Why Your Network Needs VoIP Over Wireless

Voice over wireless local area networks (VoWLAN) might just be one of those technologies whose time has come. Combining voice over IP (VoIP) and wireless networking -- the two headline network technologies of the last couple of years, VoWLAN is, quite simply a natural.

"There's a lot of pent-up demand for VoWLAN, and particularly for dual-mode cellular and wireless VoIP phones," Forrester Research principal analyst Ellen Daley says. "There's a pent-up demand because of a fear and concern of wireless phone costs. Companies are saying that 'we see people using their cell phones on office hallways,' and they're interested in reducing those costs."

Indeed, at one level, the equation is quite simple in a carpeted office environment. If you have a wireless network anyway, and your employees are using their company cell-phones to talk as they move from desk to desk and from conference room to cubicle, then you might as well see if you can put it all together and save airtime charges. With the imminent market availability of reasonably affordable dual-mode phones, it's a no-brainer.

However, Daley is quick to point out that company executives who think that it will all simply be a question of giving everyone a new phone will be sadly mistaken. The one thing you can count on, in fact, is that most companies that are thinking seriously about VoWLAN are probably underestimating the complexity involved in actually deploying the technology.

"Just look at wireless LANs," Daley says. "Most are deployed casually, providing guest-access. They're not integrated in the network infrastructure as a whole or scaled-up to be able to support voice. There will be a rude awakening. A lot more of a design process goes in to supporting VoWLAN."The main issue with mobile phones, at least as far as IP networking is concerned, is that they're, well, mobile. People invariably use their laptops sitting in one place, but the whole benefit of a mobile phone is that you can make a call while walking through a corridor, or standing in some place other than an office. "We might know where mobile data users are -- they're usually sitting at a desk," Daley says. "But with voice, we really can be mobile."

That means that a telephone conversation can move from one access point (AP) to another. If there's a dead zone, because of a wall, or because the radius of one AC doesn't quite overlap the next, calls can be rudely interrupted as the caller strolls between them. Moreover, APs have to be configured to quickly and efficiently hand-off the connection as the caller moves.

It's not so much that hand-offs are such a massive technological hurdle, Daley says. It's just that no one has actually proved its feasibility in a real-world situation. "Vendors are proving this out," she says. "But there has been no high-capacity deployment yet. I think it's going to work, but it's going to need some working-out first."

Indeed, voice is a synchronous form of communication. A connection hiccup when you're downloading e-mail, even to a handheld, might be a minor annoyance, but if you're making a deal on the phone and the connection goes dead, you have a big problem. The connection has to be seamless.

It also has to be smooth and trouble-free. One thing that VoWLAN absolutely demands is reliable quality of service (QoS). "When you're running VoWLAN, you really have to make sure that you have QoS on your wireless LAN infrastructure," Daley says. "Though many products do have the old wireless QoS standard, many don't have 802.11E."

Many of the potential problems associated with voice quality and network pervasiveness can be avoided with careful planning, Daley says. Wireless networks that were set up for convenience and grew organically from there have to be examined for holes and optimized to deal with the special demands of voice."You don't necessarily have to invest in new infrastructure," Daley says. "A lot of wireless vendors support voice, but you might need to add some new access points. You have to be much more serious about design and deployment and use tools to plan for high capacity usage instead of just data usage."

The bottom line is that, although its is carried as packets along an IP network, VoIP is not just data. That means that organizations eager to surf the coming VoWLAN wave have to consider carefully how they will move to the new technology and, perhaps more importantly, how dependent they will be on it.

"It's not rocket science," Daley says. "But there is a big difference between what works in the lab and works in the real world. We still have to see how well it will work out."