304 research outputs found
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
Quantifying Potential Energy Efficiency Gain in Green Cellular Wireless Networks
Conventional cellular wireless networks were designed with the purpose of
providing high throughput for the user and high capacity for the service
provider, without any provisions of energy efficiency. As a result, these
networks have an enormous Carbon footprint. In this paper, we describe the
sources of the inefficiencies in such networks. First we present results of the
studies on how much Carbon footprint such networks generate. We also discuss
how much more mobile traffic is expected to increase so that this Carbon
footprint will even increase tremendously more. We then discuss specific
sources of inefficiency and potential sources of improvement at the physical
layer as well as at higher layers of the communication protocol hierarchy. In
particular, considering that most of the energy inefficiency in cellular
wireless networks is at the base stations, we discuss multi-tier networks and
point to the potential of exploiting mobility patterns in order to use base
station energy judiciously. We then investigate potential methods to reduce
this inefficiency and quantify their individual contributions. By a
consideration of the combination of all potential gains, we conclude that an
improvement in energy consumption in cellular wireless networks by two orders
of magnitude, or even more, is possible.Comment: arXiv admin note: text overlap with arXiv:1210.843
Improved interference management techniques for multi-cell multi-user MIMO systems
One major limiting factor for wireless communication systems is the limited available bandwidth for cellular networks. Current technologies like Long Term Evolution (LTE) and LTE-Advanced (LTE-A) have standardised a frequency reuse factor of 1 to enable more channel resources in each cell. Also multi-layer networks that consist of overlapping macro cells and small cells like pico cells, micro cells and femto cells have also been used to improve the capacity of the cellular network system. These multi-layer networks are known as heterogeneous networks or HetNets while the single layer, traditional cellular systems are referred to as homogeneous networks or HomoNets.
Several interference management systems and techniques have been proposed in the past to deal with the effect of inter-cell interference (ICI) (i.e., the interference from a macro cell base station (BS) to a macro cell user in another macro cell) and inter-user interference (IUI) (i.e., the interference of another user's data signal to a given user within the same cell on the same time and frequency slot). Interference cancellation techniques such as beamforming, uses transmit pre-coders and receive beam-formers to limit the effect of interference. The interference alignment strategy ensures that the interference is aligned into a given subspace and leaves a residual subspace free for the desired signal. Coordinated scheduling/beam-forming and coordinated multi-point transmission (CoMP) have also been used to limit the interference within the cellular network. For HetNets, interference avoidance techniques based on radio resource management (RRM) have been used to limit the effect of interference within the network and improve the attainable system capacity. This thesis investigates the challenges of two main interference management techniques and proposes methods to alleviate these issues without impeding the expected performance already attained. The main techniques considered for HomoNets and HetNets are: CoMP transmission under the interference cancellation technique and resource block allocation (RBA) under the interference avoidance technique. The setbacks for the well known CoMP transmission strategy are high data overhead, energy consumption and other associated costs to the network provider. Further investigations were carried out and a joint selection of transmit antennas for the users was proposed with the main aim of preserving or exceeding the already achieved gains but obtaining a further reduction in the data overhead.
Fully distributed RBA solutions are required, especially since future networks tend to become self-organising networks (SON). Another major consideration in choosing the resource blocks (RBs) for the users in each cell is the RBA metric. Since the capacity of the cell is dependent on the sum-rate of the users, it is important to consider the maximisation of the sum-rate or sum-SINR (i.e the sum signal to interference and noise ratio) when assigning RBs to users. The RBA technique aims to choose the RBs such that the interference within the cell is avoided. To achieve this, a RBA metric is required to obtain the qualification matrix before allocating RBs to the users. Many authors in the past have proposed several metrics for RBA but avoided any RBA metric that required a direct estimation of the interference power on each RB for each user's allocation. This is because the SINR or interference power on each RB for any user can only be obtained with pre-knowledge of already occupied RBs in neighbouring cells. In this thesis, two distributed RBA solutions based on a direct interference estimation was proposed to obtain the required qualification matrix for the RBA under the HomoNet and HetNet system models. The gains and advantages obtained are shown and analysed using the obtained simulation results.
