Frequencies and network capacity - everything you wanted to ask
I remember in school years, many wondered: "why should I study the fundamentals of physics or mathematical analysis, if in my life it is not useful to me?". Then it seemed that one could go into adulthood, knowing only the simplest mathematical operations (so as not to be mistaken in the grocery store). But the development of technology has led to the fact that quite powerful and complex tools fell into the hands of ordinary users. Take at least a mobile connection. In order to competently choose an operator, to understand why there is a mobile connection somewhere, and somewhere it does not exist, we have to remember not only school textbooks, but also things that go far beyond them.
In order not to wander through the specialized literature, we have prepared a small educational program on the frequencies of the mobile network, which will help to navigate.
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From a school course in physics, we remember that wireless communication is data transmission using radio frequency electromagnetic waves.
Data (analog or digital) is “laid” in a wave by means of modulation — a process in which certain parameters of a high frequency (carrier) signal change with a low frequency. It is the modulation that makes it possible to use the entire radio band for transmitting various information, not limited to the frequencies corresponding to our voice.
In the process of modulation, you can vary the frequency, phase, or amplitude of oscillations, respectively, for an analog signal, frequency, amplitude, and phase modulation are selected. They can be used in pure form or in combination with each other to provide greater noise immunity during signal transmission.
Fig. 1. Example: amplitude modulation
When transmitting an analog message, the transmitter uses modulation to “lay” the useful signal into the carrier frequency, and transmits it using an antenna to the receiver. The latter performs the reverse procedure - demodulation - highlighting the original signal.
Modulation changes the spectrum of the transmitted signal — it expands from a single frequency, and the degree and nature of these changes depend on the type of modulation. Thus, to transmit a useful signal without a loss, an entire frequency band is needed, the width of which in the simplest case of modulation by a harmonic signal is roughly determined by the double frequency of the modulating signal (see Fig. 2).
Fig. 2. The simplest example: a high-frequency carrier is modulated by a low-frequency harmonic signal. Additional frequencies appear in the spectrum of the total signal.
Fig. 3. Spectrum with frequency modulation by a harmonic signal
There are ways to compress the band of the spectrum needed to transmit information, due to more clever modulation techniques.
For the transmission of a digital signal — sequences 0 and 1 — both the above-mentioned pure modulation options and more complex digital circuits can be used.
Fig. 4. Amplitude, frequency and phase modulations of a discrete signal
These include schemes in which a discrete signal undergoes preliminary processing before modulation to compress the resulting spectral band required to transmit a signal with minimal losses. A good example is the Gaussian frequency modulation used in the GSM standard with the minimum frequency shift (Gaussian Minimum Shift Keying - GMSK) - a type of frequency modulation. It reduces the spectral bandwidth and allows the use of non-linear amplifiers, which are better suited for a small mobile device with limited battery capacity. In addition to GSM, GMSK modulation is used in the automatic identification system in the fleet, in Bluetooth, GPRS, EDGE, CDPD and other applications.
LTE networks use other modulation options - OFDM and SC-FDMA , which are notable for better interference resistance. Previously, these schemes simply could not be implemented due to the high cost of the required computing power.
So far, we have been talking about wireless data transmission in isolation from real frequencies. Now let's deal with the radio range. From the point of view of physics, the boundaries of this range are conditional - it includes electromagnetic waves with a frequency of several hertz to tens of gigahertz.
Fig. 8. The position of the radio frequency scale on the EMP scale
Depending on the frequency, electromagnetic waves are scattered in different ways and reflected by obstacles. With this in mind, within the aforementioned frequency band, ranges are allocated for various needs: radio, television, military and civilian fixed services, aviation, maritime traffic, etc. For example, waves capable of penetrating deep into the water (wavelength - tens of kilometers, depth of penetration - of the order of tens of meters) are used to communicate with the submarine fleet, and the range of millimeter waves penetrating the Earth’s ionosphere is selected for space communications.
The mentioned subbands were first “reserved” for certain tasks by engineers, and then their allocated status was confirmed by international agreements that take into account the possibility of propagation of certain signals beyond geographical boundaries (cross-border coordination of frequency assignments is a topic for a separate long conversation). In the course of globalization, another goal of coordinated allocation of frequencies was defined - the import and export of communications equipment for its segment.
Fig. 9. Radio range
An ordinary user does not encounter a part of the radio band even once in his life, but there are certain frequencies that he uses almost daily, for example:
When allocating a range for specific needs, not only the frequency, but also other signal parameters are specified. It is necessary that the devices operating in this and the neighboring bands do not interfere with each other.
