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WLAN and VoIP: A match made in heaven?

Marrying wireless LAN and VoIP technology isn't easy, but one expert says that with enough effort and expertise, they can live a long, happy life together. However, one admin isn't so sure.

LOS ANGELES -- Both wireless LAN (WLAN) and VoIP technology are quickly maturing, but mix them together and problems can cascade. The two technologies are hardly meant for each other, but with enough effort and expertise, they can work well together.

During a presentation at the Internet Telephony Conference & Expo last week, Tony Rybczynski, director of strategic enterprise technology at Brampton, Ontario-based Nortel Networks Ltd., urged businesses to take the time to understand the needs and constraints of both technologies before simply adding voice service on top of a WLAN.

"If you think that Wi-Fi is like a LAN and voice is just another application, you will fail," he said.

Some businesses have already been scared to the sidelines. El Norte, a newspaper in Monterrey, Mexico, has deployed Wi-Fi and is in the process of deploying VoIP.

Attendee Blas MagaÑa Gonz&aacutelez, sub-director of technology at El Norte, said there are significant benefits to having voice over Wi-Fi. El Norte's employees can move around the office while on the phone. They may even use public hot spots. But he most likely won't add voice to his Wi-Fi network for a year or maybe more.

"We are concerned about voice quality," Gonz&aacutelez said.

Despite those concerns, Rybczynski said there are several steps businesses can take during a deployment to increase their odds of success.

Businesses should begin by planning their Wi-Fi networks with voice usage in mind. Enterprises that intend to use Wi-Fi strictly for data may only put access points in conference rooms or the lobby. But with wireless voice, Rybczynski said coverage needs to be ubiquitous, otherwise calls might drop.

Wireless networks that use 802.11a may be a better option for voice, he added, because that protocol has many more channels than the more common 802.11b protocol. It is therefore less susceptible to interference that can cause calls to break up.

In addition, bandwidth is important, Rybczynski said. Though voice is not very bandwidth intensive, it becomes more so over WLANs because of the overhead information that is transmitted with IP packets. For example, he said an 8 Kbps LAN-based call using the G.711 codec balloons into 200 Kbps over a WLAN. Because of that, he recommended that businesses consider higher throughput 802.11a and 802.11g systems.

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 Data traffic is also more resilient than voice traffic. While data can withstand network slowdowns or lost packets, voice traffic is notoriously sensitive to latency and jitter on the network.

To address that, Rybczynski recommended that businesses try to keep voice and data traffic on separate virtual LANs. But that strategy has pitfalls, too. For example, Rybczynski pointed out that an employee using a laptop with a soft phone would not be able to send voice and data over separate vLANs from the same device.

In addition, the 802.11e wireless standard, which is intended to provide the quality of service that voice traffic needs, has yet to be ratified by the Institute of Electrical and Electronics Engineers. As a result, many vendors are using pre-standard technologies.

Gonz&aacutelez said he is not sold on many of the techniques required to get voice up and running today. He prefers to wait for the 802.11e standard to be ratified and for more of the problems to be addressed before he runs voice over his Wi-Fi network.

"Some things still need to mature before we deploy voice," Gonz&aacutelez said.

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