The issue of interference coupled with limited available channels remains a major limiting factor for HetNets. Therefore, it is very important to develop techniques that maximise the utilisation of available bandwidth for each cell while minimising possible interference from neighbouring cells. Finally, this thesis considers and investigates a possible joint solution using both interference avoidance and interference mitigation techniques. Hence two solutions are proposed: joint RBA plus beam-forming and joint RBA plus CoMP transmission, to further mitigate the high interference in HetNets. The simulation results have shown significantly improved system performance especially for a highly dense HetNet
An Efficient Uplink Multi-Connectivity Scheme for 5G mmWave Control Plane Applications
The millimeter wave (mmWave) frequencies offer the potential of orders of
magnitude increases in capacity for next-generation cellular systems. However,
links in mmWave networks are susceptible to blockage and may suffer from rapid
variations in quality. Connectivity to multiple cells - at mmWave and/or
traditional frequencies - is considered essential for robust communication. One
of the challenges in supporting multi-connectivity in mmWaves is the
requirement for the network to track the direction of each link in addition to
its power and timing. To address this challenge, we implement a novel uplink
measurement system that, with the joint help of a local coordinator operating
in the legacy band, guarantees continuous monitoring of the channel propagation
conditions and allows for the design of efficient control plane applications,
including handover, beam tracking and initial access. We show that an
uplink-based multi-connectivity approach enables less consuming, better
performing, faster and more stable cell selection and scheduling decisions with
respect to a traditional downlink-based standalone scheme. Moreover, we argue
that the presented framework guarantees (i) efficient tracking of the user in
the presence of the channel dynamics expected at mmWaves, and (ii) fast
reaction to situations in which the primary propagation path is blocked or not
available.Comment: Submitted for publication in IEEE Transactions on Wireless
Communications (TWC
Analysis of hybrid schedulers for CoMP resource allocation in LTE-Advanced SU-MIMO systems
Coordinated Multi Point transmission and reception (CoMP) has been considered as a promising technique to enhance system throughput performance by reducing inter-cell interference (ICI) in cell edge area. Past studies showed that Joint Processing (JP) transmission mode is capable to provide much better throughput performance benefits than Coordinated Scheduling/Beamforming (CS/CB) both in homogeneous and heterogeneous networks; however, the robust strategy of resource block (RB) allocation and scheduling algorithms has to be specifically designed for CoMP-JP in a MIMO-OFDMA system. In this paper, an intuitive algorithm will be investigated in order to reach the highest overall system throughput but keep same level of fairness performance at same time. We first analyze the threshold of reference signal strength to determine the operating region for CoMP-JP user selection, and then calculate the robust ratio of RB allocation for CoMP and non-CoMP users. In final stage, the hybrid schedulers adopted specifically for the unique characteristics of CoMP and non-CoMP users will be analyzed and compared. Our results show that the threshold of reference signal strength should both be set at -1dB for CoMP operating region, and the parameter to the ratio of CoMP users should be set at for robust RB allocation
Eficiência energética avançada para sistema OFDMA CoMP coordenação multiponto
Doutoramento em Engenharia EletrotécnicaThe ever-growing energy consumption in mobile networks stimulated by
the expected growth in data tra ffic has provided the impetus for mobile
operators to refocus network design, planning and deployment towards reducing
the cost per bit, whilst at the same time providing a signifi cant step
towards reducing their operational expenditure. As a step towards incorporating
cost-eff ective mobile system, 3GPP LTE-Advanced has adopted the
coordinated multi-point (CoMP) transmission technique due to its ability
to mitigate and manage inter-cell interference (ICI). Using CoMP the cell
average and cell edge throughput are boosted. However, there is room for
reducing energy consumption further by exploiting the inherent
exibility of
dynamic resource allocation protocols. To this end packet scheduler plays
the central role in determining the overall performance of the 3GPP longterm
evolution (LTE) based on packet-switching operation and provide a
potential research playground for optimizing energy consumption in future
networks. In this thesis we investigate the baseline performance for down
link CoMP using traditional scheduling approaches, and subsequently go
beyond and propose novel energy e fficient scheduling (EES) strategies that
can achieve power-e fficient transmission to the UEs whilst enabling both
system energy effi ciency gain and fairness improvement. However, ICI can
still be prominent when multiple nodes use common resources with di fferent
power levels inside the cell, as in the so called heterogeneous networks (Het-
Net) environment. HetNets are comprised of two or more tiers of cells. The
rst, or higher tier, is a traditional deployment of cell sites, often referred
to in this context as macrocells. The lower tiers are termed small cells, and
can appear as microcell, picocells or femtocells. The HetNet has attracted
