2,419 research outputs found
Robust Beamforming for Wireless Information and Power Transmission
In this letter, we study the robust beamforming problem for the multi-antenna
wireless broadcasting system with simultaneous information and power
transmission, under the assumption of imperfect channel state information (CSI)
at the transmitter. Following the worst-case deterministic model, our objective
is to maximize the worst-case harvested energy for the energy receiver while
guaranteeing that the rate for the information receiver is above a threshold
for all possible channel realizations. Such problem is nonconvex with infinite
number of constraints. Using certain transformation techniques, we convert this
problem into a relaxed semidefinite programming problem (SDP) which can be
solved efficiently. We further show that the solution of the relaxed SDP
problem is always rank-one. This indicates that the relaxation is tight and we
can get the optimal solution for the original problem. Simulation results are
presented to validate the effectiveness of the proposed algorithm.Comment: 4 pages, 3 figures; IEEE Wireless Communications Letters 201
How to Understand LMMSE Transceiver Design for MIMO Systems From Quadratic Matrix Programming
In this paper, a unified linear minimum mean-square-error (LMMSE) transceiver
design framework is investigated, which is suitable for a wide range of
wireless systems. The unified design is based on an elegant and powerful
mathematical programming technology termed as quadratic matrix programming
(QMP). Based on QMP it can be observed that for different wireless systems,
there are certain common characteristics which can be exploited to design LMMSE
transceivers e.g., the quadratic forms. It is also discovered that evolving
from a point-to-point MIMO system to various advanced wireless systems such as
multi-cell coordinated systems, multi-user MIMO systems, MIMO cognitive radio
systems, amplify-and-forward MIMO relaying systems and so on, the quadratic
nature is always kept and the LMMSE transceiver designs can always be carried
out via iteratively solving a number of QMP problems. A comprehensive framework
on how to solve QMP problems is also given. The work presented in this paper is
likely to be the first shoot for the transceiver design for the future
ever-changing wireless systems.Comment: 31 pages, 4 figures, Accepted by IET Communication
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 MIMO Relaying Network: An Artificial Noise Aided Robust Design Approach
Owing to the vulnerability of relay-assisted and device-to-device (D2D)
communications, improving wireless security from a physical layer signal
processing perspective is attracting increasing interest. Hence we address the
problem of secure transmission in a relay-assisted network, where a pair of
legitimate user equipments (UEs) communicate with the aid of a multiple-input
multiple output (MIMO) relay in the presence of multiple eavesdroppers (eves).
Assuming imperfect knowledge of the eves' channels, we jointly optimize the
power of the source UE, the amplify-and-forward (AF) relaying matrix and the
covariance of the artificial noise (AN) transmitted by the relay, in order to
maximize the received signal-to-interference-plus-noise ratio (SINR) at the
destination, while imposing a set of robust secrecy constraints. To tackle the
resultant nonconvex optimization problem, a globally optimal solution based on
a bi-level optimization framework is proposed, but with high complexity. Then a
low-complexity sub-optimal method relying on a new penalized
difference-of-convex (DC) algorithmic framework is proposed, which is
specifically designed for non-convex semidefinite programs (SDPs). We show how
this penalized DC framework can be invoked for solving our robust secure
relaying problem with proven convergence. Our extensive simulation results show
that both proposed solutions are capable of ensuring the secrecy of the
relay-aided transmission and significantly improve the robustness towards the
eves' channel uncertainties as compared to the non-robust counterparts. It is
also demonstrated the penalized DC-based method advocated yields a performance
close to the globally optimal solution.Comment: 13 pages, 6 figures, one table and one supplementary documen
Algebraic Solution for Beamforming in Two-Way Relay Systems with Analog Network Coding
We reduce the problem of optimal beamforming for two-way relay (TWR) systems
with perfect channel state infomation (CSI) that use analog network coding
(ANC) to a pair of algebraic equations in two variables that can be solved
inexpensively using numerical methods. The solution has greatly reduced
complexity compared to previous exact solutions via semidefinite programming
(SDP). Together with the linearized robust solution described in (Aziz and
Thron, 2014), it provides a high-performance, low-complexity robust beamforming
solution for 2-way relays.Comment: 5 pages, 5 figure
Robust Downlink Beamforming in Multiuser MISO Cognitive Radio Networks
This paper studies the problem of robust downlink beamforming design in a
multiuser Multi-Input Single-Output (MISO) Cognitive Radio Network (CR-Net) in
which multiple Primary Users (PUs) coexist with multiple Secondary Users (SUs).
Unlike conventional designs in CR-Nets, in this paper it is assumed that the
Channel State Information (CSI) for all relevant channels is imperfectly known,
and the imperfectness of the CSI is modeled using an Euclidean ball-shaped
uncertainty set. Our design objective is to minimize the transmit power of the
SU-Transmitter (SU-Tx) while simultaneously targeting a lower bound on the
received Signal-to-Interference-plus-Noise-Ratio (SINR) for the SU's, and
imposing an upper limit on the Interference-Power (IP) at the PUs. The design
parameters at the SU-Tx are the beamforming weights, i.e. the precoder matrix.
