GSM and UMTS (P12)

Chapter 12: Radio Aspects Section 1: The Early Years from 1982 to 1995 Didier Verhulst 1 12.1.1 From Analogue Car Telephone to Digital Pocket Phone CEPT took a very much forward looking decision when it decided to create, as early as 1982, the GSM Group with the mandate to define a second generation harmonised cellular system in Europe. At that time, the true market potential for mobile systems was not known. Also many technologies, which became key to the GSM radio design, were just emerging. This is true particularly of cellular networking, digital signal processing and real-time computing. In fact, GSM work started when the telecom industry was experiencing a fundamental shift between the ‘‘circuit switched analogue’’ world and the ‘‘packet switched digital’’ world. Microprocessors had just been introduced a few years before and it was the time when the first PC was created. The PTT administrations were introducing digital switches in their telephone network to replace mechanical switches, and they were developing their first packet switched data networks. We know today that this ‘‘digital’’ revolution ultimately lead to the Internet as we know it today, but this was not at all clear at the time. As we shall see, even the decision to select a digital rather than analogue modulation was not obvious and it took almost 5 years to be settled! This technological ‘‘turning point’’ was also a wonderful opportunity for a young genera- tion of engineers who had just learned in school the beauty of digital transmission and packet switching, and had therefore the opportunity to contribute actively to the creation of a new standard. 12.1.1.1 Marketing Requirements In the early 1980s, the market for a second generation cellular system was perceived as primarily radiotelephone in vehicle. In a study called ‘‘Future mobile Communication Services in Europe’’, prepared for the Eurodata foundation in September 1981, PACTEL introduced the concept of ‘‘Personal Service’’ as opposed to ‘‘Mobile Service’’ and explained that the total market for vehicular mobile could be as high as 20 million in Europe while the demand for low-cost hand-held service could ultimately reach 50% of the European popula- 1 The views expressed in this section are those of the author and do not necessarily reflect the views of his affiliation entity. GSM and UMTS: The Creation of Global Mobile Communication Edited by Friedhelm Hillebrand Copyright q 2001 John Wiley & Sons Ltd ISBNs: 0-470-84322-5 (Hardback); 0-470-845546 (Electronic) tion. But it was also concluded in the same report that a single system could not realistically serve both vehicle-mounted and portable terminals, because vehicle terminals would require high power to insure continuous coverage and complex control function to ensure seamless handover at all speeds, while low-power hand-held terminals would use a network of non- contiguous small cells and should not be considered as truly mobile. The work of GSM started initially with the objective of providing service primarily to vehicles, but it was recognised in the process that there should also be a proportion of portable devices as these started to appear even in first generation systems. Ultimately, the radio interface selected in 1987 by GSM turned out to be efficient enough to allow a true personal service, with continuous service anywhere, and a number of users largely exceeding the most optimistic early market projections. The first commercial GSM terminals in 1992 were vehicle-mounted or bulky transportable terminals, but the terminals in use a decade later are almost exclusively very compact hand-held devices! 12.1.1.2 Technical Background The cellular concept was first described in the 1970s by the Bell Labs, and the first pre- operational cellular network was launched in 1979 in Chicago. In Europe, the NMT system started operation in the Nordic countries in 1981. The key radio features of a cellular network, i.e. its seamless handover between base stations and the reuse of frequencies between distant cells were being implemented for the very first time in commercial networks when GSM work started. We were therefore to design a second generation when the true performances of the first generation were not yet known! Around 1980, we were just seeing the first practical implementations of digital processing in commercial domains such as microwave transmission and digital switching but, while the principles of digital encoding and modulation were already well known, there was still some doubts about the amount of processing which could be implemented in cellular base stations and, particularly, in mobile terminals. When the first descriptions of the GSM radio interface were published around 1987, showing the