33,315 research outputs found
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
Effects of residual hardware impairments on secure NOMA-based cooperative systems
Non-orthogonal multiple access (NOMA) has been proposed as a promising technology that is capable of improving the spectral efficiency of fifth-generation wireless networks and beyond. However, in practical communication scenarios, transceiver architectures inevitably suffer from radio frequency (RF) front-end related impairments that cause non-negligible performance degradation. This issue can be addressed by analog and digital signal processing algorithms, however, inevitable aspects of this approach such as time-varying hardware characteristics and imperfect compensation schemes result to detrimental residual distortions. In the present contribution we investigate the physical layer security of NOMA- based amplify-and-forward relay systems under such realistically incurred residual hardware impairment (RHI) effects. Exact and asymptotic analytic expressions for the corresponding outage probability (OP) and intercept probability (IP) of the considered setup over multipath fading channels are derived and corroborated by respective simulation results. Based on this, it is shown that RHI affects both the legitimate users and eavesdroppers by increasing the OP and decreasing the IP. For a fixed OP, RHI generally increases the corresponding IP, thereby reducing the secure performance of the system. Further interesting insights are provided, verifying the importance of the offered results for the effective design and deployment of secure cooperative communication systems
A Survey of Physical Layer Security Techniques for 5G Wireless Networks and Challenges Ahead
Physical layer security which safeguards data confidentiality based on the
information-theoretic approaches has received significant research interest
recently. The key idea behind physical layer security is to utilize the
intrinsic randomness of the transmission channel to guarantee the security in
physical layer. The evolution towards 5G wireless communications poses new
challenges for physical layer security research. This paper provides a latest
survey of the physical layer security research on various promising 5G
technologies, including physical layer security coding, massive multiple-input
multiple-output, millimeter wave communications, heterogeneous networks,
non-orthogonal multiple access, full duplex technology, etc. Technical
challenges which remain unresolved at the time of writing are summarized and
the future trends of physical layer security in 5G and beyond are discussed.Comment: To appear in IEEE Journal on Selected Areas in Communication
Beamforming Techniques for Non-Orthogonal Multiple Access in 5G Cellular Networks
In this paper, we develop various beamforming techniques for downlink
transmission for multiple-input single-output (MISO) non-orthogonal multiple
access (NOMA) systems. First, a beamforming approach with perfect channel state
information (CSI) is investigated to provide the required quality of service
(QoS) for all users. Taylor series approximation and semidefinite relaxation
(SDR) techniques are employed to reformulate the original non-convex power
minimization problem to a tractable one. Further, a fairness-based beamforming
approach is proposed through a max-min formulation to maintain fairness between
users. Next, we consider a robust scheme by incorporating channel
uncertainties, where the transmit power is minimized while satisfying the
outage probability requirement at each user. Through exploiting the SDR
approach, the original non-convex problem is reformulated in a linear matrix
inequality (LMI) form to obtain the optimal solution. Numerical results
demonstrate that the robust scheme can achieve better performance compared to
the non-robust scheme in terms of the rate satisfaction ratio. Further,
simulation results confirm that NOMA consumes a little over half transmit power
needed by OMA for the same data rate requirements. Hence, NOMA has the
potential to significantly improve the system performance in terms of transmit
power consumption in future 5G networks and beyond.Comment: accepted to publish in IEEE Transactions on Vehicular Technolog
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