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A Study on the Impact of Antenna Downtilt on theOutdoor Users in an Urban EnvironmentRamachandra, Pradeepa January 2012 (has links)
Inter-site interference distribution acts as a basic limitation on how much performance a network service provider can achieve in an urban network scenario. There are many different ways of controlling this interference levels. One such method is tuning the antenna downtilt depending on the network situation. Antenna downtilt can also be seen as a powerful tool for load balancing in the network. This thesis work involves a study of the impact of the antenna downtilt in an urban environment, involving non-uniform user distribution. A realistic dual ray propagation model is used to model the path gain from the base station to a UE. Such a propagation model is used along with a directional antenna radiation pattern model to calculate the overall path gain from the base station to a UE. Under such modeling, the results of the simulations show that the antenna downtilt plays a crucial role in optimizing the network performance. The results show that the optimal antenna downtilt angle is not very sensitive to the location of the hotspot in the network. The results also show that the antenna downtilt sensitivity is very much dependent on the network scenario. The coupling between the antenna downtilt and the elevation half power beamwidth is also evaluated.
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3D Massive MIMO Systems: Channel Modeling and Performance AnalysisNadeem, Qurrat-Ul-Ain 03 1900 (has links)
Multiple-input-multiple-output (MIMO) systems of current LTE releases are capable of adaptation in the azimuth only. More recently, the trend is to enhance the system performance by exploiting the channel's degrees of freedom in the elevation through the dynamic adaptation of the vertical antenna beam pattern. This necessitates the derivation and characterization of three-dimensional (3D) channels.
Over the years, channel models have evolved to address the challenges of wireless communication technologies. In parallel to theoretical studies on channel modeling, many standardized channel models like COST-based models, 3GPP SCM, WINNER, ITU have emerged that act as references for industries and telecommunication companies to assess system-level and link-level performances of advanced signal processing techniques over real-like channels. Given the existing channels are only two dimensional (2D) in nature; a large effort in channel modeling is needed to study the impact of the channel component in the elevation direction. The first part of this work sheds light on the current 3GPP activity around 3D channel modeling and beamforming, an aspect that to our knowledge has not been extensively covered by a research publication. The standardized MIMO channel model is presented, that incorporates both the propagation effects of the environment and the radio effects of the antennas. In order to facilitate future studies on the use of 3D beamforming, the main features of the proposed 3D channel model are discussed. A brief overview of the future 3GPP 3D channel model being outlined for the next generation of wireless networks is also provided.
In the subsequent part of this work, we present an information-theoretic channel model for MIMO systems that supports the elevation dimension. The model is based on the principle of maximum entropy, which enables us to determine the distribution of the channel matrix consistent with the prior information on the angles of departure and angles of arrival of the propagation paths. Based on this model, an analytical expression for the cumulative density function (CDF) of the mutual information (MI) for systems with a single receive and finite number of transmit antennas in the general signal-to-interference-plus-noise-ratio (SINR) regime is provided. The result is extended to systems with multiple receive antennas in the low SINR regime. A Gaussian approximation to the asymptotic behavior of the MI distribution is derived for the large number of transmit antennas and paths regime. Simulation results study the performance gains realizable through meticulous selection of the transmit antenna down tilt angles, confirming the potential of elevation beamforming to enhance system performance. The results validate the proposed analytical expressions and elucidate the dependence of system performance on azimuth and elevation angular spreads and antenna patterns. We believe that the derived expressions will help evaluate the performance of 3D 5G massive MIMO systems in the future.
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Controle de potÃncia e estratÃgias de eficiÃncia energÃtica para comunicaÃÃes D2D subjacentes redes celulares / Power control and energy efficiency strategies for D2D communications underlying cellular networksYuri Victor Lima de Melo 14 July 2015 (has links)
Ericsson Brasil / Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / Em um mundo onde as pessoas contam com
smartphone, smartwatch, tablet e outros
dispositivos para mantÃ-las conectadas onde quer que vÃo, t
odos esperam que seus
aplicativos sejam executados sem problemas, tais como cham
adas abandonadas,
download
lento e vÃdeos com saltos.