mobile stations monitoring in parallel a large number of logical traffic and signalling channels multiplexed in time, we heard sometimes the comments that this was far too complicated and could never be implemented in low cost terminals. Retrospectively, it is amazing to see the amount of software found today in low cost devices such as toys and also to realize that current GSM hand-held terminals already have more processing power than most micro-computers produced only a few years ago! 12.1.1.3 Building a New System As research engineers, we faced the ideal situation whereby we had to define the most advanced system possible with a very limited number of constraints. It was really the perfect ‘‘ blank page’’ exercise. We were given access to a completely new 900 MHz spectrum, up to 25 MHz in each direction, without any requirement to ensure upward compatibility with the first generation. In fact, because there was already several incompatible analogue systems in preparation in various countries of Europe, it became clear instead that only a truly innovative and more efficient system could be adopted by all administrations. In comparison, the US mobile industry tried in the late 1980s to define their own digital GSM and UMTS: The Creation of Global Mobile Communication310 second generation system, with a constraint of upward compatibility, in terms of channel spacing and signalling protocols, with their analogue first generation ‘‘ AMPS’’ . This was seen as a key advantage to allow the production of dual-mode analogue/digital mobiles, thus allowing the operators to digitalise their network progressively according to traffic demand while maintaining continuous coverage. As it turned out, this compatibility constraint delayed the introduction, in the ‘‘ digital AMPS’’ standard, of advanced features such as detailed measurements by mobile terminals, advanced handover control, and flexibility for innovative frequency allocations schemes while these features were in GSM from day one. As a consequence it took several releases – and many years – for the American second generation cellular standard to seriously compete with GSM in terms of performance. In fact, the digital AMPS standard never became a real threat to GSM in the world market, and it was even challenged in its own market by the IS-95 CDMA proposal in the early 1990s. 12.1.2 GSM Initial Work on Radio Specifications At the beginning of GSM, some essential decisions had to be made concerning radio para- meters, including the choice between analogue and digital modulation. In the case of a digital system, there was also a number of key specifications to be produced concerning the trans- mission bit rate, the type of modulation, the multiple access principles, the source and channel coding schemes, as well as the frame structure and the detailed mechanisms to handover from one cell to another. 12.1.2.1 Establishing ‘‘Working Party 2’’ (WP2) on Radio Aspects At the GSM 03 meeting in Rome in early 1984, it was decided to set up three specific working parties to progress on key technical subjects: services, radio and networking. The second working party, WP2, was mandated to investigate radio transmission aspects. I was asked to chair that group and we worked on a general model of the radio transmission channel applicable to a digital mobile system. The activity of WP2 continued in 1984-1985 during specific sessions in parallel to the GSM plenaries, and focused on early comparisons between various digital multiple access options. Early 1985, I was leaving the French Administration and I handed over WP2 responsibility to Alain Maloberti. During 1985, it was decided by GSM that due to the increasing amount of work required, the Working Parties would hold dedicated meeting every three months during the interval between GSM plenaries. The years 1985-1987 were very important for WP2 as they allowed the selection of key parameters for the radio subsystem. This process was lead by radio experts from various PTT administrations involved in WP2, and it was supported by experi- mental programs involving manufacturers from various European countries. In February 1987, when the main options had been decided and the work was focusing on the finalization of the first release of GSM recommendations, ETSI allowed manufacturers and research institutes to contribute also directly to the work of GSM plenary as well as working parties. The production of the GSM standard was therefore a truly European effort involving all concerned parties of the industry. Chapter 12: Radio Aspects 311 12.1.2.2 Analogue Versus Digital On the comparison between analogue and digital options, it was by no means obvious at that time that the quality of encoded speech could be equivalent – not to mention