15,128 research outputs found
Retrospective Interference Alignment for Two-Cell Uplink MIMO Cellular Networks with Delayed CSIT
In this paper, we propose a new retrospective interference alignment for
two-cell multiple-input multiple-output (MIMO) interfering multiple access
channels (IMAC) with the delayed channel state information at the transmitters
(CSIT). It is shown that having delayed CSIT can strictly increase the sum-DoF
compared to the case of no CSIT. The key idea is to align multiple interfering
signals from adjacent cells onto a small dimensional subspace over time by
fully exploiting the previously received signals as side information with
outdated CSIT in a distributed manner. Remarkably, we show that the
retrospective interference alignment can achieve the optimal sum-DoF in the
context of two-cell two-user scenario by providing a new outer bound.Comment: 7 pages, 2 figures, to appear in IEEE ICC 201
Retrospective Interference Alignment
We explore similarities and differences in recent works on blind interference
alignment under different models such as staggered block fading model and the
delayed CSIT model. In particular we explore the possibility of achieving
interference alignment with delayed CSIT when the transmitters are distributed.
Our main contribution is an interference alignment scheme, called retrospective
interference alignment in this work, that is specialized to settings with
distributed transmitters. With this scheme we show that the 2 user X channel
with only delayed channel state information at the transmitters can achieve 8/7
DoF, while the interference channel with 3 users is able to achieve 9/8 DoF. We
also consider another setting where delayed channel output feedback is
available to transmitters. In this setting the X channel and the 3 user
interference channel are shown to achieve 4/3 and 6/5 DoF, respectively
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
On the Degrees of freedom of the K-user MISO Interference Channel with imperfect delayed CSIT
This work investigates the degrees of freedom (DoF) of the K-user
multiple-input single-output (MISO) interference channel (IC) with imperfect
delayed channel state information at the transmitters (dCSIT). For this
setting, new DoF inner bonds are provided, and benchmarked with
cooperation-based outer bounds. The achievability result is based on a
precoding scheme that aligns the interfering received signals through time,
exploiting the concept of Retrospective Interference Alignment (RIA). The
proposed approach outperforms all previous known schemes. Furthermore, we study
the proposed scheme under channel estimation errors (CEE) on the reported
dCSIT, and derive a closed-form expression for the achievable DoF with
imperfect dCSIT.Comment: Draft version of the accepted manuscript at IEEE ICASSP 1
Retrospective Interference Alignment for the 3-user MIMO Interference Channel with delayed CSIT
The degrees of freedom (DoF) of the 3-user multiple input multiple output
interference channel (3-user MIMO IC) are investigated where there is delayed
channel state information at the transmitters (dCSIT). We generalize the ideas
of Maleki et al. about {\it Retrospective Interference Alignment (RIA)} to be
applied to the MIMO IC, where transmitters and receivers are equipped with
antennas, respectively. We propose a two-phase transmission scheme
where the number of slots per phase and number of transmitted symbols are
optimized by solving a maximization problem. Finally, we review the existing
achievable DoF results in the literature as a function of the ratio between
transmitting and receiving antennas . The proposed scheme improves
all other strategies when .Comment: Draft version of the accepted manuscript at IEEE ICASSP 1
Achievable DoF-delay trade-offs for the K-user MIMO interference channel with delayed CSIT
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works.The degrees of freedom (DoFs) of the K-user multiple-input multiple-output (MIMO) interference channel are studied when perfect, but delayed channel state information is available at the transmitter side (delayed CSIT). Recent works have proposed schemes improving the DoF knowledge of the interference channel, but at the cost of developing transmission involving many channel uses (long delay), thus increasing the complexity at both transmitter and receiver side. This paper proposes three linear precoding strategies, limited to at most three phases, based on the concept of interference alignment, and built upon three main ingredients: delayed CSIT precoding, user scheduling, and redundancy transmission. In this respect, the interference alignment is realized by exploiting delayed CSIT to align the interference at the non-intended receivers along the space-time domain. Moreover, a new framework is proposed where the number of transmitted symbols and duration of the phases is obtained as the solution of a maximization problem, and enabling the introduction of complexity constraints, which allows deriving the achievable DoF as a function of the transmission delay, i.e., the achievable DoF-delay trade-off. Finally, the latter part of this paper settles that the assumption of time-varying channels common along all the literature on delayed CSIT is indeed unnecessary.Peer ReviewedPostprint (author's final draft
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