Introduction to mobile devices

This article introduces mobile devices from a product and engineering perspective: what makes a device mobile, how hardware constraints affect applications, and why wireless connectivity, battery, screen size and input methods shape design decisions.

Introduction

If we think about mobile devices, the first thing that comes to mind it's a phone mobile. But currently there are several mobile devices available in the world. market: laptop PCs, tablets, smart watches (smartwatches), wearable devices (wearables), etc.

This diversity entails an important problem for those who must program them, since each one has particular characteristics: it has a specific memory or it must support a specific language and environment.

For all these reasons, in this module you will see the general characteristics of the devices mobile phones and then classify them. At a more technical level, we will see the components specifics they may have and we will go over the networks they can access.

1.General characteristics of the mobile devices

A large number of electronic devices are currently classified as devices mobiles, from telephones to tablets, passing through devices such as RFID readers⁽¹⁾. With as much classified technology as mobile, it can be difficult to determine What are the characteristics of mobile devices.

Before describing some mobile devices in detail, let's specify the concept of device treated in this subject. Below we detail the Essential features that mobile devices have:

They are small devices.
Most of these devices can be carried in the owner's pocket. or in a small bag.
They have processing capacity.
They have permanent or intermittent connection to a network.
They have memory (RAM, MicroSD cards, flash, etc.).
They are normally associated with the individual use of a person, both in possession and in operation, which you can adapt them to your liking.
They have a high capacity for interaction via screen, keyboard, vibrations or sounds, for example.

In most cases, a mobile device can be defined with four characteristics that differentiate it from other devices that, although they may seem similar, lack of some of the features of true mobile devices. These four Features are:

1) mobility

2) reduced size

3) wireless communication

4) interaction with people

1.1.Mobility

Mobility is understood as the quality of a device to be transported or moved frequently and easily. Therefore, the concept of mobility is a characteristic basic. Mobile devices are those that are small enough to be transported and used during transportation.

Any mobile device should work and be usable reliably while we move, regardless of the proximity of a power source (plug) or a physical connection to the Internet. To facilitate portability, devices Mobile phones usually contain rechargeable batteries, which allow several hours or more of operation without needing access to a charger or external power source.

1.2.Small size

Reduced size is understood as the quality of a mobile device to be easily used with one or two hands without the need for any external help or support. size Reduced size also allows the device to be carried comfortably by one person.

As we have seen previously, there are several terms in English that refer to mobile devices. Specifically, some devices are called handhelds or palmtops because, to a greater or lesser extent, its dimensions are similar to those of a hand. In contrast, other slightly larger mobile devices, such as might be the case of tablets, they are not usually called that. A typical mobile device we can carry with a hand and fits in a pocket or small bag. Some mobile devices can be deployed or unfolded from a portable or compact mode to a slightly smaller size. higher and discover larger keyboards or screens. Mobile devices can have touch screens or small numeric keypads to receive input data and maintain, at the same time, its small size and independence from external interface.

Netbooks

The netbooks and compact laptops (ultrabook) are often considered mobile devices due to their similarity in terms of functionality, but if the size of the device prevents comfortable handling (for example, without the help of a table) or limits portability, it cannot be considered a true device mobile and therefore we will not consider it as such in this documentation.

1.3.Wireless communication

Another important concept is the term wireless. By Wireless communication is understood as the capacity of a communication device. Send or receive data without the need for a wired link.

Therefore, a wireless device is one capable of communicate or access to a wireless network (for example, a mobile phone or tablet).

Mobile devices are normally capable of communicating with other devices similar, as well as with other computers and systems. A typical mobile device is capable of accessing the Internet, either through Bluetooth or WiFi networks, and many models They are also equipped to access MWWAN data networks, as well as other networks wireless data.

Text messages, emails and all kinds of multimedia content are standard forms of communication using mobile devices, which also allow make and receive phone calls. Some specialized mobile devices, such as RFID devices and barcode readers, communicate directly with a central device.

The concepts of mobile and without cables many times they confuse For example, a mobile device with data on it and applications to manage said data it can be mobile, but it does not have to be wireless, as you may need a cable to connect to the computer and obtain or send data and applications. Whether the device can connect to a wireless network to obtain data while we are walking down the street or in the office, then it will also be wireless.

1.4.Interaction with people

Interaction is understood as the process of use that establishes a user with a device. Among other factors, disciplines such as usability and ergonomics.

A user interacts with a mobile device through the interface of user. There are big differences in terms of the interaction between a PC⁽³⁾ and mobile devices (e.g. even between different mobile devices). By For example, how to read the notification of a new email message It will be very different from a mobile phone than from a smart watch. You have to keep in mind physical limitations: screen size, availability physical keyboard or not, etc.

2.Types of mobile devices

The term mobile device covers a wide range of devices electronic consumption. Typically, by mobile device we mean a device that can connect to the Internet. However, digital cameras are sometimes also classified as and standard MP3 or MP4 players as mobile devices. The device category mobile phones includes the devices that we present in this section, as well as other which we will not discuss here because they are not important for the objectives of this subject. Some of these devices are the following:

mobile phones (feature phone)
organizers and personal digital assistants (personal digital assistant)
two-way pagers
smartphones
handheld pc
tablet PC
tablets
e-books (e-books)
Smart watches (smartwatches)
Wearable devices (wearables)

A lot has changed since 1996, when the PalmPilot was launched. Even in that time, when other devices that fit in the palm had already appeared hand (like the Apple Newton), the PalmPilot changed the way we understand mobility. Thanks to it, users had the option of using a small device, palm-sized, to save your plans, calendars, to-do lists, as well as to run other simple applications. This was clearly a popular option. to users, as indicated by the good reception of Palm devices. In the year 2000, the vast majority of devices palm-sized They were based on the Palm OS⁽⁴⁾.

Due to the success of Palm devices, many other companies they launched offers of mobile devices to try to take a piece of the emerging market. A As new companies entered the market, they were introduced new devices with new features.

In this section we show you the main categories of mobile devices. Some of these categories have fallen into disuse having been "phagocytosed" by the smartphones and tablets, and are presented to give a historical perspective of the evolution of mobile devices and their capabilities.

2.1.Handheld PC

The concept of handheld PC is very old. The design can be similar to that of a laptop, in which the screen It folds over the keyboard and creates a compact casing around the device. By this reason, the handheld PCs were commonly known as computers clamshell⁽⁵⁾. The devices clamshell They appeared long before the first PDAs were available.

