56 research outputs found
A Fair Individual Rate Comparison between MIMO-NOMA and MIMO-OMA
In this paper, we compare the individual rate of MIMO-NOMA and MIMO-OMA when
users are paired into clusters. A power allocation (PA) strategy is proposed,
which ensures that MIMO-NOMA achieves a higher individual rate for each user
than MIMO-OMA with arbitrary PA and optimal degrees of freedom split. In
addition, a special case with equal degrees of freedom and arbitrary PA for OMA
is considered, for which the individual rate superiority of NOMA still holds.
Moreover, it is shown that NOMA can attain better fairness through appropriate
PA. Finally, simulations are carried out, which validate the developed
analytical results
A Two-Phase Power Allocation Scheme for CRNs Employing NOMA
In this paper, we consider the power allocation (PA) problem in cognitive
radio networks (CRNs) employing nonorthogonal multiple access (NOMA) technique.
Specifically, we aim to maximize the number of admitted secondary users (SUs)
and their throughput, without violating the interference tolerance threshold of
the primary users (PUs). This problem is divided into a two-phase PA process:
a) maximizing the number of admitted SUs; b) maximizing the minimum throughput
among the admitted SUs. To address the first phase, we apply a sequential and
iterative PA algorithm, which fully exploits the characteristics of the
NOMA-based system. Following this, the second phase is shown to be quasiconvex
and is optimally solved via the bisection method. Furthermore, we prove the
existence of a unique solution for the second phase and propose another PA
algorithm, which is also optimal and significantly reduces the complexity in
contrast with the bisection method. Simulation results verify the effectiveness
of the proposed two-phase PA scheme
Joint Beamforming and User Association Design for Integrated HAPS-Terrestrial Networks
Located in the stratospheric layer of Earth's atmosphere, the high altitude
platform station (HAPS) is a promising network infrastructure, which can bring
significant advantages to sixth-generation (6G) and beyond wireless
communications systems by forming vertical heterogeneous networks (vHetNets).
However, if not dealt with properly, integrated networks suffer from several
performance challenges compared to standalone networks. In harmonized
integrated networks, where different tiers share the same frequency spectrum,
interference is an important challenge to be addressed. This work focuses on an
integrated HAPS-terrestrial network, serving users in an overlapped urban
geographic area, and formulates a fairness optimization problem, aiming to
maximize the minimum spectral efficiency (SE) of the network. Due to the highly
nonconvex nature of the formulated problem, we develop a rapid converging
iterative algorithm that designs the massive multiple-input multiple-output
(mMIMO) beamforming weights and the user association scheme such that the
propagated inter- and intra-tier interference is managed. Simulation results
demonstrate the proposed algorithm's superiority over standalone terrestrial
networks and scenario where only the beamforming weights are optimized.Comment: 8 pages singlecolumn, 5 figures, under review in IEEE Communications
Letter
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