Transcript acoe_422_9_GSM.pps

GSM
Adapted from www.mobinet.gr
Acoe 422
History of GSM
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During the 80s, analog cellular systems
experienced rapid growth in Europe, yet
they were incompatible with each other
In 1982 the Groupe special mobile (GSM)
was formed to study and develop a panEuropean public land mobile system
Commercial service started in 1991
Although standardized in Europe, GSM is
not only a European standard
GSM Growth 1992-2002
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By 1993
there were
36 GSM
networks
in 22 countries
Today, over
200 GSM
networks are
operational in
110 countries
24 Billion SMS messages are sent per month
In the UK, the market for handset ring-tones is
currently worth over €87 million annually, while young
adults spent €71 million on downloadable logos
GSM accounts for 72.0% of the World's digital market
and 70.0% of the World's wireless market
GSM Coverage
GSM Systems Worldwide
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GSM was designed to be used in the
900MHz band
Later on, the frequency band of 1800MHz
was allocated to facilitate a second
system, similar to GSM. This system,
originally called DCS1800, evolved to be
essentially the same as GSM
The American-Japanese GSM version uses
the 1900MHz, used to be called PCS1900
There are now 3 GSM systems: GSM 900,
GSM 1800 and GSM 1900
Dual Band Network Overview
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DCS 1800 cells are generally coverage
limited
GSM 900 cells tend to be capacity limited
Implying a need for more DCS 1800 cells
to provide similar coverage to a
comparable GSM 900
GSM 900
DCS 1800
Uplink Band
890 - 915 MHz
1710 - 1785 MHz
Downink Band
935 - 960 MHz
1805 - 1880 MHz
200 kHz
200 kHz
124
374
45 MHz
95 MHz
8
8
Channel Spacing
Total Number of Channels
Duplex Spacing
No of Timeslots per Channel
GSM Characteristics
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Benefits
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Support for international roaming
Distinction between user and device
identification
Excellent speech quality
Wide range of services
Interworking (e.g. with ISDN, DECT)
Extensive security features
Services Offered by GSM
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Services
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Telephony
Asynchronous & synchronous data
services (2.4/4.8/9.6 kbps)
Access to packet data network (X.25)
Telematic services (SMS, fax,
videotext, etc.)
Many value-added features (call
forwarding, caller ID, conferencing with
up to 7 participants, voice mailbox)
GSM Radio Interface
TDMA
FRAME
n+1
4.615 ms
TN 7
TN 6
TN 5
TN 4
TDMA
FRAME n
TN 3
TN 2
TN 1
TN 0
FDMA
1
2
3
FDMA
200 kHz
123 124
Channel
1
890
MHz
3
123 124
Channel
25 MHz
25 MHz
Uplink
MS Tx
2
200 kHz
915
MHz
935
MHz
Downlink
MS Tx
960
MHz
124 Channels x 8 Time Slots = 992 Duplex Channels
GSM FDMA/TDMA
Channel Structure
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The fundamental
unit of time in
the TDMA
scheme is called
a burst period
Eight burst
periods are
grouped into a
TDMA frame
Traffic Channels
(TCH) are
defined using a
26-frame
multiframe of
120ms length
Signaling Channels (SCH)
TCH/CCH
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Traffic Channel
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A TCH is used to carry speech and data traffic
In addition to the full-rate TCHs, there are also
half-rate TCHs defined to double the capacity of
the system
Control Channel
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To help the MS find the control channels
To provide information about
 voice and control channel repetition cycle.
 parameters in the cell
 surrounding cells
 paging
To allow random access attempts by the MS
Burst
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The information contained in one time slot
is a burst
Five types of burst are defined
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Normal Burst (NB)
 To carry information on traffic and control
channels
Frequency Correction Burst (FB)
 To synchronize the frequency of the mobile
Synchronization Burst (SB)
 To synchronize the frames of the mobile
Access Burst (AB)
 For random and handover access
Dummy Burst
 For padding the frame
GSM Network Architecture (1/5)
MS
PSTN
ISDN
PDN
BTS
BSC
GMSC
MS
BSC
MSC
BTS
EIR
BTS
BTS
BSC
BSS
MSC
GMSC
MS
Base transceiver station
Base station controller
Base station subsystem (BTS+BSQ)
Mobile switching center
Gateway MSC
MS
HLR
VLR
EIR
AUC
AUC
HLR
VLR
Mobile station
Home location register
Visited location register
Equipment identity register
Authentication center
GSM Network Architecture (2/5)
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Mobile Station
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Mobile Equipment
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Identified by the International Mobile
Equipment Identity (IMEI)
Subscriber Identity Module (SIM)
Contains a unique identification number
called IMSI
 It is removable, thus irrespective of a
specific terminal
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GSM Network Architecture (3/5)
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Base Station Subsystem (BSS)
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Base Transceiver Station (BTS)
 A BTS is comprised of radio transceivers,
antennas, the interface to the PCM facility
 BTS is the entity that connects the mobiles to
a cellular network
Base Station Controller (BSC)
 Its primary function is call maintenance, by
deciding when to initiate a handover, changing
the BTS transmitter power, etc.
 A BSC is connected to a group of BTSs and
manages the radio resources for them
GSM Network Architecture (4/5)
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Network Subsystem
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Mobile Switching Center (MSC)
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Home Location Register (HLR)
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Contains subscription information needed for call control,
for all mobiles in the area of the associated MSC
Equipment Identity Register (EIR)
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The HLR contains all the administrative information and
current location of each subscriber registered in the
corresponding GSM network
Visitor Location Register (VLR)
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MSC provides functions such as registration,
authentication, location updating, handovers and call
routing to a roaming subscriber
EIR is a database that contains a list of all valid mobile
equipment on the network
Authentication Center (AUC)
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Stores the secret key held in each user’s SIM card
GSM Network Architecture (5/5)
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Application Service Centers are responsible
for GSM network add-on services
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Operation and Maintenance Center (OMC)
 Monitoring and control the network
 Usually connect with MSC, BSC, HLR, and other
service centers
Short Message Service Center (SMSC)
 provide short message services
 usually connect to MSC
Unstructured Supplementary Service Data
Center (USSDC)
 provide USSD service in the form of
*ID*ID*info#
 usually connect to HLR
Mobility Management
BTS old
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BTS new
Location Registration
Call delivery
Handoff Management
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Handoff is caused by:
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signal strength deterioration
user mobility
There are two kinds of handoff:
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Handoff
margin
soft handoff
hard handoff
There are three ways to handoff:
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network-controlled handoff
mobile-assisted handoff
mobile-controlled handoff
MS
MS
BTS old
BTS new
Evolution of GSM Platform
y
log
o
n
ch
e
T
Introduction of 3rd generation radio
2001-2002
dio
New multimedia services
a
f R 2000
Mass market cost of service (IMT-2000)
o
nt
More capacity when neede (GSM 384)
e
pm 1999
o
l
ve
Internet-like IP packet services (GPRS)
De
1998
Landline-like circuit services (HSCSD)
1997
Basic GSM data at 9.6 kbps
Evolution of GSM Platform