10.3. The third generation of mobile communication systems.

As the requirements for the creation of FPLMTS were developed, it became clear to the ideologists of creating FPLMTS that, despite the widespread development of cellular communications and wireless access and the first successes of international roaming, a huge part of the territory, including the world's oceans, is not covered by communications [10.1-10.13]. Even in the future, land mobile networks will be able to serve no more than 20% of the earth's surface.

Consequently, the full coverage of world space and the provision of global mobile access to the services of the 21st century can only be realized with the help of satellite systems.

The change in the views of the International Telecommunication Union on the concept of mobile communication development is also reflected in the name, which was changed from 1996 to IMT-2000 (International Mobile Telecommunications-2000).

The new name differs from the former abbreviation FPLMTS not only because the term land was excluded from it, but also because the number two thousand was entered, symbolically indicating the approximate adoption date of the standard (after 2000) and the frequency range used located in the region of 2000 MHz.

The global mobile communications system, known today as IMT-2000, is a long-term program for developing, standardizing and facilitating the implementation of national, regional and international systems that implement a full range of services in the interests of terrestrial and satellite communications.

From an organizational point of view, IMT-2000 combines the two previous ITU-T programs, that is, the previously mentioned FPLMTS Advanced Ground Mobile Telecommunications System and the Global Mobile Personal Communications by Satellite (GMPCS) global satellite communications system. The combination of several backbone core networks within one IMT-2000 system will enable the creation of a global telecommunication infrastructure covering all regions of the world without exception, including developing countries.

Due to the flexible combination of terrestrial and satellite radio access networks and global roaming, uninterrupted communication will be provided between any corner of the world.

Based on this, within the framework of the IMT-2000 program, the priority tasks are: developing new frequency bands for satellite and terrestrial communications in the 2 GHz frequency range, increasing the transmission speed to 2.048 Mbit / s, developing new radio access technologies, expanding the range of services while reducing tariffs .

The main driving force behind the creation of a single international standard for a mobile system, covering wireless access, land cellular and satellite communications, is to provide global coverage of the globe with the provision of services to the mass consumer regardless of its location, network type and terminal used (ground or satellite).

Despite the failures of recent years associated with the termination of the operation of the personal satellite communications system IRIDIUM and the slowdown in the pace of deployment of the Globalstar and ICO systems, the idea of ​​global communications has not lost its significance. Today, there is practically no other alternative to providing truly global communications on land, at sea and in the air, besides satellite communications.

The combination of satellite and terrestrial channels will allow you to create a flexible system with a high speed of establishing communication and a short time to deploy new network infrastructures, especially in hard-to-reach areas.

The main idea of ​​creating a unified international standard is the provision of services using an inexpensive portable terminal with high performance characteristics (power consumption, quality of communication, security level).

From system positions, a single standard means a flexible radio interface with the same type of signaling and an expanded set of services, which vary depending on user requirements and communication organization scenarios. The key ITU requirements for a unified IMT-2000 standard include: a high degree of continuity of the equipment of terrestrial and satellite systems throughout the entire globe, the possibility of convergence of services such as mobile-mobile (for different mobile networks) and mobile landline ”(when communicating with PSTN subscribers), as well as providing multimedia services within the global information infrastructure.

Terminals of the 3rd generation G3 should provide high quality voice transmission, small size and the ability to transmit asymmetric data streams in the lines "up" and "down." Initially, all the prerequisites were to solve these problems. The ITU created the concept of a unified IMT-2000 standard as a series of recommendations that defined the structure of the radio interface and its main network elements. At the same time, this international body appealed to all the participating countries with a request to prepare their own projects of the 3rd generation systems.

16 projects were presented, but none of them could claim to be a single standard covering satellite and terrestrial communications. The work was immediately divided into two areas - on ground (10 projects) and satellite (6 projects) communications. Consideration of the presented projects of terrestrial and satellite systems of the 3rd generation showed that, despite the almost identical types of services provided, the TDMA and CDMA access technologies used in them are fundamentally different, that is, there are no clear ways to harmonize them or convergence. .

Nevertheless, two approaches remained to solve this problem: non-discriminatory and discriminatory.

In the first case, the allocated frequency resource for systems of the 3rd generation is distributed on an equal basis between all the participants in the work. We are talking about two frequency bands: 1980 ... 2100 MHz and 2170 ... 2200 MHz.

The discriminatory approach means the selection of one or two of the most promising technologies and the rejection of other offers.