In the mid-eighties, Psion introduced a organizer-agenda that offered the ability to run applications. Allowed users to run applications financial, scientific and data applications locally on the device. These were applications added to the calculator function, which was the main function. Even having Keep in mind that this device was not very popular, it was the origin of the line which were later followed by handheld PC.

In the early 1990s, Psion launched a computer clamshell more functional, which had a keyboard and a screen with a graphical interface (GUI) to run more sophisticated applications. Other companies, such as Casio, launched similar offerings, often too based on proprietary operating systems device-specific. These operating systems did not support applications from third parties, which was a very important limitation. Shortly after, Microsoft, that wanted to enter the PDA operating system market, appeared with Windows CE. Most companies abandoned their proprietary systems and adopted Windows CE as an operating system option for its devices, although Psion was a notable exception. The specific implementation of Windows CE for devices with these characteristics is what gave rise to the handheld PC.

Later, most of the handheld PCs started to have a VGA (480 × 320) color screen with full keyboards. they had the ability to run a wide variety of client and web-based applications. In general, the handheld PCs were not used to replace laptops, but to complement them. The use common of a handheld PC was not that of a general computer, but that of a data collection device information. The VGA display and integrated keyboard provided fast data capture, which allowed companies to increase productivity in processes that previously required manual data capture.

There were many advantages of collecting data from the lines business with applications, replacing paper-based processes: the process is faster, data collection is more accurate, employee productivity increases, Transactions in business processes are streamlined and operational costs are reduced. Even taking into account that these benefits could be achieved with a laptop, a handheld PC was ideal for the job for the following reasons:

function on and off instantaneous, so access to data is immediate.
Long life time due to the low consumption chips used in its design. a single Battery charge can last a whole day of use.
Since they had no moving parts, they withstood shocks well, so they could be used in many environments.

These characteristics, in addition to the smaller size than that of a portable, they made them the ideal device for users interested in immediate access and capture of data. Some manufacturers such as HP bet heavily on this market segment. Despite this, the pocket computer market, however, was absorbed due to the success of smartphones and tablets, which ended up replacing them.

2.2.Digital staff assistant

A personal digital assistant (better known as PDA) was, As its name suggests, a digital organizer. PDAs (sometimes called pocket computers) combined computer elements, telephone, fax, Internet and networking on a single device. A PDA could function as a telephone mobile, fax, browser website and personal organizer. As common features, PDAs basically offered calendars, notepads and phone books, so they were the substitutes traditional features of classic agendas. They also allowed you to download emails and other materials from a computer, and access the Internet. The PDAs had the capacity of on and off instant, meaning the device did not have to boot every time that it was wanted to be used.

Unlike laptops, most first PDAs had a pen as an input device, instead of a keyboard. This meant that They incorporated handwriting recognition features. Furthermore, some PDAs could also react to voice commands using recognition technologies of voice. There were PDAs available in versions with stylus or keyboard (called datapad).

They normally consisted of a screen, usually a touch screen, a processor, memory and an operating system. In addition, they allowed, as we have already said, connection with the computer desktop or Internet.

There was a wide variety of personal organizers. The screen could be blank and black or color and the memory varied between 2 MB and 64 MB.

PDAs, compared to traditional mobile phones, presented some advantages:

The screens were bigger and the viewing was better.
Interaction with the user was easier (mainly because the screen is tactile).
They were more powerful (from a computational point of view).

However, they also had some drawbacks:

They needed accessories to communicate.
The price is higher than that of traditional mobile phones.

The most common devices in this market were the Palm and the Pocket PC. These seconds offered as a lure the possibility of using office software from Microsoft, made by which it had more powerful hardware and a higher price. Unfortunately, the emergence of smartphones with touch screens made this sector disappear from the market.

2.3.Mobile phone (feature phone)

Mobile phones are, by far, the devices wireless most used on the market. Generally, the main use was for calls voice, but with text messages first and other wireless technologies to accessing the Internet after, data applications have become widespread. Thank you Due to its great popularity, the web-enabled phones have become an immediate target for applications with wireless access to the Internet.

The figure shows a web-enabled phone typical. How can you See, it has a very limited screen (normally between four and twelve lines of text), with the typical keyboard keypad twelve buttons for input data. These limitations made telephones mobiles a very poor option for browsing the Internet because the amount of data that can be viewed or entered is very limited.

Nokia 8390 Web-enabled phone

However, the strong point of mobile phones was their use extended, so which were very interesting for the user applications market. some Examples include levels of stocks, traffic information, flight information, purchase of tickets and headlines of news. In all these applications a limited amount of data is required for them to work correctly. The amount of data received is not excessive, so so the device can display it in an easy to understand way. Yes, for him On the contrary, we intend to implement more ambitious applications in terms of volume data or how to display it, we will need more capable devices.

As expected, mobile phones allow users connect to networks wireless. Once connected, users can use the mobile for both calls for voice and data applications. Furthermore, thanks to the fact that they can always be On, cell phones are ideal for text messaging applications. Since these messages are generally limited to a length of one hundred and sixty characters, the data input capacity of these devices is adequate. another Advantage of these devices is the long battery life. With its ability to limited processing, cell phones can conserve energy and thus way, last longer on than more sophisticated devices such as smartphones or PDA.

The main use of these devices was for voice, so the communication quality voice, network coverage and call packages were typically a higher priority than data services when choosing one of these devices.

Currently, in developed countries the market share of these devices It is very low. But, on the other hand, in developing countries these phones They still have an important implementation. Its low cost, its greater resistance, the better battery life and poor quality of communications networks are some of the reasons for choosing this type of devices.

2.4.smartphone

The smartphones combine the concepts of mobile phone and computers handheld on a single device. The smartphones allow you to save information (e.g. emails) and install programs, in addition to using a mobile phone on a single device. For example, a smartphone could be considered as a mobile phone with PDA functions integrated into the device or vice versa.

Smartphone functions

Smartphones are phones that support more functions that a telephone common, such as an email manager; full organizer functionality staff; and include a large number of applications with various functionalities and are designed to continuously access the Internet. Currently they also have as a common function the possibility of installing additional programs or updating them.

One of the greatest attractions of the smartphones is your simplicity. The average user can have their device working in question of minutes without having to worry about complicated configuration.

