The satellite-aerial-terrestrial network (SATN) is a promising architecture to achieve seamless global coverage and meet diverse quality-of-service (QoS) requirements in next-generation wireless communications. To support such multi-layered connectivity, we consider a mixed radio frequency (RF) and free-space optical (FSO) architecture, where heterogeneous users access a high-altitude platform (HAP) via RF links, and the HAP, acting as an aerial relay, forwards the aggregated traffic to a satellite through an FSO backhaul. Existing transmission schemes for such mixed RF-FSO SATNs, however, are not well suited to providing differentiated statistical QoS guarantees for heterogeneous users. To address this limitation, we propose a mixed RF-FSO QoS-aware uplink transmission (MRQ-UT) scheme. Specifically, we impose statistical delay-QoS constraints at both the user and HAP buffers, thereby explicitly capturing heterogeneous constraints on queueing delay and buffer overflow. On this basis, we derive the system effective capacity using a two-stage tandem queue model, which captures the sequential queuing behavior over the RF access and FSO backhaul links. Building upon this model, we develop a tractable effective-capacity-based optimization framework and propose a statistical channel-aware joint power and beamforming algorithm that enhances QoS provisioning under imperfect channel state information. Simulation results demonstrate that the proposed MRQ-UT scheme significantly outperforms benchmark schemes in terms of effective capacity and statistical QoS performance.

ABSTRACT In this paper, we investigate an unmanned aerial vehicle (UAV) enabled secure multicast communication system, where a UAV serves multiple legitimate ground users in the presence of multiple coordinated eavesdroppers. Taking into account the inherent jittering characteristics of UAVs caused by the airflow, we aim to maximise the worst‐case secrecy energy efficiency (SEE) under a constrained UAV transmission power budget. The formulated optimization problem is inherently non‐convex and challenging to solve due to the combined effects of jittering uncertainties and the max–min fractional structure of the SEE metric. To address these challenges, we first simplify the original SEE maximization problem by introducing auxiliary variables. Next, considering the impact of jittering on the antenna array response, we develop a novel second‐order Taylor series expansion‐based approach to approximate beamforming gains as quadratic functions of the angle‐of‐departure errors, which can be subsequently transformed into deterministic convex constraints by using S ‐Procedure. Based on these theoretical results, we design an iterative algorithm that combines the penalty function method with the successive convex approximation to efficiently obtain a suboptimal solution. Finally, the simulation results demonstrate the effectiveness and superiority of the proposed scheme compared to several benchmark schemes, highlighting its potential for practical implementation in UAV‐enabled secure multicast communication systems.

This paper investigates a location-based downlink transmission scheme to provide diverse services for different users in an integrated satellite-terrestrial network (ISTN). Specifically, the satellite network employs multicast communication to disseminate information to multiple satellite users, while the terrestrial network incorporates non-orthogonal multiple access (NOMA) with intelligent reflecting surface (IRS) technology to serve terrestrial users. Given that the location information-based channel state information (LoI-CSI) of each user is available, we formulate an optimization problem to minimize the outage probability (OP) of the terrestrial network by optimizing the transmit power and beamforming (BF) weight vector at the base station, the IRS phase shift vector, and the power allocation factor, while meeting the quality-of-service (QoS) requirement of the satellite network. To make the optimization problem tractable, we first propose a low-complexity BF algorithm based on the LoI-CSI, which simplifies the optimization problem while guaranteeing the QoS requirement of the satellite network. Then, assuming that terrestrial links experience Rician fading, we derive an approximate yet accurate OP of the terrestrial network, which is explored to calculate the phase shift vector. Furthermore, we propose a novel power allocation method that employs an exponential-type approximation of the first-order Marcum Q-function, to obtain the power allocation coefficient. Finally, simulation results confirm the theoretical formulas’ validity and reveal the proposed algorithms’ superiority in system performance.

This paper investigates a low-complexity downlink transmission to provide diverse services for different users in an integrated satellite-terrestrial network (ISTN). Specifically, given that the location information-based channel state information (LoI-CSI) of each user is available, we formulate an optimization problem to minimize the outage probability (OP) of the terrestrial network by jointly optimizing the transmit power and beamforming (BF) weight vector at the base station (BS), and the phase shift vector at the intelligent reflecting surface (IRS), while meeting the quality-of-service (QoS) requirement of the satellite network. To make the optimization problem tractable, we first use the LoI-CSI and propose a low-complexity BF algorithm to obtain the transmit power and BF weight vector. Then, employing IRS and non-orthogonal multiple access (NOMA) in the terrestrial network, we derive its closed-form expression for the OP of the terrestrial network, which is explored to calculate the IRS phase shift vector. Finally, simulation results confirm the validity of the theoretical formulas and reveal the proposed algorithms superiority in system performance.

High-throughput satellites (HTSs) play an important role in future millimeter-wave (mmWave) aeronautical communication to meet high speed and broad bandwidth requirements. This paper investigates the outage performance of an aeronautical broadband satellite communication system’s forward link, where the feeder link from the gateway to the HTS uses free-space optical (FSO) transmission and the user link from the HTS to aircraft operates at the mmWave band. In the user link, spot beam technology is exploited at the HTS and a massive antenna array is deployed at the aircraft. We first present a location-based beamforming (BF) scheme to maximize the expected output signal-to-noise ratio (SNR) of the forward link with the amplify-and-forward (AF) protocol, which turns out to be a phased array. Then, by supposing that the FSO feeder link follows Gamma-Gamma fading whereas the mmWave user link experiences shadowed Rician fading, we take the influence of the phase error into account, and derive the closed-form expression of the outage probability (OP) for the considered system. To gain further insight, a simple asymptotic OP expression at a high SNR is provided to show the diversity order and coding gain. Finally, numerical simulations are conducted to confirm the validity of the theoretical analysis and reveal the effects of phase errors on the system outage performance.