Satellite Internet of Things:challenges,solutions,and development trends

Satellite Internet of Things(IoT)is a promising way to provide seamless coverage to a massive number of devices all over the world,especially in remote areas not covered by cellular networks,e.g.,forests,oceans,mountains,and deserts.In general,satellite IoT networks take low Earth orbit(LEO)satellites as access points,which solves the problem of wide coverage,but leads to many challenging issues.We first give an overview of satellite IoT,with an emphasis on revealing the characteristics of IoT services.Then,the challenging issues of satellite IoT,i.e.,massive connectivity,wide coverage,high mobility,low power,and stringent delay,are analyzed in detail.Furthermore,the possible solutions to these challenges are provided.In particular,new massive access protocols and techniques are designed according to the characteristics and requirements of satellite IoT.Finally,we discuss several development trends of satellite IoT to stimulate and encourage further research in such a broad area.