Mobile systems of the III generation..

The mobile communications market in the USA and Canada is developing more under the influence of market forces than regulatory decisions. Here, when preparing the draft of the new radio interface standard, a single national proposal was rejected, so four projects from the North American region were submitted to the ITU, two of which were prepared not by standardization institutes, but by industrial firms Qualcomm and Ericsson (North American branch).

The Asian approach to 3G systems is characterized by the desire of countries in this region to lead in the latest mobile communications technologies. In this regard, the four draft standards submitted to the ITU (South Korea — 2, China, Japan) are characterized by their focus on their own equipment manufacturers.

Without tiring readers with the history of the creation and struggle for world leadership of various associations and unions created to promote these projects, as well as information about who presented which project, we can say that as a result of complex joint work, the competing parties were able to agree on 5 options for radio interfaces for terrestrial communication networks:

• IMT-DS (Direct Spread);
• IMT-TC (Time Code);
• IMT-FT (Frequency Time);
• IMT-MC (Multi-Carrier);
• IMT-SC (Single-Carrier).

The main differences between these interfaces are determined by the method of multiple access to communication channels and the method of duplex spacing.

The radio interfaces of third-generation systems are based on two methods of multiple access: TDMA and CDMA.

TDMA Technologyassumes the use of a certain common frequency resource by all subscribers, with each of them being allocated their own time interval during which they are able to transmit information. To increase the capacity of a communication network, TDMA is usually used in conjunction with frequency division multiplexing.

Code Division Multiple Access (CDMA)is based on the use of signals with an extended spectrum and the simultaneous transmission of a large number of signals in a common frequency band. The system does not have a fixed assignment of channels, and their division is carried out according to the type of subscriber code sequence. Having high spectral efficiency, this method requires high accuracy of leveling of received signals at the base station and strict synchronization of mobile stations. Instead of the speed of information transfer, CDMA systems use the concept of chip rate, which is defined as the speed of symbols of a signal with an extended spectrum (noise-like signal).

Proponents of code division multiplexing systems emphasize the advantages of these systems in terms of secrecy and confidentiality compared to other mobile communication technologies. The fact is that CDMA networks use a radio signal with a wide base D=BT>> 1, where D is the base or signal compression ratio; B is the CDMA signal bandwidth in the air, MHz; T is the duration of the information symbol, μs. It is much more difficult to detect the presence of such a signal in the air by special means than signals with frequency or time division with a small base, since the spectral power density of the CDMA signal is much lower. Communication confidentiality is achieved by using multi-stage coding.

The method of duplex spacing of communication channels determines the possibility of exchanging information over one radio line in both directions. With frequency duplex spacing (FDD Frequency Division Duplex) reception and transmission of information are carried out at different frequencies. In Time Division Duplex (TDD) modeinformation exchange is carried out over one communication line (on one carrier frequency) due to the multiplexing of the receiving and transmitting channels in different time intervals.

The IMT-DS radio interface is based on WCDMA (Wideband Code Division Access) technology, wideband multiple access with code division of channels with direct spectrum expansion (DS – Direct Spread) in a frequency band of about 5 MHz and the use of frequency duplex diversity. Clock speed – 3.84 MHz.

The IMT-TC radio interfaceis based on code-time division of TDMA/CDMA channels with time duplex spacing and is designed to organize communication in unpaired frequency bands. The frequency band is also within 5 MHz, and the clock rate coincides with IMT-DS (3.84 MHz).

In the radio interface IMT-FTuses combined frequency-time duplex spacing and is capable of operating in both paired and unpaired frequency bands. It is an extended standard of the DECT EP microcellular system prepared by ETSI. The standard allows for three data rates on the radio interface (1152, 2304 and 3456 kbit/s), which became possible due to the use of new modulation methods.

The IMT-MC radio interface is based on a modification of the cdma2000 code division multiplexing system, and the increase in throughput is based on the simultaneous transmission of signals on several carriers with frequency duplex spacing.

The IMT-SC radio interfaceis based on the development of the American UWC-136 project, which represents a single-frequency TDMA system for use in paired frequency bands.

Brief technical characteristics of the standardized radio interfaces are presented in Table 3.

Table 3.

Revolution or evolution?

