68 research outputs found
Sum Rate and Fairness Analysis for the MU-MIMO Downlink under PSK Signalling: Interference Suppression vs Exploitation
In this paper, we analyze the sum rate performance of multi-user
multiple-input multiple-output (MU-MIMO) systems, with a finite constellation
phase-shift keying (PSK) input alphabet. We analytically calculate and compare
the achievable sum rate in three downlink transmission scenarios: 1) without
precoding, 2) with zero forcing (ZF) precoding 3) with closed form constructive
interference (CI) precoding technique. In light of this, new analytical
expressions for the average sum rate are derived in the three cases, and Monte
Carlo simulations are provided throughout to validate the analysis.
Furthermore, based on the derived expressions, a power allocation scheme that
can ensure fairness among the users is also proposed. The results in this work
demonstrate that, the CI strictly outperforms the other two schemes, and the
performance gap between the considered schemes increases with increase in the
MIMO size. In addition, the CI provides higher fairness and the power
allocation algorithm proposed in this paper can achieve maximum fairness index
An Overview of Physical Layer Security with Finite-Alphabet Signaling
Providing secure communications over the physical layer with the objective of
achieving perfect secrecy without requiring a secret key has been receiving
growing attention within the past decade. The vast majority of the existing
studies in the area of physical layer security focus exclusively on the
scenarios where the channel inputs are Gaussian distributed. However, in
practice, the signals employed for transmission are drawn from discrete signal
constellations such as phase shift keying and quadrature amplitude modulation.
Hence, understanding the impact of the finite-alphabet input constraints and
designing secure transmission schemes under this assumption is a mandatory step
towards a practical implementation of physical layer security. With this
motivation, this article reviews recent developments on physical layer security
with finite-alphabet inputs. We explore transmit signal design algorithms for
single-antenna as well as multi-antenna wiretap channels under different
assumptions on the channel state information at the transmitter. Moreover, we
present a review of the recent results on secure transmission with discrete
signaling for various scenarios including multi-carrier transmission systems,
broadcast channels with confidential messages, cognitive multiple access and
relay networks. Throughout the article, we stress the important behavioral
differences of discrete versus Gaussian inputs in the context of the physical
layer security. We also present an overview of practical code construction over
Gaussian and fading wiretap channels, and we discuss some open problems and
directions for future research.Comment: Submitted to IEEE Communications Surveys & Tutorials (1st Revision
Rate-Energy Balanced Precoding Design for SWIPT based Two-Way Relay Systems
Simultaneous wireless information and power transfer (SWIPT) technique is a
popular strategy to convey both information and RF energy for harvesting at
receivers. In this regard, we consider a two-way relay system with multiple
users and a multi-antenna relay employing SWIPT strategy, where splitting the
received signal leads to a rate-energy trade-off. In literature, the works on
transceiver design have been studied using computationally intensive and
suboptimal convex relaxation based schemes. In this paper, we study the
balanced precoder design using chordal distance (CD) decomposition, which
incurs much lower complexity, and is flexible to dynamic energy requirements.
It is analyzed that given a non-negative value of CD, the achieved harvested
energy for the proposed balanced precoder is higher than that for the perfect
interference alignment (IA) precoder. The corresponding loss in sum rates is
also analyzed via an upper bound. Simulation results add that the IA schemes
based on mean-squared error are better suited for the SWIPT maximization than
the subspace alignment-based methods.Comment: arXiv admin note: text overlap with arXiv:2101.1216
Regularized Channel Inversion for Simultaneous Confidential Broadcasting and Power Transfer: A Large System Analysis
We propose for the first time new transmission
schemes based on linear precoding to enable simultaneous confidential
broadcasting and power transfer (SCBPT) in a multiuser
multi-input single-output (MISO) network, where a BS with N
antennas simultaneously transmits power and confidential messages
to K single-antenna users. We first design two transmission
schemes based on the rules of regularized channel inversion
(RCI) for both power splitting (PS) and time switching (TS)
receiver architectures, namely, RCI-PS and RCI-TS schemes.