Another attraction of these devices is that users can expand features of the device by downloading new applications using the wireless connection. This is called provisioning. over the air (OTA). Both mobile device manufacturers like telephone operators have created and are creating marketplaces or showcases where developers can Upload your apps for later downloads. Users can download the applications that interest them for a reduced price (usually between one and five euros). The profit is divided between the developer and the marketplace provider. Games have traditionally been the most downloaded applications.

2.4.1.smartphone low end

The smartphones They are called that because of their ability to run local applications and make calls of voice. Some of these devices are designed to offer a good relationship quality-price: they do not incorporate the most powerful hardware and have reduced features in exchange for having a more affordable price. These devices are known as telephones. low-end smart, and they have a good implementation in developing countries, where every time They are taking market share from feature phones.

These devices are primarily voice devices. The application support is more limited than high-end ones due to storage or capacity limitations processing. Furthermore, because these devices still have small processors and little memory, they are capable of lasting days running with a single battery charge. An example of a low-end smartphone is the Nokia 3 (2017).

2.4.2.smartphone high end

As the wireless applications market became maturing, it occurred a move toward much more powerful devices called smartphones high-end. The leading cell phone manufacturers (Nokia, Sony Mobile and Motorola, among others) began to produce these devices, which in principle They were designed for the professional market. These devices provide functionality for voice communication, as well as lightweight but useful client applications. This made them a good option for those people who did not want to carry with various devices, but who wanted to be able to continue enjoying a great variety of applications. An example is the Samsung Galaxy S7 edge.

The definition of a smartphone is located between that of a cell phone and a computer, and it increasingly resembles more to a computer. The first (especially before the massive appearance of devices with touch screen) typically had a sliding mechanism to display the screen complete and keyboard. When closed, they looked like normal cell phones, with the typical keypad with twelve keys and with a small part of the screen exposed. When were open, they had screen sizes ranging from 640 × 200 to 320 × 240. Sometimes they have also a keyboard for data entry.

Currently, devices have screens ranging from 5”, RAM memory 4Gb, several CPU cores, front and rear camera, gyroscope, GPS… The processors These devices are powerful enough to perform countless functionalities, either accessing the internet or working locally. They are very customizable (background screen, icons to display on the desktop, installed applications...) and have of markets to download applications and content.

Smartphones can be used for a few days with a single charge of battery, depending on the use made of them. The first operating systems For smartphones the most common were Symbian OS, Palm OS, Pocket PC Phone Edition and the Microsoft Smartphone 2002. Java ME support was also common.

In North America, the first smartphones they didn't have the same acceptance as in Europe and Asia due, among other reasons, to wireless network support, operating system used and market plans and distribution of manufacturers.

As exponents of the modern generation of smartphones, we can mention the iPhone 7 and the Samsung Galaxy (there are several options).

The iPhone incorporates features such as video calls, screen retina, multitasking, recording and editing in high definition and 4K, 6x digital zoom, 256Gb capacity and a 12-megapixel wide-angle and telephoto camera, support for reality virtual, among others.

The Samsung Galaxy S7 has a 12Mpx rear and 5Mpx camera in the front camera, fast charging, fingerprint reader, NFC, 4Gb of RAM, wireless charging and it is resistant to dust and water.

There are more brands in the mobile device sector than high-end, apart from Samsung and Apple, such as HTC, Sony, Huawei or Xiaomi.

2.5.Tablet PC

A tablet PC is a type of computer that has a screen tactile. Its operation is similar to that of a smartphone. Typically, you can also display a touch keyboard on the screen that is can use with a stylus or with your fingers. On this keyboard, the keys can be arranged as on a keyboard Standard QWERTY or differently. Optionally, the tablet PC may have accessories such as an external keyboard to facilitate desktop work. In fact, the border between a laptop and a tablet is very diffuse, with computers that present themselves as a "hybrid" between a laptop and a tablet, "convertible" or "2-in-1".

The tablet PCs had traditionally run Windows XP like your operating system and have the usual set of peripheral accessories for a laptop. Currently there are with Windows and Android operating system. They also have processing capabilities and similar storage. Therefore, we can consider them as an evolution of laptops, with all their features, with features of tablet added and with a longer battery life. For example, two devices in This category are Lenovo Ideapad MIIX 310-10IR (Android) or Acer SW3-013 – Tablet 10.1

The pressure of laptops on the one hand, and, above all, the tremendous evolution that have experienced the tablets pure, mean that this type of device has not had much success.

2.6.Tablet

After the historical review of the different types of devices mobiles, we arrive to touch tablets. There are two main differences between a touch tablet and a smartphone:

Connectivity: All smartphones have a connection to networks 3G/4G/5G, while most tablets only have Wi-Fi and Bluetooth connections; The 3G/4G/5G connection is an extra for the high-end models.

Screen size: Most tablets have a size around 10 inches, with slightly larger models (such as the 12.9-inch iPad Pro). On the other hand, there is also a range of "mini" tablets with a smaller screen size, around 7 inches (like the iPad Mini or the Samsung Galaxy Tab). Since the screen of smartphones grows over time, there is talk of phablets to describe devices that are intermediate in size between tablets and smart phones.

This market was initially dominated by Apple's iPad, but currently there is a large number of alternatives.

Apple iPad (EFE)

With one million iPads sold in the first month of its introduction, Apple quickly took the leading position in the touch tablet category, which it has maintained in the new versions of the device that it has been generating.

As points in favor of the iPad we can mention its elegant hardware, the App Store, which It is ideal for multimedia playback; a wide selection of games; a processor Fast, multi-touch screen, and long battery life. iPad contains A9 Chip with 64-bit architecture, Wi-Fi, LTE, gyroscope, accelerometer, barometer and others features.

As negative points it can be mentioned that users must buy software exclusively from Apple.

iPad 4

Currently there are numerous brands and models of tablet with system Android operating system. Samsung is one of the companies with the largest market share of high-end models. So, we have for example: Samsung Galaxy Tab S2 9.7”, with a 1.8 GHz 3Gb Octa-Core CPU of RAM, 4G, WiFi, accelerometer, gyroscope, fingerprint detector and other features.

2.7.Wearable devices or wearables

Wearable devices are electronic devices or devices which, due to its shape, weight and reduced size, they are designed to be transported somewhere in our body or the clothes we wear. These devices are always on and interact continuously with the user (using feedback such as sounds or vibrations, and receiving commands through gestures or voice) and with other devices in order to perform a specific function.

