# Covert Communication for Integrated Satellite-Terrestrial Relay Networks with Cooperative Jamming
###### Abstract  
We explore the influence of cooperative jamming on covert communication for integrated satellite-terrestrial relay networks (ISTRN) in this article, where one full-duplex relay is utilized to support communications and acts as a jammer to confuse eavesdroppers. A cooperative scheme is first proposed to efficiently achieve covert communication in this specific scenario. Further, the probability of detection error (PDE) is derived. Subsequently, the minimum PDE is calculated using the optimal detection threshold. Moreover, a closed-form expression of outage probability (OP) is acquired to quantify the system's covert performance. Based on this, we design a power optimization algorithm to enhance the effective covert rate under covertness constraints. Lastly, numerical simulation results are given to verify the efficiency of our cooperative jamming scheme when interrupting the eavesdroppers. Notably, an optimal power allocation factor can be obtained, leading to a higher effective covert rate. integrated satellite-terrestrial relay networks; cooperative jamming; power allocation factor; covert performance +
Footnote †: journal: Electronics Letters  
02032312  
Further, the ISTRN absorbs the merits of SatCom and terrestrial networks [8], and thus can not only satisfy gradually expanding communication demands but also diversify communication ways. Many scholars have conducted extensive and in-depth research. In [7], the authors provided a comprehensive study of emerging technologies for 6G-oriented integrated satellite-terrestrial networks, further including an analysis of the component architectures, a discussion of typical applications and a presentation of potential future challenges. Similarly, the authors of [9] explored how to design and implement a 6G-oriented integrated satellite-terrestrial network. The communication performance of the ISTRN with multi-antenna terrestrial relays was analyzed after considering hardware impairments and the effects of interference on relays and destinations in [10]. In [11], the authors introduced cognitive radio (CR) and non-orthogonal multiple access (NOMA) techniques into the ISTRN in order to significantly improve the spectrum utilization efficiency and studied the system performance in a multi-user scenario based on this. Furthermore, the authors of [12] investigated the impact of channel estimation errors (CEE) and hardware losses (HI) on the security performance of the above-mentioned ISTRN with CR and NOMA techniques. Considering the demands of different users for spectral efficiency in the ISTRN, two antenna selection strategies were proposed to balance the effectiveness and complexity of the system in [13]. In addition, the joint problem of user association and spectrum allocation in ISTRN was studied in [14; 15]. However, owing to the broadcast characters of the satellite beams and the openness of wireless communication, secrecy problems always exist in ISTRN [16]. Without loss of generality, ensuring that malicious eavesdroppers are unaware of communication behavior between legitimate parties may be the most direct and effective method of secure communication. As an emerging security technique, covert communication aims to achieve secure and reliable wireless communication with a low probability of being detected [17]. Moreover, there are various applications for this, such as secret combat operations, intelligent reflecting surfaces and unmanned aerial vehicle (UAV) networks [18]. In previous pioneering works, the authors illustrated the limits of covert communication [19; 20], such as the square root law. To enhance its effectiveness, the work by [PERSON] used an uninformed jammer, which generated artificial noise for the eavesdroppers [21]. Moreover, the authors of [22] utilized the inherent uncertainty of channels to realize covert transmission in relay networks. In [23], the feasibility and achievable performance of covert communication were examined in amplify-and-forward (AF) relay networks.