GPRS Networks
Geoff Sanders, Lionel Thorens, Manfred Reisky, Oliver Rulik and Stefan Deylitz
GmbH
Contents
Preface ix 1 Mobile Radio Evolution 1
1.1 Trend from Speech to Data Transmission 1
1.2 The Third Generation 3
1.3 GSM - The Global System for Mobile Communications 4
1.4 GSM - Evolutionary Concept 13
1.5 The Standards 15 2 The General Packet Radio Service 17
2.1 GPRS Objectives and Advantages 17
2.2 GPRS Ar-chitecture 18
2.3 Characteristics of a GPRS Connection 30
2.4 Logical Functions 4 3 Inter-faces and Protocols 59
3.1 Introduction 59
3.2 Layer Model
3.3 The Names of the GPRS Interfaces 61
3.4 GPRS Procedures 62
3.5 GPRS Attach 3
3.6 Activation of a PDP Con-text 64
3.7 Data Transfer 6
3.8 Physical Implementation in the GPRS Network 67
3.9 GPRS Signalling 74
3.10 GPRS Protocol Planes 83 4 GPRS Procedures 87
4.1 GPRS Mo-bility Management Procedures 87
4.2 Session Management Procedures 103
4.3 Packet Transfer Procedures 5 Changes in the Radio Subsystem for GPRS 109
5.1 Overview and Key Ar-chitecture 10
5.2 Introduction of EDGE, ECSD and E-GPRS 120 6 Core Network 125
6.1 Serving GPRS Support Node (SGSN) 127
6.2 Gateway GPRS Support Node (GGSN) 130
6.3 Access Network PCU -SGSN (Gb Interface) 133
6.4 Core Network SGSN, GGSN (Gn Interface) 4
6.5 Additional Elements in the Core Network 136
6.6 Additional Elements at the Gi Interface 9
6.7 Connections Towards the GSM Network 140 7 Terminal Equipment 143
7.1 Types of Terminal Equipment 143
7.2 Multi-slot Classes and GPRS MS Classes 146
7.3 The Settings in a GPRS-enabled Mobile Device 152 8 Planning and Dimensioning 155
8.1 Introduction 155
8.2 Network Dimensioning 156
8.3 GPRS Radio Subsystem 162
8.4 GPRS Core Network
8.5 User Aspects 189
8.6 Indoor Radio Networks 190 9 Towards All-IP Networks 195
9.1 The TCP/IP Protocol Suite 195
9.2 Convergence of Fixed. Mobile and Data Networks 20
9.3 The Roles of GSM, GPRS and UMTS in Converged Networks 207
10 Applications 217
10.1 Services 21
10.2 Multimedia Messaging Service (MMS) 234
10.3 GSM-R 236
10.4 m-Business and m-Commerce 240
11 Roaming and GRX 245
11.1 Introduction 245
11.2 Why do we need Roaming in GPRS? 24
11.3 Architecture 6
11.4 GPRS Roaming eXchange (GRX) Network 247
11.5 Procedures 248
11.6 Quality Aspects of GRX 250
Glossary and Abbreviations 251
Preface
The
aim of this book is to provide the reader with a thorough grounding in
the General Packet Radio Service - GPRS. The authors have assumed that
the reader will have at least a basic understanding of GSM and the
associated theory and terminology. The introduction contains a basic
review of GSM to ensure that the reader is clear on the main as-pects of
circuit switched technology, as this will make the differences and
advantages of packet oriented GPRS both more apparent and easier to
understand.
The
book will en-deavour to take the reader beyond the specifications and
into other crucial areas such as applications, implementation and other
near-future aspects such as E-GPRS, the migration towards all-IP
networks and the role played by GPRS in enabling packet data transfer
from UMTS. Wherever possible real-world examples will be given to
support and illustrate the text. Readers of GPRS Networks have the
following options with regard to obtaining further information on GPRS
and other telecommunications subjects, for questions aris-ing from the
book please write a brief email to gprs@tfk.de where the authors and
techni-cal staff will be pleased to be of assistance
Introduction
Today
no one doubts that the introduction of GSM represented a revolu-tion
in mobile communications. As this book goes to press, there are more
than 773 mil-lion GSM users worldwide and the number is growing by the
minute. This revolution, which has taken place over the last 12 years,
has had an enormous impact on our daily lives.
Mobile
telephony has changed the way we communicate and the way we do
business. Friends and colleagues can be reached almost anywhere at any
time, we are no longer tied to desk-top machines for e-mails and faxes,
and the mobiles themselves are replacing not only telephones but also
dictaphones, personal organizers and phone books. 'Conver-gence' has
been the buzzword in recent years.