signiffi cant interest by key manufacturers as one of the enablers for high
speed data at low cost. Research until now has revealed several key hurdles
that must be overcome before HetNets can achieve their full potential:
bottlenecks in the backhaul must be alleviated, as well as their seamless
interworking with CoMP. In this thesis we explore exactly the latter hurdle,
and present innovative ideas on advancing CoMP to work in synergy with
HetNet deployment, complemented by a novel resource allocation policy
for HetNet tighter interference management. As system level simulator has
been used to analyze the proposed algorithm/protocols, and results have
concluded that up to 20% energy gain can be observed.O aumento do consumo de energia nas TICs e em particular nas redes de
comunicação móveis, estimulado por um crescimento esperado do tráfego de
dados, tem servido de impulso aos operadores m oveis para reorientarem os
seus projectos de rede, planeamento e implementa ção no sentido de reduzir
o custo por bit, o que ao mesmo tempo possibilita um passo signicativo no
sentido de reduzir as despesas operacionais. Como um passo no sentido de
uma incorporação eficaz em termos destes custos, o sistema móvel 3GPP
LTE-Advanced adoptou a técnica de transmissão Coordenação Multi-Ponto
(identificada na literatura com a sigla CoMP) devido à sua capacidade de
mitigar e gerir Interferência entre Células (sigla ICI na literatura). No entanto
a ICI pode ainda ser mais proeminente quando v arios n os no interior
da célula utilizam recursos comuns com diferentes nÃveis de energia,
como acontece nos chamados ambientes de redes heterogéneas (sigla Het-
Net na literatura). As HetNets são constituÃdas por duas ou mais camadas
de células. A primeira, ou camada superiora, constitui uma implantação
tradicional de sÃtios de célula, muitas vezes referidas neste contexto como
macrocells. Os nÃveis mais baixos são designados por células pequenas, e
podem aparecer como microcells, picocells ou femtocells. A HetNet tem
atra do grande interesse por parte dos principais fabricantes como sendo
facilitador para transmissões de dados de alta velocidade a baixo custo. A
investigação tem revelado at e a data, vários dos principais obstáculos que
devem ser superados para que as HetNets possam atingir todo o seu potencial:
(i) os estrangulamentos no backhaul devem ser aliviados; (ii) bem
como sua perfeita interoperabilidade com CoMP. Nesta tese exploramos
este ultimo constrangimento e apresentamos ideias inovadoras em como a
t ecnica CoMP poder a ser aperfeiçoada por forma a trabalhar em sinergia
com a implementação da HetNet, complementado ainda com uma nova
perspectiva na alocação de recursos rádio para um controlo e gestão mais
apertado de interferência nas HetNets. Com recurso a simulação a nÃÃvel de
sistema para analisar o desempenho dos algoritmos e protocolos propostos,
os resultados obtidos concluÃram que ganhos at e a ordem dos 20% poderão
ser atingidos em termos de eficiência energética
Evolution Toward 5G Mobile Networks - A Survey on Enabling Technologies
In this paper, an extensive review has been carried out on the trends of existing as well as proposed potential enabling technologies that are expected to shape the fifth generation (5G) mobile wireless networks. Based on the classification of the trends, we develop a 5G network architectural evolution framework that comprises three evolutionary directions, namely, (1) radio access network node and performance enabler, (2) network control programming platform, and (3) backhaul network platform and synchronization. In (1), we discuss node classification including low power nodes in emerging machine-type communications, and network capacity enablers, e.g., millimeter wave communications and massive multiple-input multiple-output. In (2), both logically distributed cell/device-centric platforms, and logically centralized conventional/wireless software defined networking control programming approaches are discussed. In (3), backhaul networks and network synchronization are discussed. A comparative analysis for each direction as well as future evolutionary directions and challenges toward 5G networks are discussed. This survey will be helpful for further research exploitations and network operators for a smooth evolution of their existing networks toward 5G networks
D 3. 3 Final performance results and consolidated view on the most promising multi -node/multi -antenna transmission technologies
This document provides the most recent updates on the technical contributions and research
challenges focused in WP3. Each Technology Component (TeC) has been evaluated
under possible uniform assessment framework of WP3 which is based on the simulation guidelines
of WP6. The performance assessment is supported by the simulation results which are in their
mature and stable state. An update on the Most Promising Technology Approaches (MPTAs)
and their associated TeCs is the main focus of this document. Based on the input of all the TeCs in WP3, a consolidated view of WP3 on the role of multinode/multi-antenna transmission
technologies in 5G systems has also been provided. This consolidated view is further
supported in this document by the presentation of the impact of MPTAs on METIS scenarios
and the addressed METIS goals.Aziz, D.; Baracca, P.; De Carvalho, E.; Fantini, R.; Rajatheva, N.; Popovski, P.; Sørensen, JH.... (2015). D 3. 3 Final performance results and consolidated view on the most promising multi -node/multi -antenna transmission technologies. http://hdl.handle.net/10251/7675
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