The dawn of seamless roaming

Most of the pieces are now in place to allow mobile device users to roam seamlessly and securely between cellular and Wi-Fi networks. James Atkinson reports on the latest developments from the WBA Wi-Fi Global Congress in London last month

The dawn of seamless  roaming

Wi-Fi technology is poised to make a major leap forward over the next year with the arrival of Next Generation Hotspot (NGH), which will deliver seamless roaming between cellular and Wi-Fi networks. The change has wide implications for both Wi-Fi providers and mobile operators.

Much of the work to develop Wi-Fi is being driven by the Wireless Broadband Alliance (WBA), largely comprised of telecommunication operators, and the Wi-Fi Alliance, which is made up of Wi-Fi equipment and solutions providers. The WBA champions new initiatives, while the WFA helps to draw up common standards the equipment needs to comply with, such as the Passpoint certification scheme.

Speaking to Wireless at the WBA Wi-Fi Global Congress in June, Shrikant Shenwai, CEO of the Wireless Broadband Alliance, says: ‘The WBA and the Wi-Fi Alliance have done a lot of work to enable seamless and interoperable roaming that is secure, consistent and predictable. We are not a standards body, but we look at it from an end-to-end perspective. 

‘We have a wide mix of stakeholders with the right expertise,’ he continues. ‘We cannot deliver carrier grade Wi-Fi from just a cellular operator’s perspective. Our members include mobile operators, pure Wi-Fi players like Boingo Wireless, cable operators and fixed line providers such as the UK’s BT.’

One of the WBA and its operator members’ key tasks is to convince customers that ‘carrier grade Wi-Fi’ is what they should be using. But that means carrier grade must first be defined.

‘How do we make something so that people know what they are getting?’ asks Shenwai. ‘We need to figure out what carrier grade capable Wi-Fi actually is, so we have recently agreed to undertake some work to come up with a definition of that.’

One step the WBA has already taken is to draw up a check list for operators to measure their Wi-Fi/cellular interoperability. The Interoperability Compliance Programme (ICP) is designed to: facilitate and simplify the growth of Wi-Fi roaming; facilitate roaming agreements between partners; streamline technical information exchange; enable fast and efficient technical integrations; and offer different levels of compliancy.

Tiered approach

The WBA’s interoperability compliance form takes a three tiered approach of standard, advanced and premier level. Ton Brand, senior director, marketing and industry development at the WBA, explains: ‘We’ve finished the first round of checks with two or three mobile operators achieving the full level of interoperability compliance against the check list. We validate the self-assessment check and confirm they are premium grade.’

The WBA is overseeing Next Generation Hotspot trials, which takes Passpoint certified equipment and brings it in to the operational environment for end-to-end testing. ‘We look at whether seamless roaming between cellular and Wi-Fi networks works using a device with an AT&T or NTT Docomo SIM card, for example,’ says Shenwai. ‘It is very helpful to be able to provide this level of assurance before networks go to commercial deployment.’

Phase 1 testing covering Wi-Fi-cellular roaming using SIM-based authentication is now complete. This allows the customer to be: uniquely identified and authenticated for service; attach automatically to Wi-Fi; have any applicable charges accurately added to their bill; receive customer-specific services based on the individual customer’s preferences; and to connect to Wi-Fi without the need to manually enter log-in credentials.

Phase 2 is looking at the seamless handover between Wi-Fi and cellular. This will ensure the maintenance of the data session during handover between radio cells. In turn, this will enable IMS (IP multimedia subsystem) based voice calls that are maintained during inter-access handover and service continuity and SIM authentication on Wi-Fi for other services like RCS/joyn.

The WBA’s framework for Wi-Fi roaming is known as WRIX (Wireless Roaming Intermediary Exchange) and comprises: WRIX-i (interconnect); WRIX-d (data clearing); WRIX-f (financial clearing); and WRIX-L (location).

Adding WRIX networks into GRX (the GPRS roaming exchange) will enable Wi-Fi operators to sign roaming agreements with cellular networks. The key issue then is to find a way to settle any payment issues between the different networks. 

In April 2011, the GSMA and the WBA formed a taskforce to make Wi-Fi cellular roaming easy, seamless and transparent with commercial roaming, settlements and billing part of the scope. 

