Overview on wireless technologies: on the road to UMTS and beyond
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Transcript Overview on wireless technologies: on the road to UMTS and beyond
UNESCO/CISM SECOND ADVANCED SCHOOL OF
INFORMATICS
UNESCO PROJECT
Advanced Course on Networking
Introduction to Cellular Wireless Networks
On the Road to UMTS
Mobile Communications system
Evolution
Outline
GSM
GPRS
UMTS
CDMA
WCDMA
Summery
What is GSM??
(Global System for Mobile Communications)
GSM Architecture
Three broad parts
Mobile
Station (MS): carried by the subscriber
Base Station Subsystem: control radio link with MS
Network Subsystem: its main part is MSC
Interfaces:
Um
Interface : known as air interface or radio link.
Abis Interface: between BTS and BSC
A Interface: between BSC and MSC
Mobile Station
ME(mobile equipment)
the terminal
SIM (Subscriber identity Module)
provides personal mobility.
Can insert the SIM card into another
GSM terminal and use
Base Station Subsystem
BTS (Base Transceiver Station)
handle the radio link protocols
with the Mobile Station
many BTSs in a large urban area
BSC (Base Station Controller)
manages the radio resources for
one or more BTSs
handles such as: channel setup ,
frequence hopping and
handovers.
connection between MS and MSC
Network Subsystem
MSC (Mobile Services Switching Center)
acts like a normal switching node of
the PSTN or ISDN
provides the connection to the fixed
networks (such as the PSTN or ISDN).
HLR (Home Location Register )
contains information of each
subscriber registered in the
corresponding GSM network, along
with the current location of the mobile.
logically one HLR per GSM network
Network Subsystem cont.
VLR (Visitor Location Register)
contains selected information from the
HLR, necessary for call control and
provision of the subscribed services,
each mobile currently located in the
geographical area controlled by the VLR.
EIR (The Equipment Identity Register)
a database that contains a list of all valid
mobile equipment on the network,
AuC (The Authentication Center)
is a protected database:secret key of SIM
GSM Features
Multiple access: use TDMA/FDMA to
share the limited radio spectrum
The FDMA part involves the division by
frequency of the (maximum) 25 MHz bandwidth
into 124 carrier frequencies spaced 200 kHz apart.
Each of these carrier frequencies is then divided in
time, using a TDMA scheme.
GSM is a digital network
Based on Circuit-switch
GSM Features cont.
SMS: Short Message Service
is a bi-directional service for short (up to 160 bytes)
messages. Messages are transported in a storeand-forward fashion.
an acknowledgement of receipt is provided to the
sender.
can also be used in a cell-broadcast mode, for
sending messages such as traffic updates or news
updates. Messages can also be stored in the SIM
card for later retrieval
GPRS System
(General Packet Radio Service)
GPRS Architecture
Introduce two new nodes into GSM network
SGSN
(the Serving GPRS Support Node):
– Keep track of the location of the mobile within its
service area and send/receive packets from the
mobile , passing them on, or receiving them from the
GGSN
GGSN
(Gateway GPRS Support Node):
– convert the GSM packets into other packet protocols
(e.g.IP or X.25) and send them out into another
network.
GPRS Features
Log on to GPRS
A
GPRS-capable terminal communicates with
GSM base Stations, but unlike circuit-switched
data calls which connects to MSC, GPRS packets
are sent from the base station to SGSN, SGSN
communicates with GGSN.
Establishes a Packet Data Protocol (PDP) which is
logical connection between the mobile and GGSN
now visible to the outside fixed networks
GPRS Features Cont.
SGSN
and GGSN use GPRS tunnel protocol
(GTP) which operates over the top of TCP/IP to
encapsulate the packets
Tunnels: information may be encrypted and
additional data is added to each packet to
prevent tampering
Packed based
No
dial-up, just as with a LAN connection.
No delay for sending data
GPRS Features Cont.
pay
for the amount of data they actually
communicate, and not the idle time
users need to confirm their agreement to pay for
the delivery of content from the service. This is
performed by using WAP (Wireless Application
Protocol)
unsolicited
packets may not be charged
voice and Data Communication at the same time
can be viewed as a sub-network of the Internet
GPRS Features Cont.
Spectrum Efficiency
users
can share the resource (Radio link),it is used
only when users are actually sending or receiving
data
Speed: Based on GMSK
a
modulation technique known as Gaussian
Minimum-shift keying.
