The principle of operation and design of mobile phones. How mobile communication works: educational program
In the theoretical part, we will not delve into the history of the creation of cellular communications, its founders, the chronology of standards, etc. For those who are interested, there is plenty of material both in printed publications and on the Internet.
Let's look at what a mobile (cell) phone is.
The figure shows the principle of operation in a very simplified way:
Fig.1 How a cell phone works
A cell phone is a transceiver operating on one of the frequencies in the range 850 MHz, 900 MHz, 1800 MHz, 1900 MHz. Moreover, reception and transmission are separated by frequency.
The GSM system consists of 3 main components such as:
Base station subsystem (BSS – Base Station Subsystem);
Switching/switching subsystem (NSS – NetworkSwitchingSubsystem);
Operation and Maintenance Center (OMC);
In a nutshell it works like this:
A cellular (mobile) phone interacts with a network of base stations (BS). BS towers are usually installed either on their ground masts, or on the roofs of houses or other structures, or on rented existing towers of all kinds of radio/TV repeaters, etc., as well as on high-rise chimneys of boiler houses and other industrial structures.
After turning on the phone and the rest of the time, it monitors (listens, scans) the airwaves for the presence of a GSM signal from its base station. The phone identifies its network signal using a special identifier. If there is one (the phone is in the network coverage area), then the phone selects the best frequency in terms of signal strength and at this frequency sends a request to the BS to register in the network.
The registration process is essentially an authentication (authorization) process. Its essence lies in the fact that each SIM card inserted into the phone has its own unique identifiers IMSI (International Mobile Subscriber Identity) and Ki (Key for Identification). These same IMSI and Ki are entered into the database of the authentication center (AuC) when manufactured SIM cards are received by the telecom operator. When registering a phone on the network, the identifiers are transmitted to the BS, namely the AuC. Next, the AuC (identification center) transmits a random number to the phone, which is the key to perform calculations using a special algorithm. This calculation occurs simultaneously in the mobile phone and the AuC, after which both results are compared. If they match, then the SIM card is recognized as genuine and the phone is registered on the network.
For a phone, the identifier on the network is its unique IMEI (International Mobile Equipment Identity) number. This number usually consists of 15 digits in decimal notation. For example 35366300/758647/0. The first eight digits describe the phone model and its origin. The rest are the phone's serial number and check number.
This number is stored in the phone's non-volatile memory. In outdated models, this number can be changed using special software and an appropriate programmer (sometimes a data cable), and in modern phones it is duplicated. One copy of the number is stored in a memory area that can be programmed, and a duplicate is stored in an OTP (One Time Programming) memory area, which is programmed once by the manufacturer and cannot be reprogrammed.
So, even if you change the number in the first memory area, when the phone is turned on, it compares the data in both memory areas, and if different IMEI numbers are detected, the phone is blocked. Why change all this, you ask? In fact, the legislation of most countries prohibits this. The phone's IMEI number is tracked online. Accordingly, if a phone is stolen, it can be tracked and confiscated. And if you manage to change this number to any other (work) number, then the chances of finding the phone are reduced to zero. These issues are dealt with by the intelligence services with appropriate assistance from the network operator, etc. Therefore, I will not go deeper into this topic. We are interested in the purely technical aspect of changing the IMEI number.
The fact is that under certain circumstances this number may be damaged as a result of a software failure or incorrect update, and then the phone is absolutely unsuitable for use. This is where all means come to the rescue to restore IMEI and the functionality of the device. This point will be discussed in more detail in the software phone repair section.
Now, briefly about voice transmission from subscriber to subscriber in the GSM standard. In fact, this is a technically very complex process, which is completely different from the usual voice transmission over analog networks such as, for example, a home wired/radio telephone. Digital DECT radiotelephones are somewhat similar, but the implementation is still different.
The fact is that the subscriber's voice undergoes many transformations before it is broadcast. The analog signal is divided into segments of 20 ms duration, after which it is converted to digital, after which it is encoded using encryption algorithms with the so-called. public key - EFR system (Enhanced Full Rate - an advanced speech coding system developed by the Finnish company Nokia).