It should be noted that the situation with the development of a global standard for satellite communications is even more complex than in terrestrial networks. To the two incompatible concepts of systems based on TOMA and CDMA technologies, another 5-6 different orbital grouping options are added. The use of different orbits and, accordingly, different repeaters (transparent or with processing on board), airborne antennas with different numbers of beams will inevitably lead to the fact that the radio interface developed for one technology will not be optimal for another. In the process of transition from the stage of developing a concept to concrete projects, it became obvious that the interests of various international and regional organizations cannot be united under a single standard.

In this regard, the idea of ​​creating a family of systems of the 3rd generation was put forward.

Thus, the problem of creating a single standard of the 3rd generation in the framework of the IMT-2000 program, most likely, will not be solved. However, hopes that the mobile phone will still be universal remain. Based on the 10-year cycle of change of generations, most likely, the problem of creating a global standard will be returned in 2010-2012.

Until that time, subscribers will have to use the services of two- or three-mode terminals, similar to those used in cellular communication systems.

IMT-2000 conceptual background

The concept of IMT-2000 is based on the following principles for constructing 3rd generation systems [10.6].

Communication is always and everywhere.

The term “communication always and everywhere” (anytime, anywhere) plays a fundamental role in the concept of IMT-2000 and implies that communication services must be available anywhere on the Earth’s surface and at any time. The globalization of communication creates the prerequisites for the user to access the entire range of information services of other networks distributed throughout the globe, that is, regardless of the surrounding conditions. The implementation of services is carried out due to intersystem global roaming through base stations of a cellular network or a gateway station of a personal satellite communications network (Fig. 10.3).

ITU has developed recommendations that allow the integration of intra-office, urban, regional and global mobile communications systems within IMT-2000.

In the creation of the 3rd generation systems, an important place is occupied by the Universal Personal Telecommunication (UPT) technology. According to the UPT concept, each inhabitant of the Earth should be allocated a personal phone number by which he could enter any communication network, at any time of the day and in any place where he would not be. Associated with the UPT number is the subscriber profile, that is, the set of communication services available to a particular subscriber, and personal requirements / communication modes. The UPT profile can allow the sending / receiving of fax messages or the inclusion of a conference call, mobile access to the Internet and Web-services in various modes of searching and viewing multimedia information.

Fig. 10.3. Scheme for providing global roaming through cellular base stations or personal satellite communications network gateway stations.

Single information space.

The concept of building IMT-2000 is based on the principle of mobile access to all resources of a single global information space. The new generation of mobile communication opens up great opportunities for obtaining various types of information by increasing its transmission speed to 2.048 Mbps.

The task of building a global global telecommunications mobile network involves the development of unified methods of access to information network nodes. An important role is assigned to satellite systems, which, in combination with ground access networks, will allow information to reach every corner of the Earth.

To solve this problem, it is necessary to create a flexible radio interface that ensures compatibility of global satellite and terrestrial networks. Universal mobile access to global information resources is realized through the integration of radio networks and the Internet.

At the first stage, mobile terminals will gain access to fixed Internet sites. At subsequent stages, the mobile radio network nodes will be able to perform the functions of Web sites and Internet host systems, which will ensure global connectivity of local cellular network resources and access to them from any type of subscriber devices. For example, subscribers will be able to access the nodes of their home local area networks in a standard way, while on trains, and work with various personal information (viewing incoming messages, checking bank accounts, searching documents in home archives, etc.).

Single frequency space.

In accordance with the concept of IMT-2000, systems of the 3rd generation create a single frequency space 230 MHz wide with different use cases. It is noteworthy that the frequency bands allocated for terrestrial and satellite communications are located side by side, which makes it possible in the future to talk about the possible combination of terminals operating in neighboring frequency bands. Two fundamentally different in terms of the concept of allocating a frequency resource approach are also being implemented - this is work in the old, already mastered frequency bands, with their possible gradual expansion, and the allocation of “individual” frequency bands for 3rd generation technologies.

For IMT-2000, two continuous 230 MHz spectral regions around 2 GHz, which are divided between wireless access systems, cellular and satellite communications, are already assigned “on a worldwide basis”.

The new approach, which was first implemented in IMT-2000, is associated with the allocation of paired frequency bands for systems operating with frequency duplex spacing (FDD) and unpaired frequency bands for systems with time duplex spacing (TDD).

The combined use of two modes FDD and TDD makes the system flexible, allowing you to change the bandwidth and methods of communication. Thus, the FDD mode is more effective with large cell sizes and high speed of movement of subscribers. TDD mode, on the contrary, is intended for use in pico and micro cells, that is, where the subscriber moves at low speed. The advantage of TDD mode is the more efficient use of radio channels with asymmetric information flows transmitted in the forward and reverse directions of communication.

