Fixed-Mobile Convergence (FMC) promises to let callers use a single device to communicate over any available wireless transport, public or private. In carrier-centric FMC architectures, Unlicensed Mobile Access (UMA) plays a pivotal role by letting dual-mode handsets roam between networks without disrupting active voice calls or data sessions.
But UMA-based services to date, like T-Mobile’s Hotspot @Home, have largely been pitched to the residential market as an easy, inexpensive way to augment weak indoor cellular coverage.
This week, T-Mobile and Meru Networks announced a partnership to bring UMA into the enterprise. Specifically, business subscribers with T-Mobile dual-mode smartphones can now place calls over their employer’s Meru WLAN, then continue on T-Mobile’s GSM/GPRS network whenever they move outside Wi-Fi coverage.
Bigger WLANs bring bigger challenges
“UMA has the ability to abstract out the WLAN—that’s already been proven in the home market,” said Joe Epstein, Meru’s senior director of technology. “But in the enterprise, the big challenge has been multiple APs. You don’t want a phone that’s trying to decide when to switch [from Wi-Fi to GSM] triggering handover during ordinary AP-to-AP roaming.”
According to Epstein, Meru’s virtual cell architecture is a natural fit for UMA. In a Meru WLAN, all APs and stations share a single channel blanket, using controller-based Air Traffic coordination to avoid AP-to-AP roaming. In addition, Meru’s virtual port feature can assign each station to its very own BSSID, enabling per-user control over Wi-Fi parameters that impact QoS.
“Now the phone doesn’t have to worry about AP-to-AP roaming—it just has to decide whether it should be on Wi-Fi or cellular,” said Epstein. “If signal strength is dropping, it’s because you’re actually leaving the building, which should trigger a seamless cellular handover.”
Quality is key
UMA-enabled handsets are designed to make automated roaming decisions, switching voice calls and data sessions freely and without user intervention between carrier GSM/GPRS networks and unlicensed networks, such as home, hospitality, and enterprise WLANs. When connected to an unlicensed network, the carrier’s core mobile network is reached by tunneling GSM signaling over IPsec to a UMA Network Controller (UNC). Following handset authentication and session handover, standard VoIP protocols then relayed through the UNC.
Given this open architecture, UMA-enabled handsets like the BlackBerry Pearl 8120, BlackBerry Curve 8320, or Nokia 6086 should be capable of tunneling GSM/GPRS through any WLAN that lets them associate and send ESP, UDP, and NAT-T protocols. So why should T-Mobile bring its enterprise FMC solution to market by partnering with Meru?
“The last thing a carrier wants to see is quality degradation,” said Epstein. “We’ve gone through an extensive QA effort with T-Mobile to make sure that cellular handovers work as well as possible in a number of different Wi-Fi environments. Different handset vendors take different approaches to triggering handover. We had to do a little bit of work to make specific UMA devices like BlackBerries roam more smoothly.” Those refinements were incorporated into Meru’s mainstream releases and are available to Meru customers at no additional charge.
According to Dave Fredericks, national director for product solutions and planning, T-Mobile works with a number of UMA partners. “The big benefit that Meru brings to the table is seamless handoff,” said Fredericks. “Meru has really optimized the UMA experience for our customers, which we see as a great synergy and complement to our services.” However, T-Mobile subscribers without unlimited rate plans are still billed for call minutes over Wi-Fi, said Fredericks.
Reaping UMA benefits
According to Rachna Ahlawat, vice president of strategic marketing, Meru customers have been asking for an FMC solution to leverage their WLAN to augment cellular coverage. “Meru employees with T-Mobile phones have been using this solution for about six months now,” said Ahlawat. “At the end of last year, we started to encourage customers who had been asking for [an FMC solution] to test it themselves.”
One customer—a Seattle-area hospital—just started deploying Meru to better manage airspace and institute quality-of-service for voice. “Our first round of [UMA] is simply to gain coverage in the depths of our building without [requiring] more infrastructure and antennas [for femtocells],” said the hospital’s senior director of enterprise architecture. “Many of our buildings have little to no cellular coverage inside due to construction layouts and material.”
“We are hoping [that UMA will] allow us to continue our push to a single device for phone, pager, and mobile data services—removing the Batman belts,” he said. Eventually, the hospital hopes also to use a platform like Microsoft Office Communications Server or BlackBerry Mobile Voice System to provide a richer converged communication experience that spans both fixed and mobile devices.
In fact, UMA is just one way to tap FMC benefits—alternatives include enterprise-centric solutions based on internal PBXs (e.g., Avaya, Cisco) and FMC appliances (e.g., Agito, Divitas). But no matter how you approach it, convergence makes business sense.
“The number of mobile-phone-only users in enterprises is expected to increase six-fold over the next four years,” said Gartner analyst Phillip Redman. “Enterprises need to start looking for ways to increase the efficiency and mitigate the costs of their voice communication infrastructures. One effective way of doing this is to combine in-building wireless voice with external cellular services.”
Lisa Phifer owns Core Competence, a consulting firm focused on business use of emerging network and security technologies. A 27-year networking industry veteran, Lisa has been involved in the design, implementation, and testing of wireless products and services since 1996.