All codec signals are processed by a very useful algorithm based on the DTX (Discontinuous Transmission) principle - intermittent speech transmission. Its usefulness lies in the fact that it controls the telephone transmitter, turning it on only when speech begins and turning it off during pauses between conversations. All this is achieved using the VAD (Voice Activated Detector) included in the codec – a speech activity detector.
For the receiving subscriber, all transformations occur in the reverse order.
Mobile device diagram. I still can’t understand and imagine how it’s possible to fit several million transistors on one square millimeter of a processor. Not only to place them, but also to make them work and produce processors on an industrial scale, a million units at a time. And phone manufacturers promise to release even smaller processors and more powerful phones.In order to find out the phone device, find out GSM operating principle mobile communications wrote this review.
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Next, you can find and read about the structure of a cell phone and its main functional components. Find mobile device diagrams. Learn the principle of operation of a mobile phone and the operating diagram of the GSM channel. Design and circuitry of GSM standard cellular telephones.
Spare parts and repair of mobile phones.
Store spare parts and components for phones, tablets, smartphones
radiomaster.net- another Internet service that provides downloads to your computer or phone of phone device diagrams and instructions for simple and mobile phones and other equipment. Mobile phone diagrams are downloaded from the site for free, without advertising and SMS, directly from this site. At the time of writing this review, you can download free circuit diagrams for cell phones for more than 600 models of mobile devices.
market.yandex.ru- search and purchase of spare parts for mobile and cell phones through the irreplaceable Yandex.Market service. As always, for users of the service it is convenient to sort and search for phone parts by price and the nearest location of the cell phone spare parts store.
Articles and Lifehacks
In our article we will briefly examine the internal structure of a modern mobile phone, focusing on each of the significant blocks.
We are talking specifically about push-button “tubes”; we will talk about the structure of a smartphone another time.
Case and keyboard
Today, almost all push-button models are produced in a plastic case.The only exceptions are some designer phones, for example, titanium gadgets, but they can be ignored due to their low prevalence.
The vast majority of phones today are produced in the form factor; various clamshells and sliders have almost disappeared from the market. In them, the back panel is removable and often replaceable.
Thus, the user gets access to a slot for a SIM card, memory cards and battery.
The keyboard is most often made of rubber; usually the keys are backlit, making it easier to use the device in the dark.
Display
The screens of most modern push-button models are made using .Logic block
A mobile phone, like a smartphone, is a specialized minicomputer. However, the element base it uses is completely different, so you won’t find the Qalcomm or MediaTek processors familiar to touch gadgets in handsets.Moreover, model specifications almost never indicate either the type of chipset or even the amount of RAM.
The only thing that makes sense to talk about is the built-in storage, intended mainly for photos and music.
In addition, many cell phones support microSD cards, usually up to 32 GB in capacity. However, no more is required.
Particular mention should be made of the non-volatile memory, which stores the device’s unique code – IMEI.
Radio module
In addition to voice communication using the GSM standard, push-button devices are capable of surfing the Internet using GPRS technology.
Its data exchange speed is extremely low even in comparison with 3G, not to mention LTE, and operator tariffs make such communication completely unusable.
To ensure stable communication, the phones have an internal whip antenna.
Sometimes you can find models that have 3G Internet support. This somewhat expands the capabilities of the device.
Audio system
In its simplest form, it consists of a microtelephone and a microphone, allowing you to use the gadget for its intended purpose - for conversations.An almost integral part of the internal structure of any mobile phone is a special 3.5 mm headphone jack.
Some models also have a speaker that can be used for both hands-free communication and music playback.
SIM card
The SIM card represents the subscriber authentication key. Unlike smartphones, most handsets still use the mini-SIM standard.
There can be either one or two slots. The latter is more common in models equipped with a 3G module, so that you can separately connect a card for the Internet.