The main types are:

Smart watches (smartwatches), which allow you to receive notifications of agile way.
Smart glasses, which can offer augmented reality applications.
Smart bracelets (fitness bands), which allow controlling the activity physics.
Smart rings, which can offer similar functionality to bracelets or watches.
Smart clothing, for example, with a solar irradiation sensor to avoid burns by sunbathing excessively.

3.specific characteristics or mobile device components

In this section we will explain the different components that can have a device mobile phone, such as the keyboard, screen, sensors, connectors or batteries, and we will explain the different types that there may be of each component, as well as its main characteristics.

3.1.Keyboard of a device mobile

In this subsection we will show you the different types of keyboard what can you have a mobile device and the characteristics that each of them has. For this, We will use examples of devices with different keyboards. As you will see below, There are two large families of keyboards: physical and virtual. These last They are characterized by the fact that the keyboard appears drawn on the touch screen of the device and, therefore, does not represent a physical component of the device.

3.1.1.Physical QWERTY keyboard

When we talk about a QWERTY keyboard, we are actually talking about a distribution of keys like the one shown in the following figure. The name QWERTY comes from the same keyboard layout; If you look at the figure, you will see that the first six letters from left to right of the top row make up that word.

QWERTY keyboard

For many years, sending emails from a mobile It was something reserved to a few users. Furthermore, these emails rarely consisted of more than a few how many words, due to the difficulty of composing the message. With the appearance of text generation and social networks, a large number of users They can send countless messages, of any length. This made many devices incorporated the keyboards with the QWERTY layout that were already used in computers.

Teclado QWERTY completo de un dispositivo BlackBerry

Full QWERTY keyboard on a BlackBerry device

As far as smartphones are concerned, currently only a minority of devices maintain a physical keyboard: the vast majority have opted for a keyboard of software. In the case of tablets, this software keyboard can be supplemented by an external keyboard as an accessory, to make typing more comfortable. This keyboard It can be connected to the tablet via Bluetooth, for example.

3.1.2.Keyboards software

When we talk about keyboards software, we refer to the keyboards that touchscreen devices can present to us per screen for entering text, either by using a stylus or with our own fingers. Therefore, this category does not exclude those already seen.

The keyboards software have become very important thanks to touch screen devices such as, for example, the tablets. The arrival of the tablets forced us to rethink the use of keyboard.

In this subsection we are going to emphasize the software behind the touch keyboard. To do this, we will see some examples.

Swype

To begin with, we find the case of Swype. Swype provides a quick and easy way enter text on any touch screen. With a continuous movement of the finger or stylus along the on-screen keyboard, this technology allows users enter words faster and easier than other input methods data (about forty words per minute). The app is designed to work with a wide variety of devices (such as mobiles, tablets, video game consoles, televisions or virtual screens).

In the image you can see an example that illustrates how can generate the word quick tracing the path shown in a fraction of a second, just trying to get through by the letters of the word. A key advantage of Swype is that you do not need to be too precise, allowing for very fast text entry.

Swype Keyboard

Siine

The second keyboard example software what are we going to treat is Siine. Although with Swype there is an improvement in the way entering the data, behind Siine's philosophy is the premise that changing the way of entering the data is not enough. Siine provides textual communication. It is not a simple application, but a new form of communication, a new universal translator, a system that speaks "for the user."

As we have seen, some companies have already rethought the use of the keyboard and have replaced by programs like Swype, which allows you to write by simply moving your fingers through the screen or Swiftkey, which goes ahead and thinks of the word we are going to write at that moment (we only have to enter the first characters). The next step is textual communication.

In this context, Siine appears, a tool for communication that allows sending SMS from Android white screen. Unlike Swype or Swiftkey, not only introduces the words, but goes further. If acronyms are used, Siine detects it and can tell what they mean. With Siine you don't need any dictionary, since it can translate. The system exploits embedded meanings. Yes it is a system that incorporates intelligence and meaning, all to facilitate communication among users.

Snapkeys

Snapkeys is a virtual "keyboard" that allows you to type texts without looking and quickly. The peculiarity of this "keyboard" is that it simply does not have keys. Although not It may seem very logical, you can write relatively quickly without a keyboard some on the screen. The concept behind it is that the keyboard must be Imagine the user (2i) so you can write quickly. The creators assure which for novice users is 92% accurate and for experienced users it is 92% accurate. 99%, and that between sixty and one hundred and sixty characters can be typed per minute.

Comparison between Snapkeys and a virtual QWERTY keyboard

Features	2i	QWERTY (on screen)
Number of keys	0	101
Screen available	100 %	10-50 %
Write without seeing	Snapshot	almost never
Learn to write	Easily	Hardly
Finger movement	Minimum	too much
Data entry speed	Very fast	Slow
Interface	in your mind	Complex
Write long texts	It's a pleasure	It's tiring
Write on the move	Yes	difficult
Fun	like a video game	Never
Redesign	Not required	Necessary

Another advantage of this keyboard is the great comfort, since there is no need to move the fingers all over the screen to be able to write; just have them on each side of the screen.

The trick of this keyboard is that the developers have placed four blocks of letters in four squares, which are located at the bottom of the screen, so to type we have to click on the squares, and then these They become transparent over the interface we are using, so as not to disturb to the user.

As a last important piece of information, tell you that this application is available for various platforms (both mobile and tablets).

Blindtype

One of the worst aspects of Android was its keyboard virtual. It was not, by any means, the most comfortable in the world, and his predictions left a lot to be desired. Google it knew and, therefore, bought BlindType, a startup dedicated to improving virtual keyboards in smartphones.

Android bought it because it could earn a lot of points if implemented this improved keyboard, since it would alleviate one of the biggest headaches that touch phones cause.

The bad thing about this acquisition is that the development of keyboard for iOS stopped and left these users without enjoying this option for the keyboard. The Android ones do you can enjoy this keyboard, in addition to alternatives such as Swype, SwiftKey or SlideIT.

Graffiti

Graffiti is not a keyboard itself, but a very text entry system precise in which a pencil is used. With this pencil you can write quickly Letters and numbers in Graffiti writing area. This is a system that incorporates Palm handheld computers, along with a very intuitive graphical interface. This system recognizes a full range of upper and lower case letters, as well as digits, punctuation and special symbols. In the figure you can see examples of strokes for letters, like this such as space and the equivalent of the delete key.

