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
Data Roaming Scenarios 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 HPMN VPMN UE enodeb S-GW P-GW IMS Option 3 Option 2 Option 1 UE enodeb S-GW P-GW IMS No IMS Interworking required in options 2 & 3
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
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