Hotspot 2.0 primer: Another step toward Wi-Fi/cellular integration

Hotspot 2.0 and the IEEE 802.11u protocol could allow mobile device users to securely roam between Wi-Fi and cellular networks without stopping to authenticate.

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When Deutsche Telekom CTO Olivier Baujard took the keynote stage at the Broadband World Forum in September, he proclaimed this to be the prime time for Wi-Fi/cellular integration.

His reasoning? Ninety percent of mobile device traffic actually originates from home or work, while only about 10% takes place while users are in transit. So if users are sitting in their offices or a very nearby coffee shop, shouldn't they be able to offload traffic onto optimized Wi-Fi networks?

Deutsche Telekom and other carriers seeking congestion relief would like to answer that question with a resounding “yes.” And the same goes for most major enterprises that would like to enable users to walk out of their offices to a local coffee shop and seamlessly roam between cellular and Wi-Fi networks.

Yet in most cases, seamless roaming between the two doesn't exist since users have to authenticate every time they log onto a Wi-Fi network. Hotspot 2.0 aims to change all of that.

What is Hotspot 2.0?

Hotspot 2.0 (HS 2.0) was developed by the Wi-Fi Alliance and the Wireless Broadband Association to enable the seamless handoff of traffic between cellular and Wi-Fi networks without requiring additional user sign-on and authentication. Over the years various vendors have developed technology that automates hotspot log-on, but these attempts have been fragmented and are mostly non-interoperable.

Hotspot 2.0 relies on the newly approved IEEE 802.11u protocol to enable communication between capable devices and access points (APs) that allow for automated network discovery, access authorization and provisioning.

An 802.11u-capable mobile device would locally store operator profiles and network preference policy. Once this device finds out an 802.11u-capable AP, it sends a query using Access Network Query Protocol (ANQP) seeking information about available operators, roaming partners and EAP authentication in the hotspot. The 802.11u AP would use Generic Advertisement Service (GAS) to provide Layer 2 transport of the advertisement protocol frame between a mobile device and a server in the carrier network. The AP would then relay the server's response back to the device and if there's a match, automatically authenticate and connect the user.

The provisioning process also allows for Quality of Service mapping, or mapping between differentiated services code point (DSCP) markers to over-the-air Layer 2 priority on a per-device basis, facilitating end-to-end quality of service.

Why should enterprises care about Hotspot 2.0?

Most enterprises are focused on building wireless LANs that can be optimized to handle a storm of personal and corporate devices and be optimized to deliver multiple multimedia applications, including voice and video. Yet as enterprises grapple with handling the mobile device influx, they are looking for ways to introduce supportive cellular coverage inside the campus. That would require seamless roaming between Wi-Fi and 3G or 4G networks. Additionally, enterprises would like to extend their campus Wi-Fi coverage to cellular networks so that users can leave the office while using an application and not lose connection.

Hotspot 2.0 trials are underway and Hotspot 2.0 certification test beds will be available in 2012.

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