As it usually happens, the main controversial issue in the implementation of promising technologies is not the goal itself, but the way to achieve it. So in the case of 3G mobile systems, there is a rivalry between two transition strategies: revolutionary (W-strategy) and evolutionary (N-strategy).

Revolutionary strategyinvolves a complete replacement of the existing communications network infrastructure and the introduction of fundamentally new equipment based on wideband technologies. This strategy is characterized by high commercial risk and the need for significant capital expenditures. The revolutionary option requires a new frequency resource, which, at the same time, allows for the immediate provision of high network throughput and new communications services. Initially, the creation of a 3G communications system follows the path of building separate pilot networks with a full range of services.

Accelerated evolutionof existing narrowband mobile communication systems involves a smooth replacement of equipment depending on the demand for certain types of services. This approach allows for the consistent modernization of the existing communication network infrastructure, introducing new elements and gradually providing new communication services. Initially, the increase in bandwidth and the provision of new services are worked out within the already allocated frequency resource. The evolutionary strategy is characterized by lower commercial risk and a reduction in capital expenditures compared to the revolutionary development option.

The choice of transition strategy is of concern to all participants in the mobile communications market. It is safe to assume that powerful equipment manufacturers (Ericsson, Motorola, Nokia, Qualcomm, etc.), who have been working in this market for a long time and have sufficient investment potential, will go in both directions simultaneously, since this will allow them not to lose out in any scenario. Smaller manufacturers will have to take risks and choose a specific strategy, since there simply won’t be enough funds for parallel movement in both directions.

The same choice will have to be made by the existing mobile network operators, and it will most likely be a choice in favor of the evolutionary option for the same reason of the difficulty of finding the necessary financial resources. At the same time, the introduction of third-generation mobile networks provides an excellent chance to take their place in the group of leaders for young operator companies that are not afraid of losing their capital investments in existing networks. It should be noted that the giants of the computer and network business such as Microsoft and Oracle are planning to capture a large share of the mobile communication systems market.

Frequency resource

The creation of a single information space using third-generation mobile communication systems is impossible without the allocation of a common frequency resource necessary for their operation. Therefore, one of the main problems that the ITU had to solve when developing a strategy for the introduction of 3G communication networks was the task of allocating a single frequency range.

The main principles formulated in the IMT-2000 concept on the problem of frequency resource allocation were:

• the possibility of combining various strategies for the implementation of third-generation mobile communication services (revolutionary and evolutionary);
• ensuring flexibility in frequency allocation for freedom of choice of spectrum use option (paired and unpaired frequency bands), its volume and geographic area where the use of new communication services is expected.

Based on theoretical and expert studies, the overall frequency resource requirements for the deployment of 3G networks were estimated as a 230 MHz range. Naturally, there was no such spectrum section in the frequency range most suitable for mobile communications (up to 1 GHz). In this regard, an agreed decision was made at the WARC-92 conference to use the frequency resource in the higher frequency range for 3G. In accordance with this decision, the frequency bands of 1885–2025 and 2110–2200 MHz are intended for wireless access systems, cellular and satellite communications of the third generation (Fig. 1). At the same time, the frequency bands of 1980–2010 MHz (direction of communication “Earth-to-aircraft”) and 2170–2200 MHz (“aircraft-to-aircraft”) are allocated for the satellite segment. These decisions were later confirmed by the corresponding ITU recommendations: WRC-95 and WRC-97.

 
Fig. 1. Frequency resource allocation for IMT 2000 according to the ITU decision.

The approach to the development of frequency resources in various regions of the world is determined by the choice of a revolutionary or evolutionary option for the development of third-generation mobile systems.

In Europe, a combination of revolutionary and evolutionary options is envisaged. Therefore, for new systems, the approach to spectrum allocation practically coincided with the ITU recommendations. In accordance with the decision of the European Radiocommunications Committee (ERC), the following frequency bands have been reserved for the commercial operation of third-generation systems since 2002 (Fig. 2):

• paired frequency bands 1920–1980 and 2110–2170 MHz (2 x 60 MHz) – for terrestrial networks (macrocells) operating in FDD mode based on the IMT-DS radio interface;
• unpaired frequency bands 1900–1920 and 2010–2025 MHz – for terrestrial networks (microcells) with TDD duplex spacing and the use of the IMT-TC radio interface;
• 1980–2010 and 2170–2200 MHz – for the organization of satellite networks.