better – than plain analogue FM when considering (i) the limitation in terms of bit rate to accommodate an average spectrum utilization of about 25 kHz per carrier as in analogue systems and (ii) the fact that gross bit error rate over the fading mobile radio carrier could be as high as 10 22 . Also, while we were evaluating digital options, analogue systems such as NMT were even able to improve their capacity with channel spacing reduced from 25 to 12.5 kHz while maintaining a good quality of speech. From the early days, we did work however with the ‘‘ working assumption’’ that the GSM system would be digital, but this assumption was only formally confirmed in 1987 when we could prove, including with field trials, that a digital system would really outperform all analogue systems. 12.1.3 The Choice of the Multiple Access Scheme One interesting advantage of digital transmission is that there exists a variety of methods to multiplex several users over the same radio carrier, namely ‘‘ Frequency Division Multiple Access’’ (FDMA), ‘‘ Time Division Multiple Access’’ (TDMA) and ‘‘ Code Division Multiple Access’’ (CDMA). In comparison analogue systems are restricted to the ‘‘ one carrier per active user’’ FDMA scheme. I remember some meetings during the early years where the basics of TDMA had to be explained to experienced radio engineers who had always thought of radio resources in terms of ‘‘ frequency carriers’’ and never in terms of ‘‘ time slots’’ . The fact that several mobiles could coexist without interference on the same frequency connected to the same base station was truly intriguing for a number of delegates! During 1984, WP2 had already identified the three multiple access options FDMA, TDMA (narrowband or wideband) and CDMA (frequency hopping or direct sequence) which would be the object of much debate until 1987 when the ‘‘ narrowband TDMA/frequency hopping’’ solution was selected. Interestingly enough, several years later, quite similar discussions took place to compare wideband TDMA with CDMA in the context of UMTS. 12.1.3.1 The Selection Process GSM decided to launch a series of experimental digital systems to facilitate the selection of the radio transmission and multiple access scheme. This trial activity was initially supported by the French and the German administrations who decided to collaborate in the definition of an harmonized system, and agreed in 1985 to focus their efforts towards the selection of a digital second generation system. Accordingly, manufacturers were selected from both coun- tries to develop prototype systems implementing different digital radio subsystem concepts. Soon after, the Nordic administrations also decided to join and additional proposals were submitted to the experimentation program which took place in Paris from October 1986 to January 1987, at the France Telecom research centre, CNET, under the auspices of the GSM permanent nucleus. Eight different system proposals, corresponding to nine different radio subsystem solutions (one system proposal having two different multiple access solutions for mobile-terminated GSM and UMTS: The Creation of Global Mobile Communication312 and mobile-originated links) were proposed for the Paris trial. Sorted out by multiple access type, they were the following: GSM needed to compare on the same basis all these different radio subsystems. Quanti- tative measurements were therefore performed with identical environmental conditions created with propagation simulators, designed according to the specifications agreed by the COST 207 Working Group on propagation. The work of this group have been very important since all the previous mobile channels propagation models could be simplified assuming narrowband transmission, while a more general model and simulators, applying as well for wideband transmission had to be elaborated. In order to crosscheck the behaviour of the radio subsystems with the propagation simulator and in a real environment, qualitative field measurements were also organised in Paris around the CNET. Before the experimental program took place, GSM had decided that any new system would have to satisfy five minimum requirements and that the comparison between multiple access options would be based on eight additional comparison criteria. FDMA † MATS-D (mobile to base), by Philips/TeKaDe, Germany ‘‘ Narrowband TDMA’’ † S900-D, by ANT/BOSCH, Germany † MAX II, by Televerket, Sweden † SFH900, by LCT (now Nortel Matra Cellular), France † MOBIRA, by Mobira, Finland † DMS90, by Ericsson, Sweden † ADPM, by ELAB, Norway ‘‘ Wideband’’ TDMA (combined with CDMA) † MATS-D (base to mobile), by Philips/TeKaDe, Germany † CD900, by Alcatel SEL 1 ATR and AEG and SAT, Germany and France Minimum requirements 1. Quality: the average speech