Theoretical Max speeds up to
171.2kbps.(GSM:9.6Kbps)
GPRS Features Cont.
a
channel that is 200kHz wide, is divided into 8
separate data streams, each carrying maximum
20kbps(14.4kbps typical), GSM only use one
channel, GPRS combine up to 8 of these channels.
complement rather than replace the current
data services available through today’s GSM
doesn't
require new radio spectrum
supports
TDMA: also use for IS-136
Scenario for Migration
from 2G to 3G
What are 3G Technologies?
UMTS
(Universal Mobile Telecommunications Service)
EDGE
can co-exist with UMTS
– e.g. Edge provide high speed services for wide-area
coverage while UMTS is deployed in urban hot spots.
Cdma 2000
based
on the cdma One standard, two air
modes:
– one based on the parallel use of 3 contiguous
cdmaOne carriers (multi-carrier approach),
– the other one on the use of the corresponding 3
carriers width spreading (direct spread approach)
What does UMTS provide?
Circuit- and Packet-Oriented Services
Seamless Global Roaming
Capacity and Capability to serve more
than 50% population
A Wide Range of Services
Voice,
low-rate data and high-rate data
144kb/s, 384kb/s , 2Mb/s
UMTS coverage vs. bit rate
UMTS
Vehicle
Outdoors
Broadband Radio
Walk
Fixed
Indoors
GSM
0.5
2.0
155Mb/s
UTRAN-UMTS Terrestrial Radio Access Network
Core Network
lu
lur
lub RNC
Node B Node B
Uu
MH
lu
lur
lu
RNC
RNC
Node B Node B
Node B Node B
Frequency Allocation
1920-1980 MHz paired with 2110-2170
MHz
Total 35 MHz unpaired band
C
C
1920
MSS
A
1980
B
2010 2025
A’ MSS
2110
2170 2200
FDD vs. TDD
•Both FDD and TDD
are available in UMTS
•TDD has been
designed for use in
high density areas
•The highest bearer
rate:
•TDD-2.048Mb/s
•FDD-384kb/s
CDMA
(Coded Division Multiple Access)
In CDMA, every user assigned a unique
Code
WCDMA
Radio Parameters
Performance Improvement
Channels
Channel Generation
Power Control
Handoff
WCDMA Radio Parameters
Group 200KHz bands into 4.2-5.0 MHz
carriers
Chip Rate is 4.096 Mchips/sec
System Capacity of 128 channels per
cell provided by 5 MHz bandwidth
WCDMA Performance
Improvement
Capacity Improvement
No Frequency Planning
Multiple Services per Connection
Frequency Handoff
HCS
Hot
Spot
HCS & Hot-Spot
HCS-Scenario
Macro
Hot-Spot Scenario
Hot-Spot
Micro Macro
f2
f2
f1
f1
Handoff between layers
f1
f1
f1
Handoff at Hot-Spot
is alwayse needed
is sometimes needed
WCDMA Channels
Transport channels are the services which the
physical layer provides to higher layers.
The number of transport channels is much
higher than for GSM as more services are
needed.
Transport channels are grouped into two
classes:
Common channels (where information is
transmitted to all mobile terminals without
distinction)
Dedicated channels (where communication takes
place towards a single terminal by associating it
with a physical channel, i.e. a code and a
frequency or, in the case of TDD, also a time slot).
WCDMA Channels.. Cont.
The following common channels are provided:
BCH (Broadcast Channel): used on the downlink to transmit system
information in the entire cell.
FACH (Forward Access Channel): used on the downlink to transmit control
information to mobile terminal. It also can be used to transport short data
packets (as with GSM Short Message Service). FACH is used when the
system knows the cell in which the terminal is registered.
PCH (Paging Channel): used on the downlink to transmit control
information to mobile terminal whose location is not known. Transmission
here is associated with paging indicator which informs the mobile terminal
that the information is present on the paging channel, thus permitting
lower battery consumption.
SCH (Synchronization Channel): used on the downlink to permit
synchronization between the mobile terminal and base station.
RACH (Random Access Channel): used on the uplink to transport control
information transmitted by the mobile terminal.
CPCH (Common Packet Channel): used on the uplink to transport data
packets especially burst traffic.
