1. Architectures to support Offloading and Multi Connection APCC/ATNAC 2010
Version 0.1
Prasan de Silva
Enterprise Architect (Wireless & Convergence)
Group Technology
Telecom (NZ) Corporation

2. Disclaimer
The views presented in this presentation are not reflective of Telecom’s technology roadmap. The author is presenting his own research views on this emerging area
within the industry.

3. Contents Definition and Problem Space
Typical Use Cases for Offload and Multi Connection
Survey of Technology Options
Recap on UMTS Architecture
Recap on LTE Architecture
Femto Cell Architecture (3GPP Rel 8)
Femto Cell Architecture (3GPP Rel 10)
Local IP Access (LIPA) (3GPP Rel 10)
Integrated WLAN (I-WLAN) (3GPP Rel 7)
IP Flow Mobility (3GPP Rel 10)
ITU-T SG13 Multi Connection Architecture
Comparison of Techniques (intra-3GPP)
Comparison of Techniques (inter-3GPP)
A Target Architecture to Support Offload and Multi Connection

4. Definition and Problem Space
A mobile network is composed of finite resources which must be used optimally to maximise KPI’s such as accessibility, retainability and reduce cost per bit to serve.
While it is expected that networks scale to meet traffic demands, the key constraint is available spectrum.
Accepted (or traditional) practice for network expansion follows a pattern such as:
radio access network is optimised (e.g. antenna tilts, power budgets, interference mitigation etc)
sectorisation techniques can be employed (omni to 2/3sector to 6 sector etc)
additional carriers can be added (if spectrum is available)
coverage footprints can be reduced and new sites deployed
hierarchical cells structures can be introduced such as micro/pico cells to offload the macro carriers
.The industry is witnessing unprecedented growth in demand for capacity – primarily driven by data devices.
Reports such as Credit Sussie [*] claim that even if an extra 300MHz of required spectrum planned for allocation by the FCC in 2015 happens, 65% of the projected growth will still not be met.
This suggests that traditional methods of offloading alone will not suffice and other techniques will be needed to meet the demand from mobile devices.
This presentation focuses on state of the art mechanisms under study for offload and multi-connection techniques.
An underlying premise behind offload strategies is that the cost to serve of the recipient network or resource must be substantially lower than the primary network.
The presentation draws on current output from 3GPP and ITU T Study Group 13
*Telecom Industry Themes – Profiting From the Spectrum Crisis, 24 May 2010

5. Typical Use Cases for Offload and MC
Bandwidth Aggregation
Session Transferral
Resiliency – path diversity
Concurrent Applications
Ref: ITU-T Y.2000 Supplement 9

6. Survey of Technology Options

7. Recap on UMTS Architecture
Ref: 3GPP TS v9.1.0

8. Recap on LTE Architecture
Ref: 3GPP TS v9.1.0

9. Femto Cell Architecture (3GPP Rel 8)
The femtocell, or Home NodeB (HNB as defined by 3GPP) combines the NodeB and RNC functions.
The HNB interconnects to the Home NodeB Gateway (HN GW) via the newly defined IuH interface.
The IuH interface performs pseudo registration functions of HNB and UE’s as well as tunnelling of Non-Access Stratum (NAS) signalling to the core network.
The femtocell interconnects to the Mobile core network via the standard IuCS/PS interfaces, through the HNB GW function.
Mobility procedures employ existing mechanisms such as idle mode cell reselection through neighbour list advertisements, PLMN IDs, Closed Subsriber Group IDs, LAC, RAC, SAC and Primary Scrambling Code parameters sent via standard System Information Blocks.
With overlapping coverage, connected mode handoff is also supported.
Ref: 3GPP TS v9.1.0

10. Femto Cell Architecture (3GPP Rel 8)
Ref: 3GPP TS v9.1.0

11. Femto Cell Architecture (3GPP Rel 8)
A key concern with regards to Femto is interoperability – and the key interface is the IuH
There are two key protocols operating over IuH, namely, RANAP User Adaptation (RUA) and Home NodeB Application Part (HNBAP).
RUA implies that every HNB acts like an RNC to the core from a signalling perspective.
HNBAP is the means by which all HNB management and registrations occur.
Can an operator safely mix and match vendor products for HNB and HNB GW – and if not what are the consequences?
Ref: 3GPP TS v9.1.0

12. Femto Cell Architecture (3GPP Rel 10)
3GPP Release 10 is studying Femto architectures which integrate directly into an operator IMS core.
This approach allows offloading CS traffic from both the UTRAN and mobile CS core.
The most promising option is where the IMS Centralised Services (ICS) architecture is re-used (this effectively implies that H2=I2)
The key item to this approach is that the HNB GW natively converts UMTS layer 3 NAS signalling to SIP. The HNB GW therefore acts like an MSC enhanced for ICS.
Native protocol mapping by the HNB GW avoids the need to do conversions (like NAS<->BICC) which can lead to service transparency issues.
Ref: 3GPP TR v10.0.0

