1 Introduction and Overview

TEK nsultTelecom Engineering and Consulting

GPRS Training

Introduction and Overview

1 ORASCOM Telecom Tunisia Tunis 2004


Contents 1 Mobile Radio Evolution 3 1.1 Trend: from Speech to Data Transmission 4 1.2 The 3rd Mobile Radio Generation (3G) 6 2 GSM – Current Situation, Services & Applications 9 2.1 GSM – Global System for Mobile Communication 10 2.2 GSM – Implementation in an evolutionary Concept 12 3 GSM – Phase2+ 15 3.1 GSM Phase 2+ Solutions for Meeting Current and Future Mobile Requirements 16 3.2 Data Transmission in GSM Phase2+ 18


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Copyright TEKonsult Munich All rights reserved November 2004


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1 Mobile Radio Evolution

Subscriber trends:1982 - 2002

GermanyWorld

Fig. 1 Increase in the number of subscribers due to introduction of first and second generation of mobile communication


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1.1 Trend: from Speech to Data Transmission The first generation networks were designed to offer mainly analog voice transmission. The integration of digital techniques in the second generation networks permits to offer in addition of the speech transmission several supplementary services and low data rate transmission. Despite this evolution, the second-generation networks continued to be unable to handle high data rate services and unable to follow the increase of the need for mobile data services (Web-surfing, Tele-working, e-applications). A need for a new bearer of services is appearing and confirmed by several forecasts and research results and new techniques are appearing (HSCSD, GPRS, EDGE, E-GPRS, UMTS).


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1 G:speech transmission only

2 G:• speech transmission• supplementary services• data transmission

2 G Trends:Speech → Data transmission

DataSpeech

Fig. 2 Trend in the traffic to be transported by future mobile communications systems


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1.2 The 3rd Mobile Radio Generation (3G) The 1st and 2nd generations of cellular and wireless systems were characterized by many heterogeneous and distinct standards, and each one of these standards had his specific characteristics, advantages and disadvantages, applications and users. Added to this, most of these standards are used merely on a national or regional scale and are not compatible with each other, and even if these systems have evolved in order to enhance their services and satisfy their users, there are still a lot of needed services that cannot be offered by the actual mobile systems. Such services are indispensable for future mobile radio systems and include improved speech quality, worldwide availability and particularly a fast transfer of large amounts of data. New systems are necessary in order to better take into consideration the needs of the user. These future networks have to be universal, integrate all the existing technologies (Cellular and Wireless Networks) and constitute a worldwide standard. The IMT2000 is the standard for the mobile networks of the third generation developed within the ITU (International Telecommunication Union) and shall become the worldwide guideline followed by all the standards of the 3G. The term IMT2000 signifying International Mobile Telecommunications for the year 2000 replaced the term FPLMTS (Future Public Land Mobile Telecommunication System) used before to designate the 3rd Generation Networks and will be used in the rest of this document. The goal of the ITU has been to enable “communication with anyone, anywhere, anytime” which means the harmonization of the different radio and networks standards of the systems members of the group IMT2000 in order to ensure a complete roaming between the different 3G systems and limit the cost of the development of these systems by the constructors. High data rate services and multimedia applications are also services intended to be offered in the future 3G networks. The intended data rates will vary between 8 kbit/s and 2 Mbit/s. Note that apart from UMTS the regional standardization authorities draw up further 3G based on the IMT-2000 guidelines.


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analog MSSe.g. INMARSAT

Wireless booth

analogCordless Telephone CT

e.g. CT1, 1+

Third Generation (3G)

Paging

1G 2G

digital MSSe.g. IRIDIUM

WirelessLocal Loop

WLL

Digital CTe.g. DECT, PACS, PHS

Digital Paginge.g. ERMES

analogcellular systems

e.g. C450, NMT, AMPS

analogePrivate Mobile Radio

PMR

digitalcellular systems

e.g GSM, D-AMPS,IS-95, PDC

digitalPMR

e.g. TETRA

Multiple incompatible standardsfor different

. Applications. countries / regions

IMT-2000:UMTS, MC-CDMA,

TD-SCDMA,...

one standard (family)for all

•applications•countries / regions

compatibility within 3G••downward compatibility to2G (e.g. UMTS →GSM)

