Vo-Fi Watch: Ready When You Are

The kinks have been worked out of Voice over Wi-Fi; but when will business adopt it?

By Ted Stevenson | Posted Apr 27, 2007
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Sunnyvale, Calif.-based Aruba Networks this week announced certification of its infrastructure line for operation with SpectraLink phones from Polycom. (Note: Phone vendor Polycom's acquisition of Wi-Fi phone systems leader SpectraLink Corp. closed just a month ago.) The combination of SpectraLink phones and Aruba Wi-Fi access points (APs) and centralized network controllers gives potential customers a real alternative to Cisco equipment.

Enterprise VoIPplanet.com spoke with Aruba's product manager for voice products, Peter Thornycroft, to get details of the announcement—and his thoughts about the advent of voice over wireless LAN as a commonplace phenomenon.

"We're pretty much a natural fit with SpectraLink," he told VoIPplanet.com. "On the technology side, we've always had a very good relationship with them." An important asset SpectraLink brought to the Polycom merger, Thornycroft pointed out, is its "very detailed" testing program called VIEW (Voice Interoperability for Enterprise Wireless).

"It does a whole series of things," he said. "In particular, VIEW evaluates are the network's ability to manage quality of service (QoS)—making sure that voice gets priority when you're mixing voice and data on the WLAN, which is pretty much what all our customers are doing." [Voice, a time-dependent application, must be given priority over data, which is not time-dependent.]

Another critical network capability VIEW evaluates is call capacity. Especially with the original flavor of Wi-Fi (802.11b) and its maximum throughput rate of 11 Mbps "there was a definite capacity limit in terms of the number of calls you could put up per access point," Thornycroft explained.

Typically, Thornycroft said, with .11b phones you top out at about 0 to 12 calls per AP. "We figure we have the highest capacity in the industry. We can get 22 calls per access point with .11b. As soon as you move to .11a or [.11]g [with a 54 Mbps data rate], you're up in the 75 call per AP range—which is actually the theoretical maximum."

But to fully take advantage of the sophisticated design of the SpectraLink phones, the network infrastructure must be fully featured in other ways.

"The network can't just be a transparent pipe,'Thornycroft told VoIPplanet.com: "You have to be concerned about call admission control, for example," [one of the methods of maintaining QoS for wireless LANs].

Finally, with respect to network capabilities influencing phone performance, Thornycroft mentioned speed of "handover," the process of disconnecting a call from one access point and connecting it to another, as a mobile caller moves through the WLAN space—a thorny problem that has been a barrier to VoFi deployment for years.

Among other recently established standards capabilities Aruba has implemented to address speed of handover is 802.11k, colloquially known as the 'neighbor report.' "This allows the phone to query an AP and get back a list of its known neighbors and some info about each, which allows it very quickly to go to each in turn and decide which it wants to go to next" Thornycroft explained. (Yes, Wi-Fi phones have to do a certain amount of "decision making.")

Does Thornycroft see rapid deployment of VoFi on the horizon, now that so many of the fundamental problems have been solved? "I figure that about a quarter of our customers are seriously deploying voice," he told VoIPplanet.com; another half of them are dabbling in it—to the degree of pilots and this sort of thing."

So far, however, take-up has been quite industry specific, with hospitals far and away the most enthusiastic adopters. "We have plenty of hospitals out there with 300, 500, 600 phones deployed and being used by the nurses every day,"Thornycroft said. Wi-Fi telephony has also taken root in certain kinds of retail environments (think Home Depot), and on some university campuses where Wi-Fi networks are being built out. "Ohio State is our flagship," he said.

But adoption has been sparse among what he characterized as the 'horizontal enterprise.' "We see that they probably prefer to wait for dual-mode [cellular/Wi-Fi] phones,"Thornycroft observed, "and that means fixed/mobile convergence."

But since a new wave of dual-mode phones is already in the pipeline, perhaps we won't have too long to wait to see what businesses in general make of voice over Wi-Fi. Whenever that is, Aruba (and Polycom) will be ready with the right stuff.

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