VoIP via A5/C5 SRS vs WiFi mode


#1

We put up a single A5-14 with only 1 C5 client.

This C5 client serves general Internet as well as provides VoIP service.

Our customer was very frustrated with VoIP audio problems.

We would see jitter measured by PingPlotter jump from 0.50 to 3.0 over the A5/C5 link in SRS mode.

We tried several frequencies, updated to latest firmware on C5 and A5 and worked with a support engineer at Mimosa…moved from adaptive to fixed jitter management on the Yealink phones and nothing was a sustained fix.

Then while chatting with Mimosa support and looking at SRS mode the 8 ms the tech mentioned Mimosa had considered reducing this to a lower number. I asked would SRS 8 ms cause increased jitter and he said yes.

We switched to WiFi mode…and the audio problems appear to have vanished for the past 2 weeks. They had audio quality issues most all day every day prior to that. PingPlotter measures the jitter at 0.90 or less with the A5 in WiFi mode.

I read this post:

Is anyone using A5/C5 to provide Internet to users of VoIP who make a high volume of calls with excellent audio?

Thanks in advance.


#2

Hi @Jeff7,

We have a ton of customers who use VoIP over Mimosa equipment. I belive the majority of those use Wifi Interop mode though, for lower latency times.

Unfortunately because SRS uses TDMA timing, trying to create a smaller timing window would create more issues with clients, instead of resolving issues.

We get the occasional call from an ISP that provides VoIP service, or their customer uses VoIP service, but the issue is usually spectrum interference.


#3

You cant try other tricks to make voip better.
Don’t know if it fits with your network, but we use a cos 5 separate vlan for voip.
ap and network devices if properly engineered and configured honors the qos, giving you more constant jitter for this kind of traffic.
you can also try to fix jitter buffer sizes on phones ata and off course sip server, to have big buffers and compensate the jitter.


#4

Not sure if this will be helpful, but we have an A5-14 with 22 clients in SRS mode - 40 MHz channel. We are running a pile of different firmware because of issues with Mimosa and our Mikrotik routers and DHCP working properly.

My home office is on that link with VoIP and I have no issues. Not much call volume at all and the VoIP server is in our office which is the one wireless hope and 2 routers away. I can check pingplotter if it would help anyone.

I’m also using a G2 in my house. We have had “reports” of some customers having issues when they are using a retail router, but you never know with some of those reports. Our commercial customers with “real” routers are fine.