VoIP in 802.11b/g

[michaelux]

Hi, i dont write so mucho english but i will try...

I am proving VoIP in wlan 802.11b/g, and I am using ethereal to analyze the RTP traffic, but I have some doubts: Can be collisions en 802.11 b/g like in a Hub?, where every PC transmit at the same time? , if a use RTS and CTS the number of collisiones low?


I maked 10 calls from 4 pc to other 4 pc(using 3 softphone in a pc), and a linksys wrt54g and I can see 60 % of packet lost, is normal this? I think than that are too many packet lost for 10 calls.

Is there any who have prove VoIP in wlan? which is the number of call at the same time than can be there in an Access point?
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[spiderbite]

First, 802.11 b/g does not have collisions like you would experience in a hub.

CDMA / CD (collision detection) is the switched network / hub variety. It detects collisions and re-transmits.

CDMA / CA (collision avoidance) is the standard for 802.11. It avoids collisions using

an algorithm that decides who gets to go next. Eventually, you could time out and then re-transmit.


You could use RTS and CTS but then you are also increasing overhead which is detrimental to throughput.
Just something to think about.



60 % is horrible and un satisfactory.




The problem is many things could have contributed to this.

You may have a weak signal that cannot detect the packets from the noise. Data is more forgiving
than voice and you need a stronger signal to sucessfully deploy VoIP than you would otherwise.

Cisco says they will accept 7 simultaneous VoIP calls per AP. Maybe it's 8 and we only do 7...not sure

Hope this helps...

[John_in_NC]

try reducing MTU on VoIP devices if possible.
Also, read up on something called "Hidden Node".
Oh, your voice IS on a differerent VLAN and SSID than your data right?