This year, WLAN vendors have been heavily selling the idea of using their equipment for voice. It's an interesting idea, and has obvious paybacks. Workers away from their desk use expensive cellphone minutes, sometimes to talk to people in the same building. If the company had an in-building wireless LAN, these calls could be routed over "free" bandwidth, to their recipient, or onto the switched telephone network.

The drawbacks emerged pretty quickly:

  • The bandwidth might be free but the handsets aren't, as they (effectively) are with cell services. It takes a lot of voice-call savings to offset the cost of buying a Wi-Fi SIP phone costing more than £250.
  • Voice on Wi-Fi means a separate handset, which users will find an inconvenience.
  • Wi-Fi handsets are as yet not very good. There appears to be only one significant player, Spectralink, and its products have a short talk-time and low battery life, and tend to be bulky.
  • Quality of service is still sub-standard or non-standard at best on Wi-Fi networks, although the standards to support quality are evolving within the 802.11 family.
  • Handoffs between different access points on a wireless LAN can be slow, so that voice calls will be interrupted.

Despite this, the Wireless LAN event earlier this month in London saw the usual bunch of Wi-Fi vendors promoting the idea of wireless LANs for carrying voice. However, all were surprisingly frank about the difficulties they see.

Aruba promises security
"Voice over wireless LAN is becoming more important to the enterprise," said Keerti Melkote, vice president of product management of Aruba, launching an upgrade which attempts to push two Wi-Fi hot buttons at once - adding security to voice over WLAN.

Aruba has always emphasised security, and this upgrade is designed to make it more secure. The problem, as he sees it, is that Wi-Fi handsets from the likes of Spectralink have, along with their usability issues, problems of security, because they are simply not up-to-date with wireless security procedures.

"These handsets still use WEP and public ESSID," said Melkote. "They authenticate by MAC and that can be spoofed or stolen." What Aruba has done is allowed its switches to classify voice flows, which use SIP or Spectralink's SVP protocols. So, if a device claims to be a voice phone, it can be restricted to carrying voice traffic. This prevents laptops from spoofing their way into corporate data applications by pretending to be phones.

Other devices such as genuine corporate laptops, will have WPA authentication, and can be allowed to use the rest of the resources on the network, as well as voice, but even these will benefit from voice flow classification, he said, since it can prioritise different flows from a single client. This means that email or data applications won't cause delays to voice calls.

Aruba claims to offer a 10ms hand-off between access points on the same wireless switch, and a 25ms handoff between access points on different switches, which is good enough for voice calls roaming within a WLAN.

But all these features, he had to admit, are not getting much use yet. "There's been a lot of hype around voice on wi-Fi," said Melkote. Is anyone using it? "Enterprises want to see it on the roadmap," he said, which we translate to mean that people want to know it is possible, for the future, rather than needing it now.

Airespace pays "lip service"
This sentiment was echoed by Wi-Fi voice "veteran" Airespace: "Vendors have to pay lip service to voice on Wi-Fi," said Jeff Aaron, Airespace's senior marketing manager. The company has been doing more lipservice than most, selling Wi-Fi voice actively since at least the middle of 2003.

However, the company admits it has so far sold very few systems specifically for voice. The technology is so far let down by the poor handsets, the lack of integration with cellphones, the lack of quality of service standards and other factors, said Aaron. "Users are waiting for the second or third handset manufacturer," said Aaron.

So far, Airespace has sold systems with voice on Wi-Fi, but these have tended to be in the Us, and in specialised areas, paricularly healthcare. In hospitals, cellphones are banned, and there are a lot of highly valuable highly mobile staff, so it is worth while ironing out the problems for specific users. Many of the healthcare installations use active badges from Vocera, to replace pagers, instead of using Wi-Fi phones, said Aaron.

In Europe, IT managers are hopeful, apparently: "All the customers we are speaking to say Wi-Fi will be the replacement for DECT [the cordless digital voice standard]," said the European head of Airespace, Marcel Dridje. However, he admitted that Airespace's Wi-Fi deployments in Europe don't have voice, except as a future option. "It's on the planning horizon," he said.

Nortel shows just how immature Vo-Fi is
It fell to voice provider Nortel to expose the "immaturity" of Vo-Fi. "People choose a Wi-Fi infrastructure that is capable of supporting VoIP," said marketing leader Peter Finter, well known to Techworld as the man who explained how Nortel itself
saved $22 million on voice over Wi-Fi
. But users aren't actually doing it yet, he admitted. "If something is possible it probably will happen. No-one wants to be caught out, and different technologies have different deployment times and investment cycles."

DECT is still going to be around for a long while, explained Finter. Nortel sold 40,000 DECT handsets in Europe last year, and demand remains strong. As Airespace's Dridje points out, DECT has quality of service.

"We think mobile handsets could be the deciding factor," said Finter, presenting an optimistic view of the state of the art for Wi-Fi SIP phones. In a moment of unintentional humour, he promised that Wi-Fi voice equipment was becoming more practical, and DECT-like.

Nortel itself is getting into the market for voice over Wi-Fi handsets, he said, as part of its deal with Airespace announced earlier this year. Showing a new Nortel Vo-Fi phone, he explained that it is a great improvement and almost DECT-like in its performance.

How DECT-like? Well, there's an executive version, he explained, which is the same size as a DECT phone (ie bigger than a normal cellphone). The battery life is improving, he explained. IT now has a battery life - and this is battery life, not talk time - of three hours.

So not only does voice over Wi-Fi still require a separate handset, it is one which has to be recharged several times a day. It is no wonder that IT managers are not rushing to implement this technology right away.

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