On the Road to UMTS
(Universal Mobile Telecommunications Service)
Hongyi Wu
Xiaojun Cao
Copyright, 2000 © SUNY at Buffalo.
Outline
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Introduction to GSM
GPRS
EDGE
UMTS
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 store-andforward 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 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 minimumshift 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
GPRS Phrase
• Phrase 1
– expectedly to be available commercially in 2001, Point
to point GPRS will be supported
• Phrase 2
– net yet fully defined, but is expected to higher data
rates through possible incorporation of techniques
such as EDGE, in addition to Point-to-Multipoint
support.
EDGE
(Enhanced Data Rates for GSM Evolution)
EDGE Features
• Introduce new methods at the physical layer
– new form of modulation: 8PSK(phrase Shift Keying)
• introduced as a complement to GMSK (Gaussian Filter Minimum
Shift Keying)
• 8PSK: use 8 phrases to carry signals
– Different ways of encoding
• nine MCS(Module Coding Schemes) have been defined,
from 8.8kbps per timeslot(MCS-1 with GMSK modulation)
up to 59.2kbps per timeslot(MCS-9 with 8PSK modulation)
– High radio interface data rates (up to 384kbps)
EDGE Features cont.
• Provides an evolutionary migration path from
GPRS to UMTS
– Only one EDGE transceiver unit need to be added to
each cell.
– Software upgrades to BSC and Base Stations can be
carried out remotely.
– Higher layer protocols (GGSN, SGSN) stay the same
– Can be introduced smoothly in GPRS(doesn’t require
any new elements)
EDGE Features cont.
• EDGE is a technology both for
– HSCSD(High Speed Circuit Switched Data) is simply a
Circuit Switched Data call in which a single
user can take over up to four separate channels
at the same time.
– and for GPRS(General Packet Radio Service) to meet
the demands of wireless multimedia
applications.
– Also introduced into existing IS-136 networks
EDGE Features cont.
• The Data networking for WCDMA will
likely be based on EDGE/GPRS
infrastructure protocols, Such as GTP(GPRS
Tunneling Protocol)
• As a consequence EDGE is a way to
provide 3G services on 2G networks
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 are 3G Technologies? Cont.
• UWC-136
(USA cellular standard)
– based on GPRS and EDGE technologies defined
by ETSI for data on overlay of ANSI-136
"classical" networks for voice. Nevertheless,
UWC-136 can benefit from the expected
standardization of voice over IP (VoIP) on EDGE.
D-AMPS operators mainly promote UWC-136.
To be Continued
• Mr. HongYi Wu will give us More detail
about these topics
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
UMTS Hierarchical Cell
Structure
Satellite Mega-Cell
Satellite Mega-Cell
Macro-Cell
Micro-Cell
Pico-Cell
Micro-Cell
Pico-Cell
Macro-Cell
Micro-Cell
Pico-Cell
Micro-Cell
Pico-Cell
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
WCDMA
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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
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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
is alwayse needed
f1
f1
f1
Handoff at Hot-Spot
is sometimes needed
WCDMA Channels
• Forward WCDMA Channels
–
–
–
–
Pilot Channel
Sync Channel
Paging Channel
Forward Traffic Channel
• Forward Information Channel
• Forward Singal Channel
WCDMA Channels
• Reverse WCDMA Channels
– Access Channel
– Reverse Traffic Channel
• Reverse Information Channel
• Reverse Signaling Channel
An Example of Channel Generation
Walsh 128
4.096 Mcps
16 ksps
Convolutional
Encoder
R=1/2, k=9
16 kbps
Long Code
Generator
16 ksps
Symbol
Repetition
Block
Interleaver
16 ksps
64 ksps
16 ksps
64 ksps
A Forward WCDMA Sync Channel
WCDMA Convolutional Encoder
Input
data
a,b,...
Output
Symbols
(a1,a2)
(b1,b2)
…...
A (2,1,8) Convolutional Encoder Implemented by LFSR
WCDMA Block Interleaving
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
1
17
9
25
5
21
13
29
...
...
...
...
...
...
...
...
WCDMA Orthoganal Modulation
• Walsh Code Generation
H1  0
H
H2   1
 H1
H4
H 2
 
H 2
H1 
0

0
H1 


0
0
H2 
 

0
H2 

0
......
H 128  128  128 Matrix
0
1

0
1
0
0
0
1
1
1
0
1

1

0
CDMA Orthoganal Modulation
• Modulation
– Take 6 bit from the input stream (C0, C1, C2, C3,
C4, C5)
– Compute MSI (Modulation Symbol Index)
MSI= C0+2 C1+4 C2 +8C3+16C4+32 C5
– Each of the six symbol group is mapped to the
row(MSI) of H128
WCDMA Direct Sequence
Spreading
•Long Code Generation by LFSR
Long Code Seed
1
x
x2
x32
XOR
Long Code 4.096 Mcps
WCDMA Direct Sequence
Spreading
dw(t)
0
0
0
0
0
1
1
1
0
0
0
1
1
1
1
1
C(t)
0
0
Ds(t
)
1
1
1
0
1
1
1
1
0
1
1
1
0
0
0
0
0
1
0
1
0
1
1
1
t
0
1
1
0
0
1
t
t
Power Control In WCDMA
•Bit Error Rate and Power
e ,userP
P
 Q ( 3 N p )
N: Spread Factor
p : Carrier-to-Interference-Ratio for
Pp
subscriber P

p

K 1
P
k 0
k p
k
Power Control In WCDMA
• Perfect Power Control

p
1

k 1
Pe  Q (
3N
)
k 1
Power Control In WCDMA
• Near-Far Problem in CDMA
– Different Performance for Subcriber 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 farest 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
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Cellular system architecture
UMTS air interface
Power control in CDMA
Handoff
Satellite-UMTS traffic
Reference
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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
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http://www.umts-forum.org/reports.html
http://www.itu.int/imt/
http://www.etsi.org/
S. Dutnall, N. Lobley, A. Clapton, UMTS: The mobile part of broadband
communications for the next century IEEE Atm Workshop, Proceedings. p242252,1998
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
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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