Entering text with Graffiti

3.2.Screens of the mobile devices

3.2.1.Touch screens

Technology is evolving at great speed. Almost every day, some company launches a new device. The best example is mobile phones. There was days when people had big telephones that were called mobiles. Actually they were, but They don't have much to do with current mobile phones. Now mobile phones are compact, practical, have attractive designs and, In short, they have a large number of characteristics that make them something more than mobile phones. Currently, with a cell phone we can make calls, listen to music, watching movies, taking photos, etc. Furthermore, it seems that the generation of telephones mobile phones with buttons is approaching its end and that devices with screen touch are taking over the market. Touch screens have large sizes and they are very comfortable for the user. Touch screens have their pros and cons, but to know what they are it is necessary that you first know the different types of touch screens. There are basically three types of touch screens used currently on mobiles. We present them to you, briefly, below.

Resistive touch screen

Resistive touch screens were the most used in the mobile phones towards 2010. They were cheap and resistant to water and dust, but they break easily and cannot be used with sharp objects. We could touch them with any object (with the fingers, with the stylus, etc.). It was necessary to apply light pressure to detect the pulsation. They had a very long useful life (it is estimated that around thirty and five million keystrokes).

Capacitive touch screen

Capacitive touch screens can basically be of two types: one of them can recognize multiple contacts simultaneously and the other one cannot. They are resistant to shocks, humidity and dust.

Capacitive touch screen uses a single layer (known as grid). This layer is covered by an electroconductive material that provides current continues with a certain frequency. When you touch the screen with an object that emits a constant flow of electricity, such as a finger (the human body generates electricity), a change in current occurs and, in this way, it is determined the point of contact.

It has an extremely long lifespan (about two hundred twenty five million keystrokes). In addition, it allows around 92% of the emitted light to pass through. through the screen. There are several types: LCD, OLED, AMOLED, IPS and retina panels.

Infrared touch screens

Infrared touch screens are the most expensive of the three that we have mentioned. They do not require physical force (a gentle touch is sufficient). Furthermore, they are not influenced due to dust, moisture or scratches. They are also the most durable. There are Two types: optical and heat sensitive.

Optics use infrared beams, which are not visible to the human eye. They work with sensors located above and around the screen, which form a grid of invisible beams. If an object (finger or stylus) touches the screen, interrupts the rays in a certain area and, in this way, it is determined the point of contact. It has a lifespan of about seven years and presents serious Disadvantage: A bright environment can have a negative impact on its operation.

Heat sensitive ones are the most used, but are rarely used. used on screens. If They apply to other components of mobile devices, such as buttons.

This technology only works with hot objects, so who have a serious problem: If your fingers are cold (as can happen in winter) and you touch these phones, It may happen that the device does not respond.

Force Touch/3D Touch

Apple devices starting with the iPhone 6s incorporate to your screens a technology proprietary called Force Touch or 3D Touch. This technology allows detecting the intensity of pressure against the screen and allows you to distinguish between a light touch and a pressure more intense. Applications can leverage this information to deliver behaviors different depending on the user's action.

3.2.2.ink screens electronic

Electronic ink or electronic paper is a technology that allows you to create screens flat. These screens represent information in black and white and do not allow viewing moving images. In 2007 the first color electronic paper appeared.

In April 1997, researchers at the MIT Media Lab⁽⁶⁾ They created the company E Ink to develop electronic ink technology.

In July 2002, E Ink presented the prototype of the first screen with this technology. This screen was marketed in 2004. Other screens followed for several reading tablets.

Electronic ink is currently the main technology used in readers of e-books, also known as electronic books.

Furthermore, the first smartphones with a electronic ink rear screen, offering, for example the YotaPhone2, a 5” AMOLED screen and a 4.7” 960 electronic ink screen behind × 540 pixels, or the Oukitel U6 4G. Since the refresh time of these screens is higher than on an LED screen and are in black and white, they are not suitable for watching videos or playing games or other tasks that require refreshment more often. As advantages, they do not need feedback (the screen is visible in sunlight) and do not consume power. This means you can see notifications without unlocking the screen or looking a map without consuming energy. And the limitations are those mentioned, the lack of color and the refresh rate. There are also devices smartwatch that have ink screens electronics, such as Pebble. Pebble has of an e-ink screen 1.26-inch black and white, with a resolution of 144 x 168 pixels.

3.3.Sensors

An important technology in the world of the Internet and mobile devices is that of the sensors. Therefore, in this subsection we will explore how they are related mobile phones and sensors and what implications joining these two worlds.

There are two common scenarios that combine the concepts of sensors and mobile phones:

Everyday objects with sensors that generate data. The mobile phone reads and analyzes data such as temperature, noise and activity.
The phone used as a sensor itself. For example, the iPhone incorporates an accelerometer, which is basically a sensor movement. It is used as a control in games and also to change the layout of the screen from portrait to landscape. The iPhone also has a microphone (which is can be used as a noise sensor), a proximity sensor, an ambient light sensor, a fingerprint identity sensor, two-sensor camera, gyroscope, GPS, accelerometer and others.

Regarding the first scenario, we can say that the sensors are growing a lot as a source of data on the Internet. Proof of this is that sensor networks represent a great opportunity for some of the largest technology companies. Sensors allow real-time data collection, analysis and better decision making. Mobile devices can be the perfect recipients of that information.

These are the two main ways that sensors and mobile phones They are interacting.

In the next subsection we will study the sensors in detail more paradigmatic of the new generation of mobile devices: motion sensors.

3.3.1.Sensors movement

When the iPhone appeared, one of the most popular features attention, apart of its design and its touch screen, was the motion sensor. Although the iPhone is a paradigmatic example, of course it is not the only device that incorporates and will incorporate this type of sensors. Outside the world of mobile phones, we can find, for example, the case of the Nintendo Wii, and in the Android family of devices as well we find devices with this sensor, such as, for example, in the range of devices Samsung Galaxy.

Motion sensors in mobile devices have quickly penetrated the market and the possible applications that can be given to it are still being explored. Of course, they can be used as a game controller or to detect which orientation screen must be displayed depending on whether we hold the device horizontally or vertically, or to monitor sports activities. However, there may be more applications.

There are references to motion sensors that are used to recognize the pattern with the one that a person walks. An example of use could be the anti-theft lock of the terminal (the thief's different way of walking alerts the phone, which then asks for a password).

