VoIP over Canopy

I have been looking at VoIP, trying to fine tune the performance over the RF network.

Here are my findings, depending on what codec you use, voice required different pps (packet per second) rate.

G.711 = 400 - 50 pps
G.729 = 200 - 50 pps

Page 61 of user guide, the AP’s have a limit 300pps.

This means one customer running on the G.711 codec could max out their SM ?

Also, it doesn’t tell us what the maximum pps of an AP is as a whole.

A BH could get maxed by 5 simultaneous phone calls.

Any ideas/comments…

what if you buy a new vonage box for a customer where will it tell what codec it is using?

Vonage by default uses G711. However, you can adjust the codec from Vonage’s user configuration page to “low bandwidth”.

Did some more digging around.

Canopy AP can handle 3000pps uplink and 1500pps downlink to all the SM’s registered to it.

The key thing here is that the BH also have a limit of 3000pps, hence one single AP can max out a BH, so if you have a cluster with 6 AP’s you are very likely to run into problems.

Based on this I will be redesigning my network.

For more infomration on Voice

G.711/G.729 Codec can be run in a number of configuration, depending on your network, you have to balance the bandwidth against the pps, also the codecs have jitter buffers to smooth out network latency fluctuations.

Packet Duraion 5 20 30 40
PPS 400 100 66.7 50
Packet Size 98 218 298 378
Bandwidth 156.8 87.2 79.5 75.6 (kbps each way)

Packet Duration 10 20 30 40
Packet Size 68 78 88 98
Bandwidth 54.4 31.2 23.4 19.6

Using the G.723 it is possible to get your bandwidth down to 5.6kbps.

If you have people using voice over your network then be careful, as not only will voice not work properley, it will eat up your pps and start affecting other customers, you will see plenty of bandwith but can’t make use of it, I think this is why I am experiencing high latency.

The motorola reommended packet size is about 1500bytes, voice generates anything between 50 to 400byte sized packets, hence extremely inefficient when it comes to making use of the bandwidth.

In comparison, other wireless BH radios give you 12000pps. Not sure on the multipoint competitors, but I am sure it is much higher.

intresting to know. thanks for sharing…

but how would you know that the link is maxed out ? on pps side ?


Good question… not sure… you can pull that info from the CMM’s but I don’t trust it…

What I am doing at the moment is, mirroring the ports on my CISCO switches and running ethereal to see what is going on.

The other thing you could possibly do is NAT disable an SM, connect it to your RF cloud, and run ethereal, you will be able to see what is flying around on the network… once you got the capture you could run further analysis using ethereal which will tell you pps, however you need to consider VLAN’s if you have them as you will not pick that traffic up, and also you will only get the broadcast traffic, due to canpoy acting as a switch and not a HUB…

I don’t think there is a MIB for pps… anyone any ideas ?