247 research outputs found
NOMA Assisted Wireless Caching: Strategies and Performance Analysis
Conventional wireless caching assumes that content can be pushed to local
caching infrastructure during off-peak hours in an error-free manner; however,
this assumption is not applicable if local caches need to be frequently updated
via wireless transmission. This paper investigates a new approach to wireless
caching for the case when cache content has to be updated during on-peak hours.
Two non-orthogonal multiple access (NOMA) assisted caching strategies are
developed, namely the push-then-deliver strategy and the push-and-deliver
strategy. In the push-then-deliver strategy, the NOMA principle is applied to
push more content files to the content servers during a short time interval
reserved for content pushing in on-peak hours and to provide more connectivity
for content delivery, compared to the conventional orthogonal multiple access
(OMA) strategy. The push-and-deliver strategy is motivated by the fact that
some users' requests cannot be accommodated locally and the base station has to
serve them directly. These events during the content delivery phase are
exploited as opportunities for content pushing, which further facilitates the
frequent update of the files cached at the content servers. It is also shown
that this strategy can be straightforwardly extended to device-to-device
caching, and various analytical results are developed to illustrate the
superiority of the proposed caching strategies compared to OMA based schemes
Performance of downlink NOMA with multiple antenna base station, full-duplex and D2D transmission
The implementation of non-orthogonal multiple access (NOMA) and transmit antenna selection (TAS) technique has considered in this paper since TAS-aware base station (BS) provides the low cost, low complexity, and high diversity gains. In this paper, we investigate performance of two users by deriving outage probability. The system performance benefits from design of TAS and full-duplex (FD) scheme applied at NOMA users, and bandwidth efficiency will be enhanced although self-interference exists due to FD. The main contribution lies in the exact expressions of outage probability which are derived to exhibit system performance. Different from the simulated parameters, the analytical results show that increasing number of transmit antennas at the BS is way to improve system performance
Enabling Technologies for Ultra-Reliable and Low Latency Communications: From PHY and MAC Layer Perspectives
© 1998-2012 IEEE. Future 5th generation networks are expected to enable three key services-enhanced mobile broadband, massive machine type communications and ultra-reliable and low latency communications (URLLC). As per the 3rd generation partnership project URLLC requirements, it is expected that the reliability of one transmission of a 32 byte packet will be at least 99.999% and the latency will be at most 1 ms. This unprecedented level of reliability and latency will yield various new applications, such as smart grids, industrial automation and intelligent transport systems. In this survey we present potential future URLLC applications, and summarize the corresponding reliability and latency requirements. We provide a comprehensive discussion on physical (PHY) and medium access control (MAC) layer techniques that enable URLLC, addressing both licensed and unlicensed bands. This paper evaluates the relevant PHY and MAC techniques for their ability to improve the reliability and reduce the latency. We identify that enabling long-term evolution to coexist in the unlicensed spectrum is also a potential enabler of URLLC in the unlicensed band, and provide numerical evaluations. Lastly, this paper discusses the potential future research directions and challenges in achieving the URLLC requirements
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
Outage Performance of RIS-aided Cooperative FD-SWIPT-NOMA in Nakagami-m Channels
In this work we {derive new} analytical expressions for the outage
probability (OP) of the downlink (DL) cooperative full-duplex (FD) simultaneous
wireless information power transfer (SWIPT) non-orthogonal multiple access
(NOMA) system aided by reconfigurable intelligent surfaces (RIS). The
expressions for both the strongest and weakest NOMA users are devised assuming
Nakagami- channel fading. The derived analytical OP expressions are simple
to compute yet accurate for a wide range of RIS passive elements
configurations, energy harvesting (EH) coefficient, and residual
self-interference (SI) levels, being extensively validated by numerical
simulations, demonstrating the correctness and accuracy of the proposed
analytical method. The OP expressions reveal how paramount is to mitigate the
SI in the FD relay mode, since for reasonable values of residual SI coefficient
(dB), it is notable its detrimental effect over the
system performance; hence, new SI reduction methods for FD relays are useful
for low number of passive elements. Also, applying the proposed OP expressions
to predict the behaviour of the RIS-NOMA system equipped with a higher number
of passive elements () reveals a substantial reduction of the SI
effect, motivating the implementation of the cooperative FD communications.
Furthermore, we found the asymptotic behavior of outage probability of both
clustered users, as well as the equal diversity order for both users, given by
if the fraction of the harvest energy or
if , indicating the influence of channel parameters and number
of RIS elements in the performance.Comment: 23 pages, 8 figures, full pape
Energy-Efficient NOMA Enabled Heterogeneous Cloud Radio Access Networks
Heterogeneous cloud radio access networks (H-CRANs) are envisioned to be
promising in the fifth generation (5G) wireless networks. H-CRANs enable users
to enjoy diverse services with high energy efficiency, high spectral
efficiency, and low-cost operation, which are achieved by using cloud computing
and virtualization techniques. However, H-CRANs face many technical challenges
due to massive user connectivity, increasingly severe spectrum scarcity and
energy-constrained devices. These challenges may significantly decrease the
quality of service of users if not properly tackled. Non-orthogonal multiple
access (NOMA) schemes exploit non-orthogonal resources to provide services for
multiple users and are receiving increasing attention for their potential of
improving spectral and energy efficiency in 5G networks. In this article a
framework for energy-efficient NOMA H-CRANs is presented. The enabling
technologies for NOMA H-CRANs are surveyed. Challenges to implement these
technologies and open issues are discussed. This article also presents the
performance evaluation on energy efficiency of H-CRANs with NOMA.Comment: This work has been accepted by IEEE Network. Pages 18, Figure
Effective relaying mechanisms in future device to device communication : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in School of Food and Advanced Technology at Massey University, Palmerston North, New Zealand
Listed in 2020 Dean's List of Exceptional ThesesFuture wireless networks embrace a large number of assorted network-enabled devices
such as mobile phones, sensor nodes, drones, smart gears, etc., with different applications
and purpose, but they all share one common characteristic which is the dependence
on strong network connectivity. Growing demand of internet-connected devices
and data applications is burdensome for the currently deployed cellular wireless networks.
For this reason, future networks are likely to embrace cutting-edge technological
advancements in network infrastructure such as, small cells, device-to-device communication,
non-orthogonal multiple access scheme (NOMA), multiple-input-multiple out,
etc., to increase spectral efficiency, improve network coverage, and reduce network latency.
Individual devices acquire network connectivity by accessing radio resources in
orthogonal manner which limits spectrum utilisation resulting in data congestion and
latency in dense cellular networks. NOMA is a prominent scheme in which multiple
users are paired together and access radio resources by slicing the power domain. While
several research works study power control mechanisms by base station to communicate
with NOMA users, it is equally important to maintain distinction between the
users in uplink communication. Furthermore, these users in a NOMA pair are able to
perform cooperative relaying where one device assists another device in a NOMA pair
to increase signal diversity. However, the benefits of using a NOMA pair in improving
network coverage is still overlooked. With a varierty of cellular connected devices, use
of NOMA is studied on devices with similar channel characteristics and the need of
adopting NOMA for aerial devices has not been investigated. Therefore, this research
establishes a novel mechanism to offer distinction in uplink communication for NOMA
pair, a relaying scheme to extend the coverage of a base station by utilising NOMA
pair and a ranking scheme for ground and aerial devices to access radio resources by
NOMA
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