GSM900, DCS1800, UMTS2100, CDMA450, 3G, 4G LTE.

Uplink– communication channel from a subscriber (telephone or modem) to a base station of a cellular operator.

Downlink– communication channel from the base station to the subscriber.

GSM frequency

GSM is a 2nd generation communication. GSM 900 frequency range: Uplink 890-915 MHz, Downlink 935-960 MHz. There is an additional GSM frequency range, the so-called E-GSM - this is an additional 10 MHz. E-GSM: Uplink 880-890MHz, Downlink 925-935MHz.

3G frequency

3G cellular communication of the 3rd generation. In Russia, it operates at frequencies: Uplink 1920 - 1980 MHz and Downlink 2110 - 2170 MHz. The Skylink operator also has 3G frequencies in the CDMA 450 standard: Uplink 453-457.5 MHz and Downlink 463-467.5 MHz.

4G LTE frequency

4G cellular communication of the 4th generation. In Russia, it works in the 4G LTE (Long-Term Evolution) standard at frequencies: 2500-2700 MHz.

CDMA frequency

Skylink operates on CDMA 450 and W-CDMA (UMTS) is operated by Big Three operators. Skylink CDMA frequency - Uplink 453-457.5 MHz and Downlink 463-467.5 MHz. W-CDMA (UMTS) - Uplink 1920 - 1980 MHz and Downlink 2110 - 2170 MHz.

UMTS frequencies

UMTS (English Universal Mobile Telecommunications System - universal mobile telecommunication system). Strictly speaking, this is 3G. UMTS frequencies: Uplink 1920 - 1980 MHz and Downlink 2110 - 2170 MHz.

Frequencies of amplifiers (repeaters) of cellular communication.

If you only need voice communication, then GSM repeaters with frequencies of 900 MHz or DCS 1800 MHz (VECTOR, AnyTone) are suitable. If you also need the Internet, then the frequency of the repeater must match the frequencies of 3G / UMTS 1920-2170 MHz.

Russian GSM frequencies

GSM 900: Uplink 890-915MHz, Downlink 935-960MHz. Total 124 channels in GSM900. In each region of Russia, GSM frequencies are distributed among cellular operators individually.

GSM 1800 frequencies.

The GSM 1800 standard is more correctly called DCS1800. Its frequencies are Uplink 1710-1785 MHz and Downlink 1805-1880 MHz.

3G frequency range.

3G - in Russia it is CDMA450 (Skylink) and UMTS 2100. UMTS frequency range: Uplink 1920 - 1980 MHz and Downlink 2110 - 2170 MHz, and CDMA450 - Uplink 453-457.5 MHz and Downlink 463-467.5 MHz. For example, the mobile operator Beeline in the Moscow region is testing its 3G in the GSM900 frequency band. 3G frequencies for other regions of Russia are the same: Uplink 1920 - 1980 MHz and Downlink 2110 - 2170 MHz

3G modem frequencies.

As a rule, all 3G modems operate on 3G / UMTS frequencies: Uplink 1920 - 1980 MHz and Downlink 2110 - 2170 MHz., And support 2G network frequencies, that is, GSM900: Uplink 890-915 MHz, Downlink 935-960 MHz and DCS 1800 (aka GSM1800) Uplink 1710-1785 MHz and Downlink 1805-1880 MHz.

The largest telecom operators in Russia.

Skylink frequency.

The existing Skylink CDMA450 network is Uplink 453-457.5 MHz and Downlink 463-467.5 MHz. In September 2010, Skylink received a license for 2100 frequencies, namely 1920 - 1935 MHz and Downlink 2110 - 2125 MHz.

MTS 3G frequency.

Uplink 1950 - 1965 MHz and Downlink 2140 - 2155 MHz. MTS, like other cellular operators in the 3G range, has a width of 15 MHz.

Frequency Megaphone 3G/UMTS.

Megaphone in the 3G / UMTS range operates at frequencies: Uplink 1935 - 1950 MHz and Downlink 2125 - 2140 MHz.

Beeline 3G frequency

Beeline in the Moscow region is testing its 3G in the GSM900 frequency band. 3G frequencies for Russian regions: Uplink 1920 - 1980 MHz and Downlink 2110 - 2170 MHz

Frequency Megafon 4G

Megaphone in the 4G band operates at frequencies: 2500 - 2700 MHz.

