Interoperability
Compatibility between wireless infrastructure and VoIP equipment isn't the only issue. What about the compatibility of wireless VoIP products from different vendors?
According to Wakim, the absence of standardised quality of service mechanisms means you need to buy all the handsets and the QoS server from the same manufacturer. He expects standardisation to occur in a year or two, but notes "it hasn't really happened with fixed IP handsets yet."
But as Ablett points out, if the specific requirements of different users within the organisation call for handsets from different vendors, there's nothing to stop you installing a QoS server from each company. "802.11e needs to be ratified--once it is, there's no need for a QoS server on your network," he says.
Luxford is also more optimistic, predicting that handset manufacturers will provide broad support for SIP (Session Initiation Protocol, a signalling protocol for Internet conferencing, telephony, presence, events notification, and instant messaging) in 12 to 18 months. Phone switch companies such as Nortel have only recently begun supporting SIP, and now the manufacturers of handsets and related devices will soon ramp up their support.
Analog phones are fully interoperable, but digital phones generally can't use of their advanced features unless used in a homogenous environment, he says. VoIP has the potential for full interoperability while providing even more advanced features, although this presents an "interesting challenge" for vendors.
Winhard points out that SIP is not sufficient: "There are some ‘least common denominator' standards such as SIP and H.323 that should provide basic interoperability between different vendors' products," he says. "However, in reality each vendor needs to add certain telephony services that are not specified in the above standards by implementing proprietary protocols, so that typically a phone from one vendor cannot be used on the LAN telephony system of another." This applies to wired and wireless VoIP handsets.
Motorola, Avaya, and Proxim have announced they will collaborate on the creation and deployment of converged cellular, WLAN, and IP telephony solutions that will deliver new levels of communications mobility and network connectivity. These will be enabled by an array of new products including a WiFi/cellular dual-system phone from Motorola, SIP-enabled IP Telephony software from Avaya, and voice enabled WLAN infrastructure from Proxim.
Motorola will also create network components to control the hand-off between WLAN and cellular networks, while Proxim will facilitate hand-offs between WLAN access points.
Cost savings
Wakim says it is possible to achieve overall cost reductions with wireless VoIP just by avoiding or reducing calls placed to or from normal mobile handsets. A reduction of 40 to 60 percent in mobile bills can be achieved, he claims: for example, if you are in a meeting room waiting for the last person to arrive, the chances are that you will try to find out where they are by calling their mobile from yours.
Such savings would be particularly achievable when using hybrid GSM/VoIP handsets: when they are in range of a base station, outgoing calls are placed through the PABX at fixed line rates rather than the (normally) more expensive mobile tariffs, yet giving users the convenience of a single handset.
"The biggest driver is cost reduction," says Wakim, but there is some possibility of running applications on wireless VoIP handsets and that could provide new business opportunities. "The boundaries are starting to be pushed," he says.
"I don't think there's going to be a huge uptake just because it's wireless IP," says Wakim. "It's not going to be for everybody."
"[Wireless] voice over IP isn't cheap--it needs to be integrated well with the PABX," says Stock. A hybrid solution is needed, using wired or wireless VoIP where it makes sense, and normal phones elsewhere, he suggests. In particular, a normal phone keeps working in the event of a power failure as it is driven from an exchange with substantial battery backup; moving to VoIP means you are responsible for your own backup power arrangements.
Cost reduction isn't only about call charges. Luxford points out that wireless telephony makes good sense in a retail environment to minimise the time taken by a salesperson to deal with a phone inquiry. In a small store, a simple cordless phone might be more appropriate, but it's easy to see how wireless VoIP could be useful in a larger business.
Other phone technologies can be used in conjunction with wireless VoIP such as Nortel's Meridian Integrated Personal Call Director which provides a single number ‘follow me' service, routing calls to any or all of six different phone numbers either simultaneously or in order. Those numbers could cover fixed or wireless VoIP handsets, mobile phones, and fixed lines at home or other locations. A Web-based tool lets individuals control this routing. "People are far more mobile than they have ever been," says Luxford. "Being in contact is very important."
Winhard takes a similar tack, pointing to the productivity advantages of call centre, unified messaging, and other applications deployed on LAN-based systems such as 3Com's NBX.
