While mobile VoIP technology is finding a home in hospitals and manufacturing plants where workers need to stay connected as they roam, rollouts still require painstaking work, users say.
At San Antonio Community Hospital in Upland, Calif., VoIP is second on the list of applications being implemented over the facility’s Wi-Fi network – right after bedside and operating-room computer access to patient records and X-rays, says Irv Hoff, the hospital’s manager of converged networks.
True mobility and cost were major concerns Hoff had to overcome about Wi-Fi, but he is now convinced the technology meets his needs. Still to be worked out: details of deploying VoIP to avoid problems such as calls dropping between access points and barriers within buildings blocking calls. “We want the quality of the call to be equal to what you expect from a wired phone, given that we control the environment,” Hoff says.
The problems are complex because VoIP over Wi-Fi combines the issues of wireless LANs (WLAN) with those of IP telephony. As WLANs for data become more and more accepted, so will VoIP over Wi-Fi, says Will Stofega, an analyst with IDC, but the potential problems with VoIP must be dealt with first. “If there is packet delay or loss, you hear it with VoIP,” Stofega says. And as Wi-Fi VoIP phones proliferate, phone calls will boost the demand on wireless networks. “If you give people mobility on the LAN, you have to increase the number of access points,” he says.
Despite such issues, Wi-Fi networks are growing, with worldwide sales of wireless mobile network infrastructure gear projected to rise from about $43 billion last year to $49 billion by the end of 2008, according to IDC. As network executives get comfortable running data over these networks, they will increasingly add VoIP, Stofega says. At the moment, VoIP over Wi-Fi use is very limited. As the technology advances to make its use easier and to assure voice quality, that use will increase, he says.
Vendors selling access points and switches capable of supporting VoIP include Airespace (which is being bought by Cisco), Aruba Wireless Networks, Cisco, Siemens and Trapeze Networks. According to Siemens, the top users are hospitals, retail stores, manufacturers and warehouses.
Keys to deployment
For Hoff, the first step is making sure access points in the hospital cover every location an end user might go in the building. Then he has to make sure there are enough overlapping access points to support the likely load of simultaneous users without denying service to any of them. He is using Trapeze gear and a tool the company provides called RingMaster that maps buildings and the effective penetration of Wi-Fi frequencies through walls, floors, doors and windows.
This is a particularly big issue in hospitals, where renovations that change the configuration of walls are common, but also because some of these walls are shielded to block X-rays and are therefore unfriendly to Wi-Fi transmissions, as well. “We do a lot of remodeling – new partitions, new offices,” Hoff says. It’s an ongoing process, so as the hospital makes changes it records them in RingMaster, which identifies new blind spots. Then access points are reconfigured to get around them.
Load balancing among access points is key to efficient distribution of calls, vendors say. Airespace access points, for one, distribute users evenly in environments where they might be within range of several devices at the same time. Without this feature, user gear would vie for entry to the access point with the strongest signal. Siemens says its next round of devices will include this feature.
Assuming there are enough access points to guarantee coverage, network executives have to ensure fast handoffs between devices as callers walk in and out of range of different sites. The switchover has to take less than 50 milliseconds or callers can hear it – this means careful network design is essential. For instance, with voice and data running on the same network, the handoffs can take from a half second to 10 seconds, with the presence or absence of data on the network affecting the time unpredictably, according to Network World Clear Choice testing.
Beyond network performance, any use of VoIP over Wi-Fi should include an evaluation of voice quality. “Do you want to be on a call with a client and barely be able to hear?” Stofega says.
Future roaming outside
While roaming within a building might be good enough for staff inside a hospital, salespeople that roam the country also can benefit from wireless VoIP phones and save customers money, says Keith Waryas, an analyst with IDC.
Using VoIP wireless phones or even VoIP softphone software on a wireless PC can turn public hot spots into havens where users can avoid dipping into cellular minutes where expensive residential rates might apply, according to Waryas.
“Most business users are getting reimbursed by their companies for use of their personal cell phones,” he says. So a company would issue a VoIP wireless phone to roving users and receive fewer expense reports for cell phone reimbursement.
A key limiting factor that remains is the number of public hot spots available, although the number is growing rapidly.
Even when there are enough, corporations would have no control over the design and management of public hot-spot networks, so quality could suffer. Also, users would have to carry around two phones apiece – one for Wi-Fi, the other for cellular if they want to stay in range all the time. Apparently, though, service providers think enough customers will want these Wi-Fi phones to support new services. VoIP service provider Vonage recently announced a service supporting Wi-Fi phones. And Net2Phone is about to market a similar service in the U.S. after initiating it in Canada.
Motorola, in conjunction with partners, is field testing the first dual-mode wireless phones, access points and PBXs that let users make or receive calls on corporate Wi-Fi networks and continue them on GSM networks as they move out of Wi-Fi range.
So a doctor starting a phone conversation in the hospital via Wi-Fi could walk out of the building, get in a car and drive away but continue the call because the network flipped it over to a cellular network.
Systems involving Motorola hybrid phones require use of Avaya PBXs and Proxim access points to coordinate the handoff of calls, and are touted as a way for businesses to save on cellular costs. Businesses would buy the phones and set up corporate cellular accounts, which would let them negotiate lower cellular rates than their employees would individually.
The phones can only tap into specific Wi-Fi networks that must include Motorola presence servers that keep track of where users are.
Service providers could offer a managed service based on this technology. Waryas says he expects at least one major U.S. carrier to announce one by summer. This could give users seamless transition from cellular to Wi-fi at public hot spots.
One hospital telecom manager, who would speak only if he was not identified, is considering the technology and had a concern about billing.He says he’d want to know how the network decides which mode to use and whether there would be a fee for calls received on the Wi-Fi network.
Advocates of this type of service say businesses will be able to negotiate good cellular deals because they will need large buckets of calling minutes. Waryas says he thinks such services will allow for setting up least-cost routing to keep the cost down.
If billing isn’t a problem, these dual-mode services could relieve some of the Wi-Fi coverage issues within buildings, Waryas adds. If a user wandered into a dead spot within a building, the call would continue as a cell call rather than drop, he says.
