353 research outputs found
Dynamic Capacity Enhancement using a Smart Antenna in Mobile Telecommunications Networks
This work describes an investigation into the performance of antennas for mobile base station applications and techniques for improving the coverage and capacity within a base station cell. The work starts by tracing the development of mobile systems, both in technical and commercial terms, from the earliest analogue systems to present day broadband systems and includes anticipated future developments. This is followed by an outline of how smart antenna systems can be utilised to improve cell coverage and capacity.
A novel smart antenna system incorporating an array of slant ± 450 dual- polarised stacked patch elements four columns wide excited by a novel multi-beam forming and beam shaping network has been designed, simulated and implemented. It is found that for an ideal smart antenna array, four narrow overlapping beams, one wide “broadcast channel” beam and right and left shaped beams can be provided. Results are presented for the simulation of the smart antenna system using CST EM simulation software which inherently includes mutual coupling and the effects of a truncated ground plane on the element patterns. The results show some significant changes to the desired set of coverage patterns and various mutual coupling compensation techniques have been reviewed. An improved design technique has been developed for compensating the performance degrading effects of mutual coupling and finite ground plane dimensions in microstrip antenna arrays. The improved technique utilises combination of two previously known techniques: complex excitation weights compensation by inversion of the array mutual coupling scattering matrix and the incorporation of a WAIM (wide angle impedance matching) sheet. The technique has been applied to a novel multi-beam smart antenna array to demonstrate the efficacy of the technique by electromagnetic simulation. In addition, a demonstrator array has been constructed and tested which has yielded a positive conformation of the simulation results. For the developed demonstrator array which provides seven different beams, beams “footprints” have been predicted both for free space propagation and for urban propagation to evaluate the dynamic capacity performance of the smart antenna in a 3G mobile network. The results indicate that sector capacity can be dynamically tailored to user demand profiles by selection of the appropriate beam patterns provided by the novel smart antenna system
TĂ©cnicas de equalização hĂbridas para sistemas heterogĂ©neos na banda das ondas milimĂ©tricas
With the constant demand for better service and higher transmission rates current technologies are reaching the limits of the channel capacity. Although, technologies such as MIMO and Heterogeneous systems appear to increase the channel capacity by introducing more antennas at the transceivers making the link between users and base station more reliable. Furthermore, the current spectrum, sub-6GHz, is becoming saturated and due to the properties of such frequencies the deployment of heterogeneous systems can introduce some levels of interference. Towards improving future communication systems a new part of the frequencies spectrum available should be used, researchers have their eyes on the mmWave band. This band allows to increase the carrier frequency and respective signal bandwidth and therefore increase the transmission speeds, moreover the properties of such frequencies unlock some advantages over the frequencies used in the sub-6G band. Additionally, mmWave band can be combined with massive MIMO technology to enhance the system capacity and to deploy more antenna elements in the transceivers. One more key technology that improves the energy efficiency in systems with hundreds of antenna elements is the possibility to combine analog and digital precoding techniques denoted as hybrid architectures. The main advantages of such techniques is that contrary to the full digital precoding processing used in current systems this new architecture allows to reduce the number of RF chains per antenna leading to improved energy efficiency.
Furthermore to handle heterogeneous systems that have small-cells within the macro-cell, techniques such as Interference Alignment (IA) can be used to efficiently remove the existing multi-tier interference.
