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The future sixth-generation (6G) communication system is promising to provide differentiated communication services for massive users worldwide. To achieve the above goals, wireless sensor networks (WSNs), regarded as the critical component of the 6G system, will be widely deployed in large-scale non-urban areas such as mountain villages, forests, and oceans. To ensure the high efficiency and stability of WSNs without the support of ground facilities, unmanned aerial vehicles (UAVs) are dispatched to provide assistance for WSNs. Nevertheless, considering the limitations of both the mobility and communication capability of UAVs, the diversified communication demands pose huge challenges for UAV-aided WSNs in the large-scale application scenarios, such as how to schedule the SNs served in each time slot, how to optimize their working parameters and how to plan the UAV trajectory. Therefore, a joint user scheduling, power configuration, and trajectory planning strategy is proposed in this article, which is formulated as an optimization problem suffering from non-convexity and complication. The successive optimization scheme is adopted here to efficiently solve the above problem, which divides the original problem into three sub-problems and solves them iteratively. The simulation results prove the effectiveness and efficiency of the proposed strategy.

With the increasing number of Internet of Things (IoT), Industry 4.0 (I4.0), and mobile devices, it can be expected that base stations will have to serve more and more clients with a limited number of antennas. For their broadcast channels, nonorthogonal multiple access (NOMA) and blind interference alignment (BIA) are two efficient and commonly adopted transmission schemes. This paper conducts a comparison study on these techniques on a 3-user 2 × 1 multiple-input single-output (MISO) broadcast channel with a limited number of transmit antennas. Specifically, space-time block coding based NOMA (STBC-NOMA) and NOMA-assisted beamforming (NOMA-BF) are compared with BIA. Both perfect and imperfect successive interference cancellation (SIC) have been considered for NOMA-based schemes, and the theoretical achievable rates of all schemes have been derived. Furthermore, with a given fairness constraint among end users, the power allocation (PA) problems have been solved for cases when accurate channel state information is available at the transmitter (CSIT) as well as when only path loss information is available. Numerical results show the following: (1) none of the schemes under this study can always outperform the others under different SNR regions. (2) With imperfect SIC, NOMA-BF, and STBC-NOMA both suffer from a significant performance loss under a high SNR condition. (3) Fairness PA with only path loss information provides similar performance as that with perfect CSIT, thus partial CSIT is adequate for system or scheme designs in practice.

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