When does one plus one equal three? When the solution is voice over wireless LAN.

Reason is, organizations that have deployed wireless LANs (Wi-Fi) and VoIP are combining the two in voice over Wi-Fi, or VoFi, solutions. Such convergence delivers the mobility of Wi-Fi and the features and simplicity of VoIP -- truly a case where the whole is greater than the sum of its parts.

"VoFi solutions allow customers to leverage their investments in wireless LANs and VoIP," says Joe Berard, technology solutions engineer at Ingram Micro. "By putting the two together and adding wireless handsets, the productivity benefits and cost savings can lead to impressive ROI."

Philippe Winthrop, a research director at Aberdeen Group, agrees.

"End users are absolutely looking to leverage wireless LAN infrastructure for uses beyond traditional laptop and Internet access," Winthrop says. "One of the most logical steps is to move to a voice over Wi-Fi implementation." Recent Aberdeen research found that best-inclass organizations achieve average annual cost savings of $154 per user and a 49 percent return on investment from their mobile VoIP implementations.

Such returns have made VoFi one of the hottest convergence solutions. Infonetics Research forecasts strong double-digit growth of Wi-Fi phone revenue through 2010, when it should reach $145 billion.

To deliver the complete VoFi package, solution providers will need schooling in network infrastructure, IP voice and Wi-Fi technologies -- expertise that can open the door to profitable solution sales and the potential for trusted-advisor status.

"As voice networks change over time, customers need ongoing consulting and services," says Wade Williamson, director of product management at AirMagnet, a provider of wireless management software. "If you learn to deploy and troubleshoot wireless voice solutions efficiently, you can develop a long-term relationship with the customer as its goto technology provider."

The VoFi Benefits Parade
VoFi solutions offer users a number of attractive benefits:

• Higher productivity: Users can be reached anywhere the Wi-Fi network reaches -- in conference rooms, during lunch, when they step away from their desks, even in the restroom. Minimizing dreaded voice mail tag can mean more responsive service to customers, suppliers and fellow employees.
• VoIP functionality: In many cases, useful VoIP features such as singlenumber reach and presence can be made available to VoFi users.
• Application access: Using smartphones or PDAs, users can access productivity software, such as e-mail and CRM applications, anywhere on campus.
• Lower cellular charges: This benefit accrues because a good portion of cellular minutes are consumed within Wi-Fi coverage.
• Future readiness: VoFi sets the stage for what most experts consider the future of mobile communications: a converged network where users seamlessly roam between Wi-Fi and cellular radio on a single handset.

These benefits appeal to customers in mainstream enterprises as well as in vertical markets such as healthcare, retail and manufacturing -- anywhere users need access to voice and data as they roam the workspace.

"Think of voice over Wi-Fi as enabling users' desk phones to follow them wherever they go," says Brian Casto, CEO of ICI Networks, a provider of secure mobility solutions. "The ROI is such that solution providers should be talking to their customers about it, because it may be the quintessential reason they decide to deploy wireless. Or, if they already have wireless, it's a great opportunity to upgrade the network."

Adding Voice to Wi-Fi
Existing wireless LANs may require an upgrade because a voice network has more stringent requirements than a data-only network. Wireless voice often requires broader signal coverage, higher bandwidth, less latency and better capacity planning, as well as quality of service (QoS) to prioritize voice. If such issues aren't attended to, users can experience dropped or failed calls, dead spots, poor voice quality and choppy audio.

"Issue No. 1, the infrastructure needs to be robust enough to support voice," says Berard of Ingram Micro. "If the network is composed of hubs or dumb switches, it's not going to work." Switches and access points need to be managed to ensure adequate bandwidth and QoS, with centralized management preferred on deployments with more than a few access points.

To deliver effective voice coverage, solution providers need to master the site survey. "Careful RF measurements to capture the characteristics of the environment will ensure that access points are in the right locations and with the right density to support voice," says Kyle Klassen, director of enterprise wireless marketing at Nortel. Generally, more access points are needed for VoFi than for a data-only network. Nortel recommends one access point per 10 to 12 concurrent voice users. In addition, Call Admission Control (CAL) is useful in limiting the number of concurrent users on an access point or network segment.

It's also critical to consider allocation of the Wi-Fi spectrum between voice and data. Virtual LANs are a possibility, but Casto of ICI Networks recommends splitting voice and data between the Wi-Fi frequency bands -- data on the 2.4 GHz frequency of 802.11b/g and voice on the 5.0 GHz frequency of 802.11a. This dual-band approach can free up bandwidth and helps to maximize the number of users on any access point. Casto also suggests making sure that the Wi-Fi infrastructure offers power-saving features to extend handset battery life. The Wi-Fi Alliance offers the WMM Power Save standard, and there are proprietary standards as well.

Making the Right Choice
The mention of standards raises the question: Is VoFi mature enough for solution providers to integrate a multi-vendor solution, or is a single-vendor solution preferred?

"VARs have many solutions and manufacturers to choose from, but VoFi can be complex, and the standards are still emerging," says Berard. "My advice is to choose a single major partner such as Cisco, Nortel or 3Com to provide the complete solution." This, Berard believes, will help ensure end-to-end interoperability, from the IP PBX through the wired infrastructure to the access points and the handsets.

A single-vendor solution also makes it likely that all voice, data and management features will work as promised and that every class of user will be supported. And the majors all offer training on the competencies needed to specify, deploy and troubleshoot VoFi solutions.

Solution providers who take such training will be ready to meet customers' needs today and in the future. "It's important to realize that wireless will increasingly become the way users access the network," says Klassen of Nortel. "Developing competencies in integrating VoIP with wireless LANs is an excellent way to attract a lot of business."