Calls dropping, poor quality of voice

[benharned]

I am having a problem, and it seems to be worsening. We have 7 7920 phones, 3 1230 APs, and one 1100 AP. Each of the 1200s have one antenna (1 1728 inside, 2 2506 out).

The phones are on v2.0, APs are 12.2(13)JA4, CM 4.0.

The APs are on channels 1, 6, 11, 11 (the two 11s are on opposite sides of the building).

I have done a walk-around inside and the RSSI is generally between 35 and 45.

Would adding an additional indoor antenna increase signal and call quality? Would making all the APs on the same channel improve things? Any other suggestions?

[michaelgillespie]

If you are not using diversity then need to configure the AP as so, but recommended to use diversity for all VoWLAN deployments. Ensure you are inline w/ the design guide @ http://www.cisco.com/en/US/products/hw/phones/ps379/products_implementation_design_guide_book09186a00802a029a.html. There is a sample AP config there as well. Also ensure the signal, noise and SNR levels are met. If you need further assistance open a TAC case.

[benharned]

Diversity would only work if there are two antennas, correct? Currently they are all set on Left, with one antenna.

[michaelgillespie]

Yes, diversity is 2 antennas. The right port is considered the primary port. So if not using diversity need to configure the AP as so.

[benharned]

With regards to QoS settings: our APs are only used for our 7920s. We do have a small WLAN for our regular data network, but that uses different APs, and is on an entirely different domain.

Our VoIP APs have a QoS policy defined for the voice network, but it is not applied to any VLAN. Would this improve anything with calls being dropped, or poor voice quailty, or does QoS not matter if there are no other devices using the WLAN.

Also, I've done a site survey, and I never had a RSSI higher than 49 (CU was always 0), average was around 38. Is that RSSI reading acceptable?

[benharned]

Also, our APs are on 12.2(13)JA4. Would an version upgrade help?

[michaelgillespie]

Recommended to use 12.3(4)JA. Calls should never be dropped w/ CallManager unless a gateway or something tears down the call. If CME, then may tear down the call on ICMP destination unreachable.

[benharned]

1. To upgrade IOS from 12.2(15)JA4 to 12.3(4)JA can I go directly to 12.3, or do I need to step upgrade with the versions in-between?

2. I purchased an additional antenna for one of our points. I can just hook it up and set the tx/rx to diversity. I don't need an additional radio in the AP?

3. The APs for the phones are only used for voice traffic; only one VLAN configured. I have 2 seperate LinkSys APs for data, but they are on a different network, and set to channels 8 & 9, G-Only mode. QoS is not enabled on the Cisco voice APs. Would that help the quality?

[michaelgillespie]

Can upgrade directly. The 1200 has 2 ports for antennas to achieve diversity. By default the ports are set for diversity. Also can only have 1 2.4ghz radio per AP (802.11b or g).

7920s get priority via CDP already, but can easily set a COS of 6 for that VLAN / SSID.