5,203 research outputs found
Handoff Rate and Coverage Analysis in Multi-tier Heterogeneous Networks
This paper analyzes the impact of user mobility in multi-tier heterogeneous
networks. We begin by obtaining the handoff rate for a mobile user in an
irregular cellular network with the access point locations modeled as a
homogeneous Poisson point process. The received signal-to-interference-ratio
(SIR) distribution along with a chosen SIR threshold is then used to obtain the
probability of coverage. To capture potential connection failures due to
mobility, we assume that a fraction of handoffs result in such failures.
Considering a multi-tier network with orthogonal spectrum allocation among
tiers and the maximum biased average received power as the tier association
metric, we derive the probability of coverage for two cases: 1) the user is
stationary (i.e., handoffs do not occur, or the system is not sensitive to
handoffs); 2) the user is mobile, and the system is sensitive to handoffs. We
derive the optimal bias factors to maximize the coverage. We show that when the
user is mobile, and the network is sensitive to handoffs, both the optimum tier
association and the probability of coverage depend on the user's speed; a
speed-dependent bias factor can then adjust the tier association to effectively
improve the coverage, and hence system performance, in a fully-loaded network.Comment: Accepted for publication in the IEEE Transactions on Wireless
Communication
Small Cell Deployments: Recent Advances and Research Challenges
This paper summarizes the outcomes of the 5th International Workshop on
Femtocells held at King's College London, UK, on the 13th and 14th of February,
2012.The workshop hosted cutting-edge presentations about the latest advances
and research challenges in small cell roll-outs and heterogeneous cellular
networks. This paper provides some cutting edge information on the developments
of Self-Organizing Networks (SON) for small cell deployments, as well as
related standardization supports on issues such as carrier aggregation (CA),
Multiple-Input-Multiple-Output (MIMO) techniques, and enhanced Inter-Cell
Interference Coordination (eICIC), etc. Furthermore, some recent efforts on
issues such as energy-saving as well as Machine Learning (ML) techniques on
resource allocation and multi-cell cooperation are described. Finally, current
developments on simulation tools and small cell deployment scenarios are
presented. These topics collectively represent the current trends in small cell
deployments.Comment: 19 pages, 22 figure
Massive MIMO and Millimeter Wave for 5G Wireless HetNet: Potentials and Challenges
There have been active research activities worldwide in developing the
next-generation 5G wireless network. The 5G network is expected to support
significantly large amount of mobile data traffic and huge number of wireless
connections, achieve better cost- and energy-efficiency as well as quality of
service (QoS) in terms of communication delay, reliability and security. To
this end, the 5G wireless network should exploit potential gains in different
network dimensions including super dense and heterogeneous deployment of cells
and massive antenna arrays (i.e., massive multiple input multiple output (MIMO)
technologies) and utilization of higher frequencies, in particular millimeter
wave (mmWave) frequencies. This article discusses potentials and challenges of
the 5G heterogeneous wireless network (HetNet) which incorporates massive MIMO
and mmWave technologies. We will first provide the typical requirements of the
5G wireless network. Then, the significance of massive MIMO and mmWave in
engineering the future 5G HetNet is discussed in detail. Potential challenges
associated with the design of such 5G HetNet are discussed. Finally, we provide
some case studies, which illustrate the potential benefits of the considered
technologies.Comment: IEEE Vehicular Technology Magazine (To appear
Analytical model for mobile user connectivity in coexisting femtocell/macrocell networks
In this paper we investigate the performance of mobile user connectivity in
femtocell/macrocell networks. The femto user equipment (FUE) can connect to
femto access point (FAP) with low communication range rather than higher
communication range to macro base station (MBS). Furthermore, in such emerging
networks, the spatial reuse of resources is permissible and the transmission
range can be decreased, then the probability of connectivity is high. Thereby
in this study, we propose a tractable analytical model for the connectivity
probability based on communication range and the mobility of mobile users in
femtocell/macrocell networks. Further, we study the interplays between outage
probability and spectral efficiency in such networks. Numerical results
demonstrate the effectiveness of computing the connectivity probability in
femtocell/macrocell networks
Heterogeneous Cloud Radio Access Networks: A New Perspective for Enhancing Spectral and Energy Efficiencies
To mitigate the severe inter-tier interference and enhance limited
cooperative gains resulting from the constrained and non-ideal transmissions
between adjacent base stations in heterogeneous networks (HetNets),
heterogeneous cloud radio access networks (H-CRANs) are proposed as
cost-efficient potential solutions through incorporating the cloud computing
into HetNets. In this article, state-of-the-art research achievements and
challenges on H-CRANs are surveyed. In particular, we discuss issues of system
architectures, spectral and energy efficiency performances, and promising key
techniques. A great emphasis is given towards promising key techniques in
H-CRANs to improve both spectral and energy efficiencies, including cloud
computing based coordinated multi-point transmission and reception, large-scale
cooperative multiple antenna, cloud computing based cooperative radio resource
management, and cloud computing based self-organizing network in the cloud
converging scenarios. The major challenges and open issues in terms of
theoretical performance with stochastic geometry, fronthaul constrained
resource allocation, and standard development that may block the promotion of
H-CRANs are discussed as well.Comment: 20 pages, 6 figures, to be published in IEEE Wireless Communication
Distributed Downlink Power Control for Dense Networks with Carrier Aggregation
Given the proven benefits cell densification brings in terms of capacity and
coverage, it is certain that 5G networks will be even more heterogeneous and
dense. However, as smaller cells are introduced in the network, interference
will inevitably become a serious problem as they are expected to share the same
radio resources. Another central feature envisioned for future cellular
networks is carrier aggregation (CA), which allows users to simultaneously use
several component carriers of various widths and frequency bands. By exploiting
the diversity of the different carriers, CA can also be used to effectively
mitigate the interference in the network. In this paper, we leverage the above
key features of next-generation cellular networks and formulate a downlink
power setting problem for the different available carriers. Using game theory,
we design a distributed algorithm that lets cells dynamically adjust different
transmit powers for the different carriers. The proposed solution greatly
improves network performance by reducing interference and power consumption,
while ensuring coverage for as many users as possible. We compare our scheme to
other interference mitigation techniques, in a realistic large-scale scenario.
