8 research outputs found
Beamforming and Power Splitting Designs for AN-aided Secure Multi-user MIMO SWIPT Systems
In this paper, an energy harvesting scheme for a multi-user
multiple-input-multiple-output (MIMO) secrecy channel with artificial noise
(AN) transmission is investigated. Joint optimization of the transmit
beamforming matrix, the AN covariance matrix, and the power splitting ratio is
conducted to minimize the transmit power under the target secrecy rate, the
total transmit power, and the harvested energy constraints. The original
problem is shown to be non-convex, which is tackled by a two-layer
decomposition approach. The inner layer problem is solved through semi-definite
relaxation, and the outer problem, on the other hand, is shown to be a single-
variable optimization that can be solved by one-dimensional (1- D) line search.
To reduce computational complexity, a sequential parametric convex
approximation (SPCA) method is proposed to find a near-optimal solution. The
work is then extended to the imperfect channel state information case with
norm-bounded channel errors. Furthermore, tightness of the relaxation for the
proposed schemes are validated by showing that the optimal solution of the
relaxed problem is rank-one. Simulation results demonstrate that the proposed
SPCA method achieves the same performance as the scheme based on 1-D but with
much lower complexity.Comment: 12 pages, 6 figures, submitted for possible publicatio
Cooperative Rate-Splitting for Secrecy Sum-Rate Enhancement in Multi-antenna Broadcast Channels
In this paper, we employ Cooperative Rate-Splitting (CRS) technique to
enhance the Secrecy Sum Rate (SSR) for the Multiple Input Single Output (MISO)
Broadcast Channel (BC), consisting of two legitimate users and one
eavesdropper, with perfect Channel State Information (CSI) available at all
nodes. For CRS based on the three-node relay channel, the transmitter splits
and encodes the messages of legitimate users into common and private streams
based on Rate-Splitting (RS). With the goal of maximizing SSR, the proposed CRS
strategy opportunistically asks the relaying legitimate user to forward its
decoded common message. During the transmission, the eavesdropper keeps
wiretapping silently. To ensure secure transmission, the common message is used
for the dual purpose, serving both as a desired message and Artificial Noise
(AN) without consuming extra transmit power comparing to the conventional AN
design. Taking into account the total power constraint and the Physical Layer
(PHY) security, the precoders and time-slot allocation are jointly optimized by
solving the non-convex SSR maximization problem based on Sequential Convex
Approximation (SCA) algorithm. Numerical results show that the proposed CRS
secure transmission scheme outperforms existing Multi-User Linear Precoding
(MU-LP) and Cooperative Non-Orthogonal Multiple Access (C-NOMA) strategies.
Therefore, CRS is a promising strategy to enhance the PHY security in
multi-antenna BC systems
Optimal Precoder Designs for Sum-utility Maximization in SWIPT-enabled Multi-user MIMO Cognitive Radio Networks
In this paper, we propose a generalized framework that combines the cognitive
radio (CR) techniques for spectrum sharing and the simultaneous wireless
information and power transfer (SWIPT) for energy harvesting (EH) in the
conventional multi-user MIMO (MuMIMO) channels, which leads to an
MuMIMO-CR-SWIPT network. In this system, we have one secondary base-station
(S-BS) that supports multiple secondary information decoding (S-ID) and
secondary EH (S-EH) users simultaneously under the condition that interference
power that affects the primary ID (P-ID) receivers should stay below a certain
threshold. The goal of the paper is to develop a generalized precoder design
that maximizes the sum-utility cost function under the transmit power
constraint at the S-BS, and the EH constraint at each S-EH user, and the
interference power constraint at each P-ID user. Therefore, the previous
studies for the CR and SWIPT systems are casted as particular solutions of the
proposed framework. The problem is inherently non-convex and even the weighted
minimum mean squared error (WMMSE) transformation does not resolve the
non-convexity of the original problem. To tackle the problem, we find a
solution from the dual optimization via sub-gradient ellipsoid method based on
the observation that the WMMSE transformation raises zero-duality gap between
the primal and the dual problems. We also propose a simplified algorithm for
the case of a single S-ID user, which is shown to achieve the global optimum.
Finally, we demonstrate the optimality and efficiency of the proposed
algorithms through numerical simulation results.Comment: 12pages, 9 figures, submitted to IEEE Systems Journa