2.1 Mobile Device Characteristics
Mobile devices perform various functions ranging from a simple telephony device to those of a personal computer. Designed for mobility, they are compact in size, battery-powered, and lightweight. Most mobile devices have a basic set of comparable features and capabilities. They house a microprocessor, read-only memory (ROM), random access memory (RAM), a radio module, a digital signal processor, a microphone and speaker, a variety of hardware keys and interfaces, and a liquid crystal display (LCD). The operating system (OS) of a mobile device may be stored in either NAND or NOR memory, while code execution typically occurs in RAM.
Currently, mobile devices are equipped with system-level microprocessors that reduce the number of supporting chips required and include a considerable internal memory capacity currently up to 64GB (e.g., Stacked NAND). Built-in Secure Digital (SD) memory card slots, such as one for the micro Secure Digital eXtended Capacity (microSDXC), may support removable memory with capacities ranging from 64GB to 2TB of storage. Manufacturers can build into the devices non-cellular wireless communications such as infrared (i.e., IrDA), Bluetooth, Near Field Communication (NFC), and WiFi that support synchronization protocols to exchange other data (e.g., graphics, audio, and video file formats).
Different mobile devices have different technical and physical characteristics (e.g., size, weight, processor speed, memory capacity). Mobile devices may also use different types of expansion capabilities to provide additional functionality. Furthermore, mobile device capabilities sometimes include those of other devices such as handheld Global Positioning Systems (GPS), cameras (still and video), or personal computers. Overall, mobile devices can be classified as feature phones that are primarily simple voice and messaging communication devices or smartphones that offer more advanced capabilities and services for multimedia,
similar to those of a personal computer. Table 1 highlights the general hardware characteristics of feature and smartphone models, which underscore this diversity.
The classification scheme is illustrative and intended to give a sense of the range of hardware characteristics currently in the marketplace. Over time, characteristics found in smartphones tend to appear in feature phones as new technology is introduced to smartphones. Though the lines of delineation are somewhat fuzzy and dynamic, the classification scheme nevertheless serves as a general guide.
Both feature phones and smartphones that support voice, text messaging, and a set of basic Personal Information Management (PIM) type applications, including phonebooks and calendar facilities. Smartphones add PC-like capability for running a wide variety of general and special-purpose applications. Smartphones are typically larger than feature phones, support higher video resolutions (e.g., ~300 PPI), and have an integrated QWERTY keyboard or a touch-sensitive screen. Smartphones generally support a wide array of applications, available through an application storefront. Table 2 lists the differences in software capabilities found on these device classes.
Feature phones typically use a closed operating system with no published documentation. Many companies specializing in embedded software also offer real-time operating system solutions for manufacturers of mobile devices. Smartphones generally use either proprietary or an open-source operating system. Nearly all smartphones use one of the following operating systems: Android, BlackBerry OS, iOS, Symbian, WebOS, or Windows Phone. Unlike the more limited kernels in feature phones, these operating systems are multi-tasking and full-featured, designed specifically to match the capabilities of high-end mobile devices. Many smartphone operating systems manufacturers offer a Software Development Kit (SDK) (e.g., the Android1 or iOS2 SDKs).