Roaming seamlessly

18th July 2013
News Release from: Ruckus Wireless
Written by : ES Admin
Roaming seamlessly
With the demand for data only likely to increase, service providers are looking towards new technologies like Hotspot 2.0 to help quench consumers’ thirst for data and greatly increase the capacity of their networks. David Stephenson, Senior Principal Engineer with Ruckus Wireless, explores more in this ES Design magazine article.
Today’s cellular networks are being overwhelmed with data traffic, much of it being generated by the rapid proliferation of smartphones. Operators have realised that 4G will not alleviate the capacity demands for data; many operators understand that their data needs cannot be met by enhancements to their cellular networks and are turning to Wi-Fi as a solution. Working alongside cellular networks, it is the perfect technology to stabilise the data capacity issue. Wi-Fi is seen as an excellent option as it has access to upwards of 600 MHz of spectrum, supports dense Access Point deployments, is available on all data-centric devices, and is available in all locations where people congregate.

However, capacity and ease of deployment are only the first steps in enabling a carrier-class solution. The industry is now focussed on improving the Wi-Fi user experience while roaming, providing a service that is akin to that of cellular networks. This work is known as Hotspot 2.0 and is being driven by the Wi-Fi Alliance, which also certifies HS2.0 interoperability as part of their Passpoint program. The Wireless Broadband Alliance is also very much involved in this process through their Next Generation Hotspot initiative. It comes as no surprise that many see it as ‘the next big thing’ when it comes to wireless technologies.

Revolutionising Wi-Fi

HS2.0 is the new technology getting carriers excited, because it takes away many of today’s manual tasks — like authentication — and automates them; it also enables users to roam securely without the hassle of searching for Service Set Identifications.


Current activity within the HS2.0 sphere


The key enabling protocols are IEEE 802.11u, along with IEEE 802.1X, selected Extensible Authentication Protocol methods, and IEEE 802.11i. The latter three are part of the WPA2-Enterprise certification program in the Wi-Fi Alliance, and are standard on all smartphones. While the certification is called ‘WPA2-Enterprise’, the end result is a process that is every bit as secure and easy to use as what exists in the cellular world.

The IEEE 802.11u protocol enables a mobile device to have a dialog with a Wi-Fi AP ‘pre-association’ to determine the capabilities that the network can support. The two protocols that 802.11u uses to make this happen are the generic advertisement service and the access network query protocol. These protocols run on top of 802.11 and enable the Hotspot 2.0 experience.

When a user with an HS2.0 capable mobile device comes within range of an HS2.0 capable AP, it will automatically open up a dialog with that AP to determine its capabilities. This is done using ANQP packets that are carried at layer 2 by the GAS service (Note: the device has not yet attached and does not yet have an IP address). It is the exchange of ANQP packets that allows the mobile device to automatically learn the capabilities of an AP.

If the AP is part of the user’s home network then no roaming is required and the user can move straight to authentication. However, if the AP is not on the user’s home network, then roaming is required. In this situation, the list of roaming partners that are supported by the AP must be passed down to the mobile device via the ANQP protocol. This can be provided in the form of a PLMN (Public Land Mobile Network), ID, realm, or the organisational Identifier. Once the mobile device learns the roaming partners and the identity of the AP operator, it invokes some basic, built-in network selection policies to determine which AP to join. This means a user can roam on a Wi-Fi network even if a mobile device does not see an AP belonging to its home network provider.


1. 802.11u-capable AP broadcasts its HS2.0 support, while HS2.0-enabled devices look for support.
2. Device processes information contained in ANQP payload - such as 'reachable' authenticators, and capabilities of the hotspot.
3. (Optional) Device requests full authenticators list, the AP responds to ANQP query with requested information.
4. Device compares provisioned network-selection policy with HS2.0 data from APs and associates itself to the best BSSID.


This is the beginning of a new era where users no longer have to think about SSIDs, authentication or fumble around with passwords. It will make it possible to link a huge network of effectively random Wi-Fi access points through a web of interconnections, so that users can enjoy a seamless experience as they move between Wi-Fi networks from almost any location. This is very much like the cellular experience that we all enjoy when getting off an airplane just about anywhere in the world. Wi-Fi roaming would apply anytime a mobile device does not see an AP belonging to its home network provider. A user could roam on a Wi-Fi network that is across town or on the other side of the world. Roaming partners could now potentially include MSOs, MNOs, wireline operators, public venues, enterprises, and basically any other entity that has Wi-Fi assets.

