Mid Sweden University

Enhancing reliability and energy efficiency is a key objective of sixth-generation (6G) wireless communication systems. To support this goal, we propose a novel ambient backscatter-assisted NOMA (AmBC-NOMA) system that jointly supports device-to-device (D2D) and cellular uplink communications, aiming to improve both energy efficiency and spectral utilization for low-power IoT networks. The system introduces a passive backscatter device (BSD) that enhances data forwarding without requiring active RF transmission. We derive closed-form expressions for the outage probabilities and SINR of both D2D and cellular links, considering realistic channel impairments and interference. Numerical results reveal that our architecture achieves up to 40% improvement in D2D outage performance and 10% better cellular reliability compared to OMA counterparts under practical SINR thresholds. These findings demonstrate the feasibility of integrating AmBC with NOMA for future green 6G wireless systems.

This paper proposes a novel partial non-orthogonal multiple access (P-NOMA)-based semi-integrated sensing and communication (ISaC) system design. As an example ISaC scenario, we consider a vehicle simultaneously receiving the communication signal from infrastructure-to-vehicle (I2V) and sensing signal from vehicle-to-vehicle (V2V). P-NOMA allows exploiting both the orthogonal multiple access (OMA) and NOMA schemes for interference reduction and spectral efficiency (SE) enhancement while providing the flexibility of controlling the overlap of the sensing and communication signals according to the channel conditions and priority of the sensing and communication tasks. In this respect, we derive the closed-form expressions for communication outage probability and sensing probability of detection in Nakagami-m fading by considering the interference from the composite sensing channel. Our extensive analysis allows capturing the performance trade-offs of the communication and the sensing tasks with respect to various system parameters such as overlapping partial NOMA parameter, target range, radar cross section (RCS), and parameter m of the Nakagami-m fading channel. Our results show that the proposed P-NOMA-based semi-ISaC system outperforms the benchmark OMA-and NOMA-based systems in terms of communication spectral efficiency and probability of detection for the sensing target. 

The next generation of wireless communication systems will integrate terrestrial and nonterrestrial networks, targeting the coverage of the undercovered regions, especially those connected to marine activities. Unmanned aerial vehicle (UAV)-based connectivity solutions offer significant advances to support conventional terrestrial networks. However, the use of UAVs for maritime communication is still an unexplored area of research. Therefore, this article highlights different aspects of UAV-based maritime communication, including the basic architecture, various channel characteristics, and use cases. The article afterward discusses several open research problems, such as mobility management, trajectory optimization, interference management, and beam forming.

In this work, we consider the design of a radio resource management (RRM) solution for traffic steering (TS) use-case in the open radio access network (O-RAN). The O-RAN TS deals with the quality-of-service (QoS)-aware steering of the traffic by connectivity management (e.g., device-to-cell association, radio spectrum, and power allocation) for emerging heterogeneous networks (HetNets) in 5G-and-beyond systems. However, TS in HetNets is a complex problem in terms of efficiently assigning/utilizing the radio resources while satisfying the diverse QoS requirements of especially the cell-edge users due to their poor signal-to-interference-plus-noise ratio (SINR). In this respect, we propose an intelligent non-orthogonal multiple access (NOMA)-based RRM technique for a small cell base station (SBS) within a macro gNB. A Q-learning-assisted algorithm is designed to allocate the transmit power and frequency sub-bands at the O-RAN control layer such that interference from macro gNB to SBS devices is minimized while ensuring the QoS of the maximum number of devices. The numerical results show that the proposed method enhances the overall spectral efficiency of the NOMA-based TS use case without adding to the system's complexity or cost compared to traditional HetNet topologies such as co-channel deployments and dedicated channel deployments.