What is the last mile problem. The problem of the last mile in the energy sector: state and prospects for a solution

The desire to receive data from the Internet
using low speed technologies
like trying to suck jelly through a straw.

The traditional public switched telephone network (PSTN) allows voice and data transmission within a narrow frequency band (300 - 3400) Hz. The rapid growth of the Internet and the most widespread access to it using standard analog modems causes overloading of the PSTN, since the latter is not designed for the Internet load, which is characterized by a long average session time and greater unevenness compared to the telephone load. The second problem is that for comfortable user access to the services of the existing network (and primarily the Internet), the transmission rates that analog modems can provide are no longer sufficient. This applies not only to private (residential) users, but also to the growing category of business users who work in their home offices and who need to connect to corporate networks at significantly higher data rates than traditional analog modems can provide. ...

The difficulty in achieving the required speed of connection to the Internet lies in the fundamental principles of building telephone networks, which by their nature are not designed for high-speed data transmission. When Alexander Bell invented the telephone, his fantasy went no further than allowing people in different places to talk to each other. In addition to the fact that traditional telephone (i.e. voice) communication is carried out in a very narrow frequency band, it also allows for significantly greater signal attenuation than is possible with data transmission. In this case, the biggest problem lies (in the literal sense of the word) between the telephone exchange and the subscriber's home. During the development of telephone communication, a long way has been passed from manual switches to modern digital telephone exchanges, providing subscribers with a large number of various services, but the same twisted pair is laid between the station and the subscriber as at the dawn of telephony. And there are almost a billion such twisted pairs around the world.

As the cost of user equipment to access the Internet gradually decreases, bandwidth and cost of the connection come to the fore. Everyone who uses the Internet has to wait (wait and wait again) until the desired site is found and the required page is loaded. The situation gets worse if you need to upload large files (such as photos or videos). Moreover, the larger the number of users simultaneously using the Internet, the lower the speed of each of them individually becomes, because a sharp increase in traffic leads to a significant increase in the load on telephone networks. With the full potential of the Internet in the areas of distance learning, commerce and entertainment, it is imperative to overcome the hurdle of insufficient connection speed (and too high cost). The user wants one thing - high-speed and always-on access. However, despite the fact that the network of high-speed data transmission to one degree or another covers the entire country, access to it by end users (that very “last mile”) can be fraught with technical and economic difficulties. Trunk data transmission lines allow transferring gigabits of information, but a very small number of end users are able to transfer data at least at a speed of several hundred kilobits. It is very expensive to pull a fiber-optic line to each user. Coaxial cables (cable TV) allow high-speed transmission, but mostly in one direction. Telephone lines in the form in which they are currently used for telephone communications have a low data rate. Access at the required high speed can only be provided by broadband technologies, which are the future of the telecommunications industry.

Telecommunications of the future is based on providing each user with the possibility of high-speed data transmission. But how do you transfer data at high speeds over the critical last mile? There are several technological directions to overcome this obstacle. (Although the mere presence of several alternative technologies designed to solve the same problem does not mean that the user has a wide range of equivalent options from which to choose the best one. In most cases, the user will only have one single option.)

The following technologies are the main candidates for solving the “last mile” problem. These are xDSL digital subscriber line, cable modems, as well as wireless and satellite technologies.

None of these technologies can be considered ideal solutions to the problem of the "last mile". Many people generally say that there are only two technologies that can solve the problem of the "last mile" - cable modems and xDSL. Both of these technologies are based on the use of existing cable networks, which, quite importantly, cover almost all potential users. Another technology, landline wireless (sometimes called wireless subscriber line), lags behind the two technologies mentioned above, as it requires the creation of a certain infrastructure to start a full service.

Other data transmission technologies either simply do not solve the problem of the "last mile" (not providing sufficient transfer speed), or are too expensive for most potential users. The first includes connections using conventional analog modems, which have already reached the maximum data transfer rate over traditional twisted-pair telephone wires. The second includes fiber optic cables. There are people who advocate the complete replacement of the entire telephone cable network with new fiber-optic cables that are capable of supporting data transmission at very high speeds. However, not only at the present time, but also in the foreseeable future, such a widespread replacement will not be carried out due to its high cost. Even for the United States, which is quite prosperous in terms of telecommunications, according to the most optimistic forecasts, the widespread adoption of fiber technologies will take more than a dozen years. At the same time, there are certain configurations of the access network (for example, when a sufficiently large group of users is remote from the local station at a considerable distance), in which the use of an optical cable is economically profitable even now. It should be emphasized that in the latter case we are talking about the group use of an optical cable, i.e., about its sealing.

It would be a mistake to try to view the process of solving the “last mile” problem as a matter of choosing any one technology. In practice, these technologies are initially in unequal conditions. Not all providers have the same position in the structure of the networks they intend to use. Therefore, those operators who own cable telephone networks are unlikely to use cable modems, and operators who specialize in building wireless infrastructure are unlikely to invest in xDSL. On the other hand, thanks to the ability to use various technologies on the "last mile", operators with large and extensive networks are able to offer their customers various options for organizing high-speed access. For example, xDSL technologies and a wireless access system, or xDSL and cable modems.

Those regions where broadband coaxial cable networks have been widely developed, and later also HFC (hybrid fiber / coaxial) hybrid optical-coaxial networks designed to connect subscribers to a cable TV network, there is a powerful platform for providing high-speed access to home sector users.