13. Femto Cell Architecture (3GPP Rel 10)
Ref: 3GPP TR v10.0.0

14. Local IP Access (LIPA)
Local IP Access (LIPA) is defined as the capability that allows the UE to request that all the packet data traffic exits the mobile architecture at the base station node (i.e. eNB).
The offload in this case is to the customers LAN network (e.g. their xDSL based broadband connection).
In this scheme the user plane packet data session does not utilise the mobile RAN, backhaul or core network. The control plane, however continues to use the mobile infrastructure.
The enhancement needed in the HNB end is the support of a local gateway function which acts as the egress for the packet data user plane (i.e. a GGSN or SGW/P-GW function).
A subset of this approach is called Selected IP Traffic Offload (SIPTO).
Ref: 3GPP TR v1.2.0

15. Local IP Access (LIPA)
Ref: 3GPP TR v1.2.0

16. Integrated WLAN (I-WLAN)
I-WLAN allows a 3GPP operator to extend the cellular subscription to the WLAN domain for seamless service authentication and authorisation but not seamless handoff to/from 3GPP network.
I-WLAN reuses the USIM based credentials to authenticate WiFi access, thus offloading the entire mobile RAN and PS core.
I-WLAN introduces a new Packet Data Gateway (PDG) node which acts as an operator hosted access router and security gateway.
The PDG interworks with the operators AAA infrastructure, which in turn links to the HSS/HLR/AuC so that EAP-SIM or EAP-AKA schemes could be used in the WLAN domain. Thus the reuse of customers (U)SIM based credentials.
Ref: 3GPP TS v9.0.0

17. Integrated WLAN (I-WLAN)
Ref: 3GPP TS v9.0.0

18. IP Flow Mobility
IP flow mobility and seamless WLAN offload has been standardised in Release 10 TS
The standard allows a WiFi/Cellular device to split traffic between the two access networks simultaneously in a coordinated manner.
By coordinating traffic between the networks, it is possible to offload some or all sessions from the cellular network.
For example, a UE involved in a videoconference may send real time voice component over UMTS and the high bandwidth video over WLAN.
The Evolved Packet Core (EPC) has provided the missing pieces of flow mobility for non-3GPP access integration (e.g. for I-WLAN, WiMAX). Hence IP flows can be anchored in the common core and bearer plane tunnels moved across the IP-CANs as needed with seamless continuity of sessions.
The key enabler being derivatives of Mobile IP - specifically DSMIPv6, P-MIP, and C-MIP.
Ref: 3GPP TS v10.0.0

19. IP Flow Mobility
Ref: 3GPP TS v10.0.0

20. ITU-T SG13 Multi Connection Architecture
Multi Connection is a new and promising area under study in ITU-T SG13.
The functionality is not being addressed in other SDO’s. Though 3GPP’s new item on Inter-UE Transfer (or IUT) has some overlap.
The diagram below shows the work-in-progress mapping to the NGN reference architecture, highlighting new functional entities which need to be defined.
Ref: ITU-T SG13 Y.MC_ARCH (Draft)

21. Comparison of Techniques ( intra-3GPP)
Offload Technique
RAN Offload?
Core Offload?
Standard Complete?
Device Impact?
Network Impact?
Ideal Reference Case
Yes No
Hierarchical Cells
Yes for congested macro sector
Inter-band
Yes for congested freq. band
No (for multi band UE)
Inter-RAT
Yes (e.g. GERAN to UTRAN)
No (for multi RAT UE)
Femto (Rel8)
Yes for CSG support
Yes – new nodes needed
Femto (Rel10)
Yes for IMS alternate
LIPA
Partial (user plane offloaded)
Yes - LTE device needed
Yes - Enhancements to HeNB needed
SIPTO
Yes (partial)
Yes - Direct tunnel for UMTS and new L-GW for LTE

22. Comparison of Techniques (inter-3GPP)
Offload Technique
RAN Offload?
Core Offload?
Standard Complete?
Device Impact?
Network Impact?
I-WLAN
Yes
Yes – EAP schemes
Yes – new network node/AAA integration
IP Flow Mobility
Yes – entire session offload or partial session offload No
GAN
Yes (for GSM)
ITU-T MC
Yes – similar to IP flow mobility
Yes - TBD

23. A Target Architecture to Support Offload and MC

24. Thank you for listening
Questions?