WLAN –3GPP CELLULAR INTERWORKING (WI-FI OFFLOAD)

Techno –Functional Presentation from a AAA perspective

Biju M R

Telecom /Media OSS/BSS Functional Architect & SME

bijumr@outlook.com

WLAN Interconnection- Introduction

Spectrum shortage is driving MNOs to find alternatives to support growing sub base

Most established method is to leverage Wi-Fi to offload data from core network.

Typically Wi-Fi hotspots are positioned in locations where significant amounts of data are generated

In trusted /untrusted mode, Wi-Fi hotspots can be integrated with the fixed or mobile operator’s policy and accounting

infrastructure

Cellular – Wi-Fi(WLAN) inter mobility (cellular offload over Wi-Fi access) is a retail Wi-Fi service opportunity for MNOs to

ensure seamless connectivity and mobility between cellular infrastructure and Wi Fi hotspots. Here Wi-Fi network (of MNO

or partner WISP) is used to offload data from the mobile operator’s cellular network and onto the unlicensed Wi-Fi spectrum

.

3GPP considers following 6 scenarios for 3GPP-WLAN interworking:

Common billing and customer care

3GPP system based access control and charging

Access to 3GPP system PS(packet switched) based services

Service continuity

Seamless service provision

Access to 3GPP CS(circuit switched) services.

3

OFFLOAD INTRODUCTION

LOCAL WI-FI SERVICE PROVIDER

Non MNO Wi-Fi service Provider

• AP-WLC connectivity

• Local AAA & DHCP

• WLC/AAA property to authenticate user

• Access: Local breakout via WLAN gateway

• AAA RADIUS/DIAMETER (Non EAP)

• Local policy & Billing with interface towards AAA

OSS/BSS Solution Vendor Scope

1. Wi-Fi AAA 2. DHCP 3. Local Billing , Charging CRM 4. Captive Portal

• AP via WLC connect with Access gateway

• Gateway - 3GPP AAA interface

• 3GPP AAA used to transport authentication, authorization, and charging-

related information. (Over EAP)

• 3GPP AAA verification of user with HLR/HSS over Sigtran and Diameter.

• Possible 3GPP AAA interface with OFCS, OCS, PCRF (service

authentication)

• Alternate interface from 3GPP AAA with Wi-Fi own policy & billing system

• User story limited to Non SiM WLAN customers of MNO

• Partial MDO scenario where scope limited to user authentication only

AAA Vendor Scope

1. 3GPP AAA with interface to WLAN Gateway, HLR/HSS

2. Non 3GPP Wi-Fi Billing & Policy Management

3. OR Convergent 3GPP OCS and PCRF with option to accommodate broadband and voice service as well in addition to WLAN charging, billing & policies

4. Captive portal

MNO WI-FI SERVICE FOR NON SIM ACCESS

• Both Non SIM and SIM customers of MNO

• MDO scenario

• Non SIM customers authenticated from 3GPP AAA over HLR/HSS and connected to access via a local break out (AAA using EAP)

• Alternate approach to have a local AAA to perform initial filtration and do authenticate . Authorize for non SIM customers ..(overhead and additional cost)

• Non SIM customer policies and billing via 3GPP AAA interface with PCRF/OCS or Wi-Fi specific Billing/policy system –Diameter/Radius/web service

• SIM customer authentication using 3GPP over HLR/HSS (using EAP –AKA and SIM)-Sigtran/Diameter

• SIM customer Access , charging and policies diverted to MNO core - GGSN via WAG since the WLAN access is of MNO and is treated as trusted.

• 3GPP AAA interface with WAG/EWAG for controlling and advising the charging characteristics of SIM customer -Diameter

• WAG/PDG interface with WLC /Access Network of WiFi for data transfer towards the GGSN/PGW and to PDN

MNO –SIM & Non SIM using Trusted & Own network

AAA Vendor Scope

1. 3GPP AAA with interface to WLAN Gateway, HLR/HSS, WAG

2. Non 3GPP WIFi Billing & Policy Management

3. OR Convergent 3GPP OCS and PCRF with option to accommodate

broadband and voice service as well in addition to WLAN charging, billing &

policies

4. Captive portal

• Story belongs to both MNO SIM customers as well an Wi-Fi

service provider WLAN customer

• Both MNO and Wi-Fi service provider have a partnership to

offload MNO SIM customers to0 WLAN network whenever

there is a congestion

• Non SIM customers authenticated from WLAN AAA over own

access data base and connected to internet via a local break

out (AAA using EAP)

• SIM customer authentication using 3GPP over HLR/HSS (using

EAP –AKA and SIM)-Sigtran/Diameter . WLAN AAA will act as

proxy for 3GPP AAA in such case

• SIM customer Access , charging and policies diverted to MNO

core - GGSN via TTG since the WLAN network is of a third party

and is treated as untrusted by MNO .