The transmission of terrestrial television broadcasting over coaxial cable networks was proposed by the American E. Parson in 1948. The first such system was created in Seattle and was designed to distribute 5 television (TV) channels. The introduction of cable television systems made it possible to abandon many of the shortcomings inherent in over-the-air TV, and, first of all, to provide high-quality TV zones of unsure reception of a television signal over the air. The first CATV systems were collective reception systems that worked first in the meter wavelength range (47-240 MHz), and then in the decimeter wavelength (550-862 MHz in Europe and 600-750 MHz in the USA). These systems were relatively simple and contained a collective antenna, a headend, and a coaxial transmission path with the required number of taps and amplifiers (trunk and brownie). Strictly speaking, these were not yet KTV networks, but rather systems of collective reception of television programs. Naturally, both in the modulation method (AM) and in the position on the frequency scale, these systems were identical to the corresponding parameters of the terrestrial television signal, since they were designed for reception by standard television receivers. With the enlargement of the KTV systems, their reliability dropped, in connection with which the issue of operational maintenance of these systems arose very acutely. Therefore, the KTV systems began to be supplemented with remote control systems, which made it possible to control the state of these systems and, first of all, the parameters of the main amplifiers. To transmit information about the state of the system to the head-end, a part of the spectrum below the operating frequency range (as a rule, 5-30 MHz or 5-50 MHz) was used. An alternative possibility of transferring service information to the headend is to use a standard telephone modem of the public telephone network (PSTN) for this purpose. So, in the KTV systems, the fundamental possibility of providing the user with interactive network services has appeared.

The revolution in the field of telecommunication networks, associated with the emergence and widespread adoption of optical cables, also affected cable television networks. At this stage in the improvement of CATV networks, the purely coaxial transmission medium was replaced by the hybrid optical-coaxial HFC medium. In the architecture of CATV using HFC, television broadcasting and switched video signals are transported over optical fiber from the head-end of the CATV to the optical network unit (ONU). The latter connects the optical backbone network to the distribution coaxial network. In the ONU, the signals of the corresponding channels carrying video, voice and data signals are transferred to their assigned frequency range. Note that the coaxial segment of the HFC network requires the use of duplex amplifiers that provide two-way signal transmission. The optical network unit (ONU) board also performs some additional functions, which include the separation of upstream (from subscribers to the network) and downstream (from network to subscribers) signals. The problem of using the HFC architecture to provide voice telephone services is the insufficient quality of voice services, mainly due to external interference (ingress noise). When transmitting data, the main problem is also external interference created in the "upstream" channel by household appliances such as microwave ovens, refrigerators, etc. So, according to available statistics, less than 5% of KTV networks can use this range for its intended purpose, since this frequency range severely affected by interference from household electrical appliances (refrigerators, microwave ovens, etc.). Therefore, it is advisable to use a telephone subscriber line as an upstream channel of the KTV network.

In the mid-90s, KTV operators conducted a study of the possibility of using the infrastructure of the KTV network for broadband access to the services of the network of users of the home (residental) sector. The result was devices that were not quite aptly called cable modems. Cable modems are devices that provide high-speed access to data networks over the HFC hybrid fiber-coaxial network.

Unlike traditional dial-up PSTN modems, cable modems are part of a "point-to-multipoint" system in which multiple cable modems from different users are connected via a hybrid optical-coaxial medium to the controller at the head-end of the CATV operator. Like xDSL modems, cable modems operate in an "always on" mode, which means they are permanently connected to the headend.

The use of cable modem technology allows us to very gracefully solve the problems of analog subscriber telephone lines, trunks and resources of public switched telephone network (PSTN) switching stations. Cable modems transmit Internet traffic directly to the Internet router located at the head end of the CATV system. Another advantage of cable modem technology is that it (though not always) can use the existing cable infrastructure of CATV systems. In addition, the element base of cable modems is available and relatively inexpensive, and also (and this is perhaps the most important thing) allows for the joint operation of cable modems from different manufacturers. Most cable modems are external devices that are connected to a personal computer via a standard 10Base-T Ethernet card or USB port; they can also be designed as a card that plugs into a free ISA bus slot using plug and play technology. The Cable Modem Termination System (CMTS) based on the access concentrator is used to access the data network.

The downlink bandwidth (from the network to the subscribers) is shared by all multiple user cable modems. Each standard TV channel occupying 6 MHz of the RF spectrum provides a 27 Mbps downstream data stream using 64 QAM; when using 256 QAM modulation, the data transfer rate can be increased to 36 Mbps. Data transmission channels in the "upstream" direction theoretically allow data transmission at a rate of 500 Kbps to 10 Mbps using 16 QAM or QPSK technologies (depending on the bandwidth allocated for user service). Frequency bands allocated for the transmission of upstream and downstream data streams are shared among all active users connected to this segment of the cable network. An individual user can count on data transfer rates ranging from 500 Kbps to 1.5 Mbps - depending on the network architecture and load (this figure is significant, especially when compared with analog modems).

CATV systems using cable modems are based on a shared access platform. Due to the fact that users of these systems share the bandwidth available to them all by the time of data transmission, as the number of simultaneously active users increases, the data transfer rate for each of them decreases. It would seem that a simple calculation shows that with the simultaneous use of a 27 Mbit / s data transmission channel by two hundred users, each of them will get at best 135 Kbit / s. So why is this system better than an ISDN connection, which provides 128 kbps? Not so simple. Unlike traditional telephony, in which the subscriber receives a dedicated connection for the duration of the call, cable modems do not occupy a fixed frequency band during the entire data transfer session. As already mentioned, the bandwidth is shared among all active users who use network resources only during the actual reception or transmission of data. Therefore, instead of rigidly fixing 135 Kbps for each of 200 "active" users, the entire frequency band in each specific fraction of a second is divided only between those users who transmit or receive data - the speed can increase tens of times (after all, those who downloaded , for example, an Internet page and trying to figure out what's what, at the moment they are not "active users"). In case of constant and high activity of any group of users, the cable operator can always expand the transmission frequency band by allocating another 6 MHz channel for data transmission. Another option for increasing the average data rate for each user is to move the fiber optic cables closer to the groups of potential users. This reduces the number of users served by each network segment, which naturally leads to an increase in the bandwidth available to each of them.

