How Does a Smartphone Work?

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Close-up of a hand holding an iPhone
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Smartphones combine cellular radio technology with specially designed processors. As smartphones have evolved, app developers have found new, ingenious ways to use hardware and wireless connectivity to make information instantly available to users. Larger, more accurate touch displays enable multi-window computing with simultaneous input from all 10 fingers. Efficient multitasking and abundant memory enable recently used apps to reside in a stack without slowing down performance.


Voice, SMS and MMS

The first mobile phones needed huge batteries to transmit radio signals to towers that may have been many miles away. They relied on 1G radio technology to communicate over a relatively narrow bandwidth. Voice and SMS communication worked in much the same way as today, except that 2G radio technology introduced cellular towers and modern protocols such as GSM and CDMA, enabling mobile phones to use much less power. SMS communication works efficiently over a low-bandwidth connection by limiting messages to 160 bytes, and with the introduction of 3G technology, MMS can use the same protocol to deliver multimedia messages of unlimited size.


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Touch and Accelerometer Input

A smartphone's accelerometer measures the amount of static or dynamic force felt by the device and makes this information available to the operating system. While not all apps use accelerometer input, the accelerometer constantly polls the device's current position with respect to the Earth so that apps can retrieve it when needed. Most apps listen for touch input in the form of taps or gestures and execute program commands when the user interacts with the display in a certain way. For example, slowly sliding your thumb across the screen may not trigger a page flip, but sliding it more quickly generates an acceleration value high enough to flip the page.


Camera and Microphone Input

Most of the time, a smartphone's camera takes pictures, and its microphone records your voice during a phone call. App developers have also found creative ways to incorporate these input devices into useful software, such as QR code scanners and music identification services. A QR code is a digital code similar to a bar code, but with vertical as well as horizontal information, and a QR code scanner is a function that takes a QR code as input and produces product information, an HTTP link or some other information as output. Music identification services process a song snippet from a user's microphone input and match it with results in a database. With high-speed wireless Internet, the user immediately receives results from the service, and from these results, she may be able to download a song or follow a QR code link in a Web browser.


3-D Video Acceleration

As smartphone processor architecture has evolved, more complex software has become feasible, such as 3-D video gaming and hardware-accelerated graphics. Companies such as ARM, NVIDIA and Qualcom produce powerful CPUs and integrated GPUs that support 3-D video frameworks and use relatively little power. High-performance multi-core CPUs, such as the Snapdragon S3, achieve high clock speeds, low power consumption and low heat output by using a compact 45nm production process. Most mid-range smartphones still use processors with less powerful 65nm process CPUs and include more modest video acceleration.