In this dissertation a massive MIMO mmWave heterogeneous system is implemented and evaluated. It is designed analog-digital equalizers to efficiently remove both the intra an inter-tier interference. At digital level, an interference alignment technique is used to remove the interference and increase the spectral efficiency. The results showed that the proposed solutions are efficient to remove the macro and small cells interference.Com a constante procura de melhores serviços e taxas de transmissĂŁo mais elevadas, as tecnologias atuais estĂŁo a atingir os limites de capacidade do canal. Contudo tecnologias como o MIMO e os sistemas heterogĂ©neos permitem aumentar a capacidade do canal atravĂ©s da introdução de mais antenas nos transcetores e atravĂ©s da implementação de pequenos pontos de acesso espalhados pela cĂ©lula primária, com o intuito de tornar as ligações entre os utilizadores e a estação base mais fiáveis. Tendo tambĂ©m em atenção que o espectro atual, sub-6GHz, está sobrecarregado e que devido Ă s propriedades das frequĂŞncias utilizadas a implementação de sistemas heterogĂ©neos pode levar a nĂveis de interferĂŞncia insustentáveis. Por modo a resolver esta sobrecarga futuros sistemas de comunicação devem aproveitar uma maior parte do espectro de frequĂŞncias disponĂvel. A banda das ondas milimĂ©tricas (mmWave) tem sido apontada como solução, o que permite aumentar a frequĂŞncia utilizada para transportar o sinal e consequentemente aumentar as velocidades de transmissĂŁo. Uma outra vantagem da banda mmWave Ă© que pode ser combinada com a tecnologia MIMO massivo, permitindo implementar mais elementos de antena nos terminais e consequentemente aumentar a capacidade do sistema. Umas das tecnologias desenvolvida para melhorar a eficiĂŞncia energĂ©tica em sistemas com centenas de antenas Ă© a possibilidade de combinar tĂ©cnicas de codificação analĂłgica e digital, designadas como arquiteturas hĂbridas. A principal vantagem desta tĂ©cnica Ă© que, contrariamente ao processamento feito nos sistemas atuais, totalmente no domĂnio digital, esta nova arquitetura permite reduzir o nĂşmero de cadeias RF por antena. Com o intuito de reduzir a interferĂŞncia em sistemas heterogĂ©neos, tĂ©cnicas como o alinhamento de interferĂŞncia sĂŁo usadas para separar utilizadores das cĂ©lulas secundárias dos utilizadores das cĂ©lulas primárias de modo a reduzir a interferĂŞncia multi-nĂvel existente no sistema geral.
Nesta dissertação, Ă© implementado e avaliado um sistema heterogĂ©neo que combina MIMO massivo e ondas milimĂ©tricas. Este sistema Ă© projetado com equalizadores analĂłgico-digitais para remover com eficiĂŞncia a interferĂŞncia intra e inter-camadas. No domĂnio digital Ă© utilizada a tĂ©cnica de alinhamento de interferĂŞncia para remover a interferĂŞncia e aumentar a eficiĂŞncia espectral. Os resultados mostram que as soluções propostas sĂŁo eficientes para remover a interferĂŞncia entre as cĂ©lulas secundárias e a primária.Mestrado em Engenharia EletrĂłnica e Telecomunicaçõe
Dynamic capacity enhancement using a smart antenna in mobile telecommunications networks
This work describes an investigation into the performance of antennas for mobile base station applications and techniques for improving the coverage and capacity within a base station cell. The work starts by tracing the development of mobile systems, both in technical and commercial terms, from the earliest analogue systems to present day broadband systems and includes anticipated future developments. This is followed by an outline of how smart antenna systems can be utilised to improve cell coverage and capacity. A novel smart antenna system incorporating an array of slant ± 450 dual- polarised stacked patch elements four columns wide excited by a novel multi-beam forming and beam shaping network has been designed, simulated and implemented. It is found that for an ideal smart antenna array, four narrow overlapping beams, one wide “broadcast channel” beam and right and left shaped beams can be provided. Results are presented for the simulation of the smart antenna system using CST EM simulation software which inherently includes mutual coupling and the effects of a truncated ground plane on the element patterns. The results show some significant changes to the desired set of coverage patterns and various mutual coupling compensation techniques have been reviewed. An improved design technique has been developed for compensating the performance degrading effects of mutual coupling and finite ground plane dimensions in microstrip antenna arrays. The improved technique utilises combination of two previously known techniques: complex excitation weights compensation by inversion of the array mutual coupling scattering matrix and the incorporation of a WAIM (wide angle impedance matching) sheet. The technique has been applied to a novel multi-beam smart antenna array to demonstrate the efficacy of the technique by electromagnetic simulation. In addition, a demonstrator array has been constructed and tested which has yielded a positive conformation of the simulation results. For the developed demonstrator array which provides seven different beams, beams “footprints” have been predicted both for free space propagation and for urban propagation to evaluate the dynamic capacity performance of the smart antenna in a 3G mobile network. The results indicate that sector capacity can be dynamically tailored to user demand profiles by selection of the appropriate beam patterns provided by the novel smart antenna system.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
TD-SCDMA Relay Networks
PhDWhen this research was started, TD-SCDMA (Time Division Synchronous Code
Division Multiple Access) was still in the research/ development phase, but
now, at the time of writing this thesis, it is in commercial use in 10 large cities in
China including Beijing and Shang Hai. In all of these cities HSDPA is enabled.
