604 research outputs found
Wireless Cellular Networks
When aiming for achieving high spectral efficiency in wireless cellular networks, cochannel interference (CCI) becomes the dominant performancelimiting factor. This article provides a survey of CCI mitigation techniques, where both active and passive approaches are discussed in the context of both open- and closed-loop designs.More explicitly, we considered both the family of flexible frequency-reuse (FFR)-aided and dynamic channel allocation (DCA)-aided interference avoidance techniques as well as smart antenna-aided interference mitigation techniques, which may be classified as active approach
Separation Framework: An Enabler for Cooperative and D2D Communication for Future 5G Networks
Soaring capacity and coverage demands dictate that future cellular networks
need to soon migrate towards ultra-dense networks. However, network
densification comes with a host of challenges that include compromised energy
efficiency, complex interference management, cumbersome mobility management,
burdensome signaling overheads and higher backhaul costs. Interestingly, most
of the problems, that beleaguer network densification, stem from legacy
networks' one common feature i.e., tight coupling between the control and data
planes regardless of their degree of heterogeneity and cell density.
Consequently, in wake of 5G, control and data planes separation architecture
(SARC) has recently been conceived as a promising paradigm that has potential
to address most of aforementioned challenges. In this article, we review
various proposals that have been presented in literature so far to enable SARC.
More specifically, we analyze how and to what degree various SARC proposals
address the four main challenges in network densification namely: energy
efficiency, system level capacity maximization, interference management and
mobility management. We then focus on two salient features of future cellular
networks that have not yet been adapted in legacy networks at wide scale and
thus remain a hallmark of 5G, i.e., coordinated multipoint (CoMP), and
device-to-device (D2D) communications. After providing necessary background on
CoMP and D2D, we analyze how SARC can particularly act as a major enabler for
CoMP and D2D in context of 5G. This article thus serves as both a tutorial as
well as an up to date survey on SARC, CoMP and D2D. Most importantly, the
article provides an extensive outlook of challenges and opportunities that lie
at the crossroads of these three mutually entangled emerging technologies.Comment: 28 pages, 11 figures, IEEE Communications Surveys & Tutorials 201
Interference mitigation in cognitive femtocell networks
âA thesis submitted to the University of Bedfordshire, in partial fulfilment of the requirements for the degree of Doctor of Philosophyâ.Femtocells have been introduced as a solution to poor indoor coverage in cellular communication which has hugely attracted network operators and stakeholders. However, femtocells are designed to co-exist alongside macrocells providing improved spatial frequency reuse and higher spectrum efficiency to name a few. Therefore, when deployed in the two-tier architecture with macrocells, it is necessary to mitigate the inherent co-tier and cross-tier
interference. The integration of cognitive radio (CR) in femtocells introduces the ability of femtocells to dynamically adapt to varying network conditions through learning and reasoning.
This research work focuses on the exploitation of cognitive radio in femtocells to mitigate the mutual interference caused in the two-tier architecture. The research work presents original contributions in mitigating interference in femtocells by introducing practical approaches which comprises a power control scheme where femtocells adaptively controls its transmit power levels to reduce the interference it causes in a network. This is especially useful since femtocells are user deployed as this seeks to mitigate interference based on their blind placement in an indoor environment. Hybrid interference mitigation schemes which combine power control and resource/scheduling are also implemented. In a joint threshold power based admittance and contention free resource allocation scheme, the mutual interference between a Femtocell Access Point (FAP) and close-by User Equipments (UE) is mitigated based on admittance. Also, a hybrid scheme where FAPs opportunistically use Resource Blocks (RB) of Macrocell User Equipments (MUE) based on its traffic load use is also employed. Simulation analysis present improvements when these schemes are applied with emphasis in Long Term
Evolution (LTE) networks especially in terms of Signal to Interference plus Noise Ratio (SINR)
A Survey of Physical Layer Security Techniques for 5G Wireless Networks and Challenges Ahead
Physical layer security which safeguards data confidentiality based on the
information-theoretic approaches has received significant research interest
recently. The key idea behind physical layer security is to utilize the
intrinsic randomness of the transmission channel to guarantee the security in
physical layer. The evolution towards 5G wireless communications poses new
challenges for physical layer security research. This paper provides a latest
survey of the physical layer security research on various promising 5G
technologies, including physical layer security coding, massive multiple-input
multiple-output, millimeter wave communications, heterogeneous networks,
non-orthogonal multiple access, full duplex technology, etc. Technical
challenges which remain unresolved at the time of writing are summarized and
the future trends of physical layer security in 5G and beyond are discussed.Comment: To appear in IEEE Journal on Selected Areas in Communication
Recent advances in radio resource management for heterogeneous LTE/LTE-A networks
As heterogeneous networks (HetNets) emerge as one of the most promising developments toward realizing the target specifications of Long Term Evolution (LTE) and LTE-Advanced (LTE-A) networks, radio resource management (RRM) research for such networks has, in recent times, been intensively pursued. Clearly, recent research mainly concentrates on the aspect of interference mitigation. Other RRM aspects, such as radio resource utilization, fairness, complexity, and QoS, have not been given much attention. In this paper, we aim to provide an overview of the key challenges arising from HetNets and highlight their importance. Subsequently, we present a comprehensive survey of the RRM schemes that have been studied in recent years for LTE/LTE-A HetNets, with a particular focus on those for femtocells and relay nodes. Furthermore, we classify these RRM schemes according to their underlying approaches. In addition, these RRM schemes are qualitatively analyzed and compared to each other. We also identify a number of potential research directions for future RRM development. Finally, we discuss the lack of current RRM research and the importance of multi-objective RRM studies
Implementação e avaliação no system generator de um sistema cooperativo para os futuros sistemas 5G
With the arrival of 5G it is expected the proliferation of services in the
different fields such as healthcare, utility applications, industrial automation,
4K streaming, that the former networks can not provide. Additionally,
the total number of wireless communication devices will escalate in such
a manner that the already scarce available frequency bandwidth wonât be
enough to pack the intended objectives. Ciscoâs Annual Internet Report from
2018 predicts that by 2023 there will be nearly 30 billion devices capable of
wireless communication. Due to the exponential expiation of both services
and devices, the challenges upon both network data capacity and efficient
radio resourse use will be greater than ever, thus the urgency for solutions
is grand.
