Mobile operators are launching fixed line substitution products for the business market, as well as launching public WLAN hot spots. But could enterprise voice over WLAN pose a serious threat to both strategies, or be complementary? Bryan Betts takes a look at whether wireless IP telephony is a contender.
If voice/data convergence is inevitable and a shift to wireless networking is happening too, then the future success of products putting voice over the wireless LAN (VoWLAN) seems assured. However, life is rarely as simple as it seems, and the wireless specialists are being reminded that, as the old saying goes, there’s many a slip twixt cup and lip.
There is no doubt that interest in wireless networking also drives interest in wireless IP telephony, says Marcel Dridje, European general manager for WLAN switch supplier Airespace. “Enterprises are upgrading their laptop PCs with Centrino for data applications, but by default they also ask for the infrastructure to be able to handle voice too.” He quotes figures showing that each extra user costs just 110euros once the wireless network is place, or three time less than a new wired connection. “You have to think at the end of the day that voice is free — the Wi-Fi infrastructure is already there,” he adds.
There is a big difference between the opportunities in Europe and North America though, because many Europeans have already invested in wireless telephony in the shape of DECT and GSM, and dislodging strong incumbents is always a challenge. Nor are their backers going to give up without a fight. Philips has launched IP DECT, which connects the wireless base stations into the corporate LAN, and the GSM network operators have a number of schemes to link into corporate PBXs, as well as considerable latitude to reduce their prices if that is what it takes to stay in the game. Analysts such as META Group’s Chris Kozup warn of VoWLAN’s immaturity, suggesting this should limit it to niche and small-scale deployments. “Wireless IP phones have a limited battery life due to the relatively heavy power consumption of 802.11b,” Kozup adds.
However, VoWLAN has the same long term advantages as IP telephony in general: convergence and cheaper infrastructure. This will make it a no-brainer for anyone already using voice over IP, argues Bob Guderian, director of marketing at wireless IP phone supplier SpectraLink. “There are some data solutions for DECT but they’re not broadband and they are less integrated, whereas you can have one Wi-Fi infrastructure for voice and data,” he says.
“Some people will always choose to have GSM as their primary phone, but it doesn’t integrate well with enterprise telephony, for example with least-cost routing for long distance calls. Anyway, companies may not want to give a mobile phone to every employee, or they may want to get in touch with them but not via GSM.”
The question is no longer one of whether the technology works, but one of whether it can yet provide a more efficient and economic service than its rivals, claims Marcel Dridje.
“People are still debating whether DECT will scale to support data, but 802.11 came along at the right time,” he says. “The initial islands of WLAN found lots of security and network management issues, but they are all resolved now and the next thing is we have to understand costs and expenditures.” The most go-ahead fans admit that there are still caveats though. “Voice doesn’t need a lot of bandwidth but wireless just won’t cut it for some,” says Guderian. “Areas that require high call densities, such as call centres — it can’t support that today.” In addition, although putting voice on a WLAN is theoretically the same as adding IP phones to a wired network, the reality can be rather different.
“The main concerns are the design of the WLAN infrastructure — putting in a wireless network for data doesn’t necessarily mean it’s suitable for voice,” warns David Atkinson, Cisco’s UK business development manager for IP telephony. “For example, there is the question of coverage between APs — if you lose coverage on a laptop it is not a problem, but on a phone it is, so you need a proper site survey.
“It’s also important for APs to support Quality of Service (QoS), and you want call admission control so you don’t oversubscribe the AP with voice calls. Roaming isn’t absolutely guaranteed because you are looking at a maximum of eight simultaneous calls per AP. You may need to add APs to cater for capacity, and older APs may need a software upgrade.”
The QoS on wireless networks needs to be more sophisticated than on wired networks, to cater for the greater variety of devices and traffic. This is the show-stopper for networking giant 3Com, which has refused to take the VoWLAN route until there are defined QoS standards.
“We are advising customers that any vendors claiming to sell voice over WiFi at the moment are in fact selling proprietary products,” says Angelo Lame, 3Com’s international product marketing manager for wireless and security. “This means customers will be locked in, and as open standards come to market they will have to migrate or upgrade at an extra cost.”
Lame says that the lack of standards affects several key areas besides QoS. Included in that list is VLAN support and the ability to roam between APs without losing your call. The roaming problem is how long it takes to re-authenticate when moving to a new AP, especially given that phones are more likely to move around than PCs. This roaming delay today can be 70milliseconds or more, but while that is OK for a data connection, anything more than 50ms can break a voice call.
The IEEE is addressing these problems with the 802.11e standard in development for QoS and a newly proposed Fast Roaming study group working on call handover.
“The 802.11e workgroup has focused on methods for signalling QoS that will supersede proprietary schemes,” says Mike Banic, vp of worldwide marketing at Trapeze, whose WLAN Mobility System currently relies on proprietary technology to connect wireless handsets to the network infrastructure. “The other key area is 802.11i, ensuring that the security information moves with the user,” he adds, noting that Trapeze has contributed master key sharing technology to 802.11i for faster roaming.
“Voice has its own unique requirements,” he says. “We have implemented 802.1x for authenticating devices, and AES, the advanced encryption standard, but you can’t use the same schemes for phones as for laptops and PDAs. We authenticate a phone via its MAC address or hardware type and put it into a secure virtual LAN.”
According to many, what VoWLAN really needs to get it moving is the dual-mode GSM/wireless IP handsets from the likes of Motorola. But even on its own, it can do some clever stuff. David Atkinson cites a London-based customer who takes his wireless phone when visiting his company’s Houston HQ — it logs onto the local WLAN but registers with his London Call Manager, so he has his usual internal phone number.
“Decisions to buy wireless have been very much driven by economics,” adds Mike Banic. “People call colleagues on their mobiles because they can’t find them at their desk. If they had a WLAN phone they would save the cost of that call.”