quality must be equal to that of first generation compounded FM analogue systems 2. Peak traffic density: the system must accommodate a uniform traffic density of 25 Erl/ km 2 , with a base station separation equal or greater than 3.5 km 3. Hand-held stations: the system shall be able to accommodate hand-held stations 4. Maximum bandwidth: the maximum contiguous bandwidth occupied by one imple- mentable part shall be less than or equal to 5 MHz 5. Cost: the cost of the system, when established, shall not be greater than that of any well established public analogue system Chapter 12: Radio Aspects 313 The results of the Paris trial lead to two fundamental conclusions (for more details refer to Doc GSM 21/87 and GSM 22/87): 1. A digital system could satisfy all the minimum requirements set by GSM, and in fact a digital system would do better than any analogue system for all five criteria; 2. With respect to the comparison criteria, the radio experts of WP2 agreed on the following comparison table (Table 12.1.1) regarding the three main ‘‘ broad avenues’’ of system options. The conclusions of the WP2 work were: 1. A digital system can exceed the minimum requirements compared with an analogue system; 2. TDMA has advantages over FDMA; 3. Narrowband TDMA is preferred to wideband TDMA although both can meet the mini- mum requirements. There was a majority of countries supporting the choice for narrowband TDMA. But it was also apparent that wideband TDMA was a viable option and, as recalled by Thomas Haug in System comparison criteria 2 1. Speech quality 2. Spectrum efficiency 3. Infrastructure cost 4. Subscriber equipment cost 5. Hand portable viability 6. Flexibility to support new services 7. Spectrum management and coexistence 8. The risk associated with their timely implementation GSM and UMTS: The Creation of Global Mobile Communication314 Table 12.1.1 Comparison results for the 3 main system options Preferred option (¼ for comparable) Analogue/ digital FDMA/ TDMA Narrowband/ wideband TDMA 1. Speech quality ¼¼¼ 2. Spectrum efficiency ¼¼Narrowband 3. Infrastructure cost Digital TDMA Narrowband 4. Mobile cost Digital TDMA Narrowband 5. Hand portable viability Digital TDMA Narrowband 6. New services flexibility Digital TDMA ¼ 7. Risk Analogue FDMA Narrowband 8. Spectrum management ¼ FDMA Narrowband 2 GSM required that, for any selected digital scheme, performance with respect to criteria 1–6 would have to be at least equal to that of analogue systems and would be significantly better in at least one criteria. Candidate systems were also compared with respect to criteria 7 and 8. Chapter 3, a lot of additional technical and political discussions took place before GSM could finalize in May 1987 its choice for narrowband TDMA with frequency hopping. 12.1.4 Tuning the Details Undoubtedly, the ability of GSM to agree in 1987 on the ‘‘ narrowband TDMA’’ broad avenue was a very important achievement. But it was by no means the end of our efforts: rather it was the beginning of very intense activity which lead to the finalisation of the details to be specified in the GSM radio interface. The exact definition of the physical layer of the radio interface by WP 2 was also a prerequisite before the functional specifications and the detail protocol design of the logical layers could be progressed by WP 3. It was decided that the key radio aspects would be documented in the 05.xx series of ‘‘ Recommendations’’ (later called ‘‘ Technical Specifications’’ ) describing the different chan- nel structure, the channel coding scheme, the modulation, the transmitter and receiver char- acteristics, the measurement and handover principles, the synchronisation requirements, etc.… In comparison to many other recommendations produced by GSM, the 05.xx services may appear pretty thin: in total it was less than 200 pages! But each parameter specified was often the result of very thorough analysis and had to be supported by detailed simulations and experimental measurements. 12.1.4.1 Channels Structure It was defined that the ‘‘ physical layer’’ would support a variety of traffic and signalling channels. Hence a large number of new acronyms were created: TCH/FR, TCH/HR, BCCH, CCCH, SDCCH, SACCH, FACCH, AGCH, PCH, RACH, etc.,… To make things more confusing, it was decided also that control channel BCCH/CCCH multi-frames would be made of 51 frames (of 4.615 ms) while the traffic channel multi-frames would be made of 26 frames (these two numbers being chosen as ‘‘ prime’’ to allow a mobile in traffic having an idle time slot every 26 frames to ‘‘ slide’’ across the complete BCCH multi-frame every 51 £ 26 ¼ 1326 frames). The exact structure of each frame, composed of eight time slots of 148 bits each, was also decided together with the allocation of each bit, including those for training sequences and those for actual data, with a specific channel coding and interleaving scheme for each type of traffic and signalling channel. 