Optimizing Connectivity and Scheduling of Near/Far Field Users in Massive MIMO-NOMA System

Hierarchical Distributed Distortion Aware Beamforming with Dynamic User Association & BS Clustering for Cell-Free Massive-MIMO Systems

The simulation results reveal that the proposed HC-DA-UA framework always outperforms the existing counterparts in terms of sum-rate, whilst substantially decreasing the computational complexity and signalling overhead, thus it is an efficient and scalable solution for next-generation hardware-impaired distributed wireless communication networks.

LD-NOMA: Multiple Access for Mixed Near-Field and Far-Field Communications

Different from existing works that mostly considered multiple access in either the far-field or near-field, we consider in this paper a new and practical scenario, and propose the concept of location division-assisted non-orthogonal multiple access (LD-NOMA) in mixed-field (near-field and far-field) communications to suppress multi-user interference and further enhance system spectrum efficiency. Specifically, we formulate an optimization problem to maximize the spectrum efficiency for all users under a total transmit power constraint by optimizing user clustering, hybrid precoding design, and power allocation. To gain useful insights, we first consider a two-user mixed-field NOMA system, deriving a closed-form solution for spectrum efficiency and analyzing the impact of channel correlation on it, while establishing the criteria for applying mixed-field LD-NOMA. Interestingly, we find that the coverage area of NOMA clusters is significantly expanded compared to that in previous near-field NOMA systems, due to the energy-spread effect in mixed-field scenarios. Furthermore, we extend the two-user mixed-field LD-NOMA to a multi-user scenario, develop a location/correlation-based user clustering algorithm, and present an overall framework for the deployment of LD-NOMA in multi-user mixed-field communications. Finally, simulation results validate the effectiveness of the proposed LD-NOMA in mixed-field communications.

Hierarchical RSMA in Multi-Antenna Downlink Systems: Outage Performance and Power Allocation

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.

Optimization of Resource Allocation in 5G MIMO Networks Using Linear Assignment Algorithms

Comparison shows that, under the evaluated DeepMIMO-based scenarios, the examined assignment-based methods exhibit different trade-offs in throughput, energy-consumption-related performance, bandwidth utilization, and adaptability to varying user demands, offering useful insights for 5G MIMO resource allocation studies.

Enhancement of Cooperative NOMA Performance via Integration with m-MIMO and Caching

Design and optimization of highly reliable cognitive non-orthogonal multiple access communication systems.

In this paper, we consider a coexisting network of cellular transmission and device-to-device (D2D) communication, in which BS wants to communicate with far user, meanwhile, a D2D source desires to transmit information to a D2D destination. However, due to heavy shadowing or severe path loss, their direct links are not available. To cope with this problem, a relay is employed to assist the involved transmission. For such a relay-assisted spectrum sharing network, two transmission schemes are designed, i.e., multiple access broadcast NOMA (M-NOMA) scheme and time division broadcast NOMA (T-NOMA) scheme. For each scheme, we first perform power optimization to minimize the outage probability (OP) of D2D communication under the quality of service (QoS) constraint of cellular transmission. Based on the optimization results, we derive the OPs for both cellular and D2D signals. To gain more insights, the asymptotic OPs and the average throughput for both schemes are provided as well. On this basis, we further propose a more superior hybrid M/T-NOMA cognitive communication scheme, in which the system will adaptively select the one with higher system throughput between M-NOMA and T-NOMA as the final transmission scheme. Simulation results validate the accuracy of our analyses, and reveal the performance gain of our schemes over the benchmark schemes.