Part One 1 Introduction Ari Ahtianen, Heikki Kaaranen and Siamäk Naghian Nowadays, it is widely recognised that there are three different, implemented genera- tions as far as mobile communication is concerned (Figure 1. The first generation, 1G, is the name for the analogue or semi-analogue (analogue radio path, but digital switching) mobile networks established in the mid-1980s, such as the Nordic Mobile Telephone (NMT) system and the American Mobile Phone System (AMPS). These networks offered basic services for users and the emphasis was on speech and speech- related services. 1G networks were developed with national scope only and very often the main technical requirements were agreed between the governmental telecom oper- ator and the domestic industry without wider publication of the specifications.
Due to national specifications, 1G networks were incompatible with each other and mobile communication was considered at that time to be some kind of curiosity and added value service on top of the fixed networks. Because the need for mobile communication increased, also the need for a more global mobile communication system arose. International specification bodies started to specify what the second generation, 2G, mobile communication system should look like. The emphasis for 2G was on compatibility and international transparency; the system should be regional (e., European-wide) or semi-global and the users of the system should be able to access it basically anywhere within the region.
From the end- user’s point of view, 2G networks offered a more attractive ‘‘package’’ to buy; besides the traditional speech service these networks were able to provide some data services and more sophisticated supplementary services. Due to the regional nature of standar- disation, the concept of globalisation did not succeed completely and there are some 2G systems available on the market. Of these, the commercial success story is the Global System for Mobile Communications (GSM) and its adaptations: it has clearly exceeded all the expectations set, both technically and commercially. The third generation, 3G, is expected to complete the globalisation process of mobile communication.
Again, there are national and regional interests involved and difficul- ties can be foreseen. Anyway, the trend is that 3G will mostly be based on GSM technical solutions for two reasons: GSM technology dominates the market and the great investments made in GSM should be utilised as much as possible. Based on this, the specification bodies created a vision about how mobile telecommunication will UMTS Networks Second Edition H. Niemi # 2005 John Wiley & Sons, Ltd ISBN: 0-470-01103-3 4 UMTS Networks Figure 1.1 Cellular generations develop within the next decade.
Through this vision, some requirements for 3G were shortlisted as follows: 1. The system must be fully specified (like GSM) and major interfaces should be standardised and open. The specifications generated should be valid worldwide. The system must bring clear added value to GSM in all aspects.
However, at the start the system must be backward-compatible at least with GSM and ISDN (Integrated Services Digital Network). Multimedia and all of its components must be supported throughout the system. The radio access of 3G must provide wideband capacity that is generic enough to become available worldwide. The term ‘‘wideband’’ was adopted to reflect the capacity requirements between 2G narrowband capacity and the broadband capacity of fixed communications media.
The services for end-users must be independent of radio access technology details and the network infrastructure must not limit the services to be generated. That is, the technology platform is one issue and the services using the platform are totally another issue. While 3G specification work was still going on, the major telecommunication trends changed too. The traditional telecommunication world and up to now the separate data communications (or the Internet) have started to converge rapidly.
This has started a development chain, where traditional telecommunication and Internet Protocol (IP) technologies are combined in the same package. This common trend has many Introduction 5 names depending on the speaker’s point of view; some people call the target of this development the ‘‘Mobile Information Society’’ or ‘‘Mobile IP’’, others say it is ‘‘3G All IP’’ and in some commercial contexts the name ‘‘E2E IP’’ (End-to-End IP) is used as well. From a 3G point of view, a full-scale IP implementation is defined as a single targeted phase of the 3G development path. The 3G system experiences evolution through new phases and, actually, the work aiming to establish 4G specifications has already started.
Right now it may be too early to predict where the 3G evolution ends and 4G really starts. Rather, this future devel- opment can be thought of as an ongoing development chain where 3G will continue to introduce new ways of handling and combining all kinds of data and mobility. 4G will then emerge as a more sophisticated system concept bringing still more capacity and added value to end-users.1 Specification Process for 3G The uniform GSM standard in European countries has enabled globalisation of mobile communications. This became evident when the Japanese 2G Pacific Digital Com- munications (PDC) failed to spread to the Far East and the open GSM standard was adopted by major parts of the Asian markets and when its variant became one of the nationally standardised alternatives for the US Personal Communication System (PCS) market too.
A common, global mobile communication system naturally creates a lot of political desires. In the case of 3G this can be seen even in the naming policy of the system. The most neutral term is ‘‘third generation’’, 3G. In different parts of the world different issues are emphasised and, thus, the global term 3G has regional synonyms.
In Europe 3G has become UMTS (Universal Mobile Telecommunication System), following the European Telecommunications Institute (ETSI) perspective. In Japan and the US the 3G system often carries the name IMT-2000 (International Mobile Telephony 2000). This name comes from the International Telecommunication Union (ITU) develop- ment project. In the US the CDMA2000 (Code Division Multiple Access) is also an aspect of 3G cellular systems and represents the evolution from the IS-95 system.
