236 research outputs found
EVEREST IST - 2002 - 00185 : D23 : final report
Deliverable públic del projecte europeu EVERESTThis deliverable constitutes the final report of the project IST-2002-001858 EVEREST. After its successful completion, the project presents this document that firstly summarizes the context, goal and the approach objective of the project. Then it presents a concise summary of the major goals and results, as well as highlights the most valuable lessons derived form the project work. A list of deliverables and publications is included in the annex.Postprint (published version
Load balancing using cell range expansion in LTE advanced heterogeneous networks
The use of heterogeneous networks is on the increase, fueled by consumer demand for more data. The main objective of heterogeneous networks is to increase capacity. They offer solutions for efficient use of spectrum, load balancing and improvement of cell edge coverage amongst others. However, these solutions have inherent challenges such as inter-cell interference and poor mobility management. In heterogeneous networks there is transmit power disparity between macro cell and pico cell tiers, which causes load imbalance between the tiers. Due to the conventional user-cell association strategy, whereby users associate to a base station with the strongest received signal strength, few users associate to small cells compared to macro cells. To counter the effects of transmit power disparity, cell range expansion is used instead of the conventional strategy. The focus of our work is on load balancing using cell range expansion (CRE) and network utility optimization techniques to ensure fair sharing of load in a macro and pico cell LTE Advanced heterogeneous network. The aim is to investigate how to use an adaptive cell range expansion bias to optimize Pico cell coverage for load balancing. Reviewed literature points out several approaches to solve the load balancing problem in heterogeneous networks, which include, cell range expansion and utility function optimization. Then, we use cell range expansion, and logarithmic utility functions to design a load balancing algorithm. In the algorithm, user and base station associations are optimized by adapting CRE bias to pico base station load status. A price update mechanism based on a suboptimal solution of a network utility optimization problem is used to adapt the CRE bias. The price is derived from the load status of each pico base station. The performance of the algorithm was evaluated by means of an LTE MATLAB toolbox. Simulations were conducted according to 3GPP and ITU guidelines for modelling heterogeneous networks and propagation environment respectively. Compared to a static CRE configuration, the algorithm achieved more fairness in load distribution. Further, it achieved a better trade-off between cell edge and cell centre user throughputs. [Please note: this thesis file has been deferred until December 2016
Soft handover issues in radio resource management for 3G WCDMA networks
PhDMobile terminals allow users to access services while on the move. This unique
feature has driven the rapid growth in the mobile network industry, changing it from a
new technology into a massive industry within less than two decades.
Handover is the essential functionality for dealing with the mobility of the mobile
users. Compared with the conventional hard handover employed in the GSM mobile
networks, the soft handover used in IS-95 and being proposed for 3G has better
performance on both link and system level.
Previous work on soft handover has led to several algorithms being proposed and
extensive research has been conducted on the performance analysis and parameters
optimisation of these algorithms. Most of the previous analysis focused on the uplink
direction. However, in future mobile networks, the downlink is more likely to be the
bottleneck of the system capacity because of the asymmetric nature of new services,
such as Internet traffic.
