It seemed to be an obvious recipe: take two popular emerging technologies--voice over IP and wireless local area networks--and stir vigorously. But the end result isn't to everyone's taste.
Wireless voice over IP (VoIP) "is very much an emerging market," says Ross Chiswell, CEO of Integrity Data Systems. "As the wireless LAN market grows in Australia, so will this opportunity."
The advantages of wireless VoIP telephony (sometimes called voice over wireless LAN or VoWLAN) are that it can take advantage of existing infrastructure, it is cheaper than DECT (digital enhanced cordless telecommunications, a standard for digital cordless phones), and avoids mobile phone charges when calling other people on or off-site, says Ray Wakim, solutions manager--convergence at Avaya.
Markets
Not everyone is bullish about the technology, at least not in the short term. "I'd question if there is a market yet," says Bjarne Munch, META Group's senior research analyst, global networking strategies. "It's still early days."
META predicts there will be no mass market for VoIP until 2005, and "that limits the market in VoIP over WiFi." The main problem is the absence of standards, he says. While VoIP standards should be ratified by the first quarter of 2004, anything purchased now is based on proprietary standards and therefore limited to niche functions. Similarly, security standards have not been settled, so users must either take a proprietary route or do without security features, he says.
"Our customers are finding it hard to mount a business case for VoIP...or WiFi," says Munch, suggesting corporate trials of wireless VoIP are limited to small installations such as branch offices.
But vendors are reporting successful implementations in the various markets they are targeting for wireless VoIP. The technology is especially suited to hospitals, says Wakim, as staff are highly mobile yet need to remain in contact, and because the frequency used by 802.11b does not interfere with medical equipment or heart pacemakers.
Manufacturing, warehousing, and retail are other functions where contactability is important for employees. For example, car sales staff can be contacted on a single number whether they are in the showroom or out in the yard. There are also safety considerations: Avaya's handset can be mounted on a belt clip, in which case it generates an alert if it remains horizontal and inactive for a certain period in case the wearer has been incapacitated in a fall or other accident and is out of other workers' sight.
Chris Luxford, director of portfolio management for VoIP at Nortel, highlights the same markets as Wakim, pointing out that Symbol's handset that incorporates a barcode reader and local SMS capability is especially suitable for manufacturing and warehousing deployment.
Damian Stock, who handles business development for wireless products at Symbol, claims the company has offered a wireless VoIP phone for around five years. "We've had a long history of doing VoIP over wireless," he says.
Combining wireless data and voice on a single network reduces infrastructure costs and provides opportunities to combine voice and data in one application, Stock says. For example, workers equipped with wireless devices with integrated scanners and VoIP capability have walkie-talkie style contact with their colleagues, can receive outside calls and answer questions about stock levels and pricing (perhaps finding the nearest store that does have a particular item in stock), or--with the addition of a location system--be efficiently directed to pick goods for dispatch, scanning them as they are loaded onto a pallet to create the packing list.
In hospitals, providing patients with a PIN-protected wireless VoIP handset for the duration of their stay means no line changes are needed even if they are moved to different beds. Nurses can be equipped with a wireless device that combines the nurse call system, barcode scanning to confirm patients are being given the right medication, and a phone.
Features such as SpectraLink's Open Application Interface allow the integration of third-party messaging systems with wireless VoIP, says Mark Ablett, managing director, Asia-Pacific at SpectraLink. For example, a nurse call system can be linked to phones and pagers, and in manufacturing, alerts generated by computer-controlled machine tools can be routed directly to the appropriate supervisor's handset instead of being manually relayed to the right person.
Chiswell agrees about the suitability of wireless VoIP for hospitals, but also sees other organisations deploying handsets to key personnel such as IT support staff, senior administrators, and certain partners in accounting and law firms.
It is also very good for temporary installations such as project offices that will be in place for a year or two, for example during a major court case, but he doubts many people yet realise wireless VoIP's suitability for this purpose.
Munch thinks most companies will wait for standardisation, but SMEs may be first out of the blocks as they will take a risk with pre-standards products if they can see a financial advantage. It's too early to predict which specific market segments will take up wireless VoIP, he says.
