Beyond Equal-Power Sparse NOMA: Two User Classes and Closed-Form Bounds on the Achievable Region

Abstract

Non-orthogonal multiple access (NOMA) is a promising technology for future beyond-5G wireless networks, whose fundamental information-theoretic limits are yet to be fully explored. Considering regular sparse code-domain NOMA (with a fixed and finite number of orthogonal resources allocated to any designated user and vice versa), this paper extends previous results by the authors to a setting comprising two classes of users with different power constraints. Explicit rigorous closed-form analytical inner and outer bounds on the achievable rate (total class throughput) region in the large-system limit are derived and comparatively investigated in extreme-SNR regimes. The inner bound is based on the conditional vector entropy power inequality (EPI), while the outer bound relies on a recent strengthened version of the EPI. Valuable insights are provided into the potential performance gains of regular sparse NOMA in practically oriented settings, comprising, e.g., a combination of low-complexity devices and broadband users with higher transmit power capabilities, or combinations of cell-edge and cell-center users. The conditions for superior performance over dense code-domain NOMA (taking the form of randomly spread code-division multiple access), as well as a relatively small gap to the ultimate performance limits, are identified. The proposed bounds are also applicable for the analysis of interference networks, e.g., Wyner-type cellular models.

Joint Design of Polar Coding and Physical Network Coding for Two−User Downlink Non−Orthogonal Multiple Access

“…[8] analyzed the quasi-degradation probability and proposed an analytical framework to characterize the optimality of NOMA over Rician fading channels. Moreover, Reference [9] investigated the achievable rate region in the large-system limit of regular sparse NOMA with two users. Given a minimum target rate for the individual users, Reference [10] analyzed the outage probability with respect to the total data rates.…”

Joint Power and Time Allocation in Hybrid NoMA/OMA IoT Networks for Two-Way Communications

“…Non-orthogonal multiple access (NoMA) allows simultaneous transmission for multiple users on the same frequency via power domain superimposed coding, thereby achieving improved spectrum efficiency as compared to conventional orthogonal multiple access (OMA), such as time division multiple access (TDMA) [ 1 , 2 ]. Since its advent, NoMA has appeared in a variety of communication scenarios from Sub-6 GHz communications, ground networks, and cognitive radio networks, to mmWave and terahertz communications, space–air networks, and energy harvesting communication networks [ 3 , 4 , 5 ].…”