Camera
Unlike smartphones, not every phone has a camera. And where it does exist, its resolution is very modest - 0.3 megapixel modules are still found, at best you can hope for 3 megapixels.Nothing surprising - you can hardly hope to find a two-module camera with optical zoom in a device for 2 thousand rubles. Therefore, you should not count on receiving high-quality photos in this case.
Battery
The battery provides power to all elements of the mobile device. It is usually removable; to remove it, you just need to remove the back panel. Modern models use two types of batteries: lithium-ion and lithium-polymer.The latter are considered somewhat more progressive, since they were created in response to the tendency of lithium-ion batteries to swell and even explode.
As a result, the problems with push-button devices in this regard are the same as with smartphones: sensitivity to cold and a limited number of charge cycles.
Some users are still captivated by myths and believe that the battery has the so-called. "memory effect". There is nothing like this in modern phones.
The voltage used in modern models is usually 3.6 V.
Interfaces
This element is designed to interact with other devices.
Three options are possible:
- Complete absence of interfaces in the most primitive models.
- Bluetooth wireless interface that allows you to exchange files, for example, with another phone, desktop computer or laptop.
- A USB port that allows you to connect your phone to a PC using a cable.
Wi-Fi, which is usual for smartphone users, is absent in this case.
Other items
Feature phones have several internal devices that are not typically found in smartphones. This could be a flashlight or a vibrator that allows you to receive calls without turning on the call signal.In all other respects, these gadgets are practically no different from each other.
Finally
As you can see, in the decades since the advent of cellular communications, the design of telephones has not changed much.And, despite the dominance of smartphones in the mobile market, this category of devices is still not going to die out.
It has occupied a niche that meets the needs of those who do not require anything from the device other than its main function - the ability to talk with the interlocutor.
And if earlier push-button models appeared that had a claim to compete with touch-sensitive ones, today everything superfluous has disappeared from their design, leaving only the necessary minimum.
This allowed us to reduce the price of the device to an absolute minimum.
For those who live in rural areas, fast Internet is still just a dream, but it is only one step away from turning it into reality. To do this, you just need to assemble one of the considered 3G antenna designs and feel comfortable on the World Wide Web
Odin Multi Downloader - for flashing firmware for smartphones on the Android platform; Sim Lock 3.10 for unlocking many mobile phone models; Sim Scan and Woron Scan for reading data from your SIM cards and a bunch of other useful utilities
Phone diagram main components
1. CPU. It is usually designated on drawings as CPU or RAPIDO; RAP is the main brain of your mobile phone.
2. Flash drive This is the most common memory card, designated in service instructions by the word flash. The designations mem and memory are also found. It is usually rectangular in shape and can vary greatly in both dimensions and volume.
3. Power controller. It can be marked on mobile phone diagrams as betty, retu, tahvo or UEM. Externally, they look like small square microcircuits.
4. Also, among other things, any mobile phone contains transmitter and receiver RF chip & GSM FEM. Be very careful when replacing transmitters. Some may be similar in appearance, but differ in the last digits in the marking.
5. Some mobile device diagrams also contain thermistor and fuse. But these details are not found in all brands of mobile phones.
If your mobile phone stops turning on, you need to find the reason and try to eliminate it. All malfunctions of this type can be divided into software and hardware problems.
A good friend of mine brought a rather outdated mobile phone and asked me to change the keys. The model of the device is Samsung SVG-X680, having disassembled it in accordance with the diagram, I began the repair and restored the buttons using regular super glue.
If your mobile assistant stops seeing the SIM card, then the problem is either in the SIM itself or in the phone. The first assumption is easy to eliminate - by replacing the card with a working one, the second is much more extensive and in some cases, good amateur radio skills will be required to solve it.
I think absolutely everyone wants a new mobile phone to serve us for a long time and have an excellent appearance. To protect the display of a mobile phone or smartphone from various scratches and cracks, it is recommended to use a special protective film for the mobile phone screen.
Let's look at the detailed procedure and algorithm for disassembling the Nokia 6120 mobile phone in a fairly typical case of replacing the earpiece speaker.
When using a mobile phone, problems with its backlight may occur. It may simply not work, there are problems when the backlight turns on spontaneously, or goes out very quickly. Here I will post various cases from the practice of repairing mobile phones with this malfunction.
