A long with the swift growth of communication services,various networks have undergone multidimensional technical evolution,e.g.high transmission speed and large bandwidth for ground cellular network,high mobility for aviation network,and wide-area coverage for satellite network.As the industry demands for joint operation arise,an integrated space-air-ground collaboration network will be formed.

This feature topic intends to promote the research on the network structure,transmission technology,resource management and cooperation for integrated space-air-ground network for industrial applications,and enhance the practical system performance which a single network can never achieve.Besides,in 2021,the Ministry of Science and Technology of China issued a research project“multi-mode network and communications”aiming the combinations between the satellite aviation and ground network.Based on these situations,seven papers have been accepted in this feature topic concerning various research issues.

The feature topic begins with the paper by Chao Liu et.al.,“On Connectivity of Flying Ad hoc Networks in the Presence of Ground Terminal”,presents U2U and U2G connectivity.Based on a system prototype,the enhanced connectivity between flying ad hoc node and ground terminal was analyzed as a part of space-air-ground network.Besides,the interference was also considered and analyzed in this paper.

The paper by Yitao Li et.al.,“Benefits Analysis of Beam Hopping in Satellite Mobile System with Unevenly Distributed Traffic”describes the traffic,beam hopping and multi-color frequency reuse for distributed traffic.This paper paid attention to the efficiency,capacity,system performance etc.,and also gave a description of the comparison for multi-color reuse and traditional ones.

The paper by Fu Shu et.al.,“Multi-Resources Management in 6G-oriented Terrestrial-Satellite Network”focuses on the resource management for 6G-oritented hybrid system,setting up a 3-step method that includes data accumulation,computing and wireless communication to guarantee capacity fairness and data security in the uplink and downlink,and two relay methods were proposed and the performance and effectiveness were also given in this paper.

Since the spectrum resource is limited,and the efficiency for spectrum share is a key problem in the space-air-ground network.The paper by Tao Ni et.al.,“Spectrum Sensing via Temporal Convolutional Network”assumes satellite as a sensing node and gives the eliminations method for noise effects.The details about TCN,CNN and DNN were given in the analysis part,that might be an improved method for the hybrid system.

The paper by Chen Zhang et.al.,“Joint Precoding Schemes for Flexible Resource Allocation in High Throughput Satellite Systems Based on Beam Hopping”puts forward the resource allocation by beam hopping for High Throughput traffic.The key problem here is the contradiction efficiency and frequency interference and the dynamic method in this paper reach a requirement balance.If the beam hopping can cooperate with territorial network,the throughput performance might be enhanced in this point.

The paper by Fangjiong Chen et.al.,“Radio-Acoustic Integrated Network for Ocean Information Transmission:Framework and Enabling Technologies”highlights the radio-acoustic network,and the merit in this paper is the combination of radio and ocean acoustic technology.

Space-terrestrial or space-ocean cooperation network can minimize hop count of acoustic links as well as the terrestrial hopping count,the coordination method researched in this paper is just a suitable candidate in this feature topic.Besides,the novel net framework made a closer step towards an integrated system.

The paper by Runze Dong et.al.,“Security Enhancement of UAV Swarm Enabled Relaying Systems with Joint Beamforming and Resource Allocation”focuses on the Security performance vis AF or DF mode,and for the non-convexity of optimization,while proposing a successive method and showing the merits of DF approach for UAV swarm.