The roll-out of the commercial deployment is progressing fast with installations
in another 28 cities being underway now.
However, during the pre-commercial TD-SCDM trail in China, which started
from year 2006, some interference problems have been noticed especially in the
network planning and initialization phases. Interference is always an issue in
any network and the goal of the work reported in this thesis is to improve
network coverage and capacity in the presence of interference.
Based on an analysis of TD-SCDMA issues and how network interference arises,
this thesis proposes two enhancements to the network in addition to the
standard N-frequency technique. These are (i) the introduction of the concentric
circle cell concept and (ii) the addition of a relay network that makes use of
other users at the cell boundary. This overall approach not only optimizes the
resilience to interference but increases the network coverage without adding
more Node Bs.
Based on the cell planning parameters from the research, TD-SCDMA HSDPA
services in dense urban area and non-HSDPA services in rural areas were
simulated to investigate the network performance impact after introducing the
relay network into a TD-SCDMA network.
The results for HSDPA applications show significant improvement in the TDSCDMA
relay network both for network capacity and network interference
aspects compared to standard TD-SCDMA networks. The results for non-
HSDPA service show that although the network capacity has not changed after
adding in the relay network (due to the code limitation in TD-SCDMA), the
TD-SCDMA relay network has better interference performance and greater
coverage
Small Cells for Broadband Internet Access in Low-Income Suburban Areas in Emerging Market Environments
Mobile broadband technologies are providing the best and most commonly used broadband connectivity in many emerging markets. In some regions such as Africa, mobile networks provide the only feasible ways for extending the socio-economic benefits of broadband Internet access to the masses. The use of small cell technologies, like femtocells provide an attractive solution for such areas as femtocells are most cost – effective option for coverage and capacity expansion. Furthermore, femtocells are operator managed access points which can be easily deployed and operated by the end user.
It is well known that increased densification of cell sites is the most effective means for broadband mobile network capacity and coverage enhancements. However, cell densification through adding new macrocell sites by operators is usually a costly option. Therefore, this thesis will investigate methods to achieve mobile broadband capacity and coverage enhancements in low – income informal settlements or slum area, through more cost – effective cell densification using femtocells. Moreover this thesis will validate the performance gains of small cell concept for the case study through extensive simulations.
The impacts of femtocell in the network, the performance gain from femtocell and gain provided by different deployment strategies have been studied. Simulation results highlight the potential benefits of using femtocells in the network for extended broadband connectivity. With the femto increment the network performance increases up to a great extent
Cooperative control of relay based cellular networks
PhDThe increasing popularity of wireless communications and the higher data
requirements of new types of service lead to higher demands on wireless networks.
Relay based cellular networks have been seen as an effective way to meet users’
increased data rate requirements while still retaining the benefits of a cellular
structure. However, maximizing the probability of providing service and spectrum
efficiency are still major challenges for network operators and engineers because of
the heterogeneous traffic demands, hard-to-predict user movements and complex
traffic models.
In a mobile network, load balancing is recognised as an efficient way to increase
the utilization of limited frequency spectrum at reasonable costs. Cooperative
control based on geographic load balancing is employed to provide flexibility for
relay based cellular networks and to respond to changes in the environment.
According to the potential capability of existing antenna systems, adaptive radio
frequency domain control in the physical layer is explored to provide coverage at
the right place at the right time.
This thesis proposes several effective and efficient approaches to improve
spectrum efficiency using network wide optimization to coordinate the coverage
offered by different network components according to the antenna models and
relay station capability. The approaches include tilting of antenna sectors,
changing the power of omni-directional antennas, and changing the assignment of
relay stations to different base stations. Experiments show that the proposed
approaches offer significant improvements and robustness in heterogeneous traffic
scenarios and when the propagation environment changes. The issue of predicting
the consequence of cooperative decisions regarding antenna configurations when
applied in a realistic environment is described, and a coverage prediction model is
proposed. The consequences of applying changes to the antenna configuration on
handovers are analysed in detail. The performance evaluations are based on a
system level simulator in the context of Mobile WiMAX technology, but the
concepts apply more generally
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