellulaire vers des réseaux d'accès alternatifs. WiFi se trouve être une bonne solution qui permet à l'opérateur de tirer parti de bandes de fréquence sans licence ainsi que du très grand nombre de points d'accès déjà déployés. Dans cette thèse, nous présentons tout d'abord un état de l'art des différentes solutions de couplage entre LTE et WiFi. Nous montrons que la plupart de ces solutions ne garantissent pas la continuité de session ou sont sujettes à une duplication des procédures de sécurité. Ceci a conduit à la proposition du Very Tight Coupling entre LTE et WiFi. Dans ce type d'architecture, les points d'accès WiFi sont connectés à une station de base LTE et les mécanismes de sécurité LTE sont réutilisées afin de permettre un accès rapide au réseau WiFi. Ceci permet également d'avoir une double connectivité et de garder le trafic de signalisation sur le réseau LTE, ce qui donne la possibilité d'avoir des procédures de sélection optimisées. Nous étudions comment le Very Tight Coupling peut être implémenté et comment les points d'accès WiFi intégrés dans les passerelles résidentielles peuvent être connectées aux stations de base LTE dans le cas d'un réseau fixe/cellulaire convergent. Nous évaluons ensuite par des outils mathématiques, les performances de différents schémas de couplage et calculons le taux de capacité pouvant être économisée. Ensuite, nous présentons une implémentation du Very Tight Coupling sur une plateforme utilisant une interface radio LTE réelle basée sur Open Air Interface. Nous effectuons plusieurs expérimentations afin de trouver la meilleure configuration du protocole de la couche liaison de données. Nous démontrons que le fait d'utiliser WiFi et LTE en parallèle n'augmente pas systématiquement le débit. / The mobile data traffic has been continuously increasing. To avoid saturation of cellular network, operators need to use alternative access networks for offloading purpose. WiFi is a good solution as the operator can take advantage of its unlicensed spectrum as well as the large number of deployed WiFi access points.In this thesis, we first provide a state-of-the-art of the different coupling solutions between LTE and WiFi. We show that most solutions cannot guarantee session continuity or duplicate the security procedures. This leads to propose "Very Tight Coupling" between LTE and WiFi. In this architecture, WiFi access points are connected to the LTE base stations and the security mechanisms of LTE are reused to ensure fast access to WiFi. It allows dual connectivity and to keep control signalling in the LTE network, which gives the possibility to have optimized interface selection procedures.We study how very tight coupling can be implemented and how WiFi APs that integrated in customer residential gateways can be connected to LTE base stations in a converged fixed/cellular network. We then mathematically evaluate the performance of different deployment schemes and compute how much capacity can be saved on the LTE network. Furthermore, we implement the solution on a platform with a real LTE radio interface based on the Open Air Interface framework as a proof-of-concept. We perform several experiments to find the configuration of the link-layer protocols that gives the highest bit rate. In particular, we show that using WiFi and LTE simultaneously does not always increase the bit rate.

[pt] Atualmente, as redes celulares estão sendo utilizadas como uma saída para prover serviços de banda larga em locais que ainda não são atendidos pelas redes fixas, principalmente em países subdesenvolvidos como o Brasil. As tecnologias empregadas atualmente no Brasil, o GSM (Global System for Mobile) e o UMTS (Universal Mobile Telecommunications System), não são tecnologias desenvolvidas para absorver a grande demanda que vem sendo observada no mercado de banda larga móvel. Devido a essa demanda inesperada, acredita-se que o LTE (Long Term Evolution), a primeira tecnologia desenvolvida com o objetivo de atender não somente as chamadas de voz, mas principalmente as conexões banda larga, apresente condições de suportar com maior eficiência esta crescente necessidade. Para que todas as expectativas relacionadas à capacidade das redes LTE sejam atendidas, é extremamente necessário que um correto dimensionamento dessas redes seja realizado, pois somente desta forma será possível estabelecer o compromisso de se atender os usuários com qualidade. / [en] At the moment, the cellular networks are being used as an option to provide broadband services in places that have not yet been covered by the fixed networks, mainly in underdeveloped countries like Brazil. The employed technologies now in Brazil, GSM (Global System is Mobile) and UMTS (Mobile Universal Telecommunications System), they were not developed to absorb the great demand that has been observed at the broadband mobile market. Due to that unexpected demand, it’s being believed that LTE (Long Term Evolution), the first technology developed with the objective of supporting not only the voice calls, but mainly the broadband connections, is able to hold with larger efficiency this growing needs. For all that expectations about the LTE network’s capacity be achieved, it is extremely necessary that a correct sizing of those networks be accomplished, therefore only this way it will be possible to establish the commitment of supporting the subscribers with quality.