12.1.4.2 Modulation and Channel Coding The experimental program performed in Paris, and the additional analysis performed by WP2, had shown that particular care had to be given to the selection of the modulation and channel coding schemes. It was clear also that the performance of the radio link, under mobile propagation conditions characterized by severe multi-path conditions, would also depend strongly on the equalisation algorithms implemented in mobile station and base station receivers. In fact, as reported by Thomas Haug in Chapter 2, Section 1, the final choice of the modulation scheme was difficult to reach and the initial preference of WP2 for ADPM was finally changed to GMSK. The reason for this choice was that the latter modulation method did not include any redundancy; therefore all the redundancy could be used for channel coding, which was much more efficient by taking advantage of interleaving and Chapter 12: Radio Aspects 315 frequency hopping schemes, particularly for slowly moving terminals. It was also decided by WP2 that the equalisation method should not be specified in the standard, thus leaving free- dom of implementation in the base station and mobile receivers. As it turned out, for all manufacturers, we saw significant improvements in terms of receiver performance between early versions and more stabilised versions of their products (which ultimately performed better in terms of sensitivity than the minimum requirements set in the recommendations). GSM was right not to over-specify and to simply define minimum performances rather then decide on exact implementation. In addition to the choice of channel coding for full-rate speech 13 kbit/s, a substantial effort was dedicated very early to defining several types of data traffic channels, including full-rate at speeds ranging from 2.4 up to 9.6 kbit/s, and also half-rate from 2.4 up to 4.8 kbit/s with different levels of error protection. Retrospectively, we probably defined too many types of low bit rate data channels as the demand for high speed became quickly dominant and there is today very few mobile data applications with speed less than 9.6 kbit/s. A few years later, as part of the GSM phase 21 program, WP2 efforts would in fact be redirected towards enhanced data coding at speeds of 14.4 kbit/s instead of 9.6 kbit/s, associated with the use of multiple time slots (HSCSD and GPRS). More recently, the ‘‘ Edge’’ modulation was also proposed to increase the bit rate over a single carrier above 300 kbit/s! It is quite remarkable that a channel structure initially designed to squeeze many low bit rate data circuits on a single carrier could be adapted later, without too many difficulties, to allow bursty traffictobe transmitted at a much higher bit rate. Concerning speech, GSM decided in 1993 to introduce half-rate coding as an option to increase capacity. In more recent versions of the standard, ‘‘ Enhanced Full-Rate’’ (EFR) and ‘‘ Adaptive Multi-Rate’’ (AMR) speech coding options were also defined to provide other trade-off’s in terms of quality versus spectrum efficiency. These various options are all compatible with the initial definition of the GSM radio channels, and provide a good demon- stration of the flexibility we obtained with our digital foundation. 12.1.4.3 Handover Mechanisms In first generation analogue cellular systems, the decision to handover from one base station to another is a central process made by the network based on ‘‘ uplink’’ signal strength received at base stations. The second generation GSM system, being digital and time division multiplexed, had the flexibility to introduce innovative schemes for handover. In particular GSM Mobile Stations (MS), which are not transmitting or receiving all the time, have the capability to (i) perform measurements of the ‘‘ downlink’’ signals received from the serving as well as the neighbouring Base Transceiver Stations (BTS) and (ii) report these measure- ments regularly to the network. The handover decision algorithm, implemented in the Base Station Controller (BSC), utilizes both ‘‘ uplink’’ measurements performed by the BTS and ‘‘ downlink’’ measurements reported by the MS. This technique is referred to as ‘‘ mobile assisted handover’’ which proved to be a very efficient and future proof feature of GSM. GSM being digital, the measurements of radio transmission performance could be based not only on signal strength but also on estimates of the Bit Error Rate (BER) and Frame Erasure Rate (FER) for speech. WP2 dedicated big efforts to the definition of the precise radio measurements to be