If we turn to the facts, in the world cable modems still have more private users than, for example, ADSL technology. By mid-1999, around 1.3 million cable modems were in use around the world for high-speed data transmission, 1 million of which were in the United States.

By the end of 2002, In - Stat / MDR in the US counted about 10.2 million cable modem users, while DSL lines - about 7.6 million (it should be noted that US subscribers traditionally more actively use cable modems compared to subscribers in other countries).

But, in addition to obvious advantages, the technology under consideration also has significant disadvantages. As mentioned above, one of the disadvantages of cable modems (as opposed to, say, xDSL technologies) is that such data transmission lines are shared lines. The bandwidth available to each individual user connected to a particular site can decrease as the number of users who are connected to the same site increases. Another disadvantage is that the system is "open" (ie, each individual user is not provided with their own fixed connection). This circumstance makes cable modems less attractive for business use. The cabling system can be thought of as one big LAN, so (in theory) there is some ability to connect each to each and access the other user's data. Obviously, no one wants to share the same shared data transmission system with their competitor. In addition, cable modems provide high-speed cable TV access primarily to private users, because office buildings and businesses in most cases are not connected to the cable TV network.

Just as the proliferation of cellular and radiotelephones freed subscribers from the cable connecting the handset to a telephone connected to the telephone network, Wireless Local Loop (WLL) technology opened up access to the public telephone network for all those who had already lost hope of connecting to the telephone network. global telephone network.

This technology can be most accurately defined as the use of radio access to provide broadband network services to individual users. Moreover, this technology can be used not only in those regions where the telephone cable network is insufficiently developed, but also where the level of development of cable networks is quite high. In this case, operators using broadband wireless access technologies are already directly competing with local operators.

Broadband wireless lines can be used for high-quality data transmission, video signals and telephone communications. Historically, the telephone line has been used for the uplink, but operators are now moving towards full duplex wireless. The data rate is determined by the width of the frequency spectrum available to the operator and the modulation scheme. For example, the efficiency of digital modulation schemes ranges from 0.7 bps / Hz when using BPSK modulation to 3.5 bps / Hz when using 16QAM.

As in the case of organizing over-the-air television broadcasting, wireless data transmission lines are organized according to the principle of line of sight. The signal is transmitted from an antenna, usually located on a hill or on a high building, to special receiving antennas installed on users' buildings. Obtaining a sufficiently clean spectrum of frequencies can be challenging; another problem is the requirement for line-of-sight for most established lines. The organization of the line is quite simple, because it does not require, for example, such a volume of construction (earth) work as when laying cable systems, but it cannot be guaranteed that the organized line (based on the requirement of line of sight) will work as long as necessary. For example, a house built on a line-of-sight path may simply "chop off" such a data line. As with TV broadcasting, any obstructions (for example, dense canopy, hills, tall buildings, and even heavy rainfall) can make reception somewhat difficult. Distortion due to multipath propagation (resulting from reflections from buildings and other objects) can also seriously complicate reception. Distance should also be considered, as wireless signals can only be received within a certain distance from the transmitter. The solution to this problem can be the installation of a network of repeaters throughout the service area (on the principle of cellular communication).

Wireless networking is similar to that of a cable network. The main difference is that a digital data signal (for example, containing information requested from the Internet) is modulated into a radio frequency channel, through which it is transmitted to an antenna installed on the user's building. From the antenna, the coaxial cable goes to a converter, which converts the signal from the microwave range to the frequency range of cable television. After that, the signal goes to the modem located at the user's premises. The modem demodulates the incoming data signal and routes it to a personal computer or LAN.

Wireless subscriber line technology has several advantages over alternative access technologies. Wireless lines can be deployed in those places where, due to the impossibility of carrying out work, density or "antiquity" of the building, a cable line simply cannot be laid. Secondly, for certain distances and locations of settlements, wireless access may simply be much more cost effective than alternative technologies. Here it is necessary to take into account both labor costs and the length of the subscriber line.

The cost of cable systems depends largely on the distance between buildings and on the degree of concentration of subscriber groups. The cost of wireless systems is free of this dependency. The cost of constructing cable systems is also highly dependent on labor costs, which tend to rise steadily. At the same time, the cost of wireless systems depends mainly on the cost of subscriber equipment, which tends to become cheaper as technology improves. The third positive factor of wireless technology is the significantly shorter system deployment time compared to cable infrastructure.

The fact that radio systems provide coverage for a specific area means much easier network planning compared to cable systems. Wireless systems make it possible to react much more quickly to changes in needs and the number of users, while the planning of cable systems is largely based on preliminary estimates (it is good if the estimates coincide with reality).

There are also more prosaic considerations. If the user refuses your services and directs his attention to another operator, then with the development of cable technologies, all investments in this cable line will be lost. At the same time, when using wireless technology, the subscriber equipment can be simply removed and installed in another place at a new subscriber. In addition, it is much easier to maintain the operation and safety of a properly organized wireless line than a cable. In many countries, for example, in Africa, copper cables buried in the ground are simply stolen (unfortunately, Russia can also be counted among these countries). Even fiber optic cables have a certain value as a secondary product.

In practice, the possibility of using satellites for Internet access and high-speed data transmission is divided into two large tasks - the organization of backbone data transmission lines (which is part of a large business) and the organization of high-speed access for individual end users. End users include not only individual users, but also large corporations, medium and small businesses, and various offices (including home offices).

In short, satellite systems have several attractive features in terms of providing high-speed data services and Internet access.