For each scheme, we derive channel-independent expressions to
approximate the secrecy sum rate and the harvested power in
the large-system regime where K, N → ∞ with a fixed ratio
β = K/N. Based on the large-system results, we jointly optimize
the regularization parameter of the RCI and the PS ratio or the
TS ratio such that the secrecy sum rate is maximized subject
to an energy-harvesting constraint. We then present the tradeoff
between the secrecy sum rate and the harvested power achieved
by each scheme, and find that neither scheme always outperforms
the other one. Motivated by this fact, we design an RCI-hybrid
scheme based on the RCI and a newly proposed hybrid receiver
architecture. The hybrid receiver architecture takes advantages
of both the PS and TS receiver architectures. We show that the
RCI-hybrid scheme outperforms both the RCI-PS and RCI-TS
schemes.ARC Discovery Projects Grant DP15010390
An Overview of Physical Layer Security with Finite Alphabet Signaling
Providing secure communications over the physical layer with the objective of achieving secrecy without requiring a secret key has been receiving growing attention within the past decade. The vast majority of the existing studies in the area of physical layer security focus exclusively on the scenarios where the channel inputs are Gaussian distributed. However, in practice, the signals employed for transmission are drawn from discrete signal constellations such as phase shift keying and quadrature amplitude modulation. Hence, understanding the impact of the finite-alphabet input constraints and designing secure transmission schemes under this assumption is a mandatory step towards a practical implementation of physical layer security. With this motivation, this article reviews recent developments on physical layer security with finite-alphabet inputs. We explore transmit signal design algorithms for single-antenna as well as multi-antenna wiretap channels under different assumptions on the channel state information at the transmitter. Moreover, we present a review of the recent results on secure transmission with discrete signaling for various scenarios including multi-carrier transmission systems, broadcast channels with confidential messages, cognitive multiple access and relay networks. Throughout the article, we stress the important behavioral differences of discrete versus Gaussian inputs in the context of the physical layer security. We also present an overview of practical code construction over Gaussian and fading wiretap channels, and discuss some open problems and directions for future research
Rate Splitting with Finite Constellations: The Benefits of Interference Exploitation vs Suppression
Rate-Splitting (RS) has been proposed recently to enhance the performance of
multi-user multiple-input multiple-output (MU-MIMO) systems. In RS, a user
message is split into a common and a private part, where the common part is
decoded by all users, while the private part is decoded only by the intended
user. In this paper, we study RS under a phase-shift keying (PSK) input
alphabet for multi-user multi-antenna system and propose a constructive
interference (CI) exploitation approach to further enhance the sum-rate
achieved by RS under PSK signaling. To that end, new analytical expressions for
the ergodic sum-rate are derived for two precoding techniques of the private
messages, namely, 1) a traditional interference suppression zero-forcing (ZF)
precoding approach, 2) a closed-form CI precoding approach. Our analysis is
presented for perfect channel state information at the transmitter (CSIT), and
is extended to imperfect CSIT knowledge. A novel power allocation strategy,
specifically suited for the finite alphabet setup, is derived and shown to lead
to superior performance for RS over conventional linear precoding not relying
on RS (NoRS). The results in this work validate the significant sum-rate gain
of RS with CI over the conventional RS with ZF and NoRS
Modulation and Coding Design for Simultaneous Wireless Information and Power Transfer
In order to satisfy the power demands of IoT devices and thus extend their lifespan, radio frequency (RF) signal aided wireless power transfer (WPT) is exploited for remote charging. Carefully coordinating both the WPT and wireless information transfer (WIT) yields an emerging research trend in simultaneous wireless information and power transfer (SWIPT). However, SWIPT systems designed by assuming Gaussian distributed input signals may suffer from a substantial performance degradation in practice, when the finite alphabetical input is considered. In this article, we will provide a design guide of coding controlled SWIPT and study the modulation design in both single-user and multi-user SWIPT systems. We hope this guide may push SWIPT a step closer from theory to practice
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