5,032 research outputs found
Elements of Cellular Blind Interference Alignment --- Aligned Frequency Reuse, Wireless Index Coding and Interference Diversity
We explore degrees of freedom (DoF) characterizations of partially connected
wireless networks, especially cellular networks, with no channel state
information at the transmitters. Specifically, we introduce three fundamental
elements --- aligned frequency reuse, wireless index coding and interference
diversity --- through a series of examples, focusing first on infinite regular
arrays, then on finite clusters with arbitrary connectivity and message sets,
and finally on heterogeneous settings with asymmetric multiple antenna
configurations. Aligned frequency reuse refers to the optimality of orthogonal
resource allocations in many cases, but according to unconventional reuse
patterns that are guided by interference alignment principles. Wireless index
coding highlights both the intimate connection between the index coding problem
and cellular blind interference alignment, as well as the added complexity
inherent to wireless settings. Interference diversity refers to the observation
that in a wireless network each receiver experiences a different set of
interferers, and depending on the actions of its own set of interferers, the
interference-free signal space at each receiver fluctuates differently from
other receivers, creating opportunities for robust applications of blind
interference alignment principles
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
A hybrid TIM-NOMA scheme for the SISO Broadcast Channel
Future mobile communication networks will require enhanced network efficiency
and reduced system overhead due to their user density and high data rate
demanding applications of the mobile devices. Research on Blind Interference
Alignment (BIA) and Topological Interference Management (TIM) has shown that
optimal Degrees of Freedom (DoF) can be achieved, in the absence of Channel
State Information (CSI) at the transmitters, reducing the network's overhead.
Moreover, the recently emerged Non-Orthogonal Multiple Access (NOMA) scheme
suggests a different multiple access approach, compared to the current
orthogonal methods employed in 4G networks, resulting in high capacity gains.
Our contribution is a hybrid TIM-NOMA scheme in Single-Input-Single-Output
(SISO) K-user cells, in which users are divided into T groups, and 1/T DoF is
achieved for each user. By superimposing users in the power domain, we
introduce a two-stage decoding process, managing 'inter-group' interference
based on the TIM principles, and 'intra-group' interference based on Successful
Interference Cancellation (SIC), as proposed by NOMA. We show that for high SNR
values the hybrid scheme can improve the sum rate by at least 100% when
compared to Time Division Multiple Access (TDMA).Comment: 6 pages, 6 figures, submitted to IEEE ICC'15 - IEEE SCAN Worksho
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
Resolving Entanglements in Topological Interference Management with Alternating Connectivity
The sum-capacity of a three user interference wired network for time-varying
channels is considered. Due to the channel variations, it is assumed that the
transmitters are only able to track the connectivity between the individual
nodes, thus only the (alternating) state of the network is known. By
considering a special subset of all possible states, we show that state
splitting combined with joint encoding over the alternating states is required
to achieve the sum-capacity. Regarding upper bounds, we use a genie aided
approach to show the optimality of this scheme. This highlights that more
involved transmit strategies are required for characterizing the degrees of
freedom even if the transmitters have heavily restricted channel state
information
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