In this book, we will describe the UMTS system as it has been specified by the worldwide 3G Partnership Project (3GPP). To bring some order to the somewhat confusing naming policy, 3GPP launched a decision where it stated that the official name of 3G is the ‘‘3GPP System’’. This name should be followed by a release number describing the specification collection. With this logic, the very first version of the European-style UMTS network takes the official name ‘‘3GPP System Release 99’’.
Despite this definition, the above-mentioned names UMTS and IMT-2000 are still widely used. At the outset UMTS inherited plenty of elements and functional principles from GSM and the most considerable new development is related to the radio access part of the network. UMTS brings into the system an advanced access technology (namely, the wideband type of radio access). Wideband radio access is implemented using Wide- band Code Division Multiple Access (WCDMA) technology.
WCDMA evolved from CDMA, which, as a proven technology, has been used for military purposes and for narrowband cellular networks, especially in the US. 6 UMTS Networks UMTS standardisation was preceded by several pre-standardisation research projects founded and financed by the EU. Between 1992 and 1995 a Research in Advanced Communications in Europe (RACE) MoNet project developed the modelling technique describing the function allocation between the radio access and core parts of the network. This kind of modelling technique was needed, for example, to compare Intelligent Network (IN) and GSM Mobile Application Part (MAP) protocols as mobility management solutions.
This was, besides the discussion on the broadband versus narrowband ISDN, one of the main dissents in MoNet. In addition, discussions about the use of ATM (Asynchronous Transfer Mode) and B-ISDN as fixed transmis- sion techniques arose at the end of the MoNet project. Between 1995 and 1998 3G research activities continued within the Advanced Com- munications Technology and Services (ACTS) Future Radio Wideband Multiple Access System (FRAMES) project. The first years were used for selecting and devel- oping a suitable multiple access technology, considering mainly the TDMA (Time Division Multiple Access) versus CDMA.
The big European manufacturers preferred TDMA because it was used also in GSM. CDMA-based technology was promoted mainly by US industry, which had experience with this technology mainly due to its early utilisation in defence applications. ITU dreamed of specifying at least one common global radio interface technology. This kind of harmonisation work was done under the name ‘‘Future Public Land Mobile Telephony System’’ (FPLMTS) and later IMT-2000.
Due to many parallel activities in regional standardisation bodies this effort turned into a promotion of common architectural principles among the family of IMT-2000 systems. Europe and Japan also had different short-term targets for 3G system development. In Europe a need for commercial mobile data services with guaranteed quality (e., mobile video services) was widely recognised after the early experiences from narrowband GSM data applications. Meanwhile, in the densely populated Far East there was an urgent demand for additional radio frequencies for speech services.
The frequency bands identified by ITU in 1992 for the future 3G system called ‘‘IMT-2000’’ became the most obvious solution to this issue. In early 1998 a major push forward was achieved when ETSI TC-SMG decided to select WCDMA as its UMTS radio technology. This was also supported by the largest Japanese operator NTT DoCoMo. The core network technology was at the same time agreed to be developed on the basis of GSM core network technology.
During 1998 the European ETSI and the Japanese standardisation bodies (TTC and ARIB) agreed to make a common UMTS standard. After this agreement, the 3GPP organisation was established and the determined UMTS standardisation was started worldwide. From the UMTS point of view, the 3GPP organisation is a kind of ‘‘umbrella’’ aiming to form compromised standards by taking into account political, industrial and commercial pressures coming from the local specification bodies:. As this is a very difficult task an independent organisation called the ‘‘OHG’’ (Operator Harmonisation Group) was established immediately after the 3GPP was formed.
The main task for 3GPP is to define and maintain UMTS specifications, while the role of OHG is to look for compromise solutions for those items the 3GPP cannot handle internally. This arrangement guarantees that 3GPP’s work will proceed on schedule. To ensure that the American viewpoint will be taken into account a separate 3GPP Number 2 (3GPP2) was founded and this organisation performs specification work from the IS-95 radio technology basis. The common goal for 3GPP, OHG and 3GPP2 is to create specifications according to which a global cellular system having wideband radio access could be implemented.
To summarise, there were three different approaches towards the global cellular system, 3G. These approaches and their building blocks are, on a rough level, presented in Table 1. When globality becomes a reality, the 3G specification makes it possible to take any of the switching systems mentioned in the table and combine them with any of the specified radio access parts and the result is a functioning 3G cellular network. The second row represents the European approach known as ‘‘UMTS’’ and this book gives an overview of its first release.
The 3GPP originally decided to prepare specifications on a yearly basis, the first specification release being Release 99. This first specification set has a relatively strong ‘‘GSM presence’’. From the UMTS point of view the GSM presence is very important; first, the UMTS network must be backward-compatible with existing GSM networks and, second, GSM and UMTS networks must be able to interoperate together. The next release was originally known as ‘‘3GPP R00’’, but, because of the multiplicity of changes proposed, specification activities were scheduled into two specification releases 3GPP R4 and 3GPP R5.
3GPP R4 defines optional changes in the UMTS core network circuit-switched side; these are related to the separation of user data flows and their control mechanisms. 3GPP R5 aims to introduce a UMTS network providing mechanisms and arrangements for multimedia.