YOTA 4G LTE frequency

Internet company Yota operates in the 4G LTE band at frequencies: 2500 - 2700 MHz.

As a result, the physical channel between the receiver and the transmitter is determined by the frequency, allocated frames and the numbers of timeslots in them. Base stations typically use one or more ARFCN channels, one of which is used to identify the presence of the BTS on the air. The first timeslot (index 0) of this channel's frames is used as the base-control channel or beacon-channel. The remaining part of the ARFCN is distributed by the operator for CCH and TCH channels at its discretion.

2.3 Logical channels

Logical channels are formed on the basis of physical channels. Um-interface implies the exchange of both user information and service information. According to the GSM specification, each type of information corresponds to a special type of logical channels implemented through physical ones:

• traffic channels (TCH - Traffic Channel),
• service information channels (CCH - Control Channel).

Traffic channels are divided into two main types: TCH/F- Full rate channel with a maximum speed of up to 22.8 Kbps and TCH/H- Half rate channel with maximum speed up to 11.4 Kbps. These types of channels can be used for voice (TCH/FS, TCH/HS) and user data (TCH/F9.6, TCH/F4.8, TCH/H4.8, TCH/F2.4, TCH/H2. 4), for example, SMS.

Service information channels are divided into:

• Broadcast (BCH - Broadcast Channels).
  • FCCH - Frequency Correction Channel (frequency correction channel). Provides the information needed by the mobile phone to correct the frequency.
  • SCH - Synchronization Channel (synchronization channel). Provides the mobile phone with the information needed for TDMA synchronization with the base station (BTS) as well as its BSIC identity.
  • BCCH - Broadcast Control Channel (broadcast channel service information). It transmits basic information about the base station, such as the way the service channels are organized, the number of blocks reserved for access grant messages, and the number of multiframes (51 TDMA frames in size) between Paging requests.
• General purpose channels (CCCH - Common Control Channels)
  • PCH - Paging Channel. Looking ahead, I’ll tell you that Paging is a kind of ping of a mobile phone that allows you to determine its availability in a certain coverage area. This channel is for that.
  • RACH - Random Access Channel (random access channel). Used by mobile phones to request their own service channel SDCCH. Exclusively uplink channel.
  • AGCH - Access Grant Channel (access notification channel). On this channel, base stations respond to RACH requests from mobile phones by allocating SDCCH, or immediately TCH.
• Own channels (DCCH - Dedicated Control Channels)
  Own channels, like TCH, are allocated to specific mobile phones. There are several subspecies:
  • SDCCH - Stand-alone Dedicated Control Channel. This channel is used for mobile phone authentication, encryption key exchange, location update procedure, as well as for voice calls and SMS messaging.
  • SACCH - Slow Associated Control Channel. Used during a call or when the SDCCH is already in use. With it, BTS sends periodic instructions to the phone to change timings and signal strength. In the opposite direction, there are data on the received signal level (RSSI), TCH quality, as well as the signal level of the nearest base stations (BTS Measurements).
  • FACCH - Fast Associated Control Channel. This channel is provided together with TCH and allows the transmission of urgent messages, for example, during the transition from one base station to another (Handover).

2.4 What is burst?

Data over the air is transmitted as a sequence of bits, most commonly referred to as "burst", within timeslots. The term “burst”, the most appropriate analogue of which is the word “splash”, should be familiar to many radio amateurs, and most likely appeared when compiling graphical models for the analysis of radio air, where any activity looks like waterfalls and water splashes. You can read more about them in this wonderful article (image source), we will focus on the most important. A schematic representation of a burst might look like this:

Guard Period
To avoid interference (i.e. overlapping of two busrts), the burst duration is always less than the timeslot duration by a certain value (0.577 - 0.546 = 0.031 ms), called the "Guard Period". This period is a kind of time reserve to compensate for possible time delays in signal transmission.

tail bits
These markers define the beginning and end of the burst.

info
Burst payload, for example, subscriber data or service traffic. Consists of two parts.

Stealing Flags
These two bits are set when both parts of the TCH burst are transmitted on the FACCH. One transmitted bit instead of two means that only one part of the burst is transmitted on FACCH.

Training Sequence
This part of the burst is used by the receiver to determine the physical characteristics of the link between the phone and the base station.