In Russia, the State Radio Frequency Commission (SCRF) deals with frequency regulation (in the part of the spectrum not transferred to the military) - the process is regulated by the federal law “On Communications”.
To allocate the frequency, the operator makes an application and waits for the next meeting of the SCRF. SCR decides on the allocation of the range, but if it is positive, it does not promise to start the service. With this solution, as well as the details of the planned construction (base station locations, transmitter powers, etc.), the operator goes to the FSUE GRTC, where the compatibility of the communication standard to be used on this frequency is verified with the existing and planned equipment adjacent ranges. At this stage, the operator may be refused, for example, from the military. The procedure, by the way, is paid, regardless of the result.
Only after that the Federal Service for Supervision in the Sphere of Communications, Information Technologies and Mass Communications issues a permit. If several operators apply for the frequency, the resource is distributed on a competitive basis, and more recently - on an auction basis.
There is a procedure such as clearing frequencies - when a specific frequency range is released by the request of the operator by the military or other interested organizations. But this process is not regulated in any way - everything rests on the mutual agreement of the companies.
The frequency range can be allocated for a limited period (10 years) throughout the country or in a separate region (therefore, the federal operator may have a different set of licenses in different parts of the country). Upon the expiration of the period specified in the permit, the documents are reissued, unless, of course, there are no reasons for refusal, for example, the range is planned for another technology.
Receiving frequency, the operator undertakes certain obligations: to begin to provide services for which the frequency is allocated, within a predetermined period. Speech in this case is not only about mobile communications, but about wireless services in general - the broadcast of television, the Internet. If this condition is not met, the operator may lose the range.
The policy of paying for the use of frequencies has changed several times during the life of the mobile communication. At first, the operators paid for each communication object (base station), then for using frequencies in a separate region (the frequency allocation conditions could contain a clause to pay monetary compensation to the previous owner of the band, as was the case when LTE frequencies were allocated in the 2012 competition). And since permits for different parts of the spectrum in different regions were not formalized at the same time, the conditions were different for individual market participants, which resulted in squabbling and fighting companies for a valuable resource. In recent years, a number of measures have been taken to equalize the rights of companies to frequencies. In particular, auctions started in 2015 (this does not mean that now all frequencies are allocated within auctions, but until 2015 there was no such practice), and in 2016 a generalized decision was made on the allocation of frequencies, equalizing the conditions for using frequencies (coverage permissible technologies for certain parts of the spectrum, etc.).
The current “picture” of the frequency distribution in Moscow (as of November 2016) is presented in the figure below.
Fig. 10. Frequency distribution in Moscow
The leaders in the number of frequencies for digital mobile communications in Russia at the moment are MTS and Megaphone.
As can be seen from the diagram, quite a few segments of the frequency spectrum somewhere between 300 and 3000 MHz are allocated for civil mobile communication, which are divided between the operators operating in a given territory.
Different communication standards operate at different frequencies - this situation has evolved historically, as new generations are developed and implemented by operators, frequencies are allocated during auctions or tenders, and the spectrum is released from obsolete technologies.
About generations of mobile communications
Standards for modern mobile communications are described in the 3GPP (The 3rd Generation Partnership Project) specification - a partnership of leading organizations in the field of standardization of telecommunication technologies. The name of the partnership refers to the “third generation” of communication, but GSM is usually considered as 2 and 2.5 generations (2G and 2.5G, respectively). After completing the GSM specification, the organization took up the development of 3G (UMTS), and then pre-4G (LTE) and 4G (LTE-Advanced).
Fig. 11. The development of mobile communications
The universally developed 3GPP standards do not replace each other, but coexist together, within the framework of networks of some operators - new technologies are not simultaneously crowding out old ones.
If we look at the situation in theory, then all the indicated frequency segments can be used for 4G communication: the networks of the new generation were designed to maximize the existing infrastructure. With the expectation of this, 3GPP has classified the possible bands (bands), assigning each a serial number and giving recommendations on the details of the organization of the transmission (in particular, by dividing the channel between subscribers). A general list of channels can be found here .
In practice, some parts of the spectrum are fixed by the SCR to certain technologies, so the operator cannot start providing services there (for example, in the 2100 MHz band, 3G services should be provided, although operators would be happy to allocate it to LTE). For others, the principle of technological neutrality applies, according to which the operator, who owns the frequency, can use it not only for organizing communications using the GSM standard, but also for next-generation technologies (3G, 4G). As a result, at the time of this writing, for the 4G, only the bands 3 (1,800 MHz), 7 (2,600 MHz), 20 (800 MHz) and 38 (2,600 MHz) are used in the 3GPP classification.
