Mobile Communications/History and Development of Mobile Communication Systems

1. Mobile Communications
2. Mobile Radio Systems of the 2nd and 3rd Generation - an Overview
3. History and Development of Mobile Communication Systems

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# OVERVIEW OF THE THIRD MAIN CHAPTER #

In the following, the most important representatives of the mobile radio systems established in 2011 are briefly introduced:

• $\rm GSM$  – "Global System for Mobile Communications":   Second generation of mobile communications  $\rm (2G)$;
      detailed description in the third chapter of the book  "Examples of Communication Systems".

• $\rm UMTS$  – "Universal Mobile Telecommunications System":   Third Mobile Generation  $\rm (3G)$;
      detailed description in the fourth chapter of the book  "Examples of Communication Systems".

In detail are discussed:

• Characteristics and examples of the different mobile radio generations  $\rm (1G, 2G, 3G)$,
• some statistics on the increase in the number of mobile users,
• basic similarities and differences between GSM and UMTS,
• important system components:   speech and channel coding, interleaving, encryption,
• the multiple access methods FDMA/TDMA (GSM) and CDMA (UMTS),
• the modulation methods GMSK (GSM) and OFDM (UMTS),
• further developments HSCSD, GPRS, EDGE (GSM) as well as HSDPA, HSUPA (UMTS).

Subsequently, the  "fourth chapter"  the newer mobile radio system  $\rm LTE$  ("Long Term Evolution") is discussed.

Precursor of today's mobile radio networks

Today (2020) every child knows what mobile radio is, and only a few young people can imagine that life is possible without a smartphone, Facebook and the countless mobile phone features.  Twenty years ago, things were completely different:   Only a few people knew about the existence of such mobile communication systems and even fewer had ever held a mobile phone in their hands until then.

An important prerequisite for the realization of mobile communication systems was the theory of electromagnetic waves, which  $\text{James Clerk Maxwell}$  developed in 1864 and was decisively further developed by  $\text{Heinrich Hertz}$.  Another great pioneer of radio technology was  $\text{Guglielmo Marconi}$, who in 1896 publicly demonstrated wireless telegraphy for the first time and in 1901 succeeded in making the first transatlantic–radio transmission.  In 1909 he received the Nobel Prize for his inventions.

Since the technology of Marconi was also used intensively in transatlantic shipping and its use was even prescribed after the sinking of the Titanic (1912), the emergence of mobile communication systems can be dated to around the beginning of the 20th century.

The first mobile radio network in Germany was the  $\text{"A–Netz"}$, which was put into operation in 1958 and shut down in 1977.  It operated in the frequency range from 156 MHz to 174 MHz with analogue frequency modulation (FM) and was used nationwide by up to 11000 subscribers (but certainly not simultaneously).  The transmission technology filled the trunk of large limousines.

The  $\text{"B–Netz"}$  operating from 1972 to 1994 was also based on analogue FM around 150 MHz.  At its heyday around 1985, this was used by 27000 subscribers and provided 850 radio channels, already taking into account the reuse of the same frequencies in sufficiently distant radio cells.  The volume of the transmitting and receiving equipment was significantly smaller than that of the "A network" due to the progress made in the meantime in the field of microelectronics.

The last predecessor model of today's systems is the analogue  $\text{"C–Netz"}$  in the frequency range around 450 MHz, which was operated in Germany between 1986 and 2000 by the Deutsche Bundespost.  In 1993 it had its maximum number of subscribers of 850000, offered a coverage of 98% and provided some features which became standard for the following generations of mobile phones, for instance "Handover" and "Roaming".

The "C network" is considered to be part of the  »first generation of mobile communications«   as well as some other cellular systems that emerged almost simultaneously in other countries:

• AMPS  (Advanced Mobile Phone Service), Bell Labs, USA, 1979,
  
• ACS  (Advanced Cellular System), Comvik, Sweden, 1981,
  
• NMT  (Nordic Mobile Telephone), Sweden–Norway–Denmark, 1981 and 1986,
  
• TACS  (Total Access Communication Standard), Great Britain, 1985,
  
• RTMS  (Radio Telephones Mobile System), Italy, 1985,
  
• RC 2000  (Radio Com 2000), France, 1986.
  

