802.11u and Hotspot 2.0 promise Wi-Fi users a cellular-like experience

Although vendor-written, this contributed piece does not advocate a position that is particular to the author's employer and has been edited and approved by Network World editors.

Why can't connecting to a Wi-Fi network be as easy as connecting to a cellular network?

It's not uncommon for people living in a major city to be able to "see" tens if not hundreds of Wi-Fi networks with their smartphone or laptop. But how does the device select the right network? And often the device doesn't recognize available Wi-Fi networks (SSIDs) or know if they have the proper security credential to even connect.

Also unknown is whether Internet access is provided through a given SSID or whether email or other services the user desires will function properly. For many, selecting a Wi-Fi network -- having to fiddle with the phone to enter credentials, encryption keys and everything else -- just isn't worth it. But soon it may be much easier if the IEEE Wi-Fi Alliance (WFA) and Wireless Broadband Alliance (WBA) have anything to say about it.

BACKGROUND: Wi-Fi group plans to simplify hotspot access

A little-known protocol extension from the IEEE, 802.11u, stands to have a huge impact on the user experience of emerging mobile Wi-Fi networks being built by operators. The key for widespread adoption of 802.11u ultimately rests in the hands of the WFA and its industry certification process as part of Hotspot 2.0, as well as the WBA and its Next Generation Hotspot interoperability program.

Who's doing what?

Driven largely by vendors and network operators, Hotspot 2.0 is an industry initiative that will use 802.11u to provide seamless automatic Wi-Fi authentication and handoff, allowing mobile users to roam between the networks without additional authentication.

While Hotspot 2.0 uses 802.11u as a fundamental building block, it extends beyond the 802.11u protocol to effectively automate the network discovery, registration, provisioning and access steps a Wi-Fi user must manually go through today when connecting to a given hotspot.

A companion initiative to Hotspot 2.0 is the Next Generation Hotspot program developed by the WBA. Unlike the WFA, which is primarily focused on vendor certification, the WBA is a collection of network operators interested primarily in interoperability. The WBA's Next Generation Hotspot program defines interoperability requirements for hotspot, cable and 3G/4G mobile operators. The program includes development of comprehensive operator guidelines and an ecosystem trial to facilitate migration to Next Generation Hotspots.

Given the explosion of data traffic on cellular networks and desire for operators to offload this traffic to Wi-Fi networks, Hotspot 2.0 and Next Generation Hotspot are widely viewed as critical components to accelerating the adoption of Wi-Fi as a complementary technology to high-mobility broadband wireless options.

And it couldn't come at a better time. The number of Wi-Fi hotspots are expected to triple by 2015 with some 1.2 million venues Wi-Fi ready, according to a recent report by In-Stat. It's anticipated that usage will follow suit, increasing from 4 billion connections in 2010 to 120 billion by 2015. It's these connections and streamlining the connection process where 802.11u comes in to save the day.

802.11u and you

An emerging protocol, 802.11u, automates what is now a cumbersome and tedious process for users trying to connect to Wi-Fi networks and services. Completed by the 802.11u task group in mid-2010 and approved by the IEEE for publication in February 2011, 802.11u was developed to effectively automate how Wi-Fi devices connect to available Wi-Fi networks.

The MAC-layer enhancement assists the advertising of and connection to remote services by providing information to client devices about the external networks that are accessible via a particular hotspot prior to association. 802.11u enables Wi-Fi hotspots to advertise their capabilities and then allows devices to connect to them automatically rather than requiring the end user to manually select an SSID. Within the 802.11u specification, the primary interworking functions covered include:

Network discovery and selection: The automatic discovery of suitable networks through the advertisement of access network type, roaming consortium support and venue information (implemented as part of Hotspot 2.0).

Quality of service mapping: This provides a mapping between differentiated services code point (DSCP) markers to over-the-air Layer 2 priority on a per-device basis, thereby facilitating end-to-end quality of service (not implemented as part of Hotspot 2.0).

Emergency services: Emergency call and network alert support at link level (not implemented as part of Hotspot 2.0).

Chart comparing access with vs. access without HS 2.0/802.11u

What happens when?

When an 802.11u-capable device comes into radio range of one or more hotspots it receives the beacons of the access points (APs). If the APs support 802.11u, these beacons will indicate support for the protocol. 802.11u uses a generic advertisement service to provide Layer 2 transport of the advertisement protocol's frame between a mobile device and a server in the network prior to authentication.

An essential element within 802.11u is the use of the Access Network Query Protocol (ANQP). ANQP is a query and response protocol used between the network and a mobile device to discover a range of information such as the network authentication types supported, venue name, roaming agreements in place, throughput of the backhaul link, well-known port numbers that are open, and other metadata useful in the network selection process.

The mobile device uses generic advertisement service to post an ANQP query to an 802.11u-capable AP. In turn, the AP provides the hotspot operator's domain name and network access identifier (NAI) realm list. Generic advertisement service and ANQP effectively allow a mobile device to query the network before being authenticated to determine if the hotspot is operated by one of its roaming partners as well as the EAP method and credential type to use.

How HS 2.0 works

Armed with this information, the mobile device examines its own credentials to get the list of roaming providers with which it knows it can connect. It then compares its own realm list to the list of the roaming partner realms received from the AP to determine to which network it should be able to successfully authenticate.

If there's more than one match the device uses operator policy to determine which Wi-Fi network to join. This policy or operator profile is provided by the operator and stored within the phone itself. It typically provides an ordered list of preference levels and domain name pairs for each roaming partner. The mobile device then compares the hotspot operator's domain names with this list and selects the network having the highest preference level. After all this the mobile device authenticates automatically to the best network using its credentials without requiring any direct user action.

HS 2.0 example

The use and value of 802.11u goes beyond just making life easier for the end user. Mobile operators around the world are now keenly interested in how to leverage unlicensed wireless technologies, like Wi-Fi, to offload their mobile data networks from the explosion of media-rich data traffic running over them. Hotspot 2.0 and 802.11u are immensely useful in helping operators and their subscribers make better use Wi-Fi in a seamless manner for this purpose.

Beyond mobile operators, cable operators that don't own or operate networks using licensed wireless spectrum are also looking at potentially significant new sources of revenues from the use of 802.11u. With millions of cable modem subscribers, a cable operator can use 802.11u to help offload traffic within homes or venues where it provides cable service -- working with mobile operators to wholesale its cable plant in order to offload mobile data traffic without users even being aware of what's happening.

The cable operators can then realize revenue from the wireless operator's data traffic that is flowing over their cable network. The net effect is that the mobile operator eases congestion and increases its wireless footprint without any capital investment, and end users realize a much better wireless experience.

Ultimately, 802.11u and Hotspot 2.0 promise to make connecting to Wi-Fi services as easy, seamless and secure as today's 3G cellular experience. And just in time.

Based in Sunnyvale, Ruckus Wireless markets and manufactures next generation Wi-Fi systems to enterprises and carriers around the world. The company has been granted 47 patents in the areas of advanced wireless communications and is best known for its RF innovations that increase the range and reliability of Wi-Fi transmissions.

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Copyright © 2011 IDG Communications, Inc.