153 research outputs found
Cross Layer Resource Allocation in H-CRAN with Spectrum and Energy Cooperation
5G and beyond wireless networks are the upcoming evolution for the current
cellular networks to provide the essential requirement of future demands such
as high data rate, low energy consumption, and low latency to provide seamless
communication for the emerging applications. Heterogeneous cloud radio access
network (H-CRAN) is envisioned as a new trend of 5G that uses the advantages of
heterogeneous and cloud radio access networks to enhance both the spectral and
energy efficiency. In this paper, building on the notion of effective capacity
(EC), we propose a framework in non-orthogonal multiple access (NOMA)-based
H-CRAN to meet these demands simultaneously. Our proposed approach is to
maximize the effective energy efficiency (EEE) while considering spectrum and
power cooperation between macro base station (MBS) and radio remote heads
(RRHs). To solve the formulated problem and to make it more tractable, we
transform the original problem into an equivalent subtractive form via
Dinkelbach algorithm. Afterwards, the combinational framework of distributed
stable matching and successive convex algorithm (SCA) is then adopted to obtain
the solution of the equivalent problem. Hereby, we propose an efficient
resource allocation scheme to maximize energy efficiency while maintaining the
delay quality of service (QoS) requirements for the all users. The simulation
results show that the proposed algorithm can provide a non-trivial trade-off
between delay and energy efficiency in NOMA H-CRAN systems in terms of EC and
EEE and the spectrum and power cooperation improves EEE of the proposed
network. Moreover, our proposed solution complexity is much lower than the
optimal solution and it suffers a very limited gap compared to the optimal
method
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
Evolution of NOMA Toward Next Generation Multiple Access (NGMA) for 6G
Due to the explosive growth in the number of wireless devices and diverse
wireless services, such as virtual/augmented reality and
Internet-of-Everything, next generation wireless networks face unprecedented
challenges caused by heterogeneous data traffic, massive connectivity, and
ultra-high bandwidth efficiency and ultra-low latency requirements. To address
these challenges, advanced multiple access schemes are expected to be
developed, namely next generation multiple access (NGMA), which are capable of
supporting massive numbers of users in a more resource- and
complexity-efficient manner than existing multiple access schemes. As the
research on NGMA is in a very early stage, in this paper, we explore the
evolution of NGMA with a particular focus on non-orthogonal multiple access
(NOMA), i.e., the transition from NOMA to NGMA. In particular, we first review
the fundamental capacity limits of NOMA, elaborate on the new requirements for
NGMA, and discuss several possible candidate techniques. Moreover, given the
high compatibility and flexibility of NOMA, we provide an overview of current
research efforts on multi-antenna techniques for NOMA, promising future
application scenarios of NOMA, and the interplay between NOMA and other
emerging physical layer techniques. Furthermore, we discuss advanced
mathematical tools for facilitating the design of NOMA communication systems,
including conventional optimization approaches and new machine learning
techniques. Next, we propose a unified framework for NGMA based on multiple
antennas and NOMA, where both downlink and uplink transmissions are considered,
thus setting the foundation for this emerging research area. Finally, several
practical implementation challenges for NGMA are highlighted as motivation for
future work.Comment: 34 pages, 10 figures, a survey paper accepted by the IEEE JSAC
special issue on Next Generation Multiple Acces
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