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8.2 Wi-Fi Roaming Architectures

To provide Wi-Fi roaming services, the VNP and HSP must have interoperability mechanisms in place. Figure 20
illustrates the most common Wi-Fi-to-Wi-Fi roaming architecture based on the WRIX architecture as defined in WBA
documentation.

Figure 20. Typical WLAN roaming architecture

The visited network provides the connectivity to the client devices, but redirects the initial authentication of the
roaming client devices to the home network AAA servers, typically via RADIUS (Remote Authentication Dial in User
Service) proxy or from the Access Controller. Connection between the networks must be secured using private
circuits, MPLS or Virtual Private Network (VPN) tunnels.
The authentication can be done between the home and visitor networks while the accounting and reconciliation of
usage for billing purposes may be outsourced to a third party. RADIUS accounting is not lossless, so accounting
records between the home and visited network providers might differ from each other. If sufficient resources cannot
be allocated to compare the records and manage the discrepancies, the accounting should be outsourced to a third
party.

Figure 21 does not show a policy controller, which is mandatory in some countries and for operators of a certain size.
It is used to set the access policies to roaming customers and can provide feedback from both the visited and home
network operators as well as the venue where the users are located.

Service Providers may have different approaches when developing a roaming strategy. There are two main scenarios
available to interconnect their networks, either through a direct connection or by using a third party to facilitate that
interconnection. For the latter there could be several hybrid models from both operators using the same hub or just
one operator using a hub provider (see figures 22 and 23).

Figure 21. WLAN roaming with direct, bilateral interconnection

Report title: Connected City Blueprint
41 Issue Date: 15 December 2016 Wireless Broadband Alliance Confidential & Proprietary.
Copyright © 2016 Wireless Broadband Alliance
Document Version: 1.0