History

1982 - The Beginning

Nordic Telecom and Netherlands PTT propose to CEPT(Conference of European

Post and Telecommunications) the development of a new digital cellular standard that

would cope with the ever a burgeoning demands on European mobile networks. 

The European Commission (EC) issues a directive which requires member states

to reserve frequencies in the 900 MHz band for GSM to allow for roaming.

1986

Main GSM radio transmission techniques are chosen

1987

September - 13 operators and administrators from 12 areas in the CEPT GSM

advisory group sign the charter GSM (Groupe Spéciale Mobile) MoU "Club" agreement,

with a launch date of 1 July 1991.

The original French name was later changed to Global System for Mobile

Communications, but the original GSM acronym stuck.

GSM spec drafted.

1989

The European Telecommunications Standards Institute (ETSI) defined GSM as

the internationally accepted digital cellular telephony standard

GSM becomes an ETSI technical committee

1990

Phase 1 GSM 900 specifications are frozen

DCS adaptation starts

Validation systems implemented

First GSM World congress in Rome with 650 Participants

1991

First GSM spec demonstrated

DCS specifications are frozen

GSM World Congress Nice has 690 Participants

1992

January - First GSM network operator is Oy Radiolinja Ab in Finland

December 1992 - 13 networks on air in 7 areas

GSM World Congress Berlin - 630 Participants

1993

GSM demonstrated for the first time in Africa at Telkom '93 in Cape Town

Roaming agreements between several operators established

December 1993 - 32 networks on air in 18 areas

GSM World Congress Lisbon with 760 Participants

Telkom '93 held in Cape Town. First GSM systems shown.

1994

First GSM networks in Africa launched in South Africa

Phase 2 data/fax bearer services launched

Vodacom becomes first GSM network in the world to implement data/fax

GSM World Congress Athens with 780 Participants

December 1994 - 69 networks on air in 43 areas

1995

GSM MoU is formally registered as an Association registered in Switzerland - 156

members from 86 areas.

GSM World Congress Madrid with 1400 Participants

December 1995 117 networks on air in 69 areas

Fax, data and SMS roaming started

GSM phase 2 standardization is completed, including adaptation for PCS 1900

(PCS)

First PCS 1900 network live 'on air' in the USA

Telecom '95 Geneva - Nokia shows 33.6 kbps multimedia data via GSM

Namibia goes on-line

Ericsson  337 wins GSM phone of the year

US FCC auctions off PCS licenses

1996

GSM MoU is formally registered as an Association registered in Switzerland

December 1996 120 networks on air in 84 areas

GSM World Congress in Cannes

GSM MoU Plenary held in Atlanta GA, USA

8K SIM launched

Pre-Paid GSM SIM Cards launched

Bundled billing introduced in South Africa

Libya goes on-line

Option International  launches world's first GSM/Fixed-line modem

1997

Zimbabwe goes live

GSM World Congress Cannes 21/2/97

Mozambique goes live

Iridium  birds launched

First dual-band GSM 900-1900 phone launched by Bosch

1998

Botswana GSM goes live

GSM World Congress Cannes (2/98)

Vodacom Introduces Free VoiceMail

MTN Gets Uganda Tender

GSM SIM Cracked in USA

Over 2m GSM 1900 users

MTN Gets Rwanda Tender

MTN follows with free voicemail

Rwanda GSM Live

First HSCSD trials in Singapore

Vodacom launches Yebo!Net 10/98

Iridium Live 11/98

First GSM Africa Conference (11/98)

125m GSM 900/1800/1900 users worldwide (12/98)

Option International launches FirstFone

MTN launches CarryOver minutes

1999

GSM Conference in Cannes 2/99

165m GSM 900/1800/1900 users worldwide

GPRS trials begin and USA and Scandanavia 1/99

WAP trials in France and Italy 1/99

CellExpo Africa 5/99

Eight Bidders for Third SA Cell License

GSM MoU Joins 3GPP

MTN SA Head of GSM MoU

First GPRS networks go live

Bluetooth specification v1.0 released

2000

GSM Conference in Cannes 3/2000

By 12/2000 480m GSM 900/1800/1900 users worldwide

First GPRS networks roll out

Mobey Forum Launched

MeT Forum Launched

Location Interoperability Forum Launched

First GPRS terminals seen

Nokia releases SmartMessaging spec

SyncML spec released

2001

GSM Conference in Cannes 2/2001

By 5/2001 500m GSM 900/1800/1900 users worldwide

16 billion SMS message sent in April 2001

500 million people are GSM users (4/01)

BUILDING BLOCKS OF GSM

AMPS (Advanced Mobile Phone Service)

Advanced Mobile Phone System (AMPS) was an analog mobile phone system standard

developed by Bell Labs, and officially introduced in the Americas in 1983 and Australia in 1987.

It was the primary analog mobile phone system in North America (and other locales) through the

1980s and into the 2000s. AMPS (Advanced Mobile Phone Service) is a standard system for

analog signal cellular telephone service in the United States and is also used in other countries. It

is based on the initial frequency spectrum allocation for cellular service by the Federal

Communications Commission (FCC) in 1970. Introduced by AT&T in 1983, AMPS became and

currently still is the most widely deployed cellular system in the United States.

