216 research outputs found
Energy-Efficient Design of STAR-RIS Aided MIMO-NOMA Networks
Simultaneous transmission and reflection-reconfigurable intelligent surface
(STAR-RIS) can provide expanded coverage compared with the conventional
reflection-only RIS. This paper exploits the energy efficient potential of
STAR-RIS in a multiple-input and multiple-output (MIMO) enabled non-orthogonal
multiple access (NOMA) system. Specifically, we mainly focus on
energy-efficient resource allocation with MIMO technology in the STAR-RIS
assisted NOMA network. To maximize the system energy efficiency, we propose an
algorithm to optimize the transmit beamforming and the phases of the low-cost
passive elements on the STAR-RIS alternatively until the convergence.
Specifically, we first decompose the formulated energy efficiency problem into
beamforming and phase shift optimization problems. To efficiently address the
non-convex beamforming optimization problem, we exploit signal alignment and
zero-forcing precoding methods in each user pair to decompose MIMO-NOMA
channels into single-antenna NOMA channels. Then, the Dinkelbach approach and
dual decomposition are utilized to optimize the beamforming vectors. In order
to solve non-convex phase shift optimization problem, we propose a successive
convex approximation (SCA) based method to efficiently obtain the optimized
phase shift of STAR-RIS. Simulation results demonstrate that the proposed
algorithm with NOMA technology can yield superior energy efficiency performance
over the orthogonal multiple access (OMA) scheme and the random phase shift
scheme
Investigation on Evolving Single-Carrier NOMA into Multi-Carrier NOMA in 5G
© 2013 IEEE. Non-orthogonal multiple access (NOMA) is one promising technology, which provides high system capacity, low latency, and massive connectivity, to address several challenges in the fifth-generation wireless systems. In this paper, we first reveal that the NOMA techniques have evolved from single-carrier NOMA (SC-NOMA) into multi-carrier NOMA (MC-NOMA). Then, we comprehensively investigated on the basic principles, enabling schemes and evaluations of the two most promising MC-NOMA techniques, namely sparse code multiple access (SCMA) and pattern division multiple access (PDMA). Meanwhile, we consider that the research challenges of SCMA and PDMA might be addressed with the stimulation of the advanced and matured progress in SC-NOMA. Finally, yet importantly, we investigate the emerging applications, and point out the future research trends of the MC-NOMA techniques, which could be straightforwardly inspired by the various deployments of SC-NOMA
The Road to Next-Generation Multiple Access: A 50-Year Tutorial Review
The evolution of wireless communications has been significantly influenced by
remarkable advancements in multiple access (MA) technologies over the past five
decades, shaping the landscape of modern connectivity. Within this context, a
comprehensive tutorial review is presented, focusing on representative MA
techniques developed over the past 50 years. The following areas are explored:
i) The foundational principles and information-theoretic capacity limits of
power-domain non-orthogonal multiple access (NOMA) are characterized, along
with its extension to multiple-input multiple-output (MIMO)-NOMA. ii) Several
MA transmission schemes exploiting the spatial domain are investigated,
encompassing both conventional space-division multiple access (SDMA)/MIMO-NOMA
systems and near-field MA systems utilizing spherical-wave propagation models.
iii) The application of NOMA to integrated sensing and communications (ISAC)
systems is studied. This includes an introduction to typical NOMA-based
downlink/uplink ISAC frameworks, followed by an evaluation of their performance
limits using a mutual information (MI)-based analytical framework. iv) Major
issues and research opportunities associated with the integration of MA with
other emerging technologies are identified to facilitate MA in next-generation
networks, i.e., next-generation multiple access (NGMA). Throughout the paper,
promising directions are highlighted to inspire future research endeavors in
the realm of MA and NGMA.Comment: 43 pages, 38 figures; Submitted to Proceedings of the IEE
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