2.5 Burst types

Each logical channel corresponds to certain types of burst:

normal burst
Sequences of this type implement traffic channels (TCH) between the network and subscribers, as well as all types of control channels (CCH): CCCH, BCCH and DCCH.

Frequency Correction Burst
The name speaks for itself. Implements a one-way FCCH downlink channel, allowing mobile phones to more accurately tune to the BTS frequency.

Synchronization Burst
Burst of this type, as well as Frequency Correction Burst, implements a downlink channel, only SCH, which is designed to identify the presence of base stations on the air. By analogy with beacon packets in WiFi networks, each such burst is transmitted at full power, and also contains information about the BTS necessary to synchronize with it: frame rate, identification data (BSIC), and others.

Dummy Burst
A dummy burst sent by the base station to fill unused timeslots. The fact is that if there is no activity on the channel, the signal strength of the current ARFCN will be significantly less. In this case, the mobile phone may appear to be far from the base station. To avoid this, BTS fills unused timeslots with meaningless traffic.

Access Burst
When establishing a connection with the BTS, the mobile phone sends a dedicated SDCCH request on the RACH. The base station, having received such a burst, assigns the subscriber his FDMA system timings and responds on the AGCH channel, after which the mobile phone can receive and send Normal Bursts. It is worth noting the increased duration of Guard time, since initially neither the phone nor the base station knows information about time delays. If the RACH request does not fall into the timeslot, the mobile phone sends it again after a pseudo-random period of time.

2.6 Frequency hopping

Quote from Wikipedia:

Pseudo-random shifting of the operating frequency (FHSS - English frequency-hopping spread spectrum) is a method of transmitting information by radio, the peculiarity of which is the frequent change of carrier frequency. The frequency changes according to a pseudo-random sequence of numbers known to both the sender and the recipient. The method increases the noise immunity of the communication channel.

3.1 Main attack vectors

Since the Um-interface is a radio interface, all its traffic is "visible" to anyone who is within the range of the BTS. Moreover, you can analyze data transmitted over the air, even without leaving your home, using special equipment (for example, an old mobile phone supported by the OsmocomBB project, or a small RTL-SDR dongle) and direct hands of the most ordinary computer.

There are two types of attack: passive and active. In the first case, the attacker does not interact in any way with the network or with the attacked subscriber - only the reception and processing of information. It is not difficult to guess that it is almost impossible to detect such an attack, but it does not have as many prospects as an active one. An active attack implies the interaction of the attacker with the attacked subscriber and/or cellular network.

We can single out the most dangerous types of attacks to which subscribers of cellular networks are exposed:

• Sniffing
• Leakage of personal data, SMS and voice calls
• Location data leak
• Spoofing (FakeBTS or IMSI Catcher)
• Remote SIM Capture, Arbitrary Code Execution (RCE)
• Denial of Service (DoS)

3.2 Subscriber identification

As mentioned at the beginning of the article, subscriber identification is performed by IMSI, which is recorded in the subscriber's SIM card and the operator's HLR. Mobile phones are identified by serial number - IMEI. However, after authentication, neither IMSI nor IMEI fly in the clear over the air. After the Location Update procedure, the subscriber is assigned a temporary identifier - TMSI (Temporary Mobile Subscriber Identity), and further interaction is carried out with its help.

Attack methods
Ideally, the subscriber's TMSI is known only to the mobile phone and the cellular network. However, there are ways to bypass this protection. If you make a cyclic call to the subscriber or send SMS messages (or rather Silent SMS), monitoring the PCH channel and performing correlation, you can select the TMSI of the attacked subscriber with a certain accuracy.

In addition, having access to the SS7 interoperator network, you can find out the IMSI and LAC of its owner by the phone number. The problem is that in the SS7 network, all operators "trust" each other, thereby reducing the level of confidentiality of their subscribers' data.

3.3 Authentication

To protect against spoofing, the network authenticates the subscriber before starting its service. In addition to the IMSI, the SIM card stores a randomly generated sequence called Ki, which it returns only in hashed form. Ki is also stored in the operator's HLR and is never transmitted in the clear. In general, the authentication process is based on the principle of a four-way handshake:

1. The subscriber performs a Location Update Request, then provides the IMSI.
2. The network sends a pseudo-random RAND value.
3. The phone's SIM card hashes Ki and RAND using the A3 algorithm. A3(RAND, Ki) = SRAND.
4. The network also hashes Ki and RAND using the A3 algorithm.
5. If the SRAND value on the subscriber's side coincides with that calculated on the network side, then the subscriber has been authenticated.