AMPS allocates frequency ranges within the 800 and 900 Megahertz (MHz) spectrum to cellular

telephone. Each service provider can use half of the 824-849 MHz range for receiving signals

from cellular phones and half the 869-894 MHz range for transmitting to cellular phones. The

bands are divided into 30 kHz sub-bands, called channels. The receiving channels are called

reverse channels and the sending channels are called forward channels. The division of the

spectrum into sub-band channels is achieved by using frequency division multiple access.

The signals received from a transmitter cover an area called a cell. As a user moves out of the

cell's area into an adjacent cell, the user begins to pick up the new cell's signals without any

noticeable transition. The signals in the adjacent cell are sent and received on different channels

than the previous cell's signals to so that the signals don't interfere with each other.

AMPS was a first-generation cellular technology that uses separate frequencies, or "channels",

for each conversation. It therefore required considerable bandwidth for a large number of users.

In general terms, AMPS was very similar to the older "0G" Improved Mobile Telephone Service,

but used considerably more computing power in order to select frequencies, hand off

conversations to PSTN lines, and handle billing and call setup.

What really separated AMPS from older systems is the "back end" call setup functionality. In

AMPS, the cell centers could flexibly assign channels to handsets based on signal strength,

allowing the same frequency to be re-used in various locations without interference. This

allowed a larger number of phones to be supported over a geographical area. AMPS pioneers

fathered the term "cellular" because of its use of small hexagonal "cells" within a system.

It suffered from some weaknesses when compared to today's digital technologies. Since it was an

analog standard, it is very susceptible to static and noise and has no protection from

eavesdropping using a scanner. In the 1990s, "cloning" was an epidemic that cost the industry

millions of dollars. An eavesdropper with specialized equipment could intercept a

handset's ESN(Electronic Serial Number) and MIN (Mobile Identification Number, aka the

telephone number). An Electronic Serial Number is a packet of data which is sent by the handset

to the cellular system for billing purposes, effectively identifying that phone on the network. The

system then allows or disallows calls and or features based on its customer file. If an ESN/MIN

Pair is intercepted, it could then be cloned onto a different phone and used in other areas for

making calls without paying.

Cell phone cloning became possible with off-the-shelf technology in the '90s with the use of

three key elements. A radio receiver that could tune into the Reverse Channel (the frequency that

the phones transmit data to the tower on), such as the Icom PCR-1000, a software program called

Banpaia, and an easily clonable phone such as the Oki 900. By tuning the radio to the proper

frequency, Banpaia would decode the ESN/MIN pair, and display it on the screen. The person

could then input that data into the Oki 900, reboot it, and the phone network could not

distinguish the Oki from the original.

The problem became so large that some carriers required the use of a PIN before making calls.

Eventually, the cellular companies initiated a system called RF Fingerprinting, where it could

determine subtle differences in the signal of one phone from another and shut down some cloned

phones. Some legitimate customers had problems with this though if they made certain

modifications to their own phone, such as replacing the battery and/or antenna. The Oki 900 was

the ultimate tool of cell phone hackers because it could listen in to AMPS phone calls right out of

the box with no hardware modifications.

AMPS was originally standardized by ANSI as EIA/TIA/IS-3. This was later superseded by

EIA/TIA-553 and TIA interim standard IS-91. AMPS has been replaced by newer digital

standards, such as Digital AMPS, GSM, and CDMA2000 which brought improved security as

well as increased capacity. Though cloning is still possible even with digital technologies, the

cost of wireless service is so low that the problem has virtually disappeared.

AMPS cellular service operated in the 800 MHz Cellular FM band. For each market area, the

United States Federal Communications Commission (FCC) allowed two licensee (networks)

known as "A" and "B" carriers. Each carrier within a market uses a specified "block" of

frequencies consisting of 21 control channels and 395 voice channels. Originally, the B

(wireline) side license was usually owned by the local phone company, and the A (non-wireline)

license was given to wireless telephone providers.

At the inception of cellular in 1983, the FCC had granted each carrier within a market 333

channels (666 channels total). By the late 1980s, the cellular industry's subscriber base had

grown into the millions across America and it became necessary to add channels for additional

capacity. In 1989, the FCC granted carriers an expansion from the current 666 channels to the

final 832 (416 per carrier). The additional frequencies were from the band held in reserve for

future (inevitable) expansion. These frequencies were immediately adjacent to the existing

cellular band. These bands had previously been allocated to UHF TV channels 70–83.

The anatomy of each channel is composed of 2 frequencies. 416 of these are in the 824–

849 MHz range for transmissions from mobile stations to the base stations, paired with 416

frequencies in the 869–894 MHz range for transmissions from base stations to the mobile

stations. Each cell site will use a subset of these channels, and must use a different set than

neighboring cells to avoid interference. This significantly reduced the number of channels

available at each site in real-world systems. Each AMPS channel is 30 kHz wide.

Laws were passed in the US which prohibited the FCC type acceptance and sale of any receiver

which could tune the frequency ranges occupied by analog AMPS cellular services. Though the

service is no longer offered, these laws remain in force.