The
above is just the beginning and GPRS is the key. As multifunction
mobile devices replace cellphones, PDAs and notebook PCs, there will be
an ever increasing demand for bandwidth. Home Internet users are used
to the level of service offered by 64 kbits -1 ISDN or the higher rates
offered by the various DSL services. These users will increasingly
demand the same level of service from their mo-biles, and as the volume
of users goes up, content and service providers will respond and the
network operators will have to provide the capacity.
Originally,
3G was seen as the means to satisfy the demand for bandwidth and GPRS
was viewed by many simply as a stepping stone on the way from
narrowband GSM to wideband UMTS. However, the worldwide delay in 3G
rollout has led to GPRS being seen in a different light, particularly
with the development of E-GPRS. The promise of low-cost reliable mobile
Internet access has led to many operators implementing GPRS, but,
whereas GSM was seen as a communi-cations technology, GPRS is seen more
as an enabling technology. The ability to run an ap-plication on a
mobile device that can send and receive packet data at high speed makes
possible such things as mobile Internet, remote device control,
multi-player gaming, loca-tion-dependent information services, and
m-commerce. GPRS will continue to change the way we live, just as GSM
has already done.
1 Mobile Radio Evolution
1.1 Trend from Speech to
Data
Transmission Beginning with the first single cell mobile telephone
services in the 1940s and continuing through the first and second
generations of mobile telephone services, the primary function of the
mobile device was to enable speech calls to be set up between the mobile
user and a fixed network of base stations (BTS) and telephone
exchanges.
This scenario has changed dramatically in recent years.
With the introduction of first SMS and then WAP, few people now support
the idea that a mobile device is only for speech calls, and just as
the rate of change in mo-bile applications is accelerating, so is the
rate of acceptance. As more and more people make use of mobile
services, the multifunction portable device is becoming ever more
in-dispensable in our daily lives. This is an enormous departure from
accepted norms.
The
trend from mobile speech to data is gaining acceptance faster than any
other technology ever invented. The Internet took decades to reach its
present form, and only since the mid-1990s has it enjoyed such
widespread utilization from home users. GSM however, in just 10 short
years, achieved over 80% market penetration in some European countries!
Com-pared with other industries, the rate of change in mobile
technology is unprecedented.
The
automobile industry introduces a new model in about 5 years; the
fashion industry also measures change in terms of years. Even the
computer industry, which has experienced quantum leaps in terms of
hardware technology and applications software, has not had the kind of
acceptance which mobile telecommunications are having. The fact of the
matter is that all these industries - one could almost say all indus
tries - are going to be directly af-fected by the trend towards
applications based on mobile data transfer.
It
is already possi-ble to send an SMS during a normal speech call,
download information from the Internet via WAP, and access web sites and
e-mail via a notebook or PDA connected to a mobile phone. This is only
the beginning: it is predicted that by 2010 the volume of new mobile
phone sales in Europe and North America will start to level off.
This
is the first indicator of the coming boom in mobile services based on
packet data transmission. Already some manufacturers have started to
develop and market solutions for m-services and m-com-merce as they are
already aware that future revenues will be generated not through
equipment sales, but by providing the customer with new ways to make use
of that equipment.
We
can already see the start of this trend. The SIM tool kit introduces
extra functionality onto the SIM card, which allows the user to
subscribe to various service providers who use the tool kit to run their
own propri-etary software. This represents a major step forward in
that it is no longer necessary to modify the mobile device or the SIM
card in order to introduce new or improved services. This in turn means
that the user can take advantage of new services at any time without
having to invest in new equipment. The automobile industry is a good
example of current trends.
Almost
from the beginning of GSM, manufacturers at the top end of the market
have been installing mobile phones in their cars. More recently,
navigation systems based on GPS satellite positioning systems combined
with electronic maps stored on CD-ROMs have become standard items on
such vehicles. In recent years, these two systems have been linked
together (converged) so that the navigation system receives traffic
reports via SMS and uses this data to avoid traffic jams. A further
enhancement is to store such things as hotel and tourist information on
the navigation CD. Several manufacturers have now moved on to using
DVDs as a storage medium due to the limited storage capacity of a
CD-ROM. What is the next step? The answer is to do away with on-board
storage completely and use the general packet radio service (GPRS) to
download the required information as and when required.