Considering the difference in the nature of the propagation of the waves of each of the ranges in the room and in the open space, as well as the difference in the operators' policies regarding the support of these ranges, users have to turn into frequency control specialists when choosing equipment.
The best option would be a device with support for all the ranges we use. But the “minimally recommended” option is support for 3 bands and one more: 7 or 38 (depending on the operator).
If you do not take into account the ranges, you can remain without 4G at all, as it happens with the owners of some American iPhone SE (namely, A1662 models): in the list of LTE bands supported by the device, only the 20th develops somehow in Russia, and that’s not in all regions (in the models for the international market, there is also a range of 7, common with us, and 38 for TD-LTE).
Capacity - one of the main parameters of the operator's network. It characterizes the technical ability to provide certain services: the higher the capacity - the greater the number of subscribers that can be served simultaneously, all other things being equal.
The total capacity inevitably depends on the width of the spectral band (as well as its location in the radio band). So, operators are demanding technologies of more and more efficient use of the available spectral band, implemented in each subsequent generation of mobile communications.
In 2G, a combination of FDMA and TDMA was used to increase capacity (against the background of analog standards and digital communications of the first generation). First, the subscriber devices were divided by frequency channels according to the FDMA (Frequency Division Multiple Access) principle.
Fig. 13. TDMA and FDMA
Third-generation networks use a different frequency channel separation principle - code or CDMA (Code Division Multiple Access), which allows increasing the network capacity at the same frequency range used, and at the same time ensuring a higher level of security.
LTE networks use either time or frequency division channels (TDD and FDD, respectively), but they are implemented differently than in GSM (2G). TDD (TD-LTE) uses the entire spectral bandwidth (1.4 to 20 MHz) to transmit data in two directions in turn; however, the time intervals for data transmission in each direction may not be equal. In FDD (FD-LTE), the range is divided into 2 bands in the general case of non-equal bands: for each of the data transfer directions. The specification recommends using either FDD or TDD for each of the bands prescribed for LTE ( http://en.wikipedia.org/wiki/LTE_frequency_bands#Frequency_bands_and_channel_bandwidths ), since TDD performed better at high frequencies, and FDD, respectively, at low frequencies . It is worth noting that the feature of the LTE standard makes it relatively inexpensive to integrate support for both methods in one device, therefore, equipment supporting both FDD and TDD is not uncommon.
Additionally, the bandwidth of the available spectrum in LTE is increased due to the technology of multiple antenna MIMO (Multiple input-multiple output).
The last point that I would like to talk about in this article is how the services look through the eyes of the end users.
The data transfer rate for the subscriber inevitably depends on the width of the spectral band allotted for his information flow. While in the 2G and 3G generations, the speed was limited by the communication standard itself, thanks to the 4G innovations, the speed is largely determined by the capabilities of the device.
In 4G (more precisely, in LTE-Advanced, recognized by the International Telecommunication Union as the true 4G standard), a mechanism for increasing subscriber speed has emerged - frequency aggregation, including from different frequency bands. Depending on the characteristics, the device can operate up to 4 bands of 20 MHz each (in two capitals at the moment, it is possible to use a maximum of 3 bands at MegaFon). For 4-carrier aggregation, the device must be categorized as 16 (CAT16). 4x4 MIMO together with aggregation allows you to download data on such devices at speeds up to 980 Mbps. 3 carriers aggregate categories 9 and 12 devices (CAT9 with speeds up to 450 Mbit / s and CAT12 with 600 Mbit / s, respectively), and the simplest CAT4 devices do not aggregate at all, reaching a speed of no more than 150 Mbit / s. Read more about the models that support this or that speed directly here .
Does the theory of aggregation work in practice in real radio reception? As part of the tests, MegaFon on Huawei equipment demonstrated a speed of 1 Gbit / s. For this, aggregation of three carriers was used.
In order not to wander through the specialized literature, we have prepared a small educational program on the frequencies of the mobile network, which will help to navigate.
')
From a school course in physics, we remember that wireless communication is data transmission using radio frequency electromagnetic waves.
