3 Smart end user devices
3.1 Smartphones

The most widespread smart device today is for sure a smartphone that represents a portable (handheld) personal computer. Except for basic function - telephoning - it provides large amount of other functions. It is connected not only with its high computing power but also with support for wireless communication (in addition to mobile network access it is equipped by Wi-Fi and Bluetooth interface and in some cases by NFC). Via wireless interfaces smartphones are able to communicate with other smartphones, smart watches or glasses, or even with smart TVs and computers. Smartphones dispose of a number of sensors (Table 1) that even more extend a portfolio of possible applications [14].

Table 1 The most used sensors in smartphones
Sensors | Measured parameter
Accelerometer | Acceleration
Gyroscope | Orientation and angular velocity
Magnetometer | Magnetic field
Barometer | Atmospheric pressure
Distance sensor | Object distance from a smartphone
Light sensor | Light conditions
Touch screen | Finger touch
GPS | Position on Earth
Front and rear camera | Picture
Microphone | Sound

Fig. 7 Examples of smartphones

Smartphones provides high speed access to Internet via mobile or Wi-Fi interface. They are equipped by (SD) memory card reader and USB interface. They contain a mobile operating system that enables users to run and use huge number of applications.

These applications allow user to use following functions and services:

- telephone calls, SMS/MMS, email, online text, voice a video chat,
- taking pictures and videos, audio recording,
- satellite navigation, compass, trip planner, weather forecasting,
- multimedia content playing, reading and editing documents,
- web browser, news, educational courses, event calendar, address book, mobile payment, notes,
- clock, alarm clock, notifications, alerts (including vibration), calculator, flashlight,
- virtual assistants (Apple Siri, Amazon Alexa, Google Assistant, Microsoft Cortana, BlackBerry Assistant, Samsung Bixby),
- games and many others.

In Fig. 8 a simplified logical diagram of a smartphone is depicted [15]. The smartphone basis comprises from two to eight core processor (up to 2.8 GHz), graphical processor, RAM up to 8 GB and Flash memory up to 256 GB, modules with wireless interfaces, up to 6” touch screen (LCD, IPS, LED, OLED or AMOLED) display (with up to 3840x2160 resolution), various types of sensors, and that all powered by a rechargeable lithium-ion or lithium-polymer battery with a capacity up to 4000 mAh. Cameras for still pictures with up to 20 MPx resolution and video up to 16 Mpx are inseparable part of smartphones. Currently, there are on a mobile operating system market two leading representatives namely Android from Google (with open course) and iOS from Apple (proprietary). The other currently developing operating systems are e.g. Tizen (Samsung) or Sailfish (Jolla). In 2017 (first quarter) Android OS dominated on the market. 86.1 % of all smartphones run Android OS and 13.7 % run iOS [16].

Fig. 8 General/simplified logical diagram of a smartphone [15]