Capacity, interaction with data WLAN
The same principles of capacity planning that apply to WLANs also apply to wireless VoIP, says Wakim, such as the limits on the number of users per access point. "There is a considerable amount of work that needs to be done before deploying it."
"Current WLANs are not very well designed for voice traffic," says Claus Winhard, business development manager, voice international, 3Com. "The slowest device on a WLAN access point slows down the entire traffic. Voice traffic often breaks up, devices get disconnected, and data connections are slowed down heavily."
If a WLAN is already installed, it is very likely that additional access points will be required. Chiswell points out that there is a limit of around seven active handsets per access point with 802.11b, "but you're not going to give a handset to everyone in the organisation." Munch suggests a more realistic limit is four or five connections before quality suffers, but 802.11e (which adds quality of service features) will improve throughput once it is finalised and incorporated into products. The greater bandwidth of 802.11g will increase the number of handsets per access point. "Standards are slowly getting there," says Munch.
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“Our customers are finding it hard to mount a business case for VoIP . . . or WiFi.” |
Sniffer's "expert analysis" feature understands protocols and applications, says systems engineer Phil Coates, which lets you see how the network is set up, including an inventory of access points and if they are authorised. Sniffer can look at the different layers of an application, quantify what's happening, and then link that data to show how the network is performing.
Sniffer can examine the wireless infrastructure, for example reporting on interference, inability to connect to access points, retransmissions, encryption settings, and channels used.
According to Coates, issues of particular relevance to VoIP are end-to-end delay (excessive delay leads to people talking over each other, as happens with a call routed via satellite), jitter (variability in delay between packets--voice decoders need to be fed data at a steady rate), and out-of-sequence errors, packet losses, and contention (all of which can cause the sound to break up). "You need to know why [the network] has failed so you know what you need to fix," says Bell.
"As soon as the proposed standard for quality of service in WLANs (802.11e) is approved we believe we will see an increased offer of QoS-enabled WLAN equipment that is suitable for carrying voice traffic," Winhard adds.
Since voice is a real-time application, quality of service (QoS) control is essential yet may be unsupported by low-end access points, says Wakim. Enterprise-grade devices are unlikely to have this shortcoming, he adds.
Chiswell explains there are three design factors that affect the suitability of wireless points for VoIP:
- the processor used determines the speed of converting wireless packets to Ethernet;
- the memory size affects the amount of buffering that can be done; and
- the ROM size affects the intelligence of the device in terms of its ability to perform quality of service tagging and other functions.
According to Chiswell, SpectraLink works with major access point vendors to ensure their products can correctly tag VoIP traffic, and with Cisco and other VoIP gateway manufacturers. A gateway links VoIP traffic with a normal PABX and hence the public switched telephone network (PSTN). Wireless VoIP installations normally also include a device to prioritise voice traffic, such as SpectraLink's NetLink SVP Server. That product also handles hand-offs between access points as a user moves around.
Another problem is that inexpensive access points do not have enough processing power or memory to handle the data packets quickly enough under load, Chiswell explains. Many buyers do not realise the internal differences between access points, he claims: "it's a bit like buying a notebook based on screen size."
Reliability is an important consideration. According to Chiswell, voice network engineers work on the basis of 99.999 percent availability, but 99 percent is typically considered acceptable for LANs. While PC users might not notice a half-second network dropout every minute, someone speaking on a phone certainly would.
"There's nothing like talking to your customers," says Luxford: voice calls are the most critical business application, so it is important to deliver the same quality with wireless VoIP as a conventional phone.
"Take-up [of wireless VoIP] hasn't been as extensive as it should have been," says Stock. Australian companies have instead tended to buy DECT wireless phones from their PABX suppliers and data WLANs from other vendors. This doubles the amount of wiring and other infrastructure, and so increases costs.
While some DECT phones deliver most of the PABX functionality, that's not always the case with wireless VoIP, he says, although soft phones running on notebooks, Pocket PCs, or other handheld devices are generally better than earlier wireless VoIP handsets in this regard.
"A lot of companies have legacy DECT solutions that they've had for several years," says Ablett, and are now looking for a converged approach. Moving wireless voice traffic from DECT to an existing WLAN saves money by reducing the maintenance and management effort. "In some cases you'll need to put in additional access points, but it's not something that happens all the time," he says.
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