[asterisk-biz] Wireless SIP phones?

[Jacob Suter]

While I agree DECT is technically better, I ran into non-technical issues
that dictated our choice in using wifi phones:

A> price (we needed multiple handsets with separate extensions, without
paying a huge upfront cost)
B> coverage (DECT only exists where you build out, I wanted to be able to
use it at area hotspots and my girlfriend's house)

Around the office, I've noticed AP quality/placement dictates audio quality.
The best performing setups I've found so far are APs using Atheros 3T3R MIMO
radios (Linksys WRT300N v2).  The Airgo 2T2R radios work nearly as well for
less money (WRT54GX2).  The worst performing setups were APs using Realtek
and Broadcom 11g non-MIMO chipsets.   The 'consumer standard' Linksys WRT54G
is *not* a good VoWiFi router.  High power APs don't usually help
performance significantly for VoWiFi.  You *really* want the phone to roam
if your AP can't maintain a -75 signal or better, anyways.

If you're inside a metal structure, 3T3R MIMO will make an *AMAZING*
difference.  It lets you 'work' reflected signals, which should be wonderful
inside a metal warehouse.  Just make sure there is no metal stuff
(preferably nothing at all) within 3 ft of the antennas.  I also set my APs
to 11g-only - you lose a little fringe coverage per AP but there's much less
chance of one VoWiFi client "eating" the entire radio's transmit time up.

I've done most of my asterisk testing with Trixbox and Asterisk 1.2, and I
was never able to achieve decent VoWiFi results using it.  I'm using
FreeSwitch and I'm noticing a lot less jitter on calls, especially using the
wifi phones, or dialing out during peak internet usage time (we're kinda
short on bandwidth at the moment).  I have not tried newer versions of
Asterisk to see if this problem doesn't exist.

I'm personally using UT Starcom F3000's at this point, running 5.9ST, with
fairly good results.  They do crash/lock up/refuse to connect/refuse to
roam, but after tweaking the settings I'm achieving reasonable reliability.
You can't expect it to roam between SSIDs properly.  I've found it has no
problem (other than network issues - if you've got STP enabled on your
network you can forget maintaining calls while roaming between APs) roaming
between APs on different channels using the same SSIDs.  I've found 300
second registrations eliminates most lockups/hang-ups on this phone.

Good luck either method you use...  Radio always has some sort of excuse to
give somebody trouble :)

Jacob Suter

-----Original Message-----
From: asterisk-biz-bounces at lists.digium.com
[mailto:asterisk-biz-bounces at lists.digium.com] On Behalf Of Trixter aka Bret
McDanel
Sent: Friday, July 18, 2008 6:03 AM
To: Commercial and Business-Oriented Asterisk Discussion
Subject: Re: [asterisk-biz] Wireless SIP phones?

On Fri, 2008-07-18 at 06:27 -0400, Jason Garland wrote:
> I agree, DECT is definately the way to go for wireless since you can  
> buy repeaters, handsets from various manufacturers, etc. It is like  
> building your own cellular network. In the us DECT 6.0 phones are  
> actually cheaper then the 5.8 and 2.4 ghz phones and the FCC has given  
> DECT their own dedicated frequency so it dosent clash with wifi stuff,  
> microwave ovens, etc.

and so it doesnt clash with DECT phones from nearly everywhere else :(
If you plan on using them in Europe for example US phones wont work -
all because of frequency the rest is identical ...  sigh

Saying its like your own cellular network is a good analogy, since the
protocol is more or less like GSM, and there are even data adapters for
DECT so you can do data over the same network if you really wanted (wifi
would be faster though).

> I would also recommend using a simple fxs gateway like a sipura/ 
> linksys. I don't think there is any real reason to need your DECT base  
> to talk SIP itself, other then you may think it sounds cool.
> 

well the original question was over wireless phones, his application
(warehouse or soemthing) required them.  If you dont have a good gateawy
all wireless phones end up being the same extension which sucks.

-- 
Trixter http://www.0xdecafbad.com     Bret McDanel
Belfast +44 28 9099 6461        US +1 516 687 5200
http://www.trxtel.com the phone company that pays you!


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