* Readers lend insightful comments on running voice over WLANs
To be honest, I didn’t receive many responses to my newsletter last week about voice over wireless LANs – but the few responses I did receive were quite interesting, so I’d like to share them here.
One reader at a statewide healthcare system said WLANs have already been installed in a couple of hospitals and a support services building, with another hospital expected to go wireless in January:
“Our initial application for this WLAN will be voice. We have currently deployed the Nortel Companion phones at all of our locations. We will be initially augmenting then replacing these phones with the SpectraLink i640 phones. We currently have pilot programs going at both facilities with WLAN installed as well as our support services building and the trial is going very well.
“Very shortly, we will be adding laptops to our WLAN for Emergency Department admitting as well as an application to scan the patients bar coded wrist band and their medication using a Symbol 8846 device.”
Another reader has more of a WAN perspective, and said that the WAN wireless technology called EV-DO “will eliminate the need for WLAN for over 80% of current applications.”
“WLAN is a nice thing to have,” this reader says, “but when you have unlimited wireless data plans for less than $50/month with speeds in the 300K bit/sec to 500K bit/sec range, do we need WLAN?”
I guess the real answer is, it depends on what you’re going to do with that bandwidth.
Finally, this reader hails from a wireless systems integrator, and he had this to say about installing WLANs with voice in mind:
“It’s criminal the number of wireless systems integrators or network VARs who are telling their clients that they are putting in a ‘VoWLAN capable’ WLAN, when they know perfectly well that they are surveying to -84 dBm and instead wireless VoIP requires -70 dBm, minimum. In fact, Cisco 7920 phones stipulate -67 dBm, with 15~20% overlap (!).
“It’s also criminal how many customers cannot appreciate what amount of incremental work is required to create overlapping cells at -70dBm with low noise, such that SNR is 25+ dB or better. In general, they just don’t ‘get it,’ even though you get blue in the face explaining it in kindergarten terms.
“Sorry for the rant, but I’m just so tired of people looking at me with blank stares when I tell them that their existing data WLAN needs to get ripped out and replaced by a WLAN that is properly surveyed/engineered for voice.”
There’s no need to apologize for a rant. Just keep sending me your thoughts at mailto:jcaruso@nww.com. Many thanks to those who wrote in.