The only peculiarity is the allocation of a separate 20 MHz wide range (1880 – 1900 MHz) specifically for DECT standard systems, cutting off a 15 MHz band from the total UMTS frequency resource. Thus, a total of 155 MHz for terrestrial networks and 60 MHz for satellite networks have been allocated for third-generation systems in Europe.

The evolutionary transition to 3G systems in Europe is expected to be carried out within the spectrum areas (around 240 MHz) used by second-generation networks (GSM-900, GSM-1800 and DECT), by introducing GPRS and EDGE technologies.

 
Fig. 2. Frequency resource allocation for IMT 2000 in Europe

In the Asia-Pacific region, the situation with the distribution of frequency resources for IMT-2000 is similar to the situation in Europe. The revolutionary option for the implementation of third-generation networks chosen in Japan, South Korea and a number of other Asian countries allows for the distribution of the spectrum based on the IMT-2000 recommendations. At the same time, if the spectrum resources are free for FDD systems, then the implementation of TDD systems, at least in Japan, is complicated by the presence in the same range of the personal communication system based on portable telephones PHS (Personal Handy phone System), operating in the frequency band 1895 — 1918.1 MHz.

Satellite communication networks in the countries of this region are supposed to be created in the frequency ranges recommended by IMT-2000.

The situation in the USA, which determines the development of telecommunications systems throughout North and South America, is fundamentally different from the situation in Europe and Asia. The fact is that part of the spectrum (1850 — 1910 and 1930 — 1990 MHz), allocated for terrestrial IMT-2000 systems, has already been allocated and sold. Therefore, in the USA, at the first stage of the introduction of third-generation mobile systems, an evolutionary development option is assumed due to the introduction of new services in the frequency bands of second-generation systems, the total frequency resource of which is 190 MHz. Potentially, the free section of the spectrum 2110 — 2160 MHz can also be used for 3G networks.

However, a wider range of frequencies is provided for satellite communications in North America than in other regions: 1990 — 2025 and 2160 — 2200 MHz.

 
Fig. 4. Frequency resource allocation for IMT 2000 in America

Prospects for increasing the efficiency of using radio frequency spectrum resources are associated with both technical and organizational aspects.

From a technical point of view, the increase in spectrum efficiency can be achieved by using new spectrally efficient modulation methods and noise-resistant coding, radio access protocols, and various diversity reception methods. In addition, the capacity of mobile networks can be increased by using more efficient multimedia compression methods and flexible radio resource management.

Organizational measures involve the joint use of frequency bands by operators of terrestrial and satellite communication networks and spectrum conversion.

Services

The main distinguishing feature of third-generation mobile systems is the ability to transmit high-quality multimedia information. Trends in the development of mobile communications allow us to predict a significant increase in the number of users of multimedia communications services. According to experts at the UMTS forum, multimedia traffic may exceed 60% of the total volume of 3G network traffic as early as 2005.

With the introduction of third-generation systems, subscribers will be provided with a service comparable in level to fixed-line networks. Moreover, it will be provided anywhere. Owners of mobile terminals will be able to use high-speed Internet access, video telephony and videoconferencing services. It will become possible to receive a wide variety of broadcast programs, including even television programs.

Such services, in addition to the direct field of telecommunications, can be used in a wide variety of areas.

For example, in the sphere of security.Our magazine has already indicated some of the opportunities that may arise for law enforcement and security personnel when implementing new technologies in cellular communication systems (Nikolaev V.P. “New GSM technologies for security personnel”, Special Equipment, No. 4, 2000), however, given the subject matter of the magazine, it is appropriate to dwell on this issue once again.

With the introduction of third-generation mobile systems, it becomes possible to create effective complex remote control systems of protected objects. Security control of various components of the object can be easily organized using various sensors and portable video cameras, and the transmission of this information can be carried out via 3G network channels. It should be noted that an important advantage of such systems is the lack of need to obtain special permission to use radio frequencies.

The ability to quickly obtain reference informationfrom open and closed databases can significantly increase the efficiency of security personnel. A certain amount of analytical work can be carried out directly at the scene of the incident. The efficiency of decision-making in a wide variety of situations increases.

High data flow rate in third-generation mobile systems will enable the transmission of video information from the scene during a wide variety of events: anti-terrorist operations, surveillance of an object, technical expertise at the scene, etc.

