February 2006 was a big month for communications hardware/software vendor PCTEL. Early in the month, telecom infrastructure giant Lucent Technologies announced it was licensing PCTEL’s Roaming Client-VE [Voice Enabled] as part of its IMS (IP multimedia subsystem) networking solution. Mid-month, the company demonstrated handoffs between cellular and Wi-Fi-based calls, in conjunction with partner BridgePort Networks, at the 3GSM World Congress in Barcelona.
VoIPplanet.com spoke earlier this week with Ogi Redzic, PCTEL’s vice president of product management and business development about the technology and prospects for real-world service deployments.
In an effort to get a handle on how this handoff methodology works in relation to BrigdePort’s IMS Convergence Server (ICS), we asked Redzic in which component the best-routing decision making takes place. “We trigger it, based on a number of parameters we can control, but most of the time it’s triggered based on signal quality over time,” he explained.
“The server has the presence knowledge, so they know whether we’re connected to them through GSM or through Wi-Fi, but the server doesn’t know what the signal quality is or whether my IP path is open all the way through or not. That’s something that we have the knowledge of.” So, the client communicates with the server to set up the infrastructure handover, which the server then executes.
“What normally happens is that, for a short period of time, you would actually have two calls going on simultaneously. As soon as you’re sure the new call is established—that everything is good—you drop the other call.” The overlap is kept to a minimum so that both radios aren’t pulling power.
At this point in the evolution of the technology, the handoff can take 200, 300, even 400 milliseconds—not fast by cellular standards—depending on which direction the handoff is made. (3G-to-Wi-Fi is faster than the reverse.) Nonetheless, it meets the newly promulgated 3GPP standard known as Voice Call Continuity or VCC.
“The big problem is that the Wi-Fi chipset is not optimized for voice,” Redzic pointed out. That will change over time, as new standards and techniques are under development in the Wi-Fi arena, specifically to address the handoff speed issue—though not specifically handoffs between Wi-Fi and cellular networks.
In addition to automated handoffs based on signal strength criteria, the Roaming Client-VE interface gives users the ability to make pre-emptive choices. If, for example, you’re walking out of the office and will be leaving Wi-Fi range—or if you step into an elevator where Wi-Fi simply doesn’t work, you just click the button for a manually assisted handoff. “The user experience is simply better,” Redzic commented.
Redzic believes that customers now trialing this FMC solution will deliver product “late this year, or early next year.” In terms of markets, he told VoIPplanet.com, “There’s two paths we’re following, and they both involve carriers.” One, he termed “subcarriers,” who will be targeting enterprises with hosted IP PBX services. Typically, they will offer IMS functionality, digital network, and Wi-Fi throughout the company, with one number dialing for both types of phone connectivity.
The other path is the home. A typical business model is a wireless operator that does an MVNO deal for 3G and provides customers with the Wi-Fi infrastructure, and a dual mode phone device. When customers get home, they’re offloaded onto the Wi-Fi network.
“Different things are important in that environment,” Redzic pointed out. “It’s not three-way calls, call transfers—enterprise PBX features. What’s important is distinctive rings for family members, customization of a device—consumerizing the user interface. And making this thing much more seamless, because users aren’t going to be as educated or as patient at enterprise users.”
Another difference, Redzic pointed out, will be the cost of the device. “We’re talking about a feature phone device at home—a $200 device as opposed to the enterprise in which people are willing to spend $600 for a PBX-type phone.”
Whereas the demonstration at Barcelona was done using a pocket PC running Windows Mobile software, PCTEL has already ported Roaming Client-VE to some phone platforms. Their deal to supply software for Kyocera’s dual-mode phones has already been announced, and others are in the works. A port the full Voice-Enabled client to Symbian is also in the works (the data-only Roaming Client has been available on that platform for some time).
Pretty clearly, there’s solid momentum behind fixed-mobile convergence.
