A wireless inbuilt modem is an important feature in modern mobile systems .
Mobile operating systems combine features of a personal computer operating system with other features useful for mobile or handheld use ; usually including , and most of the following considered essential in modern mobile systems ; a wireless inbuilt modem and SIM tray for telephony and data connection , a touchscreen , cellular , Bluetooth , Wi-Fi Protected Access , Wi-Fi , Global Positioning System ( GPS ) mobile navigation , video- and single-frame picture cameras , speech recognition , voice recorder , music player , near field communication , and infrared blaster .