Mobile terminal.

The concept of 3rd generation systems involves the provision of multimedia services, including high-speed transmission of information, video and voice, faxes and data to any subscriber using a mobile terminal having a single number.

In the age of information technology, a mobile phone ceases to be just a means of voice communication, and becomes a multimedia subscriber device capable of transmitting and receiving graphic data and video images. Such services should be provided at the lowest price, to ensure an acceptable quality and level of security. The ultimate goal of the 3rd generation systems is to create a mass market to meet personal communication needs. The success of the 3rd generation systems will depend on both tariffs for mobile services, fees for using public networks, and the cost of the subscriber terminal.

A key requirement of the concept is the use of portable, low-cost and flexible subscriber terminals.

Subscribers of the new systems will have convenient and compact terminals, which by their capabilities greatly expand the traditional understanding of radio telephones. Subscribers receive mass (affordable and easy to use) terminals that provide new communication and information processing capabilities.

The IMT-2000 system is supposed to use reprogrammed terminals that adapt to user requirements.

Such terminals are designed according to a modular principle with the possibility of their modification and flexible configuration depending on user requirements. Provision is made for flexible tuning of the terminal to different radio standards and provision of

terminal operation in various operating environments. At the same time with the provision of such a wide range of services, the new terminals are very simple and easy to use, that is, they are based on the modern “turn on and use” principle.

Consolidation of mobile and fixed networks.

The problem of organizing roaming is closely related to the problem of integration and convergence (convergence, consolidation) of fixed and mobile services - FMC (Fixed / Mobile Convergence), that is, the implementation of the principle “one person - one phone”.

Despite the strategic and very significant difference in network architectures and methods of implementing fixed and mobile services, their launch capabilities are about the same, that is, subscribers need to provide an approximately identical set of converged services and tariffs. At first glance, it seems that fixed and mobile services are incompatible things, and that their implementation is very problematic. As the cellular communication is transformed from an elite service into a mass one, the problem of convergence becomes more and more urgent. For a long time, the main obstacle to convergence remained poor voice quality. At the first stage of development of mobile communication, this was somehow justified - a “reasonable price” for winning in mobility. However, modern speech codecs can bring the quality of speech in a wireless network to the level of fixed communications. A number of services for ordinary subscribers, implemented in GSM and corporate hub PBXs, are also actually combined — this is the real convergence.

Modern services on the basis of circuit switching are already able to provide stationary subscriber with elements of mobility. Services are provided directly where the subscriber is located. It is provided with a single personal number with switching between different wired networks or radio networks operating in a transparent mode relative to the caller. The main discussions in the field of FMC-convergence are currently conducted around two problems: services and tariffs. Considering that prepaid services have already had a positive impact on the growing mobile communication markets, the commercial benefits of a stable expansion of roaming for the growing subscriber fleet will have a positive effect on operator activity.

Whichever approach operators choose to integrate fixed and mobile services, two factors play a decisive role: the continuity of generations of communication systems and the optimal convergence strategy. To win against their competitors, it is necessary to solve the main task - to provide a wide range of services at a lower price.

Overcoming the "technological divide"

Recently, the world has noticeably increased the imbalance between the new capabilities of the 3rd generation systems and the telecommunications infrastructure that actually exists in many countries, that is, the so-called “technological divide” has formed.

In this regard, the ITU is looking at other opportunities that could “build bridges over the abyss” (bridge the telecommunications cap), taking into account the characteristics of the telecommunications infrastructure of underdeveloped countries: low population density and large territories.

Для таких регионов предполагается использование маловысотных летательных аппаратов с ретрансляторами на борту, позволяющими по сравнению с традиционными базовыми станциями существенно расширить зону обслуживания и снизить время развертывания системы.

Универсальная мобильная телекоммуникационная система.

На волне успехов европейской экономической интеграции и успешной реализации международного проекта GSM в начале 90-х годов возникла идея создания Универсальной мобильной телекоммуникационной системы — UMTS (Universal Mobile Telecommunication Unit) как Европейской концепции создания систем мобильной связи 3-го поколения.

In 1994, the European Commission defined the most important principles for building a promising pan-European infrastructure for mobile and personal communication systems. These requirements were set forth in a Green Paper on Mobile and Personal Communications , a policy document that defined the pan-European movement to 3rd generation systems.

Further, under the auspices of the European Commission, implementation of international research on advanced high-speed mobile and personal communications technologies, intelligent networks, etc. began. Such a program was called ACTS (Advanced Communications Technologies and Services). One of the main directions of its development was the development of the concept of UMTS.