When using any phone, an unforeseen nuisance such as water getting into a mobile phone can always happen. Unfortunately, this can happen to any of us, no matter how careful the person is.
A malfunction in which a mobile phone turns off spontaneously can occur after a damp or unsuccessful firmware, a fall or liquid, or a battery malfunction.
Simple cell phone stand designs used to secure the position of an iPhone or similar smartphone relative to a surface. This phone stand can be used for frequent Skype video calls or watching videos on the go.
It happens that your mobile phone charger stops working at the most inconvenient moment. Due to the fact that over time the properties of radio components deteriorate, wires fray and contacts oxidize, this is what happened to one ancient Samsung E700 mobile phone charger.
It is believed that the weakest point of modern mobile phones is the connectors. They wear out on almost any model and quite quickly. With daily use of the smartphone, the connector contacts become unusable within 2-3 years. But there is no need to fall into despair; the problem that has arisen can be solved by replacing the system connector.
A problem with the camera is a fairly common problem on a mobile phone or smartphone. Fixing it on your own is not so easy, but with certain amateur radio skills it is quite possible. As part of the article, we will analyze practical examples of solving a problem when the phone camera does not work.
There are many reasons why the mobile phone button does not work. Perhaps due to careless use, dirt has clogged under the button. Very often, the cause of button failure is moisture getting into the device or a software failure in the system.
If your phone has stopped charging, then before you start disassembling it and troubleshooting it, you need to do a few simple manipulations. After which there is a chance that the mobile phone will come to life.
The reason for the loss of charge can be either hardware or software. So, some applications put a very heavy load on the smartphone’s battery, so running Skype for Android, even in the background, can drain the battery in less than a day.
Sound loss on the phone is considered to be the complete absence of sound signals or if during a conversation you constantly hear extraneous noises and creaks, as well as when the interlocutor’s voice periodically changes and crackles are heard.
In modern phones, we can distinguish two types of screen breakdowns: the image is not displayed on the screen and the picture is visible, but very poorly, i.e. the display backlight has disappeared.
Capacitive and resistive touch screen design |
Most modern mobile devices, such as smartphones, mobile phones, tablet computers, and electronic readers have a touch screen. Such a touch screen, or simply a touchscreen, is nothing more than a typical input-output device that responds to touches and is capable of tracking the coordinates of the touch point.
When the vibration alert on your phone stops working, it causes a lot of inconvenience. Vibrating alert is a very convenient phone function, which is not so easy to refuse if such a malfunction occurs. It is about solving the problem of vibrating alerts in a mobile phone that we will talk in this article.
In some life situations, you need to find out if there is an active mobile phone nearby, for example, during exams. Or notify a hard of hearing person about the arrival of an SMS. For these cases, we need a mobile phone ringing indicator. Such a detector can be easily assembled with your own hands based on a simple circuit, even with basic amateur radio skills.
aslan wrote in February 2nd, 2016Cellular communications have recently become so firmly established in our daily lives that it is difficult to imagine modern society without it. Like many other great inventions, the mobile phone has greatly influenced our lives and many areas of it. It is difficult to say what the future would be like if it were not for this convenient type of communication. Probably the same as in the movie "Back to the Future 2", where there are flying cars, hoverboards, and much more, but there is no cellular communication!
But today, in a special report for, there will be a story not about the future, but about how modern cellular communications are structured and work.
In order to learn about the operation of modern cellular communications in the 3G/4G format, I invited myself to visit the new federal operator Tele2 and spent the whole day with their engineers, who explained to me all the intricacies of data transmission through our mobile phones.
But first I’ll tell you a little about the history of cellular communications.
The principles of wireless communication were tested almost 70 years ago - the first public mobile radiotelephone appeared in 1946 in St. Louis, USA. In the Soviet Union, a prototype of a mobile radiotelephone was created in 1957, then scientists in other countries created similar devices with different characteristics, and only in the 70s of the last century in America were the modern principles of cellular communication determined, after which its development began.