Digital AMPS

Later, many AMPS networks were partially converted to D-AMPS, often referred to

as TDMA (though TDMA is a generic term that applies to many cellular systems). D-AMPS is

a digital, 2G standard used mainly by AT&T Mobility and U.S. Cellular in the United

States, Rogers Wireless in Canada, Telcel in Mexico, Vivo S.A. and Telecom Italia

Mobile (TIM) in Brazil, VimpelCom in Russia, Movilnet in Venezuela. In Latin America,

AMPS is no longer offered and has been replaced by GSM and new UMTS networks.

GSM and CDMA2000

AMPS and D-AMPS have now been phased out in favor of either CDMA2000 or GSM which

allow for higher capacity data transfers for services such as WAP, Multimedia Messaging

System (MMS), and wireless Internet access. There are some phones capable of supporting

AMPS, D-AMPS and GSM all in one phone (using the GAIT standard).

Analog AMPS being replaced by digital

In 2002, the FCC decided to no longer require A and B carriers to support AMPS service as of

February 18, 2008. Since the AMPS standard is analog technology, it suffers from an inherently

inefficient use of the frequency spectrum. All AMPS carriers have converted most of their

consumer base to a digital standard such as CDMA2000 or GSM and continue to do so at a rapid

pace. Digital technologies such as GSM and CDMA2000 support multiple voice calls on the

same channel and offer enhanced features such as two-way text messaging and data services.

Unlike in the United States, the Canadian Radio-television and Telecommunications

Commission (CRTC) and Industry Canada have not set any requirement for maintaining AMPS

service in Canada. Rogers Wireless has dismantled their AMPS (along with IS-136) network, the

networks were shut down May 31, 2007. Bell Mobility and Telus Mobility, who operated AMPS

networks in Canada, announced that they would observe the same timetable as outlined by the

FCC in the United States, and as a result would not begin to dismantle their AMPS networks

until after February 2008.

OnStar relied heavily on North American AMPS service for its subscribers because, when the

system was developed, AMPS offered the most comprehensive wireless coverage in the US. In

2006, ADT asked the FCC to extend the AMPS deadline due to many of their alarm systems still

using analog technology to communicate with the control centers. Cellular companies who own

an A or B license (such as Verizon and Alltel) were required to provide analog service until

February 18, 2008. After that point, however, most cellular companies were eager to shut down

AMPS and use the remaining channels for digital services. OnStar transitioned to digital service

with the help of data transport technology developed by Airbiquity, but warned customers who

could not be upgraded to digital that their service would permanently expire on January 1, 2008.

TACS(Total Access Communication System)

The TACS (Total Access Communications System) was a network standard for mobile

phones first generation.TACS is the traditional analogue mobile phone system, introduced in the

1980s by Vodafone and Cellnet at 900MHz. ETACS is the same thing, but includes some extra

channels borrowed from military frequencies, which were added in congested areas when the

networks found new cell sites undesirable. The system worked quite well enough for most

people's needs. In fact, on a good connection, the clear, smooth sound of a TACS phone was

more pleasant than the rather harsher sound of a digital phone.

The TACS was based on analog technology, born in England and introduced in Italy in the

late eighties in which the broadcasts in every radio cell occurred at frequencies different to allow

coexistence of contiguous cells. In northern Europe and the USA were used other standards

(NMT, Nordic Mobile Telephone System, AMPS, Advanced Mobile Phone System).

The system suffered from some significant limitations:

Limited number of concurrent calls carried by each base station .

Was not able to provide services other than voice communication, as SMS , fax , e-mail .

The terminals were easily cloned using counterfeit identification code.

Could be used only in Italy .

Calls could be intercepted by anyone with a scanner or by trivial changes to certain

models of phones (eg Motorola MICROTAC).

The system ETACS (Enhanced TACS) was introduced in 1993 to increase network capacity by

using a wider range of frequencies (from 450 MHz to 890/900 MHz).The launch of the new

mobile telephone systems of second and third generation ( GSM el ' UMTS ) has rendered

obsolete the TACS, but was still maintained until 2005 to support subscribers who still use it.The

TACS has stopped working on the night between 30 and 31 December 2005 and sold its

spectrum to GSM .The importance of this system was to have allowed the rapid initial spread

of mobile telephony in Italy.For technical reasons, TACS is being phased out, and the networks

will be keen to move users away to digital services, partly because they are re-allocating the

TACS frequencies to GSM.

NMT(Nordic Mobile Telephone System )

NMT (Nordisk MobilTelefoni or Nordiska MobilTelefoni-gruppen,Nordic Mobile Telephony in

English) is the first fully-automatic cellular phone system. It was specified

by Nordic telecommunications administrations (PTTs) starting in 1970, and opened for service

in 1981 as a response to the increasing congestion and heavy requirements of the manual mobile

phone network: ARP (150MHz)in Finland and MTD (450 MHz)in Sweden, Norway , Denmark.

The Swedish electrical engineer Östen Mäkitalo is considered as the father of this system, and of

the cell phone.

NMT is based on analog technology (first generation or 1G) and two variants exist: NMT-

450 and NMT-900. The numbers indicate the frequency bands uses. NMT-900 was introduced

in 1986 because it carries more channels than the previous NMT-450 network.

