I made these using MATLAB for an undergraduate course in Mobile Communications (CSE4215 at York University). The red dots mark the positions 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. The track of one 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: