The high mobility of unmanned aerial vehicles (UAVs) could bring abundant degrees of freedom for the design of wireless communication systems, which results in that UAVs, especially UAV swarm, have attracted considerable attention. This paper considers a UAV Swarm enabled relaying communication system, where multiple UAV relays are organized via coordinated multiple points (CoMP) as a UAV swarm to enhance physical layer security of the system in the presence of an eavesdropper. In order to maximize achievable secrecy rate of downlink, we jointly optimize the beamforming vector of the virtual array shaped by the UAV swarm and bandwidth allocation on it for receiving and forwarding, and both amplify-and-forward (AF) and decode-and-forward (DF) protocols are considered on the UAV swarm. Due to the non-convexity of the joint optimization problem, we propose an alternating optimization (AO) algorithm to decompose it into two subproblems utilizing block coordinate descent technique, then each subproblem is solved by successive convex optimization method. Simulation results demonstrate that DF has competitive performance advantage compared with AF and the superiority of the proposed secure transmission strategy with optimal beamforming and bandwidth allocation compared with benchmark strategies.

An important vision of next generation mobile system is to provide global internet access. The Space-Terrestrial Integrated Network(STIN) has been proposed and intensively studied to tackle this challenge. Due to the severe attenuation of radio signals in water, the STIN cannot be directly applied in underwater scenarios. In this paper we envision a framework of integrated radio-acoustic network arming at high-efficient data transmission in underwater scenarios, where acoustic signal is for underwater communication and radio signal is for surface and air communications. Since radio links have much higher data transmission rate and lower delay, in the integrated radio-acoustic network, the acoustic links easily become congested, at the same time the radio links are not fully utilized. We therefore propose that the integrated radio-acoustic network should be properly designed to minimize the hop count of acoustic links, as well as the signaling overhead in the acoustic subnetwork. We then present a novel network framework and the relative technologies to help moving the signaling overhead to the radio subnetwork.

Beam hopping technology provides a foundation for the flexible allocation and efficient utilization of satellite resources, which is considered as a key technology for the next generation of high throughput satellite systems. To alleviate the contradiction between resource utilization and co-frequency interference in beam hopping technology, this paper firstly studies dynamic clustering to balance traffic between clusters and proposes cluster hopping pool optimization method to avoid inter-cluster interference. Then based on the optimization results, a novel joint beam hopping and precoding algorithm is provided to combine resource allocation and intra-cluster interference suppression, which can make efficient utilization of system resources and achieve reliable and near-optimal transmission capacity. The simulation results show that, compared with traditional methods, the proposed algorithms can dynamically adjust to balance demand traffic between clusters and meet the service requirements of each beam, also eliminate the co-channel interference to improve the performance of satellite network.

In this paper, we investigate a spectrum-sensing system in the presence of a satellite, where the satellite works as a sensing node. Considering the conventional energy detection method is sensitive to the noise uncertainty, thus, a temporal convolutional network (TCN) based spectrum-sensing method is designed to eliminate the effect of the noise uncertainty and improve the performance of spectrum sensing, relying on the offline training and the online detection stages. Specifically, in the offline training stage, spectrum data captured by the satellite is sent to the TCN deployed on the gateway for training purpose. Moreover, in the online detection stage, the well trained TCN is utilized to perform real-time spectrum sensing, which can upgrade spectrum-sensing performance by exploiting the temporal features. Additionally, simulation results demonstrate that the proposed method achieves a higher probability of detection than that of the conventional energy detection (ED), the convolutional neural network (CNN), and deep neural network (DNN). Furthermore, the proposed method outperforms the CNN and the DNN in terms of a lower computational complexity.

The six-generation (6G) wireless network is expected to satisfy the requirements of ubiquitous connectivity and intelligent endogenous. Terrestrial-satellite networks (TSN) enable seamless coverage for terrestrial users in a wide area, making it very promising in 6G. As data traffic in TSNs surges, the integrated management for caching, computing, and communication (3C) has attracted much research attention. In this paper, we investigate the multi-resource management in the uplink and downlink transmission of TSN, respectively. In particularly, we aim to guarantee both throughput fairness and data security in the uplink transmission of TSN. Considering the intermittent communication of the satellite, we introduce two kinds of relays, i.e., terrestrial relays (TRs) and aerial relays (ARs) to improve the system throughput performance in the downlink transmission of TSN. Finally, we study a specific case of TSN with the uplink and downlink transmission, and the corresponding simulation results validate the effectiveness of our proposed schemes.

Satellite mobile system and space-air-ground integrated network have a prominent superiority in global coverage which plays a critical role in remote and non-land regions, as well as emergency communications. However, due to the gradual angle attenuations of the satellite antennas, it is difficult to achieve full frequency multiplex among different beams as terrestrial 5G network. Multi-color frequency reuse is widely adopted in both academic and industry. Beam hopping scheme has attracted the attention of researchers recently due to the allocation flexibility. In this paper, we focus on analyzing the performance benefits of beam hopping compared with multi-color frequency reuse scheme in non-uniform user and traffic distributions in satellite system. Aerial networks are also introduced to form a space-air-ground integrated network for coverage enhancement, and the capacity improvement is analyzed. Besides, additional improved techniques are provided to make comprehensive analysis and comparisons. Theoretical analysis and simulation results indicate that the beam hopping scheme has a prominent superiority in the system capacity compared with the traditional multi-color frequency reuse scheme in both satellite mobile system and future space-air-ground integrated network.

The Unmanned Aerial Vehicle (UAV) technologies are envisioned to play an important role in the era of Air-Space-Ground integrated networks. In this paper, we investigate the connectivity of a Flying Ad hoc Network (FANET) in the presence of a ground-based terminal. In particular, the connected probability of the UAV-to-UAV (U2U) link as well as that of the UAV-to-Ground (U2G) link in a three dimensional (3D) space are analyzed. Furthermore, to mitigate the aggregate interference from UAV individuals, a priority based power control scheme is implemented for enhancing the connectivity of both U2U and U2G links. Numerical results illustrate the effectiveness of the proposed analysis.