Zone Director 1125, Zoneflex 7372 with Flying Voice Wireless SIP Phone IP542N (garbled and choppy reception)

[alexander_bas]

Hi Everyone,

I would like to seek any input to help me solve garble and choppy voice reception.
I have a ZoneDirector 1100 with 9.5.3.0 build 44, Zoneflex 7372 for Access points and Flying voice wireless sip phone IP542N.

So far here are the workarounds that i did. I already disabled the background scanning features. I also tried activating the "Tunnel to Zone director" feature in the Zonedirector to see if it will at least improve the voice quality but the devices wasn't acquiring IP addresses. It seems that the DHCP relay option is not working as well.

Hope somebody can at least give me an idea to solve this issue.

Thanks
Alex

[bas_sanders]

Alex,

When using VoWLAN, tunnelling all traffic to the ZD is in my opinion best practice. Did you configure the SSID to be tunnelled into a VLAN?

The ZD will not terminate the VLAN.. it will only bridge the SSID INTO the VLAN. The VLAN must be available on the uplink port of the ZD.

For this to work, you would have to enable VLAN tagging on the uplink port first.

After that, configure DHCP relaying and routing on the VLAN and not on the ZD as you would normally do.

For choppy audio, check for receive quality (both ways) first. First thing i would do is a simple ICMP check by continuously pinging the handset to see if thats stable.

Is this occurring continuously or only during handover or in specific areas?

Regards,

Bas

[alexander_bas]

Hi Bas,

Thank you for your response.

I've been actually trying to enable the "Tunnel to ZD" feature in the zone director but unfortunately the wireless sip phone wasn't acquiring IP addresses if this was enabled even if the DHCP option was configured. Already tried configuring the DHCP option with Cisco DHCP service and Microsoft DHCP but to no avail. BTW, do i have to trunk the cisco port where the zd is connected?

Yes VLAN tagging is configured as well. We have three Vlan taggings configured in access points. The management vlan, the voice vlan and the data vlan.

However, the cisco port where the ZD is connected was only configured same as the management VLAN of access points.

Yes, continuous pinging the wireless sip phones (IP542N) are stable with low latencies and the APs uplink throughput wasn't even reaching 50% of bandwidth.

Yes this is occurring continuously and even on non-office hours where traffic is low.

Thanks
Alex

[bas_sanders]

Hi Alex,

If the problem is intermittent there must be another issue somewhere. It feels to me there isn't necessarily an issue with the WLAN. It sounds more like an issue with the VoIP configuration if you ask me..

Is it possible for you to make a sniffer trace of the garbled voice? If so, look for the sip handshake and see if both use the correct CODEC's or look for out-of-sequence UDP packets.

Nevertheless it is recommended to have 'Tunnel to ZD' enabled.

You mention that the link between the Cisco switch and the ZD only has the management VLAN. For this configuration with tunnelling to work, you will need to add the voice and the data VLAN to the link between the Cisco switch and the ZD. Therefor these two ports (on the Cisco as well as the ZD need to have VLAN tagging enabled which also answers your question.

Some things to keep in mind:
- Cisco by default does NOT tag it's native VLAN! just don't use the native VLAN, or don't use Cisco ;-)
- Use DOT1Q tagging on the Cisco.
- The ZD will start to use VLAN tagging as soon as you have configured a VLAN ID to an SSID and you hit "tunnel to ZD".
- The VLAN will ONLY be active on the ZD port! The port where the AP is connected will not use the VLAN's configured if you tunnel them to the ZD.

also, 50% of which bandwidth? is it a 100meg or a gig port? 50mbit is a fair amount of traffic when also carrying VoIP over the same radio. Still, if the ICMP response is stable and showing low latency i don't expect this to be an issue.

Good luck!
Bas