Attack methods
Iterating over Ki, given the RAND and SRAND values, can take quite a long time. In addition, operators can use their own hashing algorithms. There is quite a bit of information on the web about brute force attempts. However, not all SIM cards are perfectly protected. Some researchers were able to directly access the file system of the SIM card and then extract the Ki.

3.4 Traffic encryption

According to the specification, there are three algorithms for encrypting user traffic:

• A5/0- a formal designation for the lack of encryption, just like OPEN in WiFi networks. I myself have never seen networks without encryption, however, according to gsmmap.org, A5 / 0 is used in Syria and South Korea.
• A5/1 is the most widely used encryption algorithm. Despite the fact that his hack has already been repeatedly demonstrated at various conferences, it is used everywhere and everywhere. To decrypt the traffic, it is enough to have 2 TB of free disk space, a regular personal computer with Linux and the Kraken program on board.
• A5/2- an encryption algorithm with intentionally weakened protection. If where and is used, then only for beauty.
• A5/3- at the moment the strongest encryption algorithm, developed back in 2002. On the Internet, you can find information about some theoretically possible vulnerabilities, but in practice no one has yet shown how to crack it. I don't know why our operators don't want to use it in their 2G networks. After all, this is far from a hindrance, because. the encryption keys are known to the operator and the traffic can be quite easily decrypted on its side. And all modern phones support it perfectly. Fortunately, modern 3GPP networks use it.

Attack methods
As already mentioned, having sniffing equipment and a computer with 2 TB of memory and the Kraken program, you can quite quickly (a few seconds) find A5 / 1 session encryption keys, and then decrypt anyone's traffic. German cryptologist Karsten Nohl demonstrated in 2009 how to crack A5/1. A few years later Karsten and Sylvian Muno demonstrated the interception and method of decrypting a telephone conversation using several old Motorola phones (OsmocomBB project).

Conclusion

My long story has come to an end. You can get acquainted with the principles of operation of cellular networks in more detail and from a practical point of view in a series of articles Acquaintance with OsmocomBB, as soon as I finish the remaining parts. I hope I managed to tell you something new and interesting. I look forward to your feedback and comments! Add tags

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DownLink - communication channel from the base station to the subscriber
UpLink is a communication channel from the subscriber to the operator's base station.

Standard 4G/LTE Frequency 2500

This type of communication is developing relatively recently and mainly in cities.

FDD (Frequency Division Duplex) - DownLink and UpLink operate on different frequency bands.
TDD (Time division duplex - time division of channels) - DownLink and UpLink operate on the same frequency band.

Yota: FDD DownLink 2620-2650 MHz, UpLink 2500-2530 MHz
Megaphone: FDD DownLink 2650-2660 MHz, UpLink 2530-2540 MHz
Megafon: TDD 2575-2595 MHz - this frequency band is allocated only in the Moscow region.
MTS: FDD DownLink 2660-2670 MHz, UpLink 2540-2550 MHz
MTS: TDD 2595-2615 MHz - this frequency band is allocated only in the Moscow region.
Beeline: FDD DownLink 2670-2680 MHz, UpLink 2550-2560 MHz
Rostelecom: FDD DownLink 2680-2690 MHz, UpLink 2560-2570 MHz
After the purchase of Yota by Megafon, Yota virtually began to work as Megafon.

Standard 4G/LTE Frequency 800

The network was launched into commercial operation at the beginning of 2014, mainly outside the city, in rural areas.

UpLink / DownLink (MHz)

Rostelecom: 791-798.5 / 832 - 839.5
MTS: 798.5-806 / 839.5 - 847.5
Megaphone: 806-813.5 / 847 - 854.5
Beeline: 813.5 - 821 / 854.5 - 862

Standard 3G/UMTS Frequency 2000

3G/UMTS2000 is the most widespread cellular communication standard in Europe and is mainly used for data transmission.

UpLink / DownLink (MHz)

Skylink: 1920-1935 / 2110 - 2125 - in the end, these frequencies are most likely to go to Rostelecom. The network is currently not in use.
Megaphone: 1935-1950 / 2125 - 2140
MTS: 1950-1965 / 2140 - 2155
Beeline: 1965 - 1980 / 2155 - 2170

Standard 2G/DCS Frequency 1800

DCS1800 - the same GSM, only in a different frequency range, mainly used in cities. But, for example, there are regions where the TELE2 operator operates only in the 1800 MHz band.

