306 research outputs found
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
Performance Enhancement Using NOMA-MIMO for 5G Networks
The integration of MIMO and NOMA technologies addresses key challenges in 5G and beyond, such as connectivity, latency, and dependability. However, resolving these issues, especially in MIMO-enabled 5G networks, required additional research. This involved optimizing parameters like bit error rate, downlink spectrum efficiency, average capacity rate, and uplink transmission outage probability. The model employed Quadrature Phase Shift Keying modulation on selected frequency channels, accommodating diverse user characteristics. Evaluation showed that MIMO-NOMA significantly improved bit error rate and transmitting power for the best user in download transmission. For uplink transmission, there was an increase in the average capacity rate and a decrease in outage probability for the best user. Closed-form formulas for various parameters in both downlink and uplink NOMA, with and without MIMO, were derived. Overall, adopting MIMO-NOMA led to a remarkable performance improvement for all users, even in challenging conditions like interference or fading channels
Short-Packet Communications for MIMO NOMA Systems over Nakagami-m Fading: BLER and Minimum Blocklength Analysis
Recently, ultra-reliable and low-latency communications (URLLC) using
short-packets has been proposed to fulfill the stringent requirements regarding
reliability and latency of emerging applications in 5G and beyond networks. In
addition, multiple-input multiple-output non-orthogonal multiple access (MIMO
NOMA) is a potential candidate to improve the spectral efficiency, reliability,
latency, and connectivity of wireless systems. In this paper, we investigate
short-packet communications (SPC) in a multiuser downlink MIMO NOMA system over
Nakagami-m fading, and propose two antenna-user selection methods considering
two clusters of users having different priority levels. In contrast to the
widely-used long data-packet assumption, the SPC analysis requires the redesign
of the communication protocols and novel performance metrics. Given this
context, we analyze the SPC performance of MIMO NOMA systems using the average
block error rate (BLER) and minimum blocklength, instead of the conventional
metrics such as ergodic capacity and outage capacity. More specifically, to
characterize the system performance regarding SPC, asymptotic (in the high
signal-to-noise ratio regime) and approximate closed-form expressions of the
average BLER at the users are derived. Based on the asymptotic behavior of the
average BLER, an analysis of the diversity order, minimum blocklength, and
optimal power allocation is carried out. The achieved results show that MIMO
NOMA can serve multiple users simultaneously using a smaller blocklength
compared with MIMO OMA, thus demonstrating the benefits of MIMO NOMA for SPC in
minimizing the transmission latency. Furthermore, our results indicate that the
proposed methods not only improve the BLER performance but also guarantee full
diversity gains for the respective users.Comment: 12 pages, 8 figures. This paper has been submitted to an IEEE journal
for possible publicatio
How URLLC can Benefit from NOMA-based Retransmissions
Among the new types of connectivity unleashed by the emerging 5G wireless
systems, Ultra-Reliable Low Latency Communication (URLLC) is perhaps the most
innovative, yet challenging one. Ultra-reliability requires high levels of
diversity, however, the reactive approach based on packet retransmission in
HARQ protocols should be applied carefully to conform to the stringent latency
constraints. The main premise of this paper is that the NOMA principle can be
used to achieve highly efficient retransmissions by allowing concurrent use of
wireless resources in the uplink. We introduce a comprehensive solution that
accommodates multiple intermittently active users, each with its own HARQ
process. The performance is investigated under two different assumptions about
the Channel State Information (CSI) availability: statistical and
instantaneous. The results show that NOMA can indeed lead to highly efficient
system operation compared to the case in which all HARQ processes are run
orthogonally
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