<p>U ovoj disertaciji razvijeni su analitički alati za izračunavanje protoka servisa, propusnog opsega i u&scaron;tede energije zahtevanim u različitim eMBMS LTE/LTE-A servisnim strukturama. Takođe, mi smo analizirali protok podataka i optimalnu dodelu parametara za prenos na fizičkom sloju za eMBMS baziran video servis u 2-klasnoj heterogenoj mreži primenom stohastičke geometrije.</p> / <p>In this dissertation we develop simple analytical tools for evaluation of average service data rates, bandwidth and energy consumption requirements in dierent eMBMS LTE/LTE-A service congurations. Also, we consider a simple approach to estimate achievable rates and optimally assign the physical layer transmission parameters for eMBMS based video service in the two-tier heterogeneous cellular systems.</p>

A compact multiband antennas for Long Term Evolution (LTE) applications is a challenge. Both the frequencies of new wireless technologies and new frequency bands must be covered. The lower end of the 0.7- 3.5 GHz band is especially difficult to handle for miniaturized terminal devices. A single layer, line-feed rectangular microstrip patch antenna is small enough for the LTE handsets. Our project proposes size reduction and bandwidth enhancement through adapted feeding techniques. By means of slits the return loss and gain can be optimized with the aid of HFSS (High Frequency Structure Simulator).

Mobile devices and their applications are continuing to develop and the more advanced they are, the more they require high data ranges and the more they demand of the available wireless communication networks. At present, LTE (Long Term Evolution) is a good solution as it provides the users of mobile devices with a good throughput and a low latency. In the future, the two most important aspects for end users will be system spectral efficiency and system power controlling. This thesis deals with LTE downlink spectral efficiency and power controlling. The thesis will show how, by using IP multicasting for the LTE downlink, the base station is able to provide the necessary data through a significantly smaller spectrum and, additionally, how cooperative diversity, i.e. the cooperation between several base stations, can improve or even maximise the total network channel capacity, regardless of bandwidth size. A Packet and Resource Plan Scheduling algorithm (PARPS) is used to schedule the transmissions, and the results are calculated in MATLAB. By this means it is possible to analyse the efficiency of the spectrum management, the coverage probability and the power controlling for the different transmitters used for the LTE downlink.The LTE downlink scheme is simulated in Matlab for different numbers of transmitters (2-3). IP multicasting over the LTE downlink manages to transmit the same amount of data using less transmission power (50- 66.6%) with a better system spectral efficiency.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2018-04-02T12:36:23Z No. of bitstreams: 1 PedroMaiaDeSantana_DISSERT.pdf: 2069422 bytes, checksum: 1a983f5131609d3cf7fe3bd96b0ef27d (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2018-04-04T13:34:35Z (GMT) No. of bitstreams: 1 PedroMaiaDeSantana_DISSERT.pdf: 2069422 bytes, checksum: 1a983f5131609d3cf7fe3bd96b0ef27d (MD5) / Made available in DSpace on 2018-04-04T13:34:36Z (GMT). No. of bitstreams: 1 PedroMaiaDeSantana_DISSERT.pdf: 2069422 bytes, checksum: 1a983f5131609d3cf7fe3bd96b0ef27d (MD5) Previous issue date: 2017-12-07 / Este trabalho tem como objetivo realizar um estudo sobre a aplica??o de redes LTE no espectro ISM (Industrial Scientific and Medical) e seu consequente impacto sobre tecnologias comumente coexistentes na mesma faixa de frequ?ncia. Inicialmente, ? realizada uma elucida??o te?rica sobre as regulamenta??es que envolvem o uso de espectro n?o-licenciado. Na sequ?ncia, s?o apresentadas as principais solu??es de coexist?ncia do LTE nesse meio, destacando-se o mecanismo recentemente padronizado pelo 3GPP, o LTE-LBT, e tecnologias espec?ficas de empresas pioneiras na ?rea, tais como a solu??o LTE-DC. Como elemento pr?tico complementar ? investiga??o te?rica inicial, s?o desenvolvidas an?lises de desempenho das respectivas solu??es utilizando o simulador ns-3. A novidade do trabalho ? materializada pela apresenta??o de uma proposta de solu??o para o mecanismo Carrier-Sensing Adaptive Transmission (CSAT). Essa solu??o, baseada em aprendizado de m?quina, visa melhorar o desempenho conjunto dos sistemas que coexistem na faixa ISM. Este trabalho tamb?m prop?e uma solu??o de coexist?ncia do LTE-DC consigo pr?prio a partir de uma abordagem utilizando teoria dos jogos. Essas solu??es s?o comparada com as solu??es cl?ssicas e o seus ganhos s?o evidenciado em cen?rios definidos por ?rg?os de padroniza??o mundial. / This work aims to perform a study about the application of LTE networks in ISM (Industrial Scientific and Medical) spectrum and its impact over technologies that communly coexist in the same frequency range. Initially, it?s made a theoretical elucidation about regulamentations involving the non licensed spectrum usage. In sequence, it?s presented the main LTE coexistence solutions in this field, highlighting the recent mechanism standardized by 3GPP, the LTE-LBT, and specific technologies of pioneering companies in this domain, like LTE-DC solution. As a practical element complementary to the initial theoretical investigation, it?s developed performance analyzes of the respective solutions using ns-3 simulator. The novelty of the work is materialized by the presentation of a solution proposal for the Carrier-Sensing Adaptive Transmission (CSAT). This solution, based on machine learning, aims to improve the joint performance of systems that coexist in the ISM band. This work also propose a solution for LTE-DC self-coexistence by a game theory approach. These solutions are compared to the classical ones and their gains are evidenced in scenarios defined by global standardization institutions.