Second generation mobile radio systems

All the first generation mobile systems mentioned above  $\rm (1G)$  were national solutions with the following consequence:

• It was not possible to communicate between the individual systems.
  
• The end devices (one should not talk yet of cellphones) could be used only in the respective network, whereby the market was very limited and the economic success failed to materialize.
  

At the beginning of the 1980s there were already initial efforts to unify the system.  The second generation  $\rm (2G)$  of mobile radio systems was created, characterized by

• a continuous digital voice transmission,
  
• the provision of data services.
  
  

In the second generation mobile radio systems, voice transmission was the central task and data transmission was rather secondary, whereas a characteristic of the third generation, for example of  $\text{UMTS}$ , was the so-called mobile Internet.

The most important 2G mobile communications standard was  $\rm GSM$  – $\rm G\hspace{-0.01cm}$lobal  $\rm S\hspace{-0.01cm}$ystem for  $\rm M\hspace{-0.01cm}$obile communications.  This system presented in the chapter  "Characteristics of GSM"  was not only widely used in Europe, but many regions worldwide have also adopted this standard.  GSM was the fastest growing communication technology of all times until then.

The different GSM systems were

• $\text{GSM 900}$:   frequencies around 900 MHz ("D networks"; in Germany TD1 and Vodafone D2),
  
• $\text{GSM/DCS 1800}$:   frequency range around 1.8 GHz ("E networks"; in Germany all operators at that time),
  
• $\text{GSM/PCS 1900}$:   frequency range around 1.9 GHz (mainly used in the USA).

In addition, second generation mobile communications systems are also included:

• the  $\rm PDC$–Netz  (Personal Digital Cellular),
  
• the cordless standard  ⇒   $\rm DECT$  (Digital Enhanced Cordless Telecommunications),
  
• the satellite system standards  $\rm LEO$  (Low Earth Orbit)  and  MEO (Medium Earth Orbit),
  
• the terrestrial aeronautical radio network  ⇒   $\rm TFTS$ (Terrestrial Flight Telephones System>),
  
• Test networks in the USA such as  $\rm D–AMPS$  and  $\text{Qualcomm–CDMA}$.
  
  

After all, 2G mobile radio systems also include wireless local loops with very limited mobility such as 

• $\rm WLL$  (Wireless Local Loop)  and 
• $\rm RLL$  (Radio in the Local Loop ).

The genesis of GSM

The GSM standard was introduced around 1990 with the aim of providing a unified pan-European mobile telephone system and network.  The use for data transmission was not the main focus, but was constantly improved by additional specifications regarding data rate.

Below are some data on the historical development of GSM:

• 1982  At the  "Conférence Européenne des Postes et Télécommunications"  (CEPT) the  "Groupe Spécial Mobile"  – abbreviated GSM – is established.
• 1987  Cooperation is formed between 17 future operators from fifteen European countries and work is begun on the GSM specification.

• 1990  Phase 1 of the GSM 900 specification (for 900 MHz) is completed.  Matching for the GSM/DCS 1800 system ("Digital Cellular System") around 1.8 GHz begins.

• 1992  Most European GSM network operators start commercial operation with voice services.  By the end of 1992, thirteen networks in seven countries were on air.

• 1995  Phase 2 of standardization begins and includes fax, data and SMS roaming and adaptations for GSM/PCS1900, which goes into operation in the USA in the same year.

• 1999  With the introduction of WAP ("Wireless Application Protocol"), it will be possible for the first time to transfer Internet content and other interactive service offerings to mobile devices.

• The introduction of HSCSD ("High Speed Circuit–Switched Data") increases the data rate from 9.6 to 14.4 kbit/s and further to 57.6 kbit/s by bundling four TDMA–channels.

• 2000  The GPRS extension ("General Packet Radio Service") simplifies wireless access to packet-switched data networks.  The (theoretically) data rate is 171 kbit/s.