These types of sensors would be much more important if will find an application appealing to operators; that is, an application whose uses were not only local, as explained above. Since the operators specify (and (certify and often subsidize) many devices, having something appealing both For the end user of the applications as well as for the operator, it is important to its introduction into the market. We can think, for example, of cameras (the user takes photographs and the operator gets the benefit of MMS⁽⁷⁾ or email, or even on Bluetooth (the user uses the hands-free in the car safely and the operator gets more minutes of use). This is one of the reasons why the incorporation of WiFi technology to mobile phones does not has moved as quickly as one would have expected, as it is often difficult to exploit for its purposes, both for the user and for the operator.

The latter leads us to wonder what the services based on motion sensor. In this type of services we could say that the context would be more important than the content. If operators had access to the sensors, They could know a lot more about how a user wants to communicate. They could determine state descriptions such as "walking", "on a train", "in a car", etc. Also we can think of services that use multi-context data: if the phone is charging and there has been no movement for an hour, then there is a high probability of that the user is out of the room or asleep. Or, for example, with a service that would detect the combination of the movement pattern of a car and record that is using a Bluetooth hands-free device, it could be inferred that the user cannot look at the screen, and then the video calls could be sent to you directly to the mailbox.

These are simply some examples of what could be get to do with these sensors. Of course, all these services can suffer with what are called fake positives and false negatives.

In any case, the motion sensor is a essential part of the multi-context paradigm, which could be the next step on mobile devices, after content multimedia.

3.4.Connectors

3.4.1.Mini USB Connectors and Micro USB

Various USB connectors have been used over the years to small devices such as PDAs, mobile phones or digital cameras. These include the now deprecated (but standardized) Mini-A and the current standard connectors Mini-B, Micro-A and Micro-B. The Mini-A and Mini-B connectors are approximately three by seven in size. millimeters.

The Micro-USB connectors have a similar width, but a thickness of approximately half, so they can be integrated into thinner portable devices.

The micro-USB connector was announced by the USB-IF⁽⁸⁾ on January 4, 2007. Mini-A connector and Mini-AB connector-receptacle were deprecated on May 23, 2007. Few devices and cables still use mini-connectors, micro-connectors have prevailed and are the most used connectors. The micro-connectors, thinner, they emerged to replace Mini connectors in new devices that were appearing, like smartphones and PDA. The design of the micro-connector is designed to endure at least ten thousand connection-disconnection cycles, a value significantly higher than the design of the mini-connector. The universal serial bus Micro-USB cables and connectors specification details the mechanical characteristics of Micro-A connectors, receptacles Micro-AB and Micro-B connectors and receptacles, plus a receptacle adapter Standard-A to Micro-A connector.

The OMTP group of cellular telephone operators⁽⁹⁾ proposed Micro-USB in 2007 as the standard connector for data and charging battery on mobile devices. This includes various types of battery chargers and thus allows the Micro-USB to be the only external cable necessary for some devices.

In early 2009, Micro-USB was accepted and used by almost all manufacturers of mobile phones (such as HTC, Motorola, Nokia, LG, Hewlett-Packard, Samsung, Sony Mobile and Research In Motion) as the standard charging port on most of the world. The GSMA⁽¹⁰⁾, together with seventeen manufacturers and suppliers, announced its agreement to implement an industry-wide standard for a universal charger for new phones mobiles.

In June 2009, after a request from the Commission European and in close cooperation with the Commission's services, the main mobile phone manufacturers reached an agreement to harmonize the latest mobile phone chargers generation sold in the European Union. Thanks to this agreement, the industry accepts Provide compatibility between chargers based on the Micro-USB connector. Therefore, consumers will be able to buy mobile phones without a charger and, In this way, reduce your cost. Following the orders of the European Commission, the European standardization bodies CEN-CENELEC⁽¹¹⁾ and ETSI⁽¹²⁾ have published the standards needed to manufacture compatible mobile phones with the new EPS⁽¹³⁾ common based on Micro-USB.

Furthermore, on October 22, 2009, the ITU⁽¹⁴⁾ announced that it would use Micro-USB for your UCS⁽¹⁵⁾, since for Its energy efficiency adapts to all new mobile phones, and based on the Micro-USB interface, he added that the UCS chargers would have a rating four stars or higher for efficiency (about three times more efficient than an unqualified charger).

3.4.2.connector lightning

It is the connector that Apple devices use. It is a cable 8 transfer pins data and current.

Examples of devices that make use of it are: iPhone 5, iPhone 7, iPod nano (seventh generation), iPad (4th generation) and Pad Air, iPad Air 2, iPad mini and Pad Pro.

3.5.Batteries

3.5.1.lithium batteries, Li-ion or lithium ion

Essentially, a battery is a container of chemicals that transmits electrons. It is an electrochemical machine; that is, a machine that creates electricity through reactions chemicals.

Batteries have two poles, one positive (+) and one negative. (–). The electrons (negatively charged) go from the negative pole to the positive pole; that is, they are picked up by the positive pole. Unless the electrons run from the negative pole Towards the positive pole, the chemical reaction does not occur. This means that the electricity is only generated when the two poles are connected (for example, when used on a telephone cell phone), the battery hardly runs out if it is stored in a drawer.

Modern batteries are generally dry batteries (they use solid as electrolytes) and can be based on a very varied range of chemicals.

For mobile phones, there are two types of batteries: Li-Ion and LiPo.

Initially, the most common batteries for phones mobile phones were NiMH, due to because they had a reduced size and weight. Batteries are often used today. lithium-ion, since they are lighter and do not have the voltage depression that They have NiMH batteries. Many mobile phone manufacturers have changed to lithium polymer batteries. The main advantages compared to The oldest lithium-ion batteries are: even lower weight and the possibility to make the shape of the battery not just that of a cube. The manufacturers cell phones have been experimenting with other energy sources, including They include solar cells.

Battery technology is complicated and expensive, and that's one of the reasons why those whose price has not decreased like the price of other components. The future of The batteries could go through the use of graphene.

The difference between Li-Ion and LiPo batteries is that the ion batteries Lithium has as its main characteristic the use of lithium salts as a "bridge" between the positive pole (anode) to the negative pole (cathode) to allow the passage of the energy that will give life to our device. In the case of polymer batteries of lithium, the difference is that the lithium salt is contained in a polymer, or ice, to keep it safe from spills. The iPhone 7 uses an ion battery lithium (Li-Ion) and BQ Aquaris M5 has a LiPo battery.

3.5.2.Chargers

As we have already seen, mobile phones get generally battery power rechargeable. There are several ways to recharge these batteries, including USB, portable batteries, plugs (with an AC adapter) and lighters electrical (with an adapter).

