5 Third-Generation Cellular: UMTS ∗ Dramatic developments have been taking place in the mobile radio area all over the world during the last couple of decades. Mobile communications is one of the fastest growing markets in the telecommunications area. According to projections, there will be a linear increase in the number of subscribers to the major GSM networks operated in Europe by the end of the decade. The political environment in Europe is the main reason for the rapid devel- opment. Without a free exchange of information, the concept of an internal market striving for a free flow of goods between EU states would be inconceiv- able. This was the line of thinking behind the liberalization and deregulation of the telecommunications industry, which promoted and accelerated compe- tition and opened up the markets. Another reason for this rapid development is the advances being made in the microelectronics, microprocessor and transmission technology areas. These advances are enabling the use of ever smaller terminal equipment, with computing power previously only possible with mainframes, and with low power consumption—factors that have improved customer acceptance. In Europe the development of uniform standards, the introduction of Euro- pean-wide radio systems and the participation of industry in the standardiza- tion process through the establishment of ETSI have further contributed to the widespread success of mobile communications. The chronological development of different kinds of mobile radio networks which conform to different user needs is presented in Figure 1.2 [23]. The systems that fall into the category of first-generation mobile commu- nications systems in which mobility is only ensured within a specific network area are the different analogue cellular systems (e.g., C-Netz, NMT), cordless systems (CT1/CT2) and various national paging systems. The second generation includes the digital systems such as GSM, DCS 1800, USDC, PDC, IS-95 and ERMES, which underwent further development and were expanded or were first introduced during the first half of the 1990s. Along with these public cellular systems that provide PSTN/ISDN ser- vices at a mobile terminal, there are other systems that fall into the second- generation or the transitional category between the second and third gen- erations, and cater specifically to mobile or moving applications. These in- clude trunked radio (ETSI/TETRA, see Section 6.3), cordless communica- ∗ With the collaboration of Arndt Kadelka, Matthias Lott and Peter Seidenberg Mobile Radio Networks: Networking and Protocols. Bernhard H. Walke Copyright © 1999 John Wiley & Sons Ltd ISBNs: 0-471-97595-8 (Hardback); 0-470-84193-1 (Electronic) 322 5 Third-Generation Cellular: UMTS Networks Core Transport UIM: User Identification Module TE: Terminal Domain Services MBS CATV WAN LAN Application Network Domain Core Transports Domain Equipment Terminal UMTS B-ISDN ISDN S-PCN DECT Networks Access UIM UIM Examples: GSM BSS TE TE Fixed Fixed Mobile TE Mobile TE Examples: GSM NSS + IN ISDN/IN-based B-ISDN + IN-based TCP/IP-based B-ISDN + TINA-based Access Network Domain Figure 5.1: Global multimedia mobility architecture tions (ETSI/DECT, see Chapter 9, and the Personal Handyphone System, PHS, see Chapter 11), local broadband communications (ETSI/HIPERLAN 1, see Section 13.1, IEEE 802.11, see Section 13.9), wireless ATM systems (ETSI/BRAN, see Section 12.1.5), mobile personal satellite radio (IRIDIUM, Globalstar, see Chapter 14) and other systems integrating aspects of these systems. Third-generation mobile radio systems, which use intelligent networks to incorporate public mobile radio services that previously were operated sep- arately, are already being developed today. Under the designation Global Multimedia Mobility (GMM), ETSI is developing an architecture that defines mobile radio networks as the access networks to an integral transport plat- form that is based on broadband (B)-ISDN and provides mobility-supported value-added services (see Figure 5.1). It is planned that these future standard mobile communications networks (UMTS and FPLMTS or IMT 2000), which aim to support the services of the terrestrial broadband ISDN, will lead to a universal worldwide public mobile radio system, which is expected to be operational by the year 2003. The main characteristics of third-generation mobile radio systems are [1]: 5.1 UMTS (Universal Mobile Telecommunications System) 323 • Support of all features currently being offered by different systems. • Support of new services with high quality of service, the same as in the fixed network. • High capacity, which will support high market penetration. • High spectral efficiency. • Lightweight, small (pocket-sized) and inexpensive handheld equipment for mobile telephone use. • High security, comparable to that of the fixed network. High demands are being placed on the third-generation systems, e.g.: • Services (voice and data, teleservices, bearer services, supplementary services). • Different bit rates (low bit rates for voice; data rates up to 2 Mbit/s). • Variable bit rates and packet-oriented services. • Use of different sized cells (macro, micro, pico) for indoor and outdoor applications, with seamless handover between indoor and outdoor base stations. • Operation in non-synchronous base station subsystems. • Advanced mobility characteristics (UPT, see Chapter 15; roaming, han- dover, etc.). • Flexible frequency management. • Flexible management of radio resources. 