Adopting IMS in WiFi Technology

1
Adopting IMS in WiFi Technology

• Mehdi Mani, Noël Crespi
• GET/INT-Institut National des Télécommunications
• Core Network and Service Architecture Lab.
• France
• September 2007, Mobility Conference
• Singapore

2
WiFi/3G Integration

• Complementary Access Technologies
• Bandwidth
• Coverage

3G Services (ie. IMS based IP Telephony)
-Tight Coupled -Loosely coupled
3G PS Core
How to create a joint Service pool accessible
For the users of these two technologies
SGSN
WLAN
UTRAN
IMS is a promising (but not the only) Solution
3
Ubiquitous and Seamless IP Telephony in 3G-WLAN
Issues

• IPT Characteristics
• Session based.
• The end users need an application layer
  identification.
• Are usually e2e
• The end users may be mobile
• Roaming
• Handover

• Desired Service Aspects
• Robust and scalable architecture.
• Seamless services
• Service mobility
• Unique Numbering
• Access to the services of one domain from other
  domain.
• Providing the new combinational services.

4
3GPP Solution for WLAN access to IMS
5
3GPP Solution for WLAN access to IMS (A Higher
View)
CS domain
2G 3G MSC
2G 3G MSC
BSC
BTS
TDM
GERAN
IP-Network (PS domain)
RNC
HSS(HLR)
Node B
UTRAN
2G 3G SGSN
3GPP IMS
WLAN
WAG
PDG
Access Router
IP address allocation, P-CSCF discovery Service
authentication and authorization IMS signaling
6
IMS Registration Through WLAN
7
Why Going Beyond?

• Master/Slave Architecture
• Complicates the participation of WiFi operators
  in providing new services.
• The admission process is controlled by 3G
  operator.
• This is a solution for 3GWLAN operators.
• Session Setup procedure is long and complicated.
• May needs dual IPv4/IPv6 stack in users side
  device.

8
Adopting IMS in WiFi, Phase 1
9
Adopting IMS in WiFi, Phase 1

• Supporting P-CSCF
• ALG
• NAPT in the edge router.
• LR

• A permanent secure connection between P-CSCF and
  the IMS entities in 3G
• Giving options for choosing the desirable message
  Criptography.
• PDG and WAG elimination.
• Control of the QoS on the edge router directly.
• No need of dual stack
• Dependednt to 3G IMS for global session routing.
• Unique Numbering

10
Adopting IMS in WiFi, Phase 2
11
Adopting IMS in WiFi, Phase 2

• HSS
• S/I-CSCF

• Providing Public/Private ID
• Carry out AAA functionalities independent of 3G
  operators.
• Simplified process of access to the services.
• Supporting simple services on board.

12
Adopting IMS in WiFi, Phase 3
SCIM/ Service Broker
13
Adopting IMS in WiFi, Phase 3

• Application Servers (AS)
• SCIM/Service Broker

• Implementation of Advanced SIP based Services in
  WiFi.
• Service invocation and triggering carry out in
  WiFi domain.
• Possibility of implementing advanced and combined
  services.

14
Conclusion

• The 3GPP solution for WLAN access to IMS is
  complicated.
• Smooth migration toward deploying IMS in WiFi
  minimize the risk of investment.
• New combinational services and applications will
  grow up fast.