In single-input single-output downlink systems, the common and private streams in rate-splitting multiple access (RSMA) fully overlap in the power domain, causing strong inter-private interference. Under imperfect successive interference cancellation (SIC), this interference significantly increases users’ decoding error probability. To overcome this limitation, we propose a semi-rate-splitting multiple access (SRMA) scheme that distributes private streams across two distinct bandwidth/time regions rather than fully overlapping them. To evaluate the proposed SRMA, we formulate two design problems: 1) maximizing the minimum ergodic capacity (EC) among users and 2) minimizing the system connection outage probability (COP). Both problems jointly optimize the rate-split ratio, power allocation coefficient, and partitioned-resource factor. To address the non-convexity in these problems, we employ successive convex approximation and analytical reformulation to relax them into tractable convex problems with closed-form solutions. Monte-Carlo simulations demonstrate that SRMA outstandingly improves COP performance while achieving EC levels comparable to RSMA and outperforming conventional non-orthogonal multiple.
Results indicate that the proposed AO-SCA framework provides an effective and practical solution for fairness-aware power allocation in downlink MN-NOMA systems, and provides a balanced fairness-efficiency tradeoff.
Sudhir Kumar Dhotre, S. Nalbalwar, A. Nandgaonkar· International Research Journ...· 0 citations
Rate-Splitting Multiple Access (RSMA) has emerged as a robust interference management strategy for future wireless networks. This paper investigates the performance of a hierarchical RSMA scheme in the downlink of a multi-antenna system, designed to efficiently serve clustered user deployments. We derive exact and asymptotic closed-form expressions for the outage probability of users under Nakagami- $m$ fading channels, considering a two-layer message splitting architecture (systemcommon, group-common, and private streams). Furthermore, to ensure fairness and reliability, we formulate a min-max power allocation problem to minimize the worst-case outage probability among users. A Geometric Programming-based algorithm is proposed to solve the resulting non-convex optimization problem. The numerical results validate the theoretical analysis and demonstrate the impact of different strategies for using this model, such as the number of users per group, user allocation strategies, and the number of base station transmit antennas.
R. P. De Souza, E. Olivo· International Mediterranean...· 0 citations
Non-orthogonal multiple access (NOMA) is a kind of 5G and 6G radio access technology, which not only enhances spectrum efficiency but also enables several users at the same time to access the network and share the same frequency resource. This paper studies the problem of jointly optimizing power allocation and channel resource assignment in the downlink multi-carrier NOMA system, with the aim of maximizing the weighted sum rate under individual quality-of-service (QoS) constraints, per-user minimum rate requirements, and total transmit power budget. We cast the problem as a mixed-integer non-linear programming (MINLP) task and decompose it into two tractable subproblems: A low-complexity channel allocation step using a bipartite matching framework, followed by an successive convex approximation (SCA) solution to the power control step with Lagrangian duality. A closed-form expression for the optimal power ratio under fixed channel assignment is derived to achieve efficient iteration between the two stages. To further reduce the computational burden for dense deployment of the network, we combined the iterative scheme with a DRL module based on the deep deterministic policy gradient (DDPG) algorithm to enable the system to respond to changes in channel state without having to solve the optimization problem at each time slot. Simulation results show that when deployed in a 3GPP-compliant urban macro-cell environment, the proposed joint scheme can achieve 38 percent more sum throughput than orthogonal frequency-division multiple access (OFDMA) baselines, a 22 percent increase over fixed NOMA power allocation, and converges within 15 iterations under moderate user density. The energy efficiency gain is 3.62 bits/J/Hz when combining the DRL-based dynamic policy, and the practical feasibility of the proposed framework for next-generation network deployment is verified.
Yuming Fu, Xiaofeng Chang, Wanze Gan· Digital Signal and Computer...· 0 citations
Simulation results demonstrate that the APS NOMA scheme outperforms both the FPS NOMA and Orthogonal Multiple Access schemes, reducing OP significantly across a range of SNRs, making it highly effective for reliable and energy-efficient communication in future wireless networks.
S. Ajibowu, O. Adeleke, M. Asafa et al.· Nigerian Journal of Technolo...· 0 citations
In this paper, we study the optimization of subband precoder for an orthogonal frequency division multiplexing rate-splitting multiple access (OFDM-RSMA) system in a multi-user multiple-input single-output (MU-MISO) downlink scenario. In conventional OFDM-space division multiple access (SDMA) systems, each subband consisting of multiple subcarriers is generally precoded using a single precoder. This can lead to a performance degradation if the channel is frequency selective within a subband. To address this issue, leveraging RSMA’s robustness to multi-user interference and imperfect channel state information (CSI), we introduce RSMA into the OFDM system where subband precoding is applied. For the proposed RSMA-based subband precoding system, the sum rate and minimum rate are maximized by jointly optimizing the subband precoders and the portion of the common rates using the successive convex approximation (SCA) technique. We also propose low-complexity algorithms that exploit the structure of the achievable rate expressions derived for proposed RSMA-based subband precoding system and leverage the characteristic of the subcarrier channels in OFDM systems. Simulation results show that the proposed RSMA-based subband precoding system outperforms the SDMA-based subband precoding system, verifying the robustness of RSMA. Furthermore, we demonstrate that the proposed low-complexity algorithms can achieve satisfactory performance compared to the proposed SCA-based algorithms and can significantly outperform the practical zero-forcing-based subband precoder with comparable complexity.
Jeonghyun Moon, Hyesang Cho, Bruno Clerckx et al.· IEEE Transactions on Wireles...· 0 citations
Environment division multiple access (EDMA) has emerged as a promising multiple access paradigm, which mitigates inter-user interference by dynamically adjusting pinching antenna (PA) positions to the underlying propagation environment. This paper investigates a multi-user PA-enabled EDMA framework that accounts for probabilistic line-of-sight (LoS) blockages, random non-LoS (NLoS) scattering, and practical inwaveguide attenuation. With the aim of maximizing the total information rate, we formulate a joint PA deployment and power allocation problem subject to statistical rate outage constraints, the transmit power budget, and the feasible deployment region of PAs. We first consider a canonical two-user two-PA scenario and derive closed-form expressions for the outage probabilities, followed by a low-complexity projected gradient descent (PGD)-based algorithm to address the reformulated problem. Then, we extend our design to the general multi-user multi-PA scenario and derive tractable approximations for the outage probabilities by assuming interfering links to be NLoS and applying the Chernoff bounding technique, where a successive convex approximation (SCA)-based algorithm is proposed to handle the resulting nonconvex problem. Simulations validate the superiority of the proposed PA-enabled EDMA design and the effectiveness of the proposed algorithms. Specifically, both the PGD-based algorithm and the SCA-based algorithm achieve near-optimal performance in comparison with the exhaustive search. Furthermore, the PA-enabled EDMA design yields significant performance gains over both PA-enabled and conventional time division multiple access designs.
Weihao Mao, Yang Lu, Yanqing Xu et al.· 0 citations