RF management the key to quality for voice over WLAN
By Bryan Betts
Self-adapting networks are the only way forward as demand grows for wireless networking,and for voice over wireless (VoWLAN), say established companies and start-ups alike.
The IEEE's proposed 802.11e standard for quality of service (QoS), due later this year, addresses voice and data applications contending for bandwidth, but the problem of too many wireless access points (APs) sharing the same radio space may be a tougher one to crack.
So far, suppliers have looked to centralised security switches as a partial solution, says Isabelle Guis, a WLAN product marketing manager at Nortel. These allow existing APs to be connected to the LAN, creating a centrally managed hybrid wired/wireless network.
Now though they are coming up with adaptive networks, which study the world around them and react accordingly. "Adaptive networks are plug and play so they are more efficient," Guis says, noting that Nortel partnered with Airespace to gain adaptive WLAN technology.
"Both adaptive and hybrid support voice, but an adaptive network has better overall QoS. For example, if an AP in a meeting room is overloaded, the system can recognise that and move users to another AP. And where before we could detect a rogue AP, now we can prevent the client from connecting to it."
Start-up company Bandspeed has also spotted the crowding problem and come up with an ingenious solution: APs that transmit on different channels in different directions, intelligently changing channels and adjusting radio power for the best coverage and least interference.
"There are capacity issues as more users come on board," says Blaine Kohl, Bandspeed's marketing VP. "Today the AP is a hub that everyone shares. Most say you can get six to 10 clients per AP, then you can have three APs per space.
She adds that VoWLAN will make the problems worse, as it will increase the number of WLAN clients and also because phones tend to move around more than PCs.
"People are struggling with RF manageability --- they quickly find out it's not scaleable, as with more than three APs in one space they will hear each other. In large public spaces like airports, it is already becoming a problem."
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