Once
this step has been taken, the on-board systems only need to be
slightly upgraded to enable full Internet access. Such systems are in
fact currently available as custom solutions, so it is only a matter of
time before they become options/standard features offered by the
manufacturer. This step is seen by many as essential to the con tin-ued
evolution of in-car systems. The problem with CD/DVD systems is that
the data is out of date almost as soon as it is released and cannot
easily be updated. Further, such storage media offer a very limited
amount of data as far as hotel and tourist information is con-cerned,
added to which price and availability details cannot be included for
the reason stat-ed previously. A GPRS based system, which accesses a
centralized server network, would always have access to the latest
traffic information and could provide web links to relevant hotel,
restaurant and tourist information web sites, based on GPS location
information provided via the mobile.
As
can be seen from the above example, there is a general trend towards
increasing convergence of previously independent systems. In this we can
also ob-serve a trend in the way the Internet is being utilized.
Previously, servers attached to the World Wide Web (www) enabled
information exchange across the net. Later, e-commerce changed the face
of the Web as it evolved from being purely an 'Information
superhigh-way' (data, e-mail, gaming) to a way of doing business on a
global scale. Now we see a fur-ther trend towards centralized.
Web-based,
servers replacing discrete/portable storage me-dia. Such servers
already provide business users with storage for their documents,
presenta-tions and other files. They can be accessed/updated online,
avoiding the risk of having im-portant information corrupted or stolen
from a portable device. Such systems could re-place in- car data storage
- or any other application that depends on information stored on CD or
DVD - using GPRS to give mobile access to the Internet. The trends
towards appli-cations which can use GPRS are plainly visible. The
success of i-mode in Japan and its sub-sequent release in Europe has
demonstrated that there is a significant deman for mobile services based
on high-speed packet data transfer.
In
it first year of business, i-mode attracted over 20 million users in
Japan. If this success is repeated in Europe (where GPRS is the bearer)
it will not only prove the technology and the business model, but will
also provide a driving force for new services based on the general
packet radio service.
1.2 The Third Generation
Among
the many questions asked about 3G, one of the most frequent is 'Why do
we need it?'. The an-swer lies in the planning. 2G was a response to a
need for cheaper, more reliable, mobile communications which could
easily cross international boundaries. The technology evolved through
different phases which can be roughly characterized as: speech —>
speech related services —> data services.
Mobile
Internet access was not initially envisaged, and this is why GSM has
had to be supplemented with such things as HSCSD, GPRS and EDGE in the
final phase (phase 2+). 3G, on the other hand, was intended from the
outset to enable high bit-rate mobile data services (in addition to
speech calls and traditional ser-vices) and has been planned
accordingly.
The
evolution towards 3G and beyond is hap-pening on different levels. On
the tech nological level we have a new radio access network, the UTRAN
(UMTS radio access network), which interfaces with the GSM circuit
switched (CS) core network for speech calls and the GPRS packet oriented
(PO) core network for data transfer. On the services level, GSM
required the addition of first the intelligent net-works (IN) platform,
to enable a greater variety of national services, and then the CAMEL
(customized applications for mobile network enhanced logic) platform to
make these ser-vices available while roaming outside the home PLMN.
Modifications were needed to the radio access technology to enable high
speed data services to be implemented. UMTS has been designed so that
the services provided to the end-user are independent of the radio
access technology. On the network level, the current evolutionary trend
is towards so called 'all-IP' networks.
The
convergence of CS and PO technologies already begun with the imple
mentation of GPRS will reach its logical conclusion at some point in the
future when the radio access networks, GERAN (GSM/EDGE radio access
network) and UTRAN, will connect directly to a packet data network.
Speech will be carried as voice over IP (VoIP) and will be routed from
the source to the destination in the same way that other data packets
are routed from one application to another. The technological evolu-tion
from FDMA in 1G, through the combination of FDMA and TDMA in 2G, and
on to CDMA in 3G, is a clear progression with each new development
seeking to solve the prob-lems of the previous generation.
The
evolution of the services offered to the end-user, however, is not
such a linear process and thus a clear development path is difficult to
iden-tify. Providers are using the Internet as a base to offer their
content and services to end-users with a great variety of terminal
equipment. To maximize their revenues, they need to reach the maximum
possible number of people and so must serve users with equipment from
different phases and different generations. SMS, HSCSD, GPRS and WAP can
all be used as means to bring value added services to the user and
here is where the real strength of GPRS can be seen.
The
GPRS infrastructure can be utilized to deliver SMS and WAP services to
both GSM and UMTS users. Here again we see evolution resulting in
conver-gence. The implementation of GPRS was originally seen as a bridge
between 2G and 3G but in actual fact has resulted in developments that
have direct affect on both generations. …
Nhận xét
Đăng nhận xét