5.1 UMTS (Universal Mobile Telecommunications System) In Europe work continues to be carried out on the development of a third- generation mobile radio system called UMTS (Universal Mobile Telecommuni- cations System) in the EU programmes RACE (1989–1994) (Research and De- velopment in Advanced Communications Technologies in Europe) and ACTS (1995–1998) (Advanced Communication Technologies and Services) in coop- eration with ETSI. Work on UMTS is also being done in COST (European Cooperation in the Field of Scientific and Technical Research) projects [20]. The technical subcommittee (STC) SMG 5 at ETSI has been given the responsibility for producing the UMTS standard. Other SMG subcommit- tees that are currently still working on the GSM 2+ standard will eventually 324 5 Third-Generation Cellular: UMTS become involved in the standardization of UMTS, e.g., SMG 2. SMG 5 will then take over the creation of the UMTS standard and the coordination of the standardization activities. There is also the UMTS Forum, comprising the European signatories to the UMTS–Memorandum of Understanding of the Introduction of UMTS defined in 1996. The main tasks of SMG 5 are [2, 15]: • Study and definition of services, system architecture, the air interface and the network interfaces for UMTS. • Generation of basic technical documentation for UMTS. • Coordination of ETSI and of SMG regarding UMTS. • Cooperation and coordination with the ITU for the definition of a world- wide standard on the basis of UMTS/FPLMTS/IMT 2000. • Cooperation with European research programmes. The aim of the UMTS concept is to provide users with a handheld terminal that will cover all areas of application—at home, in the office, en route by car, in a train, in an aircraft and as a pedestrian. UMTS will therefore offer a common air interface that will cover all fields of application and have the flexibility to integrate worldwide the different mobile communications systems available today, such as mobile telephone and telepoint, trunked radio, data radio, and satellite radio systems, into one system. What will play an important role in UMTS is the concept of intelligent networks (IN) that will provide call charging and mobility management for the localization and routing of calls across networks operated by different service providers and operators. UMTS will be the first system to offer mobile users roaming during an existing connection, with handover between networks with different applications and different operators [17]. UMTS will offer transmission capacity comparable to ISDN for services such as video telephony and wideband connections, and will support the ser- vice concept Universal Personal Telecommunications (UPT) [4]; see Chap- ter 15. With UMTS it will be possible to transmit voice, text, data and images over one connection, and subscribers will be assigned a personal tele- phone number that will allow them to be reached anytime, anywhere in the world. The first series of standards for UMTS has been completed in March 1999. The projection is that UMTS, which according to Appendix D will use the frequency band between 1.885 and 2.2 GHz, will be introduced around 2003. However, the UMTS Forum has a preference for the frequencies indicated in Figure 5.2, staggered timewise as shown, and is promoting the refarming of bands previously used for other purposes (see Appendix D) and working towards including asymmetrical bands along with the symmetrical ones. The planned frequency allocations to IMT 2000/UMTS are shown in Figure 5.3. 5.1 UMTS (Universal Mobile Telecommunications System) 325 300-500 MHz UMTS Core Band 2110 MHz 2170 2200 MHz2025 MHz2000 + 20 MHz + 15 MHz Sat Sat Year 2002: 2x30 MHz Year 2005: 2x60 MHz Year 2008: approx. 300 to 500 MHz 1900 MHz e.g., Downlink Licensed Licensed/Unlicensed Licensed e.g., Uplink 60 MHz 95 MHz Figure 5.2: UMTS frequency spectra, UMTS Forum’s perception of timetable for development MSS Reg.2 MSS Reg.2 Europe Japan USA ITU/RR MSS MSS MSS MSS IMT-2000 UMTS IMT-2000 PCS IMT-2000 MSS MSS MSSIMT-2000 UMTS MSSGSM 1800 PHS UMTS DECT UMTS 1800 1850 1900 1950 2000 2050 2100 2150 2200 2250 Frequency [MHz] Figure 5.3: Spectrum Allocation Originally it was planned to specify one air interface only able to cover all the different services and applications aimed at. From the decision made in January 1998 (see Section 5.7.5), it is now clear that at least two air interfaces will be specified—one based on paired bands with frequency division duplexing (FDD) transmission, and another air interface operating in a single band with time division