The proposed methodology is based on a worst case design scenario through which
the performance metrics of the design are immune to variations in the channels.
We propose three approaches based on convex programming for which efficient
numerical solutions exist. Finally, simulation results are provided to validate
the robustness of the proposed methods.Comment: 23 pages, 4 figures, submitted to IEEE Trans. Wireless Comms.,
accepted conference version to PIMRC'0
Low-Complexity Robust Adaptive Beamforming Algorithms Based on Shrinkage for Mismatch Estimation
In this paper, we propose low-complexity robust adaptive beamforming (RAB)
techniques that based on shrinkage methods. The only prior knowledge required
by the proposed algorithms are the angular sector in which the actual steering
vector is located and the antenna array geometry. We firstly present a
Low-Complexity Shrinkage-Based Mismatch Estimation (LOCSME) algorithm to
estimate the desired signal steering vector mismatch, in which the
interference-plus-noise covariance (INC) matrix is estimated with Oracle
Approximating Shrinkage (OAS) method and the weights are computed with matrix
inversions. We then develop low-cost stochastic gradient (SG) recursions to
estimate the INC matrix and update the beamforming weights, resulting in the
proposed LOCSME-SG algorithm. Simulation results show that both LOCSME and
LOCSME-SG achieve very good output signal-to-interference-plus-noise ratio
(SINR) compared to previously reported adaptive RAB algorithms.Comment: 8 pages, 2 figures, WSA. arXiv admin note: text overlap with
arXiv:1311.233
Simultaneous Wireless Information Power Transfer for MISO Secrecy Channel
This paper investigates simultaneous wireless information and power transfer
(SWIPT) for multiuser multiple-input-single-output (MISO) secrecy channel.
First, transmit beamfoming without artificial noise (AN) design is considered,
where two secrecy rate optimization frameworks (i.e., secrecy rate maximization
and harvested energy maximization) are investigated. These two optimization
problems are not convex, and cannot be solved directly. For secrecy rate
maximization problem, we employ bisection method to optimize the associated
power minimization problem, and first-order Taylor series expansion is consider
to approximate the energy harvesting (EH) constraint and the harvested energy
maximization problem. Moreover, we extend our proposed algorithm to the
associated robust schemes by incorporating with channel uncertainties, where
two-level method is proposed for the harvested energy maximization problem.
Then, transmit beamforming with AN design is studied for the same secrecy rate
maximization problem, which are reformulated into semidefinite programming
(SDP) based on one-dimensional search and successive convex approximation
(SCA), respectively. Moreover, tightness analysis of rank relaxation is
provided to show the optimal transmit covariance matrix exactly returns
rank-one. Simulation results is provided to validate the performance of the
proposed algorithm.Comment: 14 pages, 7 figure
A Robust Design for MISO Physical-Layer Multicasting over Line-of-Sight Channels
This paper studies a robust design problem for far-field line-of-sight (LOS)
channels where phase errors are present. Compared with the commonly used
additive error model, the phase error model is more suitable for capturing the
uncertainty in an LOS channel, as the dominant source of uncertainty lies in
the phase. We consider a multiple-input single-output (MISO) multicast
scenario, in which our goal is to design a beamformer that minimizes the
transmit power while satisfying probabilistic signal-to-noise ratio (SNR)
constraints. The probabilistic constraints give rise to a new computational
challenge, as they involve random trigonometric forms. In this work, we propose
to first approximate the random trigonometric form by its second-order Taylor
expansion and then tackle the resulting random quadratic form using a
Bernstein-type inequality. The advantage of such an approach is that an
approximately optimal beamformer can be obtained using the standard
semidefinite relaxation technique. In the simulations, we first show that if a
non-robust design (i.e., one that does not take phase errors into account) is
used, then the whole system may collapse. We then show that our proposed method
is less conservative than the existing robust design based on Gaussian
approximation and thus requires a lower power budget.Comment: This manuscript is submitted for possible journal publication on
13-Nov-201
Secure SWIPT for Directional Modulation Aided AF Relaying Networks
Secure wireless information and power transfer based on directional
modulation is conceived for amplify-and-forward (AF) relaying networks.
Explicitly, we first formulate a secrecy rate maximization (SRM) problem, which
can be decomposed into a twin-level optimization problem and solved by a
one-dimensional (1D) search and semidefinite relaxation (SDR) technique. Then
in order to reduce the search complexity, we formulate an optimization problem
based on maximizing the signal-to-leakage-AN-noise-ratio (Max-SLANR) criterion,
and transform it into a SDR problem. Additionally, the relaxation is proved to
be tight according to the classic Karush-Kuhn-Tucker (KKT) conditions. Finally,
to reduce the computational complexity, a successive convex approximation (SCA)
scheme is proposed to find a near-optimal solution. The complexity of the SCA
scheme is much lower than that of the SRM and the Max-SLANR schemes. Simulation
results demonstrate that the performance of the SCA scheme is very close to
that of the SRM scheme in terms of its secrecy rate and bit error rate (BER),
but much better than that of the zero forcing (ZF) scheme
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