The combination of navigation system services and high-speed transmission of large volumes of information over 3G networks will enable the creation of powerful location systems for mobile objects, which can be used in various areas of security.

It should be noted once again that 3G networks, especially those based on code division multiplexing systems, achieve high levels of privacy and confidentiality of communications, which is extremely important for special applications.

The greatest degree of mobile system adoption is expected to be achieved in the sphere of commerce and business. First of all, the scope of banking services provided by mobile terminals will be significantly expanded. These will be various paid information and reference services, electronic payments and other banking operations. In the near future, cellular radiotelephones, when solving the problem of ensuring the security of transmitted information, may well become a kind of mobile ATM.

The use of mobile terminals, according to some experts, will allow retail trade to be practically transferred to the hands of the client. According to Intel, the annual turnover of e-commerce at the beginning of the new century will exceed $1 trillion. Therefore, many mobile operators are absolutely seriously preparing to start working in the field of retail trade in various goods.

Application of mobile communications in in the area of ​​providing individual services (home environment, education, entertainmentetc.) with the development of multimedia information transmission are becoming an independent and very capacious market. Third generation services include the service provided by the technology of the home virtual environment VHE (Virtual Home Environment), the idea of ​​which is to provide the subscriber with services adapted to his requirements, regardless of the radio access technologies used, network standards, subscriber equipment. (As an example of the introduction of mobile communications into the market of household services, we can cite the world's first washing machine with a built-in radio modem, released by the Merloni company. To turn on such a machine, you just need to call a certain mobile phone number.)

The increase in the subscriber base of mobile communication systems due to teenagers and young people suggests a significant increase in demand for information, educational and entertainment services (pay TV channels, interactive games). Increased activity of the population contributes to an increase in the need for tele-assistance services (provision of audio and video data on request, reference information for orientation in the area, etc.). Thus, the range of applications of mobile communication in this area will constantly expand.

Universal terminal of the future

While analysts are forecasting the development of certain types of services in third-generation mobile communication systems, and operators are choosing a strategy for the transition to 3G networks, equipment manufacturers are already beginning to develop models of new cell phones that can serve as prototypes of future mobile terminals.

Based on the tasks of 3G systems, a mobile terminal, in addition to performing the functions of exchanging information via a radio channel, must provide the ability to display high-quality video information, input and store a sufficient amount of data and a certain computing power, at least to solve the problem of access to the Internet. All these additional functions are inherent in a personal computer. Therefore, the simplest of the proposed options for a 3G mobile terminal is the integration of a mobile phone and a palmtop computer. However, even here, a wide variety of design options are possible.

To solve the problem of displaying video images, Ericsson suggests expanding the size of the display by making it retractable. This will reduce the overall size of the phone.

In another design model, the display is made in the form of a flexible color screen located between two sliding plates on which the computer and the phone itself are located. Little remains to be done: all that remains is to develop a flexible color screen.

Nokia proposes to simply expand the display to the entire surface of the cell phone.

For the time being, it is proposed to use touch screens with a keyboard depicted on them or devices for reading handwritten text (such models are already on sale) to provide information input. However, the speed of information input in this case is very low. It is much more pleasant to dream about the possibility of speech input of information, but making forecasts about the time of appearance of such a service is a thankless task.

Small-sized hard disk drives can be used to store information, especially since the miniaturization of hard drives is in full swing. With their help, it is quite possible to ensure recording of ongoing negotiations.

The most promising principle for constructing 3G mobile terminals is probably the use of Bluetooth technology, which allows the use of the phone's components separately from each other, without connecting them structurally. In this case, the terminal elements exchange information via a multipoint radio channel in the 2.44 GHz range, controlled by a multilevel protocol similar to the GSM protocol. Thus, at any given moment, you can work only with those elements of the phone that are necessary: ​​either with the display, or with the intercom, or with the computer.

There is no doubt that the leading role in the mobile terminal market will be won by those companies that offer the consumer the widest choice of services and maximum convenience of using the device.

The beginning of the journey

The European approach to the creation of 3G networks is characterized by compliance with the UMTS Forum recommendations on the allocation of frequency spectrum and the leading role of recognized GSM network operators.