duplexing (TDD) transmission. Both standards will use DS-CDMA for radio transmission and channel access, and are addressed as FDD-CDMA and TDD-CDMA systems respec- tively. From the viewpoint of intellectual property right (IPR), there are still those in Europe proposing to stay with F/TDMA as the basis for UMTS and to make no use of CDMA, since QUALCOMM is the owner of some CDMA key patents but is not willing to license their use under the so-called fair rules 326 5 Third-Generation Cellular: UMTS established by ETSI. In fact, the EDGE proposal (see Section 3.11) submitted by Ericsson to ITU-R is capable of providing wideband services compatible to GSM 2+. The main driving force towards UMTS at present comes from manufactur- ers aiming to introduce new products into the market and operators aiming to get under the label UMTS access to more bandwidth for voice services only. Mobile data was still only a few percent of business in 1998. The European Commission has issued guidelines for the licensing of UMTS bands to opera- tors demanding that 50 % of the services offered should be data services for multimedia applications. The demand for more bandwidth can of course easily be covered by assign- ing UMTS frequency bands to be used by GSM networks, and does not need the introduction of a new air interface. 5.2 FPLMTS (Future Public Land Mobile Telephone System); IMT 2000 (International Mobile Communications at 2000 MHz) In 1985 the CCIR (see Annex B.1.2) set up a working group, the Task Group 8/1 (previously IWP 8/13), for the purpose of specifiying all the requirements and system parameters for a future public land mobile telecommunication system (FPLMTS). The following requirements for an FPLMTS were drawn up by the working group [5, 13, 19]: • Small, lightweight handheld equipment. • Worldwide use of terminal equipment, i.e., uniform frequencies world- wide. • Integration of different mobile radio systems and international roaming. • Integration into the fixed telephone networks (ISDN compatibility). • Integration of mobile satellite radio. • Use of terminal equipment on land, in the air and at sea. As with the UMTS, the aim with the FPLMTS is to integrate all existing services (mobile telephony, cordless telephony, paging, trunked radio, etc.) into one service. Many of the aspects of FPLMTS are the same as those of UMTS; however, since the ITU activities are globally based, there are some differences between the two systems. For example, FPLMTS defines several air interfaces for dealing with the different requirements of densely populated areas (e.g., in Europe) versus sparsely populated areas (third world countries) [22]: 5.3 Services for UMTS and IMT 2000 327 • R1: radio interface between mobile station (MS) and base station (BS) • R2: radio interface between personal station (PS) and personal base station • R3: radio interface between satellite base station and mobile earth sta- tion (MES) • R4: additional air interface for paging FPLMTS terminals The plan is to use FPLMTS as a temporary or permanent substitute for fixed networks in developing countries and in rural areas where it is not eco- nomically feasible to set up fixed networks. At W(A)RC 1992 a spectrum of 230 MHz in the frequency bands 1885– 2025 MHz and 2110–2200 MHz was allocated to the FPLMTS system world- wide. These frequency bands were not exclusively reserved for FPLMTS, and can also be used in other systems. So in Europe, for example, the lower part of the allocated frequency band is occupied by GSM 1800 and the DECT system. The UMTS Forum is now requesting that 500 MHz starting from 1900 MHz be reserved for symmetrical and asymmetrical connections (see Figure 5.2). The earliest date being envisaged for the operation of FPLMTS is sometime between 2000 and 2005, the same as for UMTS. Since about 1995, FPLMTS has often been referred to as IMT 2000, but both designations refer to the same system operating around 2000 MHz. 5.3 Services for UMTS and IMT 2000 ETSI has published a preliminary list of services [10] that are to be supported by UMTS and are based on the ITU-R/CCIR recommendations for FPLMTS and the specifications of various European research projects of the RACE 2 programme. These UMTS-supported services are described below. 5.3.1 Carrier Services UMTS should be able to support ISDN as well as broadband ISDN bearer services. The following services are to be integrated [10]: • Circuit-switched services: – Transparent 64, 2·64, 384, 1536 and 1920 kbit/s with user data rates of 8, 16 and 32 kbit/s – Voice transmission – 3.1, 5 and 7 kHz audio transmission – Alternative voice or transparent data transmission with user data rates of 8, 16, 32 and 64 kbit/s 328 5 Third-Generation Cellular: UMTS • Packet-switched services: – Virtual calls and permanent virtual channels – Connectionless ISDN – User signalling Broadband (B) ISDN services with a transmission rate of 2 Mbit/s (so- called wideband services) are also to be offered by UMTS to mobile users. According to CCITT, these services will be classified as