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We've been targerting -65dBm or better for Voice over WLAN deployments.

Our biggest challenge is finding a happy medium for the number of access points required based on data usage with voice sessions roaming from AP to AP. I've seen different studies but want to think in terms of best practice when using VoWLAN,

Q.
In a design for VoWLAN in a building with multiple floors, would you rely on placing the APs on one floor to provide the coverage and quality of service for the users above and below?

Example:

4th Floor (-55dBm)
__________________________
AP ----- AP ----- AP
________________________=3rd Floor (-30dBm)
2nd Floor (-55dBm)
__________________________
AP ----- AP ----- AP
_________________________-1st Floor (-30dBm)

Also, by implementing a switch solution, you can replace the relatively inexpensive lightweight APs with the next generation technology once available. We did this when moving from 802.11b to 802.11abg APs.

Of course, part of your question involves the potential coverage of an 802.11n solution compared to an 802.11abg solution, but I would still plan coverage based upon 802.11a capabilities.

And remember, "no body ever got fired for using standardized equipment"...

Experts,

Thanks for following up with this. Now I see , that the WIFI Alliance is going to radify the Pre-N gear here soon. The only PRE_N_WAP at the enterprise level, I've seen if BlueSocket's.

Someone will come out with one that is PoE and "Thin"since that announcement.

The biggest caveat is the RF planning. Again I think wth the better efficiency in MIMO you will you need less " PRE_N_WAPs" with VOIP.... since multipath is being "somewhat taken advantage of" and retransmissions will substantially decrease?


I would also suggest that latency and jitter that are by products of the multipath + the deadspots in a WLAN will be accomodated with the PRE_N_WAPs positioned correctly and will call for less thin APs deployed?

Capacity Planning: handled by mixture of PRE_N devices,or the later ratified N devices.

Your thoughts?

I agree that you could probably use fewer WAPs, however that number is likely insignificant when looking at the total cost of the solution. If you saved 3-6 lightweight WAPs from an installation, then you are talking less than $1000 to $3000 in hardware, which is probably not a large number after buying the VoWLAN phones, switch, etc. You also lose the benefit of capacity scaling and run the risk of having to return to troubleshoot problem areas.

The only consideration may be when having to move to another class of wireless switch because you have maxed out the supported WAPs (e.g. switch supports 12 but you spec'd out 13) and the next class is significantly more expensive.

Thanks Experts,

I love this forum.

Another factor that may comes into play is the increased need for capacity planning to enhance the new WI-FI-CELL phones that will be rapidly hitting the market. That is another reason why more APs will be needed. With the WI-FI networks indoors providing an off load for the weak in-building Cellular networks indoors. The more APs you have to handoff the calls the better. MIMO gives you a better mousetrap to reassure the customer that your network was well thought out, is scalable and cost effective.