UpLink 1710-1785 MHz and Downlink 1805-1880 MHz

It doesn't make much sense to show division by operators, because in each region, the distribution of frequencies is individual.

Standard 2G/DCS Frequency 900

GSM900 is the most common communication standard in Russia today and is considered a second generation communication.

There are 124 channels in GSM900 MHz. In all regions of the Russian Federation, GSM frequency bands are distributed between operators individually. And there is E-GSM exists as an additional GSM frequency band. It is shifted in frequency relative to the base one by 10 MHz.

UpLink 890-915MHz and Downlink 935-960MHz

UpLink 880-890MHz and Downlink 925-935MHz

Standard 3G Frequency 900

Due to the lack of channels on the 2000 frequency, frequencies of 900 MHz were allocated for 3G. Actively used in the region.

CDMA Standard Frequency 450

CDMA450 - in the central part of Russia, this standard is used only by the SkyLink operator (Skylink).

UpLink 453 - 457.5 MHz and DownLink 463 - 467.5 MHz.

Beginners don't understand the games played by standards makers. It would seem that it uses GSM frequencies 850, 1900, 900, 1800 MHz, what more? Quick answer - read the following section Phone instructions. The illegitimacy of the generally accepted interpretation will be shown. The problem is described in the following terms:

1. The second generation of 2G cellular communication has created 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, having changed them.
2. The family tree of standards is constantly expanding.
3. International versions of standards are designed to unite the heterogeneous rules of individual countries. Often direct implementation is not possible. Governments are changing the legal framework, fixing frequency plans.

The foregoing explains the origins of the misunderstanding of the problem by beginners. Returning clarity to the question, let's build a simplified hierarchy of standards, indicating the frequencies used along the way.

Genealogy of standards

The following information is intended to explain to the layman the structure of existing, extinct standards. Below, in the following sections, the technologies used in Russia will be described. The corresponding representatives of the tree that adorned the Russian forest are marked in bold.

1G

1. AMPS family: AMPS, NAMPS, TACS, ETACS.
2. Others: NMT, C-450, DataTAC, Hicap, Mobitex.

2G: 1992

1. GSM/3GPP family: GSM, HSCSD, CSD.
2. 3GPP2 family: cdmaOne.
3. AMPS family: D-AMPS.
4. Other: iDEN, PHS, PDC, CDPD.

2G+

1. 3GPP/GSM family: GPRS, EDGE.
2. 3GPP2 family: CDMA2000 1x including Advanced.
3. Others: WiDEN, DECT.

3G: 2003

1. 3GPP family: UMTS.
2. 3GPP2 family: CDMA2000 1xEV-DO R.0

3G+

1. 3GPP family: LTE, HSPA, HSPA+.
2. 3GPP2 family: CDMA2000 1xEV-DO R.A, CDMA2000 1xEV-DO R.B, CDMA2000 1xEV-DO R.C
3. IEEE family: Mobile WiMAX, Flash OFDM.

4G: 2013

1. 3GPP family: LTE-A, LTE-S Pro.
2. IEEE family: WiMAX.

5G: 2020

1. 5G-NR.

Short description

Genealogy allows you to trace extinct species. For example, modern authors often use the abbreviation GSM, misleading the reader. The technology is entirely limited to the second generation of cellular, an extinct species. Former frequencies with additions continue to be used by descendants. On 1 December 2016, Australia's Telstra ended its use of GSM, becoming the first operator in the world to completely upgrade its equipment. Technology continues to be content with 80% of the world's population (according to the GSM Association). On January 1, 2017, the American AT&T followed the example of Australian colleagues. The stop of the service by the Optus operator followed, and on April 2017, Singapore recognized the discrepancy between 2G and the growing needs of the population.

So, the term GSM is used in relation to aging equipment that has failed the RF. Descendant protocols can be called GSM successors. The frequencies are preserved by the next generations. Punctures, methods of information transfer are changing. The aspects of frequency allocation that accompany equipment upgrades are discussed below. Be sure to provide information that allows you to establish the relationship of GSM.

Phone instruction

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

1. 900 MHz - E-GSM. Uplink - 880..915 MHz, downlink - 925..960 MHz.
2. 1800 MHz - DCS. Uplink - 1710..1785 MHz, downlink - 1805..1880 MHz.

