20,364 research outputs found
Effective radio resource management for multimedia broadcast/multicast services in UMTS networks
WOS:000242097300001 (Nº de Acesso Web of Science)Broadcast and multicast offer a significant improvement of spectrum utilization, and become particularly important where information channels are shared among several users. Mobile cellular environments are expected to evolve with the technological approaches necessary to facilitate the deployment of multimedia services, such as streaming, file download, and carousel services. The perspective that video streaming in wireless networks services is an attractive service to end-users has spurred the research in this area. To provide for a video delivery platform in UMTS, the third generation partnership project (3GPP) addressed this problem with the introduction of the multimedia broadcast and multicast services (MBMS) in 3GPP Release 6. In this document we analyse several effective radio resource management techniques to provide MBMS, namely, use of nonuniform QAM constellations, multicode, and macrodiversity to guarantee the optimal distribution of QoS depending on the location of mobiles.info:eu-repo/semantics/publishedVersio
Principles of Physical Layer Security in Multiuser Wireless Networks: A Survey
This paper provides a comprehensive review of the domain of physical layer
security in multiuser wireless networks. The essential premise of
physical-layer security is to enable the exchange of confidential messages over
a wireless medium in the presence of unauthorized eavesdroppers without relying
on higher-layer encryption. This can be achieved primarily in two ways: without
the need for a secret key by intelligently designing transmit coding
strategies, or by exploiting the wireless communication medium to develop
secret keys over public channels. The survey begins with an overview of the
foundations dating back to the pioneering work of Shannon and Wyner on
information-theoretic security. We then describe the evolution of secure
transmission strategies from point-to-point channels to multiple-antenna
systems, followed by generalizations to multiuser broadcast, multiple-access,
interference, and relay networks. Secret-key generation and establishment
protocols based on physical layer mechanisms are subsequently covered.
Approaches for secrecy based on channel coding design are then examined, along
with a description of inter-disciplinary approaches based on game theory and
stochastic geometry. The associated problem of physical-layer message
authentication is also introduced briefly. The survey concludes with
observations on potential research directions in this area.Comment: 23 pages, 10 figures, 303 refs. arXiv admin note: text overlap with
arXiv:1303.1609 by other authors. IEEE Communications Surveys and Tutorials,
201
V2X Meets NOMA: Non-Orthogonal Multiple Access for 5G Enabled Vehicular Networks
Benefited from the widely deployed infrastructure, the LTE network has
recently been considered as a promising candidate to support the
vehicle-to-everything (V2X) services. However, with a massive number of devices
accessing the V2X network in the future, the conventional OFDM-based LTE
network faces the congestion issues due to its low efficiency of orthogonal
access, resulting in significant access delay and posing a great challenge
especially to safety-critical applications. The non-orthogonal multiple access
(NOMA) technique has been well recognized as an effective solution for the
future 5G cellular networks to provide broadband communications and massive
connectivity. In this article, we investigate the applicability of NOMA in
supporting cellular V2X services to achieve low latency and high reliability.
Starting with a basic V2X unicast system, a novel NOMA-based scheme is proposed
to tackle the technical hurdles in designing high spectral efficient scheduling
and resource allocation schemes in the ultra dense topology. We then extend it
to a more general V2X broadcasting system. Other NOMA-based extended V2X
applications and some open issues are also discussed.Comment: Accepted by IEEE Wireless Communications Magazin
Cellular-Broadcast Service Convergence through Caching for CoMP Cloud RANs
Cellular and Broadcast services have been traditionally treated independently
due to the different market requirements, thus resulting in different business
models and orthogonal frequency allocations. However, with the advent of cheap
memory and smart caching, this traditional paradigm can converge into a single
system which can provide both services in an efficient manner. This paper
focuses on multimedia delivery through an integrated network, including both a
cellular (also known as unicast or broadband) and a broadcast last mile
operating over shared spectrum. The subscribers of the network are equipped
with a cache which can effectively create zero perceived latency for multimedia
delivery, assuming that the content has been proactively and intelligently
cached. The main objective of this work is to establish analytically the
optimal content popularity threshold, based on a intuitive cost function. In
other words, the aim is to derive which content should be broadcasted and which
content should be unicasted. To facilitate this, Cooperative Multi- Point
(CoMP) joint processing algorithms are employed for the uni and broad-cast PHY
transmissions. To practically implement this, the integrated network controller
is assumed to have access to traffic statistics in terms of content popularity.
Simulation results are provided to assess the gain in terms of total spectral
efficiency. A conventional system, where the two networks operate
independently, is used as benchmark.Comment: Submitted to IEEE PIMRC 201
Generic Multiuser Coordinated Beamforming for Underlay Spectrum Sharing
The beamforming techniques have been recently studied as possible enablers
for underlay spectrum sharing. The existing beamforming techniques have several
common limitations: they are usually system model specific, cannot operate with
arbitrary number of transmit/receive antennas, and cannot serve arbitrary
number of users. Moreover, the beamforming techniques for underlay spectrum
sharing do not consider the interference originating from the incumbent primary
system. This work extends the common underlay sharing model by incorporating
the interference originating from the incumbent system into generic combined
beamforming design that can be applied on interference, broadcast or multiple
access channels. The paper proposes two novel multiuser beamforming algorithms
for user fairness and sum rate maximization, utilizing newly derived convex
optimization problems for transmit and receive beamformers calculation in a
recursive optimization. Both beamforming algorithms provide efficient operation
for the interference, broadcast and multiple access channels, as well as for
arbitrary number of antennas and secondary users in the system. Furthermore,
the paper proposes a successive transmit/receive optimization approach that
reduces the computational complexity of the proposed recursive algorithms. The
results show that the proposed complexity reduction significantly improves the
convergence rates and can facilitate their operation in scenarios which require
agile beamformers computation.Comment: 30 pages, 5 figure
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