214 research outputs found
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Self-organising network management for heterogeneous LTE-advanced networks
This thesis was submitted for the award of Doctor of Philosophy and awarded by Brunel University LondonSince 2004, when the Long Term Evolution (LTE) was first proposed to be publicly available in the year 2009, a plethora of new characteristics, techniques and applications have been constantly enhancing it since its first release, over the past decade. As a result, the research aims for LTE-Advanced (LTE-A) have been released to create a ubiquitous and supportive network for mobile users. The incorporation of heterogeneous networks (HetNets) has been proposed as one of the main enhancements of LTE-A systems over the existing LTE releases, by proposing the deployment of small-cell applications, such as femtocells, to provide more coverage and quality of service (QoS) within the network, whilst also reducing capital expenditure. These principal advantages can be obtained at the cost of new challenges such as inter-cell interference, which occurs when different network applications share the same frequency channel in the network. In this thesis, the main challenges of HetNets in LTE-A platform have been addressed and novel solutions are proposed by using self-organising network (SON) management approaches, which allows the cooperative cellular systems to observe, decide and amend their ongoing operation based on network conditions. The novel SON algorithms are modelled and simulated in OPNET modeler simulation software for the three processes of resource allocation, mobility management and interference coordination in multi-tier macro-femto networks. Different channel allocation methods based on cooperative transmission, frequency reuse and dynamic spectrum access are investigated and a novel SON sub-channel allocation method is proposed based on hybrid fractional frequency reuse (HFFR) scheme to provide dynamic resource allocation between macrocells and femtocells, while avoiding co-tier and cross-tier interference. Mobility management is also addressed as another important issue in HetNets, especially in hand-ins from macrocell to femtocell base stations. The existing research considers a limited number of methods for handover optimisation, such as signal strength and call admission control (CAC) to avoid unnecessary handovers, while our novel SON handover management method implements a comprehensive algorithm that performs sensing process, as well as resource availability and user residence checks to initiate the handover process at the optimal time. In addition to this, the novel femto over macro priority (FoMP) check in this process also gives the femtocell target nodes priority over the congested macrocells in order to improve the QoS at both the network tiers. Inter-cell interference, as the key challenge of HetNets, is also investigated by research on the existing time-domain, frequency-domain and power control methods. A novel SON interference mitigation algorithm is proposed, which is based on enhanced inter-cell interference coordination (eICIC) with power control process. The 3-phase power control algorithm contains signal to interference plus noise ratio (SINR) measurements, channel quality indicator (CQI) mapping and transmission power amendments to avoid the occurrence of interference due to the effects of high transmission power. The results of this research confirm that if heterogeneous systems are backed-up with SON management strategies, not only can improve the network capacity and QoS, but also the new network challenges such as inter-cell interference can also be mitigated in new releases of LTE-A network
Technical, financial and environmental evaluation of 4G long term evolution: advanced with femtocell base stations
Recent advances in mobile communication technology have allowed for considerable
growth both in traffic and user numbers. However, in order to maintain acceptable quality of
experience and service levels with increasing network capacity requirements, a mobile
communications operator is challenged with high investment costs and high operating costs.
Cost effectiveness and environmental sustainability are two major factors a mobile
telecommunications operator must take into account in order to maintain its network planning
techniques ready for the accelerated growth of traffic in future mobile networks. With the
incoming LTE-Advanced system and with the increasing popularity of femtocells, it becomes
necessary to evaluate and quantify the economic viability and sustainability of this new type
of base station when used as a standalone deployment option, as well as when used in a two-tier network.
Therefore, different cases were used with a deployment method based on capacity
used with a varying non-uniform traffic distribution in order to assess the future resistance
and flexibility of this proposed solution. A comparison was made between macro cell
coverage only, full femtocell coverage and a two-tier joint solution.
Our study has concluded that for low capacity demands, the best approach is a two-tier network with femtocells used for indoor backhaul. A joint solution also allows for the
cost-effective resolution of indoor coverage issues. According to our future capacity
requirements projected, it has been concluded that a full femtocell deployment, by far, the
most economically viable option.
A method for the quantification and suppression of carbon emissions due to energy
consumption is also proposed, through which we studied and estimated the price for the
achievement of a zero carbon emissions network.Os recentes avanços na tecnologia de comunicações móveis têm permitido um
crescimento considerável da indústria, tanto em termos de tráfego como em número de
clientes. No entanto, para conseguir manter uma qualidade de experiência aceitável e com
elevada qualidade de serviço, um operador de comunicações móveis depara-se com elevados
custos de investimento e operação.
A eficácia em termos de custos e a pegada ambiental são dois factores que, entre
outros, um operador de telecomunicações móveis deve ter em conta de modo a manter as suas
técnicas de planeamento de rede preparadas para o acelerado crescimento do tráfego nas redes
móveis do futuro. Com a chegada próxima do LTE-Advanced e com a crescente popularidade
de femtocells, torna-se necessário avaliar e quantificar a viabilidade económica e o potencial
de poupança de energia deste novo tipo de estação de base quando utilizado como uma opção
de implantação autónoma, ou quando utilizado para suporte de uma rede de macro células.
