Lower Data Rates for VoWLAN

Unanswered Question
Oct 28th, 2009

When I take a look in the deployment guides I could see that I should not use data rates in the 802.11a network below 12mbit. We do not expect more than 6 calls and 8 phones on one access point but would like to raise the coverage by using 6mbit data rate. We could not place more access points. Is there someone with experience using lower data rates?

Using:1252 Access Points and WISM Controller

I have this problem too.
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migilles Wed, 10/28/2009 - 06:19

In the deployment guide, it is outlined that with 6 Mbps you can expect to get up to 13 wireless phones on call per ap/channel.

With 12 Mbps, it will be around 20.

Our recommendations are for the typical design is to design to 12 mbps as that is also the minimum rate we use for CAC as well.

jeromehenry_2 Wed, 10/28/2009 - 06:59

Allowing speeds from 6 Mbps can technically work, but the recommendation is also to avoid retries... the larger your cell, the more chances you have to have multipath issues making packets fail. With a voice deployment, if you have more than 1 % error rate, your MOS degrades below 4.1 (the quality of the call is affected and users start complaining that voice conversation is unstable, choppy etc).

So allowing 6 Mbps is fine, but the result will depend on the quality of your RF environment...

hope it helps



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