It is a little theory of wireless data transmission
Data (analog or digital) is “laid” in a wave by means of modulation — a process in which certain parameters of a high frequency (carrier) signal change with a low frequency. It is the modulation that makes it possible to use the entire radio band for transmitting various information, not limited to the frequencies corresponding to our voice.
Analog signal modulation
In the process of modulation, you can vary the frequency, phase, or amplitude of oscillations, respectively, for an analog signal, frequency, amplitude, and phase modulation are selected. They can be used in pure form or in combination with each other to provide greater noise immunity during signal transmission.
Fig. 1. Example: amplitude modulation
When transmitting an analog message, the transmitter uses modulation to “lay” the useful signal into the carrier frequency, and transmits it using an antenna to the receiver. The latter performs the reverse procedure - demodulation - highlighting the original signal.
Modulation changes the spectrum of the transmitted signal — it expands from a single frequency, and the degree and nature of these changes depend on the type of modulation. Thus, to transmit a useful signal without a loss, an entire frequency band is needed, the width of which in the simplest case of modulation by a harmonic signal is roughly determined by the double frequency of the modulating signal (see Fig. 2).
Fig. 2. The simplest example: a high-frequency carrier is modulated by a low-frequency harmonic signal. Additional frequencies appear in the spectrum of the total signal.
Fig. 3. Spectrum with frequency modulation by a harmonic signal
There are ways to compress the band of the spectrum needed to transmit information, due to more clever modulation techniques.
Digital Signal Modulation
For the transmission of a digital signal — sequences 0 and 1 — both the above-mentioned pure modulation options and more complex digital circuits can be used.
Fig. 4. Amplitude, frequency and phase modulations of a discrete signal
These include schemes in which a discrete signal undergoes preliminary processing before modulation to compress the resulting spectral band required to transmit a signal with minimal losses. A good example is the Gaussian frequency modulation used in the GSM standard with the minimum frequency shift (Gaussian Minimum Shift Keying - GMSK) - a type of frequency modulation. It reduces the spectral bandwidth and allows the use of non-linear amplifiers, which are better suited for a small mobile device with limited battery capacity. In addition to GSM, GMSK modulation is used in the automatic identification system in the fleet, in Bluetooth, GPRS, EDGE, CDPD and other applications.
LTE networks use other modulation options - OFDM and SC-FDMA , which are notable for better interference resistance. Previously, these schemes simply could not be implemented due to the high cost of the required computing power.
Radio range
So far, we have been talking about wireless data transmission in isolation from real frequencies. Now let's deal with the radio range. From the point of view of physics, the boundaries of this range are conditional - it includes electromagnetic waves with a frequency of several hertz to tens of gigahertz.
Fig. 8. The position of the radio frequency scale on the EMP scale
Depending on the frequency, electromagnetic waves are scattered in different ways and reflected by obstacles. With this in mind, within the aforementioned frequency band, ranges are allocated for various needs: radio, television, military and civilian fixed services, aviation, maritime traffic, etc. For example, waves capable of penetrating deep into the water (wavelength - tens of kilometers, depth of penetration - of the order of tens of meters) are used to communicate with the submarine fleet, and the range of millimeter waves penetrating the Earth’s ionosphere is selected for space communications.
The mentioned subbands were first “reserved” for certain tasks by engineers, and then their allocated status was confirmed by international agreements that take into account the possibility of propagation of certain signals beyond geographical boundaries (cross-border coordination of frequency assignments is a topic for a separate long conversation). In the course of globalization, another goal of coordinated allocation of frequencies was defined - the import and export of communications equipment for its segment.
Fig. 9. Radio range
An ordinary user does not encounter a part of the radio band even once in his life, but there are certain frequencies that he uses almost daily, for example:
- the radio band assigned to FM stations (FM is a reference to the frequency modulation adopted in the band) - 87.5 - 108.0 MHz;
- “Civilian” or CIB (Citizen`s Band) range of 27 MHz (26.965–27.405 MHz) - known to hams; the range was actively used by motorists until the widespread distribution of mobile phones;
- LPD - the range for low-power user radio communications, in particular, alarm panels, baby monitors and other applications (there are as many as 3 bands: 403-410 MHz, 417-422 MHz, and 433-447 MHz);
- terrestrial television (49.75 - 56.25 MHz for 1 frequency channel, etc.);
- GSM mobile communications, in particular, 890 - 915/935 - 960 MHz for GSM-900; 1710 - 1785/1805 - 1880 MHz for GSM-1800 (GSM-450, GSM-850 and GSM-1900 are also used in other countries);
- 3G (UMTS: 1885 MHz - 2025 MHz for uplink and 2110 MHz - 2200 MHz for downlink);
- satellite television (Ku-band - 12-18 GHz).
