The Hotspot 2.0 group built on IEEE 802.11u, a mechanism for automatic handoffs under the 802.11 Wi-Fi standard that was developed starting in 2005, another project Stephenson was involved in. The 802.11u specification gives Wi-Fi network operators a standard way to automatically tell mobile devices about their roaming relationships, Stephenson said. With that information, a device can join the network using whatever credentials it may have for one of those networks.
Hotspot 2.0 combined that capability with other components including security, defining a way to protect all sessions on a hotspot using standard Wi-Fi encryption. Last June, the Wi-Fi Alliance used the complete Hotspot 2.0 standard to set up its Passpoint certification program, in which it tests and certifies Wi-Fi devices for interoperability under the standard.
Meanwhile, the WBA has been working on the back end to help make Wi-Fi networks capable of offering roaming. Under a program called Next-Generation Hotspot (NGH), the WBA has been overseeing trials for about 18 months in which devices roam among networks, said Shrikant Shenwai, CEO of the WBA.
In December, the WBA announced its Interoperability Compliancy Program, which set out a common set of requirements and procedures for Wi-Fi roaming. It includes guidelines for security, device authentication, network selection, and charging and billing. There is also a program for carriers to assess their compliance with the guidelines. If would-be roaming partners both comply, it should be easier for them to set up a roaming relationship, Shenwai said.
The WBA is also working with the GSMA to harmonize roaming systems for Wi-Fi and cellular, respectively. That ongoing effort should help carriers incorporate Wi-Fi into their regular accounting and billing systems, making it easier to set up roaming relationships with many service providers.
As an engineer, Stephenson said Hotspot 2.0 has faced only "routine" technical challenges, with the bigger issues coming from the differences between the cellular and Wi-Fi worlds. Education both ways has been needed, he said.
In the deployment phase of Wi-Fi roaming, the carriers themselves face the biggest challenges, Stephenson said. "They are big, have a lot of momentum to overcome, have to make sure via testing and trials that the Hotspot 2.0 technology is ready and that their networks are ready."