Nowadays, critical information services such as emergency management and in-situation navigation rely heavily on the assumption of a reliable networking infrastructure and stable cloud processing, which is ineffective in infrastructure-less environments where disrupted or even no telecommunication connectivity is the norm. On the other hand, fog computing is an extension of cloud computing that is at the physical proximity of end-users to enable local storage, computing, and various forms of communication between devices and users. To this end, we design a fog system spanning hardware, software and networking, thus meeting the requirements of various stakeholders in difficult surroundings. As a complement to a cloud-centred solution, this system is geo-distributed, self-powered, self-managed, location-aware, highly efficient and able to provide situational information services without Internet connectivity. The proposed system has been implemented in national parklands of Australia to achieve a personalized information service, emergency management and in-park navigation for all types of parkland users. INDEX TERMS Fog system, service provisioning, energy sustainable, infrastructure-less networking.

Space-air-ground integrated networks (SAGINs) are key elements for facilitating high-speed seamless connectivity to the devices/users in infrastructure-less environments, where the traditional terrestrial networks are critically infeasible or uneconomical to be fully deployed. This article comprehensively surveys the advanced computing technologies that support the utilization of SAGINs for infrastructure-less environments. The advanced computing technologies refer to the emerging computing techniques, tools and the processes that can be utilized to support SAGINs in handling the increasing computing tasks. The main contents include: (1) background of SAGINs, (2) typical use cases of SAGINs in infrastructure-less environments, (3) advanced computing technologies to assist SAGINs to meet the requirements of various services in infrastructure-less environments, (4) the related practical initiatives, and (5) the open research challenges and the future research directions.

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