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Cisco Unified Wireless IP Phone 7921G Administration Guide for Cisco Unified Communications Manager Release 7.0
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Chapter 10 Troubleshooting the Cisco Unified Wireless IP Phone 7921G
Resolving Voice Quality and Roaming Problems
•
Check the volume settings in the Phone Settings menu.
Symptom: Improper Roaming and Voice Quality or Lost Connection
If users report that when engaged in an active phone call and walking from one location to another
(roaming), the voice quality deteriorates or the connection is lost, you can use the following suggestions
to identify the cause of the problem.
These sections can assist you with the following symptoms:
•
Voice Quality Deteriorates While Roaming, page 10-11
•
Delays in Voice Conversation While Roaming, page 10-11
•
Phone Loses Connection with Cisco Unified Communications Manager While Roaming, page 10-11
•
Phone Does Not Roam Back to Preferred Band, page 10-12
Voice Quality Deteriorates While Roaming
Check the RSSI on the destination access point to see if the signal strength is adequate. The next access
point should have an RSSI value of -67 dBm or greater.
Check the site survey to determine if the channel overlap is adequate for the phone and the access point
to hand off the call to the next access point before the signal is lost from the previous access point.
Check to see if noise or interference in the coverage area is too great.
Check that signal to noise ratio (SNR) levels are 25 db or higher for acceptable voice quality.
Delays in Voice Conversation While Roaming
Use the Site Survey Utility on the Cisco Unified Wireless IP Phone 7921G to see if there is another
acceptable access point as a roaming option. The next access point should have an RSSI value of 35 or
greater to roam successfully.
Check the Cisco Catalyst 45xx switch to see if it has the correct version of Supervisor (SUP) blades. The
blades must be versions SUP2+ or higher to prevent roaming delays.
Phone Loses Connection with Cisco Unified Communications Manager While Roaming
Check for the following configuration or connectivity issues between the phone and the access point:
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The RF signal strength might be weak. Use the Site Survey Tool and check the RSSI value for the
next access point.
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The next access point might not have connectivity to Cisco Unified Communications Manager.
•
There might be an authentication type mismatch between the phone and the next access point.
•
The access point might be in a different subnet from the previous access point. The Cisco Unified
Wireless IP Phone 7921G is capable of Layer 2 roaming only. Layer 3 roaming requires WLSM that
uses GRE. For more information, see
“WLANs and Roaming” section on page 2-6
.
•
If using EAP-FAST, LEAP, or Auto (AKM) authentication, the access point might be using filters
to block TCP ports. The ACS server uses port 1645 for authentication and 1646 for accounting and
the RADIUS server uses port 1812 for authentication and 1813 for accounting.