DSCH (Downlink Shared Channel): used in the downlink to transport data
packets. Access is shared by various users and is regulated by the base
station.
WCDMA Channels.. Cont.
There are certain physical channels which are not associated
with a transport channel. They are used to transport physical
layer information that does not need to be sent to higher layers.
These channels are as follows:
CPICH (Common Pilot Channel): a downlink channel on which a
known un-modulated sequence is transmitted.
DPCCH (Dedicated Physical Control Channel): physical channel
present on both links and used to transport physical layer
signalling.
AICH (Acquisition Indication Channel): present on the downlink
and used to inform the mobile terminal that there is a message on
the FACH channel in response to an access attempt.
PICH (Paging indication Channel): present on the downlink and
used to inform the mobile terminal that there is a message on the
PCH channel.
WCDMA Channels.. Cont.
Physical Channels: are typically based on the
following structure:
Radio frame: has a length of 10 ms and consists of
15 time slots.
Time slot: has a length of 10/15 ms. Each slot
consists of a number of symbols which varies
according to the bit rate of the service to be
transmitted.
Symbol: this is the information element after the
channel encoding operations (i.e. after error
correction codes are inserted)
Power Control In WCDMA
Near-Far Problem in CDMA
Different
Performance for Subscriber Links
A Few Subscribers closest to the BTS may
contribute too much multiple Access
Interference.
Power Control In WCDMA
How to do power control
Force
all users to transmit the minimum
amount of power
Reduce the power transmitted by users
closest to the BTS; increase the power
transmitted by users farst to the BTS
Power Control In WCDMA
Open Loop vs. Close Loop
Open
Loop Power Control
Subscriber measures the DL power and
adjusts its transmission power
Close Loop Power Control
BS measures the UL power. MS measures
the DL power and reports to the BS. BS
instructs the user to raise or lower it
transmission power
WCDMA Soft Handoff
BS1
BS2
BS1
Active set = BS1
BS2
Active set = BS1 & BS2
BS2 SS > add threshold
BS1
BS2
Active set = BS2
BS1 SS < drop threshold
Active Research Topics
Cellular system architecture
UMTS air interface
Power control in CDMA
Handoff
Satellite-UMTS traffic
Integrated All-IP 3G-WLAN
Reference
http://www.europe.alcatel.fr/telecom/rcd/keytech/
http://www.comms.eee.strath.ac.uk/~gozalvez/gsm/
http://www.gsmworld.com/
http://www.ibctelecoms.com/
http://www.span.net.au/
http://www.cdg.org/tech/a_ross/
http://www.nokia.com/networks/mobile/
http://www.gsmdata.com/
http://www.sds.lcs.mit.edu/~turletti/gmsk/
http://www.wirelessweek.com/issues/3G/
Reference
http://www.umts-forum.org/reports.html
http://www.itu.int/imt/
http://www.etsi.org/
Flavio Muratore: UMTS, Mobile Communications for future, John Wiley &
Sons, 2001.
S. Dutnall, N. Lobley, A. Clapton, UMTS: The mobile part of broadband
communications for the next century IEEE Atm Workshop, Proceedings.
p242-252,1998
S. Breyer, G. Dega, V. Kumar, L. Szabo, Global view of the UMTS concept
Alcatel Telecommunications Review. n 3 1999. p 219-227
M. Lee, CDMA Network Security , Prentice-Hall, 1998
U. Black, Mobile & Wireless Networks, Prentice-Hall, 1999
M. Gallagher, W. Webb, UMTS: The next generation of mobile radio, IEE
Review. v 45 n 2 1999. p 59-63
Reference
A. Samukic, UMTS Universal Mobile Telecommunications
System:Development of standards for the third generation, IEEE Global
Telecommunications Conference & Exhibition. v 4 1998. p 1976-1983
N. Prasad, GSM evolution towards third generation UMTS/IMT2000, IEEE
International Conference on Personal Wireless Communications 1999,
p 50-54
A. Samukic, UMTS universal mobile telecommunications system:
Development of standards for the third generation, IEEE Transactions on
Vehicular Technology. v 47 n 4 Nov 1998. p 1099-1104
Thank you !!!
UNESCO PROJECT
Advanced Course on Networking
Professor Khalid Al-Begain
UNESCO/CISM SECOND ADVANCED SCHOOL OF
INFORMATICS
University of Damascus, Syria, 06 - 15 April 2004