Hi,

we are planning to deploy a WISP mainly for VOIP access. We plan to use MT for the AP and NS5 (and Loco5) for CPE. Each customer will need only ~64 Kbit/s up/down when in conversation.

Our main concerns are related to contention. As there is not a polling standard (eg. MT uses Nstreme which is not compatible with UBNT), we think there can be lot of problems with the service.

Can anybody give advise on previous experiences?
Number of customers per AP?
Better not to mix equipment from different providers?
What about Nstreme? I (have read contradictory opinions in the forum)

Thanks & regards,
Antonio

How many subscribers are you planning on having connected to each access point? What is the highest number of phone calls you expect to be taking place at once across each access point. What frequncy will you be using?
Because you will have only VoIP traffic and not data as well, it could be fairly low volume and this could work fine.

How many subscribers are you planning on having connected to each access point? What is the highest number of phone calls you expect to be taking place at once across each access point. What frequncy will you be using?
Because you will have only VoIP traffic and not data as well, it could be fairly low volume and this could work fine.

# of suscribers per AP -> ~200
# of simultaneous phone calls (peak) -> ~40
frequency -> 5GHz (802.11a)

As the configuration will be PtMP without visibility I plan to use only RTS-CTS. Is there any better option (non propietary)?
Regarding WMM I think it should be useless as all traffic has same priority...

Regards
Antonio

That (200) is alot of wireless clients connected to one AP. I think for sure polling with nstreme is necessary.
I think you would also benefit from setting up additional AP's to lower the number of clients per AP.
You may also want to consider different equipment such as Alvarion althought it is much more expensive.

VoIP can handle a fair amound of jitter as the phones have a built in de-jitter buffer so the connection doesn't need to be perfect.

Yes, this is lot of clients in one AP but the key is that only few (estimated 30-40 at a peak time) will be transmitting/receiving data at up to 128 kbit/s (64+64).

Rest of the time they will only send/receive SIP messages registers (1 packet every 5 minutes or so)...

Regards
Antonio

in my opinion why dont u use sectorial antennas and multiple radios in your BS (base station) because the demand of bandwidth that u will need is very high, and also the processor must be powerful,

maybe with RB433AH with 3 Radios and 3 sectors panels all with WMM voice priority will be enogh for your topology

Best Regards

http://www.zytrax.com/tech/protocols/voip_rates.htm

Study the stuff this link shows.

Your data rates are quite a bit off. With g711, your packet overhead is worth refiguring. With the smaller "more efficient" compressions schemes, the packet overhead exceeds the actual bandwidth needed.

I have measured this, and this amount of overhead is for real.

PPS is also something to consider when running lots of voice calls on a wireless network. If you want lots of PPS on your wireless network, everyone will need high modulations, good signals, you'll needed to standardize equipment, and can't be afraid to go non-standard and use nstreme or a proprietary wireless vendors. You also won't get the quantity of stations and simultaneous calls you're talking about. You won't need luck, you'll need a miracle.

Hi,
I have been studying how CSMA/CA works and doing some "homework" like calculating MAC capacity based on IP packet size, etc..
Some theoretical figures I got (for 802.11b with typical parameters without RTS-CTS):
For 802.11b network, number of simultaneous VOIP calls (G711) --> 13 (MSDU ~ 200bytes, System capacity ~ 2,1 Mbit/s)
For 802.11b network and G729 and 50% usage factor: --> 31 (MSDU ~60bytes, Capacity ~0,75Mbit/s)
Please note that such figures are for 802.11b; it will be little better at 802.11a (due to lower guard times, preambles, etc..)
I'm far from my expectations so I must go to split the AP in several sectors, send big frames (at the cost of some msecs of delay), think an admision policy, etc...

Thanks everybody for the assistance!!!

Regards,
Antonio