9,260 research outputs found
Performance Comparison of Dual Connectivity and Hard Handover for LTE-5G Tight Integration in mmWave Cellular Networks
MmWave communications are expected to play a major role in the Fifth
generation of mobile networks. They offer a potential multi-gigabit throughput
and an ultra-low radio latency, but at the same time suffer from high isotropic
pathloss, and a coverage area much smaller than the one of LTE macrocells. In
order to address these issues, highly directional beamforming and a very
high-density deployment of mmWave base stations were proposed. This Thesis aims
to improve the reliability and performance of the 5G network by studying its
tight and seamless integration with the current LTE cellular network. In
particular, the LTE base stations can provide a coverage layer for 5G mobile
terminals, because they operate on microWave frequencies, which are less
sensitive to blockage and have a lower pathloss. This document is a copy of the
Master's Thesis carried out by Mr. Michele Polese under the supervision of Dr.
Marco Mezzavilla and Prof. Michele Zorzi. It will propose an LTE-5G tight
integration architecture, based on mobile terminals' dual connectivity to LTE
and 5G radio access networks, and will evaluate which are the new network
procedures that will be needed to support it. Moreover, this new architecture
will be implemented in the ns-3 simulator, and a thorough simulation campaign
will be conducted in order to evaluate its performance, with respect to the
baseline of handover between LTE and 5G.Comment: Master's Thesis carried out by Mr. Michele Polese under the
supervision of Dr. Marco Mezzavilla and Prof. Michele Zorz
White Paper on Critical and Massive Machine Type Communication Towards 6G
The society as a whole, and many vertical sectors in particular, is becoming
increasingly digitalized. Machine Type Communication (MTC), encompassing its
massive and critical aspects, and ubiquitous wireless connectivity are among
the main enablers of such digitization at large. The recently introduced 5G New
Radio is natively designed to support both aspects of MTC to promote the
digital transformation of the society. However, it is evident that some of the
more demanding requirements cannot be fully supported by 5G networks.
Alongside, further development of the society towards 2030 will give rise to
new and more stringent requirements on wireless connectivity in general, and
MTC in particular. Driven by the societal trends towards 2030, the next
generation (6G) will be an agile and efficient convergent network serving a set
of diverse service classes and a wide range of key performance indicators
(KPI). This white paper explores the main drivers and requirements of an
MTC-optimized 6G network, and discusses the following six key research
questions:
- Will the main KPIs of 5G continue to be the dominant KPIs in 6G; or will
there emerge new key metrics?
- How to deliver different E2E service mandates with different KPI
requirements considering joint-optimization at the physical up to the
application layer?
- What are the key enablers towards designing ultra-low power receivers and
highly efficient sleep modes?
- How to tackle a disruptive rather than incremental joint design of a
massively scalable waveform and medium access policy for global MTC
connectivity?
- How to support new service classes characterizing mission-critical and
dependable MTC in 6G?
- What are the potential enablers of long term, lightweight and flexible
privacy and security schemes considering MTC device requirements?Comment: White paper by http://www.6GFlagship.co
Towards Massive Machine Type Cellular Communications
Cellular networks have been engineered and optimized to carrying
ever-increasing amounts of mobile data, but over the last few years, a new
class of applications based on machine-centric communications has begun to
emerge. Automated devices such as sensors, tracking devices, and meters - often
referred to as machine-to-machine (M2M) or machine-type communications (MTC) -
introduce an attractive revenue stream for mobile network operators, if a
massive number of them can be efficiently supported. The novel technical
challenges posed by MTC applications include increased overhead and control
signaling as well as diverse application-specific constraints such as ultra-low
complexity, extreme energy efficiency, critical timing, and continuous data
intensive uploading. This paper explains the new requirements and challenges
that large-scale MTC applications introduce, and provides a survey on key
techniques for overcoming them. We focus on the potential of 4.5G and 5G
networks to serve both the high data rate needs of conventional human-type
communications (HTC) subscribers and the forecasted billions of new MTC
devices. We also opine on attractive economic models that will enable this new
class of cellular subscribers to grow to its full potential.Comment: accepted and to appear in the IEEE Wireless Communications Magazin
Wearable Communications in 5G: Challenges and Enabling Technologies
As wearable devices become more ingrained in our daily lives, traditional
communication networks primarily designed for human being-oriented applications
are facing tremendous challenges. The upcoming 5G wireless system aims to
support unprecedented high capacity, low latency, and massive connectivity. In
this article, we evaluate key challenges in wearable communications. A
cloud/edge communication architecture that integrates the cloud radio access
network, software defined network, device to device communications, and
cloud/edge technologies is presented. Computation offloading enabled by this
multi-layer communications architecture can offload computation-excessive and
latency-stringent applications to nearby devices through device to device
communications or to nearby edge nodes through cellular or other wireless
technologies. Critical issues faced by wearable communications such as short
battery life, limited computing capability, and stringent latency can be
greatly alleviated by this cloud/edge architecture. Together with the presented
architecture, current transmission and networking technologies, including