LTE technology adds 2600 MHz area, 800 MHz channel is introduced.

The history of RF communications: frequencies

In 1983, the development of a European digital communication standard began. As a reminder, the first generation of 1G used analog transmission. Thus, engineers developed the standard in advance, anticipating the history of the development of technology. Digital communication was born by the Second World War, more precisely, by the Green Hornet encrypted transmission system. The military was well aware that the era of digital technology was coming. The civil industry caught the movement of the wind.

900 MHz

The European organization CEPT has created a GSM committee (Groupe Special Mobile). The European Commission has proposed using the 900 MHz spectrum. The developers settled in Paris. Five years later (1987), 13 EU countries submitted a memorandum to Copenhagen on the need to create a single cellular network. The community decided to request the help of GSM. In February, the first technical specification was released. Politicians from four countries (May 1987) supported the project with the Bonn Declaration. The next short period (38 weeks) is filled with general hustle and bustle, ruled by four designated persons:

1. Armin Silberhorn (Germany).
2. Philippe Dupulis (France).
3. Renzo Failli (Italy).
4. Stephen Temple (Great Britain).

In 1989, the GSM commission leaves the CEPT trusteeship, becoming part of ETSI. On July 1, 1991, the former Prime Minister of Finland, Harry Holkeri, made the first call to a subscriber (Kaarina Suonio) using the services of the Radiolinia provider.

1800 MHz

In parallel with the introduction of 2G, work was underway to use the 1800 MHz region. The first network covered the UK (1993). At the same time, the Australian operator Telecom moved in.

1900 MHz

The 1900 MHz frequency was introduced by the USA (1995). The GSM Association was created, the world number of subscribers reached 10 million people. A year later, the figure increased tenfold. The use of 1900 MHz prevented the introduction of the European version of UMTS.

800 MHz

The 800 MHz band appeared in 2002, in parallel with the introduction of the multimedia messaging service.

Attention, question!

What frequencies have become the Russian standard? The confusion is added by the ignorance by the authors of the Runet of the standards adopted by the official developers. The direct answer is discussed above (see the Phone Instructions section), we describe the work of the organizations mentioned (the UMTS section).

Why so many frequencies

Examining the results of 2010, the GSM Association stated that 80% of the planet's subscribers are covered by the standard. This means that four-fifths of the 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 20th century developed separately. Frequencies 900 MHz of the USSR were occupied by military, civil air navigation.

GSM: 900 MHz

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

• Joint functioning of navigation and the second generation of cellular communication is possible.

1. NMT-450.

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

1. NMT-450.
2. NMT-900 (1986).

Why did the Russian government choose the first answer? Probably decided to try two ranges. Please note that these standards describe analog communications (1G). Developer countries have been shutting down shop since December 2000. Iceland (Siminn) was the last to surrender (September 1, 2010). Experts note an important advantage of the 450 MHz band: range. A significant plus, appreciated by remote Iceland. The Russian government wanted to cover the area of ​​the country with a minimum of towers.

NMT was loved by fishermen. The vacated grid 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. Subsidiary (Tele 2) Skylink fills the Perm and Arkhangelsk regions with a range. The license expires in 2021.

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

American 1G networks using 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. Differs in 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 man in the street often uses used equipment. D-AMPS equipment has reached warehouses of Tele 2, Beeline. On November 17, 2007, the latter closed the shop for the Central Region. The license of the Novosibirsk region expired on December 31, 2009. The last swallow left 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.

In the period December 2002 - October 2016 specifications 1xRTT, EV-DO Rev. A (450 MHz) were used by Skylink. Now the infrastructure has been modernized, LTE has been introduced. On September 13, 2016, the news spread around the world portals: Tele 2 stops using CDMA. The American MTS began the process of introducing LTE a year earlier.

GPRS - second or third generation

The development of the CELLPAC protocol (1991-1993) was a turning point in the development of cellular communications. Received 22 US patents. The descendants of the technology are LTE, UMTS. Packet data transmission is designed to speed up the process of information exchange. The project aims to improve GSM networks (frequencies listed above). The service user is required to obtain technologies:

1. Access to the Internet.
2. Deprecated "press to speak".
3. Messenger.

The overlap of two technologies (SMS, GPRS) speeds up the process many times over. The specification supports IP, PPP, X.25 protocols. Packets keep coming even during a call.

