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I haven't figured out why so many people use G.711 - voice doesn't need this much bandwidth, and we all know this from years of working with mp3.

Simple-- there is just so much overhead that dividing your codec bandwidth does not increase the capacity much.

In fact, if you check out this good technical presentation by Spectralink, slide 13, you will see for example that a G.711 call (64 kbps both ways, i.e. at most 128 kbps) actually utilizes 4.5% of the bandwidth in "11 Mbps" mode (i.e. in the best radio conditions). That represents 500 kbps of nominal bandwidth, to carry a 128 kbps signal.

What happens when you use the G.729 (GSM) codec at 8 kbps instead, is that the quality goes down for for sure, but the capacity does not increase that much: one call utilizes 3.5% of the bandwidth in "11 Mbps" mode, which still represents 400 kbps of nominal bandwidth.

So while you divided your codec rate by 8, sacrificing quality, the capacity has only been increased by 30%, not by 700% as one would expect in a perfectly designed system.

Why bother with lousy codecs when the underlying layer adds so much overhead in any case?

• Symbol
  
• Spectralink
  

Spectralink has had an 802.11 VoIP phone for a few years. It hands off from AP to AP totally seamlessly.
I have also used the Symbol phone. Not nearly as nice.
The reason a corp would buy this instead of a cell phone is there is no reason to take the 802.11 phone home.

SpectraLink has been doing 802.11 handheld phones for a few years as well with their NetLink product line.

oh and, lets not forget this one click

assuming you have the wireless coverage for it, what a match made in heven.

Anyone know where I can get some 802.11 cordless phones? The only ones I can find are made by Symbol, but I know there has to be more out there.

In addition to Symbol (as you mentioned), Spectralink makes 802.11b wireless IP phones as well.

Cisco's 7920 Wireless IP phone will be coming out end of 1QCY2003, but out of the gate will only be supported in a Cisco CallManager environment. The Product Manager did a presentation a few weeks back here in STL, and the plans they have for the product are pretty neat (again, assuming you are in a CCM environment).

I plan on using them with Asterisk [asteriskpbx.com] and my 802.11 access point.

I'm using Asterisk at home as my IVR & Voicemail System, with Cisco's IOS Telephony Services (ITS) handling the actual call switching. ITS can scale up to 48 phones depending on the Cisco router platform you have. I'd actually prefer to us Cisco's Unity product as my IVR & Voicemail--but frankly, I'm too cheap to introduce that at home. Asterisk is, as you know, zero cost.

I like zero cost.

Big Y grocery stores in Connecticut and Mass. are all getting their phone systems upgraded, and one key feature of the new system is a half dozen cordless phones in each store for managers/supervisors out on the sales floor that use the existing 802.11b network most grocery stores have in place throughout the store for handheld scanners, scales, ESL's, etc. They're pretty cool little phones, and they tie right into the Nortel Meridian system we use. They are a bit pricey, though, at about $700 a pop. They're made my a company called SpectraLink. They have all their marketing info on them here.

Obviously phones aren't going to be moved to wireless if your in a call center.

They could be. Spectralink in one of a few companies that sell 802.11 phones. Unlike 2.4Ghz cordless phones, these wouldn't interfere with your wireless network because they _use_ it. Look here: http://www.spectralink.com/products/netlink.html