> would therefore require to move in and out of range (while the targeted user is continuously sending messages).
That, or a number of co-operating clients located at various locations in and out of the range.
A simple fix would be to have every sender generate a random vector of random length 0-100 meters (and re-generate every time you've moved at least 100 meters, you don't want to regenerate if the sender doesn't move as you'd be able to zero-in on a prolific sender), and have the message "originate" from the end of that vector.
That, or a number of co-operating clients located at various locations in and out of the range.
A simple fix would be to have every sender generate a random vector of random length 0-100 meters (and re-generate every time you've moved at least 100 meters, you don't want to regenerate if the sender doesn't move as you'd be able to zero-in on a prolific sender), and have the message "originate" from the end of that vector.