When allocating a range for specific needs, not only the frequency, but also other signal parameters are specified. It is necessary that the devices operating in this and the neighboring bands do not interfere with each other.
Legislative regulation
In Russia, the State Radio Frequency Commission (SCRF) deals with frequency regulation (in the part of the spectrum not transferred to the military) - the process is regulated by the federal law “On Communications”.
To allocate the frequency, the operator makes an application and waits for the next meeting of the SCRF. SCR decides on the allocation of the range, but if it is positive, it does not promise to start the service. With this solution, as well as the details of the planned construction (base station locations, transmitter powers, etc.), the operator goes to the FSUE GRTC, where the compatibility of the communication standard to be used on this frequency is verified with the existing and planned equipment adjacent ranges. At this stage, the operator may be refused, for example, from the military. The procedure, by the way, is paid, regardless of the result.
Only after that the Federal Service for Supervision in the Sphere of Communications, Information Technologies and Mass Communications issues a permit. If several operators apply for the frequency, the resource is distributed on a competitive basis, and more recently - on an auction basis.
There is a procedure such as clearing frequencies - when a specific frequency range is released by the request of the operator by the military or other interested organizations. But this process is not regulated in any way - everything rests on the mutual agreement of the companies.
The frequency range can be allocated for a limited period (10 years) throughout the country or in a separate region (therefore, the federal operator may have a different set of licenses in different parts of the country). Upon the expiration of the period specified in the permit, the documents are reissued, unless, of course, there are no reasons for refusal, for example, the range is planned for another technology.
Receiving frequency, the operator undertakes certain obligations: to begin to provide services for which the frequency is allocated, within a predetermined period. Speech in this case is not only about mobile communications, but about wireless services in general - the broadcast of television, the Internet. If this condition is not met, the operator may lose the range.
The policy of paying for the use of frequencies has changed several times during the life of the mobile communication. At first, the operators paid for each communication object (base station), then for using frequencies in a separate region (the frequency allocation conditions could contain a clause to pay monetary compensation to the previous owner of the band, as was the case when LTE frequencies were allocated in the 2012 competition). And since permits for different parts of the spectrum in different regions were not formalized at the same time, the conditions were different for individual market participants, which resulted in squabbling and fighting companies for a valuable resource. In recent years, a number of measures have been taken to equalize the rights of companies to frequencies. In particular, auctions started in 2015 (this does not mean that now all frequencies are allocated within auctions, but until 2015 there was no such practice), and in 2016 a generalized decision was made on the allocation of frequencies, equalizing the conditions for using frequencies (coverage permissible technologies for certain parts of the spectrum, etc.).
The current “picture” of the frequency distribution in Moscow (as of November 2016) is presented in the figure below.
Fig. 10. Frequency distribution in Moscow
The leaders in the number of frequencies for digital mobile communications in Russia at the moment are MTS and Megaphone.
Mobile Bands
As can be seen from the diagram, quite a few segments of the frequency spectrum somewhere between 300 and 3000 MHz are allocated for civil mobile communication, which are divided between the operators operating in a given territory.
Different communication standards operate at different frequencies - this situation has evolved historically, as new generations are developed and implemented by operators, frequencies are allocated during auctions or tenders, and the spectrum is released from obsolete technologies.
About generations of mobile communications
Standards for modern mobile communications are described in the 3GPP (The 3rd Generation Partnership Project) specification - a partnership of leading organizations in the field of standardization of telecommunication technologies. The name of the partnership refers to the “third generation” of communication, but GSM is usually considered as 2 and 2.5 generations (2G and 2.5G, respectively). After completing the GSM specification, the organization took up the development of 3G (UMTS), and then pre-4G (LTE) and 4G (LTE-Advanced).
Fig. 11. The development of mobile communications
The universally developed 3GPP standards do not replace each other, but coexist together, within the framework of networks of some operators - new technologies are not simultaneously crowding out old ones.
If we look at the situation in theory, then all the indicated frequency segments can be used for 4G communication: the networks of the new generation were designed to maximize the existing infrastructure. With the expectation of this, 3GPP has classified the possible bands (bands), assigning each a serial number and giving recommendations on the details of the organization of the transmission (in particular, by dividing the channel between subscribers). A general list of channels can be found here .