•resource efficiency•high data rates

•Multimedia

3G

Fig. 3 Intention of third generation as a common global standard for different applications, regions, and service areas


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2 GSM – Current Situation, Services & Applications

GSM - current situation,services & applications

Mobile RadioEvolution

Fig. 4


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2.1 GSM – Global System for Mobile Communication The idea of cell-based mobile radio systems appeared at Bell Laboratories (in USA) in the early 1970s. However, mobile cellular systems were not introduced for commercial use until the 1980s. During the early 1980s, analog cellular telephone systems experienced a very rapid growth in Europe, particularly in Scandinavia and the United Kingdom. Today cellular systems still represent one of the fastest growing telecommunications systems.

But in the beginnings of cellular systems, each country developed its own system, which was an undesirable situation for the following reasons:

• The equipment was limited to operate only within the boundaries of each country.

• The market for the mobile equipment was limited.

In order to overcome these problems, the Conference of European Posts and Telecommunications (CEPT) formed, in 1982, the Groupe Spécial Mobile (GSM) in order to develop a pan-European mobile cellular radio system (the GSM acronym became later the acronym for Global System for Mobile communications). The standardized system had to meet certain criterias:

• Spectrum efficiency • International roaming • Low mobile and base stations costs • Good subjective voice quality • Compatibility with other systems such as ISDN (Integrated Services Digital

Network) • Ability to support new services

Like in the ISDN networks, the GSM services are classified in three categories: - The bearer services: include the offer of a transmission capacity between the

users interfaces. The transmission of asynchronous and synchronous data and the voice are examples of such services.

- The tele-services: example, the Short Messages Service. - The supplementary services: include all the features that can be offered to

the user as complement of the precedent services. The call forwarding, and the call restriction are some examples of the supplementary services.


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Unlike the existing cellular systems, which were developed using an analog technology, the GSM system was developed using a digital technology. In 1989 the responsability for the GSM specifications passed from the CEPT to the European Telecommunications Standards Institute (ETSI). The aim of the GSM specifications is to describe the functionality and the interface for each component of the system, and to provide guidance on the design of the system. These specifications will then standardize the system in order to guarantee the proper interworking between the different elements of the GSM system. In 1990, the phase I of the GSM specifications were published but the commercial use of GSM did not start until mid-1991. In 1992, the majority of European operators started the commercialization of the services of the GSM 900. The specifications of the GSM phase 2 were approved in 1995. The phase 2+ is still in the phase of implementation. In contrary with the CT2 and DECT standards which precise only the specifications of the radio part, the GSM represents a complete telecommunication system because its specifications define the radio part, the core part and all the interfaces between the different elements of the system. These complete specifications allow the interconnection of the different GSM networks.

From the evolution of GSM, it is clear that GSM is not anymore only a European standard. GSM networks are operationnal or planned in over 80 countries around the world. The rapid and increasing acceptance of the GSM system is illustrated with the following figures:

• 1.3 million GSM subscribers worldwide in the beginning of 1994. • Over 5 million GSM subscribers worldwide in the beginning of 1995. • Over 10 million GSM subscribers only in Europe by December 1995.

Since the appearance of GSM, other digital mobile systems have been developed. The following paragraphs give an overview of the different mobile cellular systems developed since the commercial launch of cellular systems. E-GSM The E-GSM or Extended GSM is an extension of the GSM standard which offers further 20 MHZ for the available band of frequencies and a total band of 2 x 35 MHz for GSM.


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GSM1800 (DCS1800) The GSM 1800, known also as DCS 1800 or Digital Cellular System, is a variant the GSM standard working in the 1800 MHz area. It was defined as result of a british initiative to open-up the mass market. This standard offers in total 2 x 75 MHz. GSM1900 (PCS1900) This standard was known at first as PCS 1900 or Public Cellular System and represents an adaptation of the GSM technology to the GSM market. Its specification was in 1995 and in 1997, it was renamed GSM 1900. This standard operates in the 1900 area and offers a total band of frequencies equal to 2 x 60 MHz. GSM-R The GSM-R or GSM-Railway is an adaptation of the GSM technology to be used in the Railways systems. This standard was specified by the ETSI in and the first GSM-R systems have been in operation since 1998. this standard offers a total of 2 x 4 MHz band and operates the 900 MHz.