• 3GPP AAA interface with TTG/PDG for un trusted

internetworking and data offload (MNO interface with third

party Wisp WLAN)

• TTG/WAG/PDG interface with WLC /Access Network of Wi-Fi for

data transfer towards the GGSN/PGW and to internet

MNO - Wi-Fi SP partnership - Untrusted Network

3GPP

AAA

AAA Vendor Scope for Wi-Fi Service Provider

1. Wi-Fi AAA 2. DHCP 3. Local Billing , Charging CRM 4. Captive Portal

AAA Vendor Scope For MNO

1. 3GPP AAA 2. 3GPP OCS 3. 3GPP PCRF

Mobile Data Offload Solution

BUSINESS USER STORY & SOLUTION SCOPE

• MNO offering mobile wireless broadband and voice service to customers

• MNO also offers Wi-Fi services which can be subscribed by both mobile service subscribers and non subscribers

• MNO wants to have a central system to monitor charging , billing and policy control of all its services irrespective of access types.

• MNO also use its Wi-Fi network to offload traffic of its core mobile subscribers whenever there is a congestion in MNO’s mobile

network

• MNO also have partnership with external Wi-Fi hotspot providers, so that it may offload traffic of its core mobile customers whenever

there is a traffic congestion in the area.

• In such scenario, where MNO mobile subscribers are getting offloaded to non MNO Wi-Fi network, MNO would like to perform

authentication , charging and policies by itself instead of handing over the control also to Wi-Fi service providers.

• Whenever a offload activity to be carried out (to both MNO WIFI and Non MNO Wi-Fi locations), MNO wants to implement a SIM based

authentication to users instead of captive portal or user/password based authentication mechanisms.

MDO Solution scope to MNO :

• MDO solution (Prime Offering with this perspective)

• MDO+ Exclusive Charging /Policy for Wi-Fi subscribers of MNO (which means it does not include mobile

subscribers offloaded to WLAN (Possible option))

• MDO + Convergent charging /Policy for all service (possible option)

MDO 3GPP AAA SOLUTION –DEPLOYMENT ARCHITECTURE

3GPP AAA

Wg

Wa

D/Gr

Wx Wm

Untrusted Partner WiFi

MNO’s Trusted own WiFi

Wi-Fi Service Provider WLAN

Network (Untrusted) MNO 3GPP Core Network

MNO’s trusted WLAN Network

Wg

MDO SOLUTION –FEATURES & FUNCTIONS

System Component

• 3GPP AAA aka Mobile Data Offload AAA Solution

• Interfaces to HLR, HSS, WLAN , TTG, WAG (mandatory)

• Interface to OCS , PCRF, OFCS (optional)

System features expected :

Functions identified as part of Wx/d’ with HLR /HSS & Wa(STa,Stb) with WLAN AN

• Perform authentication , authorization of both SIM /Service for logged user , as per the interface had with WLAN AN (WLAN

AAA) and HSS/HLR. Perform request capture /response and terminates. Also accommodate reauthorization towards wlan , if

required/triggered from HSS /HLR

• Perform SIM authentication procedure by comparing SIM credentials received from both UE and HLR/HSS

• Cashing of user credentials like IMSI, MSISDN , charging attributes, APN etc. during the time of initial authentication to avoid

frequent interactions with HLR/HSS /or to be used during Wm interface with PDG

• Generate accounting records as per the operator requirement (with interaction to WLAN AN(wlan AAA) against Accounting

start /stop commands (diameter/radius). Output may be an ASCII formatted file with appropriate header and footer in addition

to a log facility in DB

Functions identified as part of Wm interface with PDG/TTG

• Verify and respond over a request from PDG/TTG (DER/DEA messages) on the availability of a user session in HSS/3GPP

AAA from the context of authentication and authorization; Further verify user has subscribed to a specific WLAN APN, has

access while roaming , monitor the number of simultaneous access to an APN by a user and respond back.

• 3GPP AAA also must have downloaded the charging characteristics provisioned within the HSS to support the charging/routing

policy implementation by PDG/WAG. In this perspective it will be cashing /storing the downloaded information to compare and

act accordingly.

Functions identified as part of Wm with PDG/TTG; Continuing…..

• AAA system against an active UE session , on receiving the session termination from PDG/TTG, shall

remove all related data of the active session of user with the specific APN mentioned; Also if required also

communicate WAN to remove charging policies if any. Similarly AAA shall initiate a termination towards the

PDG in the event of any blocking to subscriber services to WLAN happens in between

• AAA also to perform the re authorization procedure towards the PDG in the event of any updated within the

3GPP AAA related to the subscriber credentials

• Functions identified as part of Wg with WAG; Continuing…..

• 3GPP AAA need to perform upload of policy rules (extracted from HSS/HLR using Wx) to WAG against a

user session tunnel with specific APN. AAR/AAA messaging will be used to perform the same.

• Similarly 3GPP AAA need to remove policies from WAG as and when user tunnel has disconnected (as part

of user log off) or due to a change in subscriber properties. ASR/ASA will be used for this.

• WAG interface with 3GPP AAA to report removal of a policy in certain scenario, using a STR/STA message,

once received the message , 3GPP AAA to perform the removal or try to reconfigure a routing policy with

AAR/AAA

AAA VENDOR MDO SOLUTION –FEATURES & FUNCTION

Thank you

Biju M R

Telecom /Media OSS/BSS Functional Architect & SME

biju.vrindavan@gmail.com / +91- 9447006924