I made these for an undergraduate course in Mobile Communications (CSE4215 at York University). The red dots mark the locations of "mobile users" (or their wireless gadgets). The histogram on the right shows the density of users in space over time.
Mobility models simulate how wireless devices and their users move in space over time. The track of one particular user is marked in blue. The animation above shows a Random Waypoint model - the user chooses a destination and won't change direction until it reaches there.
This one shows a Random Direction model (random walk).
Here's a Random Waypoint but with pause - the users stay at their destination for a while before moving on: