6G Space–Air–Ground Integrated Networks for Unmanned Operations: Closed-Loop Model and Task-Oriented Approach

In the upcoming sixth-generation (6G) era, supporting field robots for unmanned operations has emerged as an important application direction. To provide connectivity in remote areas, the space–air–ground integrated network (SAGIN) will play a crucial role in extending coverage. Through SAGIN connections, the sensors, edge platforms, and actuators form sensing–communication–computing–control (SC3) loops that can automatically execute complex tasks without human intervention. Similar to the reflex arc, the SC3 loop is an integrated structure that cannot be deconstructed. This necessitates a systematic approach that takes the SC3 loop rather than the communication link as the basic unit of SAGINs. Given the resource limitations in remote areas, we propose a radio-map-based task-oriented framework that uses environmental and task-related information to enable task-matched service provision. We detail how the network collects and uses this information and present task-oriented scheduling schemes. In the case study, we use a control task as an example and validate the superiority of the task-oriented closed-loop optimization scheme over traditional communication schemes. Finally, we discuss open challenges and possible solutions for developing nerve system-like SAGINs.