Martin Cooper is the inventor of the Motorola DynaTAC portable cell phone prototype, weighing 1.15 kg and measuring 22.5 x 12.5 x 3.75 cm
If in Western countries by the mid-90s of the last century, cellular communications were widespread and used by most of the population, then in Russia it just began to appear, and became available to everyone a little over 10 years ago.
Bulky, brick-shaped mobile phones that worked in the first and second generation formats have become history, giving way to smartphones with 3G and 4G, better voice communications and high Internet speeds.
Why is the connection called cellular? Because the territory in which communication is provided is divided into separate cells or cells, in the center of which base stations (BS) are located. In each “cell” the subscriber receives the same set of services within certain territorial boundaries. This means that moving from one cell to another, the subscriber does not feel territorial attachment and can freely use communication services.
It is very important that there is continuity of connection when moving. This is ensured thanks to the so-called handover, in which the connection established by the subscriber is, as it were, picked up by neighboring cells in a relay race, and the subscriber continues to talk or delve into social networks.
The entire network is divided into two subsystems: the base station subsystem and the switching subsystem. Schematically it looks like this:
In the middle of the "cell", as mentioned above, there is a base station, which usually serves three "cells". The radio signal from the base station is emitted through 3 sector antennas, each of which is aimed at its own “cell”. It happens that several antennas of one base station are directed at one “cell”. This is due to the fact that the cellular network operates in several bands (900 and 1800 MHz). In addition, a given base station may contain equipment from several generations of communications (2G and 3G).
But Tele2 BS towers only have third and fourth generation equipment - 3G/4G, since the company decided to abandon old formats in favor of new ones, which help avoid interruptions in voice communication and provide a more stable Internet. Regulars of social networks will support me in the fact that nowadays Internet speed is very important, 100-200 kb/s is no longer enough, as it was a couple of years ago.
The most common location for a BS is a tower or mast built specifically for it. Surely you could see red and white BS towers somewhere far from residential buildings (in a field, on a hill), or where there are no tall buildings nearby. Like this one, which is visible from my window.
However, in urban areas it is difficult to find a place to place a massive structure. Therefore, in large cities, base stations are located on buildings. Each station picks up signals from mobile phones at a distance of up to 35 km.
These are antennas, the BS equipment itself is located in the attic, or in a container on the roof, which is a pair of iron cabinets.
Some base stations are located in places you wouldn't even guess. Like, for example, on the roof of this parking lot.
The BS antenna consists of several sectors, each of which receives/sends a signal in its own direction. If the vertical antenna communicates with phones, then the round antenna connects the BS to the controller.
Depending on the characteristics, each sector can handle up to 72 calls simultaneously. A BS can consist of 6 sectors and serve up to 432 calls, but usually fewer transmitters and sectors are installed at stations. Cellular operators such as Tele2 prefer to install more BS to improve the quality of communication. As I was told, the most modern equipment is used here: Ericsson base stations, transport network - Alcatel Lucent.
From the base station subsystem, the signal is transmitted towards the switching subsystem, where a connection is established in the direction desired by the subscriber. The switching subsystem has a number of databases that store subscriber information. In addition, this subsystem is responsible for security. To put it simply, the switch is complete It has the same functions as the female operators who used to connect you with the subscriber with their hands, only now all this happens automatically.
The equipment for this base station is hidden in this iron cabinet.
In addition to conventional towers, there are also mobile versions of base stations located on trucks. They are very convenient to use during natural disasters or in crowded places (football stadiums, central squares) during holidays, concerts and various events. But, unfortunately, due to problems in legislation, they have not yet found wide application.
To ensure optimal radio signal coverage at ground level, base stations are designed in a special way, therefore, despite the range of 35 km. the signal does not extend to aircraft flight altitude. However, some airlines have already begun installing small base stations on their boards that provide cellular communications inside the aircraft. Such a BS is connected to a terrestrial cellular network using a satellite channel. The system is complemented by a control panel that allows the crew to turn the system on and off, as well as certain types of services, for example, turning off the voice on night flights.
