The motivation is to have a simple way to be tracked while running, walking or trekking. In my case, I'm going to run (well, I think I should say walk) the ultratrail 101 Km of Ronda in Malaga, South ...

Abstract: I welcome you to the fourth issue of the IEEE Communications Surveys and Tutorials in 2021. This issue includes 23 papers covering different aspects of communication networks. In particular, ...