In this paper, we propose a unified framework for hybrid satellite/unmanned aerial vehicle (HSUAV) terrestrial non-orthogonal multiple access (NOMA) networks, where satellite aims to communicate with ground users with the aid of a decode-forward (DF) UAV relay by using NOMA protocol. All users are randomly deployed to follow a homogeneous Poisson point process (PPP), which is modeled by the stochastic geometry approach. To reap the benefits of satellite and UAV, the links of both satellite-to-UAV and UAV-to-ground user are assumed to experience Rician fading. More practically, we assume that perfect channel state information (CSI) is infeasible at the receiver, as well as the distance-determined path-loss. To characterize the performance of the proposed framework, we derive analytical approximate closed-form expressions of the outage probability (OP) for the far user and the near user under the condition of imperfect CSI. Also, the system throughput under delay-limited transmission mode is evaluated and discussed. In order to obtain more insights, the asymptotic behavior is explored in the high signal-to-noise ratio (SNR) region and the diversity orders are obtained and discussed. To further improve the system performance, based on the derived approximations, we optimize the location of the UAV to maximize the sum rate by minimizing the average distance between the UAV and users. The simulated numerical results show that: i) there are error floors for the far and the near users due to the channel estimation error; ii) the outage probability decreases as the Rician factor K increasing, and iii) the outage performance and system throughput performance can be further improved considerably by carefully selecting the location of the UAV.

The upcoming Intelligent Transportation System (ITS) supported by sixth generation (6G) communication technologies is expected to face the great challenges of spectrum scarcity, large-scale connectivity, ultra-low latency, and various security threats. To mitigate these challenges and implement the ITS in practice, we propose an overlay cognitive ambient backscatter communication non-orthogonal multiple access (ABCom-NOMA) network for the ITS. Specifically, we elaborate on the secrecy performance the overlay cognitive ABCom-NOMA based on ITS in the presence of an eavesdropping vehicle by deriving the secrecy outage probability (SOP) between the primary network, overlay secondary network, and the eavesdropping vehicle of the considered networks, respectively. For comparison, the secrecy performance of secondary receiving vehicles is taken into account, and a series of numerical simulations by Monte-Carlo methods are carried out to investigate the secrecy performance. From the numerical results yielded by the simulations, we can conclude: 1) The secrecy performance of the proposed the overlay secondary network is superior to the one of the primary network; 2) The increasing of the power allocation factor yields a positive effect on the secrecy performance of the primary receiving vehicles but a negative effect on that of the secondary receiving vehicles.

Aiming at the unclear mechanism behind the sudden instability of coal wall spalling, this study takes a fully-mechanized mining face with large mining height as an example. Through theoretical analysis and numerical simulation, the energy release mechanism governing the instability of the coal shell structure is revealed, and a theoretical failure model for spalling prediction is established. Based on the mechanical characteristics of coal shell failure and employing the theory of plastic strain localization in coal mass, a catastrophe model for coal wall instability was developed by analyzing the incremental relationship between coal shell deformation and the work done by deviatoric stress. The research outcomes derived quantitative expressions for energy release and proposed the expression for deviatoric stress strain energy, clarifying that energy exceeding a critical threshold is the fundamental cause of sudden spalling. Furthermore, expressions for the release of volumetric strain energy and gas internal energy were derived, revealing the coupling mechanism between internal and external stresses. The research outcomes can be directly applied to predict the risk of rib spalling by monitoring the degree of energy accumulation and to optimize support parameter design based on the energy release threshold, providing theoretical guidance for safe mining in high-stress coal seams. This study achieves a breakthrough from phenomenological description to mechanistic quantification, holding significant practical value for the prevention and control of rib spalling disasters in fully-mechanized mining faces.

Electromagnetic wave penetration coal-rock communication is a significant part for the smart mine communication technology, there are great challenges for electromagnetic wave is rapidly attenuated by factors such as geology and coal seam structure. In order to provide a theory basis for wireless communication technology development in coal rock, based on the Maxwell’s equations, this paper establishes a physical model of wireless communication under the conditions of coal seam. To characterize the performance of the electromagnetic wave propagation, we use the Maxwell’s equations to derive the exact expression of attenuation coefficient. Also, the parameters of coal and other factors affecting the electromagnetic wave propagation are analyzed and discussed. To further obtain more insights, the attenuation coefficient and skin depth of the very low-frequency (VLF) electromagnetic wave in coal medium with different degrees of metamorphism are studied, as well as the influence of resistivity. This provides scientific theoretical support for the application of VLF communication in coal mines. Finally, our theoretical analyses are verified by computer simulation, and the simulated numerical results show that: 1) The range of frequency of electromagnetic wave suitable for coal medium propagation is 3~3KHz (VLF); 2) The order of the electromagnetic waves attenuation coefficient in coal with different degrees of metamorphism is: anthracite > lignite > fat coal > coking coal > lean coal, and the order of skin depth is: lean coal > coking coal > fat coal > lignite > anthracite; 3) The resistivity of coal has little effect on the attenuation of electromagnetic wave when VLF is used for communication.

With the large-scale commercialization of 5G networks, the era of Internet of Things (IoT), which is oriented toward the Internet of Everything (IoE), is coming. Under the circumstance, reliable and secure communication are the great challenges for future wireless network because of the broadcasting characteristics of electromagnetic wave. Physical-layer security (PLS) is an effective way to ensure secure communication by exploiting random nature of fading channels. Motivated by this, we investigate PLS of the wireless-powered cooperative multirelaying for IoT networks in the presence of eavesdropper with the estimation errors of channel (EEC) and imbalance between in-phase and quadrature-phase (IIQ). Specifically, the relays can be charged by the source with the aid of energy harvesters, and a novel more secure modify-and-forward (MF) relay protocol is proposed. For further improving energy efficiency and reducing extra interference, the $K$ th superior relay selection scheme is proposed since some best ones are not available due to some scheduling or failure. Based on the system under study, we derive the analytical expressions for the outage probability (OP), intercept probability (IP), and secrecy OP (SOP) to evaluate the reliable and secure performance of this consideration system. Particularly, we then analyze the asymptotic behaviors of the OP, IP, and SOP, respectively. Through computer simulation, we show that: 1) with EEC, the error floors of the OP and SOP are of presence; 2) multiple relays lead to better OP and SOP performance; and 3) IIQ improves the security and is detrimental to the system reliability.

Vehicle road cooperation systems are the vital components of intelligent transportation systems, destined to play an irreplaceable role in the future smart cites. Such systems are mandated to achieve elevated data rates, ultra-low latency, and enhanced reliability. To meet these requirements, we incorporate full-duplex (FD) and rate splitting multiple access (RSMA) into vehicle road cooperation systems and propose a downlink FD RSMA vehicle road cooperation system. More importantly, we introduce a crucial metric to evaluate the influence of the delay constraints on the system performance. Specifically, analytical expressions for the effective capacity of the nearby vehicle and the distant pedestrian are derived. We also provide the approximate expressions for the effective capacity at the low and high signal-to-noise ratios (SNRs) and the upper bound on the effective capacity to gain further insights. Furthermore, we expand our evaluation to include both throughput and energy efficiency for the FD RSMA vehicle road cooperation system. Results illustrate that: The effective capacity of the nearby vehicle increases with the increasing transmitted power at low SNRs, and stabilizes at a constant level at high SNRs. Conversely, the effective capacity of the distant pedestrian increases continuously with the higher transmitted power. The effective capacities of the vehicle and pedestrian are influenced by various factors, such as the transmitted power, power allocation coefficients, and quality of service exponent.