non-orthogonal multiple access, mobile edge computing, and energy harvesting,
can greatly enhance the performance of wearable communication in terms of
spectral efficiency, energy efficiency, latency, and connectivity.Comment: This work has been accepted by IEEE Vehicular Technology Magazin
Joint Access-Backhaul Perspective on Mobility Management in 5G Networks
The ongoing efforts in the research development and standardization of 5G, by
both industry and academia, have resulted in the identification of enablers
(Software Defined Networks, Network Function Virtualization, Distributed
Mobility Management, etc.) and critical areas (Mobility management,
Interference management, Joint access-backhaul mechanisms, etc.) that will help
achieve the 5G objectives. During these efforts, it has also been identified
that the 5G networks due to their high degree of heterogeneity, high QoS demand
and the inevitable density (both in terms of access points and users), will
need to have efficient joint backhaul and access mechanisms as well as enhanced
mobility management mechanisms in order to be effective, efficient and
ubiquitous. Therefore, in this paper we first provide a discussion on the
evolution of the backhaul scenario, and the necessity for joint access and
backhaul optimization. Subsequently, and since mobility management mechanisms
can entail the availability, reliability and heterogeneity of the future
backhaul/fronthaul networks as parameters in determining the most optimal
solution for a given context, a study with regards to the effect of future
backhaul/fronthaul scenarios on the design and implementation of mobility
management solutions in 5G networks has been performed.Comment: IEEE Conference on Standards for Communications & Networking,
September 2017, Helsinki, Finlan
End-to-End Simulation of 5G mmWave Networks
Due to its potential for multi-gigabit and low latency wireless links,
millimeter wave (mmWave) technology is expected to play a central role in 5th
generation cellular systems. While there has been considerable progress in
understanding the mmWave physical layer, innovations will be required at all
layers of the protocol stack, in both the access and the core network.
Discrete-event network simulation is essential for end-to-end, cross-layer
research and development. This paper provides a tutorial on a recently
developed full-stack mmWave module integrated into the widely used open-source
ns--3 simulator. The module includes a number of detailed statistical channel
models as well as the ability to incorporate real measurements or ray-tracing
data. The Physical (PHY) and Medium Access Control (MAC) layers are modular and
highly customizable, making it easy to integrate algorithms or compare
Orthogonal Frequency Division Multiplexing (OFDM) numerologies, for example.
The module is interfaced with the core network of the ns--3 Long Term Evolution
(LTE) module for full-stack simulations of end-to-end connectivity, and
advanced architectural features, such as dual-connectivity, are also available.
To facilitate the understanding of the module, and verify its correct
functioning, we provide several examples that show the performance of the
custom mmWave stack as well as custom congestion control algorithms designed
specifically for efficient utilization of the mmWave channel.Comment: 25 pages, 16 figures, submitted to IEEE Communications Surveys and
Tutorials (revised Jan. 2018
Cooperative Hierarchical Caching in 5G Cloud Radio Access Networks (C-RANs)
Over the last few years, Cloud Radio Access Network (C-RAN) has arisen as a
transformative architecture for 5G cellular networks that brings the
flexibility and agility of cloud computing to wireless communications. At the
same time, content caching in wireless networks has become an essential
solution to lower the content-access latency and backhaul traffic loading,
which translate into user Quality of Experience (QoE) improvement and network
cost reduction. In this article, a novel Cooperative Hierarchical Caching (CHC)
framework in C-RAN is introduced where contents are jointly cached at the
BaseBand Unit (BBU) and at the Radio Remote Heads (RRHs). Unlike in traditional
approaches, the cache at the BBU, cloud cache, presents a new layer in the
cache hierarchy, bridging the latency/capacity gap between the traditional
edge-based and core-based caching schemes. Trace-driven simulations reveal that
CHC yields up to 80% improvement in cache hit ratio, 21% decrease in average
content-access latency, and 20% reduction in backhaul traffic load compared to
the edge-only caching scheme with the same total cache capacity. Before closing
the article, several challenges and promising opportunities for deploying
content caching in C-RAN are highlighted towards a content-centric mobile
wireless network.Comment: to appear on IEEE Network, July 201
Aerospace Medicine and Biology. A continuing bibliography with indexes
This bibliography lists 244 reports, articles, and other documents introduced into the NASA scientific and technical information system in February 1981. Aerospace medicine and aerobiology topics are included. Listings for physiological factors, astronaut performance, control theory, artificial intelligence, and cybernetics are included
Aerospace Medicine and Biology: A continuing bibliography with indexes, supplement 187
This supplement to Aerospace Medicine and Biology lists 247 reports, articles and other documents announced during November 1978 in Scientific and Technical Aerospace Reports (STAR) or in International Aerospace Abstracts (IAA). In its subject coverage, Aerospace Medicine and Biology concentrates on the biological, physiological, psychological, and environmental effects to which man is subjected during and following simulated or actual flight in the earth's atmosphere or in interplanetary space. References describing similar effects of biological organisms of lower order are also included. Emphasis is placed on applied research, but reference to fundamental studies and theoretical principles related to experimental development also qualify for inclusion. Each entry in the bibliography consists of a bibliographic citation accompanied in most cases by an abstract
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