Description of 1 G and 2 G communication standards - a detailed analysis of the GSM network architecture

When using a mobile phone, few people think about how calls are made and where the Internet comes from. In fact, everything is not as simple as you might think. There are specialized cellular communication standards - this is a general designation for all technologies that are used to create mobile communications. Some of these standards are similar to each other. Standards are created in a similar way and have almost the same characteristics. Based on the parameters, all standards are divided into groups called generations. This is where the well-known designations 1G, 2G, 3G and 4G come from. The letter G in this case is an abbreviation for the English word generation. You will also learn how cellular communications developed and what fundamental differences exist between its generations.

GSM History of the standard

The name GSM was originally an acronym for the group that led the development of this standard. Later its meaning was interpreted in the right way and came to mean the Global System for Mobile Communications. In 1982, the creation of GSM began. It was conducted by a coalition of 26 European companies providing communications services. The goal was to unite all European countries with a single communications standard that would operate at 900 megahertz. 7 years later, ETSI continued to work on the development of GSM. The standard began to fully operate only in mid-1991. At the same time, he completely bypassed his closest competitors, such as the North American PCS. After this, the standard was improved in 1993. Afterwards, only improvements were made to the current version.

further reading

• Redl, Siegmund M.; Weber, Matthias K.; Oliphant, Malcolm W. (February 1995). Introduction to GSM
  . Artek House. ISBN 978-0-89006-785-7.
• Redl, Siegmund M.; Weber, Matthias K.; Oliphant, Malcolm W. (April 1998). Handbook of GSM and Personal Communications
  . Artech House Mobile Communications Library. Artek House. ISBN 978-0-89006-957-8.
• Hillebrand, Friedhelm, ed. (December 2001). GSM and UMTS, creating global mobile communications
  . John Wiley and Sons. ISBN 978-0-470-84322-2.
• Mouly, Michelle; Pautet, Marie-Bernardette (June 2002). GSM system for mobile communications
  . Telecom Publishing House. ISBN 978-0-945592-15-0.
• Salges, Salges B. (April 1997). Les telecoms mobiles GSM DCS
  . Hermes (2nd ed.). Hermes Sciences Publications. ISBN 978-2866016067.

First generation of mobile communications (1G)

This generation used analog standards in its work, which were introduced during the 1980s. Subsequently, they were replaced by 2G digital technology, which was superior to the first generation in all respects. The fundamental difference between them is the ability to use SMS and encrypt calls: only a digital standard can allow this. In total, 1G supported more than 10 standards. The most famous of them: NMT, AMPS, TACS, C-450, RtMI. All of them were used separately, depending on the region of application. The download speed when using 1G did not exceed 5.6 kilobytes per second, which is simply ridiculous by today's standards.

What is WCMDA?

When talking about WCDMA or GSM and what is the difference between them, it is always appropriate to mention that WCMDA is to some extent an add-on that improves the GSM standard. Or rather, this is how everything was originally intended, but today WCDMA is a third-generation communication standard, which is based on seven international projects. But GSM remained the second generation communication standard (read 2G).

WCDMA is based on DS-CDMA technology, which, compared to TDMA, is more resistant to interference and has higher throughput. Phones that operate in the WCMDA environment can perform the same functions as in the GSM standard (transfer of voice or digital information), but the quality and speed will be much higher. Therefore, operators supporting WCMDA provide Internet access services at higher speeds.

Characteristics of analog cellular communication standards

The main analogue networks used frequencies of 450, 800 and 900 megahertz. Radiocom 2000, the standard used in France, stands out: it used the 170, 200 and 400 MHz bands.

All analog standards used frequency modulation to transmit raw data. To operate according to these standards, a mobile station had to have relatively high power - from three to five watts. The main disadvantage of these standards lies in their low capacity, which appears due to the incomplete efficiency of using a dedicated band operating at a frequency of 12.5-30 kilohertz. This entailed high efficiency losses and increased energy consumption.

LTE (4G) frequencies in Russia

Additions and/or amendments to this material are welcome.

- Attention! Read reviews carefully before purchasing products or services! — Manufacturers may change them without notice! — Therefore, the characteristics are correct at the time of publication of the material (see date of the article).