New opportunities

HS2.0 has been developed and promoted predominately by carriers and equipment suppliers, but it is very possible that it will have its greatest impact and appeal within the enterprise; that’s what will make it a game-changer. HS2.0 will be about much more than the technology enablement of a better mobile user experience; it will shift relationships between carriers and building owners who may already have a Wi-Fi footprint deployed — those who want to provide the uninterrupted service as part of their continued strategy to deliver better subscriber experiences, and those who own the locations essential for providing that continuity of service. This commercial collision course between the worlds of the Service Provider and the Enterprise, combined with an important leap forward technologically, is going to give HS2.0 its place in the Wi-Fi hall of fame.

Two principle parties are interested in the provision of Wi-Fi services: the owner of the venue or building, and the service provider. Now their interests are coinciding. The widespread and growing use of Wi-Fi across public venues such as hotels, schools, shopping centres, retail outlets, public transport, sports venues — in fact, anywhere where people gather and expect to use their mobile devices without encountering any problems — is an incredible opportunity for venue owners, and for the enterprise. These are usually the owners of the network infrastructure. Since operators want Wi-Fi network access, the real opportunity will emerge for any enterprise or venue owner to wholesale their existing wireless LAN capacity to operators; charging them recurring fees for that access.


Authentication with HS2.0


Mobile service providers want to automatically connect their subscribers to their own ‘branded broadband’ service, through the venue’s available high-speed Wi-Fi network. It is this connection that HS2.0 will make possible; giving the Wi-Fi network an interconnection with the subscribers’ ‘home’ service provider, so the device just carries on functioning in the way we all expect it to in the 21st century. These back-end connections might be direct, but more likely will be indirectly provided through third-party hubbing services. Either way, from a user perspective, the connections will be seamless and automatic, with no loss in service.

Becoming truly global

One of the key challenges for Hotspot 2.0 in becoming a truly global technology is its compatibility with mobile phone handsets and other Wi-Fi enabled devices. Passpoint is the Wi-Fi Alliance’s designation for devices and network equipment that supports the Hotspot 2.0 standard. The first signs of its uptake come from the fact that the new Samsung Galaxy S4 is Passpoint enabled. With Samsung starting to ship Passpoint on the Galaxy S4, we can expect the other major smartphone vendors to follow suit in short order.

However, challenges don’t just lie in the compatibility of devices, it is also vital that Wi-Fi access points are upgraded to become compatible with Hotspot 2.0, in order to provide the smooth transition of Wi-Fi across disparate locations. Only then will people be able to walk around with a continuous Wi-Fi connection without risk of drop out.

In addition, HS2.0 enabled APs must meet the critical requirements that carriers demand for a seamless Wi-Fi experience. In order to provide a carrier grade solution, APs must have a strong radio performance, both for access and backhaul, in order to face the unprecedented subscriber growth, high interference, and challenging high density deployments. Without addressing these issues, the APs will provide a poor user experience, with only a limited number of people able to connect to a single AP, poor signal due to intense RF environments and unreliable service in high density environments. Enterprises and carriers alike must ensure they are using the smartest Wi-Fi technology in order to provide the service that consumers crave.


HS2.0 promises transparent roaming


The impact of Hotspot 2.0

HS2.0’s impact on the industry will be enormous. Mobile operators are already seeing their networks overloaded by data traffic and are looking at all available options to increase densification. At the top of their list are technologies like Wi-Fi and LTE small cells. Cable and wireline operators are taking advantage of their backhaul capabilities to rapidly build-out an extensive Wi-Fi footprint. This technology has also been extensively deployed in public venues like hotels, airports, exhibition centres, stadiums, hospitals, etc. With HS2.0, it will now be possible to link together this huge footprint of Wi-Fi APs through a web of roaming arrangements. Users will be able to seamlessly roam onto Wi-Fi networks from almost any location.

The net result for mobile operators is much greater network capacity than could be achieved by building out a network of APs on their own and a much better experience for the subscriber. Users no longer need to know or care about SSIDs and authentication protocols. Instead, they get an always best connected experience.

Venue owners, enterprises and operators can begin to better monetize their Wi-Fi network investments through these roaming arrangements and the settlements they will entail. A mobile operator that deploys a Wi-Fi network in a stadium can now monetize that asset by allowing subscribers of other operators to roam onto that network. Enterprises can likewise allow subscribers of all different mobile operators to roam onto their in-building Wi-Fi networks, turning it into a profit centre rather than a capital expenditure cost.

In short, Hotspot 2.0 technology will radically transform the wireless industry, and it is set to emerge in 2013 in a very big way.

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