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GSM-AdaptationsGSM-R

890 1880935

EGSM

GSM

900

EGSM

GSM

900GSM1800

GSM1800

EGSM EGSM

876 880 915 921 925 960 [MHz] 1710 1785 1805 1850 1910 1930 1990 [MHz]

Fig. 5 Adaptations of GSM in frequency due to trend to mobile communication


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2.2 GSM – Implementation in an evolutionary Concept The GSM standard was developed in various phases. GSM Phase1 This phase was achieved in 1990/91 and specifies all the central prerequisites to provide a mobile digital transmission of the information. The services offered include the speech transfer, data transfer with transmission rates between 0.3 and 9.6 kbit/s, and a few supplementary services such as the Call Forwarding, the Call Barring and the Global roaming. GSM Phase2 With the conclusion of GSM phase 2 in 1995, many technical improvements were introduced and the GSM networks were able to offer supplementary services similar to those of the ISDN. Within this phase also was ensured the compatibility between the networks and equipments of the phase 1 and the terminal and equipments of the phase 2, which is named the downward compatibility. GSM Phase2+ The modifications introduced within the phase 2+ were not so important as in the phase 2 and the standard was not entirely worked. Since 1996 annual releases take place and the most important topics concern:

- The proposition of new supplementary services - Special groups of users - Connection and call control issues - IN applications - Data services with high transmission rates.


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GSM: evolutionary concept

Early concept:• closed standard• life time: until successor standardisation (3G)

Phase 1

Phase 2

Phase 1

Phase 3

Phase 2

Phase 1

Cap

abili

ties

1991 1995 1997 Year

Downward compatibility

Speech FR,standard servicesData: max. 9,6 kbit/s

multipleSupplementary Services (SS)comparable to ISDN;decision downward compatibility

Annual Releases !• new SS• IN-applications• new Bearer Services(high data rates)

Fig. 6 Evolutionary concept of the GSM standard


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3 GSM – Phase2+

GSM - Phase 2+

Mobile Radio Evolution

Fig. 7


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3.1 GSM Phase 2+ Solutions for Meeting Current and Future Mobile Requirements In order to meet numerous requirements for future mobile services, several solutions were developed within the GSM phase 2+. Such solutions include:

- The improvement of speech quality: introduction of the Enhanced Full Rate Speech code.

- The guaranty of a worldwide mobility: the use of multi-mode terminals and the availability of new techniques for the roaming (Satellite Roaming).

- A new portfolio of supplementary services: the integration of new features such as CAMEL for the IN platforms and Advanced Call Items (ASCI) in the GSM-Railway

- The standardization of new techniques: HSCSD and GPRS allowing the increase of the transmission rates up to 100 kbit/s and more.

- The offering of User-friendly equipment and new comfortable connection options to the mobile equipment (Blue Tooth)

The GSM phase 2+ was intended to be a basis on which the 3rd generation standards can be based. Thus many GSM phase 2+ features such as CAMEL and GPRS are considered as “guidelines” for UMTS and shall prepare UMTS features.


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GSMPhase2+

GSMPhase 2+Solutions

• GSM solutions fordemands to mobile radio:∗ enhanced speech quality∗ user friendly equipment∗ world-wide connectivity /“home PLMN” service∗ specific services∗ fast transfer of large data volumes• platform for UMTS:compatibility GSM �UMTScommon infrastructure

