Challenges of
Global Roaming
Syed S. Husain
WP1/SSG Chair
Motorola, USA
ITU-T Seminar on IMT-2000 and beyond Systems
Rio de Janeiro, Brazil
ITU-T Seminar on IMT-2000 and beyond
Systems, Brazil
(September 2001)
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Outline
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Global roaming - Definition & Requirements
Technical Areas of Concern
Ongoing Standards Efforts
An Assessment
Summary
ITU-T Seminar on IMT-2000 and beyond
Systems, Brazil
(September 2001)
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Global Roaming Definition
Global Roaming: Offer seamless services by hiding
network and radio access differences from the users.
Note: Global Roaming does not only mean that one has
to travel far. Within a small geographic area global
roaming requirements also apply.
ITU-T Seminar on IMT-2000 and beyond
Systems, Brazil
(September 2001)
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Global Roaming Requirements
Travel Service
High BW
Wired
Service
Interactive
Game
E-Mail Service
WLAN
Cellular Network
Office
Cellular Network
Highway
Convention Center
User
ITU-T Seminar on IMT-2000 and beyond
Systems, Brazil
(September 2001)
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Train
Global roaming – Requirements
• Multi-mode user equipment to support diverse
access technologies
• Multi-homed user equipment to support multiple
IP addresses
• Support of Enhanced services
– VHE/IN, UPT, IP Multimedia
• Mobility management across multiple service
provider domains
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Location management
Service portability
Authentication, Authorization and Accounting
QoS / bandwidth management (wired to wireless)
• Interoperability using single subscription
ITU-T Seminar on IMT-2000 and beyond
Systems, Brazil
(September 2001)
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Diverse Wireless Access Technologies
• ITU Approved 3G/IMT-2000 Radio Standards:
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CDMA Multi-carrier (cdma2000)
1xEV-DO
CDMA TDD (Universal Terrestrial Radio Access)
CDMA TDD (TD- SCDMA)
W-CDMA (UTRA FDD)
UWC-136 (FDD)
Digital Enhanced Cordless Telecommunications (DECT)
• WLAN IEEE 802.11 Series
• HIPERLAN
• Bluetooth
ITU-T Seminar on IMT-2000 and beyond
Systems, Brazil
(September 2001)
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Evolution of Mobile Services
(IP Multimedia Services)
Information and Content (Non(Non-Voice)
MOBILITY
CONTENT CONNECTIVITY
PERSONAL
Direct Link
to a Person
ITU-T Seminar on IMT-2000 and beyond
Systems, Brazil
(September 2001)
Always on,
IPIP-based
LOCATION
Knowledge
of Location
Multimedia
Messaging
Service
Intranet /
Extranet
Internet
PEOPLE
CONNECTIVITY
Customized
Infotainment
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Locationbased
Services
Evolution of Mobile Services
(Multiple Service Providers)
Supporting Networks
Service
Platforms
3rd Party Service Platforms
External
UE/CPE
ITU-T Seminar on IMT-2000 and beyond
Systems, Brazil
(September 2001)
Local
Access
Network
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Core/
Transport/
Backbone
Network
Multiple Dimensions of Mobility
-Low latency & low packet loss handoff
Internet
-Handoff between heterogeneous
networks
-Paging to locate device
-AAA
Macro Mobility
-Path optimization
IP Multimedia Domain
Access
Context Transfer
Router
Access Network 1
Examples of Access
Technologies: 3GPP,
3GPP2, 802.11,
Bluetooth, fixed IP
ITU-T Seminar on IMT-2000 and beyond
Systems, Brazil
(September 2001)
Access
Router
Access Network 2
New
Seamless mobility
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Micro-mobility
Note: This could use
mobility mechanisms
as defined in IETF
Security Challenges
• Case 1: Roaming between same network type, same generation
– Example, ANSI-41 (2G) to ANSI-41 (2G)
– A derivative of user secret (SSD) is passed between networks
• Case 2: Roaming between same network type, different
generations
– Example, UMTS (3G) to GSM (2G)
– Backwards compatible if security mechanism is unchanged
– If security mechanism is enhanced, translation is TBD
• Case 3: Roaming between dissimilar networks
– Example, ANSI-95 to GSM
– Either assign a dual subscription to the user, or
– Translate security parameters between networks
• Case 4: Roaming between cellular-based networks and IP-based
networks
– Example, WLAN to UMTS
– Methods are being studied
ITU-T Seminar on IMT-2000 and beyond
Systems, Brazil
(September 2001)
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Security Tiers
IP Multimedia Services
and Applications
IMS-Access
Network
IP Multimedia Subsystem Access
IP Service Access
IP-Access
Network
Wireless Access
Core
Network
Radio-Access
Network
ITU-T Seminar on IMT-2000 and beyond
Systems, Brazil
(September 2001)
Internet
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Core
Network
Interoperability
• Services Plane
– Voice Services
– Multimedia Services
• Transport Plane
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IPv4/IPv6 transition
SCTP to TCP/IP
MTP to M3UA
MTP/SCCP to SUA
• Control Plane
– Session Control (e.g., SIP, H.323, ISUP, BICC, PSTN)
– Mobility Management (e.g., ANSI 41, MAP, Mobile IP)
ITU-T Seminar on IMT-2000 and beyond
Systems, Brazil
(September 2001)
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Overview of Standards Development
Technical Areas
ITU-T
3GPP
3GPP2
IETF
Services Plane
SG2, SSG
SA1, SA2, CN1,
CN5
TSG-N
SIMPLE,
IMPP
Transport Plane
SSG, SG11,
SG13
SA2, CN3
TSG-A
ROHC,
DIFFSERV
Control Plane
SSG, SG13
SA2, CN1, CN4
TSG-N, TSG-P
SIP,
MMUSIC,
IPTEL
Mobility Mgmt
SSG, SG11
SA2, CN1, CN4
TSG-P, TSG-N
MOBILEIP,
SEAMOBY
Security
SG7, SSG
SA3, T3
TSG-S WG4,
TSG-P, AHAG
AAA,
RADIUS,
IPSec, AVT
Interoperability
SSG
CN3
TSG-N
PINT
Codec
SA4
TSG-C
UIM (Smart Card)
T3
TSG-S
ITU-T Seminar on IMT-2000 and beyond
Systems, Brazil
(September 2001)
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An Assessment
(Convergence Opportunities)
All Services
Common
Network Layer
Transport
IP
Common
Physical Layer
AT/ PPP
SONET/SDH
Fiber/WDM
ITU-T Seminar on IMT-2000 and beyond
Systems, Brazil
(September 2001)
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Common
Services API
An Assessment
(Gap Analysis and Technological Barriers)
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Radio system compatibility
UIM portability
Inter-system operability
Service portability
Billing/charging
Numbering plans
Authentication & privacy
ITU-T Seminar on IMT-2000 and beyond
Systems, Brazil
(September 2001)
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Conclusions
• Global roaming is a key requirement for IMT-2000
and beyond systems
• Ease of Interoperability between different
networks is demanded by users
• Global UIM based on a common UIM-MT interface
is needed
• Standards are needed to address critical issues of
global roaming
ITU-T Seminar on IMT-2000 and beyond
Systems, Brazil
(September 2001)
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