At present, almost all leading operating GSM mobile operators in European countries have already applied for 3G services. The European communications administrations are currently solving the problem of distributing paired (2-60 MHz) and unpaired (1-35 MHz) frequency bands from the public resource. Most of them allocate paired 2-10 or 2-15 MHz bands and one 1-5 MHz unpaired band for each operator.

The problem of issuing licenses for the deployment of third-generation networks was first solved in Finland. According to the results of a tender held in early 1999, licenses were received by four leading mobile operators. In some European countries, the problem of limited frequency resources for 3G networks has already emerged. In countries such as the Netherlands, England, Italy, Germany, Denmark, where four or five national operators operate, there is not enough publicly available resource for new operators planning to start providing 3G services.

European countries plan to issue national or regional licenses for work in UMTS networks in the coming years (Table 4). Provision of a wide range of 3G services is planned from 2002.

European countries make decisions on the allocation of frequency resources based on two approaches: tender or auction. Moreover, the principle of allocating frequency resources based on an auction brings in large revenues to the governments of those countries that choose this approach. For example, the largest auctions for the sale of rights to lease frequency channels brought the British treasury $34 billion, and the German treasury a record sum of $46.2 billion.

Table 4.

A number of experts believe that the commitment of European operators to GSM systems and the evolutionary path of development chosen in this regard based on the introduction of GPRS and EDGE technologies will slow down the advancement to third-generation systems, since operators will be limited to narrow-band communication modes. Therefore, it is assumed that the 3G services market will form faster in the USA and developed Asian countries, where a significant share of the market is occupied by CDMA systems, which provide certain technological advantages in the transition to third-generation systems.

For example, Japan's largest mobile operator NTT DoCoMo launched the first nationwide mobile communications service i-Mode in February 1999, providing 3G services based on packet IP network technology and mobile Internet. Today, 14 million subscribers use this service. NTT DoCoMo and other Japanese operators plan to begin deploying full-scale third-generation networks in 2001, based on network nodes and terminals implementing broadband CDMA. By 2003, the company intends to invest up to $40 billion in network deployment. The possibility of such large investments is explained by the well-thought-out policy of the Japanese government: NTT DoCoMo received a license to provide third-generation communications services free of charge in June of this year.

Samsung Electronics demonstrated third-generation technologies based on CDMA systems at the Sydney Olympics. The capabilities of organizing video conferences using small color LCD displays in mobile phones, providing “sound on demand” services (downloading music files directly from the Internet to a mobile phone), and transmitting video clips and films via mobile communication channels via the “video on demand” service were demonstrated.

Prospects for 3G in Russia

In its advancement to third-generation mobile systems, Russia is mainly guided by the evolutionary development option and European technologies developed within the framework of the UMTS concept. The design institutes of the Ministry of Communications have formulated the basic principles for the implementation of third-generation systems in Russia in a number of research papers:

• evolutionary transition from 2nd generation communication systems to third-generation systems;
• continued licensing policy aimed at supporting GSM standard operators;
• certification policy of the Ministry of Communications of Russia, interconnected with the European standardization system;
• ensuring state regulation of operator activities and market mechanisms in the allocation and use of spectrum;
• ensuring national and information security.

The “Concept for the Development of Public Cellular Mobile Communication Systems in Russia through 2010” specifies specific stages and directions for the implementation of third-generation systems. It provides for the gradual replacement of analog networks with digital ones, the modernization of NMT-450 networks based on GSM technology, the creation of multi-band GSM networks, the consolidation of existing networks and the creation of new ones, the evolution of existing digital networks to provide high-speed services, and the deployment of 3G networks based on the European version of the UMTS international standard IMT-2000.

This approach is explained by the following reasons. In Russia, with its relatively small number of mobile subscribers, the introduction of new generation mobile systems can begin only in large cities, where the services provided by these systems can be in acceptable demand. Most likely, operators who have received licenses to operate UMTS communication systems will begin creating pilot areas in Moscow and St. Petersburg, and at the first stage will provide services only in densely populated areas. Providing only UMTS services in limited areas will not attract subscribers, so third-generation network operators will need to interact with second-generation systems. They will have to use multi-mode terminals and roaming with the most developed GSM networks at present.

Readers may be interested to know how the Concept of Development of Cellular Communication Systems provides for the future of existing cellular communication systems of various standards.

