LTE Roaming

Agenda

• Introduction

• Roaming Scenarios

– Data

– SMS

– Voice

– IMS

• Other considerations

LTE Roaming Situation

• None of Verizon LTE subscribers can roam on another LTE network, not even on other 700 MHz LTE networks in the US

• Roaming on 3G networks and their HSPA+ derivates is much easier, one reason being the fairly limited number of bands involved

• Considering the 473 commercial HSPA networks in 180 countries, it is much easier to maintain current 3G roaming agreements (without LTE)

Architecture Overview

Nodes Interface ID Protocol

MME - HSS S6a Diameter Base Protocol (IETF RFC 3588 [3]) and 3GPP TS

29.272 [8])

SGW - PGW S8 GTP (GTP-C 3GPP TS 29.274 [4] and GTP-U 3GPP TS 29.281 [5])

or PMIP (IETF RFC 5213 [20]) and

3GPP TS 29.275 [23])

hPCRF - vPCRF S9 Diameter Base Protocol (IETF RFC 3588 [3]) and 3GPP TS

29.125 [6])

MAP to Diameter Transition • Today’s 2G/3G networks use SS7-MAP protocol for

location/subscriber/access/handover/authentication/security/identity management & handover services

• However, in LTE/SAE (3GPP Rel. 8), Diameter protocol has been chosen for many of these procedures and is increasingly used for inter-operator signalling network and roaming infrastructure

• In LTE environment, registration messages received would be based on Diameter (rather than SS7-MAP)

• Diameter Base Protocol is defined within IETF RFC 3588 (published in September 2003)

• Based on Diameter Base Protocol, 3GPP (like IETF) has also defined some specific Diameter applications to support more specific requirements in different scenarios

From GRX to IPX

Roaming Scenarios • Data

– 2G/3G-only VPMN (Visited Public Mobile Network)

– 2G/3G-only HPMN (Home Public Mobile Network)

– LTE-deployed with 2G/3G agreement

– LTE-deployed with 2G/3G & LTE agreement

• SMS & Voice

– SMS over SG

– CSFB (Circuit Switched Fall Back)

– VoLTE (Voice over LTE)

• IMS

2G/3G-only VPMN • From the 2G/3G VPMN, the EPS

HPMN looks like a GPRS network. • It is assumed that the MAP-Diameter

IWF function is performed by the EPS operator.

• The PDN Gateway in HPMN implements the Gp interface towards the SGSN in VPMN.

• The HPMN implements the Gr interface or supports Gr functionality via an IWF to enable the authentication of its customers in the VPMN.

• No changes to the existing GTPv1 and MAP roaming interfaces at the VPMN are required.

2G/3G-only HPMN • There is an explicit agreement with

the HPMN to allow this roaming scenario.

• The HPMN is fully aware that none of the services requiring Home Routing will work.

• The VPMN (or the HPMN, or a third party) has deployed an IWF between S6a and Gr (a MAP-Diameter translator).

• The MME in VPMN can do the mapping of the subscription data for Gn/Gp SGSN provided by the HLR.

• The HLR has been upgraded with support for LTE security parameters and supports Gr+ interface (Release 8 or later).

LTE Deployed – 2G/3G Roaming Agreement Only

Scenario 1: Legacy GPRS Roaming Scenario 2: HPMN only has PGW as the gateway for roaming

LTE Deployed – 2G/3G Roaming Agreement Only

Scenario 3: HPMN has both GGSN and PGW as the gateway for roaming

LTE Deployed – 2G/3G and LTE Roaming Agreement

Scenario 1: HPMN only has PGW as the gateway for roaming, 2G/3G Access via Gp interface.

Scenario 2: HPMN has both GGSN and PGW as the gateway for roaming, 2G/3G Access via Gp interface.

LTE Deployed – 2G/3G and LTE Roaming Agreement

Scenario 3: HPMN has only PGW as the gateway for roaming, 2G/3G Access via S4/S8 interfaces.

Scenario 4: HPMN has both PGW and GGSN as the gateway for roaming, 2G/3G Access via S4/S8 or Gp interfaces.

SMS over SG Roaming

CSFB Roaming

VoLTE Roaming Architecture

VoLTE Roaming Implementation

HPMN VPMN Roaming Implementation

VoLTE 2G/3G Only CS Roaming

2G/3G & LTE Data-only CS Roaming

2G/3G & LTE CSFB CS Roaming

2G/3G & LTE CSFB/VoLTE-SRVCC CS & IMS Roaming

2G/3G & LTE CSFB/VoLTE-SRVCC&PS-HO CS & IMS Roaming

LTE PS-HO IMS Roaming

Operational Requirements for IMS Voice and Conversational Services

• Routing of media for Voice & video over IMS (VoIMS; includes IR.58, IR.92 and IR.94) when call originator is Roaming should be at least as optimal as that of current Circuit Switched (CS) domain.

• The charging model for roaming used in CS domain shall be maintained in VoIMS.

• Allow the HPMN to decide, based on service and commercial considerations & regulatory obligations, to enforce the routing of the traffic to itself (home routing).

IMS Roaming Configurations

• P-GW/GGSN in the Visited network via Visited Network IM subsystem

• P-GW/GGSN in the Visited network

• P-GW/GGSN in the Home network

Source: 3GPP TS 23.221 & GSMA IR.65

IMS Roaming Configurations

No IMS Interworking required in options 2 & 3

UE eNodeB S-GW P-GW IMS

UE eNodeB S-GW P-GW IMS

Option 1 Option 2 Option 3 HPMN VPMN

IMS-to-IMS Interworking

Ici/Izi Interfaces

3GPP TS 29.165 Mw & Gi/Sgi Interfaces

Other Potential Impacts • Roaming Agreements • Fraud Impacts:

– Although minor, some changes are expected in fraud solution requirements • Billing & Charging, Invoicing

– Is current 2G/3G applicable to LTE?

• Impact on Roaming VAS – Some VAS platforms used in roaming are still SS7/MAP-based

• Regulation Impact: – Would VoLTE follow voice & SMS regulations or data regulations?

• Impact on Roamer Steering – Most roamer steering solutions are SS7/MAP-based

• Non-3GPP Roaming Partners: – Non-3GPP roaming partner will need to implement the GSMA roaming

guidelines

Applicable Standards GSMA • GSMA IR.88 – LTE Roaming Guidelines • GSMA IR.92 – IMS Profile for Voice & SMS (UE to IMS core interface) • GSMA IR.65 – IMS Roaming & Interworking Guidelines • GSMA PRD IR.33 - GPRS Roaming Guidelines • GSMA PRD IR.34 - Inter-PLMN Backbone Guidelines • GSMA PRD IR.40 - Guidelines for IPv4 Addressing and AS Numbering for

GRX/IPX Network Infrastructure and User Terminals • GSMA PRD BA.27 – Charging Requirements in Roaming • GSMA PRD IR.67 - DNS/ENUM Guidelines for Service Providers &

GRX/IPX Providers • GSMA PRD IR.80 - Technical Architecture Alternatives for Open

Connectivity Roaming Hubbing Model

3GPP • 3GPP TS 23.221 – Architectural Requirements

THANK YOU