On the way to 5G



    The wireless connection threshold of 1 gigabit per second was overcome on the equipment of a commercial network, and by none other than the domestic operator of the "Big Three". This is a long-awaited event for the industry, since those distant times when ITU published requirements for data transfer speeds for 4G. As time went on, attractive slogans appeared on the advertising posters of operators mentioning fourth-generation networks, experts at international forums claimed that LTE = 4G and that WiMAX was "not the same", and meanwhile no ordinary subscriber saw Gigabit in their smartphone. And this time, such a grandiose event could not be missed, did you really manage to disperse not only the terminal, but also the subscriber equipment to gigabit speeds, or is it another advertising duck? We have to deal with this issue below.

    Generational Development of Wireless Access Networks



    New generations of wireless data technologies make an evolutionary leap once every 10 years. This trend has been observed since the beginning of the emergence of analog telecommunication networks represented by NMT (Nordic Mobile Telephone) in the 80s, when the emerging first-generation 1G networks used analog modulation of the radio signal and were intended exclusively for transmitting voice traffic. Below is a brief description of 1G subscriber terminals:

    1G technology

    • Uses analog signals
    • 2.4 kbps speed
    • Frequency 150 MHz and higher

    disadvantages

    • Weak user terminal battery
    • Low voice quality
    • Big sizes
    • No data protection
    • Frequent connection breaks

    In the early 90s, a leap in development took place, and analog wireless systems were replaced by digital ones in the face of the GSM standard, which exists to this day. Thanks to the use of digital methods for processing signals and data, it has become possible to transmit digital information in the form of SMS messages and encrypted voice traffic. New revolutionary solutions were called second generation 2G networks. By the way, the term 1G appeared simultaneously with 2G, and from that moment a race began in which managers tried to overtake the development of standards, calling new technologies and services (for example, GPRS) that appeared on the market like 2.5G, 2.75G, etc.

    2G technology

    • Allows you to send SMS / MMS messages
    • 64 kbps speed
    • Better Voice Quality over 1G

    disadvantages

    • Weak digital signal
    • Poor performance, it is impossible to process complex data (for example, video)

    2.5G technology

    • Ability to transfer packet data using the GPRS add-in for GSM
    • Receive and send email
    • Ability to work in a web browser
    • Speed ​​64-144 kbps

    At the beginning of the 2000s, the International Telecommunication Union (ITU) gave the green light to the new IMT-2000 standard, which described 3G technologies of the third generation. The main requirement of the standard was to provide access to Internet services at a data transfer rate of 2 Mbit for a fixed subscriber. Due to the large number of advertisements of various telecom operators, sorting out what real 3G is may not be so simple. Indeed, in the early 00s a large number of IMT standard families appeared, among which the most widespread were: UMTS with broadband multiple access and W-CDMA code division; and CDMA2000 with IMT-MC. Most often, UMTS with the HSPA add-in, which enables high-speed transmission of packet traffic, is adopted as the standard for 3G networks.

    3G technology

    • 144 Kbps - 2 Mbps
    • Free work on the Internet: sending mail, viewing video traffic, surfing sites, etc.
    • High security of personal data when working on the network

    In the recent 2010, ITU published requirements for fourth-generation networks. 4G was supposed to provide a packet data transfer rate over IP for a mobile subscriber of 100 Mbit / s, and for a fixed one - 1 Gbit per second. It would seem that such strict requirements of the standard are unattainable in the near future, but telecom operators and developers of telecommunication equipment are doing everything possible to be "in trend" and overtake competitors. Unfortunately, where such a race begins, users suffer first. The ITU has such stringent requirements for next-generation networks that the implementation of commercial networks that meet these requirements is often an unrealizable company.

    4G technology

    • Speed ​​100 Mbps - 1 Gbps
    • High speed information processing
    • Low cost traffic
    • Large battery
    • Expensive WAN Deployment Equipment
    • A smartphone is a full-fledged Internet user working in a single network with other computers

    For several years now, 4G networks represented by LTE / LTE-Advanced are “at the hearing” of subscribers and telecom operators, but the average user will never see speeds of 1 Gigabit, because for this he must sit right below the base station and be the only subscriber in the sector her service. Meanwhile, work on the standard of fifth-generation 5G networks is in full swing. So far, only the developed roadmap is in the public domain , but even from it you can get a lot of information to understand the essence of things.

    All work on the new generation of networks is carried out within the framework of IMT-2020 - a document that is a continuation of IMT-2000 and IMT-Advanced. Thus, the implementation of commercial 5G networks is planned for 2020, and we have already overcome the equator. The maximum data transfer speed was also announced, and it is 20 Gbit / s for the stationary subscriber in the fifth generation networks. The basis for building networks with such bandwidth will be the sensational IoT (Internet of Things) with the ability to connect a million IoT devices on an area of ​​one square kilometer. In February 2018, a demonstration of the possibility of the first 5G networks has already been planned at the Olympic Games in Korea.     