Analog NMT-450 networks will be transformed based on digital GSM technology into GSM-450 networks.

Analog-digital networks of AMPS/DAMPS technology, after their transfer to the digital version in the 800 MHz range, will retain their regional status and continue to operate until the end of the amortization period.

GSM networks should develop in accordance with the latest ETSI recommendations, which provide for the introduction of GPRS and EDGE technologies.

Supporters of CDMA systems (the Sonet network) are still trying to prove the advisability of including in the concept provisions on the transition to 3G based on the modernization of existing systems with code division multiplexing.

In Russia, unlike European countries, there are no applications for the deployment of third-generation systems. However, at the end of 1999, the Russian Ministry of Communications supported the initiative of leading GSM network operators to conduct work on creating pilot zones of third-generation communication networks and determining the conditions for the implementation of 3G in Russia. Research and design institutes are involved in the research. Their work is coordinated by the recently created National Association of Third-Generation Communication Network Operators – 3G”. Within the framework of this work, the conditions for the allocation of frequency bands must be determined, problems of electromagnetic compatibility must be resolved, areas of work on the creation of packet switching networks must be determined, etc.Meanwhile, some mobile operators have already begun to develop new service applications for mobile networks, which can be considered the harbingers of third-generation mobile services. Moscow mobile operators are in the lead here: OJSC MTS and VimpelCom. These companies have begun trial operation of GPRS technology in their networks. The number of subscribers to WAP wireless protocol services in each of the networks is several thousand people. At the end of this year, MTS announced the start of providing mobile banking services in cooperation with Guta Bank. The new service is unlikely to become widespread in the near future, but it is the first sprout of mobile commerce, which sooner or later will be able to change the face of trade.

A Bit of Skepticism

It is not necessary to think that all experts are unequivocally optimistic about the prospects for the introduction of 3G networks. Here the main reason lies in the need for colossal expenses for the creation of future mobile communication systems. According to forecasts of a number of mobile operators, the deployment of third-generation networks will cost at least three times more than the acquisition of the necessary frequencies for these networks, and in Europe alone tens of billions of dollars have been invested here.

From a technical point of view, the reason is the need to increase the number of base stations compared to second-generation networks. Due to the transition to new frequency ranges in the 2 GHz region, the service areas of base stations are reduced, and their number required to cover the same territory increases. Studies show that third-generation communications will require an increase in the number of base stations by approximately 70%. In general, according to analysts' forecasts, the total cost of the pan-European 3G network, which should be put into operation no earlier than 2003, will be between $200 and $300 billion. Even according to the most optimistic opinions, the payback period for these investments will be between 5 and 7 years.

Therefore, even according to the UMTS forum's forecast, GSM and DAMPS network operators, provided that GPRS and EDGE technologies are implemented, will be able to confidently operate on the market until 2007-2010, successfully holding off competition from new third-generation systems.

The situation is further complicated by the fact that the introduction of new technologies in mobile communications is not proceeding as quickly as expected. For example, the popularity of the current wireless Internet access standard, WAP, is currently in question. A year ago, mobile network operators assumed that by the end of 2000, about 10 million subscribers across Europe would use mobile Internet services. However, today there are about 5 times fewer WAP users. Therefore, many marketers believe that new technologies such as GPRS and EDGE will not become the driving force of the cellular communications market in the near future, which, in turn, will complicate the promotion of third-generation mobile systems.

Conclusion

The information in the last section of the article about the difficulties that operators and equipment manufacturers face on the way to third-generation communication systems does not mean that the author doubts the bright future of mobile communications. This is only an attempt to provide readers with more objective information.

Various scenarios for the deployment of 3G networks cannot deny the very idea of ​​introducing new mobile communication technologies. The world is moving towards creating an open information society, and the development of mobile communication systems is aimed at providing users with access to any information resources anywhere on the planet.

A wide range of factors influences the dynamics of mobile systems development. In modern conditions, the introduction of new mobile communication technologies is facilitated by industrial and technological convergence, the arrival of giants of the computer business and consumer electronics industry in the mobile communications industry, the development of e-commerce, etc.

Thus, despite the large number of objective and subjective difficulties that operators and equipment manufacturers face when switching to third-generation systems, the introduction of a new generation of mobile systems is only a matter of time (and money).