Data rate for GSM and its further developments

• 2000  Phase 2+ defines EDGE ("Enhanced Data Rates for GSM Evolution"), which could theoretically triple the GPRS rate.  In reality, however, only 384 kbit/s are actually reached.

• 2006   T–Mobile is the first German mobile phone provider to begin providing EDGE.  In the next few years, the operators Vodafone, O2 and E–Plus will follow suit in Germany.

The graph shows the development of the GSMdata transmission rate on a linear scale.  The abscissa indicates the year of market launch (in Germany), not the year of standardization.  There were always several years in between.

Third generation mobile radio systems

Shortly after the GSM standardization it became apparent that the bandwidth requirements for the use of multimedia services could not be covered.  The next, third generation of mobile radio systems should be based on the  $\text{CDMA principle}$  ("Code Division Multiple Access").

Essential preparatory work was:

• 1949   First ideas about the CDMA principle by  $\text{Claude Elwood Shannon}$  and  $\text{John Robinson Pierce}$.
  

• 1970   Various CDMA developments for military systems, for example  $\text{GPS}$  ("Global Positioning System").
  

• 1989 –1992   Basic research on the characteristics of future mobile radio systems within the framework of the EU programme "RACE–1"
  ("Research, Analysis, Communication, Evaluation").
  

• 1992 –1995   EU programme "RACE–2" with focus "Development of system concepts", based on the results of "RACE–1".
  
  

First considerations on the standard  $\text{IMT–2000}$  ("International Mobile Telecommunications at 2000 MHz") were made by the ITU in 1992.  From this, with  $\text{UMTS}$  ("Universal Mobile Telecommunications Systems") the best known mobile radio system of the third generation (3G) developed.  However, a number of intermediate steps were still necessary before it could be launched in Germany (2004):

• 1996   Foundation of the UMTS Forum in Zurich – renaming of the planned European standard "W–CDMA" to "UMTS".

• 1998   Adoption of the modes "W–CDMA" and "TD–CDMA" into UMTS standard at the ETSI–SMG meeting in Paris.

• 1998   Foundation of the 3gpp–Forum ("3rd Generation Partnership Project") by the committees ETSI–SMG, T1P1, ARIB TTC and TTA.

• 1999   Adoption of the UMTS–R99 standard (Release 1999) by ETSI.  This standard is considered the basis for the first available UMTS terminals.

• 2001   UMTS Release 4 as a further development of UMTS–R99:  Quality of Service (QoS) is now supported not only on the radio interface but also in the fixed network.

• 2001   First commercial UMTS network of the Norwegian company TELENOR.

• 2002   UMTS Release 5:  The architecture based on the GSM fixed network is replaced by a completely IP based network.  In addition, HSDPA is defined.

• 2002   First voice and data connection from Nortel Networks and Qualcomm.  These companies are considered pioneers in the implementation of UMTS technology.

• 2005   UMTS Release 6, offering users improved QoS and providers more effective resource management.  Besides definition of HSUPA.

• 2007   UMTS Release 7:  Consideration of real-time applications such as VoIP ("Voice over IP") and "Evolved EDGE", only shortly after the market launch of 2G–EDGE.

The years in this list refer in each case to the specification.  It usually took another two to four years before a further development was actually used.

Let us briefly summarize the list so far, whereby we refer mainly to the situation in Europe and especially in Germany around the year 2011:

$\text{Definition:}$  The  »Third generation mobile communications systems«  $\rm (3G)$  include

• $\text{UTRA-FDD}$  ("UMTS Terrestrial Radio Access–Frequency Division Duplex") according to the UMTS specifications up to and including Release 7.
  

• This includes  $\rm HSDPA$  ("High Speed Downlink Packet Access") according to Release 5 and  $\rm HSUPA$  ("High Speed Uplink Packet Access") according to Release 6.
  

• The further development  $\rm EDGE$  from GSM (in higher modes with 8–PSK modulation) is assigned to  $\rm 3G$  whereas   $\rm GPRS$  still belongs to the  $\rm 2G$  systems.

