This paper conducts the performance analysis of a hybrid satellite-terrestrial cooperative network (HSTCN) having multi-antenna terrestrial relays. By assuming the availability of the direct link between the satellite and the destination, and considering the effects of hardware impairments (HIs) and interference on both relays and destination, we first propose a relay selection scheme to enhance the quality of the downlink transmission of the considered HSTCN. Then, we derive analytical expressions for the outage probability (OP) and throughput of the system using the proposed relay selection scheme. Furthermore, the asymptotic behavior of the HSTCN at high signal-to-noise-ratio (SNR) is also investigated to reveal the diversity order and array gain of the system. Finally, computer simulation results are provided to show the effectiveness of the relay selection scheme. The analysis shows that the system performance is significantly affected by the HIs and interference.

It is necessary but difficult to obtain a large number of labeled samples to train the classification model in many real scenes. This letter proposes an approach for specific emitter identification(SEI) by introducing model-agnostic meta-learning, which can achieve high accuracy in the case of a limited number of labeled training samples. Specially, we improve the approach to make it suitable for the classification of electromagnetic signals of multiple types of equipments, without spending a lot of time and data to retrain the model structure. The data collected from ZigBee devices and UAVs are used to verify the proposed approach. The simulation results shows that the accuracy of proposed approach can reach more than 90% even though the training task and testing task are two types of devices.

Satellite communication (SatCom) has attracted much attention due to its inherent characteristics. Security issues have gained severe concerns in SatCom since it is susceptible to be illegally eavesdropped by malicious ground stations within large-scale wireless coverage. In this paper, we investigate the physical layer security of a multiuser SatCom system in the presence of multiple eavesdroppers. Particularly, we propose a threshold-based scheduling scheme, where the geographically clustered eavesdroppers with both the colluded and collaborated eavesdropping scenarios are assumed. Specifically, closed-form expression for the secrecy outage probability (SOP) is derived for the passive eavesdropping scenario when the channel state information (CSI) of the eavesdroppers is unavailable. Moreover, we obtain a closed-form expression for the average secrecy capacity (ASC) of the considered system under the proposed user scheduling scheme. In order to get further insights of the proposed scheduling scheme at high signal-to-noise ratios (SNRs), the asymptotic analysis for the SOP and ASC is also demonstrated. Moreover, the reduced percentage with respect to number of user examination is also given, which validates the simplicity and efficiency of our proposed scheme compared to the traditional approaches. Numerical results deduce that with the proposed scheme, a comparable system performance with regard to the maximal selection (MS) scheme can be achieved.

This paper investigates the effect of hardware impairments on the physical layer security for a cell-free massive multiple-input multiple-output (MIMO) network in the presence of pilot spoofing attack. By employing a classical additive hardware distortion model, the joint hardware impairment effects brought by both access points (APs) and user equipments have been taken into account, whereas the eavesdropper is assumed to be equipped with perfect hardware. Thereby, we derive a closed-form lower bound for the ergodic secrecy rate in the presence of imperfect channel state information. To obtain further insights, we investigate asymptotic secrecy performance under different hardware scaling factors. It proves that the hardware-quality scaling effect vanishes as the number of APs increases in the considered secure cell-free massive MIMO system with active attack. Furthermore, by using continuous approximation and path-following algorithms, the optimal power allocation scheme is obtained to maximize the achievable secrecy rate. Numerical results validate the derived results and the efficiency of the proposed power allocation scheme.