The technical principles of NMT were ready by year 1973 and specifications for base stations

were ready in 1977. The NMT specifications were free and open, allowing many companies to

produce NMT hardware and pushing the prices down. The success of NMT meant a lot

to Nokia (then Mobira) and Ericsson. First Danish implementers were Storno (then owned

by General Electric, later taken over by Motorola) and AP (later taken over by Philips). Initial

NMT phones were designed to mount in the trunk of a car, with a keyboard/display unit at the

drivers seat. "Portable" versions existed: one could definitely move them, but they were bulky,

and battery lifetime was a big problem. Latter-day models (such as Benefon's) were as small as

100 mm and weighed only about 100 grams.

The world's first NMT call was made in Tampere, Finland, in 1978. The NMT network was

opened in Sweden and Norway in 1981, and in Denmark and Finland in 1982. Iceland joined in

1986. However, curiously for a mobile phone standard that has the word "Nordic" in it, the first

commercial service was introduced in Saudi Arabia on September 1, 1981 to 1200 users, one

month before Sweden. By 1985 the network had grown to 110,000 subscribers

in Scandinavia and Finland, 63,300 in Norway alone, which made it the world's largest mobile

network at the time. 

The NMT network has mainly been used in the Nordic countries, Switzerland, The

Netherlands, Hungary, Poland, Bulgaria, Romania, The Czech Republic, Slovakia, Slovenia, 

Serbia, Turkey, Croatia, Bosnia, Baltic countries and Russia but also in the Middle East and

in Asia. The introduction of digital mobile networks such as GSM has reduced the popularity of

NMT and some of the Nordic phone companies have suspended their NMT networks.

In Finland TeliaSonera's NMT network was suspended on December 31, 2002. Norway's last

NMT network was suspended on December 31, 2004. Sweden's TeliaSonera NMT network was

suspended on December 31, 2007. The NMT network (450 MHz) however has one big

advantage over GSM which is the range; this advantage is valuable in big but sparsely populated

countries such as Iceland. In Iceland, the GSM network reaches 98% of the country's population

but only a small proportion of its land area. The NMT system however reaches most of the

country and a lot of the surrounding waters, thus the network is popular with fishermen and those

traveling in the mountains.

The cell sizes in an NMT network range from 2 km to 30 km. With smaller ranges the network

can service more simultaneous callers; for example in a city the range can be kept short for better

service. NMT used full duplex transmission, allowing for simultaneous receiving and

transmission of voice. Car phone versions of NMT used transmission power of up to 15 watt

(NMT-450) and 6 watt (NMT-900), handsets up to 1 watt. NMT had automatic switching

(dialing) and handover of the call built into the standard from the beginning, which was not the

case with most preceding car phone services, such as the Finnish ARP. Additionally, the NMT

standard specified billing as well as national and international roaming.

A disadvantage of the original NMT specification is that voice traffic was not encrypted. So

anyone willing to listen in would just have to buy a scanner and tune it to the correct frequency.

As a result, some scanners have had the NMT bands "deleted" so they could not be accessed.

This is not particularly effective as it isn't that hard to obtain a scanner that doesn't have these

restrictions; it is also possible to re-program a scanner so that the "deleted" bands can be

accessed. Later versions of the NMT specifications defined optional analog scrambling which

was based on two-band audio frequency inversion. If both the base station and the mobile station

supported scrambling, they could agree upon using it when initiating a phone call. Also, if two

users had mobile stations (=mobile phones) supporting scrambling, they could turn it on during

conversation even if the base stations didn't support it. In this case audio would be scrambled all

the way between the two mobile stations. While the scrambling method was not at all as strong

as encryption in newer digital phones, such as GSM, it did prevent casual listening with

scanners. Scrambling is defined in NMT Doc 450-1: System Description (1999-03-23) and NMT

Doc 450-3 and 900-3: Technical Specification for the Mobile Station (1995-10-04)'s Annex 26

v.1.1: Mobile Station with Speech Scrambling - Split Inversion Method (Optional) (1998-01-27).

NMT also supported a simple but robust integrated data transfer mode called DMS (Data and

Messaging Service) or NMT-Text, which used the network's signaling channel for data transfer.

Using DMS, also text messaging was possible between two NMT handsets before SMS service

started in GSM, but this feature was never commercially available except in Russian, Polish and

Bulgarian NMT networks. Another data transfer method was called NMT Mobidigi with transfer

speeds of 380 bits per second. It required external equipment.

NMT signaling transfer speeds vary between 600 and 1200 bits per second, using FFSK

(Fast Frequency Shift Keying) modulation. Signaling between the base station and the mobile

station was implemented using the same RF channel that was used for audio, and using the 1200

bit/s FFSK modem. This caused the periodic short noise bursts, e.g. during handover, that were

uniquely characteristic to NMT sound.NMT -450 is still used in Iceland (Siminn), Russia (),

Poland (Centertel)

ARCHITECTURE

The GSM technical specifications define the different elements within the GSM network

architecture. It defines the different elements and the ways in which they interact to enable the

overall network operation to be maintained.The GSM network architecture is now well

established and with the other later cellular systems now established and other new ones being

deployed, the basic GSM network architecture has been updated to interface to the network

elements required by these systems. Despite the developments of the newer systems, the basic

GSM network architecture has been maintained, and the elements described below perform the

same functions as they did when the original GSM system was launched in the early 1990s.

