Towards the Internet of X-things: New Possibilities for Underwater, Underground, and Outer Space Exploration

The rapid growth of the world's population demands more natural resources, food, and space. World-renowned physicist Stephan Hawking has argued that soon we will require another world to live on because we are running out of space and natural resources. This ever-increasing demand for resources and space needs novel technologies to explore natural resources, produce more crops, and explore outer space. Internet of X-things (X-IoT) is an enabling technology to overcome all of the above issues. In this article, we have presented an overview of a unified framework of X-IoT. The framework of X-IoT consists of three major categories. The first one is the Internet of underwater things (IoUT) for smart oceans. The second category is the Internet of underground things (IoUGT) for smart agriculture, seismic monitoring, and Oil/Gas fields. The third category is the Internet of space things (IoST) for outer space exploration, to provide global coverage, and to enable inter-satellite communications. Through this framework, we get to know what has been done since recently and how the technical challenges across the broad spectrum of emerging use cases under the water, underground and over the space are converging toward future solutions.