Satellite systems help bypass “congestion” in terrestrial data transmission systems. They can be configured as needed to reflect the asymmetric nature of the Internet, both in terms of individual transactions and geographically. For example, most of the content on the Internet is still located in the United States. Some of the distinguishing features of satellite systems make them an attractive access technology. First of all, it is economic efficiency for the provider. The satellite's coverage area is such that it can serve a very large number of subscribers. Moreover, the cost of organizing the service does not depend at all on the geographical position of the user within the satellite coverage area. The satellite channel can be received anywhere in the coverage area, regardless of terrain conditions.

Although satellite systems have many advantages that allow them to be considered as one of the technologies for organizing high-speed data transmission on the "last mile", there are also negative aspects.

Satellite access systems do not have the highest data transfer rate (about 400 Kbps towards the user) and at the same time do not work very quickly. Imagine that you want to download some material onto your computer screen. By clicking the mouse, you send a request signal, which passes through your telephone line, through the provider and along the usual path on the Internet, and after the answer, the signal is transmitted via satellite, passing a total of about 70 thousand kilometers. Even at the speed of light, such a means of accessing the Internet remains quite slow. This is especially noticeable when implementing two-way communication in real time.

Investments in satellite communication systems amount to many billions of dollars, and success and profit are not guaranteed at all. Also worth mentioning are traffic safety, too long planning cycles for a rapidly changing industry like telecommunications, and the lack of frequencies that can be easily used.

In addition, the disadvantages of satellite systems include the need to purchase and configure fairly expensive equipment. However, there are a number of extreme situations when it is impossible to organize access to the Internet in any other way, except through a satellite (for example, for a ship in the middle of the ocean).

Now let's take a look at some specific wireless broadband technologies. Let's start with a quick look at two well-known ones.

Among the many wireless access technologies, the Local Multipoint Distribution System (LMDS) is one of the few systems providing broadband multimedia services to the user. LMDS operates in the frequency range (28 ... 32) GHz allocated by the US Federal Communications Commission FCC for the operation of broadband subscriber access systems. This system is sometimes referred to as a cellular cable TV system. The use of the cellular principle avoids many of the problems associated with the line-of-sight condition, which is mandatory in the MMDS wireless broadband access system discussed below. Carriers of neighboring cells have the same frequency ratings, but different polarizations. LMDS is able to provide the user with the latest types of interactive multimedia services, including telephone and high-speed data transmission. This technology allows some providers (for example, long distance and international service providers), which do not have their own subscriber access infrastructure, to provide relatively inexpensive and very fast communication services to business users and individual users. In the LMDS access network architecture, the so-called "last mile" access network is wireless. In this case, the user's antenna must be within the line of sight LOS (Line of Sight) with a cellular node connected to a network that provides the user with all necessary communication services.

Business LMDS is highly likely to be used for LAN interoperability in urban environments. It is also likely that the use of LMDS for the transmission of television programs is too late. LMDS, like the MMDS technology discussed below, lacks the simple ability to increase throughput. This problem is not significant in simplex television broadcast systems, where any user can receive any channel. However, there is no easy way to increase licensed bandwidth for outbound traffic to LMDS systems. A similar problem exists with the cellular telephone network.

LMDS is especially well suited for urban environments with a high population density and, therefore, potential users, where a small transmitter size and small cell area are quite acceptable and where this makes the prices for the provided services attractive to the user. However, such small cell sizes may be unacceptable in suburban and rural areas where a large number of transmitters will be required to meet the line-of-sight condition.

Another fairly well-known system of broadband wireless access is the MMDS (Multichannel (Microwave) Multipoint Distribution System (Service)). This system is very similar to LMDS, but operates in the 2.4 GHz frequency range, and the operating range is MMDS frequencies are limited compared to LMDS. Currently, the MMDS frequency range is used by cable television (KTV) providers to deliver a broadcast analog television signal to users through the head-ends of the KTV network. As a result of the liberalization of telecommunications services, this frequency range is also open to the provision of other services, including telephone and many interactive services.

Unlike LMDS, MMDS is less sensitive to external influences such as rain and thunderstorms. Therefore, the cell site clearance requirements are less stringent than LMDS. Thus, MMDS covers an area within a radius of about 80 kilometers, while LMDS has a range of no more than 10 kilometers.

The frequency band 2.2-2.7 GHz in the MMDS system is used to transmit video signals of 33 television channels from transmitting antennas to receiving antennas of users. Subscribers within a zone with a radius of about 50 kilometers can receive these signals. With digital processing and compression of video signals, the number of channels can be increased to 100-150.

MMDS can be used to transmit both analog and digital video signals. Reception of an analogue TV signal requires a relatively simple antenna installed on the roof of the user's house and a Set top box, which contains a linear TV signal to video signal converter and a descrambler. In the case of the digital version of MMDS, a more complex and expensive converter is required. The currently produced MMDS equipment provides for the ability not only to transmit television signals, but also to provide voice and high-speed data transmission services.

As another example of wireless broadband access technologies, let's focus on the Direct Broadcast Satellite (DBS) system. This is a new generation of satellite television broadcasting equipment. With the use of digital methods for converting and transmitting television signals and a small-sized receiving antenna, this technology becomes very attractive to users. Decoding of the signal received in digital format takes place in the signal splitting / combining and transformation unit of the user equipment STB (Set Top Box), which has built-in intelligent functions that provide a variety of new services, such as interactive television and information on demand.

Direct satellite broadcasting technology BSS (Broadcast satellite servises) operates in the Ku - band, occupying the 12.2 - 12.7 GHz frequency spectrum. DBS users can receive 150-200 video channels using MPEG-2 compression. In addition to video transmission, some network service providers are planning broadband data transmission in the Ku - band. Modern DBS systems support data transmission from the Internet to a subscriber at a speed of up to 400 Kbps, and to transmit control signals from a subscriber to the network, they use a standard voice frequency (PM) channel.