I also looked into the Tele2 office to see how specialists monitor the quality of cellular communications. If a few years ago such a room would have been hung to the ceiling with monitors showing network data (load, network failures, etc.), then over time the need for so many monitors has disappeared.
Technologies have developed greatly over time, and such a small room with several specialists is enough to monitor the work of the entire network in Moscow.
Some views from the Tele2 office.
At a meeting of company employees, plans to capture the capital are discussed) From the beginning of construction until today, Tele2 has managed to cover all of Moscow with its network, and is gradually conquering the Moscow region, launching more than 100 base stations weekly. Since I now live in the region, it is very important to me. so that this network comes to my town as quickly as possible.
The company's plans for 2016 include providing high-speed communications in the metro at all stations; at the beginning of 2016, Tele2 communications are present at 11 stations: 3G/4G communications at the Borisovo, Delovoy Tsentr, Kotelniki, and Lermontovsky Prospekt metro stations. , “Troparevo”, “Shipilovskaya”, “Zyablikovo”, 3G: “Belorusskaya” (Ring), “Spartak”, “Pyatnitskoye Shosse”, “Zhulebino”.
As I said above, Tele2 abandoned the GSM format in favor of third and fourth generation standards - 3G/4G. This allows you to install 3G/4G base stations with a higher frequency (for example, inside the Moscow Ring Road, the BSs are located at a distance of about 500 meters from each other) to provide more stable communications and high speed mobile Internet, which was not the case in networks of previous formats.
From the company’s office, I, in the company of engineers Nikifor and Vladimir, go to one of the points where they need to measure the communication speed. Nikifor stands in front of one of the masts on which communication equipment is installed. If you look closely, you will notice a little further to the left another such mast, with equipment from other cellular operators.
Oddly enough, cellular operators often allow their competitors to use their tower structures to place antennas (naturally on mutually beneficial terms). This is because building a tower or mast is an expensive proposition, and such an exchange can save a lot of money!
While we were measuring the communication speed, Nikifor was asked several times by passing grandmothers and uncles if he was a spy)) “Yes, we are jamming Radio Liberty!”
The equipment actually looks unusual; from its appearance one can assume anything.
The company’s specialists have a lot of work to do, considering that the company has more than 7 thousand in Moscow and the region. base stations: about 5 thousand of them. 3G and about 2 thousand. LTE base stations, and recently the number of base stations has increased by about a thousand.
In just three months, 55% of the total number of new operator base stations in the region were put on air in the Moscow region. Currently, the company provides high-quality coverage of the territory where more than 90% of the population of Moscow and the Moscow region lives.
By the way, in December, Tele2’s 3G network was recognized as the best in quality among all capital operators.
But I decided to personally check how good Tele2’s connection is, so I bought a SIM card in the nearest shopping center on Voykovskaya metro station, with the simplest tariff “Very Black” for 299 rubles (400 SMS/minutes and 4 GB). By the way, I had a similar Beeline tariff, which was 100 rubles more expensive.
I checked the speed without going far from the cash register. Reception - 6.13 Mbps, transmission - 2.57 Mbps. Considering that I am standing in the center of a shopping center, this is a good result; Tele2 communication penetrates well through the walls of a large shopping center.
At metro Tretyakovskaya. Signal reception - 5.82 Mbps, transmission - 3.22 Mbps.
And on metro station Krasnogvardeyskaya. Reception - 6.22 Mbps, transmission - 3.77 Mbps. I measured it at the exit of the subway. If you take into account that this is the outskirts of Moscow, it’s very decent. I think that the connection is quite acceptable, we can confidently say that it is stable, considering that Tele2 appeared in Moscow just a couple of months ago.
There is a stable Tele2 connection in the capital, which is good. I really hope that they will come to the region as soon as possible and I will be able to take full advantage of their connection.
Now you know how cellular communication works!
If you have a production or service that you want to tell our readers about, write to me - Aslan ( [email protected] ) and we will make the best report, which will be seen not only by readers of the community, but also by the website http://ikaketosdelano.ru
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