In this thesis, an in-depth study of the soft handover effects on the downlink
direction of WCDMA networks is carried out, leading to a new method of optimising
soft handover for maximising the downlink capacity and a new power control
approach
A survey of self organisation in future cellular networks
This article surveys the literature over the period of the last decade on the emerging field of self organisation as applied to wireless cellular communication networks. Self organisation has been extensively studied and applied in adhoc networks, wireless sensor networks and autonomic computer networks; however in the context of wireless cellular networks, this is the first attempt to put in perspective the various efforts in form of a tutorial/survey. We provide a comprehensive survey of the existing literature, projects and standards in self organising cellular networks. Additionally, we also aim to present a clear understanding of this active research area, identifying a clear taxonomy and guidelines for design of self organising mechanisms. We compare strength and weakness of existing solutions and highlight the key research areas for further development. This paper serves as a guide and a starting point for anyone willing to delve into research on self organisation in wireless cellular communication networks
Energy efficiency in heterogeneous wireless access networks
In this article, we bring forward the important aspect of energy savings in wireless access networks. We specifically focus on the energy saving opportunities in the recently evolving heterogeneous networks (HetNets), both Single- RAT and Multi-RAT. Issues such as sleep/wakeup cycles and interference management are discussed for co-channel Single-RAT HetNets. In addition to that, a simulation based study for LTE macro-femto HetNets is presented, indicating the need for dynamic energy efficient resource management schemes. Multi-RAT HetNets also come with challenges such as network integration, combined resource management and network selection. Along with a discussion on these challenges, we also investigate the performance of the conventional WLAN-first network selection mechanism in terms of energy efficiency (EE) and suggest that EE can be improved by the application of intelligent call admission control policies
Final report on the evaluation of RRM/CRRM algorithms
Deliverable public del projecte EVERESTThis deliverable provides a definition and a complete evaluation of the RRM/CRRM algorithms selected in D11 and D15, and evolved and refined on an iterative process. The evaluation will be carried out by means of simulations using the simulators provided at D07, and D14.Preprin
HARD HANDOVER OPTIMIZATION USING TIME WINDOW BASED HANDOVER ALGORITHM
ABSTRACT This paper shows and solves a handover problem occurring with current power control mechanisms in cochannel Wideband Code Division Multiple Access (WCDMA) heterogeneous networks. The problem is the mismatch between the required uplink transmits power when a user is communicating to a small cell and an underlying microcellular base-station. This paper introduces Time Window Handover (TWHO) algorithm to adapt the transmit power of the small cell users during the handover regime to prevent such Signal to Interference plus Noise Ratio (SINR) drops
Gestão comum de recursos rádio em redes sem fios de próxima geração
Mestrado em Electrónica e TelecomunicaçõesA tecnologia de sinais de rádio frequência sobre fibra óptica involve o uso
de links ópticos para transportar os sinais desde a unidade central de processamento
até aos sites remotos (e vice-versa). A centralização do processamento
dos sinais de rádio frequência permite a partilha de equipamentos,
alocação dinâmica de recursos e uma manutenção mais simplificada do sistema.
Embora o conceito de gestão comum dos recursos rádio tenha despertado
grande interesse na comunidade científica em termos da melhor utilização
desses recursos e de novos modelos de negócio, a verdade é que a sua implementação
não tem sido fácil. A interligação entre diferentes componentes
de rede, normalmente localizados em locais diferentes, introduz um grande
atraso nas comunicações; por outro lado as implementações proprietárias e
a escassez de informação global não satisfazem os requisitos de um ambiente
extremamente dinâmico, como é o ambiente wireless. Uma topologia
centralizada permite ultrapassar estas contrariedades, disponibilizando uma
interligação eficiente entre as entidades locais e comuns de gestão de recursos
rádio.
Nesta dissertação é apresentada uma nova arquitectura de gestão comum de
recursos rádio, baseada no conceito de interligação entre diferentes tecnologias
de acesso. Esta arquitectura faz a gestão dos recursos rádio de forma
centralizada, onde os sinais rádio chegam sem qualquer pré-processamento.
Essa arquitectura é avaliada com a implementação de um algoritmo simples
de balanceamento da carga que segue a politica de minimização da
interferência e aumento da capacidade.
As simulações com duas tecnologias de acesso, quando consideradas separas
ou em agregado, mostraram um aumento do débito de pelo menos 51% para
o mesmo valor de interferência enquanto que o erro de simbolo decresce pelo
menos 20%.Radio over fibre technology involves the use of optical fibre links to distribute
radio frequency signals from a central location to remote sites (and viceversa).
The centralisation of radio frequency signals processing functions
enables equipment sharing, dynamic allocation of resources, and simplified
system operation and maintenance.
Despite the unquestionable interest concept of common radio resource management
from the point of view of resource usage and novel business models,
its implementation has not been easy. The interworking between the different
local radio resource management entities, usually located on different
places will not satisfy the requirements of the wireless dynamic behaviour
due to increase of delay in communication process, less information availability
and proprietary implementations. A centralised topology can overcome
the drawbacks of former wireless systems architecture interconnection
by providing an efficient common radio communication flow with the local
radio resource management entities.
In this thesis a novel common radio resource management architecture is
presented based on the concept of inter-working between different technologies.
This is a centralised architecture where the radio frequency signals are
delivered to the central location through the optical links. The new architecture
is evaluated with a common policy that minimises interference while
the overall system capacity is increased. The policy is implemented through
the load balancing algorithm.
The simulations of two radio access technologies when separately and jointly
considered show that when the load balancing algorithm is applied the available
throughput increases in at least 51% while the symbol error rate decreases
at least 20%
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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