Whether you are talking about cost saving or revenue generation, the benefits need to be measurable because according to Wakim, "the handsets aren't going to be particularly cheap." He predicts prices in the $800-$1200 range. However, it is quite easy to analyse savings by correlating PABX records and mobile phone bills with the times people were on site. You can then determine which technology is the most appropriate to gain the desired cost savings.
"It's not going to be for the small end--it's for medium to large enterprises," says Wakim, but "it's only a matter of time before the costs are driven down."
Munch predicts that the high volume production of the chips needed for wireless VoIP handsets will eventually give hybrid GSM/wireless VoIP handsets a cost advantage over DECT, but not for another two years or so.
The ability to roam between GSM connections, voice-capable public WiFi hot spots, and a private WLAN during one call would be attractive to--perhaps even expected by--users, but is unlikely to happen, he says.
But Roger Geerts, systems engineering manager for Australia and New Zealand at Juniper Networks says carriers in the region are beginning to experiment with VoIP support at wireless hotspots, "but it's very rudimentary".
As Stock points out, a brief delay when moving between WLAN and GSM while a new connection is established is no problem for data, but it wouldn't be acceptable for voice.
| “It’s not going to be for the small end—it’s for medium to large enterprises, but it’s only a matter of time before the costs are driven down.” |
According to Luxford, Nortel expects wireless LANs to dominate deployments over a five to 10 year period. Coupled with the general growth in the adoption of VoIP, this suggests wireless VoIP will become more popular.
"In a long-term perspective, WLAN VoIP will replace existing cordless technologies such as 900 MHz DSS or DECT," says Winhard
Security
"Security is definitely key," says Wakim. Avaya's forthcoming hybrid GSM/wireless VoIP handset--due in Australia late 2003 or early 2004--will encrypt data prior to transmission and may use VPN technology, he says.
3Com takes a similar approach, using "a basic scrambling of voice packets to make it harder to eavesdrop on a conversation," says Winhard, and VPNs can be used to encrypt the entire data stream.
Chiswell says it's not normally possible to use traditional approaches such as VLAN, IPSec or 802.1x in a mobile wireless environment. For example, a VLAN connection can't usually be maintained when moving between subnets. This problem is solved by Bluesocket's wireless gateways, he says, which support IPSec and PPTP encrypted tunnelling, provide secure access to users moving around a WLAN, and offer bandwidth reservation for voice traffic or other classes of service.
If you are looking at security from the perspective of preventing access by unauthorised devices, another possibility is to take advantage of access points that can impose access controls based on MAC addresses (so "foreign" devices cannot connect), he suggests.
Security also involves protecting VoIP installations from denial of service attacks and MSBlast-style issues, says Luxford. "We don't run Windows operating systems on our core switching systems," he adds.
Executive summary
Wireless VoIP is a combination of two technologies: wireless LAN and voice over IP.
- Standards for wireless VoIP such as SIP (session initiation protocol) are emerging, and full interoperability is expected within a year or two. At present, the compatibility of different vendors’ handsets, access points, and gateways is variable, so check before buying a heterogenous system. Even then, some handsets may not provide access to every feature of a particular PABX.
- Early adopters of wireless VoIP can be found in manufacturing, warehousing, retail, and health—all areas where workers move around the premises yet need to stay in contact.
- Wireless VoIP handsets have a similar form factor to cordless or mobile phones, combined with barcode scanners or other devices, or implemented in software for PCs or handheld devices including Pocket PC.
- Around half a dozen simultaneous wireless VoIP calls will saturate an 802.11b access point, so careful capacity planning and proactive network management is needed to avoid user complaints. Specialised tools may make that job easier for technical staff lacking specific expertise.
- Hybrid wireless VoIP/GSM handsets will soon be available, connecting to the WLAN in range and otherwise automatically switching to the carrier network. Some carriers are conducting trials of wireless VoIP at WLAN hotspots, but automatic roaming between WLAN and GSM while a call is in progress is some way off.
- High levels of on-site mobile phone use can provide an opportunity for substantial cost savings from wireless VoIP. The technology also provides opportunities for productivity improvements, which can be substantial.
- Security is always a consideration when implementing WLAN, and the importance of voice traffic means even more attention is necessary.
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