We now turn to a brief review of the currently most popular wired broadband access technologies such as xDSL.

xDSL is a family of technologies for high-speed access to network services over the existing copper subscriber telephone line. In the xDSL abbreviation, "x" is used to denote a specific type of Digital Subscriber Line (DSL) technology. Any subscriber currently using telephone communication has the opportunity to use xDSL technologies to significantly increase the speed of his connection, primarily to the Internet. Thanks to the variety of DSL technologies, the user can choose the data transfer rate suitable for him - from 32 Kbps to more than 50 Mbps. In this case, the data transfer rate depends only on the parameters and length of this line.

For some reason, it is believed that the subscriber telephone line has a bandwidth of 4 kHz. This is totally wrong. The subscriber line has a limited bandwidth, because it is provided by its design, and not because the twisted pair is not capable of transmitting high-frequency signals. With the help of appropriate coding schemes, xDSL technologies can achieve a megabit data transfer rate.

The oldest and slowest technology in the xDSL family is IDSL (IDSN Digital Subscriber Line), and the fastest and youngest is VDSL (Ultra High Speed \u200b\u200bDigital Subscriber Line). In between, there are other technologies such as HDSL (High Speed \u200b\u200bDigital Subscriber Line) and ADSL (Asymmetric Digital Subscriber Line); the latter has the greatest potential in the mass market.

DSL technologies allow you to achieve high data transfer rates. For example, ADSL provides 1.5 to 8 Mbps downstream and 640 Kbps upstream 1.5 Mbps. When choosing an asymmetric scheme, VDSL provides a downstream data stream of 13 - 52 Mbit / s, and an upstream data stream of 1.5 - 2.3 Mbit / s (for symmetric VDSL, the data rate is 13 - 26 Mbit / s). DSL data rates are distance dependent; the data transfer rate decreases with increasing distance. For example, for ADSL with a line length of 3 km, a transmission rate of more than 8 Mbit / s can be achieved, and for a line length of 6 km, a data rate of 1.5 Mbit / s can be achieved. For VDSL, these numbers are approximately the same. A speed of 52 Mbit / s corresponds to a line length of about 300 meters, and a speed of 13 Mbit / s corresponds to a line length of about 1.5 km. At the same time, these technologies provide simultaneously telephone communication, high-speed Internet access, video on demand and one (for ADSL) or three (for VDSL) TV channels of DVD quality. Other DSL technologies can be used for voice and high-speed Internet access, but are not suitable for real-time high-quality video transmission.

DSL technology has certain advantages. Any subscriber connected to the public telephone network has a copper telephone line that can be used to deploy a data line. That is, there is no need to create a new infrastructure. The system requires only two ADSL devices (at the station and at the customer premises) and twisted pair wires (unfortunately, it should be borne in mind that the performance of the DSL line degrades as the distance from the station increases or the quality of the line deteriorates). The DSL line provides a reliable and permanent (unlike analog modems) connection. Compared to other access technologies, DSL requires significantly less investment in terms of achievable data rates.

XDSL technologies allow the most cost-effective way to meet the needs of users for high-speed data transmission. Different options for DSL technologies provide different data rates, but in any case, this rate is much higher than the speed of the fastest analog modem.

The variety of DSL technologies allows you to use a specific technology for a specific category of users. In particular, asymmetric ADSL technology is best suited for private users, who are more consumers of information, while symmetric technologies are more suitable for business representatives for whom the flows of transmitted and received information are close in volume. In addition, the ADSL technology retains an analog telephone and / or ISDN basic access channel (BRI ISDN). The first property allows you to maintain normal telephone communication in the event of damage to ADSL equipment, and the second allows you to protect the investment of the telecom operator. XDSL technologies can be considered as a serious competitor for cable modems. In theory, cable modems provide higher data rates than, for example, ADSL technology, but in reality most cable networks are not able to provide access through cable modems using the entire frequency band of a coaxial cable. In cases where cable systems provide an "upstream" data link, this link is shared among all users. The development of hybrid fiber-coaxial systems can alleviate this problem, but such systems are still quite expensive and will take a long time until they are sufficiently developed. Consequently, xDSL technologies remain the most viable solution to the “last mile” problem at the moment.

It should be noted that while in Russia the possibilities of obtaining high-speed access based on ADSL technology are limited. The territorial (one might say, geographical) position of the user plays a very important role, but this is far from the only obstacle. Even if a potential user is covered by a cable television network or has a telephone line, this does not mean at all that these lines can technically be used for high-speed data transmission. Much will also depend on who provides the service. Some cable and telephone companies are successful in developing and providing high-speed data services, while others prefer not to bother themselves. This neglect of some telecom operators to the development of high-speed data transmission is explained by the fact that approximately 90% of telecom operators' revenues are provided by telephone services.

Choice is a hallmark of today's digital telecommunications world. Moreover, all new technologies to some extent compete with each other, which allows us to expect an increase in the quality of services provided and a decrease in their cost.

Despite the competition among providers promoting different technologies to the market, there is no reason to assume that any of the technologies will win in the end. All technologies, due to their fundamental differences, have a chance to exist and for their share of users. The choice is up to the users.

The optimal access technology should be reasonably cheap, requiring additional costs only when new users are added; it must provide the user not only with high bandwidth, but also provide the necessary quality of QoS (Quality of Service) transmission for the ordered service (for example, the signal delay time is not more than the maximum allowable, guaranteed unevenness of this delay in the signal transmission frequency band, the required reliability, etc. etc.). All access methods, including copper or fiber optic cables, cable modems, or wireless systems, meet these requirements to some extent. Unfortunately, none of the technologies meets all the requirements at once.

In conclusion, we note another significant trend in the evolution of broadband subscriber access networks, which follows from the general trend of increasing the bandwidth of the access network and consists in the emergence of optimal solutions, which are a combination of several access methods within one network and even an access line. These technologies include, for example, HFRC mixed optical-radio-coaxial access technology, as well as VDSL technology, which essentially involves the use of mixed copper-optical transmission media in the subscriber access network.