interactive or distri- bution services. Interactive services fall into the category of conversational services, message services or interrogation services. Conversational services are implemented through end-to-end connections, which can be either symmetrical bidirec- tional, asymmetrical bidirectional or unidirectional. Message services offer communication between users that is not time transparent. Interrogation ser- vices are used for the inquiry and receipt of centrally stored data. With distribution services information can be transmitted continuously from one central location to any number of users, with the users unable to influence the start or the end of a transmission. Another distribution service offers users the possibility of influencing the start of the information trans- mission. Asynchronous Transfer Mode (ATM) was specified by ETSI as the trans- mission technology for these B-ISDN services in the fixed (core) networks. In order to derive requirements for the radio interface from the bearer services being supported, ETSI, in accordance with the functional descriptions of B- ISDN and the ATM adaptation layer (AAL) (see Section 12.2.4), divided the bearer services into four classes [11]. These four classes of bearer services differ from each other in their time responses, bit rates and types of con- nection. Maximum bit ratio, maximum bit-error probability and maximum delay time are specified within each class of bearer service for the different communication scenarios. 5.3.2 Teleservices The teleservices to be supported by UMTS are divided into three classes [10]: 1. Teleservices that already exist in the fixed network in accordance with ITU-T/CCITT recommendations of the E, F and I series: • Telephony: – Voice – Inband facsimile (tele- fax groups 2 and 3) – Inband data trans- mission (using modem) • Teleconferencing: – Multiparty, added value services – Group calls – Acknowleged group calls – Multiple calls 5.3 Services for UMTS and IMT 2000 329 2. UMTS teleservices and applications, e.g.: • Audio and video transmis- sion • Paging • Broadcast services • Database inquiries • Data transmission • Directory services (e.g., telephone book) • Emergency call broadcasts • Short-message services: – Initiated by user – Terminated by user – Voice messages – Facsimile – Electronic mail • Teleaction services (e.g., remote control) • Mobility services (e.g., navigation or localization) • Electronic mail • Emergency calls • Teleshopping • Video monitoring • Voice messages 3. The services with the largest need for bandwidth are multimedia (MM) and interactive multimedia (IMM), such as data, graphics, images, audio and video, and combinations thereof. With UMTS it should be possible to use more than one of these media at the same time. Multimedia allows the transmission of more than one type of information, e.g., video and audio information. No further specifications exist yet for this service [10]. 5.3.3 Supplementary Services In the standardization of supplementary services a differentiation has prin- cipally been made between traditional non-interactive PSTN/ISDN services and personalized interactive supplementary services. The service provider has the option of making these services accessible to user groups or to individual users. The following classes of supplementary services have been proposed in accordance with the GSM and ISDN standards: Number identification, e.g., abbreviated dialling, protection against undesir- able calls, calling party identification Call offering, e.g., call forwarding Call termination, e.g., call holding Multiparty communication, e.g., conference call Group communication, e.g., communication in closed user groups 330 5 Third-Generation Cellular: UMTS Billing, e.g., credit balance Additional information, e.g., user-to-user signalling Call rejection, e.g., blocking all incoming calls A list of different service attributes is available in [10]. 5.3.4 Value-Added Services Personal mobility Using a smart card, subscribers are able to transfer their telephone numbers to any terminal. Virtual home environment (VHE) and service portability This allows the users to set up their own personalized service portfolios and use them in any other network. VHE emulates those services that are not actually offered in the visited network, so that users notice nothing differently from their own home network environments. Moreover, this is how the preliminary UMTS services are provided. Bandwidth-on-Demand This offers an efficient use of resources for services that have heavily varying requirements for transmission bandwidth, such as short-message services and video. Furthermore it allows users the independent option of selecting between a higher bandwidth for a max- imum quality of service or a lower bandwidth for more favourable costs. 