Dual-mode office VoIP is set to boom, if market research and product announcements are anything to go by.

Demand for dual-mode devices will soar as single mode phones sag, over the next two years, according to Infonetics Research. In a survey earlier this year, 23 percent of respondents say they use dual-mode phones now, and that will grow to 30 percent in 2009.

In the same group, 45 percent say they use single-mode phones now and that will decrease to 34 percent in two years. As dual-mode phones become more available and affordable, businesses will prefer them to single mode, says Mattheus Machowinski, the Infonetics analyst who wrote the report.

Vendors are gearing up for this. Avaya is offering a software upgrade for dual-mode Nokia E-series Wi-Fi/cellular phones that link Avaya's one-X Mobile Dual Mode Edition software (on the phone), with Avaya Communications Manager IP PBXs, so users can make and receive corporate corporate phone calls on mobile devices.

Earlier this year, Nokia demonstrated dual-mode support for Cisco and Alcatel VoIP equipment, setting the stage for an expected jump in the popularity of these roaming devices. Siemens and Divitas also announced similar dual-mode capabilities earlier this year.

Nortel sees the uptake of wireless as a much broader issue, recently announcing plans to incorporate wireless capabilities in its network Ethernet access switches, combining Wi-Fi mesh and cellular technologies, so even workers tied to desks will have wireless VoIP phones and computers.

The "unwired enterprise" architecture would be appropriate for new sites where installing wireless gear would eliminate the need and expense of installing network-access wiring, Nortel says. Products are due next year.

In a nutshell, dual-mode phones are VoIP PBX extensions while on the wireless LAN (WLAN) and are standard cell phones when outside WLAN coverage areas. Avaya already teams up with Motorola (from way back) to pass calls uninterrupted between the two types of wireless networks.

Upgrading wireless LANs
Before dual-mode wireless becomes mainstream, businesses have to solve a set of problems, including the need for corporate-infrastructure upgrades, service-provider initiatives, and the fact that only the most mobile workers need the technology, experts say.

An upgrade of WLANs may be necessary to support VoIP, making some businesses reluctant, says Phillip Redman, an analyst with Gartner. "Most enterprises are hesitant to put in voice over wireless because it means adding more access points to add capacity and coverage," he says. "Wireline is already installed and inexpensive, and it works. Unless they have a need for a high degree of mobility, they're not looking to transfer it to wireless networks."

Dual-mode phones that hand off calls from Wi-Fi to cellular networks as users move around could be part of the answer, but that will also require investment by businesses for the gear needed to transfer calls between networks. That means picking vendors carefully, experts say.

Bridging voice-over-wireless LANs (VoWLAN) to cellular networks is of interest to businesses with very mobile workers - hospitals, factories and retail stores. Overall, that is a small percentage of workers. Infonetics recently found that 6 percent of users in companies surveyed use VoWLAN. That is expected to double in the next two years, but is still a small percentage.

More employees going mobile
Larger businesses are more likely to use VoWLAN because they have a better chance of having at least some employees who need to be mobile, Machowinski says. But because need for the technology is small in most businesses, they steer clear of investing in it, Redman says.

For some business users, dual-mode phones are important because they can reduce the number of devices individuals have to carry, Machowinski says. "Single-mode handsets aren't that interesting to some businesses, because it means carrying around one more device," he says.

For other users, the phone won't be an issue. "A lot of [VoWLAN] pickup will be on soft phones running on a laptop," he says.

Medical mobile

In medical settings, though, VoWi-Fi phones are valuable to nursing staffs, which spend their days moving from room to room. For instance, University of Texas Southwestern Medical Center in Dallas has deployed 600 wireless VoIP phones to hospital workers on campus, says Elwyn Hull, the centre's director of telecommunications.

"I don't know how you quantify the savings in nurses' time, but certainly that is the benefit of these phones," Hull says. "It's saving them hours every day." Rather than run back to nursing stations to check voicemail or return pager calls, they receive more calls directly on the wireless phones as they make rounds, he says. "We can respond more quickly. It's frustrating to call someone for a quick call and get voicemail," he says.

The school bought two affiliated hospitals in 2004. One of them, St. Paul's, had installed traditional 900MHz wireless phones that were integrated with the hospital's Nortel PBX. These phones required separate transmitters and wiring to tie the transmitters to the PBXs.

Other Southwestern facilities were doing similar integration using Siemens gear in conjunction with Spectralink.

At the same time, the medical centre was installing wireless LAN gear for data applications on hospital floors and in clinics, the same places the 900MHz wireless phones were installed. When it learned VOIP phones supported by Siemens over the same wireless network could replace the 900MHz wireless phones, the Southwestern medical centre stopped deploying them in favour of VoIP.

That required adding access points to handle the greater load and upgrading some LAN infrastructure to support VoIP, says Hull. The handsets are PBX extensions with all the features - hold, transfer, conferencing - that wired extensions have.

Southwestern is interested in technology to allow doctors and some other medical personnel roam beyond the campus, but has no firm plans to deploy it yet, Hull says. The school is starting with deploying Wi-Fi access points between buildings on campus to allow roaming outside individual buildings.

Hull says dual-mode phones that support VoIP over Wi-Fi and cellular and also support two phone numbers could be attractive. Users would carry one device that would work on campus and off, and could receive separate bills for business and private calls.

It is possible to extend wireless throughout a business using single-mode cellular phones, says Redman. By using interfaces with corporate PBXs, cellular phone carriers can turn over to their business customers call control as well as PBX features, such as hold and voicemail. So a call to the corporate phone network from a cell phone would be directed by the carrier to the corporate PBX.

In this scenario, there is no need for handoffs between Wi-Fi and cellular networks or dual-mode phones, because all calls are delivered over carrier cell networks.

If cell services are weak within corporate buildings and campuses, providers can install repeaters and other antenna infrastructure to provide adequate capacity and coverage, Redman says. IP phone systems from Ascendant Systems, Avaya and Divitas support this feature.

The challenge this technology faces lies in the phones, because cell phones lack dedicated feature buttons that typical PBX desk phones have. So phone makers will have to develop graphical interfaces that display buttons on the phone screens for such PBX features as conferencing and call transfer, Redman says.

The alternative is pressing number codes using phone keypads to manipulate these features. "But using short-codes adds complications to using the features," he says.

However, using the dual-mode phones offers customers the possibility of saving money by saving on cellular minutes. At outdoor retailer Gander Mountain, dual-mode phones could be a way to save on cellular minutes when travelling executives are at the headquarters building in St. Paul, Minnesota, or in stores, says Joe McClung, senior network engineer for the 110-store chain.

The company is swapping out Colubris Wi-Fi access points for those from Cisco, and that gives Gander the option to use dual mode, he says. In the meantime, sales associates in stores carry single-mode Wi-Fi phones to answer calls from customers. Incoming calls roll from wired phones to Wi-Fi phones of associates to Wi-Fi phones of managers, he says.

Calls are answered more reliably with the Wi-Fi phones, and sales associates are more productive, because they spend more time helping customers or stocking shelves. "The majority of associates are hardly ever at the wired phones," McClung says.

"I find it very intriguing," says Southwestern's Hull about dual-mode phones. "It may be where wireless is moving to."