On July 1, 2013, new energy tariffs came into effect in the Sverdlovsk Region. Generation, recall, is no longer regulated by tariffs - electricity prices are determined by the market. Electricity transmission activities, sales markups of guaranteed suppliers and electricity supplied to the population are regulated. Tariff policy is determined at the federal level in the form of special regulatory legal acts, and the regions implement them. Changes in tariffs and, as a rule, their growth for several years have been taking place in the middle of summer, and not since January, in order to slow down inflation and ease the financial burden of payers. On the eve, the Federal Tariff Service sets the benchmarks, and then the regions operate within this framework. The network tariff in the final bill for electricity for industry in Russia is already 46% (according to E-U). Moreover, from July 1 of this year it will rise within 10% in relation to July 2012 (growth over the same period a year earlier - 11%), and from July 1, 2014 - by another 10%.

According to the Deputy Chairman of the Regional Energy Commission Alexander Sobolev, the power grid complex should be stable in terms of tariff policy, since several years ago the mechanisms of the RAB method were introduced into practice, setting tariffs for the long term. Both for services for the transmission of electrical energy, and for mutual settlements between grid organizations.

Despite efforts to suppress the growth of tariffs for electricity transmission services through the networks, they will increase, Alexander Sobolev believes.

The question is crude

- Alexander Leonidovich, why are network tariffs growing?

First of all, the growth is due to inflationary processes, due to which the costs for a number of positions from power grid companies are increasing (for the purchase of electricity on the market to compensate for losses in the grids, wages, repairs). These processes are provided for by current legislation: when calculating a tariff, we must take into account inflation indices by industry.

The second reason is the emerging trend of a decrease (or rather, lack of growth) in the volume of electricity and capacity transmitted through regional networks. For example, according to the forecast for 2014, the volumes of transmitted energy are approximately at the level of the 2013 plan, but the declared capacity is reduced to 4%.

This is due to the drop in demand of some large consumers in the region. For example, the Bogoslovsky aluminum plant significantly reduces energy consumption - the situation on the aluminum market forces this. The same is happening in a number of other industrial enterprises.

There is a third reason - the problem of the so-called last mile, which has not been solved for a long time, has become aggravated. The last mile is a cross-subsidization scheme in which large consumers connected to the backbone of the Federal Grid Company pay not only its tariff, but also the tariffs of distribution networks that are not used. For this, IDGCs lease the last mile from FGC - a section of networks to which the consumer is directly connected. The mechanism increases the price of electricity for large enterprises, but allows lower tariffs for the rest, since large consumers pay extra for small and medium-sized ones.

- In fact, this is a hidden tax on industry, absorbing up to 30% of its electricity costs.

The last mile mechanism in the Russian electric power industry appeared in 2006 during the reform of the industry as a temporary measure (supposedly to avoid abrupt changes in tariffs in the energy sector of the regions and an increase in the load on end consumers) until a new tariff policy was approved. But, as usual, the temporary measure has become a constant headache.

Naturally, all these years industrialists have struggled to get away from such a system for direct contracts with FGC, starting long-term litigation with the networks. They leave, as a rule, through court decisions that have entered into legal force or through regulations that have been adopted by the RF Ministry of Energy. This move reduces their own electricity costs, but leads to an increase in the tariff burden on other consumers remaining with the network. Recently, the withdrawal has become widespread (although formally, now distribution networks and trunk lines are merged into Rosseti - Ed.).

We, the regulator, have to take this into account when making tariff decisions. Eliminating the last mile from 2014 would lead to a drop in distribution network revenues. To compensate for the shortfall in income (about 58 billion rubles a year in the country. - Ed.), The tariff for small and medium-sized consumers will need to be sharply increased.

- What will be done in the region with the last mile?

The negative consequences of leaving the last mile have been actively discussed at the federal level for a number of years. There are no decisions "at the top" yet: the bill has been submitted to the State Duma, but postponed until the autumn session. The reason is the lack of elaboration of the issue due to the opposite positions of consumers, authorities, network organizations.

The essence of the discord is this: consumers connected to FGC grids do not want to pay any more for the transportation of electricity to regional grid companies. And the authorities and networks see that it is impossible to simultaneously shift the entire problem of large industrial enterprises leaving the last mile to other consumers, small and medium-sized businesses or to the population. A compromise must be sought here. In our opinion, the Sverdlovsk Region will take five years to completely solve this problem and eliminate its negative consequences.

- What exactly will happen in these five years?

It all depends on whether other rules are adopted at the federal level. If they do not appear, industrial consumers will continue to leave the last mile. In the Sverdlovsk Region, the Kachkanarsky GOK was a pioneer: it left IDGC of Urals, OJSC directly to FGC in 2011. This year, the Sverdlovsk Railway, the Ural Electromechanical Plant and others followed suit. Of the previous total volume of consumers connected to the last mile, IDGC of Urals still has a third.

- What does this mean for grid companies?

If the consumers connected to the last mile and accounted for in the balance of regional networks do not pay, then the power grid complex will have shortfalls in income, which must be compensated for in the next regulatory periods. (So, the branch of IDGC of Urals Sverdlovenergo over the past year did not receive 1 billion rubles in revenue. - Ed.)

- So the economy of interregional distribution networks is collapsing?

I would not say that it is crumbling, but there are problems. This is due to the fact that it is impossible to proportionally reduce the revenues of the networks to reduce their costs for the transmission of electricity. The main way is to reduce the investment program. But over the past two years in the Sverdlovsk region, the costs of implementing the investment program from the profits of all power grid companies have been close to zero, that is, there is nothing to reduce. The only way to compensate for the departure of consumers is to use the internal reserves of companies, of which, unfortunately, there are not many left. In addition, the reduction can negatively affect the quality and reliability of the power supply.