Simplified GSM Network Architecture

The GSM network architecture as defined in the GSM specifications can be grouped into four

main areas:

Mobile station (MS)

Base-station subsystem (BSS)

Network and Switching Subsystem (NSS)

Operation and Support Subsystem (OSS)

Mobile station

Mobile stations (MS), mobile equipment (ME) or as they are most widely known, cell or mobile

phones are the section of a GSM cellular network that the user sees and operates. In recent years

their size has fallen dramatically while the level of functionality has greatly increased. A further

advantage is that the time between charges has significantly increased.

There are a number of elements to the cell phone, although the two main elements are the main

hardware and the SIM.

The hardware itself contains the main elements of the mobile phone including the display, case,

battery, and the electronics used to generate the signal, and process the data receiver and to be

transmitted. It also contains a number known as the International Mobile Equipment Identity

(IMEI). This is installed in the phone at manufacture and "cannot" be changed. It is accessed by

the network during registration to check whether the equipment has been reported as stolen.

The SIM or Subscriber Identity Module contains the information that provides the identity of the

user to the network. It contains are variety of information including a number known as the

International Mobile Subscriber Identity (IMSI).

Base Station Subsystem (BSS)

The Base Station Subsystem (BSS) section of the GSM network architecture that is

fundamentally associated with communicating with the mobiles on the network. It consists of

two elements:

Base Transceiver Station (BTS):   The BTS used in a GSM network comprises the

radio transmitter receivers, and their associated antennas that transmit and receive to

directly communicate with the mobiles. The BTS is the defining element for each cell.

The BTS communicates with the mobiles and the interface between the two is known as

the Um interface with its associated protocols.

Base Station Controller (BSC):   The BSC forms the next stage back into the GSM

network. It controls a group of BTSs, and is often co-located with one of the BTSs in its

group. It manages the radio resources and controls items such as handover within the

group of BTSs, allocates channels and the like. It communicates with the BTSs over what

is termed the Abis interface.

Network Switching Subsystem (NSS)

The GSM network subsystem contains a variety of different elements, and is often termed the

core network. It provides the main control and interfacing for the whole mobile network. The

major elements within the core network include:

Mobile Switching services Centre (MSC):   The main element within the core network

area of the overall GSM network architecture is the Mobile switching ServicesCentre

(MSC). The MSC acts like a normal switching node within a PSTN or ISDN, but also

provides additional functionality to enable the requirements of a mobile user to be

supported. These include registration, authentication, call location, inter-MSC handovers

and call routing to a mobile subscriber. It also provides an interface to the PSTN so that

calls can be routed from the mobile network to a phone connected to a landline.Interfaces

to other MSCs are provided to enable calls to be made to mobiles on different networks.

Home Location Register (HLR):   This database contains all the administrative

information about each subscriber along with their last known location. In this way, the

GSM network is able to route calls to the relevant base station for the MS. When a user

switches on their phone, the phone registers with the network and from this it is possible

to determine which BTS it communicates with so that incoming calls can be routed

appropriately. Even when the phone is not active (but switched on) it re-registers

periodically to ensure that the network (HLR) is aware of its latest position. There is one

HLR per network, although it may be distributed across various sub-centres to for

operational reasons.

Visitor Location Register (VLR):   This contains selected information from the HLR

that enables the selected services for the individual subscriber to be provided. The VLR

can be implemented as a separate entity, but it is commonly realised as an integral part of

the MSC, rather than a separate entity. In this way access is made faster and more

convenient.

Equipment Identity Register (EIR):   The EIR is the entity that decides whether a given

mobile equipment may be allowed onto the network. Each mobile equipment has a

number known as the International Mobile Equipment Identity. This number, as

mentioned above, is installed in the equipment and is checked by the network during

registration. Dependent upon the information held in the EIR, the mobile may be

allocated one of three states - allowed onto the network, barred access, or monitored in

case its problems.

Authentication Centre (AuC):   The AuC is a protected database that contains the secret

key also contained in the user's SIM card. It is used for authentication and for ciphering

on the radio channel.

Gateway Mobile Switching Centre (GMSC):   The GMSC is the point to which a ME

terminating call is initially routed, without any knowledge of the MS's location. The

GMSC is thus in charge of obtaining the MSRN (Mobile Station Roaming Number) from

the HLR based on the MSISDN (Mobile Station ISDN number, the "directory number" of

a MS) and routing the call to the correct visited MSC. The "MSC" part of the term

GMSC is misleading, since the gateway operation does not require any linking to an

MSC.

SMS Gateway (SMS-G):   The SMS-G or SMS gateway is the term that is used to

collectively describe the two Short Message Services Gateways defined in the GSM

standards. The two gateways handle messages directed in different directions. The SMS-

GMSC (Short Message Service Gateway Mobile Switching Centre) is for short messages

being sent to an ME. The SMS-IWMSC (Short Message Service Inter-Working Mobile

Switching Centre) is used for short messages originated with a mobile on that network.

The SMS-GMSC role is similar to that of the GMSC, whereas the SMS-IWMSC

provides a fixed access point to the Short Message Service Centre.