performed by MS and BTS, and to the detailed mechanism for the decision to handover. There was at that time a considerable debate on whether we needed GSM and UMTS: The Creation of Global Mobile Communication316 to specify the complete handover algorithm, but the GSM group took the wise decision to define only the radio measurements, and not to specify the handover algorithm itself which was to become a proprietary implementation of each base station system manufacturer. In doing so, GSM left a lot of freedom for competitive innovation and, indeed, we saw a lot of new ideas introduced in the 1990s when the GSM networks had to cope with ever increasing traffic demands. It turned out that the initial radio subsystem specifications, and therefore all the mobiles produced during the early years, could support advanced radio mechanisms introduced later such as ‘‘ concentric’’ cells and multiple layer ‘‘ micro cell\umbrella cell’’ handover. 12.1.4.4 Spectrum Efficiency Features While selecting the parameters of the GSM radio subsystem, priority was given to overall network spectrum efficiency as opposed to the efficiency of a single base station. GSM had indeed derived precise modelling of the maximum number of users per cell as a function of various parameters such as the carrier spacing, the voice activity radio, the availability of various diversity schemes, etc.,… It was concluded during the early definition stages that a good system, be it FDMA or TDMA, should always include a good level of inter-cell interference rejection even if it would be with added coding redundancy and therefore less carriers per cell. Also GSM took the decision to introduce from day 1 Slow Frequency Hopping (SFH) as a mandatory feature for terminals: this feature added some initial complexity but it turned out to be very useful many years later when GSM operators were able to implement high-capacity cellular reuse strategies taking into account the interference diversity effects provided by SFH. Examples of such innovative strategies include the utilisation of ‘‘ fractional’’ reuse clusters whereby GSM cellular planning with SFH is based on a minimum reuse distance which is non uniform for all frequencies, or the option to use all the hopping frequencies in every cell, controlling the interference level by the load of the cells. With features such as voice activity detection, interleaving, channel coding and frequency hopping, GSM had introduced very early in its TDMA design some advanced functionalities which differentiate GSM from other more traditional FDMA or TDMA systems. These advanced features also allowed GSM to compete well with the IS-95 CDMA standard when it was proposed in the early 1990s by American industry. 12.1.4.5 New Frequency Bands In the early 1990s the ‘‘ PCN’’ initiative was promoted by the UK Administration to extend the spectrum utilisation of GSM from the 900 to the 1800 MHz band. Accordingly, some adaptations of the radio subsystem were made to utilise 75 MHz of additional spectrum in the so-called ‘‘ DCS 1800’’ band. New types of mobile stations were defined, with reduced power to allow easier implementation of hand-held devices in such ‘‘ Personal’’ Communica- tion Networks. As it turned out, the majority of GSM terminals produced today are in fact dual-band as many cellular networks have increased their capacity by combining the utilisa- tion of both 900 and 1800 MHz spectrum. The flexibility of the GSM standard to adapt to new spectrum was very attractive, and the exercise was reproduced again later to accommodate, in the US, the so-called PCS spectrum Chapter 12: Radio Aspects 317 at 1900 MHz (accordingly some terminals became tri-band 900-1800-1900). Other extension bands have also been studied, including specific frequencies allocated in the 900 MHz band for railways applications, as well as more recently extensions of GSM also in the 450 MHz and the 800 MHz bands. 12.1.5 Group work towards a single standard It would be difficult to name only a few people as the main contributors to the definition of the GSM radio interface. During these early days of GSM, there was a truly open collaboration between many European organisations, originally limited to PTT’s, then rapidly extended to their industrial partners as discussed above. The discussions were very open and in a true collaborative spirit. At that time, in comparison with more recent practices in standardisation forums, we were also less concerned by the need to protect the Intellectual Property of our technical contribu- tions and, as a result, we were able to exchange rapidly and openly a lot of new ideas between many contributors. In that respect I am not sure that, today, the creation of an innovative standard like GSM could be organised again so efficiently. In the radio interface definition, we could probably isolate contributions from many speci- fic GSM participants. But the more remarkable result is that, even with a large number of inputs, the group was able to converge quite rapidly towards a consistent, well optimised and future proof foundation for its radio interface. GSM and UMTS: The Creation of Global Mobile Communication318 [...]