    The threshold of 1 Gigabit per second is overcome


    In Russian telecom, the development of fifth-generation networks does not stand still, and the threshold of mobile data transfer at a speed of 1 Gbit / s for a commercial network was overcome in June 2016. This is just a small step for the operator on the way to 20-gigabit speeds, but this is not the case when such speeds were demonstrated only in laboratory conditions. At the St. Petersburg International Economic Forum MegaFon, using the example of terminal equipment, Huawei demonstrated a peak data download speed of 1.24 Gbit / s. Here's how it looked at the presentation, on the left on the table you can see the Huawei terminal device, and on the right - the Qualcomm LTE modem:



    To demonstrate the experiment, a retrofitted base station and terminal equipment from Huawei were used, in the photo above they are removed for decorative panels in white and green. The equipment used for sale on the territory of the Russian Federation has not yet appeared, so it is not possible to indicate the exact model. It is only known that this is a modification of the Huawei DBS3900 BS, on board of which there were more powerful processor boards that allowed to process gigabit volumes of traffic. The base station was equipped with remote active antenna units AAU3961, using standard cross-polarization +45 0 , -45 0. Also required protocol configuration, allowing you to organize a gigabit connection. Today, the Chinese company Huawei is the largest investor in the fifth generation network and makes a significant contribution to the study of technologies to achieve ambitious speeds.  

    It was not possible to peek inside the boxes, but in general a visual representation of the base station used can be obtained from the figure below, respectively its RRU (left) and BBU (right) modules:



    The assembly should look like this:



    To test the bandwidth of the base station, I had to use a PC with server network card that supports speeds up to 10 Gb / s. The connection was made through an optical cable.
    As a subscriber device, a modified Qualcomm Snapdragon X16 LTE modem, supporting gigabit wireless speeds, was used:



    The processor of this modem is capable of providing digital signal processing with modulation of 256-QAM, giving a 30% increase in data transfer speed compared to 64-QAM. And of course, when it comes to such speeds, today you can not do without MIMO and Carrier Aggregation. This modem implements MIMO 4x4 on two carriers, in addition, the modem can aggregate four frequency channels with a width of 20 MHz. By the way, today in Russia there is not a single operator that could aggregate 4 carrier frequencies of 20 MHz. The closest to this figure is MegaFon, which has three carriers at its disposal. The listed features of the modem related to Downlink traffic. For Uplink, things are no less colorful: aggregation of up to two carriers at 20 MHz, 64-QAM modulation, and support for two streams up to 75 Mbit / s. Thus,

    In order to ensure the best performance of MIMO technology and to ensure 4x4 mode, the elegant Kvalkomovsky modem had to be upgraded with four external omni antennas, of course, this solution is not provided for in the basic configuration of the device.



    But the Qualcomm subscriber terminal did not go to the record, although it showed speeds close to gigabit, but the Huawei terminal device: The



    terminal device was specially configured for a specific task and used a total of 12 antennas: three for each band. Those larger ones obviously work in the 1800 MHz band. During testing of the terminal from Huawei, a maximum speed of 1.245 Gbit / s and an average speed of 1.137 Gbit / s were demonstrated:


    To demonstrate the claimed speeds overcoming the 1 Gbit / s threshold, we used the aggregation of three carriers: 20 MHz from the 1800 MHz band (Band 3), and 20 + 20 MHz in the 2600 MHz band (Band 7). Modulation was used as much as possible for this equipment - 256-QAM and MIMO 4x4 technology. By the way, MegaFon has repeatedly used its frequency advantages, so in early 2015, the company demonstrated a speed of 450 Mbps in LTE networks, also using the aggregation of three frequency channels.



    Thus, the operator’s integrators have correctly configured and debugged existing and commercially available top-end solutions for wireless technologies. The tandem of the operator with the largest manufacturers Qualcomm and Huawei allowed to realize this jump. And this time, the history of the development of generations of wireless access makes a new round, and the existing technical breakthrough is positioned as 4.5G. Once again, marketers take control of the standard in their hands, following the call of the global trend. The official name of the technical solution is LTE-Advanced Pro.    

    Answers to questions of integrators


    In what area was the speed tested and what quality will the Internet be in a metropolis?

    Testing was actually carried out under ideal conditions. One subscriber was in good radio conditions in the sector, interference from neighboring cells was excluded. To say what the data transfer rate will be in real conditions is difficult, too many different factors will affect it.