Wallets are still different

- Will the recent merger of distribution and trunk grids into a single company Rosseti change anything?

We hope that Rosseti, together with consumers, will find a way out of the last mile situation, and a compromise will be reached. From the point of view of the Regional Energy Commission of the Sverdlovsk Region, the situation in our territory is not as critical as in some other regions.

We see one of the reasonable solutions to extend the time frame for resolving the issue of the last mile by two to three years, then, within the existing conditions for increasing tariffs, we will be able to remove this problem on the territory of the Sverdlovsk Region. Strictly speaking, the problem is ultimately solved at the expense of all other consumers. But given the fact that this will be done smoothly, gradually, they will not feel the burden of payments as much as they could.

- Where exactly is this figure of tariff growth - 10%?

This figure was determined by the Ministry of Economy of the Russian Federation and fixed in the forecast of the socio-economic development of the Russian Federation. In our opinion, it reflects the objective situation.

- Is this amount insufficient for investment programs?

Yes, it is impossible to simultaneously solve two problems - the elimination of the negative consequences of consumers leaving the last mile and the search for investments for the modernization and development of worn out distribution networks. We have to admit: the investment program of the entire power grid complex has been sequestered and, apparently, will be subjected to in the future.

- And the FGC investment program is significantly increasing this year.

In my opinion, this is a certain element of the state policy in the energy sector: at the present stage it is more expedient to develop higher-level networks (220 kV and more). Hopefully, after they are properly developed, attention will be paid to regional networks.

Dial-up

Historically, the first way to organize the last mile was dial-up remote access. As with most other last mile solutions, this technology is based on the idea of \u200b\u200busing existing infrastructure for data transmission - analog telephone wires. However, this technology had a lot of drawbacks - firstly, the established Dial-up connection made it impossible to use a conventional, analog phone. The second major drawback was the low speed. Despite the fact that there were various tricks associated with active traffic compression, their application did not always give results (especially on our telephone lines), and therefore, for simplicity, we can assume that the upper speed limit for Dial-up is 56 kbps. ...

xDSL

A further development of the same basic idea (from the provider to the subscriber to organize the last mile, already laid telephone lines are used) was the xDSL family of technologies. In practice, ADSL is the most common, which allows communication over a distance of up to 5.5 km at a data rate of 24 Mbps / 3.5 Mbps. A feature of this last mile technology is asymmetry - the speed of data transmission from the provider to the subscriber is much higher than in the opposite direction. Due to asymmetry, it is possible to increase the speed of downloading information to the detriment of downloading. Such a scheme of work is the most common, and therefore ADSL has found itself the most widespread use, especially since the established ADSL connection does not interfere with using an analog phone.

Moreover, it was this technology that revolutionized the provision of Internet access in our country, actually replacing the dial-up that reigned before.

Alas, this method is not without its drawbacks. First, to connect to ADSL networks, you need a separate device - an ADSL modem. The second problem is poor compatibility with the operation of burglar alarms that use telephone lines.

Ethernet

The second most popular last mile technology is Ethernet. It is worth clarifying that the name Ethernet itself does not speak of a specific method of connection and physical media - this technology has extensions that allow using coaxial cable, twisted pair or optical channel for data transmission. However, most often this technology means twisted pair.

From the point of view of the subscriber, Ethernet is a simpler technology. To connect to the Internet via an Ethernet provider, there is no need for additional equipment (a network card built into the computer is enough), and such a connection will be symmetric by default (however, this already depends on the provider).

However, any simplicity comes with a price tag. In this case, providers will have to pay - after all, in order to organize access using this technology, it is necessary to build an Ethernet infrastructure inside the district (block of buildings) and connect an optical channel to it. The constructed infrastructure will contain a fairly large number of various equipment (first of all, these are routers), which requires regular inspection.

Thus, the provision of services based on this technology is advisable when the area already has the necessary infrastructure - for example, a local area network. Therefore, most Ethernet providers have evolved from the control structures of the district networks.

It is possible to argue for a long time about which technology of the last mile is better - ADSL or Ethernet, but, ultimately, the subscriber decides, and at the moment both technologies are in demand and are presented equally widely and with approximately the same tariff plans.

WiFi

Just like Ethernet, Wi-Fi was not originally intended for last mile equipment - it is a wireless LAN technology. However, the development of mobile devices and laptops equipped with Wi-Fi has made such a solution to this problem in demand. Strictly speaking, the use of Wi-Fi as a last mile solution is not a very correct application of this technology and requires some modification of the technology.

Providers most often do this - directional antennas are used to organize communication over a long distance, which allow connecting remote parts of the network. Since directional antennas produce a distorted waveform along one direction, several conventional WiFi access points are deployed for client access, which form a mesh network topology.

However, the peculiarity of a Wi-Fi connection is that the entire channel width (and in the case of W-iFi, this channel is quite limited) is divided between all devices connected to one access point. Therefore, as the number of subscribers increases, the connection speed in such a network begins to drop, and in order to maintain it at the same level, the provider will have to install additional access points.

In general, the equipment of the last mile for stationary use using Wi-Fi technology alone does not look very promising - scaling is too expensive. On the other hand, given the prevalence of client devices, this is currently the most common method for mobile users.

WiMAX

Despite the similarity of names, at the level of technology WiMax has nothing to do with Wi-Fi. The cardinal difference of this technology is that WiMAX was originally developed as a wireless access technology on a city scale, and therefore the range of its coverage is much greater and the transmission speed is significantly higher than in Wi-Fi networks. Therefore, the deployment of such a network on a city or district scale will be much cheaper than Wi-Fi networks.

The only drawback is the limited choice of client devices. However, a compromise is possible - there are devices that allow organizing WiMAX-WiFI gateways.

