Time sensitive data over WIFI - VoIP

[Jonny]

Hello experts :)

So I run a WISP specialising in VoIP using ATAs to connect phones to our network. Any tips or tricks to getting perfect quality all the time? We have people with perfect LOS, good signal, CCQ etc, but suffer intermittent bouts of poor voice quality from lost or out of sync packets. Any tips or tricks for newbies to VoIPoWiFi to watch out for?

Thanks!

[Willtech]

It will really depend on how you have your network set up. Do you have any other none voip traffic on the network? If you have a combination of data types flowing across the network then you will need to prioritize your voice voice traffic. When you start to prioritize your voice traffic you will need to do it through out the entire network and not in just one location. Where is your voip service originating? Are you reselling the service from another vendor through the internet or are you providing the service through your own hardware?

[Jonny]

We provide our own voip server but that does pass through to another service for the number and connection to the outside world. We have all other types of internet traffic as well and we do prioritise voip higher than everything else. This is done in the main router so applies to all connections to our network.

[Willtech]

How often do you have these problems with poor voice quality? Does it happen at any specific time of day or any specific AP? Do you have all of your subs out of one AP or do you have multiple APs connected by back hauls? How does latency look through out your network? What about port and CPU utilization on your routers? Do you have any problems with calling inside of your network?

[Jonny]

>>Does it happen at any specific time of day or any specific AP?

More noticeable on one particular sector which I think is due to signal reflection from a nearby larger building. There are issues on the other ones however at random times. There's 4sectors then another 2 further down then one grid for a back haul to another repeater.

>>Do you have all of your subs out of one AP or do you have multiple APs connected by back hauls?

The majority are fed off of the main 6 with the upper 4 being fed by an RB with 4 radio cards and another RB for the other 2. These are fed via fibre. The back haul goes to a point about 15Kms away with a few people off there. These are rural based so less prone to interference from activity in town yet there are voice issues there as well, again at random times.

>>How does latency look through out your network?

Latency is very low. <100ms and I've seen voip work ok a bit over 100. We even tried a different codec that was more fault tolerant but didn't help much.

>>What about port and CPU utilization on your routers? Do you have any problems with calling inside of your network?

Yes we have internal issues. When monitoring the load on hardware it's quite low so not sure it's that either. We have virtualised the servers.

When it faults it's usually person A can't hear person B but B can hear A ok. The majority of client hardware is ubiquiti. There are a couple of MT based antennas in use and we very rarely have voice issues with them. I don't think there'd be an issue with nanos and bullets in this kind of setup? We do notice linksys ATAs handle issues better than grandstream, but they aren't a complete fix.

[Willtech]

What frequency are you using for your APs and your backhauls? Have you done any type of site survey to see if there are any other devices competing with your APs? Have you done any testing with any type of an ethernet test set such as a JDSU HST 3000 or any other test sets? Do your routers show any errors on the ports? Have you been able to duplicate the voice problems connected directly to your voip hardware and not through your wi-fi network?

[Jonny]

So we've found the setting for Fragmentation has helped a lot. By lowering the default level to 1500 it has largely overcome most VoIP over wireless issues we were having. This hasn't solved the cause, i.e. interference etc, but has made the data stream more bulletproof.

[mobilexpi]

Should setup a lower fragmentation only in the CPE or also in the Access Point?

Best regards

[Jonny]

I believe we just set it in the CPE