    How many subscribers were connected to the network and at what distance from the base station were they while testing the network bandwidth?

    The distance between the test terminal and the antenna did not exceed 5 m.

    At what distance from the base station will the user be able to get 1 Gbit in a metropolis?

    An important condition for achieving data transfer rates of the order of 1 Gbit / s is the use of 256-QAM modulation, which gives an approximately 30% increase in data transfer speed compared to 64-QAM modulation. Peak speeds of the order of 1 Gb / s will be available to subscribers only in individual hot spots.

    Are you planning to transfer packet TV traffic over 5G networks? Perhaps special tariff plans are already being developed?

    Technically it’s possible, the issue of agreements on tariffs and content filling.

    Is it possible, as before, to smoothly integrate 5G networks by replacing some of the units / modules installed on the base station, or is a complete replacement of equipment required?

    Possible scenarios for the deployment of fifth-generation networks will be understandable after the completion of the pilot projects of the standard in 2018. Given the use of additional frequency ranges, it is likely that modernization will be required.

    Which base station modules should be replaced so that it “turns” from a 3G / 4G station into a fifth-generation base station?

    It is currently impossible to comment on this issue. First of all, radio modules.

    It was previously stated that "the network test was carried out using Huawei terminal equipment and a Qualcomm subscriber terminal prototype." What dimensions did the “prototype” of the subscriber terminal have? Obviously, he had remote antenna modules?

    The Qualcomm subscriber terminal prototype was 17.5 x 8.5 x 2 cm. Yes, the prototype had four remote antennas.

    And yet, to achieve speeds of 1 Gbps, it is necessary to organize several transmission channels between the subscriber and the base station using MIMO 4x4 technology. What power consumption does a subscriber terminal with 4 active antennas have?

    The prototype provided by Qualcomm had an external power supply. The current energy values ​​will be clear after commercially available terminals appear. It should be noted that four antennas are used only for reception. For data transmission, the terminal uses only one antenna.

    At what distance from each other should there be transceiver antennas for the correct implementation of the operating mode in MIMO?

    If we are talking about the antennas of the base station, then they can be located in one housing of a standard antenna. For example, AAU3961 has a size of 1550 x 370 x 230 mm.

    If we are talking about subscriber terminal antennas, then everything will depend on the engineering solution used by the terminal manufacturer. The prototype Qualcomm remote antennas were located at a distance of about 20 cm from each other.

    How many subscribers per sector supports Huawei tested equipment? What real speeds can be obtained with a full load of equipment?

    Maximum - 10,800 subscribers per BS card, two such cards were involved in the test layout. Actual data transfer speeds when the equipment is fully loaded depend on a large number of factors: the number of active subscribers and their distribution in a cell, interference conditions, etc.

    How many OFDMA symbols are transmitted in the frame when implementing peak data rates?

    Demonstrated the evolution of LTE-A. Normal CP was used. Accordingly, in each subframe there were 7 OFDM symbols.

    If you use a fifth-generation base station, but the subscriber’s terminal will not undergo changes (it has one antenna and old software), then today what data transmission speed can be provided to a mobile subscriber?

    There will be no backward compatibility of the 5G standard with previous generations. Accordingly, a subscriber with an old terminal will not be able to receive any services in the fifth generation networks.

    Conclusion


    Obviously, to provide real data transfer speeds over a 1 Gbit / s radio channel for each subscriber, it will take some more time, because the implementation of fifth-generation network technologies requires the replacement and modernization of not only base stations, but also mobile devices of subscribers. For them, as before, the stumbling block remains energy consumption and the subtleties of implementing MIMO technology (after all, the size of mobile devices is limited), moreover, the processors of subscriber devices have limited computing power, because performance is required to decrypt 256-QAM modulation.

    However, the world's leading manufacturers and developers of telecommunications equipment are working hard to create devices that bring us closer to 5G networks, for example, Qualcomm has already mass-produced the Snapdragon 820 chipset, which allows downloading data to a smartphone at speeds up to 600 Mbps.    

    The specifics of data transmission over a radio channel has a huge number of subtleties and nuances, and even if in a couple of years peak data transfer rates of the order of 1 Gbit / s are not available to ordinary mobile subscribers, then an increase in the speed of wireless Internet by 2-3 times is definitely guaranteed. Moreover, the speed threshold has been overcome, and the Internet of things has become even closer. Soon, the work of all engineering systems and gadgets from a single wireless computer network of the whole building will cease to be fiction. From managing a “smart home” to managing a “smart city”, it remains only a stone's throw. Just imagine: a city in which there are no traffic jams; a city where information about the health of each resident is instantly transmitted to medical centers, emergency situations will be localized and prevented before they even have time to gain momentum. Maybe,   

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