1,173 research outputs found
Performance Analysis of SSK-NOMA
In this paper, we consider the combination between two promising techniques:
space-shift keying (SSK) and non-orthogonal multiple access (NOMA) for future
radio access networks. We analyze the performance of SSK-NOMA networks and
provide a comprehensive analytical framework of SSK-NOMA regarding bit error
probability (BEP), ergodic capacity and outage probability. It is worth
pointing out all analysis also stand for conventional SIMO-NOMA networks. We
derive closed-form exact average BEP (ABEP) expressions when the number of
users in a resource block is equal to i.e., . Nevertheless, we analyze the
ABEP of users when the number of users is more than i.e., , and derive
bit-error-rate (BER) union bound since the error propagation due to iterative
successive interference canceler (SIC) makes the exact analysis intractable.
Then, we analyze the achievable rate of users and derive exact ergodic capacity
of the users so the ergodic sum rate of the system in closed-forms. Moreover,
we provide the average outage probability of the users exactly in the
closed-form. All derived expressions are validated via Monte Carlo simulations
and it is proved that SSK-NOMA outperforms conventional NOMA networks in terms
of all performance metrics (i.e., BER, sum rate, outage). Finally, the effect
of the power allocation (PA) on the performance of SSK-NOMA networks is
investigated and the optimum PA is discussed under BER and outage constraints
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
Reconfigurable Intelligent Surface (RIS) Aided Multi-User Networks: Interplay Between NOMA and RIS
This article focuses on the exploitation of reconfigurable intelligent
surfaces (RISs) in multi-user networks employing orthogonal multiple access
(OMA) or non-orthogonal multiple access (NOMA), with an emphasis on
investigating the interplay between NOMA and RIS. Depending on whether the RIS
reflection coefficients can be adjusted only once or multiple times during one
transmission, we distinguish between static and dynamic RIS configurations. In
particular, the capacity region of RIS aided single-antenna NOMA networks is
characterized and compared with the OMA rate region from an
information-theoretic perspective, revealing that the dynamic RIS configuration
is capacity-achieving. Then, the impact of the RIS deployment location on the
performance of different multiple access schemes is investigated, which reveals
that asymmetric and symmetric deployment strategies are preferable for NOMA and
OMA, respectively. Furthermore, for RIS aided multiple-antenna NOMA networks,
three novel joint active and passive beamformer designs are proposed based on
both beamformer based and cluster based strategies. Finally, open research
problems for RIS-NOMA networks are highlighted.Comment: 13 pages, 6 figure
ADMM-based Detector for Large-scale MIMO Code-domain NOMA Systems
Large-scale multi-input multi-output (MIMO) code domain non-orthogonal
multiple access (CD-NOMA) techniques are one of the potential candidates to
address the next-generation wireless needs such as massive connectivity, and
high reliability. This work focuses on two primary CD-NOMA techniques:
sparse-code multiple access (SCMA) and dense-code multiple access (DCMA). One
of the primary challenges in implementing MIMO-CD-NOMA systems is designing the
optimal detector with affordable computation cost and complexity. This paper
proposes an iterative linear detector based on the alternating direction method
of multipliers (ADMM). First, the maximum likelihood (ML) detection problem is
converted into a sharing optimization problem. The set constraint in the ML
detection problem is relaxed into the box constraint sharing problem. An
alternative variable is introduced via the penalty term, which compensates for
the loss incurred by the constraint relaxation. The system models, i.e., the
relation between the input signal and the received signal, are reformulated so
that the proposed sharing optimization problem can be readily applied.
The ADMM is a robust algorithm to solve the sharing problem in a distributed
manner. The proposed detector leverages the distributive nature to reduce
per-iteration cost and time. An ADMM-based linear detector is designed for
three MIMO-CD-NOMA systems: single input multi output CD-NOMA (SIMO-CD-NOMA),
spatial multiplexing CD-NOMA (SMX-CD-NOMA), and spatial modulated CD-NOMA
(SM-CD-NOMA). The impact of various system parameters and ADMM parameters on
computational complexity and symbol error rate (SER) has been thoroughly
examined through extensive Monte Carlo simulations
Compressive Sensing-Based Grant-Free Massive Access for 6G Massive Communication
The advent of the sixth-generation (6G) of wireless communications has given
rise to the necessity to connect vast quantities of heterogeneous wireless
devices, which requires advanced system capabilities far beyond existing
network architectures. In particular, such massive communication has been
recognized as a prime driver that can empower the 6G vision of future
ubiquitous connectivity, supporting Internet of Human-Machine-Things for which
massive access is critical. This paper surveys the most recent advances toward
massive access in both academic and industry communities, focusing primarily on
the promising compressive sensing-based grant-free massive access paradigm. We
first specify the limitations of existing random access schemes and reveal that
the practical implementation of massive communication relies on a dramatically
different random access paradigm from the current ones mainly designed for
human-centric communications. Then, a compressive sensing-based grant-free
massive access roadmap is presented, where the evolutions from single-antenna
to large-scale antenna array-based base stations, from single-station to
cooperative massive multiple-input multiple-output systems, and from unsourced
to sourced random access scenarios are detailed. Finally, we discuss the key
challenges and open issues to shed light on the potential future research
directions of grant-free massive access.Comment: Accepted by IEEE IoT Journa
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