Top five mobile device manufacturers presented in November In 2008, a new rating system was introduced to help consumers identify more energy-efficient chargers.

In 2009 they launched the first wireless charger on the market. The advantage of chargers wireless is that several devices can be recharged at the same time with maximum possible comfort. It works as follows: a device is placed with its receiver on top of a kind of mat and is recharged by an attraction magnetic.

3.6.Other features of mobile devices

3.6.1.Cameras

All mobile devices have at least one rear camera (can be more than one to improve image quality), generally of good performance. Most also incorporate a front camera, and increasingly contain better features (resolution, flash, etc.). Within this scope, the devices differ from each other according to the following characteristics:

Resolution for photos: Resolution is an indicator of the quality of the images. photos.
Resolution for videos: Resolution is also an indicator of quality of the videos.
Existence of flash and type of this.
If you have zoom digital:The zoom digital is a method for, apparently, decreasing the viewing angle of an image photographic or video.
If you have zoom optical: A zoom optical is a lens that allows vary the focal length and therefore cover a greater or lesser field of vision.
If the device has tools geo-tagging: These tools allow us to tag our images with a reference to the place where they have been taken.
If you have face detection: The function of face detection is to detect the faces of the people who are within the frame and keep the focus fixed on them.
If you have smile detection: The smile detector is a function that takes the detection system further facial. It consists of automatically activating the camera shutter when the framed subject smiles.
If you have car focus:The auto focus It is an automation that allows automatic focusing of an object.
If you have the ability to take 3D images.
If you have the ability to record on slow-motion.

3.6.2.Trackballs

A trackball It is an aiming device that It consists of a ball housed in a hole provided of sensors that detect the rotation of the ball on two axes (like a mechanical mouse turned upside down). The user moves the ball with the thumb, the rest of the fingers or the palm of the hand to move a cursor.

The trackballs large ones are common in stations CAD work⁽¹⁶⁾ for facilitate precision. Before the arrival of touchpad, small trackballs were common on laptop computers, as these devices are sometimes used in situations where a conventional mouse cannot be used.

Some mobile phones have trackballs, but every are becoming less given the majority use of software keyboards and the need Minimize the number of buttons on the device to maximize the size of the screen.

4.Possible networks you can join access a mobile device

Many mobile phones currently available support both cellular technologies like other wireless broadband technologies. This opens the door to a great range of internet applications that can be accessed from devices mobile phones using broadband wireless technologies such as WiFi and WiMAX.

4.1.Networks to get voice calls

4.1.1.How is the communication?

In order to make voice calls, phones They have to connect to a network cell phone. The corresponding mobile telephone operator divides the area into several spaces called cells. In each cell there is a transmitting base station, which It is usually a simple antenna. Each cell manages to use several dozen channels, which gives the possibility for several dozen people to communicate simultaneously by her.

When a person moves from one cell to another, they become use the frequency of the new cell and therefore leaves the previous cell free so that it can be used by another user. Since the transmission distances are not very long, the Mobile phones can transmit with little power and therefore use small batteries (allowing reduced size and weight). It is, therefore, the concept cell phone which makes it possible for mobile phones to exist as we know them today (hence the expression "cell phones").

4.1.2.Telephone systems mobile

Regarding telephone systems, the first of them was GSM⁽¹⁷⁾, which was originally designed to transmit voice, although over time, technology It also made it possible to operate in data transfer mode. The terminals operate by circuit switching. This implies that there is a phase of establishment of connection that involves waiting times and the call remains open, even when there is no data transfer. This form of transmission is extremely limited in terms of capacity, even with the use of HSCSD technology⁽¹⁸⁾, which allows a speed maximum of 56 Kbps.

The study of the limitations of GSM gives rise to the need for a system based on packet data transmission. In 1998, the ETSI⁽¹⁹⁾, the regulatory entity for European telecommunications, concluded its studies on the definition of the rules of a new system, the GPRS⁽²⁰⁾, which allows greater data transmission capacity. GPRS allows a speed Theoretical maximum of 144 Kbps, in the event that it uses all the system resources. Finally, GPRS made possible a whole new series of applications within the mobile devices, barely accessible until then, such as viewing sites, FTP, IRC, animation, etc. In summary, GPRS provided the following benefits:

Permanent Internet connection (always "online").
Instant connection establishment.
Possibility that the billing of the service would be carried out according to the amount of information transmitted or received, instead of counting connection time.
Higher data transmission speed.

As a bridge technology between 2G and 3G networks we find the telephone technology EDGE mobile⁽²¹⁾. This technology is also known as EGPRS⁽²²⁾. For what EDGE is therefore considered an evolution of GPRS. These technologies work in the 850, 900, 1,800 and 1,900 MHz bands.

The UMTS⁽²³⁾ It has been the new protocol used in Europe by the third generation of telephones mobiles. Integrated in the project to create a standard that could be used worldwide (unlike the second generation, whose American and European systems are incompatible), UMTS altered the way mobiles could be used, enabling mobile capabilities multimedia and unlimited access to the Internet.

In addition to the basic functions that mobile phones allowed until then, as simply telephone someone or send and receive messages, UMTS made it possible to increase new series of features until then almost inaccessible or present. The system allowed access to the Internet at a faster speed and therefore transmission of faxes, images, videos and data. Allows you to make video calls (while we are speaking, we can visualize on the screen, in real time, the person with whom we communicate, in case it also has a UMTS mobile). Internet access It is much faster and has no limits, so we can access any type of information from anywhere. Information, commerce and entertainment multimedia are available on the screen, in a system that integrates the networks of mobile, fixed and satellite telecommunications. In addition to the roaming On a global scale, UMTS It allowed the convergence of the various types of existing networks.

According to the European Commission, UMTS services should have the following features:

Multimedia capacity and support for great mobility.
Efficient Internet access.
High speed.
Portability between UMTS environments (so as to allow access to networks terrestrial and satellite UMTS).
Compatibility between the GSM and UMTS systems. The terminals had to have dual band or work on both systems.

This new technology radically altered the way use mobile phones. allowed that users had their cell phone in front of their eyes for more time than glued to the ear, because this became a multimedia device, like television or a computer. At the same time, data transmission would take up a larger share of the time of use of the mobile phone, due to all the existing possibilities (send faxes, emails, etc.). The voice quality became the same as that of landlines. In short, thanks to this technology, it was possible to have Internet in the palm of your hand.