Numerical results show that our solution outperforms the existing schemes in
terms of user throughput, energy and spectral efficiency.Comment: Accepted for publication in IEEE Transactions of Wireless
Communication
Load Balancing Optimization in LTE/LTE-A Cellular Networks: A Review
During the past few decades wireless technology has seen a tremendous growth.
The recent introduction of high-end mobile devices has further increased
subscriber's demand for high bandwidth. Current cellular systems require manual
configuration and management of networks, which is now costly, time consuming
and error prone due to exponentially increasing rate of mobile users and nodes.
This leads to introduction of self organizing capabilities for network
management with minimum human involvement. It is expected to permit higher end
user Quality of Service (QoS) along with less operational and maintenance cost
for telecom service providers. Self organized cellular networks incorporate a
collection of functions for automatic configuration, optimization and
maintenance of cellular networks. As mobile end users continue to use network
resources while moving from a cell boundary to other, traffic load within a
cell does not remain constant. Thus Load balancing as a part of self organized
network solution, has become one of the most active and emerging fields of
research in Cellular Network. It involves transfer of load from overloaded
cells to the neighbouring cells with free resources for more balanced load
distribution in order to maintain appropriate end-user experience and network
performance. In this paper, review of various load balancing techniques
currently used in mobile networks is presented, with special emphasis on
techniques that are suitable for self optimization feature in future cellular
networks.Comment: Preprin
Handover Management in Dense Cellular Networks: A Stochastic Geometry Approach
Cellular operators are continuously densifying their networks to cope with
the ever-increasing capacity demand. Furthermore, an extreme densification
phase for cellular networks is foreseen to fulfill the ambitious fifth
generation (5G) performance requirements. Network densification improves
spectrum utilization and network capacity by shrinking base stations' (BSs)
footprints and reusing the same spectrum more frequently over the spatial
domain. However, network densification also increases the handover (HO) rate,
which may diminish the capacity gains for mobile users due to HO delays. In
highly dense 5G cellular networks, HO delays may neutralize or even negate the
gains offered by network densification. In this paper, we present an analytical
paradigm, based on stochastic geometry, to quantify the effect of HO delay on
the average user rate in cellular networks. To this end, we propose a flexible
handover scheme to reduce HO delay in case of highly dense cellular networks.
This scheme allows skipping the HO procedure with some BSs along users'
trajectories. The performance evaluation and testing of this scheme for only
single HO skipping shows considerable gains in many practical scenarios.Comment: 7 pages, 7 figures, ICC 201
Hierarchical Cellular Structures in High-Capacity Cellular Communication Systems
In the prevailing cellular environment, it is important to provide the
resources for the fluctuating traffic demand exactly in the place and at the
time where and when they are needed. In this paper, we explored the ability of
hierarchical cellular structures with inter layer reuse to increase the
capacity of mobile communication network by applying total frequency hopping
(T-FH) and adaptive frequency allocation (AFA) as a strategy to reuse the macro
and micro cell resources without frequency planning in indoor pico cells [11].
The practical aspects for designing macro- micro cellular overlays in the
existing big urban areas are also explained [4]. Femto cells are inducted in
macro / micro / pico cells hierarchical structure to achieve the required QoS
cost effectively.Comment: 7 pages, 8 figures, International Journa
Toward Operator-to-Waveform 5G Radio Access Network Slicing
Radio access network (RAN) slicing realizes a vision where physical network
resources that belong to a specific infrastructure provider can be shared among
multiple mobile network operators (MNOs). Existing work in this area has
addressed RAN slicing at different levels of network abstractions, but has
often neglected the multitude of tightly intertwined inter-level operations
involved in real-world slicing systems. For this reason, this article discusses
a novel framework for operator-to-waveform 5G RAN slicing. In the proposed
framework, slicing operations are treated holistically, including MNO's
selection of base stations (BSs) and maximum number of users, down to the
waveform-level scheduling of resource blocks. Experimental results show that
the proposed framework provides up to 150% improvement in terms of number of
resource blocks that can be used to enable 5G transmission technologies that
require coordination and synchronization among BSs
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