45,075 research outputs found
Improving Macrocell - Small Cell Coexistence through Adaptive Interference Draining
The deployment of underlay small base stations (SBSs) is expected to
significantly boost the spectrum efficiency and the coverage of next-generation
cellular networks. However, the coexistence of SBSs underlaid to an existing
macro-cellular network faces important challenges, notably in terms of spectrum
sharing and interference management. In this paper, we propose a novel
game-theoretic model that enables the SBSs to optimize their transmission rates
by making decisions on the resource occupation jointly in the frequency and
spatial domains. This procedure, known as interference draining, is performed
among cooperative SBSs and allows to drastically reduce the interference
experienced by both macro- and small cell users. At the macrocell side, we
consider a modified water-filling policy for the power allocation that allows
each macrocell user (MUE) to focus the transmissions on the degrees of freedom
over which the MUE experiences the best channel and interference conditions.
This approach not only represents an effective way to decrease the received
interference at the MUEs but also grants the SBSs tier additional transmission
opportunities and allows for a more agile interference management. Simulation
results show that the proposed approach yields significant gains at both
macrocell and small cell tiers, in terms of average achievable rate per user,
reaching up to 37%, relative to the non-cooperative case, for a network with
150 MUEs and 200 SBSs
Cognitive Interference Alignment for OFDM Two-tiered Networks
In this contribution, we introduce an interference alignment scheme that
allows the coexistence of an orthogonal frequency division multiplexing (OFDM)
macro-cell and a cognitive small-cell, deployed in a two-tiered structure and
transmitting over the same bandwidth. We derive the optimal linear strategy for
the single antenna secondary base station, maximizing the spectral efficiency
of the opportunistic link, accounting for both signal sub-space structure and
power loading strategy. Our analytical and numerical findings prove that the
precoder structure proposed is optimal for the considered scenario in the face
of Rayleigh and exponential decaying channels.Comment: 5 pages, 4 figures. Accepted and presented at the IEEE 13th
International Workshop on Signal Processing Advances in Wireless
Communications (SPAWC), 2012. Authors' final version. Copyright transferred
to IEE
Delivery Time Minimization in Edge Caching: Synergistic Benefits of Subspace Alignment and Zero Forcing
An emerging trend of next generation communication systems is to provide
network edges with additional capabilities such as additional storage resources
in the form of caches to reduce file delivery latency. To investigate this
aspect, we study the fundamental limits of a cache-aided wireless network
consisting of one central base station, transceivers and receivers from
a latency-centric perspective. We use the normalized delivery time (NDT) to
capture the per-bit latency for the worst-case file request pattern at high
signal-to-noise ratios (SNR), normalized with respect to a reference
interference-free system with unlimited transceiver cache capabilities. For
various special cases with and that satisfy , we establish the optimal tradeoff between cache storage and latency. This
is facilitated through establishing a novel converse (for arbitrary and
) and an achievability scheme on the NDT. Our achievability scheme is a
synergistic combination of multicasting, zero-forcing beamforming and
interference alignment.Comment: submitted to ICC 2018; fixed some typo
Interference Alignment for Cognitive Radio Communications and Networks: A Survey
© 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).Interference alignment (IA) is an innovative wireless transmission strategy that has shown to be a promising technique for achieving optimal capacity scaling of a multiuser interference channel at asymptotically high-signal-to-noise ratio (SNR). Transmitters exploit the availability of multiple signaling dimensions in order to align their mutual interference at the receivers. Most of the research has focused on developing algorithms for determining alignment solutions as well as proving interference alignment’s theoretical ability to achieve the maximum degrees of freedom in a wireless network. Cognitive radio, on the other hand, is a technique used to improve the utilization of the radio spectrum by opportunistically sensing and accessing unused licensed frequency spectrum, without causing harmful interference to the licensed users. With the increased deployment of wireless services, the possibility of detecting unused frequency spectrum becomes diminished. Thus, the concept of introducing interference alignment in cognitive radio has become a very attractive proposition. This paper provides a survey of the implementation of IA in cognitive radio under the main research paradigms, along with a summary and analysis of results under each system model.Peer reviewe
Millimeter Wave Cellular Networks: A MAC Layer Perspective
The millimeter wave (mmWave) frequency band is seen as a key enabler of
multi-gigabit wireless access in future cellular networks. In order to overcome
the propagation challenges, mmWave systems use a large number of antenna
elements both at the base station and at the user equipment, which lead to high
directivity gains, fully-directional communications, and possible noise-limited
operations. The fundamental differences between mmWave networks and traditional
ones challenge the classical design constraints, objectives, and available
degrees of freedom. This paper addresses the implications that highly
directional communication has on the design of an efficient medium access
control (MAC) layer. The paper discusses key MAC layer issues, such as
synchronization, random access, handover, channelization, interference
management, scheduling, and association. The paper provides an integrated view
on MAC layer issues for cellular networks, identifies new challenges and
tradeoffs, and provides novel insights and solution approaches.Comment: 21 pages, 9 figures, 2 tables, to appear in IEEE Transactions on
Communication
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