Beginners do not understand the games undertaken by the standards developers. It would seem that it uses GSM frequencies 850, 1900, 900, 1800 MHz, what more? Quick answer - read the following section of the Phone Instructions. The inappropriateness of the generally accepted interpretation will be shown. The problem is described by the following provisions:

1. The second generation of cellular communications 2G gave rise to a lot of standards. The world knows three epicenters that set the rhythm: Europe, North America, Japan. Russia adopted the standards of the first two, changing them.
2. The family tree of standards is constantly expanding.
3. International versions of standards are intended to unify the disparate rules of individual countries. Often direct implementation is not possible. Governments are changing legislation to fix frequency plans.

The above explains the origins of beginners’ misunderstanding of the problem. Returning clarity to the issue, let’s build a simplified hierarchy of standards, indicating the frequencies used along the way.

Second generation of mobile communications (2G)

The introduction of new standards, which formed the second generation of mobile communications, was due to the impossibility of improving analogue standards into digital ones. In fact, 2G began its work in Europe in 1991, and by 1993, 36 GSM networks had already been created in 22 countries. The Japanese equivalent of the basic standards was introduced in 1994. At the same time, constant internal improvement of technologies was carried out to get rid of the shortcomings of the emerging standards. The introduction of 2G contributed to a significant acceleration in data transfer and the ability to communicate through short text messages.

Composition of the BSS base station subsystem

The BSC controls all functions related to the operation of radio channels in the GSM network. It is a switch that provides functions such as MS handover, radio channel assignment, and cell configuration data collection. Each MSC can manage multiple BSCs.

The BTS controls the radio interface with the MS. The BTS includes radio equipment such as transceivers and antennas that are needed to serve each cell in the network. The BSC controller controls multiple BTSs.

2nd generation digital cellular standards

During the transition to 2G, there were two main standards for cellular communication systems - the already mentioned GSM, used in Europe, and D-AMPS, which became widespread in North America. They were developed independently of each other. You already know the history of the formation of GSM, let’s focus on D-AMPS. Work on its creation began when it became obvious that the existing analog AMPS standard could not be completely replaced by a digital one due to the breadth of its application. But soon, they found a way to create an analog-digital system that is capable of ensuring the operation of both systems in the same frequency range. Work on this standard began in 1988 and was completed in 1992. In addition to the name D-AMPS, you may come across the abbreviation IS-54, which stands for “intermediate standard.”

Transition period (2.5G)

As technology has evolved over time, it has also become necessary to transfer data between cell phone users at significantly higher speeds. Subsequently, GPRS was created - a general packet radio receiver. GPRS is a kind of addition to the GSM standard, which allows the use of packet data transmission in the network of this standard. Payment for using GPRS is charged for the unpacked volume of traffic, and not for the time of use. The next stage in the development of GPRS was EDGE. The acronym literally stands for expanding the capabilities for the evolution of GSM. This technology has made it possible to significantly speed up the transfer of information. Sometimes EDGE is also called the 2.75 generation standard. In addition, XRTT technology was introduced, which in theory can transmit information at a speed of 144 kilobits per second, but in reality this figure rarely exceeded 60. However, this technology is still widely used, like any other that uses registered radio link.

Why are there so many frequencies?

Examining the results of 2010, the GSM Association stated: 80% of the planet's subscribers are covered by the standard. This means that four-fifths of networks cannot choose a single frequency. In addition, there are 20% foreign communication standards. Where does the root of evil come from? The countries of the second half of the twentieth century developed separately. The frequencies of 900 MHz of the USSR were occupied by military and civil air navigation.

GSM: 900 MHz

In parallel with Europe’s development of the first versions of GSM, NPO Astra, Radio Research Institute, and Research Institute of the Ministry of Defense began research that ended in full-scale tests. The verdict:

• Navigation and second generation cellular communications can function together.

On July 25, 1992, it was decided to create two systems:

Please note: again 2 standards. Each uses its own frequency grid. The announced competition for the distribution of GSM-900 was won by NPO Astra, OJSC MGTS (now MTS), Russian companies, and the Canadian BCETI.