In practice, some parts of the spectrum are fixed by the SCR to certain technologies, so the operator cannot start providing services there (for example, in the 2100 MHz band, 3G services should be provided, although operators would be happy to allocate it to LTE). For others, the principle of technological neutrality applies, according to which the operator, who owns the frequency, can use it not only for organizing communications using the GSM standard, but also for next-generation technologies (3G, 4G). As a result, at the time of this writing, for the 4G, only the bands 3 (1,800 MHz), 7 (2,600 MHz), 20 (800 MHz) and 38 (2,600 MHz) are used in the 3GPP classification.
Considering the difference in the nature of the propagation of the waves of each of the ranges in the room and in the open space, as well as the difference in the operators' policies regarding the support of these ranges, users have to turn into frequency control specialists when choosing equipment.
The best option would be a device with support for all the ranges we use. But the “minimally recommended” option is support for 3 bands and one more: 7 or 38 (depending on the operator).
If you do not take into account the ranges, you can remain without 4G at all, as it happens with the owners of some American iPhone SE (namely, A1662 models): in the list of LTE bands supported by the device, only the 20th develops somehow in Russia, and that’s not in all regions (in the models for the international market, there is also a range of 7, common with us, and 38 for TD-LTE).
Frequency Resource Usage Optimization
Capacity - one of the main parameters of the operator's network. It characterizes the technical ability to provide certain services: the higher the capacity - the greater the number of subscribers that can be served simultaneously, all other things being equal.
The total capacity inevitably depends on the width of the spectral band (as well as its location in the radio band). So, operators are demanding technologies of more and more efficient use of the available spectral band, implemented in each subsequent generation of mobile communications.
In 2G, a combination of FDMA and TDMA was used to increase capacity (against the background of analog standards and digital communications of the first generation). First, the subscriber devices were divided by frequency channels according to the FDMA (Frequency Division Multiple Access) principle.
Fig. 13. TDMA and FDMA
Third-generation networks use a different frequency channel separation principle - code or CDMA (Code Division Multiple Access), which allows increasing the network capacity at the same frequency range used, and at the same time ensuring a higher level of security.
LTE networks use either time or frequency division channels (TDD and FDD, respectively), but they are implemented differently than in GSM (2G). TDD (TD-LTE) uses the entire spectral bandwidth (1.4 to 20 MHz) to transmit data in two directions in turn; however, the time intervals for data transmission in each direction may not be equal. In FDD (FD-LTE), the range is divided into 2 bands in the general case of non-equal bands: for each of the data transfer directions. The specification recommends using either FDD or TDD for each of the bands prescribed for LTE ( http://en.wikipedia.org/wiki/LTE_frequency_bands#Frequency_bands_and_channel_bandwidths ), since TDD performed better at high frequencies, and FDD, respectively, at low frequencies . It is worth noting that the feature of the LTE standard makes it relatively inexpensive to integrate support for both methods in one device, therefore, equipment supporting both FDD and TDD is not uncommon.
Additionally, the bandwidth of the available spectrum in LTE is increased due to the technology of multiple antenna MIMO (Multiple input-multiple output).
Through the eyes of the final subscriber
The last point that I would like to talk about in this article is how the services look through the eyes of the end users.
The data transfer rate for the subscriber inevitably depends on the width of the spectral band allotted for his information flow. While in the 2G and 3G generations, the speed was limited by the communication standard itself, thanks to the 4G innovations, the speed is largely determined by the capabilities of the device.
In 4G (more precisely, in LTE-Advanced, recognized by the International Telecommunication Union as the true 4G standard), a mechanism for increasing subscriber speed has emerged - frequency aggregation, including from different frequency bands. Depending on the characteristics, the device can operate up to 4 bands of 20 MHz each (in two capitals at the moment, it is possible to use a maximum of 3 bands at MegaFon). For 4-carrier aggregation, the device must be categorized as 16 (CAT16). 4x4 MIMO together with aggregation allows you to download data on such devices at speeds up to 980 Mbps. 3 carriers aggregate categories 9 and 12 devices (CAT9 with speeds up to 450 Mbit / s and CAT12 with 600 Mbit / s, respectively), and the simplest CAT4 devices do not aggregate at all, reaching a speed of no more than 150 Mbit / s. Read more about the models that support this or that speed directly here .
Does the theory of aggregation work in practice in real radio reception? As part of the tests, MegaFon on Huawei equipment demonstrated a speed of 1 Gbit / s. For this, aggregation of three carriers was used.
Source: https://habr.com/ru/post/331082/
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