... 3GPP Release 99, UMTS contained a feature handover from UMTS to GSM To have a useful functionality, this process has to work in both directions SMG2 started therefore in 1999 to specify the conditions for a GSM to UMTS handover This feature was available on time when also the UMTS standard achieved a level of completeness As an addendum in the 3GPP Release 4 the GSM to narrowband TDD handover was incorporated... needed Class II and III (8 W and 5 W) mobiles where around, especially as vehicle mounted devices Also car modules or adapters used this power 324 GSM and UMTS: The Creation of Global Mobile Communication classes However, class II and III stayed a minority in the market The mainstream GSM mobile is the 2 W class IV mobile station The first suitable hand-held class ruled the market, and dictated also,... was simply called UIC UIC stands for Union International des Chemises This is a railway organisation, which first looked into the subject of a new generation of railway communication systems GSM was one of the candidate technologies and succeeded finally in the selection process For GSM railway, a new 2 £ 4 MHz bandslot was defined, attached to the lower band of E -GSM This guardband free allocation of course... delta concept, and I can still recall the increasing stress and tension during this phase of the work Between the question and answer workshop and the last UMTS ad-hoc meeting in Helsinki, I participated in a WBP meeting in Edinburgh This session ‘‘just’’ dealing with GSM matters was like a realm to me, down to earth on technical discussion without the tensions of the UMTS sessions At the UMTS ad-hoc... UTRAN and a GERAN which is based on the existing GSM infrastructure As a consequence this requires an Iu interface for the GERAN, and an adoption 338 GSM and UMTS: The Creation of Global Mobile Communication Table 12.2.1 GERAN high level block diagram Function Functional split with Iu interface Functional split with Gb interface Ciphering Compression (IP header and payload) Termination of LLC and SNDCP... activities to adopt GSM for the US market and this was going along with a GSM Chapter 12: Radio Aspects 323 definition for the PCS frequency band in the 1900 MHz range The initially independent work from T1P1 concluded in a reuse of channel numbers for 1900 MHz, which had already a definition in the 1800 MHz band This is troublesome for multi-band mobile stations comprising 1800 and 1900 MHz The ARFCN... chairman and vice chairman, respectively of SMG2 12.2.14 The GSM EDGE Radio Access Network (GERAN) GERAN is the name for the network evolution of GSM towards the third generation networks, based on the 200 kHz TDMA system, providing full backward compatibility to GSM GERAN is further the name of the TSG in 3GPP which continues the SMG2 work To get a better understanding it is worth comparing the UMTS and. .. is a completely implemented part of the standard However, no products followed, and it must be considered that this work ended in a dead end street 330 GSM and UMTS: The Creation of Global Mobile Communication 12.2.12 Repeater, Feeder Loss Compensator and Other Auxiliaries These entities were not originally considered as being part of the mobile network, and therefore not considered to be specified.. .GSM and UMTS: The Creation of Global Mobile Communication Edited by Friedhelm Hillebrand Copyright q 2001 John Wiley & Sons Ltd ISBNs: 0-470-84322-5 (Hardback); 0-470-845546 (Electronic) Chapter 12: Radio Aspects Section 2: The Development from 1995 to 2000 ¨ Michael Farber 1 12.2.1 The Work in SMG2 was Influenced by the Growing Success of the GSM Standard Reflecting on the time... mentioned before the system scenarios had to be considered carefully to avoid harmful effects between GSM and the railway bands As an off meeting activity Jesper Evald (this time with Danish Rail) and I re-calculated the GSM- R system scenarios to enable the preparation of the needed change requests, and to have the input for the 05.50 Once again it was found very valuable to have the 05.50 as a material . of the GSM Standard Reflecting on the time period I was asked to describe, the growing success of GSM and the work of UMTS mostly influenced the standardisation. 99. Release 99 is the first UMTS release, and can provide simultaneous real and non- real time services. Operators having GSM and UMTS developed an interest