NGH challenges

Tiago Rodrigues, Programme Director with the WBA, noted that identifying new roaming partners is challenging and implementation can be difficult and time consuming due to differing terminologies, capabilities and a lack of support for standards. He said that for Wi-Fi roaming to grow and become ubiquitous the negotiation and implementation of new contracts must be simplified.

The WBA sees three sets of challenges to the wide acceptance of NGH: technical challenges; adoption and go to market challenges; and barriers to adoption, such as carriers not deploying it because there are not enough NGH enabled handsets; or conversely, the handset manufacturers not seeing enough of an ecosystem to bother investing in NGH yet.

Brand says the user experience is just as vital to the future success of NGH as is the carrier experience. He notes that it will be important to make it clearly visible to the end user when he or she is on free Wi-Fi or on cellular and what data they are using.

‘AT&T has a roaming deal with BSkyB in the UK, for example. But as a user I want to know when I am using Wi-Fi and how much data I have consumed. The awareness needs to be there for both users and carriers,’ argues Brand. Shenwai adds: ‘Research shows that people want to save the paid-for data and use free Wi-Fi wherever possible.’

Selina Lo, President and CEO of Wi-Fi solutions provider Ruckus Wireless, pointed out that not all operators are convinced by Wi-Fi yet. ‘There are still operators who think Wi-Fi is like weeds and who say we don’t need Wi-Fi; we have enough spectrum. But users prefer it and often find it better than 3G, and according to research by Devicescape, 83% expect it to be part of their operator’s offering.’ 

Major venues are mandating Wi-Fi as the concentration of customers means they get poor service over cellular. This is driving operators to invest and operators are also working with their enterprise customers to provide a better service, particularly inside premises.

Easily scalable

Lo added that Wi-Fi is easily scalable and built to handle sharing, although the issue of neutral sharing in small cells has not been solved yet. She believes Wi-Fi is perfect to meet the growth in tablet sales, which was originally driven by professional people and high earners, but the fastest growth is now coming from the youth market and older people.

Lo points to a number of actual deployments to indicate business models. ‘PCCW in Hong Kong has exclusive rights to provide Wi-Fi in the metro stations, so it can make money by re-selling Wi-Fi services, even to its competitors. KDDI in Japan is using Wi-Fi primarily for 3G offload. It has installed Wi-Fi inside Lawson convenience stores, but its main purpose is to provide Wi-Fi outside the stores in the street. The cost of the access point and backhaul is minimal.’

She adds that Sky in the UK provides access to its TV content in 9,000 UK pubs, while cable operators in North America are rolling out Wi-Fi because they have readily available backhaul in their cable system, so adding Wi-Fi is a small capex. After adding Wi-Fi they have noticed reductions in subscriber churn, says Lo.

Interference mitigation

Lo says: ‘Wi-Fi is still not quite carrier grade in some ways. NGH and Passpoint will help, but only for SIM-based devices. We need Phase 2, which will mean non-SIM based devices can easily log on. We also have to deal with interference mitigation between the many competing networks. 

‘Channels are crowded and noisy, so all radios need an autonomous way to deal with interference. And that is not just signal and noise; the radios need real time knowledge of the changing environment around them and then be able to adapt to it.’

Lo also wonders how far off Wi-Fi is from being just another radio in a HetNet accessing the 3G core and suggests that independent quality certification of networks and devices should be looked at, with perhaps the WBA providing this rather than manufacturers.

She adds: ‘The challenge for operators is to explain why carrier grade Wi-Fi is better than other Wi-Fi suppliers; why it is more reliable and robust and therefore worth paying for.’

The WBA’s Shenwai believes that the industry now has a good handle on all the technical issues, with the Wi-Fi Alliance’s Passpoint systems certifying the equipment and the seamless roaming issues solved, including for non-SIM based devices such as Wi-Fi only tablets. ‘But whether it all works in the real world is what we need to find out. There are still issues such as handoff policies that need to be addressed,’ he notes.

All the pieces of the jigsaw are in place for seamless roaming, they now need connecting up. Aside from the challenge of getting enough NGH enabled handsets out there, defining carrier grade Wi-Fi in a way that is meaningful to customers and making them aware of it, the other key challenge is for the network and Wi-Fi providers to set up roaming and settlement of payment agreements. While this is not easy and will take time, in two to three years customers should be able to roam around the world without effort.

Written by Wireless magazine
Wireless magazine

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