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
Chapter 12: Radio Aspects
Section 2: The Development from 1995 to 2000
Michael Fa
¨
rber
1
12.2.1 The Work in SMG2 was Influenced by the Growing Success 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 work. In 1995 Alain Maloberti with-
draw from the SMG2 chairman’s position after having done this job since 1984 in an
excellent way. Niels Peter Andersen, who was with Tele Denmark mobile at this time,

was elected as the new SMG2 chairman. Niels had experience in mobile development, and
had served several years as SMG3 secretary. Furthermore, he was experienced in the way the
ETSI works. The long-term SMG2 vice chairman Henrik Ohlson was also with Tele Denmark
and the ETSI rules made it necessary to go for a new vice-chairman, due to the rule that the
officials should not be connected to the same company. In the Biarritz meeting in September
1995 I was nominated and elected as the vice-chairman of the group, and I kept the position
until SMG2 closed its activities in 2000. However, Niels and I continued to serve in similar
positions in the 3GPP GERAN structure.
When I was involved in the phase 2 activities of SMG2, a manager suggested to me, that
with the finalisation of phase 2 the standardisation work could be stopped. The estimation was
that there would be no future enhancements, and it would be sufficient to produce a product.
This prediction was not entirely correct. The growing success of GSM inspired people to get
new functions and features for the concept. Instead of a dry out of the work, a multitude of
ideas where launched. Looking at my notes during this time, I found it hard to describe the
work in a comprehensive way along a time line, because of the multitude of activities.
Therefore, I selected work items of the period, to structure the chapter. I also considered
issues, which failed to find their way into a product, and also the work items, which amounted
to big leaps of the concept. In 1995 the basic definitions of the GSM concept were 10 years
old, however the system concept showed a remarkable flexibility of integrating new functions
and features never considered 10 years ago. The key element of backward compatibility
requires sometimes painful work around solutions, but finally enables mobiles from phase
1 to still work in networks which may have a release 99 functional content.
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)
A not insignificant part of the work was influenced by the UTRA selection process and the

work on UTRA throughout 1998 before the work was continued in the 3GPP structure.
But even after the work transition of UMTS to 3GPP, SMG2 did important work related to
the third generation. For the conclusion of the 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.
Other ETSI groups steadily worked on improvements for the speech coders. The largest
leap in the late 1990s was the Adaptive Multirate Codec (AMR). This codec has the property
to align its coding rate or resource usage according to the link quality. The coder itself is a
task of another group, however SMG2 was in charge of defining the needed channel codings
and the performance thresholds. The AMR is part of Release 98, although a part of the work
penetrated into 1999.
Not all activities were entirely covered by the SMG2. Sometimes other standardisation
bodies took the lead for special needs. In that sense the US T1P1 took care of the frequency
adaptation to 1900 MHz. Later this work was integrated to the ETSI core specification. The
same applies for the location services LCS. The initial requirement was set up by the require-
ments of the US FCC authority. T1P1 took the lead work to develop the concepts for GSM
positioning. It was not a simple task, because from its properties, the GSM system is not in
any sense prepared for such a feature. Several positioning methods were allowed in the
concept, and after drafting the required CRs the discussion in SMG2 started together with
the people from T1P1. This review process was fruitful in that it catered for aspects of
compatibility and removed ambiguities. LCS based on the A-interface is part of the Release
98 functional content, although parts of the work spread largely in 1999.
For Release 5, enhancements of the LCS are planned, to allow operation via the Gb
interface and the Iu interface. This work is still ongoing.
12.2.2 Working Methods
The working methods changed significantly in the second half of the 1990s, and I think it is an
aspect worth mentioning. It also reflected the technical progress at this time, and the increas-

ing demand for data service capabilities. This may illustrate the peak of the iceberg of service
expectations for the wider consumer market of the future.
When I started my participation in GSM standardisation, just the secretary had a laptop
computer. A kind of 286 PC in the shape of a portable sewing machine, and likely of the same
weight. All documents where copied in large quantities, to have sufficient copies for all
delegates. More than one meeting followed the rule of copy availability, rather than the
agenda. Hosts were terrified by copy machine break downs, or late submission of input
documents. A part of the meeting room or parts of the corridors were filled with tables
carrying piles of documents. The delegates rushed off at every break to collect new available
documents. Experts had little notepad sheets with a matrix for the document numbers ticking
off the numbers of the documents successfully collected.
In the beginning revisions of documents resulted in a re-submission for the next meeting.
Or the document was so handsome, that a handmade version could be generated at the
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