Dessa forma, foram dimensionados diferentes casos de implementação baseados nos
requisitos de capacidade. Foi também aplicada uma distribuição de tráfego não-uniforme, a
fim de avaliar a resistência ao futuro e a flexibilidade de aplicação desta solução proposta.
Fez-se uma comparação entre uma implementação apenas com recurso a macro células, uma
implementação feita completamente com recurso a femtocells e uma solução conjunta destes
dois tipos de estação-base.
O estudo concluiu que, para requisitos de baixa capacidade, a melhor implementação
é uma rede de duas camadas, com femtocells utilizadas para o backhaul das ligações indoor.
A solução conjunta permite ainda a resolução eficaz de problemas de cobertura no interior de
edifícios. De acordo com a nossa projecção das necessidades futuras de capacidade concluiu-se que a implementação de uma rede apenas com recurso a femtocells é a melhor opção, do
ponto de vista da capacidade, financeiro e ambiental.
Também foi apresentada uma metodologia para quantificar a pegada ambiental
devida ao consumo de energia, através da qual se estudou e estimou os custos associados à
implementação de uma rede com pegada ambiental nula
Self-Healing in 5G HetNets
The main requirements of 5G are emerging through the efforts of diverse groups such as 4G America in United States, IMT-2020 (5G) promotion group in China and the 5G Private Public Partnership (5G PPP) in Europe. The 5G requirements will tremendously increase the network complexity which requires auto-integration and self-management capabilities that are well beyond today\u27s self-organising network features. Additionally, ultra-reliable communications put very stringent latency and reliability requirements on the architecture
UMTS multi-service uplink capacity and interference statistics of femtocells
The final publication is available at Springer via http://dx.doi.org/10.1007/s11277-012-0860-7In this work, the multiservice uplink capacity of single and multiple femtocells is given. The COST231 multiwall and multifloor indoor propagation model has been used to calculate the indoor propagation loss. Results show that the uplink capacity of a deployed femtocell will reduce by 2 % if two extra femtocells are deployed in the same building higher and lower of it. Results also show that the uplink capacity is slightly affected if there are several femtocells deployed in the buildings around the one at which the femtocell under study is already exists. It is demonstrated that uplink capacity is interference limited if the femtocell is deployed to serve the users in three floors. Results show that the uplink capacity will be interference and noise limited if the femtocell is deployed to serve the users in five floors. Finally, it is found that the effect of the interference due to the uniformly distributed users within the macrocell around the femtocell is insignificant
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Radio network management in cognitive LTE-Femtocell Systems
This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London.There is a strong uptake of femtocell deployment as small cell application
platforms in the upcoming LTE networks. In such two-tier networks of LTEfemtocell
base stations, a large portion of the assigned spectrum is used
sporadically leading to underutilisation of valuable frequency resources.
Novel spectrum access techniques are necessary to solve these current spectrum
inefficiency problems. Therefore, spectrum management solutions should have
the features to improve spectrum access in both temporal and spatial manner.
Cognitive Radio (CR) with the Dynamic Spectrum Access (DSA) is considered
to be the key technology in this research in order to increase the spectrum
efficiency. This is an effective solution to allow a group of Secondary Users
(SUs) to share the radio spectrum initially allocated to the Primary User (PUs) at
no interference.
The core aim of this thesis is to develop new cognitive LTE-femtocell systems
that offer a 4G vision, to facilitate the radio network management in order to
increase the network capacity and further improve spectrum access probabilities.
In this thesis, a new spectrum management model for cognitive radio networks is
considered to enable a seamless integration of multi-access technology with
existing networks. This involves the design of efficient resource allocation
algorithms that are able to respond to the rapid changes in the dynamic wireless
environment and primary users activities. Throughout this thesis a variety of
network upgraded functions are developed using application simulation
scenarios. Therefore, the proposed algorithms, mechanisms, methods, and system
models are not restricted in the considered networks, but rather have a wider
applicability to be used in other technologies.
This thesis mainly investigates three aspects of research issues relating to the
efficient management of cognitive networks: First, novel spectrum resource
management modules are proposed to maximise the spectrum access by rapidly
detecting the available transmission opportunities. Secondly, a developed pilot
power controlling algorithm is introduced to minimise the power consumption by
considering mobile position and application requirements. Also, there is
investigation on the impact of deploying different numbers of femtocell base
stations in LTE domain to identify the optimum cell size for future networks.
Finally, a novel call admission control mechanism for mobility management is
proposed to support seamless handover between LTE and femtocell domains.
This is performed by assigning high speed mobile users to the LTE system to
avoid unnecessary handovers.
The proposed solutions were examined by simulation and numerical analysis to
show the strength of cognitive femtocell deployment for the required
applications. The results show that the new system design based on cognitive
radio configuration enable an efficient resource management in terms of
spectrum allocation, adaptive pilot power control, and mobile handover. The
proposed framework and algorithms offer a novel spectrum management for self organised LTE-femtocell architecture.
Eventually, this research shows that certain architectures fulfilling spectrum
management requirements are implementable in practice and display good
performance in dynamic wireless environments which recommends the
consideration of CR systems in LTE and femtocell networks
D5.2 - Evaluation of Selected Measurement-based Techniques
Deliverable D5.2 del projecte FARAMIRPreprin
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