PLC

A relatively new way of equipping the last mile is PLC (Power line communication). The so-called "Internet from the socket" is based on the use of intra-house and intra-apartment electrical networks for high-speed information exchange. By the way, you cannot confuse 2 similar technologies - PLC and Homeplug. The latter is intended for organizing local networks and is devoid of most of the disadvantages of the PLC.

This technology is based on frequency division of the signal, whereby a high-speed data stream is divided into several low-speed ones, each of which is transmitted at a separate frequency and then combined into one signal. At the same time, PLC devices can "see" and decode information, although ordinary electrical devices - incandescent lamps, motors, etc., do not even "know" about the presence of network traffic signals and work as usual.

It would seem that this technology should revolutionize the telecommunications market and completely replace xDSL technologies. However, it has significant drawbacks. The main drawback is the horrendous amount of interference, especially on medium and short wavelengths, which is generated by this use of power grids.

However, there are also less serious ones - the network throughput for wiring is divided between all its participants, the quality of the wiring (which often leaves much to be desired for us) affects the stability and speed of the PLC, and, moreover, such a network does not work through the network filters and UPS.

These shortcomings have resulted in extremely rare last mile equipment based on this technology.

Last Mile - a channel connecting the end (client) equipment with the access node of the provider (telecom operator). For example, when providing an Internet connection service, the last kilometer is the section from the provider's switch port at its communication center to the client's router port at its office. For dial-up services, the last kilometer is the section between the user's modem and the provider's modem (modem pool). The last mile usually does not include internal wiring.

The term is used primarily by professionals in the communications industry.

The last mile technologies usually include xDSL, FTTx, Wi-Fi, WiMax, DOCSIS, power transmission lines. The last mile equipment includes xDSL modems, access multiplexers, optical modems and converters, radio multiplexers.

Last mile technology feasibility study

The problem of the last kilometer has always been a topical task for signalmen. By now, a lot of last mile technologies have appeared, and any telecom operator is faced with the task of choosing a technology that optimally solves the problem of providing communications for its subscribers. There is no universal solution to this problem, each technology has its own area of \u200b\u200bapplication, its advantages and disadvantages. The choice of one or another technological solution is influenced by a number of factors, including:

operator strategy,
the target audience,
services currently offered and planned for provision,
the amount of investments in network development and the payback period,
the state of the existing network infrastructure, the resources to maintain it in working order,
time required to launch the network and start providing services,
reliability of service provision (time of response of the service provider to technical problems),
other factors.

Each of these factors can be assigned its own weight depending on the importance, and the choice of one or another technology is taken taking into account their entire set.

There are specialized companies and divisions of large communication companies that are exclusively engaged in building the last mile.

The last mile in the service provider refers to the section of the communication line from the switching device of the provider to the switching device of the client. To put it simply, last mile equipment connects the ISP's site to your apartment or office. And this very mile is organized today in a variety of ways - both wired and wireless.

The organization of the "last mile" always implies the presence of the following components: switching equipment for receiving and sending signals and information transmission medium.

General principles of organizing the "last mile"

1. The switching point of the provider should be located in sufficient proximity to the customer's habitat. The distance is calculated depending on the degree of signal attenuation in the transmission medium.
2. The customer must have the appropriate equipment capable of connecting to the provider's switching point. The type of equipment depends on how the “last mile” is organized.

Technologies for organizing the "last mile" are divided into wireless and wired, depending on the nature of the information transmission medium. It is easy to guess that wireless networks are those in which information is transmitted directly over the air (various wave transmission methods: WiFi, WiMAX, radio transmission, optical wireless communication).

Cable networks, respectively, include cable trunks: fiber-optic or metal (telephone cable, PLC, coaxial cable).

Let's take a look at three of the most common last mile technologies today.

1. WiFi wireless connection. The advantages of a wireless connection are obvious: it is convenient, does not require laying of cable routes, and allows several client computers to be connected to the channel at once without additional equipment. Disadvantages of this solution: the WiFi coverage area is unstable, heterogeneous and subject to a wide variety of interference.
2. Twisted-pair copper connection. The most common way to connect. Cheap and cheerful: twisted pair (UTP category 5e) is laid from the switch located in the building to the user's computers. Despite the ease of installation and low cost of materials, this method of organizing a network has certain limitations: a twisted pair can be laid, but not desirable, along the street. For outdoor installation, a special shielded FTP cable with an additional protective sheath is used, however, it is not reliable enough in the long term. Copper cable is susceptible to electromagnetic interference, so do not place the cable near sources of electromagnetic radiation, along the wiring. The length of the route between the switch of the provider and the user should not exceed 100 meters.
3. Fiber optic connection. Advantages of fiber-optic technologies: completely dielectric information transmission medium (not affected by the electromagnetic field), fewer restrictions on the length of the route (you can distribute the network along a multi-storey extended building from one switching node without additional repeaters, you can combine several buildings), durability (FOC will be reliably perform its function for 25 years or more) and significantly higher throughput (10, 40 and more gigabits per second). However, organizing the "last mile" on optical fiber is expensive. Fiber optic duplex cable itself is inexpensive, but laying it can cost a pretty penny. In addition, a fiber optic network requires special equipment to convert an optical signal into an electrical one. At the same time, when connecting communication lines to offices in a modern metropolis, it is more rational to use the most modern and promising fiber-optic technologies.

In addition to these methods, the transmission of a signal over a telephone cable is still in demand (DialUp, which is practically not used anymore and is still quite common ADSL). However, due to the convenience of more modern technologies, these options for laying the "last mile" are gradually becoming a thing of the past, following the Internet over coaxial cable. Abroad, the PLC technology is gaining momentum - the transmission of information through electrical wires, but it has not yet found its buyer here.

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