Для объединения усилий всех заинтересованных сторон в 1996 г. был образован UMTS Forum [10.8] — широкий по своим функциям и сферам компетенции международный координирующий орган, определяющий европейскую политику в области мобильной и персональной связи. Основной сферой его деятельности стала выработка согласованных решений по стандартизации UMTS и регулированию радиочастотных ресурсов. Концепции UMTS и IMT-2000 во многих чертах сходны, однако с точки зрения реализации UMTS имеет ряд существенных преимуществ. Предлагаемые в UMTS технические решения были апробированы в ряде НИР/ОКР, проводимых с участием крупных фирм-производителей (Nokia, Ericsson, Alcatel, Siemens, Italtel).

UMTS разработана как глобальная система, включающая как наземные, так и спутниковые сети.

Диапазон возможностей и областей применения UMTS необычайно широк. В отличие от GSM и других систем 2-го поколения в UMTS предлагается широкий спектр услуг по высокоскоростной передаче речи, данных, мультимедийных услуг при конкурирующих их ценах в условиях динамично изменяющегося рынка связи. При этом UMTS позволяет организовать полное взаимодействие с системами GSM и их модификациями (GPRS, EDGE и др.), чтобы не потерять уже вложенные инвестиции.

В связи с тем, что процесс стандартизации UMTS в настоящее время только коснулся выбора частотного диапазона и структуры радиоинтерфейса, различные компании предлагают самостоятельные технические решения.

Технология радио доступа UMTS основана на трех методах:

- FMA1 (Frames Multiple Access) на основе TDMA с расширением спектра (FMA1 NS);

- FMA1 без расширения спектра (FMA1 S);

- FMA2 на основе CDMA.

Методы FMA1 и FMA2 детально исследовались в рамках общего проекта FRAMES (один из проектов программы ACTS). Результаты этих исследований представлены в табл. 10.3.

Table 10.3. Сравнительные характеристики FMA1 и FMA2

В рамках ETSI были рассмотрены 5 базовых концепций радиодоступа для систем 3-го поколения: а-концепция (WB-CDMA), базирующаяся на FMA2 и предложениях ряда японских фирм, Р- концепция (OFDMA), у-концепция (WB-CDMA), базирующаяся на FMA1 без расширения спектра, 6-концепция (WB-TD-CDMA), базирующаяся на FMA1 с расширением, и е-концепция (ODMA).

Три из этих концепций — ос, Р, е — легли в основу спецификации UTRA — европейского предложения по радиотехнологии 3-го поколения, представленного в ITU (табл. 10.4).

Table 10.4. Ключевые характеристики пяти концепций радиодоступа UMTS

UTRA - UMTS Terrestrial Radio Access is a draft of a radio interface standard providing radio access to the UMTS system.

The introduction of UMTS technology was planned for 2002, with the data transfer rate, as follows from the table. 10.4, for the UTRA concept, it should be about 2 Mbit / s. Further development of the system is based on more advanced technologies as they become available.

This allows you to go from the original transmission rate in the channel of 9.6 kbit / s to speeds of 144 kbit / s and 384 kbit / s.

Market research shows that telephone exchange (voice transmission) will remain the dominant UMTS service until 2005 for GSM fixed and mobile networks.

В то же время долгосрочные прогнозы показывают настоятельную потребность части пользователей в диалоговых услугах мультимедиа, а также в широкополосных приложениях типа видеотелефонии.

На более поздних стадиях развития UMTS появится потребность и в более высоких скоростях передачи, порядка 155 Мбит/с.

В UMTS предусматривается пакетная передача данных, что дает преимущества в виртуальной связанности сети, альтернативном пути составления счетов, асимметричную пропускную способность. Предусматривается также обеспечение транспортных протоколов типа Интернет (IP), что удешевляет пользование системой.

UMTS разрабатывалась как глобальная система, включающая земные и спутниковые компоненты, поэтому терминалы системы были предусмотрены многорежимными, работающими с системами стандартов GSM-DCS.

В дальнейшем их возможности будут расширяться для предоставления новой номенклатуры услуг и работы в различных сетях и системах сотовой мобильной связи. Являясь универсальной системой, UMTS опирается на аппаратно-программный комплекс UTRA, поддерживающий операционное поле с высокой спектральной эффективностью и обеспечивающий высокое качество при работе в реализуемых физических средах распространения.

UMTS базируется на перспективных технологиях, поскольку содержит современную сервисную среду, что, в свою очередь, предполагает наличие инструментальных средств высокого уровня (для испытания и поддержания заданных характеристик оборудования), включая меры защиты информации.

