Since existing mobile communication networks may not be able to meet the low latency and high-efficiency requirements of emerging technologies and applications, novel network architectures need to be investigated to support these new requirements. As a new network architecture that integrates satellite systems, air networks and ground communication, Space-Air-Ground Integrated Network (SAGIN) has attracted extensive attention in recent years. This paper summarizes the recent research work on SAGIN from several aspects, with the basic information of SAGIN first introduced, followed by the physical characteristics. Then the drive and prospects of the current SAGIN architecture in supporting new requirements are deeply analyzed. On this basis, the requirements and challenges are analyzed. Finally, it summarizes the existing solutions and prospects the future research directions.

翻译：由于现有移动通信网络可能无法满足新兴技术和应用对低延迟与高效率的需求，需要研究新型网络架构以支撑这些新需求。空天地一体化网络（Space-Air-Ground Integrated Network, SAGIN）作为一种融合卫星系统、空中网络与地面通信的新型网络架构，近年来受到广泛关注。本文从多个方面梳理了SAGIN领域的近期研究工作：首先介绍SAGIN的基本信息及物理特性，继而深入分析当前SAGIN架构在支持新需求方面的驱动力与前景，在此基础上探讨相关需求与挑战，最后总结现有解决方案并展望未来研究方向。