4 research outputs found
Robust Designs of Beamforming and Power Splitting for Distributed Antenna Systems with Wireless Energy Harvesting
In this paper, we investigate a multiuser distributed antenna system with
simultaneous wireless information and power transmission under the assumption
of imperfect channel state information (CSI). In this system, a distributed
antenna port with multiple antennas supports a set of mobile stations who can
decode information and harvest energy simultaneously via a power splitter. To
design robust transmit beamforming vectors and the power splitting (PS) factors
in the presence of CSI errors, we maximize the average worst-case
signal-to-interference-plus- noise ratio (SINR) while achieving individual
energy harvesting constraint for each mobile station. First, we develop an
efficient algorithm to convert the max-min SINR problem to a set of "dual"
min-max power balancing problems. Then, motivated by the penalty function
method, an iterative algorithm based on semi-definite programming (SDP) is
proposed to achieve a local optimal rank-one solution. Also, to reduce the
computational complexity, we present another iterative scheme based on the
Lagrangian method and the successive convex approximation (SCA) technique to
yield a suboptimal solution. Simulation results are shown to validate the
robustness and effectiveness of the proposed algorithms.Comment: To appear in IEEE Systems Journal. (10 pages, 6 figures
Secure Interference Exploitation Precoding in MISO Wiretap Channel: Destructive Region Redefinition with Efficient Solutions
In this paper, we focus on the physical layer security for a K-user
multiple-input-single-output (MISO) wiretap channel in the presence of a
malicious eavesdropper, where we propose several interference exploitation (IE)
precoding schemes for different types of the eavesdropper. Specifically, in the
case where a common eavesdropper decodes the signal directly and Eve's full
channel state information (CSI) is available at the transmitter, we show that
the required transmit power can be further reduced by re-designing the
`destructive region' of the constellations for symbol-level precoding and
re-formulating the power minimization problem. We further study the SINR
balancing problems with the derived `complete destructive region' with full,
statistical and no Eve's CSI, respectively, and show that the SINR balancing
problem becomes non-convex with statistical or no Eve's CSI. On the other hand,
in the presence of a smart eavesdropper using maximal likelihood (ML)
detection, the security cannot be guaranteed with all the existing approaches.
To this end, we further propose a random jamming scheme (RJS) and a random
precoding scheme (RPS), respectively. To solve the introduced convex/non-convex
problems in an efficient manner, we propose an iterative algorithm for the
convex ones based on the Karush-Kuhn-Tucker (KKT) conditions, and deal with the
non-convex ones by resorting to Taylor expansions. Simulation results show that
all proposed schemes outperform the existing works in secrecy performance, and
that the proposed algorithm improves the computation efficiency significantly.Comment: 13 pages, 12 figures, journa
Energy Efficiency Optimization for Secure Transmission in MISO Cognitive Radio Network with Energy Harvesting
In this paper, we investigate different secrecy energy efficiency (SEE)
optimization problems in a multiple-input single-output underlay cognitive
radio (CR) network in the presence of an energy harvesting receiver. In
particular, these energy efficient designs are developed with different
assumptions of channels state information (CSI) at the transmitter, namely
perfect CSI, statistical CSI and imperfect CSI with bounded channel
uncertainties. In particular, the overarching objective here is to design a
beamforming technique maximizing the SEE while satisfying all relevant
constraints linked to interference and harvested energy between transmitters
and receivers. We show that the original problems are non-convex and their
solutions are intractable. By using a number of techniques, such as non-linear
fractional programming and difference of concave (DC) functions, we reformulate
the original problems so as to render them tractable. We then combine these
techniques with the Dinkelbach's algorithm to derive iterative algorithms to
determine relevant beamforming vectors which lead to the SEE maximization. In
doing this, we investigate the robust design with ellipsoidal bounded channel
uncertainties, by mapping the original problem into a sequence of semidefinite
programs by employing the semidefinite relaxation, non-linear fractional
programming and S-procedure. Furthermore, we show that the maximum SEE can be
achieved through a search algorithm in the single dimensional space. Numerical
results, when compared with those obtained with existing techniques in the
literature, show the effectiveness of the proposed designs for SEE
maximization
Downlink Secrecy Rate of One-Bit Massive MIMO System with Active Eavesdropping
In this study, we consider the physical layer security in the downlink of a
Massive MIMO system employing one-bit quantization at the base station (BS). We
assume an active eavesdropper that attempts to spoiling the channel estimation
acquisition at the BS for a legitimate user, whereas overhearing on downlink
transmission. We consider the two most widespread methods for degrading the
eavesdropper's channel, the nullspace artificial noise (NS-AN) and random
artificial noise (R-AN). Then, we present a lower bound on the secrecy rate and
asymptotic performance, considering zero-forcing beamforming (ZF-BF) and
maximum-ratio transmission beamforming (MRT-BF). Our results reveal that even
when the eavesdropper is close enough to the intercepted user, a positive
secrecy rate --which tends to saturation with increasing the number of BS
antennas ---is possible, as long as the transmit power of eavesdropper is
less than that of the legitimate user during channel training. We show that
ZF-BF with NS-AN provides the best performance. It is found that MRT-BF and
ZF-BF are equivalent in the asymptotic limit of and hence the artificial
noise technique is the performance indicator. Moreover, we study the impact of
\emph{power-scaling law} on the secrecy rate. When the transmit power of BS is
reduced proportional to , the performance is independent of artificial
noise asymptotically and hence the beamforming technique is the performance
indicator. In addition, when the BS's power is reduced proportional to
, all combinations of beamforming and artificial noise schemes are
equally likely asymptotically, independent of quantization noise. We present
various numerical results to corroborate our analysis.Comment: 49 pages (onecolumn), 12 figures (Available in IEEE ACCESS(early
access): https://ieeexplore.ieee.org/document/9006840