EDGE

The next step in the evolution of GSM is conceived by AT&T (USA). Compact-EDGE has taken over the D-AMPS niche. The frequencies are listed above.

UMTS - full 3G

The first generation to require upgrades to base station hardware. The frequency grid has changed. The rate limit for a line that takes advantage of HSPA+ is 42 Mbps. Realistically achievable speeds significantly overlap 9.6 kbps GSM. Starting in 2006, the countries started a renewal. Using orthogonal frequency multiplexing, the 3GPP committee intended to achieve the 4G layer. Early Birds released in 2002. Initially, the developer laid down the following frequencies:

1. .2025 MHz. Ascending branch.
2. .2200 MHz. Descending link.

Since the US was already using 1900 MHz, it chose the segments 1710..1755; 2110..2155 MHz. Many countries have followed America's lead. The 2100 MHz frequency is too often busy. Hence the numbers given at the beginning:

• 850/1900 MHz. Moreover, 2 channels are selected using one range. Either 850 or 1900.

Agree, it is incorrect to drag in GSM, following a bad common example. The second generation used a half-duplex single channel, UMTS - used two at once (5 MHz wide).

UMTS frequency grid of Russia

The first attempt to allocate spectra took place on February 3-March 3, 1992. The decision was adapted by the Geneva conference (1997). It was the S5.388 specification that fixed the ranges:

• 1885-2025 MHz.
• 2110-2200 MHz.

The decision required further clarification. The commission identified 32 ultra-channels, 11 were unused reserves. Most of the others received clarifying names, since individual frequencies coincided. Russia rejected the European practice, despising the USA, having adopted 2 channels (band) UMTS-FDD:

1. No. 8. 900 MHz - E-GSM. Uplink - 880..915 MHz, downlink - 925..960 MHz.
2. No. 3. 1800 MHz - DCS. Uplink - 1710..1785 MHz, downlink - 1805..1880 MHz.

Cell phone characteristics should be selected according to the information provided. The Wikipedia table revealing the frequency plan of the planet Earth is completely useless. They forgot to take into account the Russian specifics. Europe operates nearby IMT Channel 1. In addition, there is a UMTS-TDD mesh. The equipment of the two overhead network options is incompatible.

LTE-3G+

Evolutionary continuation of the GSM-GPRS-UMTS bundle. It can serve as an add-on for CDMA2000 networks. Only a multi-frequency phone is capable of providing LTE technology. Experts directly indicate a place below the fourth generation. Contrary to the statements of marketers. Initially, the ITU-R organization recognized the technology as appropriate, later the position was revised.

LTE is a registered trademark of ETSI. The key idea was the use of signal processors and the introduction of innovative methods of carrier modulation. IP-addressing of subscribers was recognized as expedient. The interface has lost backward compatibility, the frequency spectrum has changed again. The first grid (2004) was launched by the Japanese company NTT DoCoMo. The exhibition version of the technology overtook Moscow in the hot May 2010.

Repeating the experience of UMTS, the developers have implemented two options for the air protocol:

1. LTE-TDD. Time division of channels. The technology is widely supported by China, South Korea, Finland, Switzerland. The presence of a single frequency channel (1850..3800 MHz). Partially covers WiMAX, upgrade is possible.
2. LTE FDD. Frequency division of channels (separately descending, ascending).

The frequency plans of the 2 technologies are different, 90% of the core design is the same. Samsung, Qualcomm produce phones capable of catching both protocols. Occupied ranges:

1. North America. 700, 750, 800, 850, 1900, 1700/2100, 2300, 2500, 2600 MHz.
2. South America. 2500 MHz.
3. Europe. 700, 800, 900, 1800, 2600 MHz.
4. Asia. 800, 1800, 2600 MHz.
5. Australia, New Zealand. 1800, 2300 MHz.

Russia

Russian operators have chosen LTE-FDD technology, use frequencies:

1. 800 MHz.
2. 1800 MHz.
3. 2600 MHz.

LTE-A-4G

Frequencies remain the same (see LTE). Launch chronology:

1. On October 9, 2012, Yota had 11 base stations.
2. Megafon on February 25, 2014 covered the Garden Ring of the capital.
3. Beeline has been operating on LTE 800, 2600 MHz frequencies since August 5, 2014.