The development of UMTS is far from being completed with the standards mentioned above:

• In December 2008, Release 8 specified, among other things, the variant  $\rm E-UTRA$  (evolved UTRA), better known as  $\text{LTE}$  ("Long Term Evolution").
  

• Already in March 2011 with the UMTS Release 10, LTE, which had not yet been introduced at all, was then further developed into  $\rm LTE-A$  ("LTE Advanced").
  
  

These mobile communications standards, which will be the latest in 2011, are discussed in detail in the fourth main chapter of this book  "Mobile Communications".  They belong to the fourth generation of mobile communications systems  $\rm (4G)$.  Already at this time it was foreseeable that further generations would follow.

But before that, we will deal in a highly compressed form with the following topics (details can be found in the book "Examples of Communication Systems")

• the  $\text{similarities between GSM and UMTS}$,
  

• the  $\text{characteristics of GSM}$, and
  

• the  $\text{characteristics of UMTS}$.
  
  

In the next section, we present some figures published on the Internet to illustrate the success of digital mobile communications in the years up to 2009, with a decline in GSM and a disproportionate increase in UMTS and LTE.

The success story of digital mobile radio

The following information is taken from the lecture notes  [Hin08]  as well as from various articles found on the Internet, for example from  [Göt08]  and  [Waa10].  Not a single entry in any of the tables is based on own research of the LNTww authors.

»Growth rates of German mobile networks«  (as the sum of the four German providers)

German mobile networks from 1992 to 2008

• In the years from 1992 to 2008, the number of registered mobile end devices rose from one million to more than 100 million (first line). Since the end of 2005, the number of mobile subscriber lines has already exceeded the population of Germany.
  

• The highest growth rates were in 1992, directly after the introduction of GSM (although still at a low level) and around the turn of the millennium (darker background in line 2).
• We remember the euphoria of that time shortly before "bursting of the Internet bubble" when the auction of the German UMTS licenses for a total of 20 years duration and 120 MHz bandwidth brought in more than 100,000,000,000 DM (≈ 50.8 billion Euro).
  

• But also the growth rates in the new millennium (between 5% and 10%) were remarkable when one considers that in 2008 every person living in Germany, including babies and old people, already owned 1.3 mobile phones on average.

• A very special success story was the introduction of short message services  $\rm (SMS)$.  In 2008, for example, almost 30 billion such short messages were sent in German mobile networks (darker background in line 4).
  

»Development of mobile communications worldwide«  (based on the URL–page of  [1])

Mobile subscriber lines worldwide 2007 – 2009 (GSM and UMTS)

• In 2009 there were more than 4.3 billion mobile subscribers worldwide.  For comparison:   The number of fixed network connections has been just under one billion since 2005 (probably also because a telephone system only counts as one connection), and since then has declined slightly but steadily.
  

• The annual growth rates worldwide have recently been well over 20% and thus above the figure for Germany.  This can certainly be explained by the fact that in some countries in 2009 there was not yet as much saturation as in Central Europe.
  

• The GSM share was stable at around 80% between 2006 and 2009.  The UMTS share (including HSDPA) increased from 4% to 9% from 2007 to 2009, mainly at the expense of the Japanese "PDC" and the American "cdma2000" systems.

»Distribution of mobile local loops on the individual continents«  (figures from 2008 and 2009)

Mobile subscriber lines (2008/2009) in the different continents

• The most interesting market for mobile communication systems is clearly Asia. In 2009, 44% of all participants were already registered there and the percentage has certainly risen further in the meantime.
  

• It should also be noted that the percentage increase in Asia's share from 42.2% (2008) to 44% (2009) meant an increase of 350 million lines in absolute terms.
  

• The relative market share of Western Europe fell from 13.4% (2008) to 11.8% (2009), although the absolute figure rose from 493 million to 510 million.  The same tendency could be seen in other "first–world regions" like USA and Canada.
  

Exercices for the chapter

Exercise 3.1: Development of the Mobile Network