NMT-450MHz - first generation

So, Moscow used, starting in 1992, the 900 MHz band (see above), because other GSM frequencies had not yet been born. In addition, NMT (Nordic Mobile Phones)… Initially, the countries of the Scandinavian Peninsula developed two options:

The reason for the Russian government choosing the first answer? They probably decided to try two ranges. Please note that these standards describe analog communications (1G). Developing countries began closing up shop in December 2000. Iceland (Siminn) was the last to surrender (September 1, 2010). Experts note an important advantage of the 450 MHz range: range. A significant plus, appreciated by remote Iceland. The Russian government wanted to cover the country's area using a minimum of towers.

NMT is loved by fishermen. The freed network was occupied by digital CDMA 450. In 2015, Scandinavian technologies mastered 4G. The Russian Uralwestcom vacated the closet on September 1, 2006, Sibirtelecom - on January 10, 2008. The subsidiary (Tele 2) Skylink fills the Perm and Arkhangelsk regions with its range. The license expires in 2021.

D-AMPS: UHF (400..890 MHz) - second generation

American 1G networks that used the AMPS specification refused to accept GSM. Instead, two alternatives have been developed to organize second generation mobile networks:

1. IS-54 (March 1990, 824-849; 869-894 MHz).
2. IS-136. Features a large number of channels.

The standard is now dead, replaced everywhere by the descendants of GSM/GPRS, CDMA2000.

Why does a Russian need D-AMPS?

The Russian average person often uses used equipment. D-AMPS equipment has reached the warehouses of Tele 2 and Beeline. On November 17, 2007, the latter closed up shop for the Central Region. The license of the Novosibirsk region expired on December 31, 2009. The last swallow flew away on October 1, 2012 (Kaliningrad region). Kyrgyzstan used the range until March 31, 2015.

CDMA2000 - 2G+

Some protocol variants use:

1. Uzbekistan – 450 MHz.
2. Ukraine – 450; 800 MHz.

GSM network architecture

Let's look at an example of an ideal network model. The figure below shows a model where each BS has 6 neighbors. For example, these stations are located on a smooth surface, without hills, trees, buildings or uneven surfaces.

A base station (BS) is a transceiver station that interacts with your mobile phone via a radio channel. The coverage area of ​​the BS under such conditions is a circle that will intersect with each other. If we connect the intersection points of the circles, we get hexagons - honeycombs.

The network is divided into 2 main systems BSS (Base Station System) - the base station subsystem and SSS - the switching system. This system includes:

BSC – base station controller.

His responsibilities include:

• Distribution of radio channels between the base station and the mobile station;
• Controls the connection with the mobile station (MS);
• Notifying the MS about an incoming call;
• Monitoring the level of output radiated power between the mobile and base station during subscriber calls.

The intermediate link between the BS and the switching system is a transcoder (TCE) - this is equipment that converts the input voice and data channel signals from the switching center into a form that complies with the GSM radio interface recommendations.

Simply put, over wired lines, digital voice is sent with V=64 Kbps. The signal is transmitted at the same speed from the output of the switching center. And between the mobile station and the BS, speech is transmitted with V=13 Kbit/s. The transcoder turns 64 Kbps into 13.

Mobile Switching Center (MSC) is translated from English as mobile switching center. The switch serves a group of cells limited in area, for example in a specific city, and performs all types of connections necessary for the operation of the MS.

Switch functions:

Home Location Register (HLR) – “home” location register. This device contains information about the location of any of the mobile stations, which allows the switching center to send a call to that station.

HLR is a reference database (DB) about regularly registered subscribers on the network:

• User credibility parameters;
• Certain numbers;
• List of communication services provided to the client;
• Specialist. routing information;
• Registration of roaming data.

Visitor Location Register (VLR) – Visitor location register.

This is a temporary database of subscribers who are within the coverage area of ​​a specific switching center. The primary role of the VLR is to minimize the number of requests that MSCs must make to the Home Location Register (HLR), which contains persistent data related to cellular network subscribers.

Ideally, there should be only one visitor location register per MSC, but it is also possible to have one VLR serving multiple MSCs.

The advantage of the system is that it reduces the load on the main database in the “home” location registry. It stores the same information as the home register while the subscriber is within the coverage area of ​​a particular switching center.

Authentication Center (AUC) – authentication center. It is a function in the GSM network used to authenticate the mobile subscriber who wants to connect to the network. Authentication is accomplished by identifying and checking the validity of the SIM card.