Neste contexto, comunicaÃÃo dispositivo-a-dispositivo (
do inglÃs, Device-to-Device (D2D))
constitui uma tecnologia promissora, pois à um tipo de comun
icaÃÃo direta e utiliza baixa
potÃncia entre dispositivos prÃximos, permitindo-se desv
iar o trÃfego da rede mÃvel, aumentar
a eficiÃncia espectral e de potÃncia. Do ponto de vista do assi
nante, D2D significa usar
aplicaÃÃo sem problemas e aumentar o tempo de vida da bateria
do celular.
No entanto, a fim de realizar os ganhos potenciais das comunic
aÃÃes D2D, algumas
questÃes-chave devem ser abordadas, pois as comunicaÃÃes D
2D podem aumentar a
interferÃncia co-canal e comprometer a qualidade do enlace
das comunicaÃÃes celulares.
Esta dissertaÃÃo foca em tÃcnicas de Gerenciamento de Recur
sos de RÃdio (do inglÃs, Radio
Resource Management (RRM)) para mitigar a interferÃncia co
-canal para comunicaÃÃes D2D
que se baseiam na EvoluÃÃo de Longo Prazo (do inglÃs, Long Ter
m Evolution (LTE)), visando
a reduÃÃo da interferÃncia intra- e inter-celular e na melho
ria da eficiÃncia energÃtica. Os
principais esquemas de Controle de PotÃncia (do inglÃs, Pow
er Control (PC)) (e.g. OLPC,CLPC
e SDPC) e um esquema hÃbrido (CLSD) sÃo calibrados e utilizad
os no cenÃrio macro ou micro
multicelular, usando diferentes cargas e InformaÃÃo do Est
ado do Canal (do inglÃs, Channel
State Information (CSI)) perfeita ou imperfeita. AlÃm diss
o, o impacto da inclinaÃÃo da antena
(
downtilt
) à analisado, que à usada para ajustar o raio de cobertura de u
ma Evolved Node
B (eNB) e reduzir a interferÃncia co-canal, aumentando o iso
lamento de cÃlulas.
Os resultados numÃricos indicam que os regimes de controle d
e potÃncia e inclinaÃÃo
da antena, devidamente calibrados, podem fornecer ganhos p
ara a comunicaÃÃo celular e
D2D. Em outras palavras, a tecnologia D2D pode ser utilizada
para aumentar ainda mais
a eficiÃncia de espectro e a eficiÃncia energÃtica se algoritm
os de RRM forem utilizados
adequadamente / In a world where people count on their smartphone, smartwatch, tablet and other devices to keep them connected wherever they go, they expect its application to run without problems, such as dropped calls, slow download and choppy videos.
In this context, Device-to-Device (D2D) communication represents a promising technology, because it is a direct and low-power communication between devices close, allowing to offload the data transport network, increase spectral and power efficiency. From the subscriber point of view, D2D means to use applications without problem and increase battery life. However, in order to realize the potential gains of D2D communications, some key issues must be tackled, because D2D communications may increase the co-channel interference and compromise the link quality of cellular communications.
This masterâs thesis focuses on Radio Resource Management (RRM) techniques, especially Power Control (PC) schemes, to mitigate the co-channel interference for D2D communications
underlaying a Long Term Evolution (LTE) network, aiming at the reduction of the intra- and inter- cell interference and at the improvement of energy efficiency. The main PC schemes (e.g. OLPC, CLPC and SDPC) and a hybrid scheme (CLSD) are calibrated and used in macro- or micro- multicell scenario, using different loads and imperfect Channel State Information (CSI).
In addition, the impact of downtilt is analyzed, which is used to adjust the coverage radius of an Evolved Node B (eNB) and reduce co-channel interference by increasing cell isolation.
The numerical results indicate that PC schemes and downtilt, duly calibrated, can provide gains to cellular and D2D communications. In other words, D2D technology can be used to further increase the spectral and energy efficiency if RRM algorithms are used suitably.
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