"It is weird because all the parameters are scalar"
Not the way you're calling your function. You're calling it using command syntax which means the first input to your function is '1500' (a 1-by-4 char vector) rather than 1500 (a 1-by-1 double scalar.) You want to call it using function syntax instead:
matlab -r "UDP_WiFi_1(1500, 19.3, 7, 12000000);exit"