Operation and Support Subsystem (OSS)

The OSS or operation support subsystem is an element within the overall GSM network

architecture that is connected to components of the NSS and the BSC. It is used to control

and monitor the overall GSM network and it is also used to control the traffic load of the

BSS. It must be noted that as the number of BS increases with the scaling of the

subscriber population some of the maintenance tasks are transferred to the BTS, allowing

savings in the cost of ownership of the system.

FEATURES

Call Forwarding

GSM supports four different types of Call Forwarding or Call Diversion. These are:

Forward all calls

Unconditionally forwards all calls made to your phone to another location, such as another phone

number or voice mail. This setting, if activated, overrides all other types

of conditional forwarding mentioned below.

Forward if busy/engaged

Forwards calls to another location if you are using your phone and you have either disabled call

waiting or if you are in the process of making an outgoing call.

Forward if no answer

Will forward calls to another location if the call is not answered after a set period of time.

Forward if unreachable

Forwards calls to another location if the handset is off or outside a service area.

Call Waiting

Activate: *43#

Cancel: #43#

Status: *#43#

To answer an incoming call waiting just hit the [SEND] key and your first caller will be put on

hold and you can talk to the second caller. Alternatively you can hit [2][SEND].To join both

callers in a conference call, select the "join" or "conference" setting on your phone (not

supported on all handsets).If you wish to take the second call and are finished talking to the first

caller then hit the [END] key and your phone will start ringing with the second caller and then hit

[SEND] to answer the call. Alternatively you can hit [1][SEND].If you do not wish to talk to the

second caller and want to continue to talk to the first caller you can either choose to ignore the

call waiting tone or hit [0][SEND].

Caller ID / Call Display

If you wish to either show or hide your phone number on outgoing calls then you may either set

this on your phone's menu or manually enter the code before dialing. These codes will override

whatever menu setting you have on a per-call basis.

Do not display: #31#[phone number]

Display: *31#[phone number]

Status: *#31#

North American GSM service providers also support the landline codes for this feature (these

also work on CDMA, TDMA, and iDEN phones):

Do not display: *67[phone number]

Display: *82[phone number]

There are also codes to show or prevent incoming numbers from being shown on your handset if

you subscribe to this feature. I'm not too sure why you'd want to do this, but just in case you do:

Do not display: #30#

Display: *30#

Status: *#30#

Call Barring

If you wish to restrict calls that can be made or received by your handset then this is referred to

as "Call Barring".

Do Not Disturb

This particular feature is available from some North American GSM, CDMA, TDMA, and iDEN

providers:

Do not disturb: *78

Cancel: *79

Other Miscellaneous Codes

These have been collected from various sources and may be specific to certain networks only.

Minutes Used: #646# (646 spells 'MIN')

Own Number: *#100#

HLR number: *#101#

Switch number: *#102#

Network Time: *#103#

Voice mailbox number: *#104#

Switch number: *#105#

Last Caller: *#147#

Vodafone Prepaid balance: *#1345# or *174#

OTHER FEATURES

Short Message Service which allows you to send and receive 126 character text

messages

Ability to use same phone in a number of network-related countries

Allows data transmission and reception across GSM networks at speeds up to

9,600 bps currently

Allows fax transmission and reception across GSM networks at speeds up to

9,600 bps currently

Forwarding of calls to another number

More capacity, ensuring rapid call set-up. Handsets also smaller and robust.

Talk to a number of other parties simultaneously

Place a call on Hold while you access another call

Notifies you of another call whilst on a call

Encrypted conservations that cannot be tapped

You can barr outgoing calls and incoming calls

CLIP Allows you to see the telephone number of the incoming caller on the LCD

screen of the handset

CLIR allows you to bar anyone from seeing your number via CLIP

Real-time call costs on the handsets's LCD screen

Allows location/cell-specific reception of text messages.

FUTURE-The Universal Mobile Telecommunication System  

1. 3G Systems

3G Systems are intended to provide a global mobility with wide range of services including

telephony, paging, messaging, Internet and broadband data. International Telecommunication

Union (ITU) started the process of defining the standard for third generation systems, referred to

as International Mobile Telecommunications 2000 (IMT-2000). In Europe European

Telecommunications Standards Institute(ETSI) was responsible of UMTS standardisation

process. In 1998 Third Generation Partnership Project (3GPP) was formed to continue the

technical specification work. 3GPP has five main UMTS standardisation areas: Radio Access

Network, Core Network, Terminals, Services and System Aspects and GERAN.

3GPP Radio Access group is responsible of:

 Radio Layer 1, 2 and 3 RR specification

 Iub, Iur and Iu Interfaces

 UTRAN Operation and Maintenance requirements

 BTS radio performance specification

 Conformance test specification for testing of radio aspects of base stations

 Specifications for radio performance aspects from the system point of view

3GPP Core Network group is responsible of:

 Mobility management, call connection control signalling between the user equipment and the

core network.

 Core network signalling between the core network nodes.

 Definition of interworking functions between the core network and external networks.

 Packet related issues.

 Core network aspects of the lu interface and Operation and Maintenance requirements

3GPP Terminal group is responsible of:

 Service capability protocols

 Messaging

 Services end-to-end interworking

 USIM to Mobile Terminal interface

 Model/framework for terminal interfaces and services (application) execution

 Conformance test specifications of terminals, including radio aspects

3GPP Services and System Aspects group is responsible of:

 Definition of services and feature requirements.