Once the subscriber is authenticated, the AUC is responsible for generating parameters used for privacy and encrypting the radio link. To ensure the privacy of a mobile subscriber, a Temporary Mobile Subscriber Identity (TMSI) is assigned for the time during which the subscriber is controlled by a specific Mobile Switching Center (MSC) associated with the AUC.

Equipment Identity Register (EIR) – equipment identification register.

The register contains special IMEI (International Mobile Station Equipment Identity) numbers on almost all mobile stations that have access to a particular communication network.

The database is divided:

• White list – for authorized MS;
• The black list includes numbers that were stolen or denied access for any other reason;
• Gray for MS with software data problems.

The control link of the network, which is not included in the switching system, is the Operation and Maintenance Center, abbreviated as TsEiTO.

The Operation and Maintenance Center inspects and manages the remaining components of the network. In the event of an emergency, CE&TO will notify personnel and record information about the emergency. Depending on the degree of damage, compulsory medical insurance allows you to eliminate the situation automatically or with personnel intervention.

To create intelligent hierarchical management of the GSM network, the Network Management Center (NMC) is suitable - a network operations center that:

see also

• Cellular network
• Increased data transfer speed for GSM development (EDGE)
• Enhanced Network Selection (ENS)
• Standard GSM forwarding codes - list of call forwarding codes that work with all operators and phones
• GSM frequency bands
• GSM services Cellular broadcast
• GSM localization
• Multimedia Messaging Service (MMS)
• NITZ Network identification and time zone
• Wireless Application Protocol (WAP)

Location Area Identifier (LAI)

Within a PLMN, a location area identifies its own authentic location area identifier (LAI). The LAI hierarchy is based on an international standard and is structured in a unique format as follows:

• Country code (CC): 3 decimal places.
• Mobile Network Code (MNC): 2 decimal places.
• Location Area Code (LAC): A maximum of 5 decimal places or a maximum of two times 8 bits encoded in hexadecimal (LAC)

Phone instructions

The phone manual will provide useful information regarding the issue. The corresponding section lists the supported frequencies. Some devices will allow you to customize the reception area. You should choose a phone model that receives generally accepted Russian channels:

1. 900 MHz – E-GSM. The ascending branch is 880..915 MHz, the descending branch is 925..960 MHz.
2. 1800 MHz – DCS. The ascending branch is 1710..1785 MHz, the descending branch is 1805..1880 MHz.

LTE technology adds a 2600 MHz region, and an 800 MHz channel has been introduced.

The evolution of GSM or what 2.5G and 2.75G are

GPRS (General Packet Radio Service) or 2.5G is an add-on to the GSM standard. The information in it is transmitted in the form of packets - messages containing information about the sender, recipient and transmitted data. A fragment of a photograph, for example.

Packages allow subscribers to exchange data not only among themselves, but also to send / receive from the Internet. Transmission speed – 85-100 kbit/sec.

EDGE (Enhanced Data rates for GSM Evolution) or 2.75G is an improved version of GPRS using 8PSK modulation. The technology increases the transmission speed to 270 kbit/sec.

How it works

Two elements are involved in signal transmission between subscribers:

1. GSM module in the phone – transmits / receives radio signals from the operator’s base station;
2. base station – connects with other subscribers, verifies the authenticity of the SIM card, protects the radio from eavesdropping.

GSM communication works as follows:

1. The radio module in the phone scans the airwaves.
2. The base station sends the module a random number generated by the algorithm.
3. The phone generates a response and sends it back. If the response code is correct, then it connects to the mobile network. With appropriate settings, the base station checks the IMEI of the device and can deny access if it is on the list of prohibited or monitored devices. This and the 3 previous stages take place when the device is turned on, before receiving + sending SMS, making calls, and reconnecting to another base station.
4. An encrypted connection is established between the elements.
5. The phone and base station exchange information.

At the end of the exchange, the connection is terminated, and the device continues to listen to the radio.

conclusions

We can say that although they are still in use, especially GSM, the truth is that both of them may be doomed to disappear in the coming years. The advent of more modern technologies such as 4G or 5G will force us to use these two technologies less and less.

We have seen that there are some clear differences, such as whether or not you can make calls and receive data at the same time. However, this does not mean that one works better than the other for everyday use. We can say that GSM is much more widespread throughout the world.