5.3.5 Service Parameters A service is characterized by different parameters, some of the most important being: • Net bit rate • Symmetry of a service • Usage level • Coding factor • Maximum bit-error ratio based on channel decoding • Maximum delay allowed in data transmission The net bit rate is the product of the average number of bits that have to be transmitted within a certain period of time. The delay parameter describes how long a waiting time is allowed in the transmission of these bits. For example, a voice service requires a small delay whereas a packet-data transmission has minimal requirements for the delay times of individual packets. However, data transfer requires a considerably lower bit-error ratio than a voice service, because the redundancy of the voice codec can be fully utilized. A higher coding factor is needed for achieving a [...]... Output mapped to one or serveral DPDCH(s) Figure 5.6: UMTS channel coding 5.6.1.7 Channel Coding Most designs for the radio interface propose block coding, convolutional coding or hybrid versions of the two Convolutional coding is especially suitable for correcting evenly distributed bit errors, thereby providing a soft decision Block coding procedures, on the other hand, are mainly used to protect against... UMTS Radio Interfaces a depth Outer coding Code Interleavinga Format [ms] Inner coding Code Interleavinga Format [ms] Transmission rate [kbit/s] Overall coding ratio Source bit rate [kbit/s] Coding conditions Category 1 Category 2 Category 3 Category 4 (tail) Interleavinga Format [ms] Transmission rate [kbit/s] Overall coding ratio Source bit rate [kbit/s] Traffic channel voice Table 5.13: Channel coding... integrity of the radio resources of its cells, e.g., for handover decisions or combining and splitting functions for macro diversity 5.7.1 Radio Interface Protocol Architecture In the style of the ISO/OSI Reference Model, the radio interface is layered into the physical (L1), the data link (L2) and the network (L3) layers; see Figure 5.8 The data link layer is split in two sublayers: the Radio Link Control... Multirate concept Channel coding (FEC) Interleaving Spreading factor Spreading code Modulation Pulse shaping Detection Diversity Power control Handover IF handover Synchronization of BS Channel structure DS-CDMA FDD 5, 10 and 20 4.096; 8.192; 16.384 10 UL and DL: variable spreading level and/or multicode Turbo coding or inner convolutional coding and outer Reed–Solomon code; coding conditions dependent on... network offering the control of specific radio resources to connect a Mobile Station (MS ) to the UTRAN The RNS consists of a Radio Network Controller (RNC ) and one or more abstract Node B entities connected to the RNC through the Iub interface A Node B is in charge of radio transmission/reception in one or more cells to/from a MS connected through the Um interface The Radio Network Controller is responsible... evaluation of proposals for a radio interface must take into account the di erent multiple-access procedures with their specific transmission delays and interference characteristics as well as the performance of the proposed handover and power control protocols 5.5 Demands on the Radio Interface 339 Table 5.11: Di erent communications environments [11] Environm Prop conditions Mobility Business use... methods • Consider new types of radio technologies, such as packet-data transmission, dynamic adaptation of the interface parameters, soft handovers • Support service-specific response times through the protocols • Carry out signalling over the radio interface • Provide parameterizable protocols to allow new characteristics of the radio interface to be implemented through modification of the protocol parameters... 5.7 UMTS Terrestrial Radio Access Network Logical Architecture C-plane signalling GC Nt 349 U-plane information DC RRC L3 RLC RLC RLC RLC RLC L2/RLC RLC RLC RLC Logical channels MAC L2/MAC Transport channels PHY L1 Figure 5.8: Radio interface protocol stack and architecture 5.7.2 FDD Mode In one version of the UMTS radio interface, called W-CDMA, uplink and downlink are realized on di erent frequencies... Table 5.13: Channel coding for CODIT 5.6 347 348 5 Third-Generation Cellular: UMTS Core Network (Evolved GSM for Phase 1) Iu Iu I ur RNS RNS RNC RNC I ub I ub Node B I ub Node B Node B I ub Node B Um MS MS MS Figure 5.7: UTRAN architecture 5.7 UMTS Terrestrial Radio Access Network Logical Architecture An UMTS Terrestrial Radio Access Network (UTRAN ) consists of a set of Radio Network Subsystems (RNS )... data is based on asymmetrical error protection for three di erent categories of bits according to order of importance The codes used, which have di erent coding ratios between 2/5 and 1/2, are based on a rate-compatible punctured convolutional code The block interleaving includes di erent interleaving depths and interleaving lengths The channel coding procedure for the traffic channels of the data services . worldwide the di erent mobile communications systems available today, such as mobile telephone and telepoint, trunked radio, data radio, and satellite radio systems,. personal satellite radio (IRIDIUM, Globalstar, see Chapter 14) and other systems integrating aspects of these systems. Third-generation mobile radio systems,