 Development of service capabilities and service architecture for cellular, fixed and cordless

applications.

 Charging and Accounting

 Network Management and Security Aspects

 Definition, evolution, and maintenance of overall architecture.

Third Generation Partnership Project 2 (3GPP) was formed for technical development of

cdma2000 technology which is a member of IMT-2000 family.

In February 1992 World Radio Conference allocated frequencies for UMTS use. Frequencies

1885 - 2025 and 2110 - 2200 MHz were identified for IMT-2000 use. See the UMTS Frequency

page for more details. All 3G standards are still under constant development. In 1999 ETSI

Standardisation finished for UMTS Phase 1 (Release '99, version 3) and next release is due

December 2001. UMTS History page has a list of all major 3G and UMTS milestones. Most of

the European countries and some countries round the world have already issued UMTS

licenses either by beauty contest or auctions.

2. UMTS Services

UMTS offers teleservices (like speech or SMS) and bearer services, which provide the capability

for information transfer between access points. It is possible to negotiate and renegotiate the

characteristics of a bearer service at session or connection establishment and during ongoing

session or connection. Both connection oriented and connectionless services are offered for

Point-to-Point and Point-to-Multipoint communication.

Bearer services have different QoS parameters for maximum transfer delay, delay variation and

bit error rate. Offered data rate targets are:

 144 kbits/s satellite and rural outdoor

 384 kbits/s urban outdoor

 2048 kbits/s indoor and low range outdoor

UMTS network services have different QoS classes for four types of traffic:

 Conversational class (voice, video telephony, video gaming)

 Streaming class (multimedia, video on demand, webcast)

 Interactive class (web browsing, network gaming, database access)

 Background class (email, SMS, downloading)

UMTS will also have a Virtual Home Environment (VHE). It is a concept for personal service

environment portability across network boundaries and between terminals. Personal service

environment means that users are consistently presented with the same personalised features,

User Interface customisation and services in whatever network or terminal, wherever the user

may be located. UMTS also has improved network security and location based services.

3. UMTS Architecture

A UMTS network consist of three interacting domains; Core Network (CN), UMTS Terrestrial

Radio Access Network (UTRAN) and User Equipment (UE). The main function of the core

network is to provide switching, routing and transit for user traffic. Core network also contains

the databases and network management functions. The basic Core Network architecture for

UMTS is based on GSM network with GPRS. All equipment has to be modified for UMTS

operation and services. The UTRAN provides the air interface access method for User

Equipment. Base Station is referred as Node-B and control equipment for Node-B's is called

Radio Network Controller (RNC). UMTS system page has an example, how UMTS network

could be build.

It is necessary for a network to know the approximate location in order to be able to page user

equipment. Here is the list of system areas from largest to smallest.

 UMTS systems (including satellite)

 Public Land Mobile Network (PLMN)

 MSC/VLR or SGSN

 Location Area

 Routing Area (PS domain)

 UTRAN Registration Area (PS domain)

 Cell

 Sub cell

4. Core Network

The Core Network is divided in circuit switched and packet switched domains. Some of the

circuit switched elements are Mobile services Switching Centre (MSC), Visitor location register

(VLR) and Gateway MSC. Packet switched elements are Serving GPRS Support Node (SGSN)

and Gateway GPRS Support Node (GGSN). Some network elements, like EIR, HLR, VLR and

AUC are shared by both domains.

The Asynchronous Transfer Mode (ATM) is defined for UMTS core transmission. ATM

Adaptation Layer type 2 (AAL2) handles circuit switched connection and packet connection

protocol AAL5 is designed for data delivery.

The architecture of the Core Network may change when new services and features are

introduced. Number Portability DataBase (NPDB) will be used to enable user to change the

network while keeping their old phone number. Gateway Location Register (GLR) may be used

to optimise the subscriber handling between network boundaries. MSC, VLR and SGSN can

merge to become a UMTS MSC. 

5. Radio Access

Wide band CDMA technology was selected to for UTRAN air interface. UMTS WCDMA is a

Direct Sequence CDMA system where user data is multiplied with quasi-random bits derived

fromWCDMA Spreading codes. In UMTS, in addition to channelisation, Codes are used for

synchronisation and scrambling. WCDMA has two basic modes of operation: Frequency

Division Duplex (FDD) and Time Division Duplex (TDD). UTRAN interfaces are shown

on UMTS Network page.

The functions of Node-B are:

 Air interface Transmission / Reception

 Modulation / Demodulation

 CDMA Physical Channel coding

 Micro Diversity

 Error Handing

 Closed loop power control

The functions of RNC are:

 Radio Resource Control

 Admission Control

 Channel Allocation

 Power Control Settings

 Handover Control

 Macro Diversity

 Ciphering

 Segmentation / Reassembly

 Broadcast Signalling

 Open Loop Power Control

6. User Equipment

The UMTS standard does not restrict the functionality of the User Equipment in any way.

Terminals work as an air interface counter part for Node-B and have many different types of

identities. Most of these UMTS identity types are taken directly from GSM specifications.