Both the capacity for wireless communications and spectral efficiency are
related to cell size and its users proximity to the access point. Thus,
shortening the distance between the transmitter and the receiver improves
both aspects of the network. This concept is what motivates the
implementation of heterogeneous networks, HetNets, that are composed
of many different small-cells, SCs, overlaid across the same coexisting
area of a conventional macro-cell, shortening the distance between the
cell users and its access point transceivers, granting a better coverage and
higher data rates. However, the HetNets potential does not come without
any challenges, as these networks suffer considerably from communication
interference between cells.
Although some interference management algorithms that allow coexistence
between cells have been proposed in recent years, most of them were
evaluated by software simulations and not implemented in real-time
platforms. Therefore, this master thesis aims to give the first step on the
implementation and evaluation of an interference mitigation technique in
hardware. Specifically, it is assumed a downlink scenario composed by a
macro-cell base station, a macro-cell primary user and a small cell user,
with the aim of implementing an algorithm that eliminates the downlink
interference that the base station may cause to the secondary users. The
study was carried out using the System Generator DSP tool, which is a tool
that generates code for hardware from schematics created in it. This tool
also offers a wide range of blocks that help the creation, and fundamentally,
the simulation and study of the system to be implemented, before being
translated into hardware. The results obtained in this work are a faithful
representation of the behavior of the implemented system, which can be
used for a future application for FPGA.Com a chegada do 5G, espera-se a proliferação de serviços nas mais diversas
ĂĄreas tal como assistĂȘncia mĂ©dica, automação industrial, transmissĂŁo em
4k, que nĂŁo eram possĂveis nas redes das geraçÔes anteriores. AlĂ©m deste
fenĂłmeno, o nĂșmero total de dispositivos capazes de conexĂ”es wireless
aumentarĂĄ de tal maneira que a escassa largura de banda disponĂvel nĂŁo
serĂĄ suficiente para abranger os objetivos pretendidos. O RelatĂłrio Anual
de 2018 sobre a Internet da Cisco prevĂȘ que atĂ© 2023 haverĂĄ quase 30
bilhÔes de dispositivos capazes de comunicação sem fio. Devido ao aumento
exponencial de serviços e dispositivos, os desafios sobre a capacidade de
dados da rede e o udo eficiente dos recursos de rĂĄdio serĂŁo maiores que
nunca. Por estes motivos, a necessidade de soluçÔes para estas lacunas é
enorme.
Tanto a capacidade da rede e o uso eficiente do espectro de frequĂȘncias
estão relacionados ao tamanho da célula e à proximidade dos usuårios com
o ponto de acesso da célula. Ao encurtar a distùncia entre o transmissor e
o recetor ocorre um melhoramento destes dois aspetos da rede. Este Ă© o
principal conceito na implementação de redes heterogéneas, HetNets, que
são compostas por diversas células pequenas que coexistem na årea de uma
macro cĂ©lula convencional, diminuĂdo a distĂąncia entre os utilizadores da
célula e os pontos de acesso, garantindo uma melhor cobertura e taxa de
dados mais elevadas. No entanto, o potencial das HatNets nĂŁo vem sem
nenhum custo, pois estas redes sofrem consideravelmente de interferĂȘncia
entre as células.
Embora nos Ășltimos anos foram propostos alguns algoritmos que permitem
a coexistĂȘncia das cĂ©lulas, a maioria destes foi sĂł testado em simulaçÔes
de software e nĂŁo em plataformas em tempo real. Por esse motivo, esta
dissertação de mestrado visa dar o primeiro passo na implementação e
a avaliação de uma tĂ©cnica de mitigação de interferĂȘncia em hardware.
Mais especificamente no cenårio de downlink entre uma estação base de
uma macro célula, um utilizador primårio da macro célula e um utilizador
secundårio de uma célula pequena, com o principal objetivo de cancelar a
interferĂȘncia que a estação base possa fazer ao utilizador secundĂĄrio. O
estudo foi realizado utilizando a ferramenta System Generator DSP, que Ă©
uma ferramenta que gera cĂłdigo para hardware a partir de esquemĂĄticos
criados na mesma. Esta ferramenta também oferece uma vasta gama de
blocos que ajudam a criação, e fundamentalmente, a simulação e o estudo do
sistema a implementar antes de ser traduzido para hardware. Os resultados
obtidos neste trabalho são uma fiel representação do comportamento do
sistema implementado. O quais podem ser utilizados para uma futura
aplicação para FPGA.Mestrado em Engenharia Eletrónica e TelecomunicaçÔe
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