As an optimization of UMTS/WCDMA spectral technology, HSDPA technology appears⁽²⁴⁾, also called 3.5G, 3G+ or turbo 3G. This technology offers a speed of Up to 2 Mbps upload and 7.2 Mbps download speed across the frequency spectrum from 900 to 2,100 MHz.

Following this evolution, we arrive at 4G. The 4G network is totally based on protocol IP⁽²⁵⁾. It is a system of systems and a network of networks. Convergence between networks is achieved wired and wireless to provide access speeds between 100 Mbps in motion and 1 Gbps at rest, and maintain end-to-end quality of service, as well as the security to be able to offer services of any kind at any time. anytime and anywhere at the lowest possible cost.

The WWRF⁽²⁶⁾ defines 4G as a network that works on Internet technology that is combined with other uses and technologies (such as WiFi and WiMAX). 4G is not a technology or standard defined, but a collection of technologies and protocols that allow maximum performance with the cheapest wireless network.

The concept of 4G included within “beyond 3G” includes wireless techniques high performance such as MIMO and OFDM. Two of the terms that define evolution of 3G, following the 3GPP standardization, will be LTE⁽²⁷⁾ for radio and SAE access⁽²⁸⁾ for the core part of the network. As main characteristics we have the following:

For radio access, it abandons the CDMA-type access characteristic of UMTS.
Use of SDR⁽²⁹⁾ to optimize radio access.
The entire network is IP.
The expected maximum peak rates are 100 Mbps downlink and 50 Mbps in uplink (with a bandwidth in both directions of 20 Mhz).

The evolution of 4G is the 5G network, which is under development and not It is still standardized. Among its features are minimum download speeds of 20 Gbps and 10 Gbps upload, and a latency of 4 ms. The aim is to optimize the devices for make them as efficient as possible for the internet of things (IoT).

4.2.Networks to access internet

To have access to the Internet, any of the technologies mentioned in the subsection above is valid, as long as there is a data contract with the telephone operator corresponding mobile.

Another option consists of a WLAN connection, a technology available in the vast majority of mobile phones and tablets current. WLAN is a wireless data communication system flexible, widely used as an alternative to LAN networks⁽³⁰⁾ wired or as extension of these. This option allows us to access the Internet through a domestic ADSL line or through other networks (infinity of public sites such as airports, restaurants, libraries or any place with an access point and an Internet connection behind).

4.3.Geolocation networks

Geolocation is a new term that has been used since mid 2009 and which refers to the detection of our geographical location in a way automatic.

There are several ways for this to happen and, naturally, the mobile devices They are the ones that most easily allow us to update our position, due to their portability.

For some time now, high-end mobile phones (and some how many range media) have integrated GPS receivers that, through the network of satellites that surround the planet, they can place us anywhere on the globe.

Although GPS is the specific technology for geolocation and, Furthermore, it is the way more accurate to do so, it is not the only one. Additionally, this option is not valid if we are inside a building, where the mobile's GPS receiver cannot receive the signal.

Another way to geolocate without having to use a GPS receiver in The mobile is via GPRS. With the help of cell phone towers you can calculate the signal intensity and triangulate the estimated position. It doesn't work with the same precision as GPS, but comes quite close.

Finally, another way to geolocate is through a connection WiFi set to that moment. This form of geolocation is not exclusive to mobile devices, any computer with an Internet connection (it does not need to be wireless) you can use it. This form of geolocation works using as a source of information the IP address of the equipment, along with information about the access points WiFi to which we have access.

4.4.Communications networks short distance

If the range of a LAN is considered short distance, we could talk in this subsection on WiFi technology in any of its versions (802.11 b/g/n). No However, this subsection will focus on WPAN technologies.

To begin with, one of the technologies that implement some mobile devices It's RFID⁽³¹⁾. RFID is a remote data storage and retrieval system using devices called RFID tags. The fundamental purpose of RFID technology is to transmit the identity of an object (similar to a unique serial number) using radio waves. RFID technologies are grouped within automatic identification technologies.

The other great technology for short distance communications is Bluetooth. Bluetooth is an industrial specification for WPAN that enables the transmission of voice and data between different devices using a radio frequency link in the band 2.4GHz ISM. Bluetooth applications are:

Facilitate communications between mobile and fixed equipment.
Eliminate cables and connectors between them.
Offer the possibility of creating small wireless networks and facilitate the synchronization of data between personal computers.

Precisely, the devices that most frequently use this technology belongs to telecommunications and personal computing sectors, such as PDAs, mobile phones, laptops, personal computers, printers or digital cameras.

Summary

Mobile devices represent a new opportunity to access the information by users. However, the diversity of characteristics of hardware and software presented by these devices complicates the very definition of the term device mobile. Therefore, in this module we try to clarify this concept by listing the characteristics generic that every mobile device should have. In this module we also review the types of existing mobile devices with a historical approach so that you understand How these devices have evolved.

Going into detail, in this module we explain the characteristics specific of the devices (such as keyboard types, screen, etc.), as well as the different networks that one of these devices can access or connect to.

Glossary

gadget m: A gadget It is a device that has a purpose and a specific function, generally small in size, practical and innovative at the same time. The gadgets They usually have a more ingenious design than that of the current technology.
Bluetooth m: Bluetooth is an industrial specification for wireless personal area networks. (WPAN) that enables voice and data transmission between different devices via a radio frequency link in the 2.4 GHz ISM band.
CENELEC m: CENELEC (European Committee for Electrotechnical Standardization) is the organization responsible for standardization in the field of electrotechnical engineering.
ETSI m: The European Telecommunications Standards Institute (ETSI) produces applicable standards globally for the information and communications technologies (ICT), which includes fixed, mobile, radio and broadcast.
Wi-Fi f: WiFi is a brand of the WiFi Alliance, the organization commercial that adopts, tests and certifies that equipment meets the 802.11 standards related to wireless local area networks.
WiMAX f: WiMAX, acronym for worldwide interoperability for microwaves access (global interoperability for microwave access), is a transmission standard data that uses radio waves at frequencies from 2.3 to 3.5 GHz.

Internet links

https://www.mobileworldcongress.com

https://www.apple.com/

https://www.nokia.com/es_es/phones

https://www.samsung.com/es

https://www.huawei.com/es

https://en.wikipedia.org/wiki/list_of_best-selling_mobile_phones

Introduction to mobile devices

Introduction

Definitions