 International Mobile Subscriber Identity (IMSI)

 Temporary Mobile Subscriber Identity (TMSI)

 Packet Temporary Mobile Subscriber Identity (P-TMSI)

 Temporary Logical Link Identity (TLLI)

 Mobile station ISDN (MSISDN)

 International Mobile Station Equipment Identity (IMEI)

 International Mobile Station Equipment Identity and Software Number (IMEISV)

UMTS mobile station can operate in one of three modes of operation:

PS/CS mode of operation: The MS is attached to both the PS domain and CS domain, and

the MS is capable of simultaneously operating PS services and CS services.

PS mode of operation: The MS is attached to the PS domain only and may only operate

services of the PS domain. However, this does not prevent CS-like services to be offered over the

PS domain (like VoIP).

CS mode of operation: The MS is attached to the CS domain only and may only operate

services of the CS domain.

UMTS IC card has same physical characteristics as GSM SIM card. It has several functions:

 Support of one User Service Identity Module (USIM) application (optionally more that one)

 Support of one or more user profile on the USIM

 Update USIM specific information over the air

 Security functions

 User authentication

 Optional inclusion of payment methods

 Optional secure downloading of new applications

Advantages and Disadvantages of GSM

GSM is still dominant in the mobile market, shares 80% worldwide market, in spite of fast

development of CDMA. There is a comparison that gives me vivid impression. Imagine a

cocktail party, where couples are talking to each other in a single room. The room represents the

available bandwidth. In GSM, a speaker takes turns talking to a listener. The speaker talks for a

short time and then stops to let another pair talk. There is never more than one speaker talking in

the room, no one has to worry about two conversations mixing. In CDMA, any speaker can talk

at any time; however each uses a different language. Each listener can only understand the

language of their partner. As more and more couples talk, the background noise (representing the

noise floor) gets louder, but because of the difference in languages, conversations do not mix.

Advantages of GSM service

Variety of handsets available for choosing. U can get a new handset almost every month (of

course if u have money lol).Its just about removing the SIM from old handset to a new handset.

And most importantly GSM services are not handset dependent.

Various service providers are available for choosing. If u aren’t satisfied with one switch over

to other. This is probably its biggest advantage. You r not in contract of any of the service

providers for any time. So u can switch over whenever u want.

Call Costs are becoming lower and lower everyday.

Call quality is much more pure and secure in GSM.

More and more value-added services like GPRS, EDGE etc are coming everyday.

Power is less consumed in GSM handsets compared to CDMA handsets.

If u have a tri-band GSM phone u can use it in almost any part of the world.

Disadvantages

Call costs will still remain higher compared to CDMA. Roaming costs are much lower in

CDMA compared to GSM.

GSM phones can be tampered with. They have their unique IMEI number which is used to

lock the phone permanently but nowadays software’s are available which can tamper them too.

If your SIM is lost then all data is lost unless u have it stored in the phone’s memory.

GSM and IS-95 (aka cdmaOne) are the two most prevalent mobile communication technologies.

Both technologies have to solve the same problem: to divide the finite RF spectrum among

multiple users.

TDMA (Time Division Multiple Access - underlying technology used in GSM's 2G) does it by

chopping up the channel into sequential time slices. Each user of the channel takes turns to

transmit and receive signals. In reality, only one person is actually using the channel at a specific

moment. This is analogous to time-sharing on a large computer server.

CDMA (Code Division Multiple Access - underlying technology used in GSM's 3G and IS-95's

2G) on the other hand, uses a special type of digital modulation called spread spectrum which

spreads the voice data over a very wide channel in pseudorandom fashion. The receiver undoes

the randomization to collect the bits together and produce the sound.

As a trivial comparison imagine a cocktail party, where couples are talking to each other in a

single room. The room represents the available bandwidth. In GSM, a speaker takes turns talking

to a listener. The speaker talks for a short time and then stops to let another pair talk. There is

never more than one speaker talking in the room, no one has to worry about two conversations

mixing. In CDMA, any speaker can talk at any time; however each uses a different language.

Each listener can only understand the language of their partner. As more and more couples talk,

the background noise (representing the noise floor) gets louder, but because of the difference in

languages, conversations do not mix.

CDMA Advantages:-

The first and the most important advantage in CDMA is the cost of calls is lower than GSM.

Although this difference is becoming transparent day by day still roaming costs will remain low.

CMDA services in India are backed up India’s most wealthy companies Tata and Reliance. 

Rite now the call quality is better than GSM. But as soon as the subscriber base increases the

call quality will start going low because of the way in which CDMA system works.

Disadvantages:-

Although many handsets are available in CDMA service u don’t find as much variety as u

would in GSM handsets.

The biggest disadvantage for CDMA handsets is they aren’t compatible with GSM handsets.

U cannot use a CDMA handset with a SIM card. So u gotta stick around with one handset for a

long time.

Another disadvantage is that in CDMA only 2 service providers are there Reliance and Tata.

While Tata is still improving so u gotta stick to Reliance u have no option. Of course Reliance is

too increasing day by day.

The web based services like messenger, downloading ringtones etc from websites are not yet

available in CDMA services yet. 

At the end I would like to tell u that I have stated the advantages and disadvantages of both

CDMA and GSM services now it depends on u which service u choose.