Новая технология требует гибкого доступа к сети с соблюдением жестких норм достоверности, задержки или времени ожидания.

Наземные и спутниковые операторы систем мобильной электросвязи планировали развернуть UMTS, начиная с 2002 г. Это потребовало завершения большого числа мероприятий, касающихся высвобождения радиоспектра, регулирования процедур и становления служб. Для того, чтобы обеспечить технический и коммерческий успех UMTS, органами стандартизации, регулирования и изготовителями оборудования в Европе и во всем мире предпринимается множество ключевых действий.

These include:

- разработка механизма прохождения сигнала между сетями, учитывающего перспективные сервисные приложения;

- обеспечение своевременной доступности лицензий для создания операторам условий для подготовки аппаратных комплексов и формирования отношений;

- распределение адекватного спектра операторам для организации реального обслуживания пользователей;

- создание необходимых стандартов для того, чтобы изготовители могли своевременно приступить к производству конкурентоспособных изделий;

- одобрение внедрения UMTS одновременно в большинстве стран.

Для реализации UMTS разрабатываются новые технологии. В частности, ETSI в методике построения системы радиодоступа для UMTS объединил две технологии — IMT-DS (IMT-DS — IMT-2000 Direct Spread — стандарт на широкополосную систему с прямым расширением спектра (DS-CDMA) и частотным дуплексным разносом (FDD) для применения в парных полосах частот (объединенное предложение WCDMA и UTRA FDD) и IMT-TC (IMT-TC — IMT-2000 Time Code — стандарт на комбинированную систему TDMA/CDMA с временным дуплексным разносом (TDD) для применения в непарных полосах частот (объединенное предложение UTRA TDD и SCDMA)). Этот подход расширяет возможности внедрения системы в различных регионах с учетом сервисных потребностей. Предполагается, что в мире будут производиться терминалы IMT-2000 различных стандартов. Операторы будут нуждаться в терминалах, совместимых с технологиями GSM/DCS, DECT. Поэтому терминалы IMT-2000 предполагаются многорежимными, чтобы они могли работать в сетях как старых, так и новых стандартов. Важнейшим шагом станет совершенствование модуля идентификации и защиты подвижного абонента. UMTS — достаточно гибкая технология доступа к сетям связи общего пользования и корпоративным сетям. Кроме того, UMTS может поддерживать IP-технологии и другие режимы, включая пакетную коммутацию по виртуальной сети.

Функции транспортной сети могут быть обеспечены мобильной сетью, такой как GSM или/и UMTS, или фиксированной сетью. Единственное требование к подобной сети — это поддержка общего интерфейса системы API, который позволит использовать широкое разнообразие приложений и типов терминалов, а также поддержит мероприятия по защите передачи информации, составление счетов, информационную службу и сервисное управление.

Широкий диапазон услуг, предоставляемых UMTS, включая глобальный мобильный доступ к Интернет, является ключевым проводником быстрого развития системы. Для оптимизации производительности сети необходимо обеспечить большую гибкость абонентской структуры и сервисного управления. Гарантом долгосрочной перспективы UMTS является прогрессивный рост ее возможностей в результате введения новых технологий. К ним относятся и реконфигурируемые терминалы. Собственно терминалы будут существовать в мире на основе многих стандартов семейства IMT-2000. Помимо способности адаптироваться к различным стандартам в терминалах заложена возможность их регулировки сетевыми операторами путем передачи новых версий по радиоканалу. Высокоэффективные антенны, автоматически настраиваемые на сигналы с непрерывным изменением параметров, позволят улучшить защиту от влияния смежных каналов, повысить точность фиксации местоположения пользователя. Модули универсальной идентификации (UIM) или смарт-карты представляют собой уникальную базу для приложений, таких как обеспечение безопасности, глобальный роуминг и предоплаченные услуги. UIM-технология известна также как SIM или SIM/IMSI.

Smart cards will allow consumers to receive services when they use any type of terminal. The ability to access all popular features and services in 3rd generation systems is called “Virtual Home” (VHP). UIM also provides a high level of "personalization" for subscribers, and operators - the ability to collect valuable marketing information. For the actual implementation of UMTS in the planned time frame, it is necessary to solve a number of problems associated with the successful development of telematic services and data transmission. Although UMTS supports voice services, its future depends on the volume of data transmission by mobile users within the mainstream market. In addition, the reliability of the billing system must be ensured, because the system itself becomes more complex and will require the coordinated work of many organizations; when creating a service environment and interfaces, it is necessary to provide a wide range of services that could be offered to end users. Further research in the area of ​​optimal use of the radio frequency spectrum in the interests of developing and improving UMTS becomes very important.