Satellite

Roaming

Multi-

Band / Mode

Multiple further

features

EFR Enhanced

Full Rate

ASC

I Adv

ance

d Sp

eech

Cal

l Ite

ms

CAMEL

Cus

tom

ized

Appl

icatio

n fo

r Mob

ile

Netw

ork

Enha

nced

ogi

c

HSCSD

High Speed Circuit

Switched Data

EDG

EEn

hanc

ed D

ata

Rat

esfo

r the

GSM

evo

lutio

n

GPRS Gen

eral

Packe

t Rad

io

Servic

e

Fig. 8 Solutions for new demands and market trends offered by GSM phase 2+


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3.2 Data Transmission in GSM Phase2+ HSCSD (High Speed Circuit Switched Data), GPRS (General Packet Radio Services) and EDGE (Enhanced Data Rates for the GSM Evolution) are three new bearer services which were proposed in order to increase the data transmission rates, in the GSM phase 2+. High Speed Circuit Switched Data HSCSD The High Speed Circuit Switched Data is specified in the recommendations 02.34. HSCSD is a Circuit Switched Data technique in which a single user can take over up to eight separate channels at the same time. The data transmission coded was changed and can enable theoretically a transmission rate equal to 14,4 kbit/s instead of 9,6 kbit/s. Then, with the combination of eight physical channels, HSCSD is able theoretically to reach a transmission rate equal to 115,2 kbit/s. Because of its characteristic of end to end connection between sender and recipient, the transmission delays are less than with other techniques, which makes the HSCSD well suitable for applications such as the video and data stream services. In the other side, HSCDS consumes a lot of resources, which is not adapted to the case of bursty traffic. General Packet Radio Services GPRS Like the HSCSD, the GPRS allow the user to combine 1-8 physical channels to transmit data with higher transmission rates than in GSM networks, but in opposition it uses a packet switching technique. Thus, the radio resources are reserved only during the packet transmission, that’s why GPRS is suited for the bursty traffic. With the GPRS, various new coding schemes are introducing allowing a transmission rate up to 21,4 kbit/s per physical channel and up to 171,2 per group of 8 physical channels. Note that this is a theoretical limit which can not be reached in practical. In addition to the applications with a short-term need for high data rates, GPRS enables point-to-multipoint transmission and volume dependent charging. The upgrade of the GSM to the GPRS need network and protocol modifications.


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TDMA-frame 8 Time Slots

HSCSD• circuit oriented

real time applications(e.g. video telephone)• bundling of channels(up to 8 time slots)• new coding scheme(9.6 kbit/s → 14.4 kbit/s)• point-to-point• small HW modifications

Comparison HSCSD / GPRS

GPRS• packet oriented

data applications(e.g. internet surfing)• bundling of channels(up to 8 time slots)• 4 new coding schemes(9.6 kbit/s → 9.05 ... 21.4 kbit/s)• point-to-multipoint• new network elements/protocols

HSCSDup to14.4kbit/s

GPRSup to21.4kbit/s

Time Slot

Fig. 9 Comparison of HSCSD and GPRS


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Enhanced Data rates for the GSM Evolution EDGE The GSM operators who are deploying GPRS networks are aware that they will not be able to offer the announced theoretical transmission rate of 170kbit/s. Thus, they are studying the use of a new modulation technique, called Enhanced Data rates for GSM Evolution. EDGE (Release`99) is an enhancement of the GSM systems proposing high user rates by the use of a new modulation (8PSK instead of GMSK) technique and new canal coding algorithms over the radio interface. The EDGE standard propose transmissions rates up to 69,2 kbit/s per physical channel and 553,6 kbit/s by combining up to 8 channels. A combination of GPRS and EDGE could offer optimum usage of Inter- and Intranet, ensuring highest economy in frequency resource utilization at the same time. The EDGE infrastructure and terminals are available on the market. The main modifications imposed by the use of the new modulation method are located at the level of the base stations, which have to integrate new TRXs and the mobile terminals. EDGE uses the same carrier of 200 Khz as GSM, which will permit the mobile operators to develop EDGE TRXs with those of the GSM/GPRS. The mobile terminal used by the user has to be small and cheap but on the other hand it has to include high quality linear amplifiers, which are needed for the 8PSK modulation. As a preliminary solution to this problem, EDGE is only used in the downlink during the introduction phase.


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EDGE:• uses a new modulation method:replaces GMSK by 8PSK

three bit of information can be transportedby one symbol of modulation (instead of one bit)

BTS has to be upgradedhardware modifications are necessary

• will possibly used only DL in the introduction phasecheap mobile phonesasymmetric data rates in UL and DL

EDGE(Enhanced Data Rates for GSM Evolution)

Fig. 10 EDGE replaces GMSK modulation method to enhance data rates

Documents

1 Introduction and Overview