UMTS: Alive and Well - 4G Americas
UMTS: Alive and Well - 4G Americas
UMTS: Alive and Well - 4G Americas
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C.2.1.6.4ROAMING AND NON-ROAMING SCENARIOSOne of the important aspects of the EPS is the support of roaming. Within the EPS specification, thereare two documents focused on roaming aspects: TS 23.401 focuses on 3GPP access roaming (<strong>and</strong>specifically GTP based roaming, over the S8 interface based on GTP), while TS 23.402 focuses onmobility <strong>and</strong> roaming with non-3GPP access using Proxy MIP (over the S8 interface based on PMIP).Figure C.9 exemplifies the roaming architecture for 3GPP access only. The roaming architecture for3GPP access for Home routed traffic consists of a Serving Gateway (SGW) in the visited network whichlinks/connects GTP based S1 interface tunnels with a GTP interface (GTP-based S8) towards a PDN GWin the home network.Figure C.10 exemplifies the roaming architecture for 3GPP access via S8 <strong>and</strong> for non-3GPP access viaS2 based on PMIP. Non-3GPP access connects via the S2 interfaces to either a SGW in the visitednetwork or a PDN GW in the home network. The connectivity via a SGW in the visited network may applyin cases where the home network operator relies on a visited network 3GPP operator to manage theagreements with non-3GPP access operators in the visited network. The connectivity with the Homenetwork PDN GW is used when there is a direct roaming agreement between visited non-3GPP networks<strong>and</strong> the Home 3GPP network. This chaining of S8 <strong>and</strong> S2 is supported only with PMIP based S8. If GTPbased S8 is used, the chaining of S8 <strong>and</strong> S2 is not allowed.The signaling of QoS to the visited network for the EPS bearer requires the deployment of an inter-carrierPCC infrastructure based on the S9 interface, when PMIP based S8 is used.A distinction is also made between Trusted non-3GPP networks <strong>and</strong> Untrusted 3GPP networks.Untrusted 3GPP network access needs to be mediated by an E-PDG (Evolved Packet Data Gateway),which terminates IPsec tunnels from the UE. See sections C.2.1.4 <strong>and</strong> C.2.1.5 for discussion of thevarious interfaces shown in Figures C.9 <strong>and</strong> C.10.181 Ibid.www.3G<strong>Americas</strong>.org February 2010 Page 156
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